Ingestion, enzymatic digestion and absorption of particles derived from different vegetal sources by the cockle Cerastoderma edule

NASA Astrophysics Data System (ADS)

Arambalza, U.; Urrutia, M. B.; Navarro, E.; Ibarrola, I.

2010-10-01

Ingestion, enzymatic digestion and absorption of particulate detrital matter derived from six different vegetal sources by the common cockle Cerastoderma edule was analyzed in a series of seasonal experiments performed in March, May and October 2005. Two green macroalgae: Ulva lactuca and Enteromorpha sp; two vascular plants: Spartina maritima and Juncus maritimus, the red macroalgae Gracilaria gracilis; and the microalgae Isochrysis galbana were used in experiments. Detrital matter was elaborated by freeze-drying, grinding and sieving (< 63 μm) vegetal tissues. Mono-specific detrital diets of similar organic content (≈ 60-70%) were elaborated by mixing detritus with ashed silt. We measured i) the biochemical composition of different detritus, ii) physiological components of the absorptive balance (i.e. clearance, ingestion, rejection and absorption rate and absorption efficiency), iii) the capability of the digestive gland to hydrolyze carbohydrates from different detritus (digestibility), as well as iv) glandular cellulase and xylanase activities. Detritus type, season and the interaction detritus-season exerted significant effects upon all the physiological components of absorptive balance. Effects were light at the pre-absorptive level, however, huge variations associated to absorption efficiency promoted large significant differences in absorption rates (AR) of different kind of detritus: irrespective of season, highest values corresponded to cockles fed the green macroalgae ( Ulva and Enteromorpha) and lowest to those fed the vascular plant Juncus maritimus. Recorded significant differences in enzymatic digestibility among detritus were found to explain ≈ 40% of differences recorded in AR, and the following regression could be fitted: AR = 0.232 (± 0.032) * Digestibility + 0,072 (± 0.015); r 2 = 0.415; F = 51.036; p < 0.001. Digestibility of Ulva and Enteromorpha was found to be significantly correlated with cellulase activity in the digestive gland, whereas digestibility of Juncus, Spartina and Gracilaria was correlated with xylanase activity. Obtained correlations are discussed in the frame of contrasting conclusions in the literature regarding the importance of detritus as a food source for bivalves.

Effects of management on aquatic tree-hole communities in temperate forests are mediated by detritus amount and water chemistry.

PubMed

Gossner, Martin M; Lade, Peggy; Rohland, Anja; Sichardt, Nora; Kahl, Tiemo; Bauhus, Jürgen; Weisser, Wolfgang W; Petermann, Jana S

2016-01-01

Arthropod communities in water-filled tree holes may be sensitive to impacts of forest management, for example via changes in environmental conditions such as resource input. We hypothesized that increasing forest management intensity (ForMI) negatively affects arthropod abundance and richness and shifts community composition and trophic structure of tree hole communities. We predicted that this shift is caused by reduced habitat and resource availability at the forest stand scale as well as reduced tree hole size, detritus amount and changed water chemistry at the tree holes scale. We mapped 910 water-filled tree holes in two regions in Germany and studied 199 tree hole inhabiting arthropod communities. We found that increasing ForMI indeed significantly reduced arthropod abundance and richness in water-filled tree holes. The most important indirect effects of management intensity on tree hole community structure were the reduced amounts of detritus for the tree hole inhabiting organisms and changed water chemistry at the tree hole scale, both of which seem to act as a habitat filter. Although habitat availability at the forest stand scale decreased with increasing management intensity, this unexpectedly increased local arthropod abundance in individual tree holes. However, regional species richness in tree holes significantly decreased with increasing management intensity, most likely due to decreased habitat diversity. We did not find that the management-driven increase in plant diversity at the forest stand scale affected communities of individual tree holes, for example via resource availability for adults. Our results suggest that management of temperate forests has to target a number of factors at different scales to conserve diverse arthropod communities in water-filled tree holes. © 2015 The Authors. Journal of Animal Ecology © 2015 British Ecological Society.

Growth and stoichiometry of a common aquatic detritivore respond to changes in resource stoichiometry.

PubMed

Fuller, Chris L; Evans-White, Michelle A; Entrekin, Sally A

2015-03-01

Consumer growth determines the quantity of nutrients transferred through food webs. The extent to which leaf composition and consumer physiology interact to constrain consumer production is not well understood. For example, detritivore growth, and thus material transfer, could change with detrital elemental composition. Detrital type and associated microbial biofilms can mediate the amount and rate of detritus consumed and used towards growth. Detritivore body stoichiometry or the threshold elemental ratio, the food ratio resulting in optimal growth, may predict taxon-specific growth response to stoichiometrically-altered detritus. Empirical measures of detritivore growth responses across a range of detrital stoichiometry are rare. We fed a common detritivore, Tipula abdominalis, maple or oak leaves that spanned a gradient of carbon:phosphorus (C:P) to examine how leaf identity and C:P interact to influence growth, consumption, assimilation efficiencies, and post-assimilatory processes. Tipula abdominalis growth and consumption varied with leaf type and stoichiometry. Individuals fed oak grew faster and ate more compared to individuals fed maple. Individuals fed maple grew faster and ate more as leaf C:P decreased. All individuals lost most of the material they assimilated through respiration and excretion regardless of leaf type or leaf stoichiometry. Consumption and growth rates of T. abdominalis increased with maple nutrient enrichment, but not oak, indicating leaf-specific nutrient enrichment affected leaf palatability. Slightly non-homeostatic T. abdominalis C:P was maintained by varied consumption, carbon assimilation, and P excretion. Our study underlines the importance of how detritivore consumption and post-assimilatory processing could influence whole-stream material storage and nutrient cycling in detrital-based ecosystems.

Assessment of forest management influences on total live aboveground tree biomass in William B Bankhead National Forest, Alabama

Treesearch

Callie Schweitzer; Dawn Lemke; Wubishet Tadesse; Yong Wang

2015-01-01

Forests contain a large amount of carbon (C) stored as tree biomass (above and below ground), detritus, and soil organic material. The aboveground tree biomass is the most rapid change component in this forest C pool. Thus, management of forest resources can influence the net C exchange with the atmosphere by changing the amount of C stored, particularly in landscapes...

Competitive Abilities in Experimental Microcosms Are Accurately Predicted by a Demographic Index for R*

PubMed Central

Murrell, Ebony G.; Juliano, Steven A.

2012-01-01

Resource competition theory predicts that R*, the equilibrium resource amount yielding zero growth of a consumer population, should predict species' competitive abilities for that resource. This concept has been supported for unicellular organisms, but has not been well-tested for metazoans, probably due to the difficulty of raising experimental populations to equilibrium and measuring population growth rates for species with long or complex life cycles. We developed an index (Rindex) of R* based on demography of one insect cohort, growing from egg to adult in a non-equilibrium setting, and tested whether Rindex yielded accurate predictions of competitive abilities using mosquitoes as a model system. We estimated finite rate of increase (λ′) from demographic data for cohorts of three mosquito species raised with different detritus amounts, and estimated each species' Rindex using nonlinear regressions of λ′ vs. initial detritus amount. All three species' Rindex differed significantly, and accurately predicted competitive hierarchy of the species determined in simultaneous pairwise competition experiments. Our Rindex could provide estimates and rigorous statistical comparisons of competitive ability for organisms for which typical chemostat methods and equilibrium population conditions are impractical. PMID:22970128

Direct and Indirect Effects of Animal Detritus on Growth, Survival, and Mass of Invasive Container Mosquito Aedes albopictus (Diptera: Culicidae)

PubMed Central

YEE, DONALD A.; KESAVARAJU, BANUGOPAN; JULIANO, STEVEN A.

2007-01-01

Compared with plant detritus, animal detritus yields higher growth rates, survival, adult mass, and population growth of container-dwelling mosquitoes. It is unclear whether the benefit from animal detritus to larvae results from greater microorganism growth, direct ingestion of animal detritus by larvae, or some other mechanism. We tested alternative mechanisms by which animal detritus may benefit the invasive container-dwelling mosquito Aedesalbopictus (Skuse) (Diptera: Culicidae). In the laboratory, larvae were reared under three conditions with access to 1) detritus, but where microorganisms in the water column were reduced through periodic flushing; 2) water column microorganisms, but larvae had no direct access to detritus; or 3) both water column microorganisms and detritus. Access treatments were conducted for three masses of animal detritus: 0.005, 0.010, and 0.020 g. Water column bacterial productivity (measured via incorporation of [3H]leucine) decreased significantly with flushing and with larval presence. Removing microorganisms through flushing significantly reduced mass of adult mosquitoes (both sexes), and it significantly prolonged developmental times of females compared with treatments where water column microorganisms or microorganisms and detritus were available. Survival to adulthood was greatest when larvae had access to both water column microorganisms and 0.020 g of detritus, but it declined when only water column microorganisms were available or when 0.005 g of detritus was used. These findings indicate both direct (as a food source) and indirect (assisting with decomposition of detritus) roles of microorganisms in producing the benefit of animal detritus to container mosquito larvae. PMID:17695011

Detritus decorations of an orb-weaving spider, Cyclosa mulmeinensis (Thorell): for food or camouflage?

PubMed

Tan, Eunice J; Li, Daiqin

2009-06-01

Many species of the orb-web spider genus Cyclosa often adorn their webs with decorations of prey remains, egg sacs and/or plant detritus, termed ;detritus decorations'. These detritus decorations have been hypothesised to camouflage the spider from predators or prey and thus reduce predation risk or increase foraging success. In the present study, we tested these two alternative hypotheses simultaneously using two types of detritus decorations (prey remain and egg sac) built by Cyclosa mulmeinensis (Thorell). By monitoring the possible responses of predators to spiders on their webs with and without decorations in the field, we tested whether web decorations would reduce the mortality of spiders. Wasp predators were observed to fly in the vicinity of webs with decorations slightly more often than in the vicinity of webs without decorations but there were very few attacks on spiders by wasps. By comparing the insect interception rates of webs with and without decorations in the field, we tested whether web decorations would increase the foraging success. Webs decorated with prey remains or egg sacs intercepted more insects than those without in the field. By calculating colour contrasts of both prey-remain and egg-sac decorations against spiders viewed by bird (blue tits) and hymenopteran (e.g. wasps) predators as well as hymenopteran (bees) prey, we showed that C. mulmeinensis spiders on webs with egg-sac decorations were invisible to both hymenopteran prey and predators and bird predators over short and long distances. While spiders on webs with prey-remain decorations were invisible to both hymenopterans and birds over short distances, spiders on webs with prey-remain decorations were visible to both predators and prey over long distances. Our results thus suggest that decorating webs with prey remains and egg sacs in C. mulmeinensis may primarily function as camouflage to conceal the spider from insects rather than as prey attractants, possibly contributing to the interception of more insect prey. However, the detritus decorations exhibit varying success as camouflage against predators, depending on whether predators are jumping spiders, wasps or birds, as well as on the decoration type.

Functional groupings and food web of an artificial reef used for sea cucumber aquaculture in northern China

NASA Astrophysics Data System (ADS)

Xu, Qinzeng; Zhang, Libin; Zhang, Tao; Zhang, Xuelei; Yang, Hongsheng

2017-01-01

Artificial reef is considered as a useful tool to remodel habitats in coastal and estuarine area. Some artificial reefs (ARs) were conducted in Shandong Peninsula for sea cucumber Apostichopus japonicus integrated multi-trophic aquaculture (IMTA). Little is known about the main feeding type and food resources of living organisms in this IMTA ecosystem. Neither is the information about other animals competing food with A. japonicus. Functional group (FG) and their food resources of mobile organisms and epifauna in ARs area were investigated. There were three types of food resources and five FGs within two trophic levels in studied area. Particle organic matter (POM), seaweed detritus and sediment were considered to be the main food resources. The first three FGs were primary consumers and were mainly epifauna, while the other two FGs were secondary consumers. FG 1 species were filter feeders, and group 2 was all deposit feeders and A. japonicus was in this group. FG 2 contained few species and this indicated that A. japonicus had few food competitors. FG 3 contained most epifauna species which were detritus feeders and this result implied that the artificial oyster shell reed can retain detritus effectively. The food sources of group 4 were complex. Species of group 5, mostly fish, occupied the top trophic level and fed primarily on species of FG 1 and FG 2. This kind of ARs can retain detritus effectively and provide suitable habitat to epifauna and surrounding natural fauna community.

Effects of cadmium and resource quality on freshwater detritus processing chains: a microcosm approach with two insect species.

PubMed

Campos, Diana; Alves, Artur; Lemos, Marco F L; Correia, António; Soares, Amadeu M V M; Pestana, João L T

2014-07-01

Detritus processing is vital for freshwater ecosystems that depend on the leaf litter from riparian vegetation and is mediated by microorganisms and aquatic invertebrates. Shredder invertebrates transform coarse particulate organic matter into fine particulate organic matter used as food by collector species. Direct and indirect effects of contaminants can impair detritus processing and thus affect the functioning of these ecosystems. Here, we assessed the combined effects of a toxic metal (cadmium) and resource quality (leaf species) on detritus processing and shredder-collector interactions. We considered two types of leaves, alder and eucalyptus that were microbially conditioned under different Cd concentrations in the laboratory. The microbial communities present on leaves were analyzed by Denaturing Gradient Gel Electrophoresis (DGGE), and we also measured microbial respiration rates. Sericostoma vittatum (a caddisfly shredder) and Chironomus riparius (a midge collector) were also exposed to Cd and allowed to consume the corresponding alder or eucalyptus leaves. We evaluated C. riparius growth and leaf mass loss in multispecies microcosms. Cadmium exposure affected leaf conditioning and fungal diversity on both leaf species, as assessed by DGGE. Cadmium exposure also affected the mass loss of alder leaves by reductions in detritivore feeding, and impaired C. riparius growth. Chironomus riparius consumed alder leaf discs in the absence of shredders, but S. vittatum appear to promote C. riparius growth in treatments containing eucalyptus. These results show that indirect effects of contaminants along detritus-processing chains can occur through effects on shredder-collector interactions such as facilitation but they also depend on the nutritional quality of detritus and on sensitivity and feeding plasticity of detritivore species.

Impact assessment of non-indigenous jellyfish species on the estuarine community dynamic: A model of medusa phase

NASA Astrophysics Data System (ADS)

Muha, Teja Petra; Teodósio, Maria Alexandra; Ben-Hamadou, Radhouan

2017-03-01

Non-indigenous jellyfish species (NIJS) Blackforida virginica have recently been introduced to the Guadiana Estuary. A modelling approach was used for the assessment of the species-specific impact on the native community, during the medusa phase. The novel interactions between NIJS and the native community are assessed through biomass variation including hydrodynamic and climatic variables. Sensitivity analysis shows that both native species, as well as NIJS highly depend on the water discharge regime, nutrient contribution and the amount of detritus production. Abiotic factors such as the Northern Atlantic Oscillation, water discharge, nutrient load and detritus production are the most influential factors for the dynamics of the estuarine ecosystem demonstrated by the model. Low water discharge and low nutrient retention rate appear to be the most favourable conditions for B. virginica. The species is a non-selective predator able to integrate into the system effectively and has caused a decrease in the biomass of other organisms in the estuarine ecosystem throughout the summer after dam removal. The B. virginica significant impact can be evaluated only when the jellyfish detritus food pathway is involved. The B. virginica predatory impact potential, as well as food preference, appears to be the most influential factors for the overall biomass variation. On the contrary, winter freshwater pulses reduce the survival rate of jellyfish polyps which results in a decrease of medusa during summer. The model presents a strong ecohydrology movement where the fluctuation of organism biomass strongly depends on the hydrological conditions including the amount of nutrient load.

Importance of kelp-derived organic carbon to the scallop Chlamys farreri in an integrated multi-trophic aquaculture system

NASA Astrophysics Data System (ADS)

Xu, Qiang; Gao, Fei; Yang, Hongsheng

2016-03-01

Bivalves and seaweeds are important cleaners that are widely used in integrated multi-trophic aquaculture (IMTA) systems. A beneficial relationship between seaweed and bivalve in the seaweed-based IMTA system has been confirmed, but the trophic importance of seaweed-derived particulate organic materials to the co-cultured bivalve is still unclear. We evaluated the trophic importance of the kelp Saccharina japonica to the co-cultured scallop Chlamys farreri in a typical IMTA farm in Sungo Bay (Weihai, North China). The dynamics of detritus carbon in the water were monitored during the culturing period. The proportion of kelp-derived organic matter in the diet of the co-cultured scallop was assessed via the stable carbon isotope method. Results showed that the detritus carbon in the water ranged from 75.52 to 265.19 μg/L, which was 25.6% to 73.8% of total particulate organic carbon (TPOC) during the study period. The amount of detritus carbon and its proportion in the TPOC changed throughout the culture cycle of the kelp. Stable carbon isotope analysis showed that the cultured scallop obtained 14.1% to 42.8% of its tissue carbon from the kelp, and that the percentages were closely correlated with the proportion of detritus carbon in the water ( F =0.993, P= 0.003). Evaluation showed that for 17 000 tons (wet weight) of annual scallop production, the kelp contributed about 139.3 tons of carbon (535.8 tons of dry mass). This confirms that cultured kelp plays a similar trophic role in IMTA systems as it does in a natural kelp bed. It is a major contributor to the detritus pool and supplies a vital food source to filter-feeding scallops in the IMTA system, especially during winter and early spring when phytoplankton are scarce.

Provenance and detrital zircon geochronologic evolution of lower Brookian foreland basin deposits of the western Brooks Range, Alaska, and implications for early Brookian tectonism

USGS Publications Warehouse

Moore, Thomas; O'Sullivan, Paul B.; Potter, Christopher J.; Donelick, Raymond A.

2015-01-01

The Upper Jurassic and Lower Cretaceous part of the Brookian sequence of northern Alaska consists of syntectonic deposits shed from the north-directed, early Brookian orogenic belt. We employ sandstone petrography, detrital zircon U-Pb age analysis, and zircon fission-track double-dating methods to investigate these deposits in a succession of thin regional thrust sheets in the western Brooks Range and in the adjacent Colville foreland basin to determine sediment provenance, sedimentary dispersal patterns, and to reconstruct the evolution of the Brookian orogen. The oldest and structurally highest deposits are allochthonous Upper Jurassic volcanic arc–derived sandstones that rest on accreted ophiolitic and/or subduction assemblage mafic igneous rocks. These strata contain a nearly unimodal Late Jurassic zircon population and are interpreted to be a fragment of a forearc basin that was emplaced onto the Brooks Range during arc-continent collision. Synorogenic deposits found at structurally lower levels contain decreasing amounts of ophiolite and arc debris, Jurassic zircons, and increasing amounts of continentally derived sedimentary detritus accompanied by broadly distributed late Paleozoic and Triassic (359–200 Ma), early Paleozoic (542–359 Ma), and Paleoproterozoic (2000–1750 Ma) zircon populations. The zircon populations display fission-track evidence of cooling during the Brookian event and evidence of an earlier episode of cooling in the late Paleozoic and Triassic. Surprisingly, there is little evidence for erosion of the continental basement of Arctic Alaska, its Paleozoic sedimentary cover, or its hinterland metamorphic rocks in early foreland basin strata at any structural and/or stratigraphic level in the western Brooks Range. Detritus from exhumation of these sources did not arrive in the foreland basin until the middle or late Albian in the central part of the Colville Basin.These observations indicate that two primary provenance areas provided detritus to the early Brookian foreland basin of the western Brooks Range: (1) local sources in the oceanic Angayucham terrane, which forms the upper plate of the orogen, and (2) a sedimentary source region outside of northern Alaska. Pre-Jurassic zircons and continental grain types suggest the latter detritus was derived from a thick succession of Triassic turbidites in the Russian Far East that were originally shed from source areas in the Uralian-Taimyr orogen and deposited in the South Anyui Ocean, interpreted here as an early Mesozoic remnant basin. Structural thickening and northward emplacement onto the continental margin of Chukotka during the Brookian structural event are proposed to have led to development of a highland source area located in eastern Chukotka, Wrangel Island, and Herald Arch region. The abundance of detritus from this source area in most of the samples argues that the Colville Basin and ancestral foreland basins were supplied by longitudinal sediment dispersal systems that extended eastward along the Brooks Range orogen and were tectonically recycled into the active foredeep as the thrust front propagated toward the foreland. Movement of clastic sedimentary material from eastern Chukotka, Wrangel Island, and Herald Arch into Brookian foreland basins in northern Alaska confirms the interpretations of previous workers that the Brookian deformational belt extends into the Russian Far East and demonstrates that the Arctic Alaska–Chukotka microplate was a unified geologic entity by the Early Cretaceous.

Woody detritus density and density reduction factors for tree species in the United States: a synthesis

Treesearch

Mark E. Harmon; Christopher W. Woodall; Becky Fasth; Jay Sexton

2008-01-01

This report presents a synthesis of published and unpublished data on woody detritus density as a step toward improving estimates of coarse woody detritus (CWD) and fine woody detritus (FWD) biomass across the forests of the United States. In the case of CWD, 88 species were found to have data on densities for five decay classes that had been published and/or collected...

Detritus cast from heron nests as an indicator of food chain contamination. [Radioactivity

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

Rickard, W.H.; Hedlund, J.D.; Schreckhise, R.G.

Approximately 40 pairs of great blue herons nest in a single colony on the Hanford Reservation in south-central Washington. Over a two-month period in the 1975 nesting season, 170 g/m/sup 2/ of detritus, dry weight, were collected on cheesecloth blankets placed on the ground beneath the nesting colony. Seven gamma-emitting radionuclides commonly associated with airborne debris (fallout) were measured in the heron detritus. Cesium-137 was the most abundant man-induced radionuclide measured in the detritus averaging 18 picocuries per gram dry weight. Regular surveillance of heron detritus appears as a useful way to measure contaminants in heron foods gathered from themore » surrounding environment.« less

Detritus utilization by Mytilus edulis

NASA Astrophysics Data System (ADS)

Williams, Phil

1981-06-01

Feeding expriments showed that salt marsh vascular plant detritus is a poor food for Mytilus edulis. In laboratory experiment tissue weight of mussels increased slightly when Spartina foliosa and Salicornia virginica detritus was added to background seawater rich in organic matter. However, mussels lost weight when detritus was added to background seawater with a lower organic matter content. Aged and unaged plant material were equally poor in food value for M. edulis. Mussels in the Tijuana Estuary grew substantially during the period of the laboratory experiments.

Feeding preference and daily ration of 12 dominant copepods on mono and mixed diets of phytoplankton, rotifers, and detritus in a tropical coastal water.

PubMed

Jagadeesan, L; Jyothibabu, R; Arunpandi, N; Anjusha, A; Parthasarathi, S; Pandiyarajan, R S

2017-09-11

Results of the experimental studies on the feeding habit and daily ration (DR) of 12 dominant copepods from a tropical coastal water (off Kochi, Southwest coast of India) on different food items (phytoplankton, rotifers, and detritus) are presented. Even though, all species of copepods consumed all types of food items in the experiments, they showed noticeable feeding preferences, having important ecological implications. Calanoid Paracalanus parvus and Acrocalanus gracilis consumed phytoplankton and rotifers equally in mono diets (74-89% of DR) and mixed diets (53-82% of DR), which indicated their ability to shift their diet in natural environment based on the availability of food items. Calanoid Acartia erythraea and A. danae consumed more phytoplankton (DR 83 and 72%, respectively) than rotifers (DR 51 and 46%, respectively) in mono diets, and in mixed diets, their consumption was high in phytoplankton combined food mixtures (P + R DR and P + D DR) rather than the R + D food type, indicated their preference for mixed diets of phytoplankton. Similarly, Calanoid Temora turbinata, Pseudodiaptomus serricaudatus, and Centropages tenuiremis preferred a herbivorous diet as evidenced by their high ingestion rate on phytoplankton mono (70 to 87% to their DR) and mixed diets (58 to 80% of DR). On the other hand, Cyclopoid Oithona similis and Poecilostomatoid Corycaeus danae preferred a carnivorous diet, consuming more rotifers (> 80% of DR) than phytoplankton (18-20% of DR) and detritus (5-6% of DR). Harpacticoids Macrosetella gracilis and Euterpina acutifrons equally preferred phytoplankton (78-92% of DR) and detritus (65-89% of DR). The study showed that the dominant copepods in the coastal waters off Kochi occupy different trophic niches available in the environment, which may be applicable in other similar environments as well.

Consumer-resource stoichiometry in detritus-based streams

Treesearch

Wyatt F. Cross; Jonathan P. Benstead; Amy D. Rosemond; J. Bruce Wallace

2003-01-01

Stoichiometric relationships between consumers and resources in detritus-based ecosystems have received little attention, despite the importance of detritus in most food webs. We analysed carbon (C), nitrogen (N), and phosphorus (P) content of invertebrate consumers, and basal food resources in two forested headwater streams (one reference and the other nutrient-...

Carbon flows in the benthic food web at the deep-sea observatory HAUSGARTEN (Fram Strait)

NASA Astrophysics Data System (ADS)

van Oevelen, Dick; Bergmann, Melanie; Soetaert, Karline; Bauerfeind, Eduard; Hasemann, Christiane; Klages, Michael; Schewe, Ingo; Soltwedel, Thomas; Budaeva, Nataliya E.

2011-11-01

The HAUSGARTEN observatory is located in the eastern Fram Strait (Arctic Ocean) and used as long-term monitoring site to follow changes in the Arctic benthic ecosystem. Linear inverse modelling was applied to decipher carbon flows among the compartments of the benthic food web at the central HAUSGARTEN station (2500 m) based on an empirical data set consisting of data on biomass, prokaryote production, total carbon deposition and community respiration. The model resolved 99 carbon flows among 4 abiotic and 10 biotic compartments, ranging from prokaryotes up to megafauna. Total carbon input was 3.78±0.31 mmol C m -2 d -1, which is a comparatively small fraction of total primary production in the area. The community respiration of 3.26±0.20 mmol C m -2 d -1 is dominated by prokaryotes (93%) and has lower contributions from surface-deposit feeding macro- (1.7%) and suspension feeding megafauna (1.9%), whereas contributions from nematode and other macro- and megabenthic compartments were limited to <1%. The high prokaryotic contribution to carbon processing suggests that functioning of the benthic food web at the central HAUSGARTEN station is comparable to abyssal plain sediments that are characterised by strong energy limitation. Faunal diet compositions suggest that labile detritus is important for deposit-feeding nematodes (24% of their diet) and surface-deposit feeding macrofauna (˜44%), but that semi-labile detritus is more important in the diets of deposit-feeding macro- and megafauna. Dependency indices on these food sources were also calculated as these integrate direct (i.e. direct grazing and predator-prey interactions) and indirect (i.e. longer loops in the food web) pathways in the food web. Projected sea-ice retreats for the Arctic Ocean typically anticipate a decrease in the labile detritus flux to the already food-limited benthic food web. The dependency indices indicate that faunal compartments depend similarly on labile and semi-labile detritus, which suggests that the benthic biota may be more sensitive to changes in labile detritus inputs than when assessed from diet composition alone. Species-specific responses to different types of labile detritus inputs, e.g. pelagic algae versus sympagic algae, however, are presently unknown and are needed to assess the vulnerability of individual components of the benthic food web.

Spatial and temporal changes in the partitioning of organic carbon in the plankton community of the Sargasso Sea off Bermuda

NASA Astrophysics Data System (ADS)

Roman, M. R.; Caron, D. A.; Kremer, P.; Lessard, E. J.; Madin, L. P.; Malone, T. C.; Napp, J. M.; Peele, E. R.; Youngbluth, M. J.

1995-06-01

The vertical distribution of plankton (bacteria, nanozooplankton, microzooplankton, mesozooplankton, macrozooplankton and salps) biomass in the photic zone near the JGOFS time series station off Bermuda was examined during 2-3 week periods in August 1989 and in March/April 1990. The amount of phytoplankton carbon in the photic zone was lower in August as compared to March/April (398 and 912 mg C m -2, respectively). Total heterotrophic biomass in the photic zone was also lower in August as compared to March/April (1106 and 1795 mg C m -2, respectively). Taken together, bacteria and nanozooplankton constituted approximately 70% of the total heterotrophic carbon in the photic zone on both cruises. Considering their high weightspecific carbon demand relative to micro-, meso-, and macrozooplankton, it is clear that most of the carbon in the surface waters of the Sargasso Sea near Bermuda cycles through bacteria and flagellates—the "microbial loop". However, both seasonal (August vs. March/April) and withincruise variations in the vertical flux of organic material were related to the biomass of macrozooplankton. Macrozooplankton biomass was lower in August than March/April (93 and 267 Mg C m -2, respectively). There was more non-living carbon (detritus) than living carbon in the photic zone during the August cruise (70% of total organic matter) but about equal amounts of detritus and living carbon in March/April.

Food supplies of stream-dwelling salmonids

USGS Publications Warehouse

Wipfli, Mark S.

2009-01-01

Much is known about the importance of the physical characteristics of salmonid habitat in Alaska and the Pacific Northwest, with far less known about the food sources and trophic processes within these habitats, and the role they play in regulating salmonid productivity. Freshwater food webs supporting salmonids in Alaska rely heavily on nutrient, detritus and prey subsidies from both marine and terrestrial ecosystems. Adult salmon provide a massive input of marine biomass to riverine ecosystems each year when they spawn, die, and decompose, and are a critical food source for young salmon in late summer and fall; riparian forests provide terrestrial invertebrates to streams, which at times comprise over half of the food ingested by stream-resident salmonids; and up-slope, fishless headwater streams are a year-round source of invertebrates and detritus for fish downstream. The quantity of these food resources vary widely depending on source, season, and spatial position within a watershed. Terrestrial invertebrate inputs from riparian habitats are generally the most abundant food source in summer. Juvenile salmonids in streams consume roughly equal amounts of freshwater and terrestrially-derived invertebrates during most of the growing season, but ingest substantial amounts of marine resources (salmon eggs and decomposing salmon tissue) when these food items are present. Quantity, quality, and timing of food resources all appear to be important driving forces in aquatic food web dynamics, community nutrition, and salmonid growth and survival in riverine ecosystems.

The short-term effects of prescribed burning on biomass removal and the release of nitrogen and phosphorus in a treatment wetland.

PubMed

White, J R; Gardner, L M; Sees, M; Corstanje, R

2008-01-01

Nutrient removal by constructed wetlands can decline over time due to the accumulation of organic matter. A prescribed burn is one of many management strategies used to remove detritus in macrophyte-dominated systems. We quantified the short-term effects on effluent water quality and the amount of aboveground detritus removed from a prescribed burn event. Surface water outflow concentrations were approximately three times higher for P and 1.5 times higher for total Kjeldhal nitrogen (TKN) following the burn event when compared to the control. The length of time over which the fire effect was significant (P < 0.05), 3 d for TKN and up to 23 d for P fractions. Over time, the concentration of soluble reactive phosphorus (SRP) in the effluent decreased, but was compensated with increases in dissolved organic phosphorus (DOP) and particulate phosphorus (PP), such that net total P remained the same. Total aboveground biomass decreased by 68.5% as a result of the burn, however, much of the live vegetation was converted to standing dead material. These results demonstrate that a prescribed burn can significantly decrease the amount of senescent organic matter in a constructed wetland. However, short-term nutrient releases following the burn could increase effluent nutrient concentrations. Therefore, management strategies should include hydraulically isolating the burned area immediately following the burn event to prevent nutrient export.

Nutrient enrichment alters storage and fluxes of detritus in a headwater stream ecosystem

Treesearch

Jonathan P. Benstead; Amy D. Rosemond; Wyatt F. Cross; J. Bruce Wallace; Susan L. Eggert; Keller Suberkropp; Vladislav Gulis; Jennifer L. Greenwood; Cynthia J. Tant

2009-01-01

Responses of detrital pathways to nutrients may differ fundamentally from pathways involving living plants: basal carbon resources can potentially decrease rather than increase with nutrient enrichment. Despite the potential for nutrients to accelerate heterotrophic processes and fluxes of detritus, few studies have examined detritus-nutrient dynamics at whole-...

Detritus fuels ecosystem metabolism but not metazoan food webs in San Francisco estuary's freshwater delta

USGS Publications Warehouse

Sobczak, W.V.; Cloern, J.E.; Jassby, A.D.; Cole, B.E.; Schraga, T.S.; Arnsberg, A.

2005-01-01

Detritus from terrestrial ecosystems is the major source of organic matter in many streams, rivers, and estuaries, yet the role of detritus in supporting pelagic food webs is debated. We examined the importance of detritus to secondary productivity in the Sacramento and San Joaquin River Delta (California, United States), a large complex of tidal freshwater habitats. The Delta ecosystem has low primary productivity but large detrital inputs, so we hypothesized that detritus is the primary energy source fueling production in pelagic food webs. We assessed the sources, quantity, composition, and bioavailability of organic matter among a diversity of habitats (e.g., marsh sloughs, floodplains, tidal lakes, and deep river channels) over two years to test this hypothesis. Our results support the emerging principle that detritus dominates riverine and estuarine organic matter supply and supports the majority of ecosystem metabolism. Yet in contrast to prevailing ideas, we found that detritus was weakly coupled to the Delta's pelagic food web. Results from independent approaches showed that phytoplankton production was the dominant source of organic matter for the Delta's pelagic food web, even though primary production accounts for a small fraction of the Delta's organic matter supply. If these results are general, they suggest that the value of organic matter to higher trophic levels, including species targeted by programs of ecosystem restoration, is a function of phytoplankton production. ?? 2005 Estuarine Research Federation.

Bottom-up limitation of a stream salamander in a detritus-based food web

Treesearch

Brent R. Johnson; J. Bruce Wallace

2005-01-01

The indirect effects that resources can have on higher trophic levels remain poorly understood for detritus-based ecosystems. Our objective was to examine effects of long-term terrestrial litter exclusion on a larval salamander, Eurycea wilderae, in a detritus-based stream. After 4 years of exclusion treatment, we conducted a mark-recapture study and...

Influence of large woody debris on stream insect communities and benthic detritus

Treesearch

A. Dennis Lemly; Robert H. Hilderbrand

2000-01-01

We examined the extent to which benthic detritus loadings and the functional feeding group structure of stream insect communities respond to channel modifications produced by experimental addition of large woody debris (LWD, entire logs) to Stony Creek, VA. Benthic detritus loadings per sample did not change after LWD additions, but large increases in pool habitats...

Nutrient enrichment differentially affects body sizes of primary consumers and predators in a detritus-based stream

Treesearch

John M. Davis; Amy D. Rosemond; Sue L. Eggert; Wyatt F. Cross; J. Bruce Wallace

2010-01-01

We assessed how a 5-yr nutrient enrichment affected the responses of different size classes of primary consumers and predators in a detritus-based headwater stream. We hypothesized that alterations in detritus availability because of enrichment would decrease the abundance and biomass of large-bodied consumers. In contrast, we found that 2 yr of enrichment increased...

Effects of harvest management practices on forest biomass and soil carbon in eucalypt forests in New South Wales, Australia: Simulations with the forest succession model LINKAGES

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

Ranatunga, Kemachandra; Keenan, Rodney J.; Wullschleger, Stan D

2008-01-01

Understanding long-term changes in forest ecosystem carbon stocks under forest management practices such as timber harvesting is important for assessing the contribution of forests to the global carbon cycle. Harvesting effects are complicated by the amount, type, and condition of residue left on-site, the decomposition rate of this residue, the incorporation of residue into soil organic matter and the rate of new detritus input to the forest floor from regrowing vegetation. In an attempt to address these complexities, the forest succession model LINKAGES was used to assess the production of aboveground biomass, detritus, and soil carbon stocks in native Eucalyptusmore » forests as influenced by five harvest management practices in New South Wales, Australia. The original decomposition sub-routines of LINKAGES were modified by adding components of the Rothamsted (RothC) soil organic matter turnover model. Simulation results using the new model were compared to data from long-term forest inventory plots. Good agreement was observed between simulated and measured above-ground biomass, but mixed results were obtained for basal area. Harvesting operations examined included removing trees for quota sawlogs (QSL, DBH >80 cm), integrated sawlogs (ISL, DBH >20 cm) and whole-tree harvesting in integrated sawlogs (WTH). We also examined the impact of different cutting cycles (20, 50 or 80 years) and intensities (removing 20, 50 or 80 m{sup 3}). Generally medium and high intensities of shorter cutting cycles in sawlog harvesting systems produced considerably higher soil carbon values compared to no harvesting. On average, soil carbon was 2-9% lower in whole-tree harvest simulations whereas in sawlog harvest simulations soil carbon was 5-17% higher than in no harvesting.« less

Influence of Three Contrasting Detrital Carbon Sources on Planktonic Bacterial Metabolism in a Mesotrophic Lake.

PubMed

Wehr; Petersen; Findlay

1999-01-01

Abstract Lakes receive organic carbon from a diversity of sources which vary in their contribution to planktonic microbial food webs. We conducted a mesocosm study to test the effects of three different detrital carbon sources (algae, aquatic macrophytes, terrestrial leaves) on several measures of microbial metabolism in a small meso-eutrophic lake (DOC approximately 5 mg/L). Small DOC additions (DeltaC < 1 mg/L) affected bacterial numbers, growth, and pathways of carbon acquisition. Macrophyte and leaf detritus significantly increased TDP and color, but bacterial densities initially (+12 h) were unaffected. After 168 h, densities in systems amended with terrestrial detritus were 60% less than in controls, while production rates in mesocosms with macrophyte detritus were 4-fold greater. Detritus treatments resulted in greater per-cell production rates either through stable cell numbers and greater growth rates (macrophyte-C) or lower densities with stable production rates (terrestrial-C). After only 12 h, rates of leucine aminopeptidase (LAPase) activity were 2.5x greater in macrophyte-C systems than in controls, but LAPase and beta-N-acetylglucosamindase activities in systems amended with terrestrial-C were only 50% of rates in controls. After 168 h, beta-xylosidase rates were significantly greater in communities with terrestrial and phytoplankton detritus. Microbial utilization of >20% of 102 carbon sources tested were affected by at least one detritus addition. Macrophyte-C had positive (6% of substrates) and negative (14%) effects on substrate use; terrestrial detritus had mainly positive effects. An ordination based on carbon-use profiles (+12 h) revealed a cluster of macrophyte-amended communities with greater use of psicose, lactulose, and succinamic acid; controls and algal-detritus systems were more effective in metabolizing two common sugars and cellobiose. After 168 h, communities receiving terrestrial detritus were most tightly clustered, exhibiting greater use of raffinose, pyroglutamic acid, and sebacic acid. Results suggest that pelagic bacterial communities respond to changes in organic carbon source rapidly and by different routes, including shifts in per-cell production rates and variations in degradation of a variety of compounds comprising the DOC pool.

Food preferences of mangrove crabs related to leaf nitrogen compounds in the Segara Anakan Lagoon, Java, Indonesia

NASA Astrophysics Data System (ADS)

Nordhaus, Inga; Salewski, Tabea; Jennerjahn, Tim C.

2011-05-01

The large amounts of leaf litter produced by tropical mangrove forests serve as a major food source for the benthic fauna. The reasons for the preferential consumption of mangrove leaves by crabs are unclear as yet. We investigated the diet, food preferences and consumption rates of 8 dominant grapsoid crab species ( Perisesarma spp., Episesarma spp., Metopograpsus latifrons, and Metaplax elegans) in mangroves of Segara Anakan, Java, Indonesia, by means of stomach-content analysis and feeding experiments. Leaves from the five most abundant mangrove tree species ( Aegiceras corniculatum, Avicennia alba, Ceriops decandra, Rhizophora apiculata, and Sonneratia caseolaris) were analyzed for organic carbon, total nitrogen, δ 13C, δ 15N and amino acids and hexosamines. This study is the first that investigated crab food preferences related to the nitrogen compound composition of leaves. Our results show that Episesarma spp. and Perisesarma spp. are omnivorous crabs which mainly feed on detritus, mangrove litter and bark, and on a small amount of roots, algae and animal matter whereas M. elegans is a detritus feeder. In feeding experiments with green, yellow and brown leaves Perisesarma spp. and E. singaporense had the highest consumption rates for brown leaves of R. apiculata and S. caseolaris, and for green leaves of A. alba. Preferred leaves were characterized by a high amount and/or freshness of nitrogenous compounds and their biochemical composition was significantly different from that of disliked leaves (all leaves of A. corniculatum and C. decandra, green and yellow leaves of R. apiculata and S. caseolaris). The presence of the hexosamine galactosamine found only in brown leaves indicates that bacteria contribute to the amount of bioavailable nitrogen compounds. We infer that the nitrogen compound composition rather than the C/N ratio alone is a determinant for bioavailability of mangrove leaves and hence may partly explain the crabs' food preferences.

Nutrient and detritus transport in the Apalachicola River, Florida

USGS Publications Warehouse

Mattraw, Harold C.; Elder, John F.

1984-01-01

The Apalachicola River in northwest Florida flows 172 kilometers southward from Jim Woodruff Dam near the Florida-Georgia border to Apalachicola Bay on the Gulf of Mexico. The basin is composed of two 3,100-squarekilometer subbasins, the Chipola and the Apalachicola. The Apalachicola subbasin includes a 454-square-kilometer bottom-land hardwood flood plain that is relatively undeveloped. The flood plain contains more than 1,500 trees per hectare that annually produce approximately 800 metric tons of litter fall per square kilometer. Spring floods of March and April 1980 carried 35,000 metric tons of particulate organic carbon derived from litter fall into Apalachicola Bay. The estuarine food web is predominantly detrital based and represents an important commercial source of oyster, shrimp, blue crab, and various species of fish. The water budget of the Apalachicola basin is heavily dominated by streamflow. For a 1-year period in 1979-80, 28.6 cubic kilometers of water flowed past the Sumatra gage on the lower river. Eighty percent of this volume flowed into the upper river near Chattahoochee, Fla., and 11 percent was contributed by its major tributary, the Chipola River. Contributions from ground water and overland runoff were less than 10 percent. Streamflow increases downstream were accompanied by equivalent increases in nitrogen and phosphorus transport. The nutrients were released to the river by the flood-plain vegetation, but also were subject to recycling. The increase in the amount of organic carbon transport downstream was greater than streamflow increases. The flood plain is an important source of organic carbon, especially in detrital form. Several methods for measurement of detritus in the river and flood plain were developed and tested. The detritus data from the flood plain added semiquantitative evidence for transport of detritus from the flood plain to the river flow, probably accounting for most of the coarse particulate organic material carried by the river. During the 1-year period of investigation, June 3, 1979, through June 2, 1980, 2.1 ? 10 5 metric tons of organic carbon were transported from the river basin to the bay. Nitrogen and phosphorus transport during the same period amounted to 2.2 ? 10 4 and 1.7 ? 10 3 metric tons, respectively. On an areal basis, it was calculated that the flood plain contributed 70 grams of organic carbon per square meter per year, 0.4 gram of nitrogen per square meter per year, and 0.5 gram of phosphorus per square meter per year. The flood plain acts as a source of detrital carbon, but for the solutes, nutrient release is approximately balanced by nutrient retention.

Ecosystem and physiological scales of microbial responses to nutrients in a detritus-based stream: results of a 5-year continuous enrichment

Treesearch

Keller Suberkropp; Vladislav Gulis; Amy D. Rosemond; Jonathan Benstead

2010-01-01

Our study examined the response of leaf detritus–associated microorganisms (both bacteria and fungi) to a 5-yr continuous nutrient enrichment of a forested headwater stream. Leaf litter dominates detritus inputs to such streams and, on a system wide scale, serves as the key substrate for microbial colonization. We determined physiological responses as microbial biomass...

Both riverine detritus and dissolved nutrients drive lagoon fisheries

NASA Astrophysics Data System (ADS)

Bonthu, Subbareddy; Ganguly, Dipnarayan; Ramachandran, Purvaja; Ramachandran, Ramesh; Pattnaik, Ajit K.; Wolanski, Eric

2016-12-01

The net ecosystem metabolism in lagoons has often been estimated from the net budget of dissolved nutrients. Such is the case of the LOICZ estuarine biogeochemistry nutrient budget model that considers riverine dissolved nutrients, but not riverine detritus. However the neglect of detritus can lead to inconsistencies; for instance, it results in an estimate of 5-10 times more seaward export of nutrients than there is import from rivers in Chilika Lagoon, India. To resolve that discrepancy the UNESCO estuarine ecohydrology model, that considers both dissolved nutrients and detritus, was used and, for Chilika Lagoon, it reproduced successfully the spatial distribution of salinity, dissolved nutrients, phytoplankton and zooplankton as well as the fish yield data. Thus the model suggests that the riverine input of both detritus and dissolved nutrients supports the pelagic food web. The model also reproduces well the observation of decreased fish yield when the mouth of the lagoon was choked in the 1990s, demonstrating the importance of the physics that determine the flushing rate of waterborne matter. Thus, both farming in the watershed by driving the nutrient and detritus inputs to the lagoon, and dredging and engineering management of the mouth by controlling the flushing rate of the lagoon, have a major influence on fish stocks in the lagoon.

Occurrence of maize detritus and a transgenic insecticidal protein (Cry1Ab) within the stream network of an agricultural landscape

PubMed Central

Tank, Jennifer L.; Rosi-Marshall, Emma J.; Royer, Todd V.; Whiles, Matt R.; Griffiths, Natalie A.; Frauendorf, Therese C.; Treering, David J.

2010-01-01

Widespread planting of maize throughout the agricultural Midwest may result in detritus entering adjacent stream ecosystems, and 63% of the 2009 US maize crop was genetically modified to express insecticidal Cry proteins derived from Bacillus thuringiensis. Six months after harvest, we conducted a synoptic survey of 217 stream sites in Indiana to determine the extent of maize detritus and presence of Cry1Ab protein in the stream network. We found that 86% of stream sites contained maize leaves, cobs, husks, and/or stalks in the active stream channel. We also detected Cry1Ab protein in stream-channel maize at 13% of sites and in the water column at 23% of sites. We found that 82% of stream sites were adjacent to maize fields, and Geographical Information Systems analyses indicated that 100% of sites containing Cry1Ab-positive detritus in the active stream channel had maize planted within 500 m during the previous crop year. Maize detritus likely enters streams throughout the Corn Belt; using US Department of Agriculture land cover data, we estimate that 91% of the 256,446 km of streams/rivers in Iowa, Illinois, and Indiana are located within 500 m of a maize field. Maize detritus is common in low-gradient stream channels in northwestern Indiana, and Cry1Ab proteins persist in maize leaves and can be measured in the water column even 6 mo after harvest. Hence, maize detritus, and associated Cry1Ab proteins, are widely distributed and persistent in the headwater streams of a Corn Belt landscape. PMID:20876106

Occurrence of maize detritus and a transgenic insecticidal protein (Cry1Ab) within the stream network of an agricultural landscape.

PubMed

Tank, Jennifer L; Rosi-Marshall, Emma J; Royer, Todd V; Whiles, Matt R; Griffiths, Natalie A; Frauendorf, Therese C; Treering, David J

2010-10-12

Widespread planting of maize throughout the agricultural Midwest may result in detritus entering adjacent stream ecosystems, and 63% of the 2009 US maize crop was genetically modified to express insecticidal Cry proteins derived from Bacillus thuringiensis. Six months after harvest, we conducted a synoptic survey of 217 stream sites in Indiana to determine the extent of maize detritus and presence of Cry1Ab protein in the stream network. We found that 86% of stream sites contained maize leaves, cobs, husks, and/or stalks in the active stream channel. We also detected Cry1Ab protein in stream-channel maize at 13% of sites and in the water column at 23% of sites. We found that 82% of stream sites were adjacent to maize fields, and Geographical Information Systems analyses indicated that 100% of sites containing Cry1Ab-positive detritus in the active stream channel had maize planted within 500 m during the previous crop year. Maize detritus likely enters streams throughout the Corn Belt; using US Department of Agriculture land cover data, we estimate that 91% of the 256,446 km of streams/rivers in Iowa, Illinois, and Indiana are located within 500 m of a maize field. Maize detritus is common in low-gradient stream channels in northwestern Indiana, and Cry1Ab proteins persist in maize leaves and can be measured in the water column even 6 mo after harvest. Hence, maize detritus, and associated Cry1Ab proteins, are widely distributed and persistent in the headwater streams of a Corn Belt landscape.

Mineralization of surfactants by the microbiota of submerged plant detritus.

PubMed

Federle, T W; Ventullo, R M

1990-02-01

In wetlands and canopied bodies of water, plant detritus is an important source of carbon and energy. Detrital materials possess a large surface area for sorption of dissolved organics and are colonized by a large and diverse microbiota. To examine the biodegradation of surfactants by these microorganisms, submerged oak leaves were obtained from a laundromat wastewater pond, its overflow, and a pristine control pond. Leaves were cut into disks and incubated in sterile water amended with 50 mug of C-labeled linear alkylbenzene sulfonate (LAS), linear alcohol ethoxylate, stearyltrimethyl ammonium chloride, distearyldimethyl ammonium chloride, benzoic acid, or mixed amino acids per liter. Sorption of the test compounds to the detritus and evolution of CO(2) were followed with time. All of the compounds sorbed to the detritus to various degrees, with LAS and stearyltrimethyl ammonium chloride the most sorptive and benzoic acid the least. All compounds were mineralized without a lag. With leaves from the laundromat wastewater pond, half-lives were 12.6 days for LAS, 8.4 days for linear alcohol ethoxylate, 14.2 days for stearyltrimethyl ammonium chloride, 1.0 days for benzoic acid, and 2.7 days for mixed amino acids. Mineralization of LAS and linear alcohol ethoxylate by control pond leaves was slower and exhibited an S-shaped rather than a typical first-order pattern. This study shows that detritus represents a significant site of surfactant removal in detritus-rich systems.

Decadal changes in potassium, calcium, and magnesium in a deciduous forest soil

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

Mulholland, Patrick J; Johnson, Dale W.; Todd Jr, Donald E

2008-01-01

Decadal changes in soil exchangeable K{sup +}, Ca{sup 2+}, and Mg{sup 2+} concentrations and contents from 1972 to 2004 in eight intensively monitored plots on Walker Branch Watershed were compared with estimates of increments or decrements in vegetation and detritus. The results from these eight plots compared favorably with those from a more extensive set from 24 soil sampling plots sampled in 1972 and 2004. Increases in exchangeable K{sup +} were noted between 1972 and 1982, but few changes were noted between 1982 and 2004 despite significant increments in vegetation and detritus and significant potential losses by leaching. Total Kmore » contents of soils in the 0- to 60-cm sampling depth were very large and a slight amount of weathering could have replenished the K{sup +} lost from exchanges sites. With one notable exception, exchangeable Ca{sup 2+} and Mg{sup 2+} concentrations and contents decreased continuously during the sampling period. Decreases in exchangeable Ca{sup 2+} could be attributed mostly to increments in biomass and detritus, whereas decreases in exchangeable Mg{sup 2+} could not and were attributed to leaching. The major exception to these patterns was in the case of exchangeable Ca{sup 2+}, where significant increases were noted in one plot and attributed to Ca release from the decomposition of Ca-rich coarse woody debris from oak (Quercus spp.) mortality. With minor exceptions, soils and changes in soils among the eight intensively sampled core plots were similar to those in a more extensive set of plots distributed across the watershed. This study shows that averaging among plots can mask significant and important spatial patterns in soil change that must be taken into account in assessing long-term trends.« less

U-series dating of impure carbonates: An isochron technique using total-sample dissolution

USGS Publications Warehouse

Bischoff, J.L.; Fitzpatrick, J.A.

1991-01-01

U-series dating is a well-established technique for age determination of Late Quaternary carbonates. Materials of sufficient purity for nominal dating, however, are not as common as materials with mechanically inseparable aluminosilicate detritus. Detritus contaminates the sample with extraneous Th. We propose that correction for contamination is best accomplished with the isochron technique using total sample dissolution (TSD). Experiments were conducted on artificial mixtures of natural detritus and carbonate and on an impure carbonate of known age. Results show that significant and unpredictable transfer of radionuclides occur from the detritus to the leachate in commonly used selective leaching procedures. The effects of correcting via leachate-residue pairs and isochron plots were assessed. Isochrons using TSD gave best results, followed by isochron plots of leachates only. ?? 1991.

Polycyclic aromatic hydrocarbons in Saccoglossus kowalewskyi (Agassiz)

NASA Astrophysics Data System (ADS)

Carey, D. A.; Farrington, J. W.

1989-08-01

Hydrocarbon extracts were analyzed from Saccoglossus kowalewskyi, a deposit-feeding enteropneust worm, and from surface sediments from Cape Cod, MA. Worms were held in experimental aquaria in sieved sediments and flowing seawater for four months and then fed sediments mixed with creosote, lampblack or clean sediment for two weeks as analogues of sediments containing degraded oil and pyrogenic compounds. Worms from all treatments contained polyaromatic hydrocarbons (PAHs) in amounts and composition that indicate that the worms were contaminated with weathered No. 2 fuel oil before our experimental treatment and that the contamination persisted for four months in clean conditions. The contamination was not detected in the clean sediments used in the experiment. The worms accumulated steroid transformation products in greater abundance than the odd chain n-alkanes that dominated the sediment extractions. This may indicate selective assimilation of algal detritus and microbial products over salt marsh detritus. Worms, actively feeding during the experiment, contained 1-3 × 10 -6 g g -1 dry weight of unknown brominated compounds which were not detected in the sediments. These compounds are similar to bromopyrroles found elsewhere in enteropneusts, polychaetes and bacteria and may cause substantial interference in analyses for some industrial pollutants.

Organic matter and nutrients associated with fine root turnover in a white oak stand. [Quercus albus

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

Joslin, J.D.; Henderson, G.S.

1987-06-01

Organic matter and nutrients cycled by fine root turnover were quantified in a mature white oak (Quercus alba L.) stand and compared to contributions from litterfall. The budget method, a revised version of the traditional repeated sampling method, was used to measure root turnover. The magnitude of the live and dead pools of three size classes of fine (<5 mm diameter) roots were monitored bimonthly for 14 months. Decomposition rates over these intervals were also measured, while production and mortality were calculated. Litterfall was collected simultaneously, and the nutrient concentrations of the various detritus components determined. Root pools fluctuated less,more » and total root turnover biomass (220 g m/sup -2/ yr/sup -1/) was also less than previously noted in most other stands studied. Fine root turnover accounted for 30% of the total detritus production and 20-40% of the turnover of the five macronutrients (N, P, K, Ca, Mg) studied. Differences with previous studies suggest that there may be rather large species and/or site-related differences in the amount of energy various stands allocate for fine root maintenance. For. Sci. 33(2):330-346.« less

Carbon and Nitrogen Sources for Shrimp Postlarvae Fed Natural Diets from a Tropical Mangrove System

NASA Astrophysics Data System (ADS)

Dittel, A. I.; Epifanio, C. E.; Cifuentes, L. A.; Kirchman, D. L.

1997-11-01

Postlarvae ofPenaeus vannameiwere fed various diets in order to examine the importance of detritus and other possible prey items in supporting postlarval growth. Stable isotopes (C and N) were used to determine the carbon and nitrogen source of the prey in the various diets. The zooplankton diet contained mostly copepods. The subtidal detritus treatment consisted mostly of plant material whereas the diets from both intertidal sites contained a mixture of plant detritus and associated meiofauna. Postlarvae reared on zooplankton and detritus plus meiofauna diets more than tripled their weight during a 6-day period. In contrast, postlarvae fed the detritus diet barely doubled their weight. Based on isotopic composition, postlarvae appear to obtain their carbon and nitrogen from various food sources. Postlarvae were enriched by 0·4‰ in13C and 2·7‰ in15N relative to the zooplankton diet, which is consistent with isotopic fractionation between successive trophic levels. In turn, the isotopic signal of the zooplankton was consistent with phytoplankton being the initial source of organic matter. In contrast, mean δ13C values of the shrimp fed detritus plus meiofauna were significantly different from their respective diets. Isotopic ratios of the postlarvae fed the mixed diet from Chomes were two trophic levels above benthic algae suggesting that the shrimp preyed on organisms that derived their carbon and nitrogen from benthic algae and/or phytoplankton.

Mineralization of Surfactants by the Microbiota of Submerged Plant Detritus

PubMed Central

Federle, Thomas W.; Ventullo, Roy M.

1990-01-01

In wetlands and canopied bodies of water, plant detritus is an important source of carbon and energy. Detrital materials possess a large surface area for sorption of dissolved organics and are colonized by a large and diverse microbiota. To examine the biodegradation of surfactants by these microorganisms, submerged oak leaves were obtained from a laundromat wastewater pond, its overflow, and a pristine control pond. Leaves were cut into disks and incubated in sterile water amended with 50 μg of 14C-labeled linear alkylbenzene sulfonate (LAS), linear alcohol ethoxylate, stearyltrimethyl ammonium chloride, distearyldimethyl ammonium chloride, benzoic acid, or mixed amino acids per liter. Sorption of the test compounds to the detritus and evolution of 14CO2 were followed with time. All of the compounds sorbed to the detritus to various degrees, with LAS and stearyltrimethyl ammonium chloride the most sorptive and benzoic acid the least. All compounds were mineralized without a lag. With leaves from the laundromat wastewater pond, half-lives were 12.6 days for LAS, 8.4 days for linear alcohol ethoxylate, 14.2 days for stearyltrimethyl ammonium chloride, 1.0 days for benzoic acid, and 2.7 days for mixed amino acids. Mineralization of LAS and linear alcohol ethoxylate by control pond leaves was slower and exhibited an S-shaped rather than a typical first-order pattern. This study shows that detritus represents a significant site of surfactant removal in detritus-rich systems. Images PMID:16348111

A Coupled Epipelagic-Meso/Bathypelagic Particle Flux Model for the Bermuda Atlantic Time-series Station (BATS)/Oceanic Flux Program (OFP) Site

NASA Astrophysics Data System (ADS)

Glover, D. M.; Conte, M.

2002-12-01

Of considerable scientific interest is the role remineralization plays in the global carbon cycle. It is the ``biological pump'' that fixes carbon in the upper water column and exports it for long time periods to the deep ocean. From a global carbon cycle point-of-view, it is the processes that govern remineralization in the mid- to deep-ocean waters that provide the feedback to the biogeochemical carbon cycle. In this study we construct an ecosystem model that serves as a mechanistic link between euphotic processes and mesopelagic and bathypelagic processes. We then use this prognostic model to further our understanding of the unparalleled time-series of deep-water sediment traps (21+ years) at the Oceanic Flux Program (OFP) and the euphotic zone measurements (10+ years) at the Bermuda Atlantic Time-series Site (BATS). At the core of this mechanistic ecosystem model of the mesopelagic zone is a model that consists of an active feeding habit zooplankton, a passive feeding habit zooplankton, large detritus (sinks), small detritus (non-sinking), and a nutrient pool. As the detritus, the primary source of food, moves through the water column it is fed upon by the active/passive zooplankton pair and undergoes bacterially mediated remineralization into nutrients. The large detritus pool at depth gains material from the formation of fecal pellets from the passive and active zooplankton. Sloppy feeding habits of the active zooplankton contribute to the small detrital pool. Zooplankton mortality (both classes) also contribute directly to the large detritus pool. Aggregation and disaggregation transform detrital particles from one pool to the other and back again. The nutrients at each depth will gain from detrital remineralization and zooplankton excretion. The equations that model the active zooplankton, passive zooplankton, large detritus, small detritus, and nutrients will be reviewed, results shown and future model modifications discussed.

Factors affecting distribution of wood, detritus, and sediment in headwater streams draining managed young-growth red alder - Conifer forests in southeast Alaska

USGS Publications Warehouse

Gomi, T.; Johnson, A.C.; Deal, R.L.; Hennon, P.E.; Orlikowska, E.H.; Wipfli, M.S.

2006-01-01

Factors (riparian stand condition, management regimes, and channel properties) affecting distributions of wood, detritus (leaves and branches), and sediment were examined in headwater streams draining young-growth red alder (Alnus rubra Bong.) - conifer riparian forests (40 years old) remained in channels and provided sites for sediment and organic matter storage. Despite various alder-conifer mixtures and past harvesting effects, the abundance of large wood, fine wood, and detritus accumulations significantly decreased with increasing channel bank-full width (0.5-3.5 m) along relatively short channel distances (up to 700 m). Changes in wood, detritus, and sediment accumulations together with changes in riparian stand characteristics create spatial and temporal variability of in-channel conditions in headwater systems. A component of alder within young-growth riparian forests may benefit both wood production and biological recovery in disturbed headwater stream channels. ?? 2006 NRC.

87Sr/86Sr ratios in some eugeosynclinal sedimentary rocks and their bearing on the origin of granitic magma in orogenic belts

USGS Publications Warehouse

Peterman, Z.E.; Hedge, C.E.; Coleman, R.G.; Snavely, P.D.

1967-01-01

Rb and Sr contents and 87Sr/86Sr values were determined for samples of eugeosynclinal sedimentary rocks, mostly graywackes, from Oregon and California. These data are compatible with the theory of anataxis of eugeosynclinal sedimentary rocks in orogenic belts to produce granitic magmas provided that the melting occurs within several hundreds of m.y. after sedimentation. The low (87Sr/86Sr)0 values of the eugeosynclinal sedimentary rocks are related to the significant amounts of volcanogenic detritus present which probably were originally derived from the mantle. ?? 1967.

Comparison of Antemortem and Environmental Samples for Zebrafish Health Monitoring and Quarantine.

PubMed

Crim, Marcus J; Lawrence, Christian; Livingston, Robert S; Rakitin, Andrei; Hurley, Shane J; Riley, Lela K

2017-07-01

Molecular diagnostic assays offer both exquisite sensitivity and the ability to test a wide variety of sample types. Various types of environmental sample, such as detritus and concentrated water, might provide a useful adjunct to sentinels in routine zebrafish health monitoring. Similarly, antemortem sampling would be advantageous for expediting zebrafish quarantine, without euthanasia of valuable fish. We evaluated the detection of Mycobacterium chelonae, M. fortuitum, M. peregrinum, Pseudocapillaria tomentosa, and Pseudoloma neurophilia in zebrafish, detritus, pooled feces, and filter membranes after filtration of 1000-, 500-, and 150-mL water samples by real-time PCR analysis. Sensitivity varied according to sample type and pathogen, and environmental sampling was significantly more sensitive than zebrafish sampling for detecting Mycobacterium spp. but not for Pseudocapillaria neurophilia or Pseudoloma tomentosa. The results of these experiments provide strong evidence of the utility of multiple sample types for detecting pathogens according to each pathogen's life cycle and ecological niche within zebrafish systems. In a separate experiment, zebrafish subclinically infected with M. chelonae, M. marinum, Pleistophora hyphessobryconis, Pseudocapillaria tomentosa, or Pseudoloma neurophilia were pair-spawned and individually tested with subsets of embryos from each clutch that received no rinse, a fluidizing rinse, or were surface-disinfected with sodium hypochlorite. Frequently, one or both parents were subclinically infected with pathogen(s) that were not detected in any embryo subset. Therefore, negative results from embryo samples may not reflect the health status of the parent zebrafish.

Comparison of Antemortem and Environmental Samples for Zebrafish Health Monitoring and Quarantine

PubMed Central

Crim, Marcus J; Lawrence, Christian; Livingston, Robert S; Rakitin, Andrei; Hurley, Shane J; Riley, Lela K

2017-01-01

Molecular diagnostic assays offer both exquisite sensitivity and the ability to test a wide variety of sample types. Various types of environmental sample, such as detritus and concentrated water, might provide a useful adjunct to sentinels in routine zebrafish health monitoring. Similarly, antemortem sampling would be advantageous for expediting zebrafish quarantine, without euthanasia of valuable fish. We evaluated the detection of Mycobacterium chelonae, M. fortuitum, M. peregrinum, Pseudocapillaria tomentosa, and Pseudoloma neurophilia in zebrafish, detritus, pooled feces, and filter membranes after filtration of 1000-, 500-, and 150-mL water samples by real-time PCR analysis. Sensitivity varied according to sample type and pathogen, and environmental sampling was significantly more sensitive than zebrafish sampling for detecting Mycobacterium spp. but not for Pseudocapillaria neurophilia or Pseudoloma tomentosa. The results of these experiments provide strong evidence of the utility of multiple sample types for detecting pathogens according to each pathogen's life cycle and ecological niche within zebrafish systems. In a separate experiment, zebrafish subclinically infected with M. chelonae, M. marinum, Pleistophora hyphessobryconis, Pseudocapillaria tomentosa, or Pseudoloma neurophilia were pair-spawned and individually tested with subsets of embryos from each clutch that received no rinse, a fluidizing rinse, or were surface-disinfected with sodium hypochlorite. Frequently, one or both parents were subclinically infected with pathogen(s) that were not detected in any embryo subset. Therefore, negative results from embryo samples may not reflect the health status of the parent zebrafish. PMID:28724491

Movement of pulsed resource subsidies from kelp forests to deep fjords.

PubMed

Filbee-Dexter, Karen; Wernberg, Thomas; Norderhaug, Kjell Magnus; Ramirez-Llodra, Eva; Pedersen, Morten Foldager

2018-05-01

Resource subsidies in the form of allochthonous primary production drive secondary production in many ecosystems, often sustaining diversity and overall productivity. Despite their importance in structuring marine communities, there is little understanding of how subsidies move through juxtaposed habitats and into recipient communities. We investigated the transport of detritus from kelp forests to a deep Arctic fjord (northern Norway). We quantified the seasonal abundance and size structure of kelp detritus in shallow subtidal (0‒12 m), deep subtidal (12‒85 m), and deep fjord (400‒450 m) habitats using a combination of camera surveys, dive observations, and detritus collections over 1 year. Detritus formed dense accumulations in habitats adjacent to kelp forests, and the timing of depositions coincided with the discrete loss of whole kelp blades during spring. We tracked these blades through the deep subtidal and into the deep fjord, and showed they act as a short-term resource pulse transported over several weeks. In deep subtidal regions, detritus consisted mostly of fragments and its depth distribution was similar across seasons (50% of total observations). Tagged pieces of detritus moved slowly out of kelp forests (displaced 4‒50 m (mean 11.8 m ± 8.5 SD) in 11‒17 days, based on minimum estimates from recovered pieces), and most (75%) variability in the rate of export was related to wave exposure and substrate. Tight resource coupling between kelp forests and deep fjords indicate that changes in kelp abundance would propagate through to deep fjord ecosystems, with likely consequences for the ecosystem functioning and services they provide.

Epibenthos of mangrove waterways and open embayments: Community structure and the relationship between exported mangrove detritus and epifaunal standing stocks

NASA Astrophysics Data System (ADS)

Daniel, P. A.; Robertson, A. I.

1990-11-01

The epibenthos inhabiting creek-bottoms in a tidally influenced mangrove forest, a mangrove-lined estuary and several sites in two open embayments, was sampled on four occasions between August 1986 and June 1987. The inshore (mangrove habitats)-offshore (embayment) patterns in total faunal taxonomic richness (means ranging from 0 to 32·5 taxa per trawl) and density (range of means, < 1·55 individuals m -2) were generally complex, with patterns across the gradient changing seasonally. Patterns in total biomass (range of means 0-740 mg.m -2) were clearer, with highest biomasses recorded in May (post-wet season) and lowest in February (mid-wet season), with no significant cross-habitat gradient in biomass. Densities and biomasses were lower than those recorded in other studies, probably owing to the physically harsh conditions available to epibenthos and to the low quality of mangrove detritus as a food source. The significant difference in the structure of epibenthic communities in mangrove and embayment habitats in the dry season months (August and October) was likely due to the longer residence time of water in mangrove water-ways at that time of the year. Greater tidal amplitudes and increased tidal current velocities in February transported mangrove detritus and many faunal taxa into embayments. Variation in the quantities of exported mangrove detritus in nettings explained significant proportions of the variance in total (and component taxa) epibenthic standing stocks in mangrove and embayment habitats. Several factors may be important in causing the positive response of different groups within the epibenthos to mangrove detritus. For penaeid shrimps it seems likely that clumps of exported mangrove detritus provide refuges from predatory fish in both mangrove and embayment habitats.

Carbon cycling and net ecosystem production at an early stage of secondary succession in an abandoned coppice forest.

PubMed

Ohtsuka, Toshiyuki; Shizu, Yoko; Nishiwaki, Ai; Yashiro, Yuichiro; Koizumi, Hiroshi

2010-07-01

Secondary mixed forests are one of the dominant forest cover types in human-dominated temperate regions. However, our understanding of how secondary succession affects carbon cycling and carbon sequestration in these ecosystems is limited. We studied carbon cycling and net ecosystem production (NEP) over 4 years (2004-2008) in a cool-temperate deciduous forest at an early stage of secondary succession (18 years after clear-cutting). Net primary production of the 18-year-old forest in this study was 5.2 tC ha(-1 )year(-1), including below-ground coarse roots; this was partitioned into 2.5 tC ha(-1 )year(-1) biomass increment, 1.6 tC ha(-1 )year(-1) foliage litter, and 1.0 tC ha(-1 )year(-1) other woody detritus. The total amount of annual soil surface CO(2) efflux was 6.8 tC ha(-1 )year(-1), which included root respiration (1.9 tC ha(-1 )year(-1)) and heterotrophic respiration (RH) from soils (4.9 tC ha(-1 )year(-1)). The 18-year forest at this study site exhibited a great increase in biomass pool as a result of considerable total tree growth and low mortality of tree stems. In contrast, the soil organic matter (SOM) pool decreased markedly (-1.6 tC ha(-1 )year(-1)), although further study of below-ground detritus production and RH of SOM decomposition is needed. This young 18-year forest was a weak carbon sink (0.9 tC ha(-1 )year(-1)) at this stage of secondary succession. The NEP of this 18-year forest is likely to increase gradually because biomass increases with tree growth and with the improvement of the SOM pool through increasing litter and dead wood production with stand development.

Richness-Productivity Relationships Between Trophic Levels in a Detritus-Based System: Significance of Abundance and Trophic Linkage.

EPA Science Inventory

Most theoretical and empirical studies of productivity–species richness relationships fail to consider linkages among trophic levels. We quantified productivity–richness relationships in detritus-based, water-filled tree-hole communities for two trophic levels: invertebrate consu...

Leaf Breakdown in a Tropical Stream

NASA Astrophysics Data System (ADS)

Gonçalves, José Francisco, Jr.; França, Juliana S.; Medeiros, Adriana O.; Rosa, Carlos A.; Callisto, Marcos

2006-05-01

The objectives of this study were to investigate leaf breakdown in two reaches of different magnitudes, one of a 3rd (closed riparian vegetation) order and the other of a 4th (open riparian vegetation) order, in a tropical stream and to assess the colonization of invertebrates and microorganisms during the processing of detritus. We observed that the detritus in a reach of 4th order decomposed 2.4 times faster than the detritus in a reach of 3rd order, in which, we observed that nitrate concentration and water velocity were greater. This study showed that the chemical composition of detritus does not appear to be important in evaluating leaf breakdown. However, it was shown to be important to biological colonization. The invertebrate community appeared not to have been structured by the decomposition process, but instead by the degradative ecological succession process. With regards to biological colonization, we observed that the density of bacteria in the initial stages was more important while fungi appeared more in the intermediate and final stages.

Ontogenetic changes in feeding and food preferences of the dog conch Laevistrombus canarium Linnaeus 1758 (Mollusca: Gastropoda) from Merambong shoal, Malaysia

NASA Astrophysics Data System (ADS)

Husna, Wan Nurul Wan Hassan; Mazlan, Abd Ghaffar; Cob, Zaidi Che

2017-09-01

Laevistrombus canarium is one of the marine gastropod mollusks that have high commercial value, particularly in the aquaculture sector in Malaysia. This study was conducted to determine the feeding and food items of L. canarium at different ontogenetic stages (juveniles, sub-adults and adults) from Merambong shoals, Malaysia. Field observations on feeding activity were conducted, followed by detailed laboratory analysis on the stomach content. Five-minutes observations on randomly selected individuals were conducted at the field sampling site and their feeding activities were recorded with reference to age stage. Various shell sizes from each ontogenetic stage were randomly collected and quickly anaesthetized with ice and preserved in 10% formalin before being transported to the laboratory for stomach content analyses. Field observations showed that L. canarium mainly grazed on epiphytes occurring on seagrass (46.67%), followed by sediment surface (40%) and epiphytes occurring on macroalgae (13.33%). Stomach content analyses showed a significant difference ( P <0.05) in gastro-somatic index (Gasi) between the juveniles (0.39±0.05), sub-adults (0.68±0.09) and adults (0.70±0.05) ( P <0.05). Food items found in the conch stomach include diatoms, detritus, foraminifera, seagrass and macroalgae fragments, sand particles and shell fragments. The Index of Relative Importance (%IRI) indicates three main types of food dominated the three ontogenetic stages namely diatoms, sand particles and detritus. However, no significant difference ( P >0.05) was detected between the three main food items (diatoms, sand particles and detritus) among the ontogenetic stages. Therefore, feeding activity revealed the role of the dog conch in the marine food network. While, classification of the types of food consumed by L. canarium through stomach content analysis determines the particular position of the gastropod in the food chain. Further studies are needed to provide a better insight between trophic relationships of L. canarium with marine ecosystem.

THE EFFECTS OF RIPARIAN MANAGEMENT ON DETRITUS PROCESSING AND INVERTEBRATE ASSEMBLAGES IN COASTAL PLAIN INTERMITTENT STREAMS

EPA Science Inventory

Silviculture is the primary land use within many Coastal Plain watersheds of the southeastern United States, where most forested wetlands are found along headwater intermittent streams. Our study compared invertebrate assemblages and breakdown of buried detritus (leaves, wood, a...

Predator effects on a detritus-based food web are primarily mediated by non-trophic interactions.

PubMed

Majdi, Nabil; Boiché, Anatole; Traunspurger, Walter; Lecerf, Antoine

2014-07-01

Predator effects on ecosystems can extend far beyond their prey and are often not solely lethally transmitted. Change in prey traits in response to predation risk can have important repercussions on community assembly and key ecosystem processes (i.e. trait-mediated indirect effects). In addition, some predators themselves alter habitat structure or nutrient cycling through ecological engineering effects. Tracking these non-trophic pathways is thus an important, yet challenging task to gain a better grasp of the functional role of predators. Multiple lines of evidence suggest that, in detritus-based food webs, non-trophic interactions may prevail over purely trophic interactions in determining predator effects on plant litter decomposition. This hypothesis was tested in a headwater stream by modulating the density of a flatworm predator (Polycelis felina) in enclosures containing oak (Quercus robur) leaf litter exposed to natural colonization by small invertebrates and microbial decomposers. Causal path modelling was used to infer how predator effects propagated through the food web. Flatworms accelerated litter decomposition through positive effects on microbial decomposers. The biomass of prey and non-prey invertebrates was not negatively affected by flatworms, suggesting that net predator effect on litter decomposition was primarily determined by non-trophic interactions. Flatworms enhanced the deposition and retention of fine sediments on leaf surface, thereby improving leaf colonization by invertebrates - most of which having strong affinities with interstitial habitats. This predator-induced improvement of habitat availability was attributed to the sticky nature of the mucus that flatworms secrete in copious amount while foraging. Results of path analyses further indicated that this bottom-up ecological engineering effect was as powerful as the top-down effect on invertebrate prey. Our findings suggest that predators have the potential to affect substantially carbon flow and nutrient cycling in detritus-based ecosystems and that this impact cannot be fully appreciated without considering non-trophic effects. © 2013 The Authors. Journal of Animal Ecology © 2013 British Ecological Society.

Effects of agricultural subsidies of nutrients and detritus on fish and plankton of shallow-reservoir ecosystems.

PubMed

Pilati, Alberto; Vanni, Michael J; González, María J; Gaulke, Alicia K

2009-06-01

Agricultural activities increase exports of nutrients and sediments to lakes, with multiple potential impacts on recipient ecosystems. Nutrient inputs enhance phytoplankton and upper trophic levels, and sediment inputs can shade phytoplankton, interfere with feeding of consumers, and degrade benthic habitats. Allochthonous sediments are also a potential food source for detritivores, as is sedimenting autochthonous phytodetritus, the production of which is stimulated by nutrient inputs. We examined effects of allochthonous nutrient and sediment subsidies on fish and plankton, with special emphasis on gizzard shad (Dorosoma cepedianum). This widespread and abundant omnivorous fish has many impacts on reservoir ecosystems, including negative effects on water quality via nutrient cycling and on fisheries via competition with sportfish. Gizzard shad are most abundant in agriculturally impacted, eutrophic systems; thus, agricultural subsidies may affect reservoir food webs directly and by enhancing gizzard shad biomass. We simulated agricultural subsidies of nutrients and sediment detritus by manipulating dissolved nutrients and allochthonous detritus in a 2 x 2 factorial design in experimental ponds. Addition of nutrients alone increased primary production and biomass of zooplanktivorous fish (bluegill and young-of-year gizzard shad). Addition of allochthonous sediments alone increased algal sedimentation and decreased seston and sediment C:P ratios. Ponds receiving both nutrients and sediments showed highest levels of phytoplankton and total phosphorus. Adult and juvenile gizzard shad biomass was enhanced equally by nutrient or sediment addition, probably because this apparently P-limited detritivore ingested similar amounts of P in all subsidy treatments. Nutrient excretion rates of gizzard shad were higher in ponds with nutrient additions, where sediments were composed mainly of phytodetritus. Therefore, gizzard shad can magnify the direct effects of nutrient subsidies on phytoplankton production, and these multiple effects must be considered in strategies to manage eutrophication and fisheries in warmwater reservoir lakes where gizzard shad can dominate fish biomass.

Record of late Pleistocene glaciation and deglaciation in the southern Cascade Range. I. Petrological evidence from lacustrine sediment in Upper Klamath Lake, southern Oregon

USGS Publications Warehouse

Reynolds, R.L.; Rosenbaum, J.G.; Rapp, J.; Kerwin, M.W.; Bradbury, J.P.; Colman, S.; Adam, D.

2004-01-01

Petrological and textural properties of lacustrine sediments from Upper Klamath Lake, Oregon, reflect changing input volumes of glacial flour and thus reveal a detailed glacial history for the southern Cascade Range between about 37 and 15 ka. Magnetic properties vary as a result of mixing different amounts of the highly magnetic, glacially generated detritus with less magnetic, more weathered detritus derived from unglaciated parts of the large catchment. Evidence that the magnetic properties record glacial flour input is based mainly on the strong correlation between bulk sediment particle size and parameters that measure the magnetite content and magnetic mineral freshness. High magnetization corresponds to relatively fine particle size and lower magnetization to coarser particle size. This relation is not found in the Buck Lake core in a nearby, unglaciated catchment. Angular silt-sized volcanic rock fragments containing unaltered magnetite dominate the magnetic fraction in the late Pleistocene sediments but are absent in younger, low magnetization sediments. The finer grained, highly magnetic sediments contain high proportions of planktic diatoms indicative of cold, oligotrophic limnic conditions. Sediment with lower magnetite content contains populations of diatoms indicative of warmer, eutrophic limnic conditions. During the latter part of oxygen isotope stage 3 (about 37-25 ka), the magnetic properties record millennial-scale variations in glacial-flour content. The input of glacial flour was uniformly high during the Last Glacial Maximum, between about 21 and 16 ka. At about 16 ka, magnetite input, both absolute and relative to hematite, decreased abruptly, reflecting a rapid decline in glacially derived detritus. The decrease in magnetite transport into the lake preceded declines in pollen from both grass and sagebrush. A more gradual decrease in heavy mineral content over this interval records sediment starvation with the growth of marshes at the margins of the lake and dilution of detrital material by biogenic silica and other organic matter.

Removal of arthropods in the spring “trash floods”

USDA-ARS?s Scientific Manuscript database

Flooding of cranberry marshes is a common practice in the spring. It is intended primarily to clean out detritus while protecting against frost danger. The water is sometimes held for longer periods to reduce pest populations. We examined the detritus being hauled off of flooded beds for any evidenc...

Source, habitat and nutrient enrichment effects on decomposition of detritus in Lower Mississippi River Basin bayous

USDA-ARS?s Scientific Manuscript database

Potential differences in storage and processing of detritus in agricultural landscapes may alter freshwater ecosystem function. We compared decomposition rates of maize (Zea mays) and willow oak (Quercus phellos) from three bayous located within the Lower Mississippi River Basin of NW Mississippi, ...

POWER FIELD MONITORING EQUIPMENT FROM WETLAND DETRITUS MATERIALS USING MICROBIAL FUEL CELL

EPA Science Inventory

The data from both laboratory and field experiments will provide useful information to assist designing an in-situ MFC system that uses detritus materials to achieve constant and useable electric energy output. The in-situ MFC systems installed in the forested wetlands at Wi...

Dynamics of phytophagous insects and their pathogens in Alaskan boreal forests

Treesearch

Richard A. Werner; Kenneth F. Raffa; Barbara L. Illman

2006-01-01

Boreal forests support an array of insects, including phytophagous (plant-eating) insects, saprophagous (detritus-eating) insects, and their associated parasites, predators, and symbionts. The phytophagous species include folivorous leaf chewers and miners, phloeophagous cambial and sapwood borers, stem gallers, and root feeders. Biological diversity and distribution...

Ingestion and absorption of particles derived from different macrophyta in the cockle Cerastoderma edule: effects of food ration.

PubMed

Arambalza, U; Ibarrola, I; Navarro, E; Urrutia, M B

2014-02-01

We analyzed the capacity of the common cockle Cerastoderma edule to utilize detrital food particles obtained from three different macrophytes: the vascular plant Juncus maritimus and two green macroalgae (Ulva lactuca and Enteromorpha sp.). We measured feeding and digestive parameters at three concentrations of detritus (0.5, 1.0 and 3.0 mm(3) l(-1)), so that functional relationships between ingestive and digestive processes could be assessed. Increasing concentrations of detritus (food) resulted in a reduction in filtering activity (clearance rate l h(-1)), but an increase in ingestion rate. Consequently, gut content also increased with increasing food concentration, irrespective of food type. In contrast, the trend followed by absorption efficiency with increasing ingestion rate was determined by food type, being significantly reduced (from 0.63 to 0.11) with Juncus but remaining almost constant with the green macroalgae (0.58 ± 0.07 with Ulva) or only minimally reduced (from 0.66 to 0.48 with Enteromorpha). This differential response had clear consequences for energy uptake: absorption rate increased with increasing particulate organic matter with Enteromorpha but decreased with Juncus. We discuss the possible role of digestive parameters such as digestibility, gut content and gut-residence time in the differential utilization of detrital matter from different vegetal origins by cockles.

Transformations of DOM in forested catchments: the pathways of DOM from litter and soil to river export

NASA Astrophysics Data System (ADS)

Lajtha, K.; Yano, Y.; Crow, S.; Kaushal, S.

2006-12-01

Although the quality and quantity of DOM ultimately derives from plant detritus and soils in watersheds, three is substantial alteration of DOM as it passes from litter through the terrestrial landscape. As DOM is generated from plant and microbial detritus and processing, different fractions may be lost via respiration, form quasi-stable soil organic matter, or be temporarily sorbed to soil minerals. We followed the fate of DOC and DON from forested plots with experimentally altered detritus loads to determine the relative roles of original plant litter chemistry and soil transformations. Our study site was the DIRT (Detrital Input and Removal Treatment) plots at the H.J. Andrews Experimental Forest in Oregon, where treatments include detrital additions (wood vs. needle litter), litter exclusion, and root exclusions. Fractionation of detritus leachate solutions demonstrated significant differences in DOC chemistry from different detrital sources. Root leachates produced high quantities of hydrophilic neutral DOC, a fraction rich in labile sugars and polysaccharides; young wood extracts produced higher quantities of weak hydrophobic acids and hydrophobic neutrals (longer chain hydrocarbons); older wood had lower quantities of most labile constituents but was rich in strong hydrophobic acids. Although laboratory extracts of different litter types showed differences in DOM chemistry, soil solutions collected just below the forest floor from the differing detrital treatments were remarkably uniform and poor in labile constituents, suggesting microbial equalization of DOM leachate in the field. DOM quality and concentrations changed significantly with passage through soil profiles. DOC concentrations decreased through the soil profile in all plots to a greater degree than did dissolved organic nitrogen (DON), most likely due to preferential sorption of high C:N hydrophobic dissolved organic matter (DOM) in upper horizons. Percent hydrophobic DOM decreased significantly with depth, and the remaining hydrophilic DOM had a much lower and narrower C:N ratio than hydrophobic DOM. We also hypothesize that protein-reactive polyphenols, or tannins, may contribute to the decreased lability of N-rich DOM in soil solutions and thus significantly influence the quality of DOM delivered to streams.

Contents and Structure Atta texana Nest in Summer

Treesearch

John C. Moser

1963-01-01

A large nest of Atta texana (Buckley) in central Louisiana was partially excavated in August 1960. Twelve dormancy, 5 detritus, and 93 fungus-garden cavities were found. Fungus-garden cavities near the surface outnumbered those at lower depths and contained most of the fungus material and brood. Inquilines were most numerous in detritus cavities....

PARADIGM: The Partnership for Advancing Interdisciplinary Global Modeling Annual Report - Year 2

DTIC Science & Technology

2004-02-01

case (a) when bacteria are able to regenerate ammonium based upon the composition of the dissolved organic pool. The export is also slightly larger...for diazotrophs and detritus. The addition of diazotrophs and detritus in the model follow the method of Fennel et al. [2002]. Time series of model

Detritus-Dependent Development of the Microbial Community in an Experimental System: Qualitative Analysis by Denaturing Gradient Gel Electrophoresis†

PubMed Central

van Hannen, Erik J.; Mooij, Wolf; van Agterveld, Miranda P.; Gons, Herman J.; Laanbroek, Hendrikus J.

1999-01-01

Correlations between the biomass of phytoplankton and the biomass of bacteria and between the biomass of bacteria and the biomass of protozoans suggest that there is coupling between these compartments of the “microbial loop.” To investigate this coupling on the species level, bacteria and protozoans from untreated lake water inocula were allowed to grow on detritus of the green alga Ankistrodesmus falcatus or the cyanobacterium Oscillatoria limnetica in continuous-flow systems for 1 month. Denaturing gradient gel electrophoresis (DGGE) of the 16S and 18S rRNA genes was used to monitor the development of the bacterial community structure and the eukaryotic community structure, respectively. Nonmetric multidimensional scaling of the DGGE profiles revealed the changes in the microbial community structure. This analysis showed that significantly different bacterial communities developed on the green algal detritus and on the cyanobacterial detritus. Although similar results were obtained for the eukaryotic communities, the differences were not significant. Hence, our findings indicate that the origin of detritus can affect the structure of at least the bacterial community. A phylogenetic analysis of 20 18S ribosomal DNA clones that were isolated from the continuous cultures revealed that many sequences were related to the sequences of bacterivorous protozoans (members of the Ciliophora, Rhizopoda, Amoeba, and Kinetoplastida). One clone grouped in a recently established clade whose previously described members are all parasites. The affiliations of about 20% of the clones could not be determined. PMID:10347030

Plant responses to simulated hurricane impacts in a subtropical wet forest, Puerto Rico

Treesearch

Aaron B. Shiels; Jess K. Zimmerman; Diana C. García-Montiel; Inge Jonckheere; Jennifer Holm; David Horton; Nicholas Brokaw

2010-01-01

1. We simulated two key components of severe hurricane disturbance, canopy openness and detritus deposition, to determine the independent and interactive effects of these components on woody plant recruitment and forest structure. 2. We increased canopy openness by trimming branches and added or subtracted canopy detritus in a factorial design. Plant responses were...

Resource utilization and trophic position of nematodes and harpacticoid copepods in and adjacent to Zostera noltii beds

NASA Astrophysics Data System (ADS)

Vafeiadou, A.-M.; Materatski, P.; Adão, H.; De Troch, M.; Moens, T.

2014-01-01

This study examines the resource use and trophic position of nematodes and harpacticoid copepods at the genus/species level in an estuarine food web in Zostera noltii beds and in adjacent bare sediments, using the natural abundance of stable carbon and nitrogen isotopes. Microphytobenthos is among the main resources of most taxa, but seagrass-associated resources (i.e. seagrass detritus and epiphytes) also contribute to meiobenthos nutrition, with seagrass detritus being available also in deeper sediments and in unvegetated patches close to seagrass beds. A predominant dependence on chemoautotrophic bacteria was demonstrated for the nematode genus Terschellingia and the copepod family Cletodidae. A predatory feeding mode is illustrated for Paracomesoma and other Comesomatidae, which were previously considered first-level consumers (deposit feeders) according to their buccal morphology. The considerable variation found in both resource use and trophic level among nematode genera from the same feeding type, and even among congeneric nematode species, shows that interpretation of nematode feeding ecology based purely on mouth morphology should be avoided.

Response of detritus food web and litter quality to elevated CO2 and crop cultivars and their feedback to soil functionality

NASA Astrophysics Data System (ADS)

Hu, Zhengkun; Chen, Xiaoyun; Zhu, Chunwu; Bonkowski, Michael; Hu, Shuijin; Li, Huixin; Hu, Feng; Liu, Manqiang

2017-04-01

Elevated atmospheric CO2 concentrations (eCO2) often increase plant growth and alter the belowground detritus soil food web. Interactions with agriculture management may further modify soil process and the associated ecosystem functionality. Little attention, however, has been directed toward assessing the responses of soil food web and their feedback to soil functionality, particularly in wetland agroecosystems. We report results from a long-term free air CO2 enrichment (FACE) experiment in a rice paddy field that examined the responses of detritus food webs to eCO2 (200 ppm higher than ambient CO2 (aCO2)) of two rice cultivars with distinctly weak and strong responses to eCO2. Soil detritus food web components, including soil microbes and microfauna, soil environment as well as resources availability variables, were determined at the rice ripening stage. To obtain the information of soil functionality, indicated by litter decomposition and enzyme activities, we adopted a reciprocal transplant approach that fully manipulate the factors of litter straw and food web components for the incubation of 120 days. Results about the field investigation showed that eCO2 lead to a higher C/N ratio of litter and soil compared to aCO2, especially for the strong responsive cultivar. eCO2-induced enhanced carbon input stimulated the fungal decomposition pathway by increasing fungal biomass, fungi: bacteria ratio and fungivorous nematode. Results from the manipulative incubation experiment showed eCO2-induced lower quality of straw decreased cumulative C mineralization, but changes in detritus food web induced by eCO2 and strongly responsive cultivar lead to an increased CO2 respiration coincidently within each straw type, mainly due to the adaption to the high C/N ratio environment which increased their functional breadth. Based on SEMs and curves of carbon mineralization rate, soil communities showed significant effects on C release at the early stage through mediating enzyme activities involved in carbon and nutrient cycling. Our results indicated that resource quality played a pivotal role in mediating soil functionality as it primarily determined the rate and degree of decomposition, but soil community composition could modify how resource quality affected this soil process. eCO2 and crop cultivar migration significantly altered straw quality and soil community composition, and thus affected soil functioning. Our findings highlight that alterations of soil functional guilds under future climate and appropriate agricultural strategy change the carbon and nutrient cycling of ecosystem. Key-words: Global change; Nitrogen input; Crop cultivar; Rhizosphere food webs; Root microbiome; Microbial community; Soil fauna

Biomass and decay rates of roots and detritus in sediments of intermittent coastal plain streams

Treesearch

Ken M. Fritz; Jack W. Feminella; Chris Colson; B. Graeme Lockaby; Robin Governo; Robert B. Rummer

2006-01-01

Biomass and breakdown of tree roots within streambed sediments were compared with leaf and wood detritus in three Coastal Plain headwater intermittent streams. Three separate riparian forest treatments were applied: thinned, clearcut, and reference. Biomass of roots (live and dead) and leaf/wood was significantly higher in stream banks than in the channel and declined...

Factors affecting distribution of wood, detritus, and sediment in headwater streams draining managed young-growth red alder-conifer forests in southeast Alaska

Treesearch

Takashi Gomi; Adelaide C. Johnson; Robert L. Deal; Paul E. Hennon; Ewa H. Orlikowska; Mark S. Wipfli

2006-01-01

Factors (riparian stand condition, management regimes, and channel properties) affecting distributions of wood, detritus (leaves and branches), and sediment were examined in headwater streams draining young-growth red alder (Alnus rubra Bong.)-conifer riparian forests (40 years old) in southeast Alaska. More riparian red alder were found along...

Whole-system nutrient enrichment increases secondary production in a detritus-based ecosystem

Treesearch

W.F. Cross; J.B. Wallace; A.D. Rosemond; S.L. Eggert

2006-01-01

Although the effects of nutrient enrichment on consumer-resource dynamics are relatively well studied in ecosystems based on living plants, little is known about the manner in which enrichment influences the dynamics and productivity of consumers and resources in detritus-based ecosystems. Because nutrients can stimulate loss of carbon at the base of detrital food webs...

Larval diet affects mosquito development and permissiveness to Plasmodium infection.

PubMed

Linenberg, Inbar; Christophides, George K; Gendrin, Mathilde

2016-12-02

The larval stages of malaria vector mosquitoes develop in water pools, feeding mostly on microorganisms and environmental detritus. Richness in the nutrient supply to larvae influences the development and metabolism of larvae and adults. Here, we investigated the effects of larval diet on the development, microbiota content and permissiveness to Plasmodium of Anopheles coluzzii. We tested three fish diets often used to rear mosquitoes in the laboratory, including two pelleted diets, Dr. Clarke's Pool Pellets and Nishikoi Fish Pellets, and one flaked diet, Tetramin Fish-Flakes. Larvae grow and develop faster and produce bigger adults when feeding on both types of pellets compared with flakes. This correlates with a higher microbiota load in pellet-fed larvae, in agreement with the known positive effect of the microbiota on mosquito development. Larval diet also significantly influences the prevalence and intensity of Plasmodium berghei infection in adults, whereby Nishikoi Fish Pellets-fed larvae develop into adults that are highly permissive to parasites and survive longer after infection. This correlates with a lower amount of Enterobacteriaceae in the midgut microbiota. Together, our results shed light on the influence of larval feeding on mosquito development, microbiota and vector competence; they also provide useful data for mosquito rearing.

Decomposition dynamic of two aquatic macrophytes Trapa bispinosa Roxb. and Nelumbo nucifera detritus.

PubMed

Zhou, Xiaohong; Feng, Deyou; Wen, Chunzi; Liu, Dan

2018-03-29

In freshwater ecosystems, aquatic macrophytes play significant roles in nutrient cycling. One problem in this process is nutrient loss in the tissues of untimely harvested plants. In this study, we used two aquatic species, Nelumbo nucifera and Trapa bispinosa Roxb., to investigate the decomposition dynamics and nutrient release from detritus. Litter bags containing 10 g of stems (plus petioles) and leaves for each species detritus were incubated in the pond from November 2016 to May 2017. Nine times litterbags were retrieved on days 6, 14, 25, 45, 65, 90, 125, 145, and 165 after the decomposition experiment for the monitoring of biomass loss and nutrient release. The results suggested that the dry masses of N. nucifera and T. bispinosa decomposed by 49.35-69.40 and 82.65-91.65%, respectively. The order of decomposition rate constants (k) is as follows: leaves of T. bispinosa (0.0122 day -1 ) > stems (plus petioles) of T. bispinosa (0.0090 day -1 ) > leaves of N. nucifera (0.0060 day -1 ) > stems (plus petioles) of N. nucifera (0.0030 day -1 ). Additionally, the orders of time for 50% dry mass decay, time for 95% dry mass decay, and turnover rate are as follows: leaves < stems (plus petioles) and T. bispinosa < N. nucifera, respectively. This result indicated that the dry mass loss, k values, and other parameters related to k values are significantly different in species- and tissue-specific. The C, N, and P concentration and the C/N, C/P, and N/P ratios presented the irregular temporal changes trends during the whole decay period. In addition, nutrient accumulation index (AI) was significantly changed depending on the dry mass remaining and C, N, and P concentration in detritus at different decomposition times. The nutrient AIs were 36.72, 8.08, 6.35, and 2.56% for N; 31.25, 9.85, 4.00, and 1.63% for P; 25.15, 16.96, 7.36, and 6.16% for C in the stems (plus petioles) of N. nucifera, leaves of N. nucifera, stems (plus petioles) of T. bispinosa, and leaves of T. bispinosa, respectively, at the day 165. These results indicated that 63.28-97.44% of N, 68.75-98.37% of P, and 74.85-93.84% of C were released from the plant detritus to the water at the day 165 of the decomposition period. The initial detritus chemistry, particularly the P-related parameters (P concentration and C/P and N/P ratios), strongly affected dry mass loss, decomposition rates, and nutrient released from detritus into water. Two-way ANOVA results also confirm that the effects on the species were significant for decomposition dynamics (dry mass loss), nutrient release (nutrient concentration, their ratios, and nutrient AI) (P < 0.01), and expected N concentration (P > 0.05). In addition, the decomposition time had also significant effects on the detritus decomposition dynamic and nutrient release. However, the contributors of species and decomposition time on detritus decomposition were significantly different on the basis of their F values of two-way ANOVA results. This study can provide scientific bases for the aquatic plant scientific management in freshwater ecosystems of the East region of China.

Response of Bacterial Communities to Different Detritus Compositions in Arctic Deep-Sea Sediments.

PubMed

Hoffmann, Katy; Hassenrück, Christiane; Salman-Carvalho, Verena; Holtappels, Moritz; Bienhold, Christina

2017-01-01

Benthic deep-sea communities are largely dependent on particle flux from surface waters. In the Arctic Ocean, environmental changes occur more rapidly than in other ocean regions, and have major effects on the export of organic matter to the deep sea. Because bacteria constitute the majority of deep-sea benthic biomass and influence global element cycles, it is important to better understand how changes in organic matter input will affect bacterial communities at the Arctic seafloor. In a multidisciplinary ex situ experiment, benthic bacterial deep-sea communities from the Long-Term Ecological Research Observatory HAUSGARTEN were supplemented with different types of habitat-related detritus (chitin, Arctic algae) and incubated for 23 days under in situ conditions. Chitin addition caused strong changes in community activity, while community structure remained similar to unfed control incubations. In contrast, the addition of phytodetritus resulted in strong changes in community composition, accompanied by increased community activity, indicating the need for adaptation in these treatments. High-throughput sequencing of the 16S rRNA gene and 16S rRNA revealed distinct taxonomic groups of potentially fast-growing, opportunistic bacteria in the different detritus treatments. Compared to the unfed control, Colwelliaceae, Psychromonadaceae , and Oceanospirillaceae increased in relative abundance in the chitin treatment, whereas Flavobacteriaceae, Marinilabiaceae , and Pseudoalteromonadaceae increased in the phytodetritus treatments. Hence, these groups may constitute indicator taxa for the different organic matter sources at this study site. In summary, differences in community structure and in the uptake and remineralization of carbon in the different treatments suggest an effect of organic matter quality on bacterial diversity as well as on carbon turnover at the seafloor, an important feedback mechanism to be considered in future climate change scenarios.

Response of Bacterial Communities to Different Detritus Compositions in Arctic Deep-Sea Sediments

PubMed Central

Hoffmann, Katy; Hassenrück, Christiane; Salman-Carvalho, Verena; Holtappels, Moritz; Bienhold, Christina

2017-01-01

Benthic deep-sea communities are largely dependent on particle flux from surface waters. In the Arctic Ocean, environmental changes occur more rapidly than in other ocean regions, and have major effects on the export of organic matter to the deep sea. Because bacteria constitute the majority of deep-sea benthic biomass and influence global element cycles, it is important to better understand how changes in organic matter input will affect bacterial communities at the Arctic seafloor. In a multidisciplinary ex situ experiment, benthic bacterial deep-sea communities from the Long-Term Ecological Research Observatory HAUSGARTEN were supplemented with different types of habitat-related detritus (chitin, Arctic algae) and incubated for 23 days under in situ conditions. Chitin addition caused strong changes in community activity, while community structure remained similar to unfed control incubations. In contrast, the addition of phytodetritus resulted in strong changes in community composition, accompanied by increased community activity, indicating the need for adaptation in these treatments. High-throughput sequencing of the 16S rRNA gene and 16S rRNA revealed distinct taxonomic groups of potentially fast-growing, opportunistic bacteria in the different detritus treatments. Compared to the unfed control, Colwelliaceae, Psychromonadaceae, and Oceanospirillaceae increased in relative abundance in the chitin treatment, whereas Flavobacteriaceae, Marinilabiaceae, and Pseudoalteromonadaceae increased in the phytodetritus treatments. Hence, these groups may constitute indicator taxa for the different organic matter sources at this study site. In summary, differences in community structure and in the uptake and remineralization of carbon in the different treatments suggest an effect of organic matter quality on bacterial diversity as well as on carbon turnover at the seafloor, an important feedback mechanism to be considered in future climate change scenarios. PMID:28286496

Effects of litter exclusion and wood removal on phosphorus and nitrogen retention in a forest stream

Treesearch

J. R. Webster; J. L. Tank; J. B. Wallace; J. L. Meyer; S. L. Eggert; T. P. Ehrman; B. R. Ward; B. L. Bennett; P. F. Wagner; M. E. McTammany

2000-01-01

Many studies in the past have shown indirect evidence of the importance of terrestrial detritus in woodland streams, but recently Wallace et al. (1997b) eliminated leaf and wood inputs to a small stream and directly demonstrated the importance of this material to stream food webs. Additionally, this whole-stream experiment has shown that terrestrial detritus is more...

Coqui frog populations are negatively affected by canopy opening but not detritus deposition following an experimental hurricane in a tropical rainforest

Treesearch

Paul D. Klawanski; Ben Dalton; Aaron B. Shiels

2014-01-01

Hurricanes, cyclones, and typhoons are common disturbances in many island and coastal forests. There is a lack of understanding of the importance to forest biota of the two major physical aspects that occur simultaneously during a hurricane: canopy disturbance and detritus (debris) deposition onto the ground. Using a replicated factorial design, our study involved...

Climate change could drive marine food web collapse through altered trophic flows and cyanobacterial proliferation

PubMed Central

Ullah, Hadayet; Goldenberg, Silvan U.; Fordham, Damien A.

2018-01-01

Global warming and ocean acidification are forecast to exert significant impacts on marine ecosystems worldwide. However, most of these projections are based on ecological proxies or experiments on single species or simplified food webs. How energy fluxes are likely to change in marine food webs in response to future climates remains unclear, hampering forecasts of ecosystem functioning. Using a sophisticated mesocosm experiment, we model energy flows through a species-rich multilevel food web, with live habitats, natural abiotic variability, and the potential for intra- and intergenerational adaptation. We show experimentally that the combined stress of acidification and warming reduced energy flows from the first trophic level (primary producers and detritus) to the second (herbivores), and from the second to the third trophic level (carnivores). Warming in isolation also reduced the energy flow from herbivores to carnivores, the efficiency of energy transfer from primary producers and detritus to herbivores and detritivores, and the living biomass of detritivores, herbivores, and carnivores. Whilst warming and acidification jointly boosted primary producer biomass through an expansion of cyanobacteria, this biomass was converted to detritus rather than to biomass at higher trophic levels—i.e., production was constrained to the base of the food web. In contrast, ocean acidification affected the food web positively by enhancing trophic flow from detritus and primary producers to herbivores, and by increasing the biomass of carnivores. Our results show how future climate change can potentially weaken marine food webs through reduced energy flow to higher trophic levels and a shift towards a more detritus-based system, leading to food web simplification and altered producer–consumer dynamics, both of which have important implications for the structuring of benthic communities. PMID:29315309

Carbon budget of leaves of the tropical intertidal seagrass Thalassia hemprichii

NASA Astrophysics Data System (ADS)

Chiu, Shih-Han; Huang, Yen-Hsun; Lin, Hsing-Juh

2013-07-01

The question of whether seagrass beds are effective carbon sinks has recently attracted much attention. Leaf production and consumption, and detrital export and decomposition were determined to quantify the carbon budget of leaf production in a southern Taiwan seagrass bed composed of the tropical intertidal seagrass Thalassia hemprichii, which is widely distributed in intertidal zones of the western Pacific. The influence of elevation in the intertidal zone on these processes was also investigated. Leaf production and consumption, and export of leaf detritus showed seasonal variations, with higher rates in the wet season (summer and autumn) and lower rates in the dry season (winter and spring). At the high-elevation site, leaf consumption by fish was significantly higher than that by sea urchins. At the low-elevation site, however, the proportion of leaves consumed by sea urchins was equivalent to that by fish. Leaf detritus decomposed rapidly within the first 9 days, then gradually slowed down, and stabilised after 212 days, at which only 8.7% of dry weight remained in the litterbags. The carbon budget of seagrass leaves demonstrated that 20% of leaf production was grazed by fish and sea urchins and 80% flowed to detritus. This suggests that seagrass leaves are important food sources for inhabiting herbivores. Most of the detritus decomposed (44% of leaf production) or was exported (32% of leaf production), and only 4% of leaf production or 22 g C m-2 yr-1 was stored in this tropical intertidal seagrass bed. Mass balance calculations support this tropical seagrass bed acting as a carbon sink and an outwelling system which exports organic detritus to neighboring coral reefs.

Use of an ecosystem model for testing ecosystem response to inaccuracies of root and microflora productivity estimates

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

Petersen, H.; O'Neill, R.V.; Gardner, R.H.

1984-01-01

A seventy-compartment model for a Danish beech forest ecosystem is described in outline. The unmodified model predicts considerable accumulation of wood litter and decreasing accumulation through secondary to final decomposition products. Increment rates are similar for all components of the detritus based food chain. Modification of fine root production rate produces strong, positive response for root litter, and less, but still significant, response for detritus, humus and the components of the decomposer food chain. Increase of microbial biomass with adjustments of metabolism and production causes reduced accumulation of detritus and humus. The soil organisms respond according to food source. Themore » use of the model for testing the sensitivity of the ecosystem to inaccuracies of rroot- and microflora estimates is discussed. 21 references, 3 figures, 1 table.« less

Evaluation of a Leaf Collection and Street Cleaning Program as a Way to Reduce Nutrients and Organic Carbon in Urban Runoff

NASA Astrophysics Data System (ADS)

Selbig, W.

2016-12-01

Organic detritus can be major sources of nutrients and organic carbon in urban stormwater, especially in areas with dense overhead tree canopy. In order to meet impending regulation to reduce nutrient loads, many cities will require information on structural and non-structural stormwater control measures that target organic detritus. Most cities already conduct some level of leaf collection and existing street cleaning programs; however, few studies have quantified their water-quality benefits. The U.S Geological Survey measured the water-quality benefits of a municipal leaf collection program coupled with street cleaning in Madison, WI, USA during the months of October through November of 2014 and 2015. The calibration phase of the study (2014) characterized nutrient and organic carbon concentrations and loads in runoff from two paired basins without leaf collection or street cleaning. During the treatment phase (2015), leaf collection and street cleaning was done in the test basin by city personnel on a weekly basis. Additionally, prior to each precipitation event, USGS personnel removed as much organic debris from the street surface as reasonably possible. The control remained without street cleaning or leaf collection for the entire monitoring period. During the fall, leaf collection and street cleaning was able to remove the increased amount of organic debris from the curb and street surface which resulted in statistically significant (p<0.05) reductions in loads of phosphorus, nitrogen and organic carbon. Total and dissolved phosphorus loads were reduced by 84 and 83 percent, respectively. Similarly, total and dissolved organic carbon was reduced by 81 and 86 percent, and total and dissolved nitrogen was reduced by 74 and 71 percent, respectively. In the control basin, 60 percent of the annual phosphorus load occurred in fall (winter excluded), the majority of which was dissolved as orthophosphorus, compared to only 16 percent in the test basin. While the leaf collection practices adopted during this study may surpass those used by most municipal programs, results from this study suggest a significant reduction of nutrient and organic carbon loads in urban stormwater is feasible when leaves and other organic detritus are removed from streets prior to precipitation events.

Dynamics of the Indian-Ocean oxygen minimum zones

NASA Astrophysics Data System (ADS)

McCreary, Julian P.; Yu, Zuojun; Hood, Raleigh R.; Vinaychandran, P. N.; Furue, Ryo; Ishida, Akio; Richards, Kelvin J.

2013-05-01

In the Indian Ocean, mid-depth oxygen minimum zones (OMZs) occur in the Arabian Sea and the Bay of Bengal. The lower part of the Arabian-Sea OMZ (ASOMZ; below 400 m) intensifies northward across the basin; in contrast, its upper part (above 400 m) is located in the central/eastern basin, well east of the most productive regions along the western boundary. The Bay-of-Bengal OMZ (BBOMZ), although strong, is weaker than the ASOMZ. To investigate the processes that maintain the Indian-Ocean OMZs, we obtain a suite of solutions to a coupled biological/physical model. Its physical component is a variable-density, 61/2 >-layer model, in which each layer corresponds to a distinct dynamical regime or water-mass type. Its biological component has six compartments: nutrients, phytoplankton, zooplankton, two size classes of detritus, and oxygen. Because the model grid is non-eddy resolving (0.5°), the biological model also includes a parameterization of enhanced mixing based on the eddy kinetic energy derived from satellite observations. To explore further the impact of local processes on OMZs, we also obtain analytic solutions to a one-dimensional, simplified version of the biological model. Our control run is able to simulate basic features of the oxygen, nutrient, and phytoplankton fields throughout the Indian Ocean. The model OMZs result from a balance, or lack thereof, between a sink of oxygen by remineralization and subsurface oxygen sources due primarily to northward spreading of oxygenated water from the Southern Hemisphere, with a contribution from Persian-Gulf water in the northern Arabian Sea. The northward intensification of the lower ASOMZ results mostly from horizontal mixing since advection is weak in its depth range. The eastward shift of the upper ASOMZ is due primarily to enhanced advection and vertical eddy mixing in the western Arabian Sea, which spread oxygenated waters both horizontally and vertically. Advection carries small detritus from the western boundary into the central/eastern Arabian Sea, where it provides an additional source of remineralization that drives the ASOMZ to suboxic levels. The model BBOMZ is weaker than the ASOMZ because the Bay lacks a remote source of detritus from the western boundary. Although detritus has a prominent annual cycle, the model OMZs do not because there is not enough time for significant remineralization to occur.

Effects of alternatives to clearcutting on invertebrate and organic detritus transport from headwaters in southeastern Alaska.

Treesearch

Jake Musslewhite; Mark S. Wipfli

2004-01-01

We examined the transport of invertebrates and coarse organic detritus from headwater streams draining timber harvest units in a selective timber harvesting study, alternatives to clearcutting (ATC) in southeastern Alaska. Transport in 17 small streams (mean measured discharge range: 1.2 to 14.6 L/s) was sampled with 250- µ m-mesh drift nets in spring, summer, and fall...

Linking the brown and green: nutrient transformation and fate in the Sarracenia microecosystem.

PubMed

Butler, Jessica L; Gotelli, Nicholas J; Ellison, Aaron M

2008-04-01

Linkages between detritus-based ("brown") food webs and producer-based ("green") food webs are critical components of ecosystem functionality, but these linkages are hard to study because it is difficult to measure release of nutrients by brown food webs and their subsequent uptake by plants. In a three-month greenhouse experiment, we examined how the detritus-based food web inhabiting rain-filled leaves of the pitcher plant Sarracenia purpurea affects nitrogen transformation and its subsequent uptake by the plant itself. We used isotopically enriched prey (detritus) and soluble inorganic nitrogen, and manipulated food web structure to determine whether the presence of a complete brown web influences uptake efficiency of nitrogen by the plant. Uptake efficiency of soluble inorganic nitrogen was greater than that of nitrogen derived from mineralized prey. Contrary to expectation, there was no effect of the presence in the food web of macroinvertebrates on uptake efficiency of either form of nitrogen. Further, uptake efficiency of prey-derived nitrogen did not differ significantly among S. purpurea and two congeneric species (S. flava and S. alata) that lack associated food webs. Although upper trophic levels of this brown food web actively process detritus, it is the activity of the microbial component of this web that ultimately determines nitrogen availability for S. purpurea.

Seasonal variation of absorption by particles and colored dissolved organic matter (CDOM) in Funka Bay, southwestern Hokkaido, Japan

NASA Astrophysics Data System (ADS)

Sasaki, Hiroaki; Miyamura, Tsuyoshi; Saitoh, Sei-ichi; Ishizaka, Joji

2005-08-01

Between November 2000 and October 2001, the seasonal variation in absorption by particles (phytoplankton and detritus) and colored dissolved organic matter (CDOM) was measured in Funka Bay (a subarctic coastal region of Japan). In autumn-winter, chlorophyll a concentration (Chl a) near the euphotic zone remained very low (<1.0 mg m -3) but markedly increased in spring (16.8 mg m -3). Chlorophyll-specific absorption coefficient for phytoplankton ( a∗ph( λ)) was high during summer and low during the spring bloom. This is because the package effect was greater during the spring bloom due to the presence of large diatoms, while small phytoplankton dominated during summer. Absorption at 440 nm by CDOM was higher than that of phytoplankton and detritus, except during the spring bloom, and the relative contribution of CDOM absorption to the total absorption coefficient was >50%. CDOM and detritus absorption did not increase with increasing Chl a, but it showed a time lag between the spring bloom. It is suggested that phytoplankton degradation started after the spring bloom; detritus absorption increased and, then, CDOM absorption increased. River runoff was not a significant influence in Funka Bay, therefore, CDOM production may be mainly related to microbial activity.

Shoot litter breakdown and zinc dynamics of an aquatic plant, Schoenoplectus californicus.

PubMed

Arreghini, Silvana; de Cabo, Laura; Serafini, Roberto José María; Fabrizio de Iorio, Alicia

2018-07-03

Decomposition of plant debris is an important process in determining the structure and function of aquatic ecosystems. The aims were to find a mathematic model fitting the decomposition process of Schoenoplectus californicus shoots containing different Zn concentrations; compare the decomposition rates; and assess metal accumulation/mobilization during decomposition. A litterbag technique was applied with shoots containing three levels of Zn: collected from an unpolluted river (RIV) and from experimental populations at low (LoZn) and high (HiZn) Zn supply. The double exponential model explained S. californicus shoot decomposition, at first, higher initial proportion of refractory fraction in RIV detritus determined a lower decay rate and until 68 days, RIV and LoZn detritus behaved like a source of metal, releasing soluble/weakly bound zinc into the water; after 68 days, they became like a sink. However, HiZn detritus showed rapid release into the water during the first 8 days, changing to the sink condition up to 68 days, and then returning to the source condition up to 369 days. The knowledge of the role of detritus (sink/source) will allow defining a correct management of the vegetation used for zinc removal and providing a valuable tool for environmental remediation and rehabilitation planning.

The exploration of trophic structure modeling using mass balance Ecopath model of Tangerang coastal waters

NASA Astrophysics Data System (ADS)

Dewi, N. N.; Kamal, M.; Wardiatno, Y.; Rozi

2018-04-01

Ecopath model approach was used to describe trophic interaction, energy flows and ecosystem condition of Tangerang coastal waters. This model consists of 42 ecological groups, of which 41 are living groups and one is a detritus group. Trophic levels of these groups vary between 1.0 (for primary producers and detritus) to 4.03 (for tetraodontidae). Groups with trophic levels 2≤TL<3 and 3≤TL<4 have a range of ecotropic efficiency from 0 to 0.9719 and 0 to 0.7520 respectively.The Mean transfer efficiency is 9.43% for phytoplankton and 3.39% for detritus. The Mixed trophic impact analysis indicates that phytoplankton havea positive impact on the majority of pelagic fish, while detritus has a positive impact on the majority of demersal fish. Leiognathidae havea negative impact on phytoplankton, zooplankton and several other groups. System omnivory index for this ecosystem is 0.151. System primary production/respiration (P/R) ratio of Tangerang coastal waters is 1.505. This coastal ecosystem is an immatureecosystem because it hasdegraded. Pedigree index for this model is 0.57. This model describes ecosystem condition affected by overfishing and antropogenic activities. Therefore, through Ecopath model we provide some suggestions about the ecosystem-based fisheries management.

Mobile epifauna on Zostera marina, and infauna of its inflorescences

NASA Astrophysics Data System (ADS)

Hellwig-Armonies, Monika

1988-06-01

The faunal colonization of the leaves and inflorescences of intertidal Zostera marina L. and of the ambient water has been studied at the Island of Sylt (North Sea). The abundance of the snail Littorina littorea L. and the isopod Jaera albifrons Leach correlates significantly with leaf surface area. This is not the case with the abundance of meiofaunal Plathelminthes, Nematoda, Copepoda, and Polychaeta. However, they increase significantly with the numbers of generative shoots in the sampled seagrass bunches. Members of these taxa inhabit the Zostera inflorescences, and average abundance increases with the degree of decay of inflorescences. This temporary microhabitat presumably offers food and shelter. Copepods and ostracods dominate in the ambient water. Planktonic calanoid copepods correlate with the amount of sampled seawater, while Ostracoda correlate with the amount of resuspended detritus suggesting that they were resuspended themselves. The study shows that some meiofaunal taxa can rapidly exploit a short-lived habitat such as the Zostera inflorescences. Juvenile polychaetes use inflorescences as a nursery.

Major Histopathologic Diagnoses of Chronic Wounds.

PubMed

Turi, George K; Donovan, Virginia; DiGregorio, Julie; Criscitelli, Theresa M; Kashan, Benjamin; Barrientos, Stephan; Balingcongan, Jose Ramon; Gorenstein, Scott; Brem, Harold

2016-08-01

To clarify the histopathology of acute osteomyelitis, chronic osteomyelitis, primary vasculitis, and secondary-type vasculitis. This continuing education activity is intended for physicians and nurses with an interest in skin and wound care. After participating in this educational activity, the participant should be better able to:1. Describe the parameters and significance of this study.2. Identify chronic wound diagnosis and treatment.3. Differentiate the histopathology of osteomyelitis and vasculitis. The presence of a chronic wound can result in significant morbidity/mortality. Understanding the pathological alterations of wound tissue that are refractory to standard wound therapy is essential for effective wound management and healing. The authors describe 4 wound etiologies, specifically, acute osteomyelitis, chronic osteomyelitis, primary vasculitis, and secondary-type vasculitis. A tertiary care hospital. A retrospective review of 1392 wound operations performed during a 24-month period at a tertiary care hospital was conducted. Tissue specimens reviewed included soft tissue infections of the lower extremity, sacrum, hip/pelvis, trunk, perineum, and buttocks. Acute osteomyelitis is defined as bone tissue with a predominance of polymorphonuclear leukocytes, evidence of osteoclast bone resorption with scalloping of the cortical bone edges, and bone detritus. Chronic osteomyelitis is defined as bone tissue with a significant amount of fibrosis surrounding devitalized tissue and heavy infiltration of lymphocytes and plasma cells. Primary-type vasculitis is defined primarily as inflammation and necrosis of blood vessel walls. In cutaneous lesions of granulomatosis with polyangiitis, ulceration with numerous inflammatory granulomas is seen in the papillary dermis. Secondary vasculitis is defined by vessel wall infiltration by inflammatory cells and fibrinoid necrosis of the small vessel wall. Pathologies of these 4 types of wounds can complicate standard algorithms designed for diagnosis and treatment, and accurate diagnosis through histopathologic analysis can help tailor targeted treatment.

Inter-annual changes in detritus-based food chains can enhance plant growth response to elevated atmospheric CO2.

PubMed

Hines, Jes; Eisenhauer, Nico; Drake, Bert G

2015-12-01

Elevated atmospheric CO2 generally enhances plant growth, but the magnitude of the effects depend, in part, on nutrient availability and plant photosynthetic pathway. Due to their pivotal role in nutrient cycling, changes in abundance of detritivores could influence the effects of elevated atmospheric CO2 on essential ecosystem processes, such as decomposition and primary production. We conducted a field survey and a microcosm experiment to test the influence of changes in detritus-based food chains on litter mass loss and plant growth response to elevated atmospheric CO2 using two wetland plants: a C3 sedge (Scirpus olneyi) and a C4 grass (Spartina patens). Our field study revealed that organism's sensitivity to climate increased with trophic level resulting in strong inter-annual variation in detritus-based food chain length. Our microcosm experiment demonstrated that increased detritivore abundance could not only enhance decomposition rates, but also enhance plant growth of S. olneyi in elevated atmospheric CO2 conditions. In contrast, we found no evidence that changes in the detritus-based food chains influenced the growth of S. patens. Considered together, these results emphasize the importance of approaches that unite traditionally subdivided food web compartments and plant physiological processes to understand inter-annual variation in plant production response to elevated atmospheric CO2. © 2015 John Wiley & Sons Ltd.

Food of larval Anopheles culicifacies and Anopheles varuna in a stream habitat in Sri Lanka.

PubMed

Piyaratne, M K; Amerasinghe, P H; Amerasinghe, F P; Konradsen, F

2005-12-01

No previous studies have been conducted on the natural food of larval Anopheles culicifacies s.l. (the major malaria vector) and An. varuna (a secondary vector) in Sri Lanka. The present study analyzed the contents of guts dissected from larvae collected from pools in a natural stream-cum-irrigation conveyance channel in the Upper Yan Oya watershed in the North Central Province of the country during August-September 1997 and July 1998. Determinations of physicochemical and biological parameters of the pools and their water were done at the same time. A fluorochromatic stain, 4',6-diamidino-2-phenylindole, was used to stain larval gut contents. Quantitative estimates of different categories of food types were made by analyzing the gut contents of 95 An. culicifacies (26 second instars and 69 fourth instars) and 52 An. varuna (21 second instars and 31 fourth instars). Detritus was the most frequent food type, comprising >74% of the gut contents in both species. Other food types included bacteria (cocci and rods), filamentous algae, diatoms, and desmids. Overall, bacteria constituted a significantly higher proportion of the gut contents in An. culicifacies than in An varuna. Significantly more detritus, bacteria, and total particulate matter occurred in 4th instars of An. culicifacies than in An. varuna, indicating a greater food intake in the former species. Second instars of An. culicifacies and An. varuna did not differ significantly in any parameter. A significant increase in food intake between 2nd and 4th instars was seen for An. culicifacies, but not An. varuna. Food indices were lower in An. varuna than in An. culicifacies when the 2 species co-occurred, indicating competition for food, and the implications of this to adult body size, survival, and fecundity are discussed.

Carbon cycling and POC turnover in the mesopelagic zone of the ocean: Insights from a simple model

NASA Astrophysics Data System (ADS)

Anderson, Thomas R.; Tang, Kam W.

2010-08-01

Carbon budgets of the mesopelagic zone are poorly constrained, highlighting our lack of understanding of the biota that inhabit this environment and their role in the cycling and sequestering of carbon in the deep ocean. A simple food web model of the mesopelagic zone is presented that traces the turnover of particulate organic carbon (POC), supplied as sinking detritus, through to its respiration by the biota via three pathways: colonization and solubilization of detritus by attached bacteria, production of free-living bacteria following losses of solubilization products during particle degradation, and consumption by detritivorous zooplankton. The relative consumption of detritus by attached bacteria was initially specified as 76%, with the remaining 24% by detritivores. Highlighting an asymmetry between consumption and respiration, the resulting predicted share of total respiration due to bacteria was 84.7%, with detritivores accounting for just 6.6% (with 6.5% and 2.2% by bacterivores and higher zooplankton, respectively). Bacteria thus dominated respiration and thereby acted as the principal sink for POC supplied to the mesopelagic zone, whereas zooplankton mainly recycled carbon back to the base of the food web as detritus or dissolved organic carbon rather than respiring it to CO 2. Estimates of respiration are therefore not necessarily a reliable indicator of the relative roles of bacteria and zooplankton in consuming and processing POC in the mesopelagic zone of the ocean. The work highlighted a number of major unknowns, including how little we know in general about the dynamics and metabolic budgets of bacteria and zooplankton that inhabit the mesopelagic zone and, specifically, the degree to which the solubilized products of enzymatic hydrolysis of POC by attached bacteria are lost to the surrounding water, the magnitude and factors responsible for bacterial growth efficiency, the role of microbes in the nutrition of detritivores, and the recycling processes by which zooplankton return what they consume to the food web as detritus and dissolved organic matter.

Interspecific competition of a new invasive mosquito, Culex coronator, and two container mosquitoes, Aedes albopictus and Cx. quinquefasciatus (Diptera: Culicidae), across different detritus environments.

PubMed

Yee, D A; Skiff, J F

2014-01-01

The mosquito Culex coronator (Dyar and Knab) (Diptera: Culicidae) has undergone rapid range expansion in the United States since 2003, with its historical distribution in the southwest expanding eastward to the Atlantic coast. Although Cx. coronator nominally use small natural aquatic habitats for development, the use of containers (e.g., tires) makes it potentially important as container invasive. To determine the potential ecological effects of Cx. coronator on resident container species, we conducted a laboratory experiment to assess its competitive ability with two common tire-inhabiting species, Aedes albopictus (Skuse) and Culex quinquefasciatus (Say) (Diptera: Culicidae). Larvae were reared under a factorial design with each species alone and in combination (Cx. coronator + Ae. albopictus, Cx. coronator + Cx. quinquefasciatus) across three different resource environments (leaf detritus only, animal detritus only, animal + leaf). Mosquito performance (survival, adult male and female mass, and development time) was measured for each species across treatments. Female Cx. coronator developed slowest when grown with Ae. albopictus, or when grown with leaves only regardless of species combinations; similar patterns emerged for males although species effects were restricted to mass. Few differences were evident in performance for male and female Cx. coronator across detritus environments when grown with Cx. quinquefasciatus. Cx. quinquefasciatus did not vary in mass or development time in the presence of Cx. coronator compared with when grown alone. Ae. albopictus female mass was 15% lower in the presence of Cx. coronator. Survival of Cx. coronator was highest in animal and leaf detritus containers, although survival was generally lower when larvae were grown with Ae. albopictus. These findings suggest that the performance of Cx. coronator is similar to that of Cx. quinquefasciatus but it suffers in the presence of Ae. albopictus under some resource environments.

The Bionomics and Vector Competence of Anopheles Albimanus and Anopheles Vestitipennis in Southern Belize, Central America

DTIC Science & Technology

2000-11-20

can be found in large numbers throughout the Yucatan , southern Mexico and Guatemala (Kumm et at. 1943, Loyola et a1. 1991, Arredondo-Jimenez et a1...material or detritus as a nutritional source as well as plant cover for shade. Anopheles yestitipennis exhibits its highest numbers during the rainy...species appears to require plant material or detritus as a nutritional source as well as plant cover for shade. Both species also have a clear seasonal

Selenium concentrations in irrigation drain inflows to the Salton Sea, California, October 2006 and January 2007

USGS Publications Warehouse

May, Thomas W.; Walther, Mike W.; Brumbaugh, William G.

2007-01-01

This report presents raw data on selenium concentrations in samples of water, sediment, detritus, and selected food-chain matrices collected from selected agricultural drains in the southern portion of the Salton Sea during October 2006 and January 2007. Total selenium and selenium species were determined in water samples, whereas total selenium was determined in sediment, detritus, algae, plankton, midge larvae (Family Chironomidae), and two fish species (western mosquitofish, Gambusia affinis, and sailfin molly, Poecilia latipinna).

Grazing experiments and model simulations of the role of zooplankton in Phaeocystis food webs

NASA Astrophysics Data System (ADS)

Verity, P. G.

2000-08-01

A combined empirical and modelling study was conducted to further examine the potential importance of grazing by zooplankton in pelagic food webs in which Phaeocystis is a significant or dominant component. Laboratory experiments were designed to measure ingestion of Phaeocystis and other potential prey items which co-occur with Phaeocystis. Grazers included copepods and ciliates, and prey included Phaeocystis colonies and solitary cells, diatoms, ciliates, bacteria, and detritus. These data were expressed in the model currency of nitrogen units, and fit to hyperbolic tangent equations which included minimum prey thresholds. These equations and literature data were used to constrain a food web model whose purpose was to investigate trophic interactions rather than to mimic actual events. Nevertheless, the model output was similar to the general pattern and magnitude of development of Phaeocystis-diatom communities in some environments where they occur, e.g. north Norwegian waters. The model included three forms of nitrogen, three phytoplankton groups, bacteria, two zooplankton groups, and detritus, with detailed flows between compartments. An important component of the model was inclusion of variable prey preferences for zooplankton. The experiments and model simulations suggest several salient conclusions. Phaeocystis globosa colonies were eaten by a medium-sized copepod species, but ingestion appeared to be strongly dependent upon a proper size match between grazer and prey. If not, colonies were eaten little if at all. Phaeocystis solitary cells were ingested rapidly by ciliate microzooplankton, in agreement with prior literature observations. In contrast, detritus was eaten comparatively slowly by both ciliates and copepods. Both types of zooplankton exhibited apparent minimum prey thresholds below which grazing did not occur or was inconsequential. Model simulations implied that transitions between life cycle stages of Phaeocystis may potentially be important to phytoplankton-zooplankton interactions, and that relative rates of ingestion of Phaeocystis by various zooplankton may have significant impacts upon material fluxes through and out of Phaeocystis-diatom ecosystems. Indirect effects of trophic interactions appear to be equally significant as direct effects.

Transport, sloughing and settling rates of estuarine macrophytes: Mechanisms and ecological implications

NASA Astrophysics Data System (ADS)

Flindt, M. R.; Pedersen, C. B.; Amos, C. L.; Levy, A.; Bergamasco, A.; Friend, P. L.

2007-05-01

The study of plant-bound nutrient transport has been largely neglected in estuaries. Lately however, it has been shown that nutrients bound to macroalgae and seagrasses can constitute a major part of the nutrient transport in shallow tidal estuaries. Organic detritus in estuaries comes from various sources. This paper looks into the source of detritus from sloughing, and the transport behaviour of plant detritus under unidirectional flows. In order to determine the extent of the sloughing of macrophytes, the threshold current velocities for the traction and resuspension of the most common submersed macrophytes in Venice Lagoon ( Ulva lactuca, Enteromorpha sp., Ceramium rubrum, Cladophora sp., and Chaetomorpha linum) were studied in a laboratory flume. It was found that all macrophytes subjected to flows of 1.5-3.0 cm s -1 move initially as bed load. The threshold for suspension of the macrophyte tissue was at current speeds >3 cm s -1. The exception was the filamentous macroalgae, C. linum, which moved as bed load at all current speeds. This implies that the advection of plant-bound nutrients in Venice Lagoon is widespread and takes place over virtually all stages of the tide. Initial experiments were carried out on unattached macroalgae. A second study focused on the sloughing of attached macroalgae by steady currents. The threshold current speeds at which sloughing commenced varied between different types of algae, and sloughing rate was related largely to current speed. The resuspension rates were uniform between the different macrophyte groups. Our results help explain why plant matter has been trapped in nets close to the bed of Venice Lagoon on ebbing tides. It shows that a major component of the bedload is organic in origin. The results verify that a large proportion of the net nutrient export from estuaries is bound in macrophyte tissue. These findings need to be included in future ecological models that describe the resuspension, sloughing and settling of macrophytes.

Shoreline as a controlling factor in commercial shrimp production

NASA Technical Reports Server (NTRS)

Faller, K. H. (Principal Investigator)

1978-01-01

An ecological model was developed that relates marsh detritus export and shrimp production, based on the hypothesis that the shoreline is a controlling factor in the production of shrimp through regulation of detritus export from the marsh. LANDSAT data were used to develop measurements of shoreline length and area of marsh having more than 5.0 km shoreline/sq km for the coast of Louisiana, demonstrating the capability of remote sensing to provide important geographic information. These factors were combined with published tidal ranges and salinities to develop a mathematical model that predicted shrimp production for nine geographic units of the Louisiana coast, as indicated by the long term average commercial shrimp yield. The mathematical model relating these parameters and the shrimp production is consistent with an energy flow model describing the interaction of detritus producing marshlands with shrimp nursery grounds and inshore shrimping areas. The analysis supports the basic hypothesis and further raises the possibility of applications to coastal zone management requirements.

A new bathyal sipunculan from Southern California, with ecological notes

NASA Astrophysics Data System (ADS)

Thompson, Bruce E.

1980-11-01

Golfingia (Nephasoma) nicolasi n. sp. is described. It is a long, slender species with a filiform introvert that is 6 to 7 times the length of the trunk. The species was often the numerically dominant taxon in samples collected from the San Nicolas Basin, California, and was also callected from several other basins off southern California. Analyses of several collections from the San Nicolas Basin show that the population was spatially patchy; temporal variation was also indicated but only one year was sampled adequately. Average population densities were highest at the base of the slopes descending into the basin from the highly productive Santa Rosa-Cortes Ridge and Tanner Bank. G. nicolasi appears to feed on the large amounts of organic detritus that accumulate from this source.

New petrofacies in upper Cretaceous section of southern California

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

Colburn, I.P.; Oliver, D.

1986-04-01

A distinctive sandstone-conglomerate petrofacies is recognized throughout the Late Cretaceous (Maestrichtian-late Campanian) Chatsworth Formation in the Simi Hills. It is named the Woolsey Canyon petrofacies after the district where it was first recognized. The petrofacies is also recognized in the Late Cretaceous (late Campanian and possibly early Maestrichtian) Tuna Canyon Formation of the central Santa Monica Mountains. The conglomerates in the petrofacies are composed predominantly of angular pebble-size clasts of argillite, quartz-rich rocks (orthoquartzarenite, metaorthoquartzarenite, mice quartz schist) and leucocratic plutoniate (granite-granodiorite). The conglomerate texture and composition are mirrored in the sandstone. The uniformly angular character of the conglomerate clastsmore » and the survival of argillite clasts indicate that the detritus underwent no more than 5 mi of subaerial transport before it entered the deep marine realm. Foraminifers collected from mudstones interbedded with the conglomerates indicate upper bathyal water depth at the site of deposition. A source terrane of low to moderate relief is indicated by the absence of cobbles and boulders. Bed forms, sedimentary structures, and textural features indicate the detritus moved north from its source terrane to be deposited by turbidity currents, debris flows, and grain flows on the Chatsworth Submarine Fan. The detritus of the Woolsey Canyon petrofacies was derived from basement rocks, now largely buried beneath the Los Angeles basin, that were being eroded during the formation of the Cretaceous Los Angeles erosion surface. The detritus came from the Los Angeles arch of that surface.« less

Processes affecting the spatial distribution of seagrass meadow sedimentary material on Yao Yai Island, Thailand

NASA Astrophysics Data System (ADS)

Quak, Michelle S. Y.; Ziegler, Alan D.; Benner, Shawn G.; Evans, Sam; Todd, Peter A.; Gillis, Lucy G.; Vongtanaboon, Sukanya; Jachowski, Nick; Bouma, Tjeerd J.

2016-12-01

Many islands throughout SE Asia are experiencing rapid development and land-cover conversion that potentially threaten sensitive coastal ecosystems, such as seagrasses, through increased loading of sediment and nutrients originating from disturbed catchments draining to the sea. To evaluate this threat for one such island in Southern Thailand (Yao Yai), we perform sediment source tracing via end-member mixing analysis using stable isotopes δ13C and δ15N in organic matter to explore sediment loading in a seagrass meadow. The analysis indicates that sedimentary material in the meadow originates mostly from ocean-associated sources (∼62% from seagrass detritus, seston, and ocean sediments). Terrestrial material comprises ∼19% of the organic material found in the seagrass meadow, with another 20% originating from an adjacent mangrove forest. Approximately one-fourth of the seagrass meadow material (24%) is detritus that has been (re)deposited internally. The high contribution of terrestrial-derived organic matter deposited near the river mouth demonstrates that substantial quantities of sediment are being transferred from upslope erosion sources into the seagrass meadow. However, only a small amount of this material is deposited throughout the entire bay because much of the terrestrial- and mangrove-derived sediment is transferred to the open ocean via channels that are periodically dredged to allow boat access to two small inland harbours. This positive affect of dredging has not received very much attention in existing literature. River water flowing to the channels during falling tide delivers sediment to these efficient pathways, where much of it bypasses the seagrass meadow at periods of time when sediment deposition would normally be the greatest. There is growing concern that ongoing land-cover changes and planned urbanization related to tourism and agriculture on the island may boost sediment/nutrients above a critical threshold, beyond that revealed in our baseline survey. Our tracer-based sediment source approach did not corroborate our observations of substantial erosion and land degradation in the upper catchment-but this could be a result of sediment flushing through the dredged channels. We encourage others to combine such methods with sediment budgeting approaches to triangulate results for consistency. Finally, from an ecological perspective, the high presence of seagrass detritus we found in bay sediments suggests seagrass is potentially a key source of nutrients for the meadow itself, as well as other connected ecosystems.

Erosional history of the Appalachians as recordeed in detrital zircon fission-track ages and lithic detritus in Atlantic Coastal Plain sediments

USGS Publications Warehouse

Naeser, C.W.; Naeser, N.D.; Edwards, Lucy E.; Weems, Robert E.; Southworth, C. Scott; Newell, Wayne L.

2016-01-01

Comparison of fission-track (FT) ages of detrital zircons recovered from Atlantic Coastal Plain sediments to FT ages of zircons from bedrock in source terranes in the Appalachians provides a key to understanding the provenance of the sediments and, in turn, the erosional and depositional history of the Atlantic passive margin.In Appalachian source terranes, the oldest zircon fission-track (ZFT) ages from bedrock in the western Appalachians (defined for this paper as the Appalachian Plateau, Valley and Ridge, and far western Blue Ridge) are notably older than the oldest ages from bedrock in the eastern Appalachians (Piedmont and main part of the Blue Ridge). The age difference is seen both in ZFT sample ages and in individual zircon grain ages and reflects differences in the thermotectonic history of the rocks. In the east, ZFT data indicate that the rocks cooled from temperatures high enough to partially or totally reset ZFT ages during the Paleozoic and (or) Mesozoic. The majority of the rocks are interpreted to have cooled through the ZFT closure temperature (∼235 °C) at various times during the late Paleozoic Alleghanian orogeny. In contrast, most of the rocks sampled in the western Appalachians have never been heated to temperatures high enough to totally reset their ZFT ages. Reflecting their contrasting thermotectonic histories, nearly 80 percent of the sampled western rocks yield one or more zircon grains with very old FT ages, in excess of 800 Ma; zircon grains yielding FT ages this old have not been found in rocks in the Piedmont and main part of the Blue Ridge. The ZFT data suggest that the asymmetry of zircon ages of exposed bedrock in the eastern and western Appalachians was in evidence by no later than the Early Cretaceous and probably by the Late Triassic.Detrital zircon suites from sands collected in the Atlantic Coastal Plain provide a record of detritus eroded from source terranes in the Appalachians during the Mesozoic and Cenozoic. In Virginia and Maryland, sands of Early Cretaceous through late early Oligocene age do not yield any old zircons comparable in age to the old zircons found in bedrock in the western Appalachians. Very old zircons yielding FT ages >800 Ma are only encountered in Coastal Plain sands of middle early Miocene and younger age.Miocene and younger fluvial-deltaic deposits associated with the major mid-Atlantic Coastal Plain rivers that now head in the western Appalachians (the Hudson, Delaware, Susquehanna, Potomac, James, and Roanoke) contain abundant clasts of fossiliferous chert and quartzite and other distinctive rock types derived from Paleozoic rocks of the western Appalachians. These distinctive clasts have not been reported in older Coastal Plain sediments.The ZFT and lithic detritus data indicate that the drainage divide for one or more east-flowing mid-Atlantic rivers migrated west into the western Appalachians, and the river(s) began transporting western Appalachian detritus to the Atlantic Coastal Plain, sometime between the late early Oligocene and middle early Miocene. By no later than late middle Miocene most if not all of the major rivers that now head west of the Blue Ridge were transporting western Appalachian detritus to the Coastal Plain. Prior to the drainage divide migrating into the western Appalachians, the ZFT data are consistent with the dominant source of Atlantic Coastal Plain sediments being detritus from the Piedmont and main part of the Blue Ridge, with possible input from distant volcanic sources.The ZFT data suggest that the rapid increase in the rate of siliciclastic sediment accumulation in middle Atlantic margin offshore basins that peaked in the middle Miocene and produced almost 30 percent of the total volume of post-rift siliciclastic sediments in the offshore basins began in the early Miocene when Atlantic river(s) gained access to the relatively easily eroded Paleozoic sedimentary rocks of the western Appalachians.

Export of Dissolved Organic Carbon following Prescribed Fire on Forested Watersheds: Implications for Watershed Management for Drinking Water Supply

NASA Astrophysics Data System (ADS)

Zhang, W.; Olivares, C. I.; Uzun, H.; Erdem, C. U.; Trettin, C.; Liu, Y.; Robinson, E. R.; Karanfil, T.; Chow, A. T.

2016-12-01

Detrital material in forest watersheds is the major terrestrial source of dissolved organic matter (DOM) and disinfection byproduct (DBP) precursors in surface source waters, but it is also the fuel for forest fires. Prescribed fire, as a fuel reduction technique is intended to reduce the amount of forest detritus, and therefore the risk of wildfire. Accordingly, periodic prescribed fire can reduce the accumulation of detritus on forest floor and the amount of DOM export after forest treatments. To evaluate the effects of prescribed fire on water quality, we conducted a controlled study on a paired first-order watershed system that includes a 160 ha treatment watershed (WS77) and 200 ha control watershed (WS80) on the Santee Experimental Forest, near Charleston South Carolina. WS77 has been used for prescribed fire research since the 1960's, the current experimental burn occurred on April, 2016. WS80 has not been managed or burned for at least 55 years. Gauging stations were equipped with in-situ TOC sensors and flow-proportional water samplers for monitoring temporal trends on water quality. Water samples taken from the first runoff event from both watersheds including rising limb, peak discharge, and falling limb were used for detailed chemical characterizations including DOC and nutrient concentrations, coagulation efficiency, and DBP formation such as trihalomethanes (THMs) and halocacetic acids (HAAs) from chlorination as well as N-nitrosodimethylamine (NDMA) from chlorination, and chemical formula assignment on DOM using Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR-MS) before and after chlorination and chloramination. Preliminary FT-ICR-MS data shows that DOM chemical compositions are different between raw samples collected from WS77 and WS80. Chlorination resulted in a shift toward lower molecular mass compared to the raw materials. While chloramination did not cause a drastic mass shift, such a treatment also produced DOM moieties that are significantly different from the raw material. Based on our understanding, this watershed-scale study is the first field-scale study to evaluate the effects of prescribed fire on treatability of drinking water supplies.

Recent storm and tsunami coarse-clast deposit characteristics, southeast Hawai'i

USGS Publications Warehouse

Richmond, B.M.; Watt, Sebastian; Buckley, M.; Jaffe, B.E.; Gelfenbaum, G.; Morton, R.A.

2011-01-01

Deposits formed by extreme waves can be useful in elucidating the type and characteristics of the depositional event. The study area on the southeast coast of the island of Hawaiʻi is characterized by the presence of geologically young basalts of known age that are mantled by recent wave-derived sedimentary deposits. The area has been impacted by large swells, storms and tsunamis over the last century, and in combination with known substrate ages makes this an ideal location to study recent deposits produced by such events. Three distinct coarse-clast deposit assemblages can be recognized based on clast size, composition, angularity, orientation, packing, elevation and inland distance of the deposit. These deposits are characterized as one of three types. 1) Gravel fields of isolated clasts, primarily boulder-size material, and scattered pockets of concentrated sand and gravel in topographic lows. 2) Shore-parallel and cuspate ridges composed mostly of rounded basalt gravel and sand with small amounts of carbonate detritus. The ridges range in height from about 1 to 3 m and are 10s of m wide. 3) Cliff-top deposits of scattered angular and sub-angular clasts along sea cliffs that are generally greater than 5 m elevation. The gravel fields are primarily of tsunami origin from either the 1975 Kalapana event, or a combination of the 1975 tsunami, and 1868 tsunami or earlier events. The ridge deposits are presently active and sediment continues to be added during high wave events. The cliff-top deposits contain evidence of deposition by both tsunami and storm processes and require further investigation.

Experimental Study on the Diet of Mosquitofish (Gambusia holbrooki) under Different Ecological Conditions in a Shallow Lake

NASA Astrophysics Data System (ADS)

Blanco, Saúl; Romo, Susana; Villena, María-José

2004-07-01

We studied the diet of the eastern mosquitofish Gambusia holbrooki with in situ experimental mesocosms located in a shallow lake. Different nutrient concentrations (phosphorus and nitrogen) and fish population densities were tested. Our results confirm that it is a planktivorous species, with also a great ingestion of algae and detritus. Nutrient fertilization caused almost no changes in this species feeding behavior, but larger mosquitofish stocks induced a shift to zooplanktivory and a decline in detritivory. When macrophytes were present, the predation effect focused on zooplankton and plant-associated animals, otherwise predation on bottom macroinvertebrates increased. Females preyed upon almost all groups more intensely, including detritus. Males and juveniles did not overlap diet, the former being more selective on ostracods, while juveniles consumed detritus, rotifers and cladoceran. Our data support the idea that mosquitofish can cause important top-down effects in shallow lakes under a wide variety of ecological conditions, being an important zooplanktivore in both turbid and plant-dominated shallow lakes especially in the Mediterranean zone, where high temperatures and absence of piscivores promote maintenance of its populations during the whole year. (

How to handle 'poor' foodstuffs: Acclimation of the common cockle (Cerastoderma edule) to detrital diets

NASA Astrophysics Data System (ADS)

Arambalza, Udane; Ibarrola, Irrintzi; Navarro, Enrique; Urrutxurtu, Iñaki; Urrutia, Miren B.

2018-04-01

As an approach to elucidating the "value" of detritus as a food source for bivalves, we analysed the capability of the common cockle (Cerastoderma edule) to modulate feeding and digestive rates during acclimation to low and high food rations of detrital diets with either low (Juncus maritimus) or high digestibility (Enteromorpha spp.). On acclimation day 3, feeding rates were similar in cockles fed different detrita; however, the absorption rate was higher in cockles fed Enteromorpha spp. With J. maritimus, rising food rations promoted an exponential decrease in absorption efficiency, whereas with Enteromorpha spp., absorption efficiency was only marginally reduced. During acclimation, cockles improved the rate at which both detritus were assimilated by means of increasing ingestion rates while maintaining absorption efficiency. When the time-course of digestive carbohydrase activities was monitored during acclimation to either detritus or phytoplankton (Isochrysis galbana), we found that only phytoplankton promoted the induction of cellulase activity in the digestive glands of cockles. This response in cockles fed phytoplankton promoted an increase in the digestibility of Enteromorpha spp., but had no effect on the digestibility of J. maritimus.

Carbon and hydrogen isotopic characterization of methane from wetlands and lakes of the Yukon-Kuskokwim Delta, Western Alaska

NASA Technical Reports Server (NTRS)

Martens, Christopher S.; Kelley, Cheryl A.; Chanton, Jeffrey P.; Showers, William J.

1992-01-01

The results are reported of a study of the carbon and hydrogen isotopic composition of methane from tundra environments of the Yukon-Kuskokwin Delta of western Alaska. The delta C-13 value of diffusive methane emissions from wet meadow tundra of the Delta is -65.82 +/- 2.21 per mil (n=18). Detritus-rich sediments of tundra lakes are loaded with methane-rich gas bubbles during the warm season. Spatial trend is the major gas concentration and isotopic values of methane in these gas bubbles appear to reflect processes associated with production rate and mechanisms; high methane concentrations, lightest delta C-13 values, the heaviest delta D value occur in detritus-rich sediments isolated from emergent vegetation. Heavier delta C-13 and lighter delta D values in methane from heavily vegetated lake margins suggest a shift toward a larger role for acetate fermentation in association with aquatic plants and plant detritus. Bubble ebullition is estimated to account for up to 17 percent of total Delta methane emissions.

Resource-Saving Cleaning Technologies for Power Plant Waste-Water Cooling Ponds

NASA Astrophysics Data System (ADS)

Zakonnova, Lyudmila; Nikishkin, Igor; Rostovzev, Alexandr

2017-11-01

One of the frequently encountered problems of power plant small cooling ponds is rapid eutrophication and related intensified development of phytoplankton ("hyperflow") and overgrowing of ponds by higher aquatic vegetation. As a result of hyper-flowering, an enormous amount of detritus settles on the condenser tubes, reducing the efficiency of the power plant operation. The development of higher aquatic vegetation contributes to the appearing of the shoals. As a result the volume, area and other characteristics of the cooling ponds are getting changed. The article describes the environmental problems of small manmade ponds of power plants and coal mines in mining regions. Two approaches to the problem of eutrophication are considered: technological and ecological. The negative effects of herbicides application to aquatic organisms are experimentally proved. An ecological approach to solving the problem by fish-land reclamation method is shown.

Root controls on soil microbial community structure in forest soils.

PubMed

Brant, Justin B; Myrold, David D; Sulzman, Elizabeth W

2006-07-01

We assessed microbial community composition as a function of altered above- and belowground inputs to soil in forest ecosystems of Oregon, Pennsylvania, and Hungary as part of a larger Detritus Input and Removal Treatment (DIRT) experiment. DIRT plots, which include root trenching, aboveground litter exclusion, and doubling of litter inputs, have been established in forested ecosystems in the US and Europe that vary with respect to dominant tree species, soil C content, N deposition rate, and soil type. This study used phospholipid fatty-acid (PLFA) analysis to examine changes in the soil microbial community size and composition in the mineral soil (0-10 cm) as a result of the DIRT treatments. At all sites, the PLFA profiles from the plots without roots were significantly different from all other treatments. PLFA analysis showed that the rootless plots generally contained larger quantities of actinomycete biomarkers and lower amounts of fungal biomarkers. At one of the sites in an old-growth coniferous forest, seasonal changes in PLFA profiles were also examined. Seasonal differences in soil microbial community composition were greater than treatment differences. Throughout the year, treatments without roots continued to have a different microbial community composition than the treatments with roots, although the specific PLFA biomarkers responsible for these differences varied by season. These data provide direct evidence that root C inputs exert a large control on microbial community composition in the three forested ecosystems studied.

Estuarine Food for Thought

NASA Astrophysics Data System (ADS)

M�ller-Solger, A. B.; M�ller-Navarra, D. B.

2002-12-01

Recent research in animal and human nutrition has shown the importance of long-chain polyunsaturated fatty acids (LC-PUFA) such as the n-3 LC-PUFA eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). These LC-PUFA are needed for healthy development and functioning of the nervous and vascular systems. De novo synthesis or elongation to LC-PUFA in animals is inefficient at best; thus sufficient amounts of these PUFA must be supplied by food sources. Algae, especially diatoms, dinoflagellates, and cryptophytes, are the quantitatively most important producers of EPA and DHA. These types of algae often dominate estuarine producer communities. The upper San Francisco Estuary is no exception, and we found its LC-PUFA-rich phytoplankton biomass, but not the quantitatively prevalent terrestrial plant detritus, to be highly predictive of zooplankton (Daphnia) growth. In contrast, in freshwater lakes dominated by relatively LC-PUFA-poor phytoplankton, EPA, not total phytoplankton biomass, best predicted Daphnia growth. The commonly high abundance of LC-PUFA-rich algae in estuaries may help explain the high trophic efficiencies in these systems and resulting high consumer production. Moreover, LC-PUFA-rich estuarine food resources may also provide essential nutrition and associated health and evolutionary benefits to land-dwelling consumers of such foods, including humans. Ensuring LC-PUFA-rich, uncontaminated estuarine production is thus an important goal for estuarine restoration and a convincing argument for estuarine conservation.

Exploring trophic strategies of exotic caprellids (Crustacea: Amphipoda): Comparison between habitat types and native vs introduced distribution ranges

NASA Astrophysics Data System (ADS)

Ros, Macarena; Tierno de Figueroa, José Manuel; Guerra-García, José Manuel; Navarro-Barranco, Carlos; Lacerda, Mariana Baptista; Vázquez-Luis, Maite; Masunari, Setuko

2014-02-01

The trophic ecology of non-native species is a key aspect to understand their invasion success and the community effects. Despite the important role of caprellid amphipods as trophic intermediates between primary producers and higher levels of marine food webs, there is very little information on their feeding habits. This is the first comprehensive study on the trophic strategies of two co-occurring introduced caprellids in the Spanish coasts: Caprella scaura and Paracaprella pusilla. The diet of 446 specimens of C. scaura and 230 of P. pusilla was analyzed to investigate whether there were differences in the feeding habits in relation to habitat characteristics (natural vs artificial hard substrata), type of host substrata (bryozoans and hydroids) and native vs introduced distribution ranges (Brazil vs Spain). Results revealed differences in diet preferences of the two species that have important implications for their trophic behaviour and showed a limited food overlap, which may favour their coexistence in introduced areas. In general terms, P. pusilla is a predator species, showing preference by crustacean prey in all of its life stages, while C. scaura feeds mainly on detritus. Although no sex-related diet shifts were observed in either of the species, evidence of ontogenetic variation in diet of C. scaura was found, with juveniles feeding on more amount of prey than adults. No diet differences were found between native and introduced populations within the same habitat type. However, P. pusilla exhibited a shift in its diet when different habitats were compared in the same distribution area, and C. scaura showed a flexible feeding behaviour between different host substrata in the same habitat type. This study shows that habitat characteristics at different scales can have greater influence on the feeding ecology of exotic species than different distribution ranges, and support the hypothesis that a switch between feeding strategies depending on habitat characteristics could favour invasion success.

Planktonic trophic structure in a coral reef ecosystem - Grazing versus microbial food webs and the production of mesozooplankton

NASA Astrophysics Data System (ADS)

Nakajima, Ryota; Yamazaki, Haruka; Lewis, Levi S.; Khen, Adi; Smith, Jennifer E.; Nakatomi, Nobuyuki; Kurihara, Haruko

2017-08-01

The relative contributions of grazing versus microbial food webs to the production of mesozooplankton communities in coral reef ecosystems remains an important and understudied field of inquiry. Here, we investigated the biomass and production of component organisms within these two food webs, and compared them to those of mesozooplankton on a coral reef in Okinawa, Japan throughout four seasons in 2011-2012. The relative production of grazing (phytoplankton) and microbial (nano and microzooplankton) food webs were on average 39% (7-77%) and 37% (19-57%), respectively, of the food requirements of particle-feeding mesozooplankton. Carbon flows within this planktonic food web suggested that primary production from the grazing food web could not satisfy the nutritional demands of mesozooplankton, and that the microbial food web contributed a significant amount of nutrition to their diets. These results also show that the heterotrophic components of the microbial food web (nano and microzooplankton) and mesozooplankton consume the equivalent of the entire phytoplankton production (particulate net production) each day, while the microzooplankton were almost entirely eaten by higher trophic levels (mesozooplankton) each day. However, even the combined production from both the grazing and microbial food webs did not fulfill mesozooplankton food requirements in some seasons, explaining 26-53%, suggesting that detritus was used to compensate for nutritional deficiencies during these periods. Understanding the flow of energy throughout coral reefs requires a detailed accounting of pelagic sources and sinks of carbon. Our results provide such an assessment and indicate that detailed investigation on the origin and production of detritus is necessary to better understand pelagic trophodynamics in coral ecosystems.

Compositional controls on early diagenetic pathways in fine-grained sedimentary rocks: Implications for predicting unconventional reservoir attributes of mudstones

USGS Publications Warehouse

Keller, Margaret A.; Macquaker, Joe H.S.; Taylor, Kevin G.; Polya, David

2014-01-01

Diagenesis significantly impacts mudstone lithofacies. Processes operating to control diagenetic pathways in mudstones are poorly known compared to analogous processes occurring in other sedimentary rocks. Selected organic-carbon-rich mudstones, from the Kimmeridge Clay and Monterey Formations, have been investigated to determine how varying starting compositions influence diagenesis.The sampled Kimmeridge Clay Formation mudstones are organized into thin homogenous beds, composed mainly of siliciclastic detritus, with some constituents derived from water-column production (e.g., coccoliths, S-depleted type-II kerogen, as much as 52.6% total organic carbon [TOC]) and others from diagenesis (e.g., pyrite, carbonate, and kaolinite). The sampled Monterey Formation mudstones are organized into thin beds that exhibit pelleted wavy lamination, and are predominantly composed of production-derived components including diatoms, coccoliths, and foraminifera, in addition to type-IIS kerogen (as much as 16.5% TOC), and apatite and silica cements.During early burial of the studied Kimmeridge Clay Formation mudstones, the availability of detrital Fe(III) and reactive clay minerals caused carbonate- and silicate-buffering reactions to operate effectively and the pore waters to be Fe(II) rich. These conditions led to pyrite, iron-poor carbonates, and kaolinite cements precipitating, preserved organic carbon being S-depleted, and sweet hydrocarbons being generated. In contrast, during the diagenesis of the sampled Monterey Formation mudstones, sulfide oxidation, coupled with opal dissolution and the reduced availability of both Fe(III) and reactive siliciclastic detritus, meant that the pore waters were poorly buffered and locally acidic. These conditions resulted in local carbonate dissolution, apatite and silica cements precipitation, natural kerogen sulfurization, and sour hydrocarbons generation.Differences in mud composition at deposition significantly influence subsequent diagenesis. These differences impact their source rock attributes and mechanical properties.

Characterization and detection of Anopheles vestitipennis and Anopheles punctimacula (Diptera: Culicidae) larval habitats in Belize with field survey and SPOT satellite imagery

NASA Technical Reports Server (NTRS)

Rejmankova, E.; Pope, K. O.; Roberts, D. R.; Lege, M. G.; Andre, R.; Greico, J.; Alonzo, Y.

1998-01-01

Surveys of larval habitats of Anopheles vestitipennis and Anopheles punctimacula were conducted in Belize, Central America. Habitat analysis and classification resulted in delineation of eight habitat types defined by dominant life forms and hydrology. Percent cover of tall dense macrophytes, shrubs, open water, and pH were significantly different between sites with and without An. vestitipennis. For An. punctimacula, percent cover of tall dense macrophytes, trees, detritus, open water, and water depth were significantly different between larvae positive and negative sites. The discriminant function for An. vestitipennis correctly predicted the presence of larvae in 65% of sites and correctly predicted the absence of larvae in 88% of sites. The discriminant function for An. punctimacula correctly predicted 81% of sites for the presence of larvae and 45% for the absence of larvae. Canonical discriminant analysis of the three groups of habitats (An. vestitipennis positive; An. punctimacula positive; all negative) confirmed that while larval habitats of An. punctimacula are clustered in the tree dominated area, larval habitats of An. vestitipennis were found in both tree dominated and tall dense macrophyte dominated environments. The forest larval habitats of An. vestitipennis and An. punctimacula seem to be randomly distributed among different forest types. Both species tend to occur in denser forests with more detritus, shallower water, and slightly higher pH. Classification of dry season (February) SPOT multispectral satellite imagery produced 10 land cover types with the swamp forest and tall dense marsh classes being of particular interest. The accuracy assessment showed that commission errors for the tall, dense marsh and swamp forest appeared to be minor; but omission errors were significant, especially for the swamp forest (perhaps because no swamp forests are flooded in February). This means that where the classification indicates there are An. vestitipennis breeding sites, they probably do exist; but breeding sites in many locations are not identified and could be more abundant than indicated.

Digestive selection underlies differential utilization of phytoplankton and sedimentary organics by infaunal bivalves: Experiments with cockles (Cerastoderma edule) using cross-labelled mixed diets.

PubMed

Navarro, Enrique; Méndez, Soco; Urrutia, Miren Begoñe; Arambalza, Udane; Ibarrola, Irrintzi

2016-09-01

Differential utilization of phytoplankton and detrital particles present in natural sediments of mud-flats was studied in a series of experiments performed on the infaunal bivalve Cerastoderma edule. In order to assess digestive selection, parameters of food processing (organic ingestion rate: OIR, gross absorption efficiency: GAE and gut passage time: GPT) were recorded for each organic component in different combinations of food particles radio-labelled with (14)C. Experimental design included the use of both labelled diets of a sole organic component and cross-labelled diets; i.e., mixed suspensions presenting alternatively labelled one of the various components tested: phytoplankton cells, sedimentary organic particles and particulate detritus from vascular salt-marsh plants. Preferential absorption of phytoplankton was accounted for by absorption efficiency values that were two-fold those for sedimentary detritus when recorded with mixed diets of both organic components. Two factors contributed to this difference: a) higher digestibility of microalgae, measured as the ratio of GAE to GPT, and b) faster gut passage of detrital particles that results from digestive selection likely involving the preferential incorporation of phytoplankton into the digestive gland. However, when diets based on a sole organic component (either phytoplankton or detritus) were compared, larger GPT were recorded for detrital particles that enabled improving GAE of this rather refractory food. Overall results of these experiments are consistent with most studies in trophic ecology based on stable isotopes enrichment, concerning both the diversity of trophic sources used by marine bivalves and its preferential utilization of phytoplankton over phyto-detritus. Copyright © 2016 Elsevier Ltd. All rights reserved.

Effects of Detrital Subsidies on Soft-Sediment Ecosystem Function Are Transient and Source-Dependent.

PubMed

Gladstone-Gallagher, Rebecca V; Lohrer, Andrew M; Lundquist, Carolyn J; Pilditch, Conrad A

2016-01-01

Detrital subsidies from marine macrophytes are prevalent in temperate estuaries, and their role in structuring benthic macrofaunal communities is well documented, but the resulting impact on ecosystem function is not understood. We conducted a field experiment to test the effects of detrital decay on soft-sediment primary production, community metabolism and nutrient regeneration (measures of ecosystem function). Twenty four (2 m2) plots were established on an intertidal sandflat, to which we added 0 or 220 g DW m-2 of detritus from either mangroves (Avicennia marina), seagrass (Zostera muelleri), or kelp (Ecklonia radiata) (n = 6 plots per treatment). Then, after 4, 17 and 46 d we measured ecosystem function, macrofaunal community structure and sediment properties. We hypothesized that (1) detrital decay would stimulate benthic primary production either by supplying nutrients to the benthic macrophytes, or by altering the macrofaunal community; and (2) ecosystem responses would depend on the stage and rate of macrophyte decay (a function of source). Avicennia detritus decayed the slowest with a half-life (t50) of 46 d, while Zostera and Ecklonia had t50 values of 28 and 2.6 d, respectively. However, ecosystem responses were not related to these differences. Instead, we found transient effects (up to 17 d) of Avicennia and Ecklonia detritus on benthic primary production, where initially (4 d) these detrital sources suppressed primary production, but after 17 d, primary production was stimulated in Avicennia plots relative to controls. Other ecosystem function response variables and the macrofaunal community composition were not altered by the addition of detritus, but did vary with time. By sampling ecosystem function temporally, we were able to capture the in situ transient effects of detrital subsidies on important benthic ecosystem functions.

Detrital shadows: estuarine food web connectivity depends on fluvial influence and consumer feeding mode.

PubMed

Howe, Emily; Simenstad, Charles A; Ogston, Andrea

2017-10-01

We measured the influence of landscape setting on estuarine food web connectivity in five macrotidal Pacific Northwest estuaries across a gradient of freshwater influence. We used stable isotopes (δ 13 C, δ 15 N, δ 34 S) in combination with a Bayesian mixing model to trace primary producer contributions to suspension- and deposit-feeding bivalve consumers (Mytilus trossulus and Macoma nasuta) transplanted into three estuarine vegetation zones: emergent marsh, mudflat, and eelgrass. Eelgrass includes both Japanese eelgrass (Zostera japonica) and native eelgrass (Zostera marina). Fluvial discharge and consumer feeding mode strongly influenced the strength and spatial scale of observed food web linkages, while season played a secondary role. Mussels displayed strong cross-ecosystem connectivity in all estuaries, with decreasing marine influence in the more fluvial estuaries. Mussel diets indicated homogenization of detrital sources within the water column of each estuary. In contrast, the diets of benthic deposit-feeding clams indicated stronger compartmentalization in food web connectivity, especially in the largest river delta where clam diets were trophically disconnected from marsh sources of detritus. This suggests detritus deposition is patchy across space, and less homogenous than the suspended detritus pool. In addition to fluvial setting, other estuary-specific environmental drivers, such as marsh area or particle transport speed, influenced the degree of food web linkages across space and time, often accounting for unexpected patterns in food web connectivity. Transformations of the estuarine landscape that alter river hydrology or availability of detritus sources can thus potentially disrupt natural food web connectivity at the landscape scale, especially for sedentary organisms, which cannot track their food sources through space. © 2017 by the Ecological Society of America.

An ecological model of the Northern and Central Adriatic Sea: Analysis of ecosystem structure and fishing impacts

NASA Astrophysics Data System (ADS)

Coll, Marta; Santojanni, Alberto; Palomera, Isabel; Tudela, Sergi; Arneri, Enrico

2007-08-01

A trophic mass-balance model was developed to characterise the food web structure and functioning of the Northern and Central Adriatic Sea and to quantify the ecosystem impacts of fishing during the 1990s. Forty functional groups were described, including target and non-target fish and invertebrate groups, and three detritus groups (natural detritus, discards and by-catch of cetaceans and marine turtles). Results highlighted that there was an important coupling between pelagic-benthic production of plankton, benthic invertebrates and detritus. Organisms located at low and medium trophic levels, (i.e. benthic invertebrates, zooplankton and anchovy), as well as dolphins, were identified as keystone groups of the ecosystem. Jellyfish were an important element in terms of consumption and production of trophic flows within the ecosystem. The analysis of trophic flows of zooplankton and detritus groups indirectly underlined the importance of the microbial food web in the Adriatic Sea. Fishing activities inflicted notable impacts on the ecosystem during the 1990s, with a high gross efficiency of the fishery, a high consumption of fishable production, high exploitation rates for various target and non target species, a low trophic level of the catch and medium values of primary production required to sustain the fishery. Moreover, the analysis of Odum's ecological indicators highlighted that the ecosystem was in a low-medium developmental stage. Bottom trawling ( Strascico), mid-water trawling ( Volante) and beam trawling ( Rapido) fleets had the highest impacts on both target and non target ecological groups. On the contrary, purse seining ( Lampara) showed medium to low impacts on the ecosystem; cetaceans, marine turtles and sea birds were not significantly involved in competition with fishing activity.

Frequent Prescribed Burning as a Long-term Practice in Longleaf Pine Forests Does Not Affect Detrital Chemical Composition.

PubMed

Coates, T Adam; Chow, Alex T; Hagan, Donald L; Wang, G Geoff; Bridges, William C; Dozier, James H

2017-09-01

The O horizon, or detrital layer, of forest soils is linked to long-term forest productivity and health. Fuel reduction techniques, such as prescribed fire, can alter the thickness and composition of this essential ecosystem component. Developing an understanding of the changes in the chemical composition of forest detritus due to prescribed fire is essential for forest managers and stakeholders seeking sustainable, resilient, and productive ecosystems. In this study, we evaluated fuel quantity, fuel structure, and detrital chemical composition in longleaf pine ( Miller) forests that have been frequently burned for the last 40 yr at the Tom Yawkey Wildlife Center in Georgetown, SC. Our results suggest that frequent prescribed fire reduces forest fuel quantity ( < 0.01) and vertical structure ( = 0.01). Using pyrolysis-gas chromatography/mass spectrometry as a molecular technique to analyze detrital chemical composition, including aromatic compounds and polycyclic aromatic hydrocarbons, we found that the chemical composition of forest detritus was nearly uniform for both unburned and burned detritus. Our burning activities varied in the short term, consisting of annual dormant, annual growing, and biennial dormant season burns. Seasonal distinctions were present for fuel quantity and vertical fuel structure, but these differences were not noted for the benzene/phenol ratio. These results are significant as more managers consider burning existing longleaf stands while determining effective management practices for longleaf stands yet to be established. Managers of such stands can be confident that frequent, low-intensity, low-severity prescribed burns in longleaf pine forests do little to affect the long-term chemical composition of forest detritus. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

Temporal variability in detritus resource maintains diversity of bacterial communities

NASA Astrophysics Data System (ADS)

Hiltunen, Teppo; Laakso, Jouni; Kaitala, Veijo; Suomalainen, Lotta-Riina; Pekkonen, Minna

2008-05-01

Competition theory generally predicts that diversity is maintained by temporal environmental fluctuations. One of the many suggested mechanisms for maintaining diversity in fluctuating environments is the gleaner-opportunist trade-off, whereby gleaner species have low threshold resource levels and low maximum growth rates in high resource concentration while opportunist species show opposite characteristics. We measured the growth rates of eight heterotrophic aquatic bacteria under different concentrations of chemically complex plant detritus resource. The growth rates revealed gleaner-opportunist trade-offs. The role of environmental variability in maintaining diversity was tested in a 28-day experiment with three different resource fluctuation regimes imposed on two four-species bacterial communities in microcosms. We recorded population densities with serial dilution plating and total biomass as turbidity. Changes in resource availability were measured from filter-sterilised medium by re-introducing the consumer species and recording short-term growth rates. The type of environmental variation had no effect on resource availability, which declined slowly during the experiment and differed in level between the communities. However, the slowly fluctuating environment had the highest Shannon diversity index, biomass, and coefficient of variation of biomass in both communities. We did not find a clear link between the gleaner-opportunist trade-off and diversity in fluctuating environments. Nevertheless, our results do not exclude this explanation and support the general view that temporal environmental variation maintains species diversity also in communities feeding chemically complex resource.

The effect of nitrogen loading on a brackish estuarine faunal community: A stable isotope approach

USGS Publications Warehouse

Keats, R.A.; Osher, L.J.; Neckles, H.A.

2004-01-01

Coastal ecosystems worldwide face increased nutrient enrichment from shoreline and watershed development and atmospheric pollution. We investigated the response of the faunal community of a small microtidal estuary dominated by Ruppia maritima (widgeon grass) in Maine, United States, to increased nitrogen loading using an in situ mesocosm enrichment experiment. Community response was characterized by assessing quantitative shifts in macroin-vertebrate community composition and identifying changes in food web structure using stable carbon and nitrogen isotope ratios of producers and consumers. The community was dominated by brackish water invertebrates including midge larvae, oligochaetes, damselfly larvae, amphipods, and ostracods. Experimental nutrient additions resulted in significantly lower densities of herbivorous chironomids and predatory damselflies and greater densities of deposit feeding oligochaetes. Grazing midge larvae (Chironomidae: Dicrotendipes, Cricotopus) consumed epiphytic algae under both natural and enriched conditions. Deposit feeding Chironomus was dependent on allochthonous sources of detritus under natural conditions and exhibited a shift to autochthonous sources of detritus under enriched conditions. Predatory Enallagma primarily consumed grazing chironomids under all but the highest loading conditions. Experimental nutrient loading resulted in an increase in generalist deposit feeders dependent on autochthonous sources of detritus.

Intertidal foraminifera (Protista) and carbon-nitrogen cycling: combined effects of temperature and diet quality

NASA Astrophysics Data System (ADS)

Wukovits, Julia; Enge, Annekatrin Julie; Oberrauch, Max; Watzka, Margarete; Wanek, Wolfgang; Heinz, Petra

2017-04-01

Benthic foraminifera (eukaryotic protists) are to a large extent acting as detrivores, feeding on microalgal detritus. Phytodetritus constitutes a main component of the intertidal carbon (C) and nitrogen (N) pool, thus making foraminifera important players in intertidal nutrient fluxes. These fluxes are strongly dependent on interactions between biotic and abiotic environmental factors, as e.g. the energetic value or the quality of phytodetritus that depends on environmental nutrient availability. Increased inorganic C concentrations in coastal water bodies (e.g. due to increased atmospheric CO2) can have a negative effect on the phytodetrital quality by increasing microalgal C:N ratios. Simultanous warming of the environment can cause increased metabolic rates of exposed heterotrophic organisms, like foraminifera. The combination of lower food quality and increased metabolic rates is supposed to cause cascading effects on organismic C cycling, potentially diminishing the role of detrivorous food as a C sink in marine food webs by increased discharge of excess C. In this study, the above described scenario was tested in laboratory feeding experiments on a common and abundant intertidal foraminiferal species (Haynesina germanica, collected in the German Wadden Sea). Two batches of artificially produced and dual isotope labeled (13C and 15N) chlorophyte detritus (1.5 gDW m-2) with different C:N ratios (5.5 and 7.6) and one batch of isotopically labelled diatom detritus (C:N 5.6) were fed under controlled conditions at three different temperatures. Results were extrapolated to the in situ abundance of live H. germanica individuals in the sampling area (sediment core data), to estimate the magnitude of the effect on an areal basis within the natural habitat. The study revealed significant, temperature induced variations in the carbon and nitrogen processing of H. germanica. The food source with an increased C:N ratio doubled the release of carbon from the H. germanica community at 20°C in relation to 15°C, causing a theoretical carbon loss of 1000 μg m-2 within 24 hours. The uptake of diatom detritus was higher relative to chlorophyte detritus uptake, though the carbon release did not differ from the chlorophyte food source of similar C:N (C:N 5.5). The results illustrate the impact of altered environmental factors on benthic nutrient fluxes in foraminiferal communities, an important but often overlooked component of intertidal microfauna associations.

Larval habitats of anopheline mosquitoes in the Upper Orinoco, Venezuela.

PubMed

Rejmánková, E; Rubio-Palis, Y; Villegas, L

1999-12-01

Survey of larval habitats of anopheline mosquitoes was conducted in Ocamo in the State of Amazonas, southern Venezuela. The sampled habitats belonged to three different hydrological types: lagoons (26 habitats), forest pools including flooded forest (16 habitats), and forest streams (4 habitats). Out of 46 habitats surveyed, 31 contained anopheline larvae. Six species were found: Anopheles darlingi, Anopheles triannulatus, Anopheles oswaldoi, Anopheles peryassui, Anopheles punctimacula, and Anopheles mediopunctatus. Anopheles triannulatus was the most abundant species. Significantly higher numbers of anopheline larvae, in general, and of An. triannulatus specifically were found in lagoons with submersed macrophytes and sparse emergent graminoids than in forest pools with detritus.

Carbon sequestration in a surface flow constructed wetland after 12 years of swine wastewater treatment.

PubMed

Reddy, Gudigopuram B; Raczkowski, Charles W; Cyrus, Johnsely S; Szogi, Ariel

2016-01-01

Constructed wetlands used for the treatment of swine wastewater may potentially sequester significant amounts of carbon. In past studies, we evaluated the treatment efficiency of wastewater in a marsh-pond-marsh design wetland system. The functionality of this system was highly dependent on soil carbon content and organic matter turnover rate. To better understand system performance and carbon dynamics, we measured plant dry matter, decomposition rates and soil carbon fractions. Plant litter decomposition rate was 0.0052 g day(-1) (±0.00119 g day(-1)) with an estimated half-life of 133 days. The detritus layer accumulated over the soil surface had much more humin than other C fractions. In marsh areas, soil C extracted with NaOH had four to six times higher amounts of humic acid, fulvic acid and humin than soil C extracted by cold and hot water, HCl/HF, and Na pyruvate. In the pond area, humic acid, fulvic acid and humin content were two to four times lower than in the marsh area. More soil C and N was found in the marsh area than in the pond area. These wetlands proved to be large sinks for stable C forms.

Variation in active and passive resource inputs to experimental pools: mechanisms and possible consequences for food webs

USGS Publications Warehouse

Kraus, Johanna M.; Pletcher, Leanna T.; Vonesh, James R.

2010-01-01

1. Cross-ecosystem movements of resources, including detritus, nutrients and living prey, can strongly influence food web dynamics in recipient habitats. Variation in resource inputs is thought to be driven by factors external to the recipient habitat (e.g. donor habitat productivity and boundary conditions). However, inputs of or by ‘active’ living resources may be strongly influenced by recipient habitat quality when organisms exhibit behavioural habitat selection when crossing ecosystem boundaries. 2. To examine whether behavioural responses to recipient habitat quality alter the relative inputs of ‘active’ living and ‘passive’ detrital resources to recipient food webs, we manipulated the presence of caged predatory fish and measured biomass, energy and organic content of inputs to outdoor experimental pools of adult aquatic insects, frog eggs, terrestrial plant matter and terrestrial arthropods. 3. Caged fish reduced the biomass, energy and organic matter donated to pools by tree frog eggs by ∼70%, but did not alter insect colonisation or passive allochthonous inputs of terrestrial arthropods and plant material. Terrestrial plant matter and adult aquatic insects provided the most energy and organic matter inputs to the pools (40–50%), while terrestrial arthropods provided the least (7%). Inputs of frog egg were relatively small but varied considerably among pools and over time (3%, range = 0–20%). Absolute and proportional amounts varied by input type. 4. Aquatic predators can strongly affect the magnitude of active, but not passive, inputs and that the effect of recipient habitat quality on active inputs is variable. Furthermore, some active inputs (i.e. aquatic insect colonists) can provide similar amounts of energy and organic matter as passive inputs of terrestrial plant matter, which are well known to be important. Because inputs differ in quality and the trophic level they subsidise, proportional changes in input type could have strong effects on recipient food webs. 5. Cross-ecosystem resource inputs have previously been characterised as donor-controlled. However, control by the recipient food web could lead to greater feedback between resource flow and consumer dynamics than has been appreciated so far.

Discovery of the early Jurassic Gajia mélange in the Bangong-Nujiang suture zone: Southward subduction of the Bangong-Nujiang Ocean?

NASA Astrophysics Data System (ADS)

Lai, Wen; Hu, Xiumian; Zhu, Dicheng; An, Wei; Ma, Anlin

2017-06-01

Mélange records a series of geological processes associated with oceanic subduction and continental collision. This paper reports for the first time the presence of Early Jurassic mélange from NW Nagqu in the southern margin of the Bangong-Nujiang suture zone, termed as the Gajia mélange. It shows typically blocks-in-matrix structure with matrix of black shale and siliceous mudstone, and several centimeters to several meters sized blocks of sandstone, silicalite, limestone and basalt. The sandstone blocks consist of homologous sandstone and two types of exotic sandstone, with different modal compositions. The Group 1 of exotic sandstone blocks consists of mainly of feldspar and quartz, whereas the Group 2 is rich in volcanic detritus. The Group 3 of homologous sandstone blocks is rich in feldspar and volcanic detritus with rare occurrence of quartz. U-Pb age data and in situ Hf isotopic compositions of detrital zircons from sandstone blocks are similar to those from the Lhasa terrane, suggesting that the sandstone blocks in the Gajia mélange most probably came from the Lhasa terrane. The YC1σ(2+) age of homologous sandstone blocks is 177 ± 2.4 Ma, suggesting an Early Jurassic depositional age for the sandstones within the Gajia mélange. The Gajia mélange likely records the southward subduction of the Bangong-Nujiang Ocean during the Early Jurassic.

Sandstone detrital modes in the Makran accretionary wedge, southwest Pakistan: implications for tectonic setting and long-distance turbidite transportation

NASA Astrophysics Data System (ADS)

Critelli, Salvatore; De Rosa, Rosanna; Platt, John Paul

1990-10-01

Detrital modes of Early Miocene to Early Pliocene sandstones from the Makran accretionary wedge in southwest Pakistan show a mainly quartzolithic composition with an evolution from the transitional recycled to quartzose recycled. The lithic types, however, indicate two distinct petrofacies. Accreted abyssal plain turbidites have Qp 11Lvm 27Lsm 62 and Lm 39Lv 27Ls 34, showing a predominant supply from sedimentary and metasedimentary source terranes whereas slope and shelf facies sediments deposited on the accretionary wedge have Qp 7Lvm 47Lsm 47 and Lm 22Lv 48Ls 30 due to an increase of volcanic detritus. The detrital modes of the abyssal plain sediments suggest a recycled orogenic source, probably the Himalayan collision zone. The facies and longitudinal dispersal pattern suggest deposition in an Oligo-Miocene analogue of the present Indus fan. The sediment must have been transported across strike, parallel to the transform structure linking the Makran wedge to the Himalayas (Chaman-Ornach Nal fault system), and fed into the fan at the western end of the subduction zone. The detrital modes also show an increase in volcanic detritus with time (Lv/L = 0.27 for the Early Miocene abyssal plain sediments to 0.47 for the slope sequences). This may have been derived from Late Mesozoic volcanic terrains in northern Baluchistan or the Ladakh Himalayas, or more probably from the Early to middle Miocene andesitic volcanic centre in the northern Makran.

Microbial loop contribution to exergy in the sediments of the Marsala lagoon (Italy)

NASA Astrophysics Data System (ADS)

Pusceddu, A.; Danovaro, R.

2003-04-01

Recent advances in ecological modelling have stressed the need for new descriptors of ecosystem health, able to consider the actual transfer of energy through food webs, including also the potential transfer/loss of (genetic) information. In ecological terms, exergy is defined as a goal function which, as sum of energy (biomass) and (genetic) information contained in a given system due to living organisms, acts as a quality indicator of ecosystems. Biopolymeric organic carbon (BPC) quantity and biochemical composition, bacteria, heterotrophic nanoflagellate and meiofauna abundance, biomass and exergy contents were investigated, on a seasonal basis, in the Marsala lagoon (Mediterranean Sea), at two stations characterized by contrasting hydrodynamic conditions. Carbohydrate (2.8 mg g-1), protein (1.6 mg g-1) and lipid (0.86 mg g-1) contents were extremely high, with values at the more exposed station about 3 times lower than those at the sheltered one. BPC (on average 2.5 mg C g-1), dominated by carbohydrates (50%), was mostly refractory and largely unaccounted for by primary organic matter (4% of BPC), indicating that the Marsala lagoon sediments act as a "detritus sink". At both stations, bacterial (on average 0.3 mg C g-1) and heterotrophic nanoflagellate (9.8 μgC g-1) biomass values were rather high, whereas meiofauna biomass was extremely low (on average 7.2 μg C cm-2). The exergy transfer along the benthic microbial loop components in the Marsala lagoon appeared largely bottlenecked by the refractory composition of organic detritus. In the more exposed station, the exergy transfer towards the higher trophic levels was more efficient than in the sheltered one. Although total exergy values were significantly higher in summer than in winter, at both stations the exergy transfer in winter was more efficient than in summer. Our results indicate that, in 'detritus sink' systems, auxiliary energy (e.g., wind-induced sediment resuspension) might be of paramount importance for increasing efficiency of organic detritus channeling to higher trophic levels.

Axial Belt Provenance: modern river sands from the core of collision orogens

NASA Astrophysics Data System (ADS)

Resentini, A.; Vezzoli, G.; Paparella, P.; Padoan, M.; Andò, S.; Malusà, M.; Garzanti, E.

2009-04-01

Collision orogens have a complex structure, including diverse rock units assembled in various ways by geodynamic processes. Consequently, orogenic detritus embraces a varied range of signatures, and unravelling provenance of clastic wedges accumulated in adjacent foreland basins, foredeeps, or remnant-ocean basins is an arduous task. Dickinson and Suczek (1979) and Dickinson (1985) recognized the intrinsically composite nature of orogenic detritus, but did not attempt to establish clear conceptual and operational distinctions within their broad "Recycled Orogenic Provenance". In the Alpine and Himalayan belts, the bulk of the detritus is produced by focused erosion of the central backbone of the orogen, characterized by high topography and exhumation rates (Garzanti et al., 2004; Najman, 2006). Detritus derived from such axial nappe pile, including slivers of thinned continental-margin lithosphere metamorphosed at depth during early collisional stages, has diagnostic general features, which allows us to define an "Axial Belt Provenance" (Garzanti et al., 2007). In detail, "Axial Belt" detrital signatures are influenced by metamorphic grade of source rocks and relative abundance of continental versus oceanic protoliths, typifying distinct subprovenances. Metasedimentary cover nappes shed lithic to quartzolithic detritus, including metapelite, metapsammite, and metacarbonate grains of various ranks; only amphibolite-facies metasediments supply abundant heavy minerals (e.g., almandine garnet, staurolite, kyanite, sillimanite, diopsidic clinopyroxene). Continental-basement nappes shed hornblende-rich quartzofeldspathic detritus. Largely retrogressed blueschist to eclogite-facies metaophiolites supply albite, metabasite and foliated antigorite-serpentinite grains, along with abundant heavy minerals (epidote, zoisite, clinozoisite, lawsonite, actinolitic to barroisitic amphiboles, glaucophane, omphacitic clinopyroxene). Increasing metamorphic grade and deeper tectonostratigraphic level of source rocks are reflected by: a) increasing rank of metamorphic rock fragments (as indicated by progressive development of schistosity and growth of micas and other index minerals; MI index of Garzanti and Vezzoli, 2003); b) increasing feldspars; c) increasing heavy-mineral concentration (HMC index); d) increasing hornblende, changing progressively in color from blue/green to green/brown (HCI index); e) successive appearance of chloritoid, staurolite, kyanite, fibrolitic and prismatic sillimanite (MMI index; Garzanti and Andò, 2007). Dickinson W.R. 1985. Interpreting provenance relations from detrital modes of sandstones. In: Zuffa G.G. (ed.), Reidel, NATO ASI Series 148: 333-361. Dickinson W.R. and C.A. Suczek. 1979. Plate tectonics and sandstone composition. Am. Assoc. Pet. Geol. Bull. 63: 2164-2172. Garzanti E. and S. Andò. 2007, Plate tectonics and heavy-mineral suites of modern sands. In: Mange M. and D. Wright (eds.), Elsevier, Developments in Sedimentology Series 58: 741-763. Garzanti E. and G. Vezzoli. 2003. A classification of metamorphic grains in sands based on their composition and grade. J. Sedimentary Res. 73: 830-837. Garzanti E., C. Doglioni, G. Vezzoli and S. Andò. 2007. Orogenic Belts and Orogenic Sediment Provenances. J. Geology 115: 315-334. Garzanti E., G. Vezzoli, S. Andó, C. France-Lanord, S.K. Singh and G. Foster. 2004. Sediment composition and focused erosion in collision orogens: the Brahmaputra case. Earth Planet. Sci. Lett. 220: 157-174. Najman Y. 2006. The detrital record of orogenesis: a review of approaches and techniques used in the Himalayan sedimentary basins. Earth Sci. Rev. 74: 1-72.

Shoreline as a controlling factor in commercial shrimp production

NASA Technical Reports Server (NTRS)

Faller, K. H. (Principal Investigator)

1979-01-01

The author has identified the following significant results. An ecological model was developed that relates marsh detritus export and shrimp production. It was based on the hypothesis that the shoreline is a controlling factor in the production of shrimp through regulation of detritus export from the marsh. LANDSAT data were used to develop measurement of shoreline length and areas of marsh having more than 5.0 kilometers of shoreline per square kilometer of area for the Louisiana coast, demonstrating the capability of remote sensing to provide important geographic information. These factors were combined with published tidal ranges and salinities to develop a mathematical model that predicted shrimp production for nine geographic units of the Louisiana coast, as indicated by the long term average commercial shrimp yield.

The origin of epigenetic graphite: evidence from isotopes

USGS Publications Warehouse

Weis, P.L.; Friedman, I.; Gleason, J.P.

1981-01-01

Stable carbon isotope ratios measured in syngenetic graphite, epigenetic graphite, and graphitic marble suggests that syngenetic graphite forms only by the metamorphism of carbonaceous detritus. Metamorphism of calcareous rocks with carbonaceous detritus is accompanied by an exchange of carbon between the two, which may result in large changes in isotopic composition of the non-carbonate phase but does not affect the relative proportions of the two reactants in the rock. Epigenetic graphite forms only from carbonaceous material or preexisting graphite. The reactions involved are the water gas reaction (C + H2O ??? CO + H2) at 800-900??C, and the Boudouard reaction (2CO ??? C + CO2), which probably takes place at temperatures about 50-100??C lower. ?? 1982.

Synoptic conditions of fine-particle transport to the last interglacial Red Sea-Dead Sea from Nd-Sr compositions of sediment cores

NASA Astrophysics Data System (ADS)

Palchan, Daniel; Stein, Mordechai; Goldstein, Steven L.; Almogi-Labin, Ahuva; Tirosh, Ofir; Erel, Yigal

2018-01-01

The sediments deposited at the depocenter of the Dead Sea comprise high-resolution archive of hydrological changes in the lake's watershed and record the desert dust transport to the region. This paper reconstructs the dust transport to the region during the termination of glacial Marine Isotope Stage 6 (MIS 6; ∼135-129 ka) and the last interglacial peak period (MIS5e, ∼129-116 ka). We use chemical and Nd and Sr isotope compositions of fine detritus material recovered from sediment core drilled at the deepest floor of the Dead Sea. The data is integrated with data achieved from cores drilled at the floor of the Red Sea, thus, forming a Red Sea-Dead Sea transect extending from the desert belt to the Mediterranean climate zone. The Dead Sea accumulated flood sediments derived from three regional surface cover types: settled desert dust, mountain loess-soils and loess-soils filling valleys in the Dead Sea watershed termed here "Valley Loess". The Valley Loess shows a distinct 87Sr/86Sr ratio of 0.7081 ± 1, inherited from dissolved detrital calcites that originate from dried waterbodies in the Sahara and are transported with the dust to the entire transect. Our hydro-climate and synoptic conditions reconstruction illustrates the following history: During glacial period MIS6, Mediterranean cyclones governed the transport of Saharan dust and rains to the Dead Sea watershed, driving the development of both mountain soils and Valley Loess. Then, at Heinrich event 11, dry western winds blew Saharan dust over the entire Red Sea - Dead Sea transect marking latitudinal expansion of the desert belt. Later, when global sea-level rose, the Dead Sea watershed went through extreme aridity, the lake retreated, depositing salt and accumulating fine detritus of the Valley Loess. During peak interglacial MIS 5e, enhanced flooding activity flushed the mountain soils and fine detritus from all around the Dead Sea and Red Sea, marking a significant "contraction" of the desert belt. At the end of MIS 5e the effect of the regional precipitation diminished and the Dead Sea and Red Sea areas re-entered sever arid conditions with extensive salt deposition at the Dead Sea.

Microbial Mechanisms Enhancing Soil C Storage

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

Zak, Donald

2015-09-24

Human activity has globally increased the amount of nitrogen (N) entering ecosystems, which could foster higher rates of C sequestration in the N-limited forests of the Northern Hemisphere. Presently, these ecosystems are a large global sink for atmospheric CO2, the magnitude of which could be influenced by the input of human-derived N from the atmosphere. Nevertheless, empirical studies and simulation models suggest that anthropogenic N deposition could have either an important or inconsequential effect on C storage in forests of the Northern Hemisphere, a set of observations that continues to fuel scientific discourse. Although a relatively simple set of physiologicalmore » processes control the C balance of terrestrial ecosystems, we still fail to understand how these processes directly and indirectly respond to greater N availability in the environment. The uptake of anthropogenic N by N-limited forest trees and a subsequent enhancement of net primary productivity have been the primary mechanisms thought to increase ecosystem C storage in Northern Hemisphere forests. However, there are reasons to expect that anthropogenic N deposition could slow microbial activity in soil, decrease litter decay, and increase soil C storage. Fungi dominate the decay of plant detritus in forests and, under laboratory conditions, high inorganic N concentrations can repress the transcription of genes coding for enzymes which depolymerize lignin in plant detritus; this observation presents the possibility that anthropogenic N deposition could elicit a similar effect under field conditions. In our 18-yr-long field experiment, we have been able to document that simulated N deposition, at a rate expected in the near future, resulted in a significant decline in cellulolytic and lignolytic microbial activity, slowed plant litter decay, and increased soil C storage (+10%); this response is not portrayed in any biogeochemical model simulating the effect of atmospheric N deposition on ecosystem C storage. Our preliminary results support the hypothesis that simulated N deposition has down-regulated the transcription of fungal genes encoding lignocellulolytic enzymes, thereby slowing litter decay and substantially increasing soil C storage over a relative short duration. The objective of this study was to understand the molecular mechanisms and metabolic processes by which simulated N deposition has slowed microbial decay of plant detritus, thereby increasing soil C storage in the wide-spread and ecologically important northern forest ecosystem. We addressed our research objective using a combination of transcriptomic and metatranscriptomic approaches in parallel with biogeochemical analyses of soil C cycling. By linking the environmental regulation of microbial genes to biogeochemical processes, we endeavor to understanding the enhanced accumulation of soil C in response to a wide-spread agent of global change.« less

Impacts of Invasive Rusty Crayfish on Stream Ecosystems of the Upper Midwestern U.S.

NASA Astrophysics Data System (ADS)

Bobeldyk, A. M.; Lamberti, G. A.

2005-05-01

Invasive species can have detrimental effects on structural characteristics of freshwater ecosystems, but relatively few studies have assessed ecosystem-level impacts of invasive species in streams. We studied the effects of invasive rusty crayfish (Orconectes rusticus) on detritus processing and invertebrate and fish abundance in northern Wisconsin and Michigan, USA, streams. We hypothesized that rusty crayfish would increase the rate of detritus processing and reduce fish and invertebrate abundance due to their aggressiveness and competitive superiority for food and habitat. We measured sugar maple (Acer saccharum) decomposition rates in three reaches of a stream with differing densities of rusty crayfish, high (5.05/m2), intermediate (2.27/m2), and none (0/m2) using leaf bags excluding crayfish and open bags allowing crayfish access. We found that open bags decayed significantly faster (k=0.143) than crayfish excluded bags at all sites (k=0.079) (p=0.0005). The reach lacking crayfish had significantly higher densities of invertebrates (p=0.005). We also surveyed an additional 7 streams that contained or lacked rusty crayfish and found significantly higher fish abundance (p=0.019) and biomass (p=0.001) in streams lacking rusty crayfish. Rusty crayfish appear to indirectly affect detritus processing via negative effects on benthic invertebrates, and may have larger-scale impacts on fishes across streams.

Determination of concentration factors for Cs-137 and Ra-226 in the mullet species Chelon labrosus (Mugilidae) from the South Adriatic Sea.

PubMed

Antovic, Ivanka; Antovic, Nevenka M

2011-07-01

Concentration factors for Cs-137 and Ra-226 transfer from seawater, and dried sediment or mud with detritus, have been determined for whole, fresh weight, Chelon labrosus individuals and selected organs. Cesium was detected in 5 of 22 fish individuals, and its activity ranged from 1.0 to 1.6 Bq kg(-1). Radium was detected in all fish, and ranged from 0.4 to 2.1 Bq kg(-1), with an arithmetic mean of 1.0 Bq kg(-1). In regards to fish organs, cesium activity concentration was highest in muscles (maximum - 3.7 Bq kg(-1)), while radium was highest in skeletons (maximum - 25 Bq kg(-1)). Among cesium concentration factors, those for muscles were the highest (from seawater - an average of 47, from sediment - an average of 3.3, from mud with detritus - an average of 0.8). Radium concentration factors were the highest for skeleton (from seawater - an average of 130, from sediment - an average of 1.8, from mud with detritus - an average of 1.5). Additionally, annual intake of cesium and radium by human adults consuming muscles of this fish species has been estimated to provide, in aggregate, an effective dose of about 4.1 μSv y(-1). 2011 Elsevier Ltd. All rights reserved.

Modelling the temporal and spatial distribution of ecological variables in Beibu Gulf

NASA Astrophysics Data System (ADS)

Pan, H.; Huang, L.; Yang, S.; Shi, D.; Pan, W.

2017-12-01

Beibu Gulf is an important semi-enclosed gulf located in northern South China Sea. It is rich in natural resources and its coastal rim is undergoing a rapid economic growth in recent years. Study on the spatial and temporal distribution of ecological variables by the influence of physical and biological processes in Beibu Gulf can provide the theoretical basis for the utilization of resources and environmental protection. Based on the MEC three-dimensional hydrodynamic model, a nutrient-phytoplankton-zooplankton-detritus (NPZD) model was applied to simulate the distribution of ecological variables in Beibu Gulf. The result shows that the ecosystem in Beibu Gulf is significantly influenced by dynamic conditions. In autumn and winter, great amount of nutrient-rich water from western Guangdong coastal area passes through Qiongzhou Strait and flows into Beibu Gulf, with about 108.3×103 t of inorganic nitrogen and 3.7×103 t of phosphate annually, leading to phytoplankton bloom. In summer, most of the nutrients come from rivers so high concentrations of nutrients and chlorophyll-a appear on estuaries. The annual net nutrient inputs from South China Sea into Beibu Gulf are 66.6×103 t for inorganic nitrogen and 4.6×103 t for phosphate. Phytoplankton plays an important role in nutrients' refreshment: a) Absorption by the process of photosynthesis is the biggest nutrient sink. b) Cellular release from dead phytoplankton is the biggest source in inorganic budget, making up for 33.4% of nitrogen consumed by photosynthesis while the process of respiration is the biggest source in phosphate budget, making up for 32.4% of phosphorus consumed by photosynthesis. c) Mineralization from detritus is also a considerable supplement of inorganic nutrients. Overall, biological process has more influence than physical process on the nutrient cycle budget in Beibu Gulf. The comparison of the result with remote sensing and in-situ data indicates that the model is able to simulate the biogeochemical characteristics in Beibu Gulf.

Mineralisation assays of some organic resources of aquatic systems.

PubMed

Bitar, A L; Bianchini, Júnior I

2002-11-01

Assays were carried out to evaluate the consumption of dissolved oxygen resulting from mineralisation processes in resources usually found in aquatic systems. They were also aimed at estimating the oxygen uptake rate of each investigated process. Experiments were conducted using substrates from 3 different places. A fixed amount of substrate was added to 5 litres of water from Lagoa do Infernão that was previously filtered with glass wool. After adding the substrates the bottles were aired and the amount of dissolved oxygen and the temperature were monitored for 55 days. The occurrence of anaerobic processes was avoided by reoxygenating the bottles. The experimental results were fitted to a first order kinetics model, from which the consumption of dissolved oxygen owing to mineralisation processes was obtained. The amount of oxygen uptake from the mineralisation processes appeared in the following decreasing order: Wolffia sp., Cabomba sp., Lemna sp., DOM (Dissolved Organic Matter), Salvinia sp., Scirpus cubensis, stem, Eichhornia azurea, sediment and humic compounds. The deoxygenation rates (day-1) were: 0.267 (humic compounds), 0.230 (Lemna sp.), 0.199 (E. azurea), 0.166 (S. cubensis), 0.132 (sediment), 0.126 (DOM), 0.093 (Cabomba sp.), 0.091 (stem), 0.079 (Salvinia sp. and Wolffia sp.). From these results, 2 groups of resources could be identified: the first one consists of detritus with higher amounts of labile (ready to use) compounds, which show a higher global oxygen uptake during the mineralisation process; the second one consists mainly of resources that show refracting characteristics. However, when the consumption rates are analysed it is noted that the mineralised parts of the refracting substrates can be easier to process than the labile fractions of the less refracting resources.

Methane hydrate - A major reservoir of carbon in the shallow geosphere?

USGS Publications Warehouse

Kvenvolden, K.A.

1988-01-01

Methane hydrates are solids composed of rigid cages of water molecules that enclose methane. Sediment containing methane hydrates is found within specific pressure-temperature conditions that occur in regions of permafrost and beneath the sea in outer continental margins. Because methane hydrates are globally widespread and concentrate methane within the gas-hydrate structure, the potential amount of methane present in the shallow geosphere at subsurface depths of < ???2000 m is very large. However, estimates of the amount are speculative and range over about three orders of magnitude, from 2 ?? 103 to 4 ?? 106 Gt (gigatons = 1015 g) of carbon, depending on the assumptions made. The estimate I favor is ??? 1 ?? 104 Gt of carbon. The estimated amount of organic carbon in the methane-hydrate reservoir greatly exceeds that in many other reservoirs of the global carbon cycle - for example, the atmosphere (3.6 Gt); terrestrial biota (830 Gt); terrestrial soil, detritus and peat (1960 Gt); marine biota (3 Gt); and marine dissolved materials (980 Gt). In fact, the amount of carbon may exceed that in all fossil fuel deposits (5 ?? 103 Gt). Because methane hydrates contain so much methane and occur in the shallow geosphere, they are of interest as a potential resource of natural gas and as a possible source of atmospheric methane released by global warming. As a potential resource, methane hydrates pose both engineering and production problems. As a contributor to a changing global climate, destabilized methane hydrates, particularly those in shallow, nearshore regions of the Arctic Ocean, may have some effect, but this effect will probably be minimal, at least during the next 100 years. ?? 1988.

Calcium oxalate contribution to calcium cycling in forests of contrasting nutrient status

USGS Publications Warehouse

Dauer, Jenny M.; Perakis, Steven S.

2014-01-01

Calcium oxalate (Ca oxalate) is an insoluble biomineral that forms in plants and fungi, and occurs in soils across many types of ecosystems. Assessing how Ca oxalate may shape ecosystem Ca cycling requires information on the distribution of Ca oxalate among plant biomass, detritus, and mineral soil, and how it varies with ecosystem Ca status. We compared two Douglas-fir forests of contrasting ecosystem Ca availability, and found that Ca oxalate was partitioned similarly among plant biomass, detritus and mineral soil major ecosystem compartments at both sites, and total pools of Ca oxalate were greater in the high-Ca forest. However, the proportional importance of Ca oxalate was greater in the low-Ca than high-Ca forest (18% versus 4% of actively cycling ecosystem Ca, respectively). And calcium oxalate in mineral soil, which is of particular interest as a potential long-term Ca reservoir, was a larger portion of total available Ca (exchangeable Ca plus Ca oxalate Ca) in the low-Ca site than the high-Ca site (9% versus 1% of available soil Ca, respectively). Calcium oxalate was the dominant form of Ca returned from plants to soil as leaf litterfall at the high-Ca site, yet calcium oxalate disappeared rapidly from decomposing litter (0.28 yr−1 or faster) at both sites. We conclude that accumulation of Ca oxalate in forest ecosystems appears most closely related to overall Ca supply for live biomass pools, and that the accumulation of Ca oxalate in forest floor and mineral soil is limited by rapid microbial degradation of putatively unavailable Ca oxalate.

Environmental Correlates of Abundances of Mosquito Species and Stages in Discarded Vehicle Tires

PubMed Central

YEE, DONALD A.; KNEITEL, JAMIE M.; JULIANO, STEVEN A.

2012-01-01

Discarded vehicle tires are a common habitat for container mosquito larvae, although the environmental factors that may control their presence or abundance within a tire are largely unknown. We sampled discarded vehicle tires in six sites located within four counties of central Illinois during the spring and summer of 2006 to determine associations between a suite of environmental factors and community composition of container mosquitoes. Our goal was to find patterns of association between environmental factors and abundances of early and late instars. We hypothesized that environmental factors correlated with early instars would be indicative of oviposition cues, whereas environmental factors correlated with late instars would be those important for larval survival. We collected 13 species of mosquitoes, with six species (Culex restuans, Cx. pipiens, Aedes albopictus, Cx. salinarius, Ae. atropalpus, and Ae. triseriatus) accounting for ≈95% of all larvae. There were similar associations between congenerics and environmental factors, with Aedes associated with detritus type (fine detritus, leaves, seeds) and Culex associated with factors related to the surrounding habitat (human population density, canopy cover, tire size) or microorganisms (bacteria, protozoans). Although there was some consistency in factors that were important for early and late instar abundance, there were few significant associations between early and late instars for individual species. Lack of correspondence between factors that explain variation in early versus late instars, most notable for Culex, suggests a difference between environmental determinants of oviposition and survival within tires. Environmental factors associated with discarded tires are important for accurate predictions of mosquito occurrence at the generic level. PMID:20180308

Analyses of stomach contents and stable isotopes reveal food sources of estuarine detritivorous fish in tropical/subtropical Taiwan

NASA Astrophysics Data System (ADS)

Lin, Hsing-Juh; Kao, Wen-Yuan; Wang, Ya-Ting

2007-07-01

Detritivorous fish generally refers to fish that primarily ingest unidentified organic detritus. We analyzed stomach contents in combination with stable isotopes to trace and compare the food sources of the large-scale mullet Liza macrolepis and other detritivorous fish species in subtropical mangrove creeks and a tropical lagoon in Taiwan. The volume of organic detritus always contributed >50% of the stomach content of L. macrolepis in the two habitats. However, consumed items were distinct between the two habitats and corresponded to the types in which they reside. The consumed items in the lagoon were more diverse than those observed in the mangroves. In the mangroves, the diet composition of L. macrolepis was primarily determined by season, not by body size. In the lagoon, there were no clear seasonal or size-dependent grouping patterns for the diet composition. There were significant seasonal and spatial variations in δ13C and δ15N values of potential food sources and L. macrolepis. However, neither δ13C nor δ15N values of L. macrolepis were correlated with fish body size. Joint analyses of stomach contents and stable isotopes indicated that benthic microalgae on sediments were the most important assimilated food in both seasons for the dominant detritivorous fish in the mangroves, whereas a greater reliance on microalgal and macroalgal periphyton on oyster-culture pens was observed in the lagoon. Mangrove and marsh plants and phytoplankton, which are mostly locally produced within each habitat, were of minor importance in the assimilated food.

3D multidisciplinary numerical model of polychlorinated biphenyl dynamics on the Black Sea north-western shelf

NASA Astrophysics Data System (ADS)

Bagaiev, Andrii; Ivanov, Vitaliy

2014-05-01

The Black Sea north-western shelf plays a key role in economics of the developing countries such as Ukraine due to food supply, invaluable recreational potential and variety of the relevant maritime shipping routes. On the other hand, a shallow flat shelf is mostly affected by anthropogenic pollution, eutrophication, hypoxia and harmful algae blooms. The research is focused on modeling the transport and transformation of PCBs (PolyChlorinated Biphenyls) because they are exceedingly toxic and highly resistant to degradation, hence cumulatively affect marine ecosystems. Being lipophilic compounds, PCBs demonstrate the distinguishing sorption/desorption activity taking part in the biogeochemical fluxes via the organic matter particles and sediments. In the framework of the research, the coastal in-situ data on PCB concentration in the water column and sediments are processed, visualized and analyzed. It is concluded that the main sources of PCBs are related to the Danube discharge and resuspension from the shallow-water sediments. Developed 3D numerical model is aimed at simulation of PCB contamination of the water column and sediment. The model integrates the full physics hydrodynamic block as well as modules, which describe detritus transport and transformation and PCB dynamics. Three state variables are simulated in PCB transport module: concentration in solute, on the settling particles of detritus and in the top layer of sediments. PCB adsorption/desorption on detritus; the reversible PCB fluxes at the water-sediment boundary; destruction of detritus are taken into consideration. Formalization of PCB deposition/resuspension in the sediments is adapted from Van Rijn's model of the suspended sediment transport. The model was spun up to reconstruct the short term scenario of the instantaneous PCB release from the St. George Arm of Danube. It has been shown that PCB transport on sinking detritus represents the natural buffer mechanism damping the spreading PCB contamination in the Black Sea shelf ecosystem. Special numerical experiments were carried out to evaluate the artificial sorbent efficiency as a possible post-accidental counter-measure. End-user application is implemented to provide operational PCB forecast in order to support decision making and minimize ecological risks. The graphical user interface allows specifying instantaneous or continuous PCB release scenarios and quick updating the prediction of PCB release trajectory and temporal variability of the mass balance components. It provides visualization of PCB contamination at the sea surface, in the water column and in the upper layer of sediments over time, including the animations of PCB movement. The integrated ocean-ecosystem-sediment-pollution approach developed is applicable to any coastal area and allows further implementation related to advances in the model representation of natural processes and to improvements of PCB monitoring.

Simulating the responses of a low-trophic ecosystem in the East China Sea to decadal changes in nutrient load from the Changjiang (Yangtze) River

NASA Astrophysics Data System (ADS)

Wang, Yucheng; Guo, Xinyu; Zhao, Liang

2018-01-01

Using a three-dimensional coupled biophysical model, we simulated the responses of a lowtrophic ecosystem in the East China Sea (ECS) to long-term changes in nutrient load from the Changjiang (Yangtze) River over the period of 1960-2005. Two major factors affected changes in nutrient load: changes in river discharge and the concentration of nutrients in the river water. Increasing or decreasing Changjiang discharge induced different responses in the concentrations of nutrients, phytoplankton, and detritus in the ECS. Changes in dissolved inorganic nitrogen (DIN), silicate (SIL), phytoplankton, and detritus could be identified over a large area of the ECS shelf, but changes in dissolved inorganic phosphate (DIP) were limited to a small area close to the river mouth. The high DIN:DIP and SIL:DIP ratios in the river water were likely associated with the different responses in DIN, DIP, and SIL. As DIP is a candidate limiting nutrient, perturbations in DIP resulting from changes in the Changjiang discharge are quickly consumed through primary production. It is interesting that an increase in the Changjiang discharge did not always lead to an increase in phytoplankton levels in the ECS. Phytoplankton decreases could be found in some areas close to the river mouth. A likely cause of the reduction in phytoplankton was a change in the hydrodynamic field associated with the river plume, although the present model is not suitable for examining the possibility in detail. Increases in DIN and DIP concentrations in the river water primarily led to increases in DIN, DIP, phytoplankton, and detritus levels in the ECS, whereas decreases in the SIL concentration in river water led to lower SIL concentrations in the ECS, indicating that SIL is not a limiting nutrient for photosynthesis, based on our model results from 1960 to 2005. In both of the above-mentioned cases, the sediment accumulation rate of detritus exhibited a large spatial variation near the river mouth, suggesting that core sample data should be carefully interpreted.

Effects of depth and crayfish size on predation risk and foraging profitability of a lotic crayfish

USGS Publications Warehouse

Flinders, C.A.; Magoulick, D.D.

2007-01-01

We conducted field surveys and experiments to determine whether observed distributions of crayfish among habitats were influenced by differential resource availability, foraging profitability, and predation rates and whether these factors differed with crayfish size and habitat depth. We sampled available food resources (detritus and invertebrates) and shelter as rock substrate in deep (>50 cm) and shallow (<30 cm) habitats. We used an enclosure-exclosure experiment to examine the effects of water depth and crayfish size on crayfish biomass and survival, and to determine whether these factors affected silt accrual, algal abundance (chlorophyll a [chl a]), and detritus and invertebrate biomass (g ash-free dry mass) differently from enclosures without crayfish. We conducted tethering experiments to assess predation on small (13-17 mm carapace length [CL]) and large (23-30 mm CL) Orconectes marchandi and to determine whether predation rates differed with water depth. Invertebrate biomass was significantly greater in shallow water than in deep water, whereas detritus biomass did not differ significantly between depths. Cobble was significantly more abundant in shallow than in deep water. Depth and crayfish size had a significant interactive effect on change in size of enclosed crayfish when CL was used as a measure of size but not when biomass was used as a measure of size. CL of small crayfish increased significantly more in enclosures in shallow than in deep water, but CL of large crayfish changed very little at either depth. Silt, chl a, and detritus biomass were significantly lower on tiles in large- than in small- and no-crayfish enclosures, and invertebrate biomass was significantly lower in large- than in no-crayfish enclosures. Significantly more crayfish were consumed in deep than in shallow water regardless of crayfish size. Our results suggest that predation and resource availability might influence the depth distribution of small and large crayfish. Small crayfish grew faster in shallow habitats where they might have had a fitness advantage caused by high prey availability and reduced predation risk. Size-dependent reduction of silt by crayfish might influence benthic habitats where large crayfish are abundant. ?? 2007 by The North American Benthological Society.

Food web flows through a sub-arctic deep-sea benthic community

NASA Astrophysics Data System (ADS)

Gontikaki, E.; van Oevelen, D.; Soetaert, K.; Witte, U.

2011-11-01

The benthic food web of the deep Faroe-Shetland Channel (FSC) was modelled by using the linear inverse modelling methodology. The reconstruction of carbon pathways by inverse analysis was based on benthic oxygen uptake rates, biomass data and transfer of labile carbon through the food web as revealed by a pulse-chase experiment. Carbon deposition was estimated at 2.2 mmol C m -2 d -1. Approximately 69% of the deposited carbon was respired by the benthic community with bacteria being responsible for 70% of the total respiration. The major fraction of the labile detritus flux was recycled within the microbial loop leaving merely 2% of the deposited labile phytodetritus available for metazoan consumption. Bacteria assimilated carbon at high efficiency (0.55) but only 24% of bacterial production was grazed by metazoans; the remaining returned to the dissolved organic matter pool due to viral lysis. Refractory detritus was the basal food resource for nematodes covering ∼99% of their carbon requirements. On the contrary, macrofauna seemed to obtain the major part of their metabolic needs from bacteria (49% of macrofaunal consumption). Labile detritus transfer was well-constrained, based on the data from the pulse-chase experiment, but appeared to be of limited importance to the diet of the examined benthic organisms (<1% and 5% of carbon requirements of nematodes and macrofauna respectively). Predation on nematodes was generally low with the exception of sub-surface deposit-feeding polychaetes that obtained 35% of their energy requirements from nematode ingestion. Carnivorous polychaetes also covered 35% of their carbon demand through predation although the preferred prey, in this case, was other macrofaunal animals rather than nematodes. Bacteria and detritus contributed 53% and 12% to the total carbon ingestion of carnivorous polychaetes suggesting a high degree of omnivory among higher consumers in the FSC benthic food web. Overall, this study provided a unique insight into the functioning of a deep-sea benthic community and demonstrated how conventional data can be exploited further when combined with state-of-the-art modelling approaches.

Food-web traits of the North Aegean Sea ecosystem (Eastern Mediterranean) and comparison with other Mediterranean ecosystems

NASA Astrophysics Data System (ADS)

Tsagarakis, K.; Coll, M.; Giannoulaki, M.; Somarakis, S.; Papaconstantinou, C.; Machias, A.

2010-06-01

A mass-balance trophic model was built to describe the food-web traits of the North Aegean Sea (Strymonikos Gulf and Thracian Sea, Greece, Eastern Mediterranean) during the mid-2000s and to explore the impacts of fishing. This is the first food-web model representing the Aegean Sea, and results were presented and discussed in comparison to other previous ecosystems modelled from the western and the central areas of the basin (South Catalan and North-Central Adriatic Seas). Forty functional groups were defined, covering the entire trophic spectrum from lower to higher trophic levels. Emphasis was placed on commercial invertebrates and fish. The potential ecological role of the invasive ctenophore, Mnemiopsis leidyi, and several vulnerable groups (e.g., dolphins) was also explored. Results confirmed the spatial productivity patterns known for the Mediterranean Sea showing, for example, that the total biomass is highest in N.C. Adriatic and lowest in N. Aegean Sea. Accordingly, food-web flows and several ecosystem indicators like the mean transfer efficiency were influenced by these patterns. Nevertheless, all three systems shared some common features evidencing similarities of Mediterranean Sea ecosystems such as dominance of the pelagic fraction in terms of flows and strong benthic-pelagic coupling of zooplankton and benthic invertebrates through detritus. The importance of detritus highlighted the role of the microbial food-web, which was indirectly considered through detritus dynamics. Ciliates, mesozooplankton and several benthic invertebrate groups were shown as important elements of the ecosystem linking primary producers and detritus with higher trophic levels in the N. Aegean Sea. Adult anchovy was shown as the most important fish group in terms of production, consumption and overall effect on the rest of the ecological groups in the model, in line with results from the Western Mediterranean Sea. The five fishing fleets considered (both artisanal and industrial) had high impacts on vulnerable species and numerous targeted groups given the multispecies nature of the fisheries in the N. Aegean Sea. Several exploitation indices highlighted that the N. Aegean Sea ecosystem was highly exploited and unlikely to be sustainably fished, similarly to other Mediterranean marine ecosystems.

[Effects of land use change on carbon storage in terrestrial ecosystem].

PubMed

Yang, Jingcheng; Han, Xingguo; Huang, Jianhui; Pan, Qingmin

2003-08-01

Terrestrial ecosystem is an important carbon pool, which plays a crucial role in carbon biogeochemical cycle. Human activities such as fossil fuel combustion and land use change have resulted in carbon fluxes from terrestrial ecosystem to the atmosphere, which increased the atmospheric CO2 concentration, and reinforced the greenhouse effect. Land use change affects the structure and function of the terrestrial ecosystem, which causes its change of carbon storage. To a great extent, the change of carbon storage lies in the type of ecosystem and the change of land use patterns. The conversion of forest to agricultural land and pasture causes a large reduction of carbon storage in vegetation and soil, and the decrease of soil carbon concentration is mainly caused by the reduction of detritus, the acceleration of soil organic matter decomposition, and the destroy of physical protection to organic matter due to agricultural practices. The loss of soil organic matter appears at the early stage after deforestation, and the loss rate is influenced by many factors and soil physical, chemical and biological processes. The conversion of agricultural land and pasture to forest and many conservative agricultural practices can sequester atmospheric carbon in vegetation and soil. Vegetation can sequester large amounts of carbon from atmosphere, while carbon accumulation in soil varies greatly because of farming history and soil spatial heterogeneity. Conservative agricultural practices such as no-tillage, reasonable cropping system, and fertilization can influence soil physical and chemical characters, plant growth, quality and quantity of stubble, and soil microbial biomass and its activity, and hence, maintain and increase soil carbon concentration.

Detritus feeding as a buffer to extinction at the end of the Cretaceous

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

Sheehan, P.M.; Hansen, T.A.

1986-10-01

At the end of the Cretaceous the principal animals that became extinct, such as dinosaurs, marine animals that lived in the water column, and benthic filter feeders, were in food chains tied directly to living plant matter. Animal groups less affected by extinction, including marine benthic scavengers and deposit feeders, small insectivorous mammals, and members of stream communities, were in food chains dependent on dead plant material. The proposal that an asteroid or comet impact at the end of the Cretaceous produced a dust cloud that cut off photosynthesis for several months is consistent with this pattern of extinction. Foodmore » chains dependent on living plant matter crashed, while food chains based on detritus were buffered from extinction because there was a food supply adequate for the interval when photosynthesis was halted.« less

The response of macroinvertebrates to artificially enhanced detritus levels in plantation streams

NASA Astrophysics Data System (ADS)

Pretty, J. L.; Dobson, M.

The leaves and wood from vegetation surrounding headwater streams constitute a major food source for aquatic invertebrates, providing they are retained upon the streambed and not transported downstream. This study investigated the response of aquatic invertebrates to artificially increased detritus retention, in an effort to reproduce the naturally occurring build up of dead organic matter associated with streams in old-growth forest. The background detrital standing stock in streams in Kielder Forest (Northumberland, UK) was low, approximately 32 gm-2. Two streams flowing through dense conifer plantation and one in open broadleaved woodland were manipulated by the addition of logs over a 10 m stream reach. After several months, log addition significantly enhanced detrital standing stocks in both conifer and broadleaved streams. Total invertebrate abundance, taxon richness and the numbers of certain numerically dominant families were significantly higher in experimental than reference reaches in both conifer and broadleaved streams. This response was most marked for detritivores, whilst non-detritivore groups often showed no response to the manipulation. Whilst in the short term the responses to enhanced retention may reflect a redistribution of the local fauna, it is argued that over a longer time-scale, a genuine increase in invertebrate density and diversity could occur. Allowing old-growth forest to develop in planted valley bottoms may be a viable management option for conservation. If established alongside streams, it would ensure continuous input of woody material and the fauna may benefit from the resulting increase in detritus retention.

Platinum-group element contents of Karelian kimberlites: Implications for the PGE budget of the sub-continental lithospheric mantle

NASA Astrophysics Data System (ADS)

Maier, W. D.; O'Brien, H.; Peltonen, P.; Barnes, Sarah-Jane

2017-11-01

We present high-precision isotope dilution data for Os, Ir, Ru, Pt, Pd and Re in Group I and Group II kimberlites from the Karelian craton, as well as 2 samples of the Premier Group I kimberlite pipe from the Kaapvaal craton. The samples have, on average, 1.38 ppb Pt and 1.33 ppb Pd, with Pt/Pd around unity. These PGE levels are markedly lower, by as much as 80%, than those reported previously for kimberlites from South Africa, Brazil and India, but overlap with PGE results reported recently from Canadian kimberlites. Primitive-mantle-normalised chalcophile element patterns are relatively flat from Os to Pt, but Cu, Ni and, somewhat less so, Au are enriched relative to the PGE (e.g., Cu/Pd > 25.000). Pd/Ir ratios are 3,6 on average, lower than in most other mantle melts. The PGE systematics can be largely explained by two components, (i) harzburgite/lherzolite detritus of the SCLM with relatively high IPGE (Os-Ir-Ru)/PPGE (Rh-Pt-Pd) ratios, and (ii) a melt component that has high PPGE/IPGE ratios. By using the concentrations of iridium in the kimberlites as a proxy for the proportion of mantle detritus in the magma, we estimate that the analysed kimberlites contain 3-27% entrained and partially dissolved detritus from the sub-continental lithospheric mantle, consistent with previous estimates of kimberlites elsewhere (Tappe S. et al., 2016, Chem. Geol. 10.1016/j.chemgeo.2016.08.019).

Clarifying functional roles: algal removal by the surgeonfishes Ctenochaetus striatus and Acanthurus nigrofuscus

NASA Astrophysics Data System (ADS)

Tebbett, Sterling B.; Goatley, Christopher H. R.; Bellwood, David R.

2017-09-01

The lined bristletooth, Ctenochaetus striatus, and the brown surgeonfish, Acanthurus nigrofuscus, are among the most abundant surgeonfishes on Indo-Pacific coral reefs. Yet, the functional role of these species has been the focus of an ongoing debate lasting at least six decades. Specifically, to what extent are C. striatus herbivorous like the visually similar A. nigrofuscus? To address this question, we used natural feeding surfaces, covered with late successional stage reef-grown algal turfs, to examine turf algal removal by the two species. Surfaces exposed to C. striatus in laboratory experiments exhibited no significant reductions in turf length or area covered by turfing algae. In marked contrast, A. nigrofuscus reduced turf length by 51% and area covered by turfing algae by 15% in 1 h. The gut contents of specimens from the reef revealed that A. nigrofuscus predominantly ingests algae (the dominant item in 79.6-94.7% of gut content quadrats), while C. striatus ingests detritus and sediments (dominant in 99.6-100% of quadrats). Therefore, C. striatus ingests detritus and sediment, leaving mature algal turfs relatively intact, while A. nigrofuscus directly removes and ingests turf algae. The function of C. striatus differs from cropping herbivorous surgeonfishes such as A. nigrofuscus. On coral reefs, C. striatus brush detrital aggregates from algal turfs, removing microorganisms, organic detritus and inorganic sediment. Confusion over the functional role of C. striatus may stem from an inability to fit it into a single functional category.

The role of wrack deposits for supralittoral arthropods: An example using Atlantic sandy beaches of Brazil and Spain

NASA Astrophysics Data System (ADS)

Ruiz-Delgado, Mª Carmen; Vieira, Jenyffer Vierheller; Veloso, Valéria Gomes; Reyes-Martínez, Mª José; Sallorenzo, Ilana Azevedo; Borzone, Carlos Alberto; Sánchez-Moyano, Juan Emilio; García García, Francisco José

2014-01-01

Wrack deposits, as accumulated detritus, are a common feature on beaches worldwide and significantly contribute to the shaping of supralittoral arthropod communities. The composition and relative age of upper-shore deposits influence the structure and taxonomic composition of invertebrate assemblages. Moreover, these influences may vary geographically, depending on the locally prevailing climatic and hydrodynamic conditions. The amount and composition of wrack deposits as well as community attributes (total density, species richness and diversity) were determined on sandy beaches in three distinct geographical regions: South (Paraná) and Southeast (Rio de Janeiro) of Brazil and SW Spain. These parameters were compared between upper and lower wrack bands on each beach and between beaches in each region. Wrack deposits were composed of mangrove propagules in the Paraná region, by macrophytes, dead invertebrates and macroalgae in Rio de Janeiro region and by seagrass and macroalgae in the SW Spain region. In all regions, the total amount of stranded wrack differed between beaches, but the amount accumulated between bands (i.e upper and lower band) was similar between beaches. Wrack bands shaped the density of common taxa (Talitridae, Tenebrionidae, and Staphylinidae), with consequences for community structures. This result could be due to their preference for specific microhabitats and food sources, which might differ according to the relative age of the wrack deposits. The results suggest that, independent of wrack composition, the distribution of wrack deposits in bands and their relative ages seems to play a role on the structure of supralittoral arthropod assemblages.

Larval salamander growth responds to enrichment of a nutrient poor headwater stream

Treesearch

Brent J. Johnson; J. Bruce Wallace; AmyD Rosemond; Wyatt F. Cross

2006-01-01

While many studies have measured effects of nutrient enrichment on higher trophic levels in grazing food webs, few such studies exist for detritus-based systems. We measured effects of nitrogen and...

Ecosystem carbon storage does not vary with mean annual temperature in Hawaiian tropical montane wet forests.

PubMed

Selmants, Paul C; Litton, Creighton M; Giardina, Christian P; Asner, Gregory P

2014-09-01

Theory and experiment agree that climate warming will increase carbon fluxes between terrestrial ecosystems and the atmosphere. The effect of this increased exchange on terrestrial carbon storage is less predictable, with important implications for potential feedbacks to the climate system. We quantified how increased mean annual temperature (MAT) affects ecosystem carbon storage in above- and belowground live biomass and detritus across a well-constrained 5.2 °C MAT gradient in tropical montane wet forests on the Island of Hawaii. This gradient does not systematically vary in biotic or abiotic factors other than MAT (i.e. dominant vegetation, substrate type and age, soil water balance, and disturbance history), allowing us to isolate the impact of MAT on ecosystem carbon storage. Live biomass carbon did not vary predictably as a function of MAT, while detrital carbon declined by ~14 Mg of carbon ha(-1) for each 1 °C rise in temperature - a trend driven entirely by coarse woody debris and litter. The largest detrital pool, soil organic carbon, was the most stable with MAT and averaged 48% of total ecosystem carbon across the MAT gradient. Total ecosystem carbon did not vary significantly with MAT, and the distribution of ecosystem carbon between live biomass and detritus remained relatively constant across the MAT gradient at ~44% and ~56%, respectively. These findings suggest that in the absence of alterations to precipitation or disturbance regimes, the size and distribution of carbon pools in tropical montane wet forests will be less sensitive to rising MAT than predicted by ecosystem models. This article also provides needed detail on how individual carbon pools and ecosystem-level carbon storage will respond to future warming. © 2014 John Wiley & Sons Ltd.

A numerical investigation of phytoplankton and Pseudocalanus elongatus dynamics in the spring bloom time in the Gdańsk Gulf

NASA Astrophysics Data System (ADS)

Dzierzbicka-Głowacka, Lidia

2005-01-01

A nutrient-phytoplankton-zooplankton-detritus (1D-NPZD) `phytoplankton {Phyt} and Pseudocalanus elongatus {Zoop} dynamics in the spring bloom time in the Gdańsk Gulf. The 1D-NPZD model consists of three coupled, partial second-order differential equations of the diffusion type for phytoplankton {Phyt}, zooplankton {Zoop}, nutrients {Nutr} and one ordinary first-order differential equation for benthic detritus pool {Detr}, together with initial and boundary conditions. In this model, the {Zoop} is presented by only one species of copepod ( P. elongatus) and {Zoop} is composed of six cohorts of copepods with weights ( Wi) and numbers ( Zi); where Zoop= limit∑i=16W iZ i. The calculations were made for 90 days (March, April, May) for two stations at Gdańsk Gulf with a vertical space step of 0.5m and a time step of 900 s. The flow field and water temperature used as the inputs in the biological model 1D-NPZD were reproduced by the prognostic numerical simulation technique using hydrographic climatological data. The results of the numerical investigations described here were compared with the mean observed values of surface chlorophyll- a and depth integrated P. elongatus biomass for 10 years, 1980-1990. The slight differences between the calculated and mean observed values of surface chlorophyll- a and zooplankton biomass are ca. 10-60 mg C m -3 and ca. 5-23 mg C m -2, respectively, depending on the location of the hydrographic station. The 1D-NPZD model with a high-resolution zooplankton module for P. elongatus can be used to describe the temporal patterns for phytoplankton biomass and P. elongatus in the centre of the Gdańsk Gulf.

Literature review of organic matter transport from marshes

NASA Technical Reports Server (NTRS)

Dow, D. D.

1982-01-01

A conceptual model for estimating a transport coefficient for the movement of nonliving organic matter from wetlands to the adjacent embayments was developed in a manner that makes it compatible with the Earth Resources Laboratory's Productive Capacity Model. The model, which envisages detritus movement from wetland pixels to the nearest land-water boundary followed by movement within the water column from tidal creeks to the adjacent embayment, can be transposed to deal with only the interaction between tidal water and the marsh or to estimate the transport from embayments to the adjacent coastal waters. The outwelling hypothesis postulated wetlands as supporting coastal fisheries either by exporting nutrients, such as inorganic nitrogen, which stimulated the plankton-based grazing food chain in the water column, or through the export of dissolved and particulate organic carbon which provided a benthic, detritus-based food web which provides the food source for the grazing food chain in a more indirect fashion.

Dams impact carbon dynamics in U.S. rivers

NASA Astrophysics Data System (ADS)

Bhattacharya, Atreyee

2012-09-01

Dissolved organic carbon (DOC)—which leaches into freshwater systems from plants, soils, and sediments, and from other detritus present in the water itself—is the major food supplement for microorganisms and plays an important role in several environmental processes and in the global carbon cycle. In some aquatic systems such as estuaries, the optically measurable colored component of dissolved organic matter (CDOM) is often proportional to the concentration of DOC. CDOM forms when light-absorbing compounds are released into the water by decaying organic material and through photochemical degradation of certain organic compounds. Hence, CDOM reflects not just the environment and ecosystem, which is the source of the detritus, but also the processes that deliver the organic matter into aquatic systems. Human activities, such as logging, agriculture, and waste water treatment, also affect CDOM levels in aquatic systems. It is relatively easy and inexpensive to measure the CDOM content in small volumes of water.

Feeding ecology of non-native Siberian prawns, Palaemon modestus (Heller, 1862) (Decapoda, Palaemonidae), in the lower Snake River, Washington, U.S.A.

USGS Publications Warehouse

Tiffan, Kenneth F.; Hurst, William

2016-01-01

We used both stomach content and stable isotope analyses to describe the feeding ecology of Siberian prawns Palaemon modestus (Heller, 1862), a non-native caridean shrimp that is a relatively recent invader of the lower Snake River. Based on identifiable prey in stomachs, the opossum shrimp Neomysis mercedis Holmes, 1896 comprised up to 34-55% (by weight) of diets of juvenile to adult P. modestus, which showed little seasonal variation. Other predominant items/taxa consumed included detritus, amphipods, dipteran larvae, and oligochaetes. Stable isotope analysis supported diet results and also suggested that much of the food consumed by P. modestus that was not identifiable came from benthic sources — predominantly invertebrates of lower trophic levels and detritus. Palaemon modestus consumption of N. mercedis may pose a competitive threat to juvenile salmon and resident fishes which also rely heavily on that prey.

Mercury bioaccumulation studies in the National Water-Quality Assessment Program--biological data from New York and South Carolina, 2005-2009

USGS Publications Warehouse

Beaulieu, Karen M.; Button, Daniel T.; Eikenberry, Barbara C. Scudder; Riva-Murray, Karen; Chasar, Lia C.; Bradley, Paul M.; Burns, Douglas A.

2012-01-01

The U.S. Geological Survey National Water-Quality Assessment Program conducted a multidisciplinary study from 2005–09 to investigate the bioaccumulation of mercury in streams from two contrasting environmental settings. Study areas were located in the central Adirondack Mountains region of New York and the Inner Coastal Plain of South Carolina. Fish, macroinvertebrates, periphyton (attached algae and associated material), detritus, and terrestrial leaf litter were collected. Fish were analyzed for total mercury; macroinvertebrates, periphyton, and terrestrial leaf litter were analyzed for total mercury and methylmercury; and select samples of fish, macroinvertebrates, periphyton, detritus, and terrestrial leaf litter were analyzed for stable isotopes of carbon (δ13C) and nitrogen (δ15N). This report presents methodology and data on total mercury, methylmercury, stable isotopes, and other ecologically relevant measurements in biological tissues.

Inferring Phytoplankton, Terrestrial Plant and Bacteria Bulk δ¹³C Values from Compound Specific Analyses of Lipids and Fatty Acids

PubMed Central

Taipale, Sami J.; Peltomaa, Elina; Hiltunen, Minna; Jones, Roger I.; Hahn, Martin W.; Biasi, Christina; Brett, Michael T.

2015-01-01

Stable isotope mixing models in aquatic ecology require δ13C values for food web end members such as phytoplankton and bacteria, however it is rarely possible to measure these directly. Hence there is a critical need for improved methods for estimating the δ13C ratios of phytoplankton, bacteria and terrestrial detritus from within mixed seston. We determined the δ13C values of lipids, phospholipids and biomarker fatty acids and used these to calculate isotopic differences compared to the whole-cell δ13C values for eight phytoplankton classes, five bacterial taxa, and three types of terrestrial organic matter (two trees and one grass). The lipid content was higher amongst the phytoplankton (9.5±4.0%) than bacteria (7.3±0.8%) or terrestrial matter (3.9±1.7%). Our measurements revealed that the δ13C values of lipids followed phylogenetic classification among phytoplankton (78.2% of variance was explained by class), bacteria and terrestrial matter, and there was a strong correlation between the δ13C values of total lipids, phospholipids and individual fatty acids. Amongst the phytoplankton, the isotopic difference between biomarker fatty acids and bulk biomass averaged -10.7±1.1‰ for Chlorophyceae and Cyanophyceae, and -6.1±1.7‰ for Cryptophyceae, Chrysophyceae and Diatomophyceae. For heterotrophic bacteria and for type I and type II methane-oxidizing bacteria our results showed a -1.3±1.3‰, -8.0±4.4‰, and -3.4±1.4‰ δ13C difference, respectively, between biomarker fatty acids and bulk biomass. For terrestrial matter the isotopic difference averaged -6.6±1.2‰. Based on these results, the δ13C values of total lipids and biomarker fatty acids can be used to determine the δ13C values of bulk phytoplankton, bacteria or terrestrial matter with ± 1.4‰ uncertainty (i.e., the pooled SD of the isotopic difference for all samples). We conclude that when compound-specific stable isotope analyses become more widely available, the determination of δ13C values for selected biomarker fatty acids coupled with established isotopic differences, offers a promising way to determine taxa-specific bulk δ13C values for the phytoplankton, bacteria, and terrestrial detritus embedded within mixed seston. PMID:26208114

EFFECTS OF ACIDIC PRECIPITATION ON BENTHOS

EPA Science Inventory

The community of organisms, the benthos, which inhabit aquatic sediments interact with biological and chemical components of the water column by processing detritus, recycling inorganic nutrients, mixing sediments, and serving as a principal food source for fish, waterfowl, and r...

Tracing Pleistocene to Holocene meltwater events and provenance of sediments in Baffin Bay using radiogenic isotope signals

NASA Astrophysics Data System (ADS)

Kirillova, Valeriia; Kasemann, Simone A.; Lucassen, Friedrich

2016-04-01

Large meltwater discharge is the principal carrier of detritus from the continent into the ocean and the dispersion of this detritus by ocean currents is a measure for the spatially focused addition of freshwater in the ocean in the high latitude areas. To trace Greenland ice sheet dynamics and freshwater routing during late Pleistocene to Holocene climate transition, we generate strontium (Sr), neodymium (Nd) and lead (Pb) isotope records on sediment cores in the Baffin Bay: GeoTÜ SL 170, covering the last 18.000 years of climate history and GeoTÜ SL 174, covering 40.000 years. Sr, Nd and Pb isotopes are used as proxies for the provenance of continental detritus and seawater sources. Isotope analyses were performed on two separated fractions from the sedimentary core material: the chemically leached fraction and the remaining detritus. Leachates are supposed to represent Fe-Mn coatings formed on the surface of the sediment grains and to reflect the bottom water signal. The detrital fraction acts as a tracer for the meltwater event and weathering regime of the nearby continental masses. For the detrital fraction of the core SL 170, a pronounced shift can be observed in all three isotope systems at ˜ 12 ka, what coincides with the Younger Dryas cold event. For the detrital fraction the 87Sr/86Sr is around ˜0,72 before the event and reaches up to ˜0,74 after. Nd isotope composition (ɛNd) changed from ˜-26 to ˜-32. The shift suggests a change in the continental sources from West and West-South Greenland to the Baffin Island and Canadian Archipelago. It can be explained by the ice sheet melting processes. The 206Pb/204Pb values for the detrital fraction range from ˜17 before the shift to ˜18 after. On the contrary, the leachates show pronounced radiogenic signatures with values changing from ˜21 to ˜23. The reason for such an unusual high values is most likely in the composition of the leached material, which doesn't seem to show the presence of Fe-Mn coatings as was suggested before. The work on the second core SL 174 is in progress. Up to now the results show similar patterns for isotope ratios as in the case of SL 170.

Net primary productivity, allocation pattern and carbon use efficiency in an apple orchard assessed by integrating eddy-covariance, biometric and continuous soil chamber measurements

NASA Astrophysics Data System (ADS)

Zanotelli, D.; Montagnani, L.; Manca, G.; Tagliavini, M.

2012-10-01

Carbon use efficiency (CUE) is a functional parameter that could possibly link the current increasingly accurate global estimates of gross primary production with those of net ecosystem exchange, for which global predictors are still unavailable. Nevertheless, CUE estimates are actually available for only a few ecosystem types, while information regarding agro-ecosystems is scarce, in spite of the simplified spatial structure of these ecosystems that facilitates studies on allocation patterns and temporal growth dynamics. We combined three largely deployed methods, eddy covariance, soil respiration and biometric measurements, to assess monthly values of CUE, net primary production (NPP) and allocation patterns in different plant organs in an apple orchard during a complete year (2010). We applied a~measurement protocol optimized for quantifying monthly values of carbon fluxes in this ecosystem type, which allows for a cross-check between estimates obtained from different methods. We also attributed NPP components to standing biomass increments, detritus cycle feeding and lateral exports. We found that in the apple orchard both net ecosystem production and gross primary production on yearly basis, 380 ± 30 g C m-2 and 1263 ± 189 g C m-2 respectively, were of a magnitude comparable to those of natural forests growing in similar climate conditions. The largest differences with respect to forests are in the allocation pattern and in the fate of produced biomass. The carbon sequestered from the atmosphere was largely allocated to production of fruits: 49% of annual NPP was taken away from the ecosystem through apple production. Organic material (leaves, fine root litter, pruned wood and early fruit falls) contributing to the detritus cycle was 46% of the NPP. Only 5% was attributable to standing biomass increment, while this NPP component is generally the largest in forests. The CUE, with an annual average of 0.71 ± 0.09, was higher than the previously suggested constant values of 0.47-0.50. Low nitrogen investment in fruits, the limited root-apparatus, and the optimal growth temperature and nutritional condition observed at the site are suggested to be explanatory variables for the high CUE observed.

Can Thin-lipped Mullet Directly Exploit the Primary and Detritic Production of European Macrotidal Salt Marshes?

NASA Astrophysics Data System (ADS)

Laffaille, P.; Feunteun, E.; Lefebvre, C.; Radureau, A.; Sagan, G.; Lefeuvre, J.-C.

2002-04-01

Juveniles and adults (>100 mm) of Liza ramada colonize macrotidal salt marsh creeks of Mont Saint-Michel bay (France) between March and November, during spring tide floods (43% of the tides) and return to coastal waters during the ebb. This fish species actively feeds during its short stay in the creek (from 1 to 2 h). On average, each fish swallows sediment including living and inert organic matter, which amounts to 8% of its fresh body weight. Their diet is dominated by small benthic items (especially diatoms and salt marsh plant detritus), that correspond to the primary and detritic production of this macrotidal salt marsh creek. Despite very short submersion periods, mullets filter and ingest large quantities of sediment and concentrated organic matter (on average organic matter in stomach content is 31%) produced by these coastal wetlands. European salt marshes are thus shown to act as trophic areas for mullets, which are well adapted to this constraining habitat which is only flooded for short periods during spring tides.

Integrating spatial and temporal variability into the analysis of fish food web linkages in Tijuana Estuary.

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

West, Janelle M.; Williams, Greg D.; Madon, Sharook P.

2003-05-14

Our understanding of fish feeding interactions at Tijuana Estuary was improved by incorporating estimates of spatial and temporal variability into diet analyses. We examined the stomach contents of 7 dominant species (n=579 total fish) collected between 1994 and 1999. General feeding patterns pooled over time produced a basic food web consisting of 3 major trophic levels: (1) primary consumers (Atherinops affinis, Mugil cephalus) that ingested substantial amounts of plant material and detritus; (2) benthic carnivores (Clevelandia ios, Hypsopsetta guttulata, Gillichthys mirabilis, and Fundulus parvipinnis) that ingested high numbers of calanoid copepods and exotic amphipods (Grandidierella japonica); and (3) piscivores (Paralichthysmore » californicus and Leptocottus armatus) that often preyed on smaller gobiids. Similarity-based groupings of individual species' diets were identified using nonmetric multidimensional scaling to characterize their variability within and between species, and in s pace and time. This allowed us to identify major shifts and recognize events (i.e., modified prey abundance during 1997-98 El Nino floods) that likely caused these shifts.« less

GEOMORPHIC CONTROLS ON CARBON AND NITROGEN PROCESSING IN A DEGRADED URBAN STREAM

EPA Science Inventory

Elevated nitrate levels in streams and groundwater pose human and ecological threats. Microbial denitrification removes nitrate from groundwater but requires anaerobic (saturated) conditions and adequate supply of dissolved organic carbon from detritus and organic soils. Condit...

SEAGRASS AND CDOM IN THE FLORIDA KEYS

EPA Science Inventory

Seagrasses play a variety of important ecological roles in coastal ecosystems. Here we present evidence that seagrass detritus from the widespread species, Thalassia testudinum, is an important source of ocean color and UV-protective substances in a low latitude coastal shelf reg...

Post-emplacement history of the Zambales Ophiolite Complex: Insights from petrography, geochronology and geochemistry of Neogene clastic rocks

NASA Astrophysics Data System (ADS)

Dimalanta, C. B.; Salapare, R. C.; Faustino-Eslava, D. V.; Ramos, N. T.; Queaño, K. L.; Yumul, G. P.; Yang, T. F.

2015-05-01

The Zambales Ophiolite Complex in Luzon, Philippines is made up of two blocks with differing geochemical signatures and ages - the Middle Jurassic to Early Cretaceous Acoje Block-San Antonio Massif that is of island arc tholeiite composition and the Eocene Coto Block-Cabangan Massif which is of transitional mid-ocean ridge basalt-island arc tholeiite affinity. These ophiolitic bodies are overlain by Miocene to Pliocene sedimentary units whose petrochemistry are reported here for the first time. Varying degrees of influences from ophiolitic detritus and from arc volcanic materials, as shown by petrography and indicator elements including Cr, Co and Ni, are observed in these sedimentary formations from north to south and from the oldest to the youngest. The Early to Middle Miocene Cabaluan Formation, whose outcrops are found to overlie only the Acoje Block, registers a more dominant ophiolitic signature as compared to the Late Miocene to Pliocene Santa Cruz Formation. The Santa Cruz Formation is generally characterized by fewer ophiolitic clasts and higher amounts of felsic components. Additionally, within this formation itself, a pronounced compositional change is observed relative to its spatial distribution. From the south to the north, an increase in ophiolitic components and a relative decrease in felsic signature is noted in units of the Santa Cruz Formation. It is therefore inferred that changes in the petrochemistry of rocks from the older Cabaluan to the younger Santa Cruz sedimentary formations record a decline in the influx of ophiolitic detritus or, conversely, the introduction of more diverse sediment sources as the deposition progressed. Detrital zircon U-Pb ages from the Santa Cruz Formation, with peaks at 46.73 ± 0.94 and 5.78 ± 0.13 Ma, reflects this change in provenance from the unroofing of an Early Eocene oceanic crust to fresh contributions from an active volcanic arc during the Late Miocene. The contrast in compositions of the southern and northern Santa Cruz Formation also indicates a closer proximity of the southern units to the source of these non-ophiolitic sources, which most likely corresponds to the Pliocene volcanoes of the West Luzon Arc.

Colony Rheology: Active Arthropods Generate Flows

NASA Astrophysics Data System (ADS)

Daniels, Karen; Mann, Michael; Charbonneau, Patrick

2015-03-01

Hydrodynamic-like flows are observed in biological systems as varied as bacteria, insects, birds, fish, and mammals. Both the phenomenology (e.g. front instabilities, milling motions) and the interaction types (hydrodynamic, direct contact, psychological, excluded-volume) strongly vary between systems, but a question common to all of them is to understand the role of particle-scale fluctuations in controlling large-scale rheological behaviors. We will address these questions through experiments on a new system, Tyrolichus casei (cheese mites), which live in dense, self-mixing colonies composed of a mixture of living mites and inert flour/detritus. In experiments performed in a Hele-Shaw geometry, we observe that the rheology of a colony is strongly dependent on the relative concentration of active and inactive particles. In addition to spreading flows, we also observe that the system can generate convective circulation and auto-compaction.

EFFECTS OF SUCCESSION ON NITROGEN EXPORT IN THE WEST-CENTRAL CASCADES, OREGON

EPA Science Inventory

Conceptual models predict that unpolluted, aggrading forest ecosystems tightly retain available nitrogen (N) until declining productivity by mature trees and storage in detritus reduces the demand for essential nutrients, and N export increases to equal input. Short-term nitrate ...

Food web structure in exotic and native mangroves: A Hawaii-Puerto Rico comparison

USGS Publications Warehouse

Demopoulos, A.W.J.; Fry, B.; Smith, C.R.

2007-01-01

Plant invasions can fundamentally alter detrital inputs and the structure of detritus-based food webs. We examined the detrital pathways in mangrove food webs in native (Puerto Rican) and introduced (Hawaiian) Rhizophora mangle forests using a dual isotope approach and a mixing model. Based on trophic-level fractionation of 0-1??? for ?? 13C and 2-3??? for ?? 15N, among the invertebrates, only nematodes, oligochaetes, and nereid polychaetes from native mangroves exhibited stable isotopes consistent with a mangrove-derived diet. Certain fauna, in particular tubificid oligochaetes, had ?? 13C values consistent with the consumption of mangrove leaves, but they were depleted in 15N, suggesting their primary nitrogen source was low in 15N, and was possibly N 2-fixing bacteria. In introduced mangroves, all feeding groups appeared to rely heavily on non-mangrove sources, especially phytoplankton inputs. Mixing model results and discriminant analysis showed clear separation of introduced and native mangrove sites based on differential food source utilization within feeding groups, with stronger and more diverse use of benthic foods observed in native forests. Observed differences between native and invasive mangrove food webs may be due to Hawaiian detritivores being poorly adapted to utilizing the tannin-rich, nitrogen-poor mangrove detritus. In addition, differential utilization of mangrove detritus between native and introduced mangroves may be a consequence of forest age. We postulate that increasing mangrove forest age may promote diversification of bacterial food webs important in N and S cycling. Our results also suggest a potentially important role for sulfur bacteria in supporting the most abundant infaunal consumers, nematodes, in the most mature systems. ?? 2007 Springer-Verlag.

Nd Isotopic Provenance of Sedimentary Rocks Along Margins of North America: ten Years of Study

NASA Astrophysics Data System (ADS)

Patchett, J.; Ross, G. M.

2001-12-01

Ten years of effort, principally employing Nd isotopes, have resulted in substantial advances in understanding of the movements of sedimentary material around North America from Cambrian to Cretaceous time. This synthesis has depended upon work of current and former students S. Samson, J. Gleason, N. Boghossian, C. Garzione, M. Roth, B. Canale and E. Rosenberg, as well as collaborators W. Dickinson and A. Embry, among others. Nd isotopes are particularly good at documenting movements of sedimentary material on the largest (continental) scale and over extended times. What has emerged is a picture of a largely exposed North America-Greenland craton from Neoproterozoic to Ordovician time, a partial to complete burial by detritus from Caledonian-Appalachian mountains starting in the Ordovician, a gradual exhumation during Late Paleozoic and Mesozoic time, followed by a partial burial with Cordilleran detritus during Late Jurassic to Tertiary time. One current question is the nature of the Mesozoic and Tertiary sedimentary material eroded from the North American Cordillera, and its relevance for Cordilleran orogenesis. Another current question is the extent to which Caledonian-Appalachian detritus covered the craton in Devonian-Carboniferous time, and the timing and manner of its removal during Mesozoic time. At first glance, available Nd isotopic data appear to suggest that the Canada-Greenland Shield was largely covered during most of Mesozoic time, a conclusion that would have profound effects on models of dynamic topography. However, this conclusion is also very dependent on the relationship between topography and erosion, because in certain situations a geographically-restricted cover sequence could dominate over low-relief cratonic terrain as a sediment source.

High diet overlap between native small-bodied fishes and nonnative fathead minnow in the Colorado River, Grand Canyon, Arizona

USGS Publications Warehouse

Seegert, Sarah E. Zahn; Rosi-Marshall, Emma J.; Baxter, Colden V.; Kennedy, Theodore A.; Hall, Robert O.; Cross, Wyatt F.

2014-01-01

River regulation may mediate the interactions among native and nonnative species, potentially favoring nonnative species and contributing to the decline of native populations. We examined food resource use and diet overlap among small-bodied fishes in the Grand Canyon section of the Colorado River as a first step in evaluating potential resource competition. We compared the diets of the predominant small-bodied fishes (native Speckled Dace Rhinichthys osculus, juvenile Flannelmouth Sucker Catostomus latipinnis, and juvenile Bluehead Sucker C. discobolus, and nonnative Fathead Minnow Pimephales promelas) across seasons at four sites downstream of Glen Canyon Dam using nonmetric multidimensional scaling and Schoener's similarity index. The diets of these fishes included diatoms, amorphous detritus, aquatic invertebrates (especially simuliid and chironomid larvae), terrestrial invertebrates, and terrestrial vegetation. Diets varied with season and were affected by high turbidity. Fish consumed more amorphous detritus and terrestrial vegetation during the summer monsoon season (July–September), when turbidity was higher. The diets of all species overlapped, but there was large variation in the degree of overlap. The diets of juvenile suckers and Fathead Minnows were most similar, while Speckled Dace had relatively distinct diets. The differences took the form of higher proportions of diatoms and amorphous detritus in the diets of Bluehead Suckers and Fathead Minnows and higher proportions of simuliids and chironomids in those of Speckled Dace. If food resources are or become limiting, diet overlap suggests that competition may occur among native and nonnative species, which could have implications for the population dynamics of these fishes and for the management of the Colorado River ecosystem in Grand Canyon.

Stratigraphy, petrography, and provenance of Archean sedimentary rocks of the Nsuze Group, Pongola Supergroup, in the Wit M'folozi Inlier, South Africa

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

Gamero de Villarroel, H.; Lowe, D.R.

1993-02-01

The Upper Archean Pongola Supergroup is a succession of clastic and volcanic rocks that represents the oldest relatively unmetamorphosed sedimentary sequence deposited on the basement of the 3.5-3.2 Ga-old Kaapvaal Craton. The Pongola Supergroup includes two subdivisions, the Nsuze and the Mozaan Groups. The Nsuze Group is composed of clastic rocks, minor carbonate units, and basalt. Nsuze sandstones are dominated by granite-derived sediments, and minor basaltic-derived detritus. Most Nsuze sedimentary rocks are sandstones that include both quartz-fieldspar and lithic-rich varieties. The mineralogy of Nsuze sandstones reflects the mixing of debris derived from two distinctive sources: (1) a sialic plutonic sourcemore » yielding quartz and microcline and (2) a basaltic source yielding basaltic lithic detritus and plagioclase. The most likely source rocks for the Nsuze sandstones in the Wit M'folozi Inlier were Archean granitic basement, represented by the Mpuluzi batholith, and Nsuze basaltic volcanic rocks. Both continental arc and rift settings have been proposed for the Pongola Supergroup. Nsuze sandstones show similarities to continental arc sandstone suites. However, there is no report of the existence of high standing stratovolcanoes, calc-alkaline plutonism, or contact and regional metamorphism of the intruded volcanic-sedimentary and basement rocks in the Pongola basin, features that are typically associated with continental arcs. The dominance of continent-derived detritus in the Nsuze Group argues that volcanic rocks made up a minor part of the exposed source area and that volcanism was largely restricted to the basin of deposition. Collectively, available evidence favors an intracratonic rift for the depositional setting of the Nsuze Group.« less

Genetic accommodation in the wild: evolution of gene expression plasticity during character displacement.

PubMed

Levis, N A; Serrato-Capuchina, A; Pfennig, D W

2017-09-01

Ecological character displacement is considered crucial in promoting diversification, yet relatively little is known of its underlying mechanisms. We examined whether evolutionary shifts in gene expression plasticity ('genetic accommodation') mediate character displacement in spadefoot toads. Where Spea bombifrons and S. multiplicata occur separately in allopatry (the ancestral condition), each produces alternative, diet-induced, larval ecomorphs: omnivores, which eat detritus, and carnivores, which specialize on shrimp. By contrast, where these two species occur together in sympatry (the derived condition), selection to minimize competition for detritus has caused S. bombifrons to become nearly fixed for producing only carnivores, suggesting that character displacement might have arisen through an extreme form of genetic accommodation ('genetic assimilation') in which plasticity is lost. Here, we asked whether we could infer a signature of this process in regulatory changes of specific genes. In particular, we investigated whether genes that are normally expressed more highly in one morph ('biased' genes) have evolved reduced plasticity in expression levels among S. bombifrons from sympatry compared to S. bombifrons from allopatry. We reared individuals from sympatry vs. allopatry on detritus or shrimp and measured the reaction norms of nine biased genes. Although different genes displayed different patterns of gene regulatory evolution, the combined gene expression profiles revealed that sympatric individuals had indeed lost the diet-induced gene expression plasticity present in allopatric individuals. Our data therefore provide one of the few examples from natural populations in which genetic accommodation/assimilation can be traced to regulatory changes of specific genes. Such genetic accommodation might mediate character displacement in many systems. © 2017 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2017 European Society For Evolutionary Biology.

MEDUSA-2.0: an intermediate complexity biogeochemical model of the marine carbon cycle for climate change and ocean acidification studies

NASA Astrophysics Data System (ADS)

Yool, A.; Popova, E. E.; Anderson, T. R.

2013-10-01

MEDUSA-1.0 (Model of Ecosystem Dynamics, nutrient Utilisation, Sequestration and Acidification) was developed as an "intermediate complexity" plankton ecosystem model to study the biogeochemical response, and especially that of the so-called "biological pump", to anthropogenically driven change in the World Ocean (Yool et al., 2011). The base currency in this model was nitrogen from which fluxes of organic carbon, including export to the deep ocean, were calculated by invoking fixed C:N ratios in phytoplankton, zooplankton and detritus. However, due to anthropogenic activity, the atmospheric concentration of carbon dioxide (CO2) has significantly increased above its natural, inter-glacial background. As such, simulating and predicting the carbon cycle in the ocean in its entirety, including ventilation of CO2 with the atmosphere and the resulting impact of ocean acidification on marine ecosystems, requires that both organic and inorganic carbon be afforded a more complete representation in the model specification. Here, we introduce MEDUSA-2.0, an expanded successor model which includes additional state variables for dissolved inorganic carbon, alkalinity, dissolved oxygen and detritus carbon (permitting variable C:N in exported organic matter), as well as a simple benthic formulation and extended parameterizations of phytoplankton growth, calcification and detritus remineralisation. A full description of MEDUSA-2.0, including its additional functionality, is provided and a multi-decadal spin-up simulation (1860-2005) is performed. The biogeochemical performance of the model is evaluated using a diverse range of observational data, and MEDUSA-2.0 is assessed relative to comparable models using output from the Coupled Model Intercomparison Project (CMIP5).

Rb-Sr, Sm-Nd, K-Ca, O, and H isotopic study of Cretaceous-Tertiary boundary sediments, Caravaca, Spain: evidence for an oceanic impact site

USGS Publications Warehouse

DePaolo, D.J.; Kyte, F.T.; Marshall, B.D.; O'Neil, J.R.; Smit, J.

1983-01-01

Isotopic ratios and trace element abundances were measured on samples of Ir-enriched clay at the Cretaceous-Tertiary boundary, and in carbonate and marl from 5 cm below and 3 cm above the boundary. Samples were leached with acetic acid to remove carbonate, and with hydrochloric acid. Leachates and residues were measured. The Sr, Nd, O and H isotopic compositions of the boundary clay residues are distinct from those of the stratigraphically neighboring materials. The data indicate that most of the clay material was derived from a terrestrial source with relatively low 87Sr/86Sr and high 143Nd/144Nd ratios. The ??18O data suggest that the detritus has been modified by submarine weathering. K-Ca and Rb-Sr systematics, as well as O isotope ratios of K-feldspar spherules within the boundary clay, suggest that they are predominantly authigenic and may have formed after the time of deposition. However, Sm-Nd and Rb-Sr isotopic data indicate that the spherules contain relict material that provides information on the nature of the original detritus. The isotopic evidence for foreign terrestrial detritus in the boundary clay, the low rare earth element concentrations and high Ni concentration, support the hypothesis of a terminal Cretaceous asteroidal impact that produced a global layer of fallout. The data are most easily explained if the impact site was on oceanic crust rather than continental crust, and if a substantial fraction of the fallout was derived from relatively deep within the lithosphere (>3 km). This would probably require a single large impactor. ?? 1983.

Denitrification in the Arabian Sea: A 3D ecosystem modelling study

NASA Astrophysics Data System (ADS)

Anderson, Thomas R.; Ryabchenko, Vladimir A.; Fasham, Michael J. R.; Gorchakov, Victor A.

2007-12-01

A three-dimensional hydrodynamic-ecosystem model was used to examine the factors determining the spatio-temporal distribution of denitrification in the Arabian Sea. The ecosystem model includes carbon and nitrogen as currencies, cycling of organic matter via detritus and dissolved organic matter, and both remineralization and denitrification as sinks for material exported below the euphotic zone. Model results captured the marked seasonality in plankton dynamics of the region, with characteristic blooms of chlorophyll in the coastal upwelling regions and central Arabian Sea during the southwest monsoon, and also in the northern Arabian Sea during the northeast monsoon as the mixed layer shoals. Predicted denitrification was 26.2 Tg N yr -1,the greatest seasonal contribution being during the northeast monsoon when primary production is co-located with the zone of anoxia. Detritus was the primary organic substrate consumed in denitrification (97%), with a small (3%) contribution by dissolved organic matter. Denitrification in the oxygen minimum zone was predicted to be fuelled almost entirely by organic matter supplied by particles sinking vertically from the euphotic zone above (0.73 mmol N m -2 d -1) rather than from lateral transport of organic matter from elsewhere in the Arabian Sea (less than 0.01 mmol N m -2 d -1). Analysis of the carbon budget in the zone of denitrification (north of 10°N and east of 55°E) indicates that the modelled vertical export flux of detritus, which is similar in magnitude to estimates from field data based on the 234Th method, is sufficient to account for measured bacterial production below the euphotic zone in the Arabian Sea.

Relief inversion in the geomorphological evolution of sub-Saharan West Africa

NASA Astrophysics Data System (ADS)

Butt, C. R. M.; Bristow, A. P. J.

2013-03-01

The geomorphology of much of sub-Saharan West Africa is dominated by the presence of plateaux and plains with ferruginous and, locally, aluminous (bauxitic) duricrusts. The plateaux occur at different elevations and have been correlated as two or more palaeosurfaces across much of the region. The duricrusts have generally been considered to be residual, formed by conformable erosion and chemical wasting of immediately underlying bedrock. This concept has been central to interpretations as diverse as the formation and evolution of the landscape and the development of geochemical exploration models. Recent regolith landform mapping, field observations and experience from mineral exploration in southern Mali and Burkina Faso, however, demonstrate that the duricrusts are mainly ferricretes, i.e., Fe oxide-cemented sediments. These observations require a re-interpretation of the geomorphological evolution of the region during the Cenozoic. The landscape has evolved by several cycles of weathering and erosion-deposition, triggered by climatic, tectonic or other environmental changes. It is proposed that an initial bauxitic/lateritic regolith was partly eroded following uplift and/or a change to a more arid climate, and that the detritus, rather than being removed, was deposited on slopes and valleys. During a subsequent humid period of lateritic weathering, Fe oxide cementation of this detritus formed ferricrete. Dehydration and hardening of the ferricrete after further uplift or aridity increased its resistance to erosion, resulting in relief inversion, with the detritus, in turn, being deposited downslope. This too has been weathered and cemented, to form a younger ferricrete. The occurrence of ferricrete landforms in adjacent countries, noted by field observation and inferred from satellite imagery, demonstrates that relief inversion is a very widespread and important phenomenon in southern Mali, Burkina Faso and adjacent countries in semi-arid West Africa.

Cryoseism Vibrational Movement and Sorting of Detritus of Mars' Regolith Bedforms (E.G., ~ Streaks, Gullies): a New, Dry, Midsummer Antarctic Analogue Mechanism

NASA Astrophysics Data System (ADS)

Ford, A. B.

2015-12-01

"SNAP!, CRACK!, POP!" The sounds reverberated across newly shaded permafrost of unusual talus aprons (Ford & Andersen, 1967; J. Geol., 75, 722-732) of interior Antarctica (lats. >84°S; Thiel, Pensacola mtns.), coming from ice cracking under tensile failure (cryoseisms). Apron regoliths show conspicuously reversed downslope particle-size sorting and downslope-oriented lineations (debris-cleared tracts; stone stripes) formed by vibrational movement of detritus by midsummer, diurnal cracking of ice. Moving laterally by vibrations away from cracks, with downslope component by gravity, finer detritus becomes concentrated downslope from coarser debris of initial cliff fall — winnowed, as if on a gigantic vibrating shaking table. Slopes outside shade zones remain free of cracking. Diurnal midday shading of solar-warmed, debris-mantled permafrost- and glacier-surface ice at low ambient midsummer temperatures produces high strain-loading rates that exceed tensile toughness of inhomogeneous, polycrystalline ice containing zones of older but sealed cracks. This dry, mechanical, cryoseism mechanism is here proposed also for now waterless Mars and other icy Solar System bodies. Regolith features of Mars' cryosphere may appear different from anrarctic analogues owing to likely operation over tens if not hundreds of millions of years longer than on Earth. The strain distributions in tensile failure of ice better explain a common spacing uniformity of many martian linear features than others' proposed origins, and for some "active" streaks and gully channels, TARS, RSL and dune-slipface channels, as well as for dune orthogonality, diurnal moonquakes and asteroid-regolith detrital sorting (e.g., "rubble-pile" 25143-Itokawa). Because periodic shade from topography (canyons, craters, etc.) is needed, the mechanism is not expected on flattish terrains where more normal annual cooling rates produce the common polygonal tensile fracturing of ice

A Trophic Model of a Sandy Barrier Lagoon at Chiku in Southwestern Taiwan

NASA Astrophysics Data System (ADS)

Lin, H.-J.; Shao, K.-T.; Kuo, S.-R.; Hsieh, H.-L.; Wong, S.-L.; Chen, I.-M.; Lo, W.-T.; Hung, J.-J.

1999-05-01

Using the ECOPATH 3.0 software system, a balanced trophic model of a sandy barrier lagoon with intensive fishery activities at Chiku in tropical Taiwan was constructed. The lagoon model comprised 13 compartments. Trophic levels of the compartments varied from 1·0 for primary producers and detritus to 3·6 for piscivorous fish. Hanging-cultured oysters accounted for 39% of the harvestable fishery biomass and were the most important fishery species. The most prominent group in terms of biomass and energy flow in the lagoon was herbivorous zooplankton. Manipulations of the biomass of herbivorous zooplankton would have a marked impact on most compartments. Both total system throughput and fishery yield per unit area were high when compared to other reported marine ecosystems. This appears mainly due to high planktonic primary production, which is probably promoted by enriched river discharges draining mangroves and aquaculture ponds. Consequently, more than half of the total system throughput originates from primary producers in the lagoon. Although half of the primary production was not immediately used by upper trophic levels and flowed into the detrital pool, most of the detritus was directly consumed, passed up the food web and was exported to the fishery. Thus only a small proportion of energy was recycled through detritus pathways. This mechanism produces short pathways with high trophic efficiencies at higher trophic levels. The high fishery yield in the lagoon is due to high primary production and short pathways. This is the first model of a tropical sandy barrier lagoon with intensive fishery activities and thus may serve as a basis for future comparisons and ecosystem management.

Effects of temperature on decomposition of a potential nuisance species: the submerged aquatic macrophyte Egeria najas Planchon (Hydrocharitaceae).

PubMed

Carvalho, P; Thomaz, S M; Bini, L M

2005-02-01

Decomposition of aquatic plants is influenced by several biotic and abiotic factors. Among them, temperature plays an important role. Despite the increasing number of studies describing the effects of temperature on the decomposition of aquatic macrophytes, little attention has been given to the decay of submerged macrophytes. In this paper, we assessed the effect of temperature on weight loss and chemical composition of detritus of the submerged aquatic macrophyte Egeria najas Planchon (Hydrocharitaceae). Fresh plant material was maintained at 17 degrees C and 27 degrees C, in the dark, in incubation chambers. The overall decay process was best described by a linear model, with rates of 0.014 day(-1) (R2= 94%) and 0.045 day(-1) (R2= 96%) obtained at 17 degrees C and 27 degrees C, respectively. The analysis of covariance (ANCOVA) indicated a significant difference between the decomposition rates at the two temperatures. The rapid breakdown of E. najas detritus, indicated by the decay coefficient, may be explained by its low content of resistant compounds such as cellulose and lignin. The variables analyzed in this study (pH, electrical conductivity, dissolved oxygen in the water and organic matter, total nitrogen and total phosphorus concentration in detritus) showed accentuated responses at 27 degrees C. It is likely that the higher temperature increased microbial activity and, therefore, oxygen consumption in the water, consequently affecting the pH and the rate of ion and nutrient liberation into the aquatic ecosystem. Due to the rapid decomposition of E. najas at high temperatures, a small exportation is expected of this species from its stands to distant regions in tropical reservoirs, where it is considered a potential nuisance species.

Shifts in the trophic base of intermittent stream food webs

USGS Publications Warehouse

Dekar, Matthew P.; Magoulick, Daniel D.; Huxel, G.R.

2009-01-01

Understanding spatial and temporal variation in the trophic base of stream food webs is critical for predicting population and community stability, and ecosystem function. We used stable isotope ratios (13C/12C, and 15N/14N) to characterize the trophic base of two streams in the Ozark Mountains of northwest Arkansas, U.S.A. We predicted that autochthonous resources would be more important during the spring and summer and allochthonous resources would be more important in the winter due to increased detritus inputs from the riparian zone during autumn leaf drop. We predicted that stream communities would demonstrate increased reliance on autochthonous resources at sites with larger watersheds and greater canopy openness. The study was conducted at three low-order sites in the Mulberry River Drainage (watershed area range: 81-232 km2) seasonally in 2006 and 2007. We used circular statistics to examine community-wide shifts in isotope space among fish and invertebrate consumers in relation to basal resources, including detritus and periphyton. Mixing models were used to quantify the relative contribution of autochthonous and allochthonous energy sources to individual invertebrate consumers. Significant isotopic shifts occurred but results varied by season and site indicating substantial variation in the trophic base of stream food webs. In terms of temporal variation, consumers shifted toward periphyton in the summer during periods of low discharge, but results varied during the interval between summer and winter. Our results did not demonstrate increased reliance on periphyton with increasing watershed area or canopy openness, and detritus was important at all the sites. In our study, riffle-pool geomorphology likely disrupted the expected spatial pattern and stream drying likely impacted the availability and distribution of basal resources.

Utilization of shallow-water seagrass detritus by Carribbean deep-sea macrofauna: δ 13C evidence

NASA Astrophysics Data System (ADS)

Suchanek, Thomas H.; Williams, Susan L.; Ogden, John C.; Hubbard, Dennis K.; Gill, Ivan P.

1985-02-01

Three dives were made using the DSRV Alvin in the deep-sea basin north of St. Croix, Virgin Islands. Detrital seagrasses and macrofaunal distributions at 2455 to 3950 m depth were assessed quantitatively. Counts of the manatee grass Syringodium filiforme ( ca. 5 to 100 blades m -2) contrasted sharply with those of the turtle grass Thalassia testudinum ( ca. 0.1 to 2.0 blades m -2), reflecting an abundance proportional to previously reported export rates of the same species from Tague Bay, a nearby shallow source lagoon. Of the macrofaunal consumers that could potentially utilize this detrital nutrient source, three species of holothurians ( Mesothuria verrilli, Psychropotes semperiana, and Benthodytes linqua) and two species of sea urchins ( Hygrosoma petersi and Salencidaris profundi) were collected and/or observed. Gut content analyses revealed that all three holothurians deposit-feed on sediment and at least one species of sea urchin ( H. petersi) feeds almost exclusively on Syringodium. Carbon: nitrogen analyses of naturally occurring abyssal Thalassia detritus showed very low nitrogen content (0.21% N) and a high C:N ratio (214.8), thus yielding a loo nutritional value. Fresh Thalassia blades held in a litter bag experiment (by R. D. Turner) at 3950 m changed little in nitrogen content and C:N ratio after four years. A comparison was made of the stable carbon isotope ratios of 13C: 12C for abyssal seagrass detritus and other potential carbon sources with those for tissues from the holothurian and urchin consumers. The results indicate that a significant proportion of the nutrition of both groups is derived from detrital seagrasses either by direct consumption (sea urchins) or indirectly by deposit-feeding on sediments enriched by decomposed seagrasses (holothurians).

Parallel ecological networks in ecosystems

PubMed Central

Olff, Han; Alonso, David; Berg, Matty P.; Eriksson, B. Klemens; Loreau, Michel; Piersma, Theunis; Rooney, Neil

2009-01-01

In ecosystems, species interact with other species directly and through abiotic factors in multiple ways, often forming complex networks of various types of ecological interaction. Out of this suite of interactions, predator–prey interactions have received most attention. The resulting food webs, however, will always operate simultaneously with networks based on other types of ecological interaction, such as through the activities of ecosystem engineers or mutualistic interactions. Little is known about how to classify, organize and quantify these other ecological networks and their mutual interplay. The aim of this paper is to provide new and testable ideas on how to understand and model ecosystems in which many different types of ecological interaction operate simultaneously. We approach this problem by first identifying six main types of interaction that operate within ecosystems, of which food web interactions are one. Then, we propose that food webs are structured among two main axes of organization: a vertical (classic) axis representing trophic position and a new horizontal ‘ecological stoichiometry’ axis representing decreasing palatability of plant parts and detritus for herbivores and detrivores and slower turnover times. The usefulness of these new ideas is then explored with three very different ecosystems as test cases: temperate intertidal mudflats; temperate short grass prairie; and tropical savannah. PMID:19451126

The Little School Pond

ERIC Educational Resources Information Center

Rawitscher-Kunkel, Erika

1973-01-01

A small pond in a schoolyard provided year-round biological activities for children. As seasons changed, concepts and life relations also changed. Besides microscopic organisms in water, children learned about microscopic algae, detritus, and food chains. Concepts of predator-prey relationships and of ecosystems were successfully developed. (PS)

Afrofuturism/Chicanafuturism: Fictive Kin

ERIC Educational Resources Information Center

Ramirez, Catherine S.

2008-01-01

The concept of Chicanafuturism, which the author introduced in "Aztlan" in 2004, borrows from theories of Afrofuturism. Chicanafuturism explores the ways that new and everyday technologies, including their detritus, transform Mexican American life and culture. It questions the promises of science, technology, and humanism for Chicanas, Chicanos,…

Efficiency promotion and its mechanisms of simultaneous nitrogen and phosphorus removal in stormwater biofilters.

PubMed

Zhou, Zijun; Xu, Peng; Cao, Xiuyun; Zhou, Yiyong; Song, Chunlei

2016-10-01

Stromwater biofilter technology was greatly improved through adding iron-rich soil, plant detritus and eutrophic lake sediment. Significant ammonium and phosphate removal efficiencies (over 95%) in treatments with iron-rich soil were attributed to strong adsorption capability resulting in high available phosphorus (P) in media, supporting the abundance and activity of nitrifiers and denitrifiers as well as shaping compositions, which facilitated nitrogen (N) removal. Aquatic and terrestrial plant detritus was more beneficial to nitrification and denitrification by stimulating the abundance and activity of nitrifiers and denitrifiers respectively, which increased total nitrogen (TN) removal efficiencies by 17.6% and 22.5%. In addition, bioaugmentation of nitrifiers and denitrifiers from eutrophic sediment was helpful to nutrient removal. Above all, combined application of these materials could reach simultaneously maximum effects (removal efficiencies of P, ammonium and TN were 97-99%, 95-97% and 60-63% respectively), suggesting reasonable selection of materials has important contribution and application prospect in stormwater biofilters. Copyright © 2016 Elsevier Ltd. All rights reserved.

Total selenium and selenium species in irrigation drain inflows to the Salton Sea, California, April and July 2007

USGS Publications Warehouse

May, Thomas W.; Walther, Michael J.; Saiki, Michael K.; Brumbaugh, William G.

2007-01-01

This report presents the results for two sampling periods during a 4-year monitoring survey to provide a characterization of selenium concentrations in selected irrigation drains flowing into the Salton Sea, California. Total selenium, selenium species, and total suspended solids were determined in water samples, and total selenium was determined in sediment, detritus, and biota that included algae, plankton, midge larvae (family, Chironomidae), and two fish species-western mosquitofish (Gambusia affinis), and sailfin molly (Poecilia latipinna). In addition, sediments were analyzed for percent total organic carbon and particle size. Total selenium concentrations in water for both sampling periods ranged from 1.43 to 47.1 micrograms per liter, predominately as selenate, which is typical of waters leached out of selenium-contaminated marine shales under alkaline and oxidizing conditions. Total selenium concentrations ranged from 0.88 to 20.2 micrograms per gram in biota, and from 0.15 to 28.9 micrograms per gram in detritus and sediment.

Antarctic ice-rafted detritus (IRD) in the South Atlantic: Indicators of iceshelf dynamics or ocean surface conditions?

USGS Publications Warehouse

Nielsen, Simon H.H.; Hodell, D.A.

2007-01-01

Ocean sediment core TN057-13PC4/ODP1094, from the Atlantic sector of the Southern Ocean, contains elevated lithogenic material in sections representing the last glacial period compared to the Holocene. This ice-rafted detritus is mainly comprised of volcanic glass and ash, but has a significant input of what was previously interpreted as quartz during peak intervals (Kanfoush et al., 2000, 2002). Our analysis of these clear mineral grains indicates that most are plagioclase, and that South Sandwich Islands is the predominant source, similar to that inferred for the volcanic glass (Nielsen et al., in review). In addition, quartz and feldspar with possible Antarctic origin occur in conjunction with postulated episodes of Antarctic deglaciation. We conclude that while sea ice was the dominant ice rafting agent in the Polar Frontal Zone of the South Atlantic during the last glacial period, the Holocene IRD variability may reflect Antarctic ice sheet dynamics.

Contaminants assessment in the coral reefs of Virgin Islands National Park and Virgin Islands Coral Reef National Monument

USGS Publications Warehouse

Bargar, Timothy A.; Garrison, Virginia H.; Alvarez, David A.; Echols, Kathy

2013-01-01

Coral, fish, plankton, and detritus samples were collected from coral reefs in Virgin Islands National Park (VIIS) and Virgin Islands Coral Reef National Monument (VICR) to assess existing contamination levels. Passive water sampling using polar organic chemical integrative samplers (POCIS) and semi-permeable membrane devices found a few emerging pollutants of concern (DEET and galaxolide) and polynuclear aromatic hydrocarbons. Very little persistent organic chemical contamination was detected in the tissue or detritus samples. Detected contaminants were at concentrations below those reported to be harmful to aquatic organisms. Extracts from the POCIS were subjected to the yeast estrogen screen (YES) to assess potential estrogenicity of the contaminant mixture. Results of the YES (estrogen equivalency of 0.17–0.31 ng/L 17-β-estradiol) indicated a low estrogenicity likelihood for contaminants extracted from water. Findings point to low levels of polar and non-polar organic contaminants in the bays sampled within VICR and VIIS.

40 CFR 63.7555 - What records must I keep?

Code of Federal Regulations, 2013 CFR

2013-07-01

.... (11) You must maintain records of the type(s) and amount(s) of fuels used during each startup and... the type(s) and amount(s) of fuels used during each startup and shutdown. [76 FR 15664, Mar. 21, 2011... type(s) of fuel and amount(s) used. (2) If you combust non-hazardous secondary materials that have been...

40 CFR 63.7555 - What records must I keep?

Code of Federal Regulations, 2014 CFR

2014-07-01

.... (11) You must maintain records of the type(s) and amount(s) of fuels used during each startup and... the type(s) and amount(s) of fuels used during each startup and shutdown. [76 FR 15664, Mar. 21, 2011... type(s) of fuel and amount(s) used. (2) If you combust non-hazardous secondary materials that have been...

Experimental reductions in stream flow alter litter processing and consumer subsidies in headwater streams

Treesearch

Robert M. Northington; Jackson R. Webster

2017-01-01

SummaryForested headwater streams are connected to their surrounding catchments by a reliance on terrestrial subsidies. Changes in precipitation patterns and stream flow represent a potential disruption in stream ecosystem function, as the delivery of terrestrial detritus to aquatic consumers and...

LARVAL SALAMANDER GROWTH RESPONDS TO ENRICHMENT OF A NUTRIENT POOR HEADWATER STREAM

EPA Science Inventory

While many studies have measured effects of nutrient enrichment on higher trophic levels in grazing food webs, few such studies exist for detritus-based systems. We measured effects of nitrogen and phosphorus addition on growth of larval Eruycea wilderae in a heterotrophic head...

MICROBIAL COMMUNITY DIVERSITY AND CARBON UTILIZATION IN ESTUARINE ECOSYSTEMS OF SOUTHEASTERN U.S.A.

EPA Science Inventory

Estuaries are very dynamic ecosystems with regard to the transport and transformation of organic matter. Detrital organic matter is abundant in most estuaries, however, the dynamics of detritus utilization is not well understood. Two questions that remain unanswered are the sou...

Long-distance multistep sediment transfer at convergent plate margins (Barbados, Lesser Antilles)

NASA Astrophysics Data System (ADS)

Limonta, Mara; Garzanti, Eduardo; Resentini, Alberto; Andò, Sergio; Boni, Maria; Bechstädt, Thilo

2015-04-01

We present a regional provenance study of the compositional variability and long distance multicyclic transport of terrigenous sediments along the convergent and transform plate boundaries of Central America, from the northern termination of the Andes to the Lesser Antilles arc-trench system. We focus on high-resolution bulk-petrography and heavy-mineral analyses of modern beach and fluvial sediments and Cenozoic sandstones of Barbados island, one of the places in the world where an active accretionary prism is subaerially exposed (Speed et al., 2012). The main source of siliciclastic sediment in the Barbados accretionary prism is off-scraped quartzose to feldspatho-litho-quartzose metasedimentaclastic turbidites, ultimately supplied from South America chiefly via the Orinoco fluvio-deltaic system. Modern sand on Barbados island is either quartzose with depleted heavy-mineral suites recycled from Cenozoic turbidites and including epidote, zircon, tourmaline, andalusite, garnet, staurolite and chloritoid, or calcareous and derived from Pleistocene coral reefs. The ubiquitous occurrence of clinopyroxene and hypersthene, associated with green-brown kaersutitic hornblende in the north or olivine in the south, points to reworking of ash-fall tephra erupted from andesitic (St. Lucia) and basaltic (St. Vincent) volcanic centers in the Lesser Antilles arc transported by the prevailing anti-trade winds in the upper troposphere. Modern sediments on Barbados island and those shed by other accretionary prisms such as the Indo- Burman Ranges and Andaman-Nicobar Ridge (Garzanti et al., 2013) define the distinctive mineralogical signature of Subduction Complex Provenance, which is invariably composite. Detritus recycled dominantly from accreted turbidites and oceanic mudrocks is mixed in various proportions with detritus from the adjacent volcanic arc or carbonate reefs widely developed at tropical latitudes. Ophiolitic detritus may be locally prominent. Quantitative provenance analysis is a basic tool in paleogeographic reconstructions when multicyclic sediment dispersal along and across convergent plate margins occur. Such analysis provides the link between faraway factories of detritus and depositional sinks, as well as clues on subduction geometry and the nature of associated growing orogenic belts, and even information on climate, atmospheric circulation and weathering intensity in source regions. REFERENCES Garzanti, E., Limonta, M., Resentini, A., Bandopadhyay, P.C., Najman, Y., Andò, S., Vezzoli, G., 2013. Sediment recycling at convergent plate margins (Indo-Burman Ranges and Andaman-Nicobar Ridge). Earth Sci. Rev., 123, 113-132. Speed, C. and Sedlock, R. 2012. Geology and geomorphology of Barbados. Geol. Soc. Am. Spec. Pap., 491, 63 p.

Is the diet of a typical shredder related to the physical habitat of headwater streams in the Brazilian Cerrado?

EPA Science Inventory

Macroinvertebrates are important for processing leaf detritus in temperate streams, but studies about their role in tropical streams are scarce and often present conflicting results. We assessed the diet of Phylloicus (Trichoptera: Calamoceratidae) larvae, that is generally class...

Soil Fungi and Macrofauna in the Neotropics

Treesearch

Yiqing Li; Grizelle Gonzalez

2008-01-01

Decomposition is a critical ecosystem function that decomposes dead organic materials, removes wastes, recycles nutrients and renews soils fertility. In natural ecosystems most nitrogen (N) and phosphorus (P) required for plant growth are supplied through the decomposition of detritus, relying therefore on the activities of soil microbes and microfauna. Decomposition...

How do nutrients affect Aedes aegypti and Zika infection in neighborhoods in San Juan, Puerto Rico?

EPA Science Inventory

Inputs of detritus have been shown to be strong drivers of container mosquito production and life history traits, including for species that are of medical importance. During 2016, Zika infection swelled throughout the Caribbean and South and Central America, a disease vectored p...

EFFECTS OF STREAM RESTORATION ON GROUND WATER NITRATE AT MINEBANK RUN, AN URBAN STREAM IN THE CHESAPEAKE BAY WATERSHED

EPA Science Inventory

Elevated nitrate levels in streams and ground water pose human and ecological threats. Microbial denitrification removes nitrate from ground water but requires anaerobic (saturated) conditions and adequate supply of dissolved organic carbon from detritus and organic soils. Con...

Decomposition of terrestrial resource subsidies in headwater streams: Does consumer diversity matter?

Treesearch

David Stoker; Amber J. Falkner; Kelly M. Murray; Ashley K. Lang; Thomas R. Barnum; Jeffrey Hepinstall-Cymerman; Michael J. Conroy; Robert J. Cooper; Catherine M. Pringle

2017-01-01

Resource subsidies and biodiversity are essential for maintaining community structure and ecosystem functioning, but the relative importance of consumer diversity and resource characteristics to decomposition remains unclear. Forested headwater streams are detritus-based systems, dependent on leaf litter inputs from adjacent riparian ecosystems, and...

Microbial incorporation of nitrogen in stream detritus

Treesearch

Diane M. Sanzone; Jennifer L. Tank; Judy L. Meyer; Patrick J. Mulholland; Stuart E.G. Findlay

2001-01-01

We adapted the chloroform fumigation method to determine microbial nitrogen (N) and microbial incorporation of 15N on three common substrates [leaves, wood and fine benthic organic matter (FBOM)] in three forest streams. We compared microbial N and 15 content of samples collected during a 6-week15N-NH...

ROLE OF SEAGRASS (THALASSIA TESTUDINUM) AS A SOURCE OF CHROMOPHORIC DISSOLVED ORGANIC MATTER IN COASTAL SOUTH FLORIDA

EPA Science Inventory

Seagrasses play a variety of important ecological roles in coastal ecosystems. Here we present evidence that seagrass detritus from the widespread species, Thalassia testudinum, is an important source of ocean color and UV-protective substances in a low latitude coastal shelf re...

EFFECT OF A WHOLE-CATCHMENT N ADDITION ON STREAM DETRITUS PROCESSING

EPA Science Inventory

The Bear Brook Watershed in Maine (BBWM) is a paired catchment study investigating ecosystem effects of N and S deposition. Because of the decade long (NH4)2SO4 addition, the treatment catchment has higher stream NO3 and enriched foliar N concentrations compared to the reference ...

Decadal changes in potassium, calcium, and magnesium in a deciduous forest soil.

Treesearch

D.W. Johnson; D.E. Todd; Carl C. Trettin; P.J. Mulholland

2009-01-01

Decadal changes in soil exchangeable K+, Ca2+, and Mg2+ concentrations and contents from 1972 to 2004 in eight intensively monitored plots on Walker Branch Watershed were compared with estimates of increments or decrements in vegetation and detritus. The results from these eight plots...

Tidal Prism Modeling of Phytoplankton and Nitrogen Concentrations in Narragansett Bay and its Sub-Embayments

EPA Science Inventory

A tidal prism model was developed to calculate temporal changes in the spatially averaged concentration of three state variables: phytoplankton, dissolved inorganic nitrogen, and detritus. Our main objective was to develop a model to help us understand the causes of phytoplankton...

DETRITUS PROCESSING AND MINERAL CYCLING IN SEAGRASS 'ZOSTERA' LITTER IN AN OREGON SALT MARSH

EPA Science Inventory

In estuaries where seagrass beds adjoin marshes, the import and decomposition of seagrass litter in the marsh provide a mechanism for retaining nutrients within the wetlands and preventing loss to adjacent oceanic waters. Several aspects of the influence of seagrass litter on an ...

Forest Management Intensity Affects Aquatic Communities in Artificial Tree Holes.

PubMed

Petermann, Jana S; Rohland, Anja; Sichardt, Nora; Lade, Peggy; Guidetti, Brenda; Weisser, Wolfgang W; Gossner, Martin M

2016-01-01

Forest management could potentially affect organisms in all forest habitats. However, aquatic communities in water-filled tree-holes may be especially sensitive because of small population sizes, the risk of drought and potential dispersal limitation. We set up artificial tree holes in forest stands subject to different management intensities in two regions in Germany and assessed the influence of local environmental properties (tree-hole opening type, tree diameter, water volume and water temperature) as well as regional drivers (forest management intensity, tree-hole density) on tree-hole insect communities (not considering other organisms such as nematodes or rotifers), detritus content, oxygen and nutrient concentrations. In addition, we compared data from artificial tree holes with data from natural tree holes in the same area to evaluate the methodological approach of using tree-hole analogues. We found that forest management had strong effects on communities in artificial tree holes in both regions and across the season. Abundance and species richness declined, community composition shifted and detritus content declined with increasing forest management intensity. Environmental variables, such as tree-hole density and tree diameter partly explained these changes. However, dispersal limitation, indicated by effects of tree-hole density, generally showed rather weak impacts on communities. Artificial tree holes had higher water temperatures (on average 2°C higher) and oxygen concentrations (on average 25% higher) than natural tree holes. The abundance of organisms was higher but species richness was lower in artificial tree holes. Community composition differed between artificial and natural tree holes. Negative management effects were detectable in both tree-hole systems, despite their abiotic and biotic differences. Our results indicate that forest management has substantial and pervasive effects on tree-hole communities and may alter their structure and functioning. We furthermore conclude that artificial tree-hole analogues represent a useful experimental alternative to test effects of changes in forest management on natural communities.

Forest Management Intensity Affects Aquatic Communities in Artificial Tree Holes

PubMed Central

Petermann, Jana S.; Rohland, Anja; Sichardt, Nora; Lade, Peggy; Guidetti, Brenda; Weisser, Wolfgang W.; Gossner, Martin M.

2016-01-01

Forest management could potentially affect organisms in all forest habitats. However, aquatic communities in water-filled tree-holes may be especially sensitive because of small population sizes, the risk of drought and potential dispersal limitation. We set up artificial tree holes in forest stands subject to different management intensities in two regions in Germany and assessed the influence of local environmental properties (tree-hole opening type, tree diameter, water volume and water temperature) as well as regional drivers (forest management intensity, tree-hole density) on tree-hole insect communities (not considering other organisms such as nematodes or rotifers), detritus content, oxygen and nutrient concentrations. In addition, we compared data from artificial tree holes with data from natural tree holes in the same area to evaluate the methodological approach of using tree-hole analogues. We found that forest management had strong effects on communities in artificial tree holes in both regions and across the season. Abundance and species richness declined, community composition shifted and detritus content declined with increasing forest management intensity. Environmental variables, such as tree-hole density and tree diameter partly explained these changes. However, dispersal limitation, indicated by effects of tree-hole density, generally showed rather weak impacts on communities. Artificial tree holes had higher water temperatures (on average 2°C higher) and oxygen concentrations (on average 25% higher) than natural tree holes. The abundance of organisms was higher but species richness was lower in artificial tree holes. Community composition differed between artificial and natural tree holes. Negative management effects were detectable in both tree-hole systems, despite their abiotic and biotic differences. Our results indicate that forest management has substantial and pervasive effects on tree-hole communities and may alter their structure and functioning. We furthermore conclude that artificial tree-hole analogues represent a useful experimental alternative to test effects of changes in forest management on natural communities. PMID:27187741

Net primary productivity, allocation pattern and carbon use efficiency in an apple orchard assessed by integrating eddy covariance, biometric and continuous soil chamber measurements

NASA Astrophysics Data System (ADS)

Zanotelli, D.; Montagnani, L.; Manca, G.; Tagliavini, M.

2013-05-01

Carbon use efficiency (CUE), the ratio of net primary production (NPP) over gross primary production (GPP), is a functional parameter that could possibly link the current increasingly accurate global GPP estimates with those of net ecosystem exchange, for which global predictors are still unavailable. Nevertheless, CUE estimates are actually available for only a few ecosystem types, while information regarding agro-ecosystems is scarce, in spite of the simplified spatial structure of these ecosystems that facilitates studies on allocation patterns and temporal growth dynamics. We combined three largely deployed methods, eddy covariance, soil respiration and biometric measurements, to assess monthly values of CUE, NPP and allocation patterns in different plant organs in an apple orchard during a complete year (2010). We applied a measurement protocol optimized for quantifying monthly values of carbon fluxes in this ecosystem type, which allows for a cross check between estimates obtained from different methods. We also attributed NPP components to standing biomass increments, detritus cycle feeding and lateral exports. We found that in the apple orchard, both net ecosystem production and gross primary production on a yearly basis, 380 ± 30 g C m-2 and 1263 ± 189 g C m-2 respectively, were of a magnitude comparable to those of natural forests growing in similar climate conditions. The largest differences with respect to forests are in the allocation pattern and in the fate of produced biomass. The carbon sequestered from the atmosphere was largely allocated to production of fruit: 49% of annual NPP was taken away from the ecosystem through apple production. Organic material (leaves, fine root litter, pruned wood and early fruit falls) contributing to the detritus cycle was 46% of the NPP. Only 5% was attributable to standing biomass increment, while this NPP component is generally the largest in forests. The CUE, with an annual average of 0.71 ± 0.12, was higher than the previously suggested constant values of 0.47-0.50. Low nitrogen investment in fruit, the limited root apparatus, and the optimal growth temperature and nutritional condition observed at the site are suggested to be explanatory variables for the high CUE observed.

Trophic flows, kelp culture and fisheries in the marine ecosystem of an artificial reef zone in the Yellow Sea

NASA Astrophysics Data System (ADS)

Wu, Zhongxin; Zhang, Xiumei; Lozano-Montes, Hector M.; Loneragan, Neil R.

2016-12-01

This study evaluates the ecosystem structure and function of the nearshore reefs in the Lidao coastal ecosystem of northern China, a region of intensive kelp aquaculture, and fisheries enhancements, including the deployment of artificial reefs and release of cultured marine species. An Ecopath model, with 20 functional groups representing 81 species, was developed for a representative area in the region and Ecosim was used to explore two scenarios for alternative fishing practices and surrounding aquaculture activities. The mean trophic levels (TLs) of the functional groups ranged from 1.0 for the primary producers (phytoplankton, benthic algae and seagrass) and detritus to 4.14 for Type III fishes (fishes found in the water column above the artificial reefs, e.g., Scomberomorus niphonius). The mean transfer efficiency through the whole system was 11.7%, and the ecosystem had a relative low maturity, stability and disturbance resistance, indicating that it was at a developing stage. Nearly half of the total system biomass (48.9% of 620.20 t km-2 year-1), excluding detritus, was comprised of benthic finfish and invertebrates. The total yield from all fisheries (86.82 t/km2/year) was dominated by low trophic level herbivorous and detritivorous species, such as the sea cucumber Apostichopus japonicus (TL = 2.1, 46.07%), other echinoderms (sea urchins Asterias amurensis and Strongylocentrotus nudus, TL = 2.1, 34.6%) and abalone Haliotis discus hannai (TL = 2.0, 18.4%), and as a consequence, the mean TL of the catch was low (2.1). The results from the Ecosim simulation of closing all fisheries for 20 years predicted an increase of about 100% in the relative biomass of the main exploited species, A. japonicus and H. discus hannai. The simulated removal of all kelp farms over 10 years resulted in a two fold increase in the relative biomass of Type III fishes and a 120% increase in their main prey (i.e. Small pelagic fish), while the relative biomass of A. japonicus and Heterotrophic bacteria decreased by 31.4% and 12.7%, respectively. These predictions indicate that nearshore kelp cultivation favours benthic, rather than water column production, and is likely to be providing energy subsidies for the stock enhancement of benthic species in this region.

Phytoplankton competition and coexistence: Intrinsic ecosystem dynamics and impact of vertical mixing

NASA Astrophysics Data System (ADS)

Perruche, Coralie; Rivière, Pascal; Pondaven, Philippe; Carton, Xavier

2010-04-01

This paper aims at studying analytically the functioning of a very simple ecosystem model with two phytoplankton species. First, using the dynamical system theory, we determine its nonlinear equilibria, their stability and characteristic timescales with a focus on phytoplankton competition. Particular attention is paid to the model sensitivity to parameter change. Then, the influence of vertical mixing and sinking of detritus on the vertically-distributed ecosystem model is investigated. The analytical results reveal a high diversity of ecosystem structures with fixed points and limit cycles that are mainly sensitive to variations of light intensity and total amount of nitrogen matter. The sensitivity to other parameters such as re-mineralisation, growth and grazing rates is also specified. Besides, the equilibrium analysis shows a complete segregation of the two phytoplankton species in the whole parameter space. The embedding of our ecosystem model into a one-dimensional numerical model with diffusion turns out to allow coexistence between phytoplankton species, providing a possible solution to the 'paradox of plankton' in the sense that it prevents the competitive exclusion of one phytoplankton species. These results improve our knowledge of the factors that control the structure and functioning of plankton communities.

Stream nutrient enrichment has a greater effect on coarse than on fine benthic organic matter

Treesearch

Cynthia J. Tant; Amy D. Rosemond; Matthew R. First

2013-01-01

Nutrient enrichment affects bacteria and fungi associated with detritus, but little is known about how biota associated with different size fractions of organic matter respond to nutrients. Bacteria dominate on fine (1 mm) fractions, which are used by different groups of detritivores. We measured the effect of experimental...

Construction of sediment budgets for drainage basins

Treesearch

William E. Dietrich; Thomas Dunne; Neil F. Humphrey; Leslie M. Reid

1982-01-01

Abstract - A sediment budget for a drainage basin is a quantitative statement of the rates of production, transport, and discharge of detritus. To construct a sediment budget for a drainage basin, one must integrate the temporal and spatial variations of transport and storage processes. This requires: recognition and quantification of transport processes, recognition...

Statistical Analysis of Geomorphic, Petrographic and Structural Characteristics of the Dartmoor Tors, Southwest England

DTIC Science & Technology

1993-05-01

slightly warmer than that of today, followed by periglacial removal of the weathered debris (Linton, 1955). The Dartmoor granite, which covers...and the distribution of its detritus in the sediments of southern England. Quarterly Journal of the Geological Society of London, vol. 87, pp. 62-96

EFFECTS OF CHRONIC LIGHT REDUCTION ON THALASSIA TESTUDINUM AT STATIONS ACROSS THE GULF OF MEXICO

EPA Science Inventory

For several decades, the role and importance of seagrasses as habitat and as a trophic source, whether grazed directly, consumed as detritus, or acting as a means of support for epiphytic algae, has been increasingly well-documented in the coastal zones of the world. However, the...

DEVELOP AND TEST METHODS FOR CHARACTERIZING THE EXPOSURE AND RESPONSE OF SENSITIVE ECOSYSTEM COMPONENTS TO NUTRIENT STRESS USING BIOMONITORS AND STABLE ISOTOPIC RATIOS

EPA Science Inventory

Bivalves filter suspended phytoplankton, detritus and bacteria from the water column. During feeding contaminants associated with these suspended materials or dissolved in the water are ingested and potentially bioaccumulated in both soft tissue and shell matrix. Consequently biv...

Elucidating the nutritional dynamics of fungi using stable isotopes

Treesearch

Jordan R. Mayor; Edward A.G. Schuur; Terry W. Henkel

2009-01-01

Mycorrhizal and saprotrophic (SAP) fungi are essential to terrestrial element cycling due to their uptake of mineral nutrients and decomposition of detritus. Linking these ecological roles to specific fungi is necessary to improve our understanding of global nutrient cycling, fungal ecophysiology, and forest ecology. Using discriminant analyses of nitrogen and carbon...

Convergence of detrital stoichiometry predicts thresholds of nutrient-stimulated breakdown in streams

Treesearch

David W. P. Manning; Amy D. Rosemond; Vladislav Gulis; Jonathan P. Benstead; John S. Kominoski; John C. Maerz

2016-01-01

Nutrient enrichment of detritus-based streams increases detrital resource quality for consumers and stimulates breakdown rates of particulate organic carbon (C). The relative importance of dissolved inorganic nitrogen (N) vs. phosphorus (P) for detrital quality and their effects on microbial- vs. detritivore-mediated detrital breakdown are poorly understood....

Interdisciplinary Modeling and Dynamics of Archipelago Straits

DTIC Science & Technology

2009-01-01

modeling, tidal modeling and multi-dynamics nested domains and non-hydrostatic modeling WORK COMPLETED Realistic Multiscale Simulations, Real-time...six state variables (chlorophyll, nitrate , ammonium, detritus, phytoplankton, and zooplankton) were needed to initialize simulations. Using biological...parameters from literature, climatology from World Ocean Atlas data for nitrate and chlorophyll profiles extracted from satellite data, a first

Reduced detrital resources limit Pycnopsyche gentilis (Trichoptera: Limnephilidae) production and growth

Treesearch

Susan L. Eggert; J. Bruce Wallace

2003-01-01

Leaf inputs in temperate forest streams may limit caddisfly production because leaf detritus serves both as a food and case-material resource. We estimated Pycnopsyche gentilis produdion in a stream experimentally decoupled fmm its riparian habitat and a reference stream for 8 y in the southern Appalachians. We also examined laboratory survivorship,...

Nutrient enrichment reduces constraints on material flows in a detritus-based food web

Treesearch

Wyatt F. Cross; Bruce Wallace; Amy D. Rosemond

2007-01-01

Most aquatic and terrestrial ecosystems are experiencing increased nutrient availability, which is affecting their structure and function. By altering community composition and productivity of consumers, enrichment can indirectly cause changes in the pathways and magnitude of material flows in food webs. These changes, in turn, have major consequences for material...

Building a Bridge to Cross a Thousand Years

ERIC Educational Resources Information Center

Lippert, Dorothy

2006-01-01

The practice of archaeology includes of a series of events in which a group of objects is transformed from their initial identities as household goods, religious objects, or detritus of everyday life into artifacts, or as the 1906 Antiquities Act describes them, "objects of antiquity." Frequently, artifacts are further re-identified as part of a…

Spider foraging strategy affects trophic cascades under natural and drought conditions.

PubMed

Liu, Shengjie; Chen, Jin; Gan, Wenjin; Schaefer, Douglas; Gan, Jianmin; Yang, Xiaodong

2015-07-23

Spiders can cause trophic cascades affecting litter decomposition rates. However, it remains unclear how spiders with different foraging strategies influence faunal communities, or present cascading effects on decomposition. Furthermore, increased dry periods predicted in future climates will likely have important consequences for trophic interactions in detritus-based food webs. We investigated independent and interactive effects of spider predation and drought on litter decomposition in a tropical forest floor. We manipulated densities of dominant spiders with actively hunting or sit-and-wait foraging strategies in microcosms which mimicked the tropical-forest floor. We found a positive trophic cascade on litter decomposition was triggered by actively hunting spiders under ambient rainfall, but sit-and-wait spiders did not cause this. The drought treatment reversed the effect of actively hunting spiders on litter decomposition. Under drought conditions, we observed negative trophic cascade effects on litter decomposition in all three spider treatments. Thus, reduced rainfall can alter predator-induced indirect effects on lower trophic levels and ecosystem processes, and is an example of how such changes may alter trophic cascades in detritus-based webs of tropical forests.

Spider foraging strategy affects trophic cascades under natural and drought conditions

PubMed Central

Liu, Shengjie; Chen, Jin; Gan, Wenjin; Schaefer, Douglas; Gan, Jianmin; Yang, Xiaodong

2015-01-01

Spiders can cause trophic cascades affecting litter decomposition rates. However, it remains unclear how spiders with different foraging strategies influence faunal communities, or present cascading effects on decomposition. Furthermore, increased dry periods predicted in future climates will likely have important consequences for trophic interactions in detritus-based food webs. We investigated independent and interactive effects of spider predation and drought on litter decomposition in a tropical forest floor. We manipulated densities of dominant spiders with actively hunting or sit-and-wait foraging strategies in microcosms which mimicked the tropical-forest floor. We found a positive trophic cascade on litter decomposition was triggered by actively hunting spiders under ambient rainfall, but sit-and-wait spiders did not cause this. The drought treatment reversed the effect of actively hunting spiders on litter decomposition. Under drought conditions, we observed negative trophic cascade effects on litter decomposition in all three spider treatments. Thus, reduced rainfall can alter predator-induced indirect effects on lower trophic levels and ecosystem processes, and is an example of how such changes may alter trophic cascades in detritus-based webs of tropical forests. PMID:26202370

A numerical study on the seasonal variability of polychlorinated biphenyls from the atmosphere in the East China Sea.

PubMed

Ono, Jun; Takahashi, Daisuke; Guo, Xinyu; Takahashi, Shin; Takeoka, Hidetaka

2012-10-01

A three-dimensional/high-resolution transport model for persistent organic pollutants (POPs) has been developed for the East China Sea (ECS). The POPs model has four compartments (gaseous, dissolved, phytoplankton-bound, and detritus-bound phases) and includes processes for diffusive air-water exchange, phytoplankton uptake/depuration to POPs, decomposition of dissolved phase, vertical sinking of phytoplankton, detritus production by phytoplankton mortality, and vertical sinking and decomposition of detritus. The POPs model is coupled with an ocean circulation model that can reproduce the seasonal variation in physical variables to represent the advection and diffusion of POPs. We applied the POPs model to the polychlorinated biphenyl congener 153 (PCB 153) from the atmosphere and examined the behavior of PCB 153 in the ocean. The model showed a remarkable seasonal variability of PCB 153. Concentrations in the dissolved and particulate phases are high in winter (January-March) and low in summer (July-September). In coastal regions, where chlorophyll a concentration is high, horizontal and vertical distributions in the dissolved and particulate PCB 153 concentrations are strongly affected by phytoplankton uptake. The sensitivity experiments on the dynamics of PCB 153 suggested that a change of Henry's law constant associated with water temperature is the major factor controlling the seasonal variability of PCB 153. The model-based yearly mass balance of PCB 153 in the ECS indicated that most of the atmospheric input (35.5 kg year(-1)) is removed by the horizontal advection outside the ECS (19.0 kg year(-1)) and accumulates to the sea bottom by vertical sinking (15.7 kg year(-1)). For comparison with PCB 153, we also conducted simulations for PCB 52, 101, and 180. The seasonal variations are similar to that of PCB 153. The mass balance of PCB 52 that has short half-life time and less hydrophobic property shows the different results compared with PCB 101, 153, and 180. Copyright © 2012 Elsevier Ltd. All rights reserved.

Microbial Preservation in Sulfates in the Haughton Impact Structure Suggests Target in Search for Life on Mars

NASA Technical Reports Server (NTRS)

Parnell, J.; Osinski, G. R.; Lee, P.; Cockell, C. S.

2005-01-01

Microbes in Haughton Crater Sulfates: Impact craters are of high interest in planetary exploration because they are viewed as possible sites for evidence of life [1]. Hydrothermal systems in craters are particularly regarded as sites where primitive life could evolve. Evidence from the Miocene Haughton impact structure shows that crater hydrothermal deposits may also be a preferred site for subsequent colonization and hence possible extant life: Hydrothermal sulfates at Haughton are colonized by viable cyanobacteria [2]. The Haughton impact structure, Devon Island, Canadian High Arctic, is a 24 km-diameter crater of mid-Tertiary age. The structure preserves an exceptional record of impact-induced hydrothermal activity, including sulfide, and sulfate mineralization [3]. The target rocks excavated at the site included massive gypsum-bearing carbonate rocks of Ordovician age. Impact-remobilized sulfates occur as metre-scale masses of intergrown crystals of the clear form of gypsum selenite in veins and cavity fillings within the crater s impact melt breccia deposits [4]. The selenite is part of the hydrothermal assemblage as it was precipitated by cooling hot waters that were circulating as a result of the impact. Remobilization of the sulfate continues to the present day, such that it occurs in soil crusts (Fig. 1) including sandy beds with a gypsum cement. The sulfate-cemented beds make an interesting comparison with the sulfate-bearing sandy beds encountered by the Opportunity MER [5]. The selenite crystals are up to 0.3 m in width, of high purity, and transparent. They locally exhibit frayed margins where cleavage surfaces have separated. This exfoliation may be a response to freeze-thaw weathering. The selenite contains traces of rock detritus, newly precipitated gypsum, and microbial colonies. The rock detritus consists of sediment particles which penetrated the opened cleavages by up to 2cm from the crystal margins. Some of the detritus is cemented into place by gypsum, which must have been dissolved and reprecipitated from the host selenite.

Towards Integrated Multi-Trophic Aquaculture: Lessons from Caprellids (Crustacea: Amphipoda)

PubMed Central

Hachero-Cruzado, Ismael; González-Romero, Pablo; Jiménez-Prada, Pablo; Cassell, Christopher; Ros, Macarena

2016-01-01

The search for alternative live feed organisms and the progression of Integrative Multi-Trophic Aquaculture (IMTA) are currently being highly prioritised in EU strategies. Caprellids could potentially be an important exploitable resource in aquaculture due to their high levels of beneficial polyunsaturated fatty acids, fast growing nature and widespread distribution. Furthermore, since they are mainly detritivorous, they could be excellent candidates for integration into IMTA systems, potentially benefitting from uneaten feed pellets and faeces released by cultured fish in fish farms and sea-cage structures. Despite this, there is a lack of experimental studies to: (i) test inexpensive diets for caprellids, such as detritus, (ii) develop sustainable caprellid culture techniques and (iii) include caprellids in IMTA systems. The main aim of this study was to determine whether detritus (D) in the form of fish faeces provided an adequate diet for caprellids in comparison to other traditional diets, such as Artemia nauplii (A) or phytoplankton (P). Adult survival rate was shown to be significantly higher for caprellids fed with D. Conversely, hatchlings had the highest survival rate with A, although the juvenile growth rate and number of moults was similar in the three diets. With regard to lipid composition, caprellids fed with A had higher concentrations of Triacylglycerols (TAG) and Phosphatidylcholine (PC) while those fed with P or D were richer in polyunsaturated fatty acids, especially 22:6(n-3) (DHA). Interestingly, caprellids fed with D were also a rich source of 18:2(n-6) (LA), considered to be an essential fatty acid in vertebrates. It was found that detritus based mainly on fish faeces and uneaten feed pellets can be considered an adequate feed for adult caprellids, providing a source of both omega-3 (DHA) and omega-6 (LA) fatty acids. Hatchlings however seem to require an additional input of TAG and PC during juvenile stages to properly grow. PMID:27124465

Enhanced Saharan dust input to the Levant during Heinrich stadials

NASA Astrophysics Data System (ADS)

Torfstein, Adi; Goldstein, Steven L.; Stein, Mordechai

2018-04-01

The history of dust transport to the Levant during the last glacial period is reconstructed using the isotope ratios of Pb, Sr, Nd, and Hf in sediments of Lake Lisan, the last glacial Dead Sea. Exposed marginal sections of the Lisan Formation were sampled near Masada, the Perazim Valley and from a core drilled at the deep floor of the modern lake. Bulk samples and size fractions display unique isotopic fingerprints: the finest detritus fraction (<5 μm) displays higher 87Sr/86Sr and lower εNd values (0.710-0.713 and -7.0 to -9.8, respectively) relative to the coarser fractions (5-20 μm and <20 μm; 0.708-0.710 and -3.4 to -8.3) and the bulk detritus samples (0.709-0.711 and -6 to -7.5). Similarly, the 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios (18.26-19.02, 15.634-15.68, and 38.25-38.82, respectively) are systematically higher in the finest detritus fraction relative to corresponding coarser fractions and bulk samples. The 87Sr/86Sr and εNd values of the finest fraction correspond with those of atmospheric dust originating from the Sahara Desert, while those of the coarse fractions are similar to loess deposits exposed in the Sinai and Negev Deserts. Pronounced excursions in the Sr-Nd-Pb isotope ratios toward more Sahara-like values coincide with the Heinrich (H) stadials 6, 5 and 1, reflecting significant increases in Saharan dust fluxes during regionally arid intervals, reflected by sharp lake level drops. Moreover, during H6 the dust came from different Saharan sources than during H1 and H5. While the relatively wet glacial climate in the Levant suppressed the transport of dust to the lake watershed, short-term hyper-arid spells during H-stadial intervals were accompanied by enhanced supply of fine Sahara dust to this region.

Generation and fate of glacial sediments in the central Transantarctic Mountains based on radiogenic isotopes and implications for reconstructing past ice dynamics

NASA Astrophysics Data System (ADS)

Farmer, G. Lang; Licht, Kathy J.

2016-10-01

The Nd, Sr and Pb isotopic compositions of glacial tills from the Byrd and Nimrod Glaciers in the central Transantarctic Mountains (TAM) in East Antarctica were obtained to assess the sources of detritus transported by these ice masses. Tills from lateral moraines along the entire extent of both glaciers have isotopic compositions consistent with their derivation predominately from erosion of adjacent bedrock. Fine- (<63μ) and coarser-grained (0.5 mm-2 mm) sediment from these tills have identical isotopic characteristics, indicating that fine-grained detritus is the product of further comminution of coarser sediments. Comparison of present-day till isotopic data to existing data from fine-grained LGM tills in the central Ross Sea confirm that these were deposited from East Antarctic ice that expanded through the TAM and indicates that the LGM sediments are mixtures of detritus eroded along the entire path of ice transiting the TAM. If specific lithologies were preferentially eroded as ice passed through the TAM, it is not clearly evident in the Ross Sea till isotopic compositions. Our data do demonstrate, however, that glacial tills generated from erosion of inboard regions of the mountain belt yield sediment with a larger component of 560 Ma to 600 Ma detrital zircons and lower average εNd(0) values (<-5) than that produced further downstream. As a result, past retreat of ice grounding-lines up the narrow valleys of the TAM resulting in active erosion of inboard region should recognizable in glacial sediments deposited in the Ross Sea and so provide a means to identify times when the East Antarctic ice sheet was smaller than today. This study highlights both the value and necessity of utilizing multiple provenance methods in evaluating glacial erosion and transport when reconstructing past ice sheet dynamics.

The potential source of lead in the Permian Kupferschiefer bed of Europe and some selected Paleozoic mineral deposits in the Federal Republic of Germany

USGS Publications Warehouse

Wedepohl, K.H.; Delevaux, M.H.; Doe, B.R.

1978-01-01

New lead isotopic compositions have been measured for Paleozoic bedded and vein ore deposits of Europe by the high precision thermal emission (triple filament) technique. Eleven samples have been analyzed from the Upper Permian Kupferschiefer bed with representatives from Poland to England, three samples from the Middle Devonian Rammelsberg deposit and one from the Middle Devonian Meggen deposit, both of which are conformable ore lenses and are in the Federal Republic of Germany (FRG); and also two vein deposits from the FRG were analyzed, from Ramsbeck in Devonian host rocks and from Grund in Carboniferous host rocks. For Kupferschiefer bed samples from Germany, the mineralization is of variable lead isotopic composition and appears to have been derived about 250 m.y. ago from 1700 m.y. old sources, or detritus of this age, in Paleozoic sedimentary rocks. Samples from England, Holland, and Poland have different isotopic characteristics from the German samples, indicative of significantly different source material (perhaps older). The isotopic variability of the samples from the Kupferschiefer bed in Germany probably favors the lead containing waters coming from shoreward (where poor mixing is to be expected) rather than basinward (where better mixing is likely) directions. The data thus support the interpretation of the metal source already given by Wedepohl in 1964. Data on samples from Rammelsberg and Meggen tend to be slightly less radiogenic than for the Kupferschiefer, about the amount expected if the leads were all derived from the same source material but 100 to 150 m.y. apart in time. The vein galena from Ramsbeck is similar to that from Rammelsberg conformable ore lenses, both in rocks of Devonian age; vein galena from Grund in Upper Carboniferous country rocks is similar to some bedded Kupferschiefer mineralization in Permian rocks, as if the lead composition was formed at about the same time and from similar source material as the bedded deposits. Although heat has played a more significant role in the formation of some of these deposits (veins and Rammelsberg-Meggen) than in others (Kupferschiefer), there is no indication of radically different sources for the lead, all apparently coming from sedimentary source material containing Precambrian detritus. One feldspar lead sample from the Brocken-Oker Granite is not the same in isotopic composition as any of the ores analyzed. ?? 1978 Springer-Verlag.

The Bolivar Channel Ecosystem of the Galapagos Marine Reserve: Energy flow structure and role of keystone groups

NASA Astrophysics Data System (ADS)

Ruiz, Diego J.; Wolff, Matthias

2011-08-01

The Bolivar Channel Ecosystem (BCE) is among the most productive zones in the Galapagos Marine Reserve (GMR). It is exposed to relatively cool, nutrient-rich waters of the Cromwell current, which are brought to the photic zone through topographic upwelling. The BCE is characterized by a heterogeneous rocky reef habitat covered by dense algae beds and inhabited by numerous invertebrate and fish species, which represent the food for higher predators including seals and sharks and exploited fish species. In addition, plankton and detritus based food chains channel large amounts of energy through the complex food web. Important emblematic species of the Galapagos archipelagos reside in this area such as the flightless cormorant, the Galapagos penguin and the marine iguanas. A trophic model of BCE was constructed for the habitats < 30 m depth that fringe the west coast of Isabela and east coast of Fernandina islands covering 14% of the total BCE area (44 km 2). The model integrates data sets from sub tidal ecological monitoring and marine vertebrate population monitoring (2004 to 2008) programs of the Charles Darwin Foundation and consists of 30 compartments, which are trophically linked through a diet matrix. Results reveal that the BCE is a large system in terms of flows (38 695 t km - 2 yr - 1 ) comparable to Peruvian Bay Systems of the Humboldt upwelling system. A very large proportion of energy flows from the primary producers (phytoplankton and macro-algae) to the second level and to the detritus pool. Catches are high (54.3 t km - 2 yr - 1 ) and are mainly derived from the second and third trophic levels (mean TL of catch = 2.45) making the fisheries gross efficiency high (0.3%). The system's degree of development seems rather low as indicated by a P/R ratio of 4.19, a low ascendency (37.4%) and a very low Finn's cycling index (1.29%). This is explained by the system's exposure to irregular changes in oceanographic conditions as related to the EL Niño Southern Oscillation. Most important keystone groups of large relative impact over other system compartments are sharks and marine mammals. In addition, the important role of macro-algae, sea stars and urchins, phytoplankton and barracudas should be emphasized for their great contribution to the trophic flows and biomass of the system.

Cyclic terpenoids of contemporary resinous plant detritus and of fossil woods, ambers and coals

USGS Publications Warehouse

Simoneit, B.R.T.; Grimalt, J.O.; Wang, T.-G.; Cox, R.E.; Hatcher, P.G.; Nissenbaum, A.

1986-01-01

Cyclic terpenoids present in the solvent extractable material of fossil woods, ambers and brown coals have been analyzed. The sample series chosen consisted of wood remains preserved in Holocene to Jurassic sediments and a set of of ambers from the Philippines (copalite), Israel, Canada and Dominican Republic. The brown coals selected were from the Fortuna Garsdorf Mine and Miocene formations on Fiji. The fossil wood extracts contained dominant diterpenoid or sesquiterpenoid skeletons, and aromatized species were present at high concentrations, with a major amount of two-ring aromatic compounds. Tricyclic diterpenoids were the predominant compounds in the ambers. Aromatized derivatives were the major components, consisting of one or two aromatic ring species with the abietane and occasionally pimarane skeletons. The saturated structures were comprised primarily of the abietane and pimarane skeletons having from three to five carbon (C1, C2, etc.) substituents. Kaurane and phyllocladane isomers were present in only minor amounts. Bicyclic sesquiterpenoids as saturated and partial or fully aromatized forms were also common in these samples, but only traces of sesterterpenoids and triterpenoid derivatives were found. The brown coal extracts were composed of major amounts of one- and two-ring aromatized terpenoids, with a greater proportion of triterpenoid derivatives than in the case of the woods and ambers. This was especially noticeable for the German coal, where the triterpenoids were predominant. Open C-ring aromatized structures were also present in this coal. Steroid compounds were not detectable, but some hopanes were found as minor components in the German brown coal. An overview of the skeletal structure classes identified in each sample, as well as the general mass spectrometric characteristics of the unknown compounds are included in the present paper. It can be concluded from these structural distributions that aromatization is the main process for the transformation of terrestrial cyclic terpenoids during diagenesis, constituting a general pathway for all terpenoids. ?? 1986 Pergamon Journals Ltd.

Accuracy of post-bomb 137Cs and 14C in dating fluvial deposits

USGS Publications Warehouse

Ely, L.L.; Webb, R.H.; Enzel, Y.

1992-01-01

The accuracy and precision of 137Cs and 14C for dating post-1950 alluvial deposits were evaluated for deposits from known floods on two rivers in Arizona. The presence of 137Cs reliably indicates that deposition occurred after intensive above-ground nuclear testing was initiated around 1950. There was a positive correlation between the measured level of 137Cs activity and the clay content of the sediments, although 137Cs was detected even in sandy flood sediments with low clay content. 137Cs is a valuable dating tool in arid environments where organic materials for 14C or tree-ring dating are scarce and observational records are limited. The 14C activity measured in different types of fine organic detritus yielded dates within 1 to 8 yr of a 1980 flood deposit, and the accuracy was species-dependent. However, undifferentiated mixtures of fine organic materials from several post-bomb deposits of various ages repeatedly yielded dates between 1958 and 1962, and detrital charcoal yielded a date range of 1676-1939. In semiarid environments, the residence time of most types of organic debris precludes accurate annual resolution of post-bomb 14C dates. ?? 1992.

Plant reproductive organs and the origin of terrestrial insects

Treesearch

Georgy V. Stadnitsky

1991-01-01

It is widely believed that plants facilitated the evolution of terrestrial insects (Southwood 1973). However, the mechanisms by which this evolution occurred are not yet fully understood. I therefore propose a hypothesis about one possible mode of formation of terrestrial insects and fauna. The soil, warm shallow lagoons, tidal zones, and accumulations of detritus are...

Short- and long-term influence of stand density on soil microbial communities in ponderosa pine forests

Treesearch

Steven T. Overby

2009-01-01

Soil microbial communities process plant detritus and returns nutrients needed for plant growth. Increased knowledge of this intimate linkage between plant and soil microbial communities will provide a better understanding of ecosystem response to changing abiotic and biotic conditions. This dissertation consists of three studies to determine soil microbial community...

Export of detritus and invertebrate from headwater streams: linking mountaintop removal and valley fill coal mining to downstream receiving waters

EPA Science Inventory

Mountaintop removal and valley fill (MTR/VF) coal mining has resulted in large scale alteration of the topography, reduced forest productivity, and burial of headwater streams in the U.S. Central Appalachians. Although MTR/VF coal mining has occurred for several decades and the ...

The Trophic Significance of Bacteria in a Detritus-Based Stream Food Web

Treesearch

Robert O. Hall; Judy L. Meyer

1998-01-01

We compared relative use of streamwater dissolved organic carbon (DOC) by bacteria and the trophic significance of bacteria to invertebrates in two headwater streams at Coweeta Hydrologic Laboratory in North Carolina: a stream with all leaf litter inputs excluded for 1 yr, and a reference stream. Leaf litter standing crop in the treatment stream was

Soil nitrogen transformations under alternative management strategies in Appalachian forests

Treesearch

T. Adam Coates; Ralph E.J. Boerner; Thomas A. Waldrop; Daniel A. Yaussy

2008-01-01

Once subject to frequent fire and strongly N limited, the forests of the Appalachian Mountain region of eastern North America have experienced almost a century of fire suppression, and changes in tree species composition, understory density and composition, and accumulations of detritus have paralleled the changes in fire frequency. In an effort to restore these...

Pholeomyia comans (Diptera: Milichiidae) an associate of Atta texana: larval anatomy and notes on biology

Treesearch

John C. Moser; Stuart E. Neff

1971-01-01

Adults of Pholeomyia comans enter the nests of Atta texana and lay eggs in the underground detritus cavities, where the maggots feed on exhausted fungus garden substrate and nest refuse recently deposited by workers. The thirdstage larva and the puparium are described. A diapriid wasp was obtained from P. comans puparia. One...

Trophic linkages between headwater forests and downstream fish habitats: implications for forest and fish management.

Treesearch

Mark S. Wipfli

2005-01-01

This study examined the fluvial transport of invertebrates (aquatic and terrestrial) and coarse organic detritus from forested - headwaters in alternatives-to-clearcutting (ATC) harvest units to aquatic habitats downstream in the coastal mountains of southeastern Alaska. Fifty small streams (mean discharge 2.7 Ls-1, range 0.1-128.1 Ls-...

Belowground Nutrient Dynamics Following Three Harvest Intensities on the Pearl River Floodplain, Mississippi

Treesearch

E.B. Schilling; B.G. Lockaby; Robert Rummer

1999-01-01

Abstract: The influence of clear and partial cut harvests on belowground nutrient cycling processes was examined on the Pearl River floodplain, Mississippi. Foci examined by this study included fine root biomass and detritus, fine root production, fine root nutrient contents, soil respiration rates, and microbial biomass C, N, and P during the first...

Assessing the trophic role and ecosystem impact of Gulf menhaden (Brevoortia patronus) with carbon and nitrogen stable isotopes

EPA Science Inventory

Gulf menhaden (Brevoortia patronus) are an important component species of the coastal ecosystem and the target of the largest fishery by landings in the Gulf of Mexico (GOM). As filter feeders, they forage on a variety of plankton and detritus and, by grazing plankton stocks, ma...

Complete excavation and mapping of a Texas leafcutting ant nest

Treesearch

John C. Moser

2006-01-01

A medium-sized nest of the Texas leafcutting ant, Atta texana (Buckley), in northern Louisiana was excavated completely, and a three-dimensional model of its external and subterranean features was constructed. In total, 97 fungus gardens, 27 dormancy cavities, and 45 detritus cavities were located. At the lower center of the funnel-shaped nest was a...

Seven-year responses of trees to experimental hurricane effects in a tropical rainforest, Puerto Rico

Treesearch

Jess K. Zimmerman; James Aaron Hogan; Aaron B. Shiels; John E. Bithorn; Samuel Matta Carmona; Nicholas Brokaw

2014-01-01

We experimentally manipulated key components of severe hurricane disturbance, canopy openness and detritus deposition, to determine the independent and interactive effects of these components on tree recruitment, forest structure, and diversity in a wet tropical forest in the Luquillo Experimental Forest, Puerto Rico. Canopy openness was increased by trimming branches...

Litterfall in the hardwood forest of a minor alluvial-floodplain

Treesearch

Calvin E. Meier; John A. Stanturf; Emile S. Gardiner

2006-01-01

within mature deciduous forests, annual development of foliar biomass is a major component of aboveground net primary production and nutrient demand. As litterfall, this same foliage becomes a dominant annual transfer of biomass and nutrients to the detritus pathway. We report litterfall transfers of a mature bottomland hardwood forest in a minor alluvial-floodplain...

The organic geochemistry of black sedimentary barite: significance and implications of trapped fatty acids

USGS Publications Warehouse

Miller, R.E.; Brobst, D.A.; Beck, P.C.

1977-01-01

Fatty acids isolated in sedimentary black barite (BaSO4) from Arkansas and Nevada were identified by gas chromatography-mass spectroscopy. The dominant or major fatty acids found in these beds of barite are C16:0, C18:0, and C18:1. The occurrence and distribution of these acids in this type of rock may serve as "molecular fingerprints" of microbial biogeochemical processes. The organic matter and associated microorganisms are shown to be trapped within the finely crystalline barite, thus forming a closed system for microbial diagenesis. Important differences that occur in the distribution of the lesser or minor fatty acids probably result from: (1) the nature of the progenitor organic detritus in the environment of barite deposition: and (2) the subsequent degree of microbiological alteration of the parent organic debris swept into and trapped in the depositional environment. Three general models of sedimentary environments are proposed in which anoxic conditions may prevail and where barium sulfate (BaSO4) may precipitate: (1) in a silled basin with semi-restricted circulation; (2) on an outer continental shelf where the slope is encroached upon by water of the oxygen minimum layer; (3) on a low-energy, inner shelf or semi-restricted embayment impinged by a wedge of anoxic water. The major geochemical and geological parameters which are believed to be the significant factors controlling the formation and high grade of these organic-rich, black bedded barites are: (1) a unique source of barium-rich fluid that only contains trace amounts of other elements; (2) the presence of an anoxic bottom environment within the depositional basin; (3) a reflux source of sulfate ion; (4) an adequate source of organic matter. The results of this study may serve as guidelines for future exploration in similar, untested sedimentary basins, especially those with rocks of middle Paleozoic age. ?? 1977.

Nonadditive effects of leaf litter species diversity on breakdown dynamics in a deteritus-bases stream

Treesearch

J.S. Kominoski; C.M. Pringle; B.A. Ball; M.A. Bradford; D.C. Coleman; D.B. Hall; M.D. Hunter

2007-01-01

Since species loss is predicted to be nonrandom, it is important to understand the manner in which those species that we anticipate losing interact with other species to affect ecosystem function. We tested whether litter species diversity, measured as richness and composition, affects breakdown dynamics in a detritus-based stream. Using full-factorial analyses of...

Effects of tree leaf litter, deer fecal pellets, and soil properties on growth of an introduced earthworm (Lumbricus terrestris): Implications for invasion dynamics

Treesearch

Kassidy N. Yatso; Erik A. Lilleskov

2016-01-01

Invasive earthworm communities are expanding into previously earthworm-free forests of North America, producing profound ecosystem changes. Lumbricus terrestris is an invasive anecic earthworm that consumes a large portion of the detritus on the soil surface, eliminating forest floor organic horizons and reducing soil organic matter. Two mesocosm...

Long–term functional group recovery of lotic macroinvertebrates from logging disturbance.Canadian Journal of Fisheries and Aquatic Sciences

Treesearch

Damon T. Ely; J. Bruce Wallace

2010-01-01

Clear-cut logging rapidly affects stream macroinvertebrates through substantial alteration of terrestrial–aquatic resource linkages; however, lesser known are the long-term influences of forest succession on benthic macroinvertebrate assemblages, which play key roles in stream ecosystem function. We compared secondary production and standing crops of detritus in two...

Ecoregion and land-use influence invertebrate and detritus transport from headwater streams

Treesearch

Christopher A. Binckley; Mark S. Wipfli; R. Bruce Medhurst; Karl Polivka; Paul Hessburg; R. Brion Salter; Joshua Y. Kill

2010-01-01

We quantified the downstream transport of invertebrates, organic matter and inorganic sediment from 60 fishless headwater streams in the Wenatchee River Basin located on the eastern slope of the Cascade Range in Washington, U.S.A. Streams were classified into four groups (each n = 15) based on their position within two ecological subregions (wet and dry) and the extent...

Effects of silvicultural practices on soil carbon and nitrogen in a nitrogen saturated central Appalachian (USA) hardwood forest ecosystem

Treesearch

Frank S. Gilliam; David A. Dick; Michelle L. Kerr; Mary Beth Adams

2004-01-01

Silvicultural treatments represent disturbances to forest ecosystems often resulting in transient increases in net nitrification and leaching of nitrate and base cations from the soil. Response of soil carbon (C) is more complex, decreasing from enhanced soil respiration and increasing from enhanced postharvest inputs of detritus. Because nitrogen (N) saturation can...

Sources of plant-derived carbon and stability of organic matter in soil: Implications for global change

Treesearch

Susan E. Crow; Kate Lajtha; Timothy R. Filley; Chris Swanston; Richard D. Bowden; Bruce A. Caldwell

2009-01-01

Alterations in forest productivity and changes in the relative proportion of above- and belowground biomass may have nonlinear effects on soil organic matter (SOM) storage. To study the influence of plant litter inputs on SOM accumulation, the Detritus Input Removal and Transfer (DIRT) Experiment continuously alters above- and belowground plant inputs to soil by a...

The relative importance of exogenous and substrate-derived nitrogen for microbial growth during leaf decomposition

Treesearch

B.M. Cheever; J. R. Webster; E. E. Bilger; S. A. Thomas

2013-01-01

Heterotrophic microbes colonizing detritus obtain nitrogen (N) for growth by assimilating N from their substrate or immobilizing exogenous inorganic N. Microbial use of these two pools has different implications for N cycling and organic matter decomposition in the face of the global increase in biologically available N. We used sugar maple leaves labeled with

Microbial gardening in the ocean's twilight zone: detritivorous metazoans benefit from fragmenting, rather than ingesting, sinking detritus: fragmentation of refractory detritus by zooplankton beneath the euphotic zone stimulates the harvestable production of labile and nutritious microbial biomass.

PubMed

Mayor, Daniel J; Sanders, Richard; Giering, Sarah L C; Anderson, Thomas R

2014-12-01

Sinking organic particles transfer ∼10 gigatonnes of carbon into the deep ocean each year, keeping the atmospheric CO2 concentration significantly lower than would otherwise be the case. The exact size of this effect is strongly influenced by biological activity in the ocean's twilight zone (∼50-1,000 m beneath the surface). Recent work suggests that the resident zooplankton fragment, rather than ingest, the majority of encountered organic particles, thereby stimulating bacterial proliferation and the deep-ocean microbial food web. Here we speculate that this apparently counterintuitive behaviour is an example of 'microbial gardening', a strategy that exploits the enzymatic and biosynthetic capabilities of microorganisms to facilitate the 'gardener's' access to a suite of otherwise unavailable compounds that are essential for metazoan life. We demonstrate the potential gains that zooplankton stand to make from microbial gardening using a simple steady state model, and we suggest avenues for future research. © 2014 The Authors. Bioessays published by WILEY Periodicals, Inc.

Total selenium and selenium species in irrigation drain inflows to the Salton Sea, California, October 2007 and January 2008

USGS Publications Warehouse

May, Thomas W.; Walther, Michael J.; Saiki, Michael K.; Brumbaugh, William G.

2008-01-01

This report presents the results for two sampling periods (October 2007 and January 2008) during a 4-year monitoring program to characterize selenium concentrations in selected irrigation drains flowing into the Salton Sea, California. Total selenium, selenium species (selenite, selenate, organoselenium), and total suspended solids were determined in water samples, and total selenium was determined in sediment, detritus, and biota that included algae, plankton, midge larvae (family, Chironomidae), and two fish species?western mosquitofish (Gambusia affinis) and sailfin molly (Poecilia latipinna). In addition, sediments were analyzed for percent total organic carbon and particle size. Mean total selenium concentrations in water for both sampling periods ranged from 0.97 to 64.5 micrograms per liter, predominately as selenate, which is typical of waters where selenium is leached out of selenium-containing marine shales and associated soils under alkaline and oxidizing conditions. Total selenium concentrations (micrograms per gram dry weight) ranged as follows: algae, 0.95 to 5.99; plankton, 0.15 to 19.3; midges, 1.39 to 15.4; fish, 3.71 to 25.1; detritus, 0.85 to 21.7; sediment, 0.32 to 7.28.

Total selenium and selenium species in irrigation drain inflows to the Salton Sea, California, April and July 2008

USGS Publications Warehouse

May, Thomas W.; Walther, Michael J.; Saiki, Michael K.; Brumbaugh, William G.

2009-01-01

This report presents the results for two sampling periods (April 2008 and July 2008) during a 4-year monitoring program to characterize selenium concentrations in selected irrigation drains flowing into the Salton Sea, California. Total selenium, selenium species (dissolved selenite, selenate, organoselenium), and total suspended solids were determined in water samples and total selenium was determined in water column particulates and in sediment, detritus, and biota that included algae, plankton, midge larvae (family, Chironomidae), and two fish species - western mosquitofish (Gambusia affinis) and sailfin molly (Poecilia latipinna). In addition, sediments were analyzed for percent total organic carbon and particle size. Mean total selenium concentrations in water for both sampling periods ranged from 1.93 to 44.2 micrograms per liter, predominately as selenate, which is typical of waters where selenium is leached out of selenium-containing marine shales and associated soils under alkaline and oxidizing conditions. Total selenium concentrations (micrograms per gram dry weight) ranged as follows: algae, 0.75 to 3.39; plankton, 0.88 to 4.03; midges, 2.52 to 44.3; fish, 3.37 to 18.9; detritus, 1.11 to 13.6; sediment, 0.11 to 8.93.

Total selenium and selenium species in irrigation drain inflows to the Salton Sea, California, October 2008 and January 2009

USGS Publications Warehouse

May, Thomas W.; Walther, Michael J.; Saiki, Michael K.; Brumbaugh, William G.

2009-01-01

This report presents the results for two sampling periods (October 2008 and January 2009) during a 4-year monitoring program to characterize selenium concentrations in selected irrigation drains flowing into the Salton Sea, California. Total selenium, selenium species (dissolved selenite, selenate, organoselenium), and total suspended solids were determined in water samples. Total selenium also was determined in water column particulates and in sediment, detritus, and biota that included algae, plankton, midge larvae (family, Chironomidae), and two fish species (western mosquitofish, Gambusia affinis, and sailfin molly, Poecilia latipinna). In addition, sediments were analyzed for percent total organic carbon and particle size. Mean total selenium concentrations in water for both sampling periods ranged from 1.00 to 33.6 micrograms per liter, predominately as selenate, which is typical of waters where selenium is leached out of selenium-containing marine shales and associated soils under alkaline and oxidizing conditions. Total selenium concentrations (micrograms per gram dry weight) ranged as follows: algae, 1.52 to 8.26; plankton, 0.79 to 3.66; midges, 2.68 to 50.6; fish, 3.09 to 30.4; detritus, 1.78 to 58.0; and sediment, 0.42 to 10.0.

Flexible digestion strategies and trace metal assimilation in marine bivalves

USGS Publications Warehouse

Decho, Alan W.; Luoma, Samuel N.

1996-01-01

Pulse-chase experiments show that two marine bivalves take optimal advantage of different types of particulate food by varying food retention time in a flexible two-phase digestive system. For example, carbon is efficiently assimilated from bacteria by subjecting nearly all the ingested bacteria to prolonged digestion. Prolonging digestion also enhances assimilation of metals, many of which are toxic in minute quantities if they are biologically available. Detritus-feeding aquatic organisms have always lived in environments naturally rich in particle-reactive metals. We suggest that avoiding excess assimilation of metals could be a factor in the evolution of digestion strategies. We tested that suggestion by studying digestion of particles containing different Cr concentrations. We show that bivalves are capable of modifying the digestive processing of food to reduce exposure to high, biologically available, Cr concentrations. The evolution of a mechanism in some species to avoid high concentrations of metals in food could influence how effects of modern metal pollution are manifested in marine ecosystems.

40 CFR 63.10032 - What records must I keep?

Code of Federal Regulations, 2013 CFR

2013-07-01

... must keep records of the type(s) and amount(s) of fuel used during each startup or shutdown. (j) If you... whether the deviation occurred during a period of startup, shutdown, or malfunction or during another... must keep records of monthly fuel use by each EGU, including the type(s) of fuel and amount(s) used. (2...

40 CFR 63.10032 - What records must I keep?

Code of Federal Regulations, 2014 CFR

2014-07-01

... must keep records of the type(s) and amount(s) of fuel used during each startup or shutdown. (j) If you... whether the deviation occurred during a period of startup, shutdown, or malfunction or during another... must keep records of monthly fuel use by each EGU, including the type(s) of fuel and amount(s) used. (2...

40 CFR 63.10032 - What records must I keep?

Code of Federal Regulations, 2012 CFR

2012-07-01

... must keep records of the type(s) and amount(s) of fuel used during each startup or shutdown. (j) If you... whether the deviation occurred during a period of startup, shutdown, or malfunction or during another... must keep records of monthly fuel use by each EGU, including the type(s) of fuel and amount(s) used. (2...

Variations in phytodetritus derived carbon uptake of the intertidal foraminifera Ammonia tepida and Haynesina germanica

NASA Astrophysics Data System (ADS)

Wukovits, Julia; Bukenberger, Patrick; Enge, Annekatrin; Wanek, Wolfgang; Watzka, Margarete; Heinz, Petra

2016-04-01

Phytodetritus represents a major component of particulate organic carbon in intertidal mudflats. Estuaries and tidal currents yield an extensive amount of these particles that display a substantial nutrient source for littoral food webs. For benthic foraminifera, a group of marine protists, phytodetritus serves as the main food source. Foraminifera are considered to play a significant role in marine carbon turnover processes and show seasonally very high population densities in intertidal sediments. Therefore, it is important to gather explicit data about the specific carbon uptake behavior of intertidal foraminiferal species. In this study, laboratory feeding experiments were carried out to observe phytodetrital carbon uptake of foraminiferal specimen collected in the German Wadden Sea. Artificially produced phytodetritus was labelled with 13C to follow carbon ingestion into foraminiferal cytoplasm over time at different simulated conditions. The experiments were performed with monocultures under exclusion of other meiofauna. Chlorophyte detritus (Dunaliella tertiolecta) was fed to the two common species Ammonia tepida and Haynesina germanica. Ammonia tepida showed a significantly higher affinity to this food source than H. germanica. Testing the effect of temperature revealed a significant decrease of carbon ingestion with increasing temperature in H. germanica. Observations focusing on A. tepida showed a rising phytodetrital carbon content in the biomass of juvenile individuals in contrast to adult foraminifera. In general, carbon uptake reaches saturation levels a few hours after food supply. Furthermore, A. tepida benefits from constant availability of fresh food rather than from a high amount of phytodetritus derived from a single food pulse. Our investigations showed that the foraminiferal impact on intertidal processing of phytodetrital carbon sources is species specific, temperature related and depends on developmental stage and input dynamics. Additionally, the presented data reveal the quantitative level of food derived carbon gathered within foraminiferal biomass.

Composition of estuarine colloidal material: organic components

USGS Publications Warehouse

Sigleo, A.C.; Hoering, T.C.; Helz, G.R.

1982-01-01

Colloidal material in the size range 1.2 nm to 0.4 ??m was isolated by ultrafiltration from Chesapeake Bay and Patuxent River waters (U.S.A.). Temperature controlled, stepwise pyrolysis of the freeze-dried material, followed by gas chromatographic-mass spectrometric analyses of the volatile products indicates that the primary organic components of this polymer are carbohydrates and peptides. The major pyrolysis products at the 450??C step are acetic acid, furaldehydes, furoic acid, furanmethanol, diones and lactones characteristic of carbohydrate thermal decomposition. Pyrroles, pyridines, amides and indole (protein derivatives) become more prevalent and dominate the product yield at the 600??C pyrolysis step. Olefins and saturated hydrocarbons, originating from fatty acids, are present only in minor amounts. These results are consistent with the composition of Chesapeake phytoplankton (approximately 50% protein, 30% carbohydrate, 10% lipid and 10% nucleotides by dry weight). The pyrolysis of a cultured phytoplankton and natural particulate samples produced similar oxygen and nitrogencontaining compounds, although the proportions of some components differ relative to the colloidal fraction. There were no lignin derivatives indicative of terrestrial plant detritus in any of these samples. The data suggest that aquatic microorganisms, rather than terrestrial plants, are the dominant source of colloidal organic material in these river and estuarine surface waters. ?? 1982.

The biomass of the deep-sea benthopelagic plankton

NASA Astrophysics Data System (ADS)

Wishner, K. F.

1980-04-01

Deep-sea benthopelagic plankton samples were collected with a specially designed opening-closing net system 10 to 100 m above the bottom in five different oceanic regions at depths from 1000 to 4700 m. Benthopelagic plankton biomasses decrease exponentially with depth. At 1000 m the biomass is about 1% that of the surface zooplankton, at 5000 m about 0.1%. Effects of differences in surface primary productivity on deep-sea plankton biomass are much less than the effect of depth and are detectable only in a few comparisons of extreme oceanic regions. The biomass at 10 m above the bottom is greater than that at 100 m above the bottom (in a three-sample comparison), which could be a consequence of an enriched near-bottom environment. The deep-sea plankton biomass in the Red Sea is anomalously low. This may be due to increased decomposition rates in the warm (22°C) deep Red Sea water, which prevent much detritus from reaching the deep sea. A model of organic carbon utilization in the benthic boundary layer (bottom 100 m), incorporating results from deep-sea sediment trap and respiration studies, indicates that the benthopelagic plankton use only a small amount of the organic carbon flux. A large fraction of the flux is unaccounted for by present estimates of benthic and benthopelagic respiration.

Microbial Diversity of Impact-Generated Habitats

NASA Astrophysics Data System (ADS)

Pontefract, Alexandra; Osinski, Gordon R.; Cockell, Charles S.; Southam, Gordon; McCausland, Phil J. A.; Umoh, Joseph; Holdsworth, David W.

2016-10-01

Impact-generated lithologies have recently been identified as viable and important microbial habitats, especially within cold and arid regions such as the polar deserts on Earth. These unique habitats provide protection from environmental stressors, such as freeze-thaw events, desiccation, and UV radiation, and act to trap aerially deposited detritus within the fissures and pore spaces, providing necessary nutrients for endoliths. This study provides the first culture-independent analysis of the microbial community structure within impact-generated lithologies in a Mars analog environment, involving the analysis of 44,534 16S rRNA sequences from an assemblage of 21 rock samples that comprises three shock metamorphism categories. We find that species diversity increases (H = 2.4-4.6) with exposure to higher shock pressures, which leads to the development of three distinct populations. In each population, Actinobacteria were the most abundant (41%, 65%, and 59%), and the dominant phototrophic taxa came from the Chloroflexi. Calculated porosity (a function of shock metamorphism) for these samples correlates (R2 = 0.62) with inverse Simpson indices, accounting for overlap in populations in the higher shock levels. The results of our study show that microbial diversity is tied to the amount of porosity in the target substrate (as a function of shock metamorphism), resulting in the formation of distinct microbial populations.

Quantitative trait loci controlling amounts and types of epicuticular waxes in onion

USDA-ARS?s Scientific Manuscript database

Natural variation exists in onion (Allium cepa L.) for amounts and types of epicuticular waxes on leaves. Wild-type waxy onion possesses copious amounts of these waxes, while the foliage of semi-glossy and glossy phenotypes accumulate significantly less wax. Reduced amounts of epicuticular waxes hav...

Abstracts of Papers Submitted in 1978 for Publication,

DTIC Science & Technology

1978-01-01

pollution may be expected to spread. accorded unassimilated heavy metal ions which are also stabilized within the soil and de - WASTEWATER RENOVATION...Chlorophyll, Particle Concentration, Carbon and Nitrogen in Resuspended Particulate Matter B-20 Michael R. Roman Salt Marhes Heavy Metal Uptake in a...the cycling of heavy S.-.., The tidal resuspension of phytoplankton metals in Great Sippiwissett Marsh as part of - *, and detritus from the mud

Understanding the key mechanisms of tropical forest responses to canopy loss and biomass deposition from experimental hurricane effects

Treesearch

A.B. Shiels; Grizelle Gonzalez

2014-01-01

To date, it is not clear which are the factors that most influence tropical forest recovery from hurricanes.Increased canopy openness and increased detritus (debris) deposition are two of the most likely factors,but due to their simultaneous occurrence during a hurricane, their relative effects cannot be separated without a manipulative experiment. Hence, in the...

The Hippest History: The Detritus of Your Library's Past Can Help with Your Present-Day Marketing, Fundraising, and Professional Pride

ERIC Educational Resources Information Center

Lear, Bernadette A.

2005-01-01

The author of this article studies the history of libraries. Few libraries capitalize on their own organizational history, however, even though it can be, at minimum, a resource of images and factoids for everything from answering administrative questions to crafting fundraising and marketing pieces. It can also be a reservoir of professional…

Aquatic Plant Control Research Program: The Rhizosphere Microbiology of Rooted Aquatic Plants.

DTIC Science & Technology

1988-04-01

acids. Acetic acid postulated as agent Thalassia Nitrogen fixation in Capone 1983 testudinwn rhizosphere and phyllosphere 13. Fungi living in the...microbial population associated with the rhizome detritus. 26. Durako and Moffler (1987) examined responses of Thalassia testudinum to nitrogen enrichment...economy of seagrasses for communities of Thalassia testudinium and Zostera maina. He concluded that nitrogen fixation is probably more important for

Climatic regions as an indicator of forest coarse and fine woody debris carbon stocks in the United States

Treesearch

Christopher W. Woodall; Greg C. Liknes

2008-01-01

Coarse and fine woody debris are substantial forest ecosystem carbon stocks; however, there is a lack of understanding how these detrital carbon stocks vary across forested landscapes. Because forest woody detritus production and decay rates may partially depend on climatic conditions, the accumulation of coarse and fine woody debris carbon stocks in forests may be...

Stable isotope trophic patterns in echinoderm megafauna in close proximity to and remote from Gulf of Mexico lower slope hydrocarbon seeps

NASA Astrophysics Data System (ADS)

Carney, Robert Spencer

2010-11-01

Hydrocarbon-seep communities in the Gulf of Mexico have a high biomass that is exploited as a food source to varying degrees by the photosynthesis-dependent fauna inhabiting the surrounding mud bottom. A decline concurrent with ocean depth in detritus influx to that background habitat results in a much lower background biomass. The biomass contrast between population-rich seeps and depauperate mud bottom leads to the prediction that seep utilization by the background fauna should be extensive at all depths and should increase with depth. Species depth zonation makes like-species comparisons over the full depth of the Gulf of Mexico impossible. Seeps and normal bottom above 1000 m have different fauna from those below 1000 m. Lower slope seeps are surrounded by a fauna rich in echinoderm species, especially asteroids, ophiuroids, and holothuroids. All three taxa have species that are abundant within seeps and are probably endemic to them. They also contain species found only in mud background or within mud and seeps backgrounds. Tissue analyses of δ13C and δ15N of echinoderms collected by ROV within seeps and trawling away from seeps indicate a pattern of utilization similar to that found in upper slope seeps exploited by different taxa. Seastar and ophiuroid species abundant in or endemic to seeps have tissue isotope values reflecting seep chemosynthetic input via a free-living microbial detritus or predation. A single seep-endemic deposit-feeding holothuroid showed distinct seep tissue values. Background deposit-feeding holothuroids collected within seeps showed either no or only minor incorporation of seep carbon, indicating either a lack of access to seep detritus or short feeding times within the seep. A predicted extensive utilization of seep productivity at the deeper seeps was not found. Seeps may be relatively closed systems that require special adaptations of species in order for them to enter, exploit, and survive. Alternately, the surrounding deep benthos may not be as food-poor as assumed from biomass measurements and flux estimates.

Single grain U/Pb geochronology of detrital zircons from Midcontinent rift arkoses, NE Kansas: Implications for depositional history

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

Martin, M.W.; Van Schmus, W.R.; Berendsen, P.

1993-03-01

The Midcontinent rift system in the subsurface south of the Lake Superior region has been well imaged by magnetic, gravity and seismic surveys, however only a few wells have penetrated and recovered core from rift-basin fill in this region. Texaco's exploratory Noel Poersch well [number sign]1 in northeastern Kansas, penetrated [approximately] 2,600 m of rift-related volcanic, igneous, and arkosic sedimentary rocks from which a total of 35 m of core was taken from fourteen different horizons in the rift-related section. To determine provenance ages and to constrain better the depositional patterns of clastic sedimentary rocks within the Mid-continent rift basin,more » the authors have undertaken U/Pb geochronology of detrital zircon from arkosic horizons along the depth of recovered core from the Texaco Poersch [number sign]1 well. Preliminary analyses indicate that the stratigraphically lowest arkoses recovered in core have provenance ages that range in age from 1.7--1.8 Ga, 1.4--1.5 Ga and 1.1--1.2 Ga. These data suggest the following conclusions: (1) The arkosic sediments were primarily derived proximally from the adjacent rift margin, which is known to consist of 1.75--1.80 Ga gneissic and granitic basement intruded by 1.35--1.45 Ga granitic plutons in Nebraska and northernmost Kansas plus 1.63--1.68 Ga granitic basement intruded by 1.35--1.45 granitic plutons in most of Kansas; 1.63--1.70 detrital zircons were absent, suggesting that most of the detritus was derived from northerly directions. (2) No Archean or 1.85 to 1.90 Ga Early proterozoic detrital zircons were found, suggesting very little to no transport of detritus along the rift axis from farther north, e.g., from Penokean, Trans-Hudson, or Superior Province regions. (3) One nearly concordant zircon with a Pb-Pb age of 1.18 Ga was found, suggesting that some of the detritus was derived either from older phases of igneous rift fill or from ca. 1.2 Ga intrusions that pre-date rifting.« less

Analysis of the ecosystem structure of Laguna Alvarado, western Gulf of Mexico, by means of a mass balance model

NASA Astrophysics Data System (ADS)

Cruz-Escalona, V. H.; Arreguín-Sánchez, F.; Zetina-Rejón, M.

2007-03-01

Alvarado is one of the most productive estuary-lagoon systems in the Mexican Gulf of Mexico. It has great economic and ecological importance due to high fisheries productivity and because it serves as a nursery, feeding, and reproduction area for numerous populations of fishes and crustaceans. Because of this, extensive studies have focused on biology, ecology, fisheries (e.g. shrimp, oysters) and other biological components of the system during the last few decades. This study presents a mass-balanced trophic model for Laguna Alvarado to determine it's structure and functional form, and to compare it with similar coastal systems of the Gulf of Mexico and Mexican Pacific coast. The model, based on the software Ecopath with Ecosim, consists of eighteen fish groups, seven invertebrate groups, and one group each of sharks and rays, marine mammals, phytoplankton, sea grasses and detritus. The acceptability of the model is indicated by the pedigree index (0.5) which range from 0 to 1 based on the quality of input data. The highest trophic level was 3.6 for marine mammals and snappers. Total system throughput reached 2680 t km -2 year -1, of which total consumption made up 47%, respiratory flows made up 37% and flows to detritus made up 16%. The total system production was higher than consumption, and net primary production higher than respiration. The mean transfer efficiency was 13.8%. The mean trophic level of the catch was 2.3 and the primary production required to sustain the catch was estimated in 31 t km -2 yr -1. Ecosystem overhead was 2.4 times the ascendancy. Results suggest a balance between primary production and consumption. In contrast with other Mexican coastal lagoons, Laguna Alvarado differs strongly in relation to the primary source of energy; here the primary producers (seagrasses) are more important than detritus pathways. This fact can be interpreted a response to mangrove deforest, overfishing, etc. Future work might include the compilation of fishing and biomass time trends to develop historical verification and fitting of temporal simulations.

The spatial variability of water chemistry and DOC in bog pools: the importance of slope position, diurnal turnover and pool type

NASA Astrophysics Data System (ADS)

Holden, Joseph; Turner, Ed; Baird, Andy; Beadle, Jeannie; Billett, Mike; Brown, Lee; Chapman, Pippa; Dinsmore, Kerry; Dooling, Gemma; Grayson, Richard; Moody, Catherine; Gee, Clare

2017-04-01

We have previously shown that marine influence is an important factor controlling regional variability of pool water chemistry in blanket peatlands. Here we examine within-site controls on pool water chemistry. We surveyed natural and artificial (restoration sites) bog pools at blanket peatland sites in northern Scotland and Sweden. DOC, pH, conductivity, dissolved oxygen, temperature, cations, anions and absorbance spectra from 220-750nm were sampled. We sampled changes over time but also conducted intensive spatial surveys within individual pools and between pools on the same sampling days at individual study sites. Artificial pools had significantly greater DOC concentrations and different spectral absorbance characteristics when compared to natural pools at all sites studied. Within-pool variability in water chemistry tended to be small, even for very large pools ( 400 m2), except where pools had a layer of loose, mobile detritus on their beds. In these instances rapid changes took place between the overlying water column and the mobile sediment layer wherein dissolved oxygen concentrations dropped from values of around 12-10 mg/L to values less than 0.5 mg/L over just 2-3 cm of the depth profile. Such strong contrasts were not observed for pools which had a hard peat floor and which lacked a significant detritus layer. Strong diurnal turnover occurred within the pools on summer days, including within small, shallow pools (e.g. < 30 cm deep, 1 m2 area). For many pools on these summer days there was an evening spike in dissolved oxygen concentrations which originated at the surface and was then cycled downwards as the pool surface waters cooled. Slope location was a significant control on several pool water chemistry variables including pH and DOC concentration with accumulation (higher concentrations) in pools that were located further downslope in both natural and artificial pool systems. These processes have important implications for our interpretation of water chemistry and gas flux data from pool systems, how we design our sampling strategies and how we upscale results.

Microbial communities mediating algal detritus turnover under anaerobic conditions

PubMed Central

Morrison, Jessica M.; Murphy, Chelsea L.; Baker, Kristina; Zamor, Richard M.; Nikolai, Steve J.; Wilder, Shawn; Elshahed, Mostafa S.

2017-01-01

Background Algae encompass a wide array of photosynthetic organisms that are ubiquitously distributed in aquatic and terrestrial habitats. Algal species often bloom in aquatic ecosystems, providing a significant autochthonous carbon input to the deeper anoxic layers in stratified water bodies. In addition, various algal species have been touted as promising candidates for anaerobic biogas production from biomass. Surprisingly, in spite of its ecological and economic relevance, the microbial community involved in algal detritus turnover under anaerobic conditions remains largely unexplored. Results Here, we characterized the microbial communities mediating the degradation of Chlorella vulgaris (Chlorophyta), Chara sp. strain IWP1 (Charophyceae), and kelp Ascophyllum nodosum (phylum Phaeophyceae), using sediments from an anaerobic spring (Zodlteone spring, OK; ZDT), sludge from a secondary digester in a local wastewater treatment plant (Stillwater, OK; WWT), and deeper anoxic layers from a seasonally stratified lake (Grand Lake O’ the Cherokees, OK; GL) as inoculum sources. Within all enrichments, the majority of algal biomass was metabolized within 13–16 weeks, and the process was accompanied by an increase in cell numbers and a decrease in community diversity. Community surveys based on the V4 region of the 16S rRNA gene identified different lineages belonging to the phyla Bacteroidetes, Proteobacteria (alpha, delta, gamma, and epsilon classes), Spirochaetes, and Firmicutes that were selectively abundant under various substrate and inoculum conditions. Within all kelp enrichments, the microbial communities structures at the conclusion of the experiment were highly similar regardless of the enrichment source, and were dominated by the genus Clostridium, or family Veillonellaceae within the Firmicutes. In all other enrichments the final microbial community was dependent on the inoculum source, rather than the type of algae utilized as substrate. Lineages enriched included the uncultured groups VadinBC27 and WCHB1-69 within the Bacteroidetes, genus Spirochaeta and the uncultured group SHA-4 within Spirochaetes, Ruminococcaceae, Lachnospiraceae, Yongiibacter, Geosporobacter, and Acidaminobacter within the Firmicutes, and genera Kluyvera, Pantoea, Edwardsiella and Aeromonas, and Buttiauxella within the Gamma-Proteobaceteria order Enterobacteriales. Conclusions Our results represent the first systematic survey of microbial communities mediating turnover of algal biomass under anaerobic conditions, and highlights the diversity of lineages putatively involved in the degradation process. PMID:28097050

Food wastes as fish feeds for polyculture of low-trophic-level fish: bioaccumulation and health risk assessments of heavy metals in the cultured fish.

PubMed

Cheng, Zhang; Lam, Cheung-Lung; Mo, Wing-Yin; Nie, Xiang-Ping; Choi, Wai-Ming; Man, Yu-Bon; Wong, Ming-Hung

2016-04-01

The major purpose of this study was to use different types of food wastes which serve as the major sources of protein to replace the fish meal used in fish feeds to produce quality fish. Two types of food waste-based feed pellets FW A (with cereals) and FW B (with cereals and meat products) and the commercial feed Jinfeng® were used to culture fingerlings of three low-trophic-level fish species: bighead carp, grass carp, and mud carp (in the ratio of 1:3:1) for 1 year period in the Sha Tau Kok Organic Farm in Hong Kong. Heavy metal concentrations in all of the fish species fed with food waste pellets and commercial pellets in Sha Tau Kok fish ponds were all below the local and international maximum permissible levels in food. Health risk assessments indicated that human consumption of the fish fed with food waste feed pellets was safe for the Hong Kong residents. The present results revealed that recycling of food waste for cultivating low-trophic-level fish (mainly herbivores and detritus feeders) is feasible, and at the same time will ease the disposal pressure of food waste, a common problem of densely populated cities like Hong Kong.

Archean foreland basin tectonics in the Witwatersrand, South Africa

NASA Technical Reports Server (NTRS)

Burke, K.; Kidd, W. S. F.; Kusky, T. M.

1986-01-01

The Witwatersrand Basin of South Africa is the best-known of Archean sedimentary basins and contains some of the largest gold reserves in the world. Sediments in the basin include a lower flysch-type sequence and an upper molassic facies, both of which contain abundant silicic volcanic detritus. The strata are thicker and more proximal on the northwestern side of the basin which is, at least locally, bound by thrust faults. These features indicate that the Witwatersrand strata may have been deposited in a foreland basin and a regional geologic synthesis suggests that this basin developed initially on the cratonward side of an Andean-type arc. Remarkably similar Phanerozoic basins may be found in the southern Andes above zones of shallow subduction. It is suggested that the continental collision between the Kaapvaal and Zimbabwe Cratons at about 2.7 Ga caused further subsidence and deposition in the Witwatersrand Basin. Regional uplift during this later phase of development placed the basin on the cratonward edge of a collision-related plateau, now represented by the Limpopo Province. Similarities are seen between this phase of Witwatersrand Basin evolution and that of active basins north of the Tibetan Plateau. The geologic evidence does not agree with earlier suggestions that the Witwatersrand strata were deposited in a rift or half-graben.

Sedimentary organic matter sources, benthic consumption and burial in west Spitsbergen fjords - Signs of maturing of Arctic fjordic systems?

NASA Astrophysics Data System (ADS)

Zaborska, Agata; Włodarska-Kowalczuk, Maria; Legeżyńska, Joanna; Jankowska, Emilia; Winogradow, Aleksandra; Deja, Kajetan

2018-04-01

Mature ecosystems sequester little organic carbon (Corg) in sediments, as the complex and effective food webs consume most available organic matter within the water column and sediment, in contrast to young systems, where a large proportion of Corg is buried in deeper sediment layers. In this paper we hypothesize that "warmer" Atlantic water influenced fjord exhibits the 'mature' system features as compared to "cooler" Arctic water influenced fjord. Corg concentrations, sources and burial rates, as well as macrobenthic community standing stocks, taxonomic and functional composition and carbon demand, were compared in two west Spitsbergen fjords that are to different extents influenced by Atlantic water and can be treated as representing a cold one (Hornsund) and a warm one (Kongsfjorden). Water, sediments and macrofauna were collected at three stations in the central basin of each fjord. Corg, Ntot, δ13Corg and δ15N were measured in suspended matter, sediment cores and possible organic matter sources. The composition of sources of sedimentary organic matter was modeled by Mix-SIAR Bayesian stable isotope mixing models. The 210Pb method was used to calculate sediment accumulation rates, Corg accumulation and burial rates. The sedimentary Corg concentration and accumulation rate were larger in Hornsund than in Kongsfjorden. The contributions of pelagic sources to the Corg in sediments were similar in both fjords, macroalgal detritus had a higher importance in Kongsfjorden, while terrestrial sources were more important in Hornsund. Similar density and species richness were noted in both fjords, but higher biomass, individual biomass, production and carbon demand of benthic communities were noted in Kongsfjorden despite the lower amounts of Corg in sediments, indicating that macrobenthos responds to quality rather than quantity of available food. Subsurface tube-building conveyer belt detritus feeders (maldanids and oweniids) were responsible for higher standing stocks and carbon consumption in Kongsfjorden. As a result of the lower Corg pool and higher benthic mineralization, the burial rates in Kongsfjorden were much lower (15 g of Corg m- 2 yr- 1) than in Hornsund (38 g of Corg m- 2 yr- 1). Our study indicates that warming of the high latitude fjordic environments may reshape the relative proportions of organic carbon sources and induce maturing of the sea bottom systems, in terms of development of stable, biologically accommodated benthic communities which more efficiently mineralize organic matter and consequently lower sequestration of organic matter in deeper sediments.

Diagenetic and compositional controls of wettability in siliceous sedimentary rocks, Monterey Formation, California

NASA Astrophysics Data System (ADS)

Hill, Kristina M.

Modified imbibition tests were performed on 69 subsurface samples from Monterey Formation reservoirs in the San Joaquin Valley to measure wettability variation as a result of composition and silica phase change. Contact angle tests were also performed on 6 chert samples from outcrop and 3 nearly pure mineral samples. Understanding wettability is important because it is a key factor in reservoir fluid distribution and movement, and its significance rises as porosity and permeability decrease and fluid interactions with reservoir grain surface area increase. Although the low permeability siliceous reservoirs of the Monterey Formation are economically important and prolific, a greater understanding of factors that alter their wettability will help better develop them. Imbibition results revealed a strong trend of decreased wettability to oil with increased detrital content in opal-CT phase samples. Opal-A phase samples exhibited less wettability to oil than both opal-CT and quartz phase samples of similar detrital content. Subsurface reservoir samples from 3 oil fields were crushed to eliminate the effect of capillary pressure and cleansed of hydrocarbons to eliminate wettability alterations by asphaltene, then pressed into discs of controlled density. Powder discs were tested for wettability by dispensing a controlled volume of water and motor oil onto the surface and measuring the time required for each fluid to imbibe into the sample. The syringe and software of a CAM101 tensiometer were used to control the amount of fluid dispensed onto each sample, and imbibition completion times were determined by high-speed photography for water drops; oil drop imbibition was significantly slower and imbibition was timed and determined visually. Contact angle of water and oil drops on polished chert and mineral sample surfaces was determined by image analysis and the Young-Laplace equation. Oil imbibition was significantly slower with increased detrital composition and faster with increased silica content in opal-CT and quartz phase samples, implying decreased wettability to oil with increased detrital (clay) content. However, contact angle tests showed that opal-CT is more wetting to oil with increased detritus and results for oil on quartz-phase samples were inconsistent between different proxies for detritus over their very small compositional range. Water contact angle trends also showed inconsistent wetting trends compared to imbibition tests. We believe this is because the small range in bulk detrital composition between the "pure" samples used in contact angle tests was close to analytical error and because small-scale spatial compositional variability may be significant enough to effect wettability. These experiments show that compositional variables significantly affect wettability, outweighing the effect of silica phase.

Contrasting cratonal provenances for upper Cretaceous Valle Group quartzite clasts, Baja California

USGS Publications Warehouse

Kimbrough, D.L.; Abbott, G.; Smith, D.P.; Mahoney, J.B.; Moore, Thomas E.; Gehrels, G.E.; Girty, G.H.; Cooper, John D.

2006-01-01

Late Cretaceous Valle Group forearcbasin deposits on the Vizcaino Peninsula of Baja California Sur are dominated by firstcycle arc-derived volcanic-plutonic detritus derived from the adjacent Peninsular Ranges batholith. Craton-derived quartzite clasts are a minor but ubiquitous component in Valle Group conglomerates. The source of these clasts has implications for tectonic reconstructions and sediment-dispersal paths along the paleo-North American margin. Three strongly contrasting types of quartzite are recognized based on petrology and detrital zircon U-Pb geochronology. The first type is ultramature quartz arenite with well-rounded, highly spherical zircon grains. Detrital zircon ages from this type are nearly all >1.8 Ga with age distributions that closely match the distinctive Middle-Late Ordovician Peace River arch detrital signature of the Cordilleran margin. This type has been previously recognized from prebatholithic rocks in northeast Baja California (San Felipe quartzite). A second quartzite type is subarkosic sandstone with strong affinity to southwestern North America; important features of the age spectra are ~1.0-1.2 Ga, 1.42 and 1.66 Ga peaks representing cratonal basement, 500-300 Ma grains interpreted as recycled Appalachian-derived grains, and 284- 232 Ma zircon potentially derived from the Early Permian-Middle Triassic east Mexico arc. This quartzite type could have been carried to the continental margin during Jurassic time as outboard equivalents of Colorado Plateau eolianites. The third quartzite type is quartz pebble conglomerate with significant ~900- 1400 Ma and ~450-650 Ma zircon components, as well as mid- and late Paleozoic grains. The source of this type of quartzite is more problematic but could match either upper Paleozoic strata in the Oaxaca terrane of southern Mexico or a southwestern North America source. The similarity of detrital 98 zircon spectra in all three Valle Group quartzite types to rocks of the adjacent Cordilleran margin support previous interpretations that Valle Group forearc basin sediments were deposited in proximity to rocks on the mainland of northwest Mexico and southwestern United States.

HEAT - Habitat Evaluation and Assessment Tools for Effective Environmental Evaluations: User’s Guide

DTIC Science & Technology

2012-12-01

surround- ing landscape (e.g., plants , animals, detritus, soil, the atmosphere, etc.) interact through a variety of physical, chemical, and... interactive geographic information system. Ecological Modelling 114:287–304. Ray, N., and M. A. Burgman. 2006. Subjective uncertainties in habitat...environmental impacts on ecological systems at numerous scales with varying degrees of success. Advances in technology have led many agen- cies to automate

Invasive woolly adelgid appears to drive seasonal hemlock and carcass inputs to a detritus-based stream

Treesearch

John S. Kominoski; Catherine M. Pringle; Becky A. Ball

2008-01-01

Ecosystems are experiencing rapid ecological changes due to human-driven alterations in climate, land-use, nutrient availability, and introduction of pests and pathogens. Many of these environmental changes are predicted to result in non-random loss of species that will alter community composition (VITOUSEK et a1. 1997, LOREAU et a1. 2001, ELLISON et a1. 200S). For...

Emplacement of pyroclastic density currents (PDCs) in a deep-sea environment: The Val d'Aveto Formation case (Northern Apennines, Italy)

NASA Astrophysics Data System (ADS)

Di Capua, Andrea; Groppelli, Gianluca

2016-12-01

The occurrence of PDC deposits in a foredeep basin sequence, named Val d'Aveto Formation (32-29 Ma, Northern Apennines, Italy), provides new information on the behavior of pyroclastic density currents entering the water. In this work, stratigraphic, petrographic and mineralogical features that characterize three pyroclastic deposits have been described and analyzed in the field (facies and lithological analysis on the blocky-size fraction) and in the laboratory (image analyses on the blocky-size detritus, optical analyses of the microtextures, mineralogical analyses through X-ray powder diffraction (XRPD) and scanning electron microscope with energy dispersive X-ray spectometry (SEM-EDS). The deposits are lapilli- to blocky-size, with a blocky-size fraction constituted of accidental detritus. In thin sections, their groundmass texture varies from porphyritic to eutaxitic where coarser particles become close each others. Growth rims have been also detected around plagioclase crystals. Pyrite habits and oxidation, and plagioclase albitization are consistent with hydrothermal temperature conditions of 200 °C. All these results have been compared with the information provided by modern examples of PDC deposits and laboratory experiments on the behavior of water/hot particles mixing. Grain-to-grain collision has been considered as the main flow mechanism that sustained and avoided the disaggregation of the PDCs entering the water.

The role of pH in structuring communities of Maine wetland macrophytes and chironomid larvae (Diptera)

USGS Publications Warehouse

Woodcock, T.S.; Longcore, J.R.; McAuley, D.G.; Mingo, T.M.; Bennatti, C.R.; Stromborg, K.L.

2005-01-01

Aquatic vascular plants, or macrophytes, are an important habitat component for many wetland organisms, and larvae of chironomid midges are ubiquitous components of wetland fauna. Many chironomids are primary consumers of algae and detritus and form an essential energetic link between allochthonous and autochthonous primary production and higher trophic levels, while others are predators and feed on smaller invertebrates. Live macrophytes serve mostly as habitat, whereas plant detritus serves as both habitat and as a food source. Assemblages of macrophytes and chironomid larvae were surveyed in ten Maine wetlands, five with low pH (5.5), and explained in terms of physical and chemical habitat variables. Macrophyte richness was significantly greater, and richness of chironomid larvae was lower, in low pH wetlands. There was no difference in chironomid abundance related to pH. However, community structure was related to pH, suggesting that competitive dominance of a few taxa was responsible for lower richness in low pH wetlands, whereas competition was weaker in high pH wetlands, making coexistence of more chironomid taxa possible. An examination of individual chironomid taxa by stepwise multiple regression showed that distribution of most taxa was controlled by water chemistry variables and macrophyte habit (i.e., floating, submergent).

Coral mucus fuels the sponge loop in warm- and cold-water coral reef ecosystems

PubMed Central

Rix, Laura; de Goeij, Jasper M.; Mueller, Christina E.; Struck, Ulrich; Middelburg, Jack J.; van Duyl, Fleur C.; Al-Horani, Fuad A.; Wild, Christian; Naumann, Malik S.; van Oevelen, Dick

2016-01-01

Shallow warm-water and deep-sea cold-water corals engineer the coral reef framework and fertilize reef communities by releasing coral mucus, a source of reef dissolved organic matter (DOM). By transforming DOM into particulate detritus, sponges play a key role in transferring the energy and nutrients in DOM to higher trophic levels on Caribbean reefs via the so-called sponge loop. Coral mucus may be a major DOM source for the sponge loop, but mucus uptake by sponges has not been demonstrated. Here we used laboratory stable isotope tracer experiments to show the transfer of coral mucus into the bulk tissue and phospholipid fatty acids of the warm-water sponge Mycale fistulifera and cold-water sponge Hymedesmia coriacea, demonstrating a direct trophic link between corals and reef sponges. Furthermore, 21–40% of the mucus carbon and 32–39% of the nitrogen assimilated by the sponges was subsequently released as detritus, confirming a sponge loop on Red Sea warm-water and north Atlantic cold-water coral reefs. The presence of a sponge loop in two vastly different reef environments suggests it is a ubiquitous feature of reef ecosystems contributing to the high biogeochemical cycling that may enable coral reefs to thrive in nutrient-limited (warm-water) and energy-limited (cold-water) environments. PMID:26740019

Maximum sedimentation ages and provenance of metasedimentary rocks from Tinos Island, Cycladic blueschist belt, Greece

NASA Astrophysics Data System (ADS)

Hinsken, Tim; Bröcker, Michael; Berndt, Jasper; Gärtner, Claudia

2016-10-01

U-Pb zircon ages of five metasedimentary rocks from the Lower Unit on Tinos Island (Cycladic blueschist belt, Greece) document supply of detritus from various Proterozoic, Paleozoic and Mesozoic source rocks as well as post-depositional metamorphic zircon formation. Essential features of the studied zircon populations are Late Cretaceous (70-80 Ma) maximum sedimentation ages for the lithostratigraphic succession above the lowermost dolomite marble, significant contributions from Triassic to Neoproterozoic source rocks, minor influx of detritus recording Paleoproterozoic and older provenance (1.9-2.1, 2.4-2.5 and 2.7-2.8 Ga) and a lack or paucity of zircons with Mesoproterozoic ages (1.1-1.8 Ga). In combination with biostratigraphic evidence, the new dataset indicates that Late Cretaceous or younger rocks occur on top of or very close to the basal Triassic metacarbonates, suggesting a gap in the stratigraphic record near the base of the metamorphic succession. The time frame for sediment deposition is bracketed by the youngest detrital zircon ages (70-80 Ma) and metamorphic overgrowths that are related to high-pressure/low-temperature overprinting in the Eocene. This time interval possibly indicates a significant difference to the sedimentation history of the southern Cyclades, where Late Cretaceous detrital zircons have not yet been detected.

Coral mucus fuels the sponge loop in warm- and cold-water coral reef ecosystems.

PubMed

Rix, Laura; de Goeij, Jasper M; Mueller, Christina E; Struck, Ulrich; Middelburg, Jack J; van Duyl, Fleur C; Al-Horani, Fuad A; Wild, Christian; Naumann, Malik S; van Oevelen, Dick

2016-01-07

Shallow warm-water and deep-sea cold-water corals engineer the coral reef framework and fertilize reef communities by releasing coral mucus, a source of reef dissolved organic matter (DOM). By transforming DOM into particulate detritus, sponges play a key role in transferring the energy and nutrients in DOM to higher trophic levels on Caribbean reefs via the so-called sponge loop. Coral mucus may be a major DOM source for the sponge loop, but mucus uptake by sponges has not been demonstrated. Here we used laboratory stable isotope tracer experiments to show the transfer of coral mucus into the bulk tissue and phospholipid fatty acids of the warm-water sponge Mycale fistulifera and cold-water sponge Hymedesmia coriacea, demonstrating a direct trophic link between corals and reef sponges. Furthermore, 21-40% of the mucus carbon and 32-39% of the nitrogen assimilated by the sponges was subsequently released as detritus, confirming a sponge loop on Red Sea warm-water and north Atlantic cold-water coral reefs. The presence of a sponge loop in two vastly different reef environments suggests it is a ubiquitous feature of reef ecosystems contributing to the high biogeochemical cycling that may enable coral reefs to thrive in nutrient-limited (warm-water) and energy-limited (cold-water) environments.

Variable δD values among major biochemicals in plants: Implications for environmental studies

NASA Astrophysics Data System (ADS)

DeBond, Nicole; Fogel, Marilyn L.; Morrill, Penny L.; Benner, Ronald; Bowden, Roxane; Ziegler, Susan

2013-06-01

The stable hydrogen isotope composition (δD) of major plant biochemicals is variable. We present δD values for cellulose, hemicelluloses and lignin of six plant species. The δD value for lignin is consistently lower than that of bulk tissue (by ˜50‰) and cellulose (by ˜100‰). We show that these differences can be used to assess the extent of degradation of organic matter from a single source. A decrease in the δDbulk of decomposing Spartina alterniflora roots and rhizomes from -72‰ to -87‰ was observed over 18 months, reflecting a relative enrichment of lignin content due to the preferential removal of polysaccharides from the detrital material. Similar changes in δ13C were observed previously during the degradation of these plant tissues. These findings indicate that the extent of organic matter degradation should be considered when using stable isotope approaches to assess possible sources of organic matter in soils and sediments. We show that the change in δDbulk of plant detritus is best described by an exponential equation, which is simpler than the multiple exponential decay (multi-G) model which best describes the change in δ13Cbulk of plant detritus. Therefore correcting for isotopic shifts caused by decomposition may be more easily accomplished using δD.

[Structure and function of Fenshuijiang Reservoir ecosystem based on the analysis with Ecopath model].

PubMed

Wu, Zhen; Jia, Pei-Qiao; Hu, Zhong-Jun; Chen, Li-Qiao; Gu, Zhi-Min; Liu, Qi-Gen

2012-03-01

Based on the 2008-2009 survey data of fishery resources and eco-environment of Fenshuijiang Reservoir, a mass balance model for the Reservoir ecosystem was constructed by Ecopath with Ecosim software. The model was composed of 14 functional groups, including silver carp, bighead carp, Hemibarbus maculates, Cutler alburnus, Microlepis and other fishes, Oligochaeta, aquatic insect, zooplankton, phytoplankton, and organic detritus, etc. , being able to better simulate Fenshuijiang Reservoir ecosystem. In this ecosystem, there were five trophic levels (TLs), and the nutrient flow mainly occurred in the first three TLs. Grazing and detritus food chains were the main energy flows in the ecosystem, but the food web was simpler and susceptible to be disturbed by outer environment. The transfer efficiency at lower TLs was relatively low, indicating that the ecosystem had a lower capability in energy utilization, and the excessive stock of nutrients in the ecosystem could lead to eutrophication. The lower connectance index, system omnivory index, Finn' s cycled index, and Finn's mean path length demonstrated that the ecosystem was unstable, while the high ecosystem property indices such as Pp/R and Pp/B showed that the ecosystem was immature and highly productive. It was suggested that Fenshuijiang Reservoir was still a developing new reservoir ecosystem, with a very short history and comparatively high primary productivity.

40 CFR 161.20 - Overview.

Code of Federal Regulations, 2011 CFR

2011-07-01

.... (1) The primary purpose of this part is to specify the types and minimum amounts of data and...)(7). (2) This part also specifies the types and minimum amounts of data and information the Agency...) Finally, this part specifies the types and minimum amounts of data and information that an applicant for...

A new genus and species of Macrochelidae (Acari:Mesostigmata) associated with the Texas leaf cutting ant, Atta texana (Buckley) in Louisiana, USA

Treesearch

Gerald W. Krantz; John Moser

2012-01-01

Adults and nymphs of a new genus and species of the family Macrochelidae are described from detritus cavities of the leaf-cutting ant, Atta texana. This new species is notable in having peritremes with no posterior loop, a series of small subterminal teeth on the fixed cheliceral digit rather than the single large tooth typical of other macrochelids...

Differences between standing and downed dead tree wood density reduction factors: A comparison across decay classes and tree species

Treesearch

Mark E. Harmon; Christopher W. Woodall; Becky Fasth; Jay Sexton; Misha Yatkov

2011-01-01

Woody detritus or dead wood is an important part of forest ecosystems and has become a routine facet of forest monitoring and inventory. Biomass and carbon estimates of dead wood depend on knowledge of species- and decay class-specifi c density or density reduction factors. While some progress has been made in determining these parameters for dead and downed trees (DD...

An Annotated Bibliography on the Biological Effects of Constructing Channels, Jetties, and other Coastal Structures.

DTIC Science & Technology

1983-01-01

was composed mostly of live seagrasses or detritus. Crustaceans were more abundant in the natural marsh than in the other two areas and showed a...measured. After more than a year no recolonization of seagrasses , Thalassia testudinwn and Syringodiwn filiforme, occurred in any dredged area. Some re...Intracoastal Waterway Dredging on Ichthyofauna and Benthic Macroinvertebrates," Technical Report Series No. 72-4, Georgia Marine Science Center, University

Integration of an Individual-Based Fish Bioenergetics Model into a Spatially Explicit Water Quality Model (CE-QUAL-ICM)

DTIC Science & Technology

2010-04-01

energy a fish can devote to growth being the difference between consumption in the form of food and the sum of life process expenditures , including...can incur an elemental deficit, and subsequently retain higher fractions of that element when it is in abun- dance to regain the target composition...Organic nitrogen and caloric content of detritus. Estuarine, Coastal, and Shelf Science 12: 39-47

Assimilation of Sea Color Data Into A Three Dimensional Biogeochemical Model: Sensitivity Experiments

NASA Astrophysics Data System (ADS)

Echevin, V.; Levy, M.; Memery, L.

The assimilation of two dimensional sea color data fields into a 3 dimensional coupled dynamical-biogeochemical model is performed using a 4DVAR algorithm. The biogeochemical model includes description of nitrates, ammonium, phytoplancton, zooplancton, detritus and dissolved organic matter. A subset of the biogeochemical model poorly known parameters (for example,phytoplancton growth, mortality,grazing) are optimized by minimizing a cost function measuring misfit between the observations and the model trajectory. Twin experiments are performed with an eddy resolving model of 5 km resolution in an academic configuration. Starting from oligotrophic conditions, an initially unstable baroclinic anticyclone splits into several eddies. Strong vertical velocities advect nitrates into the euphotic zone and generate a phytoplancton bloom. Biogeochemical parameters are perturbed to generate surface pseudo-observations of chlorophyll,which are assimilated in the model in order to retrieve the correct parameter perturbations. The impact of the type of measurement (quasi-instantaneous, daily mean, weekly mean) onto the retrieved set of parameters is analysed. Impacts of additional subsurface measurements and of errors in the circulation are also presented.

[Feeding changes for three Sphoeroides species (Tetraodontiformes: Tetraodontidae) after Isidore hurricane impact in Carbonera Inlet, Southeastern Gulf of Mexico].

PubMed

Palacios-Sánchez, Sonia Eugenia; Vega-Cendejas, María Eugenia

2010-12-01

The coexistence of ecologically similar species may occur because of resources distribution, such as prey and habitat type and segregation time, that minimizes the interspecific competition. The changes brought about by Hurricane Isidore in the distribution of food resources by three coexisting fish species of the family Tetraodontidae (Sphoeroides nephelus, S. spengleri and S testudineus), were analyzed at the Carbonera Inlet. Sphoeroides spp. based their food on benthic organisms; principally, they consume mussels (Brachidontes sp.), barnacles (Balanus sp.) and gastropods (Crepidula sp). Before hurricane impact, the three species share the available food resources in different proportions (bivalves, gastropods, barnacles and decapods), according to different strategies that enabled them to coexist and reduce interspecific competition. After the impact, the abundance of available prey decreased and the interespecific competition for food increased, leading to S. testudines and S. nephelus change their trophic spectrum (xiphosurans, amphipods, isopods and detritus) and displacing S. splengleri of the inlet. The distribution of food resources was conditioned by the abundance and diversity of prey, as well as the adaptive response of each species.

Elucidating the nutritional dynamics of fungi using stable isotopes.

PubMed

Mayor, Jordan R; Schuur, Edward A G; Henkel, Terry W

2009-02-01

Mycorrhizal and saprotrophic (SAP) fungi are essential to terrestrial element cycling due to their uptake of mineral nutrients and decomposition of detritus. Linking these ecological roles to specific fungi is necessary to improve our understanding of global nutrient cycling, fungal ecophysiology, and forest ecology. Using discriminant analyses of nitrogen (delta(15)N) and carbon (delta(13)C) isotope values from 813 fungi across 23 sites, we verified collector-based categorizations as either ectomycorrhizal (ECM) or SAP in > 91% of the fungi, and provided probabilistic assignments for an additional 27 fungi of unknown ecological role. As sites ranged from boreal tundra to tropical rainforest, we were able to show that fungal delta(13)C (26 sites) and delta(15)N (32 sites) values could be predicted by climate or latitude as previously shown in plant and soil analyses. Fungal delta(13)C values are likely reflecting differences in C-source between ECM and SAP fungi, whereas (15)N enrichment of ECM fungi relative to SAP fungi suggests that ECM fungi are consistently delivering (15)N depleted N to host trees across a range of ecosystem types.

Resource utilization and trophic position of nematodes and harpacticoid copepods in and adjacent to Zostera noltii beds

NASA Astrophysics Data System (ADS)

Vafeiadou, A.-M.; Materatski, P.; Adão, H.; De Troch, M.; Moens, T.

2014-07-01

This study examines the resource use and trophic position of nematodes and harpacticoid copepods at the genus/species level in an estuarine food web in Zostera noltii beds and in adjacent bare sediments using the natural abundance of stable carbon and nitrogen isotopes. Microphytobenthos and/or epiphytes are among the main resources of most taxa, but seagrass detritus and sediment particulate organic matter contribute as well to meiobenthos nutrition, which are also available in deeper sediment layers and in unvegetated patches close to seagrass beds. A predominant dependence on chemoautotrophic bacteria was demonstrated for the nematode genus Terschellingia and the copepod family Cletodidae. A predatory feeding mode is illustrated for Paracomesoma and other Comesomatidae, which were previously considered first-level consumers (deposit feeders) according to their buccal morphology. The considerable variation found in both resource use and trophic level among nematode genera from the same feeding type, and even among congeneric nematode species, shows that the interpretation of nematode feeding ecology based purely on mouth morphology should be avoided.

Ecological bioavailability of permethrin and p,p'-DDT: toxicity depends on type of organic matter resource.

PubMed

de Perre, Chloé; Trimble, Andrew J; Maul, Jonathan D; Lydy, Michael J

2014-02-01

Hydrophobic organic contaminants readily partition from aqueous to organic phases in aquatic systems with past research largely focusing on sediment. However, within many aquatic systems, matrices such as leaf material and detritus are abundant and ecologically important, as they may represent a primary exposure route for aquatic invertebrates. The objectives of the present study were to examine partitioning and toxicity to Hyalella azteca among permethrin and p,p'-DDT contaminated sediment, leaf, and a sediment-leaf mixture. Log organic carbon-water partitioning coefficients ranged from 4.21 to 5.82 for both insecticides, and were greatest within sediment and lowest in coarse leaf material. H. azteca lethal concentrations for 50% of the population (LC50s) ranged from 0.5 to 111μgg(-1) organic carbon, and were dependent on the matrix composition. The variation in sorption and toxicity among matrices common within stream ecosystems suggests that the ecological niche of aquatic organisms may be important for estimating risk of hydrophobic pesticides. Copyright © 2013 Elsevier Ltd. All rights reserved.

Cenozoic sedimentation in the Mumbai Offshore Basin: Implications for tectonic evolution of the western continental margin of India

NASA Astrophysics Data System (ADS)

Nair, Nisha; Pandey, Dhananjai K.

2018-02-01

Interpretation of multichannel seismic reflection data along the Mumbai Offshore Basin (MOB) revealed the tectonic processes that led to the development of sedimentary basins during Cenozoic evolution. Structural interpretation along three selected MCS profiles from MOB revealed seven major sedimentary sequences (∼3.0 s TWT, thick) and the associated complex fault patterns. These stratigraphic sequences are interpreted to host detritus of syn- to post rift events during rift-drift process. The acoustic basement appeared to be faulted with interspaced intrusive bodies. The sections also depicted the presence of slumping of sediments, subsidence, marginal basins, rollover anticlines, mud diapirs etc accompanied by normal to thrust faults related to recent tectonics. Presence of upthrusts in the slope region marks the locations of local compression during collision. Forward gravity modeling constrained with results from seismic and drill results, revealed that the crustal structure beneath the MOB has undergone an extensional type tectonics intruded with intrusive bodies. Results from the seismo-gravity modeling in association with litholog data from drilled wells from the western continental margin of India (WCMI) are presented here.

Fuzzy Classification of Ocean Color Satellite Data for Bio-optical Algorithm Constituent Retrievals

NASA Technical Reports Server (NTRS)

Campbell, Janet W.

1998-01-01

The ocean has been traditionally viewed as a 2 class system. Morel and Prieur (1977) classified ocean water according to the dominant absorbent particle suspended in the water column. Case 1 is described as having a high concentration of phytoplankton (and detritus) relative to other particles. Conversely, case 2 is described as having inorganic particles such as suspended sediments in high concentrations. Little work has gone into the problem of mixing bio-optical models for these different water types. An approach is put forth here to blend bio-optical algorithms based on a fuzzy classification scheme. This scheme involves two procedures. First, a clustering procedure identifies classes and builds class statistics from in-situ optical measurements. Next, a classification procedure assigns satellite pixels partial memberships to these classes based on their ocean color reflectance signature. These membership assignments can be used as the basis for a weighting retrievals from class-specific bio-optical algorithms. This technique is demonstrated with in-situ optical measurements and an image from the SeaWiFS ocean color satellite.

Changes and variations of polycyclic aromatic hydrocarbon concentrations in fish, barnacles and crabs following an oil spill in a mangrove of Guanabara Bay, Southeast Brazil.

PubMed

Soares-Gomes, Abílio; Neves, Roberta L; Aucélio, Ricardo; Van Der Ven, Paulo H; Pitombo, Fábio B; Mendes, Carla L T; Ziolli, Roberta L

2010-08-01

On April 26th, 2005, an accident caused a leak of 60,000L of Diesel Oil Type "B", freighted by train wagons upstream on a mangrove area within Guanabara Bay, Southeast Brazil. After the accident, samples from animals with different biological requirements were collected in order to monitor polycyclic aromatic hydrocarbons concentrations for the following 12months. Sessile, mobile, carnivorous, omnivorous, organic detritus feeders, planktivorous and suspension feeders were some of the attributes compared. Concentrations of PAHs did not vary in relation to different dietary habits and the best response was from the sessile suspensivorous barnacles. A background level of <50microgkg(-1) was suggested based on the reference site and on values observed in the following months after the accident. The highest values of PAH concentrations were observed in barnacles in the first month immediately after the spill, decreasing to background levels after few months. Barnacles are suggested as a sentinel species. Copyright 2010 Elsevier Ltd. All rights reserved.

Chemical characterization of detrital sugar chains with peptides in oceanic surface particulate organic matter

NASA Astrophysics Data System (ADS)

Tsukasaki, A.; Nishida, T.; Tanoue, E.

2016-02-01

For better understanding of the dynamics of organic matter in the ocean interior, particulate organic matter (POM) in oceanic surface water is a key material as a starting material in food chain and biological carbon pump, and the source of dissolved organic matter. POM consists of a mixture of non-living POM (detritus) and small amount of living POM (organisms). Particulate combined amino acids (PCAAs) are one of the major components of POM and the most important source of nitrogen and carbon for heterotrophic organisms in marine environments. In our previous studies of molecular-level characterization of PCAAs using electrophoretic separation (SDS-PAGE: sodium dodecyl sulfate-polyacrylamide gel electrophoresis) with specific detection of protein/peptide and sugar chains, we reported that most of PCAAs existed as small-sized peptide chains with carbohydrate-rich remnants. Although carbohydrates are one of the major carbon components of POM, the details of molecular-level structures including sugar chains are unknown. In this study, we applied electrophoretic separation for sugar chains (FACE: fluorophore-assisted carbohydrate electrophoresis) to the POM samples collected from the surface water of the Pacific Ocean. The results showed that sugar chains with various degree of polymerization were detected in POM. The possible roles of such sugar chains in marine biogeochemical cycle of organic matter are discussed in the presentation.

Rainfall changes affect the algae dominance in tank bromeliad ecosystems.

PubMed

Pires, Aliny Patricia Flauzino; Leal, Juliana da Silva; Peeters, Edwin T H M

2017-01-01

Climate change and biodiversity loss have been reported as major disturbances in the biosphere which can trigger changes in the structure and functioning of natural ecosystems. Nonetheless, empirical studies demonstrating how both factors interact to affect shifts in aquatic ecosystems are still unexplored. Here, we experimentally test how changes in rainfall distribution and litter diversity affect the occurrence of the algae-dominated condition in tank bromeliad ecosystems. Tank bromeliads are miniature aquatic ecosystems shaped by the rainwater and allochthonous detritus accumulated in the bases of their leaves. Here, we demonstrated that changes in the rainfall distribution were able to reduce the chlorophyll-a concentration in the water of bromeliad tanks affecting significantly the occurrence of algae-dominated conditions. On the other hand, litter diversity did not affect the algae dominance irrespective to the rainfall scenario. We suggest that rainfall changes may compromise important self-reinforcing mechanisms responsible for maintaining high levels of algae on tank bromeliads ecosystems. We summarized these results into a theoretical model which suggests that tank bromeliads may show two different regimes, determined by the bromeliad ability in taking up nutrients from the water and by the total amount of light entering the tank. We concluded that predicted climate changes might promote regime shifts in tropical aquatic ecosystems by shaping their structure and the relative importance of other regulating factors.

Geochemistry of a marine phosphate deposit: A signpost to phosphogenesis

USGS Publications Warehouse

Piper, David Z.; Perkins, R.B.

2014-01-01

The Permian age Phosphoria Formation in southeastern Idaho and adjoining states represents possibly the largest marine phosphate deposit in the world. The Meade Peak Member, which contains the highest concentrations and amount of carbonate fluorapatite in the formation, was not significantly altered by mechanical reworking during deposition or subsequently by chemical weathering. Thus, its present composition reflects properties of the Phosphoria Sea that were critical to its accumulation and possibly to the accumulation of most major marine phosphate deposits. These properties included the chemistry of the water column, the hydrography, and the level of primary productivity. Calculated accumulation rates of the PO43− and trace nutrients – Cd, Cu, Ni, and Zn – recorded a dynamic upwelling rate of c.30 m year−1 that supported primary productivity of 2g C m−2day−1. High accumulation rates of the hydrogenous redox-sensitive trace metals – Cr, Mo, U, and V – reflect bottom-water redox conditions that were dominantly suboxic, maintained by a balance between the oxidation of ~ 8% of the organic detritus that settled out of the photic zone and advection of bottom water with a residence time of c.10 years. A limited flux into the basin of siliciclastic lithogenous debris contributed further to elevated concentrations of the seawater-derived sediment fractions.

An indicator-based evaluation of Black Sea food web dynamics during 1960-2000

NASA Astrophysics Data System (ADS)

Akoglu, Ekin; Salihoglu, Baris; Libralato, Simone; Oguz, Temel; Solidoro, Cosimo

2014-06-01

Four Ecopath mass-balance models were implemented for evaluating the structure and function of the Black Sea ecosystem using several ecological indicators during four distinctive periods (1960s, 1980-1987, 1988-1994 and 1995-2000). The results exemplify how the Black Sea ecosystem structure started to change after the 1960s as a result of a series of trophic transformations, i.e., shifts in the energy flow pathways through the food web. These transformations were initiated by anthropogenic factors, such as eutrophication and overfishing, that led to the transfer of large quantities of energy to the trophic dead-end species, which had no natural predators in the ecosystem, i.e., jellyfish whose biomass increased from 0.03 g C m- 2 in 1960-1969 to 0.933 g C m- 2 in 1988-1994. Concurrently, an alternative short pathway for energy transfer was formed that converted significant amounts of system production back to detritus. This decreased the transfer efficiency of energy flow from the primary producers to the higher trophic levels from 9% in the 1960s to 3% between 1980 and 1987. We conclude that the anchovy stock collapse and successful establishment of the alien comb-jelly Mnemiopsis in 1989 were rooted in the trophic interactions in the food web, all of which were exacerbated because of the long-term establishment of a combination of anthropogenic stressors.

Rainfall changes affect the algae dominance in tank bromeliad ecosystems

PubMed Central

Pires, Aliny Patricia Flauzino; Leal, Juliana da Silva; Peeters, Edwin T. H. M.

2017-01-01

Climate change and biodiversity loss have been reported as major disturbances in the biosphere which can trigger changes in the structure and functioning of natural ecosystems. Nonetheless, empirical studies demonstrating how both factors interact to affect shifts in aquatic ecosystems are still unexplored. Here, we experimentally test how changes in rainfall distribution and litter diversity affect the occurrence of the algae-dominated condition in tank bromeliad ecosystems. Tank bromeliads are miniature aquatic ecosystems shaped by the rainwater and allochthonous detritus accumulated in the bases of their leaves. Here, we demonstrated that changes in the rainfall distribution were able to reduce the chlorophyll-a concentration in the water of bromeliad tanks affecting significantly the occurrence of algae-dominated conditions. On the other hand, litter diversity did not affect the algae dominance irrespective to the rainfall scenario. We suggest that rainfall changes may compromise important self-reinforcing mechanisms responsible for maintaining high levels of algae on tank bromeliads ecosystems. We summarized these results into a theoretical model which suggests that tank bromeliads may show two different regimes, determined by the bromeliad ability in taking up nutrients from the water and by the total amount of light entering the tank. We concluded that predicted climate changes might promote regime shifts in tropical aquatic ecosystems by shaping their structure and the relative importance of other regulating factors. PMID:28422988

Quantifying foodweb interactions with simultaneous linear equations: Stable isotope models of the Truckee River, USA

USGS Publications Warehouse

Saito, L.; Redd, C.; Chandra, S.; Atwell, L.; Fritsen, C.H.; Rosen, Michael R.

2007-01-01

Aquatic foodweb models for 2 seasons (relatively high- [March] and low-flow [August] conditions) were constructed for 4 reaches on the Truckee River using ??13C and ??15N data from periphyton, macroinvertebrate, and fish samples collected in 2003 and 2004. The models were constructed with isotope values that included measured periphyton signatures and calculated mean isotope values for detritus and seston as basal food sources of each food web. The pseudo-optimization function in Excel's Solver module was used to minimize the sum of squared error between predicted and observed stable-isotope values while simultaneously solving for diet proportions for all foodweb consumers and estimating ??13C and ??15N trophic enrichment factors. This approach used an underdetermined set of simultaneous linear equations and was tested by running the pseudo-optimization procedure for 500 randomly selected sets of initial conditions. Estimated diet proportions had average standard deviations (SDs) of 0.03 to 0.04??? and SDs of trophic enrichment factors ranged from <0.005 to 0.05??? based on the results of the 500 runs, indicating that the modeling approach was very robust. However, sensitivity analysis of calculated detritus and seston ??13C and ??15N values indicated that the robustness of the approach is dependent on having accurate measures of all observed foodweb-component ??13c and ??15N values. Model results from the 500 runs using the mean isotope values for detritus and seston indicated that upstream food webs were the simplest, with fewer feeding groups and trophic interactions (e.g., 21 interactions for 10 feeding groups), whereas food webs for the reach downstream of the Reno-Sparks metropolitan area were the most complex (e.g., 58 interactions for 16 feeding groups). Nonnative crayfish were important omnivores in each reach and drew energy from multiple sources, but appeared to be energetic dead ends because they generally were not consumed. Predatory macroinvertebrate diets varied along the river and affected estimated trophic positions of fish that consumed them. Differences in complexity and composition of the food webs appeared to be related to season, but could also have been caused by interactions with nonnative species, especially invasive crayfish. ?? 2007 by The North American Benthological Society.

Drastic shifts in the Levant hydroclimate during the last interglacial indicate changes in the tropical climate and winter storm tracks

NASA Astrophysics Data System (ADS)

Kiro, Y.; Goldstein, S. L.; Kushnir, Y.; Lazar, B.; Stein, M.

2017-12-01

Marine Isotope Stage (MIS) 5e was a warm interglacial with where with significantly varying insolation and hence varied significantly throughout this time suggesting highly variable climate. The ICDP Dead Sea Deep Drilling Project recovered a 460m record of the past 220ka, reflecting the variable climate along MIS 5e. This time interval is reflected by alternating halite and detritus sequences, including 20m of halite-free detritus during the peak insolation at 125 ka. The Dead Sea salt budget indicates that the Levant climate was extremely arid when halite formed, reaching 20% of the present runoff. The halite-free detritus layer reflects increased precipitation to levels similar to present day, assuming similar spatial and temporal rainfall patterns. However, the 234U/238U activity ratio in the lake, reflected by authigenic minerals (aragonite, gypsum and halite), shifts from values of 1.5 (reflecting the Jordan River, the present main water source) down to 1.3 at 125-122ka during the MIS5e insolation peak and 1.0 at 118-116ka. The low 234U/238U reflects increased flash floods and eastern water sources (234U/238U 1.05-1.2) from the drier part of the watershed in the desert belt. The intermediate 234U/238U of 1.3 suggests that the Jordan River, fed from Mediterranean-sourced storm tracks, continued to flow along with an increase in southern and eastern water sources. NCAR CCSM3 climate model runs for 125ka indicate increases in both Summer and Winter precipitation. The drastic decrease to 234U/238U 1.0 occurs during the driest period, indicating a near shutdown of Jordan River flow, and water input only through flash floods and southern and eastern sources. The 120ka climate model runs shows a decrease in Winter and increase in Fall precipitation as a result of an increased precipitation in the tropics. The extreme aridity, associated with increased flooding is similar to patterns expected due to future warming. The increase in aridity is the result of expansion of the desert-belt and increases in southern precipitation and indicates an important link between the tropical and mid-latitude climate.

PM2.5 source apportionment in the southeastern U.S.: Spatial and seasonal variations during 2001-2005

NASA Astrophysics Data System (ADS)

Chen, Yingjun; Zheng, Mei; Edgerton, Eric S.; Ke, Lin; Sheng, Guoying; Fu, Jiamo

2012-04-01

The seasonal and spatial variations of source contributions of 112 composite fine particulate matter (PM2.5) samples collected in the Southeastern Aerosol Research and Characterization Study (SEARCH) monitoring network during 2001-2005 using molecular marker-based chemical mass balance (CMB-MM) model were determined. The lowest PM2.5 concentration occurs in January with higher values in warm months (maxima in July at four inland sites versus October at the coastal sites). Sulfate shows a similar pattern and plays a primary role in PM2.5 seasonality. Carbonaceous material (organic matter plus EC) exhibits less seasonality, but more spatial variations between the inland and coastal sites. Compared with the data at coastal sites, source attributions of diesel exhaust, gasoline exhaust, other organic matter (other OM), secondary sulfate, nitrate, and ammonium in PM2.5 mass at inland sites are higher. The difference in source attributions of wood combustion, meat cooking, vegetative detritus, and road dust among the eight sites is not significant. Contributions of eight primary sources to fine OC are wood burning (17 ± 19%), diesel exhaust (9 ± 4%), gasoline exhaust (5 ± 7%), meat cooking (5 ± 5%), road dust (2 ± 3%), vegetative detritus (2 ± 2%), cigarette smoke (2 ± 2% at four urban sites), and coke production (2 ± 1% only at BHM). Primary and secondary sources explain 82-100% of measured PM2.5 mass at the eight sites, including secondary ionic species (SO42-, NH4+, and NO3-; 41.4 ± 5.7%), identified OM (24.9 ± 11.3%), "other OM" (unexplained OM, 23.3 ± 10.3%), and "other mass" (11.4 ± 9.6%). Vehicle exhaust from both diesel and gasoline contributes the lowest fraction to PM2.5 mass in July and higher fractions at BHM and JST than other sites. Wood combustion, in contrast, contributes significantly to a larger fraction in winter than in summer. Road dust shows relatively high levels in July and April across the eight sites, while minor sources such as meat cooking and other sources (e.g., vegetative detritus, coke production, and cigarette smoke) show relatively small seasonal and spatial variations in the SEARCH monitoring network.

Experimental study of reparative regeneration processes in the wound treated with bioactive dressings.

PubMed

Chekmareva, I A

2002-02-01

Quantitative and structural functional analysis of granulation tissue cells during treatment with protein-polysaccharide dressing Collahit F was carried out. The preparation effectively cleansed the wound from detritus, prevented secondary infection due to stimulation of the functional activity of macrophages and due to the effect of its antiseptic component (furagin), and stimulated proliferative activity of fibroblasts and granulation tissue microvessels on day 5 of treatment, thus promoting repair processes in the wound.

Verification and Evaluation of Aquatic Contaminant Simulation Module (CSM)

DTIC Science & Technology

2016-08-01

RECOVERY model (Boyer et al. 1994, Ruiz et al. 2000) and Water- quality Analysis Simulation Program (WASP) model (Wool et al. 2006). This technical note (TN...bacteria, and detritus). Natural waters can contain a mixture of solid particles ranging from gravel (2 mm to 20 mm) or sand (0.07 mm to 2 mm) down to... quality perspective, cohesive sediments are usually of greater importance in water quality modeling. The chemical species in the active sediment

Impacts of the Nutrient Inputs from Riverine on the Dynamic and Community Structure of Fungal-like Protists in the Coastal Ocean Ecosystems

NASA Astrophysics Data System (ADS)

Duan, Y.; Wang, G.; Xie, N.

2016-02-01

The coastal ocean connects terrestrial (e.g., rivers and estuaries) with oceanic ecosystems and is considered as a major component of global carbon cycles and budgets. The coastal waters are featured with a high biodiversity and high primary production. Because of the excessive primary production, a large fraction of primary organic matter becomes available to consumers as detritus in the coastal waters. Bacterioplankton have long been known to play a key role in the degradation of this detritus, and export and storage of organic matter in the coastal ecosystems. However, the primary and secondary production and the carbon biogeochemical processes in the ecosystems are largely regulated by nutrient inputs from riverine and other anthropogenic activities through heterotrophic microbial communities. Thraustochytrids, commonly known as fungal-like protists, are unicellular heterotrophic protists and are recently acknowledged to play a significant role in ocean carbon cycling. Their abundance exceeds that of bacterioplankton in the most time of the year in the coastal waters of China. Also, their abundance and diversity are largely regulated by nutrients inputs from riverine and other anthropogenic activities. Our findings support that thraustochytrids are a dominant heterotrophic microbial group in the coastal waters. Evidently, thraustochytrids are an import, but neglected, component in microbial carbon biogeochemical processes of the coastal ocean.

Increased sedimentation following the Neolithic Revolution in the Southern Levant

NASA Astrophysics Data System (ADS)

Lu, Yin; Waldmann, Nicolas; Nadel, Dani; Marco, Shmuel

2017-05-01

The Dead Sea drainage basin offers a rare combination of well-documented substantial climate change, intense tectonics and abundant archaeological evidence for past human activity in the Southern Levant. It serves as a natural laboratory for understanding how sedimentation rates in a deep basin are related to climate change, tectonics, and anthropogenic impacts on the landscape. Here we show how basin-wide erosion rates are recorded by thicknesses of rhythmic detritus laminae and clastic sediment accumulation rates in a long core retrieved by the Dead Sea Deep Drilling Project in the Dead Sea depocenter. During the last 11.5 kyr the average detrital accumulation rate is 3-4 times that during the last two glacial cycles (MIS 7c-2), and the average thickness of detritus laminae in the last 11.6 kyr is 4.5 times that between 21.7 and 11.6 ka, implying an increased erosion rate on the surrounding slopes during the Holocene. We estimate that this intensified erosion is incompatible with tectonic and climatic regimes during the corresponding time interval and further propose a close association with the Neolithic Revolution in the Levant (beginning at 11.5 ka). We thus suggest that human impact on the landscape was the primary driver causing the intensified erosion and that the Dead Sea sedimentary record serves as a reliable recorder of this impact since the Neolithic Revolution.

Mosquito species involved in the circulation of West Nile and Usutu viruses in Italy.

PubMed

Mancini, Giuseppe; Montarsi, Fabrizio; Calzolari, Mattia; Capelli, Gioia; Dottori, Michele; Ravagnan, Silvia; Lelli, Davide; Chiari, Mario; Santilli, Adriana; Quaglia, Michela; Quaglia, Michela; Federici, Valentina; Monaco, Federica; Goffredo, Maria; Savini, Giovanni

2017-06-30

Usutu (USUV) and West Nile (WNV) are mosquito-borne Flavivirus emerged in Italy in 1996 and 1998, respectively, and reappeared 10 years later. The aim of this work is to review the Italian mosquito species found positive for WNV and USUV between 2008 and 2014. Moreover, the role of mosquitoes in promoting the overwintering of these viruses is discussed, as a result of the mosquito collections performed in Molise region between September 2010 and April 2011. Overall 99,000 mosquitoes were collected: 337 and 457 mosquito pools tested positive by real time reverse transcriptase polymerase chain reaction (real time RT-PCR) for WNV and USUV, respectively. West Nile virus was detected in pools of Culex pipiens s.l. (329), Ochlerotatus caspius (4), Culex modestus (2), and Culex spp. (2). Positive USUV pools were from Cx. pipiens s.l. (435), Aedes albopictus (12), Oc. caspius (5), Culex spp. (2), Anopheles maculipennis s.l. (1), Culiseta annulata (1), and Ochlerotatus detritus (1). In Molise region, 1,694 mosquitoes were collected, and USUV was identi ed in Cx. pipiens s.l., Cs. annulata, and Oc. detritus pools. This paper shows that Cx. pipiens s.l. is the mosquito species most involved in the WNV and USUV circulation in Italy, although other species would also support the spread of both the viruses during Winter.

Implications of diapir-derived detritus and gypsic paleosols in Lower Triassic strata near the Castle Valley salt wall, Paradox Basin, Utah

NASA Astrophysics Data System (ADS)

Lawton, Timothy F.; Buck, Brenda J.

2006-10-01

Gypsum-bearing growth strata and sedimentary facies of the Moenkopi Formation on the crest and NE flank of the Castle Valley salt wall in the Paradox Basin record salt rise, evaporite exposure, and salt-withdrawal subsidence during the Early Triassic. Detrital gypsum and dolomite clasts derived from the middle Pennsylvanian Paradox Formation were deposited in strata within a few kilometers of the salt wall and indicate that salt rise rates roughly balanced sediment accumulation, resulting in long-term exposure of mobile evaporite. Deposition took place primarily in flood-basin or inland sabkha settings that alternated between shallow subaqueous and subaerial conditions in a hyperarid climate. Matrix-supported and clast-supported conglomerates with gypsum fragments represent debris-flow deposits and reworked debris-flow deposits, respectively, interbedded with flood-basin sandstone and siltstone during development of diapiric topography. Mudstone-rich flood-basin deposits with numerous stage I to III gypsic paleosols capped by eolian gypsum sand sheets accumulated during waning salt-withdrawal subsidence. Association of detrital gypsum, eolian gypsum, and gypsic paleosols suggests that the salt wall provided a common source for gypsum in the surrounding strata. This study documents a previously unrecognized salt weld with associated growth strata containing diapir-derived detritus and gypsic palesols that can be used to interpret halokinesis.

Morphological variation of dinoflagellate Prorocentrum lima (Ehrenberg) Dodge with geographical difference.

PubMed

Yoo, Jong Su

2004-01-01

Prorocentrum lima (Ehrenberg) Dodge, one of the cosmopolitan dinoflagellates, is basically benthic and is found on the surface of macroalgae and detritus. The identification of this species requires detailed morphological observation because of its close similarity to other benthic Prorocentrum species. The purpose of this study is to detect the morphological variability of P. lima using culture clones collected from several areas to find an adequate way of subdividing the species. In this study, 33 clones of P. lima were collected from Saipan, Tahiti, Indonesia, Japan and Bermuda, and their thecal valves and periflagellar area were observed by means of light microscopy with differential interference contrast optics and scanning electron microscopy. In general cells have two centrally located pyrenoids and a posterior nucleus. The surface of both valves has many valve pores except the center. Evenly spaced marginal pores are located along the edge of the valves. P. lima samples studied herein were subdivided into four major types (ellipsoidal, general, short, and elongate ovoid) according to their shapes, length-to-width ratio and number of valve pores. The length-to-width ratios of ellipsoidal, general, short, and elongate ovoid types were 1.32, 1.33-1.43, 1.20-1.27, and 1.53-1.60 microm respectively. Also there were slight differences in the number of valve pores. The number of valve pores examined in this study ranges from 40 to 97: ellipsoidal, general, and short ovoid types range from 40 to 91, while an elongate ovoid type ranges from 80 to 97. The combination of valve shape, number of valve pores and length-to-width ratio provides useful information on the morphological variation of P. lima.

Triassic arc-derived detritus in the Triassic Karakaya accretionary complex was not derived from either the S Eurasian margin (Istanbul terrane) or the N Gondwana margin (Taurides)

NASA Astrophysics Data System (ADS)

Ustaömer, Timur; Ayda Ustaömer, Petek; Robertson, Alastair H. F.; Gerdes, Axel; Zulauf, Gernold

2014-05-01

We present new U-Pb zircon source age data for Upper Triassic sandstones of the Istanbul Terrane (S Eurasian margin) and also for Triassic sandstones of the Taurides (N Gondwana margin). The main aim is to detect and quantify the contribution of Triassic magmatism as detritus to either of these crustal blocks. This follows the recent discovery of a Triassic magmatic arc source for the Triassic sandstones of the Palaeotethyan Karakaya subduction-accretion complex (Ustaömer et al. 2013; this meeting). Carboniferous (Variscan) zircon grains also form a significant detrital population, plus several more minor populations. Six sandstone samples were studied, two from the İstanbul Terrane (Bakırlıkıran Formation of the Kocaeli Triassic Basin) and four from the Tauride Autochthon (latest Triassic Üzümdere Formation and Mid-Triassic Kasımlar Formations; Beyşehir region). Detrital zircon grains were dated by the laser ablation-inductively coupled plasma-mass spectrometer (LA-ICP-MS) U-Pb method at Goethe University, Frankfurt. Our results do not reveal Triassic detritus in the Üzümdere Formation. The U-Pb age of the analysed zircon grains ranges from 267 Ma to 3.2 Ga. A small fraction of Palaeozoic zircons are Permian (267 to 296 Ma), whereas the remainder are Early Palaeozoic. Ordovician grains (4%) form two age clusters, one at ca. 450 Ma and the other at ca. 474 Ma. Cambrian-aged grains dominate the zircon population, while the second largest population is Ediacaran (576 to 642 Ma). Smaller populations occur at 909-997 Ma, 827-839 Ma, 1.8-2.0 Ga and 2.4-2.6 Ga. The sandstones of the Kasımlar Formation have similar zircon age cluster to those of the somewhat younger Üzümdere Formation, ranging from 239 Ma to 2.9 Ga. A few grains gave Anisian ages. Cambrian zircon grains are less pronounced than in the Kasımlar Formation compared to the Üzümdere Formation. The detrital zircon record of Tauride sandstones, therefore, not indicates significant contribution of Triassic or Carboniferous (Variscan) arc sources, in marked contrast to those of the Triassic Karakaya subduction complex. In comparison, the ages of the analysed zircons in the Upper Triassic sandstones of the Istanbul Terrane range from 294 Ma to 3.1 Ga. Triassic zircons are again absent, while Variscan-aged zircons (294 to 339 Ma) dominate the zircon population. Additional zircon populations are dated at 554 to 655 Ma, 0.9 to 1.2 Ga, 1.5 Ga, 1.65 Ga, 2.0 to 2.15 and 2.5 to 2.8 Ga. The Precambrian zircon age spectra are compatible with derivation from an Avalonian/Amazonian/Baltic crustal provenance. In summary, there is no evidence in either the Triassic sandstones of the İstanbul Terrane or of the Taurides of the Triassic magmatic arc source that dominates the Triassic Karakaya subduction-accretion complex. Where then was the source of the Karakaya arc detritus? A likely option is that the Karakaya subduction-accretion complex is an exotic terrane that was detached from a source magmatic arc and displaced to its present location, probably prior the initial deposition of the Early Jurassic cover sediments. This study was supported by TUBITAK, Project No: 111R015

Multi proxy chemical properties of freshwater sapropel

NASA Astrophysics Data System (ADS)

Stankevica, Karina; Rutina, Liga; Burlakovs, Juris; Klavins, Maris

2014-05-01

Freshwater sapropel is organic rich lake sediment firstly named "gyttja" by Hampus van Post in 1862. It is composed of organic remains such as shell detritus, plankton, chitin of insects, spores of higher plants and mineral part formed in eutrophic lake environments. The most appropriate environments for the formation of sapropel are in shallow, overgrown post-glacial lakes and valleys of big rivers in boreal zone, while thick deposits of such kind of organic sediments rarely can be found in lakes on permafrost, mountainous regions or areas with increased aridity. Organic lake sediments are divided in 3 classes according the content of organic matter and mineral part: biogenic, clastic and mixed. The value of sapropel as natural resource increases with the content of organic matter and main applications of sapropel are in agriculture, medicine, cosmetic and chemical industry. The research of sapropel in Latvia has shown that the total amount of this natural resource is close to 2 billion m3 or ~500 million tons. Sapropel has fine, dispersed structure and is plastic, but colour due to the high natural content of phosphorus usually is dark blue, later after drying it becomes light blue. Main research of the sapropel nowadays is turned to investigation of interactions among organic and mineral part of the sapropel with living organisms thus giving the inside look in processes and biological activity of the formation. From the chemical point of view sapropel contains lipids (bitumen), water-soluble substances that are readily hydrolyzed, including humic and fulvic acids, cellulose and the residual part, which does not hydrolyze. In this work we have analyzed the class of organic sapropel: peaty, cyanobacterial and green algal types, as well as siliceous sapropel, in order to determine the presence of biologically active substances, including humic substances, proteins and enzymes as well as to check free radical scavenging activity. Samples were collected from lakes which are recognized as promising for sapropel extraction and the study may benefit the use of sapropel for soil amendments, feed additives and chemical processing.

Detrital Controls on Dissolved Organic Matter in Soils: A Field Experiment

NASA Astrophysics Data System (ADS)

Lajtha, K.; Crow, S.; Yano, Y.; Kaushal, S.; Sulzman, E.; Sollins, P.

2004-12-01

We established a long-term field study in an old growth coniferous forest at the H.J. Andrews Experimental Forest, OR, to address how detrital quality and quantity control soil organic matter accumulation and stabilization. The Detritus Input and Removal Treatments (DIRT) plots consist of treatments that double leaf litter, double woody debris inputs, exclude litter inputs, or remove root inputs via trenching. We measured changes in soil solution chemistry with depth, and conducted long-term incubations of bulk soils and soil density fractions from different treatments in order to elucidate effects of detrital inputs on the relative amounts and lability of different soil C pools. In the field, the effect of adding woody debris was to increase dissolved organic carbon (DOC) concentrations in O-horizon leachate and at 30 cm, but not at 100 cm, compared to control plots, suggesting increased rates of DOC retention with added woody debris. DOC concentrations decreased through the soil profile in all plots to a greater degree than did dissolved organic nitrogen (DON), most likely due to preferential sorption of high C:N hydrophobic dissolved organic matter (DOM) in upper horizons; %hydrophobic DOM decreased significantly with depth, and hydrophilic DOM had a much lower and narrower C:N ratio. Although laboratory extracts of different litter types showed differences in DOM chemistry, percent hydrophobic DOM did not differ among detrital treatments in the field, suggesting microbial equalization of DOM leachate in the field. In long-term laboratory incubations, light fraction material did not have higher rates of respiration than heavy fraction or bulk soils, suggesting that physical protection or N availability controls different turnover times of heavy fraction material, rather than differences in chemical lability. Soils from plots that had both above- and below-ground litter inputs excluded had significantly lower DOC loss rates, and a non-significant trend for lower respiration rates . Soils from plots with added wood had similar respiration and DOC loss rates as control soils, suggesting that the additional DOC sorption observed in the field in these soils was stabilized in the soil and not readily lost upon incubation.

Star-shaped feeding traces produced by echiuran worms on the deep-sea floor of the Bay of Bengal

NASA Astrophysics Data System (ADS)

Ohta, Suguru

1984-12-01

Many star-shaped foraging traces were observed in bottom photographs of the deep-sea floor taken in the Bay of Bengal between the depths of 5025 and 2635 m. They were classified into 10 types according to their dimensions, aspect ratios (length/width) of their spokes, features of the central structure, and possible production mechanisms. The proboscis of a deep-sea bonellid echiuran worm was photographed at a depth of 2635 m in the act of producing one of the star-shaped foraging traces. On the basis of photographic observations and observations of shallow-water forms, several types of the feeding traces can be ascribed to the foraging of deep-sea echiuran worms on surface detritus. At least four types of the star-shaped trace are probably produced by deep-sea bonellid worms, and a linear correlation could be found between the aspect ratios of the spokes and maximum number of spokes around the central hole. A geometrical model experiment stimulating the feeding behavior of a bonellid worm suggested simple behavioral principles which afford maximum utilization of the surface area around a central hole with least expenditure of energy. The prediction of the maximum number of spokes for a given aspect of spokes by the model experiment agreed well with those observed, both utilizing about 76% of the fresh sediment surface within the span of the probiscis around a central hole. This efficient feeding pattern may have adaptive value in deep-sea environments such as the central part of the Bay of Bengal, where energy input is limited.

Let's Break it Down: A Study of Organic Decomposition Rates in Clay Soil

NASA Astrophysics Data System (ADS)

Weiss, E.

2016-12-01

In this experiment I will be testing if temperature affects the organic decomposition rates in clay soil. I will need to be able to clean and weigh each filter paper without disrupting my data damaging or brushing off additional paper material. From there I need to be able to analyze and interpret my data to factor anything else that may affect the decomposition rates in the soil. Soil decomposers include bacteria and fungi. They obtain energy from plant and animal detritus through aerobic decomposition, which is similar to how humans break down sugar. The formula is: C6H12O6 + O2 → CO2 + H2O + energy. Besides oxygen and sugar the organisms need nutrients such as water and sustainable temperatures. Decomposition is important to us because it helps regulate soil structure, moisture, temperature, and provides nutrients to soil organisms. This matters on a global scale since decomposers release a large amount of carbon when breaking down matter, which contributes to greenhouse gasses such as carbon dioxide and methane. These greenhouse gasses affect the earth's climate. People who care about decomposition are farmers and those in agriculture, as well as environmental scientists. Even national parks might care because decomposition may affect park safety, how the park looks, and the amount of plants and wildlife. Things that can affect decomposition are the decomposers in the soil, temperature, and water or moisture. My secondary research also showed that PH and chemical composition of the soil affect the rate of decomposition.Cold or freezing temperatures can help preserve organic material in soil because it freezes the soil and moisture, making it too dense for the organic decomposers to break down the organic matter. Soil also can be preserved by drying out and being stored at 4º Celsius (or 39º Fahrenheit) for 28 days. However, soil can degrade slowly in these conditions because it is not frozen and can be oxidized.

Relationships between forest fine and coarse woody debris carbon stocks across latitudinal gradients in the United States as an indicator of climate change effects

Treesearch

C.W. Woodall; G.C. Liknes

2008-01-01

Coarse and fine woody materials (CWD and FWD) are substantial forest ecosystem carbon (C) stocks. There is a lack of understanding how these detritus C stocks may respond to climate change. This study used a nation-wide inventory of CWD and FWD in the United States to examine how these C stocks vary by latitude. Results indicate that the highest CWD and FWD C stocks...

Records and Notes on Mosquitoes (Diptera: Culicidae) Collected in Egypt

DTIC Science & Technology

1988-01-01

Ae. detritus. 117. El- Giza Gov., Saqqara, 1.5 km north of town at entrance to Zoser’s Pyramid (36RUU285053), 18 m; 22 Apr 1983. Plantation... Giza Gov., Saqqara, 1.6 km north of town at entrance to Zoser’s Pyramid (36RUU287055), 18 m; 22 Apr 1983. Plantation/cultivated area, medium-sized...unguiculata. 119. El- Giza Gov., Saqqara, 1 km from entrance to Zoser’s Pyramid (36RUU290054), 18 m; 22 Apr 1983. Plantation, small ditch at edge of

Use of a Nafion Membrane Probe for Quick, On-the-Spot Determination of Ionic Copper Contamination Levels in Natural Waters

DTIC Science & Technology

2000-01-01

avert an environmental problem. The developed sensor uses the perfluorinated ionomeric film, Nation 117. This film has a Teflon matrix with sulfate...Dexter et al 1975, Dexter 1978). Once the surface is organically "wet" then bacteria can attach (reversible sorption ) but are removed easily (Marshall... sorption ) and the primary biofouling film forms (Little 1984). This primary film becomes attractive to algae and protozoa as well as attracting detritus

Nonlinear Relationships Between Particulate Absorption and Chlorophyll: Detritus or Pigment Packaging

DTIC Science & Technology

1993-06-15

for another polar area. For samples from Antartic waters, the mean a*pan(4 3 5 ), normalized to chl a + pheo, was 0.0 18 m2 (mg chl a)-I (Mitchell and...specific absorption coefficients, was suggested as the cause of relatively low mean specific absorption coefficients in the Antartic . The values of c1...moored optical sensors in the Sargasso Sea. J. Geophys. Res. 97, 7399-7412. Mitchell, B.G., and 0. Holm-Hansen 1991. Bio-optical properties of Antartic

Fluvial systems of Upper Cretaceous Mesaverde Group and Paleocene North Horn formation, central Utah: record of transition from thin-skinned deformation in foreland region

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

Lawton, T.F.

1985-05-01

Nonmarine strata of the upper part of the Mesaverde Group and North Horn Formation exposed between the Wasatch Plateau and the Green River in central Utah record a late Campanian tectonic transition from thrust-belt deformation to basement-cored uplift. Mesaverde Group sediments were deposited by synorogenic braided and meandering rivers. During most of Campanian time, sediment transport was east and northeast away from the thrust belt across a fluvial coastal plain. Subsequent development of the San Rafael swell, a basement uplift, between western and eastern localities caused erosional thinning of the section. Sandstones within the upper part of the Mesaverde Groupmore » form two distinct compositional suites, a lower quartzose petrofacies and an upper lithic petrofacies. Lithic grain populations of the upper petrofacies are dominated by sedimentary lithic grains were derived from the thrust belt, whereas volcanic lithic grains were derived from a volcanic terrane to the southwest. Tributary streams carrying quartzose detritus from the thrust belt entered a northeast-flowing trunk system and caused a basinward dilution of volcanic detritus. Disappearance of volcanic grains and local changes in paleocurrent directions in latest Campanian time reflect initial growth of the San Rafael swell and development of an intermontane trunk-tributary fluvial system. Depositional onlap across the Mesaverde Group by the post-tectonic North Horn Formation indicates a minimum late Paleocene age for uplift of the San Rafael swell.« less

Cretaceous shelf-sea chalk deposits

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

Hattin, D.E.

1988-01-01

The word ''chalk'' is linked etymologically to the Cretaceous, but chalky facies neither dominate that system nor are confined to it. As used commonly, the term ''chalk'' refers to a variety of marine limestone that is white to light gray very fine grained, soft and friable, porous, and composed predominantly of calcitic skeletal remains, especially those derived from coccolithophores. No simple definition suffices to embrace all Cretaceous chalks, which include sandy, marly, shelly, phospatic, glauconitic, dolomitic, pyritic and organic-rich lithotypes. Most of the world's exposed Cretaceous chalk deposits were formed at shelf depths rather than in the deep sea. Cretaceousmore » shelf-sea chalks are developed most extensively in northern Europe, the U.S. Gulf Coastal Plain and Western Interior, and the Middle East, with lesser occurrences alo in Australia. Most Cretaceous shelf-sea chalks formed in the temperature zones, and in relatively deep water. Cretaceous chalks deposited on well-oxygenated sea floors are bioturbated and massive where deficient in terrigenous detritus, or bioturbated and rhythmically interbedded with argillaceous units where influx of terrigenous detritus varied systematically with climate changes. Accumulation of sufficient pelagic mud to form vast deposits of Cretaceous shelf-sea chalk required (1) sustained high productivity of calareous plankton, (2) extensive development of stable shelf and continental platform environments, (3) highstands of seal level, (4) deficiency of aragonitic skeletal material in chalk-forming sediments, and (5) low rates of terrigenous detrital influx. These conditions were met at different times in different places, even within the same general region.« less

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.

Effects of road deicer (NaCl) and amphibian grazers on detritus processing in pond mesocosms.

PubMed

Van Meter, Robin J; Swan, Christopher M; Trossen, Carrie A

2012-10-01

Road deicers have been identified as potential stressors in aquatic habitats throughout the United States, but we know little regarding associated impacts to ecosystem function. A critical component of ecosystem function that has not previously been evaluated with respect to freshwater salinization is the impact on organic matter breakdown. The purpose of this study was to evaluate cumulative effects of road deicers and tadpole grazers on leaf litter breakdown rate (g d(-1) ) and microbial respiration (mg O(2)  g leaf(-1) h(-1) ). To test this interaction, in May 2008 the authors added dry leaf litter (Quercus spp.) to forty 600-L pond mesocosms and inoculated each with algae and zooplankton. In a full-factorial design, they manipulated a realistic level of road salt (ambient or elevated at 645 mg L(-1) Cl(-) ) and tadpole (Hyla versicolor) presence or absence. The elevated chloride treatment reduced microbial respiration by 24% in the presence of tadpoles. The breakdown of leaf litter by tadpoles occurred 9.7% faster under ambient chloride conditions relative to the elevated chloride treatment. Results of the present study suggest that the microbial community is directly impacted by road deicers and heavy tadpole grazing under ambient conditions limits microbial capacity to process detritus. Road salts and tadpoles interact to limit microbial respiration, but to a lesser extent leaf mass loss rate, thereby potentially restricting energy flow from detrital sources in pond ecosystems. Copyright © 2012 SETAC.

Pyrosequencing reveals benthic bacteria changes responsing to heavy deposition of Microcystis scum in lab — searching bacteria for bloom control

NASA Astrophysics Data System (ADS)

Tang, Yali; Cheng, Dongmei; Guan, Baohua; Zhang, Xiufeng; Liu, Zhengwen; Liu, Zejun

2017-05-01

Bacteria capable of degrading cyanobacteria Microcystis are crucial for determining the ecological consequences of Microcystis blooms in freshwater lakes. Scum derived from Microcystis blooms tends to accumulate in bays of large lakes and then sink to the sediments where it is finally consumed by benthic bacteria. Understanding the response of benthic bacterial communities to massive Microcystis deposition events may help identify the bacteria best suited to Microcystis hydrolyzation and even bloom control. For that purpose, an experimental system was set up in which intact sediment cores were incubated in the laboratory with normal and heavy deposits of Microcystis detritus. Pyrosequencing was performed in order to describe a phylogenetic inventory of bacterial communities in samples taken at 0-1, 1-2 and 2-3 cm depths in incubated sediments and in original untreated sediment. A hierarchical cluster tree was constructed expose differences between sediments. Similarity percentage calculations were also performed to identify the bacterial species contributing to variation. The results of this study suggest that: (1) deposition of Microcystis scums exerts a strong effect on the bacterial community composition in the surface (0-1 cm) and sub-surface (1-2 cm) sediment layers; (2) bacterial community responses to Microcystis detritus deposition vary across vertical gradients. A list of bacteria with potential roles in Microcystis degradation was compiled. These findings may inform the development of future measures for Microcystis bloom control in lakes.

Evaluation of building fundamental periods and effects of local geology on ground motion parameters in the Siracusa area, Italy

NASA Astrophysics Data System (ADS)

Panzera, Francesco; D'Amico, Sebastiano; Lombardo, Giuseppe; Longo, Emanuela

2016-07-01

The Siracusa area, located in the southeastern coast of Sicily (Italy), is mainly characterized by the outcropping of a limestone formation. This lithotype, which is overlain by soft sediments such as sandy clays and detritus, can be considered as the local bedrock. Records of ambient noise, processed through spectral ratio techniques, were used to assess the dynamic properties of a sample survey of both reinforced concrete and masonry buildings. The results show that experimental periods of existing buildings are always lower than those proposed by the European seismic code. This disagreement could be related to the role played by stiff masonry infills, as well as the influence of adjacent buildings, especially in downtown Siracusa. Numerical modeling was also used to study the effect of local geology on the seismic site response of the Siracusa area. Seismic urban scenarios were simulated considering a moderate magnitude earthquake (December 13th, 1990) to assess the shaking level of the different outcropping formations. Spectral acceleration at different periods, peak ground acceleration, and velocity were obtained through a stochastic approach adopting an extended source model code. Seismic ground motion scenario highlighted that amplification mainly occurs in the sedimentary deposits that are widespread to the south of the study area as well as on some spot areas where coarse detritus and sandy clay outcrop. On the other hand, the level of shaking appears moderate in all zones with outcropping limestone and volcanics.

The distribution of actin immunoreactivity in rhabdomeres of tipulid flies in relation to extracellular membrane shedding.

PubMed

Blest, A D; Stowe, S; Clausen, J A; Carter, M

1991-09-01

Rhabdomeres of tipulid flies lose membrane during turnover from a 'shedding zone' composed of microvillar tips. These distal domains lack intramicrovillar cytoskeletons and appear to be empty sacs of membrane. Recent concerns about the role of ninaC mechano-enzymes in the architecture of dipteran rhabdomeral microvilli and the dynamic role that they may play in the creation of shedding zones demand an examination of the distribution of actin in tipulid rhabdomeres. We compared rhabdomeres from tipulid retinae incubated before fixation for immunocytochemistry in a buffer without additives and a stabilising buffer that contained a cocktail of cysteine protease inhibitors; both were challenged by an anti-actin antibody for immunogold labelling after embedding in LR White Resin. Shedding zones thus processed collapse to structureless detritus. Stabilised and unstabilized shedding zones were immunonegative to anti-actin. To ensure that the negative results were not consequent upon conformational changes generated by the processing protocol, we examined microvilli of degenerating rhabdomeres of the Drosophila light-dependent retinal degeneration mutant rdgBKS222 (which separate and collapse without creating a shedding zone) and found the detritus they generate to be immunopositive to anti-actin. Stabilised and unstabilized regions of basal regions of tipulid rhabdomeres were equally immunopositive. We infer that (a) actin is absent from shedding zones; (b) actin is not degraded by microvillar cysteine proteases. The implications of these conclusions are discussed in relation to some functional models of arthropod photoreceptor microvilli.

Trimethylsilyl derivatives of organic compounds in source samples and in atmospheric fine particulate matter.

PubMed

Nolte, Christopher G; Schauer, James J; Cass, Glen R; Simoneit, Bernd R T

2002-10-15

Source sample extracts of vegetative detritus, motor vehicle exhaust, tire dust paved road dust, and cigarette smoke have been silylated and analyzed by GC-MS to identify polar organic compounds that may serve as tracers for those specific emission sources of atmospheric fine particulate matter. Candidate molecular tracers were also identified in atmospheric fine particle samples collected in the San Joaquin Valley of California. A series of normal primary alkanols, dominated by even carbon-numbered homologues from C26 to C32, the secondary alcohol 10-nonacosanol, and some phytosterols are prominent polar compounds in the vegetative detritus source sample. No new polar organic compounds are found in the motor vehicle exhaust samples. Several hydrogenated resin acids are present in the tire dust sample, which might serve as useful tracers for those sources in areas that are heavily impacted by motor vehicle traffic. Finally, the alcohol and sterol emission profiles developed for all the source samples examined in this project are scaled according to the ambient fine particle mass concentrations attributed to those sources by a chemical mass balance receptor model that was previously applied to the San Joaquin Valley to compute the predicted atmospheric concentrations of individual alcohols and sterols. The resulting underprediction of alkanol concentrations at the urban sites suggests that alkanols may be more sensitive tracers for natural background from vegetative emissions (i.e., waxes) than the high molecular weight alkanes, which have been the best previously available tracers for that source.

The dopant type and amount governs the electrochemical performance of graphene platforms for the antioxidant activity quantification

NASA Astrophysics Data System (ADS)

Hui, Kai Hwee; Ambrosi, Adriano; Sofer, Zdeněk; Pumera, Martin; Bonanni, Alessandra

2015-05-01

Graphene doped with heteroatoms can show new or improved properties as compared to the original undoped material. It has been reported that the type of heteroatoms and the doping conditions can have a strong influence on the electronic and electrochemical properties of the resulting material. Here, we wish to compare the electrochemical behavior of two n-type and two p-type doped graphenes, namely boron-doped graphenes and nitrogen-doped graphenes containing different amounts of heteroatoms. We show that the boron-doped graphene containing a higher amount of dopants provides the best electroanalytical performance in terms of calibration sensitivity, selectivity and linearity of response for the detection of gallic acid normally used as the standard probe for the quantification of antioxidant activity of food and beverages. Our findings demonstrate that the type and amount of heteroatoms used for the doping have a profound influence on the electrochemical detection of gallic acid rather than the structural properties of the materials such as amounts of defects, oxygen functionalities and surface area. This finding has a profound influence on the application of doped graphenes in the field of analytical chemistry.Graphene doped with heteroatoms can show new or improved properties as compared to the original undoped material. It has been reported that the type of heteroatoms and the doping conditions can have a strong influence on the electronic and electrochemical properties of the resulting material. Here, we wish to compare the electrochemical behavior of two n-type and two p-type doped graphenes, namely boron-doped graphenes and nitrogen-doped graphenes containing different amounts of heteroatoms. We show that the boron-doped graphene containing a higher amount of dopants provides the best electroanalytical performance in terms of calibration sensitivity, selectivity and linearity of response for the detection of gallic acid normally used as the standard probe for the quantification of antioxidant activity of food and beverages. Our findings demonstrate that the type and amount of heteroatoms used for the doping have a profound influence on the electrochemical detection of gallic acid rather than the structural properties of the materials such as amounts of defects, oxygen functionalities and surface area. This finding has a profound influence on the application of doped graphenes in the field of analytical chemistry. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr01045d

Acetoclastic methane formation from Eucalyptus detritus in pristine hydrocarbon-rich river sediments by Methanosarcinales.

PubMed

Beckmann, Sabrina; Manefield, Mike

2014-12-01

Pristine hydrocarbon-rich river sediments in the Greater Blue Mountains World Heritage Area (Australia) release substantial amounts of methane. The present study aimed to unravel for the first time the active methanogens mediating methane formation and exploiting the bacterial diversity potentially involved in the trophic network. Quantitative PCR of 16S rRNA gene and functional genes as well as 454 pyrosequencing were used to address the unknown microbial diversity and abundance. Methane-releasing sediment cores derived from three different river sites of the Tootie River. Highest methane production rates of 10.8 ± 0.5 μg g(-1)(wet weight) day(-1) were detected in 40 cm sediment depth being in congruence with the detection of the highest abundances of the archaeal 16S rRNA gene and the methyl-coenzyme M reductase (mcrA) genes. Stable carbon and hydrogen isotopic signatures of the produced methane indicated an acetoclastic origin. Long-term enrichment cultures amended with either acetate or H2/CO2 revealed acetoclastic methanogenesis as key methane-formation process mediated by members of the order Methanosarcinales. Conditions prevailing in the river sediments might be suitable for hydrocarbon-degrading bacteria observed in the river sediments that were previously unclassified or closely related to the Bacteroidetes/Chlorobi group, the Firmicutes and the Chloroflexi group fuelling acetoclastic methanogensis in pristine river sediments. © 2014 Federation of European Microbiological Societies. Published by John Wiley & Sons Ltd. All rights reserved.

Surrogate-Based Optimization of Biogeochemical Transport Models

NASA Astrophysics Data System (ADS)

Prieß, Malte; Slawig, Thomas

2010-09-01

First approaches towards a surrogate-based optimization method for a one-dimensional marine biogeochemical model of NPZD type are presented. The model, developed by Oschlies and Garcon [1], simulates the distribution of nitrogen, phytoplankton, zooplankton and detritus in a water column and is driven by ocean circulation data. A key issue is to minimize the misfit between the model output and given observational data. Our aim is to reduce the overall optimization cost avoiding expensive function and derivative evaluations by using a surrogate model replacing the high-fidelity model in focus. This in particular becomes important for more complex three-dimensional models. We analyse a coarsening in the discretization of the model equations as one way to create such a surrogate. Here the numerical stability crucially depends upon the discrete stepsize in time and space and the biochemical terms. We show that for given model parameters the level of grid coarsening can be choosen accordingly yielding a stable and satisfactory surrogate. As one example of a surrogate-based optimization method we present results of the Aggressive Space Mapping technique (developed by John W. Bandler [2, 3]) applied to the optimization of this one-dimensional biogeochemical transport model.

Life Cycle, Feeding and Production of Isoptena serricornis(Pictet, 1841)

NASA Astrophysics Data System (ADS)

Derka, Tomá; Tierno de Figueroa, José Manuel; Krno, Il'ja

2004-05-01

Some aspects of the biology and ecology (life cycle, feeding and production) of a population of Isoptena serricornis in the Rudava River (Slovakia) are studied, reported and discussed. The life cycle is annual, with slow growth in autumn-winter and fast growth in late summer and spring. The growth decreased two weeks before the Fall Equinox and increased two weeks after the Spring Equinox. The flight period spans from the end of May to the beginning of July. The presence of large sand particles in the gut of all studied nymphs is of note, and indicates that I. serricornis acts as a deposit-collector species. Nymphal food is principally composed of detritus, unicellular organisms and, in nymphs of intermediate or large size, Chironomidae larvae. Adult food is composed fundamentally of different types of pollen grains. Males usually have lower food content than females. Annual production of this species (694-750 mg · m-2) is very high in relation to other previously studied Chloroperlidae. This is probably largely responsible for I. serricornis being one of the most abundant components of the macroinvertebrate community in its habitat in the Rudava River. A negative correlation between production and temperature was observed.

Record of seismotectonic events in siliceous cyanobacterial sediments (Magadi cherts), Lake Magadi, Kenya

NASA Astrophysics Data System (ADS)

Behr, H.-J.; Röhricht, C.

The Quaternary sediments of Lake Magadi in the Kenya Rift include large volumes of chert. Before their lithification, these siliceous sediments underwent very strong deformation, as recorded by diapirism with pillow-chert mounds, extrusion along dykes and fault ramps, horizontal liquefaction slides with brecciation, slumping, as well as petee-, flow- and shear structures. Eugster (1969) considered these structures to have resulted from desiccation of Na-silicate precipitates (magadiite) that were deposited over wide areas and were several metres thick. Magadiite can remain soft over long periods; therefore, these ``Magadi-type cherts'' are called the type examples of inorganic cherts. However, field observations and microbiological studies of the cherts show that real inorganic cherts are rare at the type locality of Magadi-type cherts. Most of the cherts are older than the High Magadi Beds and developed from flat-topped calcareous bioherms of Pleurocapsa, Gloecocapsa, and other coccoid cyanobacteria, thinly bedded filamentous microbial mats, stromatolites, bacterial slimes, diatoms, Dascladiacea colonies and other organic matter. Silicification occurred from a silicasol via opal-A to opal-C with final recrystallisation to a chert of quartzine composition. The metabolic processes of cyanobacteria controlled the pH and influenced the dissolution-precipitation mechanism. Collapse, liquefaction and extrusion of the pre-lithified siliceous matrix was caused by seismotectonic rift activity, which activated fault scarplets and large-scale dyke systems. It led to liquefaction and other earthquake-induced structures along the fault ramps and on tilted blocks. Concentrated silicasols were generated by the interaction of alkaline waters with volcanic detritus, coupled with biochemical processes. After liquefaction and extrusion, the material solidified by spontaneous crystallisation in an environment that was characterised by highly variable pH and salinity. The Lake Magadi basin is a remarkable example of sedimentation in a continuously seismotectonically active basin. This paper presents a first description of the micro-organisms in Magadi-type cherts, the silicification process, and the deformation that occurred still in the putty-like state before lithification.

What collided with India at ~50 Ma? Constraints from the sedimentary record in the NW Himalaya, Ladakh.

NASA Astrophysics Data System (ADS)

Najman, Y.; Jenks, D.; Godin, L.; BouDagher-Fadel, M. K.; Bown, P. R.; Horstwood, M. S.; Garzanti, E.; Bracciali, L.; Millar, I.

2014-12-01

The timing of India-Asia collision is critical to the understanding of crustal deformation processes. In the NW Himalaya, a number of workers have proposed a ~55-50 Ma age for collision along the Indus suture zone which separates India from the Kohistan-Ladakh Intraoceanic Island arc (KLA) to the north. This is based on a number of factors including the age of youngest marine sediments in the suture (e.g. Green et al. 2008), age of eclogites indicative of onset of Indian continental subduction (e.g. de Sigoyer et al. 2000), and first evidence of detritus from north of the suture zone deposited on the Indian plate (e.g. Clift et al. 2002). Such evidence can be interpreted as documenting the age of India-Asia collision if one takes the KLA to have collided with the Asian plate prior to its collision with India (e.g. Petterson 2010 and refs therein). However, an increasing number of workers propose that the KLA collided with Asia subsequent to its earlier collision with India, dated variously at 85 Ma (Chatterjee et al. 2013), 61 Ma (Khan et al. 2009) and 50 Ma (Bouilhol et al. 2013). If correct, then the previous constraints to dating the collision as outlined above have in fact been dating the timing of India-arc collision, rather than the final ocean closure and terminal collision of India+arc with Asia as previously believed. This, plus the questioning of earlier provenance work of Clift et al. (2002) regarding the validity of their data for constraining the time when detritus from north of the suture first arrived on the Indian plate (Henderson et al. 2011) suggests that the time is right for a reappraisal of this topic. But which method to use? A provenance study now brings with it a requirement to distinguish between detritus from the KLA and Southern margin of Asia. Recently, Bouilhol et al (2013) undertook a detailed study of the KLA, using temporal and spatial variation of zircon U-Pb and Hf as well as Sr-Nd bulk analyses, to document the arc's collision with India at 50 Ma and its subsequent collision with Asia at 40 Ma. Such variation should be reflected in the detrital record of material eroded from the arc. We use zircon U-Pb and Hf analyses from Palaeogene sediments deposited in and adjacent to the Indus suture in Ladakh, to further explore the interpretations presented in that research.

U-Pb ages of detrital zircon from Cenozoic sediments in the southwestern Tarim Basin, NW China: Implications for Eocene-Pliocene source-to-sink relations and new insights into Cretaceous-Paleogene magmatic sources

NASA Astrophysics Data System (ADS)

Yang, Wei; Fu, Ling; Wu, Chaodong; Song, Yan; Jiang, Zhenxue; Luo, Qun; Zhang, Ziya; Zhang, Chen; Zhu, Bei

2018-05-01

A detailed investigation of potential provenance is still lacking in the southwestern Tarim Basin, which restricts our complete understanding of Cenozoic source-to-sink relations between the basin interior and the Pamir salient - western Kunlun Mountain Range. Debate also exists concerning the potential sources of the Paleogene and Cretaceous igneous detritus present in the Cenozoic sedimentary sequences. Here, we present U-Pb (LA-ICP-MS) ages of detrital zircons from the continuous Eocene-Pliocene sediment series in the well-exposed Aertashi section to investigate changes in sediment provenance through time. The U-Pb detrital zircon ages range widely from 45 to 3204 Ma and can be divided into seven main groups: 45-65 Ma (sub-peak at 49 Ma), 67-103 Ma (sub-peak at 95 Ma), 196-251 Ma (sub-peak at 208 Ma), 252-416 Ma (sub-peak at 296 Ma), 417-540 Ma (sub-peak at 446 Ma), 550-1429 Ma (sub-peaks at 614 Ma, 828 Ma and 942 Ma) and 1345-3204 Ma (sub-peaks at 1773 Ma and 2480 Ma). These zircons were mainly derived from the western Kunlun Mountain Range and northern Pamir salient to the west and south. The evolution of the provenance and source-to-sink relationship patterns in the southwestern Tarim Basin can be divided into three stages: (1) The Middle Eocene to Lower Oligocene sediments display a wide variety of detrital zircon ages, suggesting that the source area was extensive. (2) A major change in provenance occurred during the Late Oligocene to Early Miocene and was characterized by an abrupt increase in the proportion of Triassic and Lower Paleozoic igneous components, implying a significant adjustment in topography induced by the initial uplift and exhumation of the western Kunlun Mountain Range and northern Pamir salient. (3) In the Late Miocene, the source-to-sink system transformed again, and contributions of Triassic to Lower Paleozoic material weakened substantially due to the sufficient indentation of the Pamir salient. Our integrated analyses of zircon geochronology indicate that the main source terranes of the Paleogene and Cretaceous igneous detritus are the central and southern Pamir salient, respectively, which are speculated to have been continuously connected to the study area during Eocene-Pliocene times, although such detritus is scarce in certain formations and has not yet been detected.

Tectonic-erosion coupling? The erosional response to India-Asia collision

NASA Astrophysics Data System (ADS)

Najman, Y.; Henderson, A.; Jenks, D.; Parrish, R.; Horstwood, M.; Foster, G. L.; Green, O.

2009-04-01

In order to use the detrital record as an archive of hinterland evolution, we need to understand the erosional response to tectonics. Collision of India and Asia at ca 50 Ma [1 and refs therein] resulted in the subsequent development of the Himalayan orogen. What was the erosional response to this event? Most basins into which Himalayan detritus may have been deposited have now been researched at least at reconnaissance level. The conclusion reached is that, as yet, there appears to be no evidence of substantial detritus eroded from the southern flanks of the rising Himalayan mountain belt prior to ~40 Ma, 10 My after collision. In the Indus suture zone basin, detritus is predominantly sourced from the Trans-Himalayan arc of the northern, Asian plate, rather than the Himalaya to the south [2, 3]. In the peripheral foreland basin, the oldest substantial Himalayan-derived detritus is dated at <40 Ma [4]. To the west, in the Katawaz remnant ocean basin and offshore Indus Fan, earliest Himalayan derived deposits are poorly dated, insubstantial, and/or predominantly derived from north of the suture zone rather than the rising Himalayan thrust belt to the south [5, 6]. In the east, earliest Himalayan-derived material is dated at 38 Ma in the Bengal remnant ocean basin [7], and "post-Paleocene" in the Bengal Fan [8 and refs therein]. Paleogene sediments of the Sunda Arc accretionary prism, originally thought to be offscraped Himalayan-derived Bengal Fan [9, 10] are now shown to be predominantly derived from the arc to the east [11, 12]. What could be reason for this ~10 My delay between collision and first documented products of erosion from the mountain belt? The delay has been explained by suggesting collision occurred considerably later than commonly believed [13]. However, this is at variance with provenance data which show that material of Asian origin was deposited on the Indian plate by 50 Ma [14, 15] A second possibility is that Palaeogene Himalayan-derived detritus may lie beneath the overthrust fold-thrust belt. A third possibility is that the time gap does in fact represent a true delayed response to erosion after collision. This idea is consistent with the evidence of a transition from slow to exponentially increasing accumulation rates in offshore basins adjacent to the Himalaya around the start of the Oligocene. A 10 million year delayed response to erosion following India-Asia collision has been ascribed to either climatic causes or subdued topography in the early stages of collision, the result of a number of proposed mechanisms [16-18]. Given the bedrock evidence for metamorphism in the Himalaya that requires early crustal thickening [19, 20], we would favour those models that allow early crustal thickening, but retard erosion or uplift, if indeed early erosion was negligible. Such a study illustrates how the detrital record can inform and constrain models of crustal deformation, but also serves to show how incomplete our understanding of the principles of tectonic-erosion coupling currently stand. 1. Hodges, K.V.. GSA Bull, 2000. 112 p. 324-350. 2. Henderson, A., et al., (abstr). EGU 2009; this conference.. 3. Wu, F.Y., et al Tectonics, 2007. 26. 4. Najman, Y., et al., Nature, 2001. 410(6825): p. 194-197. 5. Clift, P.D., et al., GSA Bull, 2001. 113: p. 1039-1051. 6. Qayyum, M., et al. GSA Bull, 2001. 113: p. 320-332. 7. Najman, Y., et al., EPSL, 2008. 273: p. 1-14. 8. Curray, J.R. et al. Marine & Petrol. Geol., 2003. 19: p. 1191-1223. 9. Curray, J.R., J. Asian Earth Sci., 2005. 25: p. 187-232. 10. Curray, J.R., et al., AAPG Memoir, J.. Watkins, Ed.. 1979. p. 189-198. 11. Allen, R., et al., GSA Spec. Pap, A. Draut & P.D. Clift, Eds. 2008. p. 223-255. 12. Allen, R., et al., J. Geol. Soc. London, 2008. 165: p. 1045-1057. 13. Aitchison, J.C., J.R. Ali, and A.M. Davis, J. Geophys. Res., 2007. 112: p. B05423. 14. Critelli, S. & E. Garzanti, Sed. Geol, 1994. 89: p. 265-284. 15. Jenks, D., et al., (abstr.). EGU 2009; this conference. 16. Guillot, S., et al., G3 2003. 4: p. 1064. 17. Kohn, M.J. & C.D. Parkinson, Geology, 2002. 30: p. 591-594. 18. Metivier, F., et al., Geophys J. Internat, 1999. 137: p. 280-318. 19. Foster, G., et al., EPSL, 2000. 181: p. 327-340. 20. Vance, D. & N. Harris, Geology, 1999. 27: p. 395-398.

Food and feeding habit of barbua belayewi (menon) from a polluted river, Baghdad, Iraq

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

Khalaf, A.N.; Al-Jafery, R.; Sadek, S.E.

1988-01-01

Gut contents of 217 specimens of B. belayewi were studied. The specimens were collected from Diyala river between September, 1982 and June, 1983. The fish fed moderately during most of the time under investigation. Heavy feeding occurred only in September and December 1982. They were poorly fed only in June, 1983. Organic debris and detritus formed the major bulk of the diet followed by planktonic algae and aquatic plant parts. Zooplankton, parts of aquatic insects and nematodes also occurred occasionally but did not contribute significantly.

Sources of carbon and sulfur nutrition for consumers in three meromictic lakes of New York State

NASA Technical Reports Server (NTRS)

Fry, B.; Hayes, J. M. (Principal Investigator)

1986-01-01

The trophic importance of bacterioplankton as a source of carbon and sulfur nutrition for consumers in meromictic lakes was tested using stable carbon (delta 13C) and sulfur (delta 34S) isotopic measurements. Studies in three lakes near Syracuse, New York, showed that most consumers ultimately derive their C and S nutrition from a mixture of terrestrial detritus, phytoplankton, and littoral vegetation, rather than from bacterioplankton. Food webs in these meromictic lakes are thus similar to those in other lakes that lack dense populations of bacterioplankton.

Deformational mass transport and invasive processes in soil evolution

NASA Technical Reports Server (NTRS)

Brimhall, George H.; Chadwick, Oliver A.; Lewis, Chris J.; Compston, William; Williams, Ian S.; Danti, Kathy J.; Dietrich, William E.; Power, Mary E.; Hendricks, David; Bratt, James

1992-01-01

Channels left in soil by decayed roots and burrowing animals allow organic and inorganic precipitates and detritus to move through soil from above, to depths at which the minuteness of pores restricts further passage. Consecutive translocation-and-root-growth phases stir the soil, constituting an invasive, dilatational process which generates cumulative strains. Below the depths thus affected, mineral dissolution by descending organic acids leads to internal collapse; this softened/condensed precursor horizon is then transformed into soil via biological activity that mixes and expands the evolving residuum through root and micropore-network invasion.

Computer-implemented remote sensing techniques for measuring coastal productivity and nutrient transport systems

NASA Technical Reports Server (NTRS)

Butera, M. K.

1981-01-01

An automatic technique has been developed to measure marsh plant production by inference from a species classification derived from Landsat MSS data. A separate computer technique has been developed to calculate the transport path length of detritus and nutrients from their point of origin in the marsh to the shoreline from Landsat data. A nutrient availability indicator, the ratio of production to transport path length, was derived for each marsh-identified Landsat cell. The use of a data base compatible with the Landsat format facilitated data handling and computations.

Fungal outbreak in a show cave.

PubMed

Jurado, V; Porca, E; Cuezva, S; Fernandez-Cortes, A; Sanchez-Moral, S; Saiz-Jimenez, C

2010-08-01

Castañar de Ibor Cave (Spain) was discovered in 1967 and declared a Natural Monument in 1997. In 2003 the cave was opened to public visits. Despite of extensive control, on 26 August 2008 the cave walls and sediments appeared colonized by long, white fungal mycelia. This event was the result of an accidental input of detritus on the afternoon of 24 August 2008. We report here a fungal outbreak initiated by Mucor circinelloides and Fusarium solani and the methods used to control it. 2010 Elsevier B.V. All rights reserved.

Optimum Tolerance Design Using Component-Amount and Mixture-Amount Experiments

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

Piepel, Gregory F.; Ozler, Cenk; Sehirlioglu, Ali Kemal

2013-08-01

One type of tolerance design problem involves optimizing component and assembly tolerances to minimize the total cost (sum of manufacturing cost and quality loss). Previous literature recommended using traditional response surface (RS) designs and models to solve this type of tolerance design problem. In this article, component-amount (CA) and mixture-amount (MA) approaches are proposed as more appropriate for solving this type of tolerance design problem. The advantages of the CA and MA approaches over the RS approach are discussed. Reasons for choosing between the CA and MA approaches are also discussed. The CA and MA approaches (experimental design, response modeling,more » and optimization) are illustrated using real examples.« less

Estimation of mercury amount in the components of spent U-type lamp.

PubMed

Rhee, Seung-Whee

2017-05-01

Spent U-type lamps are strongly encouraged to be separately managed in Korea, because U-type lamps are categorized as a household waste and thereby could not be managed properly. Determination of mercury amount in the components of U-type lamp, such as plastics, glass tube and phosphor powder from 3 U-type lamp manufacturers (A, B and C), is carried out to estimate the mercury content in spent U-type lamps. Regardless of lamp manufacturers, the portion of mercury in phosphor powder was higher than 90%, but that in plastics and others was less than 1%. At an air flow rate of 1.0 L/min, the range of the initial mercury concentration in vapor phase for U-type lamp was between 849 and 2076 µg/m 3 from 3 companies. The estimated mercury amount in vapor phase of U-type lamp was in the range from 0.206 mg for company A to 0.593 mg for company B. And the portion of mercury in vapor phase in the total amount of mercury was estimated in the range from 3.0% for company A to 6.7% for company B. Hence, it is desirable to get rid of mercury from phosphor powder in order to perform U-type lamps recycling.

Epicuticular waxes on onion leaves and associated resistance to onion thrips

USDA-ARS?s Scientific Manuscript database

Natural variation exists for amounts and types of epicuticular waxes on onion foliage. Wild-type onion possesses copious amounts of these waxes and is often referred to as “waxy”. The recessively inherited “glossy” phenotype has significantly less wax relative to waxy types and shows resistance to o...

Relationship between naturally occurring human mucosal and serum antibody to the capsular polysaccharide of Haemophilus influenzae type b.

PubMed

Pichichero, M E; Insel, R A

1982-08-01

The prevalence of natural mucosal antibody to the capsular polysaccharide (polyribosylribitolphosphate [PRP]) of Haemophilus influenzae type b in adults at multiple secretory sites and the relationship between natural serum and mucosal antibodies with respect to their amount and fine binding specificity were examined. All of 16 lactating women had antibody to PRP in serum and mammary samples; 11 of 14 studied had nasal antibody and 12 of 14 had salivary antibody. The amount of serum antibody to PRP in an individual positively correlated with the amount of mucosal antibody at each of the three secretory sites examined, and the antibody amount between certain secretions were also positively correlated. Antibody to PRP that is cross-reactive with Escherichia coli K100 or Streptococcus pneumoniae type 6 capsular polysaccharides was detected in the secretions of seven and one subjects, respectively, but the amount was not correlated with serum cross-reactive antibody.

Sedimentary and tectonic evolution of the southern Qiangtang basin: Implications for the Lhasa-Qiangtang collision timing

NASA Astrophysics Data System (ADS)

Ma, Anlin; Hu, Xiumian; Garzanti, Eduardo; Han, Zhong; Lai, Wen

2017-07-01

The Mesozoic stratigraphic record of the southern Qiangtang basin in central Tibet records the evolution and closure of the Bangong-Nujiang ocean to the south. The Jurassic succession includes Toarcian-Aalenian shallow-marine limestones (Quse Formation), Aalenian-Bajocian feldspatho-litho-quartzose to feldspatho-quartzo-lithic sandstones (shallow-marine Sewa Formation and deep-sea Gaaco Formation), and Bathonian outer platform to shoal limestones (Buqu Formation). This succession is truncated by an angular unconformity, overlain by upper Bathonian to lower Callovian fan-delta conglomerates and litho-quartzose to quartzo-lithic sandstones (Biluoco Formation) and Callovian shoal to outer platform limestones (Suowa Formation). Sandstone petrography coupled with detrital-zircon U-Pb and Hf isotope analysis indicate that the Sewa and Gaaco formations contain intermediate to felsic volcanic detritus and youngest detrital zircons (183-170 Ma) with ɛHf(t) ranging widely from +13 to -25, pointing to continental-arc provenance from igneous rocks with mixed mantle and continental-crust contributions. An arc-trench system thus developed toward the end of the Early Jurassic, with the southern Qiangtang basin representing the fore-arc basin. Above the angular unconformity, the Biluoco Formation documents a change to dominant sedimentary detritus including old detrital zircons (mainly >500 Ma ages in the lower part of the unit) with age spectra similar to those from Paleozoic strata in the central Qiangtang area. A major tectonic event with intense folding and thrusting thus took place in late Bathonian time (166 ± 1 Ma), when the Qiangtang block collided with another microcontinental block possibly the Lhasa block.

How was the Triassic Songpan-Ganzi basin filled? A provenance study

USGS Publications Warehouse

Enkelmann, E.; Weislogel, A.; Ratschbacher, L.; Eide, E.; Renno, A.; Wooden, J.

2007-01-01

The Triassic Songpan-Ganzi complex comprises >200,000 km2 of 5-15 km thick turbiditic sediments. Although surrounded by several magmatic and orogenic belts, the Triassic high- and ultrahigh-pressure Qinling-Tongbai-Hong'an-Dabie (QTHD) orogen, located several hundred kilometers to the east, was proposed as its major source. Middle to Late Triassic samples from the northern and southern Songpan-Ganzi complex, studied using detrital white mica 40Ar/39Ar ages, Si-in-white mica content, and detrital zircon U/Pb ages, suggest that the northern Songpan-Ganzi deposystem obtained detritus from the north: the north China block, east Kunlun, northern Qaidam, Qilian, and western Qinling; the southern Songpan-Ganzi deposystem was supplied from the northeasterly located Paleozoic QTHD area throughout the Ladinian and received detritus from the Triassic Hong'an-Dabie orogen during the Carnian, indicative of exhumation of the orogen at that time. The QTHD orogen fed the Norian samples in the southeastern southern Songpan-Ganzi deposystem, signifying long drainage channels along the western margin of the south China block. An additional supply from the Emeishan magmatic province and/or the Yidun arc is suggested by the paucity of white mica in the southern Songpan-Ganzi deposystem. Mica ages of Rhaetian sediments from the northwestern Sichuan basin best correlate with those of the Triassic QTHD orogen. Our Si-in-white mica data demonstrate that the high- and ultrahigh-pressure rocks of the Hong'an-Dabie Shan were not exposed in the Middle to Late Triassic. Copyright 2007 by the American Geophysical Union.

Molecular marker characterization and source appointment of particulate matter and its organic aerosols.

PubMed

Choi, Jong-Kyu; Ban, Soo-Jin; Kim, Yong-Pyo; Kim, Yong-Hee; Yi, Seung-Muk; Zoh, Kyung-Duk

2015-09-01

This study was carried out to identify possible sources and to estimate their contribution to total suspended particle (TSP) organic aerosol (OA) contents. A total of 120 TSP and PM2.5 samples were collected simultaneously every third day over a one-year period in urban area of Incheon, Korea. High concentration in particulate matters (PM) and its components (NO3(-), water soluble organic compounds (WSOCs), and n-alkanoic acids) were observed during the winter season. Among the organics, n-alkanes, n-alkanoic acids, levoglucosan, and phthalates were major components. Positive matrix factorization (PMF) analysis identified seven sources of organic aerosols including combustion 1 (low molecular weight (LMW)-polycyclic aromatic hydrocarbons (PAHs)), combustion 2 (high molecular weight (HMW)-PAHs), biomass burning, vegetative detritus (n-alkane), secondary organic aerosol 1 (SOA1), secondary organic aerosol 2 (SOA2), and motor vehicles. Vegetative detritus increased during the summer season through an increase in biogenic/photochemical activity, while most of the organic sources were prominent in the winter season due to the increases in air pollutant emissions and atmospheric stability. The correlation factors were high among the main components of the organic carbon (OC) in the TSP and PM2.5. The results showed that TSP OAs had very similar characteristics to the PM2.5 OAs. SOA, combustion (PAHs), and motor vehicle were found to be important sources of carbonaceous PM in this region. Our results imply that molecular markers (MMs)-PMF model can provide useful information on the source and characteristics of PM. Copyright © 2015 Elsevier Ltd. All rights reserved.

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.

The Pliocene-Pleistocene sedimentary tectonic history of NW California

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

Stone, L.; Moley, K.; Aalto, K.R.

1993-04-01

A thick sequence of Late Miocene to Pleistocene sediments thought to represent deposition in a Neogene forearc basin are preserved in the structural basin referred to as the Eel River basin' located offshore of NW California and SE Oregon. The southern portion of this structural basin comes on land in the vicinity of Eureka where the marine and fluvial Wildcat Group is exposed. Basal Wildcat Group sediments are fluvial and littorial. Marine sandstones of the Wildcat Group contain K-spar concentrations of 5.5% and are believed to represent a fresh source. [sup 40]Ar/[sup 39]Ar laser probe analyses of Wildcat Group micasmore » yield dates of 52--57, 66--75, 128.5 and 299--303 Ma. The presence of Idaho detritus throughout the Neogene Wildcat Group indicates that the Klamath Mountains remained low during the Pliocene and early Pleistocene. Younger fluvial sediments in this region contain primarily locally derived detritus indicating local uplift of the Klamath Mountains. To the north, at Crescent City, thin remnants of the near-shore Saint George Formation and the eastern estuarine and fluvial Wimer Formation are lowermost Pliocene in age (5 ma). The presence of the highly erodible Wilmer Formation on uplifted plateaus in an area of extreme rainfall suggest that these sediments represent only the lowermost portion of an originally much thicker sequence. Consequently, the sediments confined to the present day Eel River basin do not represent the lateral extent of the original forearc basin. Sandstones and conglomerates of the Saint George and Wimer Formation indicate a local Klamath provenance derivation.« less

Depositional ages of clastic metasediments from Samos and Syros, Greece: results of a detrital zircon study

NASA Astrophysics Data System (ADS)

Löwen, Kersten; Bröcker, Michael; Berndt, Jasper

2015-01-01

Siliciclastic metasediments from the islands of Samos and Syros, Cycladic blueschist unit, Greece, were studied to determine maximum sedimentation ages. Four samples from the Ampelos unit on Samos yielded age distribution spectra that range from ~320 Ma to ~3.2 Ga with a dominance of Cambrian-Neoproterozoic zircons (500-1,100 Ma). The youngest well-constrained age groups cluster at 500-550 Ma. Our results allow to link the Samos metasediments with occurrences showing similar age distribution patterns elsewhere in the eastern Mediterranean region (Greece, Turkey, Libya, Israel and Jordan) that record the influx of `Pan-African' detritus. The lack of post-500-Ma zircons in the Samos samples is in marked contrast to the data from Syros that indicates Triassic to Cretaceous depositional ages. The samples from Syros were collected from the matrix of a meta-ophiolitic mélange that is exposed near the top of the metamorphic succession as well as from outcrops representing the basal part of the underlying marble-schist sequence. The zircon populations from Syros were mainly supplied by Mesozoic sources dominated by Triassic protolith ages. Subordinate is the importance of pre-Triassic zircons, but this may reflect bias induced by the research strategy. Sediment accumulation continued until Late Cretaceous time, but the overall contribution of Jurassic to Cretaceous detritus is more limited. Zircon populations are dominated by grains with small degree of rounding suggesting relatively short sediment transportation. Available observations are in accordance with a model suggesting deposition close to the magmatic source rocks.

Sandstone petrology and geochemistry of the Oligocene-Early Miocene Panjgur Formation, Makran accretionary wedge, southwest Pakistan: Implications for provenance, weathering and tectonic setting

NASA Astrophysics Data System (ADS)

Kassi, Akhtar Muhammad; Grigsby, Jeffry D.; Khan, Abdul Salam; Kasi, Aimal Khan

2015-06-01

The Oligocene-Early Miocene Panjgur Formation is comprised of submarine fan and abyssal plain turbidites deposited within the Makran subduction complex. Sandstones of the formation are litharenite to feldspathic litharenite. Petrographic data indicates a quartzose-recycled provenance dominated by plutonic and metamorphic fragments. Major elements concentrations reveal a moderate level of mineralogical maturity and high values of Chemical Proxy of Alteration (CPA; 88.29) coupled with a high Th/U ratio (9.37), which reveals intense weathering in the source area. The Zr, Nb, Y, and Th concentrations are comparable to upper continental crust (UCC) values and trends in Th/Cr, Th/Co, and Cr/Zr ratios support contribution from a felsic source. However, enrichment in Ni and Cr, reinforced by trends in Ni/Co, Cr/V, V/Ni and Y/Ni ratios, reveals mixing of the felsic source with mafic/ultramafic source terrains. Tectonic discrimination plots suggest continental arc to active continental margin setting. This study supports the Katawaz-delta-Panjgur submarine fan model and upholds the initial southward transport of predominantly felsic detritus from the Himalayan orogenic belt controlled by the Chaman-Ornach Nal transform fault system. This study further adds that the Bela-Muslimbagh ophiolites, associated mélanges and the West Pakistan Fold-Thrust Belt, from the east, and the Chagai-Raskoh volcanic arc, from the west, were also concurrently shedding mafic/ultramafic detritus to the basin, and that the depositional system in the Makran region turned westward, roughly parallel to the present active margin of the Makran accretionary wedge.

Selenium in aquatic biota inhabiting agricultural drains in the Salton Sea Basin, California.

PubMed

Saiki, Michael K; Martin, Barbara A; May, Thomas W

2012-09-01

Resource managers are concerned that water conservation practices in irrigated farmlands along the southern border of the Salton Sea, Imperial County, California, could increase selenium concentrations in agricultural drainwater and harm the desert pupfish (Cyprinodon macularius), a federally protected endangered species. As part of a broader attempt to address this concern, we conducted a 3-year investigation to collect baseline information on selenium concentrations in seven agricultural drains inhabited by pupfish. We collected water, sediment, selected aquatic food-chain taxa (particulate organic detritus, filamentous algae, net plankton, and midge [Chironomidae] larvae), and two poeciliid fishes (western mosquitofish Gambusia affinis and sailfin molly Poecilia latipinna) for selenium determinations. The two fish species served as ecological surrogates for pupfish, which we were not permitted to sacrifice. Dissolved selenium ranged from 0.70 to 32.8 μg/L, with selenate as the major constituent. Total selenium concentrations in other environmental matrices varied widely among drains, with one drain (Trifolium 18) exhibiting especially high concentrations in detritus, 5.98-58.0 μg Se/g; midge larvae, 12.7-50.6 μg Se/g; mosquitofish, 13.2-20.2 μg Se/g; and mollies, 12.8-30.4 μg Se/g (all tissue concentrations are based on dry weights). Although toxic thresholds for selenium in fishes from the Salton Sea are still poorly understood, available evidence suggests that ambient concentrations of this element may not be sufficiently elevated to adversely affect reproductive success and survival in selenium-tolerant poeciliids and pupfish.

Characterizing Cretaceous Glaciation Events: K-Ar Ages of Southern Ocean Sediments

NASA Astrophysics Data System (ADS)

Wright, M. A.; Hemming, S. R.; Barbeau, D. L.; Torfstein, A.; Pierce, E. L.; Williams, T.; McManus, J. F.; Gombiner, J.

2012-12-01

Evidence from paleosols and carbonate weathering models suggest that the Late Cretaceous had a supergreenhouse climate due to atmospheric CO2 concentrations two to four times greater than modern levels, tropical sea surface temperatures exceeding 35°C, and high-latitude temperatures exceeding 20°C. Despite this warmth, the Late Cretaceous was apparently punctuated by large (>25 m) and rapid (<<1 million year) sea-level changes, as recorded by marginal marine stratigraphic architectures and pelagic stable isotope compositions. The magnitude and tempo of these changes suggest a glacio-eustatic control, presumably from the growth and decay of continental ice sheets on Antarctica. Because continental glaciation tends to increase the weathering of bedrock and production of sediment delivered to the oceans, circum-Antarctic marine sediment flux would be expected to increase during periods of glaciation. In order to identify a Late Cretaceous glaciation signal from such marine records, we must first constrain the compositional signal of continental detritus in marine sediments. Here we report the results of downcore K-Ar analysis of the terrigenous sediments of Quaternary Weddell Sea cores PS1170-1 and PS1388-3 in order to identify the compositional signature of continent-derived detritus deposited in the Weddell Sea during a known glacial period. Further, we use our K-Ar analyses of circum-Antarctic Quaternary sediment cores to pinpoint potential sediment source areas. Having constrained this glaciation signal, we also present preliminary K-Ar and Sm-Nd analysis of the Campanian-Maastrictian boundary event (69 Ma) at Ocean Drilling Project site 690C to assess the controversial hypothesis of Late Cretaceous glaciation of Antarctica.

Selenium in aquatic biota inhabiting agricultural drains in the Salton Sea Basin, California

USGS Publications Warehouse

Saiki, Michael K.; Martin, Barbara A.; May, Thomas W.

2012-01-01

Resource managers are concerned that water conservation practices in irrigated farmlands along the southern border of the Salton Sea, Imperial County, California, could increase selenium concentrations in agricultural drainwater and harm the desert pupfish (Cyprinodon macularius), a federally protected endangered species. As part of a broader attempt to address this concern, we conducted a 3-year investigation to collect baseline information on selenium concentrations in seven agricultural drains inhabited by pupfish. We collected water, sediment, selected aquatic food-chain taxa (particulate organic detritus, filamentous algae, net plankton, and midge [Chironomidae] larvae), and two poeciliid fishes (western mosquitofish Gambusia affinis and sailfin molly Poecilia latipinna) for selenium determinations. The two fish species served as ecological surrogates for pupfish, which we were not permitted to sacrifice. Dissolved selenium ranged from 0.70 to 32.8 μg/L, with selenate as the major constituent. Total selenium concentrations in other environmental matrices varied widely among drains, with one drain (Trifolium 18) exhibiting especially high concentrations in detritus, 5.98–58.0 μg Se/g; midge larvae, 12.7–50.6 μg Se/g; mosquitofish, 13.2–20.2 μg Se/g; and mollies, 12.8–30.4 μg Se/g (all tissue concentrations are based on dry weights). Although toxic thresholds for selenium in fishes from the Salton Sea are still poorly understood, available evidence suggests that ambient concentrations of this element may not be sufficiently elevated to adversely affect reproductive success and survival in selenium-tolerant poeciliids and pupfish.

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.

Petrography and geochemistry of modern river sediments in an equatorial environment (Rwenzori Mountains and Albertine rift, Uganda) - Implications for weathering and provenance

NASA Astrophysics Data System (ADS)

Schneider, Sandra; Hornung, Jens; Hinderer, Matthias; Garzanti, Eduardo

2016-05-01

In hot-humid equatorial climate chemical weathering may be so strong that provenance signatures may be largely lost and even detritus derived from crystalline basement rocks reduced to quartzose sand. We tested this hypothesis in western Uganda, where stable plateau areas contrast with the active tectonic setting of the Albertine Rift (western branch of the East African Rift System, EARS), culminating in the strongly exhumed fault block of the > 5000 m high Rwenzori Mountains. In this setting, sediments derived from similar types of basement rocks including gneiss, schist, amphibolite, metasediments and granites can be traced from rapidly eroding high-altitude areas to low-altitude areas undergoing prolonged weathering. Sand and mud carried by 51 rivers overall in these two contrasting landscapes were sampled to study how and to what extent detrital modes are modified by the selective loss of unstable detrital minerals. Sediments generated in the high-relief Rwenzori Mountains show abundant feldspar (up to 32%) and rock fragments (up to 52%), which together with low SiO2/Al2O3 ratio and composition close to the Upper Continental Crust (UCC standard) reflect erosion in weathering-limited conditions. In the central Rwenzoris, low Th/Sc and Zr/Sc ratios, weak negative Eu anomaly, lower LaN/YbN values, and heavy-mineral assemblages with hornblende and epidote reflect the lithology of source rocks in the Buganda-Toro-Greenstone Belt. In contrast, sediments produced on the low-relief plateau have quartz content up to 98% and higher SiO2/Al2O3 ratio. Systematic loss of mobile elements is indicated by high chemical weathering indices CIA, PIA and WIP. However, provenance from metamorphic basement rocks is still indicated by heavy-mineral assemblages dominated by epidote and amphibole, whereas provenance from granitic rocks is revealed by high Th/Sc and Zr/Sc ratio, negative Eu anomaly and higher LaN/YbN values. We conclude that first-cycle sediments generated in high-relief areas preserve the original imprint of parent lithologies even in very humid equatorial climate. In low-relief areas, although weathering processes have proceeded over millions of years turning basement-derived detritus into an almost pure quartzose resistate, provenance signals are not erased entirely, and can be still retrieved from the residual heavy-mineral suite and relative abundance of high-field-strength trace elements.

Invertebrate colonization rates in the tailwater of a Kentucky flood-control reservoir

USGS Publications Warehouse

Swink, W.D.; Novotny, J.F.

1985-01-01

Invertebrate colonization on newly introduced rock substrates was examined from July through October 1982 in the tailwater of Barren River Lake, Kentucky. Chironomidae, the dominant taxon of benthic insects, reached full colonization by day 14. Colonization by Oligochaeta, the other major invertebrate taxon, was not completed by the end of the 95-day period of observation. It may have been delayed because insufficient food (periphyton and detritus) had accumulated on the clean rocks. Rapid recolonization of dewatered substrates may be especially critical for maintaining adequate fish food in tailwaters of flood-control reservoir.

Pb, Sr, and Nd isotopic compositions of a suite of Large Archean, igneous rocks, eastern Beartooth Mountains - Implications for crust-mantle evolution

NASA Technical Reports Server (NTRS)

Wooden, J. L.; Mueller, P. A.

1988-01-01

Compositionally diverse Late Archean rocks (2.74-2.79 Ga old) from the eastern Beartooth Mountains (Montana and Wyoming) were studied and shown to have the same initial Pb, Sr, and Nd isotopic ratios. Lead and Sr initial ratios are higher and Nd initial values lower than predicted for rocks derived from model mantle sources and strongly indicate the involvement of an older crustal reservoir in the genesis of these rocks. A model involving subduction of continental detritus and contamination of the overlying mantle is suggested.

Dynamics of dissolved organic matter in fjord ecosystems: Contributions of terrestrial dissolved organic matter in the deep layer

NASA Astrophysics Data System (ADS)

Yamashita, Youhei; McCallister, S. Leigh; Koch, Boris P.; Gonsior, Michael; Jaffé, Rudolf

2015-06-01

Annually, rivers and inland water systems deliver a significant amount of terrestrial organic matter (OM) to the adjacent coastal ocean in both particulate and dissolved forms; however, the metabolic and biogeochemical transformations of OM during its seaward transport remains one of the least understood components of the global carbon cycle. This transfer of terrestrial carbon to marine ecosystems is crucial in maintaining trophic dynamics in coastal areas and critical in global carbon cycling. Although coastal regions have been proposed as important sinks for exported terrestrial materials, most of the global carbon cycling data, have not included fjords in their budgets. Here we present distributional patterns on the quantity and quality of dissolved OM in Fiordland National Park, New Zealand. Specifically, we describe carbon dynamics under diverse environmental settings based on dissolved organic carbon (DOC) depth profiles, oxygen concentrations, optical properties (fluorescence) and stable carbon isotopes. We illustrate a distinct change in the character of DOC in deep waters compared to surface and mid-depth waters. Our results suggest that, both, microbial reworking of terrestrially derived plant detritus and subsequent desorption of DOC from its particulate counterpart (as verified in a desorption experiment) are the main sources of the humic-like enriched DOC in the deep basins of the studied fjords. While it has been suggested that short transit times and protection of OM by mineral sorption may ultimately result in significant terrestrial carbon burial and preservation in fjords, our data suggests the existence of an additional source of terrestrial OM in the form of DOC generated in deep, fjord water.

Effect of sediment composition on methane concentration and production in the transition zone of a mangrove (Sepetiba Bay, Rio de Janeiro, Brazil).

PubMed

Marinho, C C; Campos, E A; Guimarães, J R D; Esteves, F A

2012-08-01

The aim of this research was to evaluate the effect of sediment composition on methane (CH4) dynamics in sediments of different areas in the transition zone between a mangrove and the sea. This research was conducted in a mangrove at Coroa Grande, on the southern coast of Rio de Janeiro. Samples were collected at three stations: (1) region colonised by Rhizophora mangle L. on the edge of the mangrove, (2) region colonised by seagrasses and (3) infra-littoral region without vegetation. Samples were collected from the surface layer of the sediment to determine the concentrations of nutrients (C, N and P) and CH4 concentration and production. We observed that concentrations of CH4 and carbon (C) were significantly higher (p < 0.05) in station 1 than station 3. The molar ratios (C:N, C:P and N:P) suggest that the origin of the substrate is mainly autochthonous. Methanogenesis was initially low, possibly due to competition between methanogens and sulfate reducers, and increased significantly (p < 0.05) on the twenty-sixth day in the sediment of station 1, probably due to higher organic matter (OM) availability in this region. Results indicate that methanogenic activity observed herein is not regulated by the amount or quality of OM, but by other factors. The concentration of CH4 in the sea-land ecotone at Mangrove Coroa Grande is a function of available OM suggesting a possible inhibition of methanotrophy by intense oxygen consumption in the soil surface covered by detritus of Rhizophora mangle vegetation.

Growth response of a deep-water ferromanganese crust to evolution of the Neogene Indian Ocean

USGS Publications Warehouse

Banakar, V.K.; Hein, J.R.

2000-01-01

A deep-water ferromanganese crust from a Central Indian Ocean seamount dated previously by 10Be and 230Th(excess) was studied for compositional and textural variations that occurred throughout its growth history. The 10Be/9Be dated interval (upper 32 mm) yields an uniform growth rate of 2.8 ?? 0.1 mm/Ma [Frank, M., O'Nions, R.K., 1998. Sources of Pb for Indian Ocean ferromanganese crusts: a record of Himalayan erosion. Earth Planet. Sci. Lett., 158, pp. 121-130.] which gives an extrapolated age of ~ 26 Ma for the base of the crust at 72 mm and is comparable to the maximum age derived from the Co-model based growth rate estimates. This study shows that Fe-Mn oxyhydroxide precipitation did not occur from the time of emplacement of the seamount during the Eocene (~ 53 Ma) until the late Oligocene (~ 26 Ma). This paucity probably was the result of a nearly overlapping palaeo-CCD and palaeo-depth of crust formation, increased early Eocene productivity, instability and reworking of the surface rocks on the flanks of the seamount, and lack of oxic deep-water in the nascent Indian Ocean. Crust accretion began (older zone) with the formation of isolated cusps of Fe-Mn oxide during a time of high detritus influx, probably due to the early-Miocene intense erosion associated with maximum exhumation of the Himalayas (op. cit.). This cuspate textured zone extends from 72 mm to 42 mm representing the early-Miocene period. Intense polar cooling and increased mixing of deep and intermediate waters at the close of the Oligocene might have led to the increased oxygenation of the bottom-water in the basin. A considerable expansion in the vertical distance between the seafloor depth and the CCD during the early Miocene in addition to the influx of oxygenated bottom-water likely initiated Fe-Mn crust formation. Pillar structure characterises the younger zone, which extends from 40 mm to the surface of the crust, i.e., ~ 15 Ma to Present. This zone is characterised by > 25% higher content of oxide-bound elements than in the older zone, possibly corresponding to further increased oxygenation of bottom-waters, increased stability of the seamount slope, and gradually reduced input of continental detritus from the erosion of the Himalayas. Middle Miocene Antarctic glaciation, which peaked ~ 12-13 Ma ago, increased the oxic bottom-water influx to the basin resulting in accretion of the crust with low detritus. Therefore, the younger crust started to accrete in response to a shift in bottom-water circulation towards the contemporary pattern, which produced a uniform growth rate and pillar structure up to the present. (C) 2000 Published by Elsevier Science B.V.

Odorant transfer characteristics of white bread during baking.

PubMed

Onishi, Masanobu; Inoue, Michiko; Araki, Tetsuya; Iwabuchi, Hisakatsu; Sagara, Yasuyuki

2011-01-01

The potent odorants in the crust and crumb of white bread were identified and quantified by gas chromatography-mass spectrometry and gas chromatography/olfactometry. The weight loss ratio of the samples baked at 220 °C was controlled in the range of 0-28%. The odorants were classified into 5 types by the transfer characteristics: i) All amounts of odorant transferred from the crust to external space (type-I). ii) All transferred from the crust to the crumb and external space (type-II). iii) Certain amount remaining in the crust and the rest transferred to the crumb and external space (type-III). iv) All transferred from the crumb to external space (type-IV). v) Certain amount remaining in the crumb and the rest transferred to the crust and external space (type-V). The odorants of type-IV were not apparent after the crust had formed. The results indicate that the crust could be a barrier to prevent the odorants from being transferred to external space.

Soil respiration rates and δ13C(CO2) in natural beech forest (Fagus sylvatica L.) in relation to stand structure.

PubMed

Cater, Matjaz; Ogrinc, Nives

2011-06-01

Soil respiration rates were studied as a function of soil type, texture and light intensity at five selected natural beech forest stands with contrasting geology: stands on silicate bedrock at Kladje and Bricka in Pohorje, a stand on quartz sandstone at Vrhovo and two stands on a carbonate bedrock in the Karstic-Dinaric area in Kocevski Rog, Snezna jama and Rajhenav, Slovenia, during the growing season in 2005-2006. Soil respiration exhibited pronounced seasonal and spatial variations in the studied forest ecosystem plots. The CO(2) flux rates ranged from minimum averages of 2.3 μmol CO(2) m(-2) s(-1) (winter) to maximum averages of about 7 μmol CO(2) m(-2) s(-1) (summer) at all the investigated locations. An empirical model describing the relationship between soil respiration and soil temperature predicted seasonal variations in soil respiration reasonably well during 2006. Nevertheless, there were also some indications that soil moisture in relation to soil texture could influence the soil CO(2) efflux rates in both sampling seasons. It was shown that spatial variability of mean soil respiration at the investigated sites was high and strongly related to root biomass. Based on the [image omitted]  data, it was shown that new photoassimilates could account for a major part of the total soil respiration under canopy conditions in forest ecosystems where no carbonate rocks are present, indicating that microbial respiration could not always dominate bulk soil CO(2) fluxes. At Snezna jama and Rajhenav, the abiotic CO(2) derived from carbonate dissolution had a pronounced influence on CO(2) efflux accounting, on average, to ∼17%. Further spatial heterogeneity of soil respiration was clearly affected by management practice. Higher respiration rates as well as higher variability in respiration rates were observed in the virgin forest (Rajhenav) than in the management forest (Snezna jama) and could be related to a higher amount of detritus and consequently to less pronounced influence of inorganic pool to CO(2) efflux, lower mixing with atmospheric CO(2) and higher sensitivity to environmental changes. Major differences in soil carbon dynamics among these five forest ecosystems can be explained by the influence of bedrock geology (particularly, the presence or absence of carbonate minerals) and soil texture (affecting gas exchange with overlying air and soil moisture).

Estuaries of the northeastern United States: Habitat and land use signatures

USGS Publications Warehouse

Roman, C.T.; Jaworski, N.; Short, F.T.; Findlay, S.; Warren, R.S.

2000-01-01

Geographic signatures are physical, chemical, biotic, and human-induced characteristics or processes that help define similar or unique features of estuaries along latitudinal or geographic gradients. Geomorphologically, estuaries of the northeastern U.S., from the Hudson River estuary and northward along the Gulf of Maine shoreline, are highly diverse because of a complex bedrock geology and glacial history. Back-barrier estuaries and lagoons occur within the northeast region, but the dominant type is the drowned-river valley, often with rocky shores. Tidal range and mean depth of northeast estuaries are generally greater when compared to estuaries of the more southern U.S. Atlantic coast and Gulf of Mexico. Because of small estuarine drainage basins, low riverine flows, a bedrock substrate, and dense forest cover, sediment loads in northeast estuaries are generally quite low and water clarity is high. Tidal marshes, seagrass meadows, intertidal mudflats, and rocky shores represent major habitat types that fringe northeast estuaries, supporting commercially-important fauna, forage nekton and benthos, and coastal bird communities, while also serving as links between deeper estuarine waters and habitats through detritus-based pathways. Regarding land use and water quality trends, portions of the northeast have a history of over a century of intense urbanization as reflected in increased total nitrogen and total phosphorus loadings to estuaries, with wastewater treatment facilities and atmospheric deposition being major sources. Agricultural inputs are relatively minor throughout the northeast, with relative importance increasing for coastal plain estuaries. Identifying geographic signatures provides an objective means for comparing the structure function, and processes of estuaries along latitudinal gradients.

Free-living bacterial communities associated with tubeworm (Ridgeia piscesae) aggregations in contrasting diffuse flow hydrothermal vent habitats at the Main Endeavour Field, Juan de Fuca Ridge

PubMed Central

Forget, Nathalie L; Kim Juniper, S

2013-01-01

We systematically studied free-living bacterial diversity within aggregations of the vestimentiferan tubeworm Ridgeia piscesae sampled from two contrasting flow regimes (High Flow and Low Flow) in the Endeavour Hydrothermal Vents Marine Protected Area (MPA) on the Juan de Fuca Ridge (Northeast Pacific). Eight samples of particulate detritus were recovered from paired tubeworm grabs from four vent sites. Most sequences (454 tag and Sanger methods) were affiliated to the Epsilonproteobacteria, and the sulfur-oxidizing genus Sulfurovum was dominant in all samples. Gammaproteobacteria were also detected, mainly in Low Flow sequence libraries, and were affiliated with known methanotrophs and decomposers. The cooccurrence of sulfur reducers from the Deltaproteobacteria and the Epsilonproteobacteria suggests internal sulfur cycling within these habitats. Other phyla detected included Bacteroidetes, Actinobacteria, Chloroflexi, Firmicutes, Planctomycetes, Verrucomicrobia, and Deinococcus–Thermus. Statistically significant relationships between sequence library composition and habitat type suggest a predictable pattern for High Flow and Low Flow environments. Most sequences significantly more represented in High Flow libraries were related to sulfur and hydrogen oxidizers, while mainly heterotrophic groups were more represented in Low Flow libraries. Differences in temperature, available energy for metabolism, and stability between High Flow and Low Flow habitats potentially explain their distinct bacterial communities. PMID:23401293

The diffuse source at the center of LMC SNR 0509–67.5 is a background galaxy at z = 0.031

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

Pagnotta, Ashley; Walker, Emma S.; Schaefer, Bradley E., E-mail: pagnotta@amnh.org

2014-06-20

Type Ia supernovae (SNe Ia) are well-known for their use in the measurement of cosmological distances, but our continuing lack of concrete knowledge about their progenitor stars is both a matter of debate and a source of systematic error. In our attempts to answer this question, we presented unambiguous evidence that LMC SNR 0509–67.5, the remnant of an SN Ia that exploded in the Large Magellanic Cloud 400 ± 50 yr ago, did not have any point sources (stars) near the site of the original supernova explosion, from which we concluded that this particular supernova must have had a progenitormore » system consisting of two white dwarfs. There is, however, evidence of nebulosity near the center of the remnant, which could have been left over detritus from the less massive WD, or could have been a background galaxy unrelated to the supernova explosion. We obtained long-slit spectra of the central nebulous region using GMOS on Gemini South to determine which of these two possibilities is correct. The spectra show Hα emission at a redshift of z = 0.031, which implies that the nebulosity in the center of LMC SNR 0509–67.5 is a background galaxy, unrelated to the supernova.« less

Escherichia coli and enterococci at beaches in the Grand Traverse Bay, Lake Michigan: Sources, characteristics, and environmental pathways

USGS Publications Warehouse

Haack, S.K.; Fogarty, L.R.; Wright, C.

2003-01-01

This study quantified Escherichia coli(EC) and enterococci (ENT) in beach waters and dominant source materials, correlated these with ambient conditions, and determined selected EC genotypes and ENT phenotypes. Bathing-water ENT criteria were exceeded more frequently than EC criteria, providing conflicting interpretations of water quality. Dominant sources of EC and ENT were bird feces (108/d/bird), storm drains (107/d), and river water (1011/d); beach sands, shallow groundwater and detritus were additional sources. Beach-water EC genotypes and ENT phenotypes formed clusters with those from all source types, reflecting diffuse inputs. Some ENT isolates had phenotypes similar to those of human pathogens and/or exhibited high-level resistance to human-use antibiotics. EC and ENT concentrations were influenced by collection time and wind direction. There was a 48-72-h lag between rainfall and elevated EC concentrations at three southern shoreline beaches, but no such lag at western and eastern shoreline beaches, reflecting the influence of beach orientation with respect to cyclic (3-5 d) summer weather patterns. In addition to local contamination sources and processes, conceptual or predictive models of Great Lakes beach water quality should consider regional weather patterns, lake hydrodynamics, and the influence of monitoring method variables (time of day, frequency).

Variations of measured and simulated soil-loss amounts in a semiarid area in Turkey.

PubMed

Hacisalihoğlu, Sezgin

2010-06-01

The main goal of this research was soil-loss determination and comparison of the plot measurement results with simulation model (universal soil loss equation (USLE)) results in different land use and slope classes. The research took place in three different land-use types (Scotch pine forest, pasture land, and agricultural land) and in two different slope classes (15-20%, 35-40%). Within six measurement stations (for each land-use type and slope class-one station), totally 18 measurement plots have been constituted, and soil-loss amount measurements have been investigated during the research period (3 years along). USLE simulation model is used in these measurement plots for calculation the soil-loss amounts. The results pointed out that measured (in plots) and simulated (with USLE) soil-loss amounts differ significantly in each land-use type and slope class.

12 CFR 611.515 - Information statement.

Code of Federal Regulations, 2010 CFR

2010-01-01

... estimated to be associated with the transfer. (7) A description of the type and dollar amount of any... require financial assistance during the first 3 years of operation, the estimated type and dollar amount... possible tax consequences to stockholders and whether any legal opinion, ruling or external auditor's...

The significance of chemical, isotopic, and detrital components in three coeval stalagmites from the superhumid southernmost Andes (53°S) as high-resolution palaeo-climate proxies

NASA Astrophysics Data System (ADS)

Schimpf, Daniel; Kilian, Rolf; Kronz, Andreas; Simon, Klaus; Spötl, Christoph; Wörner, Gerhard; Deininger, Michael; Mangini, Augusto

2011-02-01

Stalagmites are important palaeo-climatic archives since their chemical and isotopic signatures have the potential to record high-resolution changes in temperature and precipitation over thousands of years. We present three U/Th-dated records of stalagmites (MA1-MA3) in the superhumid southern Andes, Chile (53°S). They grew simultaneously during the last five thousand years (ka BP) in a cave that developed in schist and granodiorite. Major and trace elements as well as the C and O isotope compositions of the stalagmites were analysed at high spatial and temporal resolution as proxies for palaeo-temperature and palaeo-precipitation. Calibrations are based on data from five years of monitoring the climate and hydrology inside and outside the cave and on data from 100 years of regional weather station records. Water-insoluble elements such as Y and HREE in the stalagmites indicate the amount of incorporated siliciclastic detritus. Monitoring shows that the quantity of detritus is controlled by the drip water rate once a threshold level has been exceeded. In general, drip rate variations of the stalagmites depend on the amount of rainfall. However, different drip-water pathways above each drip location gave rise to individual drip rate levels. Only one of the three stalagmites (MA1) had sufficiently high drip rates to record detrital proxies over its complete length. Carbonate-compatible element contents (e.g. U, Sr, Mg), which were measured up to sub-annual resolution, document changes in meteoric precipitation and related drip-water dilution. In addition, these soluble elements are controlled by leaching during weathering of the host rock and soils depending on the pH of acidic pore waters in the peaty soils of the cave's catchment area. In general, higher rainfall resulted in a lower concentration of these elements and vice versa. The Mg/Ca record of stalagmite MA1 was calibrated against meteoric precipitation records for the last 100 years from two regional weather stations. Carbonate-compatible soluble elements show similar patterns in the three stalagmites with generally high values when drip rates and detrital tracers were low and vice versa. δ 13C and δ 18O values are highly correlated in each stalagmite suggesting a predominantly drip rate dependent kinetic control by evaporation and/or outgassing. Only C and O isotopes from stalagmite MA1 that received the highest drip rates show a good correlation between detrital proxy elements and carbonate-compatible elements. A temperature-related change in rainwater isotope values modified the MA1 record during the Little Ice Age (˜0.7-0.1 ka BP) that was ˜1.5 °C colder than today. The isotopic composition of the stalagmites MA2 and MA3 that formed at lower drip rates shows a poor correlation with stalagmite MA1 and all other chemical proxies of MA1. 'Hendy tests' indicate that the degassing-controlled isotope fractionation of MA2 and MA3 had already started at the cave roof, especially when drip rates were low. Changing pathways and residence times of the seepage water caused a non-climatically controlled isotope fractionation, which may be generally important in ventilated caves during phases of low drip rates. Our proxies indicate that the Neoglacial cold phases from ˜3.5 to 2.5 and from ˜0.7 to 0.1 ka BP were characterised by 30% lower precipitation compared with the Medieval Warm Period from 1.2 to 0.8 ka BP, which was extremely humid in this region.

A new model for the origin of Type-B and Fluffy Type-A CAIs: Analogies to remelted compound chondrules

NASA Astrophysics Data System (ADS)

Rubin, Alan E.

2012-06-01

In the scenario developed here, most types of calcium-aluminum-rich inclusions (CAIs) formed near the Sun where they developed Wark-Lovering rims before being transported by aerodynamic forces throughout the nebula. The amount of ambient dust in the nebula varied with heliocentric distance, peaking in the CV-CK formation location. Literature data show that accretionary rims (which occur outside the Wark-Lovering rims) around CAIs contain substantial 16O-rich forsterite, suggesting that, at this time, the ambient dust in the nebula consisted largely of 16O-rich forsterite. Individual sub-millimeter-size Compact Type-A CAIs (each surrounded by a Wark-Lovering rim) collided in the CV-CK region and stuck together (in a manner similar to that of sibling compound chondrules); the CTAs were mixed with small amounts of 16O-rich mafic dust and formed centimeter-size compound objects (large Fluffy Type-A CAIs) after experiencing minor melting. In contrast to other types of CAIs, centimeter-size Type-B CAIs formed directly in the CV-CK region after gehlenite-rich Compact Type-A CAIs collided and stuck together, incorporated significant amounts of 16O-rich forsteritic dust (on the order of 10-15%) and probably some anorthite, and experienced extensive melting and partial evaporation. (Enveloping compound chondrules formed in an analogous manner.) In those cases where appreciably higher amounts of 16O-rich forsterite (on the order of 25%) (and perhaps minor anorthite and pyroxene) were incorporated into compound Type-A objects prior to melting, centimeter-size forsterite-bearing Type-B CAIs (B3 inclusions) were produced. Type-B1 inclusions formed from B2 inclusions that collided with and stuck to melilite-rich Compact Type-A CAIs and experienced high-temperature processing.

48 CFR 16.305 - Cost-plus-award-fee contracts.

Code of Federal Regulations, 2010 CFR

2010-10-01

... CONTRACTING METHODS AND CONTRACT TYPES TYPES OF CONTRACTS Cost-Reimbursement Contracts 16.305 Cost-plus-award... consisting of (a) a base amount (which may be zero) fixed at inception of the contract and (b) an award amount, based upon a judgmental evaluation by the Government, sufficient to provide motivation for...

21 CFR 601.35 - Evaluation of safety.

Code of Federal Regulations, 2013 CFR

2013-04-01

... information, the following types of data: (A) Pharmacology data, (B) Toxicology data, (C) Clinical adverse event data, and (D) Radiation safety assessment. (2) The amount of new safety data required will depend... relevant to risk and will specify the amount and type of safety data that are appropriate for each category...

48 CFR 1516.303-75 - Amount of cost-sharing.

Code of Federal Regulations, 2010 CFR

2010-10-01

.... 1516.303-75 Section 1516.303-75 Federal Acquisition Regulations System ENVIRONMENTAL PROTECTION AGENCY CONTRACTING METHODS AND CONTRACT TYPES TYPES OF CONTRACTS Cost-Reimbursement Contracts 1516.303-75 Amount of... market share position; (3) The time and risk necessary to achieve success; (4) If the results of the...

40 CFR 63.7555 - What records must I keep?

Code of Federal Regulations, 2010 CFR

2010-07-01

... (v) related to startup, shutdown, and malfunction. (3) Records of performance tests, fuel analyses... the deviation occurred during a period of startup, shutdown, or malfunction or during another period... monthly fuel use by each boiler or process heater, including the type(s) of fuel and amount(s) used. (2...

40 CFR 63.7555 - What records must I keep?

Code of Federal Regulations, 2012 CFR

2012-07-01

... (v) related to startup, shutdown, and malfunction. (3) Records of performance tests, fuel analyses... the deviation occurred during a period of startup, shutdown, or malfunction or during another period... monthly fuel use by each boiler or process heater, including the type(s) of fuel and amount(s) used. (2...

40 CFR 63.7555 - What records must I keep?

Code of Federal Regulations, 2011 CFR

2011-07-01

... (v) related to startup, shutdown, and malfunction. (3) Records of performance tests, fuel analyses... the deviation occurred during a period of startup, shutdown, or malfunction or during another period... monthly fuel use by each boiler or process heater, including the type(s) of fuel and amount(s) used. (2...

Discovering cell types in flow cytometry data with random matrix theory

NASA Astrophysics Data System (ADS)

Shen, Yang; Nussenblatt, Robert; Losert, Wolfgang

Flow cytometry is a widely used experimental technique in immunology research. During the experiments, peripheral blood mononuclear cells (PBMC) from a single patient, labeled with multiple fluorescent stains that bind to different proteins, are illuminated by a laser. The intensity of each stain on a single cell is recorded and reflects the amount of protein expressed by that cell. The data analysis focuses on identifying specific cell types related to a disease. Different cell types can be identified by the type and amount of protein they express. To date, this has most often been done manually by labelling a protein as expressed or not while ignoring the amount of expression. Using a cross correlation matrix of stain intensities, which contains both information on the proteins expressed and their amount, has been largely ignored by researchers as it suffers from measurement noise. Here we present an algorithm to identify cell types in flow cytometry data which uses random matrix theory (RMT) to reduce noise in a cross correlation matrix. We demonstrate our method using a published flow cytometry data set. Compared with previous analysis techniques, we were able to rediscover relevant cell types in an automatic way. Department of Physics, University of Maryland, College Park, MD 20742.

Disturbance and topography shape nitrogen availability and δ15 N over long-term forest succession

USGS Publications Warehouse

Perakis, Steven; Tepley, Alan J.; Compton, Jana

2015-01-01

Forest disturbance and long-term succession towards old-growth are thought to increase nitrogen (N) availability and N loss, which should increase soil δ15N values. We examined soil and foliar patterns in N and δ15N, and soil N mineralization, across 800 years of forest succession in a topographically complex montane landscape influenced by human logging and wildfire. In contrast to expectations, we found that disturbance caused declines in surface mineral soil δ15N values, both in logged forests measured 40–50 years after disturbance, and in unlogged forests disturbed by severe wildfire within the last 200 years. Both symbiotic N fixation and N transfers from disturbed vegetation and detritus could lower soil δ15N values after disturbance. A more important role for symbiotic N fixation is suggested by lower soil δ15N values in slow-successional sites with slow canopy closure, which favors early-successional N fixers. Soil δ15N values increased only marginally throughout 800 years of succession, reflecting soil N uptake by vegetation and strong overall N retention. Although post-disturbance N inputs lowered surface soil δ15N values, steady-state mass balance calculations suggest that wildfire combustion of vegetation and detritus can dominate long-term N loss and increase whole-ecosystem δ15N. On steeper topography, declining soil δ15N values highlight erosion and accelerated soil turnover as an additional abiotic control on N balances. We conclude for N-limited montane forests that soil δ15N and N availability are less influenced by nitrate leaching and denitrification loss than by interactions between disturbance, N fixation, and erosion.

Cenozoic foreland basin evolution during Andean shortening in the Malargüe region of western Argentina (35°S)

NASA Astrophysics Data System (ADS)

Ramirez, S. G.; Horton, B. K.; Fuentes, F.

2015-12-01

Cenozoic clastic deposits in western Argentina provide key opportunities to evaluate the timing and duration of Andean deformation and uplift. We studied the Malargüe segment of the Andean foreland basin at 35°S to better understand latest Cretaceous to Pliocene deformation and eastward propagation of Andean retroarc shortening. Our multi-technique approach included logging of a well-exposed ~1500m Paleocene-Miocene stratigraphic succession, paleocurrent measurements, conglomerate clast counts, and detrital zircon U-Pb geochronological analyses of basin fill exposed in the Sosneado region along the Rio Atuel. The Pircala and Coihueco Formations define the lowermost ~180 m of the section and are represented by fine to medium sandstones, siltstones, claystones and marls interpreted as distal fluvial floodplain and localized lacustrine deposits. Pircala paleocurrents show a major reversal from west- to east-directed flow. These finer deposits of the lower succession are separated from the overlying coarser-grained ~800 m thick Agua de la Piedra Formation by a conspicuous unconformity that spans up to roughly 20 Myr. The Agua de la Piedra Formation is composed of upward-coarsening amalgamated beds of massive medium to coarse sandstones and lenticular conglomerates interpreted as a prograding proximal fluvial to alluvial fan system. Conglomerate clast counts show initial dominance by Mesozoic detritus from the pre-Andean Neuquen basin system, with a progressive upsection increase in Cenozoic volcanic detritus from the Andean magmatic arc. Collectively, the paleocurrents, clast compositions, sedimentary facies associations, and emerging U-Pb results suggest a long-term shift, commencing in the Paleocene, from eastern cratonic sources to magmatic-arc and thrust-belt sources during a systematic eastward propagation of deformation, with a pronounced phase of Miocene magmatism and shortening that incorporated the proximal foreland basin into the advancing thrust belt.

Transformation of soil organic matter in leached chernozems under minimized treatment in the forest-steppe of West Siberia

NASA Astrophysics Data System (ADS)

Sharkov, I. N.; Samokhvalova, L. M.; Mishina, P. V.

2016-07-01

Changes in the contents of total organic carbon and the carbon of easily mineralizable fractions of organic matter (labile humus, detritus, and mortmass) in the layers of 0-10, 10-25, and 0-25 cm were studied in leached chernozems ((Luvic Chernozems (Loamic, Aric)) subjected to deep plowing and surface tillage for nine years. In the layer of 0-25 cm, the content of Corg did not show significant difference between these two treatments and comprised 3.68-3.92% in the case of deep plowing and 3.63-4.08% in the case of surface tillage. Tillage practices greatly affected the distribution of easily mineralizable fractions of organic matter in the layers of 0-10 and 10-25 cm, though the difference between two treatments for the entire layer (0-25 cm) was insignificant. Surface tillage resulted in the increase in the contents of mortmass (by 59%), detritus (by 32%), and labile humus (by 8%) in the layer of 0-10 cm in comparison with deep plowing. At the same time, the contents of these fractions in the layer of 10-25 cm in the surface tillage treatment decreased by 67, 46, and 3%, respectively. The estimate of the nitrogen-mineralizing capacity made according to the data on the uptake of soil nitrogen by oat plants in a special greenhouse experiment confirmed the observed regularities of the redistribution of easily mineralizable organic matter fractions by the soil layers. In case of surface tillage, it increased by 23% in the layer of 0-10 cm; for the layer of 0-25 cm, no significant differences in the uptake of nitrogen by oat plants were found for the two studied treatments.

Detrital Thermochronology Record of the Local-to-Extraregional Provenance Shift Recorded by the Northern Peninsular Ranges Forearc

NASA Astrophysics Data System (ADS)

Flores, M.; Shulaker, D. Z.

2016-12-01

Previously measured detrital zircon U-Pb age distributions have revealed that Late Cretaceous to Eocene forearc strata in the Santa Ana mountains region experienced a dramatic shift in sedimentary provenance from a 125-90 Ma northern Peninsular Ranges batholith (PRB) source region along the continental margin to a cratonal source area intruded by Late Cretaceous (85-75 Ma) plutons within the continental interior (western Sonora). To improve our understanding of the timing and magnitude of denudation prior to, and during this local to extraregional provenance shift, we have measured new detrital K-feldspar 40Ar/39Ar total fusion and zircon U-Pb age distributions from forearc sandstones. Our combined crystallization age and thermal history results confirm two pulses of rapid denudation of the PRB. These include a syn-batholith phase (Cenomanian) and a post-batholithic (Maastrichtian to Paleocene) phase attributed to shallow subduction. The new data require that significant (5-10 km) syn-batholithic erosional denudation of the northern PRB had already occurred by ca. 95 Ma and that post-emplacement denudation of the PRB accelerated again during the Maastrichtian with the eastern PRB providing the bulk of the detritus. Our new results demonstrate that deposition of the Paleocene Silverado Fm. occurred during a transitional period. Sand reaching the forearc during the Paleocene was derived from both the heavily denuded eastern PRB with additional input supplied either from Late Cretaceous plutons of northwestern Sonoran region and/or similar plutons emplaced in thrust sheets atop PRB basement within the Santa Rosa Mountains. In contrast, the Eocene Santiago Fm. was nearly entirely derived from extraregional sources that supplied abundant late Cretaceous (75-85 Ma) and Proterozoic (1.4 & 1.7 Ga) detritus with virtually no PRB-derived sediment detected.

A 3-D ecosystem model in the Pacific Ocean and its simulations

NASA Astrophysics Data System (ADS)

Xu, Y.; Ba, Q.

2011-12-01

A simple 3-D ecosystem model with nutrient, phytoplankton, zooplankton and detritus is coupled into the basinwide ocean general circulation (OGCM) of the Pacific Ocean that has been examined by the passive tracer such as tritium. The model was integrated for 500 years under the forcing of climatological monthly mean fields. The model generates similar distribution patterns of ecosystem variables to the estimates based on satellite-derived chlorophyll maps by vertically generalized production model with low water-column NPP values in the subtropical region and high values in the subarctic region and equatorial upwelling region. But the area and strength of oligotrophic gyre is much larger than that indicated in the observations. Compared with the observations, seasonal variations of surface chlorophyll concentrations and top 200-m average zooplankton biomass in the mid-high latitude regions are well simulated in the model. Because of the restoring term near the northern boundary used in the model, a false phytoplankton bloom can occur nearby 50N during winter time. An unrealistic maximum value in the vertical profile of chlorophyll near ocean weather station Papa is generated by our model. In terms of modification of model structure and sensitivity test of the associated parameters, the simulated results can be well improved. Although the division of nutrient into nitrate and ammonium and inclusion of DON in the model can alleviate the low-NPP problem in the subtropical region, modification of the sinking rate and decomposition rate of detritus in the model can be more effective. Introduction of the influence of mixed layer on the ecosystem process and modification of restraint of nutrients near the northern boundary can overcome the shortcomings of simulation of both spring bloom near 50N and vertical profile of chlorophyll at Papa to some extent.

Variation in the mobilization of mercury into Black-winged Stilt Himantopus himantopus chicks in coastal saltpans, as revealed by stable isotopes

NASA Astrophysics Data System (ADS)

Tavares, P. C.; Kelly, A.; Maia, R.; Lopes, R. J.; Serrão Santos, R.; Pereira, M. E.; Duarte, A. C.; Furness, R. W.

2008-03-01

Causes of variation in mobilization of mercury into Black-winged Stilt Himantopus himantopus chicks were studied through analysis of stable isotope ratios of carbon and nitrogen. Blood and breast feathers were collected from chicks in coastal saltpans during successive breeding seasons. Detritus samples and potential prey (macroinvertebrates) were also collected. Total mercury concentrations and stable isotope signatures were measured using atomic absorption spectroscopy and isotope ratio mass spectrometry respectively. Mercury levels in Chironomidae, Corixidae and Hydrophilidae correlated with mercury levels in chick feathers. Differences of δ 15N signatures between macroinvertebrate groups indicated that they belong to different trophic levels. δ 15N signatures of invertebrates correlated with mercury levels in invertebrates and chicks, but not with δ 15N signatures in chicks. Between-group and between-site differences of δ 15N signatures and mercury levels in invertebrates suggested that they contribute differently to mercury mobilization into chicks, and their relative contribution depends on prey availability in each site. Inter-site differences in the biomagnification factor reinforced that idea. δ 13C signatures in invertebrates marked a larger range of carbon sources than just detritus. Variation of water inflow regime and prey availability may cause between-group and between-site differences of δ 13C signatures in prey. Discrepancies between feather and blood for δ 13C signatures in Praias-Sado and Vaia suggested that temporal variation of prey availability may be the main factor affecting mercury mobilization into chicks in both those cases, since their water inflow regimes are the same. The lowest levels of δ 13C signatures in Vau suggested that water inflow regime may be the main factor in this case, since no discrepancy existed in δ 13C signatures between blood and feather.

Ecosystem structure and fishing impacts in the northwestern Mediterranean Sea using a food web model within a comparative approach

NASA Astrophysics Data System (ADS)

Corrales, Xavier; Coll, Marta; Tecchio, Samuele; Bellido, José María; Fernández, Ángel Mario; Palomera, Isabel

2015-08-01

We developed an ecological model to characterize the structure and functioning of the marine continental shelf and slope area of the northwestern Mediterranean Sea, from Toulon to Cape La Nao (NWM model), in the early 2000s. The model included previously modeled areas in the NW Mediterranean (the Gulf of Lions and the Southern Catalan Sea) and expanded their ranges, covering 45,547 km2, with depths from 0 to 1000 m. The study area was chosen to specifically account for the connectivity between the areas and shared fish stocks and fleets. Input data were based on local scientific surveys and fishing statistics, published data on stomach content analyses, and the application of empirical equations to estimate consumption and production rates. The model was composed of 54 functional groups, from primary producers to top predators, and Spanish and French fishing fleets were considered. Results were analyzed using ecological indicators and compared with outputs from ecosystem models developed in the Mediterranean Sea and the Gulf of Cadiz prior to this study. Results showed that the main trophic flows were associated with detritus, phytoplankton, zooplankton and benthic invertebrates. Several high trophic level organisms (such as dolphins, benthopelagic cephalopods, large demersal fishes from the continental shelf, and other large pelagic fishes), and the herbivorous salema fish, were identified as keystone groups within the ecosystem. Results confirmed that fishing impact was high and widespread throughout the food web. The comparative approach highlighted that, despite productivity differences, the ecosystems shared common features in structure and functioning traits such as the important role of detritus, the dominance of the pelagic fraction in terms of flows and the importance of benthic-pelagic coupling.

Anthropogenic-enhanced erosion following the Neolithic Revolution in the Southern Levant: Records from the Dead Sea deep drilling core

NASA Astrophysics Data System (ADS)

Lu, Yin; Waldmann, Nicolas; Nadel, Dani; Marco, Shmuel

2017-04-01

In addition to tectonics and climatic changes, humans have exerted a significant impact on surface erosion over timescales ranging from years to centuries. However, such kind of impact over millennial timescales remains unsubstantiated. The Dead Sea drainage basin offers a rare combination of well-documented substantial climate change, intense tectonics and abundant archaeological evidence for past human activity in the Southern Levant. It serves as a natural laboratory for understanding how sedimentation rates in a deep basin are related to climate change, tectonics, and anthropogenic impacts on the landscape. Here we show how basin-wide erosion rates are recorded by thicknesses of rhythmic detritus laminae and clastic sediment accumulation rates in a long core retrieved by the Dead Sea Deep Drilling Project in the Dead Sea depocenter. During the last 11.5 kyr the average detrital accumulation rate is 3-4 times that during the last two glacial cycles (MIS 7c-2), and the average thickness of detritus laminae in the last 11.6 kyr is 4.5 times that between 21.7 and 11.6 ka, implying an increased erosion rate on the surrounding slopes during the Holocene. We estimate that this intensified erosion is incompatible with tectonic and climatic regimes during the corresponding time interval and further propose a close association with the Neolithic Revolution in the Levant (beginning at 11.5 ka). We thus suggest that human impact on the landscape was the primary driver causing the intensified erosion and that the Dead Sea sedimentary record serves as a reliable recorder of this impact since the Neolithic Revolution.

Trophic Tangles through Time? Opposing Direct and Indirect Effects of an Invasive Omnivore on Stream Ecosystem Processes

PubMed Central

Moore, Jonathan W.; Carlson, Stephanie M.; Twardochleb, Laura A.; Hwan, Jason L.; Fox, Justin M.; Hayes, Sean A.

2012-01-01

Omnivores can impact ecosystems via opposing direct or indirect effects. For example, omnivores that feed on herbivores and plants could either increase plant biomass due to the removal of herbivores or decrease plant biomass due to direct consumption. Thus, empirical quantification of the relative importance of direct and indirect impacts of omnivores is needed, especially the impacts of invasive omnivores. Here we investigated how an invasive omnivore (signal crayfish, Pacifastacus leniusculus) impacts stream ecosystems. First, we performed a large-scale experiment to examine the short-term (three month) direct and indirect impacts of crayfish on a stream food web. Second, we performed a comparative study of un-invaded areas and areas invaded 90 years ago to examine whether patterns from the experiment scaled up to longer time frames. In the experiment, crayfish increased leaf litter breakdown rate, decreased the abundance and biomass of other benthic invertebrates, and increased algal production. Thus, crayfish controlled detritus via direct consumption and likely drove a trophic cascade through predation on grazers. Consistent with the experiment, the comparative study also found that benthic invertebrate biomass decreased with crayfish. However, contrary to the experiment, crayfish presence was not significantly associated with higher leaf litter breakdown in the comparative study. We posit that during invasion, generalist crayfish replace the more specialized native detritivores (caddisflies), thereby leading to little long-term change in net detrital breakdown. A feeding experiment revealed that these native detritivores and the crayfish were both effective consumers of detritus. Thus, the impacts of omnivores represent a temporally-shifting interplay between direct and indirect effects that can control basal resources. PMID:23209810

Oligo-Miocene Alpine Sediment Routing from Integrated Analysis of Seismic-Reflection Data and Detrital Zircon U-Pb Geochronology

NASA Astrophysics Data System (ADS)

Hubbard, S. M.; Sharman, G.; Covault, J. A.

2014-12-01

We integrate detrital zircon geochronology and 3D seismic-reflection data to reconstruct Oligo-Miocene paleogeography and sediment routing from the Alpine hinterland to Austrian Molasse foreland basin. Three-dimensional seismic-reflection data image a network of deepwater tributaries and a long-lived (>8 Ma) foredeep-axial channel belt through which predominantly southerly and westerly turbidity currents are interpreted to have transported Alpine detritus >100 km. We analyzed 793 detrital zircon grains from ten sandstone samples collected from the seismically mapped network of channel fill. Grain age populations correspond with major Alpine orogenic cycles: the Cadomian (750-530 Ma), the Caledonian (500-400 Ma), and the Variscan orogenies (350-250 Ma). Additional age populations correspond with Eocene-Oligocene Periadriatic magmatism (40-30 Ma) and pre-Alpine, Precambrian sources >750 Ma. The abundances of these age populations vary between samples. Sediment that entered the foredeep-axial channel belt from the west (freshwater Molasse) and southwest (Inntal fault zone) is characterized by statistically indistinguishable, well-distributed detrital zircon ages. Sandstone from a shallow marine unit that was deposited proximal to the northern basin margin consists of >75% Variscan (350-300 Ma) zircon, which is believed to have originated from the Bohemian Massif to the north. Mixing calculations based on the Kolmogorov-Smirnoff statistic suggest that the Alpine fold-thrust belt was an important source of detritus to the deepwater Molasse basin. We document east-to-west provenance dilution within the axial channel belt via one or more southern tributaries. Our results have important implications for sediment dispersal patterns within continental-scale orogens, including the relative role of longitudinal versus transverse sediment delivery in peripheral foreland basins.

Trophic interactions, ecosystem structure and function in the southern Yellow Sea

NASA Astrophysics Data System (ADS)

Lin, Qun; Jin, Xianshi; Zhang, Bo

2013-01-01

The southern Yellow Sea is an important fishing ground, providing abundant fishery resources. However, overfishing and climate change have caused a decline in the resource and damaged the ecosystem. We developed an ecosystem model to analyze the trophic interactions and ecosystem structure and function to guide sustainable development of the ecosystem. A trophic mass-balance model of the southern Yellow Sea during 2000-2001 was constructed using Ecopath with Ecosim software. We defined 22 important functional groups and studied their diet composition. The trophic levels of fish, shrimp, crabs, and cephalopods were between 2.78 and 4.39, and the mean trophic level of the fisheries was 3.24. The trophic flows within the food web occurred primarily in the lower trophic levels. The mean trophic transfer efficiency was 8.1%, of which 7.1% was from primary producers and 9.3% was from detritus within the ecosystem. The transfer efficiency between trophic levels II to III to IV to V to >V was 5.0%, 5.7%, 18.5%, and 19.7%-20.4%, respectively. Of the total flow, phytoplankton contributed 61% and detritus contributed 39%. Fishing is defined as a top predator within the ecosystem, and has a negative impact on most commercial species. Moreover, the ecosystem had a high gross efficiency of the fishery and a high value of primary production required to sustain the fishery. Together, our data suggest there is high fishing pressure in the southern Yellow Sea. Based on analysis of Odum's ecological parameters, this ecosystem was at an immature stage. Our results provide some insights into the structure and development of this ecosystem.

On the spatial-temporal variations in the chlorophyll- a concentration on the Peter the Great Bay shelf during the winter-spring phytoplankton bloom according to satellite and subsatellite data

NASA Astrophysics Data System (ADS)

Shtraikhert, E. A.; Zakharkov, S. P.

2016-12-01

Chlorophyll- a concentration ( C chl) variations in the cross section within and outside the Peter the Great Bay shelf during different stages of the winter-spring phytoplankton bloom in 2003-2005 has been considered based on a ship (obtained during the R/V Akademik M.A. Lavrent'ev voyage of February 26 to March 9, 2003) and MODIS-Aqua spectroradiometer and the SeaWiFS color-scanner satellite data. A comparison of the C chl variability obtained from the ship and satellite data indicates that these data are inconsistent. According to satellite data obtained at the MUMM atmospheric correction, the C chl variability is distorted less than the NIR-correction data. Studying the variations in the coefficients of light absorption by the detritus and yellow substance ( a dg) and light backscattering by suspended particles ( b bp), C chl, chlorophyll- a fluorescence ( F chl) according to the satellite data allow us to state that the variations in the discrepancy between the satellite and ship C chl values are mainly caused by the variations in the content of the detritus and yellow substance in water. Based on the satellite data, it has been revealed that the a dg values increase with increasing wind mixing after the phytoplankton bloom (about 2-5 km areas where the a dg, C chl, F chl, and bbp values abruptly increased in 2005, apparently due to eddy formation). It has been indicated that the F chl characteristic, which is close to C chl, increases when the favorable conditions for the phytoplankton bloom deteriorate. Therefore, this characteristic cannot be used to identify C chl under the indicated conditions.

Evidence of early Archean crust in northwest Gondwana, from U-Pb and Hf isotope analysis of detrital zircon, in Ediacaran surpacrustal rocks of northern Spain

NASA Astrophysics Data System (ADS)

Naidoo, Thanusha; Zimmermann, Udo; Vervoort, Jeff; Tait, Jenny

2018-03-01

The Mora Formation (Narcea Group) is one of the oldest Precambrian supracrustal successions in northern Spain. Here, we use U-Pb and in situ Hf isotope analysis on detrital zircon to determine its age and provenance. The youngest U-Pb dates constrain the maximum depositional age of the Mora Formation at 565 ± 11 Ma. Results indicate: (1) a dominant Ediacaran zircon population (33%; 565-633 Ma, Cadomian) within a spectrum of Neoproterozoic ages (40%; 636-996 Ma); and (2) smaller Mesoproterozoic (5%; 1004-1240 Ma), Palaeoproterozoic (11%; 1890-2476 Ma) and Archean (11%; 2519-3550 Ma) populations. Results here do not point to one specific cratonic source area; instead, detritus may have been derived from the West African craton and Amazonia, or even the concealed Iberian basement. The lack of 1.3-1.8 Ga grains suggests exclusion of the Sahara Craton as a major source, but this is not certain. This mixed composition favours a complex source history with reworking of detritus across terrane/craton boundaries. Hafnium isotope compositions indicate a range of crustal and juvenile sources, with initial ɛHf values between -15.8 and 11.1, and Hf model ages from 0.8 to 3.7 Ga. For Neoproterozoic zircons (80%), juvenile components (ɛHf(i) +10) may be related to Rodinia fragmentation and the onset of an active margin setting leading to the Cadomian orogeny. Palaeoproterozoic to Paleoarchean grains (20%) all have negative ɛHf values and Meso- to Eoarchean Hf model ages. This indicates an early (Archean) sialic crustal component for northwestern Gondwana.

Rust Contamination from Water Leaks in the Cosmic Dust Lab and Lunar and Meteorite Thin Sections Labs at Johnson Space Center

NASA Technical Reports Server (NTRS)

Kent, J. J.; Berger, E. L.; Fries, M. D.; Bastien, R.; McCubbin, F. M.; Pace, L.; Righter, K.; Sutter, B.; Zeigler, R. A.; Zolensky, M.

2017-01-01

On the early morning of September 15th, 2016, on the first floor of Building 31 at NASA-Johnson Space Center, the hose from a water chiller ruptured and began spraying water onto the floor. The water had been circulating though old metal pipes, and the leaked water contained rust-colored particulates. The water flooded much of the western wing of the building's ground floor before the leak was stopped, and it left behind a residue of rust across the floor, most notably in the Apollo and Meteorite Thin Section Labs and Sample Preparation Lab. No samples were damaged in the event, and the affected facilities are in the process of remediation. At the beginning of 2016, a separate leak occurred in the Cosmic Dust Lab, located in the same building. In that lab, a water leak occurred at the bottom of the sink used to clean the lab's tools and containers with ultra-pure water. Over years of use, the ultra-pure water eroded the metal sink piping and leaked water onto the inside of the lab's flow bench. This water also left behind a film of rusty material. The material was cleaned up and the metal piping was replaced with PVC pipe and sealed with Teflon plumber's tape. Samples of the rust detritus were collected from both incidents. These samples were imaged and analyzed to determine their chemical and mineralogical compositions. The purpose of these analyses is to document the nature of the detritus for future reference in the unlikely event that these materials occur as contaminants in the Cosmic Dust samples or Apollo or Meteorite thin sections.

Density of Key-Species Determines Efficiency of Macroalgae Detritus Uptake by Intertidal Benthic Communities

PubMed Central

Karlson, Agnes M. L.; Niemand, Clarisse; Savage, Candida; Pilditch, Conrad A

2016-01-01

Accumulating evidence shows that increased biodiversity has a positive effect on ecosystem functioning, but the mechanisms that underpin this positive relationship are contentious. Complete extinctions of regional species pools are comparatively rare whereas compositional changes and reductions in abundance and biomass are common, although seldom the focus of biodiversity-ecosystem functioning studies. We use natural, small-scale patchiness in the density of two species of large bivalves with contrasting feeding modes (the suspension-feeding Austrovenus stutchburyi and deposit-feeding Macomona liliana) to examine their influence on the uptake of nitrogen from macroalgae detritus (i.e. measure of ecosystem function and food web efficiency) by other infauna in a 10-d laboratory isotope-tracer experiment. We predicted that densities of these key bivalve species and functional group diversity (calculated as Shannons H, a density-independent measure of community composition) of the intact infaunal community will be critical factors explaining variance in macroalgal per capita uptake rates by the community members and hence determine total uptake by the community. Results show that only two species, M. liliana and a large orbiniid polychaete (Scoloplos cylindrifer) dominated macroalgal nitrogen taken up by the whole community due to their large biomass. However, their densities were mostly not important or negatively influenced per capita uptake by other species. Instead, the density of a head-down deposit-feeder (the capitellid Heteromastus filiformis), scavengers (mainly nemertines and nereids) and species and functional group diversity, best explained per capita uptake rates in community members. Our results demonstrate the importance of species identity, density and large body size for ecosystem functioning and highlight the complex interactions underlying loss of ecological functions with declining biodiversity and compositional changes. PMID:27414032

Tracing carbon flow through coral reef food webs using a compound-specific stable isotope approach.

PubMed

McMahon, Kelton W; Thorrold, Simon R; Houghton, Leah A; Berumen, Michael L

2016-03-01

Coral reefs support spectacularly productive and diverse communities in tropical and sub-tropical waters throughout the world's oceans. Debate continues, however, on the degree to which reef biomass is supported by new water column production, benthic primary production, and recycled detrital carbon (C). We coupled compound-specific stable C isotope ratio (δ(13)C) analyses with Bayesian mixing models to quantify C flow from primary producers to coral reef fishes across multiple feeding guilds and trophic positions in the Red Sea. Analyses of reef fishes with putative diets composed primarily of zooplankton (Amblyglyphidodon indicus), benthic macroalgae (Stegastes nigricans), reef-associated detritus (Ctenochaetus striatus), and coral tissue (Chaetodon trifascialis) confirmed that δ(13)C values of essential amino acids from all baseline C sources were both isotopically diagnostic and accurately recorded in consumer tissues. While all four source end-members contributed to the production of coral reef fishes in our study, a single-source end-member often dominated dietary C assimilation of a given species, even for highly mobile, generalist top predators. Microbially reworked detritus was an important secondary C source for most species. Seascape configuration played an important role in structuring resource utilization patterns. For instance, Lutjanus ehrenbergii showed a significant shift from a benthic macroalgal food web on shelf reefs (71 ± 13 % of dietary C) to a phytoplankton-based food web (72 ± 11 %) on oceanic reefs. Our work provides insights into the roles that diverse C sources play in the structure and function of coral reef ecosystems and illustrates a powerful fingerprinting method to develop and test nutritional frameworks for understanding resource utilization.

Using hydrofluoric acid for morphological investigations of Zoanthids (Cnidaria: Anthozoa): a critical assessment of methodology and necessity.

PubMed

Reimer, James Davis; Nakachi, Shu; Hirose, Mamiko; Hirose, Euichi; Hashiguchi, Shinji

2010-10-01

Zoanthids comprise an order of benthic, generally colonial cnidarians, which can usually be distinguished from other hexacorallians by embedded sand and detritus in their mesoglea to help strengthen their structure. These animals are becoming increasingly important research subjects in biochemistry and other research fields. Their inclusion of both calcium and silica results in the need for both decalcification and desilification for internal morphological examinations. Since the methodology of hydrofluoric acid (HF) desilification has rarely been documented in zoanthids, histological surveys for zoanthid taxonomy have often been abandoned and their taxonomy is often problematic. Recent investigations utilizing molecular methods have brought a clearer understanding of zoanthid diversity, but standardization of HF treatments are still needed to provide a link between molecular and more traditional techniques, and to properly examine specimens for which molecular methods may not be an option (e.g., formalin-preserved specimens, etc.). Here, we use both "straight" HF and, for the first time with zoanthids, buffered HF (BHF) treatments at different treatment lengths (1-48 h) on polyps from three different species of zoanthids for histological examination. Section conditions were judged based on the presence/absence of embedded detritus, drag marks, and tissue condition. Results show that the BHF treatment resulted in slightly better tissue conditions for all specimens, and suggest that desilification works well regardless of treatment time for species with smaller (polyp diameter <0.5 cm), less heavily encrusted polyps. Desilification of heavily encrusted Palythoa mutuki polyps were still problematic, with at least 24 h treatment needed. To aid future research, we provide guidelines for HF treatments of zoanthid specimens.

Leaf removal by sesarmid crabs in Bangrong mangrove forest, Phuket, Thailand; with emphasis on the feeding ecology of Neoepisesarma versicolor

NASA Astrophysics Data System (ADS)

Thongtham, Nalinee; Kristensen, Erik; Puangprasan, Som-Ying

2008-12-01

Field measurements on leaf removal by populations of sesarmid crabs at different locations in the Bangrong mangrove forest, Phuket, Thailand, indicated that crabs on average can remove 87% of the daily leaf litter fall by ingestion or burial. The removal rate is correlated positively with the number of crab burrows and negatively with tidal inundation time. The results from the field were supplemented with observations on the behavior of Neoepisesarma versicolor in laboratory microcosms and a mangrove mesocosm. N. versicolor feeds primarily at night and total time spent feeding was up to an order of magnitude higher in the artificial microcosms than under simulated in situ conditions in the mesocosm. Most of the time during both day and night was spent resting near the entrance or inside burrows. N. versicolor mainly feeds on mangrove leaves and scraps of food material from the sediment surface. This is supported by examinations of stomach content, which showed that 62% is composed of higher plant material and 38% of detritus and mineral particles from the sediment. The nutritive value of leaves and detritus is insufficient to maintain crab growth. Sesarmid crabs may instead obtain the needed nutrients by occasional consumption of nitrogen-rich animal tissues, such as carcasses of fish and crustaceans, as indicated by the presence of animal remains in the stomach and the willingness of crabs to consume fish meat. Laboratory experiments on leaf consumption and leaf preferences of N. versicolor indicate that they preferentially feed on brown leaves, if available, followed by green and yellow leaves. If all species of sesarmid crabs in the Bangrong mangrove forest consume leaves at the same rate as N. versicolor, they could potentially ingest 52% of the total litter fall.

Origin of northern Gondwana Cambrian sandstone revealed by detrital zircon SHRIMP dating

USGS Publications Warehouse

Avigad, D.; Kolodner, K.; McWilliams, M.; Persing, H.; Weissbrod, T.

2003-01-01

Voluminous Paleozoic sandstone sequences were deposited in northern Africa and Arabia following an extended Neoproterozoic orogenic cycle that culminated in the assembly of Gondwana. We measured sensitive high-resolution ion microprobe (SHRIMP) U-Pb ages of detrital zircons separated from several Cambrian units in the Elat area of southern Israel in order to unravel their provenance. This sandstone forms the base of the widespread siliciclastic section now exposed on the periphery of the Arabian-Nubian shield in northeastern Africa and Arabia. Most of the detrital zircons we analyzed yielded Neoproterozoic concordant ages with a marked concentration at 0.55–0.65 Ga. The most likely provenance of the Neoproterozoic detritus is the Arabian-Nubian shield; 0.55–0.65 Ga was a time of posttectonic igneous activity, rift-related volcanism, and strike-slip faulting there. Of the zircons, 30% yielded pre-Neoproterozoic ages grouped at 0.9–1.1 Ga (Kibaran), 1.65–1.85 Ga, and 2.45–2.7 Ga. The majority of the pre-Neoproterozoic zircons underwent Pb loss, possibly as a consequence of the Pan-African orogeny resetting their provenance. Rocks of the Saharan metacraton and the southern Afif terrane in Saudi Arabia (∼1000 km south of Elat) are plausible sources of these zircons. Kibaran basement rocks are currently exposed more than 3000 km south of Elat (flanking the Mozambique belt), but the shape of the detrital zircons of that age and the presence of feldspar in the host sandstone are not fully consistent with such a long-distance transport. Reworking of Neoproteorozoic glacial detritus may explain the presence of Kibaran detrital zircons in the Cambrian of Elat, but the possibility that the Arabian-Nubian shield contains Kibaran rocks (hitherto not recognized) should also be explored.

The Chicxulub impact at the K-Pg boundary - search for traces of the projectile

NASA Astrophysics Data System (ADS)

Deutsch, A.

2012-04-01

One of the most interesting problems in the context of the end-Cretaceous Chicxulub impact is the question after the whererabouts of the main mass of the projectile. The nature of this >10 km-sized Chicxulub projectile was constrained by an anomaly in the chromium isotope 54 in the K-Pg deposit at Stevens Klint, Denmark, to a carbonaceous chondrite of type CM2 [1]. About 1.5 % of the estimated mass of the projectile has been detected world-wide in the K-Pg boundary layer; mainly in the form of platinum group elements (PGE) as well as other siderophile elements (Ni, Co ... ). A contamination by or even a major contribution of other "projectile" elements to the K-Pg event bed was rarely proposed. The few examples in the literature (cf. compilation in [2, 3]) used rare earth elements (REE) distribution patterns that are slightly inconsistent with REE patterns typical for the upper continental crust (UCC). Ejecta consisting of UCC target rocks is expected to form the overwhelming mass of the ejecta. In most K-Pg layers, however, the ejecta is diluted or even totally masked by a component of more local origin and with features of high-energy deposition mechanisms. Numerical models [4] indicate a deposition of >500km3 projectile material, corresponding to >2 x 10exp9 tons of mainly silica, iron, and magnesium in the K-Pg event bed. Detecting the "meteoritic" origin of these major elements, however, in a matrix of siliceous detritus, is practically impossible. Recent LA-ICP-MS analyses show that siliceous impact spherules - hydrated glass or altered to chlorite - in the Chicxulub event bed at various locations (e.g., Shell Creek, La Lajilla, La Popa) have REE patterns that are flat and un-fractionated, corresponding quite well to a typical CI-pattern. The REE abundances are chondritic to sub-chondritic. Mixing calculations indicate that the maximum REE contribution of UCC material to the REE budget of these spherules is on the order of 2 %, but usually much less. These flat REE patterns cannot originate from any known alteration process; they truly reflect a "meteoritic" component in the spherules. Accepting this fact, a certain amount of the siliceous host material (i.e., the spherules) must consist also of projectile material. Depending on the sampling site, the spherules with the flat REE distribution patterns amount to between 10 and ~70 vol% of the Chicxulub event bed. The widespread occurrence of this projectile matter in the K-Pg event bed reconciles observations with impact models [4]. Ref. [1] Trinquier A. et al. (2006) EPSL 241, 780-788. [2] Smit J. (1999) Ann. Rev. Earth Planet. Sci. 27, 75-113. [3] Schulte P. et al. (2010) Science 327, 1214-1218. [4] Artemieva N. and Morgan J. (2009) Icarus 201, 768-780.

Development of a selective and sensitive flotation method for determination of trace amounts of cobalt, nickel, copper and iron in environmental samples.

PubMed

Karimi, H; Ghaedi, M; Shokrollahi, A; Rajabi, H R; Soylak, M; Karami, B

2008-02-28

A simple, selective and rapid flotation method for the separation-preconcentration of trace amounts of cobalt, nickel, iron and copper ions using phenyl 2-pyridyl ketone oxime (PPKO) has been developed prior to their flame atomic absorption spectrometric determinations. The influence of pH, amount of PPKO as collector, type and amount of eluting agent, type and amount of surfactant as floating agent and ionic strength was evaluated on the recoveries of analytes. The influences of the concomitant ions on the recoveries of the analyte ions were also examined. The enrichment factor was 93. The detection limits based on 3 sigma for Cu, Ni, Co and Fe were 0.7, 0.7, 0.8, and 0.7 ng mL(-1), respectively. The method has been successfully applied for determination of trace amounts of ions in various real samples.

Effect of percentage baghouse fines on the amount and type of anti-stripping agent required to control moisture sensitivity : final report.

DOT National Transportation Integrated Search

2003-06-30

This study investigated the effect of moisture and amount of baghouse fines on AC mixes. Two : types of baghouse fines, each with a different gradation, were used in varying concentrations to prepare : laboratory samples. The binder used was PG64-22 ...

14 CFR 232.2 - Answers to applications for review.

Code of Federal Regulations, 2010 CFR

2010-01-01

... expected actual density of mail which will be tendered to the carrier if the order in question is upheld... order in question is upheld; (5) The volume (including density of mail, amount and types of containers... (including density of mail, amount and types of containers) of mail historically carried on the flight or...

[Microbial community and its activities in canopy- and understory humus of two montane forest types in Ailao Mountains, Northwest China].

PubMed

Liu, Yong-jie; Liu, Wen-yao; Chen, Lin; Zhang, Han-bo; Wang, Gao-sheng

2010-09-01

Mid-montane moist evergreen broadleaved forest (MMF) and top-montane dwarf mossy forest (DMF) are the two major natural forest types in subtropical mountainous area of Ailao Mountains, Northwest China. In this paper, a comparative study was made on the microbial composition, quantity, biochemical activity, metabolic activity, and their seasonal dynamics in the canopy- and understory humus of the two forest types. The composition, quantity, and metabolic activity of the microbes in the canopy humus of dominant tree species in MMF and DMF were also analyzed. In the canopy humus of the two forest types, the amounts of fungi and actinomycetes, microbial biomass C and N, and intensities of nitrogen fixation and cellulose decomposition were significantly higher than those in understory humus. Meanwhile, the amount of cellulose-decomposing microbes (ACDM), cellulose decomposition intensity, microbial biomass C and N, and metabolic activity in the canopy humus of MMF were significantly higher than those of DMF. The amounts of bacteria, fungi, and aerobic nitrogen-fixing bacteria (ANFB) and the metabolic activity in the canopy humus of MMF and DMF were significantly higher in wet season than in dry season, while a contradictory trend was observed on the amount of actinomycetes. No significant difference was observed on the amount of ACDM between wet season and dry season. For the two forest types, the amounts of microbes and their biochemical activities in canopy humus had a larger seasonal variation range than those in understory humus. There was a significant difference in the amounts of the microbes in canopy humus among the dominant tree species in MMF and DMF, especially in wet season. The microbes in canopy humus played important roles in maintaining the biodiversity of epiphytes in the canopy, and in supplying the needed nutrients for the vigorous growth of the epiphytes.

Effect of 23-day muscle disuse on sarcoplasmic reticulum Ca2+ properties and contractility in human type I and type II skeletal muscle fibers.

PubMed

Lamboley, C R; Wyckelsma, V L; Perry, B D; McKenna, M J; Lamb, G D

2016-08-01

Inactivity negatively impacts on skeletal muscle function mainly through muscle atrophy. However, recent evidence suggests that the quality of individual muscle fibers is also altered. This study examined the effects of 23 days of unilateral lower limb suspension (ULLS) on specific force and sarcoplasmic reticulum (SR) Ca(2+) content in individual skinned muscle fibers. Muscle biopsies of the vastus lateralis were taken from six young healthy adults prior to and following ULLS. After disuse, the endogenous SR Ca(2+) content was ∼8% lower in type I fibers and maximal SR Ca(2+) capacity was lower in both type I and type II fibers (-11 and -5%, respectively). The specific force, measured in single skinned fibers from three subjects, decreased significantly after ULLS in type II fibers (-23%) but not in type I fibers (-9%). Western blot analyses showed no significant change in the amounts of myosin heavy chain (MHC) I and MHC IIa following the disuse, whereas the amounts of sarco(endo)plasmic reticulum Ca(2+)-ATPase 1 (SERCA1) and calsequestrin increased by ∼120 and ∼20%, respectively, and the amount of troponin I decreased by ∼21%. These findings suggest that the decline in force and power occurring with muscle disuse is likely to be exacerbated in part by reductions in maximum specific force in type II fibers, and in the amount of releasable SR Ca(2+) in both fiber types, the latter not being attributable to a reduced calsequestrin level. Furthermore, the ∼3-wk disuse in human elicits change in SR properties, in particular a more than twofold upregulation in SERCA1 density, before any fiber-type shift. Copyright © 2016 the American Physiological Society.

Ecoregion and land-use influence invertebrate and detritus transport from headwater streams

USGS Publications Warehouse

Binckley, Christopher A.; Wipfli, Mark S.; Medhurst, R. Bruce; Polivka, Karl; Hessburg, Paul F.; Salter, R. Brion; Kill, Joshua Y.

2010-01-01

4. Understanding the quantity and variation of headwater subsidies across climate and disturbance gradients is needed to appreciate the significance of ecological linkages between headwaters and associated downstream habitats. This will enable the accurate assessment of resource management impacts on stream ecosystems. Predicting the consequences of natural and anthropogenic disturbances on headwater stream transport rates will require knowledge of how both local and regional factors influence these potential subsidies. Our results suggest that resources transported from headwater streams reflect both the meso-scale land-use surrounding these areas and the constraints imposed by the ecoregion in which they are embedded.

Snail shells as larval habitat of Limatus durhamii (Diptera: Culicidae) in the Yungas of Argentina.

PubMed

Mangudo, Carolina; Campos, Raúl E; Rossi, Gustavo C; Gleiser, Raquel M

2017-03-01

The shells of dead snails collect water from rainfalls producing aquatic microenvironments called gastrotelmata. These habitats are small and hold simple detritus based on animal communities, being rotifers and culicids the most studied. Although a high diversity of aquatic microhabitats has been reported as larval habitats of mosquitoes in Argentina, the shell of snails has not been investigated yet. We report the shells of three species of native Megalobulimus genus as larval habitats of a neotropical mosquito and suspected vector of bunyaviruses, Limatus durhamii, and describe these microhabitats in the Yungas forest of Argentina. Copyright © 2016 Elsevier B.V. All rights reserved.

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

Herfort, Lydie; Peterson, Tawnya D.; McCue, Lee Ann

The Columbia River estuary is traditionally considered a detritus-based ecosystem fueled in summer by organic matter (OM) from expired freshwater diatoms. Since Estuarine Turbidity Maxima (ETM) are sites of accumulation and transformation of this phytoplankton-derived OM, to further characterize the ETM protist assemblage, we collected in August 2007 bottom waters throughout an ETM event, as well as surface water during the peak of bottom turbidity, and performed biogeochemical, microscopic and molecular (18S rRNA gene clone libraries) analyses. These data confirmed that the majority of the particulate OM in ETMs is derived from chlorophyll a-poor particulate organic carbon tagged by DNAmore » too damaged to be detected by molecular analysis.« less

Retro reproduction: an old imaging technology rewrites the rules of modern embryology.

PubMed

Fischer, Shannon

2015-01-01

On a video screen, against a black backdrop, 15 spherical blue-green cells vibrate with a quiet energy. Slowly at first, then faster, they begin to roil and roll. Within the confines of their round membrane cases, they divide, becoming two, three, four cells, then those, in turn, divide to become eight. One splits into two, then pauses, struggling to catch up and spinning off pieces of cellular detritus as it does. Near the top, another, by now many cells rich, hollows out and expands, contracts, expands, contracts. It falls in upon itself and then hatches, pouring out from its shell and ballooning to the side.

Substratum location and zoospore behaviour in the fouling alga Enteromorpha.

PubMed

Callow, M E; Callow, J A

2000-01-01

The green alga Enteromorpha is the most important macroalga that fouls ships, submarines and underwater structures. Major factors in its success in colonising new substrata are the production of enormous numbers of swimming spores and their ability to locate surfaces on which to settle. Factors facilitating the settlement and adhesion of asexual zoospores are examined in this article. Settlement and adhesion may be regulated by topographical, biological, chemical and physico-chemical cues, all of which are modified by the presence of microbial biofilm. The level of gregarious zoospore settlement is related to spore density and may be mediated by a number of external cues including fatty acids and 'detritus'.

Characterization of food waste generators: a Hawaii case study.

PubMed

Okazaki, W K; Turn, S Q; Flachsbart, P G

2008-12-01

Information on food waste disposal and on recycling methods and recycled amounts is reported. Data were obtained from a mail and phone survey of all licensed food establishments in Hawaii conducted in 2004 and 2005. Of 8253 licensed food establishments, 5033 completed surveys. It was found that relationships exist between food establishment size (measured by the number of meals served per day or the number of employees) and the amount of food an establishment recycled; establishment type and recycling behavior; and establishment type and amount recycled. The amount of food waste recycled in the state of Hawaii was estimated to be 264,000 L/day and annual food waste generation was estimated to be 336,000 tonnes.

Exploring Type and Amount of Parent Talk during Individualized Family Service Plan Meetings

ERIC Educational Resources Information Center

Ridgley, Robyn; Snyder, Patricia; McWilliam, R. A.

2014-01-01

We discuss the utility of a coding system designed to evaluate the amount and type of parent talk during individualized family service plan (IFSP) meetings. The iterative processes used to develop the "Parent Communication Coding System" (PCCS) and its associated codes are described. In addition, we explored whether PCCS codes could be…

The age and degree of diachroneity of India-Asia collision determined from the sedimentary record: a comparison of new evidence from the east (Tibet) and west (Ladakh) of the orogen

NASA Astrophysics Data System (ADS)

Najman, Y.; Boudagher-Fadel, M.; Godin, L.; Parrish, R.; Bown, P.; Garzanti, E.; Horstwood, M.; Jenks, D.

2009-12-01

The age and degree of diachroneity of India-Asia collision is critical to construction of models of orogenesis and to understanding the causes of spatial variations in Himalayan evolution along strike. The age of collision is quoted between 65-34 Ma (Jaeger et al 1989; Aitchison et al 2007) and the degree of dichroneity is considered negligible (Searle et al 1997) to substantial (Rowley 1998). We studied the youngest Tethyan succession in the east (Tingri, Tibet) and west (Ladakh, India) of the orogen and used two approaches to date collision: 1) timing of closure of Tethys, by dating the youngest marine strata and 2) first evidence of Asian detritus deposited on the Indian plate, using U-Pb ages of detrital zircon to assess provenance. Both these approaches provide a minimum age to collision. In Ladakh, Indian plate passive margin limestones of the Paleocene Dibling Fm are overlain by the youngest marine facies of the region, the marine Kong Fm and fluvio-deltaic Chulung La Fm (Garzanti et al 1987). The age of the Kong and Chulung La Formations is disputed, from P5/6 (Fuchs & Willems 1990) to P8 (Garzanti et al 1987) the discrepancy possibly the result of research at different locations. Provenance is considered to be either ophiolitic from the Indian plate (Fuchs & Willems 1990) or containing detritus from the Trans-Himalayan arc of the Asian plate (Garzanti et al 1987; Critelli & Garzanti 1994). Our samples from the Kong Fm contained planktic foraminifera indicating a Middle to Early P6 age (54-56 Ma) and larger benthic foraminifera indicating Middle SBZ8 age (53-54 Ma). U-Pb dating of detrital zircons allows discrimination between Asian provenance (dominated by Mesozoic grains from the Trans-Himalayan arc) and Indian provenance (characterized by Precambrian grains and an absence of Mesozoic grains). Our data from the Kong and Chulung La Fms shows a primary provenance from the Asian plate. Thus collision is constrained by arrival of Asian detritus on the Indian plate by 54 Ma. In Tingri, Tibet, Indian plate passive margin limestones of the Zephure Shan Fm extend to the early Eocene, overlain by marine facies of the Pengqu Fm. The youngest marine facies have been dated at 34 Ma (Wang et al. 2002), but this age is disputed by other workers who assign an age of 50 Ma (Zhu et al. 2005). Our new biostratigraphic data from the Pengqu Fm show that calcareous nannofossil species are compatible with an age corresponding to Zones NP11-12 (50.6-53.5 Ma). The dominant population of detrital zircons have Cretaceous-Paleocene ages, derived from the Asian plate, thus indicating that contact between India and Asia had occurred by this time. We therefore conclude that India-Asia collision occurred by 54 Ma in the west, with only extremely limited, if any diachroneity eastward.

Mesozoic Continental Sediment-dispersal Systems of Mexico Linked to Development of the Gulf of Mexico

NASA Astrophysics Data System (ADS)

Lawton, T. F.; Molina-Garza, R. S.; Barboza-Gudiño, R.; Rogers, R. D.

2013-05-01

Major sediment dispersal systems on western Pangea evolved in concert with thermal uplift, rift and drift phases of the Gulf of Mexico Basin, and were influenced by development of a continental arc on Pangea's western margin. Existing literature and preliminary data from fieldwork, sandstone petrology and detrital zircon analysis reveal how major drainages in Mexico changed from Late Triassic through Late Jurassic time and offer predictions for the ultimate destinations of sand-rich detritus along the Gulf and paleo-Pacific margins. Late Triassic rivers drained away from and across the present site of the Gulf of Mexico, which was then the location of a major thermal dome, the Texas uplift of recent literature. These high-discharge rivers with relatively mature sediment composition fed a large-volume submarine fan system on the paleo-Pacific continental margin of Mexico. Predictably, detrital zircon age populations are diverse and record sources as far away as the Amazonian craton. This enormous fluvial system was cut off abruptly near the Triassic-Jurassic boundary by extensive reorganization of continental drainages. Early and Middle Jurassic drainage systems had local headwaters and deposited sediment in extensional basins associated with arc magmatism. Redbeds accumulated across northern and eastern Mexico and Chiapas in long, narrow basins whose locations and dimensions are recorded primarily by inverted antiformal massifs. The Jurassic continental successions overlie Upper Triassic strata and local subvolcanic plutons; they contain interbedded volcanic rocks and thus have been interpreted as part of the Nazas continental-margin arc. The detritus of these fluvial systems is volcanic-lithic; syndepositional grain ages are common in the detrital zircon populations, which are mixed with Oaxaquia-derived Permo-Triassic and Grenville age populations. By this time, interior Pangea no longer supplied sediment to the paleo-Pacific margin, possibly because the continental-margin arc blocked westward drainage and detritus was captured in rift basins. Latest Middle Jurassic fluvial systems formed as the Yucatan block rotated counterclockwise and the Gulf of Mexico began to open. Sediment dispersal, partly equivalent to salt deposition in the Gulf, was largely southward in southern Oaxaquia, but large-volume braided river systems on the Maya (Yucatan) block, represented by the Todos Santos Formation in Chiapas, evidently flowed northward along graben axes toward the western part of the Gulf of Mexico Basin. River systems of nuclear Mexico, or Oaxaquia, occupied a broad sedimentary basin west and south of a divide formed adjacent to the translating Maya block. Despite their big-river characteristics, these deposits contain mainly Grenville and Permo-Triassic grains derived from Oaxaquia basement and subordinate Early and Middle Jurassic grains derived from volcanic rocks and plutons of the arc. Early Late Jurassic (Oxfordian) marine flooding of the entire Gulf rim and nuclear Mexico, evidently resulting in part from marginal subsidence adjoining newly-formed oceanic crust, terminated fluvial deposition adjacent to the young Gulf of Mexico.

Hydrology and ecology of the Apalachicola River, Florida : a summary of the river quality assessment

USGS Publications Warehouse

Elder, John F.; Flagg, Sherron D.; Mattraw, Harold C.

1988-01-01

During 1979-81, the U.S. Geological Survey conducted a large-scale study of the Apalachicola River in northwest Florida, the largest and one of the most economically important rivers in the State. Termed the Apalachicola River Quality Assessment, the study emphasized interrelations among hydrodynamics, the flood-plain forest, and the nutrient-detritus flow through the river system to the estuary. This report summarizes major findings of the study. Data on accumulation of toxic substances in sediments and benthic organisms in the river were also collected. Because of the multiple uses of the Apalachicola River system, there are many difficult management decisions. The river is a waterway for shipping; hence there is an economic incentive for modification to facilitate movement of barge traffic. Such modifications include the proposed construction of dams, levees, bend easings, and training dikes; ditching and draining in the flood plain; and dredging and snagging in the river channel. The river is also recognized as an important supplier of detritus, nutrients, and freshwater to the Apalachicola Bay, which maintains an economically important shellfish industry. The importance of this input to the bay creates an incentive to keep the river basin in a natural state. Other values, such as timber harvesting, recreation, sport hunting, nature appreciation, and wildlife habitat, add even more to the difficulty of selecting management strategies. Water and nutrient budgets based on data collected during the river assessment study indicate the relative importance of various inputs and outflows in the system. Waterflow is controlled primarily by rainfall in upstream watersheds and is not greatly affected by local precipitation, ground-water exchanges, or evapotranspiration in the basin. On an annual basis, the total nutrient inflow to the system is nearly equal in quantity to total outflow, but there is a difference between inflow and outflow in the chemical and physical forms in which the nutrients are carried. The flood plain tends to be a net importer of soluble inorganic nutrients and a net exporter of particulate organic material. Analysis of long-term records shows that dam construction in the upstream watersheds and at the Apalachicola headwaters has had little effect on the total annual waterflow but has probably suppressed low-flow extremes. Other effects include riverbed degradation and channelization which have to do with alteration of the habitat for aquatic biota and changes in flood-plain vegetation. Whatever management decisions are made should take into account the impact on the natural flooding cycle. Flooding is crucial to the present flood-plain plant community and to the production, decomposition, and transport of organic material from that community. Permanent, substantial changes in the natural flooding cycle would be likely to induce concomitant changes in the flood-plain environment and in the nutrient and detritus yield to the estuary.

Photodegradation of crude oil: liquid injection and headspace solid-phase microextraction for crude oil analysis by gas chromatography with mass spectrometer detector.

PubMed

D'Auria, Maurizio; Racioppi, Rocco; Velluzzi, Vincenzina

2008-04-01

The fate of crude oil under irradiation is studied. After UV irradiation, the fraction present in the highest percentage shifts from the C8-C9 fractions to C13, using gas chromatography-mass spectrometry (GC-MS) analysis in solution. An increase of the relative amount of the C13-C25 fraction is observed, while a decrease in the relative amount of the C7-C12 fractions is present. In headspace solid-phase microextraction (HS-SPME) analysis, the C8-C10 fractions represent 53% of all the compounds detected. A decrease in the relative amount of the C8-C10 fractions is observed, while C11-C15 fractions increase. The irradiation of crude oil with a solar simulator gives a mixture the analysis of which using GC-MS in solution furnishes the same type of results: the relative amounts of linear alkanes and aromatic compounds increase, while a sharp decrease in the relative amounts of branched and cyclic alkanes is observed. In the SPME analysis, a decreased relative amount of branched alkanes and alkenes, and an increase in the relative amounts of cyclic alkanes and aromatic compounds are observed. Analysis of the distribution of the compounds in all the types of compound shows that a dynamic equilibrium between different compounds and different types of compounds is present. To confirm the presence of a dynamic equilibrium, the irradiation of methylcyclohexane in the presence of 2-methylnaphthalene shows the presence in the reaction mixture of a small amount of tetradecane.

Fodder Resource Uses and Assessment of Nitrogen Flows on Livestock Farming with Crop Production

NASA Astrophysics Data System (ADS)

Shirahase, Kyoko; Kobayashi, Hisashi

With understanding the livestock farming on cattle breeding practiced increasing of self-production of fodders by the farmland's operation as “Livestock Farming with crop production”, we investigated the utilizations of actual fodder resources and farmland for two selected different types of livestock farming systems: “Multiple Type” which practices cattle raising with fodder cultivation, and “Grazing Type” which practices grazing and fodder cultivation with similar feed self-sufficiency rates. We also prepared and compared material and nitrogen flow of both livestock farming systems. The amount of nitrogen flow is clearly different between the two types though feed self-sufficiency rates are at similar level. Moreover, we defined “Internal Nitrogen Rate (INR)” which indicates the rate of internal nitrogen use to total nitrogen use in cattle raising, “Internal Nitrogen Circulation Rate (NCR)” which indicates the ratio of nitrogen amount in internal circulation to the nitrogen amount introduced from outside, and Nitrogen Outflow Potential (Op), which is the balance of nitrogen amount between input to farmlands and uptake by plants, and analyzed the balance of the amounts of nitrogen flows in both livestock farming type. It is suggested that “Grazing type”, which had the values of relatively high NCR and absolutely low Op, was the livestock farming type with high rates of nitrogen procurement from the interregional farming and low risk of nitrogen outflow.

Glacial flour in lacustrine sediments: Records of alpine glaciation in the western U.S.A. during the last glacial interval

NASA Astrophysics Data System (ADS)

Rosenbaum, J. G.; Reynolds, R. L.

2010-12-01

Sediments in Bear Lake (UT/ID) and Upper Klamath Lake (OR) contain glacial flour derived during the last glacial interval from the Uinta Mountains and the southern Cascade Range, respectively. Magnetic properties provide measures of glacial-flour content and, in concert with elemental and grain-size analyses, yield high-resolution records of glacial growth and decay. Creation and preservation of such records requires that (1) properties of glacial flour contrast with those of other sedimentary components and (2) magnetic minerals are neither formed nor destroyed after deposition. In the Bear Lake watershed, glaciers were confined to a small headwater area of the Bear River underlain by hematite-rich rocks of the Uinta Mountain Group (UMG), which are not exposed elsewhere in the catchment. Because UMG detritus is abundant only in Bear Lake sediments of glacial age, hard isothermal remanent magnetization (a measure of hematite content) provides a proxy for glacial flour. In contrast, the entire Upper Klamath Lake catchment, which lies to the east of the Cascade Range in southern Oregon, is underlain largely by basalt and basaltic andesite. Magnetic properties of fresh titanomagnetite-rich rock flour from glaciers on a composite volcano contrast sharply with those of detritus from unglaciated areas in which weathering destroyed some of the titanomagnetite. Ideally, well-dated records of the flux of glacial flour can be compared to ages of glacial features (e.g., moraines). For Upper Klamath Lake, quantitative measures of rock-flour content (from magnetic properties) and excellent chronology allow accurate calculation of flux. However, ages of glacial features are lacking and mafic volcanic rocks, which weather rapidly in this environment, are not well suited for cosmogenic exposure dating. At Bear Lake, estimates of glacial-flour content are less quantitative and chronology within the glacial interval must be interpolated from radiocarbon ages above and below the glacial-age sediments, but cosmogenic dating (by Laabs et al.) of highly resistant quartzite boulders provide ages from terminal moraines in the Bear River drainage. Glacial flour appears abruptly at ~26 cal ka in Bear Lake, whereas it is present at the base of the Upper Klamath Lake core (~37 cal ka). Both glacial flour records (1) contain millennial-scale variations (uncertainties in chronology prevent precise correlation of these features), (2) attain maxima circa 19 cal ka, and (3) rapidly decline beginning prior to 18 cal ka. At Bear Lake the age of the decline in glacial flour coincides with cosmogenic exposure ages (18.1 - 18.7 ka) of terminal moraines in the upper Bear River valley. This concurrence supports the interpretation that the maximum amount and subsequent decrease in glacial flour are indicative of maximum glacial extent and glacial retreat, respectively, and more generally that increases and decreases in rock flour in these lake sediments represent waxing and waning of glaciers. Laabs, B,J.C., et al., 2007, Chronology of the last glacial maximum in the upper Bear River basin, Utah, Arctic and Alpine Research, v. 39, p. 537 - 548.

Quantification of the nitrogen cycle in a prairie stream

USGS Publications Warehouse

Dodds, Walter K.; Evans-White, Michelle A.; Gerlanc, Nicole M.; Gray, Lawrence; Gudder, Dolly A.; Kemp, Melody J.; Lopez, Amanda L.; Stagliano, David; Strauss, Eric A.; Tank, Jennifer L.; Whiles, Matt R.; Wollheim, Wilfred M.

2000-01-01

Nitrogen (N) was added for 35 days in the form of 15NH4Cl to Kings Creek on Konza Prairie, Kansas. Standing stocks of N in key compartments (that is, nutrients, detritus, organisms) were quantified, and the amount of labeled N entering the compartments was analyzed. These data were used to calculate turnover and flux rates of N cycling through the food web, as well as nutrient transformation rates. Inorganic N pools turned over much more rapidly in the water column of this stream than in pelagic systems where comparable measurements have been made. As with other systems, the mass of ammonium was low but it was the key compartment mediating nutrient flux through the ecosystem, whereas dissolved organic N, the primary component of N flux through the system, is not actively cycled. Nitrification was also a significant flux of N in the stream, with rates in the water column and surface of benthos accounting for approximately 10% of the total ammonium uptake. Primary consumers assimilated 67% of the inorganic N that entered benthic algae and microbes. Predators acquired 23% of the N that consumers obtained. Invertebrate collectors, omnivorous crayfish (Orconectes spp.), and invertebrate shredders dominated the N flux associated with primary consumers. Mass balance calculations indicated that at least 23% of the 309 mg of 15N added during the 35 days of release was retained within the 210-m stream reach during the release. Overall, the rates of turnover of N in organisms and organic substrata were significantly greater when C:N was low. This ratio may be a surrogate for biological activity with regard to N flux in streams.

Effects of diet and body size on phosphorus utilization of Liza haematocheila T. & S.

NASA Astrophysics Data System (ADS)

Kang, Bin; Xian, Weiwei; Wu, Yunfei

2008-05-01

A 21-d laboratory experiment was conducted to study, the phosphorus (P) utilization of two different diets by redlip mullet Liza haematocheila T. & S. Sand-filtered water in salinity 30 and temperature 25°C was used. Twenty-nine fish individuals were divided into three groups: 11 to group 1 (G1) fed on diet 1, 11 to group 2 (G2) fed on diet 2, and 7 to contrast group. Diet 1 was a commercial feed, more valuable in nutrition than diet 2 that similar to natural detritus. The results show the intake phosphorus (IP) of G1 was significantly higher than that of G2, and both increased linearly with body size at a certain amount of diet. The retention phosphorus (RP) in fish of G1 was lower than G2. The relationship between retention phosphorus and body size was positive and stronger in G2. Significant difference in faecal phosphorus (FP) was found between G1 and G2. Body size significantly impacted the excretion phosphorus (EP) in G1 but G2. The loss of intake phosphorus in G1 was 10.83-20.27 mg per g fish weight gain, higher than that in G2 for 6.63-9.56. Of the phosphorus, about 10% was allocated into growth, 50% in faeces, and the rest lost in excretion. The main part of phosphorus was lost in faeces but excretion. The phosphorus budget of the fish could be described as 100IP = 7.40RP + 47.39FP + 36.63EP (Diet 1) or 100IP = 11.93RP + 56.64FP + 21.76EP (Diet 2).

Occurrence of Priming in the Degradation of Lignocellulose in Marine Sediments.

PubMed

Gontikaki, Evangelia; Thornton, Barry; Cornulier, Thomas; Witte, Ursula

2015-01-01

More than 50% of terrestrially-derived organic carbon (terrOC) flux from the continents to the ocean is remineralised in the coastal zone despite its perceived high refractivity. The efficient degradation of terrOC in the marine environment could be fuelled by labile marine-derived material, a phenomenon known as "priming effect", but experimental data to confirm this mechanism are lacking. We tested this hypothesis by treating coastal sediments with 13C-lignocellulose, as a proxy for terrOC, with and without addition of unlabelled diatom detritus that served as the priming inducer. The occurrence of priming was assessed by the difference in lignocellulose mineralisation between diatom-amended treatments and controls in aerobic sediment slurries. Priming of lignocellulose degradation was observed only at the initial stages of the experiment (day 7) and coincided with overall high microbial activity as exemplified by total CO2 production. Lignocellulose mineralisation did not differ consistently between diatom treatments and control for the remaining experimental time (days 14-28). Based on this pattern, we hypothesize that the faster initiation of lignocellulose mineralisation in diatom-amended treatments is attributed to the decomposition of accessible polysaccharide components within the lignocellulose complex by activated diatom degraders. The fact that diatom-degraders contributed to lignocellulose degradation was also supported by the different patterns in 13C-enrichment of phospholipid fatty acids between treatments. Although we did not observe differences between treatments in the total quantity of respired lignocellulose at the end of the experiment, differences in timing could be important in natural ecosystems where the amount of time that a certain compound is subject to aerobic degradation before burial to deeper anoxic sediments may be limited.

Feeding ecology of Ammothella longipes (Arthropoda: Pycnogonida) in the Mediterranean Sea: A fatty acid biomarker approach

NASA Astrophysics Data System (ADS)

Soler-Membrives, Anna; Rossi, Sergio; Munilla, Tomás

2011-05-01

Fatty acid analysis has proved valuable in determining seasonal trophic links and the feeding behavior in organisms in which these diet and trophic links cannot be inferred from stomach content analyses. Seasonal variations in total free fatty acid content (TFFA) and fatty acid composition of seston (<250 μm), the brown macroalgae Stypocaulon spp., polychaetes (Nereididae) and the pycnogonid Ammothella longipes have been used to establish their trophic links, with particular focus on seasonality and feeding ecology of A. longipes. Samples were collected in a coastal environment (NW Mediterranean Sea) at 7-10 m depth, in five different periods (August and October 2008, February, June and September 2009). Seston and Stypocaulon spp. samples did not show significant seasonal variations in TFFA content, while nereids showed a significant variation. Analysis of fatty acid profile showed high similarities of fatty acid composition between seston and Stypocaulon spp. Nereids were closer to seston and Stypocaulon spp. than A. longipes, which seemed to follow a seasonal trend. The results of this study reveal that A. longipes may change its feeding behavior depending on the season and available food. This pycnogonid species appears to be carnivore during spring and early summer but seems to feed on detritus when availability of prey diminishes during winter. Notable high amounts of odd-chain fatty acids are found in summer-autumn for this species, which may come from bacteria acquired from the detrital diet or from de novo biosynthesis from propionate. The results obtained provide new and valuable data on the understudied feeding biology of pycnogonids in general, and contribute to the understanding of their functioning of Mediterranean shallow oligotrophic systems and their trophic links.

Post-Remediation Biomonitoring of Pesticides in Marine Waters Near the United Heckathorn Superfund Site, Richmond, California

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

LD Antrim; NP Kohn

This report, PNNL-11911 Rev. 1, was published in July 2000 and replaces PNNL-11911, which was published in September 1998. The revision corrects tissue concentration units that were reported as dry weight but were actually wet weight, and updates conclusions based on the correct reporting units. Marine sediment remediation at the United Heckathorn Superfund Site was completed in April 1997. Water and mussel tissues were sampled in January 1998 from four stations near Lauritzen Canal in Richmond, California, for the first post-remediation monitoring of marine areas near the United Heckathorn Site. Dieldrin and DDT were analyzed in water samples, tissue samplesmore » from resident mussels, and tissue samples from transplanted mussels deployed for 4 months. Concentrations of dieldrin and total DDT in water and total DDT in tissue were compared to pre-remediation data available from the California State Mussel Watch program (tissues) and the Ecological Risk Assessment for the United Heckathorn Superfund Site (tissues and water). Chlorinated pesticide concentrations in water samples were similar to pre-remediation levels and did not meet remediation goals. Mean dieldrin concentrations in water ranged from 0.65 ng/L to 18.1 ng/L and were higher than the remediation goal (0.14 ng/L) at all stations. Mean total DDT concentrations in water ranged from 0.65 ng/L to 103 ng/L and exceeded the remediation goal of 0.59 ng/L. The highest concentrations of both pesticides were found in Lauritzen Canal, and the lowest levels were from the Richmond Inner Harbor Channel water. Unusual amounts of detritus in the water column at the time of sampling, particularly in Lauritzen Canal, could have contributed to the elevated pesticide concentrations and poor analytical precision.« less

Decoupled diversity dynamics in green and brown webs during primary succession in a saltmarsh.

PubMed

Schrama, Maarten; van der Plas, Fons; Berg, Matty P; Olff, Han

2017-01-01

Terrestrial ecosystems are characterized by a strong functional connection between the green (plant-herbivore-based) and brown (detritus-detritivore-based) parts of the food web, which both develop over successional time. However, the interlinked changes in green and brown food web diversity patterns in relation to key ecosystem processes are rarely studied. Here, we demonstrate changes in species richness, diversity and evenness over a wide range of invertebrate green and brown trophic groups during 100 years of primary succession in a saltmarsh ecosystem, using a well-calibrated chronosequence. We contrast two hypotheses on the relationship between green and brown food web diversity across succession: (i) 'coupled diversity hypothesis', which predicts that all trophic groups covary similarly with the main drivers of successional ecosystem assembly vs. (ii) the 'decoupled diversity hypothesis', where green and brown trophic groups diversity respond to different drivers during succession. We found that, while species richness for plants and invertebrate herbivores (green web groups) both peaked at intermediate productivity and successional age, the diversity of macrodetritivores, microarthropod microbivores and secondary consumers (brown web groups) continuously increased towards the latest successional stages. These results suggest that green web trophic groups are mainly driven by vegetation parameters, such as the amount of bare soil, vegetation biomass production and vegetation height, while brown web trophic groups are mostly driven by the production and standing stock of dead organic material and soil development. Our results show that plant diversity cannot simply be used as a proxy for the diversity of all other species groups that drive ecosystem functioning, as brown and green diversity components in our ecosystem responded differently to successional gradients. © 2016 The Authors. Journal of Animal Ecology © 2016 British Ecological Society.

Methane-Carbon Flow into the Benthic Food Web at Cold Seeps – A Case Study from the Costa Rica Subduction Zone

PubMed Central

Niemann, Helge; Linke, Peter; Knittel, Katrin; MacPherson, Enrique; Boetius, Antje; Brückmann, Warner; Larvik, Gaute; Wallmann, Klaus; Schacht, Ulrike; Omoregie, Enoma; Hilton, David; Brown, Kevin; Rehder, Gregor

2013-01-01

Cold seep ecosystems can support enormous biomasses of free-living and symbiotic chemoautotrophic organisms that get their energy from the oxidation of methane or sulfide. Most of this biomass derives from animals that are associated with bacterial symbionts, which are able to metabolize the chemical resources provided by the seeping fluids. Often these systems also harbor dense accumulations of non-symbiotic megafauna, which can be relevant in exporting chemosynthetically fixed carbon from seeps to the surrounding deep sea. Here we investigated the carbon sources of lithodid crabs (Paralomis sp.) feeding on thiotrophic bacterial mats at an active mud volcano at the Costa Rica subduction zone. To evaluate the dietary carbon source of the crabs, we compared the microbial community in stomach contents with surface sediments covered by microbial mats. The stomach content analyses revealed a dominance of epsilonproteobacterial 16S rRNA gene sequences related to the free-living and epibiotic sulfur oxidiser Sulfurovum sp. We also found Sulfurovum sp. as well as members of the genera Arcobacter and Sulfurimonas in mat-covered surface sediments where Epsilonproteobacteria were highly abundant constituting 10% of total cells. Furthermore, we detected substantial amounts of bacterial fatty acids such as i-C15∶0 and C17∶1ω6c with stable carbon isotope compositions as low as −53‰ in the stomach and muscle tissue. These results indicate that the white microbial mats at Mound 12 are comprised of Epsilonproteobacteria and that microbial mat-derived carbon provides an important contribution to the crab's nutrition. In addition, our lipid analyses also suggest that the crabs feed on other 13C-depleted organic matter sources, possibly symbiotic megafauna as well as on photosynthetic carbon sources such as sedimentary detritus. PMID:24116017

Food Web Structure in a Harsh Glacier-Fed River

PubMed Central

Clitherow, Leonie R.; Carrivick, Jonathan L.; Brown, Lee E.

2013-01-01

Glacier retreat is occurring across the world, and associated river ecosystems are expected to respond more rapidly than those in flowing waters in other regions. The river environment directly downstream of a glacier snout is characterised by extreme low water temperature and unstable channel sediments but these habitats may become rarer with widespread glacier retreat. In these extreme environments food web dynamics have been little studied, yet they could offer opportunities to test food web theories using highly resolved food webs owing to their low taxonomic richness. This study examined the interactions of macroinvertebrate and diatom taxa in the Ödenwinkelkees river, Austrian central Alps between 2006 and 2011. The webs were characterised by low taxon richness (13–22), highly connected individuals (directed connectance up to 0.19) and short mean food chain length (2.00–2.36). The dominant macroinvertebrates were members of the Chironomidae genus Diamesa and had an omnivorous diet rich in detritus and diatoms as well as other Chironomidae. Simuliidae (typically detritivorous filterers) had a diet rich in diatoms but also showed evidence of predation on Chironomidae larvae. Food webs showed strong species-averaged and individual size structuring but mass-abundance scaling coefficients were larger than those predicted by metabolic theory, perhaps due to a combination of spatial averaging effects of patchily distributed consumers and resources, and/or consumers deriving unquantified resources from microorganisms attached to the large amounts of ingested rock fragments. Comparison of food web structural metrics with those from 62 published river webs suggest these glacier-fed river food web properties were extreme but in line with general food web scaling predictions, a finding which could prove useful to forecast the effects of anticipated future glacier retreat on the structure of aquatic food webs. PMID:23613751

Chemical Data for Precipitate Samples

USGS Publications Warehouse

Foster, Andrea L.; Koski, Randolph A.

2008-01-01

During studies of sulfide oxidation in coastal areas of Prince William Sound in 2005, precipitate samples were collected from onshore and intertidal locations near the Ellamar, Threeman, and Beatson mine sites (chapter A, fig. 1; table 7). The precipitates include jarosite and amorphous Fe oxyhydroxide from Ellamar, amorphous Fe oxyhydroxide from Threeman, and amorphous Fe oxyhydroxide, ferrihydrite, and schwertmannite from Beatson. Precipitates occurring in the form of loose, flocculant coatings were harvested using a syringe and concentrated in the field by repetitive decanting. Thicker accumulations were either scraped gently from rocks using a stainless steel spatula or were scooped directly into receptacles (polyethylene jars or plastic heavy-duty zippered bags). Most precipitate samples contain small amounts of sedimentary detritus. With three jarosite-bearing samples from Ellamar, an attempt was made to separate the precipitate from the heavy-mineral fraction of the sediment. In this procedure, the sample was stirred in a graduated cylinder containing deionized water. The jarosite-rich suspension was decanted onto analytical filter paper and air dried before analysis. Eleven precipitate samples from the three mine sites were analyzed in laboratories of the U.S. Geological Survey (USGS) in Denver, Colorado (table 8). Major and trace elements were determined by inductively coupled plasma-mass spectrometry following multiacid (HCl-HNO3-HClO4-HF) digestion (Briggs and Meier, 2002), except for mercury, which was analyzed by cold-vapor atomic absorption spectroscopy (Brown and others, 2002a). X-ray diffraction (XRD) analyses were performed on powdered samples (<200 mesh) by S. Sutley of the USGS. Additional details regarding sample preparation and detection limits are found in Taggert (2002). Discussions of the precipitate chemistry and associated microbial communities are presented in Koski and others (2008) and Foster and others (2008), respectively.

Methane-carbon flow into the benthic food web at cold seeps--a case study from the Costa Rica subduction zone.

PubMed

Niemann, Helge; Linke, Peter; Knittel, Katrin; MacPherson, Enrique; Boetius, Antje; Brückmann, Warner; Larvik, Gaute; Wallmann, Klaus; Schacht, Ulrike; Omoregie, Enoma; Hilton, David; Brown, Kevin; Rehder, Gregor

2013-01-01

Cold seep ecosystems can support enormous biomasses of free-living and symbiotic chemoautotrophic organisms that get their energy from the oxidation of methane or sulfide. Most of this biomass derives from animals that are associated with bacterial symbionts, which are able to metabolize the chemical resources provided by the seeping fluids. Often these systems also harbor dense accumulations of non-symbiotic megafauna, which can be relevant in exporting chemosynthetically fixed carbon from seeps to the surrounding deep sea. Here we investigated the carbon sources of lithodid crabs (Paralomis sp.) feeding on thiotrophic bacterial mats at an active mud volcano at the Costa Rica subduction zone. To evaluate the dietary carbon source of the crabs, we compared the microbial community in stomach contents with surface sediments covered by microbial mats. The stomach content analyses revealed a dominance of epsilonproteobacterial 16S rRNA gene sequences related to the free-living and epibiotic sulfur oxidiser Sulfurovum sp. We also found Sulfurovum sp. as well as members of the genera Arcobacter and Sulfurimonas in mat-covered surface sediments where Epsilonproteobacteria were highly abundant constituting 10% of total cells. Furthermore, we detected substantial amounts of bacterial fatty acids such as i-C15∶0 and C17∶1ω6c with stable carbon isotope compositions as low as -53‰ in the stomach and muscle tissue. These results indicate that the white microbial mats at Mound 12 are comprised of Epsilonproteobacteria and that microbial mat-derived carbon provides an important contribution to the crab's nutrition. In addition, our lipid analyses also suggest that the crabs feed on other (13)C-depleted organic matter sources, possibly symbiotic megafauna as well as on photosynthetic carbon sources such as sedimentary detritus.

Joint inversion of 3-PG using eddy-covariance and inventory plot measurements in temperate-maritime conifer forests: Uncertainty in transient carbon-balance responses to climate change

NASA Astrophysics Data System (ADS)

Hember, R. A.; Kurz, W. A.; Coops, N. C.; Black, T. A.

2010-12-01

Temperate-maritime forests of coastal British Columbia store large amounts of carbon (C) in soil, detritus, and trees. To better understand the sensitivity of these C stocks to climate variability, simulations were conducted using a hybrid version of the model, Physiological Principles Predicting Growth (3-PG), combined with algorithms from the Carbon Budget Model of the Canadian Forest Sector - version 3 (CBM-CFS3) to account for full ecosystem C dynamics. The model was optimized based on a combination of monthly CO2 and H2O flux measurements derived from three eddy-covariance systems and multi-annual stemwood growth (Gsw) and mortality (Msw) derived from 1300 permanent sample plots by means of Markov chain Monte Carlo sampling. The calibrated model serves as an unbiased estimator of stemwood C with enhanced precision over that of strictly-empirical models, minimized reliance on local prescriptions, and the flexibility to study impacts of environmental change on regional C stocks. We report the contribution of each dataset in identifying key physiological parameters and the posterior uncertainty in predictions of net ecosystem production (NEP). The calibrated model was used to spin up pre-industrial C pools and estimate the sensitivity of regional net carbon balance to a gradient of temperature changes, λ=ΔC/ΔT, during three 62-year harvest rotations, spanning 1949-2135. Simulations suggest that regional net primary production, tree mortality, and heterotrophic respiration all began increasing, while NEP began decreasing in response to warming following the 1976 shift in northeast-Pacific climate. We quantified the uncertainty of λ and how it was mediated by initial dead C, tree mortality, precipitation change, and the time horizon in which it was calculated.

Lead-isotopic data from sulfide minerals from the Cascade Range, Oregon and Washington

USGS Publications Warehouse

Church, S.E.; LeHuray, A.P.; Grant, A.R.; Delevaux, M.H.; Gray, J.E.

1986-01-01

Lead-isotopic studies of mineral deposits associated with Tertiary plutons found in the Cascade Range of Oregon and Washington demonstrate a rather uniform isotopic composition in various sulfide minerals ( 206Pb 204Pb = 18.84 to 19.05; 207Pb 204Pb = 15.57 to 15.62; 208Pb 204Pb = 38.49 to 38.74), show less variation than data from the volcanic rocks of the Cascade Range and fall within the mixing array defined by the MORB regression line and continental sediments. An evaluation of the role of crustal assimilation by hydrothermal convection during emplacement was made on five sulfide deposits associated with a single composite batholith, the Cloudy Pass pluton. The Pb-isotopic data and mass balance calculations suggest that only minor amounts of the lead were derived from the overlying Precambrian (?) Swakane Biotite Gneiss during emplacement. The bulk of the metal that occurs in sulfide deposits in the Cascade mineral belt appears to have been derived from subducted continental detritus. The variation of the Pb-isotopic signature of Sulfides from specific districts or deposits suggests that there is a correlation with age and structure of the crust. 206Pb 204Pb is greater than 18.92 in northern Washington and southern Oregon where deposits have intruded Mesozoic or older crust. However, the ore deposits between the northern Oregon border and central Oregon, south of Eugene, have intruded younger crust composed largely of mafic and andesitic volcanic rocks and 206Pb 204Pb lies between 18.84 and 18.92. This region, previously called the Columbia embayment, appears to be underlain by Tertiary volcanic rocks. Lead-isotopic data may be used to define the boundaries between discontinuous blocks of Mesozoic crust and Tertiary volcanic cover. ?? 1986.

Degradation State and Sequestration Potential of Carbon in Coastal Wetlands of Texas: Mangrove Vs. Saltmarsh Ecosystems

NASA Astrophysics Data System (ADS)

Sterne, A. M. E.; Kaiser, K.; Louchouarn, P.; Norwood, M. J.

2015-12-01

The estimated magnitude of the organic carbon (OC) stocks contained in the first meter of US coastal wetland soils represents ~10% of the entire OC stock in US soils (4 vs. 52 Pg, respectively). Because this stock extends to several meters below the surface for many coastal wetlands, it becomes paramount to understand the fate of OC under ecosystem shifts, varying natural environmental constraints, and changing land use. In this project we analyze the major classes of biochemicals including total hydrolysable neutral carbohydrates, enantiomeric amino acids, phenols, and cutins/suberins at two study sites located on the Texas coastline to investigate chemical composition and its controls on organic carbon preservation in mangrove (Avicennia germinans) and saltmarsh grass (Spartina alterniflora) dominated wetlands. Results show neutral carbohydrates and lignin contribute 30-70% and 10-40% of total OC, respectively, in plant litter and surface sediments at both sites. Sharp declines of carbohydrate yields with depth occur parallel to increasing Ac/AlS,V ratios indicating substantial decomposition of both the polysaccharide and lignin components of litter detritus. Contrasts in the compositions and relative abundances of all previously mentioned compound classes are further discussed to examine the role of litter biochemistry in OC preservation. For example, the selective preservation of cellulose over hemicellulose in sediments indicates macromolecular structure plays a key role in preservation between plant types. It is concluded that the chemical composition of litter material controls the composition and magnitude of OC stored in sediments. Ultimately, as these ecosystems transition from one dominant plant type to another, as is currently observed along the Texas coastline, there is the potential for OC sequestration efficiency to shift due to the changing composition of OC input to sediments.

The geological record of life 3500 Ma ago: Coping with the rigors of a young earth during late accretion

NASA Technical Reports Server (NTRS)

Lowe, Donald R.

1989-01-01

Thin cherty sedimentary layers within the volcanic portions of the 3,500 to 3,300 Ma-old Onverwacht and Fig Tree Groups, Barberton Greenstone belt, South Africa, and Warrawoona Group, eastern Pilbara Block, Western Australia, contain an abundant record of early Archean life. Five principal types of organic and probably biogenic remains and or structures can be identifed: stromatolites, stromatolite detritus, carbonaceous laminite or flat stromalite, carbonaceous detrital particles, and microfossils. Early Archean stromatolites were reported from both the Barberton and eastern Pilbara greenstone belts. Systematic studies are lacking, but two main morphological types of stromatolites appear to be represented by these occurrences. Morphology of the stromalites is described. Preserved early Archean stromatolites and carbonaceous matter appear to reflect communities of photosynthetic cyanobacteria inhabiting shallow, probably marine environments developed over the surfaces of low-relief, rapidly subsiding, simatic volcanic platforms. The overall environmental and tectonic conditions were those that probably prevailed at Earth's surface since the simatic crust and oceans formed sometime before 3,800 Ma. Recent studies also suggest that these early Archean sequences contain layers of debris formed by large-body impacts on early Earth. If so, then these early bacterial communities had developed strategies for coping with the disruptive effects of possibly globe-encircling high-temperature impact vapor clouds, dust blankets, and impact-generated tsunamis. It is probable that these early Archean biogenic materials represent organic communities that evolved long before the beginning of the preserved geological record and were well adapted to the rigors of life on a young, volcanically active Earth during late bombardment. These conditions may have had parallels on Mars during its early evolution.

Idetification of the chemical sedimentary protolish of the early Paleoproterozoic banded iron formation from Wuyang area, in the southern margin of the North China Craton

NASA Astrophysics Data System (ADS)

Lan, C.; Zhao, T.

2016-12-01

The Paleoproterozoic banded iron formation (BIF) from Wuyang area in the southern margin of the North China Craton (NCC) were metamorphosed under granulite facies, and are characterized with an assemblage of clinopyroxene, magnetite and orthopyroxene. Two types of iron ores can be identified on the basis of macro- and micro-textures: banded quartz-clinopyroxene (±othopyroxene) -magnetite ores and massive clinopyroxene-magnetite ores. Two-pyroxene geothermometry indicates that the primary counterparts of these ores have undergone metamorphism with a peak temperature of about 762±9°. Both the banded and massive ores have also similarly BIF-like REE+Y features, and thus are proposed to have all formed from chemical sediments. Similarly, clinopyroxenes from both types have BIF-like rare earth element compositions and are rich in Fe (16-23 wt.% FeOtotoal), further suggesting that they are primary Fe-Mg-Ca-rich chemical sediments during metamorphism. Slight enrichments of TiO2, Al2O3, Zr, Hf, Ta and Th of the Wuyang IF suggest relatively low detritus input. The massive ore have magnetite containing V, Cr and Ti much higher than those of the banded ores, suggesting that they may have undergone stronger secondary alteration possibly related to the intrusion of nearby pyroxenite plutons. Different ores have seawater-like REE+Y patterns with LREE depletions and positive anomalies of La, Eu, and Y, showing that granulite facies metamorphism did not essentially modify the primary compositions of the Wuyang IF deposited from paleo-seawater. Our results suggest less than 0.1% contribution from high-temperature hydrothermal fluids.

Numerical experiments based on a coupled physical-biochemical ocean model to study the Kuroshio-induced nutrient supply on the shelf-slope region off the southwestern coast of Japan

NASA Astrophysics Data System (ADS)

Kuroda, Hiroshi; Takasuka, Akinori; Hirota, Yuichi; Kodama, Taketoshi; Ichikawa, Tadafumi; Takahashi, Daisuke; Aoki, Kazuhiro; Setou, Takashi

2018-03-01

We developed a triply nested 1/50° ocean model coupled with a NPZD-type lower trophic level ecosystem model and used it to conduct numerical experiments to identify the major processes that supply nutrients on the shelf-slope region north of the Kuroshio. Tosa Bay, an open-type bay facing the Kuroshio, was selected for our experiment. Comparisons of numerical simulations using different grid sizes revealed that a grid size no larger than 1/50° was essential to reproduce a time-independent density structure related to the Kuroshio jet that uplifted nitrate from subsurface waters into the euphotic zone north of the Kuroshio front. The monthly mean budget of nitrate within the euphotic zone on the shelf showed that primary production was nearly balanced by physical advection and the biochemical supply of nitrate via mechanisms such as remineralization of detritus. Eddy advection of nitrate based on Reynolds decomposition, attributable primarily to submesoscale variations, had both positive and negative values within the bay, the indication being that eddy advection functioned regionally to supply or remove nitrate. Lagrangian particle-tracking experiments were performed to examine the major pathways of the nitrate used for primary production in Tosa Bay during the summer, when subsurface maxima of primary production typically appeared. The experiments revealed that when the Kuroshio took a stable nearshore path, nitrate was frequently uplifted around the Kuroshio front and horizontally transported along the front and into the bay via the counterclockwise circulation within the bay; it was sometimes further uplifted onto the shelf.

Star-dust geometries in galaxies: The effect of interstellar matter distributions on optical and infrared properties of late-type galaxies

NASA Technical Reports Server (NTRS)

Capuano, J. M., Jr.; Thronson, H. A., Jr.; Witt, A. N.

1993-01-01

The presence of substantial amounts of interstellar dust in late-type galaxies affects observable parameters such as the optical surface brightness, the color, and the ratio of far-infrared to optical luminosity of these galaxies. We conducted radiative transfer calculations for late-type galaxy environments to examine two different scenarios: (1) the effects of increasing amounts of dust in two fixed geometries with different star distributions; and (2) the effects of an evolving dust-star geometry in which the total amount of dust is held constant, for three different star distributions. The calculations were done for ten photometric bands, ranging from the far-ultraviolet to the near-infrared (K), and scattered light was included in the galactic surface brightness at each wavelength. The energy absorbed throughout these ten photometric bands was assumed to re-emerge in the far-infrared as thermal dust emission. We also considered the evolutionary contraction of a constant amount of dust relative to pre-existing star distributions.

Woodcock singing-ground counts and habitat changes in the northeastern United States

USGS Publications Warehouse

Dwyer, T.J.; McAuley, D.G.; Derleth, E.L.

1983-01-01

Aerial photography from the late 1960's and the late 1970's was used to study habitat changes along 78 American woodcock (Scolopax minor) singing-ground routes in 9 northeastern states. The most noticeable changes were declines in the amount of abandoned field, cropland, shrubland, and field/pasture. The amount of land in the urban/industrial type increased 33.4% from the late 1960's to the late 1970's. We examined relationships between the woodcock call-count index and habitat variables using multiple-regression techniques. The abundance of calling male woodcock was positively correlated with the amount of abandoned field and alder (Alnus sp.) and negatively correlated with the amount of urban/industrial type. However, only the change in the urban/industrial type was significantly (P < 0.05) related to the change in the call-count index. Urban/industrial area increased, whereas the call-count index declined on average in our sample of routes by 1.4 birds/route (40.5%).

5 CFR Appendix A to Subpart F of... - Recommended Language for Court Orders Dividing Employee Annuities

Code of Federal Regulations, 2014 CFR

2014-01-01

...-210 [Reserved] ¶ 211Award based on a stated formula. ¶ 212-230 [Reserved] ¶ 231Awarding COLA's on fixed monthly amounts. ¶ 232Excluding COLA's on awards other than fixed monthly amounts. 300 Series—Type... monthly amount. OPM will not apply COLA's to a fixed monthly amount unless the court order expressly...

5 CFR Appendix A to Subpart F of... - Recommended Language for Court Orders Dividing Employee Annuities

Code of Federal Regulations, 2013 CFR

2013-01-01

...-210 [Reserved] ¶ 211Award based on a stated formula. ¶ 212-230 [Reserved] ¶ 231Awarding COLA's on fixed monthly amounts. ¶ 232Excluding COLA's on awards other than fixed monthly amounts. 300 Series—Type... monthly amount. OPM will not apply COLA's to a fixed monthly amount unless the court order expressly...

5 CFR Appendix A to Subpart F of... - Recommended Language for Court Orders Dividing Employee Annuities

Code of Federal Regulations, 2012 CFR

2012-01-01

...-210 [Reserved] ¶ 211Award based on a stated formula. ¶ 212-230 [Reserved] ¶ 231Awarding COLA's on fixed monthly amounts. ¶ 232Excluding COLA's on awards other than fixed monthly amounts. 300 Series—Type... monthly amount. OPM will not apply COLA's to a fixed monthly amount unless the court order expressly...

Songbird abundance in native and planted grassland varies with type and amount of grassland in the surrounding landscape

USGS Publications Warehouse

Davis, Stephen K.; Fisher, Ryan; Skinner, Susan; Shaffer, Terry L.; Brigham, R. Mark

2013-01-01

Agriculture and wildlife conservation programs have converted vast amounts of cropland into grasslands planted with exotic species. Understanding how landscape context influences avian use of native and planted grasslands is essential for developing effective conservation strategies in agricultural landscapes. Our primary objective was to determine the extent to which the amount and type of grassland in the surrounding landscape influences the abundance of grassland songbird species on native and planted grassland parcels in southern Saskatchewan and Alberta, Canada. Bird abundance was more strongly influenced by the amount and type of grassland within 400 m of breeding parcels than at larger spatial scales. Grassland specialists responded similarly to habitat and landscape type over both years and provinces. Sprague's pipit (Anthus spragueii) and Baird's sparrow (Ammodramus bairdii) were most common in native grassland parcels surrounded by native grassland and were more likely to occur in planted grasslands surrounded by native grassland. Bobolinks (Dolichonyx oryzivorus) were most common in planted grassland parcels, but their abundance increased with the amount of native grassland surrounding these parcels. Our findings indicate that the suitability of planted grasslands for these species is influenced by their proximity to native grassland. Grassland generalists showed mixed responses to habitat and landscape type over the 2 years (Le Conte's sparrow [Ammodramus leconteii]) and between provinces (Savannah sparrow [Passerculus sandwichensis] and western meadowlark [Sturnella neglecta]). Management to benefit grassland specialists should therefore consider the landscape context when seeding cultivated land to non-native grassland and conserve extant native grassland.

Common Alterations in Sensitivity to Type but Not Amount of Reward in ADHD and Autism Spectrum Disorders

ERIC Educational Resources Information Center

Demurie, Ellen; Roeyers, Herbert; Baeyens, Dieter; Sonuga-Barke, Edmund

2011-01-01

Background: Children with attention deficit/hyperactivity disorder (ADHD) display abnormalities in reward processing. Most reward studies have focused on the effects of material or monetary rewards. Studies with autism spectrum disorder (ASD) have focused on social rewards. In this study we compared the effects of amount and type of reward in…

The Associations between the Milk Mothers Drink and the Milk Consumed by Their School-Aged Children. Nutrition, Health and Safety.

ERIC Educational Resources Information Center

Johnson, Rachel K.; Panely, Celeste V.; Wang, Min Qi

2001-01-01

A national survey identified predictors of school-age children's and adolescents' amount and type of milk intake. Findings indicated that geographic region, child's gender, and amount of milk mothers consumed predicted the children's milk consumption. Predictors of child milk type included the children's age, gender, race, geographic region,…

The Impact of Environmental Factors on the Amount of Nitrates and Nitrites in Different Types of Soils and Ways of Their Utilization

NASA Astrophysics Data System (ADS)

Bachvarova, Darina; Rafi, Renay; Doichinov, Aleksandar

2017-03-01

Despite the last decade considerable advances in the study of nitrate and nitrite pollution of soil, there are still some gaps in research related to neglecting or ignoring the role of soil in the food chain and its effects on upper trophic units. The article presents the results of a study on the impact of air and soil humidity and temperature, as well as soil type and utilization on the amount of nitrates and nitrites in the soil solution at the end of vegetation period. It was proved that statistically significant impact on the amounts of residual nitrate and nitrite ions was caused by the temperature and moisture of soil, its type, and the specific properties of the crops grown.

Glucan-rich diet is digested and taken up by the carnivorous sundew (Drosera rotundifolia L.): implication for a novel role of plant β-1,3-glucanases.

PubMed

Michalko, Jaroslav; Socha, Peter; Mészáros, Patrik; Blehová, Alžbeta; Libantová, Jana; Moravčíková, Jana; Matušíková, Ildikó

2013-10-01

Carnivory in plants evolved as an adaptation strategy to nutrient-poor environments. Thanks to specialized traps, carnivorous plants can gain nutrients from various heterotrophic sources such as small insects. Digestion in traps requires a coordinated action of several hydrolytic enzymes that break down complex substances into simple absorbable nutrients. Among these, several pathogenesis-related proteins including β-1,3-glucanases have previously been identified in digestive fluid of some carnivorous species. Here we show that a single acidic endo-β-1,3-glucanase of ~50 kDa is present in the digestive fluid of the flypaper-trapped sundew (Drosera rotundifolia L.). The enzyme is inducible with a complex plant β-glucan laminarin from which it releases simple saccharides when supplied to leaves as a substrate. Moreover, thin-layer chromatography of digestive exudates showed that the simplest degradation products (especially glucose) are taken up by the leaves. These results for the first time point on involvement of β-1,3-glucanases in digestion of carnivorous plants and demonstrate the uptake of saccharide-based compounds by traps. Such a strategy could enable the plant to utilize other types of nutritional sources e.g., pollen grains, fungal spores or detritus from environment. Possible multiple roles of β-1,3-glucanases in the digestive fluid of carnivorous sundew are also discussed.

Microbial activity in Alaskan taiga soils contaminated by crude oil in 1976

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

Monroe, E.M.; Lindstrom, J.E.; Brown, E.J.

1995-12-31

Biodegradation, often measured via microbial activity, includes destruction of environmental pollutants by living microorganisms and is dependent upon many physical and chemical factors. Effects of mineral nutrients and organic matter on biodegradation of Prudhoe Bay crude oil were investigated at a nineteen-year-old oil spill site in Alaskan taiga. Microcosms of two different soil types from the spill site; one undeveloped soil with forest litter and detritus (O horizon) and one more developed with lower organic content (A horizon), were treated with various nitrogen and phosphorus amendments, and incubated for up to six weeks. Each microcosm was sampled periodically and assayedmore » for hydrocarbon mineralization potential using radiorespirometry, for total carbon dioxide respired using gas chromatography, and for numbers of hydrocarbon-degrading bacteria and heterotrophic bacteria using most probable number counting techniques. Organic matter in the O horizon soil along with combinations of mineral nutrients were found to stimulate microbial activity. No combination of mineral nutrient additions to the A horizon soil stimulated any of the parameters above those measured in control microcosms. The results of this study indicate that adding mineral nutrients and tilling the O horizon into the A horizon of subarctic soils contaminated with crude oil, would stimulate microbial activity, and therefore the biodegradation potential, ultimately increasing the rate of destruction of crude oil in these soils.« less

Technical Note: Linking climate change and downed woody debris decomposition across forests of the eastern United States

USGS Publications Warehouse

Russell, Matthew B.; Woodall, Christopher W.; D'Amato, Anthony W.; Fraver, Shawn; Bradford, John B.

2014-01-01

Forest ecosystems play a critical role in mitigating greenhouse gas emissions. Forest carbon (C) is stored through photosynthesis and released via decomposition and combustion. Relative to C fixation in biomass, much less is known about C depletion through decomposition of woody debris, particularly under a changing climate. It is assumed that the increased temperatures and longer growing seasons associated with projected climate change will increase the decomposition rates (i.e., more rapid C cycling) of downed woody debris (DWD); however, the magnitude of this increase has not been previously addressed. Using DWD measurements collected from a national forest inventory of the eastern United States, we show that the residence time of DWD may decrease (i.e., more rapid decomposition) by as much as 13% over the next 200 years, depending on various future climate change scenarios and forest types. Although existing dynamic global vegetation models account for the decomposition process, they typically do not include the effect of a changing climate on DWD decomposition rates. We expect that an increased understanding of decomposition rates, as presented in this current work, will be needed to adequately quantify the fate of woody detritus in future forests. Furthermore, we hope these results will lead to improved models that incorporate climate change scenarios for depicting future dead wood dynamics in addition to a traditional emphasis on live-tree demographics.

Mineralogical and Geochemical Discrimination of the Occurrence and Genesis of Palygorskite in Eocene Sediments on the Northeastern Tibetan Plateau

NASA Astrophysics Data System (ADS)

Ye, Chengcheng; Yang, Yibo; Fang, Xiaomin; Hong, Hanlie; Zhang, Weilin; Yang, Rongsheng; Song, Bowen; Zhang, Zhiguo

2018-03-01

Palygorskite is a widely used indicator of semiarid to arid environments in paleoclimate studies. In this study, we present detailed mineralogical and geochemical investigations exploring the genesis of palygorskite found in Eocene fluvial sediment in the northern Qaidam Basin on the northeastern Tibetan Plateau. The presence of two types of palygorskite is revealed, based on their crystallinity characteristics and distinctive rare earth element (REE) patterns in the coexisting clay fraction. Well-crystallized palygorskite samples are characterized by remarkably negative Ce anomalies and obvious middle rare earth element enrichment. Poorly crystallized palygorskite samples generally exhibit positive Ce anomalies and less pronounced middle rare earth element enrichment, which resemble those of nonpalygorskite-bearing clay samples. Given the presence of an overall oxidized fluvial sedimentary environment, we attribute the well-crystallized palygorskite (which has textures comprising long, interwoven fibers) to direct precipitation (i.e., neoformation) occurring within a reducing environment during early/postdepositional processes while the poorly crystallized palygorskite (which is characterized by short, club-shaped single crystals) originates as catchment-delivered detritus. These poorly crystallized palygorskites occur mostly in 49.5-47.0 Ma and are accompanied by decreasing kaolinite content, increasing chlorite content, and abundant xerophytic spore-pollen from the Qaidam Basin, and its neighboring Xining Basin. Collectively, these evidences suggest that a less humid climate followed after the Early Eocene Climate Optimum.

Effect of climate on the trophic structure of temperate forested streams. a comparison of Mediterranean and Atlantic streams.

PubMed

Sabater, Sergi; Elosegi, Arturo; Acuña, Vicenç; Basaguren, Ana; Muñoz, Isabel; Pozo, Jesús

2008-02-15

Climate affects many aspects of stream ecosystems, although the presence of riparian forests can buffer differences between streams in different climatic settings. In an attempt to measure the importance of climate, we compared the seasonal patterns of hydrology, input and storage of allochthonous organic matter, and the trophic structure (abundance of algae and macroinvertebrates) in two temperate forested streams, one Mediterranean, the other Atlantic. Hydrology played a leading role in shaping the trophic structure of both streams. Frequency and timing of floods and droughts determined benthic detritus storage. Inputs and retention of allochthonous organic matter were higher in the Atlantic stream, whereas chlorophyll concentration was lower because of stronger light limitation. Instead, light availability and scour of particulate organic matter during late winter favoured higher chlorophyll concentration in the Mediterranean stream. As a result, in the Mediterranean stream grazers were more prevalent and consumers showed a higher dependence on autotrophic materials. On the other hand, the Atlantic stream depended on allochthonous materials throughout the whole study period. The overall trophic structure showed much stronger seasonality in the Mediterranean than in the Atlantic stream, this being the most distinctive difference between these two types of temperate streams. The different patterns observed in the two streams are an indication that climatic differences should be incorporated in proper measurements of ecosystem health.

The sedimentary record of India-Asia collision: an evaluation of new and existing constraints

NASA Astrophysics Data System (ADS)

Najman, Yani; Henderson, Alex; Boudagher-Fadel, Marcelle; Godin, Laurent; Parrish, Randy; Bown, Paul; Garzanti, Eduardo; Horstwood, Matt; Jenks, Dan

2010-05-01

The age and degree of diachroneity of India-Asia collision is critical to construction of models of orogenesis and to understanding the causes of spatial variations in Himalayan evolution along strike. The age of collision is quoted between ~65-34 Ma (Jaeger et al 1989; Aitchison et al 2007) and the degree of dichroneity is considered negligible (Searle et al 1997) to substantial (Rowley 1998). Such discrepancy is, to some extent, the result of the different definitions and methods used to define the collision. Here, we evaluate constraints from the sedimentary record preserved in the suture zone and Tethyan Himalaya where a minimum age to collision has been constrained by determining 1) the timing of cessation of marine facies, 2) first evidence of Asian detritus deposited on the Indian plate and 3) first evidence of mixed Indian-Asian detritus in the sedimentary record. Extensive previous work has been carried out on the Indus molasse of the Indus Suture zone in Ladakh, India. Here, cessation of marine facies is dated at 50.5 Ma (Green et al. 2008), with the underlying Chogdo Formation considered to show first evidence of mixed Indian and Asian provenance, and be the oldest Formation of Asian-derived provenance to lie in sedimentary contact with the underlying Indian plate (Clift et al 2001, 2002), thus constraining collision at >50.5 Ma. However, our new mapping and provenance analyses on these rocks show that there is no unequivocal evidence of Indian-derived material in the Chogdo Formation, nor that the Chogdo Formation lies in sedimentary contact with the underlying Indian plate (Henderson et al., in review). Thus we question the timing of Indian-Asian collision based on these evidences. South of the suture zone in India and Tibet, we carried out similar investigations of the youngest Tethyan strata. In Ladakh, Indian plate passive margin limestones of the Paleocene Dibling Fm are overlain by the youngest marine facies of the region, the marine Kong Fm and fluvio-deltaic Chulung La Fm (Garzanti et al 1987). The age of the Kong and Chulung La Formations is disputed, from P5/6 (Fuchs & Willems 1990) to P8 (Garzanti et al 1987) the discrepancy possibly the result of research at different locations. Provenance is considered to be either ophiolitic from the Indian plate (Fuchs & Willems 1990) or containing detritus from the Trans-Himalayan arc of the Asian plate (Garzanti et al 1987; Critelli & Garzanti 1994). Our samples from the Kong Fm contained planktic foraminifera indicating a Middle to Early P6 age (54-56 Ma) and larger benthic foraminifera indicating Middle SBZ8 age (53-54 Ma). U-Pb dating of detrital zircons allows discrimination between Asian provenance (dominated by Mesozoic grains from the Trans-Himalayan arc) and Indian provenance (characterized by Precambrian grains and an absence of Mesozoic grains). Our data from the Kong and Chulung La Fms shows a primary provenance from the Asian plate. Thus collision is constrained by arrival of Asian detritus on the Indian plate by 54 Ma. In Tingri, Tibet, Indian plate passive margin limestones of the Zephure Shan Fm extend to the early Eocene, overlain by marine facies of the Pengqu Fm. The youngest marine facies have been dated at 34 Ma (Wang et al. 2002), but this age is disputed by other workers who assign an age of 50 Ma (Zhu et al. 2005). Our new biostratigraphic data from the Pengqu Fm show that calcareous nannofossil species are compatible with an age corresponding to Zones NP11-12 (50.6-53.5 Ma). The dominant population of zircons have Cretaceous-Paleocene ages, derived from the Asian plate, thus indicating that contact between India and Asia had occurred by this time. We therefore conclude that although the Indus Molasse does not provide constraint to the timing of India-Asia collision as previously thought, data from the Tethyan strata show that collision occurred by 54 Ma in the west, with only extremely limited, if any diachroneity eastward.

The effect of 7, 8-methylenedioxylycoctonine-type diterpenoid alkaloids on the toxicity of tall larkspur (Delphinium spp.) in cattle.

PubMed

Welch, K D; Green, B T; Gardner, D R; Cook, D; Pfister, J A; Panter, K E

2012-07-01

Delphinium spp. contain numerous norditerpenoid alkaloids which are structurally delineated as 7, 8-methylenedioxylycoctonine (MDL) and N-(methylsuccinimido) anthranoyllycoctonine (MSAL)-type alkaloids. The toxicity of many tall larkspur species has been primarily attributed to their increased concentration of MSAL-type alkaloids, such as methyllycaconitine (MLA), which are typically 20 times more toxic than MDL-type alkaloids. However, the less toxic MDL-type alkaloids are often more abundant than MSAL-type alkaloids in most Delphinium barbeyi and Delphinium occidentale populations. Previous research demonstrated that MDL-type alkaloids increase the acute toxicity of MSAL-type alkaloids. In this study, we examined the role of MDL-type alkaloids on the overall toxicity of tall larkspur plants to cattle while controlling for the exact dose of MSAL-type alkaloids. Cattle were dosed with plant material from 2 different populations of tall larkspur containing either almost exclusively MDL- or MSAL-type alkaloids. These 2 plant populations were combined to create mixtures with ratios of 0.3:1, 1:1, 5:1, and 10:1 MDL- to MSAL-type alkaloids. The dose that elicited similar clinical signs of poisoning in mice and cattle was determined for each mixture on the basis of the MSAL-type alkaloid content. As the ratio of MDL- to MSAL-type alkaloids increased, the amount of MSAL-type alkaloids required to elicit clinical signs decreased. These results indicate that the less toxic MDL-type alkaloids in tall larkspur exacerbate the toxicity of the MSAL-type alkaloids. Consequently, both the amount of MSAL-type alkaloids and the amount of total alkaloids should be fully characterized to determine more accurately the relative toxicity of tall larkspur plant material.

76 FR 70695 - Taking and Importing Marine Mammals: U.S. Navy Training in 12 Range Complexes and U.S. Air Force...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-11-15

... regarding the types and amounts of missile and rocket launches that the USAF conducts. DATES: Comments and... missiles and rockets that could be launched over the course of the 5-year rule and indicated that marine... flexibility in the types and amounts of missile and rocket launches that they conduct. NMFS now proposes to...

Glycans coated silver nanoparticles induces autophagy and necrosis in HeLa cells

NASA Astrophysics Data System (ADS)

Panzarini, Elisa; Mariano, Stefania; Dini, Luciana

2015-06-01

This study reports the induction of autophagy by two concentrations (2×103 or 2×104 NPs/cell) of 30 nm sized β-D-Glucose- and β-D-Glucose/Sucrose-coated silver NanoParticles (AgNPs-G and AgNPs-GS respectively) in HeLa cells treated for 6, 12, 24 and 48 hrs. Cell viability was assessed by Neutral Red (NR) test and morphological evaluation. In addition ROS generation (NBT test) and induction of apoptosis/necrosis (Annexin V/Propidium Iodide-Annexin V/PI staining) and autophagy (Monodansylcadaverine-MDC staining) were evaluated. Cytotoxicity, ROS generation and morphology changes depend on NPs type and amount, and incubation time. As a general result, AgNPs-G are more toxic than AgNPs-GS. Moreover, the lowest AgNPs-GS concentration is ineffective on cell viability and ROS generation. Only 10% and 25% of viable HeLa cells were found at the end of incubation time in the presence of higher amount of AgNPs - G and AgNPs-GS respectively and in parallel ROS generation is induced. To elucidate the type of cell death, Annexin V/PI and MDC staining was performed. Interestingly, irrespective of coating type and NPs amount the percentage of apoptotic cells (Annexin V+/PI-) is similar to viable HeLa cells. At contrary, we observed a NPs amount dependent autophagy and necrosis induction. In fact, the lower amount of NPs induces autophagy (MDC+/PI- cells) whereas the higher one induces necrosis (Annexin V+/PI+ cells). Our findings suggest that AgNPs-induced cytotoxicity depends on AgNPs amount and type and provide preliminary evidence of induction of autophagy in HeLa cells cultured in the presence of AgNPs.

Functioning efficiency of intermediate coolers of multistage steam-jet ejectors of steam turbines

NASA Astrophysics Data System (ADS)

Aronson, K. E.; Ryabchikov, A. Yu.; Brodov, Yu. M.; Zhelonkin, N. V.; Murmanskii, I. B.

2017-03-01

Designs of various types of intermediate coolers of multistage ejectors are analyzed and thermal effectiveness and gas-dynamic resistance of coolers are estimated. Data on quantity of steam condensed from steam-air mixture in stage I of an ejector cooler was obtained on the basis of experimental results. It is established that the amount of steam condensed in the cooler constitutes 0.6-0.7 and is almost independent of operating steam pressure (and, consequently, of steam flow) and air amount in steam-air mixture. It is suggested to estimate the amount of condensed steam in a cooler of stage I based on comparison of computed and experimental characteristics of stage II. Computation taking this hypothesis for main types of mass produced multistage ejectors into account shows that 0.60-0.85 of steam amount should be condensed in stage I of the cooler. For ejectors with "pipe-in-pipe" type coolers (EPO-3-200) and helical coolers (EO-30), amount of condensed steam may reach 0.93-0.98. Estimation of gas-dynamic resistance of coolers shows that resistance from steam side in coolers with built-in and remote pipe bundle constitutes 100-300 Pa. Gas-dynamic resistance of "pipein- pipe" and helical type coolers is significantly higher (3-6 times) compared with pipe bundle. However, performance by "dry" (atmospheric) air is higher for ejectors with relatively high gas-dynamic resistance of coolers than those with low resistance at approximately equal operating flow values of ejectors.

Relationship between the type and amount of physical activity and low back pain in Koreans aged 50 years and older.

PubMed

Kim, Won; Jin, Young Soo; Lee, Choon Sung; Hwang, Chang Ju; Lee, Sang Yoon; Chung, Sun G; Choi, Kyoung Hyo

2014-10-01

To examine the association between the type and amount of physical activity (PA) and low back pain (LBP) in people aged ≥50 years. Cross-sectional study. A nationwide survey. Data were obtained from the Fifth Korea National Health and Nutrition Examination Survey, which was conducted in 2010 and 2011. Overall, 1796 men and 2198 women aged ≥50 years were included. PA was categorized as vigorous, moderate, walking, strength exercises, or flexibility exercises. The total amount of PA was presented as quartiles of the total metabolic equivalent (MET)-minutes/week based on the PA questionnaire. Multivariate logistic regression analysis was performed to examine associations between LBP and the type and amount of PA. Odds ratio for LBP according to the type of PA and the quartiles of the total MET-minutes/week. After adjusting for age and body mass index, vigorous and moderate PA were associated with an increased risk of LBP in both men and women, whereas strength exercises were associated with a reduced risk of LBP. These associations were maintained after adjusting for all potential confounders. Subgroup analysis according to age revealed that these trends were most significantly demonstrated in women aged ≥65 years. The PA quartiles for total MET-minutes/week for men showed a U-shaped association with LBP, whereas only the fourth PA quartile for women showed an increased risk of LBP compared with the second quartile. These results suggest that both the type and amount of PA affect the development of LBP in people aged ≥50 years and thus activity modification might be helpful for prevention and management of LBP. Copyright © 2014 American Academy of Physical Medicine and Rehabilitation. Published by Elsevier Inc. All rights reserved.

Are work demands associated with mental distress? Evidence from women in rural India.

PubMed

Richardson, Robin A; Nandi, Arijit; Jaswal, Surinder; Harper, Sam

2017-12-01

High work demands might be a determinant of poor mental health among women in low- and middle-income countries, especially in rural settings where women experience greater amounts of labor-intensive unpaid work. Research originating from such settings is lacking. We estimated the cross-sectional association between work demands and mental distress among 3177 women living in 160 predominantly tribal communities in southern Rajasthan, India. A structured questionnaire captured the number of minutes women spent on various activities in the last 24 h, and we used this information to measure women's work demands, including the total work amount, nature of work (e.g., housework), and type of work (e.g., cooking). Mental distress was measured with the Hindi version of the 12-item General Health Questionnaire. We used negative binomial regression models to estimate the association between work demands (amount, nature, and type) and mental distress. On average, women spent more than 9.5 h a day on work activities. The most time, intensive work activity was caring for children, the elderly, or disabled (149 min). In adjusted models, we found a U-shaped association between work amount and mental distress. High amounts of housework were associated with higher distress, whereas paid work and farmwork amount were not. Certain types of housework, including collecting water and cleaning, were associated with increased distress scores. We found an association between aspects of work demands and mental distress. Research in other contexts where women perform high amounts of unpaid work, particularly within the home or farm, is warranted.

Two-step emulsification process for water-in-oil-in-water multiple emulsions stabilized by lamellar liquid crystals.

PubMed

Ito, Toshifumi; Tsuji, Yukitaka; Aramaki, Kenji; Tonooka, Noriaki

2012-01-01

Multiple emulsions, also called complex emulsions or multiphase emulsions, include water-in-oil-in-water (W/O/W)-type and oil-in-water-in-oil (O/W/O)-type emulsions. W/O/W-type multiple emulsions, obtained by utilizing lamellar liquid crystal with a layer structure showing optical anisotropy at the periphery of emulsion droplets, are superior in stability to O/W/O-type emulsions. In this study, we investigated a two-step emulsification process for a W/O/W-type multiple emulsion utilizing liquid crystal emulsification. We found that a W/O/W-type multiple emulsion containing lamellar liquid crystal can be prepared by mixing a W/O-type emulsion (prepared by primary emulsification) with a lamellar liquid crystal obtained from poly(oxyethylene) stearyl ether, cetyl alcohol, and water, and by dispersing and emulsifying the mixture in an outer aqueous phase. When poly(oxyethylene) stearyl ether and cetyl alcohol are each used in a given amount and the amount of water added is varied from 0 to 15 g (total amount of emulsion, 100 g), a W/O/W-type multiple emulsion is efficiently prepared. When the W/O/W-type multiple emulsion was held in a thermostatic bath at 25°C, the droplet size distribution showed no change 0, 30, or 60 days after preparation. Moreover, the W/O/W-type multiple emulsion strongly encapsulated Uranine in the inner aqueous phase as compared with emulsions prepared by one-step emulsification.

Optimizing the Prioritization of Natural Disaster Recovery Projects

DTIC Science & Technology

2007-03-01

collection, and basic utility and infrastructure restoration. The restoration of utilities can include temporary bridges, temporary water and sewage lines...interrupted such as in the case of the 9/11 disaster. Perhaps next time our enemies may target our power grid or water systems. It is the duty of...Transportation The amount and type of transportation infrastructure damage a repair project addresses Water The amount and type of water

Determination of soil erosion in a steep hill slope with different land-use types: a case study in Mertesdorf (Ruwertal/Germany).

PubMed

Hacisalihoglu, Sezgin

2007-04-01

Inappropriate land use is one of the main reasons for soil erosion and land degradation. Vine growing plays an important role in many semiarid regions all over the world as a permanent plant cover in terms of preventing erosion, sustainable use of land and water resources, defense against desertification and settling population in rural areas. In this paper, in a steep hill slope of the village Mertesdorf (Ruwertal/Germany), Algemeine boden abtrags gleichung (ABAG) have been applied to determine and compare the soil erosion amounts between the different land use types such as vine growing, forest lands, grasslands, shrubs and new forestations. The results show that the soil erosion amounts differs in a high ratio between the land use types. Soil erosion amounts in the vine growing areas are the highest (6.47 t/ha/year), then comes with 1.19 t/ha/year the over grazed grasslands and the lowest erosion amounts have been determined, as expected, in the forest lands (0.66 t/ha/year).

Carbon stocks of trees killed by bark beetles and wildfire in the western United States

USGS Publications Warehouse

Hicke, Jeffrey A.; Meddens, Arjan J.H.; Allen, Craig D.; Kolden, Crystal A.

2013-01-01

Forests are major components of the carbon cycle, and disturbances are important influences of forest carbon. Our objective was to contribute to the understanding of forest carbon cycling by quantifying the amount of carbon in trees killed by two disturbance types, fires and bark beetles, in the western United States in recent decades. We combined existing spatial data sets of forest biomass, burn severity, and beetle-caused tree mortality to estimate the amount of aboveground and belowground carbon in killed trees across the region. We found that during 1984-2010, fires killed trees that contained 5-11 Tg C year-1 and during 1997-2010, beetles killed trees that contained 2-24 Tg C year-1, with more trees killed since 2000 than in earlier periods. Over their periods of record, amounts of carbon in trees killed by fires and by beetle outbreaks were similar, and together these disturbances killed trees representing 9% of the total tree carbon in western forests, a similar amount to harvesting. Fires killed more trees in lower-elevation forest types such as Douglas-fir than higher-elevation forest types, whereas bark beetle outbreaks also killed trees in higher-elevation forest types such as lodgepole pine and Engelmann spruce. Over 15% of the carbon in lodgepole pine and spruce/fir forest types was in trees killed by beetle outbreaks; other forest types had 5-10% of the carbon in killed trees. Our results document the importance of these natural disturbances in the carbon budget of the western United States.

Erosion and deposition mode in a developing foreland basin: Temporal and spatial distribution of provenance in southwestern Taiwan

NASA Astrophysics Data System (ADS)

Yang, K. M.; Kun-an, H.; Chien, C. W.; Leh-chyun, W.; Chi-Cheng, Y.

2017-12-01

The foreland basin in southwestern Taiwan offers an idealistic example for the study of tectonostratigraphy in basin development. The subsidence analysis indicates that the recent basin development went through at least two rapid subsidence events, along with back-and-forth migration of the forebulge. This study aims to explore the interaction between the uplifting forebulge and coevally subsiding foredeep primarily based on petrofacies analysis, the results of which were then interpreted with the well-established tectonostratigraphic and biostratigraphic frameworks to infer the erosion and deposition mode during the basin development. The craton had been the sediment source to the west of the study area in the pre-orogenic period. In the initial stage of foreland basin development, the forebulge slowly elevated and started to obstruct sediment supplies from the craton. Before the period of NN19, the forebulge not only became the barrier of the most cratonic sediment supplies but also shed a major amount of detritus into the adjacent area. In addition, regional topographic relief, which was formed by syn-orogenic normal faulting during the NN11-15, locally changed the composition and transportation modes of the sediments; the exposed basement of the footwall also became the source of the sediments shed into the adjacent depo-centers. After the NN19, whole area was influenced predominantly by the orogenic belt from the east. Large amounts of slate fragments began to appear in the middle NN19 and relative percentage of the metamorphic lithics was increased upward and northward. As the orogen moved westward along with the foreland basin development, the studied area changed from the distal to proximal parts of the foredeep and sediment sources were controlled mainly by river systems derived from the orogen. The metamorphic lithics decreased southward and concentrated in the central part of the study area, suggesting that the slate fragments which were transported parallel with the orientation of submarine canyons since NN13 to the south of the study area. We propose that 1) from NN13 to NN18, the episodic subsidence in the foreland basin implies episodic movement of the orogenic belt, and 2) since the period of NN19, the orogenic belt and foreland basin has been developing in a continuous and steady state.

Characterization and standardization of Sabin based inactivated polio vaccine: proposal for a new antigen unit for inactivated polio vaccines.

PubMed

Westdijk, Janny; Brugmans, Debbie; Martin, Javier; van't Oever, Aart; Bakker, Wilfried A M; Levels, Lonneke; Kersten, Gideon

2011-04-18

GMP-batches of Sabin-IPV were characterized for their antigenic and immunogenic properties. Antigenic fingerprints of Sabin-IPV reveal that the D-antigen unit is not a fixed amount of antigen but depends on antibody and assay type. Instead of the D-antigen unit we propose standardization of IPV based on a combination of protein amount for dose and D-antigenicity for quality of the vaccine. Although Sabin-IPV type 2 is less immunogenic than regular wild type IPV type 2, the immunogenicity (virus neutralizing titers) per microgram antigen for Sabin-IPV type 2 is in the same order as for wild type serotypes 1 and 3. The latter observations are in line with data from human trials. This suggests that a higher dose of Sabin-IPV type 2 to compensate for the lower rat immunogenicity may not be necessary. Copyright © 2011 Elsevier Ltd. All rights reserved.

Using rate of divergence as an objective measure to differentiate between voice signal types based on the amount of disorder in the signal

PubMed Central

Calawerts, William M; Lin, Liyu; Sprott, JC; Jiang, Jack J

2016-01-01

Objective/Hypothesis The purpose of this paper is to introduce rate of divergence as an objective measure to differentiate between the four voice types based on the amount of disorder present in a signal. We hypothesized that rate of divergence would provide an objective measure that can quantify all four voice types. Study Design 150 acoustic voice recordings were randomly selected and analyzed using traditional perturbation, nonlinear, and rate of divergence analysis methods. ty Methods We developed a new parameter, rate of divergence, which uses a modified version of Wolf’s algorithm for calculating Lyapunov exponents of a system. The outcome of this calculation is not a Lyapunov exponent, but rather a description of the divergence of two nearby data points for the next three points in the time series, followed in three time delayed embedding dimensions. This measure was compared to currently existing perturbation and nonlinear dynamic methods of distinguishing between voice signals. Results There was a direct relationship between voice type and rate of divergence. This calculation is especially effective at differentiating between type 3 and type 4 voices (p<0.001), and is equally effective at differentiating type 1, type 2, and type 3 signals as currently existing methods. Conclusion The rate of divergence calculation introduced is an objective measure that can be used to distinguish between all four voice types based on amount of disorder present, leading to quicker and more accurate voice typing as well as an improved understanding of the nonlinear dynamics involved in phonation. PMID:26920858

Disentangling the root- and detritus-based food chain in the micro-food web of an arable soil by plant removal

PubMed Central

Glavatska, Olena; Müller, Karolin; Butenschoen, Olaf; Schmalwasser, Andreas; Kandeler, Ellen; Scheu, Stefan; Totsche, Kai Uwe

2017-01-01

Soil food web structure and function is primarily determined by the major basal resources, which are living plant tissue, root exudates and dead organic matter. A field experiment was performed to disentangle the interlinkage of the root-and detritus-based soil food chains. An arable site was cropped either with maize, amended with maize shoot litter or remained bare soil, representing food webs depending on roots, aboveground litter and soil organic matter as predominant resource, respectively. The soil micro-food web, i.e. microorganisms and nematodes, was investigated in two successive years along a depth transect. The community composition of nematodes was used as model to determine the changes in the rhizosphere, detritusphere and bulk soil food web. In the first growing season the impact of treatments on the soil micro-food web was minor. In the second year plant-feeding nematodes increased under maize, whereas after harvest the Channel Index assigned promotion of the detritivore food chain, reflecting decomposition of root residues. The amendment with litter did not foster microorganisms, instead biomass of Gram-positive and Gram-negative bacteria as well as that of fungi declined in the rooted zone. Likely higher grazing pressure by nematodes reduced microbial standing crop as bacterial and fungal feeders increased. However, populations at higher trophic levels were not promoted, indicating limited flux of litter resources along the food chain. After two years of bare soil microbial biomass and nematode density remained stable, pointing to soil organic matter-based resources that allow bridging periods with deprivation. Nematode communities were dominated by opportunistic taxa that are competitive at moderate resource supply. In sum, removal of plants from the system had less severe effects than expected, suggesting considerable food web resilience to the disruption of both the root and detrital carbon channel, pointing to a legacy of organic matter resources in arable soils. PMID:28704438

Mechanisms for Magnesium Isotopic Variation in Low-grade Metamorphosed Mudrocks from the British Caledonides

NASA Astrophysics Data System (ADS)

Wang, S.; Teng, F.; Rudnick, R. L.; Li, S.

2013-12-01

We report Mg isotope ratios for low-grade metamorphosed mudrocks from three lower Paleozoic basins (northern Lake District, southern Lake District and Southern Uplands) in the British Caledonides, previously analyzed for Li, Sr and Nd isotopes (Qiu et al., 2009, GCA), with the aim of understanding the behavior of Mg isotopes during subgreenschist-facies metamorphism, and the processes responsible for Mg isotopic variations in mudrocks. The δ26Mg of mudrocks varies greatly from -0.754 to 0.251, and displays no correlation with metamorphic grade, which ranges from diagenesis to subgreenschist-facies. Thus, low-grade metamorphism has no apparent influence on Mg isotopes. The variations instead likely reflect their provenance and mineralogical components. Samples from the northern Lake District, previously interpreted to derive from ancient, heavily weathered crust have δ26Mg (-0.06 × 0.11 on average) significantly heavier than that of average upper continental crust (~ -0.22), which is consistent with this interpretation. By contrast, mudrocks from the southern Lake District are characterized by low δ26Mg values (from -0.754 to -0.093) that require the presences of an unusually light component. The previously inferred provenance for these rocks of upper continental crust and arc volcanic detritus cannot explain such light isotopic compositions. Rather, such values may reflect the presence of carbonate in these samples and uptake of sea water Mg. Samples from the Southern Uplands, which contain the heaviest Li isotopes and ɛNd, and contain volcanic arc detritus, display Mg isotopic compositions divergent from a 'normal' mantle value (-0.25) towards both high and low δ26Mg values (from -0.742 to -0.079). Therefore, these mudrocks must contain a minimum of three end-members: mature felsic upper continental crust, arc lavas and carbonate. Given that limited Mg isotope fractionation occurs during low-grade metamorphism, Mg isotopes could be a potential tracer of provenance as well as carbonate involvement for fine-grained terrigenous sediments.

Disentangling the root- and detritus-based food chain in the micro-food web of an arable soil by plant removal.

PubMed

Glavatska, Olena; Müller, Karolin; Butenschoen, Olaf; Schmalwasser, Andreas; Kandeler, Ellen; Scheu, Stefan; Totsche, Kai Uwe; Ruess, Liliane

2017-01-01

Soil food web structure and function is primarily determined by the major basal resources, which are living plant tissue, root exudates and dead organic matter. A field experiment was performed to disentangle the interlinkage of the root-and detritus-based soil food chains. An arable site was cropped either with maize, amended with maize shoot litter or remained bare soil, representing food webs depending on roots, aboveground litter and soil organic matter as predominant resource, respectively. The soil micro-food web, i.e. microorganisms and nematodes, was investigated in two successive years along a depth transect. The community composition of nematodes was used as model to determine the changes in the rhizosphere, detritusphere and bulk soil food web. In the first growing season the impact of treatments on the soil micro-food web was minor. In the second year plant-feeding nematodes increased under maize, whereas after harvest the Channel Index assigned promotion of the detritivore food chain, reflecting decomposition of root residues. The amendment with litter did not foster microorganisms, instead biomass of Gram-positive and Gram-negative bacteria as well as that of fungi declined in the rooted zone. Likely higher grazing pressure by nematodes reduced microbial standing crop as bacterial and fungal feeders increased. However, populations at higher trophic levels were not promoted, indicating limited flux of litter resources along the food chain. After two years of bare soil microbial biomass and nematode density remained stable, pointing to soil organic matter-based resources that allow bridging periods with deprivation. Nematode communities were dominated by opportunistic taxa that are competitive at moderate resource supply. In sum, removal of plants from the system had less severe effects than expected, suggesting considerable food web resilience to the disruption of both the root and detrital carbon channel, pointing to a legacy of organic matter resources in arable soils.

Detrital zircon U-Pb reconnaissance of the Franciscan subduction complex in northwestern California

USGS Publications Warehouse

Dimitru, Trevor; Ernst, W. Gary; Hourigan, Jeremy K.; McLaughlin, Robert J.

2015-01-01

In northwestern California, the Franciscan subduction complex has been subdivided into seven major tectonostratigraphic units. We report U-Pb ages of ≈2400 detrital zircon grains from 26 sandstone samples from 5 of these units. Here, we tabulate each unit's interpreted predominant sediment source areas and depositional age range, ordered from the oldest to the youngest unit. (1) Yolla Bolly terrane: nearby Sierra Nevada batholith (SNB); ca. 118 to 98 Ma. Rare fossils had indicated that this unit was mostly 151-137 Ma, but it is mostly much younger. (2) Central Belt: SND; ca. 103 too 53 Ma (but poorly constrained), again mostly younger than previously thought. (3) Yager terrane: distant Idaho batholith (IB); ca. 52 to 50 Ma. Much of the Yager's detritus was shed during major core complex extension and erosion in Idaho that started 53 Ma. An eocene Princeton River-Princeton submarine canyon system transported this detritus to the Great Valley forearc basin and thence to the Franciscan trench. (4) Coastal terrane: mostly IB, ±SNB, ±nearby Cascade arc, ±Nevada Cenozoic ignimbrite belt; 52 to <32 Ma. (5) King Range terrane: dominated by IB and SNB zircons; parts 16-14 Ma based on microfossils. Overall, some Franciscan units are younger than previously thought, making them more compatible with models for the growth of subduction complexes by positive accretion. From ca. 118 to 70 Ma, Franciscan sediments were sourced mainly from the nearby Sierra Nevada region and were isolated from southwestern US and Mexican sources. From 53 to 49 Ma, the Franciscan was sourced from both Idaho and the Sierra Nevada. By 37-32 Ma, input from Idaho had ceased. The influx from Idaho probably reflects major tectonism in Idaho, Oregon, and Washington, plus development of a through-going Princeton River to California, rather than radical changes in the subduction system at the Franciscan trench itself.

Megafaunal communities in rapidly warming fjords along the West Antarctic Peninsula: hotspots of abundance and beta diversity.

PubMed

Grange, Laura J; Smith, Craig R

2013-01-01

Glacio-marine fjords occur widely at high latitudes and have been extensively studied in the Arctic, where heavy meltwater inputs and sedimentation yield low benthic faunal abundance and biodiversity in inner-middle fjords. Fjord benthic ecosystems remain poorly studied in the subpolar Antarctic, including those in extensive fjords along the West Antarctic Peninsula (WAP). Here we test ecosystem predictions from Arctic fjords on three subpolar, glacio-marine fjords along the WAP. With seafloor photographic surveys we evaluate benthic megafaunal abundance, community structure, and species diversity, as well as the abundance of demersal nekton and macroalgal detritus, in soft-sediment basins of Andvord, Flandres and Barilari Bays at depths of 436-725 m. We then contrast these fjord sites with three open shelf stations of similar depths. Contrary to Arctic predictions, WAP fjord basins exhibited 3 to 38-fold greater benthic megafaunal abundance than the open shelf, and local species diversity and trophic complexity remained high from outer to inner fjord basins. Furthermore, WAP fjords contained distinct species composition, substantially contributing to beta and gamma diversity at 400-700 m depths along the WAP. The abundance of demersal nekton and macroalgal detritus was also substantially higher in WAP fjords compared to the open shelf. We conclude that WAP fjords are important hotspots of benthic abundance and biodiversity as a consequence of weak meltwater influences, low sedimentation disturbance, and high, varied food inputs. We postulate that WAP fjords differ markedly from their Arctic counterparts because they are in earlier stages of climate warming, and that rapid warming along the WAP will increase meltwater and sediment inputs, deleteriously impacting these biodiversity hotspots. Because WAP fjords also provide important habitat and foraging areas for Antarctic krill and baleen whales, there is an urgent need to develop better understanding of the structure, dynamics and climate-sensitivity of WAP subpolar fjord ecosystems.

Intraguild predation and cannibalism among larvae of detritivorous caddisflies in subalpine wetlands

USGS Publications Warehouse

Wissinger, S.A.; Sparks, G.B.; Rouse, G.L.; Brown, W.S.; Steltzer, Heidi

1996-01-01

Comparative data from subalpine wetlands in Colorado indicate that larvae of the limnephilid caddisflies, Asynarchus nigriculus and Limnephilus externus, are reciprocally abundant among habitats - Limnephilus larvae dominate in permanent waters, whereas Asynarchus larvae dominate in temporary basins. The purpose of this paper is to report on field and laboratory experiments that link this pattern of abundance to biotic interactions among larvae. In the first field experiment, growth and survival were compared in single and mixed species treatments in littoral enclosures. Larvae, which eat mainly vascular plant detritus, grew at similar rates among treatments in both temporary and permanent habitats suggesting that exploitative competition is not important under natural food levels and caddisfly densities. However, the survival of Limnephilus larvae was reduced in the presence of Asynarchus larvae. Subsequent behavioral studies in laboratory arenas revealed that Asynarchus larvae are extremely aggressive predators on Limnephilus larvae. In a second field experiment we manipulated the relative sizes of larvae and found that Limnephilus larvae were preyed on only when Asynarchus larvae had the same size advantage observed in natural populations. Our data suggest that the dominance of Asynarchus larvae in temporary habitats is due to asymmetric intraguild predation (IGP) facilitated by a phenological head start in development. These data do not explain the dominance of Limnephilus larvae in permanent basins, which we show elsewhere to be an indirect effect of salamander predation. Behavioral observations also revealed that Asynarchus larvae are cannibalistic. In contrast to the IGP on Limnephilus larvae, Asynarchus cannibalism occurs among same-sized larvae and often involves the mobbing of one victim by several conspecifics. In a third field experiment, we found that Asynarchus cannibalism was not density-dependent and occurred even at low larval densities. We hypothesize that Asynarchus IGP and cannibalism provide a dietary supplement to detritus that may be necessary for the timely completion of development in these nutrient-poor, high-elevation wetlands.

Association of polychlorinated biphenyls (PCBs) with live algae and total lipids in rivers - A field-based approach

USGS Publications Warehouse

Fitzgerald, S.A.; Steuer, J.J.

2006-01-01

The association of PCBs and live algal cells in rivers was studied at four locations during four seasons in two Wisconsin rivers. Positive relations between particle-associated PCBs and both chlorophyll-a and algal carbon concentrations indicated that live algal cells were a significant sorption phase for dissolved PCBs. Large Pennate diatoms (Navicula, Synedra, Pinnularia, Diatoma, and Cocconeis), or more rarely, Euglenoids (Trachelomonas sp.), dominated most sample assemblages on an algal carbon basis. These assemblages made up the highest percentage of total SOC during spring (average=50%) and lowest during summer (average=15%). At the three impounded sites, most individual PCB congeners were relatively enriched in samples characterized by: (1) high concentrations of algal carbon (as a percent of SOC), (2) algal assemblages dominated (or co-dominated) by Euglenoids, and (3) high concentrations of total lipids. Despite relatively higher masses of sorbed PCBs in the most lipid-rich samples, there was no robust correlation between total lipid content and particle-associated PCBs when aggregating all samples from the study. A possible explanation is that PCBs are associated with other structural components in live algae and (or) departure from chemical equilibrium in the river due to algal growth kinetics. A kinetic uptake model was used to calculate the mass of PCBs associated with the total organic carbon content of live algae. Based on this model, PCBs were enriched in algal cells during bloom seasons (spring and fall) compared to non-bloom seasons (summer and winter). Further, although individual PCB congener partition coefficients (log) to live algal cells (range=5.3-6.4) overlapped to those for detritus (range=3.6-7.4), PCBs tended to be enriched in detrital carbon pools during non-bloom conditions. The larger range of estimated PCB partition coefficients for detritus likely reflects the more heterogeneous nature of this material compared to live algal cells.

Climatic effects on mosquito abundance in Mediterranean wetlands

PubMed Central

2014-01-01

Background The impact of climate change on vector-borne diseases is highly controversial. One of the principal points of debate is whether or not climate influences mosquito abundance, a key factor in disease transmission. Methods To test this hypothesis, we analysed ten years of data (2003–2012) from biweekly surveys to assess inter-annual and seasonal relationships between the abundance of seven mosquito species known to be pathogen vectors (West Nile virus, Usutu virus, dirofilariasis and Plasmodium sp.) and several climatic variables in two wetlands in SW Spain. Results Within-season abundance patterns were related to climatic variables (i.e. temperature, rainfall, tide heights, relative humidity and photoperiod) that varied according to the mosquito species in question. Rainfall during winter months was positively related to Culex pipiens and Ochlerotatus detritus annual abundances. Annual maximum temperatures were non-linearly related to annual Cx. pipiens abundance, while annual mean temperatures were positively related to annual Ochlerotatus caspius abundance. Finally, we modelled shifts in mosquito abundances using the A2 and B2 temperature and rainfall climate change scenarios for the period 2011–2100. While Oc. caspius, an important anthropophilic species, may increase in abundance, no changes are expected for Cx. pipiens or the salt-marsh mosquito Oc. detritus. Conclusions Our results highlight that the effects of climate are species-specific, place-specific and non-linear and that linear approaches will therefore overestimate the effect of climate change on mosquito abundances at high temperatures. Climate warming does not necessarily lead to an increase in mosquito abundance in natural Mediterranean wetlands and will affect, above all, species such as Oc. caspius whose numbers are not closely linked to rainfall and are influenced, rather, by local tidal patterns and temperatures. The final impact of changes in vector abundance on disease frequency will depend on the direct and indirect effects of climate and other parameters related to pathogen amplification and spillover on humans and other vertebrates. PMID:25030527

Litter P content drives consumer production in detritus-based streams spanning an experimental N:P gradient.

PubMed

Demi, Lee M; Benstead, Jonathan P; Rosemond, Amy D; Maerz, John C

2018-02-01

Ecological stoichiometry theory (EST) is a key framework for predicting how variation in N:P supply ratios influences biological processes, at molecular to ecosystem scales, by altering the availability of C, N, and P relative to organismal requirements. We tested EST predictions by fertilizing five forest streams at different dissolved molar N:P ratios (2, 8, 16, 32, 128) for two years and tracking responses of macroinvertebrate consumers to the resulting steep experimental gradient in basal resource stoichiometry (leaf litter %N, %P, and N:P). Nitrogen and P content of leaf litter, the dominant basal resource, increased in all five streams following enrichment, with steepest responses in litter %P and N:P ratio. Additionally, increases in primary consumer biomass and production occurred in all five streams following N and P enrichment (averages across all streams: biomass by 1.2×, production by 1.6×). Patterns of both biomass and production were best predicted by leaf litter N:P and %P and were unrelated to leaf litter %N. Primary consumer production increased most in streams where decreases in leaf litter N:P were largest. Macroinvertebrate predator biomass and production were also strongly positively related to litter %P, providing robust experimental evidence for the primacy of P limitation at multiple trophic levels in these ecosystems. However, production of predatory macroinvertebrates was not related directly to primary consumer production, suggesting the importance of additional controls for macroinvertebrates at upper trophic positions. Our results reveal potential drivers of animal production in detritus-based ecosystems, including the relative importance of resource quality vs. quantity. Our study also sheds light on the more general impacts of variation in N:P supply ratio on nutrient-poor ecosystems, providing strong empirical support for predictions that nutrient enrichment increases food web productivity whenever large elemental imbalances between basal resources and consumer demand are reduced. © 2017 by the Ecological Society of America.

Sand petrology and focused erosion in collision orogens: the Brahmaputra case

NASA Astrophysics Data System (ADS)

Garzanti, Eduardo; Vezzoli, Giovanni; Andò, Sergio; France-Lanord, Christian; Singh, Sunil K.; Foster, Gavin

2004-03-01

The high-relief and tectonically active Himalayan range, characterized by markedly varying climate but relatively homogeneous geology along strike, is a unique natural laboratory in which to investigate several of the factors controlling the composition of orogenic sediments. Coupling of surface and tectonic processes is most evident in the eastern Namche Barwa syntaxis, where the Tsangpo-Siang-Brahmaputra River, draining a large elevated area in south Tibet, plunges down the deepest gorge on Earth. Here composition of river sands changes drastically from lithic to quartzofeldspathic. After confluence with the Lohit River, draining the Transhimalayan-equivalent Mishmi arc batholiths, sediment composition remains remarkably constant across Assam, indicating subordinate contributions from Himalayan tributaries. Independent calculations based on petrographical, mineralogical, and geochemical data indicate that the syntaxis, representing only ∼4% of total basin area, contributes 35±6% to the total Brahmaputra sediment flux, and ∼20% of total detritus reaching the Bay of Bengal. Such huge anomalies in erosion patterns have major effects on composition of orogenic sediments, which are recorded as far as the Bengal Fan. In the Brahmaputra basin, in spite of very fast erosion and detrital evacuation, chemical weathering is not negligible. Sand-sized carbonate grains are dissolved partially in mountain reaches and completely in monsoon-drenched Assam plains, where clinopyroxenes are selectively altered. Plagioclase, instead, is preferentially weathered only in detritus from the Shillong Plateau, which is markedly enriched in microcline. Most difficult to assess is the effect of hydraulic sorting in Bangladesh, where quartz, garnet and epidote tend to be sequestered in the bedload and trapped on the coastal plain, whereas cleavable feldspars and amphiboles are concentrated in the suspended load and eventually deposited in the deep sea. High-resolution petrographic and dense-mineral studies of fluvial sands provide a basis for calculating sediment budgets, for tracing patterns of erosion in mountain belts, and for better understanding the complex dynamic feedback between surface processes and crustal-scale tectonics.