Predictive modelling of grain-size distributions from marine electromagnetic profiling data using end-member analysis and a radial basis function network

NASA Astrophysics Data System (ADS)

Baasch, B.; Müller, H.; von Dobeneck, T.

2018-07-01

In this work, we present a new methodology to predict grain-size distributions from geophysical data. Specifically, electric conductivity and magnetic susceptibility of seafloor sediments recovered from electromagnetic profiling data are used to predict grain-size distributions along shelf-wide survey lines. Field data from the NW Iberian shelf are investigated and reveal a strong relation between the electromagnetic properties and grain-size distribution. The here presented workflow combines unsupervised and supervised machine-learning techniques. Non-negative matrix factorization is used to determine grain-size end-members from sediment surface samples. Four end-members were found, which well represent the variety of sediments in the study area. A radial basis function network modified for prediction of compositional data is then used to estimate the abundances of these end-members from the electromagnetic properties. The end-members together with their predicted abundances are finally back transformed to grain-size distributions. A minimum spatial variation constraint is implemented in the training of the network to avoid overfitting and to respect the spatial distribution of sediment patterns. The predicted models are tested via leave-one-out cross-validation revealing high prediction accuracy with coefficients of determination (R2) between 0.76 and 0.89. The predicted grain-size distributions represent the well-known sediment facies and patterns on the NW Iberian shelf and provide new insights into their distribution, transition and dynamics. This study suggests that electromagnetic benthic profiling in combination with machine learning techniques is a powerful tool to estimate grain-size distribution of marine sediments.

Predictive modelling of grain size distributions from marine electromagnetic profiling data using end-member analysis and a radial basis function network

NASA Astrophysics Data System (ADS)

Baasch, B.; M"uller, H.; von Dobeneck, T.

2018-04-01

In this work we present a new methodology to predict grain-size distributions from geophysical data. Specifically, electric conductivity and magnetic susceptibility of seafloor sediments recovered from electromagnetic profiling data are used to predict grain-size distributions along shelf-wide survey lines. Field data from the NW Iberian shelf are investigated and reveal a strong relation between the electromagnetic properties and grain-size distribution. The here presented workflow combines unsupervised and supervised machine learning techniques. Nonnegative matrix factorisation is used to determine grain-size end-members from sediment surface samples. Four end-members were found which well represent the variety of sediments in the study area. A radial-basis function network modified for prediction of compositional data is then used to estimate the abundances of these end-members from the electromagnetic properties. The end-members together with their predicted abundances are finally back transformed to grain-size distributions. A minimum spatial variation constraint is implemented in the training of the network to avoid overfitting and to respect the spatial distribution of sediment patterns. The predicted models are tested via leave-one-out cross-validation revealing high prediction accuracy with coefficients of determination (R2) between 0.76 and 0.89. The predicted grain-size distributions represent the well-known sediment facies and patterns on the NW Iberian shelf and provide new insights into their distribution, transition and dynamics. This study suggests that electromagnetic benthic profiling in combination with machine learning techniques is a powerful tool to estimate grain-size distribution of marine sediments.

Ecology of free-living nematodes from the continental shelf of the central great barrier reef province

NASA Astrophysics Data System (ADS)

Tietjen, John H.

1991-05-01

Nematode assemblages from five sites on the continental shelf of the central Great Barrier Reef (GBR) along a transect ranging from inshore muddy quartz to offshore carbonate sands were examined in austral spring (October 1987) and summer (January 1988). Assemblages at all sites were characterized by very even distributions (low dominance) of families, genera and species. Average per cent abundances of the dominant family (Chromadoridae), genus ( Theristus) and species ( Spilophorella paradoxa), respectively, were 16, 10 and 8% of the total number of specimens identified. The diversity of species ( H' = 3·35-4·08) from the GBR was higher than that normally calculated for shelf nematode assemblages; species richness (SR = 10·64-16·67) and evenness (J' = 0·82-0·91) values approximate those characteristic of deep-sea nematode assemblages, suggesting equitable exploitation of the interstitial environment on the GBR shelf by many species. This was also indicated by a nodal analysis of the 22 dominant species, which exhibited no strong preference for any particular sediment or site. Non-selective deposit and epistrate feeders were the most abundant trophic types among the nematodes. The abundance of non-selective deposit feeders was significantly greater in the summer than spring assemblages, accompanying differences also observed in the per cent composition of several species. Shortterm fluctuations in species composition and high species diversity of nematodes on the central Great Barrier Reef shelf may be the result of high sediment heterogeneity (caused by cyclones and frequent prawn trawling), a rich bacterial flora, continuous warm temperatures and low macroinfaunal abundance.

Metabarcoding reveals environmental factors influencing spatio-temporal variation in pelagic micro-eukaryotes.

PubMed

Brannock, Pamela M; Ortmann, Alice C; Moss, Anthony G; Halanych, Kenneth M

2016-08-01

Marine environments harbour a vast diversity of micro-eukaryotic organisms (protists and other small eukaryotes) that play important roles in structuring marine ecosystems. However, micro-eukaryote diversity is not well understood. Likewise, knowledge is limited regarding micro-eukaryote spatial and seasonal distribution, especially over long temporal scales. Given the importance of this group for mobilizing energy from lower trophic levels near the base of the food chain to larger organisms, assessing community stability, diversity and resilience is important to understand ecosystem health. Herein, we use a metabarcoding approach to examine pelagic micro-eukaryote communities over a 2.5-year time series. Bimonthly surface sampling (July 2009 to December 2011) was conducted at four locations within Mobile Bay (Bay) and along the Alabama continental shelf (Shelf). Alpha-diversity only showed significant differences in Shelf sites, with the greatest differences observed between summer and winter. Beta-diversity showed significant differences in community composition in relation to season and the Bay was dominated by diatoms, while the Shelf was characterized by dinoflagellates and copepods. The northern Gulf of Mexico is heavily influenced by the Mobile River Basin, which brings low-salinity nutrient-rich water mostly during winter and spring. Community composition was correlated with salinity, temperature and dissolved silicate. However, species interactions (e.g. predation and parasitism) may also contribute to the observed variation, especially on the Shelf, which warrants further exploration. Metabarcoding revealed clear patterns in surface pelagic micro-eukaryote communities that were consistent over multiple years, demonstrating how these techniques could be greatly beneficial to ecological monitoring and management over temporal scales. © 2016 John Wiley & Sons Ltd.

41 CFR 101-27.209 - Utilization and distribution of shelf-life items.

Code of Federal Regulations, 2014 CFR

2014-07-01

... distribution of shelf-life items. 101-27.209 Section 101-27.209 Public Contracts and Property Management... PROCUREMENT 27-INVENTORY MANAGEMENT 27.2-Management of Shelf-Life Materials § 101-27.209 Utilization and distribution of shelf-life items. Where it is determined that specified quantities of both Type I and Type II...

Living and dead foraminiferal assemblages from an active submarine canyon and surrounding sectors: the Gioia Canyon system (Tyrrhenian Sea, Southern Italy)

NASA Astrophysics Data System (ADS)

Letizia, Di Bella; Martina, Pierdomenico; Roberta, Porretta; Chiocci, Francesco Latino; Eleonora, Martorelli

2017-05-01

Living (rose Bengal stained) and dead benthic foraminiferal assemblages were studied from 23 stations located between 60 and 670 m depth along the Gioia Canyon and the adjacent continental shelf and slope (Southern Tyrrhenian Sea). The aim of this study is to investigate the relationships among sedimentary processes, hydrological patterns and benthic foraminiferal distribution, in a highly dynamic environment. High sedimentation rates on the shelf and occasional turbidity flows along the canyon, lead to unstable environmental conditions at the seafloor that reflect on the microbenthic community influencing faunal density, diversity, species composition and distribution inside the sediment. The foraminiferal distribution seems to be controlled by sedimentary processes, nutrient supply and organic matter recycling, which in turn are strongly controlled by the seasonal variability of riverine inputs and current dynamics in the Gulf of Gioia. From the inner shelf to the upper continental slope (550 m depth), the living foraminiferal assemblage is dominated by agglutinated taxa, likely favored by the high terrigenous supply. Frequent eutrophic taxa (Valvulineria bradyana and Nonionella turgida) tolerant high turbidity (Leptohalysis scottii,) and low oxygen (Bolivina spp. and Bulimina spp.) are recorded on the edge of the inner shelf, where channeling, deposition of coastal deposits and occasional sediment gravity flows occur. In the outer sector of the shelf a turnover of species is observed; L. scottii replaced by the opportunistic species Reophax scorpiurus, and taxa indicative of high energy conditions (Cassidulina spp.) become dominant in association with mesotrophic species like Globocassidulina subglobosa. Along the continental slope, lower sedimentation rates and more stable environmental conditions support richer and more diversified foraminiferal assemblage. The abundance of Bulimina marginata indicates eutrophic conditions at the shallower station (300 m depth) whereas at greater depth (550 m) typical open slope species dominate (Gyroidina spp., Uvigerina mediterranea). Within the Gioia Canyon, benthic assemblage indicates environmental conditions similar to those observed in other Mediterranean and extra-Mediterranean canyons. The assemblage is characterized by eutrophic and low oxygen taxa (Bolivina spp., Bulimina spp.) in relation to periodical fluxes of sediment and organic matter. Similar relationships arise from the analysis of dead foraminiferal assemblages. However, the comparison between living and dead faunas highlight compositional and structural changes related to taphonomic processes.

Distribution, Source and Fate of Dissolved Organic Matter in Shelf Seas

NASA Astrophysics Data System (ADS)

Carr, N.; Mahaffey, C.; Hopkins, J.; Sharples, J.; Williams, R. G.; Davis, C. E.

2016-02-01

Dissolved organic matter (DOM) is a complex array of molecules containing carbon (DOC), nitrogen (DON) and phosphorous (DOP), and represents the largest pool of organic matter in the marine environment. DOM in the sea originates from a variety of sources, including allochthonous inputs of terrestrial DOM from land via rivers, and autochthonous inputs through in-situ biotic processes that include phytoplankton exudation, grazing and cell lysis. Marine DOM is a substrate for bacterial growth and can act as a source of nutrients for autotrophs. However, a large component of DOM is biologically refractory. This pool is carbon-rich and nutrient-poor, and can transport and store its compositional elements over large areas and on long time scales. The role of DOM in the shelf seas is currently unclear, despite these regions acting as conduits between the land and open ocean, and also being highly productive ecosystems. Using samples collected across the Northwest European Shelf Sea, we studied the distribution, source, seasonality and potential fate of DOM using a combination of analytical tools, including analysis of amino acids, DOM absorbance spectra and excitation emission matrices, in conjunction with parallel factor analysis (PARAFAC). Strong cross shelf and seasonal gradients in DOM source and lability were found. We observed a strong seasonally dependent significant correlation between salinity and terrestrial DOM in the bottom mixed layer, an enrichment of DOM at the shelf edge in winter and a three-fold increase in fresh marine DOM coinciding with the timing of a spring bloom. Together, our findings illustrate the dynamic nature of DOM in shelf seas over a seasonal cycle and, highlight the potential for DOM to play a key role in the carbon cycle in these regions.

Summer diet composition of walleye pollock and predator-prey relationships with copepods and euphausiids in the eastern Bering Sea, 1987-2011

NASA Astrophysics Data System (ADS)

Buckley, Troy W.; Ortiz, Ivonne; Kotwicki, Stan; Aydin, Kerim

2016-12-01

The composition of walleye pollock diets from the eastern Bering Sea continental shelf was determined from 25 years of sampling during summer surveys from 1987 through 2011. Substantial differences in the stomach contents of walleye pollock were found among the sizes and geographic strata that correspond to geographic distribution of the prey. With increasing pollock size, copepods decreased in importance in middle and outer shelf areas while mysids decreased in importance in the inner shelf. Euphausiids increased in importance with increasing pollock size in southeastern areas of the shelf, and fishes and shrimp increased in importance with increasing pollock size in northeastern areas of the middle and outer shelf. The biomass-weighted average diet composition of eastern Bering Sea pollock in each year's survey indicated perennial but variable importance of euphausiids and copepods as prey. An index of partial fullness indicated an interannual pattern of below-average consumption of copepods by the surveyed pollock from 1993 to 2004, but during this period the amount of euphausiids consumed continued to fluctuate about a mean that was similar to years surveyed before and after that period. The summer feeding success, as indicated by average stomach fullness, of intermediate sizes of pollock appears to be closely related to the consumption of copepods (especially for pollock 30-39 cm fork length (FL)) and prey other than euphausiids (especially for pollock 40-49 cm FL). Length-specific predator-prey relationships with copepods and euphausiids correspond to patterns in pollock feeding migrations. Interannual trends in the biomass of copepods in the EBS are reflected most closely in the diet of 20-29 cm FL pollock, and trends in the biomass of euphausiids in the EBS are reflected most closely in the diet of the largest pollock (60+ cm FL). Climate-mediated changes in the zooplankton community will likely have differential impacts across the demographic spectrum of pollock in the EBS.

Species Composition and Distribution of Zooplankton from Northeastern Sakhalin Shelf (Sea of Okhotsk)

NASA Astrophysics Data System (ADS)

Kasyan, V. V.

2018-03-01

The species composition, density, biomass, and distribution of zooplankton of the northeastern Sakhalin shelf, Sea of Okhotsk (Chaivo, Pil'tunskii, and Morskoi regions) were studied in October 2014. Zooplankton was represented by 15 taxonomic groups, which were dominated by Copepoda (13 species). The average density and biomass was highest in the Chaivo region (14112 ± 4322 ind./m3, 395 ± 107 mg/m3) and in the Pil'tunskii region (16692 ± 10707 ind./m3, 346 ± 233 mg/m3); the abundance of detected taxonomic groups was minimal (8-12). The average density and biomass of zooplankton was up to 4304 ± 2441 ind./m3, 133 ± 77 mg/m3 in the Morskoi region and increased with depth; the abundance of taxa was maximum (15). Four species of copepods made up the majority of the density and biomass of zooplankton: Acartia hudsonica, Eurytemora herdmani, Pseudocalanus newmani, and Oithona similis. In the Chaivo region, species of the genera Acartia, Eurytemora, and Oithona dominated and subdominated; in Pil'tunskii region, species of the genera Acartia and Oithona dominated and subdominated; and in the Morskoi region, species of the genera Oithona, Pseudocalanus, and Acartia dominated and subdominated.

Megabenthic assemblages at the Hudson Canyon head (NW Atlantic margin): Habitat-faunal relationships

NASA Astrophysics Data System (ADS)

Pierdomenico, Martina; Gori, Andrea; Guida, Vincent G.; Gili, Josep-Maria

2017-09-01

The distribution of megabenthic communities at the head of Hudson Canyon and adjacent continental shelf was studied by means of underwater video transects and still photo imagery collected using a towed camera system. The goal was to explore the relationships between faunal distribution and physical seafloor conditions and to test the hypothesis that increased seafloor heterogeneity in the Hudson Canyon supports a larger diversity of benthic communities, compared with the adjacent continental shelf. Hierarchical cluster analysis was performed to identify benthic assemblages as defined in imagery. The BIO-ENV procedure and the Canonical Correspondence Analysis were carried out to elucidate species groupings in relation to terrain variables extracted from bathymetric data. Species accumulation curves were generated to evaluate species turn over in and out of Hudson Canyon. The results indicate that seafloor morphology is the main physical factor related to benthic community composition and distribution. Assemblages dominated by sponges, zoanthids and cup corals colonized the canyon margins and flanks, and were associated with coarse-grained sediments, while sea pen assemblages were observed along muddy seafloor within the thalweg. An assemblage dominated by sea stars occurred on the shelf, associated with a sandy seafloor. Some assemblages were exclusively observed in the canyon area, suggesting that the increased variability of seafloor composition, together with the oceanographic processes specific to the canyon area, enhance beta diversity. The colonization by benthic suspension feeders within the canyon, in contrast to shelf assemblages, mainly composed of carnivores and detritus feeders could be favored the intense hydrodynamics at the canyon head that increase the availability of suspended organic matter. From the perspective of management and conservation of marine resources, the results obtained support the relevance of Hudson Canyon as a biodiversity hotspot. Such results are of particular significance in light of the recent action promoted by the Mid-Atlantic Fisheries Management Council, that restricts bottom trawling in most of the submarine canyons of the US Atlantic margin, including the Hudson Canyon, to protect cold-water corals from damage by fishing gear.

Source characterization and tsunami modeling of submarine landslides along the Yucatán Shelf/Campeche Escarpment, southern Gulf of Mexico

USGS Publications Warehouse

Chaytor, Jason D.; Geist, Eric L.; Paull, Charles K.; Caress, David W; Gwiazda, Roberto; Urrutia Fucugauchi, Jaime; Rebolledo Vieyra, Mario

2016-01-01

Submarine landslides occurring along the margins of the Gulf of Mexico (GOM) represent a low-likelihood, but potentially damaging source of tsunamis. New multibeam bathymetry coverage reveals that mass wasting is pervasive along the Yucatán Shelf edge with several large composite landslides possibly removing as much as 70 km3 of the Cenozoic sedimentary section in a single event. Using GIS-based analysis, the dimensions of six landslides from the central and northern sections of the Yucatán Shelf/Campeche Escarpment were determined and used as input for preliminary tsunami generation and propagation models. Tsunami modeling is performed to compare the propagation characteristics and distribution of maximum amplitudes throughout the GOM among the different landslide scenarios. Various factors such as landslide geometry, location along the Yucatán Shelf/Campeche Escarpment, and refraction during propagation result in significant variations in the affected part of the Mexican and US Gulf Coasts. In all cases, however, tsunami amplitudes are greatest along the northern Yucatán Peninsula.

Linking the Modern Distribution of Biogenic Proxies in High Arctic Greenland Shelf Sediments to Sea Ice, Primary Production, and Arctic-Atlantic Inflow

NASA Astrophysics Data System (ADS)

Limoges, Audrey; Ribeiro, Sofia; Weckström, Kaarina; Heikkilä, Maija; Zamelczyk, Katarzyna; Andersen, Thorbjørn J.; Tallberg, Petra; Massé, Guillaume; Rysgaard, Søren; Nørgaard-Pedersen, Niels; Seidenkrantz, Marit-Solveig

2018-03-01

The eastern north coast of Greenland is considered to be highly sensitive to the ongoing Arctic warming, but there is a general lack of data on modern conditions and in particular on the modern distribution of climate and environmental proxies to provide a baseline and context for studies on past variability. Here we present a detailed investigation of 11 biogenic proxies preserved in surface sediments from the remote High Arctic Wandel Sea shelf, the entrance to the Independence, Hagen, and Danmark fjords. The composition of organic matter (organic carbon, C:N ratios, δ13C, δ15N, biogenic silica, and IP25) and microfossil assemblages revealed an overall low primary production dominated by benthic diatoms, especially at the shallow sites. While the benthic and planktic foraminiferal assemblages underline the intrusion of chilled Atlantic waters into the deeper parts of the study area, the distribution of organic-walled dinoflagellate cysts is controlled by the local bathymetry and sea ice conditions. The distribution of the dinoflagellate cyst Polarella glacialis matches that of seasonal sea ice and the specific biomarker IP25, highlighting the potential of this species for paleo sea ice studies. The information inferred from our multiproxy study has important implications for the interpretation of the biogenic-proxy signal preserved in sediments from circum-Arctic fjords and shelf regions and can serve as a baseline for future studies. This is the first study of its kind in this area.

Seasonal cross-shelf distribution of major zooplankton taxa on the northern Gulf of Alaska shelf relative to water mass properties, species depth preferences and vertical migration behavior

NASA Astrophysics Data System (ADS)

Coyle, Kenneth O.; Pinchuk, Alexei I.

2005-01-01

The cross-shelf distribution of major zooplankton species was examined on the northern Gulf of Alaska (GOA) shelf during the production season for four years, between October 1997 and October 2001. The zooplankton community on the northern GOA shelf consisted of oceanic and neritic species of the North Pacific subarctic species complex. Cross-shelf distribution of the major zooplankton species was influenced by their depth preferences, vertical migration behavior, salinity-temperature preferences, and by cross-shelf water-mass distribution and movement. The neritic community, dominated by Pseudocalanus spp., Metridia pacifica and Calanus marshallae, had highest abundances on the inner shelf, in the Alaska Coastal Current, and in the adjacent fjords in late spring and early summer. The oceanic community, which contained primarily Neocalanus cristatus and Eucalanus bungii, was observed in the Alaskan Stream and adjacent waters near the shelf break. A mid-shelf transition zone contained a mixture of oceanic and neritic species. Prince William Sound (PWS) contained a unique species complex of large mesopelagic copepods, amphipods and shrimp. Neocalanus flemingeri and Oithona similis were abundant in all four regions during spring and early summer. The transition zone commonly crossed much of the shelf between the shelf break and the ACC, but satellite images and CTD data indicate that occasionally a narrow shelf-break front can form, in which case distinct zooplankton species groups are observed on either side of the front. Satellite data also revealed numerous large and small eddies, which probably contribute to cross-shelf mixing in the transition zone.

Biodiversity of the Deep-Sea Continental Margin Bordering the Gulf of Maine (NW Atlantic): Relationships among Sub-Regions and to Shelf Systems

PubMed Central

Kelly, Noreen E.; Shea, Elizabeth K.; Metaxas, Anna; Haedrich, Richard L.; Auster, Peter J.

2010-01-01

Background In contrast to the well-studied continental shelf region of the Gulf of Maine, fundamental questions regarding the diversity, distribution, and abundance of species living in deep-sea habitats along the adjacent continental margin remain unanswered. Lack of such knowledge precludes a greater understanding of the Gulf of Maine ecosystem and limits development of alternatives for conservation and management. Methodology/Principal Findings We use data from the published literature, unpublished studies, museum records and online sources, to: (1) assess the current state of knowledge of species diversity in the deep-sea habitats adjacent to the Gulf of Maine (39–43°N, 63–71°W, 150–3000 m depth); (2) compare patterns of taxonomic diversity and distribution of megafaunal and macrofaunal species among six distinct sub-regions and to the continental shelf; and (3) estimate the amount of unknown diversity in the region. Known diversity for the deep-sea region is 1,671 species; most are narrowly distributed and known to occur within only one sub-region. The number of species varies by sub-region and is directly related to sampling effort occurring within each. Fishes, corals, decapod crustaceans, molluscs, and echinoderms are relatively well known, while most other taxonomic groups are poorly known. Taxonomic diversity decreases with increasing distance from the continental shelf and with changes in benthic topography. Low similarity in faunal composition suggests the deep-sea region harbours faunal communities distinct from those of the continental shelf. Non-parametric estimators of species richness suggest a minimum of 50% of the deep-sea species inventory remains to be discovered. Conclusions/Significance The current state of knowledge of biodiversity in this deep-sea region is rudimentary. Our ability to answer questions is hampered by a lack of sufficient data for many taxonomic groups, which is constrained by sampling biases, life-history characteristics of target species, and the lack of trained taxonomists. PMID:21124960

Comparative organic geochemistry of Indian margin (Arabian Sea) sediments: estuary to continental slope

NASA Astrophysics Data System (ADS)

Cowie, G.; Mowbray, S.; Kurian, S.; Sarkar, A.; White, C.; Anderson, A.; Vergnaud, B.; Johnstone, G.; Brear, S.; Woulds, C.; Naqvi, S. W.; Kitazato, H.

2014-02-01

Surface sediments from sites across the Indian margin of the Arabian Sea were analysed for their carbon and nitrogen compositions (elemental and stable isotopic), grain size distributions and biochemical indices of organic matter (OM) source and/or degradation state. Site locations ranged from the estuaries of the Mandovi and Zuari rivers to depths of ~ 2000 m on the continental slope, thus spanning nearshore muds and sands on the shelf and both the semi-permanent oxygen minimum zone (OMZ) on the upper slope (~ 200-1300 m) and the seasonal hypoxic zone that impinges on the shelf. Source indices showed mixed marine and terrigenous OM within the estuaries, and overwhelming predominance (80%+) of marine OM on the shelf and slope. Thus, riverine OM is heavily diluted by autochthonous marine OM and/or is efficiently remineralised within or immediately offshore of the estuaries. Any terrigenous OM that is exported appears to be retained in nearshore muds; lignin phenols indicate that the small terrigenous OM content of slope sediments is of different origin, potentially from rivers to the north. Organic C contents of surface shelf and slope sediments varied from < 0.5 wt % in relict shelf sands to over 7 wt % at slope sites within the OMZ, decreasing to ≤ 1 wt % at 2000 m. Major variability (~ 5 wt %) was found at slope sites within the OMZ of similar depth and near-identical bottom-water oxygen concentration. A strong relationship between organic C and sediment grain size was seen for sediments within the OMZ, but lower C loadings were found for sites on the shelf and below the OMZ. Diagenetic indices confirmed that lower C content below the OMZ is associated with greater extent of OM degradation, but that C-poor shelf sediments are not consistently more degraded than those within the OMZ. Together, the results indicate that OM enrichment on the upper slope can be explained by physical controls (winnowing and/or dilution) on the shelf and progressive OM degradation with increasing oxygen exposure below the OMZ. Reduced oxygen exposure may contribute to OM enrichment at some sites within the OMZ, but hydrodynamic processes are the overriding control on sediment OM distribution.

Inter-habitat variation in density and size composition of reef fishes from the Cuban Northwestern shelf.

PubMed

Aguilar, Consuelo; González-Sansón, Gaspar; Cabrera, Yureidy; Ruiz, Alexei; Curry, R Allen

2014-06-01

Movement and exchange of individuals among habitats is critical for the dynamics and success of reef fish populations. Size segregation among habitats could be taken as evidence for habitat connectivity, and this would be a first step to formulate hypotheses about ontogenetic inter-habitat migrations. The primary goal of our research was to find evidence of inter-habitat differences in size distributions and density of reef fish species that can be classified a priori as habitat-shifters in an extensive (-600km2) Caribbean shelf area in NW Cuba. We sampled the fish assemblage of selected species using visual census (stationary and transect methods) in 20 stations (sites) located in mangrove roots, patch reefs, inner zone of the crest and fore reef (12-16m depth). In each site, we performed ten censuses for every habitat type in June and September 2009. A total of 11 507 individuals of 34 species were counted in a total of 400 censuses. We found significant differences in densities and size compositions among reef and mangrove habitats, supporting the species-specific use of coastal habitats. Adults were found in all habitats. Reef habitats, mainly patch reefs, seem to be most important for juvenile fish of most species. Mangroves were especially important for two species of snappers (Lutjanus apodus and L. griseus), providing habitat for juveniles. These species also displayed well defined gradients in length composition across the shelf.

Pigments in sediments beneath recently collapsed ice shelves: The case of Larsen A and B shelves, Antarctic Peninsula

NASA Astrophysics Data System (ADS)

Sañé, E.; Isla, E.; Grémare, A.; Gutt, J.; Vétion, G.; DeMaster, D. J.

2011-01-01

In March 2002, 3200 km 2 of the Larsen B ice shelf collapsed off the Eastern Antarctic Peninsula (EAP). In the austral summer of 2006, sea floor sediment was recovered beneath the extinct Larsen B ice shelf and in a region off the Northern Antarctic Peninsula (NAP), which has been free of ice shelves for more than 1000 yr. To assess changes in the chemical composition of the sediment after ice shelf collapses, chlorophylls and pheophytins were measured in sediment cores at six stations. This is the first time that chlorophyll pigments have been analysed in sediment samples from regions under recently collapsed ice shelves. Five years after the ice shelf collapse, Chla and Chlc concentrations were similar in the interfacial sediment (upper 1 cm) of NAP and EAP regions. However, in EAP Chla and Chlc concentrations decreased more rapidly with depth in the sediment column and were negligible below 2 cm depth. The high Chla to Pheoa ratios indicated that sedimentary pigments found in EAP had undergone limited degradation suggesting that they were locally produced rather than laterally advected. Complementary information from excess 210Pb activity and diatom valve distributions provided further evidence that the pigment fluxes to the seabed in EAP took place only after the ice shelf collapse.

Composition and temporal stability of turf sediments on inner-shelf coral reefs.

PubMed

Gordon, Sophie E; Goatley, Christopher H R; Bellwood, David R

2016-10-15

Elevated sediment loads within the epilithic algal matrix (EAM) of coral reefs can increase coral mortality and inhibit herbivory. Yet the composition, distribution and temporal variability of EAM sediment loads are poorly known, especially on inshore reefs. This study quantified EAM sediment loads (including organic particulates) and algal length across the reef profile of two bays at Orpheus Island (inner-shelf Great Barrier Reef) over a six month period. We examined the total sediment mass, organic load, carbonate and silicate content, and the particle sizes of EAM sediments. Throughout the study period, all EAM sediment variables exhibited marked variation among reef zones. However, EAM sediment loads and algal length were consistent between bays and over time, despite major seasonal variation in climate including a severe tropical cyclone. This study provides a comprehensive description of EAM sediments on inshore reefs and highlights the exceptional temporal stability of EAM sediments on coral reefs. Copyright © 2016 Elsevier Ltd. All rights reserved.

Environmental Variability, Bowhead Whale Distributions, and Inupiat Subsistence Whaling in the Coastal Arctic Ocean

NASA Astrophysics Data System (ADS)

Ashjian, C. J.; Campbell, R. G.; George, J. C.; Moore, S. E.; Okkonen, S. R.; Sherr, B. F.; Sherr, E. B.

2006-12-01

The annual migration of bowhead whales (Balaena mysticetus) past Barrow, Alaska has provided subsistence hunting opportunities to Native whalers for centuries. Bowheads regularly feed along the Arctic coast near Barrow in autumn, presumably to utilize recurrent aggregations of their zooplankton prey (e.g., copepods, euphausiids). Oceanographic field-sampling on the narrow continental shelf near Barrow and in Elson Lagoon was conducted during mid-August to mid-September of 2005 and 2006 to describe the different water mass types and plankton communities, to identify exchange of water and material between the shelf and lagoon and offshore, and to identify biological and physical mechanisms of plankton aggregation. High spatial resolution profiles of temperature, salinity, fluorescence, optical backscatter, and C-DOM were collected using an Acrobat undulating towed vehicle in the lagoon and across the shelf from near-shore to the ~150 m isobath. Discrete sampling for nutrients, chlorophyll a, and phytoplankton, and microzooplankton and mesozooplankton abundance and composition was conducted in distinct water types and across frontal boundaries identified from the high-resolution data. The distributions of bowhead whales were documented using aerial surveys. Inter-annual and shorter-term (days to weeks) variability in the distribution of water masses and intrinsic biological properties was observed. Distinct hydrographic and biological-chemical regions were located across the shelf that may contribute to the formation of bowhead whale prey aggregations. The lagoon system is an important interface between the ocean and land and may be critical to the formation of nearshore bowhead whale prey aggregations. Results from the field sampling will be coupled to biological-physical modeling and retrospective analyses to understand the response of this complex environment-whale-human system to climate variability.

Ichthyoplankton spatial pattern in the inner shelf off Bahía Blanca Estuary, SW Atlantic Ocean

NASA Astrophysics Data System (ADS)

Hoffmeyer, Mónica Susana; Clara, Menéndez María; Florencia, Biancalana; Mabel, Nizovoy Alicia; Ramón, Torres Eduardo

2009-09-01

This study focuses on the composition, abundance and distribution of ichthyoplankton in the inner shelf area off Bahía Blanca Estuary on the SW Atlantic Ocean during late spring. Eggs and larvae of Brevoortia aurea, Engraulis anchoita, Parona signata, Sciaenidae spp. - such as Cynoscion guatucupa and Micropogonias furnieri -, and Odontesthes argentinensis were found. Species richness was low probably as a result of season and shallow depths. Ichthyoplankton abundance reached values close to 10 000 per 10 m -3 (eggs) and 4000 per 10 m -3 (larvae) and displayed a spatial distribution pattern with maximum abundance values restricted to a band parallel to the coast. Differences between egg and larval patterns, probably derived from a different displacement and hydrodynamic behavior, were observed. Egg and larvae distribution patterns were found related with spawning areas and to directly depend on salinity and mesozooplankton. The larvae distribution pattern, in particular, was found to inversely depend on particulate organic carbon. In addition, the geographic location of egg and larvae maxima strongly coincided with a saline front reported for this area in springtime, thus suggesting a direct relationship with it.

Reef structure drives parrotfish species composition on shelf edge reefs in La Parguera, Puerto Rico

NASA Astrophysics Data System (ADS)

Tzadik, Orian E.; Appeldoorn, Richard S.

2013-02-01

Shelf edge reefs that exist in coral reef ecosystems provide essential habitats for a large variety of fish and other marine organisms. Marine herbivores act as differential algal grazers that advocate coral reef colonization. In the Caribbean basin parrotfishes make up a large contingency of such herbivores and act as important ecological ichthyofauna. By investigating parrotfish relationship with habitat, this study aims to aid in future predictive mapping techniques that will outline parrotfish distributions via benthic quantification. Parrotfish communities were evaluated on the shelf edge reef off of La Parguera, Puerto Rico. Parrotfish abundances were found to positively correlate with high values of overall reef structure. High values of coral cover and of rugosity were strong indicators of most parrotfish species. The lone exception, Scarus taeniopterus, negatively correlated with these factors and positively correlated with algal cover. Indications exist that Scarus taeniopterus and Scarus iseri are sympatric species and can be found in abundance at opposite locations.

Regional-scale drivers of marine nematode distribution in Southern Ocean continental shelf sediments

NASA Astrophysics Data System (ADS)

Hauquier, Freija; Verleyen, Elie; Tytgat, Bjorn; Vanreusel, Ann

2018-07-01

Many marine meiofauna taxa seem to possess cosmopolitan species distributions, despite their endobenthic lifestyle and restricted long-distance dispersal capacities. In light of this paradox we used a metacommunity framework to study spatial turnover in free-living nematode distribution and assess the importance of local environmental conditions in explaining differences between communities in surface and subsurface sediments of the Southern Ocean continental shelf. We analysed nematode community structure in two sediment layers (0-3 cm and 3-5 cm) of locations maximum 2400 km apart. We first focused on a subset of locations to evaluate whether the genus level is sufficiently taxonomically fine-grained to study large-scale patterns in nematode community structure. We subsequently used redundancy and variation partitioning analyses to quantify the unique and combined effects of local environmental conditions and spatial descriptors on genus-level community composition. Macroecological patterns in community structure were highly congruent at the genus and species level. Nematode community composition was highly divergent between both depth strata, likely as a result of local abiotic conditions. Variation in community structure between the different regions largely stemmed from turnover (i.e. genus/species replacement) rather than nestedness (i.e. genus/species loss). The level of turnover among communities increased with geographic distance and was more pronounced in subsurface layers compared to surface sediments. Variation partitioning analysis revealed that both environmental and spatial predictors significantly explained variation in community structure. Moreover, the shared fraction of both sets of variables was high, which suggested a substantial amount of spatially structured environmental variation. Additionally, the effect of space independent of environment was much higher than the effect of environment independent of space, which shows the importance of including spatial descriptors in meiofauna and nematode community ecology. Large-scale assessment of free-living nematode diversity and abundance in the Southern Ocean shelf zone revealed strong horizontal and vertical spatial structuring in response to local environmental conditions, in combination with (most likely) dispersal limitation.

Macroecological analysis of the fish fauna inhabiting Cymodocea nodosa seagrass meadows.

PubMed

Espino, F; Brito, A; Haroun, R; Tuya, F

2015-10-01

In this study, patterns in the taxonomic richness and composition of the fish fauna inhabiting Cymodocea nodosa seagrass meadows were described across their entire distribution range in the Mediterranean Sea and adjacent Atlantic Ocean. Specifically, the study tested whether there are differences in the composition of fish assemblages between those ecoregions encompassed by the distribution range of C. nodosa, and whether these differences in composition are connected with differences in bioclimatic affinities of the fish faunas. A literature review resulted in a total of 19 studies, containing 22 fish assemblages at 18 locations. The ichthyofauna associated with C. nodosa seagrass meadows comprises 59 families and 188 species. The western Mediterranean (WM) Sea has the highest species richness (87 species). Fish assemblages from the Macaronesia-Canary Islands, the Sahelian Upwelling, South European Atlantic Shelf and the WM differ, in terms of assemblage composition, relative to other ecoregions. In contrast, the composition of the fish fauna from the central and eastern Mediterranean overlaps. There is a significant serial correlation in fish assemblage composition between adjacent ecoregions along the distribution range of C. nodosa. Dissimilarities in assemblage composition are connected with the geographical separation between locations, and the mean minimum annual seawater temperature is the environmental factor that explains most variation in fish assemblage composition. © 2015 The Fisheries Society of the British Isles.

Macrofaunal Patterns in and around du Couedic and Bonney Submarine Canyons, South Australia

PubMed Central

Dittmann, Sabine; Sorokin, Shirley J.; Hendrycks, Ed

2015-01-01

Two South Australian canyons, one shelf-incising (du Couedic) and one slope-limited (Bonney) were compared for macrofaunal patterns on the shelf and slope that spanned three water masses. It was hypothesized that community structure would (H1) significantly differ by water mass, (H2) show significant regional differences and (H3) differ significantly between interior and exterior of each canyon. Five hundred and thirty-one species of macrofauna ≥1 mm were captured at 27 stations situated in depth stratified transects inside and outside the canyons from 100 to1500 m depth. The macrofauna showed a positive relationship to depth in abundance, biomass, species richness and community composition while taxonomic distinctness and evenness remained high at all depths. Biotic variation on the shelf was best defined by variation in bottom water primary production while sediment characteristics and bottom water oxygen, temperature and nutrients defined biotic variation at greater depth. Community structure differed significantly (p<0.01) among the three water masses (shelf-flowing South Australian current, upper slope Flinders current and lower slope Antarctic Intermediate Water) (H1). Although community differences between the du Couedic and Bonney regions were marginally above significance at p = 0.05 (H2), over half of the species captured were unique to each region. This supports the evidence from fish and megafaunal distributions that the du Couedic and Bonney areas are in different bioregions. Overall, the canyon interiors were not significantly different in community composition from the exterior (H3). However, both canyons had higher abundance and/or biomass, increased species dominance, different species composition and coarser sediments near the canyon heads compared to outside the canyons at the same depth (500 m), suggestive of heightened currents within the canyons that influence community composition there. At 1000–1500 m, the canyon interiors were depauperate, typical of V-shaped canyons elsewhere. The large number of species captured, given the relatively low sampling effort and focus on the larger macrofauna, support previous studies that identify the South Australian coast as a high biodiversity area. PMID:26618354

A review on the patterns of river material fluxes, coastal plume dispersal, shelf sediment facies, and anthropogenic impacts of the Tropical Land-Sea Interface, Sergipe/Alagoas, Northeast Brazil

NASA Astrophysics Data System (ADS)

Knoppers, B.; Medeiros, P. R. P.; de Souza, W. F. L.; Oliveira, E. N.; Fontes, L. C. da S.; do Carmo, M. S.; Carvalho, I. S.; Silva, M. C.; Brandini, N.; Carneiro, M. E.

2012-04-01

This study couples published and unpublished information on the alterations of continental material fluxes, plume dispersal patterns and coastal erosion induced by natural and human impacts to the distribution of sediment facies and sedimentation rates of the continental shelf of the States of Sergipe and Alagoas, northeastern Brazil (Lats. 8o56,2' and 11o20,0' S, Longs. 35o07,7' and 37o14,2' W). Historical data on river flow and material fluxes of 7 rivers, including the São Francisco river (L = 2850 km, AB = 634000 km2), were obtained from own measurements and from the national data bank of ANA (National Agency of Waters, www.ana.gov.br) with the softwares HIDRO 1.2 and SisCAH 1.0. Historical data on the distribution of sediments and their elemental composition of the shelf from the AKAROA (1965) campaign with 190 sampling stations (scale 1:1.000.000; Kempf, 1972, Summerhayes et al. 1975 & 1976, Coutinho, 1976) were revisited and new digital maps constructed with ArcGIS 9.3. Comparisons are made from new maps from recent campaigns (scale 1:250.000) performed by the consortium GEORIOEMAR/ UFS/ CENPES/ PETROBRÁS (2010). Statistical analyses with all parameters revealed that the shelf harbors 4 major regional sedimentary domains (i.e. A to D), reflecting the interaction between continental inputs and the impact of the oligotrophic South Equatorial Current (SEC) upon the shelf. The domains are: A- The Alagoas shelf. Set north of the São Francisco river with low fluvial input, dominance of SEC, recent organogenetic carbonate sediments with the calcareous algae Lithothamnium sp. and Halimeda sp. B- The São Francisco river alluvial fan and canyon. The river harbors a cascade of dams and after 1995, river flow declined by 40 % and was modulated to a constant flow of 2060 m3s-1, 95 % of the suspended matter load was retained within the reservoirs and nutrients (N,P) were impoverished by 90 % . The estuarine waters are now transparent and oligotrophic and the coastal plume lost its original turbidity and unimodal seasonal pattern of pulsation upon the shelf as indicated by In Situ sampling and Satellite imagery series (LANDSAT TM 2-5 and MODIS). The coastal plume is largely fed with suspended matter from resupension processes and coastal erosion. C- The Japaratuba river fan. The inner-mid shelf harbors relict muddy and sandy siliclastic sediments and the shelf margin biodetritic carbonates. Riverine inputs have become insignificant. D- The southern shelf of Sergipe. The muddy, sandy and carbonate Merl sediments are heterogeneously distributed,and the coast is affected by diffuse small riverine inputs and wash out by the SEC. Sedimentation rates (210Pbex chronology with the CRS model) of Domains B and C ranged between 0.7 and 0.1 cm year-1, being similar to those of the eastern Brazilian shelf.

Compositional analyses and shelf-life modeling of njangsa (ricinodendron heudelotii)seed oil using the weibull hazard method

USDA-ARS?s Scientific Manuscript database

This study investigated the compositional characteristics and shelf-life of Njangsa seed oil (NSO). Oil from Njangsa had a high polyunsaturated fatty acid (PUFA) content of which alpha eleosteric acid (alpha-ESA), an unusual conjugated linoleic acid was the most prevalent (about 52%). Linoleic acid...

Marine fish community structure and habitat associations on the Canadian Beaufort shelf and slope

NASA Astrophysics Data System (ADS)

Majewski, Andrew R.; Atchison, Sheila; MacPhee, Shannon; Eert, Jane; Niemi, Andrea; Michel, Christine; Reist, James D.

2017-03-01

Marine fishes in the Canadian Beaufort Sea have complex interactions with habitats and prey, and occupy a pivotal position in the food web by transferring energy between lower- and upper-trophic levels, and also within and among habitats (e.g., benthic-pelagic coupling). The distributions, habitat associations, and community structure of most Beaufort Sea marine fishes, however, are unknown thus precluding effective regulatory management of emerging offshore industries in the region (e.g., hydrocarbon development, shipping, and fisheries). Between 2012 and 2014, Fisheries and Oceans Canada conducted the first baseline survey of offshore marine fishes, their habitats, and ecological relationships in the Canadian Beaufort Sea. Benthic trawling was conducted at 45 stations spanning 18-1001 m depths across shelf and slope habitats. Physical oceanographic variables (depth, salinity, temperature, oxygen), biological variables (benthic chlorophyll and integrated water-column chlorophyll) and sediment composition (grain size) were assessed as potential explanatory variables for fish community structure using a non-parametric statistical approach. Selected stations were re-sampled in 2013 and 2014 for a preliminary assessment of inter-annual variability in the fish community. Four distinct fish assemblages were delineated on the Canadian Beaufort Shelf and slope: 1) Nearshore-shelf: <50 m depth, 2) Offshore-shelf: >50 and ≤200 m depths, 3) Upper-slope: ≥200 and ≤500 m depths, and 4) Lower-slope: ≥500 m depths. Depth was the environmental variable that best explained fish community structure, and each species assemblage was spatially associated with distinct aspects of the vertical water mass profile. Significant differences in the fish community from east to west were not detected, and the species composition of the assemblages on the Canadian Beaufort Shelf have not changed substantially over the past decade. This community analysis provides a framework for testing hypotheses regarding the trophic dynamics and ecosystem roles of Beaufort Sea marine fishes, including biological linkages (i.e., fish movements and trophic interactions) among offshore habitats. Understanding regional-scale habitat associations will also provide context to identify potentially unique and/or sensitive habitats and fish community characteristics, thus aiding identification of ecologically and biologically significant areas, and to inform conservation efforts.

Sedimentology and geochemistry of surface sediments, outer continental shelf, southern Bering Sea

USGS Publications Warehouse

Gardner, J.V.; Dean, W.E.; Vallier, T.L.

1980-01-01

Present-day sediment dynamics, combined with lowerings of sea level during the Pleistocene, have created a mixture of sediments on the outer continental shelf of the southern Bering Sea that was derived from the Alaskan Mainland, the Aleutian Islands, and the Pribilof ridge. Concentrations of finer-grained, higher-organic sediments in the region of the St. George basin have further modified regional distribution patterns of sediment composition. Q-mode factor analysis of 58 variables related to sediment size and composition - including content of major, minor, and trace elements, heavy and light minerals, and clay minerals - reveals three dominant associations of sediment: 1. (1) The most significant contribution, forming a coarse-grained sediment scattered over most of the shelf consists of felsic sediment derived from the generally quartz-rich rocks of the Alaskan mainland. This sediment contains relatively high concentrations of Si, Ba, Rb, quartz, garnet, epidote, metamorphic rock fragments, potassium feldspar, and illite. 2. (2) The next most important group, superimposed on the felsic group consists of andesitic sediment derived from the Aleutian Islands. This more mafic sediment contains relatively high concentrations of Na, Ca, Ti, Sr, V, Mn, Cu, Fe, Al, Co, Zn, Y, Yb, Ga, volcanic rock fragments, glass, clinopyroxene, smectite, and vermiculite. 3. (3) A local group of basaltic sediment, derived from rocks of the Pribilof Islands, is a subgroup of the Aleutian andesite group. Accumulation of fine-grained sediment in St. George basin has created a sediment group containing relatively high concentrations of C, S, U, Li, B, Zr, Ga, Hg, silt, and clay. Sediment of the Aleutian andesite group exhibits a strong gradient, or "plume", with concentrations decreasing away from Unimak Pass and toward St. George basin. The absence of present-day currents sufficient to move even clay-size material as well as the presence of Bering submarine canyon between the Aleutian Islands and the outer continental shelf and slope, indicates that Holocene sediment dynamics cannot be used to explain the observed distribution of surface sediment derived from the Aleutian Islands. We suggest that this pattern is relict and resulted from sediment dynamics during lower sea levels of the Pleistocene. ?? 1980.

Multivariate analysis of the influences of oceanic and meteorological processes on suspended particulate matter distributions in Mississippi coastal waters

NASA Astrophysics Data System (ADS)

O'Brien, S. J.; Fitzpatrick, P. J.; Dzwonkowski, B.; Dykstra, S. L.; Wallace, D. J.; Church, I.; Wiggert, J. D.

2016-02-01

The Mississippi Sound is influenced by a high volume of sediment discharge from the Biloxi River, Mobile Bay via Pas aux Herons, Pascagoula River, Pearl River, Wolf River, and Lake Pontchartrain through the Rigolets. The river discharge, variable wind speed, wind direction and tides have a significant impact on the turbidity and transport of sediments in the Sound. Level 1 Moderate Resolution Imaging Spectroradiometer (MODIS) data is processed to extract the remote sensing reflectance at the wavelength of 645 nm and binned into an 8-day composite at a resolution of 500 m. The study uses a regional ocean color algorithm to compute suspended particulate matter (SPM) concentration based on these 8-day composite images. Multivariate analysis is applied between the SPM and time series of tides, wind, turbidity and river discharge measured at federal and academic institutions' stations and moorings. The multivariate analysis also includes in situ measurements of suspended sediment concentration and advective exchanges through the Mississippi Sound's tidal inlets between the coastal shelf and the nearshore estuarine waters. Mechanisms underlying the observed spatiotemporal distribution of SPM, including material exchange between the Sound and adjacent shelf waters, will be explored. The results of this study will contribute to current understanding of exchange mechanisms and pathways with the Mississippi Bight via the Mississippi Sound's tidal inlets.

Phytoplankton community structure in relation to hydrographic features along a coast-to-offshore transect on the SW Atlantic Continental Shelf

NASA Astrophysics Data System (ADS)

Islabão, C. A.; Mendes, C. R. B.; Detoni, A. M. S.; Odebrecht, C.

2017-12-01

The continental shelf in Southern Brazil is characterized by high biological productivity associated with horizontal and vertical density gradients due to the mixing of distinct water masses. Phytoplankton biomass and composition were evaluated in summer 2013 along an on-offshore transect off the mouth of the Patos Lagoon (Lat. 32°12S). Photosynthetic active radiation, temperature, salinity and fluorescence vertical profiles were carried out and Brünt-Väisäla frequency was estimated. Three water bodies were identified: the Subtropical Shelf Water along the entire transect, the Plata Plume Water on the middle shelf surface and the Tropical Water farther offshore. The water was sampled (N = 40) for the analyses of dissolved inorganic nutrients, phytoplankton cell density and composition. Phytoplankton present in the water was identified and quantified by the classical microscope sedimentation technique, complemented with CHEMTAX analysis of high-performance liquid chromatography (HPLC) pigment data. From the results obtained, chlorophyll a concentration was higher at both coastal stations (1.6-2.0 mg m-3) where the water column was homogeneous and diatoms dominated the stations. This group was replaced by dinoflagellates in stratified conditions on the shelf and farther offshore. Along the onshore-offshore gradient, two types of dinoflagellates were found: the peridinin-containing dinoflagellates Prorocentrum and Scrippsiella with a small contribution at the coastal stations, and the fucoxantin-containing small Gymnodiniales cells (< 15 μm) with more than 50% of the total chlorophyll a at the stations on the continental shelf, especially associated with the chlorophyll maximum at the base of the euphotic zone. The positive (negative) relationship between the biomass of dinoflagellates (diatoms) with the Brünt-Väisäla frequency, respectively, support the hypothesis that stratification is the most important environmental factor that determines the biomass of phytoplankton communities and distribution on the shelf and in coastal waters off Southern Brazil in summer. Picoplankton cells (Prochlorococcus and Synechococcus), recorded for the first time in the region under study, were predominant in the nutrient-poor and well-lit surface layers along the transect, indicating the importance of their low sedimentation rates (small size) and photo-adaptive strategies to survive on the upper layers of the water column.

Detecting Habitats and Ecosystem Functions Considering the Mesozooplankton Size and Diversity Structures and Environmental Conditions in the Gulf of Lion, NW Mediterranean Sea

NASA Astrophysics Data System (ADS)

Carlotti, F.; Espinasse, B.; Zhou, M.; Jean-Luc, D.

2016-02-01

Environmental conditions and zooplankton size structure and taxonomic diversity were investigated in the Gulf of Lion in May 2010 and January 2011. The integrated physical and biological measurements provided a 3D view with high spatial resolution of the physical and biological variables and their correlations over the whole gulf. The effects of physical processes such as freshwater input, coastal upwelling, and water column mixing by winds on phytoplankton and zooplankton distributions were analyzed using these data. Several analytic tests were performed in order to define several ecoregions representing different habitats of plankton communities. Three habitats were distinguished based on statistical analysis performed on biological and physical variables: (1) the coastal area characterized by shallow waters, high chl a concentrations, and a steep slope of the normalized biomass size spectrum (NBSS); (2) the area affected by the Rhône with high stratification and flat NBSS slope; and (3) the continental shelf with a deep mixed layer, relatively low particle concentrations, and moderate NBSS slope. The zooplankton diversity was characterized by spatial differences in community composition among the Rhône plume area, the coastal shelf, and shelf break waters. Defining habitat is a relevant approach to designing new zooplankton sampling strategies, validating distribution models and including the zooplankton compartment in trophodynamic studies.

Late summer zoogeography of the northern Bering and Chukchi seas

NASA Astrophysics Data System (ADS)

Sigler, Michael F.; Mueter, Franz J.; Bluhm, Bodil A.; Busby, Morgan S.; Cokelet, Edward D.; Danielson, Seth L.; Robertis, Alex De; Eisner, Lisa B.; Farley, Edward V.; Iken, Katrin; Kuletz, Kathy J.; Lauth, Robert R.; Logerwell, Elizabeth A.; Pinchuk, Alexei I.

2017-01-01

Ocean currents, water masses, and seasonal sea ice formation contribute to determining relationships among the biota of the Bering and Chukchi seas. The Bering Sea communicates with the Chukchi Sea via northward advection of water, nutrients, organic matter, and plankton through Bering Strait. We used data from concurrent surveys of zooplankton, pelagic fishes and jellyfish, epibenthic fishes and invertebrates, and seabirds to identify faunal distribution patterns and environmental factors that are related to these faunal distributions within the US portions of the Chukchi Sea shelf and Bering Sea shelf north of Nunivak Island. Regional differences in late summer (August-September) distributions of biota largely reflected the underlying hydrography. Depth, temperature, salinity, stratification, and chlorophyll a, but less so sediment-related or nutrient-related factors, were related to the distributions of the assemblages (zooplankton: depth, salinity, stratification; pelagic fishes and jellyfish: depth, stratification, chlorophyll a; epibenthic fishes and invertebrates: depth, temperature, salinity; seabirds: temperature, salinity, stratification). These six environmental factors that most influenced distributions of zooplankton, pelagic fishes/jellyfish, epibenthic fishes and invertebrate, and seabird assemblages likely can be simplified to three factors reflecting bottom depth, water mass, and their stratification and productivity (which are tightly linked in the study region). The assemblages were principally structured from nearshore to offshore and from south to north. The nearshore to offshore contrast usually was stronger in the south, where the enormous discharge of the Yukon River is more apparent and extends farther offshore, influencing zooplankton, pelagic fish/jellyfish, and seabird assemblages. Some assemblages overlapped spatially (e.g., seabird and zooplankton), indicating shared influential environmental factors or trophic linkages among assemblages. The gradients in assemblage composition were gradual for epibenthic taxa, abrupt for zooplankton taxa, and intermediate for pelagic fish/jellyfish and seabird taxa, implying that zooplankton assemblage structure is most strongly tied to water mass, epibenthic least, with the other two taxa intermediates. Three communities (i.e., cross-assemblage groupings) emerged based on maps of ordination axes and core use areas by taxa; one associated with Alaska Coastal Water (warmer, fresher, nutrient depauperate), second associated with Chirikov Basin and the southern Chukchi Sea (colder, saltier, nutrient rich), and third associated with the northern Chukchi shelf (colder and saltier but not as nutrient rich). Gradients in species composition occurred both within and between these communities. The Chirikov Basin/southern Chukchi Sea community was characterized by distinct zooplankton and seabird taxa, but was not strongly associated with distinct pelagic or epibenthic fish and invertebrate taxa. Although comprehensive data were only available for a single year and annual variation may affect the generality of our results, our comprehensive ecosystem survey approach yielded new insights into the ecological relationships (specifically, gradients in assemblage composition and identification of communities) of this Arctic region.

Distribution of organochlorine compounds in superficial sediments from the Gulf of Lion, northwestern Mediterranean Sea

NASA Astrophysics Data System (ADS)

Salvadó, Joan A.; Grimalt, Joan O.; López, Jordi F.; Durrieu de Madron, Xavier; Pasqual, Catalina; Canals, Miquel

2013-11-01

Superficial sediments from Cap de Creus to the Rhone Delta, in the Gulf of Lion, Northwestern Mediterranean Sea, including the mid-shelf mud belt and the continental slope were collected between 2005 and 2008 to assess the levels, main sources and distribution patterns of organochlorine pollutants. Discharges from the Rhone River are the main source for all these compounds around the area. The spatial distribution of organochlorine pollutants was also related to their physicochemical properties and to sediment grain size and composition. The concentrations of polychlorobiphenyls (PCBs), dichlorodiphenyltrichloroethane (DDT) and its metabolites (DDD and DDE), and the chlorobenzenes (CBzs) - pentachlorobenzene (PeCB) and hexachlorobenzene (HCB) - decreased westwards along the mid-shelf mud belt. In contrast, hexachlorocyclohexane isomers (HCHs), namely lindane (γ-HCH), followed another concentration pattern suggesting a different transport mode. The major concentrations of organochlorine compounds were observed off the Rhone River mouth, in the prodelta, where PCB, DDT and CBz concentrations reached 38, 29 and 8.3 ng g-1, respectively. These average concentrations in the mid continental shelf were two to ten times lower than those found in a study performed about 20 years ago, albeit in almost all the sites the values of PCBs and DDTs still exceed the NOAA’s Sediment Quality Guidelines. In contrast, the concentrations in the continental slope were nearly the same as 20 years ago, which may evidence that even most of these compounds were banned decades ago, their background concentrations associated to diffuse pollution have not decreased in the deep continental margin.

Volcanic ash in surficial sediments of the Kodiak shelf - An indicator of sediment dispersal patterns

USGS Publications Warehouse

Hampton, M.A.; Bouma, A.H.; Frost, T.P.; Colburn, I.P.

1979-01-01

Surficial sediments of the Kodiak shelf, Gulf of Alaska, contain various amounts of volcanic ash whose physical properties indicate that it originated from the 1912 Katmai eruption. The distribution of ash is related to the shelf physiography and represents redistribution by oceanic circulation rather than the original depositional pattern from the volcanic event. The ash distribution can be used, in conjunction with the distribution of grain sizes, as an indicator of present-day sediment dispersal patterns on the shelf. No significant modern input of sediment is occurring on the Kodiak shelf, which is mostly covered by Pleistocene glacial deposits. Coarse-grained sediments on flat portions of shallow banks apparently are being winnowed, with the removed ash-rich fine material being deposited in shallow depressions on the banks and in three of the four major troughs that cut transversely across the shelf. The other major trough seems to be experiencing a relatively high-energy current regime, with little deposition of fine material. ?? 1979.

Spatial changes in fatty acids signatures of the great scallop Pecten maximus across the Bay of Biscay continental shelf

NASA Astrophysics Data System (ADS)

Nerot, Caroline; Meziane, Tarik; Schaal, Gauthier; Grall, Jacques; Lorrain, Anne; Paulet, Yves-Marie; Kraffe, Edouard

2015-10-01

The spatial variability of food resources along continental margins can strongly influence the physiology and ecology of benthic bivalves. We explored the variability of food sources of the great scallop Pecten maximus, by determining their fatty acid (FA) composition along an inshore-offshore gradient in the Bay of Biscay (from 15 to 190 m depth). The FA composition of the digestive gland showed strong differences between shallow and deep-water habitats. This trend was mainly driven by their content in diatom-characteristic fatty acids, which are abundant near the coast. Scallops collected from the middle of the continental shelf were characterized by higher contents of flagellate markers than scallops from shallow habitats. This could be related to a permanent vertical stratification in the water column, which reduced vertical mixing of waters, thereby enhancing organic matter recycling through the microbial loop. In the deeper water station (190 m), FA compositions were close to the compositions found in scallops from shallow areas, which suggest that scallops could have access to the same resources (i.e. diatoms). Muscle FA composition was more indicative of the physiological state of scallops over this depth range, revealing contrasting reproductive strategies among the two coastal sites and metabolic or physiological adaptation at greater depth (e.g. structural and functional adjustments of membrane composition). This study therefore revealed contrasted patterns between shallow and deeper habitats for both P. maximus muscle and digestive gland tissues. This emphasizes the variability in the diet of this species along its distribution range, and stresses the importance of analyzing different tissues for their FA composition in order to better understand their physiology and ecology.

Transport and transformation of riverine neodymium isotope and rare earth element signatures in high latitude estuaries: A case study from the Laptev Sea

NASA Astrophysics Data System (ADS)

Laukert, Georgi; Frank, Martin; Bauch, Dorothea; Hathorne, Ed C.; Gutjahr, Marcus; Janout, Markus; Hölemann, Jens

2017-11-01

Marine neodymium (Nd) isotope and rare earth element (REE) compositions are valuable tracers for present and past ocean circulation and continental inputs. Yet their supply via high latitude estuaries is largely unknown. Here we present a comprehensive dissolved Nd isotope (expressed as εNd values) and REE data set together with seawater stable oxygen isotope (δ18O) compositions of samples from the Laptev Sea recovered in two Arctic summers and one winter. The Laptev Sea is a shallow Siberian Shelf sea characterized by extensive river-runoff, sea-ice production and ice transport into the Arctic Ocean. The large variability in εNd (-6 to -17), REE concentrations (16 to 600 pmol/kg for Nd) and REE patterns is controlled by freshwater supply from distinct riverine sources and open ocean Arctic Atlantic Water. Strikingly and contrary to expectations, except for cerium no evidence for significant release of REEs from particulate phases is found, which is attributed to low amounts of suspended particulate matter and high dissolved organic carbon concentrations present in the contributing rivers. Essentially all shelf waters are depleted in light (L)REEs, while the distribution of the heavy REEs shows a deficiency at the surface and a pronounced excess in the bottom layer. This distribution is consistent with REE removal through coagulation of riverine nanoparticles and colloids starting at salinities near 10 and resulting in a drop of all REE concentrations by ∼30%. With increasing salinity preferential LREE removal is observable reaching ∼75% for Nd at a salinity of 34. Although the delayed onset of dissolved REE removal contrasts with most previous observations from other estuarine environments, it agrees remarkably well with results from recent experiments simulating estuarine mixing of seawater with organic-rich river waters. In addition, melting and formation of sea ice leads to further REE depletion at the surface and strong REE enrichment near the shelf bottom as a function of ice melting and brine transfer, respectively. The ice-related processes significantly affect the distribution of dissolved REEs in high-latitude estuaries and likely also similarly contribute to the redistribution of other dissolved seawater constituents.

No barrier to emergence of bathyal king crabs on the Antarctic shelf.

PubMed

Aronson, Richard B; Smith, Kathryn E; Vos, Stephanie C; McClintock, James B; Amsler, Margaret O; Moksnes, Per-Olav; Ellis, Daniel S; Kaeli, Jeffrey; Singh, Hanumant; Bailey, John W; Schiferl, Jessica C; van Woesik, Robert; Martin, Michael A; Steffel, Brittan V; Deal, Michelle E; Lazarus, Steven M; Havenhand, Jonathan N; Swalethorp, Rasmus; Kjellerup, Sanne; Thatje, Sven

2015-10-20

Cold-water conditions have excluded durophagous (skeleton-breaking) predators from the Antarctic seafloor for millions of years. Rapidly warming seas off the western Antarctic Peninsula could now facilitate their return to the continental shelf, with profound consequences for the endemic fauna. Among the likely first arrivals are king crabs (Lithodidae), which were discovered recently on the adjacent continental slope. During the austral summer of 2010 ‒ 2011, we used underwater imagery to survey a slope-dwelling population of the lithodid Paralomis birsteini off Marguerite Bay, western Antarctic Peninsula for environmental or trophic impediments to shoreward expansion. The population density averaged ∼ 4.5 individuals × 1,000 m(-2) within a depth range of 1,100 ‒ 1,500 m (overall observed depth range 841-2,266 m). Images of juveniles, discarded molts, and precopulatory behavior, as well as gravid females in a trapping study, suggested a reproductively viable population on the slope. At the time of the survey, there was no thermal barrier to prevent the lithodids from expanding upward and emerging on the outer shelf (400- to 550-m depth); however, near-surface temperatures remained too cold for them to survive in inner-shelf and coastal environments (<200 m). Ambient salinity, composition of the substrate, and the depth distribution of potential predators likewise indicated no barriers to expansion of lithodids onto the outer shelf. Primary food resources for lithodids--echinoderms and mollusks--were abundant on the upper slope (550-800 m) and outer shelf. As sea temperatures continue to rise, lithodids will likely play an increasingly important role in the trophic structure of subtidal communities closer to shore.

No barrier to emergence of bathyal king crabs on the Antarctic shelf

PubMed Central

Aronson, Richard B.; Smith, Kathryn E.; Vos, Stephanie C.; McClintock, James B.; Amsler, Margaret O.; Moksnes, Per-Olav; Ellis, Daniel S.; Kaeli, Jeffrey; Singh, Hanumant; Bailey, John W.; Schiferl, Jessica C.; van Woesik, Robert; Martin, Michael A.; Steffel, Brittan V.; Deal, Michelle E.; Lazarus, Steven M.; Havenhand, Jonathan N.; Swalethorp, Rasmus; Kjellerup, Sanne; Thatje, Sven

2015-01-01

Cold-water conditions have excluded durophagous (skeleton-breaking) predators from the Antarctic seafloor for millions of years. Rapidly warming seas off the western Antarctic Peninsula could now facilitate their return to the continental shelf, with profound consequences for the endemic fauna. Among the likely first arrivals are king crabs (Lithodidae), which were discovered recently on the adjacent continental slope. During the austral summer of 2010‒2011, we used underwater imagery to survey a slope-dwelling population of the lithodid Paralomis birsteini off Marguerite Bay, western Antarctic Peninsula for environmental or trophic impediments to shoreward expansion. The population density averaged ∼4.5 individuals × 1,000 m−2 within a depth range of 1,100‒1,500 m (overall observed depth range 841–2,266 m). Images of juveniles, discarded molts, and precopulatory behavior, as well as gravid females in a trapping study, suggested a reproductively viable population on the slope. At the time of the survey, there was no thermal barrier to prevent the lithodids from expanding upward and emerging on the outer shelf (400- to 550-m depth); however, near-surface temperatures remained too cold for them to survive in inner-shelf and coastal environments (<200 m). Ambient salinity, composition of the substrate, and the depth distribution of potential predators likewise indicated no barriers to expansion of lithodids onto the outer shelf. Primary food resources for lithodids—echinoderms and mollusks—were abundant on the upper slope (550–800 m) and outer shelf. As sea temperatures continue to rise, lithodids will likely play an increasingly important role in the trophic structure of subtidal communities closer to shore. PMID:26417090

Habitat quality of the coastal southeastern Bering Sea for juvenile flatfishes from the relationships between diet, body condition and prey availability

NASA Astrophysics Data System (ADS)

Yeung, Cynthia; Yang, Mei-Sun

2017-01-01

The distribution and body condition of juvenile northern rock sole (NRS), Lepidopsetta polyxystra, and yellowfin sole (YFS), Limanda aspera, were studied in relation to prey availability across the coastal shelf at the Alaska Peninsula boundary of the eastern Bering Sea (EBS) to assess spatial variability in habitat quality. Juveniles of ≤ 20 cm and adults of ≥ 30 cm total length were collected from bottom trawl catch samples at stations located 10 to 120 km from the Alaska Peninsula coast, and in bottom depths of 28 to 85 m. Stomach contents and stable isotopes of carbon and nitrogen from muscle tissue were analyzed to describe diet composition. The quantity and quality of prey did not significantly affect the distribution of juvenile NRS and YFS. Spatial mismatch between the diet composition and the infauna prey assemblage suggested that prey availability was not limiting across the area, allowing fish to select for prey, presumably to maximize net energy gain. The body condition of juvenile NRS was higher in the eastern section of the area (Bristol Bay) - where they shared spatial and dietary niches with juvenile YFS, than in the west section (Unimak Island) where juvenile YFS were largely absent. A difference in body condition suggests that habitat quality may be higher in Bristol Bay. For NRS, stomach contents and stable isotopes in muscle tissue indicated an ontogenetic diet shift from amphipods to polychaetes from juvenile to adult stages. In contrast, for YFS, amphipods seemed to remain the primary prey and polychaetes the least important prey from juvenile to adult stage. Given that the high prey availability found in this south coastal area of EBS extends to areas across the EBS shelf, favorable habitat for juvenile flatfishes should be extensive. However, much of this potential juvenile habitat is underutilized by NRS, which were mainly limited to Bristol Bay and the Alaska Peninsula, whereas YFS did extend north over 500 km from Bristol Bay along the inner shelf domain (≤ 50 m deep). Abiotic factors, particularly ocean currents and water temperature, may be more significant than prey availability in the spatial distribution of juveniles. Thus, changes in the hydrographic and thermal regime of the EBS are likely to impact juvenile flatfish distribution and habitat productivity.

Spoilage and shelf-life extension of fresh fish and shellfish.

PubMed

Ashie, I N; Smith, J P; Simpson, B K

1996-01-01

Fresh fish and shellfish are highly perishable products due to their biological composition. Under normal refrigerated storage conditions, the shelf life of these products is limited by enzymatic and microbiological spoilage. However, with increasing consumer demands for fresh products with extended shelf life and increasing energy costs associated with freezing and frozen storage, the fish-processing industry is actively seeking alternative methods of shelf life preservation and marketability of fresh, refrigerated fish and at the same time economizing on energy costs. Additional methods that could fulfill these objectives include chemical decontamination, low-dose irradiation, ultra-high pressure, and modified atmosphere packaging (MAP). This review focuses on the biochemical and microbiological composition of fresh fish/shellfish, the spoilage patterns in these products, factors influencing spoilage, and the combination treatments that can be used in conjunction with refrigeration to extend the shelf life and keeping quality of fresh fish/shellfish. The safety concerns of minimally processed/MAP fish, specifically with respect to the growth of Clostridium botulinum type E, is also addressed.

Comparative geochemistry of Indian margin (Arabian Sea) sediments: Estuary to continental slope.

NASA Astrophysics Data System (ADS)

Cowie, Greg; Mowbray, Stephen; Kurian, Siby; Sarkar, Amit; White, Carol; Anderson, Amy; Vergnaud, Bianca; Johnstone, Gisele; Brear, Samuel; Woulds, Clare; Naqvi, Wajih; Kitazato, Hiroshi

2014-05-01

Factors controlling the distribution of organic matter in the Arabian Sea have been the subject of much research and debate ever since organic-rich slope deposits were associated with the mid-water oxygen minimum zone (OMZ) However, the debate remains open, and numerous interacting factors have been invoked as important controls. A limitation of most previous studies is that they have been restricted to limited portions of the margin, and have not included molecular-level tracers that allow distinction of organic matter (OM) source and degradation state as factors in OM distribution. We report results from sites across the Indian margin of the Arabian Sea, which were analysed for carbon and nitrogen compositions (elemental and isotopic), grain size and indices of OM source and degradation state. Site locations ranged from the Mandovi/Zuari estuaries to depths of ~2000m on the continental slope, thus spanning both the semi-permanent OMZ on the upper slope (~200-1300m) and the seasonal hypoxic zone that impinges on the shelf. Source indices showed mixed marine and terrigenous OM within the estuaries, but overwhelming predominance (80%+) of marine OM on the shelf and slope, even in nearshore deposits. Thus, riverine OM is heavily diluted or efficiently remineralised within or immediately offshore of the estuaries. Any terrigenous OM that is exported appears to be retained in nearshore muds; lignin phenols indicate that the small terrigenous OM content of slope sediments is of different origin, potentially from rivers to the north. Organic C contents of surface shelf and slope sediments varied from <0.5 wt% in relict shelf sands to a maximum of >7 wt% at upper slope sites within the OMZ, then decreasing to ≤1wt% at 2000m. However, major variability (~5 wt%) occured within the OMZ at sites with near-identical depths and bottom-water oxygen. A strong relationship between organic C and grain size was seen for OMZ sediments, but lower C loadings were found for sites on the shelf and below the OMZ. Diagenetic indices confirmed that lower C content below the OMZ is associated with greater extent of OM degradation, but that C-poor shelf sediments are not consistently more degraded than those within the OMZ. Together, results indicate that OM enrichment on the upper slope, where it occurs, can be explained by winnowing or other physical processes on the shelf combined with progressive OM degradation with increasing oxygen exposure below the OMZ. Reduced oxygen exposure may contribute to observed OM enrichment with the OMZ, but hydrodynamic processes are the overriding control on sediment OM distribution, even within the OMZ.

Taxonomic and functional patterns of macrobenthic communities on a high-Arctic shelf: A case study from the Laptev Sea

NASA Astrophysics Data System (ADS)

Kokarev, V. N.; Vedenin, A. A.; Basin, A. B.; Azovsky, A. I.

2017-11-01

The studies of functional structure of high-Arctic Ecosystems are scarce. We used data on benthic macrofauna from 500-km latitudinal transect in the eastern Laptev Sea, from the Lena delta to the continental shelf break, to describe spatial patterns in species composition, taxonomic and functional structure in relation to environmental factors. Both taxonomy-based approach and Biological Trait analysis yielded similar results and showed general depth-related gradient in benthic diversity and composition. This congruence between taxonomical and functional dimensions of community organization suggests that the same environmental factors (primarily riverine input and regime of sedimentation) have similar effect on both community structure and functioning. BTA also revealed a distinct functional structure of stations situated at the Eastern Lena valley, with dominance of motile, burrowing sub-surface deposit-feeders and absence of sedentary tube-dwelling forms. The overall spatial distribution of benthic assemblages corresponds well to that described there in preceding decades, evidencing the long-term stability of bottom ecosystem. Strong linear relationship between species and traits diversity, however, indicates low functional redundancy, which potentially makes the ecosystem susceptible to a species loss or structural shifts.

Geologic?l History of E?st Siberi?n Se? Shelf

ERIC Educational Resources Information Center

Safronov, Aleksandr F.

2016-01-01

In our study we discuss the traditional and novel concepts of East Siberian Shelf origin with regards to the structure and composition of the Paleozoic and early Mesozoic sediments, coming to the surface on the Siberian Islands ?rchipel?go. The core idea is to summarize the existing concepts of East Siberian Shelf formation and to draw up the…

Wave climate model of the Mid-Atlantic shelf and shoreline (Virginian Sea): Model development, shelf geomorphology, and preliminary results

NASA Technical Reports Server (NTRS)

Goldsmith, V.; Morris, W. D.; Byrne, R. J.; Whitlock, C. H.

1974-01-01

A computerized wave climate model is developed that applies linear wave theory and shelf depth information to predict wave behavior as they pass over the continental shelf as well as the resulting wave energy distributions along the coastline. Reviewed are also the geomorphology of the Mid-Atlantic Continental Shelf, wave computations resulting from 122 wave input conditions, and a preliminary analysis of these data.

"Live" (stained) benthic foraminiferal living depths, stable isotopes, and taxonomy offshore South Georgia, Southern Ocean: implications for calcification depths

NASA Astrophysics Data System (ADS)

Dejardin, Rowan; Kender, Sev; Allen, Claire S.; Leng, Melanie J.; Swann, George E. A.; Peck, Victoria L.

2018-01-01

It is widely held that benthic foraminifera exhibit species-specific calcification depth preferences, with their tests recording sediment pore water chemistry at that depth (i.e. stable isotope and trace metal compositions). This assumed depth-habitat-specific pore water chemistry relationship has been used to reconstruct various palaeoenvironmental parameters, such as bottom water oxygenation. However, many deep-water foraminiferal studies show wide intra-species variation in sediment living depth but relatively narrow intra-species variation in stable isotope composition. To investigate this depth-habitat-stable-isotope relationship on the shelf, we analysed depth distribution and stable isotopes of living (Rose Bengal stained) benthic foraminifera from two box cores collected on the South Georgia shelf (ranging from 250 to 300 m water depth). We provide a comprehensive taxonomic analysis of the benthic fauna, comprising 79 taxonomic groupings. The fauna shows close affinities with shelf assemblages from around Antarctica. We find live specimens of a number of calcareous species from a range of depths in the sediment column. Stable isotope ratios (δ13C and δ18O) were measured on stained specimens of three species, Astrononion echolsi, Cassidulinoides porrectus, and Buccella sp. 1, at 1 cm depth intervals within the downcore sediment sequences. In agreement with studies in deep-water settings, we find no significant intra-species variability in either δ13Cforam or δ18Oforam with sediment living depth on the South Georgia shelf. Our findings add to the growing evidence that infaunal benthic foraminiferal species calcify at a fixed depth. Given the wide range of depths at which we find living, infaunal species, we speculate that they may actually calcify predominantly at the sediment-seawater interface, where carbonate ion concentration and organic carbon availability is at a maximum.

An Analysis of Artificial Reef Fish Community Structure along the Northwestern Gulf of Mexico Shelf: Potential Impacts of “Rigs-to-Reefs” Programs

PubMed Central

Ajemian, Matthew J.; Wetz, Jennifer J.; Shipley-Lozano, Brooke; Shively, J. Dale; Stunz, Gregory W.

2015-01-01

Artificial structures are the dominant complex marine habitat type along the northwestern Gulf of Mexico (GOM) shelf. These habitats can consist of a variety of materials, but in this region are primarily comprised of active and reefed oil and gas platforms. Despite being established for several decades, the fish communities inhabiting these structures remain poorly investigated. Between 2012 and 2013 we assessed fish communities at 15 sites using remotely operated vehicles (ROVs). Fish assemblages were quantified from standing platforms and an array of artificial reef types (Liberty Ships and partially removed or toppled platforms) distributed over the Texas continental shelf. The depth gradient covered by the surveys (30–84 m) and variability in structure density and relief also permitted analyses of the effects of these characteristics on fish richness, diversity, and assemblage composition. ROVs captured a variety of species inhabiting these reefs from large transient piscivores to small herbivorous reef fishes. While structure type and relief were shown to influence species richness and community structure, major trends in species composition were largely explained by the bottom depth where these structures occurred. We observed a shift in fish communities and relatively high diversity at approximately 60 m bottom depth, confirming trends observed in previous studies of standing platforms. This depth was also correlated with some of the largest Red Snapper captured on supplementary vertical longline surveys. Our work indicates that managers of artificial reefing programs (e.g., Rigs-to-Reefs) in the GOM should carefully consider the ambient environmental conditions when designing reef sites. For the Texas continental shelf, reefing materials at a 50–60 m bottom depth can serve a dual purpose of enhancing diving experiences and providing the best potential habitat for relatively large Red Snapper. PMID:25954943

Sediment and organic carbon transport in Cap de Creus canyon, Gulf of Lions (France)

NASA Astrophysics Data System (ADS)

Tesi, T.; Puig, P.; Palanques, A.; Goni, M. A.; Miserocchi, S.; Langone, L.

2009-04-01

The off-shelf transport of particles in continental margins is responsible for much of the flux of organic matter (OM)and nutrients towards deep-sea ecosystems, playing a key role in the global oceanic biogeochemical cycles. Off-shelf sediment transport mechanism have been well described for many continental margins being triggered by a series of physical forcings such as tides, storms, internal waves, floods, earthquakes, as well as the combination of some of these processes, while topographic structures such as submarine canyons act as preferential sedimentary conduits toward deep ocean. However, the composition of the material supplied to the deep ocean during these events is still poorly understood since most studies have only investigated the magnitude of the down-slope fluxes or limited their analysis to the major bulk components. A special opportunity to characterize the biogeochemical composition of the off-shelf export in the Gulf of Lions (GoL) margin was provided during the winter 2004-2005, when an exceptional dense water cascading event occurred. Dense water overflowing off the shelf in the GoL has been recently recognized as one of the main process affecting particulate shelf-to-slope exchange in northwestern Mediterranean Sea. During the 2004-2005 cascading event, moored instruments were deployed at the Cap de Creus (CdC) canyon head to monitor the physical parameters and to characterize the temporal variability of the exported material. Post-cascading sediment cores were collected along the sediment dispersal system to trace the sediment transport pathway. In this study we developed a source tracing method using elemental compositions, alkaline CuO reaction products (lignin, cutin, lipids, hydroxy benzenes, proteins, lipids, and polysaccharides products), biogenic silica, carbon stable isotope composition, radiocarbon measurements, and grain size as a fingerprint for each sample. The aforementioned analyses were carried out on both sediment trap and sediment samples to obtain a homogeneous data matrix. The dynamic mixture of OM sources and shelf sediments was then analyzed using multivariate statistics. A quantitative mixing model was used to assess the relative contribution of allochthonous and autochthonous OM and to identify the relationship between sediment export from the shelf and down-slope particulate fluxes (sediment provenance).

Quantitative mineralogy of surface sediments of the Iceland shelf, and application to down-core studies of holocene ice-rafted sediments

USGS Publications Warehouse

Andrews, John T.; Eberl, D.D.

2007-01-01

Quantitative X-ray diffraction analyses on the < 2 mm sediment fraction from the Iceland shelves are reported for subglacial diamictons, seafloor surface sediments, and the last 2000 cal yr BP from two cores. The overall goal of the paper is to characterize the spatial variability of the mineralogy of the present-day surface sediments (18 non-clay minerals and 7 clay minerals), compare that with largely in situ erosional products typified by the composition of subglacial diamictons, and finally examine the late Holocene temporal variability in mineral composition using multi-mineral compositions. The subglacial diamictons are dominated in the non-clay-mineral fraction by the plagioclase feldspars and pyroxene with 36.7 ?? 6.1 and 17.9 ?? 3.5 wt % respectively, with smectites being the dominant clay minerals. The surface seafloor sediments have similar compositions although there are substantial amounts of calcite, plus there is a distinct band of sites from NW to N-central Iceland that contain 1-6 wt% of quartz. This latter distribution mimics the modern and historic pattern of drift ice in Iceland waters. Principal component analysis of the transformed wt% (log-ratio) non-clay minerals is used to compare the subglacial, surface, and down-core mineral compositions. Fifty-eight percent of the variance is explained by the first two axes, with dolomite, microcline, and quartz being important "foreign" species. These analyses indicate that today the NW-N-central Iceland shelf is affected by the import of exotic minerals, which are transported and released from drift ice. The down-core mineralogy indicates that this is a process that has varied over the last 2000 cal yr BP. Copyright ?? 2007, SEPM (Society for Sedimentary Geology).

Reconstruction of the Nd isotope composition of seawater on epicontinental seas: Testing the potential of Fe-Mn oxyhydroxide coatings on foraminifera tests for deep-time investigations

NASA Astrophysics Data System (ADS)

Charbonnier, Guillaume; Pucéat, Emmanuelle; Bayon, Germain; Desmares, Delphine; Dera, Guillaume; Durlet, Christophe; Deconinck, Jean-François; Amédro, Francis; Gourlan, Alexandra T.; Pellenard, Pierre; Bomou, Brahimsamba

2012-12-01

The Fe-Mn oxide fraction leached from deep-sea sediments has been increasingly used to reconstruct the Nd isotope composition of deep water masses, that can be used to track changes in oceanic circulation with a high temporal resolution. Application of this archive to reconstruct the Nd isotope composition of bottom seawater in shallow shelf environments remained however to be tested. Yet as the Nd isotope composition of seawater on continental margins is particularly sensitive to changes in erosional inputs, establishment of neritic seawater Nd isotope evolution around areas of deep water formation would be useful to discriminate the influence of changes in oceanic circulation and in isotopic composition of erosional inputs on the Nd isotope record of deep waters. The purpose of this study is to test the potential of Fe-Mn coatings leached from foraminifera tests to reconstruct the Nd isotope composition of seawater in shelf environments for deep-time intervals. Albian to Turonian samples from two different outcrops have been recovered, from the Paris Basin (Wissant section, northern France) and from the Western Interior Seaway (Hot Spring, South Dakota, USA), that were deposited in epicontinental seas. Rare Earth Element (REE) spectra enriched in middle REEs in the foraminifera leach at Wissant highlight the presence of Fe-Mn oxides. The similarity of the Nd isotopic signal of the Fe-Mn oxide fraction leached from foraminifera tests with that of fish teeth suggests that Fe-Mn oxides coating foraminifera can be good archives of shelf bottom seawater Nd isotopic composition. Inferred bottom shelf water Nd isotope compositions at Wissant range from -8.5 to -9.7 ɛ-units, about 1.5-2 ɛ-units higher than that of the contemporaneous local detrital fraction. At Hot Spring, linear REE spectra characterizing foraminifera leach may point to an absence of authigenic marine Fe-Mn oxide formation in this area during the Late Cenomanian-Early Turonian, consistent with dysoxic to anoxic conditions at Hot Spring, contemporaneous to an Oceanic Anoxic Event. The similarity of the Nd isotopic signal of the carbonate matrix of foraminifera with that of fish teeth suggests that it records the Nd isotope composition of bottom shelf seawater as well. Inferred bottom shelf water Nd isotope compositions at Hot Spring are quite radiogenic, between -7 and -6 ɛ-units, about 2.5-4 ɛ-units higher than that of the contemporaneous local detrital fraction. In contrast, in both sections Fe-Mn oxides leached directly from the decarbonated sediment tend to yield a less radiogenic Nd isotopic composition, typically between 0.2 and 0.8 ɛ-units lower, that is intermediate between that of fish teeth and of the detrital fraction. This suggests the contribution of pre-formed continental Fe-Mn oxides to the Nd isotopic signal, along with authigenic marine oxides, or a detrital contamination during leaching.

A Comparison Study: The New Extended Shelf Life Isopropyl Ester PMR Technology versus The Traditional Methyl Ester PMR Approach

NASA Technical Reports Server (NTRS)

Alston, William B.; Scheiman, Daniel A.; Sivko, Gloria S.

2005-01-01

Polymerization of Monomeric Reactants (PMR) monomer solutions and carbon cloth prepregs of PMR II-50 and VCAP-75 were prepared using both the traditional limited shelf life methanol based PMR approach and a novel extended shelf life isopropanol based PMR approach. The methyl ester and isopropyl ester based PMR monomer solutions and PMR prepregs were aged for up to four years at freezer and room temperatures. The aging products formed were monitored using high pressure liquid chromatography (HPLC). The composite processing flow characteristics and volatile contents of the aged prepregs were also correlated versus room temperature storage time. Composite processing cycles were developed and six ply cloth laminates were fabricated with prepregs after various extended room temperature storage times. The composites were then evaluated for glass transition temperature (Tg), thermal decomposition temperature (Td), initial flexural strength (FS) and modulus (FM), long term (1000 hours at 316 C) thermal oxidative stability (TOS), and retention of FS and FM after 1000 hours aging at 316 C. The results for each ester system were comparable. Freezer storage was found to prevent the formation of aging products for both ester systems. Room temperature storage of the novel isopropyl ester system increased PMR monomer solution and PMR prepreg shelf life by at least an order of magnitude while maintaining composite properties.

Transformations and Fates of Terrigenous Dissolved Organic Matter in River-influenced Ocean Margins

NASA Astrophysics Data System (ADS)

Fichot, Cedric G.

Rivers contribute about 0.25 Pg of terrigenous dissolved organic carbon (tDOC) to the ocean each year. The fate and transformations of this material have important ramifications for the metabolic state of the ocean, air-sea CO2 exchange, and the global carbon cycle. Stable isotopic compositions and terrestrial biomarkers suggest tDOC must be efficiently mineralized in ocean margins. Nonetheless, the extent of tDOC mineralization in these environments remains unknown, as no quantitative estimate is available. The complex interplay of biogeochemical and physical processes in these systems compounded by the limited practicality of chemical proxies (organic biomarkers, isotopic compositions) make the quantification of tDOC mineralization in these dynamic systems particularly challenging. In this dissertation, new optical proxies were developed (Chapters 1 and 2) and facilitated the first quantitative assessment of tDOC mineralization in a dynamic river-influenced ocean margin (Chapter 3) and the monitoring of continental runoff distributions in the coastal ocean using remote sensing (Chapter 4). The optical properties of chromophoric dissolved organic matter (CDOM) were used as optical proxies for dissolved organic carbon concentration ([DOC]) and %tDOC. In both proxies, the CDOM spectral slope coefficient ( S275-295) was exploited for its informative properties on the chemical nature and composition of dissolved organic matter. In the first proxy, a strong relationship between S275-295 and the ratio of CDOM absorption to [DOC] facilitated accurate retrieval (+/- 4%) of [DOC] from CDOM. In the second proxy, the existence of a strong relationship between S275-295 and the DOC-normalized lignin yield facilitated the estimation of the %tDOC from S 275-295. Using the proxies, the tDOC concentration can be retrieved solely from CDOM absorption coefficients (lambda = 275-295 nm) in river-influenced ocean margins. The practicality of optical proxies facilitated the calculation of tDOC mineralization rates on the Louisiana shelf. Seasonal tDOC mass balances for the shelf revealed that between 26% (winter) and 71% (summer) of the mixed layer tDOC is mineralized during its residence on the shelf. Independent approaches further indicated biomineralization accounts for 60% of the tDOC mineralization whereas photomineralization contributes only 8%. The remaining 32% was attributed to the coupled photo-biomineralization. On an annual basis, our results indicated ˜40% of the tDOC discharged by the Mississippi and Atchafalaya rivers to the Louisiana shelf (˜1 Tg tDOC) is mineralized within 2 to 3 months. This extensive mineralization on the shelf is direct evidence ocean margins act as efficient filters of tDOC between the land and ocean. Finally, the amenability of S275-295 to ocean color remote sensing was demonstrated, and facilitates the real-time, synoptic monitoring of tDOC and freshwater runoff in coastal waters. Implementation of this approach provided the first pan-Arctic distributions of tDOC and continental runoff in surface polar waters, and will help understand the manifestations of climate change in this remote region.

Nutrient distributions, transports, and budgets on the inner margin of a river-dominated continental shelf

EPA Science Inventory

Physical and biogeochemical processes determining the distribution and fate of nutrients delivered by the Mississippi and Atchafalaya rivers to the inner (<50 m depth) Louisiana continental shelf (LCS) were examined using a three-dimensional hydrodynamic model of the LCS and obse...

Ice shelf structure and stability: Larsen C Ice Shelf, Antarctica

NASA Astrophysics Data System (ADS)

Hubbard, B. P.; Ashmore, D.; Bevan, S. L.; Booth, A. D.; Holland, P.; Jansen, D.; Kuipers Munneke, P.; Kulessa, B.; Luckman, A. J.; Sevestre, H.; O'Leary, M.

2017-12-01

We report on recent empirical investigations of the internal structure and stability (or otherwise) of Larsen C Ice Shelf (LCIS), Antarctica, focusing on research carried out for the MIDAS research project between 2014 and 2017. Borehole- and surface geophysics-based fieldwork carried out in austral springs 2014 and 2015 revealed that ephemeral surface ponds, preferentially located within the major inlets within the northern sector of the ice shelf, result in the formation of several tens of metres of (relatively dense) subsurface ice within what would otherwise have been a progressively densifying snow and firn column. Five boreholes were drilled throughout the sector and logged by optical televiewer, showing this refrozen ice to be extensive and of variable composition depending on its process of formation. Mapping the depth-distribution of the resulting ice types and associating each with a simple flow-line model of ice motion and accumulation indicates that this area of LCIS has experienced substantial melting for some centuries but that surface ponding has only occurred in recent decades, possibly restricted to the past 20 years. We also present near-surface temperature data that reveal surprising temporal patterns in foehn wind activity and intensity. Finally, we report on the geometrical extension and widening of a rift that was responsible for calving a 5,800 km^2 iceberg from the LCIS in July 2017. The nature of rift propagation through `suture' ice bands, widely considered to be composed of marine ice, is contrasted with that of its propagation through meteoric ice.

Controls of bioclastic turbidite deposition in eastern Muertos Trough northeast Caribbean Sea

DOE Office of Scientific and Technical Information (OSTI.GOV)

Forsthoff, G.M.; Holcombe, T.L.

1985-02-01

A study of seismic-reflection profiles and sediment cores establishes regional bathymetric and source area control over the composition, transport, and distribution of turbidites in the eastern Muertos Trough, Bioclastic (carbonate) turbidites dominate the eastern portion of the trough. Analyses of carbon content and sand-sized components suggest that the bioclastic turbidites (characterized by planktonic foraminifera, pteropods, and sponge spicules) are reworked pelagic oozes originally deposited on the outer-shelf and upper-slope areas south of St. Croix and eastern Puerto Rico. The presence of several intrashelf and upper-slope basins prohibits shallow-water carbonate sediments from entering the Muertos Trough. Volcanic rock fragments derived frommore » Puerto Rico are transported to the trough via the Guayanilla Canyon system. Mixing of the volcanic fragments with outer-shelf and upper-slope lutites results in mixed bioclastic-terrigenous turbidites south of central and western Puerto Rico. The paucity of shallow-water carbonate sediments in the trough suggests that the submarine canyons are effective conduits for the rapid transport of volcaniclastic sands across the shelf and thereby prevent extensive mixing with inner- and middle-shelf carbonate sediments. Sediment transport within the trough is primarily axial in an east-west direction. Outer trench-wall fault scarps, south of Guayanilla Canyon, limit the southerly progradation of the trench-wedge facies and deflect incoming gravity flows in a down-axis (westward) direction. Where no faults exist, the trench wedge progrades southward and interfingers with the pelagic sediments of the northern Venezuelan basin.« less

Distribution and abundance of anthropogenic marine debris along the shelf and slope of the US West Coast.

PubMed

Keller, Aimee A; Fruh, Erica L; Johnson, Melanie M; Simon, Victor; McGourty, Catherine

2010-05-01

As marine debris levels continue to grow worldwide, defining sources, composition, and distribution of debris, as well as potential effects, becomes increasingly important. We investigated composition and abundance of man-made, benthic marine debris at 1347 randomly selected stations along the US West Coast during Groundfish Bottom Trawl Surveys in 2007 and 2008. Anthropogenic debris was observed in 469 tows at depths of 55-1280 m. Plastic and metallic debris occurred in the greatest number of hauls followed by fabric and glass. Mean density was 67.1 items km(-2) throughout the study area but was significantly higher south of 36 degrees 00'N latitude. Mean density significantly increased with depth, ranging from 30 items km(-2) in shallow (55-183 m) water to 128 items km(-2) in the deepest depth stratum (550-1280 m). Debris densities observed along the US West Coast were comparable to those seen elsewhere and provide a valuable backdrop for future comparisons. (c) 2010 Elsevier Ltd. All rights reserved.

The 3D Distribution of Dissolved and Colloidal Fe, Mn, Zn, Cu, Ni, Cd and Pb in the Western Antarctic Peninsula Shelf Region; Implications for Natural Fe Fertilization

NASA Astrophysics Data System (ADS)

Sherrell, R. M.; Fitzsimmons, J. N.; Roccanova, J.; Schofield, O.; Meredith, M. P.

2016-02-01

The Western Antarctic Peninsula (WAP) shelf region is is a natural Fe fertilization zone where primary production exceeds that of the adjacent open Southern Ocean. Until recently, however, distributions of Fe and of other bioactive metals were completely lacking for the WAP, and the sources and delivery mechanisms of Fe to the euphotic zone were only speculated upon. We have previously presented surface water (2m) dissolved (dTM, <0.2µm) and particulate (pTM, >0.45µm) distributions for Fe and a suite of other bioactive metals over the WAP shelf, covering the Palmer LTER sampling grid for Jan. 2010, 2011 and 2012. We now report the first complete 3D distribution of dissolved and colloidal Fe (and Mn, Zn, Cu, Ni, Cd and Pb) over the LTER grid in Jan. 2015, allowing assessment of dFe size speciation, sources and transport pathways in this dynamic shelf system. Dissolved metals were analyzed by automated offline preconcentration (seaFAST-pico, ESI) followed by sector-field ICP-MS. We confirm previous findings of low ( 0.1nM) dFe in surface waters on the mid-outer shelf in the northern portion of the grid, and now find that concentrations at this level or below persist through the euphotic zone. However, dFe increases rapidly with depth, with low surface values underlain by substantially higher concentrations even at 50m. Inner shelf surface waters are generally substantially > 0.1nM, suggesting Fe replete conditions in this region. Vertical profiles reveal that dFe generally increases with depth, much moreso in the inner shelf (dFe up to 5.0nM) than the outer shelf. A general N-S gradient in dFe is also evident, with concentrations higher in the southern WAP, especially in Marguerite Bay. In addition, shelf stations often show a dFe maximum suggesting remineralization from sinking biogenic particles. These findings for dFe and for the other metals, will be used to help unravel the biogeochemical workings of natural Fe fertilization in this region.

A four-dimensional primitive equation model for coupled coastal-deep ocean studies

NASA Technical Reports Server (NTRS)

Haidvogel, D. B.

1981-01-01

A prototype four dimensional continental shelf/deep ocean model is described. In its present form, the model incorporates the effects of finite amplitude topography, advective nonlinearities, and variable stratification and rotation. The model can be forced either directly by imposed atmospheric windstress and surface pressure distributions, and energetic mean currents imposed by the exterior oceanic circulation; or indirectly by initial distributions of shoreward propagation mesoscale waves and eddies. To avoid concerns over the appropriate specification of 'open' boundary conditions on the cross-shelf and seaward model boundaries, a periodic channel geometry (oriented along-coast) is used. The model employs a traditional finite difference expansion in the cross-shelf direction, and a Fourier (periodic) representation in the long-shelf coordinate.

Origin and processing of terrestrial organic carbon in the Amazon system: lignin phenols in river, shelf, and fan sediments

NASA Astrophysics Data System (ADS)

Sun, Shuwen; Schefuß, Enno; Mulitza, Stefan; Chiessi, Cristiano M.; Sawakuchi, André O.; Zabel, Matthias; Baker, Paul A.; Hefter, Jens; Mollenhauer, Gesine

2017-05-01

The Amazon River transports large amounts of terrestrial organic carbon (OCterr) from the Andean and Amazon neotropical forests to the Atlantic Ocean. In order to compare the biogeochemical characteristics of OCterr in the fluvial sediments from the Amazon drainage basin and in the adjacent marine sediments, we analysed riverbed sediments from the Amazon mainstream and its main tributaries as well as marine surface sediments from the Amazon shelf and fan for total organic carbon (TOC) content, organic carbon isotopic composition (δ13CTOC), and lignin phenol compositions. TOC and lignin content exhibit positive correlations with Al / Si ratios (indicative of the sediment grain size) implying that the grain size of sediment discharged by the Amazon River plays an important role in the preservation of TOC and leads to preferential preservation of lignin phenols in fine particles. Depleted δ13CTOC values (-26.1 to -29.9 ‰) in the main tributaries consistently correspond with the dominance of C3 vegetation. Ratios of syringyl to vanillyl (S / V) and cinnamyl to vanillyl (C / V) lignin phenols suggest that non-woody angiosperm tissues are the dominant source of lignin in the Amazon basin. Although the Amazon basin hosts a rich diversity of vascular plant types, distinct regional lignin compositions are not observed. In the marine sediments, the distribution of δ13CTOC and Λ8 (sum of eight lignin phenols in organic carbon (OC), expressed as mg/100 mg OC) values implies that OCterr discharged by the Amazon River is transported north-westward by the North Brazil Current and mostly deposited on the inner shelf. The lignin compositions in offshore sediments under the influence of the Amazon plume are consistent with the riverbed samples suggesting that processing of OCterr during offshore transport does not change the encoded source information. Therefore, the lignin compositions preserved in these offshore sediments can reliably reflect the vegetation in the Amazon River catchment. In sediments from the Amazon fan, low lignin content, relatively depleted δ13CTOC values and high (Ad / Al)V ratios indicating highly degraded lignin imply that a significant fraction of the deposited OCterr is derived from petrogenic (sourced from ancient rocks) sources.

Patterns in larval fish assemblages under the influence of the Brazil current

NASA Astrophysics Data System (ADS)

Katsuragawa, M.; Dias, J. F.; Harari, J.; Namiki, C.; Zani-Teixeira, M. L.

2014-10-01

The present work investigates the composition of larval fish assemblages in the area under the influence of the Brazil Current (BC) off the Southeastern Brazilian Bight. Ichthyoplankton was sampled during two oceanographic cruises (November-December/1997 - spring; May/2001 - autumn) with bongo nets oblique tows. Seasonal variation and a coastal-ocean pattern in the distribution of larval fish was observed and was influenced by the dynamics of the water masses, Coastal Water (CW), Tropical Water (TW) and South Atlantic Central Water (SACW), the last two of which were transported by the BC. During spring, the shelf assemblage was dominated by larvae of small pelagic fishes, such as Sardinella brasiliensis, Engraulis anchoita and Trachurus lathami, and was associated with the enrichment of shallow water by the SACW upwelling. In autumn, the abundance of coastal species larvae was reduced, and the shelf assemblage was dominated by Bregmaceros cantori. A transitional assemblage occurred during the spring, and comprised mesopelagic and coastal species. In both seasons, the oceanic assemblage was dominated by the mesopelagic families, Myctophidae, Sternopthychidae and Phosichthyidae. The oceanographic conditions also demonstrated clear differences between the northern and southern subareas, particularly in the shelf zone. This was especially the case during autumn when a latitudinal gradient in larval fish assemblages became more pronounced.

Distribution and Composition of Thiotrophic Mats in the Hypoxic Zone of the Black Sea (150–170 m Water Depth, Crimea Margin)

PubMed Central

Jessen, Gerdhard L.; Lichtschlag, Anna; Struck, Ulrich; Boetius, Antje

2016-01-01

At the Black Sea chemocline, oxygen- and sulfide-rich waters meet and form a niche for thiotrophic pelagic bacteria. Here we investigated an area of the Northwestern Black Sea off Crimea close to the shelf break, where the chemocline reaches the seafloor at around 150–170 m water depth, to assess whether thiotrophic bacteria are favored in this zone. Seafloor video transects were carried out with the submersible JAGO covering 20 km2 on the region between 110 and 200 m depth. Around the chemocline we observed irregular seafloor depressions, covered with whitish mats of large filamentous bacteria. These comprised 25–55% of the seafloor, forming a belt of 3 km width around the chemocline. Cores from the mats obtained with JAGO showed higher accumulations of organic matter under the mats compared to mat-free sediments. The mat-forming bacteria were related to Beggiatoa-like large filamentous sulfur bacteria based on 16S rRNA sequences from the mat, and visual characteristics. The microbial community under the mats was significantly different from the surrounding sediments and enriched with taxa affiliated with polymer degrading, fermenting and sulfate reducing microorganisms. Under the mats, higher organic matter accumulation, as well as higher remineralization and radiotracer-based sulfate reduction rates were measured compared to outside the mat. Mat-covered and mat-free sediments showed similar degradability of the bulk organic matter pool, suggesting that the higher sulfide fluxes and subsequent development of the thiotrophic mats in the patches are consequences of the accumulation of organic matter rather than its qualitative composition. Our observations suggest that the key factors for the distribution of thiotrophic mat-forming communities near to the Crimean shelf break are hypoxic conditions that (i) repress grazers, (ii) enhance the accumulation and degradation of labile organic matter by sulfate-reducers, and (iii) favor thiotrophic filamentous bacteria which are adapted to exploit steep gradients in oxygen and sulfide availability; in addition to a specific seafloor topography which may relate to internal waves at the shelf break. PMID:27446049

IMPACTS OF GLOBAL CHANGE ON UV EXPOSURE IN COASTAL SHELF REGIONS OF THE SOUTHEASTERN UNITED STATES

EPA Science Inventory

Global change has a variety of impact on UV exposure in coastal shelf regions of the southeastern United States. Changes in solar UV reaching the water surface have been caused by human alterations of atmospheric composition such as depletion of the ozone layer.

Phytoplankton distributions and their nutrient environment in the Eastern Bering Sea.

NASA Astrophysics Data System (ADS)

Zhang, J.; Nishitani, H.; Narita, H.; Jordan, R. W.

2004-12-01

After 1997, coccolithophorids blooms have been frequently observed by research vessels and satellites in the Eastern Bering Sea shelf, where diatoms have previously been dominate. Here, we present CTD, Chl-a, nutrient and phytoplankton data collected during cruises of the T/S Oshoro-Maru and R/V Mirai vessels from 2000 to 2003. Our goal is to refine the relation between phytoplankton distribution and water characteristics, and the controlling features of coccolithophorids blooms in the Eearstern Bering Sea. Samplings were carried out alone 166_E#8249;W from 55_E#8249;N to 59_E#8249;N. For cell counting, seawater samples were filtered through a 25-mm Millipore HA filter, and identification and counting of phytoplankton was performed with a scanning electron microscope. The scale of bloom and abundance of coccolithophorids were different in each year. The most dominant phytoplankton group was coccolithophorids in 2000, which agrees with the large bloom observed by satellite. In 2001, diatoms dominated at 70% and coccolithophorids accounted for 30% at 58, 58.5_E#8249;N. In 2002 and 2003, diatoms dominated at nearly 100% at all stations. Coccolithophorids abundance was nearly halted by pycnocline, since coccolithophorids existed in the middle shelf domain, which is known to be an area of cold-water pool distribution. The difference in density between the surface mixed layer and the cold-water pool gradually increased from 1980 to 2002, that is, seawater stratification in the middle shelf domain was strengthened as the result of the increased surface temperature and decreased salinity that have occurred recently. When stratification strengthens, the supply of nutrients to the surface from the cold-water pool is reduced. Consequently, coccolithophorids take precedence over diatoms in this condition. However, if the decreased salinity in the surface water depended on the increased river discharge, then the nutrients in the surface water would increase. River discharge has two peaks (spring and late summer) in one year (Chikita, 2001). Since river water contains high volumes of silicate and iron, an increase in river discharge would lead to the predominance of diatoms. The frequency and timing of storms, which influence the thickness of the surface mixed layer, may be another controlling factor of coccolithophorids blooms. In fact, there was a second peak in October 2000 and in August 2001. In 2000, the thickness of the surface mixed layer increased from July to September. Because the timing of storms and river discharges in summer controlled the stratification in the middle shelf domain, it greatly influenced the species_f composition of phytoplankton. In 2002 and 2003, the phytoplankton concetrations distribute peaks respectively at the south and north. The dominant classes are centric diatoms in the south, and is penate diatoms in the north, caused by defferent nutrients and temperature distribution. The sources of nutrients to the Estern bering Sea can be classified into three groups: up welling at the shelf edge, from the cold water pool, and from riverwater. The nutrients of surface water are high in the south and are low in the north, and dispense the diffenrent phytoplankton distribution.

Short-lived radium isotopes on the Scotian Shelf: Unique distribution and tracers of cross-shelf CO2 and nutrient transport

NASA Astrophysics Data System (ADS)

Burt, William; Thomas, Helmuth

2013-04-01

Radium (Ra) isotopes have become a common tool for investigating mixing rates on continental shelves, and more recently have been used to quantify the release of dissolved compounds enriched in pore-waters into the water column. We present results from Ra sampling of the Scotian Shelf region of the Canadian northwestern Atlantic Ocean, which reveal cross-shelf Ra distributions that are unique compared to other coastal regions. We explain the observations of lower 224Ra activities near the coast, relatively high activities at large distances offshore (>100km), and gradients in both offshore and onshore directions by inferring the regional geomorphology, as well as shelf bathymetry and circulation patterns. Ra gradients are used to calculate individual estimates of eddy diffusion in both the cross-shelf (KX) and vertical (KZ) directions using 1-D eddy diffusion models. Enhanced vertical mixing above offshore banks allows for Ra enrichments in offshore surface waters, while horizontal dispersion of this bank-related signal can transport Ra off the shelf break in surface waters, and towards the shore beneath the surface mixed layer. Similar onshore gradients in CO2 and nutrient species combined with Ra-derived KX values can yield onshore carbon and nutrient fluxes in subsurface waters, which in turn supply the CO2 outgassing from the Scotian Shelf. Our results thus provide constraints for cross-shelf transports of carbon and nutrients on the Scotian Shelf in order to guide mass balance or model based budget approaches in future studies.

Optimization of Steamed Meals Based on Composite Flour (Taro, Banana, Green Bean) and Its Predicted Shelf Life

NASA Astrophysics Data System (ADS)

Sunarmani; Setyadjit; Ermi, S.

2018-05-01

Ongol-ongol is for food diversification by mixing composite flour of taro, banana and mung bean, then was steamed by hot air. The purpose of this study was to find out the optimum way to produce ‘ongol-ongol’ from composite flour and to know the storage life by prediction method. The research consisted of two stages, namely the determination of the optimum formula of ‘ongol-ongol’ with Design Expert DX 8.1.6 software and the estimation of product shelf life of the optimum formula by ASLT (Accelerated Shelf Life Test) method. The optimum formula of the steamed meal was produced from composite flour and arenga flour with ratio of 50: 50 and flour to water ratio of 1: 1. The proximate content of steamed meal of optimum formula is 36.53% moisture content, ash content of 1,36%, fat content of 14.48%, protein level of 28.5%, and carbohydrate of 44.77% (w/w). Energy Value obtained from 100 g of ‘ongol-ongol’ was 320.8 Kcal. Recommended for steamed meal storage life is 12.54 days at ambient temperature.

Fitness consequences of habitat variability, trophic position, and energy allocation across the depth distribution of a coral-reef fish

NASA Astrophysics Data System (ADS)

Goldstein, E. D.; D'Alessandro, E. K.; Sponaugle, S.

2017-09-01

Environmental clines such as latitude and depth that limit species' distributions may be associated with gradients in habitat suitability that can affect the fitness of an organism. With the global loss of shallow-water photosynthetic coral reefs, mesophotic coral ecosystems ( 30-150 m) may be buffered from some environmental stressors, thereby serving as refuges for a range of organisms including mobile obligate reef dwellers. Yet habitat suitability may be diminished at the depth boundary of photosynthetic coral reefs. We assessed the suitability of coral-reef habitats across the majority of the depth distribution of a common demersal reef fish ( Stegastes partitus) ranging from shallow shelf (SS, <10 m) and deep shelf (DS, 20-30 m) habitats in the Florida Keys to mesophotic depths (MP, 60-70 m) at Pulley Ridge on the west Florida Shelf. Diet, behavior, and potential energetic trade-offs differed across study sites, but did not always have a monotonic relationship with depth, suggesting that some drivers of habitat suitability are decoupled from depth and may be linked with geographic location or the local environment. Feeding and diet composition differed among depths with the highest consumption of annelids, lowest ingestion of appendicularians, and the lowest gut fullness in DS habitats where predator densities were highest and fish exhibited risk-averse behavior that may restrict foraging. Fish in MP environments had a broader diet niche, higher trophic position, and higher muscle C:N ratios compared to shallower environments. High C:N ratios suggest increased tissue lipid content in fish in MP habitats that coincided with higher investment in reproduction based on gonado-somatic index. These results suggest that peripheral MP reefs are suitable habitats for demersal reef fish and may be important refuges for organisms common on declining shallow coral reefs.

Femtosecond FBG Written through the Coating for Sensing Applications.

PubMed

Habel, Joé; Boilard, Tommy; Frenière, Jean-Simon; Trépanier, François; Bernier, Martin

2017-11-02

Type I fiber Bragg gratings (FBG) written through the coating of various off-the-shelf silica fibers with a femtosecond laser and the phase-mask technique are reported. Inscription through most of the common coating compositions (acrylate, silicone and polyimide) is reported as well as writing through the polyimide coating of various fiber cladding diameters, down to 50 µm. The long term annealing behavior of type I gratings written in a pure silica core fiber is also reported as well as a comparison of the mechanical resistance of type I and II FBG. The high mechanical resistance of the resulting type I FBG is shown to be useful for the fabrication of various distributed FBG arrays written using a single period phase-mask. The strain sensing response of such distributed arrays is also presented.

Inorganic geochemistry of surface sediments of the Ebro shelf and slope, northwestern Mediterranean

USGS Publications Warehouse

Gardner, J.V.; Dean, W.E.; Alonso, B.

1990-01-01

Distributions of major, minor, and trace elements in surface sediment of the continental shelf and upper slope of the northeastern Spanish continental margin reflect the influences of discharge from the Ebro River and changes in eustatic sea levels. Multivariate factor analysis of sediment geochemistry was used to identify five groupings of samples (factors) on the shelf and slope. The first factor is an aluminosilicate factor that represents detrital clastic material. The second factor is a highly variable amount of excess SiO2 and probably represents a quartz residuum originating from winnowing of relict detrital sediments. A carbonate factor (Factor 3) has no positive correlation with other geochemical parameters but is associated with the sand-size fraction. The carbonate in these sediments consists of a mixture of biogenic calcite and angular to subangular detrital grains. Organic carbon is associated with the aluminosilicate factor (Factor 1) but also factors out by itself (Factor 4); this suggests that there may be two sources of organic matter, terrestrial and marine. The fifth factor comprises upper slope sediments that contain high concentrations of manganese. The most likely explanation for these high manganese concentrations is precipitation of Mn oxyhydroxides at the interface between Mn-rich, oxygen-deficient, intermediate waters and oxygenated surface waters. During eustatic low sea levels of the glacial Pleistocene, the Ebro Delta built across the outer continental shelf and deposited sediment with fairly high contents of organic carbon and continental components. The period of marine transgression from eustatic low (glacial) to eustatic high (interglacial) sea levels was characterized by erosion of the outer shelf delta and surficial shelf sediments and the transport of sediment across the slope within numerous canyons. Once eustatic high sea level was reached, delta progradation resumed on the inner shelf. Today, coarse-grained sediment (silt and sand) is transported to the continental shelf by Ebro River and is distributed along the inner shelf by currents generated by dominant northeasterly winds. Clay-size material is deposited on the mid- and outer-shelf. However, erosion and delta progradation during the last glacial period, and fine-grained Holocene sedimentation, have probably produced a distribution of sediment on a diachronous surface. ?? 1990.

Coccolithophorid blooms in the global ocean

NASA Technical Reports Server (NTRS)

Brown, Christopher W.; Yoder, James A.

1994-01-01

The global distribution pattern of coccolithophrid blooms was mapped in order to ascertain the prevalence of these blooms in the world's oceans and to estimate their worldwide production of CaCO3 and dimethyl sulfide (DMS). Mapping was accomplished by classifying pixels of 5-day global composites of coastal zone color scanner imagery into bloom and nonbloom classes using a supervised, multispectral classification scheme. Surface waters with the spectral signature of coccolithophorid blooms annually covered an average of 1.4 x 10(exp 6) sq km in the world oceans from 1979 to 1985, with the subpolar latitudes accounting for 71% of this surface area. Classified blooms were most extensive in the Subartic North Atlantic. Large expanses of the bloom signal were also detected in the North Pacific, on the Argentine shelf and slope, and in numerous lower latitude marginal seas and shelf regions. The greatest spatial extent of classified blooms in subpolar oceanic regions occurred in the months from summer to early autumn, while those in lower latitude marginal seas occurred in midwinter to early spring. Though the classification scheme was effcient in separating bloom and nonbloom classes during test simulations, and biogeographical literature generally confirms the resulting distribution pattern of blooms in the subpolar regions, the cause of the bloom signal is equivocal in some geographic areas, particularly on shelf regions at lower latitudes. Standing stock estimates suggest that the presumed Emiliania huxleyi blooms act as a significant source of calcite carbon and DMS sulfur on a regional scale. On a global scale, however, the satellite-detected coccolithophorid blooms are estimated to play only a minor role in the annual production of these two compounds and their flux from the surface mixed layer.

Compositional Analyses and Shelf-Life Modeling of Njangsa (Ricinodendron heudelotii) Seed Oil Using the Weibull Hazard Analysis.

PubMed

Abaidoo-Ayin, Harold K; Boakye, Prince G; Jones, Kerby C; Wyatt, Victor T; Besong, Samuel A; Lumor, Stephen E

2017-08-01

This study investigated the compositional characteristics and shelf-life of Njangsa seed oil (NSO). Oil from Njangsa had a high polyunsaturated fatty acid (PUFA) content of which alpha eleostearic acid (α-ESA), an unusual conjugated linoleic acid was the most prevalent (about 52%). Linoleic acid was also present in appreciable amounts (approximately 34%). Our investigations also indicated that the acid-catalyzed transesterification of NSO resulted in lower yields of α-ESA methyl esters, due to isomerization, a phenomenon which was not observed under basic conditions. The triacylglycerol (TAG) profile analysis showed the presence of at least 1 α-ESA fatty acid chain in more than 95% of the oil's TAGs. Shelf-life was determined by the Weibull Hazard Sensory Method, where the end of shelf-life was defined as the time at which 50% of panelists found the flavor of NSO to be unacceptable. This was determined as 21 wk. Our findings therefore support the potential commercial viability of NSO as an important source of physiologically beneficial PUFAs. © 2017 Institute of Food Technologists®.

Clay mineralogy and source-to-sink transport processes of Changjiang River sediments in the estuarine and inner shelf areas of the East China Sea

NASA Astrophysics Data System (ADS)

Zhao, Yifei; Zou, Xinqing; Gao, Jianhua; Wang, Chenglong; Li, Yali; Yao, Yulong; Zhao, Wancang; Xu, Min

2018-02-01

We examined the source-to-sink sediment transport processes from the Changjiang River to the estuarine coastal shelf area by analyzing the clay mineral assemblages in suspended sediment samples from the Changjiang River catchment and surface samples from the estuarine coastal shelf area following the impoundment of the Three Gorges Dam (TGD) in 2003. The results indicate that the clay mineral compositions throughout the study area are dominated by illite, with less abundant kaolinite and chlorite and scarce smectite. The clay minerals display distinct differences in the tributaries and exhibit obvious changes in the trunk stream compared with the periods before 2003, and the source of sediment has largely shifted to the mid- to lower reaches of the river after 2003. Spatially, the clay mineral assemblages in the estuarine area define two compositionally distinct provinces. Province I covers the mud area of the Changjiang River estuary and the Zhe-Min coastal region, where sediment is primarily supplied by the Changjiang River. Province II includes part of the Changjiang River estuary and the southeastern portion of the study area, where the sediment is composed of terrestrial material from the Changjiang River and re-suspended material from the Huanghe River carried by the Jiangsu coastal current. Moreover, the other smaller rivers in China (including the Oujiang and Minjiang rivers of mainland China and the rivers of West Taiwan) also contribut sediments to the estuarine and inner shelf areas. In general, the clay mineral assemblages in the Changjiang River estuarine area are have mainly been controlled by sediment supplied from upstream of the Changjiang River tributaries. However, since the completion of the TGD in 2003, the mid- to downstream tributaries have become the main source of sediments from the Changjiang catchment into the East China Sea. These analyses further demonstrate that the coastal currents and the decrease in the sediment load of the river have the greatest impacts on the distribution and transport of clay minerals assemblages in the sediments.

Effect of light-emitting diode (LED) vs. fluorescent (FL) lighting on laying hens in aviary hen houses: Part 2 - Egg quality, shelf-life and lipid composition.

PubMed

Long, H; Zhao, Y; Xin, H; Hansen, H; Ning, Z; Wang, T

2016-01-01

In this 60-wk study, egg quality, egg shelf-life, egg cholesterol content, total yolk lipids, and yolk fatty acid composition of eggs produced by Dekalb white laying hens in commercial aviary houses with either light-emitting diode (LED) or fluorescent (FL) lighting were compared. All parameters were measured at 27, 40, and 60 wk of age, except for egg shelf-life, which was compared at 50 wk of age. The results showed that, compared to the FL regimen, the LED regimen resulted in higher egg weight, albumen height, and albumen weight at 27 wk of age, thicker shells at 40 wk of age, but lower egg weight at 60 wk of age. Egg quality change was similar between the lighting regimens during the 62-d egg storage study, indicating that LED lighting did not influence egg shelf-life. Eggs from both lighting regimens had similar cholesterol content. However, cholesterol concentration of the yolk (15.9 to 21.0 mg cholesterol/g wet weight yolk) observed in this study was higher than that of United States Department of Agriculture (USDA) database (10.85 mg/g). No significant differences in total lipids or fatty acid composition of the yolks were detected between the two lighting regimens. © 2015 Poultry Science Association Inc.

Source and dispersal of silt on northern Gulf of Mexico continental shelf

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peterson, M.; Mazzullo, J.

1988-01-01

The surficial sediment on the continental shelf of the northern Gulf of Mexico is characterized by abundant silty clay which was deposited during the late Pleistocene lowstand and reworked during and after the Holocene transgression. The purposes of this study were to determine the sources of the silt fraction in this surficial sediment by quartz grain roundness and surface texture analysis, and to determine the effects of modern shelf currents upon the distribution of silt. Areal variations in quartz grain roundness and surface texture define six silt provinces on the northern Gulf of Mexico continental shelf. The Mississippi province ismore » the largest province and stretches from the Chandeleur Islands to Matagorda Bay. It is characterized by a mixture of rounded grains that were derived from the sedimentary rocks of the Gulf coastal plain and the Mid-Continent, and angular, fractured grains that were derived from glacial deposits in the northern United States. A comparison of the areal distribution of these six provinces with the late Pleistocene paleogeography of the continental shelf shows evidence for varying degrees of shore-parallel transport of silt by modern shelf currents.« less

The influence of shelf processes in delivering dissolved iron to the HNLC waters of the Drake Passage, Antarctica

NASA Astrophysics Data System (ADS)

Measures, C. I.; Brown, M. T.; Selph, K. E.; Apprill, A.; Zhou, M.; Hatta, M.; Hiscock, W. T.

2013-06-01

Dissolved trace element distributions near Elephant Island in the Drake Passage show extremely high levels of dissolved Fe and Mn in waters above the shelf. The entrainment of this enriched shelf water by the Fe-poor Antarctic Circumpolar Current (ACC) as it passes through the Shackleton Gap delivers an estimated 2.8×106 mol yr-1 dissolved Fe to the offshore waters of the Drake Passage. The magnitude and spatial distribution of dissolved Fe, Mn and Al over the shelf are consistent with a diagenetically produced sedimentary source, but are inconsistent with eolian or upwelling sources. The systematics of the Mn and Fe concentrations suggest that there are two distinct sources of dissolved Fe to the surface waters of this region. The highest Fe concentrations are associated with Bransfield Strait water, which can be identified by its characteristic temperature and salinity (T/S) properties both inside the Bransfield Strait and in the Bransfield Current outflow between Elephant and Clarence Islands. Most of the shelf area is dominated by a second water type with T/S properties that are typical of modified Antarctic Surface Water, which while also enriched has a lower Fe:Mn ratio. The predominantly linear relationships between the Fe and Mn concentrations at the stations in each of these water mass types suggest that the distribution of these elements is largely controlled by physical mixing processes and that biological removal of Fe on the shelf, while certainly occurring, is limited, perhaps as a result of rapid physical flushing processes and relatively slow biological growth rates. The consequent export of large quantities of this shelf-derived Fe into the ACC is likely responsible for the extensive regions of enhanced primary production seen in satellite imagery downstream of the Drake Passage.

Phytoplankton assemblages within the Chesapeake Bay plume and adjacent waters of the continental shelf

NASA Technical Reports Server (NTRS)

Marshall, H. G.

1981-01-01

The Chesapeake Bay plume was identified and plotted in relation to the presence and high concentrations of phytoplankton assemblages. Seasonal differences occurred within the plume during the collection period, with Skeletonema costatum and an ultraplankton component the dominant forms. Patchiness was found along the transects, with variations in composition and concentrations common on consecutive day sampling within the plume in its movement along the shelf. The presence of 236 species is noted, with their presence indicated for plume and shelf stations during the March, June, and October 1980 collections.

Modern sedimentation on the shoreface and inner continental shelf at wrightsville beach, North Carolina, U.S.A

USGS Publications Warehouse

Thieler, R.E.; Pilkey, O.H.; Cleary, W.J.; Schwab, W.C.

2001-01-01

The geologic framework and surficial morphology of the shoreface and inner continental shelf off the Wrightsville Beach, North Carolina, barrier island were mapped using high-resolution sidescansonar, bathyme??trie, and seismic-reflection surveying techniques, a suite of over 200 diver vibracores, and extensive seafloor observations by divers. The inner shelf is a sediment-starved, active surface of marine erosion; modern sediments, where present, form a patchy veneer over Tertiary and Quaternary units. The lithology of the underlying units exerts a primary control on the distribution, texture, and composition of surficial sediments, as well as inner-shelf bathymetry. The shoreface is dominated by a linear, cross-shore morphology of rippled scour depressions (RSDs) extending from just seaward of the surf zone onto the inner shelf. On the upper shoreface, the RSDs are incised up to l m below surrounding areas of fine sand, and have an asymmetric cross section that is steeper-sided to the north. On the inner shelf, the RSDs have a similar but more subdued cross-sectional profile. The depressions are floored primarily by shell hash and quartz gravel. Vibracore data show a thick (up to 1.5 m) sequence of RSD sediments that unconformably overlies ancient coastal lithosomes. In this sediment-starved inner shelf setting, rippled scour depressions probably form initially on preexisting coarse-sediment substrates such as modern lag deposits of paleofluvial channel lithosomes or ancient tidal inlet thalwegs. Interannual observations of seafloor morphologic change and the longer-term record contained in vibracores suggest that the present seafloor morphology is either relatively stable or represents a recurring, preferential morphologic state to which the seafloor returns after storm-induced perturbations. The apparent stability is interpreted to be the result of interactions at several scales that contribute to a repeating, self-reinforcing pattern of forcing and sedimentary response which ultimately causes the RSDs to be maintained as sediment-starved bedforms responding to both along-shore and acrossshore flows. Sediment accumulation from over 30 years of extensive beach nourishment at Wrightsville Beach appears to have exceeded the local shoreface accommodation space, resulting in the "leaking" of beach and shoreface sediment to the inner shelf. A macroscopically identifiable beach nourishment sediment on the shoreface and inner shelf was used to identify the decadal-scale pattern of sediment dispersal. The nourishment sediment is present in a seaward-thinning wedge that extends from the beach over a kilometer onto the inner shelf to waters depths of 14 m. This wedge is best developed offshore of the shoreline segment that has received the greatest volume of beach nourishment. 

Rare Earth Elements of the Permian-Triassic Conodonts from Shelf Basin to Shallow Platform: Implications for Oceanic Redox Conditions immediately After the End-Permian Mass Extinction

NASA Astrophysics Data System (ADS)

Li, Y.; Zhao, L.; Chen, Z.; Chen, J.; Chen, Y.

2013-12-01

Rare-earth elements (REEs) can provide information regarding the influence of weathering fluxes and hydrothermal inputs on seawater chemistry as well as processes that fractionate REEs between solid and aqueous phases. Of these, cerium (Ce) distributions may provide information about variations in dissolved oxygen in seawater, and thus assess the redox conditions. The short residence times of REEs in seawater (~300-1,000 yr) can result in unique REE signatures in local watermasses. REE patterns preserved in biogenic apatite such as conodonts are ideal proxies for revealing original seawater chemistry. Here, we measured the REE content of in-situ, single albid crowns using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) in combination with an ArF (λ=193 nm) excimer laser (Lambda Physiks GeoLas 2005) and quadrupole ICP-MS (Agilent 7500a). LA-ICP-MS is ideally suited for analyzing conodonts due to its ability to measure compositional variation within single conodont elements. It has the capability to determine, with high spatial resolution, continuous compositional depth profiles through the concentric layered structure of component histologies. To evaluate paleoceanographic conditions immediately after the Permian-Triassic (P-Tr) mass extinction in various depositional settings, we sampled a nearly contemporaneous strata unit, the P-Tr boundary bed, just above the extinction horizon from six sections in South China. They represent various depositional settings from shelf basin (Chaohu and Daxiakou sections), lower part of ramp (Meishan section), normal shallow platform (Yangou section), and platform microbialite (Chongyang and Xiushui sections). The sampled unit is constrained by conodonts Hindeodus changxingensis, H. parvus, and H. staeschei Zones in Meishan. REE results obtained from conodont albid crowns show that the seawater in lower ramp and shelf basin settings contains much higher REE concentrations than that in shallow platform. Ce/Ce* ratios in shelf basin and lower ramp are similar to one another, ranging from 0.7-1.0. The same ratios, however, are much lower in shallow platform and microbialite settings, ranging from 0.17-0.22 and 0.2-0.45, respectively. Eu/Eu+ ratios also show similar patterns: 0.7-1.0 in shelf basin and lower ramp and 0.3-0.7 in shallow platform. If the Ce/Ce* was truly influenced by environmental redox conditions, then Ce/Ce* values of 0.7-1.0 in shelf basin and lower ramp settings are indicative of a suboxic to anoxic depositional system, while the same proxy of 0.17-0.45 in shallow platform and microbialite points to a well-oxygenated setting immediately after the P-Tr mass extinction.

Phenologically distinct phytoplankton regions on the Faroe Shelf - identified by satellite data, in-situ observations and model

NASA Astrophysics Data System (ADS)

Eliasen, Sólvá Káradóttir; Hátún, Hjálmar; Larsen, Karin Margretha H.; Hansen, Bogi; Rasmussen, Till Andreas S.

2017-05-01

Marked inter-annual fluctuations in the primary production on the Faroe shelf propagate to higher trophic levels and influence commercial fish stocks. This has previously been demonstrated based on weekly chlorophyll samples from a coastal station, dating back to 1997. However, the spatial extent, for which the coastal samples are representative, has not been well defined, and potential bio-geographical segregations of the shelf have not been considered. By integrating 18 years of chlorophyll satellite data, supplemented by in-situ, model, and meteorological reanalysis data, we identify three regions with unique characteristics with regards to surface chlorophyll and vertical structure - the Central Shelf, the Outer Shelf and the Eastern Banks. The observed difference in timing of the spring bloom in these regions helps explain different spawning patterns of important fish stocks, and the spatial division of the Faroe Shelf should be considered when studying biology and hydrography in these waters. A positive correlation between annual means on the outer Faroe Shelf and parts of the outer northwest Scottish Shelf indicates similarities between these neighbouring regions. We suggest that this similarity arises from the commonality in nutrient composition of the water masses shared by these neighbouring regions.

Monitoring Antarctic ice sheet surface melting with TIMESAT algorithm

NASA Astrophysics Data System (ADS)

Ye, Y.; Cheng, X.; Li, X.; Liang, L.

2011-12-01

Antarctic ice sheet contributes significantly to the global heat budget by controlling the exchange of heat, moisture, and momentum at the surface-atmosphere interface, which directly influence the global atmospheric circulation and climate change. Ice sheet melting will cause snow humidity increase, which will accelerate the disintegration and movement of ice sheet. As a result, detecting Antarctic ice sheet melting is essential for global climate change research. In the past decades, various methods have been proposed for extracting snowmelt information from multi-channel satellite passive microwave data. Some methods are based on brightness temperature values or a composite index of them, and others are based on edge detection. TIMESAT (Time-series of Satellite sensor data) is an algorithm for extracting seasonality information from time-series of satellite sensor data. With TIMESAT long-time series brightness temperature (SSM/I 19H) is simulated by Double Logistic function. Snow is classified to wet and dry snow with generalized Gaussian model. The results were compared with those from a wavelet algorithm. On this basis, Antarctic automatic weather station data were used for ground verification. It shows that this algorithm is effective in ice sheet melting detection. The spatial distribution of melting areas(Fig.1) shows that, the majority of melting areas are located on the edge of Antarctic ice shelf region. It is affected by land cover type, surface elevation and geographic location (latitude). In addition, the Antarctic ice sheet melting varies with seasons. It is particularly acute in summer, peaking at December and January, staying low in March. In summary, from 1988 to 2008, Ross Ice Shelf and Ronnie Ice Shelf have the greatest interannual variability in amount of melting, which largely determines the overall interannual variability in Antarctica. Other regions, especially Larsen Ice Shelf and Wilkins Ice Shelf, which is in the Antarctic Peninsula region, have relative stable and consistent melt occurrence from year to year.

Marine pelagic ecosystems: the West Antarctic Peninsula

PubMed Central

Ducklow, Hugh W; Baker, Karen; Martinson, Douglas G; Quetin, Langdon B; Ross, Robin M; Smith, Raymond C; Stammerjohn, Sharon E; Vernet, Maria; Fraser, William

2006-01-01

The marine ecosystem of the West Antarctic Peninsula (WAP) extends from the Bellingshausen Sea to the northern tip of the peninsula and from the mostly glaciated coast across the continental shelf to the shelf break in the west. The glacially sculpted coastline along the peninsula is highly convoluted and characterized by deep embayments that are often interconnected by channels that facilitate transport of heat and nutrients into the shelf domain. The ecosystem is divided into three subregions, the continental slope, shelf and coastal regions, each with unique ocean dynamics, water mass and biological distributions. The WAP shelf lies within the Antarctic Sea Ice Zone (SIZ) and like other SIZs, the WAP system is very productive, supporting large stocks of marine mammals, birds and the Antarctic krill, Euphausia superba. Ecosystem dynamics is dominated by the seasonal and interannual variation in sea ice extent and retreat. The Antarctic Peninsula is one among the most rapidly warming regions on Earth, having experienced a 2°C increase in the annual mean temperature and a 6°C rise in the mean winter temperature since 1950. Delivery of heat from the Antarctic Circumpolar Current has increased significantly in the past decade, sufficient to drive to a 0.6°C warming of the upper 300 m of shelf water. In the past 50 years and continuing in the twenty-first century, the warm, moist maritime climate of the northern WAP has been migrating south, displacing the once dominant cold, dry continental Antarctic climate and causing multi-level responses in the marine ecosystem. Ecosystem responses to the regional warming include increased heat transport, decreased sea ice extent and duration, local declines in ice-dependent Adélie penguins, increase in ice-tolerant gentoo and chinstrap penguins, alterations in phytoplankton and zooplankton community composition and changes in krill recruitment, abundance and availability to predators. The climate/ecological gradients extending along the WAP and the presence of monitoring systems, field stations and long-term research programmes make the region an invaluable observatory of climate change and marine ecosystem response. PMID:17405208

p,p'-DDE bioaccumulation in female sea lions of the California Channel Islands

NASA Astrophysics Data System (ADS)

Connolly, John P.; Glaser, David

2002-05-01

An area of sediment on the Palos Verdes shelf and in Santa Monica Bay off Los Angeles, CA is contaminated with DDE and other breakdown products of DDT as a result of discharges of DDT through the Whites Point outfall. Elevated concentrations of DDE have been found in the water column of the Palos Verdes Shelf and in various fish species inhabiting the shelf and Santa Monica Bay. High concentrations have also been found in California sea lions from San Miguel Island and sea lion carcasses on Santa Catalina Island. These islands are located some distance from the Palos Verdes shelf and Santa Monica Bay. It was the purpose of this study to determine if it is likely that the Palos Verdes Shelf/Santa Monica Bay sediments were the principal source of the DDE in the Channel Island sea lions via a pathway from sediments to water and fish preyed on by sea lions. A time variable, age dependent, physiologically based toxicokinetic model of female California sea lions was developed. Mass and energy balance equations describe the uptake and loss of contaminants. The contaminants are partitioned among multiple body compartments, including lipid and non-lipid body tissue and milk. Contaminants are distributed into a fetus of females. Physiological and toxicokinetic data were used to establish rates of growth, respiration, reproduction and lactation, internal partitioning of DDE, efficiency of DDE uptake and rates of DDE excretion. The model was used to estimate the likely DDE exposure history of the sea lions in view of their DDE body burdens. Field-measured dietary composition and prey contaminant levels were then used to establish potential exposure to DDE from various regions within the Southern California Bight. Comparison of the estimated exposure history with that attainable from the various regions indicated that the more highly contaminated lactating females were exposed to prey at levels found only on the Palos Verdes Shelf and in Santa Monica Bay. Thus, it is likely that the sediments impacted by the Whites Point outfall were the source of much of the DDE and PCBs in these animals.

Evidence of microplastic ingestion in the shark Galeus melastomus Rafinesque, 1810 in the continental shelf off the western Mediterranean Sea.

PubMed

Alomar, Carme; Deudero, Salud

2017-04-01

Microplastic (<5 mm) ingestion has been recorded in Galeus melastomus, the blackmouth catshark, around the Balearic Islands. In total 125 individuals were analyzed for microplastic ingestion. Results have shown that 16.80% of the specimens had ingested a mean value of 0.34 ± 0.07 microplastics/individual. Stomach fullness index ranged from 0.86 to 38.89% and regression analyses showed that fuller stomachs contained more microplastics. A higher quantity of filament type microplastics were identified compared to granular or hard plastic type. No significant differences were given between ingestion values of two locations over the continental shelf providing further evidence of the ubiquitous distribution of microplastics. The findings in this study reflect the availability of this man made contaminant to marine species in seafloor habitats. Based on results from this study, data on microplastic ingestion could be used to study trends in the amount and composition of litter ingested by marine animals in accordance with descriptor 10 of the Marine Strategy Framework Directive. Copyright © 2017 Elsevier Ltd. All rights reserved.

Femtosecond FBG Written through the Coating for Sensing Applications

PubMed Central

Habel, Joé; Boilard, Tommy; Frenière, Jean-Simon; Bernier, Martin

2017-01-01

Type I fiber Bragg gratings (FBG) written through the coating of various off-the-shelf silica fibers with a femtosecond laser and the phase-mask technique are reported. Inscription through most of the common coating compositions (acrylate, silicone and polyimide) is reported as well as writing through the polyimide coating of various fiber cladding diameters, down to 50 µm. The long term annealing behavior of type I gratings written in a pure silica core fiber is also reported as well as a comparison of the mechanical resistance of type I and II FBG. The high mechanical resistance of the resulting type I FBG is shown to be useful for the fabrication of various distributed FBG arrays written using a single period phase-mask. The strain sensing response of such distributed arrays is also presented. PMID:29099077

Distribution patterns of the mesozooplankton, principally siphonophores and medusae, in the vicinity of the Antarctic Slope Front (eastern Weddell Sea)

NASA Astrophysics Data System (ADS)

Pagès, Francesc; Schnack-Schiel, Sigrid B.

1996-12-01

The composition, abundance and vertical distribution of mesozooplankton, particularly siphonophores and medusae (27 species), collected along two transects in the eastern Weddell Sea have been analysed. Both transects were characterized by a steep thermocline that on approaching the coastline defined the Antarctic Slope Front. The front acted as a strong boundary in the shelf-slope and caused a pronounced cross frontal gradient in the populations of cnidarians. Few species and low abundances were found in the upper cold waters and most of the populations concentrated in and below the thermocline. The analysis of the gastrozooids of the physonect siphonophore Pyrostephos vanhoeffeni showed a wide variety of prey but the relatively high contribution of krill larvae reveals a substantial trophic impact when both organisms co-occur.

Transport processes near coastal ocean outfalls

USGS Publications Warehouse

Noble, M.A.; Sherwood, C.R.; Lee, Hooi-Ling; Xu, Jie; Dartnell, P.; Robertson, G.; Martini, M.

2001-01-01

The central Southern California Bight is an urbanized coastal ocean where complex topography and largescale atmospheric and oceanographic forcing has led to numerous sediment-distribution patterns. Two large embayments, Santa Monica and San Pedro Bays, are connected by the short, very narrow shelf off the Palos Verdes peninsula. Ocean-sewage outfalls are located in the middle of Santa Monica Bay, on the Palos Verdes shelf and at the southeastern edge of San Pedro Bay. In 1992, the US Geological Survey, together with allied agencies, began a series of programs to determine the dominant processes that transport sediment and associated pollutants near the three ocean outfalls. As part of these programs, arrays of instrumented moorings that monitor currents, waves, water clarity, water density and collect resuspended materials were deployed on the continental shelf and slope information was also collected on the sediment and contaminant distributions in the region. The data and models developed for the Palos Verdes shelf suggest that the large reservoir of DDT/DDE in the coastal ocean sediments will continue to be exhumed and transported along the shelf for a long time. On the Santa Monica shelf, very large internal waves, or bores, are generated at the shelf break. The near-bottom currents associated with these waves sweep sediments and the associated contaminants from the shelf onto the continental slope. A new program underway on the San Pedro shelf will determine if water and contaminants from a nearby ocean outfall are transported to the local beaches by coastal ocean processes. The large variety of processes found that transport sediments and contaminants in this small region of the continental margin suggest that in regions with complex topography, local processes change markedly over small spatial scales. One cannot necessarily infer that the dominant transport processes will be similar even in adjacent regions.

A long term glider study of shelf sea oxygen dynamics

NASA Astrophysics Data System (ADS)

Williams, Charlotte; Palmer, Matthew; Mahaffey, Claire; Davis, Clare

2017-04-01

Oxygen is involved in most biogeochemical processes in the ocean, and dissolved oxygen (DO) is a well-established indicator for biological activity via the estimate of apparent oxygen utilisation (AOU). In the deep waters of the open ocean, the AOU provides a valuable insight into the ocean's biological carbon pump. However, in the physically dynamic and highly productive shallow shelf seas, interpretation of the oxygen distribution and the magnitude of AOU is complex. Physical processes, such as diapycnal mixing, entrainment and horizontal advection act to ventilate waters below the thermocline and thus increase oxygen and decrease AOU. In contrast, biological remineralisation of organic material below the thermocline will consume oxygen and increase AOU. We aim to address the following: 1. Does AOU change seasonally in a shelf sea in response to seasonal changes in productivity? 2. How important is turbulence in redistributing oxygen in a shelf sea? Using 9 months of high-resolution data from >20 glider deployments in the seasonally stratified NW European Shelf Sea we identify and quantify the physical and biological processes that control the DO distribution and magnitude of AOU in shelf seas. A 200km transect between the shelf edge and the central Celtic Sea (CCS) was repeated between November 2014 and August 2015, thus capturing key periods in the seasonal cycling in shelf seas, specifically the onset of stratification, the spring bloom, stratified summer period and breakdown of stratification. The gliders collected data for DO, temperature, salinity, chlorophyll fluorescence, CDOM, backscatter and turbulence. In addition, direct measurements of turbulent dissipation from the Ocean Microstructure Glider deployed during the campaign provided estimates of mixing at CCS and the shelf break, allowing accurate quantification of the vertical fluxes of oxygen. We find that oxygen decreases ubiquitously across the shelf as soon as stratification takes hold, though BML oxygen decreases at a slower rate during summer compared to spring at the shelf break and also across the inner shelf. This appears to be due to a stronger oxycline and potentially more efficient, sporadic mixing of oxygen across the thermocline during summer. Biological oxygen consumption is greater at the shelf break than on shelf even when accounting for enhanced oxygen diapycnal fluxes at the shelf break. Gliders prove to be a good tool in monitoring long term oxygen changes in shelf seas and we find that accurate estimation of AOU in the shelf sea requires inclusion of mixing processes.

How Vial Geometry Variability Influences Heat Transfer and Product Temperature During Freeze-Drying.

PubMed

Scutellà, Bernadette; Passot, Stéphanie; Bourlés, Erwan; Fonseca, Fernanda; Tréléa, Ioan Cristian

2017-03-01

Vial design features can play a significant role in heat transfer between the shelf and the product and, consequently, in the final quality of the freeze-dried product. Our objective was to investigate the impact of the variability of some geometrical dimensions of a set of tubing vials commonly used for pharmaceuticals production on the distribution of the vial heat transfer coefficients (K v ) and its potential consequence on product temperature. Sublimation tests were carried out using pure water and 8 combinations of chamber pressure (4-50 Pa) and shelf temperature (-40°C and 0°C) in 2 freeze-dryers. K v values were individually determined for 100 vials located in the center of the shelf. Vial bottom curvature depth and contact area between the vial and the shelf were carefully measured for 120 vials and these data were used to calculate K v distribution due to variability in vial geometry. At low pressures commonly used for sensitive products (below 10 Pa), the vial-shelf contact area appeared crucial for explaining K v heterogeneity and was found to generate, in our study, a product temperature distribution of approximately 2°C during sublimation. Our approach provides quantitative guidelines for defining vial geometry tolerance specifications and product temperature safety margins. Copyright © 2017 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Macrobenthic assemblages of the Changjiang River estuary (Yangtze River, China) and adjacent continental shelf relative to mild summer hypoxia

NASA Astrophysics Data System (ADS)

Liao, Yibo; Shou, Lu; Tang, Yanbin; Zeng, Jiangning; Gao, Aigen; Chen, Quanzhen; Yan, Xiaojun

2017-05-01

To assess the effects of hypoxia, macrobenthic communities along an estuarine gradient of the Changjiang estuary and adjacent continental shelf were analyzed. This revealed spatial variations in the communities and relationships with environmental variables during periods of reduced dissolved oxygen (DO) concentration in summer. Statistical analyses revealed significant differences in macrobenthic community composition among the three zones: estuarine zone (EZ), mildly hypoxic zone (MHZ) in the continental shelf, and normoxic zone (NZ) in the continental shelf (Global R =0.206, P =0.002). Pairwise tests showed that the macrobenthic community composition of the EZ was significantly different from the MHZ (pairwise test R =0.305, P =0.001) and the NZ (pairwise test R =0.259, P =0.001). There was no significant difference in macrobenthic communities between the MHZ and the NZ (pairwise test R =0.062, P =0.114). The taxa included small and typically opportunistic polychaetes, which made the greatest contribution to the dissimilarity between the zones. The effects of mild hypoxia on the macrobenthic communities are a result not only of reduced DO concentration but also of differences in environmental variables such as temperature, salinity, and nutrient concentrations caused by stratification.

Sources and distribution of allochthonous organic matter in surface sediment from the Seomjin River to the southern inner shelf of Korea

NASA Astrophysics Data System (ADS)

Badejo, Adegoke Olugboyega; Hyun, Sangmin; Kim, Wonnyon; Ju, Se-Jong; Song, Bareum

2017-12-01

The spatial distributions of δ13C, δ15N, and n-alkanes were investigated to determine the source and transportation of allochthonous organic matter from the mouth of the Seomjin River to the southern inner shelf break of Korea. Total organic carbon (%) ranged from 0.3% to 1.6% (average = 0.80%, n = 81), and the C/N ratio varied from 2.4 to 12.4 (average = 6.76, n = 81). The δ13C values ranged from -25.86 to -20.26‰ (average = -21.47‰, n = 81), and δ15N values ranged from 4.37‰ to 8.57‰ (average = 6.72‰, n = 81). The contribution of the terrestrial fraction of organic matter to the total ranged from 4.4% to 97.7% (average = 24.4%, n = 81), suggesting higher amounts around the catchment area and lower amounts in the offshore area. The concentration of total n-alkanes ( nC25 - nC35) was higher at the boundary between the outer bay and inner shelf break (BOBIS). Average chain length and the carbon preference index both indicated that major leaf wax n-alkanes accounted for the observed distribution of terrestrial organic matter, and were dominant in the inner shelf break (around BOBIS) and outer shelf break. Based on the spatial distribution of the total n-alkanes and the sum of nC27, nC29, and nC31, the terrestrial organic matter distribution was considered to be controlled by local oceanographic conditions, especially at the center of the BOBIS. In addition to enabling the distribution and source of terrestrial organic matter to be identified, the n-alkanes indicated that minor anthropogenic allochthonous organic materials were superimposed on the total organic materials in the central part of Yeosu Bay and the catchment area. The n-alkane indices revealed weathered petroleum contamination, with contamination levels being relatively low at the present time.

Effect of shelf aging on vibration transmissibility of anti-vibration gloves

PubMed Central

SHIBATA, Nobuyuki

2017-01-01

Anti-vibration gloves have been used in real workplaces to reduce vibration transmitted through hand-held power tools to the hand. Generally materials used for vibration attenuation in gloves are resilient materials composed of certain synthetic and/or composite polymers. The mechanical characteristics of the resilient materials used in anti-vibration gloves are prone to be influenced by environmental conditions such as temperature, humidity, and photo-irradiation, which cause material degradation and aging. This study focused on the influence of shelf aging on the vibration attenuation performance of air-packaged anti-vibration gloves following 2 yr of shelf aging. Effects of shelf aging on the vibration attenuation performance of anti-vibration gloves were examined according to the Japan industrial standard JIS T8114 test protocol. The findings indicate that shelf aging induces the reduction of vibration attenuation performance in air-packaged anti-vibration gloves. PMID:28978817

Nonlinear Internal Waves on the Inner Shelf: Observations Using a Distributed Temperature Sensing (DTS) System.

NASA Astrophysics Data System (ADS)

Davis, K. A.; Reid, E. C.; Cohen, A. L.

2016-02-01

Internal waves propagating across the continental slope and shelf are transformed by the competing effects of nonlinear steepening and dispersive spreading, forming nonlinear internal waves (NLIWs) that can penetrate onto the shallow inner shelf, often appearing in the form of bottom-propagating nonlinear internal bores or boluses. NLIWs play a significant role in nearshore dynamics with baroclinic current amplitudes on the order of that of wind- and surface wave-driven flows and rapid temperature changes on the order of annual ranges. In June 2014 we used a Distributed Temperature Sensing (DTS) system to give a continuous cross-shelf view of nonlinear internal wave dynamics on the forereef of Dongsha Atoll, a coral reef in the northern South China Sea. A DTS system measures temperature continuously along the length of an optical fiber, resolving meter-to-kilometer spatial scales. This unique view of cross-shelf temperature structure made it possible to observe internal wave reflection, variable propagation speed across the shelf, bolus formation and dissipation. Additionally, we used the DTS data to track internal waves across the shallow fore reef and onto the reef flat and to quantify spatial patterns in temperature variability. Shoaling internal waves are an important process affecting physical variability and water properties on the reef.

Geochemistry and magnetic sediment distribution at the western boundary upwelling system of southwest Atlantic

NASA Astrophysics Data System (ADS)

Cruz, Anna P. S.; Barbosa, Catia F.; Ayres-Neto, Arthur; Munayco, Pablo; Scorzelli, Rosa B.; Amorim, Nívea Santos; Albuquerque, Ana L. S.; Seoane, José C. S.

2018-02-01

In order to investigate the chemical and magnetic characteristics of sediments of the western boundary upwelling system of Southwest Atlantic we analyzed magnetic susceptibility, grain size distribution, total organic carbon, heavy mineral abundance, Fe associated with Mössbauer spectra, and Fe and Mn of pore water to evaluate the deposition patterns of sediments. Four box-cores were collected along a cross-shelf transect. Brazil Current and coastal plume exert a primary control at the inner and outer shelf cores, which exhibited similar depositional patterns characterized by a high abundance of heavy minerals (mean 0.21% and 0.08%, respectively) and very fine sand, whereas middle shelf cores presented low abundances of heavy minerals (mean 0.03%) and medium silt. The inner shelf was dominated by sub-angular grains, while in middle and outer shelf cores well-rounded grains were found. The increasing Fe3+:Fe2+ ratio from the inner to the outer shelf reflects farther distance to the sediment source. The outer shelf presented well-rounded minerals, indicating abrasive processes as a result of transport by the Brazil Current from the source areas. In the middle shelf, cold-water intrusion of the South Atlantic Central Water contributes to the primary productivity, resulting in higher deposition of fine sediment and organic carbon accumulation. The high input of organic carbon and the decreased grain size are indicative of changes in the hydrodynamics and primary productivity fueled by the western boundary upwelling system, which promotes loss of magnetization due to the induction of diagenesis of iron oxide minerals.

Summer distributions of forage fish in the eastern Bering Sea

NASA Astrophysics Data System (ADS)

Parker-Stetter, Sandra L.; Horne, John K.; Farley, Edward V.; Barbee, David H.; Andrews, Alexander G.; Eisner, Lisa B.; Nomura, Jennifer M.

2013-10-01

Juvenile and small adult fish, typically called forage fish, are an important but poorly studied part of the eastern Bering Sea (EBS) ecosystem. Acoustic and trawl data from a non-target survey were used to evaluate distributions of capelin (Mallotus villosus), age-0 Pacific cod (Gadus macrocephalus), and age-0 walleye pollock (Theragra chalcogramma, herein pollock) in 2006-2010. Within the surface zone (15 m to ~35 m, evaluated 2006-2010), capelin occurred throughout the EBS but primarily in the middle shelf. Capelin were also present in the midwater zone (~35 m to 0.5 m off-bottom) in both 2009 and 2010 (evaluated 2009-2010), and resulted in water column zone (15 m to 0.5 m off-bottom) distributions that differed from surface zone characterizations. Age-0 Pacific cod occurred primarily in the surface zone of the middle and outer shelf regions in all years. As midwater and surface zone age-0 Pacific cod were often coincident, water column zone distributions in 2009-2010 were similar to surface zone distributions. Age-0 pollock were found in the EBS surface zone in all years, primarily in the middle and outer shelf regions. High densities of age-0 pollock occurred in the midwater zone in 2006-2007 and 2009-2010. Water column zone distributions of age-0 pollock were similar to surface zone distributions in 2006-2007, but differed in 2009-2010 due to low numbers of age-0 pollock in the surface zone and presence of high densities in the midwater zone of the outer shelf region. While general patterns in capelin distribution in the surface zone were similar between the present and the previous studies, the acoustic-trawl characterization suggested that capelin densities were high in the middle shelf region. As expected, surface zone distributions of age-0 Pacific cod and age-0 pollock were similar to previous characterizations. Observed high densities of midwater age-0 pollock have not been described by previous studies. Annual abundance indices based on bottom or surface trawl data alone will not be sufficient in all years. Data and conclusions from non-target surveys may be constrained compared to dedicated survey efforts, but can provide baseline distributions, potential abundance indices, and insight for planning future research.

USAID negotiating Depo purchase, but shelf life proves problematic.

PubMed

1993-01-01

The discussion focused on the variations in purchasing agreements for the injectable Depo-Provera. Negotiations are in process between the manufacturer in the US (the UpJohn Company) and USAID regarding size of purchase, prices, and time schedules. A glitch is that the US production plant provides a two-year shelf life for the product, while the Belgian plants provide a three-year shelf life. The one year difference could be significant in the distribution to hard-to-reach places, but the balancing point is that USAIDs effort are a positive development for expanding distribution. The UN Population Fund (UNFPA) and the International Planner Parenthood Federation (IPPF) already distribute Depo-Provera and were charged 72 and 75 cents, respectively; UpJohn recently increased the prices to 80 and 85 cents. The UNFPA prices were slightly lower due to larger purchases, and both concerns will be awaiting the outcome of USAID's price negotiations. Other manufacturers are a company in Indonesia, which sells only within the country, and Organon in Holland, which produces the drug under the name Megstron. UpJohn has the major share of the market. The cost of supplying Depo-Provera also includes the purchase of needles and syringes. Other international agencies are not limited by anything other than finding the lowest cost. UNFPA buys its supplies in Belgium at low cost and its contraceptives in Holland. USAID, however, must purchase needles and syringes from American facilities. IPPF will be watching to assure international organizations that no duplication of effort will occur with the USAID distribution and expects the shelf life problem to be resolved. The issue may be cleared up when UpJohn has sufficient time to resubmit its application with enough research to support the 3-year shelf life; the FDA had rejected Depo-Provera repeatedly since 1961, and the approval was granted on a rushed application that only included some of the Belgian research and could empirically only support a 2-year shelf life.

Geology and geochemistry of gas-charged sediment on Kodiak Shelf, Alaska

USGS Publications Warehouse

Hampton, M.A.; Kvenvolden, K.A.

1981-01-01

Methane concentrations in some sediment cores from the Kodiak Shelf and adjacent continental slope increase with depth by three or four orders of magnitude and exceed the solubility in water at ambient conditions. Acoustic anomalies in seismic-reflection records imply that methane-rich sediment is widespread. Molecular composition of hydrocarbon gases and isotopic composition of methane indicate gas formation by shallow biogenic processes. Stratigraphic positions of acoustic anomalies in Quaternary glacial and posttransgressive sediments suggest that these units are likely sources of gas. A seep along the extension of a fault may be gas venting from a deeper thermogenic source. ?? 1981 A.M. Dowden, Inc.

Zooplankton species composition, abundance and biomass on the eastern Bering Sea shelf during summer: The potential role of water-column stability and nutrients in structuring the zooplankton community

NASA Astrophysics Data System (ADS)

Coyle, Kenneth O.; Pinchuk, Alexei I.; Eisner, Lisa B.; Napp, Jeffrey M.

2008-08-01

The southeastern Bering Sea sustains one of the largest fisheries in the United States, as well as wildlife resources that support valuable tourist and subsistence economies. The fish and wildlife populations in turn are sustained by a food web linking primary producers to apex predators through the zooplankton community. Recent shifts in climate toward warmer conditions may threaten these resources by altering productivity and trophic relationships in the ecosystem on the southeastern Bering Sea shelf. We examined the zooplankton community near the Pribilof Islands and on the middle shelf of the southeastern Bering Sea in summer of 1999 and 2004 to document differences and similarities in species composition, abundance and biomass by region and year. Between August 1999 and August 2004, the summer zooplankton community of the middle shelf shifted from large to small species. Significant declines were observed in the biomass of large scyphozoans ( Chrysaora melanaster), large copepods ( Calanus marshallae), arrow worms ( Sagitta elegans) and euphausiids ( Thysanoessa raschii, T. inermis) between 1999 and 2004. In contrast, significantly higher densities of the small copepods ( Pseudocalanus spp., Oithona similis) and small hydromedusae ( Euphysa flammea) were observed in 2004 relative to 1999. Stomach analyses of young-of-the-year (age 0) pollock ( Theragra chalcogramma) from the middle shelf indicated a dietary shift from large to small copepods in 2004 relative to 1999. The shift in the zooplankton community was accompanied by a 3-fold increase in water-column stability in 2004 relative to 1999, primarily due to warmer water above the thermocline, with a mean temperature of 7.3 °C in 1999 and 12.6 °C in 2004. The elevated water-column stability and warmer conditions may have influenced the zooplankton composition by lowering summer primary production and selecting for species more tolerant of a warm, oligotrophic environment. A time series of temperature from the middle shelf indicates that the warmer conditions in 2004 are part of a trend rather than an expression of interannual variability. These results suggest that if climate on the Bering Sea shelf continues to warm, the zooplankton community may shift from large to small taxa which could strongly impact apex predators and the economies they support.

Phytoplankton Distribution in Relation to Environmental Drivers on the North West European Shelf Sea.

PubMed

Siemering, Beatrix; Bresnan, Eileen; Painter, Stuart C; Daniels, Chris J; Inall, Mark; Davidson, Keith

2016-01-01

The edge of the North West European Shelf (NWES) is characterised by a steep continental slope and a northward flowing slope current. These topographic/hydrographic features separate oceanic water and shelf water masses hence potentially separate phytoplankton communities. The slope current may facilitate the advective transport of phytoplankton, with mixing at the shelf edge supporting nutrient supply and therefore phytoplankton production. On the west Scottish shelf in particular, little is known about the phytoplankton communities in and around the shelf break and adjacent waters. Hence, to improve our understanding of environmental drivers of phytoplankton communities, biological and environmental data were collected on seven cross-shelf transects across the Malin and Hebridean Shelves during autumn 2014. Density profiles indicated that shelf break and oceanic stations had a 100 m deep mixed surface layer while stations on the shelf were generally well mixed. Analysis of similarity and multidimensional scaling of phytoplankton counts revealed that phytoplankton communities on the shelf were significantly different to those found at the shelf break and at oceanic stations. Shelf stations were dominated by dinoflagellates, with diatoms contributing a maximum of 37% of cells. Shelf break and oceanic stations were also dinoflagellate dominated but displayed a lower species diversity. Significant difference between shelf and shelf break stations suggested that the continental slope limited cross shelf phytoplankton exchange. Northern and southern phytoplankton communities on the shelf were approximately 15% dissimilar while there was no latitudinal gradient for stations along the slope current, suggesting this current provided south to north connectivity. Fitting environmental data to phytoplankton ordination showed a significant relationship between phytoplankton community dissimilarities and nutrient concentrations and light availability on the shelf compared to shelf break and oceanic stations in the study area.

Phytoplankton Distribution in Relation to Environmental Drivers on the North West European Shelf Sea

PubMed Central

Siemering, Beatrix; Bresnan, Eileen; Painter, Stuart C.; Daniels, Chris J.; Inall, Mark; Davidson, Keith

2016-01-01

The edge of the North West European Shelf (NWES) is characterised by a steep continental slope and a northward flowing slope current. These topographic/hydrographic features separate oceanic water and shelf water masses hence potentially separate phytoplankton communities. The slope current may facilitate the advective transport of phytoplankton, with mixing at the shelf edge supporting nutrient supply and therefore phytoplankton production. On the west Scottish shelf in particular, little is known about the phytoplankton communities in and around the shelf break and adjacent waters. Hence, to improve our understanding of environmental drivers of phytoplankton communities, biological and environmental data were collected on seven cross-shelf transects across the Malin and Hebridean Shelves during autumn 2014. Density profiles indicated that shelf break and oceanic stations had a 100 m deep mixed surface layer while stations on the shelf were generally well mixed. Analysis of similarity and multidimensional scaling of phytoplankton counts revealed that phytoplankton communities on the shelf were significantly different to those found at the shelf break and at oceanic stations. Shelf stations were dominated by dinoflagellates, with diatoms contributing a maximum of 37% of cells. Shelf break and oceanic stations were also dinoflagellate dominated but displayed a lower species diversity. Significant difference between shelf and shelf break stations suggested that the continental slope limited cross shelf phytoplankton exchange. Northern and southern phytoplankton communities on the shelf were approximately 15% dissimilar while there was no latitudinal gradient for stations along the slope current, suggesting this current provided south to north connectivity. Fitting environmental data to phytoplankton ordination showed a significant relationship between phytoplankton community dissimilarities and nutrient concentrations and light availability on the shelf compared to shelf break and oceanic stations in the study area. PMID:27736920

Distribution of planktonic cnidarians in response to South Atlantic Central Water intrusion in the South Brazilian Bight

NASA Astrophysics Data System (ADS)

Nogueira Júnior, Miodeli; Brandini, Frederico P.; Codina, Juan C. U.

2014-10-01

Five oceanographic cruises were made between November 2005 and June 2006, sampling a cross-shelf transect off the South Brazilian Bight (SBB; 26°46‧S) to follow the seasonal development of the South Atlantic Central Water (SACW) intrusion over the shelf and its influence on the assemblage of planktonic cnidarians. An onshore wind-driven bottom intrusion of the SACW was clearly perceptible, reaching the coast in January. From March onward, the SACW influence was gradually displaced seaward due to wind and tidal mixing. By late June the SACW influence was offshore and the inshore was dominated by low-salinity waters (<34.5). The abundance, distribution, and general taxonomic composition of both medusae and siphonophores were strongly influenced by the onshore intrusion of the SACW. An inshore-offshore gradient was clear. The Canonical Correspondence Analysis suggested that coastal species - dominated by Liriope tetraphylla, actinula larvae and Muggiaea kochi - were mostly related to food availability and a vertically mixed environment inshore, and their abundance and extent were reduced during intrusion periods. In contrast, species with offshore affinities tended to increase their abundance and distribution during intrusion periods, and were mostly related to the presence of thermal stratification and a deep chlorophyll maximum layer. Most of these offshore species, such as Aglaura hemistoma, Rhopalonema velatum and many calycophorans, are associated with the warm upper layer. However, high concentrations of large (>20 mm in diameter) Solmaris corona were observed exclusively in cold waters, suggesting this medusa is a SACW indicator.

Updating the distribution and habitat pattern of Maurolicus stehmanni (Sternoptychidae, Stomiformes) in the Southwest Atlantic Ocean

NASA Astrophysics Data System (ADS)

Belleggia, Mauro; Villanueva-Gomila, Gabriela Lujan; Buratti, Claudio; Colombo, Gustavo Alvarez; Figueroa, Daniel Enrique; Venerus, Leonardo Ariel

2018-06-01

We updated the distribution and habitat patterns of Maurolicus stehmanni in the Southwest Atlantic Ocean by compiling data obtained from research surveys conducted on the Argentinean continental shelf, as well as from opportunistic records. This paper confirms the presence of M. stehmanni in the Argentinean continental shelf, extending its southernmost distributional limit by ca. 1000 km (from 43.0°S to 52.2°S). Adult specimens of M. stehmanni were collected in various locations from 2004 to 2016. Eggs and larvae of Maurolicus spp. were caught during ichthyoplankton tows carried out from 2003 to 2013. The present paper furthermore extends the habitat type in which this species was recorded: specimens were found in the inner continental shelf (between 46.2°S and 52.2°S) instead of the shelf break and continental slope. Two specimens were found lying dead upon the beach of Puerto Madryn, Nuevo Gulf (42.8°S). The presence of eggs and larvae in coastal embayments (San Matías and San José gulfs), in concomitant occurrence with adults, may suggest the establishment of this species in the region.

Composition and provenance of terrigenous organic matter transported along submarine canyons in the Gulf of Lion (NW Mediterranean Sea)

NASA Astrophysics Data System (ADS)

Pasqual, Catalina; Goñi, Miguel A.; Tesi, Tommaso; Sanchez-Vidal, Anna; Calafat, Antoni; Canals, Miquel

2013-11-01

Previous projects in the Gulf of Lion have investigated the path of terrigenous material in the Rhone deltaic system, the continental shelf and the nearby canyon heads. This study focuses on the slope region of the Gulf of Lion to further describe particulate exchanges with ocean’s interior through submarine canyons and atmospheric inputs. Nine sediment traps were deployed from the heads to the mouths of Lacaze-Duthiers and Cap de Creus submarine canyons and on the southern open slope from October 2005 to October 2006. Sediment trap samples were analyzed by CuO oxidation to investigate spatial and temporal variability in the yields and compositional characteristics of terrigenous biomarkers such as lignin-derived phenols and cutin acids. Sediment trap data show that the Dense Shelf Water Cascading event that took place in the months of winter 2006 (January, February and March) had a profound impact on particle fluxes in both canyons. This event was responsible for the majority of lignin phenol (55.4%) and cutin acid (42.8%) inputs to submarine canyons, with lignin compositions similar to those measured along the mid- and outer-continental shelf, which is consistent with the resuspension and lateral transfer of unconsolidated shelf sediment to the canyons. The highest lithogenic-normalized lignin derived phenols contents in sediment trap samples were found during late spring and summer at all stations (i.e., 193.46 μg VP g-1 lithogenic at deep slope station), when river flow, wave energy and total particle fluxes were relatively low. During this period, lignin compositions were characterized by elevated cinnamyl to vanillyl phenol ratios (>3) at almost all stations, high p-coumaric to ferulic acid ratios (>3) and high yields of cutin acids relative to vanillyl phenols (>1), all trends that are consistent with high pollen inputs. Our results suggest marked differences in the sources and transport processes responsible for terrigenous material export along submarine canyons, mainly consisting of fluvial and shelf sediments during winter and atmospheric dust inputs during spring and summer.

Sources and Distribution of Organic Matter in Sediments of the Louisiana Continental Shelf

EPA Science Inventory

Both riverine and marine sources of organic matter (OM) contribute to sediment organic pools, and either source can contribute significantly to sediment accumulation, burial, and remineralization rates on river dominated continental shelf systems. For the Louisiana continental sh...

Use of riverine through reef habitat systems by dog snapper ( Lutjanus jocu ) in eastern Brazil

NASA Astrophysics Data System (ADS)

Moura, Rodrigo L.; Francini-Filho, Ronaldo B.; Chaves, Eduardo M.; Minte-Vera, Carolina V.; Lindeman, Kenyon C.

2011-11-01

The early life history of Western Atlantic snappers from the Southern hemisphere is largely unknown. Habitat use of different life stages (i.e. size categories) of the dog snapper ( Lutjanus jocu) was examined across the largest South Atlantic reef-estuarine complex (Abrolhos Shelf, Brazil, 16-19° S). Visual surveys were conducted in different habitats across the shelf (estuary, inner-shelf reefs and mid-shelf reefs). Lutjanus jocu showed higher densities on inner-shelf habitats, with a clear increase in fish size across the shelf. Individuals <7 cm were associated with both the estuary (mangrove and rocky habitats) and inner-shelf reefs (particularly shallow fore-reefs and tide pools). Individuals ranging 10-30 cm were broadly distributed, but consistently more abundant on inner-shelf reefs. Individuals between 30 and 40 cm were more common on mid-shelf reefs, while individuals >40 cm were recorded only on mid-shelf reefs. Literature data indicate that individuals ranging 70-80 cm are common on deep offshore reefs. This pattern suggests that the dog snapper performs ontogenetic cross-shelf migrations. Protecting portions of the different habitats used by the dog snapper during its post-settlement life cycle is highlighted as an important conservation and management measure.

Environmental drivers of vertical distribution in diapausing Calanus copepods in the Northwest Atlantic

NASA Astrophysics Data System (ADS)

Krumhansl, Kira A.; Head, Erica J. H.; Pepin, Pierre; Plourde, Stéphane; Record, Nicholas R.; Runge, Jeffrey A.; Johnson, Catherine L.

2018-03-01

Copepods of the genus Calanus play a critical trophic role in the North Atlantic ecosystems, where they serve as an important source of energy-rich food for fish and marine mammals, including the endangered North Atlantic right whale. As a strategy for coping with unfavorable near-surface conditions, Calanus enter diapause and migrate to deep water in late summer and fall after feeding and accumulating lipid stores in spring and summer. In order to assess the most important physical drivers of vertical distribution of diapausing Calanus, we synthesized existing depth-stratified abundance data of Calanus finmarchicus and Calanus hyperboreus from the Northwest Atlantic continental shelf and slope regions, spanning Newfoundland in the northeast to the Gulf of Maine in the southwest. Bottom depth strongly constrained the depth and shape of vertical distributions, with distributions becoming deeper and less compact as bottom depth increased. Diapausing Calanus, observed across a broad range of temperature (T) and in-situ density (σ) conditions (T = -1.0 to 14.4 °C, σ = 25.3-28.1 kg m-3), tended to distribute at depths with the coldest temperatures locally available. Over the shelf, diapausing Calanus in the GOM and SS generally did not have access to temperatures considered optimal for diapause (<5 °C), in many cases occurring at temperatures well above this threshold. Diapausing Calanus in both habitats were most commonly below the Cold Intermediate Layer (CIL), a feature formed through wind-driven mixing during the winter, but this effect was more obvious over the shelf than in slope waters. Our analysis highlights key differences in the vertical distributions of diapausing Calanus over the shelf vs. the slope, having regional implications for ecological dynamics and population persistence in the face of warming temperatures. In general, understanding factors that influence vertical distributions of diapausing Calanus will allow us to more accurately predict how the environmental conditions they encounter while overwintering may shift during climate change, which has implications for survival through diapause, and consequently, shelf-wide population dynamics.

Mapping Mesophotic Reefs Along the Brazilian Continental Margin

NASA Astrophysics Data System (ADS)

Bastos, A.; Moura, R.; Amado Filho, G.; Ferreira, L.; Boni, G.; Vedoato, F.; D'Agostini, D.; Lavagnino, A. C.; Leite, M. D.; Quaresma, V.

2017-12-01

Submerged or drowned reefs constitute an important geological record of sea level variations, forming the substrate for the colonization of modern benthic mesophotic communities. Although mapping mesophotic reefs has increased in the last years, their spatial distribution is poorly known and the worldwide occurrence of this reef habitat maybe underestimated. The importance in recognizing the distribution of mesophotic reefs is that they can act as a refuge for corals during unsuitable environmental conditions and a repository for shallow water corals. Here we present the result of several acoustic surveys that mapped and discovered new mesophotic reefs along the Eastern and Equatorial Brazilian Continental Margin. Seabed mapping was carried out using multibeam and side scan sonars. Ground truthing was obtained using drop camera or scuba diving. Mesophotic reefs were mapped in water depths varying from 30 to 100m and under distinct oceanographic conditions, especially in terms of river load input and shelf width. Reefs showed distinct morphologies, from low relief banks and paleovalleys to shelf edge ridges. Extensive occurrence of low relief banks were mapped along the most important coralline complex province in the South Atlantic, the Abrolhos Shelf. These 30 to 40m deep banks, have no more than 3 meters in height and may represent fringing reefs formed during sea level stabilization. Paleovalleys mapped along the eastern margin showed the occurrence of coralgal ledges along the channel margins. Paleovalleys are usually deeper than 45m and are associated with outer shelf rhodolith beds. Shelf edge ridges (80 to 120m deep) were mapped along both margins and are related to red algal encrusting irregular surfaces that have more than 3m in height, forming a rigid substrate for coral growth. Along the Equatorial Margin, off the Amazon mouth, shelf edge patch reefs and rhodolith beds forming encrusting surfaces and shelf edge ridges were mapped in water depths greater than 100m. Thus, the occurrence of mesophotic reefs along the Brazilian Margin is influenced by transgressive morphological features, which could be used as a surrogate for mesophotic reef distribution. The extensive occurrence of rhodolith beds on the outer shelf characterizes most of these reefs.

Influence of the Kingak Shale ultimate shelf margin on frontal structures of the Brooks Range in the National Petroleum Reserve in Alaska

USGS Publications Warehouse

Stier, Natalie E.; Connors, Christopher D.; Houseknecht, David W.

2014-01-01

The Jurassic–Lower Cretaceous Kingak Shale in the National Petroleum Reserve in Alaska (NPRA) includes several southward-offlapping depositional sequences that culminate in an ultimate shelf margin, which preserves the depositional profile in southern NPRA. The Kingak Shale thins abruptly southward across the ultimate shelf margin and grades into condensed shale, which is intercalated with underlying condensed shale and chert of the Upper Triassic Shublik Formation and overlying condensed shale of the Lower Cretaceous pebble shale unit and the gamma-ray zone (GRZ) of the Hue Shale. This composite of condensed shale forms a thin (≈300-meter) and mechanically weak section between much thicker and mechanically stronger units, including the Sadlerochit and Lisburne Groups below and the sandstone-prone foredeep wedge of the Torok Formation above. Seismic interpretation indicates that the composite condensed section acted as the major detachment during an Early Tertiary phase of deformation in the northern foothills of the Brooks Range and that thrust faults step up northward to the top of the Kingak, or to other surfaces within the Kingak or the overlying Torok. The main structural style is imbricate fault-bend folding, although fault-propagation folding is evident locally, and large-displacement thrust faults incorporate backthrusting to form structural wedges. The Kingak ultimate shelf margin served as a ramp to localize several thrust faults, and the spatial relationship between the ultimate shelf margin and thrust vergence is inferred to have controlled many structures in southern NPRA. For example, the obliqueness of the Carbon Creek anticline relative to other structures in the foothills is the result of northward-verging thrust faults impinging obliquely on the Kingak ultimate shelf margin in southwestern NPRA.

Diagenetic fate of organic contaminants on the Palos Verdes Shelf, California

USGS Publications Warehouse

Eganhouse, R.P.; Pontolillo, J.; Leiker, T.J.

2000-01-01

Municipal wastes discharged through deepwater submarine outfalls since 1937 have contaminated sediments of the Palos Verdes Shelf. A site approximately 6-8 km downcurrent from the outfall system was chosen for a study of the diagenetic fate of organic contaminants in the waste-impacted sediments. Concentrations of three classes of hydrophobic organic contaminants (DDT + metabolites, polychlorinated biphenyls (PCBs), and the long-chain alkylbenzenes) were determined in sediment cores collected at the study site in 1981 and 1992. Differences between the composition of effluent from the major source of DDT (Montrose Chemical) and that found in sediments suggests that parent DDT was transformed by hydrolytic dehydrochlorination during the earliest stages of diagenesis. As a result, p,p'-DDE is the dominant DDT metabolite found in shelf sediments, comprising 60-70% of ??DDT. The p,p-DDE/p,p'-DDMU concentration ratio decreases with increasing sub-bottom depth in sediment cores, indicating that reductive dechlorination of p,p'-DDE is occurring. Approximately 9-23% of the DDE inventory in the sediments may have been converted to DDMU since DDT discharges began ca. 1953. At most, this is less than half of the decline in p,p'-DDE inventory that has been observed at the study site for the period 1981-1995. Most of the observed decrease is attributable to remobilization by processes such as sediment mixing coupled to resuspension, contaminant desorption, and current advection. Existing field data suggest that the in situ rate of DDE transformation is 102-103 times slower than rates determined in recent laboratory microcosm experiments (Quensen, J.F., Mueller, S.A., Jain, M.K., Tiedje, J.M., 1998. Reductive dechlorination of DDE to DDMU in marine sediment microcosms. Science, 280, 722-724.). This explains why the DDT composition (i.e. o,p'-, p,p'-isomers of DDE, DDD, DDT) of sediments from this site have not changed significantly since at least 1972. Congener-specific PCB compositions in shelf sediments are highly uniform and show no evidence of diagenetic transformation. Apparently, the agents/factors responsible for reductive dechlorination of DDE are not also effecting alteration of the PCBs. Two types of long-chain alkylbenzenes were found in the contaminated sediments. Comparison of chain length and isomer distributions of the linear alkylbenzenes in wastewater effluent and surficial sediment samples indicate that these compounds undergo biodegradation during sedimentation. Further degradation of the linear alkylbenzenes occurs after burial despite relatively invariant isomer compositions. The branched alkylbenzenes are much more persistent than the linear alkylbenzenes, presumably due to extensive branching of the alkyl side chain. Based on these results, p,p'-DDE, PCBs, and selected branched alkylbenzenes are sufficiently persistent for use in molecular stratigraphy. The linear alkylbenzenes may also provide information on depositional processes. However, their application as quantitative molecular tracers should be approached with caution.

Long-Term Changes in the Distributions of Larval and Adult Fish in the Northeast U.S. Shelf Ecosystem.

PubMed

Walsh, Harvey J; Richardson, David E; Marancik, Katrin E; Hare, Jonathan A

2015-01-01

Many studies have documented long-term changes in adult marine fish distributions and linked these changes to climate change and multi-decadal climate variability. Most marine fish, however, have complex life histories with morphologically distinct stages, which use different habitats. Shifts in distribution of one stage may affect the connectivity between life stages and thereby impact population processes including spawning and recruitment. Specifically, many marine fish species have a planktonic larval stage, which lasts from weeks to months. We compared the spatial distribution and seasonal occurrence of larval fish in the Northeast U.S. Shelf Ecosystem to test whether spatial and temporal distributions changed between two decades. Two large-scale ichthyoplankton programs sampled using similar methods and spatial domain each decade. Adult distributions from a long-term bottom trawl survey over the same time period and spatial area were also analyzed using the same analytical framework to compare changes in larval and adult distributions between the two decades. Changes in spatial distribution of larvae occurred for 43% of taxa, with shifts predominately northward (i.e., along-shelf). Timing of larval occurrence shifted for 49% of the larval taxa, with shifts evenly split between occurring earlier and later in the season. Where both larvae and adults of the same species were analyzed, 48% exhibited different shifts between larval and adult stages. Overall, these results demonstrate that larval fish distributions are changing in the ecosystem. The spatial changes are largely consistent with expectations from a changing climate. The temporal changes are more complex, indicating we need a better understanding of reproductive timing of fishes in the ecosystem. These changes may impact population productivity through changes in life history connectivity and recruitment, and add to the accumulating evidence for changes in the Northeast U.S. Shelf Ecosystem with potential to impact fisheries and other ecosystem services.

Long-Term Changes in the Distributions of Larval and Adult Fish in the Northeast U.S. Shelf Ecosystem

PubMed Central

2015-01-01

Many studies have documented long-term changes in adult marine fish distributions and linked these changes to climate change and multi-decadal climate variability. Most marine fish, however, have complex life histories with morphologically distinct stages, which use different habitats. Shifts in distribution of one stage may affect the connectivity between life stages and thereby impact population processes including spawning and recruitment. Specifically, many marine fish species have a planktonic larval stage, which lasts from weeks to months. We compared the spatial distribution and seasonal occurrence of larval fish in the Northeast U.S. Shelf Ecosystem to test whether spatial and temporal distributions changed between two decades. Two large-scale ichthyoplankton programs sampled using similar methods and spatial domain each decade. Adult distributions from a long-term bottom trawl survey over the same time period and spatial area were also analyzed using the same analytical framework to compare changes in larval and adult distributions between the two decades. Changes in spatial distribution of larvae occurred for 43% of taxa, with shifts predominately northward (i.e., along-shelf). Timing of larval occurrence shifted for 49% of the larval taxa, with shifts evenly split between occurring earlier and later in the season. Where both larvae and adults of the same species were analyzed, 48% exhibited different shifts between larval and adult stages. Overall, these results demonstrate that larval fish distributions are changing in the ecosystem. The spatial changes are largely consistent with expectations from a changing climate. The temporal changes are more complex, indicating we need a better understanding of reproductive timing of fishes in the ecosystem. These changes may impact population productivity through changes in life history connectivity and recruitment, and add to the accumulating evidence for changes in the Northeast U.S. Shelf Ecosystem with potential to impact fisheries and other ecosystem services. PMID:26398900

Prediction of Ripple Properties in Shelf Seas. Mark 2 Predictor for Time Evolution

DTIC Science & Technology

2005-12-01

respectively. It is seen in Figure 15 that the time -evolving ripple predictor manages to predict many of the features seen in the data: the growth from a...UNCLASSIFIED Prediction of Ripple Properties in Shelf Seas Mark 2 Predictor for Time Evolution Final Technical Report Prepared for US Office of Naval...distribution is unlimited j~j HR Wallingford UNCLASSIFIED Prediction of Ripple Properties in Shelf Seas Mark 2 Predictor for Time Evolution

Sediment studies associated with drilling activity on a tropical shallow shelf.

PubMed

Souza, Claudete R; Vital, Helenice; Melo, Germano; Souza, Cleuneide R; da Silva Nogueira, Mary Lucia; Tabosa, Werner Farkatt

2015-02-01

Environmental monitoring studies were developed in an area located on the outer shelf in the Potiguar Basin, Brazilian equatorial margin. This tropical shelf represents a modern, highly dynamic mixed carbonate-siliciclastic system. Field sampling was carried out during 3 cruises surrounding a shallow-water exploratory well to compare sediment properties of the seafloor, including grain size, texture, mineral composition, carbonate content, and organic matter, prior to drilling with samples obtained 3 and 12 months after drilling. The sample grid used had 16 stations located along 4 radials from 50 m the well up to a distance of 500 m. Sediments were analyzed in the first 0-2 cm and 0-10 cm layers. The results show that sedimentary cover around the well is dominated by bioclastic sediments, poor to very poorly sorted. Only minor sedimentological variations occurred in the area affected by drilling operations. The most noticeable effects were observed during the second cruise, in terms of a change in grain size distribution associated to a slight increase in siliciclastic content. This impact occurred in the most surficial sediment (0-2 cm), in the radials closest to the well (50 m), and could suggest the effects of drilling. However, in the third cruise, 1 year after drilling, the sediments return to show the same characteristics as in the first cruise. These results show no significant sedimentological variations due to drilling activity and indicate that ocean dynamics in this area was high enough to recover the environment original characteristics.

Shelf-Slope Exchanges near Submarine Canyons in the Southern Mid-Atlantic Bight

NASA Astrophysics Data System (ADS)

Wang, H.; Gong, D.

2016-02-01

Shelf-slope exchange processes are major physical drivers of biological productivity near the shelf-break. Observations from two Slocum ocean gliders in Fall 2013 are used to explore the driving mechanisms of cross-shelf-slope exchanges near Norfolk Canyon and Washington Canyon in the southern Mid-Atlantic Bight. Offshore excursion of bottom "cold pool" water, and shoreward intrusion of slope water at surface layer and thermocline depth occurred during northeasterly along-shelf winds. The saline intrusions of surface slope water resided between the cold pool and surface shelf water, and reached the bottom on the outer and mid-shelf, while the offshore excursion of cold pool water was found between the surface and intermediate slope-water over the canyon. Ekman transport calculation shows wind-driven cross-shelf transport can partially explain this interleaving pattern of intrusions. Scaling analysis of double diffusive processes demonstrate that they also likely played a role in the cross-shelf-slope exchange. A unique canyon upwelling event was captured in and around Washington Canyon during a period of southwesterly along-shelf wind and along-shelf flow to the northeast. The water mass distributions and isopycnal responses in both along-canyon and cross-canyon transects are consistent with scaling analysis and numerical studies of canyon upwelling. Temperature-Salinity properties of water masses in the canyon suggest active mixing between shelf and slope water masses near the canyon head. These results point to the importance of wind, double diffusion, and canyon topography on shelf-slope exchange in the MAB.

Sorting and degradation of permafrost-derived organic carbon during across-shelf transport in the Laptev and East Siberian shelves

NASA Astrophysics Data System (ADS)

Tesi, Tommaso; Semiletov, Igor; Dudarev, Oleg; Andersson, August; Gustafsson, Örjan

2015-04-01

The flux of permafrost-derived organic carbon to the vast Siberian marginal seas has been receiving growing attention because its magnitude is expected to considerably increase due to changes in both river discharge and coastal permafrost stability. To what extent this relocated terrigenous organic carbon (TerrOC) pool will affect climate and biogeochemistry is currently unknown but it will largely depend on its reactivity in the marine environment. This study seeks an improved mechanistic understanding of TerrOC cycling during across-shelf transport in the vast East Siberian Arctic Seas (ESAS). Surface sediments were collected in both river-dominated and coastal erosion-dominated regions as well as at increasing distances from the shore. The organic composition in different density, size and settling velocity fractions was characterized using bulk parameters (δ13C and Δ14C) and terrigenous biomarkers including CuO-derived reaction products (lignin phenols and cutin acids) and solvent extractable HMW lipids (n-alkanoic acids, n-alkanols and n-alkanes). Key insights were gained by understanding how different TerrOC pools, operationally defined at bulk and molecular level, are distributed among different density, size and settling velocity fractions and how they change over the margin in relative concentration and composition. Our results show that the partitioning and mobility of TerrOC pools is intimately linked to density and size of particles. A large fraction of TerrOC entering the margin is associated with large, lignin-rich plant fragments which are hydrodynamically retained in coastal sediments. The across-shelf transport of TerrOC occurs primarily in the form of mineral-bound OC through the preferential mobilization of fine lithogenic particles rich in HMW lipids. Despite the mineral-association, noticeable decrease of TerrOC was observed at molecular and bulk level which indicates extensive degradation during transport across the margin. Altogether our results indicate that, considering the susceptibility of TerrOC towards degradation during transport, the expected increase of river runoff and coastal erosion in the Siberian region followed by TerrOC mobilization across the shelf will likely represent a positive feedback to climate (e.g., increased pCO2) and it will affect the Arctic biogeochemistry (e.g., ocean acidification).

Growing Crack in Antarctica Larsen C Ice Shelf Spotted by NASA MISR

NASA Image and Video Library

2016-08-31

Project MIDAS, a United Kingdom-based group that studies the Larsen Ice Shelf in Antarctica, reported Aug. 18, 2016, that a large crack in the Larsen C shelf has grown by another 13 miles (22 kilometers) in the past six months. The crack is now more than 80 miles (130 kilometers) long. Larsen C is the fourth largest ice shelf in Antarctica, with an area of about 19,300 square miles (50,000 square kilometers), greater than the size of Maryland. Computer modeling by Project MIDAS predicts that the crack will continue to grow and eventually cause between nine and twelve percent of the ice shelf to collapse, resulting in the loss of 2,300 square miles (6,000 square kilometers) of ice -- more than the area of Delaware. This follows the collapse of the Larsen B shelf in 2002 and the Larsen A shelf in 1995, which removed about 1,255 square miles (3,250 square kilometers) and 580 square miles (1,500 square kilometers) of ice, respectively. The Multiangle Imaging SpectroRadiometer (MISR) instrument aboard NASA's Terra satellite flew over Larsen C on Aug. 22, 2016. The MISR instrument views Earth with nine cameras pointed at different angles, which provides information about the texture of the surface. On the left is a natural-color image of the shelf from MISR's vertical-viewing camera. Antarctica is slowly emerging from its polar night, and the low light gives the scene a bluish tint. The Larsen C shelf is on the left, while thinner sea ice is present on the right. A variety of cracks are visible in the Larsen C shelf, all appearing roughly the same. The image is about 130 by 135 miles (210 by 220 kilometers) in size. On the right is a composite image made by combining data from MISR's 46-degree backward-pointing camera (plotted as blue), the vertical-pointing camera (plotted as green), and the 46-degree forward-pointing camera (plotted as red). This has the effect of highlighting surface roughness; smooth surfaces appear as blue-purple, while rough surfaces appear as orange. Clouds near the upper left appear multi-hued because their elevation above the surface causes the different angular views to be slightly displaced. In this composite, the difference between the rough sea ice and the smoother ice shelf is immediately apparent. An examination of the cracks in the ice shelf shows that the large crack Project MIDAS is tracking (indicated by an arrow) is orange in color, demonstrating that it is actively growing. These data were acquired during Terra orbit 88717 http://photojournal.jpl.nasa.gov/catalog/PIA20894

Shelf width and river base level on active margins controlled by a combination of eustasy and local uplift rate, illustration from the Pacific NW of the United States.

NASA Astrophysics Data System (ADS)

Malatesta, L. C.; Finnegan, N. J.; Kushwaha, G.

2017-12-01

Sea level defines the elevation where wave-base erosion is the dominant erosive process. Hence, submarine erosion of the margin and creation of a continental shelf depend on the time distribution of sea level relative to bedrock by correcting eustasy for local rock uplift. Eustasy and wave-base erosion also impact most fluvial systems on Earth by affecting the vertical and lateral position of their lower boundary condition, the coastline. When uplift rate is slow, the concentration of wave-base erosion on a restricted range of elevation promotes the creation of wide shelves and of a relatively stable average base level for coastal rivers. While interfluves above the shelf are steep, fluvial valleys in slow uplift regions grade into the shelf and form estuaries that trap sediment at high stand. Alternatively, a fast coastal uplift rate distributes wave-base erosion over a wide range of bedrock elevations that are quickly uplifted above the eustatic range, preventing the beveling of a shelf and the establishment of a river profile equilibrated around an average sea-level. In that case, river base level is highly dependent on the gradient of the continental slope. We show that the width of the shelf is inversely correlated with the uplift rate along the Oregon and northern California coast. The extent of the shelf can be a valuable counterpart to (often absent) marine terraces that provides a record for coastline retreat, local uplift rate and river base level.

West Florida Shelf: A natural laboratory for the study of ocean acidificiation

USGS Publications Warehouse

Hallock, Pamela; Robbins, Lisa L.; Larson, Rebekka A.; Beck, Tanya; Schwing, Patrick; Martinez-Colon, Michael; Gooch, Brad

2010-01-01

Declining oceanic pH and carbonate-ion concentrations are well-known consequences of increased atmospheric and surface-ocean partial pressure of carbon dioxide (pCO2). The possible subject of shifts in seawater carbonate chemistry on biocalcification and survival rates of marine organisms provides questions amenable to both experimental and field study (Kleypas and Langdon, 2006). To date, limited quantitative data exist with which to formalize and test hypotheses regarding such impacts, particularly in continental-shelf settings. The continental shelves of Florida provide an ideal natural laboratory in which to test latitudinal (and temperature and depth) shifts in habitat ranges of calcifying organisms. Both the east and west Florida shelves extend from warm temperate to subtropical latitudes; additionally, the west Florida shelf has very little siliciclastic influx to mask the carbonate production. This study utilizes the natural laboratory of the west and southwest Florida shelf (fig 1.1) to examine the transition from foramol (predominately foraminifera and molluscan) carbonate sediments, characteristic of the west-central Florida shelf, to chlorozoan (algal and coral) sediments characteristic of the southwest Florida shelf. The west Florida shelf is a mixed siliciclastic carbonate ramp that to the south transitions to the carbonate-dominated southwest Florida shelf (Enos, 1977; Brooks and others, 2003). The west Florida shelf is a distally steepened carbonate ramp that is ~250 kilometers (km) wide (Read, 1985). It is covered by a veneer of unconsolidated sediment consisting of mainly biogenic carbonate and quartz in the near shore, with subordinate amounts of phosphate. The sediment-distribution pattern is largely a function of proximity to source, with physical processes playing a minor role in distribution. The carbonate sand-and-gravel fraction is produced by organisms within the depositional basin of the west Florida shelf (Brooks and others, 2003). The southwest Florida shelf is a rimmed carbonate margin where organisms produce virtually all of the substrate; it also exhibits a greater sediment thickness as compared to the west Florida shelf (Enos, 1977). Temperature, which is usually associated with latitude, plays a major role in locations of foramol versus chlorozoan assemblages, but other factors beyond latitude influence temperature on the west and southwest Florida shelves. The potential of cooler, deep-water upwelling and transport over the bottom waters of the shelf may have a significant role in the species assemblage at the sediment/water interface and ultimately on location of foramol versus chlorozoan production. Deep water transported onto and over the shelf may also have environmental ramifications beyond temperature by bringing in water of different chemistry.

NAC-NOR mutations in tomato Penjar accessions attenuate multiple metabolic processes and prolong the fruit shelf life.

PubMed

Kumar, Rakesh; Tamboli, Vajir; Sharma, Rameshwar; Sreelakshmi, Yellamaraju

2018-09-01

Several Penjar accessions of tomato grown in the Mediterranean exhibit prolonged shelf life and harbor alcobaca mutation. To uncover the metabolic basis underlying shelf life, we compared four Penjar accessions to Ailsa Craig. Three accessions bore alcobaca mutation, whereas the fourth was a novel NAC-NOR allele. Cuticle composition of Penjars varied widely during fruit ripening. All Penjars exhibited delayed ripening, prolonged on-vine and off-vine shelf life, low ethylene emission, and carotenoid levels. Metabolic profiling revealed shifts in Krebs cycle intermediates, amino acids, and γ-aminobutyric acid levels indicating the attenuation of respiration in Penjars during post-harvest storage. Penjar fruits also showed concerted downregulation of several cell-wall modifying genes and related metabolites. The high ABA and sucrose levels at the onset of senescence in Penjar fruits likely contribute to reduced water loss. Our analyses reveal that the attenuation of various metabolic processes by NAC-NOR mutation likely prolongs the shelf life of Penjar fruits. Copyright © 2018 Elsevier Ltd. All rights reserved.

Shelf Sea Oxygen Dynamics: A year of Glider Measurements

NASA Astrophysics Data System (ADS)

Williams, C. A. J.; Palmer, M.; Mahaffey, C.; Jardine, J.

2016-02-01

Oxygen (O) is involved in most biogeochemical processes in the ocean, and dissolved oxygen (DO) is a well-established indicator for biological activity via the estimate of apparent oxygen utilisation (AOU). In the deep waters of the open ocean, the AOU provides a valuable insight into the ocean's biological carbon pump. However, in the physically dynamic and highly productive shallow shelf seas, interpretation of the O distribution and the magnitude of AOU is complex. Physical processes, such as diapycnal mixing, entrainment and horizontal advection act to ventilate waters below the thermocline and thus increase O and decrease AOU. In contrast, biological remineralisation of organic material below the thermocline will consume O and increase AOU. Here, we use 1 year of high-resolution data from >20 glider deployments in the seasonally stratified NW European Shelf Sea to identify and quantify the physical and biological processes that control the DO distribution and magnitude of AOU in shelf seas. A 200km transect between the shelf edge and the central Celtic Sea (CCS) was repeated between November 2014 and August 2015, thus capturing key periods in the seasonal cycling in shelf seas, specifically the onset of stratification, the spring bloom, stratified summer period and breakdown of stratification. The gliders collected data for DO, temperature, salinity, chlorophyll fluorescence, CDOM, backscatter and turbulence. In addition, direct measurements of turbulent dissipation from the Ocean Microstructure Glider deployed during the campaign provided estimates of mixing at CCS and the shelf break, allowing accurate quantification of the vertical fluxes of O. At the end of the stratified period the DO concentration was higher and AOU was lower at the shelf break (80 µM) compared to at CCS on shelf (>95 µM) (Fig 1). Estimates of vertical DO fluxes indicate that this horizontal variation in DO and AOU was partly attributed to enhanced mixing via internal waves at the shelf break ventilating waters below the thermocline, rather than decreased biological O consumption at the shelf break. Taking into consideration physical mixing processes, we provide a robust estimate of the biological O consumption over a seasonal cycle and highlight the need to consider the impact of physical processes on O dynamics in shallow shelf sea systems.

Habitat Specialization in Tropical Continental Shelf Demersal Fish Assemblages

PubMed Central

Fitzpatrick, Ben M.; Harvey, Euan S.; Heyward, Andrew J.; Twiggs, Emily J.; Colquhoun, Jamie

2012-01-01

The implications of shallow water impacts such as fishing and climate change on fish assemblages are generally considered in isolation from the distribution and abundance of these fish assemblages in adjacent deeper waters. We investigate the abundance and length of demersal fish assemblages across a section of tropical continental shelf at Ningaloo Reef, Western Australia, to identify fish and fish habitat relationships across steep gradients in depth and in different benthic habitat types. The assemblage composition of demersal fish were assessed from baited remote underwater stereo-video samples (n = 304) collected from 16 depth and habitat combinations. Samples were collected across a depth range poorly represented in the literature from the fringing reef lagoon (1–10 m depth), down the fore reef slope to the reef base (10–30 m depth) then across the adjacent continental shelf (30–110 m depth). Multivariate analyses showed that there were distinctive fish assemblages and different sized fish were associated with each habitat/depth category. Species richness, MaxN and diversity declined with depth, while average length and trophic level increased. The assemblage structure, diversity, size and trophic structure of demersal fishes changes from shallow inshore habitats to deeper water habitats. More habitat specialists (unique species per habitat/depth category) were associated with the reef slope and reef base than other habitats, but offshore sponge-dominated habitats and inshore coral-dominated reef also supported unique species. This suggests that marine protected areas in shallow coral-dominated reef habitats may not adequately protect those species whose depth distribution extends beyond shallow habitats, or other significant elements of demersal fish biodiversity. The ontogenetic habitat partitioning which is characteristic of many species, suggests that to maintain entire species life histories it is necessary to protect corridors of connected habitats through which fish can migrate. PMID:22761852

Nutrient Distributions, Transports, and Budgets on the Inner Margin of a River-Dominated Continental Shelf

DTIC Science & Technology

2013-10-02

and budgets on the inner margin of a river-dominated continental shelf, J. Geophys. Res. Oceans , 118, 4822–4838, doi:10.1002/jgrc.20362. 1...13/10.1002/jgrc.20362 4822 JOURNAL OF GEOPHYSICAL RESEARCH: OCEANS , VOL. 118, 4822–4838, doi:10.1002/jgrc.20362, 2013 Report Documentation Page Form...shelf, and current velocities obtained from a three-dimensional (3-D) hydro- dynamic model (the Navy Coastal Ocean Model). The budget terms were used to

Tracing the recently increasing anthropogenic Pb inputs into the East China Sea shelf sediments using Pb isotopic analysis.

PubMed

Wang, Deli; Zhao, Zhiqi; Dai, Minhan

2014-02-15

This study examined the Pb content and Pb isotopic composition in a sediment core taken from the East China Sea (ECS) shelf, and it was observed that since 2003 the increasing anthropogenic Pb inputs have impacted as far as the ECS shelf sediments. The ECS shelf sediments were generally characterized with low bulk Pb contents (12.5-15.0 μg/g) and relatively lithogenic Pb isotopic signatures (both HCl-leached and residual fractions). However, elevated Pb records along with lighter Pb isotopic signals have occurred in the post-2003 sediments, as a result of a small but increasing anthropogenic Pb contribution from the heavily human perturbed coastal sediments due to the sharply increasing coal consumption in mainland China since 2003. Copyright © 2013 Elsevier Ltd. All rights reserved.

Impact of Satellite Remote Sensing Data on Simulations of Coastal Circulation and Hypoxia on the Louisiana Continental Shelf

EPA Science Inventory

We estimated surface salinity flux and solar penetration from satellite data, and performed model simulations to examine the impact of including the satellite estimates on temperature, salinity, and dissolved oxygen distributions on the Louisiana continental shelf (LCS) near the ...

Composition and Process for Retarding the Premature Aging of PMR Monomer Solutions and PMR Prepegs

NASA Technical Reports Server (NTRS)

Alston, William B. (Inventor); Gahn, Gloria S. (Inventor)

2000-01-01

Polyimides are derived from solutions of at least one low-boiling organic solvent, e.g. isopropanol containing a mixture of polyimide-forming monomers. The monomeric solutions have an extended shelf life at ambient (room) temperatures as high as 80 C, and consist essentially of a mixture of monoalkyl ester-acids, alkyl diester-diacids and aromatic polyamines wherein the alkyl radicals of the esteracids are derived from lower molecular weight aliphatic secondary alcohols having 3 to 5 carbon atoms per molecule such as isopropanol, secondary butanol, 2-methyl-3-butanol, 2 pentanol or 3-pentanol. The solutions of the polyimide-forming monomers have a substantially improved shelf-life and are particularly useful in the aerospace and aeronautical industry for the preparation of polyimide reinforced fiber composites such as the polyimide cured carbon composites used in jet engines, missiles, and for other high temperature applications.

Ecofriendly Fruit Switches: Graphene Oxide-Based Wrapper for Programmed Fruit Preservative Delivery To Extend Shelf Life.

PubMed

Sharma, Sandeep; Biswal, Badal Kumar; Kumari, Divya; Bindra, Pulkit; Kumar, Satish; Stobdan, Tsering; Shanmugam, Vijayakumar

2018-05-21

According to Food and Agriculture Organization 2015 report, post-harvest agricultural loss accounts for 20-50% annually; on the other hand, reports about preservatives toxicity are also increasing. Hence, preservative release with response to fruit requirement is desired. In this study, acid synthesized in the overripe fruits was envisaged to cleave acid labile hydrazone to release preservative salicylaldehyde from graphene oxide (GO). To maximize loading and to overcome the challenge of GO reduction by hydrazine, two-step activation with ethylenediamine and 4-nitrophenyl chloroformate respectively, are followed. The final composite shows efficient preservative release with the stimuli of the overripe fruit juice and improves the fruit shelf life. The composite shows less toxicity as compared to the free preservative along with the additional scope to reuse. The composite was vacuum-filtered through a 0.4 μm filter paper, to prepare a robust wrapper for the fruit storage.

Geographic and Oceanographic Information within Trace Metals in Moray Eel Otoliths

NASA Astrophysics Data System (ADS)

Savidge, W.; Windom, H.; Buck, C.

2016-02-01

Adult moray eels exhibit high site fidelity to particular reefs. We hypothesized that the trace metal composition of otoliths of eels could potentially provide insight into gradients in oceanographic processes on the South Atlantic Bight continental shelf where eels are resident on patchy hardbottom reefs throughout the entire region. Otoliths of moray eels collected from the mid-shelf of South Carolina were examined for their trace metal composition (Ba, Sr, Pb, Cu, Li, Mg, V, Mn, Zn). Samples were broadly lumped into four regions: "North," "North Cape Romain," "South Cape Romain," and "South". Trace metal composition within otoliths showed no latitudinal trends. However, factor analysis of the trace metals revealed that otoliths from the South Cape Romain region appeared as a compositionally distinct subgroup, based primarily on their Li and Mg content. Recent work on corals (Montagna et al. 2014) has shown the Li/Mg ratio within coral skeletons is sensitive to calcification temperature and can be used as a paleothermometer. If analogous processes influence Li/Mg ratios within otoliths, the data suggest that the bottom water at the South Cape Romain site is colder than other locations along the South Carolina shelf, perhaps as a result of locally enhanced upwelling. Additional samples from NC, SC, GA, and FL are being examined to see if other sites within the South Atlantic Bight show similar patterns. Montagna, P., McCulloch, M., Douville, E., et al. 2014. Li/Mg systematics in scleratinian corals: Calibration of the thermometer. Geochim Cosmochim Acta 132: 288-310.

Pharmaceutical quality of generic isotretinoin products, compared with Roaccutane.

PubMed

Taylor, Peter W; Keenan, Michael H J

2006-03-01

Isotretinoin is the drug of choice for the management of severe recalcitrant nodular acne. Several generic products are available. However, their pharmaceutical quality, in particular particle size distribution, which may affect safety and efficacy is unknown. Hence, prescribing of some generic products may be problematic. To assess the pharmaceutical quality of 14 generic isotretinoin products compared with Roaccutane (F. Hoffmann-La Roche Ltd). Tests were performed according to Roche standard procedures, European and US pharmacopoeia specifications. Tests included isotretinoin content, identity and amount of impurities and degradation products, effect of accelerated shelf-life studies on stability, particle size distribution and composition of non-active ingredients. The 14 isotretinoin products differed by 30-fold in median particle size and showed variation in their non-active ingredients. The average isotretinoin content of Acnotin and Acne-Tretin fell outside the 95-105% Roche specifications. Following accelerated shelf-life tests, only four products retained isotretinoin content within Roche specifications, whilst Acne-Tretin (the only powder formulation) lost 72.5% isotretinoin content. Two generic products exceeded the +/- 2% specification (Ph. Eur.) and a further three exceeded the +/- 1% (USP) for tretinoin content, eight exceeded the 2.54% specification for total impurities and six contained >or= 5 unknown impurities. Isotretinoin-5.6-epoxide content exceeded the 1.04% specification in five generic products. Thirteen generic products failed to match Roaccutane in one or more tests and 11 failed in three or more tests. It cannot be assumed that all generic isotretinoin products are as therapeutically effective or safe as Roaccutane.

Clay mineralogy of surface sediments as a tool for deciphering river contributions to the Cariaco Basin (Venezuela)

NASA Astrophysics Data System (ADS)

Bout-Roumazeilles, V.; Riboulleau, A.; du Châtelet, E. Armynot; Lorenzoni, L.; Tribovillard, N.; Murray, R. W.; Müller-Karger, F.; Astor, Y. M.

2013-02-01

The mineralogical composition of 95 surface sediment samples from the Cariaco Basin continental shelf and Orinoco delta was investigated in order to constrain the clay-mineral main provenance and distribution within the Cariaco Basin. The spatial variability of the data set was studied using a geo-statistical approach that allows drawing representative clay-mineral distribution maps. These maps are used to identify present-day dominant sources for each clay-mineral species in agreement with the geological characteristics of the main river watersheds emptying into the basin. This approach allows (1) identifying the most distinctive clay-mineral species/ratios that determine particle provenance, (2) evaluating the respective contribution of local rivers, and (3) confirming the minimal present-day influence of the Orinoco plume on the Cariaco Basin sedimentation. The Tuy, Unare, and Neveri Rivers are the main sources of clay particles to the Cariaco Basin sedimentation. At present, the Tuy River is the main contributor of illite to the western part of the southern Cariaco Basin continental shelf. The Unare River plume, carrying smectite and kaolinite, has a wide westward propagation, whereas the Neveri River contribution is less extended, providing kaolinite and illite toward the eastern Cariaco Basin. The Manzanares, Araya, Tortuga, and Margarita areas are secondary sources of local influence. These insights shed light on the origin of present-day terrigenous sediments of the Cariaco Basin and help to propose alternative explanations for the temporal variability of clay mineralogy observed in previously published studies.

Examining the mean vertical attenuation of scalar quantum irradiance (PAR) over the Louisiana-Texas shelf (northern Gulf of Mexico)

NASA Astrophysics Data System (ADS)

Lugo-Fernández, A.; Gravois, M.; Green, R. E.; Montgomery, T.

2012-04-01

We examined freshwater and ocean circulation effects on the distribution of vertical quantum diffuse attenuation coefficients (Kq0) of photosyntheticaly available radiation (PAR) in waters of the northern Gulf of Mexico's Louisiana-Texas shelf. Mean Kq0 coefficients were estimated from 509 vertical profiles of PAR collected during 10 cruises spanning 30 months (1992-1994). Vertical profiles of density revealed that the shelf waters are divided into two periods: a stratified period with an upper layer 10 m thick of turbid waters (0.06≤Kq0≤1.18 m-1) and a lower layer of more transparent waters (0.01≤Kq0≤0.49 m-1). The second or non-stratified period consists of a homogenous layer ˜55 m thick and less turbid waters (0.03≤Kq0≤1.00 m-1). Horizontally, the distribution of Kq0 reveals nearshore coastal or case 2 waters followed by offshore oceanic or case 1 waters that separate near the 70-m isobath regardless of time and place. The Kq0 distribution reflects the freshwater influx from the Mississippi and Atchafalaya Rivers which causes a turbid surface trapped river plume, the shelf wind-driven circulation, and ensuing mixing. To investigate Kq0 we used two regression models involving salinity, suspended particulate matter (SPM), chlorophyll-a (Chl), and water depth. The best statistical model explained 57% to 85% of the observed Kq0 variability and involved the reciprocal of water depth, salinity, and SPM. However, a more bio-optically relevant model involving salinity, SPM, and Chl, explained only 32% to 64% of the observed Kq0 variability. Estimates of Kq0 for the upper layer indicate compensation depths of 30-92 m in waters deeper than 70 m which help account for the presence of coral communities on submerged banks near the shelf edge. The observed temporal and spatial distribution of Kq0 agrees qualitatively with that of satellite-derived values of the diffuse attenuation coefficient, Kd(4 9 0) over this shelf.

Surface-water radon-222 distribution along the west-central Florida shelf

USGS Publications Warehouse

Smith, C.G.; Robbins, L.L.

2012-01-01

In February 2009 and August 2009, the spatial distribution of radon-222 in surface water was mapped along the west-central Florida shelf as collaboration between the Response of Florida Shelf Ecosystems to Climate Change project and a U.S. Geological Survey Mendenhall Research Fellowship project. This report summarizes the surface distribution of radon-222 from two cruises and evaluates potential physical controls on radon-222 fluxes. Radon-222 is an inert gas produced overwhelmingly in sediment and has a short half-life of 3.8 days; activities in surface water ranged between 30 and 170 becquerels per cubic meter. Overall, radon-222 activities were enriched in nearshore surface waters relative to offshore waters. Dilution in offshore waters is expected to be the cause of the low offshore activities. While thermal stratification of the water column during the August survey may explain higher radon-222 activities relative to the February survey, radon-222 activity and integrated surface-water inventories decreased exponentially from the shoreline during both cruises. By estimating radon-222 evasion by wind from nearby buoy data and accounting for internal production from dissolved radium-226, its radiogenic long-lived parent, a simple one-dimensional model was implemented to determine the role that offshore mixing, benthic influx, and decay have on the distribution of excess radon-222 inventories along the west Florida shelf. For multiple statistically based boundary condition scenarios (first quartile, median, third quartile, and maximum radon-222 inshore of 5 kilometers), the cross-shelf mixing rates and average nearshore submarine groundwater discharge (SGD) rates varied from 100.38 to 10-3.4 square kilometers per day and 0.00 to 1.70 centimeters per day, respectively. This dataset and modeling provide the first attempt to assess cross-shelf mixing and SGD on such a large spatial scale. Such estimates help scale up SGD rates that are often made at 1- to 10-meter resolution to a coarser but more regionally applicable scale of 1- to 10-kilometer resolution. More stringent analyses and model evaluation are required, but results and analyses presented in this report provide the foundation for conducting a more rigorous statistical assessment.

Determination of shelf heat transfer coefficients along the shelf flow path of a freeze dryer using the shelf fluid temperature perturbation approach.

PubMed

Kuu, Wei Y; Nail, Steven L; Hardwick, Lisa M

2007-01-01

The spatial distribution of local shelf heat transfer coefficients, Ks, was determined by mapping the transient temperature response of the shelf surface along the serpentine internal channels of the shelf while the temperature of the heat transfer fluid was ramped from -40 degrees to 40 degrees C. The solution of a first-order non-steady-state differential equation resulted in a predicted shelf surface temperature as a function of the shelf fluid temperature at any point along the flow path. During the study, the shelf surfaces were maintained under a thermally insulated condition so that the heat transfers by gas conduction and radiation were negligible. To minimize heat conduction by gas, the chamber was evacuated to a low pressure, such as 100 mTorr. To minimize heat transfers between shelves, shelves were moved close together, with a gap of approximately 3 mm between any two shelves, because the shelf surface temperatures at corresponding vertical locations of two shelves are virtually equal. In addition, this also provides a shielding from radiation heat transfer from shelf to walls. Local heat transfer coefficients at the probed locations h(x) ( approximately Ks) were calculated by fitting the experimental shelf temperature response to the theoretical value. While the resulting values of K(s) are in general agreement with previously reported values, the values of Ks close to the inlet are significantly higher than those of other locations of the shelf channel. This observation is most likely attributed to the variation of the flow pattern of heat transfer fluid within the channels.

Remote Characterization of Ice Shelf Surface and Basal Processes: Examples from East Antarctica

NASA Astrophysics Data System (ADS)

Greenbaum, J. S.; Blankenship, D. D.; Grima, C.; Schroeder, D. M.; Soderlund, K. M.; Young, D. A.; Kempf, S. D.; Siegert, M. J.; Roberts, J. L.; Warner, R. C.; van Ommen, T. D.

2017-12-01

The ability to remotely characterize surface and basal processes of ice shelves has important implications for conducting systematic, repeatable, and safe evaluations of their stability in the context of atmospheric and oceanic forcing. Additionally, techniques developed for terrestrial ice shelves can be adapted to orbital radar sounding datasets planned for forthcoming investigations of icy moons. This has been made possible through recent advances in radar signal processing that enable these data to be used to test hypotheses derived from conceptual and numerical models of ice shelf- and ice shell-ocean interactions. Here, we present several examples of radar sounding-derived characterizations of surface and basal processes underway on ice shelves in East Antarctica. These include percolation of near-surface meltwater in warm austral summers, brine infiltration along ice shelf calving fronts, basal melt rate and distribution, and basal freeze distribution. On Europa, near-surface brines and their migration may impact local geological variability, while basal processes likely control the distribution of melt and freeze. Terrestrially, we emphasize radar-sounding records of the Totten Glacier Ice Shelf which hosts each of these processes as well as the highest known density of basal melt channels of any terrestrial ice shelf. Further, with a maximum floating ice thickness of over 2.5 km, the pressure at Totten's basal interface may be similar to that at Europa's ice-ocean interface; therefore, evaluating surface and basal processes of Totten Glacier and other ice shelves could serve as analogs for understanding melting processes of Europa's ice shell.

Spatial distribution of Munida intermedia and M. sarsi (crustacea: Anomura) on the Galician continental shelf (NW Spain): Application of geostatistical analysis

NASA Astrophysics Data System (ADS)

Freire, J.; González-Gurriarán, E.; Olaso, I.

1992-12-01

Geostatistical methodology was used to analyse spatial structure and distribution of the epibenthic crustaceans Munida intermedia and M. sarsi within sets of data which had been collected during three survey cruises carried out on the Galician continental shelf (1983 and 1984). This study investigates the feasibility of using geostatistics for data collected according to traditional methods and of enhancing such methodology. The experimental variograms were calculated (pooled variance minus spatial covariance between samples taken one pair at a time vs. distance) and fitted to a 'spherical' model. The spatial structure model was used to estimate the abundance and distribution of the populations studied using the technique of kriging. The species display spatial structures, which are well marked during high density periods and in some areas (especially northern shelf). Geostatistical analysis allows identification of the density gradients in space as well as the patch grain along the continental shelf of 16-25 km diameter for M. intermedia and 12-20 km for M. sarsi. Patches of both species have a consistent location throughout the different cruises. As in other geographical areas, M. intermedia and M. sarsi usually appear at depths ranging from 200 to 500 m, with the highest densities in the continental shelf area located between Fisterra and Estaca de Bares. Althouh sampling was not originally designed specifically for geostatistics, this assay provides a measurement of spatial covariance, and shows variograms with variable structure depending on population density and geographical area. These ideas are useful in improving the design of future sampling cruises.

Sodium lactate addition on the quality and shelf life of refrigerated sliced poultry sausage packaged in air or nitrogen atmosphere.

PubMed

Cegielska-Radziejewska, Renata; Pikul, Jan

2004-03-01

The aim of this study was to determine the effect of sodium lactate addition on shelf-life extension of sliced poultry sausage packaged both in air and nitrogen atmospheres and stored in refrigerated conditions. Basic chemical composition, pH, and malonaldehyde content were assayed and color measurement using the reflection method was carried out. Microbiological examination consisted of determination of total number of aerobic psychrotrophic bacteria and number of lactic acid bacteria. Sensory evaluation of products was performed. Microbiological and sensory quality of sliced poultry meat sausage was dependent on the addition during production of sodium lactate and the composition of gases (air or nitrogen) used in packaging. Slices of poultry sausage with 1% as well as 2% of sodium lactate maintained their initial quality of evaluated sensory attributes longer, irrespective of the applied gases. Sodium lactate inhibited growth of aerobic psychrotrophic bacteria and lactic acid bacteria during refrigerated storage. Sodium lactate also inhibited the formation of malonaldehyde in sliced poultry sausage during refrigerated storage. The effectiveness of this process depended on the concentration of sodium lactate addition. It was concluded that 1% as well as 2% addition of sodium lactate could extend the shelf life of sliced poultry sausage packaged in air atmosphere and stored at 5 to 7 degrees C by 3 or 4 times, respectively. Sliced poultry sausage treated with 2% sodium lactate packed in nitrogen had the longest (35-day) shelf life. This was a sevenfold increase in the shelf life of sliced poultry sausage compared with the control.

Distribution of Upper Circumpolar Deep Water on the warming continental shelf of the West Antarctic Peninsula

NASA Astrophysics Data System (ADS)

Couto, Nicole; Martinson, Douglas G.; Kohut, Josh; Schofield, Oscar

2017-07-01

We use autonomous underwater vehicles to characterize the spatial distribution of Upper Circumpolar Deep Water (UCDW) on the continental shelf of the West Antarctic Peninsula (WAP) and present the first near-synoptic measurements of mesoscale features (eddies) containing UCDW on the WAP. Thirty-three subsurface eddies with widths on the order of 10 km were detected during four glider deployments. Each eddy contributed an average of 5.8 × 1016 J to the subpycnocline waters, where a cross-shelf heat flux of 1.37 × 1019 J yr-1 is required to balance the diffusive loss of heat to overlying winter water and to the near-coastal waters. Approximately two-thirds of the heat coming onto the shelf diffuses across the pycnocline and one-third diffuses to the coastal waters; long-term warming of the subpycnocline waters is a small residual of this balance. Sixty percent of the profiles that contained UCDW were part of a coherent eddy. Between 20% and 53% of the lateral onshore heat flux to the WAP can be attributed to eddies entering Marguerite Trough, a feature in the southern part of the shelf which is known to be an important conduit for UCDW. A northern trough is identified as additional important location for eddy intrusion.

The colors of icebergs

NASA Astrophysics Data System (ADS)

Warren, S. G.

2017-12-01

Ordinary icebergs of meteoric glacier ice appear bluish-white, i.e. intermediate in color between the white of snow and the blue of pure ice, depending on the bubble content. However, clear dark bubble-free icebergs are occasionally seen in the Antarctic Ocean; they originate from freezing of seawater to the base of ice shelves. On parts of the Amery Ice Shelf, frozen seawater contributes up to one-third of the ice-shelf thickness. Many of the icebergs produced by the Amery are therefore composite icebergs; the upper part consists of meteoric glacier ice from snowfall, but the lower part is frozen seawater ("marine ice"). When these icebergs capsize, the marine ice is exposed to view; it can be accessed for study in springtime when the icebergs are embedded in shorefast sea ice. The marine ice varies in color from blue to green depending on the content of dissolved organic matter. The color is therefore an indicator of biological productivity in the seawater from which the ice froze. To infer processes at the ice-shelf base, these icebergs may be examined and cored for spectral reflectance, hydrogen and oxygen isotopes, organic matter, particles, and distribution of cracks and stripes. Seasonal and interannual variations may be quantified from samples collected along the marine ice-growth trajectory at the meteoric/marine-ice interface. The scale of small turbulent eddies at the ice-shelf base, which govern the transfer of heat between ocean and ice, can be inferred from the size of scallops in the iceberg surface (typically a few centimeters). Dark stripes within meteoric ice result from tension-cracks at the grounding line, forming basal crevasses that fill suddenly with seawater; their width, spacing, and salinity can give clues to processes at the grounding line. Results will be shown from icebergs sampled on Australian expeditions near Davis and Mawson stations. Marine ice is more readily accessed by sampling an iceberg than by drilling through an ice shelf; investigation of icebergs can guide future coring of ice shelves. Warming of Antarctic intermediate water is expected to cause a declining trend in the abundance of marine-ice icebergs.

Multidecadal warming of Antarctic waters.

PubMed

Schmidtko, Sunke; Heywood, Karen J; Thompson, Andrew F; Aoki, Shigeru

2014-12-05

Decadal trends in the properties of seawater adjacent to Antarctica are poorly known, and the mechanisms responsible for such changes are uncertain. Antarctic ice sheet mass loss is largely driven by ice shelf basal melt, which is influenced by ocean-ice interactions and has been correlated with Antarctic Continental Shelf Bottom Water (ASBW) temperature. We document the spatial distribution of long-term large-scale trends in temperature, salinity, and core depth over the Antarctic continental shelf and slope. Warming at the seabed in the Bellingshausen and Amundsen seas is linked to increased heat content and to a shoaling of the mid-depth temperature maximum over the continental slope, allowing warmer, saltier water greater access to the shelf in recent years. Regions of ASBW warming are those exhibiting increased ice shelf melt. Copyright © 2014, American Association for the Advancement of Science.

Shelf life of packaged bakery goods--a review.

PubMed

Galić, K; Curić, D; Gabrić, D

2009-05-01

Packaging requirements for fresh bakery goods are often minimal as many of the products are for immediate consumption. However, packaging can be an important factor in extending the shelf life of other cereal-based goods (toast, frozen products, biscuits, cakes, pastas). Some amount of the texture changes and flavor loss manifest over the shelf life of a soft-baked good can usually be minimized or delayed by effective use of packaging materials. The gains in the extension of shelf life will be application specific. It is recognized that defining the shelf life of a food is a difficult task and is an area of intense research for food product development scientists (food technologists, microbiologists, packaging experts). Proper application of chemical kinetic principles to food quality loss allows for efficiently designing appropriate shelf-life tests and maximizing the useful information that can be obtained from the resulting data. In the development of any new food product including reformulating, change of packaging, or storage/distribution condition (to penetrate into a new market), one important aspect is the knowledge of shelf life.

A comparison of the physics of the northern and southern shelves of the eastern Bering Sea and some implications for the ecosystem

NASA Astrophysics Data System (ADS)

Stabeno, Phyllis J.; Farley, Edward V., Jr.; Kachel, Nancy B.; Moore, Sue; Mordy, Calvin W.; Napp, Jeffrey M.; Overland, James E.; Pinchuk, Alexei I.; Sigler, Michael F.

2012-06-01

Sufficient oceanographic measurements have been made in recent years to describe the latitudinal variation in the physics of the eastern Bering Sea shelf and the potential impact of climate change on the species assemblages in the two ecosystems (north and south). Many of the predicted ecosystem changes will result from alterations in the timing and extent of sea ice. It is predicted that the sea ice in the northern Bering Sea will be less common in May, but will continue to be extensive through April. In contrast, the southern shelf will have, on average, much less sea ice than currently observed, but with large interannual and multiyear variability until at least 2050. Thus, even under current climate warming scenarios, bottom temperatures on the northern shelf will remain cold. Based on biophysical measurements, the southern and northern ecosystems were divided by a North-South Transition at ˜60°N. The northern middle shelf was characterized by a freshwater lens at the surface, cold bottom temperatures, and a thicker pycnocline than found on the southern shelf. Subsurface phytoplankton blooms were common. In contrast, the southern shelf stratification was largely determined by temperature alone; the pycnocline was thin (often<3 m) and subsurface blooms were uncommon. Biological responses to climate warming could include greater north-south differences in zooplankton community structure, the transport of large Outer Shelf Domain crustacean zooplankton to the middle shelf, and the disappearance of two principal prey taxa (Calanus spp. and Thysanoessa spp.) of planktivorous fish, seabirds and whales. The response of commercially and ecologically important fish species is predicted to vary. Some species of fish (e.g., juvenile sockeye salmon, Oncorhynchus nerka) may expand their summer range into the northern Bering Sea; some (e.g., pink salmon, O. gorbuscha) may increase in abundance while still other species (e.g., walleye pollock and arrowtooth flounder; Theragra chalcogramma and Atheresthes stomias, respectively) are unlikely to become common in the north. The projected warming of the southern shelf will limit the distribution of arctic species (e.g., snow crab, Chionoecetes opilio) to the northern shelf and will likely permit expansion of subarctic species into the southern Bering Sea. The distribution and abundance of baleen whales will respond to shifts in prey availability; for instance, if prey are advected northward from the southeastern Bering Sea, an extension of range and an increase in seasonally migratory baleen whale numbers is anticipated. Thus, alteration of this ecosystem in response to climate change is expected to result in something other than a simple northward shift in the distribution of all species.

Novel biodiversity baselines outpace models of fish distribution in Arctic waters

NASA Astrophysics Data System (ADS)

Christiansen, Jørgen S.; Bonsdorff, Erik; Byrkjedal, Ingvar; Fevolden, Svein-Erik; Karamushko, Oleg V.; Lynghammar, Arve; Mecklenburg, Catherine W.; Møller, Peter D. R.; Nielsen, Julius; Nordström, Marie C.; Præbel, Kim; Wienerroither, Rupert M.

2016-02-01

During a recent marine biological expedition to the Northeast Greenland shelf break (latitudes 74-77 °N), we made the first discovery of Atlantic cod ( Gadus morhua), beaked redfish ( Sebastes mentella) and capelin ( Mallotus villosus). Our novel observations shift the distribution range of Atlantic cod >1000 km further north in East Greenland waters. In light of climate change, we discuss physical forcing and putative connections between the faunas of the Northeast Greenland shelf and the Barents Sea. We emphasise the importance of using real data in spread scenarios for understudied Arctic seas.

Novel biodiversity baselines outpace models of fish distribution in Arctic waters.

PubMed

Christiansen, Jørgen S; Bonsdorff, Erik; Byrkjedal, Ingvar; Fevolden, Svein-Erik; Karamushko, Oleg V; Lynghammar, Arve; Mecklenburg, Catherine W; Møller, Peter D R; Nielsen, Julius; Nordström, Marie C; Præbel, Kim; Wienerroither, Rupert M

2016-02-01

During a recent marine biological expedition to the Northeast Greenland shelf break (latitudes 74-77 °N), we made the first discovery of Atlantic cod (Gadus morhua), beaked redfish (Sebastes mentella) and capelin (Mallotus villosus). Our novel observations shift the distribution range of Atlantic cod >1000 km further north in East Greenland waters. In light of climate change, we discuss physical forcing and putative connections between the faunas of the Northeast Greenland shelf and the Barents Sea. We emphasise the importance of using real data in spread scenarios for understudied Arctic seas.

Marine ice regulates the future stability of a large Antarctic ice shelf

PubMed Central

Kulessa, Bernd; Jansen, Daniela; Luckman, Adrian J.; King, Edward C.; Sammonds, Peter R.

2014-01-01

The collapses of the Larsen A and B ice shelves on the Antarctic Peninsula in 1995 and 2002 confirm the impact of southward-propagating climate warming in this region. Recent mass and dynamic changes of Larsen B’s southern neighbour Larsen C, the fourth largest ice shelf in Antarctica, may herald a similar instability. Here, using a validated ice-shelf model run in diagnostic mode, constrained by satellite and in situ geophysical data, we identify the nature of this potential instability. We demonstrate that the present-day spatial distribution and orientation of the principal stresses within Larsen C ice shelf are akin to those within pre-collapse Larsen B. When Larsen B’s stabilizing frontal portion was lost in 1995, the unstable remaining shelf accelerated, crumbled and ultimately collapsed. We hypothesize that Larsen C ice shelf may suffer a similar fate if it were not stabilized by warm and mechanically soft marine ice, entrained within narrow suture zones. PMID:24751641

Cetacean distribution and abundance in relation to oceanographic domains on the eastern Bering Sea shelf: 1999-2004

NASA Astrophysics Data System (ADS)

Friday, Nancy A.; Waite, Janice M.; Zerbini, Alexandre N.; Moore, Sue E.

2012-06-01

Visual line transect surveys for cetaceans were conducted on the eastern Bering Sea shelf in association with pollock stock assessment surveys aboard the NOAA ship Miller Freeman in June and July of 1999, 2000, 2002, and 2004. Transect survey effort ranged from 1188 km in 1999 to 3761 km in 2002. Fin whales (Balaenoptera physalus) were the most common large whale in all years except 2004 when humpback whales (Megaptera novaeangliae) were more abundant. Dall's porpoise (Phocoenoides dalli) were the most common small cetacean in all years. Abundance estimates were calculated by year for each oceanographic domain: coastal, middle, and outer/slope. The middle and outer/slope domains were divided into two strata ("north" and "south") because of variable survey effort. The distribution and abundance of baleen whales changed between the earlier (colder) and later (warmer) survey years. Fin whales consistently occupied the outer shelf and secondarily the middle shelf, and their abundance was an order of magnitude greater in cold compared to warm years. Humpback whales "lived on the margin" of the northern Alaska Peninsula, eastern Aleutian Islands and Bristol Bay; their preferred habitat is possibly associated with areas of high prey availability due to nutrient upwelling and aggregation mechanisms. Minke whales (Balaenoptera acutorostrata) occur shoreward of fin whales in the outer and middle shelf and in coastal habitats along the Alaska Peninsula. The highest abundance for this species was observed in a cold (1999) year. No clear relationship emerged for odontocetes with regard to warm and cold years. Dall's porpoise occupied both outer and middle domains and harbor porpoise (Phocoena phocoena) were more common in middle and coastal domains. This study provided a unique, broad-scale assessment of cetacean distribution and abundance on the eastern Bering Sea shelf and a baseline for future comparisons.

Velocity models and images using full waveform inversion and reverse time migration for the offshore permafrost in the Canadian shelf of Beaufort Sea, Arctic

NASA Astrophysics Data System (ADS)

Kang, S. G.; Hong, J. K.; Jin, Y. K.; Kim, S.; Kim, Y. G.; Dallimore, S.; Riedel, M.; Shin, C.

2015-12-01

During Expedition ARA05C (from Aug 26 to Sep 19, 2014) on the Korean icebreaker RV ARAON, the multi-channel seismic (MCS) data were acquired on the outer shelf and slope of the Canadian Beaufort Sea to investigate distribution and internal geological structures of the offshore ice-bonded permafrost and gas hydrates, totaling 998 km L-km with 19,962 shots. The MCS data were recorded using a 1500 m long solid-type streamer with 120 channels. Shot and group spacing were 50 m and 12.5 m, respectively. Most MCS survey lines were designed perpendicular and parallel to the strike of the shelf break. Ice-bonded permafrost or ice-bearing sediments are widely distributed under the Beaufort Sea shelf, which have formed during periods of lower sea level when portions of the shelf less than ~100m water depth were an emergent coastal plain exposed to very cold surface. The seismic P-wave velocity is an important geophysical parameter for identifying the distribution of ice-bonded permafrost with high velocity in this area. Recently, full waveform inversion (FWI) and reverse time migration (RTM) are commonly used to delineate detailed seismic velocity information and seismic image of geological structures. FWI is a data fitting procedure based on wave field modeling and numerical analysis to extract quantitative geophysical parameters such as P-, S-wave velocities and density from seismic data. RTM based on 2-way wave equation is a useful technique to construct accurate seismic image with amplitude preserving of field data. In this study, we suggest two-dimensional P-wave velocity model (Figure.1) using the FWI algorithm to delineate the top and bottom boundaries of ice-bonded permafrost in the Canadian shelf of Beaufort Sea. In addition, we construct amplitude preserving migrated seismic image using RTM to interpret the geological history involved with the evolution of permafrost.

Diversity, distribution and population size structure of deep Mediterranean gorgonian assemblages (Menorca Channel, Western Mediterranean Sea)

NASA Astrophysics Data System (ADS)

Grinyó, Jordi; Gori, Andrea; Ambroso, Stefano; Purroy, Ariadna; Calatayud, Clara; Dominguez-Carrió, Carlos; Coppari, Martina; Lo Iacono, Claudio; López-González, Pablo J.; Gili, Josep-Maria

2016-06-01

Gorgonians are a key group of organisms in benthic marine communities with a wide bathymetric and geographical distribution. Although their presence on continental shelves and slopes has been known for more than 100 years, knowledge concerning the ecology of deep gorgonian species is still in a very preliminary stage. To overcome this situation, gorgonian assemblages located at 40-360 m depth were studied over a large geographical area on the continental shelf and upper slope of the Menorca Channel (Western Mediterranean Sea). A quantitative analysis of video transects recorded by a manned submersible and a remotely operated vehicle, were used to examine the diversity, distribution and demography of gorgonian species. Results showed high gorgonian diversity within this depth range (a total of nine species were observed) compared to Mediterranean coastal areas. Gorgonian assemblages on the continental shelf and upper slope were mostly monospecific (respectively 73% and 76% of occupied sampling units contained one single species), whereas shelf edge assemblages were highly multispecific (92% of occupied sampling units contained several species). This contrasts with the monospecificity of Mediterranean coastal gorgonian assemblages. Gorgonian populations on the continental shelf were mostly dominated by small colonies (88% of measured colonies) with few intermediate and large colonies (12% of measured colonies). In deeper areas small colonies were still dominant (60% of measured colonies), but intermediate and large colonies were much more abundant (40% of measured colonies). This suggests high recruitment rates on the continental shelf, but perturbations (trammel nets, long lines and strong storms) may limit the presence of intermediate and large colonies. Conversely, on the shelf edge and upper slope a more stable environment may allow colonies to reach larger dimensions. The identification and ecological characterization of these deep assemblages further extends the current knowledge about Mediterranean gorgonians, and is fundamental in improving the management and conservation of deep benthic ecosystems.

Benthic study of the continental slope off Cape Hatteras, North Carolina. Volume 3. Appendices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Diaz, R.J.; Blake, J.A.; Lohse, D.P.

1993-03-01

The Point is an area that supports a most productive pelagic fishery, including tuna, swordfish, marlin, and more. The objective of the study is to analyze video tapes from near the Point, in order to provide data on epibenthic, megafaunal invertebrates including species composition, relative abundances, and large scale (1 km) distribution. The Point is not a defined spot on a chart. Although fishermen do use the steep shelf break for location, they generally look for the west wall of the Gulf Stream. The Point and the oil lease site coincidentally occur where the Gulf Stream parts the continental slope,more » just north of the eastern-most tip of Cape Hatteras.« less

Silver hake tracks changes in Northwest Atlantic circulation.

PubMed

Nye, Janet A; Joyce, Terrence M; Kwon, Young-Oh; Link, Jason S

2011-08-02

Recent studies documenting shifts in spatial distribution of many organisms in response to a warming climate highlight the need to understand the mechanisms underlying species distribution at large spatial scales. Here we present one noteworthy example of remote oceanographic processes governing the spatial distribution of adult silver hake, Merluccius bilinearis, a commercially important fish in the Northeast US shelf region. Changes in spatial distribution of silver hake over the last 40 years are highly correlated with the position of the Gulf Stream. These changes in distribution are in direct response to local changes in bottom temperature on the continental shelf that are responding to the same large scale circulation change affecting the Gulf Stream path, namely changes in the Atlantic meridional overturning circulation (AMOC). If the AMOC weakens, as is suggested by global climate models, silver hake distribution will remain in a poleward position, the extent to which could be forecast at both decadal and multidecadal scales.

The effect of stratification and topography on high-frequency internal waves in a continental shelf sea

NASA Astrophysics Data System (ADS)

Domina, Anastasiia; Palmer, Matthew; Vlasenko, Vasil; Sharples, Jonathan; Green, Mattias; Stashchuk, Nataliya

2017-04-01

Internal gravity waves (IWs) have been recognised as one of the main drivers of climate controlling circulation, sustaining fisheries in shelf seas and CO2-pump system. High frequency IWs are particularly important to internal mixing in the shelf seas, where they contain an enhanced fraction of the available baroclinic energy. The origin, generation mechanism, propagation and spatial distribution of these waves are unfortunately still poorly understood since they are difficult to measure and simulate, and are therefore not represented in the vast majority of ocean and climate models. In this study we aim to increase our understanding of high frequency IWs dynamics in shelf seas through a combination of observational (from moorings and ocean gliders) and modelling methods (MITgcm), and test the hypothesis that "Solitary waves are responsible for driving a large fraction of the vertical diffusivity at the shelf edge and adjacent shelf region". A new high-resolution (50m horizontal) MITgcm configuration is employed to identify the generation and propagation of IWs in a regional shelf sea and subsequently identify internal wave generation hotspots by using calculated Froude number and body force maps. We assess the likely impact of changing seasonal and climate forcing on IWs with a range of different density structures. Our model suggests that under increasing stratification, the IW field becomes more energetic at all frequencies, however the increase in energy is not evenly distributed. While energy in the dominant low frequency IWs increase by 20-40%, energy associated with high frequency waves increases by as much as 90%. These model results are compared to varying stratification scenarios from observations made during 2012 and 2013 to interpret the impact on continental shelf sea IW generation and propagation. We use the results from a turbulence enabled ocean glider to assess the impact that this varying wavefield has on internal mixing, and discuss the implications this might have on future climate scenarios.

Circulation in the Hudson Shelf Valley: MESA physical oceanographic studies in New York Bight, 1

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mayer, D.A.; Hansen, D.V.; Han, G.C.

1982-11-20

Over 900 days of current velocity data were obtained at mainly two locations in the inner and outer Hudson Shelf Valley (HSV). The large cross-axis depth gradients in the HSV, together with the strong winter cyclones and the baroclinic density distribution over the shelf, are primarily responsible for the major circulation features observed in the valley. CSTD data from 12 cruises and meteorological data from JFK International Airport and an environmental buoy were collected concurrently with the current meter data.

Diatom valve distribution and sedimentary fatty acid composition in Larsen Bay, Eastern Antarctica Peninsula

NASA Astrophysics Data System (ADS)

Sañé, E.; Isla, E.; Pruski, A. M.; Bárcena, M. A.; Vétion, G.; DeMaster, D.

2011-08-01

During austral summer 2006-2007, five sediment cores were recovered from the Eastern Antarctic Peninsula (EAP) continental shelf. Microscopic observations and sediment fatty acid (FA) composition analyses were carried out to investigate whether the drastic changes at the sea surface in EAP may be reflected in the sedimentary record. A sharp decrease in the number of diatom valves was observed below 2 cm depth. This difference between the upper 2 cm of sediment and the deeper part of the sediment column was attributed to the drastic change in the upper water column conditions after the collapse of the ice shelves, which allowed the arrival of phytoplankton debris and fresh organic matter to the sea floor in EAP. The presence of bacterial-, zooplankton- and detrital-related FA throughout EAP cores suggests that there has been an input of older and more refractory organic matter into the region, presumably by lateral transport before the Larsen ice shelves disintegration.

Phenotypic and molecular characterization of a tomato (Solanum lycopersicum L.) F2 population segregation for improving shelf life.

PubMed

Yogendra, K N; Ramanjini Gowda, P H

2013-02-27

Breeding for better quality fruits is a major focus for tomatoes, which are continuously subjected to post-harvest losses. Several methods have been used to improve the fruit shelf life of tomatoes, including the use of ripening gene mutants of Solanum lycopersicum. We developed extended shelf-life tomato hybrids with better quality fruits using ripening mutants. Nine tomato crosses were developed using 3 fruit ripening gene mutants of S. lycopersicum [alcobaca (alc), non-ripening, and ripening inhibitor] and 3 agronomically superior Indian cultivars ('Sankranti', 'Vaibhav', and 'Pusaruby') with short shelf life. The hybrid progenies developed from alc x 'Vaibhav' had the highest extended shelf life (up to 40 days) compared with that of other varieties and hybrids. Further, the F(2) progenies of alc x 'Vaibhav' were evaluated for fruit quality traits and yield parameters. A wide range of genetic variability was observed in shelf life (5-106 days) and fruit firmness (0.55-10.65 lbs/cm(2)). The potential polymorphic simple sequence repeat markers underlying shelf life traits were identified in an F(2) mapping population. The marker association with fruit quality traits and yield was confirmed with single-marker analysis and composite interval mapping. The genetic parameters analyzed in the parents and F(1) and F(2) populations indicated that the cross between the cultivar 'Vaibhav' and ripening gene mutant alc yielded fruit with long shelf life and good quality.

Seasonal cycle of circulation in the Antarctic Peninsula and the off-shelf transport of shelf waters into southern Drake Passage and Scotia Sea

NASA Astrophysics Data System (ADS)

Jiang, Mingshun; Charette, Matthew A.; Measures, Christopher I.; Zhu, Yiwu; Zhou, Meng

2013-06-01

The seasonal cycle of circulation and transport in the Antarctic Peninsula shelf region is investigated using a high-resolution (˜2 km) regional model based on the Regional Oceanic Modeling System (ROMS). The model also includes a naturally occurring tracer with a strong source over the shelf (radium isotope 228Ra, t1/2=5.8 years) to investigate the sediment Fe input and its transport. The model is spun-up for three years using climatological boundary and surface forcing and then run for the 2004-2006 period using realistic forcing. Model results suggest a persistent and coherent circulation system throughout the year consisting of several major components that converge water masses from various sources toward Elephant Island. These currents are largely in geostrophic balance, driven by surface winds, topographic steering, and large-scale forcing. Strong off-shelf transport of the Fe-rich shelf waters takes place over the northeastern shelf/slope of Elephant Island, driven by a combination of topographic steering, extension of shelf currents, and strong horizontal mixing between the ACC and shelf waters. These results are generally consistent with recent and historical observational studies. Both the shelf circulation and off-shelf transport show a significant seasonality, mainly due to the seasonal changes of surface winds and large-scale circulation. Modeled and observed distributions of 228Ra suggest that a majority of Fe-rich upper layer waters exported off-shelf around Elephant Island are carried by the shelfbreak current and the Bransfield Strait Current from the shallow sills between Gerlache Strait and Livingston Island, and northern shelf of the South Shetland Islands, where strong winter mixing supplies much of the sediment derived nutrients (including Fe) input to the surface layer.

Arctic Deep Water Ferromanganese-Oxide Deposits Reflect the Unique Characteristics of the Arctic Ocean

NASA Astrophysics Data System (ADS)

Hein, James R.; Konstantinova, Natalia; Mikesell, Mariah; Mizell, Kira; Fitzsimmons, Jessica N.; Lam, Phoebe J.; Jensen, Laramie T.; Xiang, Yang; Gartman, Amy; Cherkashov, Georgy; Hutchinson, Deborah R.; Till, Claire P.

2017-11-01

Little is known about marine mineral deposits in the Arctic Ocean, an ocean dominated by continental shelf and basins semi-closed to deep-water circulation. Here, we present data for ferromanganese crusts and nodules collected from the Amerasia Arctic Ocean in 2008, 2009, and 2012 (HLY0805, HLY0905, and HLY1202). We determined mineral and chemical compositions of the crusts and nodules and the onset of their formation. Water column samples from the GEOTRACES program were analyzed for dissolved and particulate scandium concentrations, an element uniquely enriched in these deposits. The Arctic crusts and nodules are characterized by unique mineral and chemical compositions with atypically high growth rates, detrital contents, Fe/Mn ratios, and low Si/Al ratios, compared to deposits found elsewhere. High detritus reflects erosion of submarine outcrops and North America and Siberia cratons, transport by rivers and glaciers to the sea, and distribution by sea ice, brines, and currents. Uniquely high Fe/Mn ratios are attributed to expansive continental shelves, where diagenetic cycling releases Fe to bottom waters, and density flows transport shelf bottom water to the open Arctic Ocean. Low Mn contents reflect the lack of a mid-water oxygen minimum zone that would act as a reservoir for dissolved Mn. The potential host phases and sources for elements with uniquely high contents are discussed with an emphasis on scandium. Scandium sorption onto Fe oxyhydroxides and Sc-rich detritus account for atypically high scandium contents. The opening of Fram Strait in the Miocene and ventilation of the deep basins initiated Fe-Mn crust growth ˜15 Myr ago.

Arctic deep-water ferromanganese-oxide deposits reflect the unique characteristics of the Arctic Ocean

USGS Publications Warehouse

Hein, James; Konstantinova, Natalia; Mikesell, Mariah; Mizell, Kira; Fitzsimmons, Jessica N.; Lam, Phoebe; Jensen, Laramie T.; Xiang, Yang; Gartman, Amy; Cherkashov, Georgy; Hutchinson, Deborah; Till, Claire P.

2017-01-01

Little is known about marine mineral deposits in the Arctic Ocean, an ocean dominated by continental shelf and basins semi-closed to deep-water circulation. Here, we present data for ferromanganese crusts and nodules collected from the Amerasia Arctic Ocean in 2008, 2009, and 2012 (HLY0805, HLY0905, HLY1202). We determined mineral and chemical compositions of the crusts and nodules and the onset of their formation. Water column samples from the GEOTRACES program were analyzed for dissolved and particulate scandium concentrations, an element uniquely enriched in these deposits.The Arctic crusts and nodules are characterized by unique mineral and chemical compositions with atypically high growth rates, detrital contents, Fe/Mn ratios, and low Si/Al ratios, compared to deposits found elsewhere. High detritus reflects erosion of submarine outcrops and North America and Siberia cratons, transport by rivers and glaciers to the sea, and distribution by sea ice, brines, and currents. Uniquely high Fe/Mn ratios are attributed to expansive continental shelves, where diagenetic cycling releases Fe to bottom waters, and density flows transport shelf bottom water to the open Arctic Ocean. Low Mn contents reflect the lack of a mid-water oxygen minimum zone that would act as a reservoir for dissolved Mn. The potential host phases and sources for elements with uniquely high contents are discussed with an emphasis on scandium. Scandium sorption onto Fe oxyhydroxides and Sc-rich detritus account for atypically high scandium contents. The opening of Fram Strait in the Miocene and ventilation of the deep basins initiated Fe-Mn crust growth ∼15 Myr ago.

Plankton community structure and connectivity in the Kimberley-Browse region of NW Australia

NASA Astrophysics Data System (ADS)

McKinnon, A. D.; Duggan, S.; Holliday, D.; Brinkman, R.

2015-02-01

We describe the zooplankton and ichthyoplankton communities of coastal waters of the Kimberley coast (North West Australia), sampled in macrotidal Camden Sound during both the wet and dry seasons of 2011, and compare these to six other Kimberley embayments during the wet season of 2013. Zooplankton abundance in Camden Sound was 7038 ± 3913 SD ind. m-3 in the wet season and 1892 ± 708 SD ind. m-3 in the dry season, with copepods accounting for 85% by number. In all, 78 species of copepods were recorded, with the families Paracalanidae and Oithonidae dominant. In Camden Sound, 48 families of larval fish occurred, with ichthyoplankton more abundant in the wet season than the dry season (1.16 ± 0.2 ind. m-3 cf 0.76 ± 0.2 ind. m-3). Larval gobiids (Subfamily Gobiinae) were most abundant, with other common families associated with either pelagic or soft-bottom habitats as adults. Multivariate analyses of both copepod and ichthyoplankton communities demonstrated strong seasonal contrasts, although an along-shelf gradient in copepod community composition was apparent along the embayments sampled in 2013. There was little spatial variation in plankton communities within Camden Sound as a result of the large tidal range (up to 11.7 m, with 2.5 m-1 velocities), although gradients in abundance and composition on cross-shelf transects occurred in the more northern embayments that had a lower tidal range, such as Napier Broome Bay. Copepod communities of the Kimberley-Browse region were placed in regional perspective by multivariate analyses of similar data collected in the eastern Indian Ocean at Scott Reef, in the Arafura Sea and on the southern North West (NW) shelf. The plankton communities of the NW shelf form a series of along-shore metacommunities linked by advection, with weaker cross-shelf connectivity. The presence of the larvae of mesopelagic fishes of the family Myctophidae in coastal waters confirms seasonal cross-shelf connectivity.

McMurdo Ice Shelf Sounding and Radar Statistical Reconnaissance at 60-MHz: Brine Infiltration Extent and Surface Properties

NASA Astrophysics Data System (ADS)

Grima, C.; Rosales, A.; Blankenship, D. D.; Young, D. A.

2014-12-01

McMurdo Ice Shelf, Antarctica, is characterized by two particular geophysical processes. (1) Marine ice accretion supplies most of the ice shelf material rather than meteoric ice from glacier outflow and snow-falls. (2) A brine layer infiltrates the ice shelf laterally up to 20-km inward. The infiltration mainly initiates at the ice-front from sea water percolation when the firn/snow transition is below sea-level. A better characterization of the McMurdo ice shelf could constrain our knowledges of these mechanisms and assess the stability of the region that hosts numerous human activities from the close McMurdo station (USA) and Scott base (New-Zealand). McMurdo ice shelf is also an analog for the Jovian icy moon Europa where brine pockets are supposed to reside in the ice crust and accretion to occur at the 10-30-km deep ice-ocean interface.The University of Texas Institute for Geophysics (UTIG) acquired two radar survey grids over the McMurdo Ice Shelf during southern summers 2011-2012 and 2012-2013 with the High Capability Radar Sounder (HiCARS) on-board a Basler DC-3 aircraft. HiCARS transmits a chirped signal at 60-MHz central frequency and 15-MHz bandwidth. The corresponding vertical resolution in ice is 5-10 m. An important design goal of the radar was to maintain sufficient dynamic range to correctly measure echo intensities.Here we present the brine infiltration extent and bathymetry derived from its dielectric horizon well distinguishable on the HiCARS radargram. We complement the ice-shelf characterization by classifying its surface thanks to the novel Radar Statistical Reconnaissance (RSR) methodology. The RSR observable is the statistical distribution of the surface echo amplitudes from successive areas defined along-track. The distributions are best-fitted with a theoretical stochastic envelop parameterized with the signal reflectance and scattering. Once those two components are deduced from the fit, they are used in a backscattering model to invert surface properties such as roughness, density, and/or impurity load. This combined analysis gives new insights into the superficial processes and exchanges at the McMurdo ice shelf.

Subsea ice-bearing permafrost on the U.S. Beaufort Margin: 2. Borehole constraints

USGS Publications Warehouse

Ruppel, Carolyn D.; Herman, Bruce M.; Brothers, Laura L.; Hart, Patrick E.

2016-01-01

Borehole logging data from legacy wells directly constrain the contemporary distribution of subsea permafrost in the sedimentary section at discrete locations on the U.S. Beaufort Margin and complement recent regional analyses of exploration seismic data to delineate the permafrost's offshore extent. Most usable borehole data were acquired on a ∼500 km stretch of the margin and within 30 km of the contemporary coastline from north of Lake Teshekpuk to nearly the U.S.-Canada border. Relying primarily on deep resistivity logs that should be largely unaffected by drilling fluids and hole conditions, the analysis reveals the persistence of several hundred vertical meters of ice-bonded permafrost in nearshore wells near Prudhoe Bay and Foggy Island Bay, with less permafrost detected to the east and west. Permafrost is inferred beneath many barrier islands and in some nearshore and lagoonal (back-barrier) wells. The analysis of borehole logs confirms the offshore pattern of ice-bearing subsea permafrost distribution determined based on regional seismic analyses and reveals that ice content generally diminishes with distance from the coastline. Lacking better well distribution, it is not possible to determine the absolute seaward extent of ice-bearing permafrost, nor the distribution of permafrost beneath the present-day continental shelf at the end of the Pleistocene. However, the recovery of gas hydrate from an outer shelf well (Belcher) and previous delineation of a log signature possibly indicating gas hydrate in an inner shelf well (Hammerhead 2) imply that permafrost may once have extended across much of the shelf offshore Camden Bay.

Marine species distribution shifts on the U.S. Northeast Continental Shelf under continued ocean warming

NASA Astrophysics Data System (ADS)

Kleisner, Kristin M.; Fogarty, Michael J.; McGee, Sally; Hare, Jonathan A.; Moret, Skye; Perretti, Charles T.; Saba, Vincent S.

2017-04-01

The U.S. Northeast Continental Shelf marine ecosystem has warmed much faster than the global ocean and it is expected that this enhanced warming will continue through this century. Complex bathymetry and ocean circulation in this region have contributed to biases in global climate model simulations of the Shelf waters. Increasing the resolution of these models results in reductions in the bias of future climate change projections and indicates greater warming than suggested by coarse resolution climate projections. Here, we used a high-resolution global climate model and historical observations of species distributions from a trawl survey to examine changes in the future distribution of suitable thermal habitat for various demersal and pelagic species on the Shelf. Along the southern portion of the shelf (Mid-Atlantic Bight and Georges Bank), a projected 4.1 °C (surface) to 5.0 °C (bottom) warming of ocean temperature from current conditions results in a northward shift of the thermal habitat for the majority of species. While some southern species like butterfish and black sea bass are projected to have moderate losses in suitable thermal habitat, there are potentially significant increases for many species including summer flounder, striped bass, and Atlantic croaker. In the north, in the Gulf of Maine, a projected 3.7 °C (surface) to 3.9 °C (bottom) warming from current conditions results in substantial reductions in suitable thermal habitat such that species currently inhabiting this region may not remain in these waters under continued warming. We project a loss in suitable thermal habitat for key northern species including Acadian redfish, American plaice, Atlantic cod, haddock, and thorney skate, but potential gains for some species including spiny dogfish and American lobster. We illustrate how changes in suitable thermal habitat of important commercially fished species may impact local fishing communities and potentially impact major fishing ports along the U.S. Northeast Shelf. Given the complications of multiple drivers including species interactions and fishing pressure, it is difficult to predict exactly how species will shift. However, observations of species distribution shifts in the historical record under ocean warming suggest that temperature will play a primary role in influencing how species fare. Our results provide critical information on the potential for suitable thermal habitat on the U.S. Northeast Shelf for demersal species in the region, and may contribute to the development of ecosystem-based fisheries management strategies in response to climate change.

Formulation, sensory evaluation, proximate composition and storage stability of cassava strips produced from the composite flour of cassava and cowpea.

PubMed

Dada, Toluwase A; Barber, Lucretia I; Ngoma, Lubanza; Mwanza, Mulunda

2018-03-01

The study developed an acceptable formula for the production of cassava strips (a deep fried product) using composite flour of cassava/cowpea at four different levels of cowpea substitutions (100:0, 90:10, 80:20, and 70:30). Sensory properties, proximate composition, and shelf life at ambient temperature were determined. Proximate composition, shelf life, and microbial analysis were further done on the most preferred sample (80:20) and the control (100:0). Results showed a significant difference between the tested sample and the control, except in their moisture (4.1%-4.2%) and fiber (5.0%) contents which were similar. Protein content increased from 0.9% to 2.6%, fat 24.6% to 28.5%, carbohydrate 59.7% to 61.1%, and ash 1.8% to 2.5% in both control and most preferred sample. Results showed no changes in their peroxide value (2.4 mEq/kg), moisture content (4.1%), and bacterial count of 0 × 10 2  CFU/g at ambient storage temperature for 4 weeks. The addition of cowpea flour increased the nutritional quality of the cassava strips.

Zinc composite anode for batteries with solid electrolyte

NASA Astrophysics Data System (ADS)

Tedjar, F.; Melki, T.; Zerroual, L.

A new negative composite anode for batteries with a solid electrolyte is studied. Using a complex of zinc ammonium chloride mixed with zinc metal powder, the advantage of the Zn/Zn 2+ electrode ( e = -760 mV) is kept while the energy density and the shelf-life of the battery are increased.

Chemical composition of black rockfish (Sebastes melanops) fillets and byproducts

USDA-ARS?s Scientific Manuscript database

Black rockfish are important in the near shore fishery of Southeast Alaska. They are the only species among the pelagic shelf rockfishes for which there is a directed fishery in state waters. The purpose of this study was to determine the composition black rockfish fillets and its major processing b...

Wind-induced interannual variability of sea level slope, along-shelf flow, and surface salinity on the Northwest Atlantic shelf

NASA Astrophysics Data System (ADS)

Li, Yun; Ji, Rubao; Fratantoni, Paula S.; Chen, Changsheng; Hare, Jonathan A.; Davis, Cabell S.; Beardsley, Robert C.

2014-04-01

In this study, we examine the importance of regional wind forcing in modulating advective processes and hydrographic properties along the Northwest Atlantic shelf, with a focus on the Nova Scotian Shelf (NSS)-Gulf of Maine (GoM) region. Long-term observational data of alongshore wind stress, sea level slope, and along-shelf flow are analyzed to quantify the relationship between wind forcing and hydrodynamic responses on interannual time scales. Additionally, a simplified momentum balance model is used to examine the underlying mechanisms. Our results show significant correlation among the observed interannual variability of sea level slope, along-shelf flow, and alongshore wind stress in the NSS-GoM region. A mechanism is suggested to elucidate the role of wind in modulating the sea level slope and along-shelf flow: stronger southwesterly (northeastward) winds tend to weaken the prevailing southwestward flow over the shelf, building sea level in the upstream Newfoundland Shelf region, whereas weaker southwesterly winds allow stronger southwestward flow to develop, raising sea level in the GoM region. The wind-induced flow variability can influence the transport of low-salinity water from the Gulf of St. Lawrence to the GoM, explaining interannual variations in surface salinity distributions within the region. Hence, our results offer a viable mechanism, besides the freshening of remote upstream sources, to explain interannual patterns of freshening in the GoM.

Short communication: Variation in the composition and properties of Swedish raw milk for ultra-high-temperature processing.

PubMed

Karlsson, Maria A; Langton, Maud; Innings, Fredrik; Wikström, Malin; Lundh, Åse Sternesjö

2017-04-01

The composition and properties of raw milk are of great importance for the quality and shelf life of the final dairy product, especially in products with a long shelf life [e.g., ultra-high-temperature (UHT)-treated milk]. The objective of this study was to investigate the compositional variation in raw milk samples before processing at the dairy plant. Moreover, we wanted to investigate the effect of the UHT process on this variation (i.e., if the same variation could be observed in the corresponding UHT milk). The quality traits analyzed included detailed milk composition, counts of total and psychrotrophic bacteria, proteolytic activity, and color, as well as predictive measures of stability (i.e., ethanol stability and heat coagulating time). Samples of raw milk and the corresponding produced UHT milk were collected and analyzed on a monthly basis during 1 yr. Principal component analysis was used to identify months showing similarities and differences with respect to total variation. In contrast to previous studies, we observed only small variations between months and no clear effect of season for the raw milk. For the UHT milk, July and the winter months (December, January, and February) tended to separate from the other months. Quality traits showing significant variation were only to some extent identical in raw milk and UHT-processed milk. A better understanding of the natural variation in raw milk quality will provide opportunities to improve the shelf life of UHT-treated milk products. Copyright © 2017 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Cyclonic entrainment of preconditioned shelf waters into a frontal eddy

NASA Astrophysics Data System (ADS)

Everett, J. D.; Macdonald, H.; Baird, M. E.; Humphries, J.; Roughan, M.; Suthers, I. M.

2015-02-01

The volume transport of nutrient-rich continental shelf water into a cyclonic frontal eddy (entrainment) was examined from satellite observations, a Slocum glider and numerical simulation outputs. Within the frontal eddy, parcels of water with temperature/salinity signatures of the continental shelf (18-19°C and >35.5, respectively) were recorded. The distribution of patches of shelf water observed within the eddy was consistent with the spiral pattern shown within the numerical simulations. A numerical dye tracer experiment showed that the surface waters (≤50 m depth) of the frontal eddy are almost entirely (≥95%) shelf waters. Particle tracking experiments showed that water was drawn into the eddy from over 4° of latitude (30-34.5°S). Consistent with the glider observations, the modeled particles entrained into the eddy sunk relative to their initial position. Particles released south of 33°S, where the waters are cooler and denser, sunk 34 m deeper than their release position. Distance to the shelf was a critical factor in determining the volume of shelf water entrained into the eddy. Entrainment reduced to 0.23 Sv when the eddy was furthest from the shelf, compared to 0.61 Sv when the eddy was within 10 km of the shelf. From a biological perspective, quantifying the entrainment of shelf water into frontal eddies is important, as it is thought to play a significant role in providing an offshore nursery habitat for coastally spawned larval fish.

Determining the inventory impact of extended-shelf-life platelets with a network simulation model.

PubMed

Blake, John T

2017-12-01

The regulatory shelf life for platelets (PLTs) in many jurisdictions is 5 days. PLT shelf life can be extended to 7 days with an enhanced bacterial detection algorithm. Enhanced testing, however, comes at a cost, which may be offset by reductions in wastage due to longer shelf life. This article describes a method for estimating systemwide reductions in PLT outdates after PLT shelf life is extended. A simulation was used to evaluate the impact of an extended PLT shelf life within a national blood network. A network model of the Canadian Blood Services PLT supply chain was built and validated. PLT shelf life was extended from 5 days to 6, 7, and 8 days and runs were completed to determine the impact on outdates. Results suggest that, in general, a 16.3% reduction in PLT wastage can be expected with each additional day that PLT shelf life is extended. Both suppliers and hospitals will experience fewer outdating units, but wastage will decrease at a faster rate at hospitals. No effect was seen by blood group, but there was some evidence that supplier site characteristics influences both the number of units wasted and the site's ability to benefit from extended-shelf-life PLTs. Extended-shelf-life PLTs will reduce wastage within a blood supply chain. At 7 days, an improvement of 38% reduction in wastage can be expected with outdates being equally distributed between suppliers and hospital customers. © 2017 AABB.

Bacterial communities in Great Barrier Reef calcareous sediments: Contrasting 16S rDNA libraries from nearshore and outer shelf reefs

NASA Astrophysics Data System (ADS)

Uthicke, S.; McGuire, K.

2007-03-01

Bacterial communities in eight 16S rDNA clone libraries from calcareous sediments were investigated to provide an assessment of the bacterial diversity on sediments of the Great Barrier Reef (GBR) and to investigate differences due to decreased water quality. Sample effort was spread across two locations on each of four coral reefs, with two reefs located nearshore and two reefs on the outer shelf to allow robust statistical comparison of nearshore reefs (subjected to enhanced runoff) and outer shelf reefs (pristine conditions). Out of 221 non-chimeric sequences, 189 (85.5%) were unique and only one sequence occurred in more than one library. Rarefaction analyses and coverage calculations indicated that only a small fraction of the diversity was sampled. Cluster analyses and comparison to published sequences indicated that sequences retrieved belonged to the α, γ and δ subdivision of the Proteobacteria (6.8, 29.4 and 13.6% of the total, respectively), Cytophaga-Flavobacteria-Bacteroidetes (CFB) group (20.4%), Cyanobacteria (5.4%), Planctomycetaceae (7.7%), Verrucomicrobiaceae (6.8%), Acidobacteriaceae (2.7%). Analysis of Similarity (ANOSIM, based on grouping all retrieved sequences into 9 phylogenetic groups) indicated that subtle differences do exist in the community composition between nearshore and outer shelf reefs. Similarity percentage analysis (SIMPER) indicated that Acidobacteriaceae and Cyanobacteriaceae were the main contributors to the dissimilarity. A significant difference between bacteria on nearshore and outer shelf reefs also existed on the molecular level ( FST = 0.008, p = 0.007 for all samples, 0.006, p = 0.022 when repeated sequences within libraries were removed). Thus, bacterial communities on carbonate sediments investigated were highly diverse and differences in community composition may provide important leads for the search for indicator species or communities for water quality differences.

Mid-late Holocene climate variability in the Indian monsoon: Evidence from continental shelf sediments adjacent to Rushikulya river, eastern India

NASA Astrophysics Data System (ADS)

Ankit, Yadav; Kumar, Prem; Anoop, Ambili; Mishra, Praveen K.; Varghese, Saju

2017-04-01

We present elemental and grain-size distributions obtained from the sediment core of the continental shelf adjacent to the Rushikulya river mouth, eastern India to quantify the paleoclimatic changes. The retrieved 1.60 m long well-dated core spans the past ca. 6800 cal BP. The modern spatial distribution of grain size and geochemistry of the inner-mid shelf sediments has been carried out to understand the seafloor morphology and sedimentary processes. Based on the mod- ern investigations, the proportion of particle size (clay vs sand) and variation in elemental values (TiO2 vs Al2O3) has been used to interpret the changes in terrigenous supply. The grain-size and elemental distribution data from the core sediments indicates a period of enhanced surface water runoff from 6800 to 3100 cal BP followed by a drier condition (3100 cal BP to present) suggesting weakening of monsoon. The weakening of the monsoonal strength is coeval with other records from the Indian sub-continent and suggests response of Indian monsoon to changing solar insolation during late Holocene.

Fine-scale planktonic habitat partitioning at a shelf-slope front revealed by a high-resolution imaging system

NASA Astrophysics Data System (ADS)

Greer, Adam T.; Cowen, Robert K.; Guigand, Cedric M.; Hare, Jonathan A.

2015-02-01

Ocean fronts represent productive regions of the ocean, but predator-prey interactions within these features are poorly understood partially due to the coarse-scale and biases of net-based sampling methods. We used the In Situ Ichthyoplankton Imaging System (ISIIS) to sample across a front near the Georges Bank shelf edge on two separate sampling days in August 2010. Salinity characterized the transition from shelf to slope water, with isopycnals sloping vertically, seaward, and shoaling at the thermocline. A frontal feature defined by the convergence of isopycnals and a surface temperature gradient was sampled inshore of the shallowest zone of the shelf-slope front. Zooplankton and larval fishes were abundant on the shelf side of the front and displayed taxon-dependent depth distributions but were rare in the slope waters. Supervised automated particle counting showed small particles with high solidity, verified to be zooplankton (copepods and appendicularians), aggregating near surface above the front. Salps were most abundant in zones of intermediate chlorophyll-a fluorescence, distinctly separate from high abundances of other grazers and found almost exclusively in colonial form (97.5%). Distributions of gelatinous zooplankton differed among taxa but tended to follow isopycnals. Fine-scale sampling revealed distinct habitat partitioning of various planktonic taxa, resulting from a balance of physical and biological drivers in relation to the front.

A time-dependent, three-dimensional model of the Delaware Bay and River system. Part 2: Three-dimensional flow fields and residual circulation

NASA Astrophysics Data System (ADS)

Galperin, Boris; Mellor, George L.

1990-09-01

The three-dimensional model of Delaware Bay, River and adjacent continental shelf was described in Part 1. Here, Part 2 of this two-part paper demonstrates that the model is capable of realistic simulation of current and salinity distributions, tidal cycle variability, events of strong mixing caused by high winds and rapid salinity changes due to high river runoff. The 25-h average subtidal circulation strongly depends on the wind forcing. Monthly residual currents and salinity distributions demonstrate a classical two-layer estuarine circulation wherein relatively low salinity water flows out at the surface and compensating high salinity water from the shelf flows at the bottom. The salinity intrusion is most vigorous along deep channels in the Bay. Winds can generate salinity fronts inside and outside the Bay and enhance or weaken the two-layer circulation pattern. Since the portion of the continental shelf included in the model is limited, the model shelf circulation is locally wind-driven and excludes such effects as coastally trapped waves and interaction with Gulf Stream rings; nevertheless, a significant portion of the coastal elevation variability is hindcast by the model. Also, inclusion of the shelf improves simulation of salinity inside the Bay compared with simulations where the salinity boundary condition is specified at the mouth of the Bay.

What a drag: Quantifying the global impact of chronic bottom trawling on continental shelf sediment

USGS Publications Warehouse

Oberle, Ferdinand K.J.; Storlazzi, Curt; Hanebuth, Till J.J.

2016-01-01

Continental shelves worldwide are subject to intense bottom trawling that causes sediment to be resuspended. The widely used traditional concepts of modern sedimentary transport systems on the shelf rely only on estimates for naturally driven sediment resuspension such as through storm waves, bottom currents, and gravity-driven flows but they overlook a critical anthropogenic factor. The strong influence of bottom trawling on a source-to-sink sediment budget is explored on the NW Iberian shelf. Use of Automated Information System vessel tracking data provides for a high-resolution vessel track reconstruction and the accurate calculation of the spatial distribution of bottom trawling intensity and associated resuspended sediment load. The mean bottom trawling-induced resuspended sediment mass for the NW Iberian shelf is 13.50 Mt yr− 1, which leads to a six-fold increase in off-shelf sediment transport when compared to natural resuspension mechanisms. The source-to-sink budget analysis provides evidence that bottom trawling causes a rapid erosion of the fine sediment on human time scales. Combining global soft sediment distribution data of the shelves with worldwide bottom trawling intensity estimates we show that the bottom trawling-induced resuspended sediment mass amounts to approximately the same mass of all sediment entering the shelves through rivers. Spatial delineations between natural and anthropogenic sediment resuspension areas are presented to aid in marine management questions.

Satellite-Derived Distributions, Inventories and Fluxes of Dissolved and Particulate Organic Matter Along the Northeastern U.S. Continental Margin

NASA Technical Reports Server (NTRS)

Mannino, A.; Hooker, S. B.; Hyde, K.; Novak, M. G.; Pan, X.; Friedrichs, M.; Cahill, B.; Wilkin, J.

2011-01-01

Estuaries and the coastal ocean experience a high degree of variability in the composition and concentration of particulate and dissolved organic matter (DOM) as a consequence of riverine and estuarine fluxes of terrigenous DOM, sediments, detritus and nutrients into coastal waters and associated phytoplankton blooms. Our approach integrates biogeochemical measurements, optical properties and remote sensing to examine the distributions and inventories of organic carbon in the U.S. Middle Atlantic Bight and Gulf of Maine. Algorithms developed to retrieve colored DOM (CDOM), Dissolved (DOC) and Particulate Organic Carbon (POC) from NASA's MODIS-Aqua and SeaWiFS satellite sensors are applied to quantify the distributions and inventories of DOC and POC. Horizontal fluxes of DOC and POC from the continental margin to the open ocean are estimated from SeaWiFS and MODIS-Aqua distributions of DOC and POC and horizontal divergence fluxes obtained from the Northeastern North Atlantic ROMS model. SeaWiFS and MODIS imagery reveal the importance of estuarine outflow to the export of CDOM and DOC to the coastal ocean and a net community production of DOC on the shelf.

Recent rift formation and impact on the structural integrity of the Brunt Ice Shelf, East Antarctica

NASA Astrophysics Data System (ADS)

De Rydt, Jan; Hilmar Gudmundsson, G.; Nagler, Thomas; Wuite, Jan; King, Edward C.

2018-02-01

We report on the recent reactivation of a large rift in the Brunt Ice Shelf, East Antarctica, in December 2012 and the formation of a 50 km long new rift in October 2016. Observations from a suite of ground-based and remote sensing instruments between January 2000 and July 2017 were used to track progress of both rifts in unprecedented detail. Results reveal a steady accelerating trend in their width, in combination with alternating episodes of fast ( > 600 m day-1) and slow propagation of the rift tip, controlled by the heterogeneous structure of the ice shelf. A numerical ice flow model and a simple propagation algorithm based on the stress distribution in the ice shelf were successfully used to hindcast the observed trajectories and to simulate future rift progression under different assumptions. Results show a high likelihood of ice loss at the McDonald Ice Rumples, the only pinning point of the ice shelf. The nascent iceberg calving and associated reduction in pinning of the Brunt Ice Shelf may provide a uniquely monitored natural experiment of ice shelf variability and provoke a deeper understanding of similar processes elsewhere in Antarctica.

Note On The Ross Sea Shelf Water Downflow Processes (antarctica)

NASA Astrophysics Data System (ADS)

Bergamasco, A.; Defendi, V.; Spezie, G.; Budillon, G.; Carniel, S.

In the framework of the CLIMA Project of the Italian National Program for Research in Antarctica, three different experimental data sets were acquired along the continental shelf break; two of them (in 1997 and 2001) close to Cape Adare, the 1998 one in the middle of the Ross Sea (i.e. 75 S, 177 W). The investigations were chosen in order to explore the downslope flow of the bottom waters produced in the Ross Sea, namely the High Salinity Shelf Water (HSSW, the densest water mass of the southern ocean coming from its formation site in the polynya region in Terra Nova bay), and the Ice Shelf Water (ISW, originated below the Ross Ice Shelf and outflowing northward). Both bottom waters spill over the shelf edge and mix with the Circumpolar Deep Water (CDW) contributing to the formation of the Antarctic Bottom Waters (AABW). Interpreting temperature, salinity and density maps in terms of cascading processes, both HSSW and ISW overflows are evidenced during, respectively, 1997 and 1998. During the 2001 acquisition there is no presence of HSSW along the shelf break, nevertheless distribution captures the evidence of a downslope flow process.

Controlled atmosphere storage of wild strawberry fruit (Fragaria vesca L.).

PubMed

Almenar, Eva; Hernández-Muñoz, Pilar; Lagarón, José M; Catalá, Ramón; Gavara, Rafael

2006-01-11

Controlled atmosphere storage technology to extend the shelf life of "Reina de los Valles" wild strawberry fruit (Fragaria vesca L.) was studied. Fruits were stored at 3 degrees C for three weeks in different atmosphere compositions: 0.05% CO2/21% O2 (air), 3% CO2/18% O2, 6% CO2/15% O2, 10% CO2/11% O2, and 15% CO2/6% O2. The effect of gas composition on soluble solids content, titrable acidity, pH, off-flavor, aroma volatiles, and consumer preference was monitored. The result showed that the 10% CO2/11% O2 combination can efficiently prolong the shelf life of wild strawberries by maintaining the quality parameters within acceptable values, through inhibiting the development of Botrytis cinerea, without significantly modifying consumer acceptance.

Structure and function of nematode communities across the Indian western continental margin and its oxygen minimum zone

NASA Astrophysics Data System (ADS)

Singh, R.; Ingole, B. S.

2016-01-01

We studied patterns of nematode distribution along the western Indian continental margin to determine the influence of habitat heterogeneity and low oxygen levels on the community's taxonomic and functional structure. A single transect, perpendicular to the coast at 14° N latitude was sampled from 34 to 2546 m depth for biological and environmental variables during August 2007. The oxygen minimum zone extended from 102 to 1001 m. Nematodes (described and undescribed) were identified to species and classified according to biological and functional traits. A total of 110 nematode species belonging to 24 families were found along the transect. Three depth zones were identified: the shelf (depth range: 34-102 m; highest nematode mean density: 176.6 ± 37 ind 10 cm-2), the slope (525-1524 m; 124.3 ± 16 ind 10 cm-2), and the basin (2001-2546 m; 62.9 ± 2 ind 10 cm-2). Across the entire study area, the dominant species were Terschellingia longicaudata, Desmodora sp. 1, Sphaerolaimus gracilis, and Theristus ensifer; their maximum density was at shelf stations. Nematode communities in different zones differed in species composition. Chromadorita sp. 2 (2.78 %) and Sphaerolaimus gracilis (2.21 %) were dominant on the shelf, whereas Terschellingia longicaudata (4.73 %) and Desmodora sp. 1 (4.42 %) were dominant on the slope, but in the basin, Halalaimus sp. 1(1.11 %) and Acantholaimus elegans (1.11 %) were dominant. The information in a particular functional group was not a simple reflection of the information in species abundance. Ecological information captured by adult length, adult shape, and life-history strategy was less site-specific and thus differed notably from information contained in other taxonomic groups. The functional composition of nematodes was strongly linked to the organic-carbon and dissolved-oxygen concentration. Seven species were found exclusively in the oxygen minimum zone: Pselionema sp. 1, Choanolaimus sp. 2, Halichoanolaimus sp. 1, Cobbia dentata, Daptonema sp. 1, Trissonchulus sp. 1, and Minolaimus sp. 1. Correlation with a number of environmental variables indicated that food quantity (measured as the organic-carbon content and chlorophyll content) and oxygen level were the major factors that influenced nematode community structure and function.

Fish community diversity in the middle continental shelf of the East China Sea

NASA Astrophysics Data System (ADS)

Shan, Xiujuan; Jin, Xianshi; Zhou, Zhipeng; Dai, Fangqun

2011-11-01

The status of fishery stocks in the coastal waters of China is far from ideal, mainly due to climate change and the impacts of human activities (e.g., pollution and overfishing). Thus, the restoration and protection of fishery resources have become critical and complex. The stability and balanced structure of the fish community is a basic foundation for the protection of fishery resources. Based on data collected from bottom trawls by the R/V Beidou in continental shelf of the East China Sea in November 2006 and February 2007, changes in the composition and diversity of fish species and functional groups were analyzed. The research area was divided into offshore waters and inshore waters by the two-way indicator species analysis (TWIA). The results showed that the dominant species were different between offshore waters and inshore waters and also varied with the survey time. The most abundant family was Sciaenidae and Teraponidae in November 2006, Sciaenidae, Engraulidae and Triglidae were most abundant in February 2007. The species belonged mainly to mobile piscivores (G6), benthivores/piscivores (G4), benthivores (G3) and planktivores (G1), and the dominant species in November 2006 were commercial species (e.g. Larimichthys polyactis and Trichiurus japonicus), but small-sized species were dominant in February 2007 (e.g., Harpadon nehereus, Benthosema pterotum, Champsodon capensis, and Acropoma japonicum). The species diversity showed a similar trend as the functional group diversity. Stations with higher diversity were mainly distributed in inshore waters in February 2007, whereas higher diversity was found in offshore waters in November 2006. The highest biomass and species number were found in G6 group, followed by the G4, G5 and G1 groups. The distribution of the number of individuals of each functional group showed the opposite trend as that of the biomass distribution. In addition, the size spectra were mainly concentrated around 3-29 cm, and the individual number of fish species gradually decreased with the increase in body size, but the relative biomass showed a moderate fluctuation in each size class. These changes showed that species with faster growth rate and earlier maturity age became dominant in continental shelf of the East China Sea. So the variations in biological characteristics of fish should be fully considered in maintaining sustainable utilization of fishery resource.

Nutrients in waters on the inner shelf between Cape Charles and Cape Hatteras

NASA Technical Reports Server (NTRS)

Wong, G. T. F.; Todd, J. F.

1981-01-01

The distribution of nutrients in the shelf waters of the southern tip of the Middle Atlantic Bight was investigated. It is concluded that the outflow of freshwater from the Chesapeake Bay is a potential source of nutrients to the adjacent shelf waters. However, a quantitative estimation of its importance cannot yet be made because (1) there are other sources of nutrients to the study area and these sources cannot yet be quantified and (2) the concentrations of nutrients in the outflow from Chesapeake Bay exhibit significant short-term and long-term temporal variabilities.

Storm-Generated Sediment Distribution Along the Northwest Florida Inner Continental Shelf

DTIC Science & Technology

2009-10-04

grain shape, direct shear, radiocarbon isotope, and lignin -phenol analyses were performed on grab or vibracore samples collected after the storm...near-shore continental shelf. 15. SUBJECT TERMS Lignin , seafloor imagery, sedimentation, sediments 16. SECURITY CLASSIFICATION OF: a. REPORT...direct shear, radiocarbon isotope, and lignin -phenol analyses were performed on grab or vibracore samples collected after the storm. Sonar

Composite coating of alginate-olive oil enriched with antioxidants enhances postharvest quality and shelf life of Ber fruit (Ziziphus mauritiana Lamk. Var. Gola).

PubMed

Ramana Rao, T V; Baraiya, Nilanjana S; Vyas, Pinal B; Patel, Dhara M

2016-01-01

The present study has been carried out to evaluate the effect of a composite edible coating of 2 % Sodium alginate and 0.2 % Olive oil with combination of 1 % ascorbic acid and 1 % citric acid on the post harvest nutritional quality and shelf life of Ber fruit stored at 25 ± 2 °C and 65 % R.H. The coatings reduced the decay occurrence, weight loss, accumulation of total soluble solids (TSS) and total sugars in Ber fruit and enhanced the level of antioxidants. The delayed activity of polygalacturonase (PG), Pectate lyase (PL) and Pectin methyl esterase (PME) was noticed in coated fruits than that of the control fruit indicating the reduced softening and ripening process. These findings suggest that the composite edible coating tested under the current study has the potential to control decaying incidence of Ber fruit, extends its storage life and also improves its valuable nutritional characteristics.

Lightweight, Rack-Mountable Composite Cold Plate/Shelves

NASA Technical Reports Server (NTRS)

Hurlbert, Kathryn M.; Ruemmele, Warren; Nguyen, Hai D.; Andish, Kambiz; McCalley, Sean

2004-01-01

Rack-mountable composite-material structural components that would serve as both shelves and cold plates for removing heat from electronic or other equipment mounted on the shelves have been proposed as lightweight alternatives to all-metal cold plate/shelves now in use. A proposed cold plate/shelf would include a highly thermally conductive face sheet containing oriented graphite fibers bonded to an aluminum honeycomb core, plus an extruded stainless-steel substructure containing optimized flow passages for a cooling fluid, and an inlet and outlet that could be connected to standard manifold sections. To maximize heat-transfer efficiency, the extruded stainless-steel substructure would be connected directly to the face sheet. On the basis of a tentative design, the proposed composite cold plate/shelf would weigh about 38 percent less than does an all-aluminum cold plate in use or planned for use in some spacecraft and possibly aircraft. Although weight is a primary consideration, the tentative design offers the additional benefit of reduction of thickness to half that of the all-aluminum version.

Movement and effects of spilled oil over the outer continental shelf; inadequacy of existent data for the Baltimore Canyon Trough area

USGS Publications Warehouse

Knebel, Harley J.

1974-01-01

A deductive approach to the problem of determining the movement and effects of spilled oil over the Outer Continental Shelf requires that the potential paths of oil be determined first, in order that critical subareas may be defined for later studies. The paths of spilled oil, in turn, depend primarily on the temporal and spatial variability of four factors: the thermohaline structure of the waters, the circulation of the water, the winds, and the distribution of suspended matter. A review of the existent data concerning these factors for the Baltimore Canyon Trough area (a relatively well studied segment of the Continental Shelf) reveals that the movement and dispersal of potential oil spills cannot be reliably predicted. Variations in the thermohaline structure of waters and in the distribution of suspended matter are adequately known; the uncertainty is due to insufficient wind and storm statistics and to the lack of quantitative understanding of the relationship between the nontidal drift and its basic driving mechanisms. Similar inadequacies should be anticipated for other potentially leasable areas of the shelf because an understanding of the movement of spilled oil has not been the underlying aim of most previous studies.

Relationship of Powder Feedstock Variability to Microstructure and Defects in Selective Laser Melted Alloy 718

NASA Technical Reports Server (NTRS)

Smith, T. M.; Kloesel, M. F.; Sudbrack, C. K.

2017-01-01

Powder-bed additive manufacturing processes use fine powders to build parts layer by layer. For selective laser melted (SLM) Alloy 718, the powders that are available off-the-shelf are in the 10-45 or 15-45 micron size range. A comprehensive investigation of sixteen powders from these typical ranges and two off-nominal-sized powders is underway to gain insight into the impact of feedstock on processing, durability and performance of 718 SLM space-flight hardware. This talk emphasizes an aspect of this work: the impact of powder variability on the microstructure and defects observed in the as-fabricated and full heated material, where lab-scale components were built using vendor recommended parameters. These typical powders exhibit variation in composition, percentage of fines, roughness, morphology and particle size distribution. How these differences relate to the melt-pool size, porosity, grain structure, precipitate distributions, and inclusion content will be presented and discussed in context of build quality and powder acceptance.

Map of Distribution of Bottom Sediments on the Continental Shelf, Gulf of Alaska

USGS Publications Warehouse

Evans, Kevin R.; Carlson, Paul R.; Hampton, Monty A.; Marlow, Michael S.; Barnes, Peter W.

2000-01-01

Introduction The U.S. Geological Survey has a long history of exploring marine geology in the Gulf of Alaska. As part of a cooperative program with other federal and state agencies, the USGS is investigating the relations between ocean-floor geology and benthic marine biohabitats. This bottom sediment map, compiled from published literature will help marine biologists develop an understanding of sea-floor geology in relation to various biological habitats. The pattern of sea-floor sedimentation and bottom morphology in the Gulf of Alaska reflects a complex interplay of regional tectonism, glacial advances and retreats, oceanic and tidal currents, waves, storms, eustatic change, and gravity-driven processes. This map, based on numerous cruises during the period of 1970-1996, shows distribution of bottom sediments in areas of study on the continental shelf. The samples were collected with piston, box, and gravity corers, and grab samplers. The interpretations of sediment distribution are the products of sediment size analyses combined with interpretations of high-resolution seismic reflection profiles. The sea floor was separated into several areas as follows: Cook Inlet -- Hazards studies in this embayment emphasized sediment distribution, sediment dynamics, bedforms, shallow faults, and seafloor stability. Migrating mega-sandwaves, driven by strong tidal currents, influence seabed habitats and stability of the seafloor, especially near pipelines and drilling platforms. The coarseness of the bottom sediment reinforces the influence of the strong tidal currents on the seafloor habitats. Kodiak Shelf -- Tectonic framework studies demonstrate the development of an accretionary wedge as the Pacific Plate underthrusts the Alaskan landmass. Seismic data across the accretionary wedge reveal anomalies indicative of fluid/gas vent sites in this segment of the continental margin. Geologic hazards research shows that movement along numerous shallow faults poses a risk to sea floor structures. Sea-floor sediment on shallow banks is eroded by seasonal wave-generated currents. The winnowing action of the large storm waves results in concentrations of gravel over broad segments of the Kodiak shelf. Northeastern Gulf of Alaska -- Tectonic framework studies demonstrate that rocks of distant origin (Yakutat terrane) are currently attached to and moving with the Pacific Plate, as it collides with and is subducted beneath southern Alaska. This collision process has led to pronounced structural deformation of the continental margin and adjacent southern Alaska. Consequences include rapidly rising mountains and high fluvial and glacial sedimentation rates on the adjacent margin and ocean floor. The northeastern Gulf of Alaska shelf also has concentrations of winnowed (lag) gravel on Tarr Bank and on the outer shelf southeast of Yakutat Bay. Between Kayak Island and Yakutat Bay the outer shelf consists of pebbly mud (diamict). This diamict is a product of glacial marine sedimentation during the Pleistocene and is present today as a relict sediment. A prograding wedge of Holocene sediment consisting of nearshore sand grading seaward into clayey silt and silty clay covers the relict pebbly mud to mid-shelf and beyond. Shelf and slope channel systems transport glacially derived sediment across the continental margin into Surveyor Channel, an abyssal fan and channel system that reaches over 1,000 km to the Aleutian Trench.

Recognition, correlation, and hierarchical stacking patterns of cycles in the Ferry Lake - Uppe Glen Rose, East Texas Basin: Implications for grainstone reservoir distribution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fitchen, W.M.; Bebout, D.G.; Hoffman, C.L.

1994-12-31

Core descriptions and regional log correlation/interpretation of Ferry Lake-Upper Glen Rose strata in the East Texas Basin exhibit the uniformity of cyclicity in these shelf units. The cyclicity is defined by an upward decrease in shale content within each cycle accompanied by an upward increase in anhydrite (Ferry Lake) or carbonate (Upper Glen Rose). Core-to-log calibration of facies indicates that formation resistivity is inversely proportional to shale content and thus is a potential proxy for facies identification beyond core control. Cycles (delineated by resistivity log patterns) were correlated for 90 mi across the shelf; they show little change in logmore » signature despite significant updip thinning due to the regional subsidence gradient. The Ferry-Lake-Upper Glen Rose intervals is interpreted as a composite sequence composed of 13 high-frequency sequences (4 in the Ferry Lake and 9 in the Upper Glen Rose). High-frequency sequences contain approximately 20 ({+-}5) cycles; in the Upper Glen Rose, successive cycles exhibit decreasing proportions of shale and increasing proportions of grain-rich carbonate. High-frequency sequences were terminated by terrigenous inundation, possibly preceded by subaerial exposure. Cycle and high-frequency sequence composition is interpreted to reflect composite, periodic(?) fluctuations is terrigeneous dilution from nearby source areas. Grainstones typically occur (stratigraphically) within the upper cycles of high-frequency sequences, where terrigeneous dilution and turbidity were least and potential for carbonate production and shoaling was greatest. Published mid-Cretaceous geographic reconstructions and climate models suggest that precipitation and runoff in the area were controlled by the seasonal amplitude in solar insolation. In this model, orbital variations, combined with subsidence, hydrography, and bathymetry, were in primary controls on Ferry Lake-Upper Glen Rose facies architecture and stratigraphic development.« less

Impacts of sediment supply and local tectonics on clinoform distribution: the seismic stratigraphy of the mid Pleistocene-Holocene Indus Shelf

NASA Astrophysics Data System (ADS)

Limmer, David R.; Henstock, Timothy J.; Giosan, Liviu; Ponton, Camilo; Tabrez, Ali R.; Macdonald, David I. M.; Clift, Peter D.

2012-09-01

We present results from the first high-resolution seismic reflection survey of the inner Western Indus Shelf, and Indus Delta, Arabian Sea. The results show major regional differences in sedimentation across the shelf from east to west, as well as north to south, both since the Last Glacial Maximum (~20 ka) and over longer time scales. We identify 10 major regional reflectors, interpreted as representing sea level lowstands. Strong compressive folding is observed underlying a reflector we have called Horizon 6 in the north-western shelf, probably compression associated with the transpressional deformation of the Murray Ridge plate boundary. Downslope profiles show a series of well developed clinoforms, principally at the shelf edge, indicating significant preservation of large packages of sediment during lowstands. These clinoforms have developed close to zones of deformation, suggesting that subsidence is a factor in controlling sedimentation and consequently erosion of the Indus Shelf. These clinoforms fan out from dome features (tectonic anticlines) mostly located close to the modern shoreline.

Arsenic enrichment in shelf and coastal sediment of the Brazilian subtropics

NASA Astrophysics Data System (ADS)

Mirlean, N.; Medeanic, S.; Garcia, F. A.; Travassos, M. P.; Baisch, P.

2012-03-01

High levels of As (i.e., above the nationally legislated threshold of 70 mg kg-1) were found in shelf sediment of the Espirito Santo state of Brazil. The elevated content of this metalloid propagated in the sediment to a depth of approximately 1.5 m. The adjacent beach sands and mangrove sediments were also enriched in As. The variation in As levels along the shelf sediment profiles was acompained by calcareous-material distribution, which reflects the paleogeographical circumstances that promote local reef development during the corresponding intervals of sedimentation. Arsenic-rich calcareous bioclast materials migrate to a beach from the surface horizon of nearby shelf sediment, thereby replacing the part of the As that previously entered the marine environment with eroded material from the continent to the littoral zone. The segment of the Brazilian tropical shelf that was studied clearly demonstrated that the As enrichment of the shelf sediment is determined by the exposure of the Barreiras formation on the coast and the development of reefs, which are favorable sites for the settling of bodies of biogenic carbonates.

Estimation of the processes controlling variability in phytoplankton pigment distributions on the southeastern U.S. continental shelf

NASA Technical Reports Server (NTRS)

Mcclain, Charles R.; Ishizaka, Joji; Hofmann, Eileen E.

1990-01-01

Five coastal-zone-color-scanner images from the southeastern U.S. continental shelf are combined with concurrent moored current meter measurements to assess the processes controlling the variability in chlorophyll concentration and distribution in this region. An equation governing the space and time distribution of a nonconservative quantity such as chlorophyll is used in the calculations. The terms of the equation, estimated from observations, show that advective, diffusive, and local processes contribute to the plankton distributions and vary with time and location. The results from this calculation are compared with similar results obtained using a numerical physical-biological model with circulation fields derived from an optimal interpolation of the current meter observations and it is concluded that the two approaches produce different estimates of the processes controlling phytoplankton variability.

Shelf-life prediction models for ready-to-eat fresh cut salads: Testing in real cold chain.

PubMed

Tsironi, Theofania; Dermesonlouoglou, Efimia; Giannoglou, Marianna; Gogou, Eleni; Katsaros, George; Taoukis, Petros

2017-01-02

The aim of the study was to develop and test the applicability of predictive models for shelf-life estimation of ready-to-eat (RTE) fresh cut salads in realistic distribution temperature conditions in the food supply chain. A systematic kinetic study of quality loss of RTE mixed salad (lollo rosso lettuce-40%, lollo verde lettuce-45%, rocket-15%) packed under modified atmospheres (3% O 2 , 10% CO 2 , 87% N 2 ) was conducted. Microbial population (total viable count, Pseudomonas spp., lactic acid bacteria), vitamin C, colour and texture were the measured quality parameters. Kinetic models for these indices were developed to determine the quality loss and calculate product remaining shelf-life (SL R ). Storage experiments were conducted at isothermal (2.5-15°C) and non-isothermal temperature conditions (T eff =7.8°C defined as the constant temperature that results in the same quality value as the variable temperature distribution) for validation purposes. Pseudomonas dominated spoilage, followed by browning and chemical changes. The end of shelf-life correlated with a Pseudomonas spp. level of 8 log(cfu/g), and 20% loss of the initial vitamin C content. The effect of temperature on these quality parameters was expressed by the Arrhenius equation; activation energy (E a ) value was 69.1 and 122.6kJ/mol for Pseudomonas spp. growth and vitamin C loss rates, respectively. Shelf-life prediction models were also validated in real cold chain conditions (including the stages of transport to and storage at retail distribution center, transport to and display at 7 retail stores, transport to and storage in domestic refrigerators). The quality level and SL R estimated after 2-3days of domestic storage (time of consumption) ranged between 1 and 8days at 4°C and was predicted within satisfactory statistical error by the kinetic models. T eff in the cold chain ranged between 3.7 and 8.3°C. Using the validated models, SL R of RTE fresh cut salad can be estimated at any point of the cold chain if the temperature history is known. Shelf-life models of validated applicability can serve as an effective tool for shelf-life assessment and the development of new products in the fresh produce food sector. Copyright © 2016. Published by Elsevier B.V.

Stable Carbon Isotope Composition of Remineralizing Organic Matter in the Northern Gulf of Mexico Continental Shelf

NASA Astrophysics Data System (ADS)

Hu, X.; Wang, H.; Rabalais, N. N.

2016-02-01

Despite years of study, whether water column or benthic respiration controls oxygen consumption in the seasonally hypoxic Northern Gulf of Mexico (nGOM) waters remains contentious. Elucidating this control is essential for long-term nutrient management purposes. In this study, we examined stable carbon isotope composition (δ13C) of organic matter that was remineralized in subsurface water of the nGOM continental shelf using both shipboard incubations (water and sediment) and a three-endmember mixing model. Based on our 2014 data, sediment and water incubations yielded disparate δ13C signatures in the respiration produced CO2, with the sediment incubation generating substantially more 13C-enriched CO2 (-16 -21‰ in sediment vs. -27 -29‰ in water), though water column bulk particulate organic matter (POM) had δ13C ranging from -23‰ to -25‰. However, from the three-endmember mixing model, our calculated CO2-δ13C due to respiration in the entire surveyed nGOM shelf was -18.5‰. This value was consistent with the results obtained in previous annual shelfwide cruises (-17.2 -19.5‰). The close agreement between respirational CO2-δ13C from the mixing model and that from sediment incubation suggests that benthic process likely played a dominant role in subsurface respiration in the nGOM shelf. This result also indicates that hydrocarbon remineralization was likely insignificant on the ecosystem level after the 2010 Deepwater Horizon oil spill.

Controls on reef development and the terrigenous-carbonate interface on a shallow shelf, Nicaragua (Central America)

NASA Astrophysics Data System (ADS)

Roberts, H. H.; Murray, S. P.

1983-06-01

Marine geology and physical oceanographic data collected during two field projects (˜4 months) on the Caribbean shelf of Nicaragua indicate a surprising dominance of carbonate deposition and reef growth on a shelf that is receiving an abnormally large volume of terrigenous sediments. High rainfall rates (˜400 500 cm/year), coupled with a warm tropical climate, encourage rapid denudation of the country's central volcanic highland and transport of large volumes of terrigenous sediment and fresh water to the coast. Estimates suggest that three times more fresh water and fifteen times more sediment are introduced per unit length of coastline than on the east coast of the United States. Distribution of the terrigenous facies, development of carbonate sediment suites, and the location and quality of viable reefs are strongly controlled by the dynamic interaction near the coasts of highly turbid fresh to brackish water effluents from thirteen rivers with clear marine waters of the shelf. Oceanic water from the central Caribbean drift current intersects the shelf and moves slowely in a dominant northwest direction toward the Yucatan Channel. A sluggish secondary gyre moves to the south toward Costa Rica. In contrast, the turbid coastal water is deflected to the south in response to density gradients, surface water slopes, and momentum supplied by the steady northeast trade winds. A distinct two-layered flow is commonly present in the sediment-rich coastal boundary zone, which is typically 10 20 km wide. The low-salinity upper layer is frictionally uncoupled from the ambient shelf water and therefore can expand out of the normally coherent coastal boundary zone during periods of abnormal flooding or times when instability is introduced into the northeast trades. Reef distribution, abruptness of the terrigenous-carbonate interface, and general shelf morphology reflect the long-term dynamic structure of the shelf waters. A smooth-bottomed ramp of siliciclastic sands to silts and clays mantles the inner shelf floor in a linear belt paralleling the coast. This belt generally corresponds to the western flank of the coastal boundary zone. Occurrence of reefs is generally confined to areas outside this zone. Terrigenous clays and silts of the inner shelf are abruptly (<20 km from the coast) replaced by Halimeda-rich sediment of the middle and outer shelf. Within the carbonate facies belt, reef complexes thrive as small, isolated masses; large, reef-capped platforms; reef fringes around islands; and shelfedge structures with vertical relief that can exceed 25 m. In general, the frequency and proliferation of reefs increase away from the turbid coastal boundary layer and toward the cooler and saltier water that upwells at the shelf margin.

Development of the benethic nepheloid layer on the south Texas continental shelf, western Gulf of Mexico

USGS Publications Warehouse

Shideler, G.L.

1981-01-01

A monitoring study of suspended sediment on the South Texas Continental Shelf indicates that a turbid benthic nepheloid layer is regionally persistent. A sequence of quasi-synoptic measurements of the water column obtained during six cruises in an 18-month period indicates substantial spatial and temporal variability in nepheloidlayer characteristics. Regionally, the thickness of the shelf nepheloid layer increases both seaward and in a convergent alongshelf direction. Greatest thicknesses occur over a muddy substrate, indicating a causal relationship; maximum observed local thickness is 35 m which occurs along the southern shelf break. Analyses of suspended particulate matter in shelf bottom waters indicate mean concentrations ranging from 49 ?? 104 to 111 ?? 104 particle counts/cc; concentrations persistently increase shoreward throughout the region. Bottom particulate matter is predominantly composed of inorganic detritus. Admixtures of organic skeletal particles, primarily diatoms, are generally present but average less than 10% of the total particulate composition. Texturally, the particulate matter in bottom waters is predominantly poorly sorted sediment composed of very fine silt (3.9-7.8 ??m). The variability in nepheloid-layer characteristics indicates a highly dynamic shelf feature. The relationship of nepheloid-layer characteristics to hydrographic and substrate conditions suggests a conceptual model whereby nepheloid-layer development and maintenance are the results of the resuspension of sea-floor sediment. Bottom turbulence is attributed primarily to vertical shear and shoaling progressive internal waves generated by migrating shelf-water masses, especially oceanic frontal systems, and secondarily to shoaling surface gravity waves. ?? 1981.

Temporal and spatial variations in suspended matter in continental shelf and slope waters off the north-eastern United States

USGS Publications Warehouse

Bothner, Michael H.; Parmenter, Carol M.; Milliman, John D.

1981-01-01

Seston in waters of Georges Bank originates primarily from biological production and from resuspension of bottom sediments. The concentrations of suspended matter observed on the central shoals are more influenced by storms than by seasonal changes. Winter storms produce highest concentrations of non-combustible material throughout the water column, and summer storms appear to increase biological production by mixing additional nutrients into the photic zone. On the south-east flank of the bank, in water depths between 80 and 200 in, the concentrations of total suspended matter and non-combustible material show little variation compared with the central shoals, and storm effects are far less noticeable.Highest concentrations (>15 mg 1−1) of suspended matter occur in bottom waters south of Nantucket Island after winter storms and appear to be primarily resuspended bottom sediment. Resuspended sediment is also common in near-bottom waters of the south-western Gulf of Maine, and occasionally near the intersection of the shelf/slope water mass front and the bottom.Seasonal variations were observed in the distribution and species composition of phytoplankton. Coccoliths are predominant on the central bank during the winter, but during the spring and summer they are concentrated on the eastern flank at deeper depths.

The internal structure of the Brunt Ice Shelf, Antarctica from ice-penetrating radar

NASA Astrophysics Data System (ADS)

King, Edward; De Rydt, Jan; Gudmundsson, Hilmar

2016-04-01

The Brunt Ice Shelf is a small feature on the Coats Land Coast of the Weddell Sea, Antarctica. It is unusual among Antarctic ice shelves because the ice crossing the grounding line from the ice sheet retains no structural integrity, so the ice shelf comprises icebergs of continental ice cemented together by sea ice, with the whole blanketed by in-situ snowfall. The size and distribution of the icebergs is governed by the thickness profile along the grounding line. Where bedrock troughs discharge thick ice to the ice shelf, the icebergs are large and remain close together with little intervening sea ice. Where bedrock ridges mean the ice crossing the grounding line is thin, the icebergs are small and widely-scattered with large areas of sea ice between them. To better understand the internal structure of the Brunt Ice Shelf and how this might affect the flow dynamics we conducted ice-penetrating radar surveys during December 2015 and January 2016. Three different ground-based radar systems were used, operating at centre frequencies of 400, 50 and 10 MHz respectively. The 400 MHz system gave detailed firn structure and accumulation profiles as well as time-lapse profiles of the active propagation of a crevasse. The 50 MHz system provided intermediate-level detail of iceberg distribution and thickness as well as information on the degree of salt water infiltration into the accumulating snow pack. The 10 MHz system used a high-power transmitter in an attempt to measure ice thickness beneath salt-impregnated ice. In this poster we will present example data from each of the three radar systems which will demonstrate the variability of the internal structure of the ice shelf. We will also present preliminary correlations between the internal structure and the surface topography from satellite data.

Teardown analysis for detecting shelf-life degradation

NASA Technical Reports Server (NTRS)

Eckstein, A. S.

1971-01-01

Analysis is guideline in examining component materials, analytically determining physical properties and chemical compositions, and developing control data necessary for ascertaining effects of environments and their influence on deterioration and degradation mechanisms.

Carbon mineralization in Laptev and East Siberian sea shelf and slope sediment

NASA Astrophysics Data System (ADS)

Brüchert, Volker; Bröder, Lisa; Sawicka, Joanna E.; Tesi, Tommaso; Joye, Samantha P.; Sun, Xiaole; Semiletov, Igor P.; Samarkin, Vladimir A.

2018-01-01

The Siberian Arctic Sea shelf and slope is a key region for the degradation of terrestrial organic material transported from the organic-carbon-rich permafrost regions of Siberia. We report on sediment carbon mineralization rates based on O2 microelectrode profiling; intact sediment core incubations; 35S-sulfate tracer experiments; pore-water dissolved inorganic carbon (DIC); δ13CDIC; and iron, manganese, and ammonium concentrations from 20 shelf and slope stations. This data set provides a spatial overview of sediment carbon mineralization rates and pathways over large parts of the outer Laptev and East Siberian Arctic shelf and slope and allows us to assess degradation rates and efficiency of carbon burial in these sediments. Rates of oxygen uptake and iron and manganese reduction were comparable to temperate shelf and slope environments, but bacterial sulfate reduction rates were comparatively low. In the topmost 50 cm of sediment, aerobic carbon mineralization dominated degradation and comprised on average 84 % of the depth-integrated carbon mineralization. Oxygen uptake rates and anaerobic carbon mineralization rates were higher in the eastern East Siberian Sea shelf compared to the Laptev Sea shelf. DIC / NH4+ ratios in pore waters and the stable carbon isotope composition of remineralized DIC indicated that the degraded organic matter on the Siberian shelf and slope was a mixture of marine and terrestrial organic matter. Based on dual end-member calculations, the terrestrial organic carbon contribution varied between 32 and 36 %, with a higher contribution in the Laptev Sea than in the East Siberian Sea. Extrapolation of the measured degradation rates using isotope end-member apportionment over the outer shelf of the Laptev and East Siberian seas suggests that about 16 Tg C yr-1 is respired in the outer shelf seafloor sediment. Of the organic matter buried below the oxygen penetration depth, between 0.6 and 1.3 Tg C yr-1 is degraded by anaerobic processes, with a terrestrial organic carbon contribution ranging between 0.3 and 0.5 Tg yr-1.

Macrofaunal production and biological traits: Spatial relationships along the UK continental shelf

NASA Astrophysics Data System (ADS)

Bolam, S. G.; Eggleton, J. D.

2014-04-01

Biological trait analysis (BTA) is increasingly being employed to improve our understanding of the ecological functioning of marine benthic invertebrate communities. However, changes in trait composition are seldomly compared with concomitant changes in metrics of ecological function. Consequently, inferences regarding the functional implications of any changes are often anecdotal; we currently have a limited understanding of the functional significance of the traits commonly used. In this study, we quantify the relationship between benthic invertebrate trait composition and secondary production estimates using data spanning almost the breadth of the UK continental shelf. Communities described by their composition of 10 traits representing life history, morphology and behaviour showed strong relationships with variations in total secondary production. A much weaker relationship was observed for community productivity (or P:B), a measure of rate of energy turnover. Furthermore, the relationship between total production and multivariate taxonomic community composition was far weaker than that for trait composition. Indeed, the similarities between communities as defined by taxonomy were very different from those depicted by their trait composition. That is, as many studies have demonstrated, taxonomically different communities may display similar trait compositions, and vice versa. Finally, we found that descriptions of community trait composition vary greatly depending on whether abundance or biomass is used as the enumeration weighting method during BTA, and trait assessments based on biomass produced better relations with secondary production than those based on abundance. We discuss the significance of these findings with respect to BTA using marine benthic invertebrates.

Impact of the Extreme Warming of 2012 on Shelfbreak Frontal Structure North of Cape Hatteras

NASA Astrophysics Data System (ADS)

Gawarkiewickz, G.

2014-12-01

Continental shelf circulation north of Cape Hatteras is complex, with southward flowing Middle Atlantic Bight shelf water intersecting the Gulf Stream and subducting offshore into the Gulf Stream. In May, 2012, a cruise was conducted in order to study the shelf circulation and acoustic propagation through fish schools in the area. An important aspect of the study was to use Autonomous Underwater Vehicles to map fish schools with a sidescan sonar. High-resolution hydrographic surveys to map the continental shelf water masses and shelfbreak frontal structure were sampled to relate oceanographic conditions to the fish school distributions. The cold pool water mass over the continental shelf in May 2012 was extremely warm, with temperature anomalies of up to 5 Degrees C relative to observations from the same area in May, 1996. The normal cross-shelf temperature gradients within the shelfbreak front were not present because of the warming. As a result, the shelf density field was much more buoyant than usual, which led to an accelerated shelfbreak jet. Moored velocity measurements at the 60 m isobath recorded alongshelf flow of as much as 0.6 m/s. The anticipated fish species were not observed over the continental shelf. Some comments on the forcing leading to the large scale warming will be presented, along with a brief discussion of the impact of the warming on the marine ecosystem in the northeast U.S.

Impacts of Outer Continental Shelf (OCS) development on recreation and tourism. Volume 5. Program logic manual

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

The final report for the project is presented in five volumes. This volume is the Programmer's Manual. It covers: a system overview, attractiveness component of gravity model, trip-distribution component of gravity model, economic-effects model, and the consumer-surplus model. The project sought to determine the impact of Outer Continental Shelf development on recreation and tourism.

Hydroelastic analysis of ice shelves under long wave excitation

NASA Astrophysics Data System (ADS)

Papathanasiou, T. K.; Karperaki, A. E.; Theotokoglou, E. E.; Belibassakis, K. A.

2015-05-01

The transient hydroelastic response of an ice shelf under long wave excitation is analysed by means of the finite element method. The simple model, presented in this work, is used for the simulation of the generated kinematic and stress fields in an ice shelf, when the latter interacts with a tsunami wave. The ice shelf, being of large length compared to its thickness, is modelled as an elastic Euler-Bernoulli beam, constrained at the grounding line. The hydrodynamic field is represented by the linearised shallow water equations. The numerical solution is based on the development of a special hydroelastic finite element for the system of governing of equations. Motivated by the 2011 Sulzberger Ice Shelf (SIS) calving event and its correlation with the Honshu Tsunami, the SIS stable configuration is studied. The extreme values of the bending moment distribution in both space and time are examined. Finally, the location of these extrema is investigated for different values of ice shelf thickness and tsunami wave length.

Hydroelastic analysis of ice shelves under long wave excitation

NASA Astrophysics Data System (ADS)

Papathanasiou, T. K.; Karperaki, A. E.; Theotokoglou, E. E.; Belibassakis, K. A.

2015-08-01

The transient hydroelastic response of an ice shelf under long wave excitation is analysed by means of the finite element method. The simple model, presented in this work, is used for the simulation of the generated kinematic and stress fields in an ice shelf, when the latter interacts with a tsunami wave. The ice shelf, being of large length compared to its thickness, is modelled as an elastic Euler-Bernoulli beam, constrained at the grounding line. The hydrodynamic field is represented by the linearised shallow water equations. The numerical solution is based on the development of a special hydroelastic finite element for the system of governing of equations. Motivated by the 2011 Sulzberger Ice Shelf (SIS) calving event and its correlation with the Honshu Tsunami, the SIS stable configuration is studied. The extreme values of the bending moment distribution in both space and time are examined. Finally, the location of these extrema is investigated for different values of ice shelf thickness and tsunami wave length.

Diets and niche overlap among nine co-occurring demersal fishes in the southern continental shelf of East/Japan Sea, Korea

NASA Astrophysics Data System (ADS)

Myun Park, Joo; Nam Kwak, Seok; Huh, Sung-Hoi; Han, In-Seong

2017-09-01

Dietary niches and food resource partitioning can support the coexistence of many fishes in benthic marine systems, which can lead to the greater abundances of those species that can potentially support their fisheries. Diets and niche overlap among nine demersal fish species were investigated in the southern continental shelf of East/Japan Sea, Korea. Specimens were collected monthly from January to November 2007 on soft bottoms between 40 and 100 m depth using a bottom trawl. A total of 20 prey taxa were found in 1904 stomachs of the nine species. Comparison of the stomach contents among the nine species showed that inter-specific dietary compositions differed significantly. Although all fish species consumed similar types of prey items, their contributions to the diet of different species varied. Among prey taxa, carid shrimps contributed greatly to the diets of Amblychaeturichthys hexanema, Amblychaeturichthys sciistius, Coelorinchus multispinulosus, Lepidotrigla guentheri, and Liparis tanakae, whereas polychaetes and teleosts contributed to the diets of Callionymus lunatus and Lophius litulon, respectively. On the other hand, carid shrimps and teleosts together contributed to the diets of Pseudorhombus pentophthalmus. Non-metric multivariate analysis of the mass contributions of dietary categories for food resources emphasized visually that the dietary compositions of the nine species differed. Although C. multispinulosus, L. guentheri, L. litulon, and L. tanakae showed similar dietary compositions between small and large size classes, ontogenetic diet changes of the remaining six species were evident. Feeding relationships among the nine demersal species were complicated, but inter- and intra-specific differences in dietary composition among the species reduced potential competition for food resources within the fish community in the southern continental shelf of East/Japan Sea, Korea.

Vertical diffusivity in the benthic boundary layer of the Oregon shelf from a deliberate tracer release experiment

NASA Astrophysics Data System (ADS)

Ferrón, S.; Ho, D. T.; Hales, B. R.

2010-12-01

A Fluorescein/SF6 deliberate tracer release experiment was conducted in benthic boundary layer (BBL) waters of the outer shelf of Oregon, as part of a multi-disciplinary research project that aims to study cross-shelf carbon transport and biogeochemical reaction rates within the BBL. The purpose of the tracers release was to examine physical transport processes, the rate of turbulent mixing and to provide a Lagrangian frame of reference for tracking other chemical species (pCO2, O2, CH4, DIC, DOC, POC, NO3-, NH4+, Fe). The tracers were injected on May 2009 during moderate upwelling favorable conditions with weak near-bottom currents, along a 4-km N-S line near the shelf streak at the 150 m isobath. Tracers distribution in the patch were tracked for over 5 days by tow-yo surveys using a winch-controlled pumping profiling vehicle that incorporated several in situ instruments such as CTD sensors, a 1200 kHz ADCP and a dye fluorometer for Fluorescein. Dissolved SF6 concentrations were analyzed on board from the underway water stream pumped from the towed vehicle by using an automated high-resolution chromatographic system equipped with an electron capture detector (ECD). The work presented here focuses on the estimation of the effective vertical diffusivity (Kz) in the BBL of the Oregon Shelf from the change in moment of the tracers’ vertical distribution, calculated using a 1D advection-diffusion model.

Distribution and ventilation of water masses in the western Ross Sea inferred from CFC measurements

NASA Astrophysics Data System (ADS)

Rivaro, Paola; Ianni, Carmela; Magi, Emanuele; Massolo, Serena; Budillon, Giorgio; Smethie, William M.

2015-03-01

During the CLIMA Project (R.V. Italica cruise PNRA XVI, January-February 2001), hydrographic and chlorofluorocarbons (CFCs) observations were obtained, particularly in the western Ross Sea. Their distribution demonstrated water mass structure and ventilation processes in the investigated areas. In the surface waters (AASW) the CFC saturation levels varied spatially: CFCs were undersaturated in all the areas (range from 80 to 90%), with the exception of few stations sampled near Ross Island. In particular, the Terra Nova Bay polynya, where high salinity shelf water (HSSW) is produced, was a low-saturated surface area (74%) with respect to CFCs. Throughout most of the shelf area, the presence of modified circumpolar deep water (MCDW) was reflected in a mid-depth CFC concentration minima. Beneath the MCDW, CFC concentrations generally increased in the shelf waters towards the seafloor. We estimated that the corresponding CFCs saturation level in the source water region for HSSW was about 68-70%. Waters with high CFC concentrations were detected in the western Ross Sea on the down slope side of the Drygalski Trough, indicating that AABW was being supplied to the deep Antarctic Basin. Estimates of ventilation ages depend strongly on the saturation levels. We calculated ventilation ages using the saturation level calibrated tracer ratio, CFC11/CFC12. We deduced a mean residence time of the shelf waters of about 6-7 years between the western Ross Sea source and the shelf break.

Mapping and classifying the seabed of the West Greenland continental shelf

NASA Astrophysics Data System (ADS)

Gougeon, S.; Kemp, K. M.; Blicher, M. E.; Yesson, C.

2017-03-01

Marine benthic habitats support a diversity of marine organisms that are both economically and intrinsically valuable. Our knowledge of the distribution of these habitats is largely incomplete, particularly in deeper water and at higher latitudes. The western continental shelf of Greenland is one example of a deep (more than 500 m) Arctic region with limited information available. This study uses an adaptation of the EUNIS seabed classification scheme to document benthic habitats in the region of the West Greenland shrimp trawl fishery from 60°N to 72°N in depths of 61-725 m. More than 2000 images collected at 224 stations between 2011 and 2015 were grouped into 7 habitat classes. A classification model was developed using environmental proxies to make habitat predictions for the entire western shelf (200-700 m below 72°N). The spatial distribution of habitats correlates with temperature and latitude. Muddy sediments appear in northern and colder areas whereas sandy and rocky areas dominate in the south. Southern regions are also warmer and have stronger currents. The Mud habitat is the most widespread, covering around a third of the study area. There is a general pattern that deep channels and basins are dominated by muddy sediments, many of which are fed by glacial sedimentation and outlets from fjords, while shallow banks and shelf have a mix of more complex habitats. This first habitat classification map of the West Greenland shelf will be a useful tool for researchers, management and conservationists.

Mean residence time of the shelf water in the East China and the Yellow Seas determined by 228Ra/226Ra measurements

NASA Astrophysics Data System (ADS)

Nozaki, Yoshiyuki; Kasemsupaya, Vimonrut; Tsubota, Hiroyuki

1989-11-01

Increasing attention of oceanographers has recently been paied on East Asian marginal seas regarding their role on the global environment, yet geochemical investigations have been few to date. We here report new data on the distribution of 228Ra and 226Ra in the surface water of the East China and the Yellow seas in an effort to constrain the time necessary for the coastal and shelf waters to exchange with offshore waters. Such information is needed in evaluating the exchange of heat and water across the air-sea interface that affects the local climate and the fate of pollutants, nutrients and weathering products supplied from the continent. Based on the Ra isotope signals, we have estimated that the shelf water component contributes ˜ 20 % of the Tsushima Current water passing through the Tsushima Strait and the mean residence time for the shelf water to mix with the Kuroshio surface water is ˜ 2.3 years. As many of materials derived from the continent such as heavy metals and the nutrients have their mean residence times less than a few months in the nearshore and shelf waters, they must largely deposit on the shelf sediments prior to the transport from the shelf to the open sea by mixing.

Speciation of phosphorus in the continental shelf sediments in the Eastern Arabian Sea

NASA Astrophysics Data System (ADS)

Acharya, Shiba Shankar; Panigrahi, Mruganka Kumar; Kurian, John; Gupta, Anil Kumar; Tripathy, Subhasish

2016-03-01

The distributions of various forms of phosphorus (P) and their relation with sediment geochemistry in two core sediments near Karwar and Mangalore offshore have been studied through the modified SEDEX procedure (Ruttenberg et al., 2009) and bulk chemical analysis. The present study provides the first quantitative analysis of complete phosphorus speciation in the core sediments of the Eastern Arabian shelf. The chemical index of alteration (CIA), chemical Index of Weathering (CIW) and Al-Ti-Zr ternary diagram suggest low to moderate source area weathering of granodioritic to tonalitic source rock composition, despite the intense orographic rainfall in the source area. Due to the presence of same source rock and identical oxic depositional environment, the studied sediments show the same range of variation of total phosphorus (24 to 83 μmol/g) with a down-depth depleting trend. Organic bound P and detrital P are the two major chemical forms followed by iron-bound P, exchangeable/loosely bound P and authigenic P. The authigenic P content in the sediments near Mangalore coast varies linearly with calcium (r=0.88) unlike that of Karwar coast. The different reactive-phosphorus pools exhibit identical depleting trend with depth. This indicates that the phosphorus released from the organic matter and Fe bound fractions are prevented from precipitating as authigenic phosphates in the deeper parts of the sediment column. The low concentration of total P, dominance of detrital non-reactive fraction of P and inhibition of formation of authigenic phosphate result in the absence of active phosphatization in the Eastern Arabian Shelf in the studied region. High sedimentation rate (35-58 cm/kyr) and absence of winnowing effect appear to be the dominant factor controlling the P-speciation in the studied sediments.

Source identification, geochemical normalization and influence factors of heavy metals in Yangtze River Estuary sediment.

PubMed

Sun, Xueshi; Fan, Dejiang; Liu, Ming; Tian, Yuan; Pang, Yue; Liao, Huijie

2018-06-18

Sediment samples, including 40 surface samples and 12 sediment cores, were collected from 52 stations of the Yangtze River Estuary (YRE) in 2015 and 2016. The 95% linear prediction intervals (LPI) and principal components analysis (PCA), were conducted to evaluate the metal sources and grain-size effect (GSE). The in situ physico-chemical properties of pH, Eh, DO, salinity, temperature and turbidity were combined to elucidate the relationships between environmental factors and the fate of heavy metals in the river-estuary-shelf system. This study indicates a decreasing trend of metals in sediments from the estuary towards the adjacent shelf and the river channel and that Zn, Cu and Cr are mainly derived from natural processes throughout the catchment, whereas Pb appears to have anthropogenic inputs via atmospheric deposition. Furthermore, considering the best fit regression lines between the concentrations of Al and heavy metals as well as the deficiencies of the conventional C elements /C Al method, we introduce an approach (Al-SN: Al-scope normalization) that can eliminate the GSE on heavy metals and be applied to other estuaries. After Al-scope normalization, the relatively constant levels of Zn, Cu and Cr that remain in sediments from the river channel to the estuary and shelf confirmed that the variation of grain size in sediments almost entirely explained the distribution patterns of sediment toxicity in the YRE, while the enrichment of Pb in estuarine sediments could be attributed to its chemical species and physico-chemical properties. The results further suggest that the relationship between grain size and spatial behavior of sediment pollutants should be given priority over the contamination assessment and provenance discrimination in estuarine or similar environments with complex sediment compositions. Copyright © 2018 Elsevier Ltd. All rights reserved.

Natural and human-induced variability in the composition of fish assemblages in the Northwestern Cuban shelf.

PubMed

González-Sansón, Gaspar; Aguilar, Consuelo; Hernández, Ivet; Cabrera, Yureidy; Suarez-Montes, Noelis; Bretos, Fernando; Guggenheim, David

2009-09-01

The main goal of the study was to obtain field data to build a baseline of fish assemblage composition that can be used comparatively for future analyses of the impact of human actions in the region. A basic network of 68 sampling stations was defined for the entire region (4,050 km2). Fish assemblage species and size composition was estimated using visual census methods at three different spatial scales: a) entire region, b) inside the main reef area and c) along a human impact coastal gradient. Multivariate numerical analyses revealed habitat type as the main factor inducing spatial variability of fish community composition, while the level of human impact appears to play the main role in fish assemblage composition changes along the coast. A trend of decreasing fish size toward the east supports the theory of more severe human impact due to overfishing and higher urban pollution in that direction. This is the first detailed study along the northwest coast of Cuba that focuses on fish community structure and the natural and human-induced variations at different spatial scales for the entire NW shelf. This research also provides input for a more comprehensive understanding of coastal marine fish communities' status in the Gulf of Mexico basin.

The infauna of three widely distributed sponge species (Hexactinellida and Demospongiae) from the deep Ekström Shelf in the Weddell Sea, Antarctica

NASA Astrophysics Data System (ADS)

Kersken, Daniel; Göcke, Christian; Brandt, Angelika; Lejzerowicz, Franck; Schwabe, Enrico; Anna Seefeldt, Meike; Veit-Köhler, Gritta; Janussen, Dorte

2014-10-01

Due to their high abundance and large body size sponges have a central position in Antarctic zoobenthos, where they form the most extensive sponge grounds of the world. Though research on Antarctic benthos communities is quite established, research on sponge-associated infauna communities is scarce. We analyzed associated infauna of fifteen individuals of the sponge species Mycale (Oxymycale) acerata Kirkpatrick, 1907 (Demospongiae: Mycalina), Rossella antarctica Carter, 1872 and R. racovitzae Topsent, 1901 (both Hexactinellida: Lyssacinosida). Samples were collected from the deep Ekström Shelf at 602 m in the South-Eastern Weddell Sea, Antarctica, during the ANT XXIV-2 (SYSTCO I) expedition of RV Polarstern. The number of species, α- and β-diversity and the significantly different species composition of infauna communities related to sponge species were calculated, the latter via cluster analysis. The sponge-associated infauna consisted of five phyla: Foraminifera, Nematoda, Polychaeta, Mollusca and Arthropoda. In total 11,463 infaunal specimens were extracted and we found at least 76 associated species. Highest values of α-diversity were calculated for a sample of R. antarctica with a Shannon-Index of 1.84 and Simpson-Index of 0.72 respectively. Our results of the cluster-analysis show significant differences between infauna communities and a unique species composition for single sponge species. Polychaetes of the genus Syllis Lamarck, 1818 were numerous in M. acerata and genera like Pionosyllis Malmgren, 1867 and Cirratulus Lamarck, 1801 were numerous in R. antarctica. Individuals of the amphipod species Seba cf. dubia Schellenberg, 1926 were often found in R. antarctica and R. racovitzae while Colomastix fissilingua Schellenberg, 1926 was frequent in samples of M. acerata. Molluscs were present in M. acerata and R. antarctica but absent in R. racovitzae.

A comparison of ship and Coastal Zone Color Scanner mapped distribution of phytoplankton in the southeastern Bering Sea

NASA Technical Reports Server (NTRS)

Mcclain, C. R.; Sambrotto, R. N.; Ray, G. C.; Muller-Karger, F. E.

1990-01-01

Twenty-one Coastal Zone Color Scanner (CZCS) images of the southeastern Bering Sea are examined in order to map the near-surface distribution of phytoplankton during 1979 and 1980. The information is compared with the mesoscale (100-1000 km) distribution of phytoplankton inferred from pooled ship sampling obtained during the Processes and Resources of the Bering Shelf (PROBES) intensive field study during the late 1970s and early 1980s. The imagery indicates that open-water phytoplankton blooms occur first in late April in coastal waters, peak in early May over the middle shelf, and decay rapidly afterwards, reaching concentration minima in June in both regions. These patterns show that the earlier ship observations are valid for most of the eastern Bering shelf. A very tight correlation is found between the PROBES surface chlorophyll a concentrations and mean mixed-layer chlorophyll concentrations. The significant discrepancies between CZCS and ship-based chlorophyll estimates may be due to aliasing in time by the CZCS. It is concluded that neither satellite nor ship alone can do an adequate job of characterizing the physics or biological dynamics of the ocean.

Vertical distribution of the sound-scattering layer in the Amundsen Sea, Antarctica

NASA Astrophysics Data System (ADS)

Lee, Hyungbeen; La, Hyoung Sul; Kang, Donhyug; Lee, SangHoon

2018-03-01

Mid-trophic level at high-latitude coastal water in the Southern Ocean reside unique geographical condition with sea ice, coastal polynya, and ice shelf. To investigate the regional differences in their vertical distribution during summer, we examined acoustic backscatter data from scientific echo sounder, collected in the three representative regions in the Amundsen Sea: pack ice zone, coastal polynya zone, and ice shelf zone. The weighted mean depths (WMDs) representing zooplankton were calculated with the high resolution acoustic backscatter (1-m depth) to identify the vertical variability of the sound-scattering layer (SSL). WMDs were mainly distributed between 50 and 130 m exhibiting clear regional differences. The WMDs were detected in the shallow depth ranged between 48 and 84 m within the pack ice and coastal polynya, whereas they were observed at deeper depths around near ice shelf ranged between 117 and 126 m. WMDs varied with changing the stratification of water column structure representing strong linear relationship with the mixed layer depth (r = 0.69). This finding implies that understanding the essential forcing of zooplankton behavior will improve our ability to assess the coastal ecosystem in the Southern Ocean facing dramatic change.

Statistical models for sediment/detritus and dissolved absorption coefficients in coastal waters of the northern Gulf of Mexico

NASA Astrophysics Data System (ADS)

Green, Rebecca E.; Gould, Richard W., Jr.; Ko, Dong S.

2008-06-01

We developed statistically-based, optical models to estimate tripton (sediment/detrital) and colored dissolved organic matter (CDOM) absorption coefficients ( a sd, a g) from physical hydrographic and atmospheric properties. The models were developed for northern Gulf of Mexico shelf waters using multi-year satellite and physical data. First, empirical algorithms for satellite-derived a sd and a g were developed, based on comparison with a large data set of cruise measurements from northern Gulf shelf waters; these algorithms were then applied to a time series of ocean color (SeaWiFS) satellite imagery for 2002-2005. Unique seasonal timing was observed in satellite-derived optical properties, with a sd peaking most often in fall/winter on the shelf, in contrast to summertime peaks observed in a g. Next, the satellite-derived values were coupled with the physical data to form multiple regression models. A suite of physical forcing variables were tested for inclusion in the models: discharge from the Mississippi River and Mobile Bay, Alabama; gridded fields for winds, precipitation, solar radiation, sea surface temperature and height (SST, SSH); and modeled surface salinity and currents (Navy Coastal Ocean Model, NCOM). For satellite-derived a sd and a g time series (2002-2004), correlation and stepwise regression analyses revealed the most important physical forcing variables. Over our region of interest, the best predictors of tripton absorption were wind speed, river discharge, and SST, whereas dissolved absorption was best predicted by east-west wind speed, river discharge, and river discharge lagged by 1 month. These results suggest the importance of vertical mixing (as a function of winds and thermal stratification) in controlling a sd distribution patterns over large regions of the shelf, in comparison to advection as the most important control on a g. The multiple linear regression models for estimating a sd and a g were applied on a pixel-by-pixel basis and results were compared to monthly SeaWiFS composite imagery. The models performed well in resolving seasonal and interannual optical variability in model development years (2002-2004) (mean error of 32% for a sd and 29% for a g) and in predicting shelfwide optical patterns in a year independent of model development (2005; mean error of 41% for a sd and 46% for a g). The models provide insight into the dominant processes controlling optical distributions in this region, and they can be used to predict the optical fields from the physical properties at monthly timescales.

Geochemistry of polycyclic aromatic hydrocarbons in the bottom sediments of the eastern Arctic shelf

NASA Astrophysics Data System (ADS)

Petrova, V. I.; Batova, G. I.; Kursheva, A. V.; Litvinenko, I. V.; Savinov, V. M.; Savinova, T. N.

2008-04-01

Sources and pathways of supply of polycyclic aromatic hydrocarbons (PAH) in the surface sediments of the Laptev and East Siberian seas were identified based on an analysis of the lithological-geochemical characteristics and distribution of organic matter (OM). The distribution of organic carbon, humic acids, bitumoids, and hydrocarbons demonstrates the determining role of the riverine runoff in the formation of the recent sediments. The total average content of PAH in the sediments of this region approximates 37 ng/g, not exceeding 80 ng/g of dry sediment. The biogenic components of the PAH (alkylphenanthrenes, alkylchrysenes, perylene) dominate in the estuarine-shelf and coastal-shelf sediments enriched with plant detritus and significantly decrease in the pelagic zone. The anthropogenic influence is observed in sediments of the port of Tiksi, where the total content of PAH with dominant pyrogenic components is two orders of magnitude higher as compared with the background values in the study region.

A synthetic map of the north-west European Shelf sedimentary environment for applications in marine science

NASA Astrophysics Data System (ADS)

Wilson, Robert J.; Speirs, Douglas C.; Sabatino, Alessandro; Heath, Michael R.

2018-01-01

Seabed sediment mapping is important for a wide range of marine policy, planning and scientific issues, and there has been considerable national and international investment around the world in the collation and synthesis of sediment datasets. However, in Europe at least, much of this effort has been directed towards seabed classification and mapping of discrete habitats. Scientific users often have to resort to reverse engineering these classifications to recover continuous variables, such as mud content and median grain size, that are required for many ecological and biophysical studies. Here we present a new set of 0.125° by 0.125° resolution synthetic maps of continuous properties of the north-west European sedimentary environment, extending from the Bay of Biscay to the northern limits of the North Sea and the Faroe Islands. The maps are a blend of gridded survey data, statistically modelled values based on distributions of bed shear stress due to tidal currents and waves, and bathymetric properties. Recent work has shown that statistical models can predict sediment composition in British waters and the North Sea with high accuracy, and here we extend this to the entire shelf and to the mapping of other key seabed parameters. The maps include percentage compositions of mud, sand and gravel; porosity and permeability; median grain size of the whole sediment and of the sand and the gravel fractions; carbon and nitrogen content of sediments; percentage of seabed area covered by rock; mean and maximum depth-averaged tidal velocity and wave orbital velocity at the seabed; and mean monthly natural disturbance rates. A number of applications for these maps exist, including species distribution modelling and the more accurate representation of sea-floor biogeochemistry in ecosystem models. The data products are available from https://doi.org/10.15129/1e27b806-1eae-494d-83b5-a5f4792c46fc.

Anatomy of a shoreface sand ridge revisited using foraminifera: False Cape Shoals, Virginia/North Carolina inner shelf

USGS Publications Warehouse

Robinson, M.M.; McBride, R.A.

2008-01-01

Certain details regarding the origin and evolution of shelf sand ridges remain elusive. Knowledge of their internal stratigraphy and microfossil distribution is necessary to define the origin and to determine the processes that modify sand ridges. Fourteen vibracores from False Cape Shoal A, a well-developed shoreface-attached sand ridge on the Virginia/North Carolina inner continental shelf, were examined to document the internal stratigraphy and benthic foraminiferal assemblages, as well as to reconstruct the depositional environments recorded in down-core sediments. Seven sedimentary and foraminiferal facies correspond to the following stratigraphic units: fossiliferous silt, barren sand, clay to sandy clay, laminated and bioturbated sand, poorly sorted massive sand, fine clean sand, and poorly sorted clay to gravel. The units represent a Pleistocene estuary and shoreface, a Holocene estuary, ebb tidal delta, modern shelf, modern shoreface, and swale fill, respectively. The succession of depositional environments reflects a Pleistocene sea-level highstand and subsequent regression followed by the Holocene transgression in which barrier island/spit systems formed along the Virginia/North Carolina inner shelf ???5.2 ka and migrated landward and an ebb tidal delta that was deposited, reworked, and covered by shelf sand.

Anatomy of a shoreface sand ridge revisted using foraminifera: False Cape Shoals, Virginia/North Carolina inner shelf

USGS Publications Warehouse

Robinson, Marci M.; McBride, Randolph A.

2008-01-01

Certain details regarding the origin and evolution of shelf sand ridges remain elusive. Knowledge of their internal stratigraphy and microfossil distribution is necessary to define the origin and to determine the processes that modify sand ridges. Fourteen vibracores from False Cape Shoal A, a well-developed shoreface-attached sand ridge on the Virginia/North Carolina inner continental shelf, were examined to document the internal stratigraphy and benthic foraminiferal assemblages, as well as to reconstruct the depositional environments recorded in down-core sediments. Seven sedimentary and foraminiferal facies correspond to the following stratigraphic units: fossiliferous silt, barren sand, clay to sandy clay, laminated and bioturbated sand, poorly sorted massive sand, fine clean sand, and poorly sorted clay to gravel. The units represent a Pleistocene estuary and shoreface, a Holocene estuary, ebb tidal delta, modern shelf, modern shoreface, and swale fill, respectively. The succession of depositional environments reflects a Pleistocene sea-level highstand and subsequent regression followed by the Holocene transgression in which barrier island/spit systems formed along the Virginia/North Carolina inner shelf not, vert, ~5.2 ka and migrated landward and an ebb tidal delta that was deposited, reworked, and covered by shelf sand.

Subsea ice-bearing permafrost on the U.S. Beaufort Margin: 1. Minimum seaward extent defined from multichannel seismic reflection data

USGS Publications Warehouse

Brothers, Laura; Herman, Bruce M.; Hart, Patrick E.; Ruppel, Carolyn D.

2016-01-01

Subsea ice-bearing permafrost (IBPF) and associated gas hydrate in the Arctic have been subject to a warming climate and saline intrusion since the last transgression at the end of the Pleistocene. The consequent degradation of IBPF is potentially associated with significant degassing of dissociating gas hydrate deposits. Previous studies interpreted the distribution of subsea permafrost on the U.S. Beaufort continental shelf based on geographically sparse data sets and modeling of expected thermal history. The most cited work projects subsea permafrost to the shelf edge (∼100 m isobath). This study uses a compilation of stacking velocity analyses from ∼100,000 line-km of industry-collected multichannel seismic reflection data acquired over 57,000 km2 of the U.S. Beaufort shelf to delineate continuous subsea IBPF. Gridded average velocities of the uppermost 750 ms two-way travel time range from 1475 to 3110 m s−1. The monotonic, cross-shore pattern in velocity distribution suggests that the seaward extent of continuous IBPF is within 37 km of the modern shoreline at water depths < 25 m. These interpretations corroborate recent Beaufort seismic refraction studies and provide the best, margin-scale evidence that continuous subsea IBPF does not currently extend to the northern limits of the continental shelf.

Projecting the effects of climate change on Calanus finmarchicus distribution within the U.S. Northeast Continental Shelf.

PubMed

Grieve, Brian D; Hare, Jon A; Saba, Vincent S

2017-07-24

Calanus finmarchicus is vital to pelagic ecosystems in the North Atlantic Ocean. Previous studies suggest the species is vulnerable to the effects of global warming, particularly on the Northeast U.S. Shelf, which is in the southern portion of its range. In this study, we evaluate an ensemble of six different downscaled climate models and a high-resolution global climate model, and create a generalized additive model (GAM) to examine how future changes in temperature and salinity could affect the distribution and density of C. finmarchicus. By 2081-2100, we project average C. finmarchicus density will decrease by as much as 50% under a high greenhouse gas emissions scenario. These decreases are particularly pronounced in the spring and summer in the Gulf of Maine and Georges Bank. When compared to a high-resolution global climate model, the ensemble showed a more uniform change throughout the Northeast U.S. Shelf, while the high-resolution model showed larger decreases in the Northeast Channel, Shelf Break, and Central Gulf of Maine. C. finmarchicus is an important link between primary production and higher trophic levels, and the decrease projected here could be detrimental to the North Atlantic Right Whale and a host of important fishery species.

Fate of internal waves on a shallow shelf

NASA Astrophysics Data System (ADS)

Davis, Kristen; Arthur, Robert; Reid, Emma; Decarlo, Thomas; Cohen, Anne

2017-11-01

Internal waves strongly influence the physical and chemical environment of coastal ecosystems worldwide. We report novel observations from a distributed temperature sensing (DTS) system that tracked the transformation of internal waves from the shelf break to the surf zone over a shelf-slope region of a coral atoll in the South China Sea. The spatially-continuous view of the near-bottom temperature field provided by the DTS offers a perspective of physical processes previously available only in laboratory settings or numerical models. These processes include internal wave reflection off a natural slope, shoreward transport of dense fluid within trapped cores, internal ``tide pools'' (dense water left behind after the retreat of an internal wave), and internal run-down (near-bottom, offshore-directed jets of water preceding a breaking internal wave). Analysis shows that the fate of internal waves on this shelf - whether they are transmitted into shallow waters or reflected back offshore - is mediated by local water column density and shear structure, with important implications for nearshore distributions of energy, heat, and nutrients. We acknowledge the US Army Research Laboratory DoD Supercomputing Resource Center for computer time on Excalibur, which was used for the numerical simulations in this work. Funding for field work supported by Academia Sinica and for K.D. and E.R. from NSF.

Features of distribution and quality of organic matter in the bottom sediments of the Great Peter Bay (Sea of Japan)

NASA Astrophysics Data System (ADS)

Nesterova, Olga; Tregubova, Valentina; Semal, Victoria; Vasenev, Ivan

2017-04-01

The nature and distribution of organic carbon in marine waters depends on: 1) biological productivity and revenue of the autochthonous organic matter to the bottom; 2) sediment grain-size composition and conditions of dumping, which in turn depends of hydrothermic regime, topography, speed River mist and received major erosion products; 3) living conditions of the benthos (the quantity consumed of OM, gas regime of habitats, physiological capacity of heterotrophs). Autochthonous OM of phytoplankton plays a dominant role in the processes of formation of humus in aquatic conditions. Bottom sediments at different distance from the shoreline to depths from 0.5 up to 480 m of the Sea of Japan, which are formed in various conditions of facies, were selected as the objects of study. There is no clear relationships to the amount of organic matter in bottom sediments on the characteristics of the distribution and nature of living matter in the oceans and seas. This is because the process of sedimentation and fossilization of organic matter on the seabed and the ocean floor depends on many factors (currents, depth). Humus of studied bottom sediments in composition can be attributed mainly to the humic type. Nonhydrolyzing rest is 70-90%. This is characteristic of bottom sediments formed in facial types of small bays, internal coastal shelf bights and the underwater slope. At a fraction of the carbon of humic acids in organic matter, ranging from 4 to 80% of the amount of humic and fulvic acids. Fulvic acids content is much less. This is due to more favourable conservation situation of humic acids in precipitation with high content of organic matter, whereas fulvic acids in aquatic environments are more labile and almost not dumped. Despite the fact humic acids are not the most stable component (s), however, with increased content of humic acids, the mobility of organic matter and removing it from the bottom sediments are reduced. Internal shelf facies of the Great Peter Bay is the most diverse on the content of the various components of the bottom sediments humus. This is because modern processes of sedimentations and humus formation are active in this zone. The greatest concentration of organic matter in conjunction with the submarine and coastal slope at depths of more than 120 m. Slight variations parameters that characterize the composition of humus, are notable for all bottom sediments, as well as the marine environment, largely cancels the General conditions of humus formation around the basin of the Sea of Japan. Organic substance moving in the water colomn and transforms. Only sustainable to mineralization of organic substance reaches the bottom.

The distribution of life cycle stages of two deep-water pleuronectids, Dover sole ( Microstomus pacificus) and rex sole ( Glyptocephalus zachirus), at the northern extent of their range in the Gulf of Alaska

NASA Astrophysics Data System (ADS)

Abookire, Alisa A.; Bailey, Kevin M.

2007-02-01

Dover sole ( Microstomus pacificus) and rex sole ( Glyptocephalus zachirus) are both commercially valuable, long-lived pleuronectids that are distributed widely throughout the North Pacific. While their ecology and life cycle have been described for southern stocks, few investigations have focused on these species at higher latitudes. We synthesized historical research survey data among critical developmental stages to determine the distribution of life cycle stages for both species in the northern Gulf of Alaska (GOA). Bottom trawl survey data from 1953 to 2004 (25 519 trawls) were used to characterize adult distribution during the non-spawning and spawning seasons, ichthyoplankton data from 1972 to 2003 (10 776 tows) were used to determine the spatial and vertical distribution of eggs and larvae, and small-meshed shrimp trawl survey data from 1972 to 2004 (6536 trawls) were used to characterize areas utilized by immature stages. During the non-spawning season, adult Dover sole and rex sole were widely distributed from the inner shelf to outer slope. While both species concentrated on the continental slope to spawn, Dover sole spawning areas were more geographically specific than rex sole. Although spawned in deep water, eggs of both species were found in surface waters near spawning areas. Dover sole larvae did not appear to have an organized migration from offshore spawning grounds toward coastal nursery areas, and our data indicated facultative settling to their juvenile habitat in winter. Rex sole larvae progressively moved cross-shelf toward shore as they grew from April to September, and larvae presumably settled in coastal nursery areas in the autumn. In contrast with studies in the southern end of their range, we found no evidence in the GOA that Dover or rex sole have pelagic larval stages longer than nine months; however, more sampling for large larvae is needed in winter offshore of the continental shelf as well as sampling for newly settled larvae over the shelf to verify an abbreviated pelagic larval stage for both species at the northern end of their range.

Modelling the bathymetry of the Antarctic continental shelf

USGS Publications Warehouse

ten Brink, Uri S.; Rogers, William P.; Kirkham, R.M.

1992-01-01

Continental shelves are typically covered by relatively shallow waters (<200 m) which deepen gradually from the coast to the shelf edge. The continental shelf around Antarctica is deeper than normal (400-700m) and is characterized in many areas by a nearshore trough (up to 1 km deep) that gradually shallows toward the shelf edge. We examine the cause for the unusual shelf bathymetry of Antarctica by 2-D numerical models that simulate the bathymetry along seismic line ODP-119 in Prydz Bay. Line ODP-119 was chosen because it is tied to to 5 ODP boreholes, and because the margin underwent little recent tectonic activity or changes in the glacial drainage pattern. The numerical models incorporate several factors that are likely to influence the bathymetry, such as the load of the ice cap, the isostatic response of the lithosphere, thermal and tectnoic subsidence of the margin, sea level changes, and the patterns of erosion and sedimentation across the margin. The models show that the observed bathymetry can be produced almost entirely by the sum of the outer-shelf sediment loading and inner-shelf unloading and by the load of the slope sediments. A simple statistical mdoel demonstrates that this distribution pattern of erosion and deposition can be generated by multiple cycles of ice sheet advances across the shelf, whereby in each cycle a thin (a few tens of meters) uniform layer of sediments is eroded from under the ice sheet and is redeposited seaward of the grounding line.

Airborne thickness and freeboard measurements over the McMurdo Ice Shelf, Antarctica, and implications for ice density

NASA Astrophysics Data System (ADS)

Rack, Wolfgang; Haas, Christian; Langhorne, Pat J.

2013-11-01

We present airborne measurements to investigate the thickness of the western McMurdo Ice Shelf in the western Ross Sea, Antarctica. Because of basal accretion of marine ice and brine intrusions conventional radar systems are limited in detecting the ice thickness in this area. In November 2009, we used a helicopter-borne laser and electromagnetic induction sounder (EM bird) to measure several thickness and freeboard profiles across the ice shelf. The maximum electromagnetically detectable ice thickness was about 55 m. Assuming hydrostatic equilibrium, the simultaneous measurement of ice freeboard and thickness was used to derive bulk ice densities ranging from 800 to 975 kg m-3. Densities higher than those of pure ice can be largely explained by the abundance of sediments accumulated at the surface and present within the ice shelf, and are likely to a smaller extent related to the overestimation of ice thickness by the electromagnetic induction measurement related to the presence of a subice platelet layer. The equivalent thickness of debris at a density of 2800 kg m-3 is found to be up to about 2 m thick. A subice platelet layer below the ice shelf, similar to what is observed in front of the ice shelf below the sea ice, is likely to exist in areas of highest thickness. The thickness and density distribution reflects a picture of areas of basal freezing and supercooled Ice Shelf Water emerging from below the central ice shelf cavity into McMurdo Sound.

Bathymetric and oceanic controls on Abbot Ice Shelf thickness and stability

NASA Astrophysics Data System (ADS)

Cochran, J. R.; Jacobs, S. S.; Tinto, K. J.; Bell, R. E.

2014-05-01

Ice shelves play key roles in stabilizing Antarctica's ice sheets, maintaining its high albedo and returning freshwater to the Southern Ocean. Improved data sets of ice shelf draft and underlying bathymetry are important for assessing ocean-ice interactions and modeling ice response to climate change. The long, narrow Abbot Ice Shelf south of Thurston Island produces a large volume of meltwater, but is close to being in overall mass balance. Here we invert NASA Operation IceBridge (OIB) airborne gravity data over the Abbot region to obtain sub-ice bathymetry, and combine OIB elevation and ice thickness measurements to estimate ice draft. A series of asymmetric fault-bounded basins formed during rifting of Zealandia from Antarctica underlie the Abbot Ice Shelf west of 94° W and the Cosgrove Ice Shelf to the south. Sub-ice water column depths along OIB flight lines are sufficiently deep to allow warm deep and thermocline waters observed near the western Abbot ice front to circulate through much of the ice shelf cavity. An average ice shelf draft of ~200 m, 15% less than the Bedmap2 compilation, coincides with the summer transition between the ocean surface mixed layer and upper thermocline. Thick ice streams feeding the Abbot cross relatively stable grounding lines and are rapidly thinned by the warmest inflow. While the ice shelf is presently in equilibrium, the overall correspondence between draft distribution and thermocline depth indicates sensitivity to changes in characteristics of the ocean surface and deep waters.

Shelf life extension as solution for environmental impact mitigation: A case study for bakery products.

PubMed

Bacenetti, Jacopo; Cavaliere, Alessia; Falcone, Giacomo; Giovenzana, Valentina; Banterle, Alessandro; Guidetti, Riccardo

2018-06-15

Over the last years, increasing attention has been paid to environmental concerns related to food production and potential solutions to this issue. Among the different strategies being considered to reduce the impact food production has on the environment, only moderate has been paid to the extension of shelf life; a longer shelf life can reduce food losses as well as the economic and environmental impacts of the distribution logistics. The aim of this study is to assess the environmental performance of whole-wheat breadsticks with extended shelf lives and to evaluate whether the shelf-life extension is an effective mitigation solution from an environmental point of view. To this purpose, the life cycle assessment (LCA) approach was applied from a "cradle-to-grave" perspective. Rosmarinic acid was used as an antioxidant to extend the shelf life. To test the robustness of the results and to investigate the influence of the choices made in the modelling phase, a sensitivity and uncertainty analysis were carried out. The achieved results highlighted how, for 10 of the 12 evaluated impact categories, the shelf-life extension is a proper mitigation solution, and its effectiveness depends on the magnitude of product loss reduction that is achieved. The shelf-life extension doesn't allow for the reduction of environmental impact in the categories of human toxicity, cancer effects and freshwater eutrophication. Copyright © 2018 Elsevier B.V. All rights reserved.

Effect of antioxidant protection of must on volatile compounds and aroma shelf life of Falanghina (Vitis vinifera L.) wine.

PubMed

Moio, Luigi; Ugliano, Maurizio; Genovese, Alessandro; Gambuti, Angelita; Pessina, Rita; Piombino, Paola

2004-02-25

Two vinification methods involving different degrees of antioxidant protection of Falanghina must during prefermentative steps, and referred as HAMP (high antioxidant must protection) and LAMP (low antioxidant must protection), were compared in terms of fermentation performances of four different yeast strains, composition of the volatile fraction of wines at the end of alcoholic fermentation, and shelf life of wines during storage. The use of HAMP technology resulted in wines with lower volatile acidity and higher concentrations of medium-chain fatty acid ethyl esters, acetates, and volatile fatty acids. For two of the four strains a lower concentration of isoamyl alcohol was also observed. HAMP wines also revealed increased shelf life because of the higher concentration of odor active esters at the end of storage and better preservation of varietal aromas.

Distribution and sources of organic matter in surface marine sediments across the North American Arctic margin

NASA Astrophysics Data System (ADS)

Goñi, Miguel A.; O'Connor, Alison E.; Kuzyk, Zou Zou; Yunker, Mark B.; Gobeil, Charles; Macdonald, Robie W.

2013-09-01

As part of the International Polar Year research program, we conducted a survey of surface marine sediments from box cores along a section extending from the Bering Sea to Davis Strait via the Canadian Archipelago. We used bulk elemental and isotopic compositions, together with biomarkers and principal components analysis, to elucidate the distribution of marine and terrestrial organic matter in different regions of the North American Arctic margin. Marked regional contrasts were observed in organic carbon loadings, with the highest values (≥1 mg C m-2 sediment) found in sites along Barrow Canyon and the Chukchi and Bering shelves, all of which were characterized by sediments with low oxygen exposure, as inferred from thin layers (<2 cm) of Mn oxihydroxides. We found strong regional differences in inorganic carbon concentrations, with sites from the Canadian Archipelago and Lancaster Sound displaying elevated values (2-7 wt %) and highly depleted 14C compositions consistent with inputs from bedrock carbonates. Organic carbon:nitrogen ratios, stable carbon isotopes, and terrigenous organic biomarkers (lignin phenols and cutin acids) all indicate marked regional differences in the proportions of marine and terrigenous organic matter present in surface sediments. Regions such as Barrow Canyon and the Mackenzie River shelf were characterized by the highest contributions of land-derived organic matter, with compositional characteristics that suggested distinct sources and provenance. In contrast, sediments from the Canadian Archipelago and Davis Strait had the smallest contributions of terrigenous organic matter and the lowest organic carbon loadings indicative of a high degree of post-depositional oxidation.

Properties of coarse particles in suspended particulate matter of the North Yellow Sea during summer

NASA Astrophysics Data System (ADS)

Zhang, Kainan; Wang, Zhenyan; Li, Wenjian; Yan, Jun

2018-01-01

Fine particles in seawater commonly form large porous aggregates. Aggregate density and settling velocity determine the behavior of this suspended particulate matter (SPM) within the water column. However, few studies of aggregate particles over a continental shelf have been undertaken. In our case study, properties of aggregate particles, including size and composition, over the continental shelf of the North Yellow Sea were investigated. During a scientific cruise in July 2016, in situ effective particle size distributions of SPM at 10 stations were measured, while temperature and turbidity measurements and samples of water were obtained from surface, middle, and bottom layers. Dispersed and inorganic particle size distributions were determined in the laboratory. The in situ SPM was divided into (1) small particles (<32 μm), (2) medium particles (32-256 μm) and (3) large particles (>256 μm). Large particles and medium particles dominated the total volume concentrations (VCs) of in situ SPM. After dispersion, the VCs of medium particles decreased to low values (<0.1 μL/L). The VCs of large particles in the surface and middle layers also decreased markedly, although they had higher peak values (0.1-1 μL/L). This suggests that almost all in situ medium particles and some large particles were aggregated, while other large particles were single particles. Correlation analysis showed that primary particles <32 μm influenced the formation of these aggregates. Microscopic examination revealed that these aggregates consisted of both organic and inorganic fine particles, while large particles were mucus-bound organic aggregates or individual plankton. The vertical distribution of coarser particles was clearly related to water stratification. Generally, medium aggregate particles were dominant in SPM of the bottom layer. A thermocline blocked resuspension of fine material into upper layers, yielding low VCs of medium-sized aggregate particles in the surface layer. Abundant large biogenic particles were present in both surface and middle layers.

Mesozooplankton structure and functioning during the onset of the Kerguelen phytoplankton bloom during the KEOPS2 survey

NASA Astrophysics Data System (ADS)

Carlotti, F.; Jouandet, M.-P.; Nowaczyk, A.; Harmelin-Vivien, M.; Lefèvre, D.; Richard, P.; Zhu, Y.; Zhou, M.

2015-07-01

This paper presents results on the spatial and temporal distribution patterns of mesozooplankton in the naturally fertilized region to the east of the Kerguelen Islands (Southern Ocean) visited at early bloom stage during the KEOPS2 survey (15 October to 20 November 2011). The aim of this study was to compare the zooplankton response in contrasted environments localized over the Kerguelen Plateau in waters of the east shelf and shelf edge and in productive oceanic deep waters characterized by conditions of complex circulation and rapidly changing phytoplankton biomass. The mesozooplankton community responded to the spring bloom earlier on the plateau than in the oceanic waters, where complex mesoscale circulation stimulated initial more or less ephemeral blooms before a broader bloom extension. Taxonomic compositions showed a high degree of similarity across the whole region, and the populations initially responded to spring bloom with a large production of larval forms increasing abundances, without biomass changes. Taxonomic composition and stable isotope ratios of size-fractionated zooplankton indicated the strong domination of herbivores, and the total zooplankton biomass values over the survey presented a significant correlation with the integrated chlorophyll concentrations in the mixed layer. The biomass stocks observed at the beginning of the KEOPS2 cruise were around 1.7 g C m-2 above the plateau and 1.2 g C m-2 in oceanic waters. Zooplankton biomass in oceanic waters remained on average below 2 g C m-2 over the study period, except for one station in the Polar Front zone (F-L), whereas zooplankton biomasses were around 4 g C m-2 on the plateau at the end of the survey. The most remarkable feature during the sampling period was the stronger increase in abundance in the oceanic waters (25 × 103 to 160 × 103 ind m-2) than on the plateau (25 × 103 to 90 × 103 ind m-2). The size structure and taxonomic distribution patterns revealed a cumulative contribution of various larval stages of dominant copepods and euphausiids particularly in the oceanic waters, with clearly identifiable stages of progress during a Lagrangian time series survey. The reproduction and early stage development of dominant species were sustained by mesoscale-related initial ephemeral blooms in oceanic waters, but growth was still food-limited and zooplankton biomass stagnated. In contrast, zooplankton abundance and biomass on the shelf were both in a growing phase, at slightly different rates, due to growth under sub-optimal conditions. Combined with our observations during the KEOPS1 survey (January-February 2005), the present results deliver a consistent understanding of patterns in mesozooplankton abundance and biomass from early spring to summer in the poorly documented oceanic region east of the Kerguelen Islands.

Influence of Flood and Drought Conditions on Dissolved Organic Matter Distribution in Northern Gulf of Mexico Shelf Waters

NASA Astrophysics Data System (ADS)

Shank, G. C.; Liu, Q.; Patterson, L.; Kowalczuk, P.

2012-12-01

DOC, CDOM, and EEM PARAFAC analyses were used to examine DOM distribution along the Louisiana (LA) and Texas (TX) continental shelves in the northern Gulf of Mexico during cruises in May and August of the 2011 Mississippi basin flood year, and May, June, and August of the 2012 Mississippi basin drought year. For both 2011 and 2012, CDOM and DOC levels were well-correlated with salinity on the LA shelf. However, the mixing curves for each parameter were markedly different between 2011 and 2012 and CDOM:DOC ratios, indicative of terrestrial organic matter inputs, were much higher during 2011 than during 2012. EEM PARAFAC results confirmed a much higher terrestrial DOM signature in LA shelf waters for 2011, but also a higher terrestrial DOM signature for TX waters in 2012 as the drought in the western Gulf region subsided. CDOM:DOC ratios were anomalously high offshore of Atchafalaya Bay and the Breton-Chandeleur Sound complex indicating coastal wetlands augment the terrestrial DOM discharged through the Mississippi and Atchafalaya Rivers. At several sites along the LA and TX shelves during both 2011 and 2012, CDOM was higher near bottom than at mid-depth without concomitant DOC increases, possibly due to microbial processing of settling phytoplankton cells, sedimentary fluxes, and benthic algal activity which was especially prevalent along the TX shelf. Results from simulated solar radiation experiments indicate that shelf water CDOM readily photobleaches with losses of >50% likely in surface waters over the summer, while DOC photooxidation is at least an order of magnitude slower than CDOM photobleaching.;

Seasonal variation in chaetognath and parasite species assemblages along the northeastern coast of the Yucatan Peninsula.

PubMed

Lozano-Cobo, Horacio; Prado-Rosas, María Del Carmen Gómez Del; Sánchez-Velasco, Laura; Gómez-Gutiérrez, Jaime

2017-03-30

Chaetognaths are abundant carnivores with broad distributions that are intermediate hosts of trophically transmitted parasites. Monthly variations in chaetognath and parasite species distributions, abundance, prevalence, and intensity related to seasonal environmental changes were recorded in 2004 and 2005 in Laguna Nichupté, a coral reef, and the adjoining continental shelf of Quintana Roo, Mexico. Of 12 chaetognath species plus Sagitta spp., only 5 (Ferosagitta hispida, Flaccisagitta enflata, Sagitta spp., Serratosagitta serratodentata, and Pterosagitta draco) were parasitized. These species were parasitized with 33 types of flatworms and unidentified cysts (likely protozoan ciliates), having an overall mean prevalence of 6%. Digenean metacercaria larvae numerically dominated the parasite assemblages. Cluster analysis defined 2 chaetognath species assemblages. One included 7 species inside Laguna Nichupté, where F. hispida was numerically dominant (98.9%); the other contained 13 chaetognath species in the continental shelf-coral reef region, where F. enflata was abundant (53%). Canonical correspondence analysis showed that Laguna Nichupté had highly variable and hostile conditions (relatively low salinity and high temperature) for chaetognath species except for F. hispida. The higher density of F. hispida promoted greater parasite diversity (23 types), dominated by Brachyphallus sp. metacercariae. F. enflata prevailed in the continental shelf-coral reef area, which had stable high salinity and relatively low temperature. Monilicaecum and unidentified digenean 'type g' infected 5 chaetognath species on the continental shelf. Distinct primary hosts (mollusks and copepods) and contrasting environmental conditions (salinity, dissolved oxygen concentration, and temperature) between Laguna Nichupté and the continental shelf promoted distinct chaetognath species assemblages, resulting in distinct parasite diversity and prevalence patterns.

Inorganic carbon fluxes on the Mackenzie Shelf of the Beaufort Sea

NASA Astrophysics Data System (ADS)

Mol, Jacoba; Thomas, Helmuth; Myers, Paul G.; Hu, Xianmin; Mucci, Alfonso

2018-02-01

The Mackenzie Shelf in the southeastern Beaufort Sea is a region that has experienced large changes in the past several decades as warming, sea-ice loss, and increased river discharge have altered carbon cycling. Upwelling and downwelling events are common on the shelf, caused by strong, fluctuating along-shore winds, resulting in cross-shelf Ekman transport, and an alternating estuarine and anti-estuarine circulation. Downwelling carries dissolved inorganic carbon (DIC) and other remineralization products off the shelf and into the deep basin for possible long-term storage in the world's oceans. Upwelling carries DIC and nutrient-rich waters from the Pacific-origin upper halocline layer (UHL) onto the shelf. Profiles of DIC and total alkalinity (TA) taken in August and September of 2014 are used to investigate the cycling of carbon on the Mackenzie Shelf. The along-shore transport of water and the cross-shelf transport of DIC are quantified using velocity field output from a simulation of the Arctic and Northern Hemisphere Atlantic (ANHA4) configuration of the Nucleus of European Modelling of the Ocean (NEMO) framework. A strong upwelling event prior to sampling on the Mackenzie Shelf took place, bringing CO2-rich (elevated pCO2) water from the UHL onto the shelf bottom. The maximum on-shelf DIC flux was estimated at 16.9×103 mol C d-1 m-2 during the event. The maximum on-shelf transport of DIC through the upwelling event was found to be 65±15×10-3 Tg C d-1. TA and the oxygen isotope ratio of water (δ18O-H2O) are used to examine water-mass distributions in the study area and to investigate the influence of Pacific Water, Mackenzie River freshwater, and sea-ice melt on carbon dynamics and air-sea fluxes of carbon dioxide (CO2) in the surface mixed layer. Understanding carbon transfer in this seasonally dynamic environment is key to quantify the importance of Arctic shelf regions to the global carbon cycle and provide a basis for understanding how it will respond to the aforementioned climate-induced changes.

Observations of Cross-Surf-zone / Inner-shelf Dye Exchange from Aerial Hyperspectral and in Situ Data.

NASA Astrophysics Data System (ADS)

Grimes, D. J.; Giddings, S. N.; Kumar, N.; Pawlak, G. R.; Feddersen, F.

2016-12-01

Understanding the cross-shelf exchange of nearshore sourced tracers across the surfzone and onto the stratified inner-shelf is critical to be able to predict the evolution of pollution events, HAB, and larval transport, which will enable policy and mitigation efforts. The CSIDE (Cross Surfzone / Inner-shelf Dye Exchange) experiment (Sept & Oct 2015) provides observations to quantify dye tracer exchange across the surfzone/inner-shelf region with 3 dye release experiments. Shoreline released dye and temperature is tracked for 48 hrs and 20 km using aerial hyperspectral and IR imagery, in situ near-shoreline fluorometers, moored wire-walkers, AUV, and boat based towed observations. Here, we focus on the 3rd release, where dye was pumped into the mouth of the Tijuana River / Estuary during an ebb tide with low river discharge. The dye field was transported alongshore in a large coherent patch extending 1 km from shore. The plume persisted overnight with weak dilution and its center of mass was observed to move 3+ km north over 18 hrs. Aerial hyperspectral and in situ observations are analyzed to examine the horizontal and vertical dye distribution. In particular, we will explore the extent to which the stratified inner-shelf is a "material barrier," whether an observed surfzone dye and temperature correlation is maintained on the stratified inner-shelf, at what time- and length-scales, and the processes influencing this relationship.

Quantifying ocean and ice sheet contributions to nutrient fluxes in Sermilik Fjord, Southeast Greenland

NASA Astrophysics Data System (ADS)

Cape, M. R.; Straneo, F.; Beaird, N.; Bundy, R.; Charette, M. A.

2016-12-01

Meltwater discharged at the margins of the Greenland Ice Sheet (GrIS) represents a potential source of nutrients to biological communities downstream. In Greenland's glacial fjords, this discharge occurs at depth below and along the face of deeply grounded marine-terminating glaciers. This process drives vigorous circulation and mixing between melt and ambient waters at the ice-ocean margins, giving rise to a new glacially modified water mass (GMW) which constitutes the primary vehicle for transport of meltwater in the marine environment. While previous field studies have noted nutrient enrichment in GMW with respect to unmodified waters along the shelf, the source of this enrichment, whether due to entrainment of deep ambient waters or input by meltwater, remains poorly understood. This knowledge is however critical in order to evaluate the current and future contributions of the GrIS to marine biogeochemical cycling. Here we shed light on the distribution, composition, and properties of GMW along the GrIS margin by analyzing integrated physical and chemical measurements collected in August 2015 in Sermilik Fjord, a major glacial freshwater export pathway. Our results document up to a doubling of nutrient concentrations (nitrate, silicate, phosphate, and iron) in GMW, which is distributed in the top 300 m of the water column throughout the fjord. Partitioning of ocean and ice sheet contributions to GMW nutrient load demonstrates that upwelled waters are the primary source of macro-nutrients to GMW. We expand on these results to discuss the magnitude of fluxes in context of previous observations along the GrIS margins, export pathways of GMW to the shelf, and knowledge gaps needed to be addressed to better constrain ice sheet contributions to marine ecosystem processes.

Large-scale production of lipoplexes with long shelf-life.

PubMed

Clement, Jule; Kiefer, Karin; Kimpfler, Andrea; Garidel, Patrick; Peschka-Süss, Regine

2005-01-01

The instability of lipoplex formulations is a major obstacle to overcome before their commercial application in gene therapy. In this study, a continuous mixing technique for the large-scale preparation of lipoplexes followed by lyophilisation for increased stability and shelf-life has been developed. Lipoplexes were analysed for transfection efficiency and cytotoxicity in human aorta smooth muscle cells (HASMC) and a rat smooth muscle cell line (A-10 SMC). Homogeneity of lipid/DNA-products was investigated by photon correlation spectroscopy (PCS) and cryotransmission electron microscopy (cryo-TEM). Studies have been undertaken with DAC-30, a composition of 3beta-[N-(N,N'-dimethylaminoethane)-carbamoyl]-cholesterol (DAC-Chol) and dioleylphosphatidylethanolamine (DOPE) and a green fluorescent protein (GFP) expressing marker plasmid. A continuous mixing technique was compared to the small-scale preparation of lipoplexes by pipetting. Individual steps of the continuous mixing process were evaluated in order to optimise the manufacturing technique: lipid/plasmid ratio, composition of transfection medium, pre-treatment of the lipid, size of the mixing device, mixing procedure and the influence of the lyophilisation process. It could be shown that the method developed for production of lipoplexes on a large scale under sterile conditions led to lipoplexes with good transfection efficiencies combined with low cytotoxicity, improved characteristics and long shelf-life.

Massive shelf dense water flow influences plankton community structure and particle transport over long distance.

PubMed

Bernardi Aubry, Fabrizio; Falcieri, Francesco Marcello; Chiggiato, Jacopo; Boldrin, Alfredo; Luna, Gian Marco; Finotto, Stefania; Camatti, Elisa; Acri, Francesco; Sclavo, Mauro; Carniel, Sandro; Bongiorni, Lucia

2018-03-14

Dense waters (DW) formation in shelf areas and their cascading off the shelf break play a major role in ventilating deep waters, thus potentially affecting ecosystem functioning and biogeochemical cycles. However, whether DW flow across shelves may affect the composition and structure of plankton communities down to the seafloor and the particles transport over long distances has not been fully investigated. Following the 2012 north Adriatic Sea cold outbreak, DW masses were intercepted at ca. 460 km south the area of origin and compared to resident ones in term of plankton biomass partitioning (pico to micro size) and phytoplankton species composition. Results indicated a relatively higher contribution of heterotrophs in DW than in deep resident water masses, probably as result of DW-mediated advection of fresh organic matter available to consumers. DWs showed unusual high abundances of Skeletonema sp., a diatom that bloomed in the north Adriatic during DW formation. The Lagrangian numerical model set up on this diatom confirmed that DW flow could be an important mechanism for plankton/particles export to deep waters. We conclude that the predicted climate-induced variability in DW formation events could have the potential to affect the ecosystem functioning of the deeper part of the Mediterranean basin, even at significant distance from generation sites.

Surrogate Joint Aerial Layer Network (JALN) Experiment: Applications of Commercial-Off-The-Shelf Technologies for Researching Future JALN Challenges

DTIC Science & Technology

2014-12-01

CHALLENGES DECEMBER 2014 TECHNICAL REPORT APPROVED FOR PUBLIC RELEASE; DISTRIBUTION UNLIMITED STINFO COPY AIR FORCE RESEARCH LABORATORY INFORMATION...JOINT AERIAL LAYER NETWORK (JALN) EXPERIMENT: APPLICATION OF COMMERCIAL-OFF-THE-SHELF TECHNOLOGIES FOR RESEARCHING FUTURE JALN CHALLENGES 5a... challenge JALN developers. The use of low-cost COTS wireless technology is found to be a suitable surrogate for military hardware for investigating

Dust control by air-blocking shelves and dust collector-to-bailing airflow ratios for a surface mine drill shroud

PubMed Central

Zheng, Y.; Reed, W.R.; Potts, J.D.; Li, M.; Rider, J.P.

2018-01-01

The National Institute for Occupational Safety and Health (NIOSH) recently developed a series of validated models utilizing computational fluid dynamics (CFD) to study the effects of air-blocking shelves on airflows and respirable dust distribution associated with medium-sized surface blasthole drill shrouds as part of a dry dust collector system. Using validated CFD models, three different air-blocking shelves were included in the present study: a 15.2-cm (6-in.)-wide shelf; a 7.6-cm (3-in.)-wide shelf; and a 7.6-cm (3-in.)-wide shelf at four different shelf heights. In addition, the dust-collector-to-bailing airflow ratios of 1.75:1, 1.5:1, 1.25:1 and 1:1 were evaluated for the 15.2-cm (6-in.)-wide air-blocking shelf. This paper describes the methodology used to develop the CFD models. The effects of air-blocking shelves and dust collector-to-bailing airflow ratios were identified by the study, and problem regions were revealed under certain conditions.

On the pattern of WAIS retreat in eastern Ross Sea based on a regional synthesis of new geophysical and geological data acquired during NBP1502

NASA Astrophysics Data System (ADS)

McGlannan, A. J.; Bart, P. J.; Anderson, J. B.

2016-02-01

New multibeam and seismic data acquired during NBP1502 reveal that a series of backstepping grounding zone wedges (GZWs) were constructed on the middle shelf as the West Antarctic Ice Sheet (WAIS) retreated from the Whales Deep paleo-ice stream trough. The geomorphological information provided by these geophysical data were used to acquire a regional grid of jumbo-piston and kasten cores. Here, we present our regional synthesis of the new geophysical and geological data. The distributions of upcore transitions from diamict to sub-ice-shelf facies on the outer-most shelf demonstrate that as the grounded ice retreated in four discrete backsteps, the calving front remained in the vicinity of the shelf edge, approximately 50 kilometers to the north. In contrast, the upcore transition at the fourth backstep shows GZW diamict directly overlain by open-marine facies. We interpret this to indicate that a major retreat of both grounded and floating ice was associated with the termination of the middle-shelf grounding event. The minimum retreat distance was greater than 100 kilometers.

Isotope and fatty acid trends along continental shelf depth gradients: Inshore versus offshore hydrological influences on benthic trophic functioning

NASA Astrophysics Data System (ADS)

Chouvelon, T.; Schaal, G.; Grall, J.; Pernet, F.; Perdriau, M.; A-Pernet, E. J.; Le Bris, H.

2015-11-01

Anthropogenic activities and land-based inputs into the sea may influence the trophic structure and functioning of coastal and continental shelf ecosystems, despite the numerous opportunities and services the latter offer to humans and wildlife. In addition, hydrological structures and physical dynamics potentially influence the sources of organic matter (e.g., terrestrial versus marine, or fresh material versus detrital material) entering marine food webs. Understanding the significance of the processes that influence marine food webs and ecosystems (e.g., terrestrial inputs, physical dynamics) is crucially important because trophic dynamics are a vital part of ecosystem integrity. This can be achieved by identifying organic matter sources that enter food webs along inshore-offshore transects. We hypothesised that regional hydrological structures over wide continental shelves directly control the benthic trophic functioning across the shelf. We investigated this issue along two transects in the northern ecosystem of the Bay of Biscay (north-eastern Atlantic). Carbon and nitrogen stable isotope analysis (SIA) and fatty acid analysis (FAA) were conducted on different complementary ecosystem compartments that include suspended particulate organic matter (POM), sedimentary organic matter (SOM), and benthic consumers such as bivalves, large crustaceans and demersal fish. Samples were collected from inshore shallow waters (at ∼1 m in depth) to more than 200 m in depth on the offshore shelf break. Results indicated strong discrepancies in stable isotope (SI) and fatty acid (FA) compositions in the sampled compartments between inshore and offshore areas, although nitrogen SI (δ15N) and FA trends were similar along both transects. Offshore the influence of a permanently stratified area (described previously as a ;cold pool;) was evident in both transects. The influence of this hydrological structure on benthic trophic functioning (i.e., on the food sources available for consumers) was especially apparent across the northern transect, due to unusual carbon isotope compositions (δ13C) in the compartments. At stations under the cold pool, SI and FA organism compositions indicated benthic trophic functioning based on a microbial food web, including a significant contribution of heterotrophic planktonic organisms and/or of SOM, notably in stations under the cold pool. On the contrary, inshore and shelf break areas were characterised by a microalgae-based food web (at least in part for the shelf break area, due to slope current and upwelling that can favour fresh primary production sinking on site). SIA and FAA were relevant and complementary tools, and consumers better medium- to long-term system integrators than POM samples, for depicting the trophic functioning and dynamics along inshore-offshore transects over continental shelves.

Déjà-vu all over again: using simulation to evaluate the impact of shorter shelf life for red blood cells at Héma-Québec.

PubMed

Blake, John T; Hardy, Matthew; Delage, Gilles; Myhal, Geneviève

2013-07-01

Since the 1970s red blood cells (RBCs) have had a rated shelf life of 42 days. Recently, studies have suggested poorer patient outcomes when older blood is transfused. However, shortening the shelf life of RBCs may increase costs and lead to greater instances of outdates and shortages. A simulation method to evaluate the impact of a shorter shelf life for RBCs on a regional blood network was developed. A network model of the production and distribution system in the province of Quebec was built and validated. The model suggests that a shelf life of 21 or 28 days will have modest impact on outdate and shortage rates. A shelf life of 14 days will create significant challenges for both blood suppliers and hospitals and will result in systemwide outdate rates of 6.64% and shortage rates of 2.75%. The impact of a shorter shelf life for RBCs will disproportionately affect smaller and midsize hospitals. A shelf life of 28 or 21 days is feasible without excessive increases to systemwide outdate, shortage, or emergency ordering rates. Large hospitals will see minimal impact; smaller hospitals will see larger increases and may be unable to find inventory policies that maintain both low outdate and shortage rates. Reducing the shelf life to 14 days, or lower, results in significant challenges for suppliers and hospitals of all sizes. All hospitals will see an impact on outdate and shortage rates; overall systemwide outdate rates (6% or more) will reach levels that would currently be considered unacceptably high. © 2012 American Association of Blood Banks.

Geology of the head of Lydonia Canyon, U.S. Atlantic outer continental shelf

USGS Publications Warehouse

Twichell, David C.

1983-01-01

The geology of the part of Lydonia Canyon shoreward of the continental shelf edge on the southern side of Georges Bank was mapped using high-resolution seismic-reflection and side-scan sonar techniques and surface sediment grab samples. The head of the canyon incises Pleistocene deltaic deposits and Miocene shallow marine strata. Medium sand containing some coarse sand and gravel covers the shelf except for a belt of very fine sand containing no gravel on either side of the canyon in water depths of 125–140 m. Gravel and boulders, presumably ice-rafted debris, cover the rim of the canyon. The canyon floor and canyon wall gullies are covered by coarse silt of Holocene age which is as much as 25 m thick, and Miocene and Pleistocene strata are exposed on the spurs between gullies. The Holocene sediment is restricted to the canyon shoreward of the shelf edge and has been winnowed from the shelf. Furrows cut in the shelf sands and ripples on the shelf and in the canyon suggest that sediment continues to be moved in this area. Sediment distribution, however, is inconsistent with that expected from the inferred westward sediment transport on the shelf. Either the fine-grained deposits on the shelf to either side of the canyon head are relict or there is a significant component of offshore transport around the canyon head.In the head of Oceanographer Canyon, only 40 km west of Lydonia Canyon, present conditions are strikingly different. The floor of Oceanographer Canyon is covered by sand waves, and their presence indicates active reworking of the bottom sediments by strong currents. The close proximity of the two canyons suggests that the relative importance of processes acting in canyons can be variable over short distances.

The Influence of a Western Boundary Current on Continental Shelf Processes Along Southeastern Australia.

NASA Astrophysics Data System (ADS)

Roughan, M.

2016-02-01

The East Australian Current (EAC) flows as a jet over the narrow shelf of southeastern Australia, dominating shelf circulation, and shedding vast eddies at the highly variable separation point. These characteristics alone make it a dynamically challenging region to measure, model and predict. In recent years a significant effort has been placed on understanding continental shelf processes along the coast of SE Australia, adjacent to the EAC, our major Western Boundary Current. We have used a multi-pronged approach by combining state of the art in situ observations and data assimilation modelling. Observations are obtained from a network of moorings, HF Radar and ocean gliders deployed in shelf waters along SE Australia, made possible through Australia's Integrated Marine Observing System (IMOS). In addition, we have developed a high resolution reanalysis of the East Australian Current using ROMS and 4DVar data Assimilation. In addition to the traditional data streams (SST, SSH and ARGO) we assimilate the newly available IMOS observations in the region. These include velocity and hydrographic observations from the EAC transport array, 1km HF radar measurements of surface currents, CTD casts from ocean gliders, and temperature, salinity and velocity measurements from a network of shelf mooring arrays. We use these vast data sets and numerical modelling tools combined with satellite remote sensed data to understand spatio-temporal variability of shelf processes and water mass distributions on synoptic, seasonal and inter-annual timescales. We have quantified the cross shelf transport variability inshore of the EAC, the driving mechanisms, the seasonal cycles in shelf waters and to some extent variability in the biological (phytoplankton) response. I will present a review of some of the key results from a number of recent studies.

Seasonal Dynamics of Dissolved Organic Carbon Under Complex Circulation Schemes on a Large Continental Shelf: The Northern South China Sea

NASA Astrophysics Data System (ADS)

Meng, Feifei; Dai, Minhan; Cao, Zhimian; Wu, Kai; Zhao, Xiaozheng; Li, Xiaolin; Chen, Junhui; Gan, Jianping

2017-12-01

We examined the distribution and seasonality of dissolved organic carbon (DOC) based on a large data set collected from the northern South China Sea (NSCS) shelf under complex circulation schemes influenced by river plume, coastal upwelling, and downwelling. The highest surface values of ˜117 μmol L-1 were observed nearshore in summer suggesting high DOC supplies from the river inputs, whereas the lowest surface values of ˜62 μmol L-1 were on the outer shelf in winter due to entrainment of DOC-poor subsurface water under strengthened vertical mixing. While the summer coastal upwelling brought lower DOC from offshore depth to the nearshore surface, the winter coastal downwelling delivered higher surface DOC to the midshelf deep waters from the inner shelf fueled by the China Coastal Current (CCC) transporting relatively high DOC from the East China Sea to the NSCS. The intensified winter downwelling generated a cross-shelf DOC transport of 3.1 × 1012 g C over a large shelf area, which induced a significant depression of the NSCS DOC inventory in winter relative to in autumn. In addition to the variable physical controls, net biological production of DOC was semiquantified in both the river plume (2.8 ± 3.0 μmol L-1) and coastal upwelling (3.1 ± 1.3 μmol L-1) in summer. We demonstrated that the NSCS shelf had various origins of DOC including riverine inputs, inter-shelf transport and in situ production. Via cross-shelf transport, the accumulated DOC would be exported to and stored in the deep ocean, suggesting that continental shelves are a potentially effective carbon sink.

Patterns of primary productivity and biomass in a coastal upwelling region

NASA Astrophysics Data System (ADS)

Small, Lawrence F.; Menzies, David W.

1981-02-01

Average distributions of chlorophyll α during upwelling in areas of smooth bathymetry off Oregon have been computed from historical data. Chlorophyll concentrations in cross-shelf sections over the Oregon continental shelf (44°40'N) were similar to those in cross-shelf sections off northwest Africa during JOINT-1 studies but differed from those in similar sections over an adjacent narrow region of the Oregon shelf (44°55'N to 45°12'N). The fact that larger concentration differences can occur along short sections of one coastline than between upwelling regions half a world apart bears on the time and space scales of sampling and might have bearing on the support and distributions of other trophic levels. Relationships between the local winds and the broader-scale BAKUN (1975) upwelling indices were used to classify various phytoplankton biomass and primary productivity distributions according to whether they were in strong upwelling steady state, weak upwelling steady state, or one of two transition states. The upwelling steady state conforms to the 'upwelling event' scale (about 3 to 10 days) of WALSH, WHITLEDGE, KELLEY, HUNTSMAN and PILLSBURY (1977) and the transition state of approximately one-day duration might specify the critical scale for driving the upwelling off Oregon. Under strong steady-state upwelling in early summer a single band of high primary productivity and biomass develops in the surface layer parallel to the bottom contours, but under similar upwelling conditions in later summer a two-celled zonal circulation occurs and two parallel bands develop. Our strong upwelling distributions are discussed in light of current models of the Oregon upwelling system. Maintenance of biological properties through time in the upwelling bands is also discussed. Under weak steady-state upwelling the primary productivity and biomass bands are farther inshore or immediately against the coast. Productivity in the weak upwelling bands can be twice that of the strong upwelling bands and often 20 times that in surrounding water. Under transient conditions in which the local winds are favorable for strong upwelling but the slower-responding Bakun index indicates weak upwelling, chlorophyll distributions change within a day to resemble distributions during strong steady-state upwelling. Under transient conditions in which the local winds weaken dramatically but the Bakun index still indicates strong upwelling, chlorophyll concentrations are high and widely distributed throughout the upwelling region.

Modeling the spatial and temporal population dynamics of the copepod Centropages typicus in the northwestern Mediterranean Sea during the year 2001 using a 3D ecosystem model

NASA Astrophysics Data System (ADS)

Carlotti, F.; Eisenhauer, L.; Campbell, R.; Diaz, F.

2014-07-01

The spatio-temporal dynamics of a simulated Centropages typicus (Kröyer) population during the year 2001 at the regional scale of the northwestern Mediterranean Sea are addressed using a 3D coupled physical-biogeochemical model. The setup of the coupled biological model comprises a pelagic plankton ecosystem model and a stage-structured population model forced by the 3D velocity and temperature fields provided by an eddy-resolving regional circulation model. The population model for C. typicus (C. t. below) represents demographic processes through five groups of developmental stages, which depend on underlying individual growth and development processes and are forced by both biotic (prey and predator fields) and abiotic (temperature, advection) factors from the coupled physical-biogeochemical model. The objective is to characterize C. t. ontogenic habitats driven by physical and trophic processes. The annual dynamics are presented for two of the main oceanographic stations in the Gulf of Lions, which are representative of shelf and open sea conditions, while the spatial distributions over the whole area are presented for three dates during the year, in early and late spring and in winter. The simulated spatial patterns of C. t. developmental stages are closely related to mesoscale hydrodynamic features and circulation patterns. The seasonal and spatial distributions on the Gulf of Lions shelf depend on the seasonal interplay between the Rhône river plume, the mesoscale eddies on the shelf and the Northern Current acting as either as a dynamic barrier between the shelf and the open sea or allowing cross-shelf exchanges. In the central gyre of the northwestern Mediterranean Sea, the patchiness of plankton is tightly linked to mesoscale frontal systems, surface eddies and filaments and deep gradients. Due to its flexibility in terms of its diet, C. t. succeeds in maintaining its population in both coastal and offshore areas year round. The simulations suggest that the winte-spring food conditions are more favorable on the shelf for C. t., whereas in late summer and fall, the offshore depth-integrated food biomasses represent a larger resource for C. t., particularly when mesoscale structures and vertical discontinuities increase food patchiness. The development and reproduction of C. t. depend on the prey field within the mesoscale structures that induce a contrasting spatial distribution of successive developmental stages on a given observation date. In late fall and winter, the results of the model suggest the existence of three refuge areas where the population maintains winter generations near the coast and within the Rhone River plume, or offshore within canyons within the shelf break, or in the frontal system related to the Northern Current. The simulated spatial and temporal distributions as well as the life cycle and physiological features of C. t. are discussed in light of recent reviews on the dynamics of C. t. in the northwestern Mediterranean Sea.

Centuries of intense surface melt on Larsen C Ice Shelf

NASA Astrophysics Data System (ADS)

Bevan, Suzanne L.; Luckman, Adrian; Hubbard, Bryn; Kulessa, Bernd; Ashmore, David; Kuipers Munneke, Peter; O'Leary, Martin; Booth, Adam; Sevestre, Heidi; McGrath, Daniel

2017-12-01

Following a southward progression of ice-shelf disintegration along the Antarctic Peninsula (AP), Larsen C Ice Shelf (LCIS) has become the focus of ongoing investigation regarding its future stability. The ice shelf experiences surface melt and commonly features surface meltwater ponds. Here, we use a flow-line model and a firn density model (FDM) to date and interpret observations of melt-affected ice layers found within five 90 m boreholes distributed across the ice shelf. We find that units of ice within the boreholes, which have densities exceeding those expected under normal dry compaction metamorphism, correspond to two climatic warm periods within the last 300 years on the Antarctic Peninsula. The more recent warm period, from the 1960s onwards, has generated distinct sections of dense ice measured in two boreholes in Cabinet Inlet, which is close to the Antarctic Peninsula mountains - a region affected by föhn winds. Previous work has classified these layers as refrozen pond ice, requiring large quantities of mobile liquid water to form. Our flow-line model shows that, whilst preconditioning of the snow began in the late 1960s, it was probably not until the early 1990s that the modern period of ponding began. The earlier warm period occurred during the 18th century and resulted in two additional sections of anomalously dense ice deep within the boreholes. The first, at 61 m in one of our Cabinet Inlet boreholes, consists of ice characteristic of refrozen ponds and must have formed in an area currently featuring ponding. The second, at 69 m in a mid-shelf borehole, formed at the same time on the edge of the pond area. Further south, the boreholes sample ice that is of an equivalent age but which does not exhibit the same degree of melt influence. This west-east and north-south gradient in the past melt distribution resembles current spatial patterns of surface melt intensity.

Acoustically-inferred zooplankton distribution in relation to hydrography west of the Antarctic Peninsula

NASA Astrophysics Data System (ADS)

Lawson, Gareth L.; Wiebe, Peter H.; Ashjian, Carin J.; Gallager, Scott M.; Davis, Cabell S.; Warren, Joseph D.

2004-08-01

The relationship between the distribution of zooplankton, especially euphausiids ( Euphausia and Thysanoessa spp.), and hydrographic regimes of the Western Antarctic Peninsula continental shelf in and around Marguerite Bay was studied as part of the Southern Ocean GLOBEC program. Surveys were conducted from the RVIB N.B. Palmer in austral fall (April-June) and winter (July-August) of 2001. Acoustic, video, and environmental data were collected along 13 transect lines running across the shelf and perpendicular to the Western Antarctic Peninsula coastline, between 65°S and 70°S. Depth-stratified net tows conducted at selected locations provided ground-truthing for acoustic observations. In fall, acoustic volume backscattering strength at 120 kHz was greatest in the southern reaches of the survey area and inside Marguerite Bay, suggestive of high zooplankton and micronekton biomass in these regions. Vertically, highest backscattering was in the 150-450 m depth range, associated with modified Circumpolar Deep Water (CDW). The two deep troughs that intersect the shelf break were characterized by reduced backscattering, similar to levels observed off-shelf and indicative of lower zooplankton biomass in recent intrusions of CDW onto the continental shelf. Estimates of dynamic height suggested that geostrophic circulation likely caused both along- and across-shelf transport of zooplankton. By winter, scattering had decreased by an order of magnitude (10 dB) in the upper 300 m of the water column in most areas, and high backscattering levels were found primarily in a deep (>300 m) scattering layer present close to the bottom. The seasonal decrease is potentially explained by advection of zooplankton, vertical and horizontal movements, and mortality. Predictions of expected backscattering levels based on net samples suggested that large euphausiids were the dominant source of backscattering only at very particular locations and depths, and that copepods, siphonophores, and pteropods were more important in many locations.

Combined statistical analyses for long-term stability data with multiple storage conditions: a simulation study.

PubMed

Almalik, Osama; Nijhuis, Michiel B; van den Heuvel, Edwin R

2014-01-01

Shelf-life estimation usually requires that at least three registration batches are tested for stability at multiple storage conditions. The shelf-life estimates are often obtained by linear regression analysis per storage condition, an approach implicitly suggested by ICH guideline Q1E. A linear regression analysis combining all data from multiple storage conditions was recently proposed in the literature when variances are homogeneous across storage conditions. The combined analysis is expected to perform better than the separate analysis per storage condition, since pooling data would lead to an improved estimate of the variation and higher numbers of degrees of freedom, but this is not evident for shelf-life estimation. Indeed, the two approaches treat the observed initial batch results, the intercepts in the model, and poolability of batches differently, which may eliminate or reduce the expected advantage of the combined approach with respect to the separate approach. Therefore, a simulation study was performed to compare the distribution of simulated shelf-life estimates on several characteristics between the two approaches and to quantify the difference in shelf-life estimates. In general, the combined statistical analysis does estimate the true shelf life more consistently and precisely than the analysis per storage condition, but it did not outperform the separate analysis in all circumstances.

Resuspension and Shelf-Deep Ocean Exchange in the Northern California Current: New Insights From Underwater Gliders

NASA Astrophysics Data System (ADS)

Erofeev, A.; Barth, J. A.; Shearman, R. K.; Pierce, S. D.

2016-02-01

Shelf-deep ocean exchange is dominated by wind-driven upwelling and downwelling in the northern California Current. The interaction of strong, along-shelf jets with coastline and bottom topographic features can also create significant cross-margin exchange. We are using data from over 60,000 kilometers of autonomous underwater glider tracks to understand the temporal and spatial distribution of shelf-deep ocean exchange off central Oregon. Year-round glider observations of temperature, salinity, depth-averaged currents, chlorophyll fluorescence, light backscatter, and colored dissolved organic matter fluorescence from a single cross-margin transect are used to examine shelf-deep ocean exchange mechanisms. During summer, cross-margin exchange is dominated by wind-driven upwelling and the relaxation or reversal of the dominant southward winds. This process has been fairly well observed and studied due to the relatively low sea states and winds during summer. There is far less data from fall and winter off Oregon, a time of strong winds and large waves. We use autonomous underwater gliders to sample during the winter, including through the fall and spring transitions. Glider observations of suspended material detected via light backscatter, show time-space variations in resuspension in the bottom boundary layer due to winds, waves and currents. Examples of shelf-deep ocean exchange are shown by layers with high light backscatter separating from the bottom near the shelf break and extending into the interior along isopycnals. We describe these features and events in relationship to wind-forcing, along-shelf flows, and other forcing mechanisms.

Estimation of Nutrients Flux of Water-sediment Interface in the Chukchi Sea, the Western Arctic Ocean

NASA Astrophysics Data System (ADS)

Zhang, H.

2016-02-01

Nutrients regeneration in pore water is one of the important ways to supply nutrients of upper water column in the shelf. The pore water in sediment of the central Chukchi Sea continental shelf, showed a typical benthic distribution of nutrients at water-sediment interface, in where physical and bioturbation was weak. The nutrient samples in multi-tubular short column sediment and water column were obtained from the Forth Chinese National Arctic Research Expedition, to measure the nutrient concentrations of pore water, overlying water and water column. The results show that, the typical distribution can be separated into three layers. The first layer is the exponential increasing layer (I), in which the concentrations of nutrients increased rapidly with depth. Then was the steady layer (II), the sediment demineralization was equal to the nutrient transference and nutrients' concentrations were substantially constant at this stage. The third layer was a slowly descending layer (III), in which NO3- and PO43- were reduced by bacteria and lost oxygen ions due to organic materials degradation depleting oxygen. By a two-layer mode and the Fick's first law of diffusion, diffusive fluxes of silicate, phosphate and nitrate in R06 station of the Chukchi Sea shelf can be calculated, and the fluxes were 1.660 mmol/(m2 · d), 0.008 mmol/(m2 · d) and 0.117 mmol/(m2 · d), respectively. The diffusive fluxes of silicate for CC1, R06, C07 and S23 stations were 3.101 mmol/(m2 · d), 1.660 mmol/(m2 · d), 1.307 mmol/(m2 · d) and mmol/(m2 · d), respectively, which show obvious distribution characteristics with latitude. Distribution of N * in the pore water suggested that a strong denitrification process in sedimentary environment of the Chukchi Sea shelf, which is an important sink for nitrate.

Antarctic Crabs: Invasion or Endurance?

PubMed Central

Griffiths, Huw J.; Whittle, Rowan J.; Roberts, Stephen J.; Belchier, Mark; Linse, Katrin

2013-01-01

Recent scientific interest following the “discovery” of lithodid crabs around Antarctica has centred on a hypothesis that these crabs might be poised to invade the Antarctic shelf if the recent warming trend continues, potentially decimating its native fauna. This “invasion hypothesis” suggests that decapod crabs were driven out of Antarctica 40–15 million years ago and are only now returning as “warm” enough habitats become available. The hypothesis is based on a geographically and spatially poor fossil record of a different group of crabs (Brachyura), and examination of relatively few Recent lithodid samples from the Antarctic slope. In this paper, we examine the existing lithodid fossil record and present the distribution and biogeographic patterns derived from over 16,000 records of Recent Southern Hemisphere crabs and lobsters. Globally, the lithodid fossil record consists of only two known specimens, neither of which comes from the Antarctic. Recent records show that 22 species of crabs and lobsters have been reported from the Southern Ocean, with 12 species found south of 60°S. All are restricted to waters warmer than 0°C, with their Antarctic distribution limited to the areas of seafloor dominated by Circumpolar Deep Water (CDW). Currently, CDW extends further and shallower onto the West Antarctic shelf than the known distribution ranges of most lithodid species examined. Geological evidence suggests that West Antarctic shelf could have been available for colonisation during the last 9,000 years. Distribution patterns, species richness, and levels of endemism all suggest that, rather than becoming extinct and recently re-invading from outside Antarctica, the lithodid crabs have likely persisted, and even radiated, on or near to Antarctic slope. We conclude there is no evidence for a modern-day “crab invasion”. We recommend a repeated targeted lithodid sampling program along the West Antarctic shelf to fully test the validity of the “invasion hypothesis”. PMID:23843974

Wind modulation of upwelling at the shelf-break front off Patagonia: Observational evidence

NASA Astrophysics Data System (ADS)

Carranza, M. M.; Gille, S. T.; Piola, A. R.; Charo, M.; Romero, S. I.

2017-03-01

The South-Atlantic Patagonian shelf is the largest chlorophyll-a (Chl-a) hot spot in Southern Ocean color images. While a persistent 1500 km long band of high Chl-a along the shelf-break front (SBF) is indicative of upwelling, the mechanisms that drive it are not entirely known. Along-front wind oscillations can enhance upwelling and provide a nutrient pumping mechanism at shelf-break fronts of western boundary currents. Here we assess wind-induced upwelling at the SBF off Patagonia from daily satellite Chl-a and winds, historical hydrographic observations, cross-shelf Chl-a fluorescence transects from two cruises, and in situ winds and water column structure from a mooring site. Satellite Chl-a composites segregated by along-front wind direction indicate that surface Chl-a is enhanced at the SBF with southerly winds and suppressed with northerly winds. Northerly winds also result in enhanced Chl-a further offshore (˜25-50 km). Synoptic transects as well as mean hydrographic sections segregated by along-front winds show isopycnals tilted upward for southerly winds. Spring observations from the mooring also suggest that southerly winds destratify the water column and northerly winds restratify, in agreement with Ekman transport interacting with the front. Moreover, changes in water column temperature lag along-front wind forcing by 2-4 days. Our results suggest that oscillations in along-front winds, on timescales typical of atmospheric storms (2-10 days), can significantly modulate the upwelling and Chl-a concentrations at the SBF off Patagonia, revealing the importance of wind-induced upwelling for shelf-slope exchange at shelf-break fronts of western boundary currents.

Optimization of Microencapsulation Composition of Menthol, Vanillin, and Benzyl Acetate inside Polyvinyl Alcohol with Coacervation Method for Application in Perfumery

NASA Astrophysics Data System (ADS)

Sahlan, Muhamad; Raihani Rahman, Mohammad

2017-07-01

One of many applications of essential oils is as fragrance in perfumery. Menthol, benzyl acetate, and vanillin, each represents olfactive characteristic of peppermint leaves, jasmine flowers, and vanilla beans, are commonly used in perfumery. These components are highly volatile, hence the fragrance components will quickly evaporate resulting in short-lasting scent and low shelf life. In this research, said components have been successfully encapsulated simultaneously inside Polyvinyl Alcohol (PVA) using simple coacervation method to increase its shelf life. Optimization has been done using Central Composite Diagram with 4 independent variables, i.e. composition of menthol, benzyl acetate, vanillin, and tergitol 15-S-9 (as emulsifier). Encapsulation efficiency, loading capacity, and microcapsule size have been measured. In optimized composition of menthol (13.98 %w/w), benzyl acetate (14.75 %w/w), vanillin (17.84 %w/w), and tergitol 15-S-9 (13.4 %w/w) encapsulation efficiency of 97,34% and loading capacity of 46,46% have been achieved. Mean diameter of microcapsule is 20,24 μm and within range of 2,011-36,24 μm. Final product was achieved in the form of cross linked polyvinyl alcohol with hydrogel consistency and orange to yellow in color.

Offshore survey provides answers to coastal stability and potential offshore extensions of landslides into Abalone Cove, Palos Verdes peninsula, Calif

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dill, R.F.; Slosson, J.E.

1993-04-01

The configuration and stability of the present coast line near Abalone Cove, on the south side of Palos Verdes Peninsula, California is related to the geology, oceanographic conditions, and recent and ancient landslide activity. This case study utilizes offshore high resolution seismic profiles, side-scan sonar, diving, and coring, to relate marine geology to the stability of a coastal region with known active landslides utilizing a desk top computer and off-the-shelf software. Electronic navigation provided precise positioning that when applied to computer generated charts permitted correlation of survey data needed to define the offshore geology and sea floor sediment patterns. Amore » mackintosh desk-top computer and commercially available off-the-shelf software provided the analytical tools for constructing a base chart and a means to superimpose template overlays of topography, isopachs or sediment thickness, bottom roughness and sediment distribution patterns. This composite map of offshore geology and oceanography was then related to an extensive engineering and geological land study of the coastal zone forming Abalone Cove, an area of active landslides. Vibrocoring provided ground sediment data for high resolution seismic traverses. This paper details the systems used, present findings relative to potential landslide movements, coastal erosion and discuss how conclusions were reached to determine whether or not onshore landslide failures extend offshore.« less

Dynamic estuarine plumes and fronts: importance to small fish and plankton in coastal waters of NSW, Australia

NASA Astrophysics Data System (ADS)

Kingsford, M. J.; Suthers, I. M.

1994-05-01

In 1990, low density estuarine plumes in the vicinity of Botany Bay, Australia, extended up to 11 km across a narrow continental shelf ( ca 25 km) on ebb tides. The shape and seaward extent of plumes varied according to a combination of state of the tide, freshwater input and the direction and intensity of coastal currents. Offshore plumes dissipated on the flood tide and fronts reformed at the entrance of Botany Bay. Major differences in the abundance and composition of ichthyoplankton and other zooplankton were found over a 400-800 m stretch of water encompassing waters of the plume, front and ocean on seven occasions. For example, highest abundances of the fishes Gobiidae, Sillaginidae, Gerreidae and Sparidae as well as barnacle larvae and fish eggs were found in plumes. Cross-shelf distribution patterns of zooplankton, therefore, are influenced by plumes. Distinct assemblages of plankters accumulated in fronts, e.g. fishes of the Mugilidae and Gonorynchidae and other zooplankters (e.g. Jaxea sp.). Accumulation in fronts was variable and may relate to variable convergence according to the tide. We argue that plumes provide a significant cue to larvae in coastal waters that an estuary is nearby. Moreover, although many larvae may be retained in the turbid waters of plumes associated with riverine input, larvae are potentially exported in surface waters on ebb tides.

Heavy mineral analysis for assessing the provenance of sandy sediment in the San Francisco Bay Coastal System

USGS Publications Warehouse

Wong, Florence L.; Woodrow, Donald L.; McGann, Mary

2013-01-01

Heavy or high-specific gravity minerals make up a small but diagnostic component of sediment that is well suited for determining the provenance and distribution of sediment transported through estuarine and coastal systems worldwide. By this means, we see that surficial sand-sized sediment in the San Francisco Bay Coastal System comes primarily from the Sierra Nevada and associated terranes by way of the Sacramento and San Joaquin Rivers and is transported with little dilution through the San Francisco Bay and out the Golden Gate. Heavy minerals document a slight change from the strictly Sierran-Sacramento mineralogy at the confluence of the two rivers to a composition that includes minor amounts of chert and other Franciscan Complex components west of Carquinez Strait. Between Carquinez Strait and the San Francisco Bar, Sierran sediment is intermingled with Franciscan-modified Sierran sediment. The latter continues out the Gate and turns southward towards beaches of the San Francisco Peninsula. The Sierran sediment also fans out from the San Francisco Bar to merge with a Sierran province on the shelf in the Gulf of the Farallones. Beach-sand sized sediment from the Russian River is transported southward to Point Reyes where it spreads out to define a Franciscan sediment province on the shelf, but does not continue southward to contribute to the sediment in the Golden Gate area.

Quality changes of fresh filled pasta during storage: influence of modified atmosphere packaging on microbial growth and sensory properties.

PubMed

Sanguinetti, A M; Del Caro, A; Mangia, N P; Secchi, N; Catzeddu, P; Piga, A

2011-02-01

This study evaluated the shelf life of fresh pasta filled with cheese subjected to modified atmosphere packaging (MAP) or air packaging (AP). After a pasteurization treatment, fresh pasta was packaged under a 50/50 N(2)/CO(2) ratio or in air (air batch). Changes in microbial growth, in-package gas composition, chemical-physical parameters and sensory attributes were monitored for 42 days at 4 (°)C. The pasteurization treatment resulted in suitable microbiological reduction. MAP allowed a mold-free shelf life of the fresh filled pasta of 42 days, whereas air-packaged samples got spoilt between 7 and 14 days. The hurdle approach used (MAP and low storage temperature) prevented the growth of pathogens and alterative microorganisms. MAP samples maintained a high microbiological standard throughout the storage period. The panel judged MAP fresh pasta above the acceptability threshold throughout the shelf life.

Provenance of sand on the Poverty Bay shelf, the link between source and sink sectors of the Waipaoa River sedimentary system

NASA Astrophysics Data System (ADS)

Parra, Julie G.; Marsaglia, Kathleen M.; Rivera, Kevin S.; Dawson, Shelby T.; Walsh, J. P.

2012-12-01

The Poverty Shelf, North Island, New Zealand, is a segment of the Waipaoa Sedimentary System (WSS), a MARGINS Source-to-Sink focus site. Our petrographic analysis of sand from shelf core samples indicates that the sand fraction is mainly derived from intra- and potentially extrabasinal sources, but surprisingly, the major fluvial system that drains into Poverty Bay, the Waipaoa River (mean %QFL = xQyFzL), is not the dominant source. Only one vibracore at the mouth of Poverty Bay contained sand (%QFL = xQyFzL) potentially derived from the Waipaoa River. The shelf sand (mean %QFL = xQyFzL) more strongly resembles beach sand (mean %QFL = xQyFzL) collected along the coast, which is likely sourced from pervasive local cliff erosion of Miocene-Pliocene sedimentary units that exhibit similar sandstone detrital modes (mean %QFL = xQyFzL). Texturally, coarser, more poorly sorted and more angular sand is located along the outer shelf, while finer, well-sorted sand characterizes the mid-shelf. These findings suggest a shorter transport history for the material near the outer-shelf bathymetric high areas, and this observation along with the composition data suggests that they were sourced by erosion of locally exposed Miocene-Pliocene units. A potential extrabasinal source of shelf sediment is indicated by anomalous prolate and equant-shaped greywacke (Torlesse) and minor red chert pebbles collected in two outer-shelf box cores on the Lachlan anticline; these are not lithologies found within the terrestrial segment of the WSS or strata comprising the outer-shelf highs. The clast shapes are also distinctly different from the oblate-shaped, pebble-sized greywacke gravel clasts on beaches in Hawke Bay. Rather, these sediments are more similar to Torlesse stream gravel. Seismic and multibeam data support the possibility that during the most recent sea-level lowstand, the Hawke Bay fluvial system flowed into Poverty Canyon, bringing these unique gravels onto what is now the Poverty outer shelf. The presence of the Torlesse gravel is significant in that it highlights how the WSS was not a closed sedimentary system in the past, just as recent sedimentary research has shown in the case today.

Molecular characterization of benthic foraminifera communities from the Northeastern Gulf of Mexico shelf and slope following the Deepwater Horizon event

NASA Astrophysics Data System (ADS)

Moss, Joseph A.; McCurry, Chelsea; Schwing, Patrick; Jeffrey, Wade H.; Romero, Isabel C.; Hollander, David J.; Snyder, Richard A.

2016-09-01

Benthic foraminifera are globally distributed protozoa in the world's oceans, which have been used as ecological indicators in both current and palaeo oceanography. The ecological properties and distribution of these organisms in various regions of the Gulf of Mexico (GOM) have been evaluated using microscopy; however molecular approaches for these purposes have been limited, especially in deeper regions. The BP Deepwater Horizon oil well failure in the northern Gulf of Mexico highlighted the need to better understand the distribution and abundance of these organisms relative to environmental factors and ecosystem perturbations such as the oil spill. Sediment samples were collected using a Shipek grab along transects on the northwest Florida GOM shelf (18-270 m depth). Clone libraries were developed from PCR amplified 18S rDNA genes for sequence analysis. Analysis of random clones from libraries were used as a proxy for community structure (presence and relative abundance) to document the spatial and temporal dynamics of benthic foraminifera on the Northwest Florida Shelf in the NE GOM shelf. Additional continental slope samples (200-1600 m depth) were obtained by a multicorer and treated in similar fashion. Mean species diversity in this study (H=2.49-3.36), agreed with pre-DWH event estimates, however the dominant agglutinated species in the deep-water samples did not match previous studies. Additionally, the dominant calcareous taxa from this study such as Allogromida sp. and Psammophaga sp., were inconsistent with previous reports. The dominant taxa in both coastal and deep-water sites include Glabratellina sp., Trochammina hadai, and Trochammina sp., and Textularia sagittula and Bathysiphon argenteus as well as members of genera Astrammina, Bolivina, Cibicides and Cibicidoides.

Changes in the diet and feeding of the hake Merluccius merluccius at the shelf-break of the Balearic Islands: Influence of the mesopelagic-boundary community

NASA Astrophysics Data System (ADS)

Cartes, Joan E.; Hidalgo, Manuel; Papiol, Vanesa; Massutí, Enric; Moranta, Joan

2009-03-01

Short spatio-temporal variations in the feeding intensity and the diet of the European hake, Merluccius merluccius, together with the abundance of their potential prey were studied between August 2003 and June 2004 at two locations, northwest (Sóller) and south (Cabrera), off the island of Mallorca (Balearic Islands, Western Mediterranean) at depths between 150 and 750 m. The two areas present different oceanographic conditions. Hake was mainly distributed along the shelf-slope break and the upper slope (between 166 and 350 m) where recruits (TL<18 cm) were dominant. The hake's diet varied as a function of size. Recruits fed mainly on micronektonic prey, and the diet was influenced primarily by seasonality, with two dietary patterns (identified by MDS analyses) corresponding to August-September 2003 (summer) and to November 2003/February-April 2004 (autumn-winter). The summer pattern was consistent with a thermally stratified water column, while November and April were consistent with homogenized temperature and salinity throughout all the water column. The main prey of recruits were the euphausiid Meganyctiphanes norvegica and the midwater fish Maurolicus muelleri in autumn-winter and myctophids (mainly Ceratoscopelus maderensis) in summer. In contrast to recruits, the geographic factor (NW vs. S) was the main factor influencing the diets of post-recruits (TL between 18 and 21.9 cm) and adults (TL⩾22 cm). Hake recruits (and to a lesser extent post-recruits) and their preferred prey occupied different depth ranges during daylight periods. Meganyctiphanes norvegica and Ceratoscopelus maderensis were, for instance, distributed as much as 500 m deeper than hake that had eaten them. All these trends were especially obvious at NW, an area with a more abrupt slope and with a greater influence by northern winter intermediate water (WIW) inflow in early spring than the S area. These factors probably enhanced micronekton aggregation in April, when feeding intensity (stomach fullness) increased among recruits and post-recruits only at NW. All these factors may have a crucial role in the diet, distribution and probably recruitment success of small hake. Biological factors were also important in trophic shifts in the diet and feeding of hake. Multi-linear regression models pointed to a trend of higher fullness with higher hepato-somatic index (HSI). Therefore greater food consumption by hake may enhance its metabolic condition. Within the framework of shelf-break and slope ecology, we show how the 'boundary' mesopelagic community inhabiting the middle slope sustains the trophic requirements of hake, a species distributed at shallower depths along the shelf-slope break. Mesopelagic euphausiids and myctophids are often found in the diets of shelf-break fish. Because the boundary mesopelagic community is distributed worldwide, the high levels of fish biomass often found at shelf-slope breaks could be sustained trophically by deeper, offshore mesopelagic communities, an inverse energy transfer from deep to shallow-water marine ecosystems.

Crossflow microfiltration in the dairy industry

USDA-ARS?s Scientific Manuscript database

The introduction of crossflow membrane technologies presented the dairy industry with tools that made possible the physical removal of microorganisms from milk that reduce its shelf life and manipulation of its composition to create new ingredients. This chapter focuses on crossflow microfiltration ...

Influence of the Yukon River on the Bering Sea

NASA Technical Reports Server (NTRS)

Dean, K.; Mcroy, C. P.

1986-01-01

The relationships between the discharge of the Yukon River to the currents and biological productivity in the northern Bering Sea were studied. Specific objectives were: to develop thermal, sediment, and chlorophyll surface maps using Thematic Mapper (TM) data of the discharge of the Yukon River and the Alaskan Coastal Current during the ice free season; to develop a historical model of the distribution of the Yukon River discharge and the Alaskan Coastal Current using LANDSAT Multispectral band scanner (MSS) and NOAA satellite imagery; and to use high resolution TM data to define the surface dynamics of the front between the Alaskan Coastal Current and the Bering Shelf/Anadyr Current. LANDSAT MSS, TM, and Advanced Very High Resolution Radiometer (AVHRR) data were recorded during the 1985 ice free period. The data coincided with shipboard measurements acquired by Inner Shelf Transfer and Recycling (ISTAR) project scientists. An integrated model of the distribution of turbid water discharged from the Yukon River was compiled. A similar model is also being compiled for the Alaskan Coastal and Bering Shelf/Anadyr water masses based on their thermal expressions seen on AVHRR imagery.

Surface Sediment Geochemistry in and around the Hudson Shelf Valley Offshore of New York

NASA Astrophysics Data System (ADS)

Mecray, E. L.; ten Brink, M. B.; Butman, B.; Denny, J.; Murray, R. W.

2001-05-01

The Hudson Shelf Valley, an ancient submerged portion of the Hudson River, extends across the continental shelf offshore of New York and New Jersey. Between 1959 and 1987, the area near the head of the valley was used for disposal of approximately 1.20 x 108 m3 of dredged material and sewage sludge. The distribution of metal concentrations and sediment characteristics were used to investigate the transport and fate of the sediments and their associated contaminants. Surface (0-2cm) sediments collected at 440 stations throughout the New York Bight between 1993 and 1998 were used to establish the regional distribution of pollutant metals, grain size, organic carbon, and Clostridium perfringens spores. Sediments in the New York Bight are generally sandy, however fine-grained sediments are found in the axis of the Valley. Statistical methods identified common sources and chemical mobility within groups of anthropogenic and naturally-occurring elements. High metal concentrations, fine-grained sediments, and higher organic carbon concentrations co-occur in depo-centers within the Valley. Normalization of the metal concentrations to these factors shows higher metal concentrations on the fine-grained particles in sandy areas of the Bight, particularly along the southern shore of Long Island. These distributions have implications for evaluating the impact of the mass distribution for contaminated metals in different habitats and areas. Decreasing concentrations of pollutants with time are observed, reflecting reduced contaminant loading in the upper region of the Valley; however, concentrations are still above natural background levels.

Maps Showing Composition of Surficial Sediments on the Insular Shelf of Southwestern Puerto Rico

USGS Publications Warehouse

Shideler, Gerald L.

1980-01-01

The limited availability of onshore sand deposits for use in construction appears to be a future major problem in Puerto Rico (U.S. Bureau of Mines, 1972; Committee on Puerto Rico and the Sea, 1974). Consequently, the mining of offshore sand deposits as supplemental sources of construction aggregate may becom e necessary. For this reason, the U.S. Geological Survey and the Department of Natural Resources of the Commonwealth of Puerto Rico have conducted investigations of potential offshore sand deposits on the Puerto Rico insular shelf. This report provides information on the composition of surficial sediments on the southwestern Puerto Rico shelf (fig. 1), an area that may be one of the more favorable potential sites for offshore sand resources. Water depths over most of the study area are less than 22 meters (m). The sea floor is composed of live and dead patch and fringing reefs, areas of rock exposures, and sedim ent-covered areas. The adjacent coastline includes prominent embaym ents and a conspicuous rock promontory (Cabo Rojo) connected by a tombolo to the mainland of Puerto Rico. The study area is in the belt of northeast trade winds. Waves approach the coast predominantly from the southeast, resulting in a predominantly westward littoral drift along the south coast (Grove and Trumbull, 1978). Local sand movement on the southern shelf is shown by an active sand wave field south of Bah1a Sucia in which the sand wave crests have migrated toward the southwest (Grove and Trumbull, 1978). The presence of the sand wave field suggests that large volumes of sand having potential for mining are locally present in the study area.

Composition and fate of terrigenous organic matter along the Arctic land-ocean continuum in East Siberia: Insights from biomarkers and carbon isotopes

NASA Astrophysics Data System (ADS)

Tesi, Tommaso; Semiletov, Igor; Hugelius, Gustaf; Dudarev, Oleg; Kuhry, Peter; Gustafsson, Örjan

2014-05-01

Climate warming is predicted to translocate terrigenous organic carbon (TerrOC) to the Arctic Ocean and affect the marine biogeochemistry at high latitudes. The magnitude of this translocation is currently unknown, so is the climate response. The fate of the remobilized TerrOC across the Arctic shelves represents an unconstrained component of this feedback. The present study investigated the fate of permafrost carbon along the land-ocean continuum by characterizing the TerrOC composition in three different terrestrial carbon pools from Siberian permafrost (surface organic rich horizon, mineral soil active layer, and Ice Complex deposit) and marine sediments collected on the extensive East Siberian Arctic Shelf (ESAS). High levels of lignin phenols and cutin acids were measured in all terrestrial samples analyzed indicating that these compounds can be used to trace the heterogeneous terrigenous material entering the Arctic Ocean. In ESAS sediments, comparison of these terrigenous biomarkers with other TerrOC proxies (bulk δ13C/Δ14C and HMW lipid biomarkers) highlighted contrasting across-shelf trends. These differences could indicate that TerrOC in the ESAS is made up of several pools that exhibit contrasting reactivity toward oxidation during the transport. In this reactive spectrum, lignin is the most reactive, decreasing up to three orders of magnitude from the inner- to the outer-shelf while the decrease of HMW wax lipid biomarkers was considerably less pronounced. Alternatively, degradation might be negligible while sediment sorting during the across-shelf transport could be the major physical forcing that redistributes different TerrOC pools characterized by different matrix-association.

Patterns of Deep-Water Coral Diversity in the Caribbean Basin and Adjacent Southern Waters: An Approach based on Records from the R/V Pillsbury Expeditions

PubMed Central

Hernández-Ávila, Iván

2014-01-01

The diversity of deep-water corals in the Caribbean Sea was studied using records from oceanographic expeditions performed by the R/V Pillsbury. Sampled stations were sorted according to broad depth ranges and ecoregions and were analyzed in terms of species accumulation curves, variance in the species composition and contributions to alpha, beta and gamma diversity. According to the analysis of species accumulation curves using the Chao2 estimator, more diversity occurs on the continental slope (200–2000 m depth) than on the upper continental shelf (60–200 m depth). In addition to the effect of depth sampling, differences in species composition related to depth ranges were detected. However, the differences between ecoregions are dependent on depth ranges, there were fewer differences among ecoregions on the continental slope than on the upper continental shelf. Indicator species for distinctness of ecoregions were, in general, Alcyonaria and Antipatharia for the upper continental shelf, but also the scleractinians Madracis myriabilis and Cladocora debilis. In the continental slope, the alcyonarian Placogorgia and the scleractinians Stephanocyathus and Fungiacyathus were important for the distinction of ecoregions. Beta diversity was the most important component of gamma diversity in the Caribbean Basin. The contribution of ecoregions to alpha, beta and gamma diversity differed with depth range. On the upper continental shelf, the Southern Caribbean ecoregion contributed substantially to all components of diversity. In contrast, the northern ecoregions contributed substantially to the diversity of the Continental Slope. Strategies for the conservation of deep-water coral diversity in the Caribbean Basin must consider the variation between ecoregions and depth ranges. PMID:24671156

Late Pleistocene to Holocene sedimentation and hydrocarbon seeps on the continental shelf of a steep, tectonically active margin, southern California, USA

USGS Publications Warehouse

Draut, Amy E.; Hart, Patrick E.; Lorenson, T.D.; Ryan, Holly F.; Wong, Florence L.; Sliter, Ray W.; Conrad, James E.

2009-01-01

Small, steep, uplifting coastal watersheds are prolific sediment producers that contribute significantly to the global marine sediment budget. This study illustrates how sedimentation evolves in one such system where the continental shelf is largely sediment-starved, with most terrestrial sediment bypassing the shelf in favor of deposition in deeper basins. The Santa Barbara-Ventura coast of southern California, USA, is considered a classic area for the study of active tectonics and of Tertiary and Quaternary climatic evolution, interpretations of which depend upon an understanding of sedimentation patterns. High-resolution seismic-reflection data over >570 km2 of this shelf show that sediment production is concentrated in a few drainage basins, with the Ventura and Santa Clara River deltas containing most of the upper Pleistocene to Holocene sediment on the shelf. Away from those deltas, the major factor controlling shelf sedimentation is the interaction of wave energy with coastline geometry. Depocenters containing sediment 5-20 m thick exist opposite broad coastal embayments, whereas relict material (bedrock below a regional unconformity) is exposed at the sea floor in areas of the shelf opposite coastal headlands. Locally, natural hydrocarbon seeps interact with sediment deposition either to produce elevated tar-and-sediment mounds or as gas plumes that hinder sediment settling. As much as 80% of fluvial sediment delivered by the Ventura and Santa Clara Rivers is transported off the shelf (some into the Santa Barbara Basin and some into the Santa Monica Basin via Hueneme Canyon), leaving a shelf with relatively little recent sediment accumulation. Understanding factors that control large-scale sediment dispersal along a rapidly uplifting coast that produces substantial quantities of sediment has implications for interpreting the ancient stratigraphic record of active and transform continental margins, and for inferring the distribution of hydrocarbon resources in relict shelf deposits.

Characteristics of the near-bottom suspended sediment field over the continental shelf off northern California based on optical attenuation measurements during STRESS and SMILE

NASA Astrophysics Data System (ADS)

Trowbridge, J. H.; Butman, B.; Limeburner, R.

1994-08-01

Time-series measurements of current velocity, optical attenuation and surface wave intensity obtained during the Sediment Transport Events on Shelves and Slopes (STRESS) experiments, combined with shipboard measurements of conductivity, temperature and optical attenuation obtained during the Shelf Mixed Layer Experiment (SMILE), provide a description of the sediment concentration field over the central and outer shelf off northern California. The questions addressed are: (1) existence and characteristics of bottom nepheloid layers and their relationship to bottom mixed layers; (2) characteristics of temporal fluctuations in sediment concentration and their relationship to waves and currents; (3) spatial scales over which suspended sediment concentrations vary horizontally; and (4) vertical distribution of suspended sediment.

Distribution of dissolved manganese in the Peruvian Upwelling and Oxygen Minimum Zone

NASA Astrophysics Data System (ADS)

Vedamati, Jagruti; Chan, Catherine; Moffett, James W.

2015-05-01

The geochemistry of manganese (Mn) in seawater is dominated by its redox chemistry, as Mn(II) is soluble and Mn(IV) forms insoluble oxides, and redox transformations are mediated by a variety of processes in the oceans. Dissolved Mn (DMn) accumulates under reducing conditions and is depleted under oxidizing conditions. Thus the Peruvian upwelling region, characterized by highly reducing conditions over a broad continental shelf and a major oxygen minimum zone extending far offshore, is potentially a large source of Mn to the eastern Tropical South Pacific. In this study, DMn was determined on cruises in October 2005 and February 2010 in the Peruvian Upwelling and Oxygen Minimum Zone, to evaluate the relationship between Mn, oxygen and nitrogen cycle processes. DMn concentrations were determined using simple dilution and matrix-matched external standardization inductively coupled mass spectrometry. Surprisingly, DMn was depleted under the most reducing conditions along the Peruvian shelf. Concentrations of dissolved Mn in surface waters increased offshore, indicating that advection of Mn offshore from the Peruvian shelf is a minor source. Subsurface Mn maxima were observed within the oxycline rather than within the oxygen minimum zone (OMZ), indicating they arise from remineralization of organic matter rather than reduction of Mn oxides. The distribution of DMn appears to be dominated by non-redox processes and inputs from the atmosphere and from other regions associated with specific water masses. Lower than expected DMn concentrations on the shelf probably reflect limited fluvial inputs from the continent and efficient offshore transport. This behavior is in stark contrast to Fe, reported in a companion study which is very high on the shelf and undergoes dynamic redox cycling.

Hydrographic and particle distributions over the Palos Verdes continental shelf: Spatial, seasonal and daily variability

USGS Publications Warehouse

Jones, B.H.; Noble, M.A.; Dickey, T.D.

2002-01-01

Moorings and towyo mapping were used to study the temporal and spatial variability of physical processes and suspended particulate material over the continental shelf of the Palos Verdes Peninsula in southwestern Los Angeles, California during the late summer of 1992 and winter of 1992-93. Seasonal evolution of the hydrographic structure is related to seasonal atmospheric forcing. During summer, stratification results from heating of the upper layer. Summer insolation coupled with the stratification results in a slight salinity increase nearsurface due to evaporation. Winter cooling removes much of the upper layer stratification, but winter storms can introduce sufficient quantities of freshwater into the shelf water column again adding stratification through the buoyancy input. Vertical mixing of the low salinity surface water deeper into the water column decreases the sharp nearsurface stratification and reduces the overall salinity of the upper water column. Moored conductivity measurements indicate that the decreased salinity persisted for at least 2 months after a major storm with additional freshwater inputs through the period. Four particulate groups contributed to the suspended particulate load in the water column: phytoplankton, resuspended sediments, and particles in treated sewage effluent were observed in every towyo mapping cruise; terrigenous particles are introduced through runoff from winter rainstorms. Terrigenous suspended particulate material sinks from the water column in <9 days and phytoplankton respond to the stormwater input of buoyancy and nutrients within the same period. The suspended particles near the bottom have spatially patchy distributions, but are always present in hydrographic surveys of the shelf. Temporal variations in these particles do not show a significant tidal response, but they may be maintained in suspension by internal wave and tide processes impinging on the shelf. ?? 2002 Elsevier Science Ltd. All rights reserved.

Surface current patterns suggested by suspended sediment distribution over the outer continental margin, Bering Sea

USGS Publications Warehouse

Karl, Herman A.; Carlson, P.R.

1987-01-01

Samples of total suspended matter (TSM) were collected at the surface over the northern outer continental margin of the Bering Sea during the summers of 1980 and 1981. Volume concentrations of surface TSM averaged 0.6 and 1.1 mg l-1 for 1980 and 1981, respectively. Organic matter, largely plankton, made up about 65% of the near-surface TSM for both years. Distributions of TSM suggested that shelf circulation patterns were characterized either by meso- and large- scale eddies or by cross-shelf components of flow superimposed on a general northwesterly net drift. These patterns may be caused by large submarine canyons which dominate the physiography of this part of the Bering Sea continental margin. ?? 1987.

Understanding Ice Shelf Basal Melting Using Convergent ICEPOD Data Sets: ROSETTA-Ice Study of Ross Ice Shelf

NASA Astrophysics Data System (ADS)

Bell, R. E.; Frearson, N.; Tinto, K. J.; Das, I.; Fricker, H. A.; Siddoway, C. S.; Padman, L.

2017-12-01

The future stability of the ice shelves surrounding Antarctica will be susceptible to increases in both surface and basal melt as the atmosphere and ocean warm. The ROSETTA-Ice program is targeted at using the ICEPOD airborne technology to produce new constraints on Ross Ice Shelf, the underlying ocean, bathymetry, and geologic setting, using radar sounding, gravimetry and laser altimetry. This convergent approach to studying the ice-shelf and basal processes enables us to develop an understanding of the fundamental controls on ice-shelf evolution. This work leverages the stratigraphy of the ice shelf, which is detected as individual reflectors by the shallow-ice radar and is often associated with surface scour, form close to the grounding line or pinning points on the ice shelf. Surface accumulation on the ice shelf buries these reflectors as the ice flows towards the calving front. This distinctive stratigraphy can be traced across the ice shelf for the major East Antarctic outlet glaciers and West Antarctic ice streams. Changes in the ice thickness below these reflectors are a result of strain and basal melting and freezing. Correcting the estimated thickness changes for strain using RIGGS strain measurements, we can develop decadal-resolution flowline distributions of basal melt. Close to East Antarctica elevated melt-rates (>1 m/yr) are found 60-100 km from the calving front. On the West Antarctic side high melt rates primarily develop within 10 km of the calving front. The East Antarctic side of Ross Ice Shelf is dominated by melt driven by saline water masses that develop in Ross Sea polynyas, while the melting on the West Antarctic side next to Hayes Bank is associated with modified Continental Deep Water transported along the continental shelf. The two sides of Ross Ice Shelf experience differing basal melt in part due to the duality in the underlying geologic structure: the East Antarctic side consists of relatively dense crust, with low amplitude magnetic anomalies, and deep bathymetry. The West Antarctic side displays high amplitude magnetic anomalies, lower densities and shallower water depths. The geologically-controlled bathymetry influences the access of water masses capable of basal melting into the ice shelf cavity with the deep troughs on the East Antarctic side facilitating melting.

Deductive Verification of Cryptographic Software

NASA Technical Reports Server (NTRS)

Almeida, Jose Barcelar; Barbosa, Manuel; Pinto, Jorge Sousa; Vieira, Barbara

2009-01-01

We report on the application of an off-the-shelf verification platform to the RC4 stream cipher cryptographic software implementation (as available in the openSSL library), and introduce a deductive verification technique based on self-composition for proving the absence of error propagation.

Structure, distribution, and evolution history of the Early Holocene erosional mud ridge system on the inner East China Sea shelf near the Yangtze River estuary

NASA Astrophysics Data System (ADS)

Feng, Zhibing; Liu, Baohua; Zhao, Yuexia; Li, Xishuang; Dada, Olusegun A.; Jiang, Li; Si, Shaokun

2017-04-01

Utilizing the collected high-resolution seismic dataset and accompanying borehole and bathymetric data, we systematically evaluated the morphology, architecture, sedimentology, and evolution of erosional mud ridges within the inner East China Sea (ECS) shelf. We identified 20 mud ridges, i.e., seismic reflection profile crossings of exposed or buried mud ridges, which are 3.0-30.1 km in width and 2.5-17.3 m in height. The mud ridges are composed predominantly of gray clayey silt, and on seismic profiles contain parallel to subparallel reflectors. They formed around 10-12 ka BP within an estuarine environment. Scouring features of some mud ridges on the eastern part of the study area can be recognized. Consideration of the relative positions of mud ridges, together with the topographical features, enables us to map four linear mud ridges (LMRs). The SE-NW oriented LMRs are > 50 km in length, 3.0-9.5 km in width and running parallel to each other. They also display asymmetric shapes, with steeper slopes to the SW. The eastern segments of some LMRs are exposed on the present seafloor whereas other segments are mainly overlain by the mid- and late Holocene strata. Since the LMRs share similarities with the modern tidal sand ridges in shape and orientation, we hypothesize that they are formed under a uniform tidal current. Seismic data highlight that the internal reflectors of sand ridges consist of dipping clinoforms and are significantly different from LMRs, a feature which is largely due to the difference in grain-size composition of sediments between the inner and mid-outer ECS shelf. The mid- to outer ECS shelf is capped by coarser-grained sediments (i.e., medium to fine-grained), which were reworked and deposited at locations near the erosional areas under a polycyclic tidal current, thus forming multiphase sand ridges. However, fine-grained sediments (i.e., silty clay and clayey silt) overlain on the inner ECS shelf with light mass were carried far away from the erosional areas by the tidal currents, and the relict mud ridges were built. Evidence shows that the LMRs were formed by the early Holocene strata being scoured by a persistent southeasterly flowing current during 8-10 ka BP. The evolution of the LMRs occurred in three stages: (a) formation of the transgressional strata at 10-12 ka BP, (b) strong trough erosion at 8-10 ka BP, and (c) local adjustment (i.e., local erosion slightly and preservation) after 8 ka BP.

The response of inorganic carbon distributions and dynamics to upwelling-favorable winds on the northern Gulf of Mexico during summer

NASA Astrophysics Data System (ADS)

Huang, W.-J.; Cai, W.-J.; Wang, Y.; Hu, X.; Chen, B.; Lohrenz, S. E.; Chakraborty, S.; He, R.; Brandes, J.; Hopkinson, C. S.

2015-12-01

Upwelling-favorable winds and an offshore-distributed Mississippi and Atchafalaya River plume trajectory were observed in summer 2009 in contrast to the mean conditions from 2002 to 2010 (upwelling-unfavorable winds and an alongshore river plume trajectory), a set of conditions which was also observed in summer 2007. The responses of dissolved inorganic carbon (DIC) distributions and dynamics to upwelling-favorable winds are studied by comparing the contrasting conditions between summer 2009 and summer 2007 on the northern Gulf of Mexico. Patterns of surface water partial pressure of CO2 (pCO2), DIC, δ13C in DIC, and total alkalinity (TA) determined in July 2009 and August 2007 were strongly related to river plume trajectories, and differed between the two summers. The slope of the relationship between dissolved oxygen (DO) and DIC in summer 2007 was comparable to the Redfield O/C ratio of 1.3, which was attributed to respiration of organic matter in the bottom water. The slope of the DO and DIC relationship and δ13CDIC values in bottom waters during July 2009 were clearly affected by mixing since their salinities were <35. A three end-member mixing model was used to remove mixing effects in (1) δ13CDIC, to estimate the organic source of respiration, and (2) in DIC concentrations, to calculate DIC removal and release. δ13CDIC results in both summers were consistent with an apparent release of DIC in hypoxic waters (DO less than 2 mg L-1) associated with respiration of surface organic matter. The area-weighted surface DIC removal (i.e., biological production) was lower in 2009 than in 2007 on the shelf, as the plume was distributed offshore. The release of DIC in bottom waters was higher over the shelf in 2009 and was surmised to be related to stronger mixing, which was favorable for the DO supply for respiration. Overall, surface waters on the continental shelf in the region of study in July 2009 acted as a weak CO2 source to the atmosphere, but a weak CO2 sink in August 2007. We contend that the inorganic carbon distribution and concentrations on the shelf were related to regional wind forcing, through its influence on the distribution of coastal currents and plume trajectories and their subsequent impact on biogeochemical processes.

Shelf-life of minimally processed cabbage treated with neutral electrolysed oxidising water and stored under equilibrium modified atmosphere.

PubMed

Gómez-López, Vicente M; Ragaert, Peter; Ryckeboer, Jaak; Jeyachchandran, Visvalingam; Debevere, Johan; Devlieghere, Frank

2007-06-10

Minimally processed vegetables (MPV) have a short shelf-life. Neutral electrolysed oxidising water (NEW) is a novel decontamination method. The objective of this study was to test the potential of NEW to extend the shelf-life of a MPV, namely shredded cabbage. Samples of shredded cabbage were immersed in NEW containing 40 mg/L of free chlorine or tap water (control) up to 5 min, and then stored under equilibrium modified atmosphere at 4 degrees C and 7 degrees C. Proliferation of aerobic mesophilic bacteria, psychrotrophic bacteria, lactic acid bacteria and yeasts were studied during the shelf-life. Also pH and sensorial quality of the samples as well as O(2) and CO(2) composition of the headspace of the bags was evaluated. From the microbial groups, only psychrotrophic counts decreased significantly (P<0.05) due to the effect of NEW, but the counts in treated samples and controls were similar after 3 days of storage at 4 degrees C and 7 degrees C. Packaging configurations kept O(2) concentration around 5% and prevented CO(2) accumulation. pH increased from 6.1-6.2 to 6.4 during the shelf-life. No microbial parameter reached unacceptable counts after 14 days at 4 degrees C and 8 days of storage at 7 degrees C. The shelf-life of controls stored at 4 degrees C was limited to 9 days by overall visual quality (OVQ), while samples treated with NEW remained acceptable during the 14 days of the experiment. The shelf-life of controls stored at 7 degrees C was limited to 6 days by OVQ and browning, while that of samples treated with NEW were limited to 9 days by OVQ, browning and dryness. According to these results, a shelf-life extension of at least 5 days and 3 days in samples stored respectively at 4 degrees C and 7 degrees C can be achieved by treating shredded cabbage with NEW. NEW seems to be a promising method to prolong the shelf-life of MPV.

Variations of marine pore water salinity and chlorinity in Gulf of Alaska sediments (IODP Expedition 341)

NASA Astrophysics Data System (ADS)

März, Christian; Mix, Alan C.; McClymont, Erin; Nakamura, Atsunori; Berbel, Glaucia; Gulick, Sean; Jaeger, John; Schneider (LeVay), Leah

2014-05-01

Pore waters of marine sediments usually have salinities and chlorinities similar to the overlying sea water, ranging around 34-35 psu (Practical Salinity Units) and around 550 mM Cl-, respectively. This is because these parameters are conservative in the sense that they do not significantly participate in biogeochemical cycles. However, pore water studies carried out in the frame of the International Ocean Discovery Program (IODP) and its predecessors have shown that salinities and chlorinities of marine pore waters can substantially deviate from the modern bottom water composition in a number of environmental settings, and various processes have been suggested to explain these phenomena. Also during the recent IODP Expedition 341 that drilled five sites in the Gulf of Alaska (Northeast Pacific Ocean) from the deep Surveyor Fan across the continental slope to the glaciomarine shelf deposits, several occurrences of pore waters with salinities and chlorinities significantly different from respective bottom waters were encountered during shipboard analyses. At the pelagic Sites U1417 and U1418 (~4,200 and ~3,700 m water depth, respectively), salinity and chlorinity maxima occur around 20-50 m sediment depth, but values gradually decrease with increasing drilling depths (down to 30 psu in ~600 m sediment depth). While the pore water freshening at depth is most likely an effect of clay mineral dehydration due to increasing burial depth, the shallow salinity and chlorinity maxima are interpreted as relicts of more saline bottom waters that existed in the North Pacific during the Last Glacial Maximum (Adkins et al., 2002). In contrast, the glaciomarine slope and shelf deposits at Site U1419 to U1421 (~200 to 1,000 m water depth) are characterised by unexpectedly low salinitiy and chlorinity values (as low as 16 psu and 295 mM Cl-, respectively) already in very shallow sediment depths (~10 m), and their records do not show systematic trends with sediment depth. Freshening of pore waters in continental margin settings has been reported in association with dissociating gas hydrate deposits (Hesse, 2003), but neither seismic profiles nor sediment records showed any indications for the presence of gas hydrates at the Gulf of Alaska sites. An alternative and intriguing explanation for these almost brackish waters in the glaciomarine shelf and slope deposits is the presence of glacial meltwater that could either be "fossil" (stored in the glaciomarine sediments since the last glacial termination) or "recent" (i.e., actively flowing from currently melting glaciers of the St. Elias Mountain Range along permeable layers within the shelf deposits). As these relatively fresh waters are found at three distinct drill sites, it can be assumed that they are distributed all along the Gulf of Alaska shelf and slope, and similar findings have been reported at other glaciated continental margins, e.g., off East Greenland (DeFoor et al., 2011) and Antarctica (Mann and Gieskes, 1975; Chambers, 1991; Lu et al., 2010). While a recent review has highlighted the importance of fresh and brackish water reservoirs in continental shelf deposits worldwide (Post et al., 2013), we suggest that climatic and depositional processes affecting glaciated continental margins (e.g., the release of huge amounts of fresh water from ice sheets and glaciers during glacial terminations, and the rapid deposition of unconsolidated sediments on the adjacent shelf) are particularly favourable for the storage and/or flow of meltwater below the present sea floor. Adkins JF, McIntyre K, Schrag DP (2002) The salinity, temperature, and d18O of the glacial deep ocean. Science 298, 1769-1773. Chambers SR (1991) Solute distributions and stable isotope chemistry of interstitial waters from Prydz Bay, Antarctica. Proceedings of the Ocean Drilling Program 119, 375-392. DeFoor W, Person M, Larsen HC, Lizarralde D, Cohen D, Dugam B (2011) Ice sheet-derived submarine groundwater discharge on Greenland's continental shelf. Water Resources Research 47, W07549. Hesse R (2003) Pore water anomalies of submarine gas-hydrate zones as tool to assess hydrate abundance and distribution in the subsurface: What have we learned in the past decade? Earth-Science Reviews 61, 149-179. Lu Z, Rickaby REM, Wellner J, Georg B, Charnley N, Anderson JB, Hensen C (2010) Pore fluid modeling approach to identify recent meltwater signals on the West Antarctic Peninsula. Geochemistry, Geophysics, Geosystems 11, doi: 10.1029/2009GC002949. Mann R, Gieskes JM (1975) Interstitial water studies, Leg 28. Deep Sea Drilling Project Initial Reports 28, 805-814. Post VEA, Groen J, Kooi H, Person M, Ge S, Edmunds M (2013) Offshore fresh groundwater reserves as a global phenomenon. Nature 504, 71-78.

Approaches to quantifying long-term continental shelf sediment transport with an example from the Northern California STRESS mid-shelf site

NASA Astrophysics Data System (ADS)

Harris, Courtney K.; Wiberg, Patricia L.

1997-09-01

Modeling shelf sediment transport rates and bed reworking depths is problematic when the wave and current forcing conditions are not precisely known, as is usually the case when long-term sedimentation patterns are of interest. Two approaches to modeling sediment transport under such circumstances are considered. The first relies on measured or simulated time series of flow conditions to drive model calculations. The second approach uses as model input probability distribution functions of bottom boundary layer flow conditions developed from wave and current measurements. Sediment transport rates, frequency of bed resuspension by waves and currents, and bed reworking calculated using the two methods are compared at the mid-shelf STRESS (Sediment TRansport on Shelves and Slopes) site on the northern California continental shelf. Current, wave and resuspension measurements at the site are used to generate model inputs and test model results. An 11-year record of bottom wave orbital velocity, calculated from surface wave spectra measured by the National Data Buoy Center (NDBC) Buoy 46013 and verified against bottom tripod measurements, is used to characterize the frequency and duration of wave-driven transport events and to estimate the joint probability distribution of wave orbital velocity and period. A 109-day record of hourly current measurements 10 m above bottom is used to estimate the probability distribution of bottom boundary layer current velocity at this site and to develop an auto-regressive model to simulate current velocities for times when direct measurements of currents are not available. Frequency of transport, the maximum volume of suspended sediment, and average flux calculated using measured wave and simulated current time series agree well with values calculated using measured time series. A probabilistic approach is more amenable to calculations over time scales longer than existing wave records, but it tends to underestimate net transport because it does not capture the episodic nature of transport events. Both methods enable estimates to be made of the uncertainty in transport quantities that arise from an incomplete knowledge of the specific timing of wave and current conditions. 1997 Elsevier Science Ltd

Benthic oxygen consumption on continental shelves off eastern Canada

NASA Astrophysics Data System (ADS)

Grant, Jonathan; Emerson, Craig W.; Hargrave, Barry T.; Shortle, Jeannette L.

1991-08-01

The consumption of phytoplankton production by the benthos is an important component of organic carbon budgets for continental shelves. Sediment texture is a major factor regulating benthic processes because fine sediment areas are sites of enhanced deposition from the water column, resulting in increased organic content, bacterial biomass and community metabolism. Although continental shelves at mid- to high latitudes consist primarily of coarse relict sediments ( PIPER, Continental Shelf Research, 11, 1013-1035), shelf regions of boreal and subarctic eastern Canada contain large areas of silt and clay sediments ( FADER, Continental Shelf Research, 11, 1123-1153). We collated estimates of benthic oxygen consumption in coarse (<20% silt-clay, <0.5% organic matter) and fine sediments (20% silt-clay, 0.5% organic matter) for northwest Atlantic continental shelves including new data for Georges Bank, the Scotian Shelf, the Grand Banks of Newfoundland and Labrador Shelf. Estimates were applied to the areal distribution of sediment type on these shelves to obtain a general relationship between sediment texture and benthic carbon consumption. Mean benthic oxygen demand was 2.7 times greater in fine sediment than in coarse sediment, when normalized to mean annual temperature. In terms of carbon equivalents, shelf regions with minimal fine sediment (Georges Bank, the Grand Banks of Newfoundland-northeast Newfoundland) consumed only 5-8% of annual primary production. Benthos of the Gulf of Maine (100% fine sediment) and the Scotian Shelf (35% fine sediment) utilized 16-19% of primary production. Although 32% of the Labrador Shelf area contained fine sediments, benthic consumption of pelagic production (8%) was apparently limited by low mean annual temperature (2°C). These results indicate that incorporation of sediment-specific oxygen uptake into shelf carbon budgets may increase estimates of benthic consumption by 50%. Furthermore, respiration and production by large macrofauna allow an even greater proportion of primary production to enter benthic pathways. Fine sediment areas (shelf basins or "depocenters") are postulated to be sites of enhanced biological activity which must be considered in the modelling of shelf carbon budgets and the role of the benthos in demersal fisheries.

Early diagenesis and trace element accumulation in North American Arctic margin sediments

NASA Astrophysics Data System (ADS)

Kuzyk, Zou Zou A.; Gobeil, Charles; Goñi, Miguel A.; Macdonald, Robie W.

2017-04-01

Concentrations of redox-sensitive elements (S, Mn, Mo, U, Cd, Re) were analyzed in a set of 27 sediment cores collected along the North American Arctic margin (NAAM) from the North Bering Sea to Davis Strait via the Canadian Archipelago. Sedimentary distributions and accumulation rates of the elements were used to evaluate early diagenesis in sediments along this section and to estimate the importance of this margin as a sink for key elements in the polar and global oceans. Distributions of Mn, total S and reduced inorganic S demonstrated that diagenetic conditions and thus sedimentary carbon turnover in the NAAM is organized regionally: undetectable or very thin layers (<0.5 cm) of surface Mn enrichment occurred in the Bering-Chukchi shelves; thin layers (1-5 cm) of surface Mn enrichment occurred in Barrow Canyon and Lancaster Sound; and thick layers (5-20 cm) of surface Mn enrichment occurred in the Beaufort Shelf, Canadian Archipelago, and Davis Strait. Inventories of authigenic S below the Mn-rich layer decreased about fivefold from Bering-Chukchi shelf and Barrow Canyon to Lancaster Sound and more than ten-fold from Bering-Chukchi shelf to Beaufort Shelf, Canadian Archipelago and Davis Strait. The Mn, total S and reduced inorganic S distributions imply strong organic carbon (OC) flux and metabolism in the Bering-Chukchi shelves, lower aerobic OC metabolism in Barrow Canyon and Lancaster Sound, and deep O2 penetration and much lower OC metabolism in the Beaufort Shelf, Canadian Archipelago, and Davis Strait. Accumulation rates of authigenic S, Mo, Cd, Re, and U displayed marked spatial variability along the NAAM reflecting the range in sedimentary redox conditions. Strong relationships between the accumulation rates and vertical carbon flux, estimated from regional primary production values and water depth at the coring sites, indicate that the primary driver in the regional patterns is the supply of labile carbon to the seabed. Thus, high primary production combined with a shallow water column (average 64 m) leads to high rates of authigenic trace element accumulation in sediments from the Bering-Chukchi shelves. High to moderate primary production combined with deep water (average 610 m) leads to moderate rates of authigenic trace element accumulation in sediments from Lancaster Sound. Low to very low primary production combined with moderate water depths (average 380 m) leads to low rates of authigenic trace element accumulation in sediments in the Beaufort Shelf, Davis Strait and Canadian Archipelago. Authigenic Mo accumulation rates show a significant relationship with vascular plant input to the sediments, implying that terrestrial organic matter contributes significantly to metabolism in Arctic margin sediments. Our results suggest that the broad and shallow shelf of the Chukchi Sea, which has high productivity sustained by imported nutrients, contributes disproportionately to global biogeochemical cycles.

Observed platelet ice distributions in Antarctic sea ice: An index for ocean-ice shelf heat flux

NASA Astrophysics Data System (ADS)

Langhorne, P. J.; Hughes, K. G.; Gough, A. J.; Smith, I. J.; Williams, M. J. M.; Robinson, N. J.; Stevens, C. L.; Rack, W.; Price, D.; Leonard, G. H.; Mahoney, A. R.; Haas, C.; Haskell, T. G.

2015-07-01

Antarctic sea ice that has been affected by supercooled Ice Shelf Water (ISW) has a unique crystallographic structure and is called platelet ice. In this paper we synthesize platelet ice observations to construct a continent-wide map of the winter presence of ISW at the ocean surface. The observations demonstrate that, in some regions of coastal Antarctica, supercooled ISW drives a negative oceanic heat flux of -30 Wm-2 that persists for several months during winter, significantly affecting sea ice thickness. In other regions, particularly where the thinning of ice shelves is believed to be greatest, platelet ice is not observed. Our new data set includes the longest ice-ocean record for Antarctica, which dates back to 1902 near the McMurdo Ice Shelf. These historical data indicate that, over the past 100 years, any change in the volume of very cold surface outflow from this ice shelf is less than the uncertainties in the measurements.

Bacterial biogeography influenced by shelf-basin exchange in the Arctic surface sediment at the Chukchi Borderland.

PubMed

Han, Dukki; Nam, Seung-Il; Ha, Ho Kyung; Kim, Hyoungjun; Sadowsky, Michael J; Lee, Yoo Kyung; Hur, Hor-Gil

2016-02-01

It has been known that continental shelves around the Arctic Ocean play a major role in the ventilation of the deep basins as a consequence of shelf-basin exchange. In the present study, we found that bacterial assemblage of the surface sediment was different from that of seawater while seawater harboured local bacterial assemblages in response to the Arctic hydrography. This finding suggests that the Arctic seafloor sediments may have distinctive bacterial biogeography. Moreover, the distribution of bacterial assemblages and physicochemical properties in surface sediments changed gradually from the Arctic continental shelf to deep-sea basin. Based on the results, bacterial biogeography in the Arctic seafloor sediments may be influenced by winnowing and re-deposition of surface sediments through the sediment gravity flow. The present study offers a deeper understanding of shelf convection and its role for the construction of bacterial assemblages in the Arctic Ocean. © 2015 Society for Applied Microbiology and John Wiley & Sons Ltd.

Hydrocarbons in sediments along a tropical estuary-shelf transition area: Sources and spatial distribution.

PubMed

Maciel, Daniele Claudino; de Souza, José Roberto Botelho; Taniguchi, Satie; Bícego, Márcia Caruso; Schettini, Carlos Augusto França; Zanardi-Lamardo, Eliete

2016-12-15

Estuaries generally act as sediment traps and may retain a range of contaminants associated to this matrix. Aliphatic hydrocarbons (AHs) were investigated in Capibaribe Estuarine System and adjacent shelf, Northeast of Brazil, to evaluate the contamination and to better understand its functionality related to the coast. Fourteen sediment samples were analyzed, using gas chromatography with flame ionization detection. Total AHs concentrations ranged from 7.5 to 190.3μgg -1 and n-alkanes ranged from below detection limit (

Growth and Mortality of Coccolithophores during spring in the Celtic Sea

NASA Astrophysics Data System (ADS)

Mayers, K.; Poulton, A. J.; Giering, S. L. C.; Daniels, C. J.; Wells, S. R.; Tarran, G.

2016-02-01

Coccolithophores are an important group of single celled protists which dominate pelagic calcite production, however little is currently known about the mortality rates within this group, or their importance in shelf seas regarding productivity and nutrient recycling. Measurements of coccolithophore calcification and cellular calcite quotas, as well as dilution experiments for microzooplankton grazing rates, were made during a spring cruise (April, 2015) in the Celtic Sea (NW European Shelf) and within an April bloom of Emiliania huxleyi. Calcite production and coccolithophore cell numbers showed a general positive trend throughout the progression of the spring bloom, ranging from 15 - 34µmol C m-3d-1 and 6 - 94 cells ml-1. Cell normalised calcification rates declined from 3 - 0.6 pmol C cell-1d-1 due to a shift from a mixed community to an E. huxleyi dominated one. Within the E. huxleyi bloom we recorded high daily calcite production (6049 µmol C m-3d-1) and cell normalised calcification of 3 pmol C cell-1d-1. This is significantly higher than E. huxleyi dominated sites in the Iceland Basin and more similar to a bloom on the Patagonian Shelf. Within the E. huxleyi bloom, mortality rates were 0.23 d-1 compared with growth rates of 0.29 d-1, meaning 80% of daily calcification was removed by grazers. In this study, coccolithophore mortality rates are presented from the central Celtic Sea throughout spring, and compared with an April E. huxleyi bloom in terms of species composition, trends in calcite production and composition of the phytoplankton community. These observations will potentially elucidate the role grazing plays in the fate of calcium carbonate, bloom formation and community composition.

Seasonal and spatial variabilities in northern Gulf of Alaska surface water iron concentrations driven by shelf sediment resuspension, glacial meltwater, a Yakutat eddy, and dust

NASA Astrophysics Data System (ADS)

Crusius, John; Schroth, Andrew W.; Resing, Joseph A.; Cullen, Jay; Campbell, Robert W.

2017-06-01

Phytoplankton growth in the Gulf of Alaska (GoA) is limited by iron (Fe), yet Fe sources are poorly constrained. We examine the temporal and spatial distributions of Fe, and its sources in the GoA, based on data from three cruises carried out in 2010 from the Copper River (AK) mouth to beyond the shelf break. April data are the first to describe late winter Fe behavior before surface water nitrate depletion began. Sediment resuspension during winter and spring storms generated high "total dissolvable Fe" (TDFe) concentrations of 1000 nmol kg-1 along the entire continental shelf, which decreased beyond the shelf break. In July, high TDFe concentrations were similar on the shelf, but more spatially variable, and driven by low-salinity glacial meltwater. Conversely, dissolved Fe (DFe) concentrations in surface waters were far lower and more seasonally consistent, ranging from 4 nmol kg-1 in nearshore waters to 0.6-1.5 nmol kg-1 seaward of the shelf break during April and July, despite dramatic depletion of nitrate over that period. The reasonably constant DFe concentrations are likely maintained during the year across the shelf by complexation by strong organic ligands, coupled with ample supply of labile particulate Fe. The April DFe data can be simulated using a simple numerical model that assumes a DFe flux from shelf sediments, horizontal transport by eddy diffusion, and removal by scavenging. Given how global change is altering many processes impacting the Fe cycle, additional studies are needed to examine controls on DFe in the Gulf of Alaska.

The INDIGO-Datacloud Authentication and Authorization Infrastructure

NASA Astrophysics Data System (ADS)

Ceccanti, A.; Hardt, M.; Wegh, B.; Millar, AP; Caberletti, M.; Vianello, E.; Licehammer, S.

2017-10-01

Contemporary distributed computing infrastructures (DCIs) are not easily and securely accessible by scientists. These computing environments are typically hard to integrate due to interoperability problems resulting from the use of different authentication mechanisms, identity negotiation protocols and access control policies. Such limitations have a big impact on the user experience making it hard for user communities to port and run their scientific applications on resources aggregated from multiple providers. The INDIGO-DataCloud project wants to provide the services and tools needed to enable a secure composition of resources from multiple providers in support of scientific applications. In order to do so, a common AAI architecture has to be defined that supports multiple authentication mechanisms, support delegated authorization across services and can be easily integrated in off-the-shelf software. In this contribution we introduce the INDIGO Authentication and Authorization Infrastructure, describing its main components and their status and how authentication, delegation and authorization flows are implemented across services.

Benthic macrofauna assemblages and biochemical properties of sediments in two Antarctic regions differently affected by climate change

NASA Astrophysics Data System (ADS)

Sañé, E.; Isla, E.; Gerdes, D.; Montiel, A.; Gili, J.-M.

2012-03-01

Lipid, protein and carbohydrate concentrations have been determined in sediment cores from the continental shelf in the South Eastern Weddell Sea (SEWS), where no ice shelves have been present at least for thousands of years, and the continental shelf off the Eastern Antarctic Peninsula (EAP), in the area where two ice shelf collapses occurred in 1995 and 2002. On one hand, SEWS presents an important flux of fresh organic matter to the seabed during summer, whereas on the other hand, the presence of ice shelves in EAP hampered photosynthesis restricting the input of organic matter to advected refractory material. In the present study, biochemical variables and benthic macrofauna abundance, biomass and diversity confirmed differences between the two regions. Lipid concentrations were higher in SEWS than in EAP, whereas carbohydrate concentrations were higher in the latter region. These differences were attributed to the higher concentration of labile and refractory material, respectively. Biomass, abundance and diversity of the macrofauna were higher in SEWS than in EAP, where benthic communities started receiving a fresh organic matter input only after the recent ice shelf collapses. As regards macrofauna composition, both regions presented macrobenthic communities associated to early stages of recolonization.

Shelf-life extension of preservative-free hydrated feed using gamma pasteurization and its effect on growth performance of eel

NASA Astrophysics Data System (ADS)

Kim, Dongho; Song, Hyunpa; Lim, Sangyong; Jo, Minho; Song, Duseop; Jo, Cheorun

2012-08-01

Hydrated feed (HF) promotes the growth performance and shortens the feeding time of fish by increasing the efficiency of digestion. However, the shelf-life of HF is a concern due to its relatively higher water content. In this study, radiation pasteurization was applied to improve the shelf-life and microbiological quality of HF for fish farming. Preservative-free HF containing 25% moisture was gamma-irradiated and its microbiological and nutritional properties evaluated in addition to a practical feeding trial carried out using eel. The viable counts of bacteria and fungi in HF were 106 and 104 CFU/g, respectively. All coliform bacteria and yeast in HF were eliminated by irradiation at a dose of 5 kGy, and total aerobic bacteria were eliminated at 10 kGy. The shelf-life of the preservative-free and irradiated (10 kGy) HF was estimated as 6 months under ambient conditions. The nutritional composition of HF was stable up to 10 kGy of irradiation. Based on a feeding trial, it was proven that eel fed HF had about 20% higher growth rate than that fed dried feed.

New constraints on the spatial distribution and morphology of the Halimeda bioherms of the Great Barrier Reef, Australia

NASA Astrophysics Data System (ADS)

McNeil, Mardi A.; Webster, Jody M.; Beaman, Robin J.; Graham, Trevor L.

2016-12-01

Halimeda bioherms occur as extensive geological structures on the northern Great Barrier Reef (GBR), Australia. We present the most complete, high-resolution spatial mapping of the northern GBR Halimeda bioherms, based on new airborne lidar and multibeam echosounder bathymetry data. Our analysis reveals that bioherm morphology does not conform to the previous model of parallel ridges and troughs, but is far more complex than previously thought. We define and describe three morphological sub-types: reticulate, annulate, and undulate, which are distributed in a cross-shelf pattern of reduced complexity from east to west. The northern GBR bioherms cover an area of 6095 km2, three times larger than the original estimate, exceeding the area and volume of calcium carbonate in the adjacent modern shelf-edge barrier reefs. We have mapped a 1740 km2 bioherm complex north of Raine Island in the Cape York region not previously recorded, extending the northern limit by more than 1° of latitude. Bioherm formation and distribution are controlled by a complex interaction of outer-shelf geometry, regional and local currents, coupled with the morphology and depth of continental slope submarine canyons determining the delivery of cool, nutrient-rich water upwelling through inter-reef passages. Distribution and mapping of Halimeda bioherms in relation to Great Barrier Reef Marine Park Authority bioregion classifications and management zones are inconsistent and currently poorly defined due to a lack of high-resolution data not available until now. These new estimates of bioherm spatial distribution and morphology have implications for understanding the role these geological features play as structurally complex and productive inter-reef habitats, and as calcium carbonate sinks which record a complete history of the Holocene post-glacial marine transgression in the northern GBR.

Mass-physical properties of surficial sediments on the Rhoˆne continental margin: implications for the nepheloid benthic layer

NASA Astrophysics Data System (ADS)

Chassefiere, Bernard

1990-09-01

Mass-physical properties of the surficial (upper 5 m) sediments on the Gulf of Lions continental margin were analysed, from more than 100 short (1 m) and longer (5 m) cores obtained during several cruises. Data include water content, unit weight, Atterberg limits (liquid limit, plastic limit, plasticity index), shear strength and compression index, and are used to determine: first, the mass property distribution, according to the main parameters influencing mass-physical properties; the relationships between these properties and the nepheloid layer on the shelf. The shoreline (lagoons) and inner shelf are characterized by low density and shear strength and high water content deposits, due to electrochemical flocculation of the sediment. The outer shelf is blanketed by higher density and shear strength and lower water content deposits generated by normal settling of suspended particles. On the inner shelf, during river peak discharges, a short-term thin bottom layer of "yogurt-like" [ FASS (1985) Geomarine Letters, 4, 147-152; FASS (1986) Continental Shelf Research, 6, 189-208] fluid-mud (unit weight lower than 1.3 mg m -3) is supplied, by a bottom nepheloid layer. During stormy periods, this "yogurt-like" layer (about 10 cm thick) partly disappears by resuspension of suspended particulate matter; this is advected, in the bottom nepheloid layer, over the shelf and the canyons within the upper slope.

Ecological and taphonomical influences on coccoliths in surface sediments in the shelf of the Yellow and East China Seas

NASA Astrophysics Data System (ADS)

Jin, Xiaobo; Liu, Chuanlian

2017-05-01

Coccoliths, combined with sediment grain size, carbonate calcium and organic matters content, were analyzed to assess the ecological and taphonomical influences on coccolith distribution patterns in surface sediments in the continental shelf of the Yellow and East China Seas. Coccolith abundances ranged from 0 to 2.08×109 coccoliths g-1 sediment. The increasing abundance from the coastal inner shelf to the seaward middle shelf generally reflects the ecological fact that living coccolithophores are more abundant in the mesotrophic shelf waters than in the eutrophic coastal waters, although their deposits are still controlled by taphonomical effects, such as bottom (tidal) currents and calcite preservation conditions. Most abundant coccoliths are found in the fine-grained sediments of southwestern Cheju Island, where both ecology and taphonomy favor coccolith preservation. Still, large densities of coccoliths (>108 coccoliths g-1 sediment) are also found in coarse-grained relict sediments in the middle shelf. Coccolith assemblages were predominated by Gephyrocapsa oceanica and Emiliania huxleyi. The relative abundance of E. huxleyi, in addition to ecological reasons, may relate to selective post-mortem dissolution, since small E. huxleyi coccoliths are more susceptible to dissolution. Coccolith calcite has minor contributions (<1% to 12%) to total sediment CaCO3, and the main parts are attributed to terrigenous CaCO3 debris and relict shell fragments.

Environmental controls on spatial variability of summer phytoplankton structure and biomass in the Bering Sea

NASA Astrophysics Data System (ADS)

Wang, Yu; Xiang, Peng; Kang, Jian-hua; Ye, You-yin; Lin, Geng-ming; Yang, Qing-liang; Lin, Mao

2018-01-01

The subarctic Bering Sea, one of the most productive regions of the world's oceans, is undergoing significant ecological shifts possibly linked to global climate change. During the Fourth Chinese National Arctic Research Expedition (CHINARE) from July 10 to 20 of 2010, phytoplankton community structure, species diversity, spatial distribution, community types, abundance and biomass variations were investigated in a large scale study extending from the Bering Strait into the open waters down to the subarctic Pacific. These patterns were linked to potential environmental drivers, including effects of water masses and seasonal sea ice retreat. Results showed a marked spatial zonation in the taxonomic composition, abundance and biomass. A total of 149 phytoplankton taxa distributed among 57 genera of 5 phyla were identified, characterized into three ecological groups, namely Arctic, Boreal-temperate and cosmopolitan species. Phytoplankton included 101 species of diatoms, 44 species of dinoflagellates, 2 species of Chrysophyta, 1 species of each Chlorophyta and Euglenophyta. Both abundance and biomass were highest in the Bering Shelf, moderate on the Bering Slope, and lowest on the Bering Basin. Chlorophyll a was found highest in the subsurface chlorophyll maxima (SCM) close to the thermocline and halocline layers but its depth varied regionally. Multi-dimensional scaling (MDS) revealed two types of assemblages, one a deep-sea assemblage associated with the Bering Basin and a neritic assemblage found in the Bering Slope and Shelf. Average abundance (10.22 × 103 cells/L), biomass (0.43 mg/m3), species diversity (2.60) and species richness (1.66) were established for deep-sea assemblage with the dominant species ranked as Neodenticula seminae, Chaetoceros atlanticus, Pseudonitzschia delicatissima, and Thalassionema nitzschioides. Neritic assemblage had higher values with 12.73 × 103 cells/L, 2.41 mg/m3, and 2.55 species richness but lower (2.41) species diversity, and the community was mainly dominated by Thalassiosira nordenskiöldii, Leptocylindrus danicus, Chaetoceros socialis, Chaetoceros debilis, Fragilariopsis oceanica, Nitzschia closterium and Chaetoceros furcellatus. A diatom bloom was observed near the Bering Strait in the summer of 2010 induced by high availability of nitrate particularly in the Bering Shelf, while water mass transportation mainly influenced communities in the Bering Basin and Slope. The observed fluctuation in both biomass and summer phytoplankton communities in the Bering Sea were mostly influenced by events related to the spring sea ice retreat in 2010.

The Açu Reef morphology, distribution, and inter reef sedimentation on the outer shelf of the NE Brazil equatorial margin

NASA Astrophysics Data System (ADS)

do Nascimento Silva, Luzia Liniane; Gomes, Moab Praxedes; Vital, Helenice

2018-05-01

Submerged reefs, referred to as the Açu Reefs, have been newly observed on both sides of the Açu Incised Valley on the northeastern equatorial Brazilian outer shelf. This study aims to understand the roles of shelf physiography, its antecedent morphologies, and its inter reef sedimentation on the different development stages of the biogenic reef during last deglacial sea-level rise. The data sets consist of side-scan sonar imagery, one sparker seismic profile, 76 sediment samples, and underwater photography. Seven backscatter patterns (P1 to P7) were identified and associated with eleven sedimentary carbonate and siliciclastic facies. The inherited relief, the mouth of the paleo incised valley, and the interreef sediment distribution play major controls on the deglacial reef evolution. The reefs occur in a depth-limited 25-55 m water depth range and in a 6 km wide narrow zone of the outer shelf. The reefs crop out in a surface area over 100 km2 and occur as a series of NW-SE preferentially orientated ridges composed of three parallel ridge sets at 45, 35, and 25 m of water depth. The reefs form a series of individual, roughly linear ridges, tens of km in length, acting as barriers in addition to scattered reef mounds or knolls, averaging 4 m in height and grouped in small patches and aggregates. The reefs, currently limited at the transition between the photic and mesophotic zones, are thinly covered by red algae and scattered coral heads and sponges. Taking into account the established sea-level curves from the equatorial Brazilian northeastern shelf / Rochas Atoll and Barbados, the shelf physiography, and the shallow bedrock, the optimal conditions for reef development had to occur during a time interval (11-9 kyr BP) characterized by a slowdown of the outer shelf flooding, immediately following Meltwater Pulse-1B. This 2 kyr short interval provided unique conditions for remarkable reef backstepping into distinct parallel ridge sets. Furthermore, the Açu Reefs have trapped relict siliciclastic sediments within the three sets of reefs, west of the Açu Incised Valley and adjacent coasts. Lines evidence of easterly nearshore currents carried sediments from the old Açu Incised Valley and adjacent coasts. These incipiently drowned reefs influence the water circulation patterns of the modern shelf system, its carbonate sedimentation, and sediment transport. This study provides a new example of reef occurrence which might be more commonly observed on similar equatorial continental shelves.

Warming shelf seas drive the subtropicalization of European pelagic fish communities.

PubMed

Montero-Serra, Ignasi; Edwards, Martin; Genner, Martin J

2015-01-01

Pelagic fishes are among the most ecologically and economically important fish species in European seas. In principle, these pelagic fishes have potential to demonstrate rapid abundance and distribution shifts in response to climatic variability due to their high adult motility, planktonic larval stages, and low dependence on benthic habitat for food or shelter during their life histories. Here, we provide evidence of substantial climate-driven changes to the structure of pelagic fish communities in European shelf seas. We investigated the patterns of species-level change using catch records from 57,870 fisheries-independent survey trawls from across European continental shelf region between 1965 and 2012. We analysed changes in the distribution and rate of occurrence of the six most common species, and observed a strong subtropicalization of the North Sea and Baltic Sea assemblages. These areas have shifted away from cold-water assemblages typically characterized by Atlantic herring and European sprat from the 1960s to 1980s, to warmer-water assemblages including Atlantic mackerel, Atlantic horse mackerel, European pilchard and European anchovy from the 1990s onwards. We next investigated if warming sea temperatures have forced these changes using temporally comprehensive data from the North Sea region. Our models indicated the primary driver of change in these species has been sea surface temperatures in all cases. Together, these analyses highlight how individual species responses have combined to result in a dramatic subtropicalization of the pelagic fish assemblage of the European continental shelf. © 2014 John Wiley & Sons Ltd.

Determination of grain-size characteristics from electromagnetic seabed mapping data: A NW Iberian shelf study

NASA Astrophysics Data System (ADS)

Baasch, Benjamin; Müller, Hendrik; von Dobeneck, Tilo; Oberle, Ferdinand K. J.

2017-05-01

The electric conductivity and magnetic susceptibility of sediments are fundamental parameters in environmental geophysics. Both can be derived from marine electromagnetic profiling, a novel, fast and non-invasive seafloor mapping technique. Here we present statistical evidence that electric conductivity and magnetic susceptibility can help to determine physical grain-size characteristics (size, sorting and mud content) of marine surficial sediments. Electromagnetic data acquired with the bottom-towed electromagnetic profiler MARUM NERIDIS III were analysed and compared with grain size data from 33 samples across the NW Iberian continental shelf. A negative correlation between mean grain size and conductivity (R=-0.79) as well as mean grain size and susceptibility (R=-0.78) was found. Simple and multiple linear regression analyses were carried out to predict mean grain size, mud content and the standard deviation of the grain-size distribution from conductivity and susceptibility. The comparison of both methods showed that multiple linear regression models predict the grain-size distribution characteristics better than the simple models. This exemplary study demonstrates that electromagnetic benthic profiling is capable to estimate mean grain size, sorting and mud content of marine surficial sediments at a very high significance level. Transfer functions can be calibrated using grains-size data from a few reference samples and extrapolated along shelf-wide survey lines. This study suggests that electromagnetic benthic profiling should play a larger role for coastal zone management, seafloor contamination and sediment provenance studies in worldwide continental shelf systems.

Hydroacoustical evidence of the expansion of pelagic swarms of Munida gregaria (Decapoda, Munididae) in the Beagle Channel and the Argentine Patagonian Shelf, and its relationship with habitat features

NASA Astrophysics Data System (ADS)

Diez, Mariano J.; Cabreira, Ariel G.; Madirolas, Adrián; Lovrich, Gustavo A.

2016-08-01

Squat lobsters are highly diversified and widespread decapods, of which only three species form pelagic swarms. Here we infer the expansion of Munida gregaria populations in the Beagle Channel and the Argentine Patagonian Shelf by means of acoustic surveys of pelagic swarms. We also describe the habitat characteristics in which these swarms occur. Acoustic data was collected during three multidisciplinary scientific cruises on board of the R/V Puerto Deseado during 2009, 2012 and 2014. Despite differences in the environmental conditions between the two surveyed areas, between 2009 and 2014 pelagic swarms increased their occurrence and abundance both in the Beagle Channel and on the Argentine Patagonian Shelf. Towards the end of the studied period, pelagic swarms of M. gregaria occurred in new locations, supporting the notion of a population expansion. Within the Beagle Channel swarm expansions were more marked than on the Patagonian Shelf. We here postulate that M. gregaria expansions occur in association with productive areas of the Argentine continental shelf, such as frontal zones, favoured by the squat lobster phenotypic plasticity that permit to exploit resources in both the neritic and benthic environments. At a regional scale on the Patagonian Shelf, three main groups of pelagic swarms of M. gregaria were clearly associated to respective frontal zones. The information presented here is necessary to understand fluctuations in both distribution and abundance patterns of a key species on the Argentine continental shelf. These fluctuations could be direct or indirect indicators of changes in the ecosystem.

Coastal currents and mass transport of surface sediments over the shelf regions of Monterey Bay, California

USGS Publications Warehouse

Wolf, S.C.

1970-01-01

In Monterey Bay, the highest concentrations of medium and fine sands occur nearshore between ten and thirty fathoms. Silt and clay accumulate in greater depths. Contours of median diameter roughly parallel the isobaths. Fine-grained materials are supplied to the bay region from erosion of cliffs which partly surround Monterey Bay, from sediment laden river discharge, and from continual reworking of widespread Pleistocene and Recent sea floor sediments. These sediments in turn are picked up by coastal currents and distributed over the shelf regions by present day current regimes. Studies of bottom currents over the shelf regions and in Monterey Canyon have revealed patterns which vary with seasonal changes. Current patterns during August and September exhibit remarkable symmetry about the axis of Monterey Submarine Canyon. Central Shelf currents north and south of Monterey Canyon flowed northwest at an average rate of 0.2 knots and south at 0.3 knots respectively. On the North Shelf between January and March currents flowed east to southeast at 0.3-0.5 knots with mirror image patterns above the South Shelf during the same period. Irregular current flow in the canyon indicates a complex current structure with frequent shifts in counterclockwise and clockwise direction over very short periods of time. Bottom topography of the canyon complex often causes localization of canyon currents. One particular observation at a depth of 51 fathoms indicated up-canyon flow at a rate of 0.2 knots. Most of the observed currents are related to seasonal variations, upwelling, ocean swell patterns, and to changes in the California and Davidson currents. Changes in current regimes are reflected in the patterns of sediment distribution and transport. Sediment transport is chiefly parallel to the isobaths, particularly on the North and South Shelf regions. Complex dispersal patterns are observed near Monterey Canyon and Moss Landing Harbor jetties. Longshore currents move sediments southward except near Monterey Canyon which acts as a physiographic barrier and the extreme southern end of the bay where currents are non persistent. Some sediments are also transported offshore by rip currents and other agencies and deposited in deeper, quieter waters. Supply of sediments to the canyon head results in over-filling and steepening with subsequent mass movement of sediments seaward followed by deposition in channels and on the broad deep sea fan. ?? 1970.

Hydrodynamic Controls on Archaeal Tetraether Lipid Compositions in Washington Margin Sediments: Insights From Compound-Specific Radiocarbon Measurements

NASA Astrophysics Data System (ADS)

Uchida, M.; Eglinton, T. I.; Montlucon, D. B.; Pearson, A.; Hayes, J. M.

2008-12-01

Continental margin sediments represent a large sink of organic carbon derived from marine and terrestrial sources. Archaeal glycerol dibiphytanyl glycerol tetraether lipids (GDGTs) are derived from both marine and terrestrial sources and have been used both for reconstruction of paleo sea surface temperatures and as an index of terrestrial carbon input to the marine sediments. However, the sources and modes of supply as well as the preservation of GDGTs in marginal sediments are poorly understood. The distribution and deposition of GDGTs is further complicated by hydrodynamic processes. We have analyzed a suite of surface sediment samples collected along a transect from the mouth of the Columbia River, across the Washington Margin, to the Cascadia Basin in the northeast Pacific Ocean. Sediments were separated according to their grain size and hydrodynamic properties, and the organic matter characterized in terms of its bulk elemental, isotopic, and molecular properties. Here we present radiocarbon measurements on individual GDGTs, alkenones, and fatty acids from size-fractionated sediments from shelf and slope sediments, and discuss the results in the context of previous studies of the molecular abundances and isotopic compositions of sedimentary organic matter for in this region. Systematic variations in elemental, isotopic and molecular-level composition are observed across the different particle classes. Moreover, these variations are manifested in the isotopic composition of different molecular markers of both marine and terrestrial sources organic matter. Both marine-derived lipids, including alkenones and marine archaeal tetraethers, and soil microbe-derived tetraether lipids show strong distributional and isotopic variations among the size-fractionated sediments. These variations in terrestrial and marine biomarker properties inform on the sources, particle dynamics, and transport history of organic matter buried on river-influenced continental margins. The implications of these findings for the application of molecular markers as proxies of organic matter input, and on the interpretation of past marine and continental environmental conditions from sedimentary records will also be discussed.

Large-Scale Spatial Distribution Patterns of Gastropod Assemblages in Rocky Shores

PubMed Central

Miloslavich, Patricia; Cruz-Motta, Juan José; Klein, Eduardo; Iken, Katrin; Weinberger, Vanessa; Konar, Brenda; Trott, Tom; Pohle, Gerhard; Bigatti, Gregorio; Benedetti-Cecchi, Lisandro; Shirayama, Yoshihisa; Mead, Angela; Palomo, Gabriela; Ortiz, Manuel; Gobin, Judith; Sardi, Adriana; Díaz, Juan Manuel; Knowlton, Ann; Wong, Melisa; Peralta, Ana C.

2013-01-01

Gastropod assemblages from nearshore rocky habitats were studied over large spatial scales to (1) describe broad-scale patterns in assemblage composition, including patterns by feeding modes, (2) identify latitudinal pattern of biodiversity, i.e., richness and abundance of gastropods and/or regional hotspots, and (3) identify potential environmental and anthropogenic drivers of these assemblages. Gastropods were sampled from 45 sites distributed within 12 Large Marine Ecosystem regions (LME) following the NaGISA (Natural Geography in Shore Areas) standard protocol (www.nagisa.coml.org). A total of 393 gastropod taxa from 87 families were collected. Eight of these families (9.2%) appeared in four or more different LMEs. Among these, the Littorinidae was the most widely distributed (8 LMEs) followed by the Trochidae and the Columbellidae (6 LMEs). In all regions, assemblages were dominated by few species, the most diverse and abundant of which were herbivores. No latitudinal gradients were evident in relation to species richness or densities among sampling sites. Highest diversity was found in the Mediterranean and in the Gulf of Alaska, while highest densities were found at different latitudes and represented by few species within one genus (e.g. Afrolittorina in the Agulhas Current, Littorina in the Scotian Shelf, and Lacuna in the Gulf of Alaska). No significant correlation was found between species composition and environmental variables (r≤0.355, p>0.05). Contributing variables to this low correlation included invasive species, inorganic pollution, SST anomalies, and chlorophyll-a anomalies. Despite data limitations in this study which restrict conclusions in a global context, this work represents the first effort to sample gastropod biodiversity on rocky shores using a standardized protocol across a wide scale. Our results will generate more work to build global databases allowing for large-scale diversity comparisons of rocky intertidal assemblages. PMID:23967204

The summertime plankton community at South Georgia (Southern Ocean): Comparing the historical (1926/1927) and modern (post 1995) records

NASA Astrophysics Data System (ADS)

Ward, Peter; Meredith, Michael P.; Whitehouse, Mick J.; Rothery, Peter

2008-09-01

The earliest comprehensive plankton sampling programme in the Southern Ocean was undertaken during the early part of last century by Discovery Investigations to gain a greater scientific understanding of whale stocks and their summer feeding grounds. An initial survey was carried out around South Georgia during December 1926 and January 1927 to describe the distribution of plankton during the summer, and to serve as a baseline against which to compare future surveys. We have reanalysed phytoplankton and zooplankton data from this survey and elucidated patterns of community distribution and compared them with our recent understanding of the ecosystem based on contemporary data. Analysis of Discovery data identified five groups of stations with characteristic phytoplankton communities which were almost entirely consistent with the original analysis conducted by [Hardy A.C., Gunther, E.R., 1935. The plankton of the South Georgia whaling grounds and adjacent waters 1926-1927. Discovery Report 11, 1-456]. Major groupings were located at the western end of the island and over the northern shelf where Corethron spp. were dominant, and to the south and east where a more diverse flora included high abundances of Nitzschia seriata. Major zooplankton-station groupings were located over the inner shelf which was characterised by a high abundance of Drepanopus forcipatus and in oceanic water >500 m deep that were dominated by Foraminifera, Oithona spp., Ctenocalanus vanus, and Calanoides acutus. Stations along the middle and outer shelf regions to the north and west, were characterised by low overall abundance. There was some evidence that groupings of stations to the north of the island originated in different water masses on either side of the Southern Antarctic Circumpolar Current Front, the major frontal system in the deep ocean close to South Georgia. However, transect lines during 1926/1927 did not extend far enough offshore to sample this frontal region adequately. Interannual variability of zooplankton abundance was assessed from stations which were sampled repeatedly during seven recent British Antarctic Survey cruises (1995-2005) to the region and following taxonomic harmonization and numerical standardization (ind. m -3), a subset of 45 taxonomic categories of zooplankton (species and higher taxa) from 1926/1927, were compared with similar data obtained during the BAS cruises using a linear model. Initially comparisons were restricted to BAS stations that lay within 40 km of Discovery stations although a comparison was also made using all available data. Despite low abundance values in 1926/1927, in neither comparison did Discovery data differ significantly from BAS data. Calculation of the percentage similarity index across cruises did not reveal any systematic differences in species composition between 1926 and 1927 and the present. In the light of ocean warming trends, the existence of more subtle changes in species composition is not ruled out, but an absence of finely resolved time-series data make this impossible to determine.

Assessing spatial and temporal variability of phytoplankton communities' composition in the Iroise Sea ecosystem (Brittany, France): A 3D modeling approach. Part 1: Biophysical control over plankton functional types succession and distribution

NASA Astrophysics Data System (ADS)

Cadier, Mathilde; Gorgues, Thomas; Sourisseau, Marc; Edwards, Christopher A.; Aumont, Olivier; Marié, Louis; Memery, Laurent

2017-01-01

Understanding the dynamic interplay between physical, biogeochemical and biological processes represents a key challenge in oceanography, particularly in shelf seas where complex hydrodynamics are likely to drive nutrient distribution and niche partitioning of phytoplankton communities. The Iroise Sea includes a tidal front called the 'Ushant Front' that undergoes a pronounced seasonal cycle, with a marked signal during the summer. These characteristics as well as relatively good observational sampling make it a region of choice to study processes impacting phytoplankton dynamics. This innovative modeling study employs a phytoplankton-diversity model, coupled to a regional circulation model to explore mechanisms that alter biogeography of phytoplankton in this highly dynamic environment. Phytoplankton assemblages are mainly influenced by the depth of the mixed layer on a seasonal time scale. Indeed, solar incident irradiance is a limiting resource for phototrophic growth and small phytoplankton cells are advantaged over larger cells. This phenomenon is particularly relevant when vertical mixing is intense, such as during winter and early spring. Relaxation of wind-induced mixing in April causes an improvement of irradiance experienced by cells across the whole study area. This leads, in late spring, to a competitive advantage of larger functional groups such as diatoms as long as the nutrient supply is sufficient. This dominance of large, fast-growing autotrophic cells is also maintained during summer in the productive tidally-mixed shelf waters. In the oligotrophic surface layer of the western part of the Iroise Sea, small cells coexist in a greater proportion with large, nutrient limited cells. The productive Ushant tidal front's region (1800 mgC·m- 2·d- 1 between August and September) is also characterized by a high degree of coexistence between three functional groups (diatoms, micro/nano-flagellates and small eukaryotes/cyanobacteria). Consistent with previous studies, the biogeography of phytoplankton functional types at the Ushant front during summer displays an intermediate community composition between contrasted sub-regions on either side of the front. Strong mixing conditions within the frontal sub-region result in a short residence time of water masses, not allowing speciation or long term adaptation to occur.

Gelcasting compositions having improved drying characteristics and machinability

DOEpatents

Janney, Mark A.; Walls, Claudia A. H.

2001-01-01

A gelcasting composition has improved drying behavior, machinability and shelf life in the dried and unfired state. The composition includes an inorganic powder, solvent, monomer system soluble in the solvent, an initiator system for polymerizing the monomer system, and a plasticizer soluble in the solvent. Dispersants and other processing aides to control slurry properties can be added. The plasticizer imparts an ability to dry thick section parts, to store samples in the dried state without cracking under conditions of varying relative humidity, and to machine dry gelcast parts without cracking or chipping. A method of making gelcast parts is also disclosed.

Molecular markers reveal spatially segregated cryptic species in a critically endangered fish, the common skate (Dipturus batis).

PubMed

Griffiths, Andrew M; Sims, David W; Cotterell, Stephen P; El Nagar, Aliya; Ellis, Jim R; Lynghammar, Arve; McHugh, Matthew; Neat, Francis C; Pade, Nicolas G; Queiroz, Nuno; Serra-Pereira, Bárbara; Rapp, Toby; Wearmouth, Victoria J; Genner, Martin J

2010-05-22

Many sharks and skates are particularly vulnerable to overfishing because of their large size, slow growth, late maturity and low fecundity. In Europe dramatic population declines have taken place in common skate (Dipturus batis L.), one of the largest demersal fish in regional shelf seas, leading to extirpations from substantial parts of its former range. Here we report the discovery of cryptic species in common skate collected from the northeast Atlantic continental shelf. Data from nuclear microsatellite markers indicated two clearly distinct clades and phylogenetic analysis of mitochondrial DNA sequences demonstrated monophyly of each one of them. Capture locations showed evidence of strong spatial segregation, with one taxon occurring mainly in waters off the southern British Isles and around Rockall, while the other was restricted to more northerly shelf waters. These apparently cryptic species showed overlapping substrate and depth preferences, but distributional limits were closely related to temperature gradients, potentially indicating thermal limits to their distributions. This discovery of hidden diversity within a large, critically endangered marine vertebrate demonstrates how marine biodiversity can be underestimated, even in such a relatively well-studied and heavily exploited region.

Alkylphenols in surface sediments of the Yellow Sea and East China Sea inner shelf: occurrence, distribution and fate.

PubMed

Duan, Xiao-yong; Li, Yan-xia; Li, Xian-guo; Zhang, Da-hai; Gao, Yi

2014-07-01

Alkylphenols (APs) have been found as ubiquitous environmental pollutants with reproductive and developmental toxicity. In this study, APs in surface sediments of the Yellow Sea (YS) and East China Sea (ECS) inner shelf were analyzed to assess influences of riverine and atmospheric inputs of pollutants on the marine environment. NP concentrations ranged from 349.5 to 1642.8 ng/g (average 890.1 ng/g) in the YS sediments and from 31.3 to 1423.7 ng/g (average 750.1 ng/g) in the ECS inner shelf sediments. NP distribution pattern was mainly controlled by the sedimentary environment. OP concentration was 0.8-9.3 ng/g (average 4.7 ng/g) in the YS sediments and 0.7-11.1 ng/g (average 5.1 ng/g) in the ECS sediments. Assessment of the influence of distances from land on OP concentrations provided evidence for the predominance of coastal riverine and/or atmospheric inputs rather than long-range transport. And the biological pump may play an important role for sequestration of OP in the nearshore area. Copyright © 2013 Elsevier Ltd. All rights reserved.

Molecular markers reveal spatially segregated cryptic species in a critically endangered fish, the common skate (Dipturus batis)

PubMed Central

Griffiths, Andrew M.; Sims, David W.; Cotterell, Stephen P.; El Nagar, Aliya; Ellis, Jim R.; Lynghammar, Arve; McHugh, Matthew; Neat, Francis C.; Pade, Nicolas G.; Queiroz, Nuno; Serra-Pereira, Bárbara; Rapp, Toby; Wearmouth, Victoria J.; Genner, Martin J.

2010-01-01

Many sharks and skates are particularly vulnerable to overfishing because of their large size, slow growth, late maturity and low fecundity. In Europe dramatic population declines have taken place in common skate (Dipturus batis L.), one of the largest demersal fish in regional shelf seas, leading to extirpations from substantial parts of its former range. Here we report the discovery of cryptic species in common skate collected from the northeast Atlantic continental shelf. Data from nuclear microsatellite markers indicated two clearly distinct clades and phylogenetic analysis of mitochondrial DNA sequences demonstrated monophyly of each one of them. Capture locations showed evidence of strong spatial segregation, with one taxon occurring mainly in waters off the southern British Isles and around Rockall, while the other was restricted to more northerly shelf waters. These apparently cryptic species showed overlapping substrate and depth preferences, but distributional limits were closely related to temperature gradients, potentially indicating thermal limits to their distributions. This discovery of hidden diversity within a large, critically endangered marine vertebrate demonstrates how marine biodiversity can be underestimated, even in such a relatively well-studied and heavily exploited region. PMID:20106849

Environmental drivers of epibenthic megafauna on a deep temperate continental shelf: A multiscale approach

NASA Astrophysics Data System (ADS)

Lacharité, Myriam; Metaxas, Anna

2018-03-01

Evaluating the role of abiotic factors in influencing the distribution of deep-water (>75-100 m depth) epibenthic megafaunal communities at mid-to-high latitudes is needed to estimate effects of environmental change, and support marine spatial planning since these factors can be effectively mapped. Given the disparity in scales at which these factors operate, incorporating multiple spatial and temporal scales is necessary. In this study, we determined the relative importance of 3 groups of environmental drivers at different scales (sediment, geomorphology, and oceanography) on epibenthic megafauna on a deep temperate continental shelf in the eastern Gulf of Maine (northwest Atlantic). Twenty benthic photographic transects (range: 611-1021 m; total length surveyed: 18,902 m; 996 images; average of 50 ± 16 images per transect) were performed in July and August 2009 to assess the abundance, composition and diversity of these communities. Surficial geology was assessed using seafloor imagery processed with a novel approach based on computer vision. A bathymetric terrain model (horizontal resolution: 100 m) was used to derive bathymetric variability in the vicinity of transects (1.5, 5 km). Oceanography at the seafloor (temperature, salinity, current speed, current direction) over 10 years (1999-2008) was determined using empirical (World Ocean Database 2013) and modelled data (Finite-Volume Community Ocean Model; 45 vertical layers; horizontal resolution: 1.7-9.5 km). The relative influence of environmental drivers differed between community traits. Abundance was enhanced primarily by swift current speeds, while higher diversity was observed in coarser and more heterogeneous substrates. In both cases, the role of geomorphological features was secondary to these drivers. Environmental variables were poor predictors of change in community composition at the scale of the eastern Gulf of Maine. This study demonstrated the need for explicitly incorporating scales into habitat modelling studies in these regions, and targeting specific drivers for community traits of interest.

Deep divers in shallow seas: Southern elephant seals on the Patagonian shelf

NASA Astrophysics Data System (ADS)

Campagna, Claudio; Piola, Alberto R.; Marin, Maria Rosa; Lewis, Mirtha; Zajaczkovski, Uriel; Fernández, Teresita

2007-10-01

Elephant seals are wide-ranging, pelagic, deep-diving (average of 400-600 m) predators that typically travel to open waters and continental shelf edges thousands of kilometers from their land breeding colonies. We report a less common pattern of foraging in the shallow waters of a continental shelf. Southern elephant seals, Mirounga leonina, that breed at Península Valdés (Argentina), face an extended (˜1,000,000 km 2; 400-700 km-wide, depending on track), shallow (<150 m) and seasonally productive plateau, the Patagonian shelf. Adults of both sexes usually cross it in rapid transit to other potential foraging grounds on the shelf edge or in the Argentine Basin, but 2-4 year-old juveniles spread over the plateau and spent months in shallow waters. This behavior was recorded for 9 seals (5 males and 4 females) of 23 satellite-tracked juveniles (springs of 2004 and 2005) and for 2 subadult males studied in previous seasons. Trips included travel trajectories and time spent in areas where swim speed decreased, suggesting foraging. Preferred locations of juvenile females were in the proximity of the shelf break, where stratified waters had relatively high phytoplankton concentrations, but young and subadult males used the relatively cold (7-8 °C), low-salinity (˜33.3) mid-shelf waters, with depths of 105-120 m and a poorly stratified water column. Three of the latter seals, instrumented with time-depth recorders, showed dives compatible with benthic feeding and no diel pattern of depths distribution. Regions of the mid-shelf were used in different seasons and were associated with low chlorophyll- a concentration at the time of the visit, suggesting that surface productivity does not overlap with putative quality habitat for benthic foragers. Benthic diving on the shallow mid-shelf would be a resource partitioning strategy advantageous for young males prior to greater energetic demands of a high growth rate and a large body size. Later in life, the more predictable, bathymetry-forced, shelf-break front may offer the food resources that explain the uninterrupted increase of this population over several decades.

NASA MISR Tracks Growth of Rift in the Larsen C Ice Shelf

NASA Image and Video Library

2017-04-11

A rift in Antarctica's Larsen C ice shelf has grown to 110 miles (175 km) long, making it inevitable that an iceberg larger than Rhode Island will soon calve from the ice shelf. Larsen C is the fourth largest ice shelf in Antarctica, with an area of almost 20,000 square miles (50,000 square kilometers). The calving event will remove approximately 10 percent of the ice shelf's mass, according to the Project for Impact of Melt on Ice Shelf Dynamics and Stability (MIDAS), a UK-based team studying the ice shelf. Only 12 miles (20 km) of ice now separates the end of the rift from the ocean. The rift has grown at least 30 miles (50 km) in length since August, but appears to be slowing recently as Antarctica returns to polar winter. Project MIDAS reports that the calving event might destabilize the ice shelf, which could result in a collapse similar to what occurred to the Larsen B ice shelf in 2002. The Multi-angle Imaging SpectroRadiometer (MISR) instrument aboard NASA's Terra satellite captured views of Larsen C on August 22, 2016, when the rift was 80 miles (130 km) in length; December 8, 2016, when the rift was approximately 90 miles (145 km) long; and April 6, 2017. The MISR instrument has nine cameras, which view the Earth at different angles. The overview image, from December 8, shows the entire Antarctic Peninsula -- home to Larsen A, B, and C ice shelves -- in natural color (similar to how it would appear to the human eye) from MISR's vertical-viewing camera. Combining information from several MISR cameras pointed at different angles gives information about the texture of the ice. The accompanying GIF depicts the inset area shown on the larger image and displays data from all three dates in false color. These multiangular views -- composited from MISR's 46-degree backward-pointing camera, the nadir (vertical-viewing) camera, and the 46-degree forward-pointing camera -- represent variations in ice texture as changes in color, such that areas of rough ice appear orange and smooth ice appears blue. The Larsen C shelf is on the left in the GIF, bordered by the Weddell Sea on the upper right. The ice within the rift is orange, indicating movement, and the end of the rift can be tracked across the shelf between images. In addition, between December and April, the rift widened, pushing the future iceberg away from the shelf at its southern end. These data were acquired during Terra orbits 88717, 90290 and 92023. https://photojournal.jpl.nasa.gov/catalog/PIA21581

Alkane, terpene and polycyclic aromatic hydrocarbon geochemistry of the Mackenzie River and Mackenzie shelf: Riverine contributions to Beaufort Sea coastal sediment

NASA Astrophysics Data System (ADS)

Yunker, Mark B.; Macdonald, Robie W.; Cretney, Walter J.; Fowler, Brian R.; McLaughlin, Fiona A.

1993-07-01

To study the largest source of river sediment to the Arctic Ocean, we have collected suspended particulates from the Mackenzie River in all seasons and sediments from the Mackenzie shelf between the river mouth and the shelf edge. These samples have been analyzed for alkanes, triterpenes and polycyclic aromatic hydrocarbons (PAHs). We found that naturally occurring hydrocarbons predominate in the river and on the shelf. These hydrocarbons include biogenic alkanes and triterpenes with a higher plant/peat origin, diagenetic PAHs from peat and plant detritus, petrogenic alkanes, triterpenes and PAHs from oil seeps and/or bitumens and combustion PAHs that are likely relict in peat deposits. Because these components vary independently, the season is found to strongly influence the concentration and composition of hydrocarbons in the Mackenzie River. While essentially the same pattern of alkanes, diagenetic hopanes and alkyl PAHs is observed in all river and most shelf sediment samples, alkane and triterpene concentration variations are strongly linked to the relative amount of higher plant/peat material. Polycyclic aromatic hydrocarbon molecular-mass profiles also appear to be tied primarily to varying proportions of peat, with an additional petrogenic component which is most likely associated with lithic material mobilized by the Mackenzie River at freshet. Consistent with the general lack of alkyl PAHs in peat, the higher PAHs found in the river are probably derived from forest and tundra fires. A few anthropogenic/pyrogenic compounds are manifest only at the shelf edge, probably due to a weakening of the river influence. We take this observation of pyrogenic PAHs and the pronounced source differences between two sediment samples collected at the shelf edge as evidence of a transition from dominance by the Mackenzie River to the geochemistry prevalent in Arctic regions far removed from major rivers.

Combined effect of temperature and controlled atmosphere on storage and shelf-life of 'Rocha' pear treated with 1-methylcyclopropene.

PubMed

Gago, Custódia M L; Miguel, Maria G; Cavaco, Ana M; Almeida, Domingos P F; Antunes, Maria D C

2015-03-01

The combination of temperature and atmosphere composition for storage of Pyrus communis L. 'Rocha' treated with 1-methylcyclopropene was investigated. Fruits treated with 312 nl l(-1) 1-methylcyclopropene were stored at 0 ℃ and 2.5 ℃ in air and controlled atmosphere (CA) (3.04 kPa O2+ 0.91 kPa CO2). Fruits were removed from storage after 14, 26 and 35 weeks, transferred to shelf-life at approximately 22 ℃ and assessed for ripening and quality, symptoms of superficial scald and internal browning and the accumulation of biochemical compounds related to scald after 0, 1 and 2 weeks. Superficial scald occurred only in fruits stored for 35 weeks in air at 2.5 ℃. Levels of conjugated trienols and α-farnesene increased during the first 26 weeks in storage, remaining constant thereafter. During shelf-life, conjugated trienols were higher in fruits stored in air at 2.5 ℃. Internal browning developed in shelf-life after 26 weeks at 2.5 ℃. Pears in air at 2.5 ℃ were not able to stand a 2-week shelf-life after 35 weeks of storage, while fruits stored at 0 ℃ under CA ripened slowly after the same storage period. The retention of firmness during shelf-life of 1-methylcyclopropene-treated 'Rocha' pear can be overcome by elevating the storage temperature from 0 ℃ to 2.5 ℃, but CA is a required complement to avoid excessive softening after long-term storage. The ratio carotenoid/chlorophyll increased during storage and shelf-life, as plastids senesced. CA reduced the rate of chlorophyll loss during the first 14 weeks in storage, but its effect was reduced afterwards. 'Rocha' pear treated with 1-methylcyclopropene had a similar post-harvest behaviour during long-term storage at 0 ℃ in air or at 2.5 ℃ under CA. © The Author(s) 2013 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

Advances in food crystallization.

PubMed

Hartel, Richard W

2013-01-01

Crystals often play an important role in food product quality and shelf life. Controlling crystallization to obtain the desired crystal content, size distribution, shape, and polymorph is key to manufacturing products with desired functionality and shelf life. Technical developments in the field have improved the tools with which we study and characterize crystals in foods. These developments also help our understanding of the physico-chemical phenomena that govern crystallization and improve our ability to control it during processing and storage. In this review, some of the more important recent developments in measuring and controlling crystallization are discussed.

Total mesophilic counts underestimate in many cases the contamination levels of psychrotrophic lactic acid bacteria (LAB) in chilled-stored food products at the end of their shelf-life.

PubMed

Pothakos, Vasileios; Samapundo, Simbarashe; Devlieghere, Frank

2012-12-01

The major objective of this study was to determine the role of psychrotrophic lactic acid bacteria (LAB) in spoilage-associated phenomena at the end of the shelf-life of 86 various packaged (air, vacuum, modified-atmosphere) chilled-stored retail food products. The current microbiological standards, which are largely based on the total viable mesophilic counts lack discriminatory capacity to detect psychrotrophic LAB. A comparison between the total viable counts on plates incubated at 30 °C (representing the mesophiles) and at 22 °C (indicating the psychrotrophs) for 86 food samples covering a wide range - ready-to-eat vegetable salads, fresh raw meat, cooked meat products and composite food - showed that a consistent underestimation of the microbial load occurs when the total aerobic mesophilic counts are used as a shelf-life parameter. In 38% of the samples, the psychrotrophic counts had significantly higher values (+0.5-3 log CFU/g) than the corresponding total aerobic mesophilic counts. A total of 154 lactic acid bacteria, which were unable to proliferate at 30 °C were isolated. In addition, a further 43 with a poor recovery at this temperature were also isolated. This study highlights the potential fallacy of the total aerobic mesophilic count as a reference shelf-life parameter for chilled food products as it can often underestimate the contamination levels at the end of the shelf-life. Copyright © 2012 Elsevier Ltd. All rights reserved.

Multi-Scale Approach for Predicting Fish Species Distributions across Coral Reef Seascapes

PubMed Central

Pittman, Simon J.; Brown, Kerry A.

2011-01-01

Two of the major limitations to effective management of coral reef ecosystems are a lack of information on the spatial distribution of marine species and a paucity of data on the interacting environmental variables that drive distributional patterns. Advances in marine remote sensing, together with the novel integration of landscape ecology and advanced niche modelling techniques provide an unprecedented opportunity to reliably model and map marine species distributions across many kilometres of coral reef ecosystems. We developed a multi-scale approach using three-dimensional seafloor morphology and across-shelf location to predict spatial distributions for five common Caribbean fish species. Seascape topography was quantified from high resolution bathymetry at five spatial scales (5–300 m radii) surrounding fish survey sites. Model performance and map accuracy was assessed for two high performing machine-learning algorithms: Boosted Regression Trees (BRT) and Maximum Entropy Species Distribution Modelling (MaxEnt). The three most important predictors were geographical location across the shelf, followed by a measure of topographic complexity. Predictor contribution differed among species, yet rarely changed across spatial scales. BRT provided ‘outstanding’ model predictions (AUC = >0.9) for three of five fish species. MaxEnt provided ‘outstanding’ model predictions for two of five species, with the remaining three models considered ‘excellent’ (AUC = 0.8–0.9). In contrast, MaxEnt spatial predictions were markedly more accurate (92% map accuracy) than BRT (68% map accuracy). We demonstrate that reliable spatial predictions for a range of key fish species can be achieved by modelling the interaction between the geographical location across the shelf and the topographic heterogeneity of seafloor structure. This multi-scale, analytic approach is an important new cost-effective tool to accurately delineate essential fish habitat and support conservation prioritization in marine protected area design, zoning in marine spatial planning, and ecosystem-based fisheries management. PMID:21637787

Multi-scale approach for predicting fish species distributions across coral reef seascapes.

PubMed

Pittman, Simon J; Brown, Kerry A

2011-01-01

Two of the major limitations to effective management of coral reef ecosystems are a lack of information on the spatial distribution of marine species and a paucity of data on the interacting environmental variables that drive distributional patterns. Advances in marine remote sensing, together with the novel integration of landscape ecology and advanced niche modelling techniques provide an unprecedented opportunity to reliably model and map marine species distributions across many kilometres of coral reef ecosystems. We developed a multi-scale approach using three-dimensional seafloor morphology and across-shelf location to predict spatial distributions for five common Caribbean fish species. Seascape topography was quantified from high resolution bathymetry at five spatial scales (5-300 m radii) surrounding fish survey sites. Model performance and map accuracy was assessed for two high performing machine-learning algorithms: Boosted Regression Trees (BRT) and Maximum Entropy Species Distribution Modelling (MaxEnt). The three most important predictors were geographical location across the shelf, followed by a measure of topographic complexity. Predictor contribution differed among species, yet rarely changed across spatial scales. BRT provided 'outstanding' model predictions (AUC = >0.9) for three of five fish species. MaxEnt provided 'outstanding' model predictions for two of five species, with the remaining three models considered 'excellent' (AUC = 0.8-0.9). In contrast, MaxEnt spatial predictions were markedly more accurate (92% map accuracy) than BRT (68% map accuracy). We demonstrate that reliable spatial predictions for a range of key fish species can be achieved by modelling the interaction between the geographical location across the shelf and the topographic heterogeneity of seafloor structure. This multi-scale, analytic approach is an important new cost-effective tool to accurately delineate essential fish habitat and support conservation prioritization in marine protected area design, zoning in marine spatial planning, and ecosystem-based fisheries management.

Hydrodynamically-driven distribution of lanternfish larvae in the Southeast Brazilian Bight

NASA Astrophysics Data System (ADS)

Namiki, Cláudia; Katsuragawa, Mario; Napolitano, Dante Campagnoli; Zani-Teixeira, Maria de Lourdes; Mattos, Rafael Augusto de; Silveira, Ilson Carlos Almeida da

2017-06-01

This study analyzes the influence of the Brazil Current and Ekman transport on the distribution of lanternfish larvae in the Southeast Brazilian Bight during summer and winter. Larvae of 19 taxa of lanternfish were identified, and Diaphus spp. and M. affine were the most abundant. Three water masses were present in the area: Coastal Water, Tropical Water and South Atlantic Central Water. Lanternfish larvae were associated with the Tropical Water in both seasons. During summer, species of Lampanyctinae were associated with the shallowest layers and Myctophinae in the deepest layers. In winter most species of both subfamilies were associated with intermediate depths, probably because greater mixing of water masses occurred at the surface and 100 m depth, limiting their distribution. During both cruises, the presence of lanternfish larvae in the continental shelf was related to the pattern of Tropical Water intrusion, which was mostly driven by the mesoscale activity of the Brazil Current and its interaction with the continental shelf.

Coupling of Coastal Zone Color Scanner data to a physical-biological model of the southeastern U.S. continental shelf ecosystem. I - CZCS data description and Lagrangian particle tracing experiments. II - An Eulerian model. III - Nutrient and phytoplankton fluxes and CZCS data assimilation

NASA Technical Reports Server (NTRS)

Ishizaka, Joji

1990-01-01

Surface phytoplankton biomass of the southeastern U.S. continental shelf area is discussed based on coastal zone color scanner (CZCS) images obtained in April 1980. Data of chlorophyll distributions are analyzed in conjunction with concurrent flow and temperature fields. Lagrangian particle tracing experiments show that the particles move consistently with the evolution of the chlorophyll patterns. A four-component physical-biological model for a horizontal plane at a nominal depth of 17 m is presented. Model simulations using various physical-biological dynamics and boundary conditions show that the variability of chlorophyll distributions is controlled by horizontal advection. Phytoplankton and nutrient fluxes, calculated using the model, show considerable variability with time. The chlorophyll distributions obtained from the CZCS images are assimilated into the model to improve the phytoplankton flux estimates.

Stratigraphic response across a structurally dynamic shelf: The latest guadalupian composite sequence at Walnut Canyon, New Mexico, U.S.A

USGS Publications Warehouse

Rush, J.; Kerans, C.

2010-01-01

The uppermost Yates and Tansill formations (Late Permian), as exposed along Walnut Canyon in Carlsbad Caverns National Park, New Mexico, USA, provide a unique opportunity to document the depositional architecture of a progradational, oversteepened, and mechanically failure-prone carbonate platform. Detailed facies mapping permitted critical assessment of depositional processes operating along this structurally dynamic platform margin. At the shelf crest, thick (12 m), vertically stacked fenestral-pisolite-tepee complexes indicate a stable shoreline. Early lithification of sediments and extensive cementation fostered rapid vertical accretion and allowed the shelf crest to easily adjust to base-level oscillations by stepping landward, stepping seaward, or aggrading. This production imbalance-in combination with syndepositional brittle failure and down-to-the-basin tilting(< 5??)-generated 22 m of depositional relief as measured from nearly horizontal (< 2??) shelf-crest toplap to an outer-shelf downlap surface (< 1??). Mechanical failure of Capitan-equivalent back-reef strata is constrained by stratigraphic architecture, fracture properties, and a highly refined fusulinid biostratigraphic framework. Where fractures tip out, down-to-the-basin rotation is often observed with concurrent seaward thickening of overlying beds, indicating that such fractures functioned as a syndepositional hinge. A facies disjunction and horizontally juxtaposed fusulinid zonation were documented across an 80?? seaward-dipping dilational fracture filled with polymict breccia. An overlying damage zone consisting of spar-cemented fractures nested within silt-filled fractures illustrates periodic reactivation. Field relationships indicate that the dilational fracture approximates a paleoescarpment that resulted from catastrophic failure of the Capitan platform margin. Younger strata onlapped the paleoescarpment and gradually filled the reentrant. This mechanically compromised paleoescarpment was subsequently reactivated during the latest Guadalupian lowstand and was subaerially filled by siliciclastics and polymict breccia derived from the platform top. Results from Walnut Canyon indicate that shelf crest aggradation dominantly controlled the shelf-crest to outer-shelf profile, although this was temporarily modified by brittle failure and down-to-the-basin tilting, and mass wasting. Copyright ?? 2010, SEPM (Society for Sedimentary Geology).

Stratigraphic framework of inner shelf storm-dominated sand ridges, Alabama EEZ: Implications for sequence stratigraphy, global climate change, and petroleum exploration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Davies, D.J.; Parker, S.J.

The Alabama exclusive economic zone (EEZ) contains an abundance of orthoquartzitic shelf sand ridges elongate northwest-southeast diagonally from the shoreline. Soft-sediment peels from 59 Vibracores[sup TM] from the Alabama inner shelf permit detailed description of sand ridge sedimentary structures, fabrics, and eight sea-floor sediment types. These overlie the pre-Holocene sequence boundary and lower Holocene transgressive sediments. In general, the ridges are capped by coarse stacked graded shelly sands, echinoid sands, and clean sands deposited well above storm wave base. The graded shelly sand microfacies, the most common sediment type, is inferred to represent shelf storm deposits because of its gradedmore » nature, sharp base, and variable thickness (0.1 to 4 m). Considerable patchiness of facies is found on a single sand ridge. The facies patchiness may result from the interplay between relict sediment distribution, present hydrodynamics and local difference in preserved shell content. Due to the microtidal regime of the Alabama EEZ and the prevalence of the graded sands on the ridge crests, the ridges are interpreted to be dominantly storm-wave in origin. This type of coarse, clean sandy deposit is a poorly studied yet important possible model for many shelf-sand petroleum reservoirs.« less

Analysis of the Spectral Backscattering Coefficient Variability on the Northeastern shelf of the Gulf of Mexico

NASA Astrophysics Data System (ADS)

Gallegos, S. C.; Gould, R. W.; Arnone, R. A.; Teague, W. J.; Mitchell, D. A.; Ko, D.

2005-05-01

The continental shelf of the northeastern Gulf of Mexico between 87.5 W and 88.5 W is an ideal place to study coastal processes. In this region, the shelf slopes gently down to depths of 100 m, and then increases rapidly to depths greater than a mile. The Naval Research Laboratory at Stennis Space Center in Mississippi is currently undertaking an intensive measurement and modeling program to determine the cross-shelf exchange processes and their relation to the optical parameters of this area. In this study, we report our efforts to quantify the variability of the spectral backscattering coefficient derived from SeaWiFS imagery via empirical orthogonal functions. We compare the most relevant modes with the spatial distribution of Eddy Kinetic Energy (EKE) computed by the Inter Americas Seas (IAS) model and in-situ measurements by acoustic Doppler current profilers deployed between May 2004 and May 2005. The results indicate that most of the backscattering variability is contained in areas north of 29.2N which coincides with the edge of the continental shelf (100 m depth). Sporadic increases in backscattering are observed as far south as 29.0 N and to the east of 88.1W. These increases can be explained by fluctuations in surface EKE.

Geology and petroleum resources of the Barents-northern Kara shelf in light of new geologic data

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ulmishek, G.

1985-10-01

The Barents-northern Kara shelf, one of the largest continental shelves in the world, is still in the earliest stage of exploration for oil and gas. During the last several years, numerous seismic surveys have been conducted, a number of wells have been drilled, and several gas fields have been discovered. This report summarizes the geological data gathered during recent exploration activities and presents the changes in earlier concepts necessitated by consideration of these new data. The revised assessment of undiscovered petroleum resources is based on new information about the distribution and quality of source rocks and reservoir rocks and themore » structural framework of the shelf. Special attention is paid to evaluating the oil versus gas potential of the shelf, an evaluation that strongly depends on the expected offshore extension of oil-source facies in the Lower-Middle Triassic section. The most probable amounts of undiscovered petroleum resources of the shelf are estimated at 14.2 x 10/sup 9/ barrels of oil and 312.2 x 10/sup 12/ cubic feet of gas. The Finnmark trough, the south Barents and North Novaya Zemlya depressions, and the offshore continuation of the Timan-Pechora basin possess the great majority of these resources. 103 refs., 12 figs., 1 tab.« less

Frequency changes of tropical cyclones during the last century recorded in a canyon of the northern Bay of Bengal

NASA Astrophysics Data System (ADS)

Kudrass, Hermann; Machalett, Björn; Palamenghi, Luisa; Meyer, Inka

2017-04-01

Frequent cyclones originating in the Bay of Bengal and landfall to the southern delta of the Ganges and Brahmaputra are well recorded in sediment cores from a canyon which deeply incises into the shelf and ends at the foreset beds of the submarine Ganges Brahmaputra delta. The large sediment supply by the two rivers during the monsoonal floods forms temporary deposits on the inner shelf, which are mobilized by waves and currents during the passage of cyclones. The resulting sand-silt-clay suspension forms high-density water masses, which plunge from the inner shelf into the shelf canyon, where they deposit graded beds evenly draping the broad canyon floor. A simple model was used to rank the historical known cyclones according to their capacity to transfer sediment from the submarine delta into the canyon. In a 362 cm-long sediment core ranging from the year 1985 to 2006, 48 graded beds can be correlated with the observed 41 cyclones. The cyclonic impact on the sediment transport has decreased by a factor of three during the last decade. The highest cyclonic impact occurred during the seventies. Compared to the sediment transfer by cyclones, the input by tidal currents and monsoonal floods is negligible. Thus cyclones are the dominating process for mobilizing and distributing sediment on the Bangladesh shelf and probably also on all shelf areas, which lie in the track of tropical cyclones.

Qualitative Characteristics and Determining Shelf-Life of Milk Beverage Product Supplemented with Coffee Extracts

PubMed Central

Kim, Jae-Hoon; Oh, Duk-Geun

2017-01-01

This study was conducted to establish the shelf-life of a milk beverage product supplemented with coffee extracts. Qualitative changes including peroxide value (PV), microorganism content, caffeine content, and sensory evaluation were measured periodically in beverages kept at 10, 20, and 30°C for 8 wk. Lipid oxidation of the product was measured by peroxide value analysis, and apparent changes were observed during a 4 wk storage period. Caffeine analysis revealed that the changes in caffeine content were negligible during the storage period. Total aerobic bacteria, Escherichia coli, yeast, and mold were not detected in the products during an 8 wk storage period. Sensory evaluation revealed that after 4 wk of storage overall acceptance was less than 3 points on a 5-point scale. In this study, PV was used as an indicator of the shelf-life of the milk beverage product. PV analysis revealed that a value of 20 meq/kg was the end of the shelf-life using the Arrhenius equation and the accelerated shelf-life test (ASLT). Assuming that the beverages are kept at 4°C during distribution, calculation of when the PV reached the quality limit point (20 meq/kg) was done with the equation ln(PV) = 0.3644X − 2.21834 and, using that equation, PV = e0.3644X-2.21834 was calculated. Therefore, 14.3086 wk was determined to be the shelf-life of the milk beverage supplemented with coffee when stored at 4°C. PMID:28515654

The coupled response to slope-dependent basal melting

NASA Astrophysics Data System (ADS)

Little, C. M.; Goldberg, D. N.; Sergienko, O. V.; Gnanadesikan, A.

2009-12-01

Ice shelf basal melting is likely to be strongly controlled by basal slope. If ice shelves steepen in response to intensified melting, it suggests instability in the coupled ice-ocean system. The dynamic response of ice shelves governs what stable morphologies are possible, and thus the influence of melting on buttressing and grounding line migration. Simulations performed using a 3-D ocean model indicate that a simple form of slope-dependent melting is robust under more complex oceanographic conditions. Here we utilize this parameterization to investigate the shape and grounding line evolution of ice shelves, using a shallow-shelf approximation-based model that includes lateral drag. The distribution of melting substantially affects the shape and aspect ratio of unbuttressed ice shelves. Slope-dependent melting thins the ice shelf near the grounding line, reducing velocities throughout the shelf. Sharp ice thickness gradients evolve at high melting rates, yet grounding lines remain static. In foredeepened, buttressed ice shelves, changes in grounding line flux allow two additional options: stable or unstable retreat. Under some conditions, slope-dependent melting results in stable configurations even at high melt rates.

The carbon dioxide system on the Mississippi River‐dominated continental shelf in the northern Gulf of Mexico: 1. Distribution and air‐sea CO2 flux

PubMed Central

Huang, Wei‐Jen; Wang, Yongchen; Lohrenz, Steven E.; Murrell, Michael C.

2015-01-01

Abstract River‐dominated continental shelf environments are active sites of air‐sea CO2 exchange. We conducted 13 cruises in the northern Gulf of Mexico, a region strongly influenced by fresh water and nutrients delivered from the Mississippi and Atchafalaya River system. The sea surface partial pressure of carbon dioxide (pCO2) was measured, and the air‐sea CO2 flux was calculated. Results show that CO2 exchange exhibited a distinct seasonality: the study area was a net sink of atmospheric CO2 during spring and early summer, and it was neutral or a weak source of CO2 to the atmosphere during midsummer, fall, and winter. Along the salinity gradient, across the shelf, the sea surface shifted from a source of CO2 in low‐salinity zones (0≤S<17) to a strong CO2 sink in the middle‐to‐high‐salinity zones (17≤S<33), and finally was a near‐neutral state in the high‐salinity areas (33≤S<35) and in the open gulf (S≥35). High pCO2 values were only observed in narrow regions near freshwater sources, and the distribution of undersaturated pCO2 generally reflected the influence of freshwater inputs along the shelf. Systematic analyses of pCO2 variation demonstrated the importance of riverine nitrogen export; that is, riverine nitrogen‐enhanced biological removal, along with mixing processes, dominated pCO2 variation along the salinity gradient. In addition, extreme or unusual weather events were observed to alter the alongshore pCO2 distribution and to affect regional air‐sea CO2 flux estimates. Overall, the study region acted as a net CO2 sink of 0.96 ± 3.7 mol m−2 yr−1 (1.15 ± 4.4 Tg C yr−1). PMID:27656331

Ages, distributions, and origins of upland coastal dune sheets in Oregon, USA

USGS Publications Warehouse

Peterson, C.D.; Stock, E.; Price, D.M.; Hart, R.; Reckendorf, F.; Erlandson, J.M.; Hostetler, S.W.

2007-01-01

A total of ten upland dune sheets, totaling 245??km in combined length, have been investigated for their origin(s) along the Oregon coast (500??km in length). The ages of dune emplacement range from 0.1 to 103??ka based on radiocarbon (36 samples) and luminescence (46 samples) dating techniques. The majority of the emplacement dates fall into two periods of late-Pleistocene age (11-103??ka) and mid-late-Holocene age (0.1-8??ka) that correspond to marine low-stand and marine high-stand conditions, respectively. The distribution of both the late-Pleistocene dune sheets (516??km2 total surface area) and the late-Holocene dune sheets (184??km2) are concentrated (90% of total surface area) along a 100??km coastal reach of the south-central Oregon coast. This coastal reach lies directly landward of a major bight (Heceta-Perpetua-Stonewall Banks) on the continental shelf, at depths of 30-200??m below present mean sea level (MSL). The banks served to trap northward littoral drift during most of the late-Pleistocene conditions of lowered sea level (- 50 ?? 20??m MSL). The emerged inner-shelf permitted cross-shelf, eolian sand transport (10-50??km distance) by onshore winds. The depocenter sand deposits were reworked by the Holocene marine transgression and carried landward by asymmetric wave transport during early- to mid-Holocene time. The earliest dated onset of Holocene dune accretion occurred at 8??ka in the central Oregon coast. A northward migration of Northeast Pacific storm tracks to the latitude of the shelf depocenter (Stonewall, Perpetua, Heceta Banks) in Holocene time resulted in eastward wave transport from the offshore depocenter. The complex interplay of coastal morphology, paleosea-level, and paleoclimate yielded the observed peak distribution of beach and dune sand observed along the south-central Oregon coast. ?? 2007 Elsevier B.V. All rights reserved.

Diversity and Distribution Patterns of Cetaceans in the Subtropical Southwestern Atlantic Outer Continental Shelf and Slope

PubMed Central

Di Tullio, Juliana Couto; Gandra, Tiago B. R.; Zerbini, Alexandre N.; Secchi, Eduardo R.

2016-01-01

Temporal and spatial patterns of cetacean diversity and distribution were investigated through eight ship-based surveys carried out during spring and autumn between 2009 and 2014 on the outer continental shelf (~150m) and slope (1500m) off southeastern and southern Brazil (~23°S to ~34°S). The survey area was divided into southeast and south areas according to their oceanographic characteristics. Twenty-one species were observed in 503 sightings. The overall number of species was similar between the two areas, though it was higher in the spring in the south area. Five species were dominant and diversity varied more seasonally than spatially. ANOVA and kernel analyses showed that overall cetacean densities were higher in spring compared to autumn. Physeter macrocephalus, the most frequent species, concentrated throughout the south area at depths over 1000m in both seasons. Despite the overlapped occurrence at a broader scale, small delphinids presented latitudinal and in-offshore gradients as well as seasonal variation in distribution patterns, which could indicate habitat partitioning between some species. Delphinus delphis was only recorded in the south and its density decreased in areas where the presence of Stenella frontalis increased, mainly beyond the 250m isobath. Densities of S. longirostris and S. attenuata increased in lower latitudes and beyond the shelf break. The large delphinids Tursiops truncatus and Globicephala melas formed mixed groups in many occasions and were observed along the study area around depths of 500m. Grampus griseus was twice as frequent in the south area and densities increased in waters deeper than 600m. As expected, densities of both small and large migratory whales were higher during spring, over the continental slope, in the southeast area. The results presented here provided strong evidence on the importance of the outer continental shelf and slope to a diverse community of cetaceans occurring in the subtropical Southwestern Atlantic. PMID:27243455

Diversity and Distribution Patterns of Cetaceans in the Subtropical Southwestern Atlantic Outer Continental Shelf and Slope.

PubMed

Di Tullio, Juliana Couto; Gandra, Tiago B R; Zerbini, Alexandre N; Secchi, Eduardo R

2016-01-01

Temporal and spatial patterns of cetacean diversity and distribution were investigated through eight ship-based surveys carried out during spring and autumn between 2009 and 2014 on the outer continental shelf (~150m) and slope (1500m) off southeastern and southern Brazil (~23°S to ~34°S). The survey area was divided into southeast and south areas according to their oceanographic characteristics. Twenty-one species were observed in 503 sightings. The overall number of species was similar between the two areas, though it was higher in the spring in the south area. Five species were dominant and diversity varied more seasonally than spatially. ANOVA and kernel analyses showed that overall cetacean densities were higher in spring compared to autumn. Physeter macrocephalus, the most frequent species, concentrated throughout the south area at depths over 1000m in both seasons. Despite the overlapped occurrence at a broader scale, small delphinids presented latitudinal and in-offshore gradients as well as seasonal variation in distribution patterns, which could indicate habitat partitioning between some species. Delphinus delphis was only recorded in the south and its density decreased in areas where the presence of Stenella frontalis increased, mainly beyond the 250m isobath. Densities of S. longirostris and S. attenuata increased in lower latitudes and beyond the shelf break. The large delphinids Tursiops truncatus and Globicephala melas formed mixed groups in many occasions and were observed along the study area around depths of 500m. Grampus griseus was twice as frequent in the south area and densities increased in waters deeper than 600m. As expected, densities of both small and large migratory whales were higher during spring, over the continental slope, in the southeast area. The results presented here provided strong evidence on the importance of the outer continental shelf and slope to a diverse community of cetaceans occurring in the subtropical Southwestern Atlantic.

Foraging responses of black-legged kittiwakes to prolonged food-shortages around colonies on the Bering Sea shelf.

PubMed

Paredes, Rosana; Orben, Rachael A; Suryan, Robert M; Irons, David B; Roby, Daniel D; Harding, Ann M A; Young, Rebecca C; Benoit-Bird, Kelly; Ladd, Carol; Renner, Heather; Heppell, Scott; Phillips, Richard A; Kitaysky, Alexander

2014-01-01

We hypothesized that changes in southeastern Bering Sea foraging conditions for black-legged kittiwakes (Rissa tridactyla) have caused shifts in habitat use with direct implications for population trends. To test this, we compared at-sea distribution, breeding performance, and nutritional stress of kittiwakes in three years (2008-2010) at two sites in the Pribilof Islands, where the population has either declined (St. Paul) or remained stable (St. George). Foraging conditions were assessed from changes in (1) bird diets, (2) the biomass and distribution of juvenile pollock (Theragra chalcogramma) in 2008 and 2009, and (3) eddy kinetic energy (EKE; considered to be a proxy for oceanic prey availability). In years when biomass of juvenile pollock was low and patchily distributed in shelf regions, kittiwake diets included little or no neritic prey and a much higher occurrence of oceanic prey (e.g. myctophids). Birds from both islands foraged on the nearby shelves, or made substantially longer-distance trips overnight to the basin. Here, feeding was more nocturnal and crepuscular than on the shelf, and often occurred near anticyclonic, or inside cyclonic eddies. As expected from colony location, birds from St. Paul used neritic waters more frequently, whereas birds from St. George typically foraged in oceanic waters. Despite these distinctive foraging patterns, there were no significant differences between colonies in chick feeding rates or fledging success. High EKE in 2010 coincided with a 63% increase in use of the basin by birds from St. Paul compared with 2008 when EKE was low. Nonetheless, adult nutritional stress, which was relatively high across years at both colonies, peaked in birds from St. Paul in 2010. Diminishing food resources in nearby shelf habitats may have contributed to kittiwake population declines at St Paul, possibly driven by increased adult mortality or breeding desertion due to high foraging effort and nutritional stress.

Changes in water mass exchange between the NW shelf areas and the North Atlantic and their impact on nutrient/carbon cycling

NASA Astrophysics Data System (ADS)

Gröger, Matthias; Maier-Reimer, Ernst; Mikolajewicz, Uwe; Segschneider, Joachim; Sein, Dimitry

2010-05-01

Despite their comparatively small extension on a global scale, shelf areas are of interest for several economic reasons and climatic processes related to nutrient cycling, sea food supply, and biological productivity. Moreover, they constitute an important interface for nutrients, pollutants and freshwater on their pathway from the continents to the open ocean. This modelling study aims to investigate the spatial and temporal variability of water mass exchange between the North Atlantic and the NW European shelf and their impact on nutrient/carbon cycling and biological productivity. For this, a new modeling approach has been set up which bridges the gap between pure shelf models where water mass transports across the model domain too strongly depend on the formulation of open boundaries and global models suffering under their too coarse resolution in shelf regions. The new model consists of the global ocean and carbon cycle model MPIOM/HAMOCC with strongly increased resolution in the North Sea and the North Atlantic coupled to the regional atmosphere model REMO. The model takes the full luni-solar tides into account. It includes further a 12 layer sediment module with the relevant pore water chemistry. The main focus lies on the governing mechanisms of water mass exchange across the shelf break and the imprint on shelf biogeochemistry. For this, artificial tracers with a prescribed decay rate have been implemented to distinguish waters arriving from polar and shelf regions and those that originate from the tropics. Experiments were carried out for the years 1948 - 2007. The relationship to larger scale circulation patterns like the position and variability of the subtropical and subpolar gyres is analyzed. The water mass exchange is analyzed with respect to the nutrient concentration and productivity on the European shelf areas. The implementation of tides leads to an enhanced vertical mixing which causes lower sea surface temperatures compared to simulations without tidal forcing. The simulated tidal currents exceed velocities of 30cm per second in the near bottom layer which leads to a strong resuspension of sediment particles. These effects are most pronounced along narrow and shallow topographic structures like e.g. the English Channel. Experiments with artificial tracers show that the composition of water column changes along with the induced climate warming.

Population genetic structure of Patagonian toothfish (Dissostichus eleginoides) in the Southeast Pacific and Southwest Atlantic Ocean

PubMed Central

Canales-Aguirre, Cristian B.; Galleguillos, Ricardo; Oyarzun, Fernanda X.; Hernández, Cristián E.

2018-01-01

Previous studies of population genetic structure in Dissostichus eleginoides have shown that oceanographic and geographic discontinuities drive in this species population differentiation. Studies have focused on the genetics of D. eleginoides in the Southern Ocean; however, there is little knowledge of their genetic variation along the South American continental shelf. In this study, we used a panel of six microsatellites to test whether D. eleginoides shows population genetic structuring in this region. We hypothesized that this species would show zero or very limited genetic structuring due to the habitat continuity along the South American shelf from Peru in the Pacific Ocean to the Falkland Islands in the Atlantic Ocean. We used Bayesian and traditional analyses to evaluate population genetic structure, and we estimated the number of putative migrants and effective population size. Consistent with our predictions, our results showed no significant genetic structuring among populations of the South American continental shelf but supported two significant and well-defined genetic clusters of D. eleginoides between regions (South American continental shelf and South Georgia clusters). Genetic connectivity between these two clusters was 11.3% of putative migrants from the South American cluster to the South Georgia Island and 0.7% in the opposite direction. Effective population size was higher in locations from the South American continental shelf as compared with the South Georgia Island. Overall, our results support that the continuity of the deep-sea habitat along the continental shelf and the biological features of the study species are plausible drivers of intraspecific population genetic structuring across the distribution of D. eleginoides on the South American continental shelf. PMID:29362690

Trichodesmium slicks associated with environmental conditions of continental shelf-break at the southwestern of the Atlantic Ocean

NASA Astrophysics Data System (ADS)

Detoni, A. M. S.; Yunes, J. S., Sr.; Ciotti, Á. M.; Calil, P. H. R.; Tavano, V. M.

2016-02-01

Trichodesmium can accumulate high biomass, particularly in the oligotrophic regions of North and Tropical Atlantic, and North Pacific. Large Trichodesmium slicks have been reported in the South Atlantic as well, associated with the Brazil Currrent (BC) that flows southwards over the continental shelf-break. Regional variations of the width of the Brazilian continental shelf, as well as changes in the bottom topography, generate cyclonic and anti-cyclonic eddies as BC crosses the southeastern Brazil. Thus, the general conditions of the BC - characterized as a warm, saline and oligotrophic current - are expected to change not only with latitude but also by the influence of mesoscale instabilities. In this study, three oceanographic cruises were carried out to characterize the distribution of Trichodesmium along the southeastern Brazilian continental shelf-break and their relationship with temperature and upper layer nutrients concentrations. As in other oceanic regions, high concentrations of Trichodesmium (maximum 212.6 × 105 trichomes L-1) were observed in waters with temperatures between 22° C to 25° C, low nitrogen (< 2.4 μM), and moderate phosphate concentrations (> 0.08 μM), where wind speeds were low (< 11 m s-1). Generally, slicks were present where phosphate concentration in the upper 25 m was slightly higher than that of adjacent waters. Wind and hydrographic observations suggested that wind divergence at micro-regions (approximately 625 km2), as well as shelf-break dynamics can drive sporadic shelf-break upwelling, favouring Trichodesmium growth between 23° S to 28° S. Although shelf-break upwelling may occur along the entire domain of the BC flow, Trichodesmium densities were low at latitudes between 28° S to 33° S likely a result of the lower sea surface temperature.

Eddy-resolving simulations of the Fimbul Ice Shelf cavity circulation: Basal melting and exchange with open ocean

NASA Astrophysics Data System (ADS)

Hattermann, T.; Smedsrud, L. H.; Nøst, O. A.; Lilly, J. M.; Galton-Fenzi, B. K.

2014-10-01

Melting at the base of floating ice shelves is a dominant term in the overall Antarctic mass budget. This study applies a high-resolution regional ice shelf/ocean model, constrained by observations, to (i) quantify present basal mass loss at the Fimbul Ice Shelf (FIS); and (ii) investigate the oceanic mechanisms that govern the heat supply to ice shelves in the Eastern Weddell Sea. The simulations confirm the low melt rates suggested by observations and show that melting is primarily determined by the depth of the coastal thermocline, regulating deep ocean heat fluxes towards the ice. Furthermore, the uneven distribution of ice shelf area at different depths modulates the melting response to oceanic forcing, causing the existence of two distinct states of melting at the FIS. In the simulated present-day state, only small amounts of Modified Warm Deep Water enter the continental shelf, and ocean temperatures beneath the ice are close to the surface freezing point. The basal mass loss in this so-called state of "shallow melting" is mainly controlled by the seasonal inflow of solar-heated surface water affecting large areas of shallow ice in the upper part of the cavity. This is in contrast to a state of "deep melting", in which the thermocline rises above the shelf break depth, establishing a continuous inflow of Warm Deep Water towards the deep ice. The transition between the two states is found to be determined by a complex response of the Antarctic Slope Front overturning circulation to varying climate forcings. A proper representation of these frontal dynamics in climate models will therefore be crucial when assessing the evolution of ice shelf basal melting along this sector of Antarctica.

Lessons in microbial geochemistry from the Coal Oil Point seep field: progress as prospects.

NASA Astrophysics Data System (ADS)

Valentine, D. L.; Kinnaman, F.; Wardlaw, G.; Redmond, M.; Ding, H.; Kimball, J.; Busso, L.; Larson, A.

2005-12-01

The hydrocarbon seeps located offshore Coal Oil Point, Santa Barbara, CA, are estimated to emit 1010 grams of methane and 50 thousand barrels of oil annually, and are among the most prolific in the world. The seep field spans a range of shelf depths and many of the seeps are accessible by SCUBA, making this an ideal location to investigate the impact of microbes on the biogeochemical cycling of methane and other hydrocarbons. With funding provided by the National Science Foundation, the Minerals Management Service and the Petroleum Research Fund, we have begun to investigate the interactions between microbes, hydrocarbon distributions, and environmental dynamics in the seep environment. This presentation will provide an overview of Coal Oil Point seep field and the biogeochemical research being conducted there. Several topics will be incorporated including i) the dynamics of oil and gas seepage, ii) the microbial consumption of methane, ethane, propane, butane and crude oil, iii) the distribution and composition of microbial mats, iv) redox differentiation in seep sediments and the importance of advection, and v) the development of experimental tools for the investigation of seep environments. Prospects for future biochemical research in the Coal Oil Point seep field will also be discussed.

Relation of phytoplankton species to ecosystem definition in the northwest Atlantic using remote sensing data

NASA Astrophysics Data System (ADS)

Devred, Emmanuel; Sathyendranath, Shubha; Fuentes-yaco, Cesar; Maass, Heidi; Platt, Trevor

2005-08-01

In this work, we present a new method for dynamic assignment of the boundaries of the ecological provinces of the North West Atlantic. The results are compared with the distribution of diatoms in the study area. Both analyses rely on ocean-colour data for the region. Diatoms were identified using remoteely-sensed data on the basis of their species-dependent absorption characteristics, which were embedded in a simple reflectance model(Sathyendranath et al., 2004). Maps of diatom distributions were produced for the area. Satellite-derived chlorophyll biomass and sea surface temperature (MODIS data) for the same period were used to redefine, in a dynamic way, the static borders of the ecological provinces (Sathyendranath et al., 1995; Longhurst 1998). The analyses were carried on two-week composite images, at different times of the year (April-May, July and October), to examine seasonal variability in the boundaries. The boundaries of provinces and the occurrence of diatoms were spatially coherent. Diatoms were favoured in rich waters on the continental shelf and in cold waters at high latitudes. In provinces labelled as oligotrophic (subtropical gyre and Gulf Stream), very negligible fractions of diatoms were found at any time of the year.

Pattern of distribution and diversity of demersal assemblages in the central Mediterranean Sea

NASA Astrophysics Data System (ADS)

Colloca, F.; Cardinale, M.; Belluscio, A.; Ardizzone, G.

2003-03-01

A highly diversified mix of fish species, cephalopods and crustaceans, together with several macro-epibenthic organisms, compose trawl catches in the Mediterranean Sea. Management of Mediterranean trawling needs a multispecies approach that considers the community and not the single species as the basic unit of the analysis. While many studies have correlated several environmental factors to the spatial organizations of demersal organisms, few have focused on the role of macro-epibenthic communities in structuring demersal assemblages. In this paper, the following hypotheses were tested: (1) there are discrete demersal assemblages in the central Mediterranean Sea; (2) the distribution and diversity of demersal communities does not change on small temporal scales (1 year); (3) the demersal assemblages were segregated across both different epibenthic assemblages and depth gradients. Shallow stations were separated into coastal and middle-deep shelf assemblages while stations on the slope formed three main assemblages: slope edge, upper slope and middle slope assemblages. The demersal community did not show a substantial change at the small temporal scale. Sandy, sand-muddy and detritic epibenthic communities characterized coastal shelf assemblages, while epibenthic assemblage on muddy bottoms were dominant in the deeper areas of the shelf. A well-defined difference in macro-epibenthic faunal associations among stations on the slope (depth >200 m) was not found. Depth appeared to affect diversity of the main taxa of demersal organisms in different ways. Teleostean diversity did not show any trend with depth, the number of cephalopod species increased on the shelf and decreased on the slope while crustacean and elasmobranch species richness increased significantly from the shelf to the middle slope. The strong correlation shown in this study between epifaunal benthic communities and demersal fish assemblages requires the formulation of an ecosystem-based management for the Mediterranean Sea trawl fisheries. The existence of such biological diversity certainly contributes to the Mediterranean ecosystem health and its conservation should become one of the main objective of demersal resources management in the future.

Late Holocene estuarine-inner shelf interactions; is there evidence of an estuarine retreat path for Tampa Bay, Florida?

USGS Publications Warehouse

Donahue, B.T.; Hine, A.C.; Tebbens, S.; Locker, S.D.; Twichell, D.C.

2003-01-01

The purpose of this study was to determine if and how a large, modern estuarine system, situated in the middle of an ancient carbonate platform, has affected its adjacent inner shelf both in the past during the last, post-glacial sea-level rise and during the present. An additional purpose was to determine if and how this inner shelf seaward of a major estuary differed from the inner shelves located just to the north and south but seaward of barrier-island shorelines. Through side-scan sonar mosaicking, bathymetric studies, and ground-truthing using surface grab samples as well as diver observations, two large submarine sand plains were mapped - one being the modern ebb-tidal delta and the other interpreted to be a relict ebb-tidal delta formed earlier in the Holocene. The most seaward portion of the inner shelf studied consists of a field of lobate, bathymetrically elevated, fine-sand accumulations, which were interpreted to be sediment-starved 3D dunes surrounded by small 2D dunes composed of coarse molluscan shell gravel. Additionally, exposed limestone hardbottoms supporting living benthic communities were found as well. This modern shelf sedimentary environment is situated on a large, buried shelf valley, which extends eastward beneath the modern Tampa Bay estuary. These observations plus the absence of an incised shelf valley having surficial bathymetric expression, and the absence of sand bodies normally associated with back-tracking estuarine systems indicate that there was no cross-shelf estuarine retreat path formed during the last rise in sea level. Instead, the modern Tampa Bay formed within a mid-platform, low-relief depression, which was flooded by rising marine waters late in the Holocene. With continued sea-level rise in the late Holocene, this early embayment was translated eastward or landward to its present position, whereby a larger ebb-tidal delta prograded out onto the inner shelf. Extensive linear sand ridges, common to the inner shelves to the north and south, did not form in this shelf province because it was a low-energy, open embayment lacking the wave climate and nearshore zone necessary to create such sand bodies. The distribution of bedforms on the inner shelf and the absence of seaward-oriented 2D dunes on the modern ebb-tidal delta indicate that the modern estuarine system has had little effect on its adjacent inner shelf. ?? 2003 Elsevier B.V. All rights reserved.

The salinity signature of the cross-shelf exchanges in the Southwestern Atlantic Ocean: Satellite observations.

PubMed

Guerrero, Raul A; Piola, Alberto R; Fenco, Harold; Matano, Ricardo P; Combes, Vincent; Chao, Yi; James, Corinne; Palma, Elbio D; Saraceno, Martin; Strub, P Ted

2014-11-01

Satellite-derived sea surface salinity (SSS) data from Aquarius and SMOS are used to study the shelf-open ocean exchanges in the western South Atlantic near 35°S. Away from the tropics, these exchanges cause the largest SSS variability throughout the South Atlantic. The data reveal a well-defined seasonal pattern of SSS during the analyzed period and of the location of the export of low-salinity shelf waters. In spring and summer, low-salinity waters over the shelf expand offshore and are transferred to the open ocean primarily southeast of the river mouth (from 36°S to 37°30'S). In contrast, in fall and winter, low-salinity waters extend along a coastal plume and the export path to the open ocean distributes along the offshore edge of the plume. The strong seasonal SSS pattern is modulated by the seasonality of the along-shelf component of the wind stress over the shelf. However, the combined analysis of SSS, satellite-derived sea surface elevation and surface velocity data suggest that the precise location of the export of shelf waters depends on offshore circulation patterns, such as the location of the Brazil Malvinas Confluence and mesoscale eddies and meanders of the Brazil Current. The satellite data indicate that in summer, mixtures of low-salinity shelf waters are swiftly driven toward the ocean interior along the axis of the Brazil/Malvinas Confluence. In winter, episodic wind reversals force the low-salinity coastal plume offshore where they mix with tropical waters within the Brazil Current and create a warmer variety of low-salinity waters in the open ocean. Satellite salinity sensors capture low-salinity detrainment events from shelves SW Atlantic low-salinity detrainments cause highest basin-scale variability In summer low-salinity detrainments cause extended low-salinity anomalies.

Algal Turf Sediments and Sediment Production by Parrotfishes across the Continental Shelf of the Northern Great Barrier Reef

PubMed Central

Goatley, Christopher H. R.; Bellwood, David R.

2017-01-01

Sediments are found in the epilithic algal matrix (EAM) of all coral reefs and play important roles in ecological processes. Although we have some understanding of patterns of EAM sediments across individual reefs, our knowledge of patterns across broader spatial scales is limited. We used an underwater vacuum sampler to quantify patterns in two of the most ecologically relevant factors of EAM sediments across the Great Barrier Reef: total load and grain size distribution. We compare these patterns with rates of sediment production and reworking by parrotfishes to gain insights into the potential contribution of parrotfishes to EAM sediments. Inner-shelf reef EAMs had the highest sediment loads with a mean of 864.1 g m-2, compared to 126.8 g m-2 and 287.4 g m-2 on mid- and outer-shelf reefs, respectively. High sediment loads were expected on inner-shelf reefs due to their proximity to the mainland, however, terrigenous siliceous sediments only accounted for 13–24% of total mass. On inner-shelf reef crests parrotfishes would take three months to produce the equivalent mass of sediment found in the EAM. On the outer-shelf it would take just three days, suggesting that inner-shelf EAMs are characterised by low rates of sediment turnover. By contrast, on-reef sediment production by parrotfishes is high on outer-shelf crests. However, exposure to oceanic swells means that much of this production is likely to be lost. Hydrodynamic activity also appears to structure sediment patterns at within-reef scales, with coarser sediments (> 250 μm) typifying exposed reef crest EAMs, and finer sediments (< 250 μm) typifying sheltered back-reef EAMs. As both the load and grain size of EAM sediments mediate a number of important ecological processes on coral reefs, the observed sediment gradients are likely to play a key role in the structure and function of the associated coral reef communities. PMID:28122042

The salinity signature of the cross-shelf exchanges in the Southwestern Atlantic Ocean: Satellite observations

PubMed Central

Guerrero, Raul A; Piola, Alberto R; Fenco, Harold; Matano, Ricardo P; Combes, Vincent; Chao, Yi; James, Corinne; Palma, Elbio D; Saraceno, Martin; Strub, P Ted

2014-01-01

Satellite-derived sea surface salinity (SSS) data from Aquarius and SMOS are used to study the shelf-open ocean exchanges in the western South Atlantic near 35°S. Away from the tropics, these exchanges cause the largest SSS variability throughout the South Atlantic. The data reveal a well-defined seasonal pattern of SSS during the analyzed period and of the location of the export of low-salinity shelf waters. In spring and summer, low-salinity waters over the shelf expand offshore and are transferred to the open ocean primarily southeast of the river mouth (from 36°S to 37°30′S). In contrast, in fall and winter, low-salinity waters extend along a coastal plume and the export path to the open ocean distributes along the offshore edge of the plume. The strong seasonal SSS pattern is modulated by the seasonality of the along-shelf component of the wind stress over the shelf. However, the combined analysis of SSS, satellite-derived sea surface elevation and surface velocity data suggest that the precise location of the export of shelf waters depends on offshore circulation patterns, such as the location of the Brazil Malvinas Confluence and mesoscale eddies and meanders of the Brazil Current. The satellite data indicate that in summer, mixtures of low-salinity shelf waters are swiftly driven toward the ocean interior along the axis of the Brazil/Malvinas Confluence. In winter, episodic wind reversals force the low-salinity coastal plume offshore where they mix with tropical waters within the Brazil Current and create a warmer variety of low-salinity waters in the open ocean. Key Points Satellite salinity sensors capture low-salinity detrainment events from shelves SW Atlantic low-salinity detrainments cause highest basin-scale variability In summer low-salinity detrainments cause extended low-salinity anomalies PMID:26213672

Concentrations and isotope ratios of mercury in sediments from shelf and continental slope at Campos Basin near Rio de Janeiro, Brazil.

PubMed

Araujo, Beatriz Ferreira; Hintelmann, Holger; Dimock, Brian; Almeida, Marcelo Gomes; Rezende, Carlos Eduardo

2017-07-01

Mercury (Hg) may originate from both anthropogenic and natural sources. The measurement of spatial and temporal variations of Hg isotope ratios in sediments may enable source identification and tracking of environmental processes. In this study we establish the distribution of mercury concentrations and mercury isotope ratios in surface sediments of three transects along the continental shelf and slope in Campos Basin-RJ-Brazil. The shelf showed on average lower total Hg concentrations (9.2 ± 5.3 ng g -1 ) than the slope (24.6 ± 8.8 ng g -1 ). MMHg average concentrations of shelf 0.15 ± 0.12 ng g -1 and slope 0.13 ± 0.06 ng g -1 were not significantly different. Distinct differences in Hg isotope ratio signatures were observed, suggesting that the two regions were impacted by different sources of Hg. The shelf showed more negative δ 202 Hg and Δ 199 Hg values ranging from -0.59 to -2.19‰ and from -0.76 to 0.08‰, respectively. In contrast, the slope exhibited δ 202 Hg values from -0.29 to -1.82‰ and Δ 199 Hg values from -0.23 to 0.09‰. Mercury found on the shelf, especially along the "D" and "I" transects, is depleted in heavy isotopes resulting in more negative δ 202 Hg compared to the slope. Isotope ratios observed in the "D" and "I" shelf region are similar to Hg ratios commonly associated with plants and vegetation and very comparable to those detected in the estuary and adjoining mangrove forest, which suggests that Hg exported from rivers may be the dominating source of Hg in near coastal regions along the northern part of the shelf. Copyright © 2017 Elsevier Ltd. All rights reserved.

Post-breeding season distribution of black-footed and Laysan albatrosses satellite-tagged in Alaska: Inter-specific differences in spatial overlap with North Pacific fisheries

USGS Publications Warehouse

Fischer, K.N.; Suryan, R.M.; Roby, D.D.; Balogh, G.R.

2009-01-01

We integrated satellite-tracking data from black-footed albatrosses (Phoebastria nigripes; n = 7) and Laysan albatrosses captured in Alaska (Phoebastria immutabilis; n = 18) with data on fishing effort and distribution from commercial fisheries in the North Pacific in order to assess potential risk from bycatch. Albatrosses were satellite-tagged at-sea in the Central Aleutian Islands, Alaska, and tracked during the post-breeding season, July-October 2005 and 2006. In Alaskan waters, fishing effort occurred almost exclusively within continental shelf and slope waters. Potential fishery interaction for black-footed albatrosses, which most often frequented shelf-slope waters, was greatest with sablefish (Anoplopoma fimbria) longline and pot fisheries and with the Pacific halibut (Hippoglossus stenolepsis) longline fishery. In contrast, Laysan albatrosses spent as much time over oceanic waters beyond the continental shelf and slope, thereby overlapping less with fisheries in Alaska than black-footed albatrosses. Regionally, Laysan albatrosses had the greatest potential fishery interaction with the Atka mackerel (Pleurogrammus monopterygius) trawl fishery in the Western Aleutian Islands and the sablefish pot fishery in the Central Aleutian Islands. Black-footed albatrosses ranged further beyond Alaskan waters than Laysan albatrosses, overlapping west coast Canada fisheries and pelagic longline fisheries in the subarctic transition domain; Laysan albatrosses remained north of these pelagic fisheries. Due to inter-specific differences in oceanic distribution and habitat use, the overlap of fisheries with the post-breeding distribution of black-footed albatrosses is greater than that for Laysan albatrosses, highlighting inter-specific differences in potential vulnerability to bycatch and risk of population-level impacts from fisheries. ?? 2008 Elsevier Ltd.

Contribution of phytoplankton and benthic microalgae to inner shelf sediments of the north-central Gulf of Mexico

NASA Astrophysics Data System (ADS)

Grippo, M. A.; Fleeger, J. W.; Rabalais, N. N.; Condrey, R.; Carman, K. R.

2010-03-01

Marine sediment may contain both settled phytoplankton and benthic microalgae (BMA). In river-dominated, shallow continental shelf systems, spatial, and temporal heterogeneity in sediment type and water-column characteristics (e.g., turbidity and primary productivity) may promote spatial variation in the relative contribution of these two sources to the sediment organic matter pool available to benthic consumers. Here we use photosynthetic pigment analysis and microscopic examination of sediment microalgae to investigate how the biomass, composition, and degradation state of sediment-associated microalgae vary along the Louisiana (USA) inner shelf, a region strongly influenced by the Mississippi River. Three sandy shoals and surrounding muddy sediments with depths ranging from 4 to 20 m were sampled in April, August, and October 2007. Pigment composition suggested that sediment microalgae were primarily diatoms at all locations. We found no significant differences in sediment chlorophyll a concentrations (8-77 mg m -2) at the shoal and off-shoal stations. Epipelic pennate diatoms (considered indicative of BMA) made up a significantly greater proportion of sediment diatoms at sandy (50-98%) compared to more silty off-shoal stations (16-56%). The percentage of centric diatoms (indicators of settled phytoplankton) in the sediment was highest in August. Sediment total pheopigment concentrations on sandy stations (<20 mg m -2) were significantly lower than concentrations at nearby muddy stations (>40 mg m -2), suggesting differences in sediment microalgal degradation state. These observations suggest that BMA predominate in shallow sandy sediments and that phytodetritus predominates at muddy stations. Our results also suggest that the relative proportion of phytodetritus in the benthos was highest where phytoplankton biomass in the overlying water was greatest, independent of sediment type. The high biomass of BMA found on shoals suggests that benthic primary production on sandy sediments represents a potentially significant local source of sediment microalgal carbon that may be utilized by benthic consumers in continental shelf food webs.

Coral records of reef-water pH across the central Great Barrier Reef, Australia: assessing the influence of river runoff on inshore reefs

NASA Astrophysics Data System (ADS)

D'Olivo, J. P.; McCulloch, M. T.; Eggins, S. M.; Trotter, J.

2015-02-01

The boron isotopic (δ11Bcarb) compositions of long-lived Porites coral are used to reconstruct reef-water pH across the central Great Barrier Reef (GBR) and assess the impact of river runoff on inshore reefs. For the period from 1940 to 2009, corals from both inner- and mid-shelf sites exhibit the same overall decrease in δ11Bcarb of 0.086 ± 0.033‰ per decade, equivalent to a decline in seawater pH (pHsw) of ~0.017 ± 0.007 pH units per decade. This decline is consistent with the long-term effects of ocean acidification based on estimates of CO2 uptake by surface waters due to rising atmospheric levels. We also find that, compared to the mid-shelf corals, the δ11Bcarb compositions of inner-shelf corals subject to river discharge events have higher and more variable values, and hence higher inferred pHsw values. These higher δ11Bcarb values of inner-shelf corals are particularly evident during wet years, despite river waters having lower pH. The main effect of river discharge on reef-water carbonate chemistry thus appears to be from reduced aragonite saturation state and higher nutrients driving increased phytoplankton productivity, resulting in the drawdown of pCO2 and increase in pHsw. Increased primary production therefore has the potential to counter the more transient effects of low-pH river water (pHrw) discharged into near-shore environments. Importantly, however, inshore reefs also show a consistent pattern of sharply declining coral growth that coincides with periods of high river discharge. This occurs despite these reefs having higher pHsw, demonstrating the overriding importance of local reef-water quality and reduced aragonite saturation state on coral reef health.

Coral records of reef-water pH across the central Great Barrier Reef, Australia: assessing the influence of river runoff on inshore reefs

NASA Astrophysics Data System (ADS)

D'Olivo, J. P.; McCulloch, M. T.; Eggins, S. M.; Trotter, J.

2014-07-01

The boron isotopic (δ11Bcarb) compositions of long-lived Porites coral are used to reconstruct reef-water pH across the central Great Barrier Reef (GBR) and assess the impact of river runoff on inshore reefs. For the period from 1940 to 2009, corals from both inner as well as mid-shelf sites exhibit the same overall decrease in δ11Bcarb of 0.086 ± 0.033‰ per decade, equivalent to a~decline in seawater pH (pHsw) of ~ 0.017 ± 0.007 pH units per decade. This decline is consistent with the long-term effects of ocean acidification based on estimates of CO2 uptake by surface waters due to rising atmospheric levels. We also find that compared to the mid-shelf corals, the δ11Bcarb compositions for inner shelf corals subject to river discharge events, have higher and more variable values and hence higher inferred pHsw values. These higher δ11Bcarb values for inner-shelf corals are particularly evident during wet years, despite river waters having lower pH. The main effect of river discharge on reef-water carbonate chemistry thus appears to be from higher nutrients driving increased phytoplankton productivity, resulting in the drawdown of pCO2 and increase in pHsw. Increased primary production therefore has the potential to counter the more transient effects of low pH river water (pHrw) discharged into near-shore environments. Importantly however, inshore reefs also show a consistent pattern of sharply declining coral growth that coincides with periods of high river discharge. This occurs despite these reefs having higher pHsw values and hence higher seawater aragonite saturation states, demonstrating the over-riding importance of local reef-water quality on coral reef health.

Shelf-life extension of fresh Tuber aestivum and Tuber melanosporum truffles by modified atmosphere packaging with microperforated films.

PubMed

Rivera, Carmen Susana; Blanco, Domingo; Salvador, María Luisa; Venturini, María Eugenia

2010-05-01

The aim of this study was to design a modified atmosphere packaging suitable for Tuber melanosporum and Tuber aestivum truffles that extend their shelf life and their availability as a fresh product. Their respiration rates were determined by O(2) depletion and CO(2) formation in closed systems performed at different temperatures: 4, 10, and 23 degrees C. The results were fitted by exponential equations and derivatives of these equations were used to obtain the experimental respiration rates. Our results revealed high respiration rates in both species of truffles and respiratory quotients (RQ) higher than 1 in all the cases studied. A linear dependence of respiration rate, both R(O2) and R(CO2), on O(2) concentration was revealed. A mathematical model was used to predict the evolution of the gaseous composition at 4 degrees C in the interior of polypropylene trays (250 mL) heat sealed with 4 microperforated films of different transmission rates. A microperforated film with 2 holes (90 x 50 microm) was selected to produce an internal atmosphere of 15%CO(2)/7%O(2) at 4 degrees C. The predicted atmosphere composition was confirmed by the experimental results. The quality and microbiological characteristics of fresh truffles, packaged in these conditions, revealed that the microbial counts of pseudomonads and Enterobacteriaceae were decreased, the weight loss was reduced, the typical hard texture was maintained, and the development of mycelium growth was delayed, enabling good scores for aroma and flavor, and therefore prolonging the shelf life of T. melanosporum and T. aestivum truffles to 28 and 21 d, respectively. Practical Application: This study describes the benefits of using MAP with microperforated films in the postharvest storage of Tuber melanosporum and Tuber aestivum fresh truffles. The shelf life of T. aestivum is prolonged to 21 d and of T. melanosporum to beyond 28 d increasing the possibilities for a foreign market.

Development, acceptability, and nutritional characteristics of a low-cost, shelf-stable supplementary food product for vulnerable groups in Kenya.

PubMed

Kunyanga, Catherine; Imungi, Jasper; Okoth, Michael; Vadivel, Vellingiri; Biesalski, Hans Konrad

2012-03-01

Food-based approaches have been advocated as the best strategies to curb hunger and malnutrition in developing countries. The use of low-cost, locally available, nutritious foods in the development of supplementary foods has been recommended. To develop low-cost food supplements using different traditionally processed local foods, consisting of cereals, legumes, nuts, fish, and vegetables, to meet the nutrient requirements for vulnerable groups in Kenya. Four food supplements were developed and evaluated by taste panel procedures. The product containing amaranth grain, pigeon pea, sweet potato, groundnuts, and brown sugar was found to be the most acceptable supplement. Evaluation of nutritional composition, shelf-life, and cost analysis of the acceptable supplement was carried out to assess if it could satisfactorily provide more than 50% of the Recommended Dietary Allowances (RDAs) of the basic nutrients for vulnerable groups. The acceptable supplement contained 453.2 kcal energy, 12.7 g crude protein, 54.3 g soluble carbohydrates, 20.8 g crude fat, and 10.1 g crude fiber per 110 g. The micronutrient contents were 93.0 mg calcium, 172.4 mg magnesium, 2.7 mg zinc, 5.7 mg iron, 0.8 mg vitamin B₁, 0.2 mg vitamin B₂, 7.9 mg niacin, 100 microg folic acid, and 140 microg retinol equivalent per 110 g. The supplement also contained 21% total essential amino acid in addition to appreciable levels of palmitic, stearic, oleic, linoleic, and alpha-linolenic fatty acids. The shelf-life study showed that it could be stored in different packaging materials (polythene bags, gunny bags, and kraft paper) at 26°C without deleterious effects on its chemical composition for up to 4 months. Cost analysis of the supplement indicated that the product could be competitively sold at US$0.812/kg (KES 65.50/kg). Locally available indigenous foods can be used in the formulation of acceptable, low-cost, shelf-stable, nutritious supplementary foods for vulnerable groups.

Effect of growing location on seed oil composition in the cultivated peanut germplasm collection

USDA-ARS?s Scientific Manuscript database

A particularly important component of seed oils is the content of oleic acid as this fatty acid has several health benefits and contributes to increased oil stability, i.e. longer shelf life. We measured 8846 available accessions of the USDA peanut germplasm collection to gauge the range of variatio...

Decontamination Efficacy of Three Commercial Off-the-Shelf Sporicidal Agents on Medium-Sized Panels Contaminated with Surrogates of Bacillus anthracis

DTIC Science & Technology

2012-04-01

chlorine dioxide (CD) or vapor hydrogen peroxide ( VHP ). A wide-area release and contamination of building exteriors and the outdoors would likely...from the panels. Depending on the surface composition and the decontamination technology tested, viable spore recovery from the panels varied after

A summary of chemical and biological testing of proposed disposal of sediment from Richmond Harbor relative to the Deep Off-Shelf Reference Area, the Bay Farm Borrow Area, and the Alcatraz Environs Reference Area

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mayhew, H.L.; Karle, L.M.; Gruendell, B.D.

The US Army Corps of Engineers was authorized to dredge Richmond Harbor to accomodate large, deep-draft vessels. An ecological evaluation of the Harbor sediments was performed describing the physical characteristics, toxic substances, effects on aquatic organisms,and potential for bioaccumulation of chemical contaminants. The objective of this report is to compare the sediment chemistry, acute toxicity, and bioaccumulation results of the Richmond Harbor sediments to each of the reference areas; i.e., the Deep Off-Shelf Reference Area, the Bay Farm Borrow Area, and the Alcatraz Environs Reference Area. This report will enable the US Army Corps of Engineers to determine whether disposalmore » at a reference area is appropriate for all or part of the dredged material from Richmond Harbor. Chemical analyses were performed on 30 sediment samples; 28 of those samples were then combined to form 7 composites. The seven composites plus sediment from two additional stations received both chemical and biological evaluations.« less

Spectroscopy and multivariate analyses applications related to solid rocket nozzle bondline

NASA Technical Reports Server (NTRS)

Arendale, W. F.; Hatcher, Richard; Benson, Brian; Workman, Gary L.

1991-01-01

Chemical composition and molecular orientation define the properties of materials. Information related to chemical composition and molecular configuration is obtained by various forms of spectroscopy. Software algorithms developed for multivariate analyses, expert systems, and Artificial Intelligence (AI) are used to conduct repetitive operations. The techniques are believed to be of particular significance toward achieving TQM objectives. The objective was to obtain information related to the quality of the bondline in the solid rocket motor, SRM, nozzle. Hysol 934 NA, a room temperature curing epoxide resin, is used as the bonding agent. A good bond requires that the adhesive be placed on a properly prepared metal surface, the adhesives Part A and B be mixed in appropriate ratio from material within shelf life specifications. Spectroscopic data was obtained for surfaces prepared according to specifications, contaminated metal surfaces, samples of the epoxide adhesive at times that represent shelf aging from 3 months to 2 years, several mix ratio of A to B, and curing material. Temperature was found to be a significant factor. The study concentrated on pot life and mix ratio.

Hypsometry, volume and physiography of the Arctic Ocean and their paleoceanographic implications

NASA Astrophysics Data System (ADS)

Jakobsson, M.; Macnab, R.; Grantz, A.; Kristoffersen, Y.

2003-04-01

Recent analyses of the International Bathymetric Chart of the Arctic Ocean (IBCAO) grid model include: Hypsometry (the distribution of surface area at various depths); ocean volume distribution; and physiographic provinces [Jakobsson 2002; Jakobsson et al., in press]. The present paper summarizes the main results from these recent studies and expands on the paleoceanographic implications for the Arctic Ocean, which in this work is defined as the broad continental shelves of the Barents, Kara, Laptev, East Siberian and Chukchi Seas, the White Sea and the narrow continental shelves of the Beaufort Sea, the Arctic continental margins off the Canadian Arctic Archipelago and northern Greenland. This, the World's smallest ocean, is a virtually land-locked ocean that makes up merely 2.6 % of the area, and 1.0 % of the volume, of the entire World Ocean. The continental shelf area, from the coastline out to the shelf break, comprises as much as 52.9 % of the total area in the Arctic Ocean, which is significantly larger in comparison to the rest of the world oceans where the proportion of shelves, from the coastline out to the foot of the continental slope, only ranges between about 9.1 % and 17.7 %. In Jakobsson [2002], the seafloor area and water volume were calculated for different depths starting from the present sea level and progressing in increments of 10 m to a depth of 500 m, and in increments of 50 m from 550 m down to the deepest depth within each of the analyzed Arctic Ocean seas. Hypsometric curves expressed as simple histograms of the frequencies in different depth bins were presented, along with depth plotted against cumulative area for each of the analyzed seas. The derived hypsometric curves show that most of the Arctic Ocean shelf seas besides the Barents Sea, Beaufort Sea and the shelf off northern Greenland have a similar shape with the largest seafloor area between 0 and 50 m. The East Siberian and Laptev seas, in particular, show area distributions concentrated in this shallow depth range, and together with the Chukchi Sea they form a large flat shallow shelf province comprising as much as 22 % of the entire Arctic Ocean area, but only 1 % of the volume. Given this vast shelf area it may be speculated that the Arctic Ocean circulation is more sensitive to eustatic sea level changes compared to the other world oceans. For example, during the LGM when the sea level was ca 120 m lower than today most, if not all, of the Arctic Ocean shelf region could not play a role in the ocean circulation. Besides being the world's smallest ocean with the by far largest shelf area in proportion to its size, the Arctic Ocean is unique in terms of its physiographic setting. The Fram Strait is the only real break in the barrier of vast continental shelves enclosing the Arctic Ocean. The second largest physiographic province after the continental shelves consists of ridges, which is in contrast to the rest of the World's oceans where abyssal plains dominate. As much as 15.8 % of the area is underlain by ridges indicating the profound effect they have on ocean circulation. Jakobsson, M., Grantz, A., Kristoffersen, Y., and Macnab, R., in press, Physiographic Provinces of the Arctic Ocean, GSA Bulletin. Jakobsson, M., 2002, Hypsometry and volume of the Arctic Ocean and its constituent’s seas, Geochemistry Geophysics Geosystems, v. 3, no. 2.

Shallow geology, seafloor texture, and physiographic zones of the Inner Continental Shelf from Nahant to northern Cape Cod Bay, Massachusetts

USGS Publications Warehouse

Pendleton, Elizabeth A.; Baldwin, Wayne E.; Barnhardt, Walter A.; Ackerman, Seth D.; Foster, David S.; Andrews, Brian D.; Schwab, William C.

2013-01-01

The Massachusetts inner continental shelf between Nahant and northern Cape Cod Bay has been profoundly affected by the occupation and retreat of glacial ice sheets and relative sea-level change during the Quaternary. Marine geologic mapping of this area is a component of a statewide cooperative effort involving the U.S. Geological Survey and the Massachusetts Office of Coastal Zone Management. Interpretation of high-resolution geophysical data (interferometric and multibeam swath bathymetry, lidar, backscatter, and seismic reflection), sediment samples, and bottom photographs was used to produce a series of maps that describe the distribution and texture of seafloor sediments, shallow geologic framework, and physiographic zones of this inner-shelf region. These data and interpretations are intended to aid efforts to inventory and manage coastal and marine resources, and provide baseline information for research focused on coastal evolution and environmental change.

Direct observations of American eels migrating across the continental shelf to the Sargasso Sea

PubMed Central

Béguer-Pon, Mélanie; Castonguay, Martin; Shan, Shiliang; Benchetrit, José; Dodson, Julian J.

2015-01-01

Since inferring spawning areas from larval distributions in the Sargasso Sea a century ago, the oceanic migration of adult American eels has remained a mystery. No adult eel has ever been observed migrating in the open ocean or in the spawning area. Here, we track movements of maturing eels equipped with pop-up satellite archival tags from the Scotian Shelf (Canada) into the open ocean, with one individual migrating 2,400 km to the northern limit of the spawning site in the Sargasso Sea. The reconstructed routes suggest a migration in two phases: one over the continental shelf and along its edge in shallow waters; the second in deeper waters straight south towards the spawning area. This study is the first direct evidence of adult Anguilla migrating to the Sargasso Sea and represents an important step forward in the understanding of routes and migratory cues. PMID:26505325

Benthic exchange and biogeochemical cycling in permeable sediments.

PubMed

Huettel, Markus; Berg, Peter; Kostka, Joel E

2014-01-01

The sandy sediments that blanket the inner shelf are situated in a zone where nutrient input from land and strong mixing produce maximum primary production and tight coupling between water column and sedimentary processes. The high permeability of the shelf sands renders them susceptible to pressure gradients generated by hydrodynamic and biological forces that modulate spatial and temporal patterns of water circulation through these sediments. The resulting dynamic three-dimensional patterns of particle and solute distribution generate a broad spectrum of biogeochemical reaction zones that facilitate effective decomposition of the pelagic and benthic primary production products. The intricate coupling between the water column and sediment makes it challenging to quantify the production and decomposition processes and the resultant fluxes in permeable shelf sands. Recent technical developments have led to insights into the high biogeochemical and biological activity of these permeable sediments and their role in the global cycles of matter.

Seabed fluid expulsion along the upper slope and outer shelf of the U.S. Atlantic continental margin

USGS Publications Warehouse

Brothers, D.S.; Ruppel, C.; Kluesner, J.W.; ten Brink, Uri S.; Chaytor, J.D.; Hill, J.C.; Andrews, B.D.; Flores, C.

2014-01-01

Identifying the spatial distribution of seabed fluid expulsion features is crucial for understanding the substrate plumbing system of any continental margin. A 1100 km stretch of the U.S. Atlantic margin contains more than 5000 pockmarks at water depths of 120 m (shelf edge) to 700 m (upper slope), mostly updip of the contemporary gas hydrate stability zone (GHSZ). Advanced attribute analyses of high-resolution multichannel seismic reflection data reveal gas-charged sediment and probable fluid chimneys beneath pockmark fields. A series of enhanced reflectors, inferred to represent hydrate-bearing sediments, occur within the GHSZ. Differential sediment loading at the shelf edge and warming-induced gas hydrate dissociation along the upper slope are the proposed mechanisms that led to transient changes in substrate pore fluid overpressure, vertical fluid/gas migration, and pockmark formation.

Early Spring Phytoplankton Dynamics in the Western Antarctic Peninsula

NASA Astrophysics Data System (ADS)

Arrigo, Kevin R.; van Dijken, Gert L.; Alderkamp, Anne-Carlijn; Erickson, Zachary K.; Lewis, Kate M.; Lowry, Kate E.; Joy-Warren, Hannah L.; Middag, Rob; Nash-Arrigo, Janice E.; Selz, Virginia; van de Poll, Willem

2017-12-01

The Palmer Long-Term Ecological Research program has sampled waters of the western Antarctic Peninsula (wAP) annually each summer since 1990. However, information about the wAP prior to the peak of the phytoplankton bloom in January is sparse. Here we present results from a spring process cruise that sampled the wAP in the early stages of phytoplankton bloom development in 2014. Sea ice concentrations were high on the shelf relative to nonshelf waters, especially toward the south. Macronutrients were high and nonlimiting to phytoplankton growth in both shelf and nonshelf waters, while dissolved iron concentrations were high only on the shelf. Phytoplankton were in good physiological condition throughout the wAP, although biomass on the shelf was uniformly low, presumably because of heavy sea ice cover. In contrast, an early stage phytoplankton bloom was observed beneath variable sea ice cover just seaward of the shelf break. Chlorophyll a concentrations in the bloom reached 2 mg m-3 within a 100-150 km band between the SBACC and SACCF. The location of the bloom appeared to be controlled by a balance between enhanced vertical mixing at the position of the two fronts and increased stratification due to melting sea ice between them. Unlike summer, when diatoms overwhelmingly dominate the phytoplankton population of the wAP, the haptophyte Phaeocystis antarctica dominated in spring, although diatoms were common. These results suggest that factors controlling phytoplankton abundance and composition change seasonally and may differentially affect phytoplankton populations as environmental conditions within the wAP region continue to change.

Fishes associated with North Carolina shelf-edge hardbottoms and initial assessment of a proposed marine protected area

USGS Publications Warehouse

Quattrini, A.M.; Ross, Steve W.

2006-01-01

Fish community data are limited from deeper shelf-edge hardbottoms along the southeastern U.S. continental shelf. This lack of data Hampers the design of recently proposed marine protected areas (MPAs) on the outer shelf of the southeastern U.S. During 2001-2004, sampling was conducted (57-25 m) to describe habitats and fish communities within and outside of the North Carolina proposed MPA (p-MPA) using the JOHNSON-SEA-LINK submersible, remotely operated vehicles, otter trawls, and hook and line. Habitats observed included soft substrate or non-hardbottom (NH), a shipwreck ("Snowy Wreck"), low relief hardbottoms (LRH), boulder fields (BF), and high relief ledges (HRL), the latter of which were divided into three mi-crohabitats. Non-metric, multi-dimensional scaling indicated that hardbottom fish assemblages were distinct from NH, and fish assemblages among microhabitats on HRL were different. In total, 152 fish species were documented. Thirty-five species were observed only on NH and 117 were observed or hardbottoms and the Snowy Wreck. Several species of anthiines were the most abundant fishes on most hardbottoms, whereas triglids, synodontids, and Seriola spp. were abundant on NH. Species richness was highest on HRL, and species composition was unique at the Snowy Wreck (238-253 m) and on BF. Future shelf-edge hardbottom research should include more standardized surveys using direct observations. Further, we recommend that the boundaries of the North Carolina p-MPA be redrawn to include more hardbottom habitat. ?? 2006 Rosenstiel School of Marine and Atmospheric Science of the University of Miami.

In situ measurements of particle settling velocity on the northern California continental shelf

NASA Astrophysics Data System (ADS)

Hill, P. S.; Sherwood, C. R.; Sternberg, R. W.; Nowell, A. R. M.

1994-08-01

As part of the Sediment TRansport Events on Shelves and Slopes (STRESS) program, a remote optical settling ☐ was deployed on the northern California continental shelf. The device operates by isolating a volume of sediment-laden fluid from the environment and then monitoring its sedimentation behavior with a transmissometer. Results show a bimodal distribution of suspended sediment during low-energy periods on the shelf that reflects the size distribution of bottom sediments. The coarse mode sinks at 0.026 cm s -1 (22 m day -1) and the fine mode settles at 0.0025 cm s -1 (2 m day -1). Between one-quarter and two-thirds of the total mass resides in the coarse mode. Roughly one-quarter is in the fine mode. The remainder sinks too slowly (<0.0015cm s -1 or <1.3m day -1) to be resolved during the 18-h measurement cycles. Greatest uncertainty in assigning mass to the various settling velocity classes comes from sensitivity to ill-constrained particle geometry of the conversion from light attenuation to mass. The device failed during higher energy periods, probably due to penetration of fluid into the ☐. Complete isolation of the fluid from the environment would improve the performance of settling ☐es in energetic settings.

Authigenesis of trace metals in energetic tropical shelf environments

USGS Publications Warehouse

Breckel, E.J.; Emerson, S.; Balistrieri, L.S.

2005-01-01

We evaluated authigenic changes of Fe, Mn, V, U, Mo, Cd and Re in suboxic, periodically remobilized, tropical shelf sediments from the Amazon continental shelf and the Gulf of Papua. The Cd/Al, Mo/Al, and U/Al ratios in Amazon shelf sediments were 82%, 37%, and 16% less than those in Amazon River suspended sediments, respectively. Very large depletions of U previously reported in this environment were not observed. The Cd/Al ratios in Gulf of Papua sediments were 76% lower than measurements made on several Papua New Guinea rivers, whereas U/Al ratios in the shelf sediments were enriched by approximately 20%. Other metal/Al ratios in the Papua New Guinea river suspended sediments and continental shelf sediments were not distinguishably different. Comparison of metal/Al ratios to grain size distributions in Gulf of Papua samples indicates that our observations cannot be attributed to differences in grain size between the river suspended sediments and continental shelf sediments. These two shelves constitute a source of dissolved Cd to the world ocean equal to 29-100% of the dissolved Cd input from rivers, but only 3% of the dissolved Mo input and 4% of the dissolved U input. Release of Cd, Mo, and U in tropical shelf sediments is likely a result of intense Fe and Mn oxide reduction in pore waters and resuspension of the sediments. Since we do not observe depletions of particulate Fe and Mn in the shelf sediments most of these dissolved metals must reoxidize in the overlying waters and reprecipitate. As Cd exhibits the largest losses on these tropical shelves, we examined the ability of newly formed Fe and Mn oxides to adsorb dissolved Cd using a geochemical diffuse double-layer surface complexation model and found the oxide surfaces are relatively ineffective at readsorbing Cd in seawater due to surface-site competition by Mg and Ca. If the remobilization and reoxidation of Fe and Mn occurs frequently enough before sediment is buried significant amounts of Cd may be removed from the oxide surfaces. Because a much greater percentage of Mn than Fe becomes remobilized in these shelf sediments, metals closely associated with Mn oxides (like Cd) are more likely to show losses during deposition. ?? 2005 Elsevier Ltd. All rights reserved.

Sources, extent and history of methane seepage on the continental shelf off northern Norway

NASA Astrophysics Data System (ADS)

Sauer, Simone; Lepland, Aivo; Chand, Shyam; Schubert, Carsten J.; Eichinger, Florian; Knies, Jochen

2014-05-01

Active natural hydrocarbon gas seepage was recently discovered in the Hola area on the continental shelf off Vesterålen, northern Norway. We conducted acoustic and geochemical investigations to assess the modern and past extent, source and pathways of the gas seepage . Water column echosounder surveys showed bubble plumes up to several tens of metres above the seafloor. Analyses of dissolved methane in the water column indicated slightly elevated concentrations (50 nM) close to the seafloor. To identify fluxes and origin of methane in the sediments we analysed sediment pore water chemistry, the isotopic composition of methane and of dissolved inorganic carbon (d13CCH4, d2HCH4, d13CDIC) in three closely spaced (

Spatial patterns of mesozooplankton communities in the Northwestern Iberian shelf during autumn shaped by key environmental factors

NASA Astrophysics Data System (ADS)

Domínguez, Rula; Garrido, Susana; Santos, A. Miguel P.; dos Santos, Antonina

2017-11-01

The autumn mesozooplankton community structure and spatial distribution was investigated in relation to the prevalent hydrographic conditions at the Northwestern Iberian shelf (38.5°-41.6°N), a major spawning ground for small pelagic fish species. Copepods clearly dominated the mesozooplankton community, followed by Cladocera, Appendicularia, Cirripedia, Bivalvia larvae and Chaetognata. Three different groups were identified according to their distribution: a northern coastal group (A), a southern coastal group with two stations in the northern area (B), and a shelf group (C), each delimited to areas with distinct oceanographic conditions. The boundary between the coastal groups A and B was coincident with areas of prominent geographic features, particularly a submarine canyon (Nazaré canyon) and a cape (Cabo Carvoeiro), both inducing abrupt changes in the local/regional patterns of water mass circulation. Group B includes a few northern stations that can be related to river discharges while the southern stations can be defined by upwelling conditions at that time. The distribution of some relevant species can be related to biophysical variables (temperature, salinity, Chlorophyll a). Some copepod taxa were generally coincident with high concentrations of chlorophyll a abundance (e.g. Temora spp., Oncaea spp.), while the distribution of other groups such as Cladocera or bivalve veliger larvae was correlated to temperature and/or salinity gradients caused by river discharges. Other important taxa as Paracalanus and Clausocalanus spp. or Oithona spp. showed no particular influence of any of the measured hydrological variables. This work is the first description of mesozooplankton assemblages and their distribution pattern in a broad area off Western Iberia during autumn. It contributes to understanding the dynamics of zooplankton in the area, increasing the knowledge of the drivers of plankton community variability and providing information about their potential as food for small pelagic fish species spawning in the area throughout the season.

Towards a Universal Calving Law: Modeling Ice Shelves Using Damage Mechanics

NASA Astrophysics Data System (ADS)

Whitcomb, M.; Bassis, J. N.; Price, S. F.; Lipscomb, W. H.

2017-12-01

Modeling iceberg calving from ice shelves and ice tongues is a particularly difficult problem in glaciology because of the wide range of observed calving rates. Ice shelves naturally calve large tabular icebergs at infrequent intervals, but may instead calve smaller bergs regularly or disintegrate due to hydrofracturing in warmer conditions. Any complete theory of iceberg calving in ice shelves must be able to generate realistic calving rate values depending on the magnitudes of the external forcings. Here we show that a simple damage evolution law, which represents crevasse distributions as a continuum field, produces reasonable estimates of ice shelf calving rates when added to the Community Ice Sheet Model (CISM). Our damage formulation is based on a linear stability analysis and depends upon the bulk stress and strain rate in the ice shelf, as well as the surface and basal melt rates. The basal melt parameter in our model enhances crevasse growth near the ice shelf terminus, leading to an increased iceberg production rate. This implies that increasing ocean temperatures underneath ice shelves will drive ice shelf retreat, as has been observed in the Amundsen and Bellingshausen Seas. We show that our model predicts broadly correct calving rates for ice tongues ranging in length from 10 km (Erebus) to over 100 km (Drygalski), by matching the computed steady state lengths to observations. In addition, we apply the model to idealized Antarctic ice shelves and show that we can also predict realistic ice shelf extents. Our damage mechanics model provides a promising, computationally efficient way to compute calving fluxes and links ice shelf stability to climate forcing.

Off-the-shelf Control of Data Analysis Software

NASA Astrophysics Data System (ADS)

Wampler, S.

The Gemini Project must provide convenient access to data analysis facilities to a wide user community. The international nature of this community makes the selection of data analysis software particularly interesting, with staunch advocates of systems such as ADAM and IRAF among the users. Additionally, the continuing trends towards increased use of networked systems and distributed processing impose additional complexity. To meet these needs, the Gemini Project is proposing the novel approach of using low-cost, off-the-shelf software to abstract out both the control and distribution of data analysis from the functionality of the data analysis software. For example, the orthogonal nature of control versus function means that users might select analysis routines from both ADAM and IRAF as appropriate, distributing these routines across a network of machines. It is the belief of the Gemini Project that this approach results in a system that is highly flexible, maintainable, and inexpensive to develop. The Khoros visualization system is presented as an example of control software that is currently available for providing the control and distribution within a data analysis system. The visual programming environment provided with Khoros is also discussed as a means to providing convenient access to this control.

Recent warming leads to a rapid borealization of fish communities in the Arctic

NASA Astrophysics Data System (ADS)

Fossheim, Maria; Primicerio, Raul; Johannesen, Edda; Ingvaldsen, Randi B.; Aschan, Michaela M.; Dolgov, Andrey V.

2015-07-01

Arctic marine ecosystems are warming twice as fast as the global average. As a consequence of warming, many incoming species experience increasing abundances and expanding distribution ranges in the Arctic. The Arctic is expected to have the largest species turnover with regard to invading and locally extinct species, with a modelled invasion intensity of five times the global average. Studies in this region might therefore give valuable insights into community-wide shifts of species driven by climate warming. We found that the recent warming in the Barents Sea has led to a change in spatial distribution of fish communities, with boreal communities expanding northwards at a pace reflecting the local climate velocities. Increased abundance and distribution areas of large, migratory fish predators explain the observed community-wide distributional shifts. These shifts change the ecological interactions experienced by Arctic fish species. The Arctic shelf fish community retracted northwards to deeper areas bordering the deep polar basin. Depth might limit further retraction of some of the fish species in the Arctic shelf community. We conclude that climate warming is inducing structural change over large spatial scales at high latitudes, leading to a borealization of fish communities in the Arctic.

Distribution of Some Rare and Trace Elements in Ice-Rafted Sediments in the Yermak Plateau Area, the Arctic Ocean

NASA Astrophysics Data System (ADS)

Shevchenko, V. P.; Maslov, A. V.; Stein, R.

2017-11-01

The distribution of V, Co, Ni, Sr, Nb and rare earth elements (REE) in ice-rafted sediments (IRS) collected in the Yermak Plateau area (the Arctic Ocean) during cruise ARK-XX/3 of the R/V Polarstern in September 2004 has been analyzed. It was determined that the Nb/V ratio in these IRS has an intermediate value between the average ratio values in suspended particulate matter of the Yenisei and Khatanga rivers and Mesozoic-Cenozoic basalts, on the one hand, and suspended matter of the Ob and Lena rivers and post-Archean Australian Shale (PAAS), on the other hand. The REE distribution demonstrates the same pattern. The IRS data points in Nb-Sr, Ni-Co, and Co-Sr and some other diagrams are close mainly to the average chemical composition of suspended particulate matter of the Ob and Lena rivers, i.e., waterways draining watersheds composed predominantly of sedimentary rocks. The Nb, Sr, Ni, and Co contents in the studied IRS samples are close to those in the PAAS. In accordance with this, we were able to conclude that the main provenance areas of the studied IRS samples are situated in the eastern part of the Laptev Sea and the East Siberian Sea, on shelf of which the erosion products of sedimentary and metamorphic rocks of the Verkhoyansk Fold Belt dominate.

Historical polycyclic aromatic and petrogenic hydrocarbon loading in Northern Central Gulf of Mexico shelf sediments.

PubMed

Overton, E B; Ashton, B M; Miles, M S

2004-10-01

The distribution of selected hydrocarbons within ten dated sediment cores taken from the Mississippi River Bight off coastal Louisiana suggests a chronic contaminant loading from several sources including the river itself, oil and gas exploration in the central Gulf of Mexico (GOM) shelf area, and natural geologic hydrocarbon seeps. Data were grouped as either total polycyclic aromatic hydrocarbons (PAH's), which were indicative of pyrogenic PAH's; or estimated total hopanes (indicative of petrogenic hydrocarbons). The total PAH concentrations and estimated total hopanes begin increasing above background levels (approximately 200 ng g(-1)) after the 1950s. The distribution of these hydrocarbons and hopanes within the dated sediment cores suggests that the Mississippi River is a regional source of pyrogenic PAH's, and that the hopanes are from natural geologic hydrocarbon seeps, oil and gas exploration in the GOM, or both.

Probabilistic Model for Listeria monocytogenes Growth during Distribution, Retail Storage, and Domestic Storage of Pasteurized Milk ▿

PubMed Central

Koutsoumanis, Konstantinos; Pavlis, Athanasios; Nychas, George-John E.; Xanthiakos, Konstantinos

2010-01-01

A survey on the time-temperature conditions of pasteurized milk in Greece during transportation to retail, retail storage, and domestic storage and handling was performed. The data derived from the survey were described with appropriate probability distributions and introduced into a growth model of Listeria monocytogenes in pasteurized milk which was appropriately modified for taking into account strain variability. Based on the above components, a probabilistic model was applied to evaluate the growth of L. monocytogenes during the chill chain of pasteurized milk using a Monte Carlo simulation. The model predicted that, in 44.8% of the milk cartons released in the market, the pathogen will grow until the time of consumption. For these products the estimated mean total growth of L. monocytogenes during transportation, retail storage, and domestic storage was 0.93 log CFU, with 95th and 99th percentiles of 2.68 and 4.01 log CFU, respectively. Although based on EU regulation 2073/2005 pasteurized milk produced in Greece belongs to the category of products that do not allow the growth of L. monocytogenes due to a shelf life (defined by law) of 5 days, the above results show that this shelf life limit cannot prevent L. monocytogenes from growing under the current chill chain conditions. The predicted percentage of milk cartons—initially contaminated with 1 cell/1-liter carton—in which the pathogen exceeds the safety criterion of 100 cells/ml at the time of consumption was 0.14%. The probabilistic model was used for an importance analysis of the chill chain factors, using rank order correlation, while selected intervention and shelf life increase scenarios were evaluated. The results showed that simple interventions, such as excluding the door shelf from the domestic storage of pasteurized milk, can effectively reduce the growth of the pathogen. The door shelf was found to be the warmest position in domestic refrigerators, and it was most frequently used by the consumers for domestic storage of pasteurized milk. Furthermore, the model predicted that a combination of this intervention with a decrease of the mean temperature of domestic refrigerators by 2°C may allow an extension of pasteurized milk shelf life from 5 to 7 days without affecting the current consumer exposure to L. monocytogenes. PMID:20139308

Extension of the shelf life of guava by individual packaging with cling and shrink films.

PubMed

Rana, Seema; Siddiqui, Saleem; Goyal, Ankit

2015-12-01

Guava is a climacteric fruit so physico-chemical changes continuously occur after harvest till fruit become unfit for consumption and suffers from post harvest losses. The main objective of this work was to assess the effectiveness of individual film in form of Shrink and Cling wrap on shelf life of guava. Fruits were individually packed in polythene bags (LDPE) of 200 gauge thickness by Shrink and Cling wrapping and stored at 7 ± 3 °C. Individual wrapping reduced the magnitude of changes during storage i.e., ripening process drastically as evident from lower total soluble solids, higher ascorbic acid, polyphenol content with lower polyphenol oxidase activity and physiological loss of weight (PLW) was less than 3.5 %. Film wrapping preserved freshness of wrapped fruits as they remained acceptable for whole storage time in contrast to control fruits which turned unacceptable by 15(th) day of storage. Control fruits showed significant compositional changes as well as in polyphenol content, ascorbic acid and reduced number of marketable fruits while Cling and Shrink wrapping enhanced the shelf life by 10 days.

Shelf-Life Extension of Chill-Stored Beef Longissimus Steaks Packaged under Modified Atmospheres with 50% O2 and 40% CO2.

PubMed

Yang, Xiaoyin; Niu, Lebao; Zhu, Lixian; Liang, Rongrong; Zhang, Yimin; Luo, Xin

2016-07-01

This study was conducted to compare the shelf-life of beef steaks stored in different packaging conditions: overwrapped (OW) packaging and 2 modified atmosphere packaging systems (MAP): 80% O2 MAP (80% O2 /20% CO2 ) and 50% O2 MAP (50% O2 /40% CO2 /10% N2 ). Steaks were stored at 2 °C for 20 d. Headspace gas composition, microbial counts, color stability, pH, purge loss, and lipid oxidation were monitored. Among the packaging types, 50% O2 MAP was superior to OW packaging and 80% O2 MAP in delaying bacterial growth and extending shelf-life to 20 d. 50% O2 MAP also gave steaks an acceptable color during storage. No significant differences were observed in color stability of steaks packaged in both 50% O2 MAP and 80% O2 MAP. This study reveals 50% O2 MAP is a realistic alternative to preserve beef steaks efficiently. © 2016 Institute of Food Technologists®

Mineralogical Characterization of the Miocene Olcese Formation, Southern San Joaquin Valley, California

NASA Astrophysics Data System (ADS)

Lopez, K. A.; Baron, D.; Guo, J.; Woolford, J. M.

2016-12-01

The early to middle Miocene Olcese Formation in the southern San Joaquin Valley of California consists of shallow marine shelf sands in its lower and upper parts, and non-marine, frequently pumiceous sands in its middle part, and varies in thickness up to 1800 ft. There is little known as to the origin, nature, quantity, and distribution of clay minerals throughout the formation. This study examined 95 sidewall core samples from three wells, as well as 388 cutting samples from four wells and 12 samples from 3 outcrops. Well samples were from depths between 1,800 and 4,000 ft. Qualitative and quantitative mineralogy including clay minerals of the sidewall samples and selected cutting samples was determined by powder X-ray diffraction (XRD). XRD analyses were supplemented by scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS) and petrographic microscopy of selected samples. The main minerals of bulk samples include composite clay, quartz, potassium feldspar/plagioclase, calcite, and clinoptilolite. Content of composite clay varies between 17% and 51%. The clay-size fraction is predominantly composed of smectite, illite, kaolinite and chlorite with smectite being the most abundant. Smectite and clinoptilolite may be the alteration products of deeper burial of volcanic materials. The formation permeability could be significantly lowered by these authigenic minerals.

Distribution of Hydrocarbon-Utilizing Microorganisms and Hydrocarbon Biodegradation Potentials in Alaskan Continental Shelf Areas

PubMed Central

Roubal, George; Atlas, Ronald M.

1978-01-01

Hydrocarbon-utilizing microorganisms were enumerated from Alaskan continental shelf areas by using plate counts and a new most-probable-number procedure based on mineralization of 14C-labeled hydrocarbons. Hydrocarbon utilizers were ubiquitously distributed, with no significant overall concentration differences between sampling regions or between surface water and sediment samples. There were, however, significant seasonal differences in numbers of hydrocarbon utilizers. Distribution of hydrocarbon utilizers within Cook Inlet was positively correlated with occurrence of hydrocarbons in the environment. Hydrocarbon biodegradation potentials were measured by using 14C-radiolabeled hydrocarbon-spiked crude oil. There was no significant correlation between numbers of hydrocarbon utilizers and hydrocarbon biodegradation potentials. The biodegradation potentials showed large seasonal variations in the Beaufort Sea, probably due to seasonal depletion of available nutrients. Non-nutrient-limited biodegradation potentials followed the order hexadecane > naphthalene ≫ pristane > benzanthracene. In Cook Inlet, biodegradation potentials for hexadecane and naphthalene were dependent on availability of inorganic nutrients. Biodegradation potentials for pristane and benzanthracene were restricted, probably by resistance to attack by available enzymes in the indigenous population. PMID:655706

Effect of Aging and Freezing Conditions on Meat Quality and Storage Stability of 1++ Grade Hanwoo Steer Beef: Implications for Shelf Life

PubMed Central

Chang, Sunsik; Park, Beomyoung

2017-01-01

This study was conducted to establish the shelf life of 1++ grade Hanwoo beef by evaluating the changes in meat quality and storage stability under distribution conditions similar to those during export to Hong Kong and China. Four muscles of the loin, striploin, tenderloin, and top round muscles were obtained from 10 animals of 1++ grade Hanwoo steers. The distribution conditions were 0, 7, or 14 d of aging at 2°C and continuous storage at −18°C for 0, 3, 6, or 9 mon. The lightness (CIE L*) values decreased as the duration of freezer storage increased (p<0.05). The water-holding capacity of 4 muscles increased as the aging time increased when they were frozen for 3 mon (p<0.05). The cooking loss values of the four muscles were significantly increased as the duration of freezer storage increased (p<0.05). The Warner-Bratzler shear force values were significantly decreased in the loin, striploin, and top round muscles as the aging time increased (p<0.05). The changes in volatile basic nitrogen (16.67-18.49 mg%) and thiobarbituric reactive substance values (0.75-0.82 mg MA/kg meat) were significantly increased when the meat was frozen for 9 mon after 14 d of aging. On the basis of these observations, the shelf life of 1++ grade Hanwoo beef during distribution should be limited to less than 9 mon of freezer storage at −18°C after 14 d of aging at 2°C. PMID:28747830

Spatial and Temporal Distributions of Carbonate Saturation State on the Mississippi River Dominated Northern Gulf of Mexico

NASA Astrophysics Data System (ADS)

Huang, W. J.; Cai, W. J.; Wang, Y.; Hu, X.

2016-02-01

Carbonate saturation state (ΩAr) serves as an index of ocean acidification; however, its variation on river-dominated continental shelves remains unclear. Samples of total alkalinity (TA), dissolved inorganic carbon (DIC), and nutrients were taken from nine cruises on the Mississippi and Atchafalaya River dominated continental shelf during 2006 to 2010. The distributions of TA and DIC on sea surface generally follow salinity distributions, i.e. low on the inner shelf and high on the outer shelf. The riverine calcium concentration was considered to calculate ΩAr and the result showed high ΩAr (4 to 6) along the axis of the river plume trajectory, moderate ( 4) on the surface open gulf, and low (< 3) in the deep gulf. Strong seasonal variation of ΩAr was observed in the river endmembers, high in spring and low in winter. The ΩAr variation was dominated by mixing when salinities < 18. In waters of higher salinities, deficits of DIC from the conservative mixing lines were positively correlated to deficits of NO3 and the slope of regression line was close to the Redfield ratio after removing data affected by unbalanced Si and N. The fact that ΩAr was highly correlated to ΔDIC suggests that ΩAr was dominated by biological activity. Finally, model simulations suggest that the effect of increasing riverine TA (increasing ΩAr in low salinities zone) and the effect of decreasing riverine nitrate flux (decreasing ΩAr in middle-to-high salinities zone) on ΩAr might compensate each other in this study area.

Provenance and petrofacies, Upper Devonian sandstones, Philip Smith Mountains and Arctic quandrangles, Brooks Range, Alaska: Final report, Project No. 3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anderson, A.V.; Coney, P.J.

1987-11-01

Late Devonian sandstone beds are exposed as allochthonous sequences that extend for over 1000 km along the east-west strike of the Brooks Range in northern Alaska. These horizons, at least in part, record Late Devonian tectonism and deposition along the southern margin of the Arctic Alaska block. This study identifies clastic petrofacies in the western Philip Smith Mountains and southern Arctic quadrangles and infers the composition of the source terrane. The paleogeography is not known and the original distribution of lithofacies is uncertain, owing to the extensive post-depositional tectonism. In the study area the sandstones are exposed along rugged mountainmore » tops and high ridges. Although exposures are excellent, access is often difficult. Samples were collected from exposures near the western end of the Chandalar Shelf, Atigun Pass, and the Atigun River valley in the Philip Smith Mountains quadrangle and from the Crow Nest Creek and Ottertail Creek areas in the Arctic quadrangle. 34 refs., 17 figs.« less

New multi-scale perspectives on the stromatolites of Shark Bay, Western Australia.

PubMed

Suosaari, E P; Reid, R P; Playford, P E; Foster, J S; Stolz, J F; Casaburi, G; Hagan, P D; Chirayath, V; Macintyre, I G; Planavsky, N J; Eberli, G P

2016-02-03

A recent field-intensive program in Shark Bay, Western Australia provides new multi-scale perspectives on the world's most extensive modern stromatolite system. Mapping revealed a unique geographic distribution of morphologically distinct stromatolite structures, many of them previously undocumented. These distinctive structures combined with characteristic shelf physiography define eight 'Stromatolite Provinces'. Morphological and molecular studies of microbial mat composition resulted in a revised growth model where coccoid cyanobacteria predominate in mat communities forming lithified discrete stromatolite buildups. This contradicts traditional views that stromatolites with the best lamination in Hamelin Pool are formed by filamentous cyanobacterial mats. Finally, analysis of internal fabrics of stromatolites revealed pervasive precipitation of microcrystalline carbonate (i.e. micrite) in microbial mats forming framework and cement that may be analogous to the micritic microstructures typical of Precambrian stromatolites. These discoveries represent fundamental advances in our knowledge of the Shark Bay microbial system, laying a foundation for detailed studies of stromatolite morphogenesis that will advance our understanding of benthic ecosystems on the early Earth.

Real-time particulate mass measurement based on laser scattering

NASA Astrophysics Data System (ADS)

Rentz, Julia H.; Mansur, David; Vaillancourt, Robert; Schundler, Elizabeth; Evans, Thomas

2005-11-01

OPTRA has developed a new approach to the determination of particulate size distribution from a measured, composite, laser angular scatter pattern. Drawing from the field of infrared spectroscopy, OPTRA has employed a multicomponent analysis technique which uniquely recognizes patterns associated with each particle size "bin" over a broad range of sizes. The technique is particularly appropriate for overlapping patterns where large signals are potentially obscuring weak ones. OPTRA has also investigated a method for accurately training the algorithms without the use of representative particles for any given application. This streamlined calibration applies a one-time measured "instrument function" to theoretical Mie patterns to create the training data for the algorithms. OPTRA has demonstrated this algorithmic technique on a compact, rugged, laser scatter sensor head we developed for gas turbine engine emissions measurements. The sensor contains a miniature violet solid state laser and an array of silicon photodiodes, both of which are commercial off the shelf. The algorithmic technique can also be used with any commercially available laser scatter system.

Dust contributes an important flux of iron to Gulf of Alaska surface waters beyond the shelf break, while shelf sediments and glacial meltwater drive Fe supply over the northern Gulf of Alaska shelf

NASA Astrophysics Data System (ADS)

Crusius, J.; Schroth, A.; Resing, J.; Cullen, J. T.; Campbell, R. W.

2016-12-01

Particulate matter (PM) in the atmosphere is known to cause adverse cardiorespiratory health effects. It has been suggested that the ability of PM to generate oxidative stress leads to a proinflammatory response. In this work, we study the biological relevance of using a chemical oxidative potential (OP) assay to evaluate proinflammatory response in airway epithelial cells. Here we study the OPs of laboratory secondary organic aerosol (SOA) and metal mixtures, ambient PM from India, ash from the 2016 Alberta wildfires, and diesel exhaust particles. We use SOA derived from naphthalene and from monoterpenes as model systems for SOA. We measure OP using the dithiothreitol (DTT) assay, and cytosolic reactive oxygen species (ROS) production in BEAS-2B cell culture was measured using CellROX assay. We found that both SOA and copper show high OPs individually, but the OP of the combined SOA/copper mixture, which is more atmospherically relevant, was lower than either of the individual OPs. The reduced activity is attributed to chelation between metals and organic compounds using proton nuclear magnetic resonance. There is reasonable association between DTT activity and cellular ROS production within each particle type, but weak association across different particle types, suggesting that particle composition plays an important role in distinguishing between antioxidant consumption and ROS production. Our results highlight that while oxidative potential is a useful metric of PM's ability to generate oxidative stress, the chemical composition and cellular environment should be considered in understanding health impacts of PM.

Seabed images from Southern Ocean shelf regions off the northern Antarctic Peninsula and in the southeastern Weddell Sea

NASA Astrophysics Data System (ADS)

Piepenburg, Dieter; Buschmann, Alexander; Driemel, Amelie; Grobe, Hannes; Gutt, Julian; Schumacher, Stefanie; Segelken-Voigt, Alexandra; Sieger, Rainer

2017-07-01

Recent advances in underwater imaging technology allow for the gathering of invaluable scientific information on seafloor ecosystems, such as direct in situ views of seabed habitats and quantitative data on the composition, diversity, abundance, and distribution of epibenthic fauna. The imaging approach has been extensively used within the research project DynAMo (Dynamics of Antarctic Marine Shelf Ecosystems) at the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research Bremerhaven (AWI), which aimed to comparatively assess the pace and quality of the dynamics of Southern Ocean benthos. Within this framework, epibenthic spatial distribution patterns have been comparatively investigated in two regions in the Atlantic sector of the Southern Ocean: the shelf areas off the northern tip of the Antarctic Peninsula, representing a region with above-average warming of surface waters and sea-ice reduction, and the shelves of the eastern Weddell Sea as an example of a stable high-Antarctic marine environment that is not (yet) affected by climate change. The AWI Ocean Floor Observation System (OFOS) was used to collect seabed imagery during two cruises of the German research vessel Polarstern, ANT-XXIX/3 (PS81) to the Antarctic Peninsula from January to March 2013 and ANT-XXXI/2 (PS96) to the Weddell Sea from December 2015 to February 2016. Here, we report on the image and data collections gathered during these cruises. During PS81, OFOS was successfully deployed at a total of 31 stations at water depths between 29 and 784 m. At most stations, series of 500 to 530 pictures ( > 15 000 in total, each depicting a seabed area of approximately 3.45 m2 or 2.3 × 1.5 m) were taken along transects approximately 3.7 km in length. During PS96, OFOS was used at a total of 13 stations at water depths between 200 and 754 m, yielding series of 110 to 293 photos (2670 in total) along transects 0.9 to 2.6 km in length. All seabed images taken during the two cruises, including metadata, are available from the data publisher PANGAEA via the two persistent identifiers at https://doi.org/10.1594/PANGAEA.872719 (for PS81) and https://doi.org/10.1594/PANGAEA.862097 (for PS96).

New Data on the Stable Isotopes and Vertical Distribution of Benthic Foraminifers in the Western Barents Sea

NASA Astrophysics Data System (ADS)

Yamskova, E.; Ivanova, E.; Risebrobakken, B.

2006-12-01

Despite a wide use of benthic foraminifers in paleoceanographic and paleoclimatic studies, notably in the Arctic seas, their ecology is still poorly known. We studied the distribution of living (Rose Bengal stained) and dead benthic foraminifers, as well as oxygen and carbon isotope composition of monospecific samples in the upper 10 cm of sediment in six box corers retrieved from the Western Barents Sea and the West Spitsbergen shelf during cruise 63 of RV Professor Shtokman. Living specimens of five common infaunal species and C. lobatulus, generally considered as epifaunal species, penetrate down to 7-10 cm except for the West Spitsbergen shelf where the habitat depth of all six species is limited to the upper 3-7 cm. The highest species diversity and amount of living specimens per 50 cm\\3 were found in the seasonally ice-free areas notably on the West Spitsbergen shelf and in the mouth of Isfjorden (Svalbard), areas characterized by very high primary production. In general, four species show higher abundance among living calcareous foraminifers as compared to the dead assemblages, whereas two species, C. reniforme and I. norcrossi, demonstrate an opposite behavior, i.e. are accumulated in the sediments. In most cases, the uppermost thin oxidized brownish layer of the sediment contains more living specimens and more fragile agglutinated foraminifers than olive-grey and grey (reduced) sediments below. If the latter two findings will be confirmed by further studies they may have important implications for paleoceanographic reconstructions as an evidence of a transformation of biocoenoses into thanathocoenoses in the Arctic seas. The epifunal species C. lobatulus demonstrate the heaviest (positive) carbon isotope values and the lowest oxygen isotope values as compared to all other species. Three infaunal species show relatively similar negative δ \\13 C values due to the microhabitat effect (i.e. oxidation of organic matter within the sediment). The heaviest oxygen isotope values are typical for N.labradoricum which is consistent with the previous studies. All species show heavier values in box-corers from the Persey Trough where the warm Atlantic water does not chill the sea floor unlike the other studied locations. Both δ 18 O and δ \\13 C measurements reveal different downcore trends with changing offsets between the species. This may be related to a vital effect of specific ontogenetic stages, but may also result from insufficient time resolution to obtain simultaneous data for all species.

Distribution pattern and mass budget of sedimentary polycyclic aromatic hydrocarbons in shelf areas of the Eastern China Marginal Seas

NASA Astrophysics Data System (ADS)

Wang, C. L.; Zou, X. Q.; Zhao, Y. F.; Li, Y. L.; Song, Q. C.; Wang, T.; Yu, W. W.

2017-06-01

This study conducted the first extensive and comprehensive investigation of the regional-scale sedimentary polycyclic aromatic hydrocarbons (PAHs) concentration, flux, and budget in the continental shelves of the Eastern China Marginal Seas (ECMSs). Surface sediment samples from multiple sites were collected and assessed, and the latest data from current research were assessed. The spatial distribution pattern of PAHs in the ECMSs was significantly influenced by the regional hydrodynamics, sediment properties (grain-size, total organic carbon [TOC] content, and sedimentation rate), and anthropogenic impacts. Relatively higher PAHs concentrations occurred in areas with fine-grained sediment. Results of source apportionment found that the relative proportions of PAHs showed significant regional variation, mainly influenced by socioeconomic differences between north and south China. The PAHs burial flux in the study area ranged from 11.2 to 1308 ng cm-2 yr-1 with an average value of 101 ± 104 ng cm-2 yr-1. The area-integrated sedimentary PAHs burial flux across the ECMSs was 494 t yr-1. A mass budget calculation revealed that riverine input and atmospheric deposition were the most significant sources contributing, 28.4% and 71.6%, respectively. The study demonstrated that net PAHs transportation occurs between the Bohai Sea (BS) and Yellow Sea (YS), with a flux of approximately 10.2 t yr-1. PAHs were also transported from YS to the East China Sea (ECS), due to water exchange between the YS and ECS. Additionally, substantial amounts of PAHs in the inner shelf of the ECS were transported out of the shelf area due to cross-shelf plume.

Distribution and photoreactivity of chromophoric dissolved organic matter in northern Gulf of Mexico shelf waters

NASA Astrophysics Data System (ADS)

Shank, G. Christopher; Evans, Anne

2011-07-01

The distribution and photoreactivity of chromophoric dissolved organic matter (CDOM) in the northern Gulf of Mexico along the Louisiana coastal shelf were examined during three cruises in summer 2007, fall 2007, and summer 2008. The influence of the Mississippi River plume was clearly evident as CDOM levels (defined as a305) and dissolved organic carbon (DOC) concentrations were well-correlated with salinity during all cruises. Elevated CDOM and CDOM:DOC ratios of surface samples collected offshore of Atchafalaya Bay and the Breton-Chandeleur Sound complex indicated emanations of organic-rich waters from coastal wetlands are also an important source to nearshore shelf waters. Generally, CDOM and DOC levels were highest in surface waters and decreased with depth, but during summer 2007 and summer 2008, CDOM levels in near-bottom samples were occasionally higher than at mid-depths without concomitant increases in DOC. CDOM photobleaching was measured during 24 irradiations using a SunTest XLS+ solar simulator with photobleaching rate coefficients ( k305) ranging from 0.011 to 0.32 h -1. For fall 2007 and summer 2008, higher k305 values were generally observed in samples with higher initial CDOM levels. However, samples collected during summer 2007 did not exhibit a similar pattern nor were there differences in photobleaching rates between surface and bottom samples. Spectral slope coefficients ( S275-295 or S350-400) and DOC levels were largely unchanged after 24 h irradiations. Modeled CDOM photobleaching for northern Gulf of Mexico mid-shelf waters predicts that during the summer when solar irradiance is high and the water column becomes stratified, nearly 90% of the CDOM in the upper 1 m may be lost to photobleaching, with losses up to 20% possible even at 10 m depth.

Top predators in relation to bathymetry, ice and krill during austral winter in Marguerite Bay, Antarctica

USGS Publications Warehouse

Ribic, C.A.; Chapman, E.; Fraser, William R.; Lawson, G.L.; Wiebe, P.H.

2008-01-01

A key hypothesis guiding the US Southern Ocean Global Ocean Ecosystems Dynamics (US SO GLOBEC) program is that deep across-shelf troughs facilitate the transport of warm and nutrient-rich waters onto the continental shelf of the Western Antarctic Peninsula, resulting in enhanced winter production and prey availability to top predators. We tested aspects of this hypothesis during austral winter by assessing the distribution of the resident pack-ice top predators in relation to these deep across-shelf troughs and by investigating associations between top predators and their prey. Surveys were conducted July-August 2001 and August-September 2002 in Marguerite Bay, Antarctica, with a focus on the main across-shelf trough in the bay, Marguerite Trough. The common pack-ice seabird species were snow petrel (Pagodroma nivea, 1.2 individuals km-2), Antarctic petrel (Thalassoica antarctica, 0.3 individuals km-2), and Ade??lie penguin (Pygoscelis adeliae, 0.5 individuals km-2). The most common pack-ice pinniped was crabeater seal (Lobodon carcinophagus). During both winters, snow and Antarctic petrels were associated with low sea-ice concentrations independent of Marguerite Trough, while Ade??lie penguins occurred in association with this trough. Krill concentrations, both shallow and deep, also were associated with Ade??lie penguin and snow petrel distributions. During both winters, crabeater seal occurrence was associated with deep krill concentrations and with regions of lower chlorophyll concentration. The area of lower chlorophyll concentrations occurred in an area with complex bathymetry close to land and heavy ice concentrations. Complex or unusual bathymetry via its influence on physical and biological processes appears to be one of the keys to understanding how top predators survive during the winter in this Antarctic region. ?? 2007 Elsevier Ltd. All rights reserved.

Dispersal of the Pearl River plume over continental shelf in summer

NASA Astrophysics Data System (ADS)

Chen, Zhaoyun; Gong, Wenping; Cai, Huayang; Chen, Yunzhen; Zhang, Heng

2017-07-01

Satellite images of turbidity were used to study the climatological, monthly, and typical snapshot distributions of the Pearl River plume over the shelf in summer from 2003 to 2016. These images show that the plume spreads offshore over the eastern shelf and is trapped near the coast over the western shelf. Eastward extension of the plume retreats from June to August. Monthly spatial variations of the plume are characterized by eastward spreading, westward spreading, or both. Time series of monthly plume area was quantified by applying the K-mean clustering method to identify the turbid plume water. Decomposition of the 14-year monthly turbidity data by the empirical orthogonal function (EOF) analysis isolated the 1st mode in both the eastward and westward spreading pattern as the time series closely related to the Pearl River discharge, and the 2nd mode with out-of-phase turbidity anomalies over the eastern and western shelves that is associated with the prevailing wind direction. Eight typical plume types were detected from the satellite snapshots. They are characterized by coastal jet, eastward offshore spreading, westward spreading, bidirectional spreading, bulge, isolated patch, offshore branch, and offshore filaments, respectively. Their possible mechanisms are discussed.

Seasonal variability of living benthic foraminifera from the outer continental shelf of the Bay of Biscay

NASA Astrophysics Data System (ADS)

Duchemin, Gérald; Jorissen, Frans J.; Le Loc'h, François; Andrieux-Loyer, Françoise; Hily, Christian; Thouzeau, Gérard

2008-08-01

Living benthic foraminiferal faunas of six stations from the continental shelf of the Bay of Biscay have been investigated during three successive seasons (spring, summer and autumn 2002). For the three investigated stations, bottom water oxygen concentration, oxygen penetration into the sediment and sediment organic carbon contents are all relatively similar. Therefore, we think that the density and the composition of the foraminiferal faunas is mainly controlled by the quantity and quality of organic input resulting from a succession of phytoplankton bloom events, occurring from late February to early September. The earliest blooms are positioned at the shelf break, late spring and early summer blooms occur off Brittany, whereas in late summer and early autumn, only coastal blooms appear, often in the vicinity of river outlets. In spring, the benthic foraminiferal faunas of central (B, C and D) and outer (E) continental shelf stations are characterised by strong dominance in the first area and strong presence in the second area of Nonionella iridea. In fact, station E does not serve as a major depocenter for the remains of phytoplankton blooms. If station E is not considered, the densities of this taxon show a clear gradient from the shelf-break, where the species dominates the assemblages, to the coast, where it attains very low densities. We explain this gradient as a response to the presence, in early spring, of an important phytoplankton bloom, mainly composed of coccolithophorids, over the shelf break. This observation is supported by the maximum particles flux values at stations close to the shelf break (18.5 g m - 2 h - 1 ) and lower values in a station closer to the coast (6.8 g m - 2 h - 1 ). In summer, the faunal density is maximum at station A, relatively close to more varied phytoplancton blooms that occur off Brittany until early June. We suggest that the dominant species, Nonion fabum, Cassidulina carinata and Bolivina ex. gr. dilatata respond to phytodetritus input from these blooms. In autumn, the rich faunas of inner shelf station G are dominated by N. fabum, B. ex. gr. dilatata, Hyalinea balthica and Nonionella turgida. These taxa seem to be correlated with the presence of coastal blooms phenomena, in front of river outlets. They may be favoured by an organic input with a significant contribution of terrestrial, rather low quality organic matter.

Circulation in the Hudson Shelf Valley: MESA Physical Oceanographic Studies in New York Bight, 1

NASA Astrophysics Data System (ADS)

Mayer, Dennis A.; Han, Gregory C.; Hansen, Donald V.

1982-11-01

Over 900 days of current velocity data were obtained at mainly two locations in the inner and outer Hudson Shelf Valley (HSV). The large cross-axis depth gradients in the HSV, together with the strong winter cyclones and the baroclinic density distribution over the shelf, are primarily responsible for the major circulation features observed in the valley. CSTD data from 12 cruises and meteorological data from JFK International Airport and an environmental buoy were collected concurrently with the current meter data. Although the mean cross-shelf pressure gradient is generally seaward in the Middle Atlantic Bight, it is shoreward in the HSV below the level of the adjacent continental shelf (shelf horizon), thus imposing a bias toward upvalley flow. The average velocity below the surrounding shelf horizon in the HSV is upvalley or shoreward (west-northwestward ≈ 290° T) in the range of 2-5 cm/s. The circulation in the HSV is seasonal and individual events can drastically alter the mean picture. The several day average upvalley flow can sometimes approach 20 cm/s when intense winter cyclones pass over the bight and can sometimes also be directed downvalley depending upon the path of the winter cyclone. A topographically controlled barotropic flow commonly opposes the dominant (southeast-ward) wind direction even near the surface in the winter. In the context of circulation on the open shelf, upvalley (downvalley) flow events generated by winter cyclones are associated with reduced (enhanced) southwestward flow or flow reversals that are northeastward in the lower half of the water column at LTM, a typical mid/shelf site (Mayer et al., 1979). Current meter data suggest that whether or not reversals occur on the open shelf depends upon the interannual variability of the winter wind regime. Upvalley flow events are not confined only to the winter (unstratified) season but are stronger in the winter and can last for several days and longer. During the summer (stratified) season the maximum horizontal KE in the upper part of the water column shifts from the meteorological forcing band, characteristic of winter, to diurnal inertial and semidiurnal frequencies. In the diurnal band there appears to be a strong relationship between the diurnal wind and currents near the surface in the HSV as well as on the open shelf (LTM). The structure of the semidiurnal motions in the inner valley where the depth gradients are larger than in the outer valley has a significant depth dependence unlike most regions on the shelf, i.e., during all times of the year the semidiurnal tidal ellipse is anticlockwise in the lower 20 m of the water column.

Characterization of Queso Fresco made with Na/K salt blends and stored for 12 weeks

USDA-ARS?s Scientific Manuscript database

Health-conscious consumers are looking for ways to reduce dietary sodium yet want their cheeses to have the flavor, texture, and shelf-life of full-salt cheese. The objectives of this study were to determine the effects of different Na-K salt blends and storage on the compositional, sensorial, micro...

The use of SKYLAB in the study of productivity along the eastern shelf waters of the United States

NASA Technical Reports Server (NTRS)

Marshall, H. G.; Bowker, D. E.

1976-01-01

Data sampling from the Rappahannock River and Assateague Island areas are discussed correlating Skylab and ground based measurements. At all sampling stations, information was obtained on composition and density of phytoplankton, total chlorophyll, salinity and water temperature. The results of the water analysis are presented in tables.

Discrimination of fine-grained sediment provenance using geochemical elements on the inner shelf of the Korean Strait (South Sea), Korea

NASA Astrophysics Data System (ADS)

Um, I. K.; Choi, M. S.

2017-12-01

The central South Sea mud (CSSM) is located between the Heuksan mud belt (HMB) in the Yellow Sea and Korea Strait shelf mud (KSSM) in the East Sea and developed along the eastward transport pathway in the South Sea. Major elements (Al, Fe, Mg, and Ti), trace elements (Li, Cs, Sc, and Rb), and rare earth elements (REEs) in the fine-grained sediments (<15 μm) of thirty-two surface sediment samples on the CSSM were analyzed to determine the fine-grained sediment provenance. The spatial distribution of the analyzed elements showed a clear separation of the western (W-CSSM) and eastern (E-CSSM) regions of the CSSM. Concentrations of Fe, Ti, Mg, Sc, and REEs were higher in the W-CSSM, whereas concentrations of Al, Cs, Li, and Rb were higher in the E-CSSM. The ratios of trace metals ((Cs+Sc)/Li and Rb/Li) can be successfully used as a provenance indicator in the study area but REEs compositions could not be used to track the provenance of fine-grained sediments because of a grain size effect. The mixing relationships of the provenance indicators showed that the fine-grained sediments of the CSSM comprise a mixture of the sediments discharged from the Seomjin River (SRS) and sediments eroded and transported from the Heuksan mud belt (HMBS) area by the Korean coastal current. Sediments originating from the HMB were deposited mostly in the W-CSSM, whereas those from the Seomjin River were deposited mostly in the E-CSSM

The effects of trawling, dredging and ocean dumping on the eastern Canadian continental shelf seabed

NASA Astrophysics Data System (ADS)

Messieh, S. N.; Rowell, T. W.; Peer, D. L.; Cranford, P. J.

1991-08-01

This paper presents an overview of current knowledge on the effects of trawling, dredging and ocean dumping on the eastern Canadian continental shelf seabed. The impact of trawling and dredging for fish and shellfish on marine habitats has recently attracted international attention among fisheries and environmental scientists. In Atlantic Canada, trawling and dredging are the principal methods of harvesting groundfish and scallops and ocean clams, respectively. It is estimated that fish trawlers and scallop dredges have swept tracks, cris-crossing the Canadian continental shelf, approximately 4.3 million km in length in 1985. In the past few years several studies were carried out by scientists from Canada, the United States and Europe to assess the impacts of trawling and dredging but results were inconclusive. Some studies showed physical damage as well as biological effects, whereas others indicated that the adverse effects were not considered to be serious. Fishermen are not the only potential users of the resources of the continental shelf. There is an increasing demand for good-quality sand and gravel aggregate and the ocean seabed is being seen as a possible source. The eastern Canadian continental shelf also exhibits hydrocarbon potential and operational and accidental discharges are an environmental concern. Increased marine transportation and expansion of the fishing fleet have resulted in a greater need for harbour dredging. Dredging and dredge spoil disposal were controlled by the Ocean Dumping Control Act and now the Canadian Environmental Protection Act which places restrictions on the composition of material that can be disposed of in the sea. Nevertheless some harbours contain contaminant concentrations exceeding the maximum allowable limits. It is concluded that the impacts of human activities on the continental shelf seabed environment are inevitable and the long-term effects, while difficult to determine, must be assessed. The sub-lethal effects of increased suspended sediment loads on benthic organisms and potential changes to benthic community structure are major concerns and should be the focus of further research.

Infilling and flooding of the Mekong River incised valley during deglacial sea-level rise

NASA Astrophysics Data System (ADS)

Tjallingii, Rik; Stattegger, Karl; Wetzel, Andreas; Van Phach, Phung

2010-06-01

The abrupt transition from fluvial to marine deposition of incised-valley-fill sediments retrieved from the southeast Vietnamese shelf, accurately records the postglacial transgression after 14 ka before present (BP). Valley-filling sediments consist of fluvial mud, whereas sedimentation after the transgression is characterized by shallow-marine carbonate sands. This change in sediment composition is accurately marked in high-resolution X-ray fluorescence (XRF) core scanning records. Rapid aggradation of fluvial sediments at the river mouth nearly completely filled the Mekong incised valley prior to flooding. However, accumulation rates strongly reduced in the valley after the river-mouth system flooded and stepped back. This also affected the sediment supply to deeper parts of the southeast Vietnamese shelf. Comparison of the Mekong valley-filling with the East Asian sea-level history of sub- and inter-tidal sediment records shows that the transgressive surface preserved in the incised-valley-fill records is a robust sea-level indicator. The valley was nearly completely filled with fluvial sediments between 13.0 and 9.5 ka BP when sea-level rose rather constantly with approximately 10 mm/yr, as indicated by the East Asian sea-level record. At shallower parts of the shelf, significant sediment reworking and the establishment of estuarine conditions at the final stage of infilling complicates accurate dating of the transgressive surface. Nevertheless, incised-valley-fill records and land-based drill sites indicate a vast and rapid flooding of the shelf from the location of the modern Vietnamese coastline to the Cambodian lowlands between 9.5 ka and 8.5 ka BP. Fast flooding of this part of the shelf is related with the low shelf gradient and a strong acceleration of the East Asian sea-level rise from 34 to 9 meter below modern sea level (mbsl) corresponding to the sea-level jump of melt water pulse (MWP) 1C.

Flexible chitosan-nano ZnO antimicrobial pouches as a new material for extending the shelf life of raw meat.

PubMed

Rahman, P Mujeeb; Mujeeb, V M Abdul; Muraleedharan, K

2017-04-01

As a breakthrough to open up the industrial use of novel environmentally benign packaging material, we propose the first report on portable chitosan-ZnO nano-composite pouches that will serve as elite entrants in smart packaging. A facile, one pot procedure was adopted for the preparation of the C-ZnC films. In order to tune the property of C-ZnC films, four different composite films were prepared by varying the concentration of ZnO. The prepared films were found to be much superior when compared to bare chitosan and other conventional films. Two bacterial strains that commonly contaminate in packed meat were selected as target microbes to elucidate the antimicrobial activity of the prepared C-ZnO film. Detailed investigations revealed that the antimicrobial efficiency is linearly related to the amount of ZnO nano-particles in the composite. The C-2 films exhibited excellent antimicrobial activity and was fabricated into packaging pouches for raw meat. The prepared pouches showed significant action against the microbes in raw meat owing to its complete inhibition of microbial growth on the sixth day of storage at 4°C. The C-2 pouches stand as a top-notch material when compared to polyethylene bag in extending the shelf life of raw meat. Copyright © 2017 Elsevier B.V. All rights reserved.

Pathways of warm water to the Northeast Greenland outlet glaciers

NASA Astrophysics Data System (ADS)

Schaffer, Janin; Timmermann, Ralph; Kanzow, Torsten; Arndt, Jan Erik; Mayer, Christoph; Schauer, Ursula

2015-04-01

The ocean plays an important role in modulating the mass balance of the Greenland Ice Sheet by delivering heat to the marine-terminating outlet glaciers surrounding the Greenland coast. The warming and accumulation of Atlantic Water in the subpolar North Atlantic has been suggested to be a potential driver of the glaciers' retreat over the last decades. The shelf regions thus play a critical role for the transport of Atlantic Water towards the glaciers, but also for the transfer of freshwater towards the deep ocean. A key region for the mass balance of the Greenland Ice Sheet is the Northeast Greenland Ice Stream. This large ice stream drains the second-largest basin of the Greenland Ice Sheet and feeds three outlet glaciers. The largest one is Nioghalvfjerdsfjorden (79°N-Glacier) featuring an 80 km long floating ice tongue. Both the ocean circulation on the continental shelf off Northeast Greenland and the circulation in the cavity below the ice tongue are weakly constrained so far. In order to study the relevant processes of glacier-ocean interaction we combine observations and model work. Here we focus on historic and recent hydrographic observations and on the complex bathymetry in the Northeast Greenland shelf region, which is thought to steer the flux of warm Atlantic water onto the continental shelf and into the sub-ice cavity beneath the 79°N-Glacier. We present a new global topography data set, RTopo-2, which includes the most recent surveys on the Northeast Greenland continental shelf and provides a detailed bathymetry for all around Greenland. In addition, RTopo-2 contains ice and bedrock surface topographies for Greenland and Antarctica. Based on the updated ocean bathymetry and a variety of hydrographic observations we show the water mass distribution on the continental shelf off Northeast Greenland. These maps enable us to discuss possible supply pathways of warm modified Atlantic waters on the continental shelf and thus potential ways of heat transport towards the base of the 79°N-Glacier.

Stratigraphic framework of sediment-starved sand ridges on a mixed siliciclastic/carbonate inner shelf; west-central Florida

USGS Publications Warehouse

Edwards, J.H.; Harrison, S.E.; Locker, S.D.; Hine, A.C.; Twichell, D.C.

2003-01-01

Seismic reflection profiles and vibracores have revealed that an inner shelf, sand-ridge field has developed over the past few thousand years situated on an elevated, broad bedrock terrace. This terrace extends seaward of a major headland associated with the modern barrier-island coastline of west-central Florida. The overall geologic setting is a low-energy, sediment-starved, mixed siliciclastic/carbonate inner continental shelf supporting a thin sedimentary veneer. This veneer is arranged in a series of subparallel, shore-oblique, and to a minor extent, shore-parallel sand ridges. Seven major facies are present beneath the ridges, including a basal Neogene limestone gravel facies and a blue-green clay facies indicative of dominantly authigenic sedimentation. A major sequence boundary separates these older units from Holocene age, organic-rich mud facies (marsh), which grades upward into a muddy sand facies (lagoon or shallow open shelf/seagrass meadows). Cores reveal that the muddy shelf facies is either in sharp contact or grades upward into a shelly sand facies (ravinement or sudden termination of seagrass meadows). The shelly sand facies grades upward to a mixed siliciclastic/carbonate facies, which forms the sand ridges themselves. This mixed siliciclastic/carbonate facies differs from the sediment on the beach and shoreface, suggesting insignificant sediment exchange between the offshore ridges and the modern coastline. Additionally, the lack of early Holocene, pre-ridge facies in the troughs between the ridges suggests that the ridges themselves do not migrate laterally extensively. Radiocarbon dating has indicated that these sand ridges can form relatively quickly (???1.3 ka) on relatively low-energy inner shelves once open-marine conditions are available, and that frequent, high-energy, storm-dominated conditions are not necessarily required. We suggest that the two inner shelf depositional models presented (open-shelf vs. migrating barrier-island) may have co-existed spatially and/or temporally to explain the distribution of facies and vertical facies contacts. ?? 2003 Elsevier B.V. All rights reserved.

Impacts and recovery from severe tropical cyclone Yasi on the Great Barrier Reef.

PubMed

Beeden, Roger; Maynard, Jeffrey; Puotinen, Marjetta; Marshall, Paul; Dryden, Jen; Goldberg, Jeremy; Williams, Gareth

2015-01-01

Full recovery of coral reefs from tropical cyclone (TC) damage can take decades, making cyclones a major driver of habitat condition where they occur regularly. Since 1985, 44 TCs generated gale force winds (≥17 metres/second) within the Great Barrier Reef Marine Park (GBRMP). Of the hurricane strength TCs (≥H1-Saffir Simpson scale; ≥ category 3 Australian scale), TC Yasi (February, 2011) was the largest. In the weeks after TC Yasi crossed the GBRMP, participating researchers, managers and rangers assessed the extent and severity of reef damage via 841 Reef Health and Impact Surveys at 70 reefs. Records were scaled into five damage levels representing increasingly widespread colony-level damage (1, 2, 3) and reef structural damage (4, 5). Average damage severity was significantly affected by direction (north vs south of the cyclone track), reef shelf position (mid-shelf vs outer-shelf) and habitat type. More outer-shelf reefs suffered structural damage than mid-shelf reefs within 150 km of the track. Structural damage spanned a greater latitudinal range for mid-shelf reefs than outer-shelf reefs (400 vs 300 km). Structural damage was patchily distributed at all distances, but more so as distance from the track increased. Damage extended much further from the track than during other recent intense cyclones that had smaller circulation sizes. Just over 15% (3,834 km2) of the total reef area of the GBRMP is estimated to have sustained some level of coral damage, with ~4% (949 km2) sustaining a degree of structural damage. TC Yasi likely caused the greatest loss of coral cover on the GBR in a 24-hour period since 1985. Severely impacted reefs have started to recover; coral cover increased an average of 4% between 2011 and 2013 at re-surveyed reefs. The in situ assessment of impacts described here is the largest in scale ever conducted on the Great Barrier Reef following a reef health disturbance.

Impacts and Recovery from Severe Tropical Cyclone Yasi on the Great Barrier Reef

PubMed Central

Beeden, Roger; Maynard, Jeffrey; Puotinen, Marjetta; Marshall, Paul; Dryden, Jen; Goldberg, Jeremy; Williams, Gareth

2015-01-01

Full recovery of coral reefs from tropical cyclone (TC) damage can take decades, making cyclones a major driver of habitat condition where they occur regularly. Since 1985, 44 TCs generated gale force winds (≥17 metres/second) within the Great Barrier Reef Marine Park (GBRMP). Of the hurricane strength TCs (≥H1—Saffir Simpson scale; ≥ category 3 Australian scale), TC Yasi (February, 2011) was the largest. In the weeks after TC Yasi crossed the GBRMP, participating researchers, managers and rangers assessed the extent and severity of reef damage via 841 Reef Health and Impact Surveys at 70 reefs. Records were scaled into five damage levels representing increasingly widespread colony-level damage (1, 2, 3) and reef structural damage (4, 5). Average damage severity was significantly affected by direction (north vs south of the cyclone track), reef shelf position (mid-shelf vs outer-shelf) and habitat type. More outer-shelf reefs suffered structural damage than mid-shelf reefs within 150 km of the track. Structural damage spanned a greater latitudinal range for mid-shelf reefs than outer-shelf reefs (400 vs 300 km). Structural damage was patchily distributed at all distances, but more so as distance from the track increased. Damage extended much further from the track than during other recent intense cyclones that had smaller circulation sizes. Just over 15% (3,834 km2) of the total reef area of the GBRMP is estimated to have sustained some level of coral damage, with ~4% (949 km2) sustaining a degree of structural damage. TC Yasi likely caused the greatest loss of coral cover on the GBR in a 24-hour period since 1985. Severely impacted reefs have started to recover; coral cover increased an average of 4% between 2011 and 2013 at re-surveyed reefs. The in situ assessment of impacts described here is the largest in scale ever conducted on the Great Barrier Reef following a reef health disturbance. PMID:25874718

Nd isotopic composition and REE pattern in the surface waters of the eastern Indian Ocean and its adjacent seas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amakawa, Hiroshi; Alibo, D.S.; Nozaki, Yoshiyuki

2000-05-01

The Nd isotopic composition and dissolved rare earth elements (REEs) have been measured in the surface waters along the 1996/97 R.V. Hakuho-Maru Expedition route from Tokyo to the Southern Ocean, southwest of Australia, through the Philippine and Indonesian Archipelago, the eastern Indian Ocean, the Bay of Bengal and the South China Sea. The radiogenic {epsilon}{sub Nd} values of {minus}1.3 and {minus}1.4 were found in the Sulu Sea and near the Lombok Strait, indicating the strong influence of surrounding volcanic islands, whereas non-radiogenic {epsilon}{sub Nd} values of less than {minus}10 were found in the Southern Ocean and the Bay of Bengalmore » suggesting Nd of continental origin. The dissolved Nd concentrations also showed a wide range of variation from 2.8 to 19.6 pmol/kg and the trivalent REE patterns exhibited characteristic features that can be grouped into each different oceanic province. The geographical distribution of dissolved Nd is different from that of atmospherically derived {sup 210}Pb, but generally resembles that of coastally derived {sup 228}Ra. This strongly suggests that fluvial and coastal input predominates over eolian input for dissolved Nd in the surface ocean. However, the riverine dissolved Nd flux appears to be relatively minor, and remobilization of Nd from coastal and shelf sediments may play an important role in the total Nd input to the ocean. By modeling the distributions of the isotopic composition and concentration of Nd together with the activity ratio of {sup 228}Ra/{sup 226}Ra in the southeastern Indian Ocean, the authors estimate a mean residence time of Nd in the surface mixed layer to be 1.5--2.6 years. The short mean residence time is comparable with, or slightly longer than that of {sup 210}Pb suggesting similar chemical reactivity.« less

Late quaternary geologic framework, north-central Gulf of Mexico

USGS Publications Warehouse

Kindinger, Jack G.; Penland, Shea; Williams, S. Jeffress; Brooks, Gregg R.; Suter, John R.; McBride, Randolph A.

1991-01-01

The geologic framework of the north-central Gulf of Mexico shelf is composed of multiple, stacked, delta systems. Shelf and nearshore sedimentary facies were deposited by deltaic progradation, followed by shoreface erosion and submergence. A variety of sedimentary facies has been identified, including prodelta, delta fringe, distributary, lagoonal, barrier island, and shelf sand sheet. This study is based on the interpretation and the synthesis of > 6,700 km of high-resolution seismic profiles, 75 grab samples, and 77 vibracores. The nearshore morphology, shallow stratigraphy, and sediment distribution of the eastern Louisiana shelf are the products of transgressive sedimentary processes reworking the abandoned St. Bernard delta complex. Relatively recent Mississippi delta lobe consists primarily of fine sand, silt, and clay. In the southern portion of the St. Bernard delta complex, asymmetrical sand ridges (>5 m relief) have formed as the result of marine reworking of distributary mouth-bar sands. Silty sediments from the modern Mississippi Birdsfoot delta onlap the St. Bernard delta complex along the southern edge. The distal margin of the St. Bernard complex is distinct and has a sharp contact on the north near the Mississippi Sound barrier island coastline and a late Wisconsinan delta to the south. The Chandeleur Islands and the barrier islands of Mississippi Sound have been formed by a combination of Holocene and Pleistocene fluvial processes, shoreface erosion, and ravinement of the exposed shelf. Sediments underlying the relatively thin Holocene sediment cover are relict fluvial sands, deposited during the late Wisconsinan lowstand. Subsequent relative sea-level rise allowed marine processes to rework and redistribute sediments that formed the nearshore fine-grained facies and the shelf sand sheet.

Significance of a Shelf-wide Dissolution Event during the Paleocene-Eocene Thermal Maximum, Maryland and New Jersey, USA

NASA Astrophysics Data System (ADS)

Bralower, T. J.; Kump, L. R.; Robinson, M. M.; Self-Trail, J. M.; Zachos, J. C.

2016-12-01

Continental-shelf sediments of the US Atlantic margin experienced a brief episode of carbonate dissolution during the onset of the Paleocene-Eocene Thermal Maximum (PETM). Dissolution is represented by reduced percentages of carbonate, and calcareous microfossil distribution and preservation trends, in cores from Maryland and New Jersey. The base and the top of the dissolution zone are abrupt compared to the gradual nature of the onset of the carbon isotope excursion (CIE). The thickness of the dissolution zone varies from 9 cm in the Bass River core (outer paleoshelf) to 1.6 m in the CamDor core (middle paleoshelf). The decrease in %CaCO3 suggests dissolution locally removed 83 to 100% of the initial biogenic carbonate. Shelf-wide dissolution during the onset of the PETM may be a regional event, associated, for example, with eutrophication. Samples from across the paleoshelf contain abundant fine-grained framboidal pyrite, which suggests photic-zone euxinia occurred before, during, and after the dissolution event. Dissolution may also be associated with oxidation of this pyrite during later exposure to oxidizing groundwaters, although the restricted duration of the dissolution interval argues against this. Alternatively, the dissolution event may have global significance related to surface ocean-water acidification or shoaling of the calcite compensation depth (CCD) to shelf depths. The event began near the onset of the CIE on the shelf, whereas dissolution in deep-sea sections began later. Earlier shelf dissolution is consistent with surface ocean acidification while later deep-sea dissolution is thought to be associated with shoaling of the CCD. In our presentation, we weigh evidence for each of these possibilities and test them using the global dataset.

Evaluation of Water Residence Time, Submarine Groundwater Discharge, and Maximum New Production Supported by Groundwater Borne Nutrients in a Coastal Upwelling Shelf System

NASA Astrophysics Data System (ADS)

Luo, Xin; Jiao, Jiu Jimmy; Liu, Yi; Zhang, Xiaolang; Liang, Wenzhao; Tang, Danling

2018-01-01

The biogeochemical processes in the continental shelf systems are usually extensively influenced by coastal upwelling and submarine groundwater discharge (SGD). Using eastern Hainan upwelling shelf system as an example, this study fully investigates SGD and coastal upwelling and their effects on the coastal nutrient loadings to the mixing layer of eastern Hainan shelf. Based on the spatial distributions of 223Ra and 228Ra, water residence time is estimated to be 16.9 ± 8.9 days. Based on the mass balance models of 226Ra and 228Ra, the total SGD of the eastern Hainan shelf is estimated to be 0.8 × 108 and 1.4 × 108 m3 d-1, respectively. The groundwater borne dissolved inorganic nitrogen (DIN) and dissolved inorganic phosphate (DIP) are estimated to be up to 1121.8 and 20.4 μM m2 d-1. The coastal upwelling delivers 2741.8 μM m2 d-1 DIN and 217.7 μM m2 d-1 DIP into the mixing layer, which are predominant in all the exogenous nutrient inputs. The groundwater borne DIN will support a maximum new production of 7.5 mM C m2 d-1, about up to 24.0% of the total new production in the study area. SGD-derived nutrient could be significant as a missing DIN to support the new production in the mixing layer of eastern Hainan shelf. The findings contribute to a better understanding of biogeochemical processes under the influences of SGD and coastal upwelling in the study area and other similar coastal upwelling systems.

Satellite and hydrographic observations of the Bering Sea ‘Green Belt’

NASA Astrophysics Data System (ADS)

Okkonen, Stephen R.; Schmidt, G. M.; Cokelet, E. D.; Stabeno, P. J.

2004-05-01

Green Belt is the aptly named region of high productivity occurring principally along and above the shelf-slope boundary in the Bering Sea. TOPEX altimeter measurements of sea-surface topography, SeaWiFS imagery of chlorophyll a concentration, and shipboard measurements of salinity and fluorescence are used to describe the surface structure of the Green Belt and its relationship to the Bering Slope Current eddy field during the 2000, 2001, and 2002 spring blooms. During spring 2000, high surface chlorophyll a concentrations (>10 mg m -3) were observed within a ˜200-km wide band adjacent to and seaward of the shelf break in the northwest Bering Sea. This high concentration chlorophyll band was associated with an anticyclonic eddy group that propagated along isobaths above the continental slope and entrained chlorophyll from the shelf-slope front. During spring 2001, anticyclonic eddies in the northwest Bering Sea had propagated off-slope prior to the onset of the spring bloom and were too far from the shelf-slope front to entrain frontal chlorophyll during the bloom. A second chlorophyll front associated with the leading edge of the off-slope eddies was observed. Between these two fronts was a region of relatively low chlorophyll a concentration (˜1 mg m -3). The eddy field during the 2002 spring bloom was observed to propagate northwestward adjacent to the shelf-break and entrain chlorophyll from the shelf-slope region in a manner similar to what was observed during the 2000 spring bloom. These observations suggest that eddies are important, if not the principal, agents that cause variability in the distribution of chlorophyll during the spring bloom in the central Bering Sea.

Maps showing the change in modern sediment thickness on the Inner Continental Shelf offshore of Fire Island, New York, between 1996-97 and 2011

USGS Publications Warehouse

Schwab, William C.; Baldwin, Wayne E.; Denny, Jane F.

2015-01-01

The U.S. Geological Survey mapped approximately 336 square kilometers of the lower shoreface and inner continental shelf offshore of Fire Island, New York, in 1996 and 1997, using high-resolution sidescan-sonar and seismic-reflection systems, and again in 2011, using interferometric sonar and high-resolution chirp seismic-reflection systems. This report presents a comparison of sediment thickness and distribution as mapped during these two investigations. These spatial data support research on the Quaternary evolution of the Fire Island coastal system and provide baseline information for research on coastal processes along southern Long Island.

Matrix association effects on hydrodynamic sorting and degradation of terrestrial organic matter during cross-shelf transport in the Laptev and East Siberian shelf seas

NASA Astrophysics Data System (ADS)

Tesi, Tommaso; Semiletov, Igor; Dudarev, Oleg; Andersson, August; Gustafsson, Örjan

2016-03-01

This study seeks an improved understanding of how matrix association affects the redistribution and degradation of terrigenous organic carbon (TerrOC) during cross-shelf transport in the Siberian margin. Sediments were collected at increasing distance from two river outlets (Lena and Kolyma Rivers) and one coastal region affected by erosion. Samples were fractionated according to density, size, and settling velocity. The chemical composition in each fraction was characterized using elemental analyses and terrigenous biomarkers. In addition, a dual-carbon-isotope mixing model (δ13C and Δ14C) was used to quantify the relative TerrOC contributions from active layer (Topsoil) and Pleistocene Ice Complex Deposits (ICD). Results indicate that physical properties of particles exert first-order control on the redistribution of different TerrOC pools. Because of its coarse nature, plant debris is hydraulically retained in the coastal region. With increasing distance from the coast, the OC is mainly associated with fine/ultrafine mineral particles. Furthermore, biomarkers indicate that the selective transport of fine-grained sediment results in mobilizing high-molecular weight (HMW) lipid-rich, diagenetically altered TerrOC while lignin-rich, less degraded TerrOC is retained near the coast. The loading (µg/m2) of lignin and HMW wax lipids on the fine/ultrafine fraction drastically decreases with increasing distance from the coast (98% and 90%, respectively), which indicates extensive degradation during cross-shelf transport. Topsoil-C degrades more readily (90 ± 3.5%) compared to the ICD-C (60 ± 11%) during transport. Altogether, our results indicate that TerrOC is highly reactive and its accelerated remobilization from thawing permafrost followed by cross-shelf transport will likely represent a positive feedback to climate warming.

Surface and basal ice shelf mass balance processes of the Southern McMurdo Ice Shelf determined through radar statistical reconnaissance

NASA Astrophysics Data System (ADS)

Grima, C.; Koch, I.; Greenbaum, J. S.; Soderlund, K. M.; Blankenship, D. D.; Young, D. A.; Fitzsimons, S.

2017-12-01

The McMurdo ice shelves (northern and southern MIS), adjacent to the eponymous station and the Ross Ice Shelf, Antarctica, are known for large gradients in surface snow accumulation and snow/ice impurities. Marine ice accretion and melting are important contributors to MIS's mass balance. Due to erosive winds, the southern MIS (SMIS) shows a locally negative surface mass balance. Thus, marine ice once accreted at the ice shelf base crops out at the surface. However, the exact processes that exert primary control on SMIS mass balance have remained elusive. Radar statistical reconnaissance (RSR) is a recent technique that has been used to characterize the surface properties of the Earth's cryosphere, Mars, and Titan from the stochastic character of energy scattered by the surface. Here, we apply RSR to map the surface density and roughness of the SMIS and extend the technique to derive the basal reflectance and scattering coefficients of the ice-ocean interface. We use an airborne radar survey grid acquired over the SMIS in the 2014-2015 austral summer by the University of Texas Institute for Geophysics with the High Capability Radar Sounder (HiCARS2; 60-MHz center frequency and 15-MHz bandwidth). The RSR-derived snow density values and patterns agree with directly -measured ice shelf surface accumulation rates. We also compare the composition of SMIS ice surface samples to test the ability of RSR to discriminate ices with varying dielectric properties (e.g., marine versus meteoric ice) and hypothesize relationships between the RSR-derived basal reflectance/scattered coefficients and accretion or melting at the ice-ocean interface. This improved knowledge of air-ice and ice-ocean boundaries provides a new perspective on the processes governing SMIS surface and basal mass balance.

Mineralogical influences on porosity-depth trends of shelf deposits (Miocene-Pleistocene) along the northwest shelf of Australia (IODP Expedition 356)

NASA Astrophysics Data System (ADS)

Knierzinger, Wolfgang; Lee, Eun Young; Wagreich, Michael

2017-04-01

Porosity in sediments is influenced by various factors such as mineralogical composition, burial depth, connate fluids, and stratigraphic layering. This work focuses on processes underlying porosity anomalies in carbonate shelf deposits along the northwest shelf of Australia by using different techniques (polarization microscopy, electron microscopy, XRD, XRF). IODP expedition 356 recovered cored seven sites (U1458-U1464), covering a latitudinal range of 29°S-18°S on the northwest shelf. Strong negative deviations from general porosity-depth trends for these carbonate rich sediments are clear for samples with higher contents of dolomite, calcium sulfates, and non-skeletal calcite. No significant influence of aragonite on porosity values has yet been detected. However, it is likely that the occurrence of high amounts of aragonite is a crucial element with regard to porosity values in these carbonate rich deposits, since elongated aragonite needles commonly enhance interparticle porosity. Further insight might be gained through the application of electron microscopy. In general, sediments in the northern part of the study area (Sites U1462, U1463, U1464) tend to show slightly higher porosity values compared to sediments form the south (Sites U1459, U1460). This may reflect the influence of calcium sulfate, because mineralogical analyses show, calcium sulfate is relatively rare at the southern sites, whereas higher amounts of calcium sulfates occur in the north. The lack of detrital particles in calcium sulfate components indicates an evaporitic origin. Deposits at Site U 1461 differ from other analyzed sediments insofar as higher amounts of feldspars and micas are apparent. *This research is conducted within the frame of the 'International Ocean Discovery Program', funded by the Ministry of Oceans and Fisheries, Korea.

Aragonite undersaturation in the Arctic Ocean: effects of ocean acidification and sea ice melt.

PubMed

Yamamoto-Kawai, Michiyo; McLaughlin, Fiona A; Carmack, Eddy C; Nishino, Shigeto; Shimada, Koji

2009-11-20

The increase in anthropogenic carbon dioxide emissions and attendant increase in ocean acidification and sea ice melt act together to decrease the saturation state of calcium carbonate in the Canada Basin of the Arctic Ocean. In 2008, surface waters were undersaturated with respect to aragonite, a relatively soluble form of calcium carbonate found in plankton and invertebrates. Undersaturation was found to be a direct consequence of the recent extensive melting of sea ice in the Canada Basin. In addition, the retreat of the ice edge well past the shelf-break has produced conditions favorable to enhanced upwelling of subsurface, aragonite-undersaturated water onto the Arctic continental shelf. Undersaturation will affect both planktonic and benthic calcifying biota and therefore the composition of the Arctic ecosystem.

Preliminary Results from Acoustic Survey Offshore Kefken, Southwestern Black Sea Margin

NASA Astrophysics Data System (ADS)

Dondurur, Derman; Karaca, Onur; Nasıf, Aslıhan

2017-04-01

In March 2016, different marine acoustic datasets were collected aboard of R/V K. Piri Reis research vessel of Dokuz Eylül University within the scope of Turkish Research Council (Tübitak) Project (115Y218) to reveal submarine morphology and seismo-acoustical structure of the continental shelf and upper slope of Şile-Kefken region in the southwest of the Black Sea. A total of 1564 km high resolution seismic, multibeam bathymetry and Chirp sub-bottom profiler data were collected. Seismic data was collected using a 1500 m long digital streamer with 240 active channels. Group and shot intervals were 6.25 m and 25 m, respectively. Collected data were analyzed by means of (i) stratigraphic and (ii) structural components, and (iii) the structure of upper slope and shelf break. The stratigraphic elements in the region indicate the existence of Eocene and younger units. A distinctive acoustical basement in the seismic data observed throughout the shelf which is interpreted as uplifted Cretaceous basement of the Black Sea, that is Akveren or Yemişliçay Formation. The basement also outcrops around the Kefken Island. Chirp data is used to map the shallow stratigraphy of the shelf including the Holocene sediment distribution which exists on a very restricted area on the shelf. To the east, there is a large outcrop zone offshore Kefken where no Holocene sediments are observed. Initial evaluation of the collected data indicates that there is no present day delta formation in the area due to a few weak streams observed in the study area. The penetration of Chirp data in the western and the southern parts of the shelf area is very limited while it increases towards to upper continental slope to the North, and east of Kefken Cape. The acoustic data suggests that the study area is under the influence of the Pontide overthrust. Possible existence of reverse faults of Pontide overthrust is evident on the seismic data from southwestern shelf. In addition to the reverse faults to the SW, the whole shelf is highly affected by a northwards trending strike slip fault system with a significant vertical slip. Canyon heads and shelf break is deformed by numerous near vertical normal faults. Multibeam bathymetric data indicate that the upper slope is formed by highly steep canyon heads with several small scale gullies connecting to the thalweg at low angles.

Seasonal uranium distributions in the coastal waters off the Amazon and Mississippi Rivers

USGS Publications Warehouse

Swarzenski, P.W.; McKee, B.A.

1998-01-01

The chemical reactivity of uranium was investigated across estuarine gradients from two of the world's largest river systems: the Amazon and Mississippi. Concentrations of dissolved (<0.45 ??m) uranium (U) were measured in surface waters of the Amazon shelf during rising (March 1990), flood (June 1990) and low (November 1991) discharge regimes. The dissolved U content was also examined in surface waters collected across estuarine gradients of the Mississippi outflow region during April 1992, August 1993, and November (1993). All water samples were analyzed for U by isotope dilution inductively coupled plasma mass spectrometry (ICP-MS). In Amazon shelf surface waters uranium increased nonconservatively from about 0.01 ??g l-1 at the river's mouth to over 3 ??g l-1 at the distal site, irrespective of river discharge stage. Observed large-scale U removal at salinities generally less than 15 implies a) that riverine dissolved U was extensively adsorbed by freshly-precipitated hydrous metal oxides (e.g., FeOOH, MnO2) as a result of flocculation and aggregation, and b) that energetic resuspension and reworking of shelf sediments and fluid muds on the Amazon shelf released a chemically reactive particle/colloid to the water column which can further scavenge dissolved U across much of the estuarine gradient. In contrast, the estuarine chemistry of U is inconclusive within surface waters of the Mississippi shelf-break region. U behavior is most likely controlled less by traditional sorption and/or desorption reactions involving metal oxides or colloids than by the river's variable discharge regime (e.g., water parcel residence time during estuarine mixing, nature of particulates, sediment storage and resuspension in the confined lower river), and plume dispersal. Mixing of the thin freshwater lens into ambient seawater is largely defined by wind-driven rather than physical processes. As a consequence, in the Mississippi outflow region uranium predominantly displays ConserVative behavior; removal is evident only during anomalous river discharge regimes. 'Products-approach' mixing experiments conducted during the Flood of 1993 suggest the importance of small particles and/or colloids in defining a depleted U versus salinity distribution.

Southeast Georgia embayment high-resolution seismic-reflection survey

USGS Publications Warehouse

Edsall, Douglas W.

1979-01-01

A high-resolution seismic survey of the offshore part of the Southeast Georgia Embayment on about a 20 km spacing was completed in 1976. A stratigraphic analyses of the data shows that the largest controlling factor in the depositional history of the shelf has been the Gulf Stream. These currents have shifted back and forth across the shelf, at times incising into shelf sediments, and at all times blocking much of the accumulation of Cenozoic sediments seaward of the Florida-Hatteras Slope. In the southern region the Gulf Stream maintained its present position since Miocene time, blocking the accumulation of Pliocene and younger rocks on the Plateau. Northward, in the middle, region the currents turned slightly to the northeast. The inner portion of the Blake Plateau has been scoured of sediments since the Paleocene in this area, and scouring has also occurred on the shelf from time to time. In the northern part of the survey area a more easterly flow of the Gulf Stream has allowed Eocene and younger rocks to be deposited on the Plateau. Line drawings and a geologic map show the distribution of the various Cretaceous and Cenozoic units. A number of potential environmental hazards or constraints to petroleum development seen in the reflection data are identified. Besides current scour and erosion features, these include gravity faults on the slope, a slump, faulting on the inner Blake Plateau, the shelf edge reef, and deep water reefs on the Blake Plateau.

The NOWESP research data base

NASA Astrophysics Data System (ADS)

Radach, G.; Gekeler, J.; Becker, G.; Bot, P.; Castaing, P.; Colijn, F.; Damm, P.; Danielssen, D.; Føyn, L.; Gamble, J.; Laane, R.; Mommaerts, J. P.; Nehring, D.; Pegler, K.; van Raaphorst, W.; Wilson, J.

1996-09-01

In the NOWESP project historical data from the Northwest European Shelf were compiled and evaluated to estimate the variability and trends in water movements, concentrations of dissolved and particulate constituents, and fluxes of the relevant substances across the shelf. As an integral part of the project, the NOWESP Research Data Base was created as a research tool to provide the data and data products needed for the analyses within the project. The tasks of the NOWESP Research Data Base group were the acquisition of the relevant data sets, with the intensive support of all partners, organization of the data sets in the NOWESP Research Data Base, merging of the specific data sets for the ten main state variables used in NOWESP, and the provision of data products for analysis within NOWESP. The data compiled during NOWESP represent a unique data set for the Northwest European Shelf. The data set is sufficiently comprehensive to allow the definition of long time series at about 14 sites in eight areas. It further enables the derivation of mean annual cycles of horizontal distributions of nine main state variables. NOWESP thus has provided valuable data sets for estimating budgets and fluxes across the shelf and, in addition, important data sets for the forcing and validation of ecological shelf sea models. An overview of the NOWESP data set is given. The organization of the data base is described in some detail, and examples of the products obtained for NOWESP are displayed.

Chemical evidence of the changes of the Antarctic Bottom Water ventilation in the western Ross Sea between 1997 and 2003

NASA Astrophysics Data System (ADS)

Rivaro, Paola; Massolo, Serena; Bergamasco, Andrea; Castagno, Pasquale; Budillon, Giorgio

2010-05-01

Data from three Italian CLIMA project cruises between 1997 and 2003 were used to obtain sections of the hydrographic and chemical properties of the main water masses across the shelf break off Cape Adare (western Ross Sea, Antarctica). Dissolved oxygen, nitrate and phosphate data were combined on the basis of the Redfield ratio to obtain the quasi-conservative tracers NO (9[NO 3]+[O 2]), PO (135[PO 4]+[O 2]) and phosphate star PO4* ( PO4*=[PO 4]+[O 2]/175-1.95). In 1997 and 2003 the presence of the High Salinity Shelf Water at the bottom depth near the sill was traced by both physical and chemical measurements. In 2001 the Modified Shelf Water, characterized by warmer temperature and by a lower dissolved oxygen content than High Salinity Shelf Water, was observed at the shelf edge. The distribution of the chemical tracers together with the hydrographic observations showed recently formed Antarctic Bottom Water on the continental slope during all of the cruises. These observations were confirmed by the extended optimum multiparameter analysis. The calculated thickness of the new Antarctic Bottom Water, as well as the tracer content, were variable in time and in space. The estimated volume of the new Antarctic Bottom Water and the export of dissolved oxygen and nutrient associated with the overflowing water were different over the examined period. In particular, a lower (˜55%) export was evidenced in 2001 compared to 1997.

A seismic study of the Mekong subaqueous delta: Proximal versus distal sediment accumulation

NASA Astrophysics Data System (ADS)

Liu, J. Paul; DeMaster, David J.; Nittrouer, Charles A.; Eidam, Emily F.; Nguyen, Thanh T.

2017-09-01

The Mekong River Delta is one of the largest in Asia. To understand its sediment distribution, thickness, mass budget, stratigraphic sequences and sediment-transport process, extensive geophysical and geochemical surveys were conducted on the inner portions of the adjacent continental shelf. Analyses of > 80 high-resolution Chirp-sonar profiles show the Mekong River has formed a classic sigmoidal cross-shelf clinoform in the proximal areas, up to 15 m thick, with topset, foreset and bottomset facies, but constrained to water depths of < 20 m. Beyond this depth, the East Sea/western South China Sea shelf is dominated by relict silt, sand and gravel with patches of early to middle Holocene mud deposits. Parallel to shore, the Mekong-derived sediment has extended > 250 > 300 km southwestward to the tip of the Ca Mau Peninsula, forming a distal mud depocenter up to 22 m thick, and extending into the Gulf of Thailand. A large erosional trough or channel (up to 8 m deeper than the surrounding seafloor and parallel to the shore) was found on the top of the clinoform, east of the Ca Mau Peninsula. Based on the thicknesses and distribution revealed by Chirp sonar profiles, the total estimated volume of the Mekong River subaqueous clinoform on the shelf is 120 km3, which is equivalent to 120-140 × 109 t of sediment using an average sediment dry-bulk density of 1.0-1.2 g/cm3. Assuming the subaqueous deltaic deposit has formed within 1000 yr, the calculated millennial-timescale average sediment discharge to the shelf could be 120-140 × 106 t per year. Spatially, the proximal subaqueous delta has accumulated 45 × 109 t ( 33%) of sediment; the distal part around the Ca Mau Peninsula has received 55 × 109 t ( 42%) of sediment; and the remaining 35 × 109 t ( 25%) has accumulated within the central transition area, although the coastline and shoreface in this area are presently eroding. The spatially averaged 1000-yr-scale accumulate rate is up to 2 cm/yr. Compared to other tide-dominated fluvial dispersal systems, the Mekong River system has a relatively young (≤1000 yr) subaqueous delta, a shallow rollover at 4-6 m water depth, gentle foreset gradients (0.03-0.57°), and a short cross-shelf dimension of 15-20 km within 20-m water depth. Like the Amazon, Po, and Yangtze rivers, the Mekong River has developed a pervasive along-shelf deposit, which in this case extends > 250 > 300km to the southwest as a result of the superimposed tidal processes, wave-induced resuspension, and a strong low-flow season coastal current.

Pathways and supply of dissolved iron in the Amundsen Sea (Antarctica)

NASA Astrophysics Data System (ADS)

St-Laurent, P.; Yager, P. L.; Sherrell, R. M.; Stammerjohn, S. E.; Dinniman, M. S.

2017-09-01

Numerous coastal polynyas fringe the Antarctic continent and strongly influence the productivity of Antarctic shelf systems. Of the 46 Antarctic coastal polynyas documented in a recent study, the Amundsen Sea Polynya (ASP) stands out as having the highest net primary production per unit area. Incubation experiments suggest that this productivity is partly controlled by the availability of dissolved iron (dFe). As a first step toward understanding the iron supply of the ASP, we introduce four plausible sources of dFe and simulate their steady spatial distribution using conservative numerical tracers. The modeled distributions replicate important features from observations including dFe maxima at the bottom of deep troughs and enhanced concentrations near the ice shelf fronts. A perturbation experiment with an idealized drawdown mimicking summertime biological uptake and subsequent resupply suggests that glacial meltwater and sediment-derived dFe are the main contributors to the prebloom dFe inventory in the top 100 m of the ASP. The sediment-derived dFe depends strongly on the buoyancy-driven overturning circulation associated with the melting ice shelves (the "meltwater pump") to add dFe to the upper 300 m of the water column. The results support the view that ice shelf melting plays an important direct and indirect role in the dFe supply and delivery to polynyas such as the ASP.

Substituting Sodium Hydrosulfite with Sodium Metabisulfite Improves Long-Term Stability of a Distributable Paper-Based Test Kit for Point-of-Care Screening for Sickle Cell Anemia.

PubMed

Torabian, Kian; Lezzar, Dalia; Piety, Nathaniel Z; George, Alex; Shevkoplyas, Sergey S

2017-09-20

Sickle cell anemia (SCA) is a genetic blood disorder that is particularly lethal in early childhood. Universal newborn screening programs and subsequent early treatment are known to drastically reduce under-five SCA mortality. However, in resource-limited settings, cost and infrastructure constraints limit the effectiveness of laboratory-based SCA screening programs. To address this limitation our laboratory previously developed a low-cost, equipment-free, point-of-care, paper-based SCA test. Here, we improved the stability and performance of the test by replacing sodium hydrosulfite (HS), a key reducing agent in the hemoglobin solubility buffer which is not stable in aqueous solutions, with sodium metabisulfite (MS). The MS formulation of the test was compared to the HS formulation in a laboratory setting by inexperienced users ( n = 3), to determine visual limit of detection (LOD), readout time, diagnostic accuracy, intra- and inter-observer agreement, and shelf life. The MS test was found to have a 10% sickle hemoglobin LOD, 21-min readout time, 97.3% sensitivity and 99.5% specificity for SCA, almost perfect intra- and inter-observer agreement, at least 24 weeks of shelf stability at room temperature, and could be packaged into a self-contained, distributable test kits comprised of off-the-shelf disposable components and food-grade reagents with a total cost of only $0.21 (USD).

Key sources and distribution patterns of particulate material in the South Atlantic: data from the UK GEOTRACES A10 cruise

NASA Astrophysics Data System (ADS)

Milne, A.; Palmer, M.; Lohan, M. C.

2016-02-01

Particles play a fundamental role in the biogeochemical cycling of both major- and micro-nutrients in marine systems, including trace elements and isotopes. However, knowledge of particulate distributions, and their potential to regulate dissolved elemental concentrations, remains limited and poorly understood. The paradox is, that the oceanic inventory of trace metals is dominated by particulate inputs (e.g. aerosol deposition, shelf sediment resuspension). Moreover the labile fraction of particulate trace elements could be an important regulator of dissolved concentrations. Here we present particulate data from the UK GEOTRACES South Atlantic transect (GA10) from South Africa to Uruguay. Data from a range of elements (e.g. Fe, Al, Mn) revealed a greater input of particulate metals from the Argentine shelf (up to 290 nM of pFe) in comparison to the South African shelf (< 40 nM of pFe). Overall, higher concentrations of all metals were observed in the bottom waters of the Argentine basin and penetrated deeper up the water column (up to 1300 m), a result of intense benthic storms. The imprint of leakage from the Agulhas Current, identified through temperature and salinity, was observed in the upper water column profile of numerous particulate data (e.g. Pb, Ni, Cd). Measured elemental gradients, combined with measurements from a vertical mixing-profiler, will allow estimates of particulate fluxes to be calculated.

Paleoenvironmental evolution based on benthic foraminifera biofacies of the Paraíba do Sul Deltaic Complex, eastern Brazil

NASA Astrophysics Data System (ADS)

Gasparini, Sarah Pereira; Vilela, Claudia Gutterres

2017-12-01

The paleoecology and distribution of benthic foraminiferal assemblages were analyzed in the core 2-MU-1-RJ well, drilled in the Paraíba do Sul Deltaic Complex, Rio de Janeiro (Brazil). An abundant assemblage was found in the upper portion of the well core, inferred to be pleistocenic deposits. The coastal dynamic was recognized from five biofacies based on clusters, the Planktonic/Benthic (P/B) ratios and indicator species distribution in the core. Several biofacies were identified along the core depending on the species dominance. From the bottom to the top of the core, the biofacies succession represents the environmental changes in the coastal area associated to sea-level oscillations. The biofacies ABP dominated by Ammonia parkinsoniana and Bolivina spp. and Pararotalia cananeiaensis represents an inner shelf environment; biofacies QP dominated by shelf miliolids species; biofacies PGH, dominated by P. cananeiaensis, Gavelinopsis praegeri, and Hanzawaia nitidula, represents the estuary complex with middle or outer shelf influence; biofacies QL represents hypersaline waters dominated by lagoonal miliolids; and biofacies HP characterized by Haynesina germanica and P. cananeiaensis is associated with paralic environments. Marine ingressions are recorded and those biofacies show the pleistocenic coastal hydrodinamic in the deltaic complex. The foraminiferal biofacies contribute with detailed information to sedimentary facies previously characterized in the study area by the reconstruction of paleoenvironment succession.

Distributed situation awareness in complex collaborative systems: A field study of bridge operations on platform supply vessels.

PubMed

Sandhåland, Hilde; Oltedal, Helle A; Hystad, Sigurd W; Eid, Jarle

2015-06-01

This study provides empirical data about shipboard practices in bridge operations on board a selection of platform supply vessels (PSVs). Using the theoretical concept of distributed situation awareness, the study examines how situation awareness (SA)-related information is distributed and coordinated at the bridge. This study thus favours a systems approach to studying SA, viewing it not as a phenomenon that solely happens in each individual's mind but rather as something that happens between individuals and the tools that they use in a collaborative system. Thus, this study adds to our understanding of SA as a distributed phenomenon. Data were collected in four field studies that lasted between 8 and 14 days on PSVs that operate on the Norwegian continental shelf and UK continental shelf. The study revealed pronounced variations in shipboard practices regarding how the bridge team attended to operational planning, communication procedures, and distracting/interrupting factors during operations. These findings shed new light on how SA might decrease in bridge teams during platform supply operations. The findings from this study emphasize the need to assess and establish shipboard practices that support the bridge teams' SA needs in day-to-day operations. Provides insights into how shipboard practices that are relevant to planning, communication and the occurrence of distracting/interrupting factors are realized in bridge operations.Notes possible areas for improvement to enhance distributed SA in bridge operations.

Nutritional value and acceptability of homemade maize/sorghum-based weaning mixtures supplemented with rojo bean flour, ground sardines and peanut paste.

PubMed

Mosha, Theobald C E; Vicent, Mary M

2004-06-01

Low nutrient density in weaning foods is the major cause of under-nutrition among infants and young children in developing countries. Ten types of composite weaning diets (namely, maize-rojo beans-peanut, maize-peanut-sardines, maize-peanut-sardine-rojo beans, maize-peanut-soaked rojo beans, maize-peanut-germinated rojo beans, sorghum-rojo beans-peanut, sorghum-peanut-sardines, sorghum-peanut-sardine-rojo beans, sorghum-peanut-soaked rojo beans, and sorghum-peanut-germinated rojo beans) were formulated and assayed for proximate composition, energy, mineral density, tannin content and residual urease activity. The diets were also evaluated for storage stability under ambient conditions, sensory quality and overall acceptability. Results of the study indicated that, concentrations of protein, fat, ash, calcium, iron, zinc and copper were significantly (P<0.05) increased when plain maize and sorghum gruels were enriched with rojo beans, peanut paste and/or ground sardines. Soaking and germinating the rojo beans and dehulling the sorghum reduced the concentration of tannins in the gruels significantly (P<0.05). Residual urease activity ranged between 0.00 and 0.07 units, about 10-fold lower than the maximum level (0.8 units) allowed in weaning foods. Both maize and sorghum-based composite gruels had a short shelf-life under ambient conditions (26.4 degrees C) ranging between 4 and 6 h, with gruels containing ground sardines showing a tendency to spoil faster. All composite gruels except those containing germinated rojo beans were highly liked and accepted by consumers (P<0.05), similar to the plain maize and sorghum gruels. The maize and sorghum-based composite products therefore have a potential for use as weaning and/or supplementary foods for older infants and young children. Further investigations are suggested to extend the shelf-life of the composite products and improve the organoleptic quality of the diets containing germinated rojo beans.

Biophysical Factors Affecting the Distribution of Demersal Fish around the Head of a Submarine Canyon Off the Bonney Coast, South Australia

PubMed Central

Currie, David R.; McClatchie, Sam; Middleton, John F.; Nayar, Sasi

2012-01-01

We sampled the demersal fish community of the Bonney Canyon, South Australia at depths (100–1,500 m) and locations that are poorly known. Seventy-eight species of demersal fish were obtained from 12 depth-stratified trawls along, and to either side, of the central canyon axis. Distributional patterns in species richness and biomass were highly correlated. Three fish assemblage groupings, characterised by small suites of species with narrow depth distributions, were identified on the shelf, upper slope and mid slope. The assemblage groupings were largely explained by depth (ρw = 0.78). Compared to the depth gradient, canyon-related effects are weak or occur at spatial or temporal scales not sampled in this study. A conceptual physical model displayed features consistent with the depth zonational patterns in fish, and also indicated that canyon upwelling can occur. The depth zonation of the fish assemblage was associated with the depth distribution of water masses in the area. Notably, the mid-slope community (1,000 m) coincided with a layer of Antarctic Intermediate Water, the upper slope community (500 m) resided within the core of the Flinders Current, and the shelf community was located in a well-mixed layer of surface water (<450 m depth). PMID:22253907

Shelf-Stable Adhesive for Reduction of Composite Repair Hazardous Waste

DTIC Science & Technology

2008-09-01

1. Our microencapsulation approach is compatible with commonly used epoxy resins and catalyst accelerants 2. The microcapsules can be...thermally stable barrier to diffusion of accelerant and/or epoxy resin through the capsule’s walls [14]. 3.2 Microencapsulation Microcapsules ... microencapsulation of the catalyst accelerant. Thermal analysis of microcapsules made from carrageenan blends showed that they formed an effective

Minimum distribution of subsea ice-bearing permafrost on the US Beaufort Sea continental shelf

USGS Publications Warehouse

Brothers, Laura L.; Hart, Patrick E.; Ruppel, Carolyn D.

2012-01-01

Starting in Late Pleistocene time (~19 ka), sea level rise inundated coastal zones worldwide. On some parts of the present-day circum-Arctic continental shelf, this led to flooding and thawing of formerly subaerial permafrost and probable dissociation of associated gas hydrates. Relict permafrost has never been systematically mapped along the 700-km-long U.S. Beaufort Sea continental shelf and is often assumed to extend to ~120 m water depth, the approximate amount of sea level rise since the Late Pleistocene. Here, 5,000 km of multichannel seismic (MCS) data acquired between 1977 and 1992 were examined for high-velocity (>2.3 km s−1) refractions consistent with ice-bearing, coarse-grained sediments. Permafrost refractions were identified along <5% of the tracklines at depths of ~5 to 470 m below the seafloor. The resulting map reveals the minimum extent of subsea ice-bearing permafrost, which does not extend seaward of 30 km offshore or beyond the 20 m isobath.

Anomalous topography on the continental shelf around Hudson Canyon

USGS Publications Warehouse

Knebel, H.J.

1979-01-01

Recent seismic-reflection data show that the topography on the Continental Shelf around Hudson Canyon is composed of a series of depressions having variable spacings (< 100 m to 2 km), depths (1-10 m), outlines, and bottom configurations that give the sea floor an anomalous "jagged" appearance in profile. The acoustic and sedimentary characteristics, the proximity to relict shores, and the areal distribution indicate that this rough topography is an erosional surface formed on Upper Pleistocene silty sands about 13,000 to 15,000 years ago by processes related to Hudson Canyon. The pronounced southward extension of the surface, in particular, may reflect a former increase in the longshore-current erosion capacity caused by the loss of sediments over the canyon. Modern erosion or nondeposition of sediments has prevented the ubiquitous sand sheet on the Middle Atlantic shelf from covering the surface. The "anomalous" topography may, in fact, be characteristic of areas near other submarine canyons that interrupt or have interrupted the longshore drift of sediments. ?? 1979.

Holocene water mass history off NE Greenland - A first high-resolution sediment record from the western Fram Strait

NASA Astrophysics Data System (ADS)

Zehnich, Marc; Palme, Tina; Spielhagen, Robert F.; Hass, H. Christian; Bauch, Henning A.

2017-04-01

While the Holocene history of the eastern Fram Strait seems well investigated, no high-resolution paleoenvironmental records were available from the western Fram Strait so far. A new sedimentary record, obtained during expedition PS93.1 (2015) of RV Polarstern on the outermost NE Greenland shelf, allows for the first time to reconstruct Holocene changes in near-surface salinities, temperature, stratification and water masses (polar waters vs. Atlantic Water), potentially related to variations of the freshwater and sea ice export from the Arctic Ocean. The 260 cm long sedimentary record from site PS93/025 (80.5°N, 8.5°W) was investigated for sediment composition, foraminifer contents, grain size variations (sortable silt) and the isotopic composition of planktic foraminifers. Radiocarbon datings reveal an age of 10.2 cal-ka for the core base and continuous sedimentation throughout most of the Holocene. The sediments are generally very fine-grained (<2% sand). The grain size record reveals a fining-upwards trend and sediments from <6.5 cal-ka consist of <0.5% coarse fraction. A comparison of foraminifer and coarse fraction abundances shows strong similarities. Apparently the contribution of coarse terrestrial material from iceberg transport was extremely low throughout the last 10.2 cal-ka. Foraminifer abundances (both planktic and benthic) are high in Early Holocene sediments until ca. 7 cal-ka and decrease rapidly thereafter. This is interpreted to reflect a relatively strong advection of Atlantic Water to the NW Fram Strait, which correlates well with similar findings on the eastern side of the Arctic Gateway. Sortable silt grain sizes are high (27-32 µm) in the older part of the record and gradually decrease between 7 cal-ka and 4 cal-ka. After ca. 4 cal-ka, sortable silt shows values of 20-22 µm and little variation. Considering also the grain-size distribution curves, we propose a decline of bottom current velocities on the outer NE Greenland shelf after 7 cal-ka, related to a decrease of Atlantic Water advection. These preliminary results reveal a strong coupling of Holocene environments on both sides of the Fram Strait.

Spatial Distribution and Conservation of Speckled Hind and Warsaw Grouper in the Atlantic Ocean off the Southeastern U.S.

PubMed Central

Farmer, Nicholas A.; Karnauskas, Mandy

2013-01-01

There is broad interest in the development of efficient marine protected areas (MPAs) to reduce bycatch and end overfishing of speckled hind (Epinephelus drummondhayi) and warsaw grouper (Hyporthodus nigritus) in the Atlantic Ocean off the southeastern U.S. We assimilated decades of data from many fishery-dependent, fishery-independent, and anecdotal sources to describe the spatial distribution of these data limited stocks. A spatial classification model was developed to categorize depth-grids based on the distribution of speckled hind and warsaw grouper point observations and identified benthic habitats. Logistic regression analysis was used to develop a quantitative model to predict the spatial distribution of speckled hind and warsaw grouper as a function of depth, latitude, and habitat. Models, controlling for sampling gear effects, were selected based on AIC and 10-fold cross validation. The best-fitting model for warsaw grouper included latitude and depth to explain 10.8% of the variability in probability of detection, with a false prediction rate of 28–33%. The best-fitting model for speckled hind, per cross-validation, included latitude and depth to explain 36.8% of the variability in probability of detection, with a false prediction rate of 25–27%. The best-fitting speckled hind model, per AIC, also included habitat, but had false prediction rates up to 36%. Speckled hind and warsaw grouper habitats followed a shelf-edge hardbottom ridge from North Carolina to southeast Florida, with speckled hind more common to the north and warsaw grouper more common to the south. The proportion of habitat classifications and model-estimated stock contained within established and proposed MPAs was computed. Existing MPAs covered 10% of probable shelf-edge habitats for speckled hind and warsaw grouper, protecting 3–8% of speckled hind and 8% of warsaw grouper stocks. Proposed MPAs could add 24% more probable shelf-edge habitat, and protect an additional 14–29% of speckled hind and 20% of warsaw grouper stocks. PMID:24260126

Attributes and origins of ancient submarine slides and filled embayments: examples from the Gulf Coast basin

USGS Publications Warehouse

Morton, Robert

1993-01-01

Submarine slides exhibit landward-dipping, wavy, mounded, and chaotic seismic reflections that are manifestations of slump blocks and other mass transport material. Composition of these internally derived slide deposits depends on the composition of the preexisting shelf margin. Embayment fill above the slide consists mostly of externally derived mudstones and sandstones deposited by various disorganized slope processes, as well as more organized submarine channel-levee systems. Thickest slope sandstones, which are potential hydrocarbon reservoirs, commonly occur above the basal slide mudstones where seismic reflections change from chaotic patterns to overlying wavy or subhorizontal reflections.

Wind-driven upwelling effects on cephalopod paralarvae: Octopus vulgaris and Loliginidae off the Galician coast (NE Atlantic)

NASA Astrophysics Data System (ADS)

Otero, Jaime; Álvarez-Salgado, X. Antón; González, Ángel F.; Souto, Carlos; Gilcoto, Miguel; Guerra, Ángel

2016-02-01

Circulation patterns of coastal upwelling areas may have central consequences for the abundance and cross-shelf transport of the larval stages of many species. Previous studies have provided evidences that larvae distribution results from a combination of subtidal circulation, species-specific behaviour and larval sources. However, most of these works were conducted on organisms characterised by small-sized and abundant early life phases. Here, we studied the influence of the hydrography and circulation of the Ría de Vigo and adjacent shelf (NW Iberian upwelling system) on the paralarval abundance of two contrasting cephalopods, the benthic common octopus (Octopus vulgaris) and the pelagic squids (Loliginidae). We sampled repeatedly a cross-shore transect during the years 2003-2005 and used zero inflated models to accommodate the scarcity and patchy distribution of cephalopod paralarvae. The probability of catching early stages of both cephalopods was higher at night. Octopus paralarvae were more abundant in the surface layer at night whereas loliginids preferred the bottom layer regardless of the sampling time. Abundance of both cephalopods increased when shelf currents flowed polewards, water temperature was high and water column stability was low. The probability of observing an excess of zero catches decreased during the year for octopus and at high current speed for loliginids. In addition, the circulation pattern conditioned the body size distribution of both paralarvae; while the average size of the captured octopuses increased (decreased) with poleward currents at daylight (nighttime), squids were smaller with poleward currents regardless of the sampling time. These results contribute to the understanding of the effects that the hydrography and subtidal circulation of a coastal upwelling have on the fate of cephalopod early life stages.

Offshore sand resources for coastal erosion control in Louisiana

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ramsey, K.E.; Penland, S.; McBride, R.A.

1990-09-01

An inventory of existing geophysical data supplemented by more than 15,000 km of high-resolution seismic profiles and 400 vibracores collected cooperatively by the Louisiana Geological Survey and US Geological Survey since 1981 indicates that a wide range of aggregate minerals occurs on the continental shelf in a variety of depositional settings. The distribution of these deposits is controlled by the geometry of the preexisting fluvial and deltaic channel systems and the stratigraphic signature of the Holocene Transgression across these features. The geology of coastal and offshore Louisiana is tied to the depositional history of the Mississippi River. Offshore of themore » delta plain, five types of aggregate sources can be identified: inner shelf shoals, submerged barrier islands, tidal inlets, distributary channels, and barrier platforms. This paper describes the geology of offshore Louisiana, the available geophysical data sets, and the distribution of aggregate mineral resources. On the continental shelf of the Mississippi River delta plain, two extensive seismic survey grids have been developed by the Louisiana Geological Survey and US Geological Survey. The most prospective resources found are the huge sand bodies of Ship Shoal and associated distributaries, Cat Island Pass tidal channels and associated tidal deltas, and Barataria Pass/Grand Terre tidal channels and associated tidal deltas. East of the mouth of the Mississippi River are the Chandeleur Islands, where LGS identified seven major sand resource targets, truncated barrier-spit and tidal inlet deposits, submerged beach ridges, and distributaries associated with abandoned St. Bernard delta complexes. Abundant sand resources can be found in offshore Louisiana. Many of the sand bodies contain heavy minerals, but their concentration and distribution is unknown. Other potential sand resources not yet adequately explored include Sabine Bank, the Outer Shoal, and the St. Bernard shoal.« less

Soft-sediment crustacean diversity and distribution along the Portuguese continental shelf

NASA Astrophysics Data System (ADS)

Sampaio, Leandro; Mamede, Renato; Ricardo, Fernando; Magalhães, Luísa; Rocha, Hélder; Martins, Roberto; Dauvin, Jean-Claude; Rodrigues, Ana Maria; Quintino, Victor

2016-11-01

This study analyzed the crustacean diversity, distribution and relationship with environmental factors in the western and the southern Portuguese continental shelf, between 10 and 200 m depth. A total of 10,639 specimens belonging to 242 taxa from 90 families were identified, mostly amphipods (55.8% of the total taxa). The mysid Gastrosaccus spinifer and the amphipods Socarnes erythrophthalmus and Cheirocratus sundevallii were the most abundant and the amphipods Ampelisca brevicornis, Leucothoe incisa and Autonoe spiniventris were the most frequent species. The highest abundance and diversity was found in coarser sediments with up to 306 individuals per 0.1 m2. Alpha diversity ranged from 1 to 28 sp./0.1 m2. Moreover, this study confirmed six previously doubtful first records and added an additional 19 new records to the Portuguese fauna. The results also confirmed the Portuguese coast as a transition zone of mixed Atlantic and Mediterranean faunas and exposed a noticeable North African and Macaronesian influence. A multivariate analysis based on the abundance of crustaceans revealed six affinity groups characterized by: (a) C. sundevallii, Guernea (Guernea) coalita and Sarsinebalia cristoboi on very coarse sands; (b) G. spinifer, Nototropis falcatus and Pontocrates arenarius on coarse sands; (c) Othomaera othonis, Processa modica modica and Animoceradocus semiserratus on heterogeneous medium sands; (d) A. brevicornis, Urothoe pulchella and Necalianassa truncata on fine sands; (e) Ampelisca pectenata, Bodotria scorpioides and Astacilla dilatata on heterogeneous fine sands and (f) Callianassa subterranea, Ampelisca tenuicornis and Ampelisca typica on muddy fine sands. Sediment grain-size and depth were the variables best related to the benthic crustacean spatial distribution patterns along the Portuguese continental shelf.

Radionuclide tracers of sediment-water interactions on the Amazon shelf

NASA Astrophysics Data System (ADS)

Moore, Willard S.; DeMaster, David J.; Smoak, Joseph M.; McKee, Brent A.; Swarzenski, Peter W.

1996-04-01

A comprehensive study of a variety of radionuclide tracers has been coupled with other geochemical investigations and with sedimentary and physical oceanographic measurements to elucidate processes and their characteristic time scales at the mouth of the Amazon River. This two-year field study on the Amazon continental shelf involved four cruises designed to provide information during different stages of the river hydrograph. Although the cruises were coordinated with river stage, other physical variables including spring-neap tidal stages, the flow of the North Brazil Current and trade-wind stress caused important effects on the shelf environment. Partitioning of uranium among dissolved, colloidal and particulate phases was investigated during AmasSeds. A detailed examination of uranium water-column behavior during low river discharge found that most (89%) of the uranium near the Amazon River mouth was associated with the particulate phase and that most (92%) of the riverine dissolved-phase uranium was in the colloidal size fraction (0.001-0.4 μm). A non-conservative uranium/salinity distribution was observed for dissolved uranium, indicating large-scale uranium removal from surface waters with salinities less than 20 ppt. Colloidal uranium was non-conservative across the entire salinity regime, exhibiting removal of colloidal uranium from waters with salinities less than 12 ppt and a significant input at higher salinities. A short-lived particle-reactive tracer, 234Th, was used to evaluate the rates of particle scavenging on the shelf. Suspended-sediment concentrations respond to each turn of the tide, thus limiting the time available for equilibrium to be established between the particles and the tracers. Experiments demonstrated that on the Amazon shelf the partitioning and distribution of trace elements are governed by particle dynamics (particle residence times < sorption times). The high suspended load, including fluid muds, retards the incorporation of adsorbed 234Th into the seabed. Once scavenged, 234Th remains part of the suspended-sediment and fluid-mud inventory for periods of at least 4-8 weeks. Another particle-reactive tracer, 210Pb, was used to evaluate the potential supply of reactive metals from offshore waters to the shelf. As open-ocean waters move into the Amazon mixing zone, in response to the estuarine-like circulation, they lose 210Ph through scavenging processes associated with delta formation. This oceanic input of 210Pb dominates other inputs to the Amazon shelf system. Based on 210Pb analyses from more than 40 ☐ and kasten cores, the flux of water moving shoreward and depositing 210Pb in the sediments was calculated to be on the order of 6 × 10 161y -1 ˜10 times the riverine flux from the Amazon. The distribution of 210Pb in the sediments suggests that if particle-reactive species (such as certain trace metals) are released in dissolved form on the shelf, they will be scavenged quickly in this turbid environment, with the largest inventories occurring in the foreset beds (although the highest concentrations occur in the bottomset beds). The large landward flow of water indicates that if particle-reactive species are released in the western equatorial Atlantic via aerosol transport or other mechanisms, there is a good chance that a sizeable portion will be buried in the Amazon delta. Fluxes of radium isotopes, 226Ra, 228Ra and 224Ra, from the bottom sediments were used to evaluate sediment resuspension across the shelf. The average flux of 226Ra from the Amazon shelf balanced the annual desorption of 226Ra from river-derived sediments; however, departures between the 226Ra flux and sediment necessary to support the flux occurred for different sampling periods. During falling and low discharge, less sediment entered the system than was required to support the sedimentary desorption 226Ra flux. During rising and high discharge, more sediment entered than was necessary to sustain the 226Ra flux. Considerable recycling of particles between the seabed and water column was required to wash away most of the desorbable 226Ra from the sediment. To support the sedimentary 228Ra flux, 3.4 × 10 16 g of sediment must be resuspended each year. Such mixing would resuspend the top 35 em of sediment over the entire shelf each year, or mix the surface layer (SL, the region of uniform sedimentary 210Pb depth profiles) to a depth of 90 cm annually. Such mixing would turn over the entire SL every 1-2 years. Desorption of sedimentary radium isotopes must be accompanied by the desorption of other exchangeable species including phosphate, cesium and cadmium. Correlations among phosphate and radium isotopes, infer that phosphate is being released from bottom sediments as the sediments are resuspended into the water column. As was the case for 226Ra, bottom sediment must be repeatedly suspended into the water column to release all of the exchangeable phosphate. The desorption of 224Ra from shelf sediments provides a tracer of the Amazon plume into the Atlantic. In July and September 1989, the ship crossed the Demerara retroflection 380 km from the Amazon shelf and excess 224Ra activities up to 8 dpm 100 kg -1 were measured. It was concluded that these waters were <5 days removed from the Amazon shelf. A sustained current of >80 em s -1 would be required to advect the water this distance in <5 days, an observation that agrees well with drogue releases during August 1989.

Basal melt rates of Filchner Ice Shelf, Antarctica

NASA Astrophysics Data System (ADS)

Humbert, A.; Nicholls, K. W.; Corr, H. F. J.; Steinhage, D.; Stewart, C.; Zeising, O.

2017-12-01

Thinning of ice shelves around Antarctica has been found to be partly driven by an increase in basal melt as a result of warmer waters entering the sub-ice shelf cavity. In-situ observations of basal melt rate are, however, sparse. A new robust and efficient phase sensitive radio echo sounder (pRES) allows to measure change in ice thickness and vertical strain at high accuracy, so that the contribution of basal melt to the change in thickness can be estimated. As modeling studies suggest that the cavity beneath Filchner Ice Shelf, Antarctica, might be prone to intrusion of warm water pulses within this century, we wished to derive a baseline dataset and an understanding of its present day spatial variability. Here we present results from pRES measurements over two field seasons, 2015/16-16/17, comprising 86 datasets over the southern Filchner Ice Shelf, covering an area of about 6500km2. The maximum melt rate is only slightly more than 1m/a, but the spatial distribution exhibits a complex pattern. For the purpose of testing variability of basal melt rates on small spatial scales, we performed 26 measurements over distances of about 1km, and show that the melt rates do not vary by more than 0.25m/a.

The Halekulani Sand Channel and Makua Shelf sediment deposits: Are they a sand resource for replenishing Waikiki's beaches?

USGS Publications Warehouse

Hampton, M.A.; Fletcher, C. H.; Barry, J.H.; Lemmo, S.J.; ,

2000-01-01

The Halekulani Sand Channel and the Makua Shelf off the south shore of Oahu contain at least 1.3 million m3 of sediment that is a possible resource for nourishing degraded sections of Waikiki Beach. A sidescan sonar survey indicates continuous sediment cover within the channel and on the shelf, and samples from the top and bottom of vibracores from the channel and shelf contain from 29% to 77% of grains between 0 to 2.5 phi (1 to 0.177 mm), the size range of four samples from Waikiki Beach. Compositional analyses indicate high variability, but the vibracore samples normally have relatively high Halimeda content compared to beach sand samples. Laboratory tests show a positive correlation of abrasion with Halimeda content, suggesting that the offshore sediment would abrade more than beach sediment under nearshore wave action. The common gray color of the offshore sediment can be aesthetically undesirable for sand on popular tourist beaches such as Waikiki; however, visual observation of native beach sand indicates that a significant component of gray color is endemic to many Hawaiian beaches. The gray color was removed in the laboratory by soaking in heated hydrogen peroxide. The geological properties of the offshore sediment indicate potential as a resource for beach nourishment, but industrial treatment might be necessary to remove excess fine and coarse grains, and possibly the gray color. Further, the abrasion potential might have to be considered in calculating beach sand losses over time.

Particulate and dissolved spectral absorption on the continental shelf of the southeastern United States

NASA Astrophysics Data System (ADS)

Nelson, James R.; Guarda, Sonia

1995-05-01

Visible absorption spectra of particulate and dissolved materials were characterized on the continental shelf off the southeastern United States (the South Atlantic Bight), emphasizing cross-shelf and seasonal variability. A coastal front separates turbid coastal waters from clearer midshelf waters. Spatial and seasonal patterns were evident in absorption coefficients for phytoplankton, detritus, and colored dissolved organic matter (CDOM); spectral shape parameters for CDOM and detritus; and phytoplankton chlorophyll-specific absorption. The magnitude of CDOM absorption reflected seasonal differences in freshwater discharge and the salinity of the midshelf waters. In the spring of 1993 (high discharge), CDOM absorption at 443 nm was >10 times that of total particulate absorption between 12 and 50 km offshore (0.28-0.69 m-1 versus 0.027-0.062 m-1) and up to 10 times the CDOM absorption measured in the previous summer (low discharge). Phytoplankton chlorophyll-specific absorption in the blue increased with distance from shore (from <0.03 m2 mg-1 in inner shelf waters to ˜0.1 m2 mg-1 at the most seaward stations in summer) and, for similar chlorophyll concentrations, was higher in summer than in the winter-spring. These spatial and seasonal patterns in phytoplankton chlorophyll-specific absorption can be attributed to a shift in phytoplankton species composition (from predominantly diatoms inshore to a cyanobacteria-dominated assemblage midshelf in summer), pigment packaging, and higher carotenoid:chlorophyll with distance from shore.

Seasonal distribution and abundance of cetaceans within French waters- Part II: The Bay of Biscay and the English Channel

NASA Astrophysics Data System (ADS)

Laran, Sophie; Authier, Matthieu; Blanck, Aurélie; Doremus, Ghislain; Falchetto, Hélène; Monestiez, Pascal; Pettex, Emeline; Stephan, Eric; Van Canneyt, Olivier; Ridoux, Vincent

2017-07-01

From the Habitat Directive to the recent Marine Strategy Framework Directive, the conservation status of cetaceans in European water has been of concern for over two decades. In this study, a seasonal comparison of the abundance and distribution of cetaceans was carried out in two contrasted regions of the Eastern North Atlantic, the Bay of Biscay and the English Channel. Estimates were obtained in the two sub-regions (375,000 km²) from large aerial surveys conducted in the winter (November 2011 to February 2012) and in the summer (May to August 2012). The most abundant species encountered in the Channel, the harbour porpoise, displayed strong seasonal variations in its distribution but a stable abundance (18,000 individuals, CV=30%). In the Bay of Biscay, abundance and distribution patterns of common / striped dolphins varied from 285,000 individuals (95% CI: 174,000-481,000) in the winter, preferentially distributed close to the shelf break, to 494,000 individuals (95% CI: 342,000-719,000) distributed beyond the shelf break in summer. Baleen whales also exhibited an increase of their density in summer. Seasonal abundances of bottlenose dolphins were quite stable, with a large number of 'pelagic' encounters offshore in winter. No significant seasonal difference was estimated for pilot whales and sperm whale. These surveys provided baseline estimates to inform policies to be developed, or for existing conservation instruments such as the Habitats Directive. In addition, our results supported the hypothesis of a shift in the summer distributions of some species such as harbour porpoise and minke whale in European waters.

Unusual distribution of floating seaweeds in the East China Sea in the early spring of 2012.

PubMed

Komatsu, Teruhisa; Mizuno, Shizuha; Natheer, Alabsi; Kantachumpoo, Attachai; Tanaka, Kiyoshi; Morimoto, Akihiko; Hsiao, Sheng-Tai; Rothäusler, Eva A; Shishidou, Hirotoshi; Aoki, Masakazu; Ajisaka, Tetsuro

2014-01-01

Floating seaweeds play important ecological roles in offshore waters. Recently, large amounts of rafting seaweed have been observed in the East China Sea. In early spring, juveniles of commercially important fish such as yellowtail accompany these seaweed rafts. Because the spatial distributions of seaweed rafts in the spring are poorly understood, research cruises were undertaken to investigate them in 2010, 2011, and 2012. Floating seaweed samples collected from the East China Sea during the three surveys contained only Sargassum horneri . In 2010 and 2011, seaweed rafts were distributed only in the continental shelf and the Kuroshio Front because they had become trapped in the convergence zone of the Kuroshio Front. However, in 2012, seaweed was also distributed in the Kuroshio Current and its outer waters, and massive strandings of seaweed rafts were observed on the northern coast of Taiwan and on Tarama Island in the Ryukyu Archipelago. Environmental data (wind, currents, and sea surface height) were compared among the surveys of 2010, 2011, and 2012. Two factors are speculated to have caused the unusual distribution in 2012. First, a continuous strong north wind produced an Ekman drift current that transported seaweed southwestward to the continental shelf and eventually stranded seaweed rafts on the coast of Taiwan. Second, an anticyclonic eddy covering northeast Taiwan and the Kuroshio Current west of Taiwan generated a geostrophic current that crossed the Kuroshio Current and transported the rafts to the Kuroshio Current and its outer waters. Such unusual seaweed distributions may influence the distribution of fauna accompanying the rafts.

21 CFR 137.165 - Enriched flour.

Code of Federal Regulations, 2010 CFR

2010-04-01

...) of this section will be deemed to have been met if reasonable overages of the vitamins and minerals... vitamins and minerals are maintained throughout the expected shelf life of the food under customary conditions of distribution and storage. The quantitative content of the following vitamins shall be...

Absorption properties of chromophoric dissolved organic matter (CDOM) in the East China Sea and the waters off eastern Taiwan

NASA Astrophysics Data System (ADS)

Zhou, Fengxia; Gao, Xuelu; Song, Jinming; Chen, Chen-Tung Arthur; Yuan, Huamao; Xing, Qianguo

2018-05-01

The absorption properties of chromophoric dissolved organic matter (CDOM) in the East China Sea (ECS) and the waters off eastern Taiwan (WET) were studied during May 2014. CDOM absorption coefficient (a280) and spectral slope (S275-295) revealed considerable spatial variations. In the ECS, the values of a280 and S275-295 presented a reverse distribution pattern. In the WET, a280 values were generally low while S275-295 values were generally high. Vertical distributions of a280 and S275-295 also varied in different regions. Terrestrial input, phytoplankton production, sediment release or photobleaching may be responsible for the dynamics of CDOM. Relationships among CDOM related parameters could partly support this conclusion. a280 were also used to trace different water masses and the result showed that the influence of Changjiang Diluted Water could reach the outer shelf of the northern ECS, and that the Kuroshio Current had a strong influence on the middle shelf of the southern ECS.

The plume of the Yukon River in relation to the oceanography of the Bering Sea

NASA Technical Reports Server (NTRS)

Dean, Kenneson G.; Mcroy, C. Peter; Ahlnas, Kristina; Springer, Alan

1989-01-01

The ecosystem of the northern Bering-Sea shelf was studied using data from the NOAA Very High Resolution Radiometer and AVHRR and the Landsat MSS and Thematic Mapper (TM) in conjunction with shipboard measurements. Emphasis was placed on the influence of the Yukon River on this inner shelf environment and on the evaluation of the utility of the new Landsat TM data for oceanography. It was found that the patterns of water mass distribution obtained from satellite images agreed reasonably well with the areal patterns of temperature, salinity, and phytoplankton distributions. The AVHRR, MSS, and TM data show that the Yukon-River discharge is warmer and more turbid than the surrounding coastal water that originates to the south; thus, the Yukon water contributes to the higher temperatures and lower transmissivity of the coastal water. The high resolution of the TM thermal IR band made it possible to observe complex patterns and structures in the surface water that could not be resolved on previous data sets.

Effects of acerola fruit extract on sensory and shelf-life of salted beef patties from grinds differing in fatty acid composition.

PubMed

Realini, C E; Guàrdia, M D; Díaz, I; García-Regueiro, J A; Arnau, J

2015-01-01

The effects of added acerola fruit extract on sensory and shelf-life of beef patties were evaluated. Ground beef was obtained from young bulls fed one of four diets (CON: control, LIN: linseed, CLA: conjugated linoleic acid, LINCLA: LIN plus CLA). Pre-salted (1.8% w/w) beef patties (7.7% fat) with (0.15% w/w) or without acerola were packed in modified atmosphere (80%O2:20%CO2) and displayed in a retail case for 8days. There were no interactions between diet and antioxidant treatments. LIN and/or CLA had no effect on color and lipid stability during display. However, LIN increased n-3 fatty acids in beef and tended to increase intensity of rancid flavor. Addition of acerola extended shelf-life by at least 3 days by improving color and lipid stability and a decreased trend in intensity of rancid flavor of patties without affecting microbial counts. Thus, the use of acerola as a natural antioxidant can be considered an effective method to retard color and lipid oxidation in beef patties. Copyright © 2014 Elsevier Ltd. All rights reserved.

Influence of modified atmosphere packaging on the shelf life of prebaked pizza dough with and without preservative added.

PubMed

Rodríguez, Valle; Medina, Luis; Jordano, Rafael

2003-04-01

The possible effect of different modified atmospheres on the shelf life of prebaked pizza dough, with and without added calcium propionate, was investigated. Three packaging atmospheres were tested: 20% CO2: 80% N2, 50% CO2: 50% N2, 100% CO2, and air (control). Samples were examined daily for visible mold growth and analysed after 2, 8, 17 and 31 days throughout storage (15-20 degrees C and 54-65% relative humidity, RH) for changes in gaseous composition, pH and microbial populations (mesophilic aerobic and anaerobic bacteria, lactic acid bacteria (LAB), and yeasts and molds). Microbiological results showed that molds had a greater sensitivity to CO2 than bacteria and yeasts. Products containing calcium propionate did not show mold growth throughout storage (31 days) when packaged in air or in CO2-enriched atmospheres (20, 50 and 100%). However, in pizza dough without preservative (calcium propionate), mold growth was evident after 7 days, except under 100% CO2 atmosphere (13 days) regardless of the packaging atmosphere. From these results we conclude that the addition of calcium propionate had more and decisive influence on the shelf life extension of prebaked pizza dough.

In Situ and Ex Situ Estimates of Benthic Silica Fluxes in NGOM Shelf Sediments

NASA Astrophysics Data System (ADS)

Ebner, B. C.; Ghaisas, N. A.; Maiti, K.

2017-12-01

Biogenic silica (bSi), plays an important role in regulating primary productivity of diatoms in coastal and shelf ecosystems fed by major rivers. In the Northern Gulf of Mexico (NGOM), loading of nitrogen (N) and phosphorous (P) have increased compared to a decline in silicic acid in the Mississippi River (MR). Continued decreasing in silicic acid concentration could lead to limited diatom growth and production, therefore, it is important understand the role of benthic fluxes in providing silica to the overlying water column. The benthic flux of Si from shelf sediments can thus represent an important source of Si to be utilized by diatoms. Sediment core incubations and benthic chamber deployments were conducted at 5 sites in the Mississippi river plume with varying salinities during periods of high river discharge (May 2017), low river discharge (August 2016) and peak in hypoxia (July 2017). Preliminary data indicates large spatial and temporal variability in benthic silica fluxes ranging between 1.1 to 5.9 mmol/m2/d. This large variability in benthic silica flux is probably related to the seasonal changes in river discharge, primary production, community composition and sediment biogeochemistry in the region.

Interannual variability in lower trophic levels on the Alaskan Shelf

NASA Astrophysics Data System (ADS)

Batten, Sonia D.; Raitsos, Dionysios E.; Danielson, Seth; Hopcroft, Russell; Coyle, Kenneth; McQuatters-Gollop, Abigail

2018-01-01

This study describes results from the first 16 years of the Continuous Plankton Recorder (CPR) program that has sampled the lower trophic levels (restricted to larger, hard-shelled phytoplankton and robust zooplankton taxa) on the Alaskan shelf. Sampling took place along transects from the open ocean across the shelf (to the entrance to Prince William Sound from 2000 to 2003 and into Cook Inlet from 2004 to 2015) to provide plankton abundance data, spring through autumn of each year. We document interannual variability in concentration and composition of the plankton community of the region over this time period. At least in part and through correlative relationships, this can be attributed to changes in the physical environment, particularly direct and indirect effects of temperature. For example; spring mixed layer depth is shown to influence the timing of the spring diatom peak and warmer years are biased towards smaller copepod species. A significant positive relationship between temperature, diatom abundance and zooplankton biomass existed from 2000 to 2013 but was not present in the warm years of 2014 and 2015. These results suggest that anomalous warming events, such as the "heat wave" of 2014-2015, could fundamentally influence typical lower trophic level patterns, possibly altering trophic interactions.

Is there a distinct continental slope fauna in the Antarctic?

NASA Astrophysics Data System (ADS)

Kaiser, Stefanie; Griffiths, Huw J.; Barnes, David K. A.; Brandão, Simone N.; Brandt, Angelika; O'Brien, Philip E.

2011-02-01

The Antarctic continental slope spans the depths from the shelf break (usually between 500 and 1000 m) to ˜3000 m, is very steep, overlain by 'warm' (2-2.5 °C) Circumpolar Deep Water (CDW), and life there is poorly studied. This study investigates whether life on Antarctica's continental slope is essentially an extension of the shelf or the abyssal fauna, a transition zone between these or clearly distinct in its own right. Using data from several cruises to the Weddell Sea and Scotia Sea, including the ANDEEP (ANtarctic benthic DEEP-sea biodiversity, colonisation history and recent community patterns) I-III, BIOPEARL (BIOdiversity, Phylogeny, Evolution and Adaptive Radiation of Life in Antarctica) 1 and EASIZ (Ecology of the Antarctic Sea Ice Zone) II cruises as well as current databases (SOMBASE, SCAR-MarBIN), four different taxa were selected (i.e. cheilostome bryozoans, isopod and ostracod crustaceans and echinoid echinoderms) and two areas, the Weddell Sea and the Scotia Sea, to examine faunal composition, richness and affinities. The answer has important ramifications to the link between physical oceanography and ecology, and the potential of the slope to act as a refuge and resupply zone to the shelf during glaciations. Benthic samples were collected using Agassiz trawl, epibenthic sledge and Rauschert sled. By bathymetric definition, these data suggest that despite eurybathy in some of the groups examined and apparent similarity of physical conditions in the Antarctic, the shelf, slope and abyssal faunas were clearly separated in the Weddell Sea. However, no such separation of faunas was apparent in the Scotia Sea (except in echinoids). Using a geomorphological definition of the slope, shelf-slope-abyss similarity only changed significantly in the bryozoans. Our results did not support the presence of a homogenous and unique Antarctic slope fauna despite a high number of species being restricted to the slope. However, it remains the case that there may be a unique Antarctic slope fauna, but the paucity of our samples could not demonstrate this in the Scotia Sea. It is very likely that various ecological and evolutionary factors (such as topography, water-mass and sediment characteristics, input of particulate organic carbon (POC) and glaciological history) drive slope distinctness. Isopods showed greatest species richness at slope depths, whereas bryozoans and ostracods were more speciose at shelf depths; however, significance varied across Weddell Sea and Scotia Sea and depending on bathymetric vs. geomorphological definitions. Whilst the slope may harbour some source populations for localised shelf recolonisation, the absence of many shelf species, genera and even families (in a poorly dispersing taxon) from the continental slope indicate that it was not a universal refuge for Antarctic shelf fauna.

The Effects of Sub-Regional Climate Velocity on the Distribution and Spatial Extent of Marine Species Assemblages.

PubMed

Kleisner, Kristin M; Fogarty, Michael J; McGee, Sally; Barnett, Analie; Fratantoni, Paula; Greene, Jennifer; Hare, Jonathan A; Lucey, Sean M; McGuire, Christopher; Odell, Jay; Saba, Vincent S; Smith, Laurel; Weaver, Katherine J; Pinsky, Malin L

2016-01-01

Many studies illustrate variable patterns in individual species distribution shifts in response to changing temperature. However, an assemblage, a group of species that shares a common environmental niche, will likely exhibit similar responses to climate changes, and these community-level responses may have significant implications for ecosystem function. Therefore, we examine the relationship between observed shifts of species in assemblages and regional climate velocity (i.e., the rate and direction of change of temperature isotherms). The assemblages are defined in two sub-regions of the U.S. Northeast Shelf that have heterogeneous oceanography and bathymetry using four decades of bottom trawl survey data and we explore temporal changes in distribution, spatial range extent, thermal habitat area, and biomass, within assemblages. These sub-regional analyses allow the dissection of the relative roles of regional climate velocity and local physiography in shaping observed distribution shifts. We find that assemblages of species associated with shallower, warmer waters tend to shift west-southwest and to shallower waters over time, possibly towards cooler temperatures in the semi-enclosed Gulf of Maine, while species assemblages associated with relatively cooler and deeper waters shift deeper, but with little latitudinal change. Conversely, species assemblages associated with warmer and shallower water on the broad, shallow continental shelf from the Mid-Atlantic Bight to Georges Bank shift strongly northeast along latitudinal gradients with little change in depth. Shifts in depth among the southern species associated with deeper and cooler waters are more variable, although predominantly shifts are toward deeper waters. In addition, spatial expansion and contraction of species assemblages in each region corresponds to the area of suitable thermal habitat, but is inversely related to assemblage biomass. This suggests that assemblage distribution shifts in conjunction with expansion or contraction of thermal habitat acts to compress or stretch marine species assemblages, which may respectively amplify or dilute species interactions to an extent that is rarely considered. Overall, regional differences in climate change effects on the movement and extent of species assemblages hold important implications for management, mitigation, and adaptation on the U.S. Northeast Shelf.

The Effects of Sub-Regional Climate Velocity on the Distribution and Spatial Extent of Marine Species Assemblages

PubMed Central

Kleisner, Kristin M.; Fogarty, Michael J.; McGee, Sally; Barnett, Analie; Fratantoni, Paula; Greene, Jennifer; Hare, Jonathan A.; Lucey, Sean M.; McGuire, Christopher; Odell, Jay; Saba, Vincent S.; Smith, Laurel; Weaver, Katherine J.; Pinsky, Malin L.

2016-01-01

Many studies illustrate variable patterns in individual species distribution shifts in response to changing temperature. However, an assemblage, a group of species that shares a common environmental niche, will likely exhibit similar responses to climate changes, and these community-level responses may have significant implications for ecosystem function. Therefore, we examine the relationship between observed shifts of species in assemblages and regional climate velocity (i.e., the rate and direction of change of temperature isotherms). The assemblages are defined in two sub-regions of the U.S. Northeast Shelf that have heterogeneous oceanography and bathymetry using four decades of bottom trawl survey data and we explore temporal changes in distribution, spatial range extent, thermal habitat area, and biomass, within assemblages. These sub-regional analyses allow the dissection of the relative roles of regional climate velocity and local physiography in shaping observed distribution shifts. We find that assemblages of species associated with shallower, warmer waters tend to shift west-southwest and to shallower waters over time, possibly towards cooler temperatures in the semi-enclosed Gulf of Maine, while species assemblages associated with relatively cooler and deeper waters shift deeper, but with little latitudinal change. Conversely, species assemblages associated with warmer and shallower water on the broad, shallow continental shelf from the Mid-Atlantic Bight to Georges Bank shift strongly northeast along latitudinal gradients with little change in depth. Shifts in depth among the southern species associated with deeper and cooler waters are more variable, although predominantly shifts are toward deeper waters. In addition, spatial expansion and contraction of species assemblages in each region corresponds to the area of suitable thermal habitat, but is inversely related to assemblage biomass. This suggests that assemblage distribution shifts in conjunction with expansion or contraction of thermal habitat acts to compress or stretch marine species assemblages, which may respectively amplify or dilute species interactions to an extent that is rarely considered. Overall, regional differences in climate change effects on the movement and extent of species assemblages hold important implications for management, mitigation, and adaptation on the U.S. Northeast Shelf. PMID:26901435

An unusual early Holocene diatom event north of the Getz Ice Shelf (Amundsen Sea): Implications for West Antarctic Ice Sheet development

NASA Astrophysics Data System (ADS)

Esper, O.; Gersonde, R.; Hillenbrand, C.; Kuhn, G.; Smith, J.

2011-12-01

Modern global change affects not only the polar north but also, and to increasing extent, the southern high latitudes, especially the Antarctic regions covered by the West Antarctic Ice Sheet (WAIS). Consequently, knowledge of the mechanisms controlling past WAIS dynamics and WAIS behaviour at the last deglaciation is critical to predict its development in a future warming world. Geological and palaeobiological information from major drainage areas of the WAIS, like the Amundsen Sea Embayment, shed light on the history of the WAIS glaciers. Sediment records obtained from a deep inner shelf basin north of Getz Ice Shelf document a deglacial warming in three phases. Above a glacial diamicton and a sediment package barren of microfossils that document sediment deposition by grounded ice and below an ice shelf or perennial sea ice cover (possibly fast ice), respectively, a sediment section with diatom assemblages dominated by sea ice taxa indicates ice shelf retreat and seasonal ice-free conditions. This conclusion is supported by diatom-based summer temperature reconstructions. The early retreat was followed by a phase, when exceptional diatom ooze was deposited around 12,500 cal. years B.P. [1]. Microscopical inspection of this ooze revealed excellent preservation of diatom frustules of the species Corethron pennatum together with vegetative Chaetoceros, thus an assemblage usually not preserved in the sedimentary record. Sediments succeeding this section contain diatom assemblages indicating rather constant Holocene cold water conditions with seasonal sea ice. The deposition of the diatom ooze can be related to changes in hydrographic conditions including strong advection of nutrients. However, sediment focussing in the partly steep inner shelf basins cannot be excluded as a factor enhancing the thickness of the ooze deposits. It is not only the presence of the diatom ooze but also the exceptional preservation and the species composition of the diatom assemblage, which point to specific scenarios involving e.g. changes in the food web that can be related to warmer surface water temperatures. Such warming of shelf waters may be related with an overshooting Atlantic Meridional Overturning Circulation (AMOC) and strong injection of warmer North Atlantic Deep Water into the Southern Ocean water masses at Termination I as reported by [2]. Such finding may highlight the effects of AMOC changes on Antarctic ice shelf extent and coastal ecosystems. [1] Hillenbrand et al., 2010. J. Quat. Sci. 25 (3), 280-295. [2] Barker et al., 2010. Nature Geosci. 3, 567-571.

Stable isotope geochemistry of pore waters from the New Jersey shelf - No evidence for Pleistocene melt water

NASA Astrophysics Data System (ADS)

van Geldern, Robert; Hayashi, Takeshi; Böttcher, Michael E.; Mottl, Michael J.; Barth, Johannes A. C.; Stadler, Susanne

2013-04-01

Scientific drillings in the 1970s revealed the presence of a large fresh water lens below the New Jersey Shelf. The origin and age of this fresh water body is still under debate. Groundwater flow models suggest that the water mainly originates from glacial melt water that entered the ground below large continental ice sheets during the last glacial maximum (LGM), whereas other studies suggest an age up to late Miocene. In this study, interstitial water was sampled during the Integrated Ocean Drilling Program (IODP) expedition 313 "New Jersey Shallow Shelf" (Mountain et al., 2010) and analyzed for water chemistry and stable isotope ratios (van Geldern et al, 2013). The pore fluid stable isotope values define a mixing line with end members that have oxygen and hydrogen isotope values of -7.0‰ and -41‰ for fresh water, and -0.8‰ and -6‰ for saltwater, respectively. The analyses revealed the following sources of fluids beneath the shelf: (1) modern rainwater, (2) modern seawater, and (3) a brine that ascends from deep sediments. The stable isotope composition of the water samples indicates modern meteoric recharge from New Jersey onshore aquifers as the fresh-water end member. This contradicts earlier views on the formation of the New Jersey fresh water lens, as it does not support the ice-age-origin theory. The salt-water end member is identical to modern New Jersey shelf seawater. Lower core parts of the drilling sites are characterized by mixing with a brine that originates from evaporites in the deep underground and that ascends via faults into the overlying sediments. The geochemical data from this study may provide the basis for an approach to construct a transect across the New Jersey shallow shelf since they fill a missing link in the shelf's geochemical profile. They also lay foundations for future research on hardly explored near-shore freshwater resources. References Mountain, G. and the Expedition 313 Scientists, 2010, Proceedings of the Integrated Ocean Drilling Program, Volume 313, Tokyo, available at: http://publications.iodp.org/proceedings/313/313toc.htm. van Geldern, R., Hayashi, T., Böttcher, M. E., Mottl, M. J., Barth, J. A. C., and Stadler, S., 2013, Stable isotope geochemistry of pore waters and marine sediments from the New Jersey shelf: Methane formation and fluid origin: Geosphere, v. 9, no. 1, p. in press.

Shelf life and quality study of minced tilapia with Nori and Hijiki seaweeds as natural additives.

PubMed

Ribeiro, Ingridy Simone; Shirahigue, Ligianne Din; Ferraz de Arruda Sucasas, Lia; Anbe, Lika; da Cruz, Pedro Gomes; Gallo, Cláudio Rosa; Carpes, Solange Teresinha; Marques, Marcos José; Oetterer, Marília

2014-01-01

The extraction of mechanically separated meat has emerged as an attractive process. However, it increases the incorporation of oxygen and, consequently, of flavors due to rancidity. Thus, preservatives must be added. The objective of this study was to evaluate the shelf life of minced tilapia to replace synthetic preservatives with Hijiki and Nori seaweeds extracts. The application of the extracts had no effect on the chemical composition of the minced tilapia. The seaweed extracts had inhibitory effect on total volatile base nitrogen. The minced tilapia complied with the microbiological standard set by Brazilin law. The panelists detected no differences in the rancid aroma and only minor differences were detected in the color of the products. It can be concluded that the minced tilapia with added seaweed extracts were within quality standards during frozen storage.

Seasonal temperature-salinity changes and thermocline development in the mid-Atlantic Bight as recorded by the isotopic composition of bivalves

NASA Astrophysics Data System (ADS)

Arthur, Michael A.; Williams, Douglas F.; Jones, Douglas S.

1983-11-01

Stable isotope records across annual growth increments in specimens of the surf clam Spisula solidissima from the mid-Atlantic Bight shelf from 10 m and 45 m depths reflect the changes in temperature and nutrient concentrations on the shelf over the year. The δ18O and δ13C records from clams at the two depths record well-mixed conditions in the water column during the winter months and the development of a thermocline during the summer. Spring high productivity and a transient salinity excursion in surface waters are also recorded. Reconstructing the paleoceanography of late Cenozoic temperate continental shelves may be possible using stable isotope records from fossil Spisula solidissima and other bivalves. *Present address: Graduate School of Oceanography, University of Rhode Island, Narragansett, Rhode Island 02882

California State Waters Map Series: Drakes Bay and vicinity, California

USGS Publications Warehouse

Watt, Janet T.; Dartnell, Peter; Golden, Nadine E.; Greene, H. Gary; Erdey, Mercedes D.; Cochrane, Guy R.; Johnson, Samuel Y.; Hartwell, Stephen R.; Kvitek, Rikk G.; Manson, Michael W.; Endris, Charles A.; Dieter, Bryan E.; Sliter, Ray W.; Krigsman, Lisa M.; Lowe, Erik N.; Chinn, John L.; Watt, Janet T.; Cochran, Susan A.

2015-01-01

Sediment transport in the map area largely is controlled by surface waves and tidal currents in the nearshore and, at depths greater than 20 to 30 m, by tidal and subtidal currents. In the map area, nearshore littoral drift of sand and coarse sediment is to the south, owing to the dominant west-northwest swell direction, and scour from large waves and tidal currents removes and redistributes sediment over large areas of the inner shelf. Tidal currents are particularly strong over the shelf in the map area, and they dominate the current regime in the nearshore. Further offshore, bottom currents generally flow to the northwest, distributing finer grained sediment accordingly.

Outer Continental Shelf environmental assesment program. Final reports of principal investigators. volume 37

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

1986-03-01

A compilation of seven final reports dealing with seal/sea lion and walrus surveys of the Navarin Basin; potential impacts of man-made noise on ringed seals; modern populations, migrations, demography, trophics, and historical status of the Pacific Walrus; distribution of marine mammals in the coastal zone of the eastern Chukchi Sea during summer and autumn; and early spring distribution, density and abundance of the Pacific Walrus in 1976.

Summer and winter living coccolithophores in the Yellow Sea and the East China Sea

NASA Astrophysics Data System (ADS)

Gu, X. Y.; Feng, Y. Y.; Jin, S. F.; Jiang, W. S.; Jin, H. Y.; Chen, J. F.; Sun, J.

2013-05-01

To date, very little information on living coccolithophores species composition and distribution, especially the vertical profile has been reported around the world. This paper tries to fill this gap by descripting on living coccolithophores (LCs) distribution in the Yellow Sea and the East China Sea in summer and winter time in detail, and its relationship among enviromental factors by canonical correspondence analysis (CCA). We carried out the investigations on LC distribution in the Yellow Sea and the East China Sea in July and December 2011. 210 samples from different depths were collected from 44 stations in summer and 217 samples were collected from 45 stations in winter. Totally 20 taxa belonging to coccolithophyceae were identified using a polarized microscope at the 1000 × magnification. The dominant species of the two seasons were Gephyrocapsa oceanica, Emiliania huxleyi, Helicosphaera carteri, and Algirosphaera robusta. In summer the abundance of cells and coccoliths ranged 0 ~ 176.40 cells mL-1, and 0 ~ 2144.98 coccoliths mL-1, with the average values of 8.45 cells mL-1, and 265.42 coccoliths mL-1, respectively. And in winter the abundance of cells and coccoliths ranged 0 ~ 71.66 cells mL-1, and 0 ~ 4698.99 coccoliths mL-1, with the average values of 13.91 cells mL-1 and 872.56 coccoliths mL-1 respectively. In summer the LCs in surface layer were mainly observed on the coastal belt and southern part of the survey area. The highest abundance was found at the bloom station. In winter the LCs in surface layer had high value in the continental shelf area of section P. The comparison among section A, section F, section P and section E indicated lower species diversity and less abundance in the Yellow Sea than those of the East China Sea in both seasons. Temperature and the nitrate concentration may be the major environmental factors controlling the distribution and species composition of LCs in the studying area based on CCA.

Species composition and distribution of the Antarctic plunderfishes (Pisces, Artedidraconidae) from the Ross Sea off Victoria Land

NASA Astrophysics Data System (ADS)

La Mesa, Mario; Cattaneo-Vietti, Riccardo; Vacchi, Marino

2006-04-01

Among the notothenioid fish, the Antarctic plunderfishes (family Artedidraconidae) are a poorly known component of the bottom fauna of the continental shelf despite their relative importance. The family is composed of 25 small- to medium-sized endemic species and four genera, Artedidraco, Dolloidraco, Histiodraco and Pogonophryne, which are the most benthic and sedentary of the notothenioid fish. In the framework of "Victoria Land Transect Project", several samples of plunderfishes were collected by means of an Agassiz trawl. Sampling activities were carried out between 100 and 500 m depth in five sites over nearly 4° latitude off Victoria Land. Overall, trawling yielded 80 specimens of plunderfish, including all species of Artedidraco reported from the Ross Sea, i.e. Artedidraco glareobarbatus, A. loennbergi, A. orianae, A. shackletoni and A. skottsbergi, and the monotypic genus Histiodraco. The use of multivariate statistical analyses on catch data indicated sampling site as the main factor affecting species composition. Histiodraco velifer and A. skottsbergi were caught almost exclusively in the southernmost sites, characterizing the artedidraconid fauna of Cape Russell. A. orianae was sampled only in the northernmost sites, such as Cape Adare and Hallett Peninsula. A. loennbergi appeared to be a ubiquitous species, whereas A. glareobarbatus was caught only at the Hallett Peninsula. Plunderfishes showed a particular distribution pattern in relation to depth as well. A. glareobarbatus was the shallowest species, being sampled within 100 m. A. orianae and A. shackletoni showed a similar distribution, being caught mostly at 100-200 m, whereas A. skottsbergi was mainly sampled at 200-300 m. H. velifer was caught in a wide depth range, but mostly in deeper waters (400 m). A. loennbergi was eurybathic, showing a wider depth distribution than other species. Univariate measures of diversity indicated Cape Adare as the poorer site in terms of species richness and diversity. Number of species, diversity and equitability were quite similar off Hallett Peninsula and Cape Russell, indicating the absence of a latitudinal trend. Generally, all univariate indices decreased from shallow (100 m) to deep waters (500 m).

Highlighting patterns of fungal diversity and composition shaped by ocean currents using the East China Sea as a model.

PubMed

Li, Wei; Wang, Mengmeng; Pan, Haoqin; Burgaud, Gaëtan; Liang, Shengkang; Guo, Jiajia; Luo, Tian; Li, Zhaoxia; Zhang, Shoumei; Cai, Lei

2018-01-01

How ocean currents shape fungal transport, dispersal and more broadly fungal biogeography remains poorly understood. The East China Sea (ECS) is a complex and dynamic habitat with different water masses blending microbial communities. The internal transcribed spacer 2 region of fungal rDNA was analysed in water and sediment samples directly collected from the coastal (CWM), Kuroshio (KSWM), Taiwan warm (TWM) and the shelf mixed water mass (MWM), coupled with hydrographic properties measurements, to determine how ocean currents impact the fungal community composition. Almost 9k fungal operational taxonomic units (OTUs) spanning six phyla, 25 known classes, 102 orders and 694 genera were obtained. The typical terrestrial and freshwater fungal genus, Byssochlamys, was dominant in the CWM, while increasing abundance of a specific OTU affiliated with Aspergillus was revealed from coastal to open ocean water masses (TWM and KSWM). Compared with water samples, sediment harboured an increased diversity with distinct fungal communities. The proximity of the Yangtze and Qiantang estuaries homogenizes the surface water and sediment communities. A significant influence of ocean currents on community structure was found, which is believed to reduce proportionally the variation explained by environmental parameters at the scale of the total water masses. Dissolved oxygen and depth were identified as the major parameters structuring the fungal community. Our results indicate that passive fungal dispersal driven by ocean currents and river run-off, in conjunction with the distinct hydrographic conditions of individual water masses, shapes the fungal community composition and distribution pattern in the ECS. © 2017 John Wiley & Sons Ltd.

Changes in chemical composition and antioxidative properties of rye ginger cakes during their shelf-life.

PubMed

Zieliński, Henryk; del Castillo, Maria Dolores; Przygodzka, Małgorzata; Ciesarova, Zuzana; Kukurova, Kristina; Zielińska, Danuta

2012-12-15

Changes in chemical composition and antioxidative properties of rye ginger cakes during their shelf-life were investigated in this study. In particular, the changes in antioxidants content, antioxidative and reducing capacity, and Maillard reaction development in rye ginger cakes after long-term storage were addressed. Ginger cakes produced according to the traditional and current recipe were stored for 5 years at room temperature in a dark place. The total phenolic compounds (TPC), inositol hexaphosphate (IP6), reduced (GSH) and oxidised glutathione (GSSG) contents, antioxidant and reducing capacity and Maillard reaction products (MRPs) were determined in ginger cakes after storage and then compared to those measured after baking. After long-term storage a decrease in TPC and IP6 contents in cakes was noted. In contrast, an increase in antioxidative and reducing capacity of stored cakes was observed. Long-term storage induced formation of furosine, advanced and final Maillard reaction products and caused changes in both reduced and oxidised forms of glutathione. After long-term storage the modest changes in furosine, FAST index and browning in ginger cake formulated with dark rye flour may suggest that this product is the healthiest among others. Therefore, traditional rye ginger cakes can be considered as an example of a healthy food that is also relatively stable during long term storage as noted by the small chemical changes observed in its composition. Copyright © 2012 Elsevier Ltd. All rights reserved.

Tooling Foam for Structural Composite Applications

NASA Technical Reports Server (NTRS)

DeLay, Tom; Smith, Brett H.; Ely, Kevin; MacArthur, Doug

1998-01-01

Tooling technology applications for composite structures fabrication have been expanded at MSFC's Productivity Enhancement Complex (PEC). Engineers from NASA/MSFC and Lockheed Martin Corporation have developed a tooling foam for use in composite materials processing and manufacturing that exhibits superior thermal and mechanical properties in comparison with other tooling foam materials. This tooling foam is also compatible with most preimpregnated composite resins such as epoxy, bismaleimide, phenolic and their associated cure cycles. MARCORE tooling foam has excellent processability for applications requiring either integral or removable tooling. It can also be tailored to meet the requirements for composite processing of parts with unlimited cross sectional area. A shelf life of at least six months is easily maintained when components are stored between 50F - 70F. The MARCORE tooling foam system is a two component urethane-modified polyisocyanurate, high density rigid foam with zero ozone depletion potential. This readily machineable, lightweight tooling foam is ideal for composite structures fabrication and is dimensionally stable at temperatures up to 350F and pressures of 100 psi.

Polyfibroblast: A Self-Healing and Galvanic Protection Additive

DTIC Science & Technology

2011-09-27

TESTING 8 3.5 ADHESION OF SPRAY COATINGS WITH MICROCAPSULES 8 3.6 CONTROLLING METAL COMPOSITION 9 3.7 SHEAR STRESS TESTING 9 Polyfibroblast...observed self-healing in real time using electrochemical impedance spectroscopy, we now show through this same technique the importance of the microcapsules ...OTS rich microcapsules have an improved shelf-life in comparison to polyurethane resin-filled microcapsules . Salt spray measurements, now completed

Improvements to the Processing and Characterization of Needled Composite Laminates

DTIC Science & Technology

2014-01-01

the automated processing equipment are shown and discussed. The modifications allow better spatial control at the penetration sites and the ability... automated processing equipment are shown and discussed. The modifications allow better spatial control at the penetration sites and the ability to...semi- automated processing equipment, commercial off-the-shelf (COTS) needles and COTS aramid mat designed for other applications. Needled material

Living (Rose-Bengal-Stained) benthic foraminifera along the Kveithola Trough (NW Barents Sea), environmental implications

NASA Astrophysics Data System (ADS)

Sabbatini, Anna; Morigi, Caterina; Lucchi, Renata G.; de Vittor, Cinzia; Bazzano, Matteo

2017-04-01

The distribution and composition of benthic foraminiferal fauna in the Kveithola Trough (NW Barents Sea) were studied in three depositional settings identified on the basis of surface depositional structures, sediment types and present ecosystem characteristics. Sediment samples were collected during the CORIBAR cruise (Hanebuth et al., 2013) aimed at drilling glacigenic sediments in a palaeo-ice stream depositional system in the western Barents Sea. In particular, we report the quantitative data of the living benthic foraminiferal density, biodiversity and vertical distribution in three box-core sediment samples (0-10 cm) collected in two inner trough sites, the drift area and the channel/fault area and one outer shelf site. Rose-Bengal-stained foraminiferal assemblages were investigated from two different size fractions (63-150 and >150 micrometres). In the drift area, the living benthic foraminiferal assemblage is characterized by the presence of oxygen-depleted environmental taxa with low foraminiferal density and biodiversity. This area appears a stagnant environment, strongly affected by low-oxygen, stressed environmental conditions in which foraminifera developed a life strategy aimed to increase the efficiency of food utilization and maximum resistance to ecological stress. As a further support to this interpretation, all the sediments recovered in the drift area are rich in organic matter and in Siboglinid-like tubes together with pockmark evidences on the surface of the box-corer. The sedimentation in the channel/fault area is very similar to that described for the drift area, evidencing stressed environmental conditions. Opportunistic species dominate the benthic foraminiferal fauna. The species distribution of the internal trough sites is consistent with the lithology and with data of quantity and biochemical composition (in terms of phytopigment, protein, lipid, carbohydrate and biopolymeric carbon) of the organic matter. Values of biopolymeric carbon are typical of eutrophic setting and the presence of tolerant low oxygen condition species as Nonionellina labradorica, Nonionella iridea and Fursenkoina fusiformis suggests that the sediment is dysoxic. In the inner part of the trough, the presence of Leptohalysis scottii and the decreasing of N. labradorica could indicate the presence of organic carbon input with higher nutritional quality, probably due to the shallower depth of the station (151 m water depth). The site corresponding to the outer shelf is characterized by the presence of diverse and abundant benthic foraminiferal assemblage suggesting a high oxygenated and mesotrophic environment. The sedimentological evidences characterized by clean sand with large-scale ripple-like features suggest the presence of moderately strong, and persistent bottom currents. We notice in all sites the presence of delicate monothalamous taxa (organic-walled allogromiids, agglutinated saccamminids, psammosphaerids and tubular forms). Therefore, preliminary faunal and sedimentological data allow to describe sediments of the Kveithola Drift, deposited under persistent dense bottom currents, appears today as a stagnant environment strongly affected by low-oxygen concentration, possibly chemosynthetic conditions with likely ongoing gas seep activity from pockmarks.

Mercury in sediments from shelf and continental slope at Campos Basin near Rio de Janeiro, Brazil

NASA Astrophysics Data System (ADS)

Araujo, Beatriz; Hintelmann, Holger; Dimock, Brian; Gomes de Almeida, Marcelo; Falcão, Ana Paula; de Rezende, Carlos Eduardo

2016-04-01

Mercury (Hg) is a global pollutant due to its ability to undergo long-range transport from source regions to remote parts of the world, and its ubiquitous presence in aquatic ecosystems. The Hg isotope ratios could be an effective tool for tracing the sources and process of Hg in the environment. This study aimed to establish the distribution of mercury in surface sediments of three transects (25- 3000m water depth) in continental shelf and slope in Campos Basin-RJ-Brazil, using the Hg isotopes to understand the geochemical processes relating to Hg cycling that occur in a subtropical coastal environment. The study area was divided into three transects: A (located to the south and close to a upwelling area), D (located opposite the mouth of the Paraiba do Sul River) and I (located north near the top of Vitória-ES). Sampling isobaths were 25, 50, 75, 100, 150, 400, 700, 1000, 1300, 1900, 2500 and 3000m. The Total Hg, MMHg and Hg stable isotopes were determined based on EPA Method 1631, EPA method 1630 and Foucher and Hintelmann (2006), respectively. The silt/clay ranged from 0.05 to 95%, and the organic carbon (OC) from 0.07 to 1.43 % for all transects. THg and MMHg concentrations in the shelf were 11.9 ± 7.2 (1.7- 22.2) ng.g-1 and 0.15 ± 0.12 (0.02 - 0.40) ng.g-1; in the slope 30.3 ± 9.2 (11.6 - 51.6) ng.g-1 and 0.13 ± 0.06 (0.03 -0.29) ng.g-1 , respectively. The δ202Hg and Δ199Hg varied from -0.32 to -1.85 ‰ (-0.79 ± 0.44‰) and -0.41 to 0.09 ‰ (-0.03 ± 0.12 ‰) for all transects, respectively. The delta values between both regions are significantly different, the shelf region showed δ202Hg from -0.59 to -2.19 ‰ (mean: -1.52 ±0.65) and Δ199Hg from - 0.53 to 0.08 ‰ (mean: -0.27 ±0.55) and the slope region were observed δ202Hg values from -0.32 to -1.82 ‰ (mean: -0.73 ±0.39 ‰ n=18) and gΔ199Hg from -0.23 to 0.09‰ (mean: -0.02 ±0.08‰ n=5). The slope appears to be enriched with heavier isotopes compared to the shelf, however, in the upper slope we can observe some points with ligther isotopes. the Some in the transect D, located closer to the cost (25 and 50 m of depth), showed the most negative isotope signature. This transect receives direct influence from the Paraíba do Sul river, so the Hg composition may be explained the riverine contribution characterized by Hg of different origin. Moreover, the negative δ202Hg values mainly observed in some stations in the shelf region, can be caused by process such as degassing of dissolved Hg0, volatilization, microbial reduction and photoreduction, which tend to deplete the lighter Hg isotopes in the product Hg0. Likewise, process such as physical settling of Hg adsorbed to particles and atmospheric deposition of Hg could also be a possible cause of the lower δ202Hg values. In addition, the positive Δ199Hg values could be caused due atmospheric Hg deposition, which represents a significant source in the biogeochemical cycle of Hg in oceans.

Sylhet-Kopili/Barail-Tipam Composite Total Petroleum System, Assam Geologic Province, India

USGS Publications Warehouse

Wandrey, Craig J.

2004-01-01

The Sylhet-Kopili/Barail-Tipam Composite total petroleum system (TPS) (803401) is located in the Assam Province in northeasternmost India and includes the Assam Shelf south of the Brahmaputra River. The area is primarily a southeast-dipping shelf overthrust by the Naga Hills on the southeast and the Himalaya Mountain range to the north. The rocks that compose this TPS are those of the Sylhet-Kopili/Barail-Tipam composite petroleum system. These rocks are those of the Eocene-Oligocene Jaintia Group Sylhet and Kopili Formations, the Oligocene Barail Group, the Oligocene-Miocene Surma and Tipam Groups. These groups include platform carbonates, shallow marine shales and sandstones, and the sandstones, siltstones, shales, and coals of deltaic and lagoonal facies. Source rocks include the Sylhet and Kopili Formation shales, Barail Group coals and shales, and in the south the Surma Group shales. Total organic content is generally low, averaging from 0.5 to 1.8 percent; it is as high as 9 percent in the Barail Coal Shales. Maturities are generally low, from Ro 0.45 to 0.7 percent where sampled. Maturity increases to the southeast near the Naga thrust fault and can be expected to be higher in the subthrust. Generation began in early Pliocene. Migration is primarily updip to the northwest (< 5 to 15 kilometers) along the northeast-trending slope of the Assam Shelf, and vertical migration occurs through reactivated basement-rooted faults associated with the plate collisions. Reservoir rocks are carbonates of the Sylhet Formation, interbedded sandstones of the Kopili Formation and sandstones of the Barail, Surma, and Tipam Groups. Permeability ranges from less than 8 mD (millidarcies) to as high as 800 mD in the Tipam Group. Porosity ranges from less than 7 percent to 30 percent. Traps are primarily anticlines and faulted anticlines with a few subtle stratigraphic traps. There is also a likelihood of anticlinal traps in the subthrust. Seals include interbedded Oligocene and Miocene shales and clays, and the thick clays of the Pliocene Gurjan Group.

Shelf life determinants and enzyme activities of pearl millet: a comparison of changes in stored flour of hybrids, CMS lines, inbreds and composites.

PubMed

Goyal, Preeti; Chugh, L K

2017-09-01

Shelf life of pearl millet flour is very short because of rapid development of rancidity. This investigation was carried out in view of generating breeding material for development of low rancid pearl millet hybrids/varieties. Flour of twenty-one genotypes; seven hybrids, seven CMS lines, five inbreds and two composites stored in covered aluminium boxes at 37 °C for 30 days along with respective fresh flour was analysed for shelf life indicators/determinants. Crude fat content and fat acidity (FA) of fresh flour of the genotypes varied from 3.8 to 7.2% and 11 to 75 mg KOH/100 g d.m., respectively. FA in stored flour ranged between 180 and 330 mg KOH/100 g d.m. After storage, magnitude of decrease in pH of water extract of flour of the genotypes varied from 0.15 to 0.44. Activity of peroxidase (POX) varied from 378 to 588 units in control flour and irrespective of the genotypes decreased upon storage. Increase in FA (difference between FA of fresh and stored flour) rather total build up of FA was positively associated with crude fat content (r = 0.440*) indicated comparatively more prominent role of lipolytic enzymes. Chemical changes taking place in water soluble fraction of flour were independent of fat content as no correlation was discerned between fat content and decrease in pH. Among the hybrids, HHB 197 had lowest crude fat content (4.7%), lowest total build up FA (212 mg KOH/100 g d.m.), slowest increase in FA (191 mg KOH/100 g d.m.), least decrease in pH (0.31) of water soluble fraction flour during storage and lowest activity of POX in fresh flour (377 units/g d.m). Among all the tested CMS lines, inbreds and composites, HBL 11 showed pattern of quantitative changes in FA, pH and POX activity similar to the hybrid HHB 197 and was identified a promising inbred for developing low-rancid pearl millet variety or hybrid.

Protection of fish spawning habitat for the conservation of warm-temperature reef-fish fisheries of shelf-edge reefs of Florida

USGS Publications Warehouse

Koenig, Christopher C.; Coleman, Felicia C.; Grimes, Churchill B.; Fitzhugh, Gary R.; Scanlon, Kathryn M.; Gledhill, Christopher T.; Grace, Mark

2000-01-01

We mapped and briefly describe the surficial geology of selected examples of shelf-edge reefs (50–120 m deep) of the southeastern United States, which are apparently derived from ancient Pleistocene shorelines and are intermittently distributed throughout the region. These reefs are ecologically significant because they support a diverse array of fish and invertebrate species, and they are the only aggregation spawning sites of gag (Mycteroperca microlepis), scamp (M. phenax), and other economically important reef fish. Our studies on the east Florida shelf in the Experimental Oculina Research Reserve show that extensive damage to the habitat-structuring coral Oculina varicosa has occurred in the past, apparently from trawling and dredging activities of the 1970s and later. On damaged or destroyed Oculina habitat, reef-fish abundance and diversity are low, whereas on intact habitat, reef-fish diversity is relatively high compared to historical diversity on the same site. The abundance and biomass of the economically important reef fish was much higher in the past than it is now, and spawning aggregations of gag and scamp have been lost or greatly reduced in size. On the west Florida shelf, fishers have concentrated on shelf-edge habitats for over 100 yrs, but fishing intensity increased dramatically in the 1980s. Those reefs are characterized by low abundance of economically important species. The degree and extent of habitat damage there is unknown. We recommend marine fishery reserves to protect habitat and for use in experimentally examining the potential production of unfished communities.

Neogene evolution of northern Mahakam Delta, East Kalimantan, Indonesia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Armin, R.A.; Abdoerrias, R.; Boer, W.D. de

1996-01-01

A regional sequence-stratigraphic study of the lower Kutei basin, embracing present coastal and offshore East Kalimantan, was undertaken to decipher the Neogene history of an important oil-producing province. The chronostratigraphic framework developed during this study was applied to facies analyses, organic geochemistry, and 2-D basin modeling. Integration of these disciplines powerfully illuminated the relationships between structuring, sedimentation, and hydrocarbon migration, Sedimentation in the lower Kutei basin since the late Middle Miocene has been dominated by the tidal-fluvial Mahakam delta system. During this time the principal river transport system has remained in about the same location as the present-day Mahakam River.more » Thick successions of monotonously similar deltaic facies were stacked vertically, punctuated by progradational or backstepping (flooding) units. Middle to Upper Miocene shelf edges of the delta platform, which are commonly sites of carbonate buildups, offlap from west to east towards the present-day shelf edge. Growth faults active during ca. 12-9 Ma are clustered just basinward of a prominent aggradational Middle Miocene shelf margin, and they exerted profound control on facies distribution. Tectonic quiescence prevailed during ca. 9-4 Ma, and in this period widespread regressive deltaic deposition over a broad, stable delta platform created the most important reservoirs. Subsequently, during Late Pliocene and younger time, many early growth faults were reactivated, and new faults also formed eastward toward the present shelf margin. Here, economically significant intervals consist mainly of lowstand deposits that accumulated in shelf-margin half-grabens created by these Plio-Pleistocene faults.« less

Neogene evolution of northern Mahakam Delta, East Kalimantan, Indonesia

DOE Office of Scientific and Technical Information (OSTI.GOV)

Armin, R.A.; Abdoerrias, R.; Boer, W.D. de

1996-12-31

A regional sequence-stratigraphic study of the lower Kutei basin, embracing present coastal and offshore East Kalimantan, was undertaken to decipher the Neogene history of an important oil-producing province. The chronostratigraphic framework developed during this study was applied to facies analyses, organic geochemistry, and 2-D basin modeling. Integration of these disciplines powerfully illuminated the relationships between structuring, sedimentation, and hydrocarbon migration, Sedimentation in the lower Kutei basin since the late Middle Miocene has been dominated by the tidal-fluvial Mahakam delta system. During this time the principal river transport system has remained in about the same location as the present-day Mahakam River.more » Thick successions of monotonously similar deltaic facies were stacked vertically, punctuated by progradational or backstepping (flooding) units. Middle to Upper Miocene shelf edges of the delta platform, which are commonly sites of carbonate buildups, offlap from west to east towards the present-day shelf edge. Growth faults active during ca. 12-9 Ma are clustered just basinward of a prominent aggradational Middle Miocene shelf margin, and they exerted profound control on facies distribution. Tectonic quiescence prevailed during ca. 9-4 Ma, and in this period widespread regressive deltaic deposition over a broad, stable delta platform created the most important reservoirs. Subsequently, during Late Pliocene and younger time, many early growth faults were reactivated, and new faults also formed eastward toward the present shelf margin. Here, economically significant intervals consist mainly of lowstand deposits that accumulated in shelf-margin half-grabens created by these Plio-Pleistocene faults.« less

Regional modeling of the water masses and circulation annual variability at the Southern Brazilian Continental Shelf

NASA Astrophysics Data System (ADS)

Mendonça, L. F.; Souza, R. B.; Aseff, C. R. C.; Pezzi, L. P.; Möller, O. O.; Alves, R. C. M.

2017-02-01

The Southern Brazilian Continental Shelf (SBCS) is one of the more productive areas for fisheries in Brazilian waters. The water masses and the dynamical processes of the region present a very seasonal behavior that imprint strong effects in the ecosystem and the weather of the area and its vicinity. This paper makes use of the Regional Ocean Modeling System (ROMS) for studying the water mass distribution and circulation variability in the SBCS during the year of 2012. Model outputs were compared to in situ, historical observations and to satellite data. The model was able to reproduce the main thermohaline characteristics of the waters dominating the SBCS and the adjacent region. The mixing between the Subantarctic Shelf Water and the Subtropical Shelf Water, known as the Subtropical Shelf Front (STSF), presented a clear seasonal change in volume. As a consequence of the mixing and of the seasonal oscillation of the STSF position, the stability of the water column inside the SBCS also changes seasonally. Current velocities and associated transports estimated for the Brazil Current (BC) and for the Brazilian Coastal Current (BCC) agree with previous measurements and estimates, stressing the fact that the opposite flow of the BCC occurring during winter in the study region is about 2 orders of magnitude smaller than that of the BC. Seasonal maps of simulated Mean Kinetic Energy and Eddy Kinetic Energy demonstrate the known behavior of the BC and stressed the importance of the mean coastal flow off Argentina throughout the year.

Hypoxia Hotspots in the Mississippi Bight

DTIC Science & Technology

2006-04-01

settings (see Sen Gupta and Machain- Pyrite framboid size and size distribution have been used Castillo , 1993, and references therein; Grantham and as...today/lASNFS-gom.html#msb. (eds.), Modem and Ancient Continental Shelf Anoxia: Geological NELSEN, T. A., BLACKWELDER, P., HOOD, T., MCKEE, B., ROMER , N

Shelf life and microbial profile of peeled onions

USDA-ARS?s Scientific Manuscript database

The increased usage of peeled onions over the past ten years by food service operations and fast-food restaurants has been plagued by black mold decay during cold-chain storage. This study examined the epiphytic microbiological distribution on onions and what effects various processing steps have on...

Demersal Fish Assemblages and Spatial Diversity Patterns in the Arctic-Atlantic Transition Zone in the Barents Sea

PubMed Central

Johannesen, Edda; Høines, Åge S.; Dolgov, Andrey V.; Fossheim, Maria

2012-01-01

Direct and indirect effects of global warming are expected to be pronounced and fast in the Arctic, impacting terrestrial, freshwater and marine ecosystems. The Barents Sea is a high latitude shelf Sea and a boundary area between arctic and boreal faunas. These faunas are likely to respond differently to changes in climate. In addition, the Barents Sea is highly impacted by fisheries and other human activities. This strong human presence places great demands on scientific investigation and advisory capacity. In order to identify basic community structures against which future climate related or other human induced changes could be evaluated, we analyzed species composition and diversity of demersal fish in the Barents Sea. We found six main assemblages that were separated along depth and temperature gradients. There are indications that climate driven changes have already taken place, since boreal species were found in large parts of the Barents Sea shelf, including also the northern Arctic area. When modelling diversity as a function of depth and temperature, we found that two of the assemblages in the eastern Barents Sea showed lower diversity than expected from their depth and temperature. This is probably caused by low habitat complexity and the distance to the pool of boreal species in the western Barents Sea. In contrast coastal assemblages in south western Barents Sea and along Novaya Zemlya archipelago in the Eastern Barents Sea can be described as diversity “hotspots”; the South-western area had high density of species, abundance and biomass, and here some species have their northern distribution limit, whereas the Novaya Zemlya area has unique fauna of Arctic, coastal demersal fish. (see Information S1 for abstract in Russian). PMID:22545093

Vertical distribution, diversity and assemblages of mesopelagic fishes in the western Mediterranean

NASA Astrophysics Data System (ADS)

Olivar, M. P.; Bernal, A.; Molí, B.; Peña, M.; Balbín, R.; Castellón, A.; Miquel, J.; Massutí, E.

2012-04-01

The mesopelagic fish community of the western Mediterranean was studied during two cruises carried out in December 2009 and July 2010 in the shelf and slope zones around the Balearic Islands. Much of what was previously known about this deep water group of fishes in the Mediterranean Sea came from studies performed using planktonic and small midwater nets. This study was the first attempt to use large pelagic trawls and small nets combined with information about the main sound scattering layers to analyse mesopelagic fish composition, diversity and species assemblages. This community is characterised by a relatively low diversity compared to other oceanic regions of the world, with Myctophiformes and Stomiiformes being the main contributors. Bathymetry and the level of the water column were the most important factors structuring the investigated fish assemblages, and similar vertical patterns were observed for the different species collected during the two study periods. A shelf assemblage composed of a few species of myctophids, with Notoscopelus elongatus being the main contributor, was distinguished. The slope assemblage included both Myctophiformes and Stomiiformes that showed differences in their day-night main location along the water column. In terms of species behaviour, two important groups were detected. The first was non-migrant or weakly migrant species, with the paradigmatic example being the gonostomatid Cyclothone braueri, which occurred at a depth of 400-600 m; this species is partly responsible for the permanent acoustic (38 kHz) response at this depth. The second group, near-surface migrants at night, was represented by most of the juvenile and adult myctophids, exemplified by Ceratoscopelus maderensis, with the exception of just a few of the largest size classes of some species, such as Lampanyctus crocodilus and N. elongatus that remain near the bottom.

Activity and Phylogenetic Diversity of Bacterial Cells with High and Low Nucleic Acid Content and Electron Transport System Activity in an Upwelling Ecosystem

PubMed Central

Longnecker, K.; Sherr, B. F.; Sherr, E. B.

2005-01-01

We evaluated whether bacteria with higher cell-specific nucleic acid content (HNA) or an active electron transport system, i.e., positive for reduction of 5-cyano-2,3-ditolyl tetrazolium chloride (CTC), were responsible for the bulk of bacterioplankton metabolic activity. We also examined whether the phylogenetic diversity of HNA and CTC-positive cells differed from the diversity of Bacteria with low nucleic acid content (LNA). Bacterial assemblages were sampled both in eutrophic shelf waters and in mesotrophic offshore waters in the Oregon coastal upwelling region. Cytometrically sorted HNA, LNA, and CTC-positive cells were assayed for their cell-specific [3H]leucine incorporation rates. Phylogenetic diversity in sorted non-radioactively labeled samples was assayed using denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S rRNA genes. Cell-specific rates of leucine incorporation of HNA and CTC-positive cells were on average only slightly greater than the cell-specific rates of LNA cells. HNA cells accounted for most bacterioplankton substrate incorporation due to high abundances, while the low abundances of CTC-positive cells resulted in only a small contribution by these cells to total bacterial activity. The proportion of the total bacterial leucine incorporation attributable to LNA cells was higher in offshore regions than in shelf waters. Sequence data obtained from DGGE bands showed broadly similar phylogenetic diversity across HNA, LNA, and CTC-positive cells, with between-sample and between-region variability in the distribution of phylotypes. Our results suggest that LNA bacteria are not substantially different from HNA bacteria in either cell-specific rates of substrate incorporation or phylogenetic composition and that they can be significant contributors to bacterial metabolism in the sea. PMID:16332746

Activity and phylogenetic diversity of bacterial cells with high and low nucleic acid content and electron transport system activity in an upwelling ecosystem.

PubMed

Longnecker, K; Sherr, B F; Sherr, E B

2005-12-01

We evaluated whether bacteria with higher cell-specific nucleic acid content (HNA) or an active electron transport system, i.e., positive for reduction of 5-cyano-2,3-ditolyl tetrazolium chloride (CTC), were responsible for the bulk of bacterioplankton metabolic activity. We also examined whether the phylogenetic diversity of HNA and CTC-positive cells differed from the diversity of Bacteria with low nucleic acid content (LNA). Bacterial assemblages were sampled both in eutrophic shelf waters and in mesotrophic offshore waters in the Oregon coastal upwelling region. Cytometrically sorted HNA, LNA, and CTC-positive cells were assayed for their cell-specific [3H]leucine incorporation rates. Phylogenetic diversity in sorted non-radioactively labeled samples was assayed using denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S rRNA genes. Cell-specific rates of leucine incorporation of HNA and CTC-positive cells were on average only slightly greater than the cell-specific rates of LNA cells. HNA cells accounted for most bacterioplankton substrate incorporation due to high abundances, while the low abundances of CTC-positive cells resulted in only a small contribution by these cells to total bacterial activity. The proportion of the total bacterial leucine incorporation attributable to LNA cells was higher in offshore regions than in shelf waters. Sequence data obtained from DGGE bands showed broadly similar phylogenetic diversity across HNA, LNA, and CTC-positive cells, with between-sample and between-region variability in the distribution of phylotypes. Our results suggest that LNA bacteria are not substantially different from HNA bacteria in either cell-specific rates of substrate incorporation or phylogenetic composition and that they can be significant contributors to bacterial metabolism in the sea.

Zooplankton research off Peru: A review

NASA Astrophysics Data System (ADS)

Ayón, Patricia; Criales-Hernandez, Maria I.; Schwamborn, Ralf; Hirche, Hans-Jürgen

2008-10-01

A review of zooplankton studies conducted in Peruvian marine waters is given. After a short history of the development of zooplankton research off Peru, we review zooplankton methodology, taxonomy, biodiversity, spatial distribution, seasonal and interannual variability, trophodynamics, secondary production, and modelling. We review studies on several micro-, meso-, macro-, and meroplankton groups, and give a species list from both published and unpublished reports. Three regional zooplankton groups have been identified: (1) a continental shelf group dominated by Acartia tonsa and Centropages brachiatus; (2) a continental slope group characterized by siphonophores, bivalves, foraminifera and radiolaria; (3) and a species-rich oceanic group. The highest zooplankton abundances and biomasses were often found between 4-6°S and 14-16°S, where continental shelves are narrow. Species composition changes with distance from the shore. Species composition and biomass also vary strongly on short time scales due to advection, peaks of larval production, trophic interactions, and community succession. The relation of zooplankton to climatic variability (ENSO and multi-decadal) and fish stocks is discussed in the context of ecological regime shifts. An intermediate upwelling hypothesis is proposed, based on the negative effects of low upwelling intensity in summer or extremely strong and enduring winter upwelling on zooplankton abundance off Peru. According to this hypothesis, intermediate upwelling creates an optimal environmental window for zooplankton communities. Finally, we highlight important knowledge gaps that warrant attention in future.

A finite element model of myocardial infarction using a composite material approach.

PubMed

Haddad, Seyyed M H; Samani, Abbas

2018-01-01

Computational models are effective tools to study cardiac mechanics under normal and pathological conditions. They can be used to gain insight into the physiology of the heart under these conditions while they are adaptable to computer assisted patient-specific clinical diagnosis and therapeutic procedures. Realistic cardiac mechanics models incorporate tissue active/passive response in conjunction with hyperelasticity and anisotropy. Conventional formulation of such models leads to mathematically-complex problems usually solved by custom-developed non-linear finite element (FE) codes. With a few exceptions, such codes are not available to the research community. This article describes a computational cardiac mechanics model developed such that it can be implemented using off-the-shelf FE solvers while tissue pathologies can be introduced in the model in a straight-forward manner. The model takes into account myocardial hyperelasticity, anisotropy, and active contraction forces. It follows a composite tissue modeling approach where the cardiac tissue is decomposed into two major parts: background and myofibers. The latter is modelled as rebars under initial stresses mimicking the contraction forces. The model was applied in silico to study the mechanics of infarcted left ventricle (LV) of a canine. End-systolic strain components, ejection fraction, and stress distribution attained using this LV model were compared quantitatively and qualitatively to corresponding data obtained from measurements as well as to other corresponding LV mechanics models. This comparison showed very good agreement.

Biological, physical and chemical properties at the Subtropical Shelf Front Zone in the SW Atlantic Continental Shelf

NASA Astrophysics Data System (ADS)

Muelbert, José H.; Acha, Marcelo; Mianzan, Hermes; Guerrero, Raúl; Reta, Raúl; Braga, Elisabete S.; Garcia, Virginia M. T.; Berasategui, Alejandro; Gomez-Erache, Mónica; Ramírez, Fernando

2008-07-01

The physical aspects of the Subtropical Shelf Front (STSF) for the Southwest Atlantic Continental Shelf were previously described. However, only scarce data on the biology of the front is available in the literature. The main goal of this paper is to describe the physical, chemical and biological properties of the STSF found in winter 2003 and summer 2004. A cross-section was established at the historically determined location of the STSF. Nine stations were sampled in winter and seven in summer. Each section included a series of conductivity-temperature-depth (CTD) stations where water samples from selected depths were filtered for nutrient determination. Surface samples were taken for chlorophyll a (Chl- a) determination and plankton net tows carried out above and below the pycnocline. Results revealed that winter was marked by an inner-shelf salinity front and that the STSF was located on the mid-shelf. The low salinity waters in the inner-shelf indicated a strong influence of freshwater, with high silicate (72 μM), suspended matter (45 mg l -1), phosphate (2.70 μM) and low nitrate (1.0 μM) levels. Total dissolved nitrogen was relatively high (22.98 μM), probably due to the elevated levels of organic compound contribution close to the continental margin. Surface Chl -a concentration decreased from coastal well-mixed waters, where values up to 8.0 mg m -3 were registered, to offshore waters. Towards the open ocean, high subsurface nutrients values were observed, probably associated to South Atlantic Central Waters (SACW). Zooplankton and ichthyoplankton abundance followed the same trend; three different groups associated to the inner-, mid- and outer-shelf region were identified. During summer, diluted waters extended over the shelf to join the STSF in the upper layer; the concentration of inorganic nutrients decreased in shallow waters; however, high values were observed between 40 and 60 m and in deep offshore waters. Surface Chl -a ranged 0.07-1.5 mg m -3; winter levels were higher. Three groups of zoo and ichthyoplankton, separated by the STSF, were also identified. Results of the study performed suggest that the influence of freshwater was stronger during winter and that abundance distribution of Chl -a, copepods and ichthyoplankton was related to the Plata Plume Waters (PPW), rather than to the presence of the STSF. During summer, when the presence of freshwater decreases, plankton interactions seem to take place in the STSF.

Surficial sediments on the western Canadian continental shelf

NASA Astrophysics Data System (ADS)

Bornhold, Brian D.; Barrie, J. Vaughn

1991-08-01

The active continental margin off western Canada is characterized in the south by convergence between the Explorer and Juan de Fuca Plates and the America Plate, and in the north by transform fault motion between the Pacific and America Plates along the Queen Charlotte Fault. Except in some of the deepest troughs and basins shelf sediments are dominated by immature lithic arenites reflecting this tectonic setting. The Vancouver Island shelf is from 5 to 75 km wide and displays complex topography on the inner shelf and a relatively featureless mid- and outer shelf. An exception is the area off southwestern Vancouver Island where large basins bounded by morainal deposits extend more than two-thirds of the distance across the shelf. The shelf edge varies from 180 to 225 m depth and is indented by numerous canyons. Nearshore sediments consist mainly of gravels and boulders and become finer offshore such that muds are slowly accumulating in depths greater than 100 m. Off northwestern Vancouver Island calcareous sediments are abundant with carbonate values often exceeding 75%. High wave and current energies and efficient sediment trapping in coastal fiords have resulted in low rates of accumulation. Olive, glauconitic, Holocene muds and muddy sands are generally less than 0.3 m thick and accumulate only on the outer shelf over an extensive stiff, gray, glaciomarine sandy mud. Queen Charlotte Sound exhibits three broad, shallow, glacially scoured troughs, filled mainly with clayey silts and fine sands and separated by sand and gravel covered banks. Hecate Strait, between the Queen Charlotte Islands and the mainland, consists of a prominent southward-opening trough along the east side of the Strait bounded by Dogfish and Laskeek Banks on the west adjacent to Graham and Moresby Islands, respectively. The trough below 200 m is filled by silts. The banks are covered by discontinuous sands and gravels of variable calcareous content. The bank edges often display megaripples and sand waves. Shore-parallel and oblique sand and gravel ridges occur along northernmost Dogfish Bank. Except for the inshore area (less than 100 m) off northern Graham Island little is known of the sediment distribution in Dixon Entrance. Off northwestern Graham Island the near shore zone is dominated by bedrock and discontinuous sands and gravels made up of up to 90% skeletal carbonate. Off northeastern Graham Island sandy sediments predominate in the nearshore. No studies have been undertaken on the narrow shelf off the western Queen Charlotte Islands.

Holocene sediment distribution on the inner continental shelf of northeastern South Carolina: implications for the regional sediment budget and long-term shoreline response

USGS Publications Warehouse

Denny, Jane F.; Schwab, William C.; Baldwin, Wayne E.; Barnhardt, Walter A.; Gayes, Paul T.; Morton, R.A.; Warner, John C.; Driscoll, Neal W.; Voulgaris, George

2013-01-01

High-resolution geophysical and sediment sampling surveys were conducted offshore of the Grand Strand, South Carolina to define the shallow geologic framework of the inner shelf. Results are used to identify and map Holocene sediment deposits, infer sediment transport pathways, and discuss implications for the regional coastal sediment budget. The thickest deposits of Holocene sediment observed on the inner shelf form shoal complexes composed of moderately sorted fine sand, which are primarily located offshore of modern tidal inlets. These shoal deposits contain ~67 M m3 of sediment, approximately 96% of Holocene sediment stored on the inner shelf. Due to the lack of any significant modern fluvial input of sand to the region, the Holocene deposits are likely derived from reworking of relict Pleistocene and older inner-shelf deposits during the Holocene marine transgression. The Holocene sediments are concentrated in the southern part of the study area, due to a combination of ancestral drainage patterns, a regional shift in sediment supply from the northeast to the southwest in the late Pleistocene, and proximity to modern inlet systems. Where sediment is limited, only small, low relief ridges have formed and Pleistocene and older deposits are exposed on the seafloor. The low-relief ridges are likely the result of a thin, mobile veneer of sediment being transported across an irregular, erosional surface formed during the last transgression. Sediment textural trends and seafloor morphology indicate a long-term net transport of sediment to the southwest. This is supported by oceanographic studies that suggest the long-term sediment transport direction is controlled by the frequency and intensity of storms that pass through the region, where low pressure systems yield net along-shore flow to the southwest and a weak onshore component. Current sediment budget estimates for the Grand Strand yield a deficit for the region. Volume calculations of Holocene deposits on the inner shelf suggest that there is sufficient sediment to balance the sediment budget and provide a source of sediment to the shoreline. Although the processes controlling cross-shelf sediment transport are not fully understood, in sediment-limited environments such as the Grand Strand, erosion of the inner shelf likely contributes significant sediment to the beach system.

Recent seasonal hypoxia on the Western Black Sea shelf recorded in adjacent slope sediments

NASA Astrophysics Data System (ADS)

Roepert, Anne; Jilbert, Tom S.; Slomp, Caroline P.

2015-04-01

Bottom water hypoxia is a major environmental problem afflicting estuarine and marine environments across the globe (Diaz and Rosenberg, 2008). Hypoxia is often attributed to human-induced increased nutrient discharge from rivers and related eutrophication. The Western Black Sea shelf is a typical example of a system where such anthropogenic impacts are thought to have contributed to the development of seasonal hypoxia in the late 20th century. However, due to the lack of spatially and temporally consistent monitoring in the region, questions remain about the evolution, causes and consequences of the seasonal hypoxia on the Western Black Sea shelf and whether or not the ecological state has recently improved (Capet et al., 2013). In this study a resin-embedded sediment core from a location below the chemocline on the Western Black Sea slope (water depth 377 m) was analyzed for its elemental composition by means of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), recovering a continuous geochemical record at a sub-annual resolution for the last 100 years. Relative enrichments in organic carbon, Pb, Fe, S, and Mo were observed in the depth interval corresponding to the 1970s until the 1990s, suggesting an increased carbon flux to the sediments as well as an anthropogenic pollution signal. We propose that the expansion of eutrophication on the Western Black Sea shelf was responsible for the enhanced carbon flux to our study site, while the associated hypoxia enhanced the shuttling of redox-sensitive elements to locations below the chemocline. The subsequent decrease in organic carbon and metal enrichments at the core top suggests a recent rise in oxygen concentrations and improvement of the ecological state of the Western Black Sea shelf. References: Capet, A., Beckers, J.-M., Grégoire, M. (2013). "Drivers, mechanisms and long-term variability of seasonal hypoxia on the Black Sea northwestern shelf-is there any recovery after eutrophication?" Biogeosciences 10(6): 3943-3962. Diaz, R. J., and Rosenberg, R. (2008). Spreading dead zones and consequences for marine ecosystems. Science 321(5891): 926-929.

3D Thermomechanical Modeling of Rifted Margins with Coupled Surface Processes: the North West Shelf, Australia

NASA Astrophysics Data System (ADS)

Moresi, L. N.; Beucher, R.; Morón, S.; Rey, P. F.; Salles, T.; Brocard, G. Y.; Farrington, R.; Giordani, J.; Mansour, J.

2017-12-01

Thermo-mechanical numerical models and analogue experiments with a layered lithosphere have emphasised the role played by the composition and thermal state of the lithosphere on the style of extension. The variation in rheological properties and the coupling between lithospheric layers promote depth-dependent extension with the potential for complex rift evolution over space and time. Local changes in the stress field due to loading / unloading of the lithosphere can perturb the syn and post-rift stability of the margins. We investigate how erosion of the margins and sedimentation within the basins integrate with the thermo-mechanical processes involved in the structural and stratigraphic evolution of the North West Shelf (NWS), one of the most productive and prospective hydrocarbon provinces in Australia. The complex structural characteristics of the NWS include large-scale extensional detachments, difference between amounts of crustal and lithospheric extension and prolonged episodes of thermal sagging after rifting episodes. It has been proposed that the succession of different extensional styles mechanisms (Cambrian detachment faulting, broadly distributed Permo-Carboniferous extension and Late Triassic to Early Cretaceous localised rift development) is best described in terms of variation in deformation response of a lithosphere that has strengthened from one extensional episode to the next. However, previous models invoking large-scale detachments fail to explain changes in extensional styles and overestimate the structural importance of relatively local detachments. Here, we hypothesize that an initially weak lithosphere would distribute deformation by ductile flow within the lower crust and that the interaction between crustal flow, thermal-evolution and sediment loading/unloading could explain some of the structural complexities recorded by the NWS. We run a series of fully coupled 3D thermo-mechanical numerical experiments that include realistic thermal and mechanical properties, as well as surface processes (erosion, sediments transport and sedimentation). This modeling approach aims to provide insights into the thermal and structural history of the NWS, and a better understanding of the complex interactions between tectonics and surface processes at rifted margins.

Facies dimensions within carbonate reservoirs - guidelines from satellite images of modern analogs

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harris, P.M.; Kowalik, W.S.

1995-08-01

Modern analogs illustrate the distribution of carbonate facies within an overall depositional setting and can be an integral part of a subsurface geologic model in indicating the dimensions, trend, and interrelationships of facies that might be related to reservoir and non-reservoir distribution. Satellite images from several modern carbonate areas depict the geologic characteristics that can be expected in ancient shallow-water settings. Isolated carbonate platforms- the Bahamas, Caicos Platform in the British West Indies, Chinchorro Bank offshore of Yucatan, and portions of the Belize area; Ramp-style shelf-to-basin transitions - Abu Dhabi and northern Yucatan; Rimmed shelf margins - South Florida, portionsmore » of Belize, and the Great Barrier Reef of Australia; Broad, deep shelf lagoons - the Great Barrier Reef and Belize; Reef variability - South Florida, the Bahamas, Caicos, Northern Yucatan, and Abu Dhabi; Shallow lagoon/tidal flat settings - South Florida, the Bahamas, Caicos, Northern Yucatan, Shark Bay in Western Australia, Abu Dhabi; Mixed carbonate and siliciclastic depostion - South Florida, Belize, the Great Barrier Reef, Shark Bay and Abu Dhabi. The geologic framework as illustrated by these areas is important at the development scale where lateral variation of porosity and permeability, i.e. reservoir quality, is commonly tied to facies changes and facies dimensions are required as input to reservoir models. The geologic framework is essential at the exploration scale for reservoir facies prediction and stratigraphic play concepts which are related directly to depositional facies patterns.« less

The ESASSI-08 cruise in the South Scotia Ridge region: preliminary analysis of hydrodynamic and biogeochemical data

NASA Astrophysics Data System (ADS)

Gomis, D.; Flexas, M. M.; Palmer, M.; Jordà, G.; Orsi, A. H.; Yvon-Lewis, S. A.

2009-04-01

The ESASSI-08 oceanographic cruise carried out in January 2008 was the major milestone of ESASSI, the Spanish component of SASSI (a core project of the International Polar Year devoted to study the shelf-slope exchanges in different locations of Antarctica). The sampling strategy of the cruise consisted of 11 full-depth CTD/ADCP sections across the northern and southern slope of the South Scotia Ridge (SSR), between Elephant and Orkney Islands. The sections extend from shelf waters to open sea and the profiles were gathered at an unprecedented spatial resolution over the slope (about 2 nm). Water samples for chemical and biological analysis were also collected at each station; the analyzed parameters include trace gases (CFCs), oxygen isotopes, carbon-related parameters, and nutrients. In this presentation we show the overall distribution of the main variables across the different sections. Namely, we present: a water mass analysis (in terms of potential temperature, salinity and neutral density), estimates of velocities and fluxes across different transects and distributions of biogeochemical parameters. The ultimate aims of the ESASSI project are: 1) to elucidate the fate of the ASF when it enters the SSR from the Weddell Sea; 2) to estimate the shelf-slope exchanges for different parameters; and 3) to quantify the importance of the ventilation associated with intermediate waters flowing over the SSR with respect to the ventilation associated with bottom waters that are blocked by the SSR and flow around the Orkney Plateau.

Distributed situation awareness in complex collaborative systems: A field study of bridge operations on platform supply vessels

PubMed Central

Sandhåland, Hilde; Oltedal, Helle A; Hystad, Sigurd W; Eid, Jarle

2015-01-01

This study provides empirical data about shipboard practices in bridge operations on board a selection of platform supply vessels (PSVs). Using the theoretical concept of distributed situation awareness, the study examines how situation awareness (SA)-related information is distributed and coordinated at the bridge. This study thus favours a systems approach to studying SA, viewing it not as a phenomenon that solely happens in each individual's mind but rather as something that happens between individuals and the tools that they use in a collaborative system. Thus, this study adds to our understanding of SA as a distributed phenomenon. Data were collected in four field studies that lasted between 8 and 14 days on PSVs that operate on the Norwegian continental shelf and UK continental shelf. The study revealed pronounced variations in shipboard practices regarding how the bridge team attended to operational planning, communication procedures, and distracting/interrupting factors during operations. These findings shed new light on how SA might decrease in bridge teams during platform supply operations. The findings from this study emphasize the need to assess and establish shipboard practices that support the bridge teams' SA needs in day-to-day operations. Practitioner points Provides insights into how shipboard practices that are relevant to planning, communication and the occurrence of distracting/interrupting factors are realized in bridge operations. Notes possible areas for improvement to enhance distributed SA in bridge operations. PMID:26028823

The central branch of the North Anatolian Fault In The Southern Marmara Sea: Evidence for a distributed, Holocene-active fault system

NASA Astrophysics Data System (ADS)

Barın, Burcu; Okay, Seda; Çifçi, Günay; Dondurur, Derman; Cormier, Marie Helene; Sorlien, Christopher; Meriç İlkimen, Elif

2015-04-01

The North Anatolian Fault (NAF) is a major right-lateral transform fault in northern Turkey that branches westward into several strands in the vicinity of the Sea of Marmara. The main northern branch bisects the Marmara Sea from east to west, and seismic reflection profiles acquired over the past 15 years have revealed its complex geometry. Further, the several basins that developed along that branch record stratigraphic sequences that provide the needed framework to interpret the relative timing of tectonic deformation in the Marmara Sea. In contrast, the central branch, which snakes across the shallow southern shelf of the Marmara Sea, has been much less investigated. Here, we analyze a comprehensive dataset of high-resolution multi-channel, sparker, and CHIRP seismic profiles, which were collected with the facilities of Seismic Laboratory (SeisLab) in the Institute of Marine Sciences and Technology and R/V K. Piri Reis belonging to Dokuz Eylül University, along the central branch in 2008 (TAMAM expedition) and in 2013-2014 (SoMAR expedition), within the framework of a bilateral TÜBİTAK - NSF project. In combination with other existing seismic profiles, these new data reveal that the Central Branch consists of multiple faults strands that are distributed across the broad southern shelf. They also reveal that many of these strands are Holocene-active, although they slip at slower rates than the northern branch and are associated with slower basin subsidence or local uplift. Lastly, seismic data image a system of half-grabens across the southern shelf that are associated with the strands of the central branch. Strata within these half-grabens are progressively tilted and consistently dip to the south. Further analysis will be conducted to determine whether the formation of these grabens are controlled by oblique slip on the strands of the central branch, or by slip on detachment faults beneath the southern shelf.