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1

Origin and Maintenance of the Benthic Nepheloid Layer Primary Investigator: Nathan Hawley -NOAA GLERL  

E-print Network

Origin and Maintenance of the Benthic Nepheloid Layer Primary Investigator: Nathan Hawley - NOAA of chemical substances. In the Great Lakes the benthic nepheloid layer (bnl) may play a significant role transparency in the benthic nepheloid layer. The deployments will be made at a greater depth than the previous

2

Benthic nepheloid layers in the Gulf of Maine and Alexandrium cyst inventories  

E-print Network

Benthic nepheloid layers in the Gulf of Maine and Alexandrium cyst inventories C.H. Pilskaln a nepheloid layer Suspended particulate matter Gulf of Maine Alexandrium fundyense Cysts a b s t r a c t Cysts residing in benthic nepheloid layers (BNLs) documented in the Gulf of Maine have been proposed

McGillicuddy Jr., Dennis J.

3

Response of the benthic nepheloid layer to near-inertial internal waves in southern Lake Michigan  

E-print Network

Response of the benthic nepheloid layer to near-inertial internal waves in southern Lake Michigan of suspended sediment in the benthic nepheloid layer. Although a direct causal link between internal wave action and changes in the nepheloid layer could not be established, the data suggest that local

4

Seasonal benthic nepheloid layer in the Gulf of Riga, Baltic Sea: Sources, structure and geochemical interactions  

Microsoft Academic Search

The sources of particles, as well as the geochemical structure and interfacial exchange were studied for the summer benthic nepheloid layer of the shallow (50m) Gulf of Riga. The material was sampled at nine stations during three cruises of August 2001–2003 with a main focus on the deep waters. Suspended particulate matter (SPM) and its major (N, Si, P, Al,

Aivars Yurkovskis

2005-01-01

5

Observations of Nepheloid Layers Made With an Autonomous Vertical Profiler  

E-print Network

Observations of Nepheloid Layers Made With an Autonomous Vertical Profiler Nathan Hawley nepheloid layer located near the base of the thermocline and a benthic nepheloid layer at the bottom together. Changes in both the intermediate nepheloid layer and the benthic nepheloid layer occurred

6

Suspended sediment transport in the benthic nepheloid layer in southeastern Lake Michigan  

SciTech Connect

Time series observations of water temperature, water transparency, and current velocity were made at four stations located on the lake slope of southeastern Lake Michigan. The observations show that during stratified conditions the benthic nepheloid layer is probably not maintained by the local resuspension of bottom sediment. A more likely source is sediment resuspended further inshore and then transported across the shelf and slope during downwelling events. Internal wave action may be an important source of energy for this transport. Although sediment trap studies suggest that resuspension does occur, it is more likely that increased fluxes observed near the bottom are due to the vertical redistribution of material already in suspension. A benthic nepheloid layer also exists at times during the unstratified period, when occassionally enough energy reaches the bottom to directly resuspend bottom material at the sites.

Hawley, N. [Great Lakes Environmental Research Lab., Ann Arbor, MI (United States); Lesht, B.M. [Argonne National Lab., IL (United States)

1995-02-01

7

Quantifying tidal signatures of the benthic nepheloid layer in Gaoping Submarine Canyon in Southern Taiwan  

Microsoft Academic Search

The benthic nepheloid layer (BNL) has been observed in the head region of the Gaoping\\/Kaoping Submarine Canyon (KPSC) throughout a year. The top of the BNL could be as high as 100m above the canyon floor in which the suspended sediment concentration (SSC) could be as high as 30mg\\/l. In the BNL, sand-sized particles comprise the largest size-class in the

James T. Liu; Yu Huai Wang; I-Huan Lee; Ray T. Hsu

2010-01-01

8

Benthic Nepheloid Layers and the Ekman Thermal Pump  

Microsoft Academic Search

Near-bottom layers of high and homogeneous turbidity capped by high-turbidity gradients are found on the continental rise and the Blake-Bahama outer ridge off the coast of the eastern United States. These layers average about 200 m in thickness and are characterized by suspended sediment concen. trations of about 100 g\\/1. The layers are highly time variable in their thickness and

Stephen Eittreim; Pierre E. Biscaye; Anthony F. Amos

1975-01-01

9

Benthic nepheloid layers in the Gulf of Maine and Alexandrium cyst inventories  

NASA Astrophysics Data System (ADS)

Cysts residing in benthic nepheloid layers (BNLs) documented in the Gulf of Maine have been proposed as a possible source of inoculum for annual blooms of a toxic dinoflagellate in the region. Herein we present a spatially extensive data set of the distribution and thickness of benthic nepheloid layers in the Gulf of Maine and the abundance and inventories of suspended Alexandrium fundyense cysts within these near-bottom layers. BNLs are pervasive throughout the gulf and adjacent Bay of Fundy with maximum layer thicknesses of 50-60 m observed. Mean BNL thickness is 30 m in the eastern gulf and Bay of Fundy, and 20 m in the western gulf. Cyst densities in the near-bottom particle resuspension layers varied by three orders of magnitude across the gulf with maxima of 105 cysts m-3. An important interconnection of elevated BNL cyst densities is observed between the Bay of Fundy, the Maine Coastal Current and the south-central region of the gulf. BNL cyst inventories estimated for the eastern and western gulf are each on the order of 1015 cysts, whereas the BNL inventory in the Bay of Fundy is on the order of 1016. Although BNL cyst inventories in the eastern and western gulf are 1-2 orders of magnitude smaller than the abundance of cysts in the upper 1 cm of sediment in those regions, BNL and sediment-bound cyst inventories are comparable in the Bay of Fundy. The existence of widespread BNLs containing substantial cyst inventories indicates that these near-bottom layers represent an important source of germinating A. fundyense cysts in the region.

Pilskaln, C. H.; Hayashi, K.; Keafer, B. A.; Anderson, D. M.; McGillicuddy, D. J.

2014-05-01

10

Benthic nepheloid layers in the Gulf of Maine and Alexandrium cyst inventories  

PubMed Central

Cysts residing in benthic nepheloid layers (BNLs) documented in the Gulf of Maine have been proposed as a possible source of inoculum for annual blooms of a toxic dinoflagellate in the region. Herein we present a spatially extensive data set of the distribution and thickness of benthic nepheloid layers in the Gulf of Maine and the abundance and inventories of suspended Alexandrium fundyense cysts within these near-bottom layers. BNLs are pervasive throughout the gulf and adjacent Bay of Fundy with maximum layer thicknesses of 50–60 m observed. Mean BNL thickness is 30 m in the eastern gulf and Bay of Fundy, and 20 m in the western gulf. Cyst densities in the near-bottom particle resuspension layers varied by three orders of magnitude across the gulf with maxima of 105 cysts m?3. An important interconnection of elevated BNL cyst densities is observed between the Bay of Fundy, the Maine Coastal Current and the south-central region of the gulf. BNL cyst inventories estimated for the eastern and western gulf are each on the order of 1015 cysts, whereas the BNL inventory in the Bay of Fundy is on the order of 1016 . Although BNL cyst inventories in the eastern and western gulf are 1–2 orders of magnitude smaller than the abundance of cysts in the upper 1 cm of sediment in those regions, BNL and sediment-bound cyst inventories are comparable in the Bay of Fundy. The existence of widespread BNLs containing substantial cyst inventories indicates that these near-bottom layers represent an important source of germinating A. fundyense cysts in the region.

Pilskaln, C.H.; Hayashi, K.; Keafer, B.A.; Anderson, D.M.; McGillicuddy, D.J.

2014-01-01

11

Sedimentary sources of old high molecular weight dissolved organic carbon from the ocean margin benthic nepheloid layer  

SciTech Connect

Average {sup 14}C ages of dissolved organic carbon (DOC) in the ocean are 3--6,000 years, and are influenced by old DOC from continental margins. However, sources of DOC from terrestrial, autochthonous, and sedimentary organic carbon seem to be too young to be responsible for the old DOC observed in the ocean. Since colloidal organic carbon (COC, i.e., high molecular weight DOC), which is chemically very similar to that of bulk DOC, can be effectively isolated from seawater using cross-flow ultrafiltration, it can hold clues to sources and pathways of DOC turnover in the ocean. Radiocarbon measurements on COC in the water column and benthic nepheloid layer (BNL) from two continental margin areas (the Middle Atlantic Bight and the Gulf of Mexico) and controlled laboratory experiments were carried out to study sources of old DOC in the ocean margin areas. Vertical distributions of suspended particulate matter (SPM), particulate organic carbon (POC), nitrogen (PON), and DOC in the water column and bottom waters near the sediment-water interface all demonstrate a well developed benthic nepheloid layer in both ocean margin areas. COC from the BNL was much older than COC from the overlying water column. These results, together with strong concentration gradients of SPM, POC, PON, and DOC, suggest a sedimentary source for organic carbon species and possibly for old COC as well in BNL waters. This is confirmed by the results from controlled laboratory experiments. The heterogeneity of {Delta}{sup 14}C signatures in bulk SOC thus points to a preferential release of old organic components from sediment resuspension, which can be the transport mechanism of the old benthic COC observed in ocean margin areas. Old COC from continental margin nepheloid layers may thus be a potential source of old DOC to the deep ocean.

Guo, L. Santschi, P.H.

2000-02-01

12

Resuspension and particle transport in the benthic nepheloid layer in and near Fram Strait in relation to faunal abundances and 234Th depletion  

Microsoft Academic Search

The West Spitsbergen Current, flowing northward through Fram Strait, causes a benthic nepheloid layer (BNL) on the western slope of the Yermak Plateau. This BNL is weaker on the eastern side of the Plateau and absent on the Greenland side of the Fram Strait, where the East Greenland Current flows south. In this BNL we find throughout a depletion of

R. Meyer; B. Rudels; E. Rachor

2002-01-01

13

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

NASA Astrophysics Data System (ADS)

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

Chassefiere, Bernard

1990-09-01

14

Tidal Signatures of the Benthic Nepheloid Layer (BNL) in the Gaoping/Kaoping Submarine Canyon off Southwestern Taiwan  

NASA Astrophysics Data System (ADS)

Temporal and spatial variations of benthic nepheloid layer (BNL) have been observed in the head region of the Gaoping/Kaoping Submarine Canyon (KPSC) along the canyon thalweg in different seasons between 1999 and 2000. The top of the BNL could be as high as 100 m above the canyon floor whose suspended sediment concentration (SSC) could be as high as 30 mg/l. In the BNL, silt comprises the largest size-class in the suspended sediment population. In 2000, 2002, and 2004 three taut-line moorings were deployed at different locations in the head region of the KPSC for one month. Time series measurements of along- canyon flow velocity, water temperature, and the volume concentration (VC) of clay, very-fine-to-medium silt, coarse silt and sand size-classes were obtained near the canyon floor from each mooring. Results show that the BNL is strongly modulated by the tides in the descending order at semidiurnal, diurnal, and spring-neap frequencies. In the course of a semidiurnal tidal cycle, the flood (up-canyon) current brings colder water from seaward part of the canyon and the SSC and thickness of the BNL increases. The SSC near the canyon floor also increases in response to the peaks of flood and ebb currents of the semidiurnal tide. The tidal-to-total energy ratio (ER) for the along-canon flow is between 70-80%, and between 50-80% among the suspended sediment of clay, very-fine-to-medium silt, coarse silt and sand size-classes. M2 is the most important constituent in the along-canyon flow, water temperature, and the VC of the four size-classes. The local phase difference between the forcing (velocity), and the responses (temperature and VC) at the M2 frequency suggest the a mixture of progressive and standing waves and that topographic effect caused the phase varied along the canyon. The VC tidal amplitude ratio between M4 and M2 constituents of the four size-classes indicates that the temporal fluctuations of the suspended sediment concentration in the BNL are highly nonlinear. The generation of nonlinearity could be through the flow-topography interaction and through the alternate entrainment and deposition of suspended sediment in the course of a semidiurnal tidal cycle. At this point, the relationship among barotropic tides, internal tides, and typhoon events and BNL is not clear. The role of the BNL in the sediment transport and sedimentation in submarine canyons worldwide is also not fully understood. Studies on these subjects in the KPSC are in progress.

Liu, J. T.; Lee, I.; Wang, Y.

2008-12-01

15

Nepheloid layer distribution in the Benguela upwelling area offshore Namibia.  

E-print Network

Nepheloid layer distribution in the Benguela upwelling area offshore Namibia. Maik Inthorna of nepheloid layers across the outer shelf and upper continental slope off Namibia was studied during a cruise to relate the nepheloid layers to hydrographic structures. The particle content of surface water

Mohrholz, Volker

16

Research papers Sediment resuspension and nepheloid layers induced by long internal  

E-print Network

Research papers Sediment resuspension and nepheloid layers induced by long internal solitary waves online 7 November 2013 Keywords: Internal solitary wave Sediment Nepheloid layer Numerical modelling is mainly within boluses, while seaward movement is within intermediate nepheloid layers. Several

17

An intermittent, intermediate nepheloid layer in Emerald Basin, Scotian Shelf  

Microsoft Academic Search

Intermittent, intermediate nepheloid layers were observed on the Scotian Shelf in late April, 1987. These 10–30 m thick nepheloid layers were found between 140 and 200 m in the main part of Emerald Basin and 120–140 m in the northern basin, well below the surface mixed layer and about 90 m above the sea bed in both cases. Both biological

Kumiko Azetsu-Scott; Bruce D. Johnson; Brian Petrie

1995-01-01

18

The nepheloid bottom layer and water masses at the shelf break of the western Ross Sea  

Microsoft Academic Search

In the austral summers of 2000\\/2001 and 2002\\/2003 the Italian CLIMA Project carried out two oceanographic cruises along the northwestern margin of the Ross Sea, where the Antarctic Bottom Water forms. Here there is an interaction between the water masses on the sea floor of the outer shelf and slope with a consequent evolution of benthic nepheloid layers and an

Marco Capello; Giorgio Budillon; Laura Cutroneo; Sergio Tucci

2009-01-01

19

Intermediate nepheloid layers observed over the continental margins off Oregon  

Microsoft Academic Search

Intermediate nepheloid layers were observed by a beam transmissometer operating at 650 nm during 3 to 8 November 1976 over the continental shelf and slope off Oregon. Two well defined intermediate nepheloid layers were observed. One was located at about 150 m depth and extended westward from a point 10 NM offshore. The second was at about 375 m depth

H. Pak; J. R. V. Zaneveld

1978-01-01

20

Nepheloid layer dynamics in the northern Portuguese shelf  

Microsoft Academic Search

A general hydrographic and nephelometric survey of the NW Portuguese continental shelf and upper slope was undertaken, under winter and spring conditions. The nepheloid layer dynamics along the shelf during three cruises were controlled, principally by the following factors: (a) the hydrography of the shelf-slope waters, i.e. the nepheloid layers followed isopycnals and water masses; (b) prevalence of upwelling or

A. Oliveira; J Vitorino; A Rodrigues; J. M Jouanneau; J. A Dias; O Weber

2002-01-01

21

Intermediate nepheloid layers observed off Oregon and Washington  

Microsoft Academic Search

Two distinct kinds of particle maxima (nepheloid layers) were observed off Oregon in November 1977 and off Washington in October 1978 by an in situ light transmissometer: one in the thermocline in the euphotic zone and the other at intermediate depth well below the thermocline. The thermocline nepheloid layer is associated with well-defined maxima of dissolved oxygen, chlorophyll-a, and phaeophytin,

Hasong Pak; J. Ronald; V. Zaneveld; J. Kitchen

1980-01-01

22

Intermediate nepheloid layers observed off Oregon and Washington  

SciTech Connect

Two distinct kinds of particle maxima were observed off Oregon in November 1977 and off Washington in October 1978 by an in situ light transmissometer: one in the thermocline in the euphotic zone and the other at intermediate depth well below the thermocline. The thermocline nepheloid layer is associated with well-defined maxima of dissolved oxygen, chlorophyll-a, and phaeophytin, and these associations suggest that the nepheloid layer is primarily composed of phytoplankton undergoing active photosynthesis. The intermediate nepheloid layer is found in connection with the bottom waters near the shelf break and shares some of the characteristic properties of the bottom water: high concentration of suspended particles, low concentrations of dissolved oxygen, chlorophyll-a, and phaeophytin. The particle size distributions in the intermediate nepheloid layer are different from those in the clear water above the nepheloid layer but similar to those in the bottom nepheloid layer. Two hypotheses for the generation of intermediate nepheloid layers, settling and horizontal advection, are examined, and the data support the latter hypothesis.

Pak, H.; Zaneveld, J.R.V.; Kitchen, J.

1980-11-20

23

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

USGS Publications Warehouse

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

Shideler, G.L.

1981-01-01

24

Responses of deep-water shrimp populations to intermediate nepheloid layer detachments on the Northwestern Mediterranean continental margin  

Microsoft Academic Search

A clear link between the distribution of intermediate nepheloid layer detachments on the Northwestern Mediterranean continental margin and the population structure of five congeneric megafaunal species of deep-water benthic shrimps inhabiting different depth ranges between 100 and 1100m was found. The results of the multidisciplinary approach presented in this study provide evidence for the ecological conditions that affect the spatial

Pere Puig; Francesc Sardà; Albert Palanques

2001-01-01

25

Light Scattering and Suspended Matter in Nepheloid Layers  

Microsoft Academic Search

tion of suspended particles with diameters greater than 2.22  was measured with a Coulter counter. Nepheloid layers with thicknesses of up to 930 meters were observed at 38 of the 46 stations. Except for greater total concentrations, particle size distributions of material obtained from within the layers were indistinguishable from those obtained from the clearer water above. Statistical analysis

William S. Plank; Hasong Pak

1972-01-01

26

Nepheloid layer distribution in the Benguela upwelling area offshore Namibia  

Microsoft Academic Search

The distribution of nepheloid layers across the outer shelf and upper continental slope off Namibia was studied during a cruise with R.V. Meteor in late austral summer 2003. Optical measurements, carried out with a transmissometer and a backscattering fluorometer, are correlated with suspended particulate matter (SPM) and particulate organic carbon (POC) values from water sample filtration. Conductivity-temperature-depth and oxygen data

Maik Inthorn; Volker Mohrholz; Matthias Zabel

2006-01-01

27

The nepheloid layer and horizontal sedimentary matter fluxes in the Norwegian Sea  

Microsoft Academic Search

In this paper, the results of long-term studies of the nepheloid layer in the Norwegian Sea in the Komsomolets test area are considered. Its principal characteristics such as its thickness, the particulate matter concentration in the\\u000a nepheloid layer, and its standing crop are presented. The nepheloid layer is formed by the near-bottom current, which, together\\u000a with the particulate standing crop,

V. N. Lukashin; A. D. Shcherbinin

2007-01-01

28

Nepheloid layer distribution in the Gulf of Valencia, northwestern Mediterranean  

NASA Astrophysics Data System (ADS)

According to previous studies, the surface circulation of the Gulf of Valencia (GoV) is characterized by a convergence between the southwestward Northern Current carrying old Atlantic Waters (oAW) and the northward intrusions of recent Atlantic Waters (rAW) imported through the Ibiza Channel. This paper focuses on the distribution of the suspended sediment concentration in the GoV obtained from a dense grid of CTD observations in June 1995 during the oceanographic cruise MESO'95 (MESOscale processes). We evaluate the relation between currents, water masses and the nepheloid structure at the time of the survey. Results showed higher suspended sediment concentration (SSC) in the oAW than in the rAW. At the shelf-break depth, an important detachment of particulate matter was observed off Cap La Nao, extending seawards all across the Ibiza Channel. The presence of this intermediate nepheloid layer detachment indicates a preferential off-shelf sediment export at the southern end of the GoV, where the orientation of the continental margin changes, and oAW and rAW merge. On the continental slope, several nepheloid layers detachments were observed between 400 and 600 m, where the Levantine Intermediate Water (LIW) interacts with the seafloor, suggesting the possible presence of internal waves causing sediment resuspension and/or maintaining particles in suspension in the mid-slope region. A bottom nepheloid layer was also observed at deeper locations along the central and southern part of the GoV continental slope, but not at the Ibiza Sill.

Ribó, M.; Puig, P.; Salat, J.; Palanques, A.

2013-02-01

29

The nepheloid bottom layer and water masses at the shelf break of the western Ross Sea  

NASA Astrophysics Data System (ADS)

In the austral summers of 2000/2001 and 2002/2003 the Italian CLIMA Project carried out two oceanographic cruises along the northwestern margin of the Ross Sea, where the Antarctic Bottom Water forms. Here there is an interaction between the water masses on the sea floor of the outer shelf and slope with a consequent evolution of benthic nepheloid layers and an increase in total particulate matter. We observed three different situations: (a) the presence of triads (bottom structures characterized by a concomitant jump in turbidity, temperature, and salinity data) and high re-suspension phenomena related to the presence of the Circumpolar Deep Water and its mixing with cold, salty shelf waters associated with gravity currents; (b) the absence of triads with high re-suspension, implying that when the gravity currents are no longer active the benthic nepheloid layer may persist until the suspended particles settle to the sea floor, suggesting that the turbidity data can be used to study recent gravity current events; and (c) the absence of turbidity and sediment re-suspension phenomena supports the theory that a steady situation had been re-established and the current interaction no longer occurred or had finished sometime before.

Capello, Marco; Budillon, Giorgio; Cutroneo, Laura; Tucci, Sergio

2009-06-01

30

Phytoplankton associations with the variable nepheloid layer on the Texas continental shelf  

Microsoft Academic Search

Four 24-h cruises occupied a station at 33m depth on the Texas continental shelf during June, July, September and November 1978. Samples collected at 4-h intervals investigated the state of selected physical, chemical and biological factors potentially important to phytoplankton associated with the nepheloid layer. The nepheloid layer varied in thickness and in density within and between cruises. Phytoplankton biomass

Daniel Kamykowski; Jerry L. Bird

1981-01-01

31

The importance of subsurface nepheloid layers in transport and delivery of sediments to the eastern Cariaco Basin, Venezuela  

E-print Network

The importance of subsurface nepheloid layers in transport and delivery of sediments to the eastern: Nepheloid layers Cariaco Basin Particulate organic matter Sediment transport a b s t r a c t Optical of September 2003 and 2006. Our results suggest that nepheloid layers originating at the mouth of small

Benitez-Nelson, Claudia

32

The nepheloid layer and horizontal sedimentary matter fluxes in the Norwegian Sea  

NASA Astrophysics Data System (ADS)

In this paper, the results of long-term studies of the nepheloid layer in the Norwegian Sea in the Komsomolets test area are considered. Its principal characteristics such as its thickness, the particulate matter concentration in the nepheloid layer, and its standing crop are presented. The nepheloid layer is formed by the near-bottom current, which, together with the particulate standing crop, determines the horizontal flux of the sedimentary matter over the continental slope. Also presented are data about the currents in different years of observations as well as estimates of the horizontal fluxes.

Lukashin, V. N.; Shcherbinin, A. D.

2007-12-01

33

Bottom nepheloid layers and bottom mixed layers observed on the continental shelf off Oregon  

Microsoft Academic Search

One hundred and seventy pairs of temperature and light transmission profiles were obtained by simultaneous conductivity-temperature-depth (CTD) and light transmissometer casts in three cruises on the R\\/V Yaquina over the continental shelf off Oregon. These were analyzed for bottom nepheloid layers (BNL) and bottom mixed layers (BML). Supplementing these data were 1177 CTD profiles taken during the Coastal Upwelling Ecosystems

Hasong Pak; J. Ronald V. Zaneveld

1977-01-01

34

Geochemistry of rare earth elements in benthic layer particulate matter and sediments of Lake Superior  

Microsoft Academic Search

Samples of suspended particulate matter from the nepheloid layer and the benthic sediment layer (fluff zone), as well as core samples of the underlying sediment column, were collected from two locations in Lake Superior during manner submersible dives. All samples were analyzed for eight rare earth elements (REE's), biogenic silica, and organic carbon. The REE patterns indicate lithogenous material is

Annette M. Olivarez; Robert M. Owen; David T. Long

1989-01-01

35

Optics, Acoustics, and Stress in a Nearshore Bottom Nepheloid Layer Emmanuel Boss  

E-print Network

Optics, Acoustics, and Stress in a Nearshore Bottom Nepheloid Layer Emmanuel Boss School of Marine dynamics on the distribution of particles in the bottom boundary layer; · Understand how the properties depth of 15 m as part of the Coupled Boundary Layers and Air-Sea Transfer (CBLAST) program, sponsored

Boss, Emmanuel S.

36

Optics, Acoustics, and Stress in a Nearshore Bottom Nepheloid Layer Emmanuel Boss  

E-print Network

Optics, Acoustics, and Stress in a Nearshore Bottom Nepheloid Layer Emmanuel Boss School of Marine the effects of aggregation dynamics on the size distribution of particles in the bottom boundary layer; 2 in the bottom boundary layer. The #12;instrumentation is mounted on bottom tripods and includes a 9-wavelength

Boss, Emmanuel S.

37

Nepheloid layers and internal waves over continental shelves and slopes  

Microsoft Academic Search

Theoretical and laboratory results indicate that bottom velocities within shoaling internal gravity waves intensify upslope approximately inversely proportional to the water depth. The elevated velocities (and bottom stresses) caused by shoaling and, possibly, breaking internal waves might explain the generation and maintenance of near-bottom nepheloid zones and attached turbid plumes that have been observed over certain continental shelves and slopes.

D. A. Cacchione; D. E. Drake

1986-01-01

38

Optics, Acoustics, and Stress in a Nearshore Bottom Nepheloid Layer Emmanuel Boss  

E-print Network

Optics, Acoustics, and Stress in a Nearshore Bottom Nepheloid Layer Emmanuel Boss School of Marine stresses and how this packaging of sediment affects optical and acoustical properties in the water column and acoustical properties of the water column. 3. Develop models describing the associations between particle

Boss, Emmanuel S.

39

Observations of intermediate nepheloid layers on the northern California continental margin  

Microsoft Academic Search

Conductivity–temperature–depth and transmissometer surveys were undertaken to investigate the characteristics and seasonal nature of intermediate nepheloid layers (INLs) over the outer shelf and upper slope of the northern California margin, near Eureka, CA. Observed INLs could generally be grouped into one of two categories: INLs that formed and spread seaward from the continental shelf, and INLs generated at continental slope

E. E. McPhee-Shaw; R. W. Sternberg; B. Mullenbach; A. S. Ogston

2004-01-01

40

Nepheloid layers and internal waves over continental shelves and slopes  

USGS Publications Warehouse

Theoretical and laboratory results indicate that bottom velocities within shoaling internal gravity waves intensify upslope approximately inversely proportional to the water depth. The elevated velocities (and bottom stresses) caused by shoaling and, possibly, breaking internal waves might explain the generation and maintenance of near-bottom nepheloid zones and attached turbid plumes that have been observed over certain continental shelves and slopes. This process is proposed as an explanation of zones of relatively low transmissibility that emanate from the upper continental slope near Newport submarine canyon off southern California. ?? 1986 Springer-Verlag New York Inc.

Cacchione, D.A.; Drake, D.E.

1986-01-01

41

Role of internal waves in the generation of nepheloid layers on the northwestern Alboran slope: Implications for continental margin shaping  

Microsoft Academic Search

The role of internal waves in the sediment dynamics of the northwestern Alboran continental slope was investigated in a selected area around the Guadiaro submarine canyon. Nepheloid layer distribution was identified using closely spaced CTD\\/transmissometer profiles collected during two hydrographic surveys. A well-defined pattern of suspended sediment distribution consisting of surface, intermediate, and near-bottom nepheloid layers was found. Intermediate and

P. Puig; A. Palanques; J. Guillén; M. El Khatab

2004-01-01

42

The importance of subsurface nepheloid layers in transport and delivery of sediments to the eastern Cariaco Basin, Venezuela  

NASA Astrophysics Data System (ADS)

Optical transmissometer measurements were coupled with particulate organic matter (POM) observations to understand suspended sediment composition and distribution in the eastern Cariaco Basin during the rainy seasons of September 2003 and 2006. Our results suggest that nepheloid layers originating at the mouth of small mountainous rivers discharging into the eastern Basin are a major delivery mechanism of terrigenous sediments to the Basin interior. Intermediate nepheloid layers (INL) were observed near the shelf break (˜100 m) and appear to effectively transport terrigenous material laterally from the shelf to deep waters, thereby providing a plausible supply mechanism of the terrestrial material observed in sediment traps. These findings highlight the importance of small, local rivers in the Cariaco Basin as sources of terrestrial material. In contrast, these nepheloid layers contained only limited POM. When this information is combined with published sediment trap POM data, it suggests that nepheloid layers may not be a primary mechanism for delivering terrigenous POM to the deeper waters of the basin during the rainy season. Rather, BNL may redistribute marine-derived POM from shallow waters to the Basin's interior by providing ballast materials, particularly during episodic events driven by wind and precipitation. Though we have determined that nepheloid layers play an important role in the seaward transport of particulate material in the Cariaco Basin, their composition and temporal variability have not been fully characterized. This is critical to understand lateral particle transport, since nepheloid layers constitute a significant source of sediment to the deep Cariaco Basin.

Lorenzoni, Laura; Thunell, Robert C.; Benitez-Nelson, Claudia R.; Hollander, David; Martinez, Nahysa; Tappa, Eric; Varela, Ramón; Astor, Yrene; Muller-Karger, Frank E.

2009-12-01

43

Comparison of pelagic and nepheloid layer marine snow: implications for carbon cycling  

Microsoft Academic Search

Marine snow from upper and mid-water (i.e., pelagic) depths on the California margin is texturally and compositionally different from that traveling in the nepheloid layer. Transmission electron microscopy shows that pelagic marine snow consists primarily of bioclasts (e.g., diatom frustules, foram tests), organic matter, and microbes. These components are entrained as discrete particles or small aggregates (?10 ?m in diameter)

Barbara Ransom; Kevin F Shea; Patti Jo Burkett; Richard H Bennett; Roy Baerwald

1998-01-01

44

Estuarine sediment transport by gravity-driven movement of the nepheloid layer, Long Island Sound  

Microsoft Academic Search

Interpretation of sidescan-sonar imagery provides evidence that down-slope gravity-driven movement of the nepheloid layer\\u000a constitutes an important mode of transporting sediment into the basins of north-central Long Island Sound, a major US East\\u000a Coast estuary. In the Western Basin, this transport mechanism has formed dendritic drainage systems characterized by branching\\u000a patterns of low backscatter on the seafloor that exceed 7.4 km

L. J. Poppe; K. Y. McMullen; S. J. Williams; J. M. Crocker; E. F. Doran

2008-01-01

45

Removal of thorium-234 by scavenging in the bottom nepheloid layer of the ocean  

Microsoft Academic Search

Concentrations of 234Th were measured in deep-sea bottom waters to assess the extent of chemical scavenging near the ocean floor. At five stations in the eastern tropical Pacific, where no appreciable bottom nepheloid layer (BNL) was observed, total 234Th was in secular equilibrium with its parent 238U, confirming earlier published results. In contrast, samples from a well-developed BNL in the

Michael P. Bacon; Michiel M. Rutgers van der Loeff

1989-01-01

46

Geochemistry of rare earth elements in benthic layer particulate matter and sediments of Lake Superior  

SciTech Connect

Samples of suspended particulate matter from the nepheloid layer and the benthic sediment layer (fluff zone), as well as core samples of the underlying sediment column, were collected from two locations in Lake Superior during manner submersible dives. All samples were analyzed for eight rare earth elements (REE's), biogenic silica, and organic carbon. The REE patterns indicate lithogenous material is a dominant component in all samples but that significant amounts of REE's derived from the water column are also present. Biogenous sources (diatom shells), on the other hand, contribute negligibly to the REE geochemistry of these samples. Statistical analyses of the geochemical data suggest that the mechanism by which REE's are removed from the water column involve scavenging by particulate phases of Fe. The Precambrian banded iron formations around Lake Superior represent an abundant source of dissolved and particulate Fe to the lake. Absolute concentrations of both REE's and Fe are greater in the fluff layer than in the nepheloid layer; however, the nepheloid layer contains 24-57% more REE's on a per unit Fe basis. This difference may be due to longer exposure of nepheloid particulate matter to lake waters than fluff, diminished scavenging efficiency at higher Fe levels, and/or to the fact that particulate matter in the fluff layer is derived from surficial sediments which have lost some REE's during early diagenesis. A comparison of the Ce-anomalies of the suspended layers with the sediments indicates the sediments have undergone some degree of early diagenesis.

Olivarez, A.M.; Owen, R.M.; Long, D.T.

1989-01-01

47

The importance of subsurface nepheloid layers in transport and delivery of sediments to the eastern Cariaco Basin, Venezuela  

Microsoft Academic Search

Optical transmissometer measurements were coupled with particulate organic matter (POM) observations to understand suspended sediment composition and distribution in the eastern Cariaco Basin during the rainy seasons of September 2003 and 2006. Our results suggest that nepheloid layers originating at the mouth of small mountainous rivers discharging into the eastern Basin are a major delivery mechanism of terrigenous sediments to

Laura Lorenzoni; Robert C Thunell; Claudia R. Benitez-Nelson; David Hollander; Nahysa Martinez; Eric Tappa; Ramón Varela; Yrene Astor; Frank E. Muller-Karger

2009-01-01

48

Sediment resuspension and nepheloid layers induced by long internal solitary waves shoaling orthogonally on uniform slopes  

NASA Astrophysics Data System (ADS)

Two-dimensional, nonlinear and nonhydrostatic field-scale numerical simulations are used to examine the resuspension, dispersal and transport of mud-like sediment caused by the shoaling and breaking of long internal solitary waves on uniform slopes. The patterns of erosion and transport are both examined, in a series of test cases with varying conditions. Shoreward sediment movement is mainly within boluses, while seaward movement is within intermediate nepheloid layers. Several relationships between properties of the suspended sediment and control parameters are determined such as the horizontal extent of the nehpeloid layers, the total mass of resuspended sediment and the point of maximum bed erosion. The numerical results provide a plausible explanation for acoustic backscatter patterns observed during and after the shoaling of internal solitary wavetrains in a natural coastal environment. The results may be useful in the interpretation of some sedimentary structures, and suggest an effective mechanism for offshore dispersal of muddy sediments.

Bourgault, D.; Morsilli, M.; Richards, C.; Neumeier, U.; Kelley, D. E.

2014-01-01

49

Formation of thick bottom nepheloid layers in the western Mediterranean basin after major dense shelf water cascading events  

NASA Astrophysics Data System (ADS)

The analysis of a compilation of deep CTD cast conducted in the western Mediterranean from 1998 to 2009 have documented the role that dense shelf water cascading off the Gulf of Lions plays in transporting suspended particulate matter from the coastal regions down to the basin. Deep CTD casts revealed that after the 1999 and 2005-2006 major cascading events, the Western Mediterranean Deep Water was characterized by the presence of a thick bottom nepheloid layer that scaled in thickness with a thermo-haline anomaly generated by the mixture of dense waters formed by deep convection at open sea and by cascading off the Gulf of Lions shelf. Thicknesses of the observed thermo-haline and turbidity anomalies were variable, being up to 650 and 1450 m thick after the1999 and 2005-2006 events, respectively. Concentrations within the bottom nepheloid layers in the central part of the basin were usually around 0.3 mg/l (i.e. 0.1 mg/l above background levels), reaching higher concentrations close to the continental rise, with near-bottom values up to 2 mg/l. These bottom nepheloid layers could be observed to progress from the Gulf of Lions and Catalan margin towards the central part of the northwestern Mediterranean basin, reaching south of the Balearic Islands and west of Sardinia after the 1999 event, and covering the entire basin after the 2005 and 2006 events. Thickness and concentration of the bottom nepheloid layer diminished with distance away from their source and also with time. The turbidity signal could be barely distinguished one year after the 1999 event, but the one generated after the 2005-2006 events can be still clearly detected, confirming that fine particles in deep bottom nepheloid layers can have residence times of several years.

Puig, Pere; Durrieu de Madron, Xavier; Schroeder, Katrin; Salat, Jordi; López-Jurado, José Luis; Pietro Gasparini, Gian; Palanques, Albert; Emelianov, Mikhail; Karageorgis, Aristomenis; Theocharis, Alekos

2010-05-01

50

Estuarine sediment transport by gravity-driven movement of the nepheloid layer, Long Island Sound  

USGS Publications Warehouse

Interpretation of sidescan-sonar imagery provides evidence that down-slope gravity-driven movement of the nepheloid layer constitutes an important mode of transporting sediment into the basins of north-central Long Island Sound, a major US East Coast estuary. In the Western Basin, this transport mechanism has formed dendritic drainage systems characterized by branching patterns of low backscatter on the seafloor that exceed 7.4 km in length and progressively widen down-slope, reaching widths of over 0.6 km at their southern distal ends. Although much smaller, dendritic patterns of similar morphology are also present in the northwestern part of the Central Basin. Because many contaminants display affinities for adsorption onto fine-grained sediments, and because the Sound is affected by seasonal hypoxia, mechanisms and dispersal pathways by which inorganic and organic sediments are remobilized and transported impact the eventual fate of the contaminants and environmental health of the estuary. ?? Springer-Verlag 2008.

Poppe, L.J.; McMullen, K.Y.; Williams, S.J.; Crocker, J.M.; Doran, E.F.

2008-01-01

51

Estuarine sediment transport by gravity-driven movement of the nepheloid layer, Long Island Sound  

NASA Astrophysics Data System (ADS)

Interpretation of sidescan-sonar imagery provides evidence that down-slope gravity-driven movement of the nepheloid layer constitutes an important mode of transporting sediment into the basins of north-central Long Island Sound, a major US East Coast estuary. In the Western Basin, this transport mechanism has formed dendritic drainage systems characterized by branching patterns of low backscatter on the seafloor that exceed 7.4 km in length and progressively widen down-slope, reaching widths of over 0.6 km at their southern distal ends. Although much smaller, dendritic patterns of similar morphology are also present in the northwestern part of the Central Basin. Because many contaminants display affinities for adsorption onto fine-grained sediments, and because the Sound is affected by seasonal hypoxia, mechanisms and dispersal pathways by which inorganic and organic sediments are remobilized and transported impact the eventual fate of the contaminants and environmental health of the estuary.

Poppe, L. J.; McMullen, K. Y.; Williams, S. J.; Crocker, J. M.; Doran, E. F.

2008-08-01

52

COMPOSITION AND BIOLOGICAL IMPLICATIONS OF A NEPHELOID LAYER OVER THE INNER AGULHAS BANK NEAR MOSSEL BAY, SOUTH AFRICA  

Microsoft Academic Search

Water from the nepheloid layer associated with the mud belts on the inner Agulhas Bank near Mossel Bay contained a concentration of 19,0 mg.l total suspended particulate matter. Particulate organic matter (POM) formed only 7 per cent of this and was 3–4 times less than that of comparable coastal waters. Particle size distribution was skewed to the lower size range

P. Zoutendyk; I. R. Duvenage

1989-01-01

53

Suspended particulate loads and transports in the nepheloid layer of the abyssal Atlantic Ocean  

USGS Publications Warehouse

Vertical profiles of light scattering from over 1000 L-DGO nephelometer stations in the Atlantic Ocean have been used to calculate mass concentrations of suspended particles based on a calibration from the western North American Basin. From these data are plotted the distributions of particulate concentrations at clear water and in the more turbid near-bottom water. Clear water is the broad minimum in concentration and light scattering that occurs at varying mid-depths in the water column. Concentrations at clear water are as much as one-to-two orders of magnitude lower than those in surface water but still reflect a similar geographic distribution: relatively higher concentrations at ocean margins, especially underneath upwelling areas, and the lowest concentrations underneath central gyre areas. These distributions within the clear water reflect surface-water biogenic productivity, lateral injection of particles from shelf areas and surface circulation patterns and require that the combination of downward vertical and horizontal transport processes of particles retain this pattern throughout the upper water column. Below clear water, the distribution of standing crops of suspended particulate concentrations in the lower water column are presented. The integration of mass of all particles per unit area (gross particulate standing crop) reflects a relative distribution similar to that at the surface and at clear water levels, superimposed on which is the strong imprint of boundary currents along the western margins of the Atlantic. Reducing the gross particulate standing crop by the integral of the concentration of clear water yields a net particulate standing crop. The distribution of this reflects primarily the interaction of circulating abyssal waters with the ocean bottom, i.e. a strong nepheloid layer which is coincident with western boundary currents and which diminishes in intensity equatorward. The resuspended particulate loads in the nepheloid layer of the basins west of the Mid-Atlantic Ridge, resulting from interaction of abyssal currents with the bottom, range from ??? 2 ?? 106 tons in the equatorial Guyana Basin to ??? 50 ?? 106 tons in the North American Basin. The total resuspended particulate load in the western basins (111 ?? 106 tons) is almost an order of magnitude greater than that in the basins east of the Mid-Atlantic Ridge (13 ?? 106 tons). The net northward flux of resuspended particles carried in the AABW drops from ??? 8 ?? 106 tons/year between the southern and northern ends of the Brazil Basin and remains ??? 1 ?? 106 tons/year across the Guyana Basin. ?? 1977.

Biscaye, P.E.; Eittreim, S.L.

1977-01-01

54

Acquiring Peak Samples from Phytoplankton Thin Layers and Intermediate Nepheloid Layers by an Autonomous Underwater Vehicle with Adaptive Triggering  

NASA Astrophysics Data System (ADS)

Phytoplankton thin layers (PTLs) affect many fundamental aspects of coastal ocean ecology including primary productivity, development of harmful algal blooms (HABs) and the survival and growth of zooplankton and fish larvae. Intermediate nepheloid layers (INLs) that contain suspended particulate matter transported from the bottom boundary layer of continental shelves and slopes also affect biogeochemistry and ecology of ocean margins. To better understand the impacts of these types of layers, we have developed an adaptive sampling method for an autonomous underwater vehicle (AUV) to detect a layer (adjusting detection parameters in situ), acquire water samples from peaks in the layer, and acquire control samples outside the layer. We have used the method in a number of field experiments with the AUV Dorado, which is equipped with ten water samplers (called "gulpers"). In real time, the algorithm tracks background levels of fluorescence and optical backscatter and the peaks' baseline to ensure that detection is tuned to the ambient conditions. The algorithm cross-checks fluorescence and backscatter signals to differentiate PTLs from INLs. To capture peak water samples with minimal delay, the algorithm exploits the AUV's sawtooth (i.e., yo-yo) trajectory: the vehicle crosses the detected layer twice in one yo-yo cycle. At the first crossing, it detects the layer's peak and saves its signal height. Sampling is triggered at the second crossing when the signal reaches the saved peak height plus meeting additional timing and depth conditions. The algorithm is also capable of triggering gulpers to acquire control samples outside the layer for comparison with ambient water. The sequence of peak and control samples can be set based on need. In recent AUV Dorado missions, the algorithm triggered the gulpers to acquire peak and control samples from INLs and PTLs in Monterey Bay. Zooplankton analysis of some peak samples showed very high concentrations of mussel and barnacle larvae in addition to a variety of copepod signals.

Zhang, Y.; McEwen, R.; Ryan, J. P.; Bellingham, J. G.; Harvey, J.; Vrijenhoek, R.

2010-12-01

55

Thick bottom nepheloid layers in the western Mediterranean generated by deep dense shelf water cascading  

NASA Astrophysics Data System (ADS)

The analysis of a compilation of deep CTD casts conducted in the western Mediterranean from 1998 to 2011 has documented the role that dense water formation, and particularly deep dense shelf water cascading off the Gulf of Lions, plays in transporting suspended particulate matter from the coastal regions down to the basin. Deep CTD casts reveal that after the 1999 and 2005-2006 deep cascading events the Western Mediterranean Deep Water (WMDW) was characterized by the presence of a thick bottom nepheloid layer (BNL) that corresponded in thickness with a thermohaline anomaly generated by the mixture of dense waters formed by deep convection in the open sea and by deep cascading. This BNL can be hundreds of meters thick and in the central part of the basin usually exhibits suspended sediment concentrations of <0.1 mg/l above background levels, reaching higher concentrations close to the continental rise, with near-bottom peaks >1 mg/l. After winter 1999 the BNL spread from the Gulf of Lions and the Catalan margin over the northwestern Mediterranean basin, reaching west of the Balearic Islands and the Ligurian Sea, while after winters 2005-2006 the BNL covered the entire western Mediterranean basin. Thickness and concentration of the BNL tend to diminish with time but this trend is highly dependent on the volume of dense water generated, both by convection and cascading. After winter 1999 the BNL signal vanished in one year, but after winters 2005-2006 it lasted for longer and the turbidity signal can still be distinguished at present (2011). Particle size distribution in the BNL reveals the presence of large aggregates up to 1 mm in size formed by a mixture of single particles with the same bimodal grain size distribution as the surface sediments found in the northwestern Mediterranean slope and basin. Results presented in this paper highlight the fact that the WMDW can be periodically affected by the arrival of new dense waters loaded with suspended particles mainly introduced by resuspension processes during major cascading events, being a key process that could ultimately affect deep-sea biogeochemical cycles in the western Mediterranean.

Puig, Pere; Madron, Xavier Durrieu de; Salat, Jordi; Schroeder, Katrin; Martín, Jacobo; Karageorgis, Aristomenis P.; Palanques, Albert; Roullier, François; Lopez-Jurado, José Luis; Emelianov, Mikhail; Moutin, Thierry; Houpert, Loïc

2013-04-01

56

Transfer mechanisms and biogeochemical implications in the bottom nepheloid layer. A case study of the coastal zone off the Rhone River (France)  

Microsoft Academic Search

Particles supplied to the coastal zone are involved in numerous biogeochemical processes that rapidly modify particulate composition. The Bottom Nepheloid Layer (BNL) thus plays a significant role on the budget of elements transferred to the coastal zone. Although it should not be ignored in flux studies, little is known about the quantity and the quality of particles transported within it,

J. J. Naudin; G. Cauwet

1997-01-01

57

Stalk-eyed views of the Gulf of Maine--Through a nepheloid layer dimly School of Marine Sciences, 5706 Aubert Hall, University of Maine, Orono, Maine, 04469-5706  

E-print Network

1 Stalk-eyed views of the Gulf of Maine--Through a nepheloid layer dimly School of Marine Sciences of the beam attenuation coefficient from the surface to the depth that they occupy during daylight. Spring

Jumars, Pete

58

Microbial activity and particulate matter in the benthic nepheloid layer (BNL) of the deep Arabian Sea  

Microsoft Academic Search

The distribution of suspended particulate matter as well as bacterial biomass and activity in near-bottom waters was investigated at six stations in the deep Arabian Sea (2000–4500m water depth). Water samples were obtained from heights between 0.1–1000 m above bottom (m a.b.) with a bottom water sampler or with a CTD-rosette during two cruises in May 1997 and February 1998.

Antje Boetius; Barbara Springer; Carolin Petry

2000-01-01

59

The Response of the Benthic Nepheloid Layer to a Downwelling Event  

Microsoft Academic Search

Time series observations of water temperature, current velocity, and water transparency were made at three elevations at a mooring in southwestern Lake Ontario over a 14-day period. Although a strong downwelling event occurred during the deployment, there was no indication of either local sediment resuspension or of downslope transport of suspended material. Our observations, when combined with those of Hawley

Nathan Hawley; C. R. Murthy

1995-01-01

60

Variability of bottom nepheloid layers near the Flower Garden Banks, Gulf of Mexico  

E-print Network

/I) and transmissivity (Martek and sea Tech) for controlled water tank calibration study. 31 SPM concentration (ug/I) and transmissivity (a/m) for March 1981 pHISH stations. SpM concentration (pg/I) and transmissivity ( 0/m) for July 1981 PHISH stations. BNL type... Plot of dye speed versus height from bottom during October 1980 sub dives. 27 12 March 1981 PHZSH profile 16S. Notice bottom transmissivity spike. 30 13 Relation between Martek and Sea Tech transmissivity. 32 Intermediate turbid layers of March...

Cecil, Thomas Martin

2012-06-07

61

Benthic boundary layer processes in the Lower Florida Keys  

USGS Publications Warehouse

This special issue of Geo-Marine Letters, "Benthic Boundary Layer Processes in the Lower Florida Keys," includes 12 papers that present preliminary results from the Key West Campaign. The Dry Tortugas and Marquesas Keys test sites were selected by a group of 115 scientists and technicians to study benthic boundary layer processes in a carbonate environment controlled by bioturbation and biogeochemical processes. Major activities included remote sediment classification; high-frequency acoustic scattering experiments; sediment sampling for radiological, geotechnical, biological, biogeochemical, physical, and geoacoustic studies; and hydrodynamic studies using an instrumented tetrapod. All these data are being used to improve our understanding of the effects of environmental processes on sediment structure and behavior.

Lavoie, D.L.; Richardson, M.D.; Holmes, C.

1997-01-01

62

A Study of the Optical Characteristics of the Suspended Particles in the Benthic Nepheloid Layer of the Scotian Rise  

Microsoft Academic Search

Light transmission profiles have been used to study the optical properties of the suspended particles which are characteristic of the area of the Scotian Rise in the North Atlantic Ocean. This area is typified by very strong bottom currents and a highly variable bedform morphology. A good correlation (r = 0.96) has been found between the suspended volume and the

Richard W. Spinrad; J. Ronald V. Zaneveld; James C. Kitchen

1983-01-01

63

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

Microsoft Academic Search

Mass-physical properties of the surficial (upper 5 m) sediments on the Gulf of Lions continental margin were analysed, from more than 100 short (1 m) and longer (5 m) cores obtained during several cruises. Data include water content, unit weight, Atterberg limits (liquid limit, plastic limit, plasticity index), shear strength and compression index, and are used to determine: first, the

Bernard Chassefiere

1990-01-01

64

The Benthic Nepheloid Layer (BNL) North of the Keweenaw Peninsula in Lake Superior: Composition, Dynamics, and Role in Sediment Transport  

Microsoft Academic Search

As part of the Keweenaw Interdisciplinary Transport Experiment in Superior (KITES) project, measurements were made of the extent and the composition of the BNL in Lake Superior off the northwest coast of the Keweenaw Peninsula. Between 1998 and 2000, transmissometer profiles were obtained frequently along three transects oriented perpendicularly to the coast. Large-volume water samples were filtered, and the BNL

Noel R. Urban; J. Jeong; Yingtao Chai

2004-01-01

65

Development of Technologies for Coastal Observing Systems and the Study of Benthic Boundary Layer Processes  

NSF Publications Database

Development of Technologies for Coastal Observing Systems and the Study of Benthic Boundary Layer ... Information Program Title: Development of Technologies for Coastal Observing Systems and the Study ...

66

Time-space variability of the near bottom nepheloid layer at the West Sahara continental slope and shelf  

Microsoft Academic Search

Turbidity vertical profiles, being good indicators of sediment concentration in the near bottom oceanic layer, were obtained by Sea Tech Mark nephelometer simultaneously with Neil Brown temperature, salinity, and density profiles. Measurements were carried out at the continental slope and shelf off the Western Sahara at the regular grid (45 miles×41 miles) of one hundred stations separated by five minutes

M. A. Evdoshenko; I. D. Lozovatski

1994-01-01

67

Evaluation of processes occurring in the bottom nepheloid layer (BNL) of an eastern Mediterranean area using 234Th/238U disequilibria.  

PubMed

Particle-reactive radionuclide (234)Th and its ratios with the conservative (238)U were used to trace the marine processes occurring over short timescales in the bottom nepheloid layer (BNL) of seven stations in the Saronikos Gulf and the Elefsis Bay (Greece) during three seasons (summer 2008, autumn 2008 and winter 2009). Summer was considered as a steady season where low physical processes occur and stratification is well established, autumn as a commutative period and winter as period of extensive trawling and physical activities. The obtained ratio profiles showed excess of (234)Th relative to (238)U in the BNL of the sampling area during summer, caused by the dissolved fraction of (234)Th. During autumn, the situation was different with large (234)Th deficit throughout the water column leading to large export fluxes of particles from the water column. Finally, during winter the ratios showed that predominant phenomenon in the area was likely resuspension of bottom sediments. The resuspension signature was additionally evaluated by total suspended matter (TSM) inventories in the BNL. Despite the intense resuspension, small scavenging of dissolved (234)Th was recorded in the BNL resulting in high residence times of dissolved (234)Th. A 1 order of magnitude difference between dissolved and particulate (234)Th residence times was observed indicating that scavenging from dissolved to particulate (234)Th could be highly variable and, as a result, the Saronikos Gulf is a highly dynamic environment, in terms of temporal and spatial particle uptake and removal. Comparing these values to literature ones consistent results were obtained. The possibility of sediment resuspension in the BNL during winter was amplified by the bloom of phytoplankton resulting in even decreased residence times of particulate (234)Th (average values). In contrast, the respective residence times of the dissolved fraction of (234)Th in the BNL were higher showing a maximum in winter at the stations where resuspension concluded. Nevertheless, (234)Th cycling in the area is not controlled by TSM, probably due to the presence of colloids, which could play an essential role in (234)Th scavenging. PMID:23334526

Evangeliou, Nikolaos; Florou, Heleny

2013-09-01

68

On the links between a river’s hyperpycnal plume and marine benthic nepheloid layer in the wake of a typhoon  

NASA Astrophysics Data System (ADS)

In 2010 two moorings each configured with a CTD and an ADCP, one with an additional non-sequential sediment trap (NSST), were deployed in the head region of the Gaoping Submarine Canyon 3 days after the typhoon-induced peaks of the runoff and suspended sediment concentration (SSC) of the Gaoping River in southern Taiwan. Our data show a demarcation between tidal and hyperpycnal regimes in the temperature, salinity, and flow fields. The latter existed in the first 5 days out of the 18-day deployment, as defined by higher water density due to high SSC. Several lines of evidence indicate the presence of the tail end of a hyperpycnal turbidity current (HTC), including the retention of warm water near the canyon floor, high SSC, down-canyon directed residual flow and its vertical structure, and high terrestrial fraction (larger than 70%) of the organic particles carried by the flow. The decreasing mass flux during the deployment is also an indication of a waning HTC. Our findings also show that the vertical flow structure and the direction of the gravity-driven down-canyon HTC were retarded by the instantaneous up-canyon-directed tidal oscillations in the submarine canyon.

Hsu, Ray T.; Liu, James T.; Su, Chih-Chieh; Kao, Shuh-Ji; Chen, Shih-Nan; Kuo, Fang-Hsu; Huang, Jeff C.

2014-09-01

69

Dynamics of the benthic boundary layer in a strongly forced stratified lake  

Microsoft Academic Search

Field data and the three-dimensional (3D) Estuary and Lake Computer Model (ELCOM) were used to investigate the impact of periodic\\u000a forcing on the structure and dynamics of the benthic boundary layer (BBL) in Lake Kinneret, Israel, a large lake that experiences\\u000a strong thermal stratification and wind forcing events. Microstructure data were used to derive the thickness of the BBL and

Clelia Luisa Marti; Jörg Imberger

2006-01-01

70

Internal tidal bores and bottom nepheloid layers  

Microsoft Academic Search

During a littoral optical environment project field study in shallow water off Oceanside, California, large spikes in optical attenuation (dominated by suspended particles) were observed in a near-bottom mooring. Using moored current meters together with aircraft remote imaging overflights and profiling anchor stations, we established that the spikes were associated with the trailing edges of internal solitary waves of depression

Donald R. Johnson; Alan Weidemann; W. Scott Pegau

2001-01-01

71

Processes in the benthic boundary layer at continental margins and their implication for carbon mineralization  

NASA Astrophysics Data System (ADS)

The presentation evaluates the role of biogeochemical processes in the cycling of organic matter within the benthic boundary layer (BBL). The data suggest an important additional mechanism of carbon mineralization at hydrodynamically energetic continental margins: that the near-bed fluid layer of the BBL is a major region for organic carbon minerlisation and the amount of carbon finally buried depends on the BBL exposure time of aggregates. Long term data reveal a tidally modulated flow field withe repetitive cycling of particles between seabed and suspension, representing altogether a situation of prolonged particle resuspension time. Data on the bioavailability of organic carbon within the BBL suggest fast mineralization rates but also a carbon protection mechanism so that labile organic carbon can still reach areas far offslope.

Thomsen, L.; Hedges, J.; Gust, G.; van Weering, T.

2003-04-01

72

An instrument system for monitoring and sampling suspended sediment in the benthic boundary layer  

USGS Publications Warehouse

An instrument system has been constructed that can monitor and sample suspended sediment distributions in the benthic boundary layer. It consists of miniature nephelometers and suspended sediment samplers placed within one meter of the seabed. The system is capable of continuously monitoring suspended sediment profiles at eight levels between 14 and 100 cm above the seabed and collecting suspended sediment samples at four levels (20, 50, 70 and 100 cm) at three times during a deployment period. The suspended sediment system is designed to fit onto the instrumented tripod GEOPROBE which contains four electromagnetic current meters, pressure sensor, bottom stereo camera, two temperature sensors, transmissometer, and a Savonius rotor current meter. Sensor operation, data recording, and sediment sampling events are synchronized. Thus detailed measurements of the near-bottom flow conditions are made concurrently with suspended sediment measurements. The combined system has been used in sediment transporting environments within San Francisco Bay, California, and Puget Sound, Washington. ?? 1986.

Sternberg, R.W.; Johnson, R.V., II; Cacchione, D.A.; Drake, D.E.

1986-01-01

73

Chemistry of water and sediment from the benthic boundary layer at a site in the Northwest Atlantic Ocean  

Microsoft Academic Search

A primary objective of this study was to characterize the corrosive potential of the benthic boundary layer at a site where selected metal alloys were being exposed. Those properties of sea water and sediment likely to affect the corrosion of alloys that were measured in this study include salinity, pH, scale-forming cations, redox potential, dissolved gases, heavy metal ions, abrasive

1979-01-01

74

Nepheloid structure and hydrographic control on the Barcelona continental margin, northwestern Mediterranean  

Microsoft Academic Search

Contemporary processes controlling the off-shelf transport of sediment particles on the Barcelona continental margin were identified using CTD\\/transmissometer profiles during three hydrographic surveys. A well defined pattern of particulate matter distribution consisting in surface, intermediate and near-bottom nepheloid layers related with topographic and hydrographic structures was observed. Suspended sediment supplied by rivers or resuspended on the shelf is transferred to

Pere Puig; Albert Palanques

1998-01-01

75

Nitrogen15 Isotope Enrichment in Benthic Boundary Layer Gases of a Stratified Eutrophic Iron and Manganese Rich Lake  

Microsoft Academic Search

The applicability of the natural abundance of nitrogen gas isotope ratios was used to indicate the spatial distribution of\\u000a nitrogen transformations in the water column and sediment pore waters of Lake Ngapouri, a small (area 0.19 km2), monomictic, eutrophic lake in the Taupo Volcanic Zone, North Island, New Zealand. Samples were collected from the epilimnion,\\u000a hypolimnion, benthic boundary layer and at

L. K. Pearson; C. H. Hendy; D. P. Hamilton; W. B. Silvester

76

Bioturbation and Holocene sediment accumulation fluxes in the north-east Atlantic Ocean (Benthic Boundary Layer experiment sites)  

Microsoft Academic Search

Bioturbation and Holocene sediment accumulation are quantified in the three experimental areas of the Benthic Boundary Layer (BENBO) programme by means of the natural radionuclides 14C and 210Pb and the artificial radionuclides 137Cs and 241Am. The Holocene accumulation rates, determined by the radiocarbon method, are 4.4 and 6.5cmkyr?1 at sites B (Rockall Plateau, 1100m water depth) and C (Feni Drift,

J. Thomson; L. Brown; S. Nixon; G. T. Cook; A. B. MacKenzie

2000-01-01

77

Finite dispersal of a separative nepheloid plume by an internal hydraulic jump in a tropical mountainous river estuary  

NASA Astrophysics Data System (ADS)

This paper investigates the dynamics of an internal hydraulic jump in a river plume and associated suspended sediment dispersal. Field investigations were undertaken into the river plume generated by the Herbert River, Australia, following a moderate flood event induced by Cyclone Fritz in 2004. The forced plume experiences an abrupt transition from supercritical to subcritical via an internal hydraulic jump, as defined by a mode-1 internal Froude number computed using the phase speeds from the Taylor-Goldstein equation. The hydraulic theory of a two-layer stratified flow was used to identify the plume shape and the mechanical energy loss within the jump. The hydraulic jump energy loss is primarily transferred to the buoyancy-driven potential energy, uplifting the river plume. Intense stratification decreases the bottom stress, damping the resuspension. Therefore, a separative nepheloid dispersal system occurs at the jump section. Both the upper and lower nepheloid flows are confined to the inner shelf, but have different dispersal behaviors and mechanisms. The upper nepheloid flow, which is primarily controlled by advection and settling, satisfies an exponential decay law of the total suspended sediment concentrations versus the offshore distance. The lower nepheloid flow dominated by deposition is detached seaward near the lift-off point of the river plume. A turbidity front associated with the jump may accumulate a large quantity of suspended sediments, enhancing sediment release from the river plume. These findings will promote in-depth understanding of both the cross-shelf sediment dispersal and muddy deposit on the shelf.

Wu, Jiaxue; Ametistova, Lioudmila; Heron, Malcolm; Lemckert, Charles J.; Kalangi, Patrice

2006-11-01

78

PII S0016-7037(99)00335-X Sedimentary sources of old high molecular weight dissolved organic carbon from the ocean  

E-print Network

from the ocean margin benthic nepheloid layer LAODONG GUO* and PETER H. SANTSCHI Department. Radiocarbon measurements on COC in the water column and benthic nepheloid layer (BNL) from two continental nepheloid layer in both ocean margin areas. 14 C values of COC isolated from the BNL (ranging from 362 4

Guo, Laodong

79

Sediment Resuspension and Transport in Lake Michigan Primary Investigator: Nathan Hawley -NOAA GLERL  

E-print Network

Nepheloid Layer (BNL), which is found in many ocean basins and all of the Great Lakes are also not well responsible for maintaining the benthic nepheloid layer was submitted to the Journal of Geophysical Research in the thickness of the benthic nepheloid layer occurred with the same periodicity as changes in other water

80

Trophic relationships of deep-sea calanoid copepods from the benthic boundary layer of the Santa Catalina Basin, California  

NASA Astrophysics Data System (ADS)

Benthopelagic zooplankton were collected and preserved in situ in the benthic boundary layer of the Santa Catalina Basin, using a multiple sampling opening-closing net system attached to the DSRV Alvin. Gut content analysis performed with transmission electron microscopy (TEM) showed that the majority of benthopelagic calanoid copepods examined were predominantly detritivores. They had ingested detritus and associated bacteria, including metal-precipitating bacteria; no attached enteric bacteria were observed in the copepods' guts. The gut particles indicated generalized feeding and qualitatively resembled material present in the environment at the time of collection, i.e. suspended particles, large fecal pellets, particles from the surface layer of the sediment, and phaeodia of phaeodarian radiolarians. TEM was necessary for identifying some of the amorphous material in copepod guts as either digested tissue or detrital material; some of the amorphous material was unidentifiable even with the resolution of TEM. TEM was also essential for detecting metal-precipitating bacteria and their capsules from the copepod guts and from particles in the water. Because they ingest metal-precipitating bacteria, detritivorous copepods may influence the distribution of metals in the ocean.

Gowing, Marcia M.; Wishner, Karen F.

1986-07-01

81

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

NASA Astrophysics Data System (ADS)

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

Ferrón, S.; Ho, D. T.; Hales, B. R.

2010-12-01

82

Light availability in the coastal ocean: impact on the distribution of benthic photosynthetic organisms and their contribution to primary production  

NASA Astrophysics Data System (ADS)

One of the major features of the coastal zone is that part of its sea floor receives a significant amount of sunlight and can therefore sustain benthic primary production by seagrasses, macroalgae, microphytobenthos and corals. However, the contribution of benthic communities to the primary production of the global coastal ocean is not known, partly because the surface area where benthic primary production can proceed is poorly quantified. Here, we use a new analysis of satellite (SeaWiFS) data collected between 1998 and 2003 to estimate, for the first time at a nearly global scale, the irradiance reaching the bottom of the coastal ocean. The following cumulative functions provide the percentage of the surface (S) of the coastal zone receiving an irradiance greater than Ez (in mol photons m-2 d-1): SNon-polar = 29.61 - 17.92 log10(Ez) + 0.72 log102(Ez) + 0.90 log103(Ez) SArctic = 15.99 - 13.56 log10(Ez) + 1.49 log102(Ez) + 0.70 log103(Ez) Data on the constraint of light availability on the major benthic primary producers and net community production are reviewed. Some photosynthetic organisms can grow deeper than the nominal bottom limit of the coastal ocean (200 m). The minimum irradiance required varies from 0.4 to 5.1 mol photons m-2 d-1 depending on the group considered. The daily compensation irradiance of benthic communities ranges from 0.24 to 4.4 mol photons m-2 d-1. Data on benthic irradiance and light requirements are combined to estimate the surface area of the coastal ocean where (1) light does not limit the distribution of primary producers and (2) net community production (NCP, the balance between gross primary production and community respiration) is positive. Positive benthic NCP can occur over 33% of the global shelf area. The limitations of this approach, related to the spatial resolution of the satellite data, the parameterization used to convert reflectance data to irradiance, the lack of global information on the benthic nepheloid layer, and the relatively limited biological information available, are discussed.

Gattuso, J.-P.; Gentili, B.; Duarte, C. M.; Kleypas, J. A.; Middelburg, J. J.; Antoine, D.

2006-11-01

83

Nepheloid Layers and Bottom Currents in the Arctic Ocean  

Microsoft Academic Search

Between 1965 and 1969, fifty-one profiles of light scattering were made in the central Arctic Ocean from Fletcher's Ice Island (T-3). The profiles, taken with an in situ photographic nephelometer extend from just below the surface to the bottom. Two distinctly different types of profiles were observed. At all stations the strongest scattering occurs near the surface, decreasing with depth

Kenneth Hunkins; Edward M. Thorndike; Guy Mathieu

1969-01-01

84

Katz et al. 2009 Fish induced sediment focusing Sediment resuspension by groundfish facilitates the transport and  

E-print Network

quantities of bottom sediments which create a particle rich layer above the seafloor (benthic nepheloid layer). The resuspended particles are advected offshore by the weak bottom currents, form a mid-water nepheloid layer The lateral transport of marine sediments in the ocean is a key process in both the formation of nepheloid

Yahel, Gitai

85

Benthic foraminifera from Capbreton Canyon revisited; faunal evolution after repetitive sediment disturbance  

NASA Astrophysics Data System (ADS)

At a 650 m deep site in the axis of Capbreton Canyon an 18-cm-thick turbidite was deposited in December 1999. During subsequent campaigns, an almost monospecific fauna of the benthic foraminifer Technitella melo, considered as a pioneer species, was found in May 2000. In 2001 this fauna had disappeared and was replaced by an exceptionally rich fauna strongly dominated by the opportunistic species Bolivina subaenariensis. We present sedimentological, radionuclide and foraminiferal data of new cores, sampled in 2005 and 2011, taken with the aim to study the further evolution of the benthic ecosystem. Cores sampled in 2005 show that in the canyon axis a new, ca. 5 cm thick, turbidite has been deposited. The live benthic foraminiferal faunas were much poorer than in 2001, but still had a high dominance and low diversity, although less extreme than in 2001. We conclude that in the canyon axis, benthic foraminiferal faunas remain in an early stage of ecosystem colonization. It appears that the very thick 1999 turbidite marks an exceptional event. The uncommonly rich faunas observed in 2001 could be a response to the concentration of organic-rich material in the fine-grained top of this deposit. In 2011, cores were sampled at a slightly different site, on the lower canyon flank. The sedimentary sequence here is marked by the absence of coarse turbidite layers, although some levels show slightly increased grain size, and lower 210Pbxs activities, indicative of an admixture with advected older sediments. Live foraminiferal faunas are much more equilibrated, as shown by their higher diversity, lower dominance, and deeper penetration into the sediment. All these characteristics are indicative of a much more stable ecosystem. Dead faunas are present throughout the core, indicating that the levels with slightly elevated grain size are not typical turbidites resulting from hyperpycnal currents (which are characterized by levels barren of foraminifera) but denote other, more long-term sedimentary processes leading to the advection of older material, such as bottom nepheloid layers, or repetitive fine-grained turbidite deposits due to small-scale slumping. The comparison of live and dead fauna shows that at both sites, the foraminiferal turnover rates are fairly low. At the lower canyon flank site sampled in 2011, the foraminiferal faunas are renewed every 1.5-2 years. Such a fairly long foraminiferal lifespan corresponds to earlier estimates, but is surprisingly high for the opportunistic taxa that dominate the faunal assemblages in these unstable and food-enriched submarine canyon settings.

Bolliet, T.; Jorissen, F. J.; Schmidt, S.; Howa, H.

2014-06-01

86

Characterization of particulate material dynamics and composition in the benthic layer of the East Siberian Sea and adjacent part of the Laptev Sea: Fine vertical structure.  

NASA Astrophysics Data System (ADS)

The near-shore zone of the Laptev and East Siberian seas is the most climatically sensitive area in the Arctic and has the highest rates of coastal retreat (Grigoriev, EGU-2010, this session). Our multi-year data (1999-2009) show that major transport of terrestrial organic material to the East Siberian Arctic marine system results from coastal erosion. Biodegradation of this coastal material is a regional source of high pCO2 in waters of the East Siberian Arctic Shelf (ESAS) (Anderson et al., 2009; Pipko et al., EGU-2010, this session; Semiletov et al., 2007). Partitioning between eroded particulate organic carbon (POC) degradation in water and in sediment is still poorly studied. Here we present and discuss peculiarities of particulate material (PM) and POC distribution in the ESAS benthic layer obtained during the 50-day International Siberian Shelf Study (ISSS-2008) onboard the H/V Yakob Smirnitsky. Basic materials were obtained using a GEMAX corer, which allows the sampling of undisturbed surface sediments (down to 1 m in depth) and bottom water. It was found that the vertical PM gradient in the thin benthic layer was 3000 times larger than the PM gradient across the pycnocline. The highest gradients were found in the river paleocanyons and along the Chaunsky -Kolymski Trench. Vertical profiles of POC and its C13 and C/N ratio in the benthic layer demonstrate the increasing contribution of terrestrial organic carbon with increasing depth. References Anderson L.G., Jutterstro¨m S., S. Hjalmarsson S., I. Wahlstro¨m I., and I. P. Semiletov, 2009. Out-gassing of CO2 from Siberian Shelf seas by terrestrial organic matter decomposition. Geophysical Research Letters, 36, L20601, doi:10.1029/2009GL040046, 2009 Semiletov, I., I.I. Pipko, I.A. Repina, and N. Shakhova, 2007, Carbonate dynamics and carbon dioxide fluxes across the atmosphere-ice-water interfaces in the Arctic Ocean Pacific sector of the Arctic, Journal of Marine Systems, 66 (1-4), 204-226.

Dudarev, Oleg; Charkin, Alexander; Semiletov, Igor; Gustafsson, Örjan; Vonk, Jorien; Sánchez-García, Laura

2010-05-01

87

MARINE ECOLOGY PROGRESS SERIES Mar Ecol Prog Ser  

E-print Network

on stationary and mobile platforms. Where these fish were present, a distinct benthic nepheloid layer (BNL in nutrient concentration in the benthic boundary layer and a drop in oxygen concentration. Over longer time

Yahel, Gitai

88

Dynamics of the bathyal Benthic Boundary Layer in the northwestern Mediterranean: depth and temporal variations in macrofaunal–megafaunal communities and their possible connections within deep-sea trophic webs  

Microsoft Academic Search

The distribution patterns of benthopelagic fauna and the macrofauna–megafauna trophic relationships in the Benthic Boundary Layer (BBL) were studied. The study is based on data collected during 6 sampling cruises off the Catalan coast (western Mediterranean) during 1991–1995 at depths ranging from 389–1355 m. Crustaceans were the dominant benthopelagic macrofauna in the BBL level closest to the sea bed (~0–1.5

Joan E. Cartes

1998-01-01

89

Benthic Cyanobacterial Mats in the High Arctic: Multi-Layer Structure and Fluorescence Responses to Osmotic Stress  

PubMed Central

Cyanobacterial mats are often a major biological component of extreme aquatic ecosystems, and in polar lakes and streams they may account for the dominant fraction of total ecosystem biomass and productivity. In this study we examined the vertical structure and physiology of Arctic microbial mats relative to the question of how these communities may respond to ongoing environmental change. The mats were sampled from Ward Hunt Lake (83°5.297?N, 74°9.985?W) at the northern coast of Arctic Canada, and were composed of three visibly distinct layers. Microsensor profiling showed that there were strong gradients in oxygen within each layer, with an overall decrease from 100% saturation at the mat surface to 0%, at the bottom, accompanied by an increase of 0.6 pH units down the profile. Gene clone libraries (16S rRNA) revealed the presence of Oscillatorian sequences throughout the mat, while Nostoc related species dominated the two upper layers, and Nostocales and Synechococcales sequences were common in the bottom layer. High performance liquid chromatography analyses showed a parallel gradient in pigments, from high concentrations of UV-screening scytonemin in the upper layer to increasing zeaxanthin and myxoxanthin in the bottom layer, and an overall shift from photoprotective to photosynthetic carotenoids down the profile. Climate change is likely to be accompanied by lake level fluctuations and evaporative concentration of salts, and thus increased osmotic stress of the littoral mat communities. To assess the cellular capacity to tolerate increasing osmolarity on physiology and cell membrane integrity, mat sections were exposed to a gradient of increasing salinities, and PAM measurements of in vivo chlorophyll fluorescence were made to assess changes in maximum quantum yield. The results showed that the mats were tolerant of up to a 46-fold increase in salinity. These features imply that cyanobacterial mats are resilient to ongoing climate change, and that in the absence of major biological perturbations, these vertically structured communities will continue to be a prominent feature of polar aquatic ecosystems. PMID:22557996

Lionard, Marie; Pequin, Berangere; Lovejoy, Connie; Vincent, Warwick F.

2012-01-01

90

Benthic cyanobacterial mats in the high arctic: multi-layer structure and fluorescence responses to osmotic stress.  

PubMed

Cyanobacterial mats are often a major biological component of extreme aquatic ecosystems, and in polar lakes and streams they may account for the dominant fraction of total ecosystem biomass and productivity. In this study we examined the vertical structure and physiology of Arctic microbial mats relative to the question of how these communities may respond to ongoing environmental change. The mats were sampled from Ward Hunt Lake (83°5.297'N, 74°9.985'W) at the northern coast of Arctic Canada, and were composed of three visibly distinct layers. Microsensor profiling showed that there were strong gradients in oxygen within each layer, with an overall decrease from 100% saturation at the mat surface to 0%, at the bottom, accompanied by an increase of 0.6 pH units down the profile. Gene clone libraries (16S rRNA) revealed the presence of Oscillatorian sequences throughout the mat, while Nostoc related species dominated the two upper layers, and Nostocales and Synechococcales sequences were common in the bottom layer. High performance liquid chromatography analyses showed a parallel gradient in pigments, from high concentrations of UV-screening scytonemin in the upper layer to increasing zeaxanthin and myxoxanthin in the bottom layer, and an overall shift from photoprotective to photosynthetic carotenoids down the profile. Climate change is likely to be accompanied by lake level fluctuations and evaporative concentration of salts, and thus increased osmotic stress of the littoral mat communities. To assess the cellular capacity to tolerate increasing osmolarity on physiology and cell membrane integrity, mat sections were exposed to a gradient of increasing salinities, and PAM measurements of in vivo chlorophyll fluorescence were made to assess changes in maximum quantum yield. The results showed that the mats were tolerant of up to a 46-fold increase in salinity. These features imply that cyanobacterial mats are resilient to ongoing climate change, and that in the absence of major biological perturbations, these vertically structured communities will continue to be a prominent feature of polar aquatic ecosystems. PMID:22557996

Lionard, Marie; Péquin, Bérangère; Lovejoy, Connie; Vincent, Warwick F

2012-01-01

91

Trophic interactions in the benthic boundary layer of the Beaufort Sea shelf, Arctic Ocean: Combining bulk stable isotope and fatty acid signatures  

NASA Astrophysics Data System (ADS)

The food web structure and diets of 26 taxa of benthic boundary layer (BBL) zooplankton on the Beaufort Sea shelf were studied using carbon and nitrogen stable isotopes and fatty acids. Mean ?15N values ranged from 7.3‰ for the amphipod Melita formosa to 14.9‰ for an unidentified polychaete, suggesting that taxa sampled came from three trophic levels. For 8 taxa, the lightest carbon signature occurred near the mouth of the Mackenzie River. Stable isotope ratios helped clarify the origin of signature fatty acids. Levels of certain polyunsaturated fatty acids (PUFA) were negatively correlated with ?15N, with the exception of 22:6?3, which was positively correlated with ?15N, suggesting that this essential PUFA was retained through the food web. Discriminant analysis proved to be a powerful tool, predicting taxa from fatty acid profiles with 99% accuracy, and revealing strong phylogenetic trends in fatty acid profiles. The amphipod Arrhis phyllonyx had higher levels of ?6 PUFA, especially 20:4?6 with several possible sources, than other peracarid crustaceans. The holothurian had high levels of odd numbered and branched chain fatty acids, indicative of bacterial consumption, while fatty acids of phytoplankton origin were important discriminants for Calanus hyperboreus and the chaetognaths Eukrohnia hamata and Parasagitta elegans. This relationship indicates that the conventional phytoplankton-copepod-chaetognath food web found in the water column also exists in the BBL. This observation, as well as generally low ?15N and high levels of certain PUFA in samples with lower ?15N, strongly suggests that BBL zooplankton on the Beaufort Sea shelf have access to fresh material of phytoplankton origin either by feeding on sedimenting matter or by active migration to surface waters.

Connelly, Tara L.; Deibel, Don; Parrish, Christopher C.

2014-01-01

92

Boundary layer intrusions from a sloping bottom: A mechanism for generating intermediate nepheloid layers  

Microsoft Academic Search

Laboratory experiments were used to investigate the growth of intrusions due to internal-wave reflection from a sloping boundary. When normalized by the incident energy density flux, the average intrusion spreading velocity was found to be a linear function of the frequency ratio omega\\/omegac, where omega is the frequency of the incident wave and omegac is the critical frequency, at which

Erika E. McPhee-Shaw; Eric Kunze

2002-01-01

93

Clay mineral evidence of nepheloid layer contributions to the Heinrich layers in the northwest Atlantic  

Microsoft Academic Search

The clay fraction of four cores drilled in the north Atlantic Ocean was studied at a very high resolution over the last 150 ka in order to record the mineralogical signature of Heinrich events. Factor analysis of clay mineralogy establishes that three independent factors represent the main variations: a `detrital factor' (illite + chlorite + kaolinite), a `smectite factor', and

Viviane Bout-Roumazeilles; Elsa Cortijo; Laurent Labeyrie; Pierre Debrabant

1999-01-01

94

Mechanics of deposition of fine-grained sediments from nepheloid layers  

Microsoft Academic Search

The ways by which fine sediment may reach the sea bed are examined, and it is shown that gravitational settling through the sublayer dominates over both Brownian diffusion and scavenging by large fast-sinking particles. The settling process is modulated by bed shear stress, which provides a mechanism for preventing deposition of the finest sizes. This allows fractionation during deposition of

I. Nicholas McCave

1984-01-01

95

Particulate Size Spectra, Behavior, and Origin of Nepheloid Layers over the Nova Scotian Continental Rise  

Microsoft Academic Search

1.26-32 #m measured by Coulter Counter on 10 cm 3 samples correlate linearly with light beam attenuation coefficient. Correlation between particle volume and weight concentration indicates lower apparent particle density for low-concentration suspensions, a feature that is attributed to aggregation during aging of the suspension. Particle size distributions show unimodal form with a peak at ~4 #m in high concentrations

I. N. McCave; Woods Hole

1983-01-01

96

Annual growth layers as proxies of past growth conditions for benthic microbial mats in a perennially ice-covered Antarctic lake.  

PubMed

Perennial microbial mats can be the dominant autotrophic community in Antarctic lakes. Their seasonal growth results in clearly discernible annual growth layering. We examined features of live microbial mats from a range of depths in Lake Hoare, Antarctica, that are likely to be preserved in these layers to determine their potential as proxies of past growth performance. Cyanobacteria dominated the mat for all but the deepest depth sampled. Changes in areal concentrations of phycobilin pigments, organic matter and extracellular polysaccharide and in species composition did not correspond to changes in various water column properties, but showed a linear relationship with irradiance. Carbonate accumulation in the mats correlated with biomass markers and may be inferred as an index of mat performance. We examined the carbonate content of annual layers laid down from 1958-1959 to 1994-1995 in sediment cores from 12 m depth. The carbonate content in the layer showed a significant correlation with the mean summer air temperature. These data suggest a link between air temperature and microbial mat growth performance, and suggest that it is mediated via irradiance. Laminated microbial mats in Antarctic lakes have the potential to act as fine-resolution records of environmental conditions in the recent past, although interpretation is complex. PMID:19120468

Sutherland, Donna L; Hawes, Ian

2009-02-01

97

Benthic macroinvertebrate community results  

SciTech Connect

As part of an extensive program to monitor the health of reservoirs in the TVA system, dredges were used to sample benthic life at 36 locations on 12 Tennessee Valley Authority reservoirs and the Tennessee River downstream from the lowest reservoir in the system. Up to ten dredge samples were collected from forebay, transition zone, and inflow locations of typical reservoirs. The survey was conducted between mid March and mid April, 1990. Results are described.

Jenkinson, J.J.

1991-06-01

98

Benthic-Pelagic coupling in the Black Sea northwestern shelf  

NASA Astrophysics Data System (ADS)

A new approach for modeling the benthic compartment in 3D ocean models is applied to analyze the benthic-pelagic coupling in the Black Sea northwestern shelf (BS-NWS) and to review the contribution of sedimentary diagenesis to the BS-NWS biogeochemical cycles (nitrogen, oxygen and carbon). This approach combines an explicit representation of sediment organic matter deposition and resuspension, controlled by the bottom shear stress, and a parameterization of mineralization pathways control by bottom environmental properties. The model reproduces the magnitude and inter-regional and seasonal variability depicted by in situ benthic fluxes estimates obtained by benthic chambers and sediment cores incubations. The model illustrates how this observed variability results from both variable sedimentation rate and variable diagenetic pathways in the sediment layer. Three distinct areas are identified based on the analysis of the simulated seasonal cycle of bottom environmental conditions, benthic-pelagic fluxes and diagenetic processes. These areas extend along a gradient from the land-ocean interface to the open sea boundary and are each characterized by a particular diagenetic pathway, in a way similar as they succeed vertically in a sediment profile. (1) In the hypoxic zone, high remineralization rates lead to a seasonal peak in anoxic diagenesis and under certain conditions to hydrogen sulphide effluxes from the sediment, (2) in the denitrification zone, benthic denitrification rates are maximal and (3) in the oxic zone, where organic matter accumulation are low, oxic diagenesis prevails and seasonality is less marked. This study underlines that representing resuspension and deposition processes in coupled benthic-pelagic models is essential to realistically describe the horizontal distribution of benthic-pelagic fluxes and the export from the shelf region to the deep sea.

Capet, Arthur; Akoumianaki, Ionna; Meysman, Filip; Soetaert, Karline; Grégoire, Marilaure

2014-05-01

99

Benthic foraminiferal thanatocoenoses from the Cap-Ferret Canyon area (NE Atlantic): A complex interplay between hydro-sedimentary and biological processes  

NASA Astrophysics Data System (ADS)

Benthic foraminiferal thanatocoenoses from the Cap-Ferret Canyon area were studied in the >150-?m fraction of 4-5 cm deep sediment levels, at 13 stations. The shallowest station (151 m depth) is located at the shelf break, close to the canyon head. All other stations are located along two bathymetric transects: seven stations along the canyon axis between 300 and 3000 m depth, and five stations from 300 m to 2000 m depth along the southern flank of the canyon. The comparison between the live (Rose-Bengal-stained) and dead assemblages shows that biological (i.e. population dynamic) and taphonomic processes (i.e. test destruction, transport) generate important discrepancies between live and dead assemblages. An important question is, to what degree post-mortem transport and redeposition of foraminiferal tests contribute to the difference between living and dead assemblages? The composition of the thanatocoenoses (<1% of neritic species) indicates that there is no substantial transport of shells >150 ?m from the inner continental shelf to the Cap-Ferret Canyon axis. However, transport of tests from outer shelf or upper canyon axis towards deeper sites occurs, as indicated by an increase of diversity indices of the dead fauna along the canyon axis. Moreover, some species (e.g., Cassidulina carinata) are observed in the living fauna restricted to the shallow sites, but occur in important amounts in the dead fauna at deeper stations, suggesting that these taxa have been transported from upper canyon stations toward deeper sites. Since Cap-Ferret Canyon is inactive in terms of massive sediment transport (i.e. gravity events), downslope transport of foraminiferal tests probably takes place in nepheloid layers. Downslope transports of foraminiferal tests may create important biases for the utilisation of paleoceanographic proxies using the assemblage characteristics and/or the geochemical composition of selected species. However, the study of dead assemblages along a canyon axis can give important clues about the sedimentary dynamics, especially an idea of the quantity of reworked foraminifera transported through the canyon axis. Along the adjacent flank, such evidence of downslope transport was not observed. Despite taphonomic (test destruction) and biological processes (population dynamics), the live fauna closely resembles the distribution and the composition of the dead assemblage. Therefore, ecological information obtained from the fossil flank samples can be more reliably used to reconstruct paleoenvironmental conditions.

Duros, P.; Jorissen, F. J.; Cesbron, F.; Zaragosi, S.; Schmidt, S.; Metzger, E.; Fontanier, C.

2014-06-01

100

Hydrophobicity as an Adhesion Mechanism of Benthic Cyanobacteria  

PubMed Central

The capacity of benthic cyanobacteria to adhere to solid substrates was examined in terms of their cell surface properties. By using a biphasic water-hydrocarbon test system, it was demonstrated that benthic cyanobacteria from divergent habitats were all hydrophobic, whereas all the planktonic cyanobacteria tested were hydrophilic. Divalent cations were found more efficient than monovalent cations in effecting the expression of hydrophobicity. Mechanical shearing of the cell surface, as well as chemical removal of the cell wall, demonstrated that the hydrophobicity was confined to the outer surface layers. The hydrophobic sites were distributed along the whole length of the cyanobacterial filament. Hydrophilic hormogonia of benthic cyanobacteria became hydrophobic within 48 h when grown in the light; chloramphenicol, 3(3,4-dichlorophenyl)1,1 dimethylurea, or incubation in the dark prevented this transition. Hydrophobicity of Phormidium filaments was masked in late stationary phase; this effect was removed by gentle washing. Images PMID:16346453

Fattom, Ali; Shilo, Moshe

1984-01-01

101

Distribution patterns of particulate trace metals in the water column and nepheloid layer of the Gulf of Riga  

Microsoft Academic Search

The dynamics (fate) of trace metals in suspended particulate matter within the Gulf of Riga has not yet been adequately addressed in the scientific literature. Therefore, during a two year period (2001–2002) samples of suspended particulate matter and surface sediments for trace metal analysis were collected in the Gulf of Riga and the Daugava river, and these data were combined

Rita Poik?ne; Jacob Carstensen; Ingela Dahllöf; Juris Aigars

2005-01-01

102

The Three-Parameter Model of the Submarine Light Field: Radiant Energy Absorption and Energy Trapping in Nepheloid Layers  

Microsoft Academic Search

The three-parameter model of the submarine light field is here proposed. The model consists of three ph_ysical parameters: the scalar irradiance (Eo), downwelling vector irradiance (Ez), and average cosine (\\/x) of the submarine light field. This model is derived from a general exponential decay equation that is valid for all submarine light fields free of horizontal divergence. From the exponential

Robert Hans Stavn

1982-01-01

103

Formation of thick bottom nepheloid layers in the western Mediterranean basin after major dense shelf water cascading events  

Microsoft Academic Search

The analysis of a compilation of deep CTD cast conducted in the western Mediterranean from 1998 to 2009 have documented the role that dense shelf water cascading off the Gulf of Lions plays in transporting suspended particulate matter from the coastal regions down to the basin. Deep CTD casts revealed that after the 1999 and 2005-2006 major cascading events, the

Pere Puig; Xavier Durrieu de Madron; Katrin Schroeder; Jordi Salat; José Luis López-Jurado; Gian Pietro Gasparini; Albert Palanques; Mikhail Emelianov; Aristomenis Karageorgis; Alekos Theocharis

2010-01-01

104

EPA'S BENTHIC HABITAT DATA FOR YAQUINA ESTUARY  

EPA Science Inventory

Scientists at EPA's National Health and Environmental Effects Research Laboratory, Western Ecology Division (WED) have been studying seafloor (benthic) habitats in Yaquina estuary for several years. Those studies were conducted as parts of several research projects, including: e...

105

The benthic biological submodel in the European regional seas ecosystem model  

NASA Astrophysics Data System (ADS)

The submodel describing benthic biology including a bioturbation module as incorporated in the European Regional Seas Ecosystem Model (ERSEM) is discussed. It is linked to a nutrient dynamic model. The structure of the benthic model food web is presented. There are four macrobenthic functional groups, meiobenthos and aerobic and anaerobic bacteria. The modelling uses 'standard organisms' as basic building blocks. The choice of parameter values is discussed. The results demonstrate the dependence of the benthic system on the pelagic system. The importance of features such as predation within functional groups for stability of the system is investigated. Detritus input from the pelagic system and detritus recycling is most important in the benthic food web. The web of carbon and nutrient fluxes through the system is analysed. On the basis of the food web analysis, the trophic positions of the functional groups are calculated. Besides the benthic biology, the mathematical formulation of the bioturbation and diffusion enhancement is discussed. Macrobenthic presence and activity enhance diffusion in the sediment and contribute essentially to vertical transport of particulate matter. This is of great importance for the vertical distribution of detritus, and as a consequence, for microbial activity in the sediment layers.

Ebenhöh, W.; Kohlmeier, C.; Radford, P. J.

106

Using Regional Distribution of Estuarine and Coastal Benthic Invertebrates to Calibrate Benthic Indices of Ecological Condition  

EPA Science Inventory

The biogeography of marine benthic macroinvertebrates of the U.S. Atlantic coast from Delaware Bay north to Passamaquoddy Bay, Maine, was studied to define physical-chemical factors affecting broad taxa distributions and provide information needed to calibrate benthic indices of ...

107

The role of benthic foraminifera in the benthic nitrogen cycle of the Peruvian oxygen minimum zone  

NASA Astrophysics Data System (ADS)

The discovery that foraminifera are able to use nitrate instead of oxygen as energy source for their metabolism has challenged our understanding of nitrogen cycling in the ocean. It was evident before that only prokaryotes and fungi are able to denitrify. Rate estimates of foraminiferal denitrification were very sparse on a regional scale. Here, we present estimates of benthic foraminiferal denitrification rates from six stations at intermediate water depths in and below the Peruvian oxygen minimum zone (OMZ). Foraminiferal denitrification rates were calculated from abundance and assemblage composition of the total living fauna in both, surface and subsurface sediments, as well as from individual species specific denitrification rates. A comparison with total benthic denitrification rates as inferred by biogeochemical models revealed that benthic foraminifera account for the total denitrification on the shelf between 80 and 250 m water depth. They are still important denitrifiers in the centre of the OMZ around 320 m (29-56% of the benthic denitrification) but play only a minor role at the lower OMZ boundary and below the OMZ between 465 and 700 m (3-7% of total benthic denitrification). Furthermore, foraminiferal denitrification was compared to the total benthic nitrate loss measured during benthic chamber experiments. Foraminiferal denitrification contributes 1 to 50% to the total nitrate loss across a depth transect from 80 to 700 m, respectively. Flux rate estimates ranged from 0.01 to 1.3 mmol m-2 d-1. Furthermore we show that the amount of nitrate stored in living benthic foraminifera (3 to 705 µmol L-1) can be higher by three orders of magnitude as compared to the ambient pore waters in near surface sediments sustaining an important nitrate reservoir in Peruvian OMZ sediments. The substantial contribution of foraminiferal nitrate respiration to total benthic nitrate loss at the Peruvian margin, which is one of the main nitrate sink regions in the world oceans, underpins the importance of previously underestimated role of benthic foraminifera in global biochemical cycles.

Glock, N.; Schönfeld, J.; Eisenhauer, A.; Hensen, C.; Mallon, J.; Sommer, S.

2012-12-01

108

Benthic nutrient regeneration in the ERSEM ecosystem model of the North Sea  

NASA Astrophysics Data System (ADS)

In any ecosystem modelling approach to shallow seas an adequate description of the sediment-water interactions to all the essential nutrients is necessary. With this aim a fairly simple concept has been developed and applied for the modelling of the nutrient cycles of N, P and Si which includes the essential diagenetic processes such as vertical transport, oxic and anoxic mineralization, silicate dissolution, adsorption, nitrification and denitrification. All these processes are explicitly formulated for one or more distinct layers in the sediment. The model contains a low number of variables and is efficient with respect to computer time. The model is part of the European Regional Seas Ecosystem Model (ERSEM) of the North Sea, a joint effort of several institutes around the North Sea. The benthic-pelagic coupling of the ERSEM model is discussed with emphasis on the consequences for the benthic nutrient cycling and the interrelations between the different benthic nutrient submodels. The results show that the model is able to describe the seasonal variation of nutrient fluxes including the sediment-water exchanges and the vertical profiles in the pore water. From the model results is concluded that changes in organic matter deposition directly influence the benthic nitrification and denitrification through changes in the oxygen availability to the nitrifiers and, due to this, the supply of nitrate to the denitrifiers. Short fluctuations in organic deposition ( e.g. after the spring bloom) are not reflected in the fluxes due to sorption buffering of phosphate in the oxidized surface layer of the sediment.

Ruardij, Piet; Van Raaphorst, Wim

109

Status of Lake Superior Benthic Macroinvertebrates, 1994-2003  

Microsoft Academic Search

Recently documented changes to benthic communities in the lower Great Lakes have created concerns about the status of benthic macroinvertebrates in Lake Superior. This lakewide study was conducted to ascertain their status in U.S. nearshore waters of Lake Superior. Benthic macroinvertebrates were collected from 27 sites representing the U.S. nearshore waters (20 to 110 m) of Lake Superior in 1994,

J. Scharold; S. J. Lozano; T. D. Corry

2005-01-01

110

Assessing benthic community condition in Chesapeake Bay: does the use of different benthic indices matter?  

Microsoft Academic Search

Federal and state environmental agencies conduct several programs to characterize the environmental condition of Chesapeake\\u000a Bay. These programs use different benthic indices and survey designs, and have produced assessments that differ in the estimate\\u000a of the extent of benthic community degradation in Chesapeake Bay. Provided that the survey designs are unbiased, differences\\u000a may exist in the ability of these indices

Roberto J. Llansó; Jon H. Vølstad; Daniel M. Dauer; Jodi R. Dew

2009-01-01

111

Analyses of phosphorus and nitrogen cyclings in the estuarine ecosystem of Hiroshima Bay by a pelagic and benthic coupled model  

Microsoft Academic Search

A pelagic and benthic coupled model expressing both phosphorus and nitrogen cyclings in the ecosystem of Hiroshima Bay, Japan was developed to investigate the fate and transportation of these elements and their annual budgets. The Bay was divided into eight (8) boxes, wherein two (2) areas ran horizontally and four (4) layers vertically. The model consists of equations representing all

J. Kittiwanich; T. Yamamoto; O. Kawaguchi; T. Hashimoto

2007-01-01

112

Effects of benthic filamentous algae on the sediment–water interface in an acidic mining lake  

Microsoft Academic Search

Natural alkalinity generation by microbial sulphate reduction in acidic lakes is usually inhibited by the low pH and a low\\u000a primary production which results in a lack of suitable organic carbon sources. In some acidic mining lakes mass developments\\u000a of filamentous benthic algae occur. The effects of this periphyton layer on the biogeochemistry of the sediment–water interface\\u000a were investigated by

Matthias Koschorreck; Andreas Kleeberg; Peter Herzsprung; Katrin Wendt-Potthoff

2007-01-01

113

Cenozoic history of Antarctic benthic diatoms  

Microsoft Academic Search

Antarctic Cenozoic climate changes have influenced the development of the Southern Ocean benthic diatom flora. When Antarctica and South America separated in the late Eocene (?37 Ma), giving rise to the proto-Antarctic Circumpolar Current (ACC), the environment gradually changed from temperate alpine glacial to subpolar with ice sheet development. By the early Oligocene (? 30 Ma), at least thirteen new

Jason M. Whitehead

2005-01-01

114

Paleodepth determination from Antarctic benthic diatom assemblages  

Microsoft Academic Search

Analysis of modern surface sediments from fjords in the Vestfold Hills (Antarctica) indicates that 58% of the variation in benthic diatom assemblages can be attributed to changes in environmental parameters with water depth. Attenuation of light through the water column is suggested to account for 45% of the variation, and the decrease in substrate grain size with depth possibly accounts

Jason M. Whitehead; Andrew McMinn

1997-01-01

115

Suspended particulate matter and nepheloid layers over the southern margin of the Cretan Sea (N.E. Mediterranean): seasonal distribution and dynamics  

Microsoft Academic Search

Seawater along the southern margin of the Cretan Sea (May 1994–September 1995) has been found to have light transmission values ranging from 79% to 94%, corresponding to SPM values ranging from 1.5 mg l?1 to 0.2 mg l?1. The highest SPM concentrations (mostly of terrigenous origin) were found close to the sea-bed over the shelf-break and upper slope. The origins

G. Chronis; V Lykousis; D Georgopoulos; V Zervakis; S Stavrakakis; S Poulos

2000-01-01

116

Sediment Diagenesis and Benthic Flux  

NASA Astrophysics Data System (ADS)

Chemical reactions in marine sediments and the resulting fluxes across the sediment-water interface influence the global carbon cycle and the pH of the sea and affect the abundance of CaCO3 and opal-forming plankton in the ocean. On very long timescales these diagenetic reactions control carbon burial in sedimentary rocks and the oxygen content of the atmosphere. Sedimentary deposits that remain after diagenesis are the geochemical artifacts used for interpreting past changes in ocean circulation, biogeochemical cycles, and climate. This chapter is about the processes of diagenesis and burial of the chemical elements that make up the bulk of the particulate matter that reaches the seafloor (organic matter, CaCO3, SiO2, Fe, Mn, and aluminosilicates).Understanding of sediment diagenesis and benthic fluxes has evolved with advances in both experimental methods and modeling. Measurements of chemical concentrations in sediments, their associated pore waters and fluxes at the sediment-water interface have been used to identify the most important reactions. Because transport in pore waters is usually by molecular diffusion, this medium is conducive to interpretation by models of heterogeneous chemical equilibrium and kinetics. Large chemical changes and manageable transport mechanisms have led to elegant models of sediment diagenesis and great advances in understanding of diagenetic processes.We shall see, though, that the environment does not yield totally to simple models of chemical equilibrium and chemical kinetics, and laboratory determined constants often cannot explain the field observations. For example, organic matter degradation rate constants determined from modeling are so variable that there are essentially no constraints on these values from laboratory experiments. In addition, reaction rates of CaCO3 and opal dissolution determined from modeling pore waters usually cannot be reproduced in laboratory experiments of these reactions. The inability to mechanistically understand reaction kinetics calculated from diagenesis models is an important uncertainty in the field today.Processes believed to be most important in controlling the preservation of organic matter have evolved from a focus on the lability of the substrate to the protective mechanisms of mineral-organic matter interactions. The specific electron acceptor is not particularly important during very early diagenesis, but the importance of oxygen to the degradation of organic matter during later stages of diagenesis has been clarified by the study of diagenesis in turbidites deposited on the ocean floor during glacial periods.Evolution of thinking about the importance of reactions between seawater and detrital clay minerals has come full circle since the mid-1960s. "Reverse weathering" reactions were hypothesized in very early chemical equilibrium (Sillen, 1961) and mass-balance ( Mackenzie and Garrels, 1966) models of the oceans. Subsequent observations that marine clay minerals generally resemble those weathered from adjacent land and the discovery of hydrothermal circulation put these ideas on the back burner. Recent studies of silicate and aluminum diagenesis, however, have rekindled awareness of this process, and it is back in the minds of geochemists as a potentially important process for closing the marine mass balance of some elements.

Emerson, S.; Hedges, J.

2003-12-01

117

The role of benthic foraminifera in the benthic nitrogen cycle of the Peruvian oxygen minimum zone  

NASA Astrophysics Data System (ADS)

The discovery that foraminifera are able to use nitrate instead of oxygen as an electron acceptor for respiration has challenged our understanding of nitrogen cycling in the ocean. It was thought before that only prokaryotes and some fungi are able to denitrify. Rate estimates of foraminiferal denitrification have been very sparse and limited to specific regions in the oceans, not comparing stations along a transect of a certain region. Here, we present estimates of benthic foraminiferal denitrification rates from six stations at intermediate water depths in and below the Peruvian oxygen minimum zone (OMZ). Foraminiferal denitrification rates were calculated from abundance and assemblage composition of the total living fauna in both surface and subsurface sediments, as well as from individual species specific denitrification rates. A comparison with total benthic denitrification rates as inferred by biogeochemical models revealed that benthic foraminifera probably account for the total denitrification in shelf sediments between 80 and 250 m water depth. The estimations also imply that foraminifera are still important denitrifiers in the centre of the OMZ around 320 m (29-50% of the benthic denitrification), but play only a minor role at the lower OMZ boundary and below the OMZ between 465 and 700 m (2-6% of total benthic denitrification). Furthermore, foraminiferal denitrification has been compared to the total benthic nitrate loss measured during benthic chamber experiments. The estimated foraminiferal denitrification rates contribute 2 to 46% to the total nitrate loss across a depth transect from 80 to 700 m, respectively. Flux rate estimates range from 0.01 to 1.3 mmol m-2 d-1. Furthermore we show that the amount of nitrate stored in living benthic foraminifera (3 to 3955 ?mol L-1) can be higher by three orders of magnitude as compared to the ambient pore waters in near-surface sediments sustaining an important nitrate reservoir in Peruvian OMZ sediments. The substantial contribution of foraminiferal nitrate respiration to total benthic nitrate loss at the Peruvian margin, which is one of the main nitrate sink regions in the world ocean, underpins the importance of the previously underestimated role of benthic foraminifera in global biogeochemical cycles.

Glock, N.; Schönfeld, J.; Eisenhauer, A.; Hensen, C.; Mallon, J.; Sommer, S.

2013-07-01

118

Assessing benthic community condition in Chesapeake Bay: does the use of different benthic indices matter?  

PubMed

Federal and state environmental agencies conduct several programs to characterize the environmental condition of Chesapeake Bay. These programs use different benthic indices and survey designs, and have produced assessments that differ in the estimate of the extent of benthic community degradation in Chesapeake Bay. Provided that the survey designs are unbiased, differences may exist in the ability of these indices to identify environmental degradation. In this study we compared the results of three indices calculated on the same data, and the assessments of two programs: the Chesapeake Bay Program and the Mid-Atlantic Integrated Assessment (MAIA). We examined the level of agreement of index results using site-based measures of agreement, evaluated sampling designs and statistical estimation methods, and tested for significant differences in assessments. Comparison of ratings of individual sites was done within separate categories of water and sediment quality to identify which indices summarize best pollution problems in Chesapeake Bay. The use of different benthic indices by these programs produced assessments that differed significantly in the estimate of degradation. A larger fraction of poor sites was classified as good by the Environmental Monitoring and Assessment Program's Virginian Province and MAIA benthic indices compared to the Chesapeake Bay benthic index of biotic integrity, although overall classification efficiencies were similar for all indices. Differences in survey design also contributed to differences in assessments. The relative difference between the indices remained the same when they were applied to an independent dataset, suggesting that the indices can be calibrated to produce consistent results. PMID:19052886

Llansó, Roberto J; Vølstad, Jon H; Dauer, Daniel M; Dew, Jodi R

2009-03-01

119

Harnessing the self-harvesting capability of benthic cyanobacteria for use in benthic photobioreactors  

PubMed Central

Benthic species of algae and cyanobacteria (i.e., those that grow on surfaces), may provide potential advantages over planktonic species for some commercial-scale biotechnological applications. A multitude of different designs of photobioreactor (PBR) are available for growing planktonic species but to date there has been little research on PBR for benthic algae or cyanobacteria. One notable advantage of some benthic cyanobacterial species is that during their growth cycle they become positively buoyant, detach from the growth surface and form floating mats. This 'self-harvesting' capability could be advantageous in commercial PBRs as it would greatly reduce dewatering costs. In this study we compared the growth rates and efficiency of 'self-harvesting' among three species of benthic cyanobacteria; Phormidium autumnale; Phormidium murrayi and Planktothrix sp.. Phormidium autumnale produced the greatest biomass and formed cohesive mats once detached. Using this strain and an optimised MLA media, a variety of geometries of benthic PBRs (bPBRs) were trialed. The geometry and composition of growth surface had a marked effect on cyanobacterial growth. The highest biomass was achieved in a bPBR comprising of a vertical polyethylene bag with loops of silicone tubing to provide additional growth surfaces. The productivity achieved in this bPBR was a similar order of magnitude as planktonic species, with the additional advantage that towards the end of the exponential phase the bulk of the biomass detached forming a dense mat at the surface of the medium. PMID:21906375

2011-01-01

120

Microbial mediation of benthic biogenic silica dissolution  

NASA Astrophysics Data System (ADS)

Pore water profiles from 24 stations in the South Atlantic (located in the Guinea, Angola, Cape, Guyana, and Argentine basins) show good correlations of oxygen and silicon, suggesting microbially mediated dissolution of biogenic silica. We used simple analytical transport and reaction models to show the tight coupling of the reconstructed process kinetics of aerobic respiration and silicon regeneration. A generic transport and reaction model successfully reproduced the majority of Si pore water profiles from aerobic respiration rates, confirming that the dissolution of biogenic silica (BSi) occurs proportionally to O2 consumption. Possibly limited to well-oxygenated sediments poor in BSi, benthic Si fluxes can be inferred from O2 uptake with satisfactory accuracy. Compared to aerobic respiration kinetics, the solubility of BSi emerged as a less influential parameter for silicon regeneration. Understanding the role of bacteria for silicon regeneration requires further investigations, some of which are outlined. The proposed aerobic respiration control of benthic silicon cycling is suitable for benthic-pelagic models. The empirical relation of BSi dissolution to aerobic respiration can be used for regionalization assessments and estimates of the silicon budget to increase the understanding of global primary and export production patterns.

Holstein, Jan M.; Hensen, Christian

2010-10-01

121

State of the benthic ecosystem on western Black Sea shelf in spring 2008  

NASA Astrophysics Data System (ADS)

Since the changes in the economies in the Black Sea countries in the 1990's, the momentarily associated decrease in anthropogenic pressures has put the ecosystem of Black Sea western shelf on a trajectory to recovery. However, the suspected non-linearity of recovery and the ecological instability of the benthic shelf ecosystem in particular became evident in the field surveys supported by the BSERP in 2003, 2004, 2005 and 2006, e.g. in the spread of opportunistic species taking new niches and the re-occurrence of large-scale bottom water hypoxia like in 2001. The temporal dynamics of the recovery (as well as of the decline) may also be tied to climatic effects. The Black Sea is known to respond to north Atlantic oscillation (NAO) forcing and decadal climate changes. The target of the 363th cruise of R/V Poseidon in March 2008 has been to map the current state of the benthic ecosystem in a quasi-winter situation. We assessed: a) the current state of the benthic ecosystem on the north-western shelf; to what degree it recovered during the past decade from its collapse in the 1980's. In this respect, we investigated the role of the seabed as storage media of nutrients from past eutrophication, and the role of the sediments as internal source of nutrients to the pelagic system. We focused on zoo- and phytobenthos distribution, the interaction of benthic biota with the sediment, accumulation of nutrients in the sediment, and the flux of nutrients from the sediments to the water. b) The benthic-pelagic coupling, i.e. how the nutrients nitrogen, phosphorus and silica for algal growth are transported from the seafloor to the sea surface and thus fuel biologic productivity. c) The exchange of water between the shelf and the open Black Sea, and hence the transport of nutrients, i.e. the fertilization of the open Black Sea with nutrients from the shelf. Here, we are presenting results from the spring 2008 survey and compare them to findings from a summer survey in 2006: thermal heating and freshwater input created a double front structure on the western shelf, and intrusion of the Cold Intermediate Layer (CIL) into shelf waters was observed. Surface distribution of dissolved nutrients reflects clear signals of silica and total dissolved nitrogen input from the Danube River. Phosphate appears to have a different source, e.g. benthic and/or from the CIL. The benthic ecosystem remains fragile; diversity indices reflect small recovery, quantities in biomass of both zoo- and phytobenthos indicate ongoing perturbations in nearshore areas. A full recovery of historical beds of Phyllophora is not evident, coverage both in winter and summer is less than 10%, and its role as habitat could be compromised by overgrowth of filamentous algae. The benthic system with an epibenthic community in balance releases less nutrients than a disturbed system without benthic life. Nutrients release from the sediment is lower in winter than in summer. The oxygen penetration depth in the sediment triggers denitrification. A spectacular population development of opportunistic species both in zoo- and phytobenthos was observed. The question remains whether or not those opportunistic species can ensure ecosystem functionality and stability. Our findings will help to identify locations crucial for the functioning for the benthic shelf ecosystem, to define "Good Environmental Status" and help to provide recommendations for Marine protected areas on the western Black Sea shelf. It is hoped that the data will make an important contribution to the information base underpinning the new European Marine Strategy Directive and the Bucharest Convention for the Protection of the Black Sea.

Friedrich, J.; Aleynik, D.; Eulenburg, A.; Kusch, St.; Mee, L. D.; Minicheva, G.; Stevens, T. F.; Teaca, A.; Shapiro, G. I.; Soloviev, D.

2009-04-01

122

Benthic fluxes of dissolved organic carbon in three temperate Australian estuaries: Implications for global estimates of benthic DOC fluxes  

NASA Astrophysics Data System (ADS)

Light and dark benthic dissolved organic carbon (DOC) fluxes and sediment characteristics (total organic carbon (TOC), total nitrogen (TN), TOC isotope ratio (?13C), phospholipid fatty acid (PLFA) concentration, and compound-specific ?13C) were measured seasonally in a range of habitats in three warm-temperate Australian estuaries to determine what factors control benthic DOC fluxes. Benthic DOC fluxes were seasonal with the highest rates generally observed during summer. Most habitats displayed uptake of DOC during the dark and efflux during the light, and were a net source of DOC to the overlying waters over the diel cycle. Macrophyte habitats (seagrass and macroalgae) had the highest benthic fluxes of DOC (up to ˜50 mmol C m-2 d-1). Organic matter supply to the sediment was dominated by in situ production, and both quantity and source exerted control over benthic DOC fluxes. DOC flux was tightly coupled to bacteria and algal PLFA concentrations during summer, and algal PLFA concentrations during winter, indicating a strong influence of microbial interactions on benthic DOC flux and a temperature-related decoupling of algae and bacteria under cooler conditions. Estimates of the global estuarine benthic DOC flux indicate that these areas are a significant source of DOC to the ocean (1-41 Tg C yr -1). Inclusion of macrophyte, salt marsh, mangrove, and intertidal benthic DOC flux estimates resulted in a higher global continental margin benthic DOC flux (106-416 Tg C yr -1) than the previous estimate (90 Tg C yr-1).

Maher, D. T.; Eyre, B. D.

2010-12-01

123

Benthic fluxes in San Francisco Bay  

USGS Publications Warehouse

Measurements of benthic fluxes have been made on four occasions between February 1980 and February 1981 at a channel station and a shoal station in South San Francisco Bay, using in situ flux chambers. On each occasion replicate measurements of easily measured substances such as radon, oxygen, ammonia, and silica showed a variability (??1??) of 30% or more over distances of a few meters to tens of meters, presumably due to spatial heterogeneity in the benthic community. Fluxes of radon were greater at the shoal station than at the channel station because of greater macrofaunal irrigation at the former, but showed little seasonal variability at either station. At both stations fluxes of oxygen, carbon dioxide, ammonia, and silica were largest following the spring bloom. Fluxes measured during different seasons ranged over factors of 2-3, 3, 4-5, and 3-10 (respectively), due to variations in phytoplankton productivity and temperature. Fluxes of oxygen and carbon dioxide were greater at the shoal station than at the channel station because the net phytoplankton productivity is greater there and the organic matter produced must be rapidly incorporated in the sediment column. Fluxes of silica were greater at the shoal station, probably because of the greater irrigation rates there. N + N (nitrate + nitrite) fluxes were variable in magnitude and in sign. Phosphate fluxes were too small to measure accurately. Alkalinity fluxes were similar at the two stations and are attributed primarily to carbonate dissolution at the shoal station and to sulfate reduction at the channel station. The estimated average fluxes into South Bay, based on results from these two stations over the course of a year, are (in mmol m-2 d-1): O2 = -27 ?? 6; TCO2 = 23 ?? 6; Alkalinity = 9 ?? 2; N + N = -0.3 ?? 0.5; NH3 = 1.4 ?? 0.2; PO4 = 0.1 ?? 0.4; Si = 5.6 ?? 1.1. These fluxes are comparable in magnitude to those in other temperate estuaries with similar productivity, although the seasonal variability is smaller, probably because the annual temperature range in San Francisco Bay is smaller. Budgets constructed for South San Francisco Bay show that large fractions of the net annual productivity of carbon (about 90%) and silica (about 65%) are recycled by the benthos. Substantial rates of simultaneous nitrification and denitrification must occur in shoal areas, apparently resulting in conversion to N2 of 55% of the particulate nitrogen reaching the sediments. In shoal areas, benthic fluxes can replace the water column standing stocks of ammonia in 2-6 days and silica in 17-34 days, indicating the importance of benthic fluxes in the maintenance of productivity. Pore water profiles of nutrients and Rn-222 show that macrofaunal irrigation is extremely important in transport of silica, ammonia, and alkalinity. Calculations of benthic fluxes from these profiles are less accurate, but yield results consistent with chamber measurements and indicate that most of the NH3, SiO2, and alkalinity fluxes are sustained by reactions occurring throughout the upper 20-40 cm of the sediment column. In contrast, O2, CO2, and N + N fluxes must be dominated by reactions occurring within the upper one cm of the sediment-water interface. While most data support the statements made above, a few flux measurements are contradictory and demonstrate the complexity of benthic exchange. ?? 1985 Dr W. Junk Publishers.

Hammond, D.E.; Fuller, C.; Harmon, D.; Hartman, B.; Korosec, M.; Miller, L.G.; Rea, R.; Warren, S.; Berelson, W.; Hager, S.W.

1985-01-01

124

Classification of threespine stickleback along the benthic-limnetic axis.  

PubMed

Many species of fish display morphological divergence between individuals feeding on macroinvertebrates associated with littoral habitats (benthic morphotypes) and individuals feeding on zooplankton in the limnetic zone (limnetic morphotypes). Threespine stickleback (Gasterosteus aculeatus L.) have diverged along the benthic-limnetic axis into allopatric morphotypes in thousands of populations and into sympatric species pairs in several lakes. However, only a few well known populations have been studied because identifying additional populations as either benthic or limnetic requires detailed dietary or observational studies. Here we develop a Fisher's linear discriminant function based on the skull morphology of known benthic and limnetic stickleback populations from the Cook Inlet Basin of Alaska and test the feasibility of using this function to identify other morphologically divergent populations. Benthic and limnetic morphotypes were separable using this technique and of 45 populations classified, three were identified as morphologically extreme (two benthic and one limnetic), nine as moderately divergent (three benthic and six limnetic) and the remaining 33 populations as morphologically intermediate. Classification scores were found to correlate with eye size, the depth profile of lakes, and the presence of invasive northern pike (Esox lucius). This type of classification function provides a means of integrating the complex morphological differences between morphotypes into a single score that reflects the position of a population along the benthic-limnetic axis and can be used to relate that position to other aspects of stickleback biology. PMID:21221422

Willacker, James J; von Hippel, Frank A; Wilton, Peter R; Walton, Kelly M

2010-11-01

125

BENTHIC NUTRIENT FLUX IN A SMALL ESTUARY IN NORTHWESTERNFLORIDA (USA)  

EPA Science Inventory

Benthic Nutrient Flux in a Small Estuary in Northwestern Florida(USA).Gulf and Caribbean Research 18, 15-25, 2006. Benthic nutrient fluxes of ammonium (NH4+), nitrite/nitrate (NO2-+NO3-), phosphate (PO4-), and dissolved silica (DSi) were measured in Escambia Bay, an estuar...

126

LATITUDINAL GRADIENTS IN BENTHIC COMMUNITY COMPOSITION IN WESTERN ATLANTIC ESTUARIES  

EPA Science Inventory

The community structure of benthic macroinvertebrates from estuaries along the Atlantic coast of North America from Cape Cod, MA, to Biscayne Bay, FL, were compared. Benthic data were collected over a 5 year period (1990 to 1995) by the U.S. Environmental Protection Agency's Envi...

127

Comparison of Rapid Versus Extended Sampling Methods for Benthic Macro-  

E-print Network

in comparison to extended methods · Sample and identify macro-invertebrates for P.R.R.P. monitoring purposes: Periphyton, benthic macro- invertebrates and fish, 2nd edition. EPA 841-B-99-002. U.S. Environmental8/21/13 1 Comparison of Rapid Versus Extended Sampling Methods for Benthic Macro

Gray, Matthew

128

FRESHWATER POTOMAC LONG-TERM BENTHIC MONITORING PROGRAM  

EPA Science Inventory

The Maryland Department of the Environments Freshwater Potomac Long-Term Benthic Monitoring Program provides seasonal information on abundance and composition for the benthic fauna of the freshwater portion of the Potomac River for use in recommendations to State agencies accordi...

129

Classification of threespine stickleback along the benthic-limnetic axis  

PubMed Central

Many species of fish display morphological divergence between individuals feeding on macroinvertebrates associated with littoral habitats (benthic morphotypes) and individuals feeding on zooplankton in the limnetic zone (limnetic morphotypes). Threespine stickleback (Gasterosteus aculeatus L.) have diverged along the benthic-limnetic axis into allopatric morphotypes in thousands of populations and into sympatric species pairs in several lakes. However, only a few well known populations have been studied because identifying additional populations as either benthic or limnetic requires detailed dietary or observational studies. Here we develop a Fisher’s linear discriminant function based on the skull morphology of known benthic and limnetic stickleback populations from the Cook Inlet Basin of Alaska and test the feasibility of using this function to identify other morphologically divergent populations. Benthic and limnetic morphotypes were separable using this technique and of 45 populations classified, three were identified as morphologically extreme (two benthic and one limnetic), nine as moderately divergent (three benthic and six limnetic) and the remaining 33 populations as morphologically intermediate. Classification scores were found to correlate with eye size, the depth profile of lakes, and the presence of invasive northern pike (Esox lucius). This type of classification function provides a means of integrating the complex morphological differences between morphotypes into a single score that reflects the position of a population along the benthic-limnetic axis and can be used to relate that position to other aspects of stickleback biology. PMID:21221422

Willacker, James J.; von Hippel, Frank A.; Wilton, Peter R.; Walton, Kelly M.

2010-01-01

130

Chemistry of Benthic Foraminiferal Shells for Recording Ocean Environments: Cd\\/Ca, ? ? ? ? ?13C and Mg\\/Ca  

Microsoft Academic Search

Cd\\/Ca, ?13C and Mg\\/Ca of six species of benthic foraminifera with different microhabitat were analysed from throughout the sediment mixed layer at three well-characterised sites in the Northeastern Atlantic: Cibicidoides wuellerstorfi, Uvigerina peregrina, Cibicides bradyi, Melonis barleeanum, Bulimina striata and Hoeglundina elegans. Reductive cleaning decreased Mn\\/ Ca and Cd\\/Ca of C. wuellerstorfi but did not significantly influence Mg\\/Ca and Sr\\/Ca

Kazuyo TACHIKAWA; Henry ELDERFIELD

131

Optics, Acoustics and Stress in Situ (OASIS): Effects of Aggregation, Vertical Structure, and Relation to Physical Forcing.  

E-print Network

Plan Rationale Naval operations in the nearshore environment are complicated by bottom nepheloid layers. Background Optical and acoustical attenuation in nepheloid layers depends on sediment concentration, which are nearbed layers of enhanced sediment concentration generated by resuspension of particles from

Boss, Emmanuel S.

132

WASP7 BENTHIC ALGAE - MODEL THEORY AND USER'S GUIDE  

EPA Science Inventory

The standard WASP7 eutrophication module includes nitrogen and phosphorus cycling, dissolved oxygen-organic matter interactions, and phytoplankton kinetics. In many shallow streams and rivers, however, the attached algae (benthic algae, or periphyton, attached to submerged substr...

133

DECLINE IN LAKE ONTARIO POPULATIONS OF BENTHIC MACROINVERTEBRATES  

EPA Science Inventory

Surveys of benthic macroinvertebrates conducted in Lake Ontario during 1994 and 1997 revealed declines in populations of three major groups of organisms: oligochaetes, sphariids, and Diporeia spp. (Amphipoda), with the most drastic reductions occurring in the latter. Based on phy...

134

BENTHIC MACROFAUNA-HABITAT ASSOCIATIONS IN WILLAPA BAY, WASHINGTON, USA  

EPA Science Inventory

Estuary-wide benthic macrofauna-habitat associations in Willapa Bay, Washington, United States, were determined for 4 habitats (eelgrass [Zostera marina], Atlantic cordgrass [Spartina alterniflora], mud shrimp [Upogebia pugettensis], ghost shrimp [Neotrypaea californiensis]) in 1...

135

BENTHIC MACROFAUNA-HABITAT RELATIONSHIPS IN WILLAPA BAY, WA  

EPA Science Inventory

Benthic macrofauna-habitat relationships were determined estuary-wide in Willapa Bay, WA for four intertidal habitats ((1) eelgrass, Zostera marina, (2) Atlantic cordgrass, Spartina alterniflora, (3) ghost shrimp, Neotrypaea californiensis, (4) mud shrimp, Upogebia pugettensis) i...

136

Benthic fluxes of nutrients in the northwestern Black Sea  

Microsoft Academic Search

The exchange of O2, NH4+, Si(OH)4, ortho-phosphate, Fe2+, Mn2+ and H2S between the sediment and the overlying water (benthic flux) was determined at 6 locations on the northwestern shelf of the Black Sea using an in situ benthic lander. Oxygen consumption by the sediments ranged from 0 to 33 mmol m?2 d?1 depending mostly on the initial oxygen concentration in

Gabriela Friedl; Christian Dinkel; Bernhard Wehrli

1998-01-01

137

Benthic Metabolism as an Indicator of Stream Ecosystem Health  

Microsoft Academic Search

We tested direct and indirect measures of benthic metabolism as indicators of stream ecosystem health across a known agricultural\\u000a land-use disturbance gradient in southeast Queensland, Australia. Gross primary production (GPP) and respiration (R24) in benthic chambers in cobble and sediment habitats, algal biomass (as chlorophyll a) from cobbles and sediment cores, algal biomass accrual on artificial substrates and stable carbon isotope

Christine S. Fellows; Joanne E. Clapcott; James W. Udy; Stuart E. Bunn; Bronwyn D. Harch; Michael J. Smith; Peter M. Davies

2006-01-01

138

Recent benthic foraminifera from offshore Taranaki, New Zealand  

Microsoft Academic Search

Paleobathymetric estimates based on fossil foraminiferal faunas play an important role in understanding the paleogeographic, structural, and burial history of New Zealand's most important hydrocarbon?bearing sedimentary basin—the Taranaki Basin. Bathyal and abyssal estimates have large ranges of uncertainty, which might be improved using knowledge of the depth distribution patterns of Recent benthic foraminifera in the same region.Four benthic foraminiferal groups

Bruce W. Hayward; Hugh R. Grenfell; Ashwaq Sabaa; Jessica J. Hayward

2003-01-01

139

Lake Malawi cichlid evolution along a benthic/limnetic axis  

PubMed Central

Divergence along a benthic to limnetic habitat axis is ubiquitous in aquatic systems. However, this type of habitat divergence has largely been examined in low diversity, high latitude lake systems. In this study, we examined the importance of benthic and limnetic divergence within the incredibly species-rich radiation of Lake Malawi cichlid fishes. Using novel phylogenetic reconstructions, we provided a series of hypotheses regarding the evolutionary relationships among 24 benthic and limnetic species that suggests divergence along this axis has occurred multiple times within Lake Malawi cichlids. Because pectoral fin morphology is often associated with divergence along this habitat axis in other fish groups, we investigated divergence in pectoral fin muscles in these benthic and limnetic cichlid species. We showed that the eight pectoral fin muscles and fin area generally tended to evolve in a tightly correlated manner in the Lake Malawi cichlids. Additionally, we found that larger pectoral fin muscles are strongly associated with the independent evolution of the benthic feeding habit across this group of fish. Evolutionary specialization along a benthic/limnetic axis has occurred multiple times within this tropical lake radiation and has produced repeated convergent matching between exploitation of water column habitats and locomotory morphology. PMID:23919168

Hulsey, C D; Roberts, R J; Loh, Y-H E; Rupp, M F; Streelman, J T

2013-01-01

140

Scientific requirements for an abyssal benthic laboratory  

NASA Astrophysics Data System (ADS)

For over thirty years man has studied "outer space" and installed satellites which watch the surface of the Earth. The great depths of the world ocean are, however, practically unknown and there is an urgent need to put abyssal benthic laboratories into "inner space" in order to study basic phenomena of interest to marine science and climatology as well as man's impact on the oceans. In view of the numerous problems related to global change, as a first step emphasis should first be on the role of the oceans and their inherent processes, which are the focus of such international programmes as the World Ocean Circulation Experiment (WOCE) and the Joint Global Ocean Flux Study (JGOFS). Multi-disciplinary registration of key events at selected key sites investigating the variability in time and space are of the utmost importance. The same methods and techniques must be used for the study of human impacts on the deep oceans caused by mining of metalliferous resources and by waste disposal as well as in basic studies. However, the investigation of the inner space of our planet has certain requirements. As long-term and large-scale investigations become more and more important, development of automized systems, largely independent from research vessels will be required. This will demand high capacities of energy for all technical functions as well as high storage capacities for data and samples. As a consequence the needs for two different—although overlapping—functional approaches are defined for future deep-sea deployments. (A) A system for long-term registration of the natural variability and long-term monitoring of human impacts: (B) A system for short-term observations and short-time experimentations. This report summarizes their technological demands. The envisioned interdisciplinary technology should deliver information on physical, biological and geochemical processes and their variabilities in the deep oceans. The prospected systems need to have the ability for real time video observation, data transfer and experimental manipulation, as well as sensing and sampling facilities with large storage capacities for long-term deployments. Prospective costs of the described multipurpose abyssal benthic laboratory will presumably exceed the funds for deep-sea research of a single country. A joint European effort could solve this problem and help to manifest a leading role for European marine science in international deep-sea and global change research.

Thiel, H.; Kirstein, K.-O.; Luth, C.; Luth, U.; Luther, G.; Meyer-Reil, L.-A.; Pfannkuche, O.; Weydert, M.

1994-03-01

141

Parameterisation of clastic sediments including benthic structures  

NASA Astrophysics Data System (ADS)

The sediment transport processes in the south-western Baltic Sea are predicted by means of a numerical model in the project DYNAS. There are two sediment parameters that influence the results of modelling remarkably: critical shear stress velocity and bottom roughness. This paper presents the way how to parameterise these factors and extrapolate them into the investigation area. The critical shear stress velocity is parameterised basing on grain size data, combining approximations after Hjulström [Hjulström, F., 1935: Studies in the morphological activity of rivers as illustrated by the river Fyris. Geological Institution of University of Uppsala: Bulletin (25): 221-528.], Shields [Shields, A., 1936: Anwendung der Ähnlichkeits-Mechanik und der Turbulenzforschung auf die Geschiebebewegung. Mitteilungen der Preussischen Versuchsanstalt für Wasserbau und Schiffahrt (26): 26 pp.] and Bohling [Bohling, B., 2003: Untersuchungen zur Mobilität natürlicher und anthropogener Sedimente in der Mecklenburger Bucht. unpublished doctoral thesis, Mathematisch-Naturwissenschaftliche Fakultät, Ernst-Moritz-Arndt-Universität Greifswald/Germany, 156 pp.]. The roughness length, in the case of absence of macro zoo-benthos and their structures, is parameterised basing on grain size too employing Soulsby [Soulsby, R.L., 1997: Dynamics of Marine Sands: a Manual for Practical Applications. London, Thomas Telford Publications. 249 pp.], Nielsen [Nielsen, P., 1983: Analytical determination of nearshore wave height variation due to refraction shoaling and friction. Coastal Engineering 7, 233-251.] and Yalin [Yalin, M.S., 1977: Mechanics of Sediment Transport. Pergamon Press, New York. 298 pp.]. No equivalent simple parameterisations for biologically caused bed roughness exist. Here, findings of Friedrichs [Friedrichs, M., 2004: Flow-induced effects of macro zoo-benthic structures on the near-bed sediment transport. Dissertation, Universität Rostock, 80 S.] and estimations by the DYNAS biologists group were combined in order to derive roughness lengths from abundance measurements of four previously selected key species which represent the originators of the dominating benthic structures at the sea floor in the south-western Baltic Sea. Critical shear stress velocity and bed roughness are known at few sample sites only. They were extrapolated into the larger investigation area using a proxy-target concept. The mean near bottom milieu (bathymetry, median grain size, salinity, oxygen) which was derived using results from numerical modelling serves as the proxy. Since the milieu parameters are measured at the sampling sites for which the target parameters have been determined, a combined hierarchical and supervised classification was employed to transfer the local knowledge into the unknown investigation area.

Bobertz, B.; Harff, J.; Bohling, B.

2009-02-01

142

Phototoxicity of TiO? nanoparticles to a freshwater benthic amphipod: are benthic systems at risk?  

PubMed

This study investigated phototoxicity of TiO? nanoparticles (nano-TiO?) to a freshwater benthic amphipod (Hyalella azteca) using 48-h and 96-h bioassays. Thorough monitoring of particle interactions with exposure media (Lake Superior water, LSW) and the surface of organisms was performed using dynamic light scattering, UV/Vis spectroscopy, and Scanning Electron Microscopy. Large agglomeration and sedimentation (>77%) in LSW was observed after 0.5h. A simulated solar radiation (SSR)-favored surface attachment of nanoparticles was observed, indicating enhanced phototoxicity with the increased attachment. A 96-h median lethal concentration (LC50) of 29.9 mg/L in H. azteca was calculated, with a daily 4-h UV exposure of 2.2 W/m(2). Phototoxicity of nano-TiO? under SSR had a 21-fold increase as compared to that under ambient laboratory light. This phototoxicity was also dependent on UV dose, with calculated LC50s around 22.9 (95% CI, 20.5-23.3)Wh/m(2) when exposed to 20 mg/L nano-TiO?. Also, H. azteca exhibited negative phototaxis in the presence of shelters, indicating that other factors might play a role in environmental systems. Finally, the environmental implications of nano-TiO? to benthic organisms were illustrated, emphasizing the importance of various environmental factors in the ultimate phototoxicity. This increased phototoxicity and its complex interactions with various environmental factors suggest further investigations are needed for future risk assessment of photoactive nanomaterials to benthic organisms. PMID:23973546

Li, Shibin; Wallis, Lindsay K; Ma, Hongbo; Diamond, Stephen A

2014-01-01

143

Benthic foraminiferal extinction and repopulation in response to latest Paleocene Tethyan anoxia  

NASA Astrophysics Data System (ADS)

The latest Paleocene benthic foraminiferal extinction event has been studied in two marlstone successions in the Tethys: at Wadi Nukhl (Egypt) and Torangly (Turkmenistan). Both sections yield a sapropelic layer at the level of the extinction event. At Nukhl, this layer underlies a thin calcareous bed that has also been found in other Middle East upper Paleocene sections. With the onset of anoxia at the Tethyan sea floor, the aerobic and oligotrophic Gavelinella beccariiformis deep-sea community collapsed. Eutrophic-to-mesotrophic and low-oxygen conditions, most likely resulting from enhanced organic carbon fluxes to the sea floor, triggered an ˜100 200 k.y. repopulation sequence, marked by downslope migration of several neritic communities that were dominated by opportunistic and tolerant taxa. The initial ecosystem restoration was completed when an aerobic and oligotrophic Nuttallides truempyi deep-sea community became established. We suggest that this repopulation mode could be typical for the central Tethys.

Speijer, Robert P.; Schmitz, Birger; van der Zwaan, Gijsbert J.

1997-08-01

144

Deep-Sea Research II 52 (2005) 25432559 Suspended Alexandrium spp. hypnozygote cysts in  

E-print Network

collected at depths just off the bottom (within 5 m), at the top of the bottom nepheloid layer, and near-bottom and top of the bottom nepheloid layer samples than in near-surface water samples; densities were

Townsend, David W.

145

Ecology and role of benthic copepods in northern lakes  

NASA Astrophysics Data System (ADS)

Freshwater benthic Harpacticoida consist of species capable of swimming, but mostly burrowing in organic sediments, and small, vermiform species that are poor swimmers and live in interstitial systems. Freshwater benthic Cyclopoida are either agile epibenthic and often relatively large herbivores, carnivores and omnivores, or small infaunal omnivores. Harpacticoids seem to have few, mainly invertebrate, predators, and consequently low mortality and long life span. These are evolutionarily linked to slow growth and low production to biomass ratio (typically 1-7 a -1). Cyclopoids are characterized by more rapid growth and higher production to biomass ratio (typically 3-13 a -1). Due to their active mode of life, they are preyed upon by fish and other predators, which results in high mortality and a short adult life span. Harpacticoid numbers and biomass may reach 250,000 ind/m 2 and 120 mgC/m 2. True benthic cyclopoids are usually much less abundant (up to 20,000 ind/m 2 and 9 mgC/m 2). Thus, although the quantitative importance of freshwater meiofauna as a whole may often be comparable to that of macrofauna, the few biomass and production data on benthic copepods suggest that at least harpacticoids have a minor role in the benthic food web of northern lakes.

Sarvala, J.

1998-06-01

146

Status of Lake Superior Benthic Macroinvertebrates, 1994-2003  

NASA Astrophysics Data System (ADS)

Recently documented changes to benthic communities in the lower Great Lakes have created concerns about the status of benthic macroinvertebrates in Lake Superior. This lakewide study was conducted to ascertain their status in U.S. nearshore waters of Lake Superior. Benthic macroinvertebrates were collected from 27 sites representing the U.S. nearshore waters (20 to 110 m) of Lake Superior in 1994, 2000, and 2003. No significant differences in total benthic macroinvertebrate abundance, or abundances of oligochaetes, clams or chironomids were detected between years. Abundance of the amphipod Diporeia spp. was lower in 2000 than in 1994 and 2003. The oligochaete trophic index, a measure of relative abundance of species tolerant of varying degrees of organic enrichment, did not differ between years. Diporeia exhibited a bimodal depth distribution, with peaks in abundance at depths of 30 to 40 and 60 to 70 m. Oligochaetes were most abundant at 50 to 60 m depth, clams between 30 and 70 m, and chironomids at less than 30 m, with a secondary peak at 50 to 60 m. The spatial and temporal variability observed in Lake Superior benthic macroinvertebrate communities has implications for sampling design for environmental assessment. This abstract does not necessarily reflect USEPA policy.

Scharold, J.; Lozano, S. J.; Corry, T. D.

2005-05-01

147

Application of multiple index development approaches to benthic invertebrate data from the Virginian Biogeographic Province  

EPA Science Inventory

Benthic invertebrate indices have commonly been utilized to assess benthic invertebrate communities. These indices have been constructed using different techniques, but have shown different levels of application success. For example, the EMAP Virginian Province Index did not pe...

148

Early Cenozoic benthic foraminiferal isotopes: Species reliability and interspecies correction factors  

E-print Network

Early Cenozoic benthic foraminiferal isotopes: Species reliability and interspecies correction Cenozoic benthic foraminifera commonly used for isotopic measurements (Cibicidoides spp., Nuttallides isotopic offsets appear to have changed through the Cenozoic, either (1) as a result of evolutionary

Royer, Dana

149

RELATIONSHIPS BETWEEN ENVIRONMENTAL VARIABLES AND BENTHIC DIATOM ASSEMBLAGES IN CALIFORNIA CENTRAL VALLEY STREAMS (USA)  

EPA Science Inventory

Streams and rivers in the California Central Valley Ecoregion have been substantially modified by human activities. This study examines distributional patterns of benthic diatom assemblages in relation to environmental characteristics in streams and rivers of this region. Benthic...

150

An assessment of benthic condition in several small watersheds of the Chesapeake Bay, USA  

Microsoft Academic Search

We examined benthic condition in three small watersheds in the Chesapeake Bay. Characterization of benthic condition was based\\u000a on the combined measurements of benthic fauna, sediment toxicity, and sediment contaminant loads. Significant differences\\u000a between watersheds were detected for sediment contaminant concentrations and water quality. The intensity of benthic impairment\\u000a was greatest in the river surrounded by the most developed watershed.

Andrew K. Leight; Ward H. Slacum; Ed F. Wirth; Mike H. Fulton

2011-01-01

151

Clinch River remedial investigation task 9 -- benthic macroinvertebrates  

SciTech Connect

This report summarizes the results of Task 9 of the TVA/Department of Energy (DOE) Interagency Agreement supporting DOE`s Clinch River Remedial Investigation. Species lists and densities (numbers/m{sup 2}) of benthic macroinvertebrates sampled at 16 sites in the Clinch River and Poplar Creek embayments of upper Watts Bar Reservoir near Oak Ridge, Tennessee, in March, 1994, are presented and briefly discussed. Data are also analyzed to assess and compare quality of benthic communities at each site, according to methods developed for TVA`s Reservoir Vital Signs Monitoring Program. Results of this study will be incorporated with other program tasks in a comprehensive report prepared by Oak Ridge National Laboratory in 1995, which will, in part, assess the effect of sediment contaminants on benthic macroinvertebrate communities in Watts Bar Reservoir.

Scott, E.M. Jr.

1994-08-01

152

Benthic metabolic feedbacks to carbonate chemistry on coral reefs:implications for ocean acidification  

NASA Astrophysics Data System (ADS)

The metabolic activity of resident organisms can cause spatio-temporal variability in carbonate chemistry within the benthic boundary layer, and thus potentially buffer the global impacts of ocean acidification. But, little is known about the capacity for particular species assemblages to contribute to natural daily variability in carbonate chemistry. We encapsulated replicate areas (~3m2) of reef across six Northern Line Islands in the central Pacific for 24 hrs to quantify feedbacks to carbonate chemistry within the benthic boundary layer from community metabolism. Underneath each 'tent', we quantified relative abundance and biomass of each species of corals and algae. We coupled high temporal resolution time series data on the natural diurnal variability in pH, dissolved oxygen, salinity, and temperature (using autonomous sensors) with resident organisms' net community calcification and productivity rates (using change in total dissolved carbon and total alkalinity over time) to examine feedbacks from reef metabolism to boundary layer carbonate chemistry. These reefs experienced large ranges in pH (> 0.2 amplitude) each day, similar to the magnitude of 'acidification' expected over the next century. Daily benthic pH, pCO2, and aragonite saturation state (?aragonite) were contrasted with seasonal threshold values estimated from open ocean climatological data extrapolated at each island to determine relative inter-island feedbacks. Diurnal amplitude in pH, pCO2, and ?aragonite at each island was dependent upon the resident species assemblage of the benthos and was particularly reliant upon the biomass, productivity, and calcification rate of Halimeda. Net primary productivity of fleshy algae (algal turfs and Lobophora spp.) predominated on degraded, inhabited islands where net community calcification was negligible. In contrast, the chemistry over reefs on 'pristine', uninhabited islands was driven largely by net calcification of calcareous algae and stony corals. Knowledge about species specific physiological rates and relative abundances of key taxa whose metabolism significantly alters carbonate chemistry may give insight to the ability for a reef to buffer against or exacerbate ocean acidification.

Price, N.; Rohwer, F. L.; Stuart, S. A.; Andersson, A.; Smith, J.

2012-12-01

153

This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research  

E-print Network

's personal copy The importance of subsurface nepheloid layers in transport and delivery of sediments August 2009 Keywords: Nepheloid layers Cariaco Basin Particulate organic matter Sediment transport a b the rainy seasons of September 2003 and 2006. Our results suggest that nepheloid layers originating

Meyers, Steven D.

154

Exploration of Submerged Sinkhole Ecosystems in Thunder Bay National Marine Sanctuary, Lake Huron  

E-print Network

of the sinkhole, and a dark cloudy nepheloid-like plume layer prevailed just over the site of submarine of nutrient efflux and microbial activity. In comparison to surrounding deep water, the nepheloid-like layer was able to sample the nepheloid layer occurring about 1 m above the lake floor, it was unable to sample

155

Alexandrium fundyense cyst viability and germling survival in light vs. dark at a constant low temperature  

E-print Network

-bottom nepheloid layers at water depths exceeding 100 m. The germling cells and their vegetative progeny of germling cells. In addition to viability of cysts in surface sediments and the near-bottom nepheloid layer stage (cyst) that remains in bottom sediments or near- bottom nepheloid layers when conditions

McGillicuddy Jr., Dennis J.

156

Impacts of altered benthic invertebrate communities on the feeding ecology of yellow  

E-print Network

Impacts of altered benthic invertebrate communities on the feeding ecology of yellow perch (Perca of benthic macroinvertebrate communities. Benthic macroinvertebrates and yellow perch (Perca flavescens) were). For example, young-of-the-year yellow perch (Perca flavescens) are predominantly pelagic foragers. By the end

Rasmussen, Joseph

157

COMPARISON OF TWO INDICES OF BENTHIC COMMUNITY CONDITION IN CHESAPEAKE BAY  

EPA Science Inventory

The Chesapeake Benthic Index of Biotic Integrity (B-IBI) and the EMAP-VP Benthic Index were applied to samples from 239 sites in Chesapeake Bay. The B-IBI weights several community measures equally and uses a simple scoring system while the EMAP-VP Benthic Index uses discriminant...

158

Effects of Coral Reef Benthic Primary Producers on Dissolved Organic Carbon and Microbial Activity  

Microsoft Academic Search

Benthic primary producers in marine ecosystems may significantly alter biogeochemical cycling and microbial processes in their surrounding environment. To examine these interactions, we studied dissolved organic matter release by dominant benthic taxa and subsequent microbial remineralization in the lagoonal reefs of Moorea, French Polynesia. Rates of photosynthesis, respiration, and dissolved organic carbon (DOC) release were assessed for several common benthic

Andreas F. Haas; Craig E. Nelson; Linda Wegley Kelly; Craig A. Carlson; Forest Rohwer; James J. Leichter; Alex Wyatt; Jennifer E. Smith

2011-01-01

159

APPLICATION OF TWO INDICES OF BENTHIC COMMUNITY CONDITION IN CHESAPEAKE BAY  

EPA Science Inventory

The Chesapeake Bay Benthic Index of Biotic Integrity (B-161) and the Environmental Monitoring and Assessment Program's Virginian Province Benthic Index (EMAP-VP BI) were applied to 294 sampling events in Chesapeake Bay and the results were compared. These benthic indices are inte...

160

Do mangrove root structures function to shelter benthic macrofauna from predators?  

Microsoft Academic Search

Clarification of the role of mangrove root structures as shelter from predators for benthic animals was investigated by considering (1) the impact of predation on benthic faunal communities in a mangrove forest as indicated by a predator exclusion experiment, and (2) the uses and effects of mangrove root structures by benthic animals under laboratory conditions. In the exclusion experiment, three

Koetsu Kon; Hisashi Kurokura; Prasert Tongnunui

2009-01-01

161

Microcosm approach for brine impact assessment from seawater desalination on benthic assemblages  

Microsoft Academic Search

The brine discharge from seawater desalination has a strong impact on marine community, especially benthic community near brine outlet. The aim of this study is to examine the effect of brine discharge over soft bottom benthic community and changes of sediment quality by periodic brine exposure and water circulation confinement using small-scale benthic microcosms. Transparent acrylic cylinder (1?m in length

Sung Jin Yoon; Gyung Soo Park

2012-01-01

162

An analysis of benthic biological dynamics in a North Sea ecosystem model  

Microsoft Academic Search

This paper presents an overview and analysis of the benthic biological submodel of the European Regional Seas Ecosystem Model II (ERSEM II). This submodel consists of a detailed model description of the benthic system which is integrated with a marine ecosystem model which attempts to address the full range of pelagic and benthic biogeochemical and physical processes. The submodel simulates

J. C. Blackford

1997-01-01

163

Geophysical Conceptual Model for Benthic Flux and Submarine Groundwater Discharge  

NASA Astrophysics Data System (ADS)

Numerous investigators characterize benthic flux and submarine groundwater discharge (SGD) using a geochemical conceptual model that relies on the estimation of tracer fluxes into and out of a control volume. (Benthic flux is the rate of flow across the bed of any water body, per unit area of bed. Benthic flux is a vector that includes both discharge and recharge components. SGD is a benthic water discharge flux to a marine water body.) For the geochemical approach, benthic discharge flux or SGD is estimated by summing the flux of tracer into or out of the control volume---a water body or portion of a water body---and deducing that tracer deficiency within the control volume must be explained by SGD. Typically, estimated or measured fluxes include advection and mixing in surface-water, diffusion, evasion across the air-water interface, production, and decay. The geochemical model, however, does not account for fluxes that do not transport tracer. For example, investigators found equivalent (<10 dpm per liter) radon activities in both surface water, and in pore fluid within the upper 30 cm of sediment in the Indian River Lagoon, Florida, in June and July 2003. At this location, a surface-gravity wave with a five-centimeter amplitude and one-second period in 0.5 m of water forced a 12-cm-per-day SGD. The radon tracer technique may not characterize SGD forced by the one-second wave due to the time scale of the wave, the absence of a radon activity gradient between bed medium and surface water, and the <30 cm depth to which the wave affects the flow field within the porous medium. A new geophysical conceptual model for benthic flux is proposed. The model parses benthic flux into components driven by individual forcing mechanisms. The model recognizes that benthic flux components may interact in a constructive or destructive manner, such that benthic flux generated by multiple forcing mechanisms at the same location may not be equivalent to the linear sum of benthic flux generated by single forcing mechanisms. Restated: the whole may be different than the sum of the parts. Individual forcing mechanisms that drive benthic flux components include: the terrestrial hydraulic gradient, tide, surface gravity waves, density gradients, chemical gradients, diagenesis, bio-irrigation, sea-level rise, and bedform-current interaction. Other forcing mechanisms surely exist. Although many of these component forcing mechanisms can be characterized, component interactions are not fully understood. Differences exist between the geophysical and geochemical conceptual models. The geochemical model integrates the contribution of forcing mechanisms over both the control volume and duration of study. Because a tracer can not characterize a flux that does not transport the tracer, and because the time-scale or spatial-scale of some SGD forcing mechanisms is not resolved by certain tracers, the geochemical model may not describe all SGD to a water body. Restated: the geochemical model may only describe the component of SGD that transports the tracer. Some components of the geophysical model may be difficult or impossible to measure in natural systems. Interaction between specific components of the geophysical model may be intractable.

King, J. N.

2010-12-01

164

The PROWQM physical biological model with benthic pelagic coupling applied to the northern North Sea  

NASA Astrophysics Data System (ADS)

PROWQM, a 1-D depth resolving model which couples physical and microbiological processes in the water column with sedimentation/resuspension and benthic mineralisation processes, has been used to simulate seasonal changes of chlorophyll, nutrients and oxygen at the PROVESS north site (59°20'N 1°00'E) in the North Sea. PROWQM is derived from the 3-D model COHERENS, and improves COHEREN's benthic and pelagic biology. The physical sub-model of PROWQM implicitly solves turbulence closure equations forced by climatological, or realistic high-frequency, meteorological and tidal data. The pelagic biological sub-model 2MPPD includes a 'diatomy' microplankton (mp1) and a 'flagellatey' (or microbial loop) microplankton (mp2), the cycling of silicon and nitrogen, slow-sinking detritus, and fast-sinking phytodetritus. Phytodetritus is formed by shear-driven aggregation of particulate material, using a simple algorithm for bulk processes that is derived by considering the interactions of single cells. The microplankton compartments include heterotrophic bacteria and protozoa as well as phytoplankton, and most microplankton rates are specified with the aid of a 'heterotroph fraction' parameter, which was 0.125 for mp1 and 0.6 for mp2. The microbiological system is closed by mesozooplankton grazing pressures imposed as time varying series determined from observed zooplankton abundance. The benthic boundary sub-model includes a superficial fluff layer and a nutrient element reservoir in the consolidated sediment. Particulate material in the fluff layer can be resuspended (in response to bed stress by near-bed flows), mineralised or carried by bioturbation into the underlying, consolidated, sediment, where it is mineralised and its nutrients returned to the water-column at rates mainly dependent on (implicit) macrobenthic pumping. Benthic denitrification can occur when mineralisation rates exceed oxygen supply. Verification of the PROWQM numerical implementation used test cases and checks for nutrient element conservation. Simulations with realistic forcing, for a range of parameter values, were compared with historic observations in the NOWESP data set and during FLEX76, and with those made during the PROVESS cruises in autumn 1998. PROWQM provided a good simulation of the seasonal succession from a diatom-dominated spring bloom to summer dominance by small flagellates. The simulations included sedimentation of organic matter from the spring bloom, and qualitatively realistic behaviour of the fluff layer, but decay rates were too slow and there was almost no denitrification. The simulated surface mixed layer was too shallow during the summer. Simulated annual net microplankton primary production was in between 59 and 91 g C m -2 y -1. A large proportion of mineralisation, 28-47% of nitrogen and 40-67% of silicon mineralisation, took place as a result of the decay of sinking and resuspended detritus whilst in the water column. PROWQM is discussed in relation to other models that have been used to simulate this part of the North Sea, in particular the simpler ECOHAM1 and the more complex ERSEM, and in relation to PROWQM's evolution from COHERENS.

Lee, Jae-Young; Tett, Paul; Jones, Ken; Jones, Sarah; Luyten, Patrick; Smith, Claire; Wild-Allen, Karen

2002-12-01

165

Ecological stoichiometry in freshwater benthic systems: recent progress and perspectives  

E-print Network

, invertebrate primary consumers, and fungi. Differences in consumer C : nutrient ratios appear to be related of Georgia, Athens, GA, U.S.A. The Ecosystems Center, Marine Biological Laboratory, Woods Hole, MA, U. Description of elemental patterns among benthic resources and consumers provides a useful starting point

Benstead, Jon

166

Topographic complexity and roughness of a tropical benthic seascape  

NASA Astrophysics Data System (ADS)

Topographic complexity is a fundamental structural property of benthic marine ecosystems that exists across all scales and affects a multitude of processes. Coral reefs are a prime example, for which this complexity has been found to impact water flow, species diversity, nutrient uptake, and wave-energy dissipation, among other properties. Despite its importance, only limited assessments are available regarding the distribution or range of topographic complexity within or between benthic communities. Here, we show substantial variability in topographic complexity over the entire inner-shelf seascape of a tropical island. Roughness, estimated in terms of fractal dimension, served as a proxy for topographic complexity, and was computed for linear transects (DT), as well as the benthic surface (DS). Spatial variability in both DT and DS was correlated with the known distribution of benthic cover types in the seascape. Transect roughness values ranged from 1.0 to 1.7, with features along the shelf edge being markedly anisotropic with an along-shore bias, whereas regions with high scleractinian coral cover were nearly isotropic and exhibited minimal directional bias. Surface-roughness values ranged from 2.0 in predominantly hardbottom areas with low coral cover to 2.5 in areas with high coral cover. Quantifying roughness across the substrates and biological communities for an entire seascape provides a synoptic view of its spatial variability at scales appropriate for numerous research efforts, including ecosystem studies, parameterizing hydrodynamic models, and designing monitoring programs.

Zawada, David G.; Piniak, Gregory A.; Hearn, Clifford J.

2010-07-01

167

Relating remotely sensed optical variability to marine benthic biodiversity.  

PubMed

Biodiversity is important in maintaining ecosystem viability, and the availability of adequate biodiversity data is a prerequisite for the sustainable management of natural resources. As such, there is a clear need to map biodiversity at high spatial resolutions across large areas. Airborne and spaceborne optical remote sensing is a potential tool to provide such biodiversity data. The spectral variation hypothesis (SVH) predicts a positive correlation between spectral variability (SV) of a remotely sensed image and biodiversity. The SVH has only been tested on a few terrestrial plant communities. Our study is the first attempt to apply the SVH in the marine environment using hyperspectral imagery recorded by Compact Airborne Spectrographic Imager (CASI). All coverage-based diversity measures of benthic macrophytes and invertebrates showed low but statistically significant positive correlations with SV whereas the relationship between biomass-based diversity measures and SV were weak or lacking. The observed relationships did not vary with spatial scale. SV had the highest independent effect among predictor variables in the statistical models of coverage-derived total benthic species richness and Shannon index. Thus, the relevance of SVH in marine benthic habitats was proved and this forms a prerequisite for the future use of SV in benthic biodiversity assessments. PMID:23405180

Herkül, Kristjan; Kotta, Jonne; Kutser, Tiit; Vahtmäe, Ele

2013-01-01

168

dam logic: qualitative reasoning about benthic macroinvertebrate responses  

E-print Network

quickly from sediment releases #12;but...the dam bugs · declines in densities and shifts in species composition of macroinvertebrate communities observed with sediment flushing of reservoirs (Zuellig et aldam logic: qualitative reasoning about benthic macroinvertebrate responses to dam removal desiree

Tullos, Desiree

169

Organic wastewater effects on benthic invertebrates in the Manawatu River  

Microsoft Academic Search

The effects of the 3 main wastewater discharges on the benthic fauna of the Manawatu River were studied between March 1979 and January 1980. At least 4 replicate Surber samples were taken from each of 6 sites, on 5 occasions during this period. Deleatidium sp. (Ephemeroptera), Hydora sp. (Coleoptera), and the Chironomidae were the most useful indicator organisms, according to

D. M. Suckling

1982-01-01

170

Benthic Fluxes of Radium in Indian River Lagoon, Florida  

NASA Astrophysics Data System (ADS)

We examine three radium isotopes (224Ra, 223Ra and 226Ra) as a sediment-water interface tracer in upper Indian River Lagoon. Benthic fluxes are estimated using lagoon budgets, benthic chambers and pore water profiles. The lagoon budget approach estimates range from ~20 dpm/m2-d for 224Ra to ~7 dpm/ m2-d for 223Ra to zero for 226Ra. Benthic Chamber flux estimates determined over an 8 hour time period are statistically no different than zero for all three isotopes. Pore water profile flux estimates are low with 0.5 dpm/m2-d for 224Ra to 0.2 dpm/m2-d for 223Ra and zero for 226Ra. Benthic flux estimates correlate with the regeneration rates of the individual isotopes. Radium-224 has the largest flux value and is the isotope with the fastest regeneration rates due to a short half-life. The isotope with the slowest regeneration rate (226Ra) due to a 1600-year half-life, cannot be distinguished from zero in any of the estimates. The short half-life of 224Ra and 223Ra, allow for the examination of exchange processes at the sediment-water interface that cannot be achieved with the long-lived radium isotope (226Ra).

Smoak, J. M.; Swarzenski, P. W.; Cable, J. E.; Martin, J. B.

2002-12-01

171

Benthic metabolism in San Quintin Bay, Baja California, Mexico  

Microsoft Academic Search

Benthic metabolism was measured at 3 representative lagoon bottom sites in San Quintin Bay, Baja California, Mexico, during winter and summer from 1997 to 2000. At each site, and in every sampling period, three 0.5 m diameter transparent acrylic hemispherical domes were installed on bare sediment for ~24 h to determine fluxes of dissolved inorganic carbon (DIC), total alkalinity (TA),

Silvia E. Ibarra-Obando; Stephen V. Smith; Miriam Poumian-Tapia; Victor Camacho-Ibar; José D. Carriquiry; Martin Montes-Hugo

2004-01-01

172

Page 1 of 30 Fundamentals of Benthic Microbial Fuel Cells  

E-print Network

Page 1 of 30 17 Fundamentals of Benthic Microbial Fuel Cells: Theory, Development and Application to examine fundamental attributes of MFC performance and microbial physiology (e.g. ohmic resistance, current of harvesting electricity from natural systems, and the potential role(s) that BMFCs may play in power

Girguis, Peter R.

173

Relating Remotely Sensed Optical Variability to Marine Benthic Biodiversity  

PubMed Central

Biodiversity is important in maintaining ecosystem viability, and the availability of adequate biodiversity data is a prerequisite for the sustainable management of natural resources. As such, there is a clear need to map biodiversity at high spatial resolutions across large areas. Airborne and spaceborne optical remote sensing is a potential tool to provide such biodiversity data. The spectral variation hypothesis (SVH) predicts a positive correlation between spectral variability (SV) of a remotely sensed image and biodiversity. The SVH has only been tested on a few terrestrial plant communities. Our study is the first attempt to apply the SVH in the marine environment using hyperspectral imagery recorded by Compact Airborne Spectrographic Imager (CASI). All coverage-based diversity measures of benthic macrophytes and invertebrates showed low but statistically significant positive correlations with SV whereas the relationship between biomass-based diversity measures and SV were weak or lacking. The observed relationships did not vary with spatial scale. SV had the highest independent effect among predictor variables in the statistical models of coverage-derived total benthic species richness and Shannon index. Thus, the relevance of SVH in marine benthic habitats was proved and this forms a prerequisite for the future use of SV in benthic biodiversity assessments. PMID:23405180

Herkul, Kristjan; Kotta, Jonne; Kutser, Tiit; Vahtmae, Ele

2013-01-01

174

Bacterial nitrification activity directly associated with isolated benthic marine animals  

Microsoft Academic Search

Potential nitrification rates (PNR) directly associated with isolated marine macrobenthic invertebrates were measured for a range of benthic epifaunal and infaunal species (bivalves, gastropods, polychaetes and crustaceans) collected from the Sacca di Goro, Po River delta, Italy. In the case of the filter-feeding bivalves, Tapes philippinarum and Mytilus galloprovicialis the PNR associated with the shell surfaces and dissected animal tissues

D. T. Welsh; G. Castadelli

2004-01-01

175

Effect of light intensity upon salt marsh benthic microalgal photosynthesis  

Microsoft Academic Search

The rate of photosynthesis was measured in the field with in-situ populations of benthic microalgae during both summer and winter in three distinct areas of the salt marshes adjacent to Sapelo Island, Georgia, USA. In the vegetated portions of the marsh, maximum rates of photosynthesis occurred at light intensities higher than the average light intensities beneath the canopy. In the

D. E. Whitney; W. M. Darley

1983-01-01

176

BENTHIC MACROFAUNA-HABITAT RELATIONSHIPS IN TWO PACIFIC NORTHWEST ESTUARIES  

EPA Science Inventory

Habitat-based ecological risk assessments rely, in part, on estimates of the ecological value of the habitats at risk. As part of a larger programmatic effort to estimate estuarine habitat values, we determined benthic macrofauna-habitat relationships for 8 intertidal habitats i...

177

Microhabitat preferences of benthic fauna in a woodland stream  

Microsoft Academic Search

Estimates of numbers, biomass, and diversity of benthic macroinvertebrates were made quarterly over a two-year period to investigate microhabitat preferences. Although biomass of most taxa was significantly different among sampling times, physical factors also appeared to be important in determining abundance of many taxa. Optimum depth, velocity, substrate type, and turbulence were determined for major taxa. Optimum conditions for diversity

Donald J. Orth; O. Eugene Maughan

1983-01-01

178

Benthic Nitrogen Loss in the Arabian Sea Off Pakistan  

PubMed Central

A pronounced deficit of nitrogen (N) in the oxygen minimum zone (OMZ) of the Arabian Sea suggests the occurrence of heavy N-loss that is commonly attributed to pelagic processes. However, the OMZ water is in direct contact with sediments on three sides of the basin. Contribution from benthic N-loss to the total N-loss in the Arabian Sea remains largely unassessed. In October 2007, we sampled the water column and surface sediments along a transect cross-cutting the Arabian Sea OMZ at the Pakistan continental margin, covering a range of station depths from 360 to 1430?m. Benthic denitrification and anammox rates were determined by using 15N-stable isotope pairing experiments. Intact core incubations showed declining rates of total benthic N-loss with water depth from 0.55 to 0.18?mmol?N?m?2?day?1. While denitrification rates measured in slurry incubations decreased from 2.73 to 1.46?mmol?N?m?2?day?1 with water depth, anammox rates increased from 0.21 to 0.89?mmol?N?m?2?day?1. Hence, the contribution from anammox to total benthic N-loss increased from 7% at 360?m to 40% at 1430?m. This trend is further supported by the quantification of cd1-containing nitrite reductase (nirS), the biomarker functional gene encoding for cytochrome cd1-Nir of microorganisms involved in both N-loss processes. Anammox-like nirS genes within the sediments increased in proportion to total nirS gene copies with water depth. Moreover, phylogenetic analyses of NirS revealed different communities of both denitrifying and anammox bacteria between shallow and deep stations. Together, rate measurement and nirS analyses showed that anammox, determined for the first time in the Arabian Sea sediments, is an important benthic N-loss process at the continental margin off Pakistan, especially in the sediments at deeper water depths. Extrapolation from the measured benthic N-loss to all shelf sediments within the basin suggests that benthic N-loss may be responsible for about half of the overall N-loss in the Arabian Sea. PMID:23226143

Sokoll, Sarah; Holtappels, Moritz; Lam, Phyllis; Collins, Gavin; Schluter, Michael; Lavik, Gaute; Kuypers, Marcel M. M.

2012-01-01

179

Synthesis of benthic flux components in the Patos Lagooncoastal zone, Rio Grande do Sul, Brazil  

USGS Publications Warehouse

The primary objective of this work is to synthesize components of benthic flux in the Patos Lagoon coastal zone, Rio Grande do Sul, Brazil. Specifically, the component of benthic discharge flux forced by the terrestrial hydraulic gradient is 0.8 m3 d-1; components of benthic discharge and recharge flux associated with the groundwater tidal prism are both 2.1 m3 d-1; components of benthic discharge and recharge flux forced by surface-gravity wave setup are both 6.3 m3 d-1; the component of benthic discharge flux that transports radium-228 is 350 m3 d-1; and components of benthic discharge and recharge flux forced by surface-gravity waves propagating over a porous medium are both 1400 m3 d-1. (All models are normalized per meter shoreline.) Benthic flux is a function of components forced by individual mechanisms and nonlinear interactions that exist between components. Constructive and destructive interference may enhance or diminish the contribution of benthic flux components. It may not be possible to model benthic flux by summing component magnitudes. Geochemical tracer techniques may not accurately model benthic discharge flux or submarine groundwater discharge (SGD). A conceptual model provides a framework on which to quantitatively characterize benthic discharge flux and SGD with a multifaceted approach.

King, Jeffrey

2012-01-01

180

Benthic macrofauna habitat associations in Willapa Bay, Washington, USA  

NASA Astrophysics Data System (ADS)

Estuary-wide benthic macrofauna-habitat associations in Willapa Bay, Washington, United States, were determined for 4 habitats (eelgrass [ Zostera marina], Atlantic cordgrass [ Spartina alterniflora], mud shrimp [ Upogebia pugettensis], ghost shrimp [ Neotrypaea californiensis]) in 1996 and 7 habitats (eelgrass, Atlantic cordgrass, mud shrimp, ghost shrimp, oyster [ Crassostrea gigas], bare mud/sand, subtidal) in 1998. Most benthic macrofaunal species inhabited multiple habitats; however, 2 dominants, a fanworm, Manayunkia aestuarina, in Spartina, and a sand dollar, Dendraster excentricus, in subtidal, were rare or absent in all other habitats. Benthic macrofaunal Bray-Curtis similarity varied among all habitats except eelgrass and oyster. There were significant differences among habitats within- and between-years on several of the following ecological indicators: mean number of species ( S), abundance ( A), biomass ( B), abundance of deposit (AD), suspension (AS), and facultative (AF) feeders, Swartz's index (SI), Brillouin's index ( H), and jackknife estimates of habitat species richness (HSR). In the 4 habitats sampled in both years, A was about 2.5× greater in 1996 (a La Niña year) than 1998 (a strong El Niño year) yet relative values of S, A, B, AD, AS, SI, and H among the habitats were not significantly different, indicating strong benthic macrofauna-habitat associations despite considerable climatic and environmental variability. In general, the rank order of habitats on indicators associated with high diversity and productivity (high S, A, B, SI, H, HSR) was eelgrass = oyster ? Atlantic cordgrass ? mud shrimp ? bare mud/sand ? ghost shrimp = subtidal. Vegetation, burrowing shrimp, and oyster density and sediment %silt + clay and %total organic carbon were generally poor, temporally inconsistent predictors of ecological indicator variability within habitats. The benthic macrofauna-habitat associations in this study can be used to help identify critical habitats, prioritize habitats for environmental protection, index habitat suitability, assess habitat equivalency, and as habitat value criteria in ecological risk assessments in Willapa Bay.

Ferraro, Steven P.; Cole, Faith A.

2007-02-01

181

Hadal disturbance in the Japan Trench induced by the 2011 Tohoku-Oki earthquake.  

PubMed

In situ video observations and sediment core samplings were performed at two hadal sites in the Japan Trench on July, 2011, four months after the Tohoku-Oki earthquake. Video recordings documented dense nepheloid layers extending ~30-50 m above the sea bed. At the trench axis, benthic macrofauna was absent and dead organisms along with turbid downslope current were observed. The top 31 cm of sediment in the trench axis revealed three recent depositions events characterized by elevated (137)Cs levels and alternating sediment densities. At 4.9 km seaward from the trench axis, little deposition was observed but the surface sediment contained (134)Cs from the Fukushima Dai-ichi nuclear disaster. We argue that diatom blooms observed by remote sensing facilitated rapid deposition of (134)Cs to hadal environment and the aftershocks induced successive sediment disturbances and maintained dense nepheloid layers in the trench even four months after the mainshock. PMID:23715086

Oguri, Kazumasa; Kawamura, Kiichiro; Sakaguchi, Arito; Toyofuku, Takashi; Kasaya, Takafumi; Murayama, Masafumi; Fujikura, Katsunori; Glud, Ronnie N; Kitazato, Hiroshi

2013-01-01

182

Hadal disturbance in the Japan Trench induced by the 2011 Tohoku-Oki Earthquake  

PubMed Central

In situ video observations and sediment core samplings were performed at two hadal sites in the Japan Trench on July, 2011, four months after the Tohoku–Oki earthquake. Video recordings documented dense nepheloid layers extending ~30–50?m above the sea bed. At the trench axis, benthic macrofauna was absent and dead organisms along with turbid downslope current were observed. The top 31?cm of sediment in the trench axis revealed three recent depositions events characterized by elevated 137Cs levels and alternating sediment densities. At 4.9?km seaward from the trench axis, little deposition was observed but the surface sediment contained 134Cs from the Fukushima Dai–ichi nuclear disaster. We argue that diatom blooms observed by remote sensing facilitated rapid deposition of 134Cs to hadal environment and the aftershocks induced successive sediment disturbances and maintained dense nepheloid layers in the trench even four months after the mainshock. PMID:23715086

Oguri, Kazumasa; Kawamura, Kiichiro; Sakaguchi, Arito; Toyofuku, Takashi; Kasaya, Takafumi; Murayama, Masafumi; Fujikura, Katsunori; Glud, Ronnie N.; Kitazato, Hiroshi

2013-01-01

183

Phototoxicity of TiO2 nanoparticles to a freshwater benthic amphipod: are benthic systems at risk?  

EPA Science Inventory

This study investigated phototoxicity of TiO2 nanoparticles (nano-TiO2) to a freshwater benthic amphipod (Hyalella azteca) using 48-h and 96-h bioassays. Thorough monitoring of particle interactions with exposure media (Lake Superior water, LSW) and the surface of organisms was p...

184

The Benthic Terrain Modeler (BTM) is an ArcGIS-based tool that can be used by coastal and marine resource managers to examine the deepwater benthic  

E-print Network

, bathymetric position, and rugosity. The BTM contains a set of tools that allow users to create these products Scale BPI Classification Dictionary Benthic Structures Benthic ZonesRugosity Input Data The BTM Tool) to seascape features. Rugosity Rugosity is a measure of terrain complexity or the "bumpiness" of the terrain

Wright, Dawn Jeannine

185

Age and correlation of California Paleogene benthic foraminiferal stages  

USGS Publications Warehouse

Comparisons of age determinations and correlations derived from calcareous plankton with those derived from benthic foraminifers in a number of sections in California show significant overlap in time of the Ynezian through the Ulatisian Stages. Thus interbasin time correlations deduced from these stage assignments must be treated with caution. Calcareous plankton occasionally associated with benthic foraminifers diagnostic of the Narizian through the Zemorrian Stages indicate that the Narizian-Refugian boundary is within the upper Eocene of international usage and that the Refugian is entirely upper Eocene. Overlap of the Narizian and the Refugian appears to be minimal. The Zemorrian correlates, mostly, with the Oligocene, although the upper limit of the Zemorrian might be in the lower Miocene.

Poore, Richard Z.

1980-01-01

186

A Benthic Terrain Classification Scheme for American Samoa  

Microsoft Academic Search

Coral reef ecosystems, the most varied on earth, continually face destruction from anthropogenic and natural threats. The U.S. Coral Reef Task Force seeks to characterize and map priority coral reef ecosystems in the U.S.\\/Trust Territories by 2009. Building upon NOAA Biogeography shallow-water classifications based on Ikonos imagery, presented here are new methods, based on acoustic data, for classifying benthic terrain

Emily R. Lundblad; Dawn J. Wright; Joyce Miller; Emily M. Larkin; Ronald Rinehart; David F. Naar; Brian T. Donahue; S. Miles Anderson; Tim Battista

2006-01-01

187

Reservoir vital signs monitoring, 1991: Benthic macroinvertebrate community results  

SciTech Connect

As part of an extensive Reservoir Monitoring program to examine the ecological health of reservoirs in the TVA system, benthic communities were sampled and evaluated at 41 locations on 14 TVA reservoirs. Up to ten dredge samples were collected at locations from the forebay, inflow and transition zones. Surveys were conducted between mid-March and mid-April, 1991. The results of these surveys are presented and discussed in this report.

Masters, A.E.

1992-08-01

188

Benthic macroinvertebrate community results. Reservoir vital signs monitoring, 1990  

SciTech Connect

As part of an extensive program to monitor the health of reservoirs in the TVA system, dredges were used to sample benthic life at 36 locations on 12 Tennessee Valley Authority reservoirs and the Tennessee River downstream from the lowest reservoir in the system. Up to ten dredge samples were collected from forebay, transition zone, and inflow locations of typical reservoirs. The survey was conducted between mid March and mid April, 1990. Results are described.

Jenkinson, J.J.

1991-06-01

189

Benthic macroinvertebrates associated with four species of macrophytes  

Microsoft Academic Search

Benthic macroinvertebrates associated with four species of macrophytes (Nymphoides peltata, Ceratophyllum demersum, Polygonum amphibium and Carex sp.) were investigated during two growing seasons (2001 and 2002) in the slow-flowing ?onakut Channel in the Kopa?ki rit\\u000a Nature Park in Croatia. A total of 31 macroinvertebrate taxa were found. C. demersum, a submerged plant with dissected leaves, supported the highest macroinvertebrate abundance,

Irella Bogut; Jasna Vidakovi?; Goran Palijan; Dubravka ?erba

2007-01-01

190

Ecology of benthic and epiphytic nematodes in brackish waters  

Microsoft Academic Search

Abundances of benthic nematodes from shallow waters in Tvärminne, Finland and in Ringkøbing Fjord, Denmark averaged 1.2–1.5\\u000a 106 individuals m?2. Less than 20 species were found. More than 80% of the individuals were made up by Anoplostoma viviparum, Chromadorita fennica, Axonolaimus spinosus, Daptonema trabeculosum and Sabatieria pulchra. S. pulchra is designated as an anoxybiotic species and is attracted to the

P. Jensen

1984-01-01

191

Modelling benthic denitrification processes over a whole drainage network  

NASA Astrophysics Data System (ADS)

SummaryDenitrification is an important process of nitrogen cycling in river ecosystems as it can regulate nitrogen availability, and therefore primary production, controlling the degree of eutrophication. The strength of denitrification within a river network can alternate very rapidly in space and time and is essentially driven by the interactions between surface water, river geomorphology and microbial process rates. In this study, benthic denitrification was quantified over an entire drainage network by linking a deterministic sediment module [Thouvenot M., Billen G., Garnier J., 2007. Modelling nutrient exchange at the sediment-water interface of river systems. J. Hydrol. 341(1-2), 55-78] to a hydrological/biogeochemical model (Riverstrahler). The benthic module included the calculation of nutrient exchanges across the sediment-water interface as a result of the sedimentation flux of organic material provided by Riverstrahler. Along the Seine, the coupled model was able to reproduce nutrients concentrations in the water and the impact of pollution from point sources in terms of fluxes across the sediment-water interface. Over the entire drainage network of the Seine river system the model simulated the observed increase of organic matter content in the sediment with stream order and its subsequent increase of oxygen and nutrients fluxes at the sediment-water interface. Moreover, due to the high variability of denitrification in space and time, Riverstrahler is a better tool to approximate denitrification over an entire year and drainage network than a calculation based on sparse direct measurements of benthic denitrification. Finally, the nitrogen budgets of two different hydrological years (wet and dry) showed that although for both years riparian denitrification was more important than benthic denitrification, the latter could not be neglected during dry years as it contributed to up to 10% of the losses from river inputs.

Thouvenot-Korppoo, Marie; Billen, Gilles; Garnier, Josette

2009-12-01

192

Benthic foraminifera from polluted marine environment of Sulaibikhat Bay (Kuwait)  

Microsoft Academic Search

Quantitative analyses of recent benthic foraminiferal assemblages (living and dead) were carried out on the surface sediments\\u000a of Sulaibikhat Bay. Marked contrast in foraminiferal assemblages between the shallow tidal mudflats and the deep tidal channel\\u000a and their relation to the extent of pollution were observed. Cluster analysis of quantitative data on the distribution of\\u000a foraminiferal tests revealed three assemblages that

A. Z. Al-Zamel; M. A. Al-Sarawi; S. R. Khader; I. A. Al-Rifaiy

2009-01-01

193

Environmental conditions in high mountain lakes containing toxic benthic cyanobacteria  

Microsoft Academic Search

In glacial lakes on an alpine pasture in Switzerland, benthic cyanobacteria produced microcystin, a cyclic hepatotoxic heptapeptide.\\u000a The cyanobacteria formed dense mats on sediments and submerged stones. The mats consisted mainly of Oscillatoria limosa, Phormidium\\u000a konstantinosum (= Oscillatoria tenuis) and Tychonema granulatum (= Oscillatoria granulata). In order to characterize the ecological\\u000a conditions of these cyanobacteria, nutrient concentrations were determined, and

Konstanze Mez; Kurt Hanselmann; Hans Rudolf Preisig

1998-01-01

194

Declines in benthic macroinvertebrate populations in southern Lake Michigan  

Microsoft Academic Search

Abstract: Densities of the major benthic macroinvertebrate groups declined dramatically at sites shallower than 50 m in southern Lake Michigan between 1980 and 1993. Declines in Diporeia, Oligochaeta, and Sphaeriidae ranged from 40 to 75% at these depths. Total densities declined from 16 800·m, in 1980?1987. We hypothesize that the filtering activities of large populations of Dreissena polymorpha,in nearshore waters

Thomas F. Nalepa; David J. Hartson; David L. Fanslow; Gregory A. Lang; J. Lozano

195

Modern benthic foraminifer distribution in the Amerasian Basin, Arctic Ocean  

USGS Publications Warehouse

A total of 38 box cores were collected from the Amerasian Basin, Arctic Ocean during the U.S. Geological Survey 1992 (PI92-AR) and 1993 (PI93-AR) Arctic Cruises aboard the U.S. Coast Guard Icebreaker Polar Star. In addition, the cruises collected geophysical data, piston cores and hydrographic data to address the geologic and oceanographic history of the western Arctic Ocean. This paper reports the results of the quantitative analyses of benthic foraminifer distribution data of the total (live + dead) assemblages derived from 22 box core-top samples. The results show that a distinct depth distribution of three dominant benthic foraminifer assemblages, the Textularia spp. - Spiroplectammina biformis, Cassidulina teretis and Oridorsalis tener - Eponides tumidulus Biofacies are strongly controlled by the dominant water masses within the Canada Basin: the Arctic Surface Water, Arctic Intermediate Water and Canada Basin Deep Water. The faunal distributions and their oceanographic associations in the Canada Basin are consistent with observations of benthic foraminifer distributions from other regions within the Arctic Ocean.

Ishman, S. E.; Foley, K. M.

1996-01-01

196

Zebra mussel effects on benthic invertebrates: physical or biotic?  

USGS Publications Warehouse

In soft sediments, Dreissena spp. create firm substrate in the form of aggregates of living mussels (druses) that roll free on the sediments. Druses provide physical structure which increases habitat heterogeneity, and the mussels increase benthic organic matter through the production of pseudofeces and feces. Descriptive and experimental studies were used to determine: 1) whether the density of benthic invertebrates in soft sediments increased in the presence of druses, and 2) whether the invertebrate assemblage responded to the physical structure provided by a druse or to some biotic effect associated with the presence of living mussels. In core samples collected biweekly during summer in Presque Isle Bay, Erie, Pennsylvania, amphipods, chironomids, oligochaetes, turbellarians, and hydrozoans were significantly more abundant in sand with druses than in bare sand. When mesh bags containing either a living druse, non-living druse, or no druse were incubated in the bay for 33 d, we found that chironomids were significantly more abundant in treatments with living druses than with non-living druses, and in treatments with non-living druses than with no druse; turbellarians, amphipods, and hydrozoans were significantly more abundant in treatments with living or non-living druses than with no druse; oligochaetes showed no significant differences among treatments. This study demonstrates that most taxa of benthic invertebrates in soft substrate respond specifically to the physical structure associated with aggregates of mussel shells, but further study is needed to examine chironomid responses to some biotic effect dependent on the presence of living mussels.

Botts, P. Silver; Patterson, Benjamin A.; Schloesser, Don W.

1996-01-01

197

Improved oxygen isotope temperature calibrations for cosmopolitan benthic foraminifera  

NASA Astrophysics Data System (ADS)

Despite decades of use as a paleoceanographic proxy, considerable uncertainty still surrounds the temperature dependence of benthic foraminiferal ?18O. Widely applied paleotemperature equations may mix non-equilibrium foraminifera with equilibrium synthetic calcite, resulting in temperature sensitivities that are too large. Warm-water foraminiferal calibrations may give temperature sensitivities that are too small for very cold waters. Here we combine new core top measurements from the Florida Straits and the Arctic Ocean with published data to derive new ?18O:temperature relationships for three groups of benthic foraminifera. We derive a quadratic equation for Cibicidoides and Planulina that agrees well with equilibrium synthetic calcite, and that should be applicable over all oceanographic temperatures. We find that Uvigerina is not at equilibrium and is isotopically heavier than Cibicidoides and Planulina by 0.47‰, in contrast to the historically used 0.64‰. Hoeglundina elegans is further enriched and appears to be slightly heavier than equilibrium aragonite. Finally we discuss the implications of the Florida Straits observations for the hypothesis that benthic foraminifera precipitate their shells from a pH-dependent mixture of bicarbonate and carbonate ions.

Marchitto, T. M.; Curry, W. B.; Lynch-Stieglitz, J.; Bryan, S. P.; Cobb, K. M.; Lund, D. C.

2014-04-01

198

Benthic fluxes of cadmium, copper, nickel, zinc and lead in the coastal environment  

NASA Astrophysics Data System (ADS)

Fluxes of trace metals across the sediment-water interface were measured in situ at 6 m depth in Gullmarsfjorden, Sweden, using diver-operated stirred benthic flux-chambers. These were equipped so that dissolved oxygen and pH could be maintained near ambient seawater values (regulated chamber) or be allowed to change in response to benthic respiration (unregulated chamber). In the regulated chamber, Cd, Cu, Ni, and Zn were released from the sediment at constant rates both during a winter experiment (water temperature -1 °C) and during a fall experiment (+ 10°C). During the fall experiment, fluxes (in nmol m -2 d -1) of 13 (Cd), 118 (Cu), 209 (Ni), and 1400 (Zn) were measured. In winter, the release rates were lower by factors of 5 and 10 for Cu and Ni but not significantly different for Cd and Zn. Neither release nor uptake by the sediment could be demonstrated for Pb. The pore-water in a diver-collected core was depleted in Cd, Cu, and Zn and slightly enriched in Ni and Pb, relative to the ambient seawater. There was no correspondence between fluxes calculated from porewater profiles and actually measured fluxes; nor could the fluxes be directly related to the degradation rate of organic matter. In the unregulated chamber, initial trace metal release rates were lower than in the regulated chamber. As the oxygen concentration decreased, the metal fluxes decreased as well and were ultimately reversed as sulfide began to appear in the water. The fluxes of trace metals are sensitive to the oxygen regime in the flux chamber because the solubilization of these metals, which takes place in a thin oxic layer near the sediment surface, depends on the oxygen flux across the sediment-water interface.

Westerlund, Stig F. G.; Anderson, Leif G.; Hall, Per O. J.; Iverfeldt, Åke; Van Der Loeff, Michiel M. Rutgers; Sundby, Bjørn

1986-06-01

199

An assessment of benthic condition in several small watersheds of the Chesapeake Bay, USA.  

PubMed

We examined benthic condition in three small watersheds in the Chesapeake Bay. Characterization of benthic condition was based on the combined measurements of benthic fauna, sediment toxicity, and sediment contaminant loads. Significant differences between watersheds were detected for sediment contaminant concentrations and water quality. The intensity of benthic impairment was greatest in the river surrounded by the most developed watershed. Spatial patterns of benthic condition were detected within all three watersheds. In contrast to current, intense focus on nutrient pollution in the Chesapeake Bay, qualitative comparison of our findings to land-use patterns supports findings of other studies that suggest benthic condition in tributaries of the Chesapeake Bay may more closely relate to urbanization than agricultural land uses. PMID:20632087

Leight, Andrew K; Slacum, Ward H; Wirth, Ed F; Fulton, Mike H

2011-05-01

200

Effects of an oil spill on benthic community production and respiration on subtropical intertidal sandflats.  

PubMed

This study determined effects of an oil spill on subtropical benthic community production and respiration by monitoring CO2 fluxes in benthic chambers on intertidal sandflats during emersion before and after an accidental spill. The oil spill decreased sediment chlorophyll a concentrations, altered benthic macrofaunal community, and affected ecological functioning by suppressing or even stopping microalgal production, increasing bacterial respiration, and causing a shift from an autotrophic system to a heterotrophic system. Effects of the oil spill on the macrofauna were more severe than on benthic microalgae, and affected sedentary infauna more than motile epifauna. Despite the oil spill's impact on the benthic community and carbon metabolism, the affected area appeared to return to normal in about 23 days. Our results suggest that the prompt response of benthic metabolism to exposure to petroleum hydrocarbons can serve as a useful indicator of the impact of an oil spill. PMID:23743269

Lee, Li-Hua; Lin, Hsing-Juh

2013-08-15

201

Predictive models of benthic invertebrate methylmercury in Ontario and Quebec lakes  

Microsoft Academic Search

Multivariate analyses on benthic invertebrate methylmercury concentrations ((MeHg)) and water chemistry from 12 Quebec water bodies were used to guide the construction of simple, predictive models of benthic invertebrate (MeHg) in 23 lakes in Ontario and Quebec. Separate predictive models for collector-shredder and predatory benthic invertebrates were constructed using multiple regression and were assessed for their predictive utility by cross-

M. D. Rennie; N. C. Collins; C. F. Purchase; A. Tremblay

2005-01-01

202

Benthic production and processes off Baja California, northwest Africa and Peru: a classification of benthic subsystems in upwelling ecosystems  

SciTech Connect

Estimates of the standing stocks, secondary production and metabolism of the benthos have been compared in the coastal upwelling ecosystems off northwest Africa, Baja California, and southern Peru. Northwest Africa is characterized by shelf break upwelling and as a result standing stocks, macrobenthic production and sediment organic matter are highest out at the shelf-slope boundary. Sediment microbial activity and biomass on the other hand are highest nearshore in the dynamic zone where aeolian silt and sand are being blown into the sea from the Sahara Desert. Baja California is dominated by the red crab, Pleuroncodes planipes, having high rates of growth and metabolic utilization of organic matter, both on bottom and in the water. Peru benthos and metabolism are very different from the above areas because of the low oxygen concentrations in the bottom water. Organic matter is far higher in the sediment and heterotrophic metabolism is principally anaerobic rather than aerobic. A normal offshore benthic fauna is replaced by a mat of sulfur bacteria with unknown production and metabolic rates. Benthic subsystems in upwelling ecosystems can be placed in two categories: those overloaded with organic matter, depleted of oxygen and dominated by sulfate reduction and those that are not overloaded and remain aerobic. Peru and southwest Africa typify overloaded systems whereas NW Africa and Baja California are examples of aerobic systems. Although benthic metabolism and ionorganic nutrient regeneration are high in both types of subsystems, all upwelling ecosystems, with their dynamic open boundaries, export organic particulate matter and import inorganic nutrients at rates that are far in excess of that consumed or produced by benthic metabolism. 42 refs., 7 figs., 8 tabs.

Rowe, G.T.

1983-01-01

203

USGS-NPS Servicewide Benthic Mapping Program (SBMP) workshop report  

USGS Publications Warehouse

The National Park Service (NPS) Inventory and Monitoring (I&M) Program recently allocated funds to initiate a benthic mapping program in ocean and Great Lakes parks in alignment with the NPS Ocean Park Stewardship 2007-2008 Action Plan. Seventy-four (ocean and Great Lakes) parks, spanning more than 5,000 miles of coastline, many affected by increasing coastal storms and other natural and anthropogenic processes, make the development of a Servicewide Benthic Mapping Program (SBMP) timely. The resulting maps and associated reports will be provided to NPS managers in a consistent servicewide format to help park managers protect and manage the 3 million acres of submerged National Park System natural and cultural resources. Of the 74 ocean and Great Lakes park units, the 40 parks with submerged acreage will be the focus in the early years of the SBMP. The NPS and U.S. Geological Survey (USGS) convened a workshop (June 3-5, 2008) in Lakewood, CO. The assembly of experts from the NPS and other Federal and non-Federal agencies clarified the needs and goals of the NPS SBMP and was one of the key first steps in designing the benthic mapping program. The central needs for individual parks, park networks, and regions identified by workshop participants were maps including bathymetry, bottom type, geology, and biology. This workshop, although not an exhaustive survey of data-acquisition technologies, highlighted the more promising technologies being used, existing sources of data, and the need for partnerships to leverage resources. Workshop products include recommended classification schemes and management approaches for consistent application and products similar to other long-term NPS benthic mapping efforts. As part of the SBMP, recommendations from this workshop, including application of an improved version of the Coastal and Marine Ecological Classification Standard (CMECS), will be tested in several pilot parks. In 2008, in conjunction with the findings of this workshop, the NPS funded benthic mapping projects in Glacier Bay National Park and Preserve, Golden Gate National Recreational Area, Sleeping Bear Dunes National Lakeshore, Gulf Islands National Seashore, Virgin Islands National Park, and Virgin Islands Coral Reef National Monument.

Moses, Christopher S.; Nayagandhi, Amar; Brock, John; Beavers, Rebecca

2010-01-01

204

RESPONSES OF BENTHIC MICROORGANISMS (THECAMOEBIANS) TO OIL SANDS PROCESS-AFFECTED MATERIALS; PROVIDING  

E-print Network

RESPONSES OF BENTHIC MICROORGANISMS (THECAMOEBIANS) TO OIL SANDS PROCESS-AFFECTED MATERIALS) are protists (unicellular microorganisms) that comprise an important component within the microbial trophic

Patterson, Timothy

205

Benthic habitat characterisation of soft-bottom continental shelves: Integration of acoustic surveys, benthic samples and trawling disturbance intensity  

NASA Astrophysics Data System (ADS)

Eleven sites were located on Mediterranean continental shelves to explore the link between the physical characteristics and epibenthic fauna from soft-sediment habitats. These sites, at 32-82 m in depth, were associated with fishing grounds and the trawling intensity was estimated at the site scale to assess the effects of trawling on benthic communities. Each site was surveyed with Multi-Beam (bathymetry and backscatter), side-scan sonar, benthic grabs and a surface dredge. The sites were clustered in three habitat types. Habitat 1, with moderate trawling disturbance, was characterised by homogeneous mud and associated epifauna that was also highly homogeneous across sites. Habitat 2, with sandy mud and scattered gravel and rocks, had a high abundance of sessile suspension feeders that probably attach to the coarser substratum and benefit from the low fishing disturbance in these sites. Habitat 3 included sites with heterogeneous sediments with maërl as the prevailing biocenosis and having the highest species richness, despite being subjected to variable trawling intensity. Statistical models were used to relate environmental parameters and the species abundance. More than 3 physical variables were necessary to explain the epifaunal patterns across sites, including the percentage of mud, sediment heterogeneity and fishing effort. These analyses are an essential step for extrapolating information from benthic samples to the larger scale of habitats, mapped through acoustic surveys. Despite this, a good integration is required between the mapping of physical habitat distribution and the ecological knowledge of communities.

de Juan, S.; Lo Iacono, C.; Demestre, M.

2013-01-01

206

A Servicewide Benthic Mapping Program for National Parks  

USGS Publications Warehouse

In 2007, the National Park Service (NPS) Inventory and Monitoring Program directed the initiation of a benthic habitat mapping program in ocean and coastal parks in alignment with the NPS Ocean Park Stewardship 2007-2008 Action Plan. With 74 ocean and Great Lakes parks stretching over more than 5,000 miles of coastline across 26 States and territories, this Servicewide Benthic Mapping Program (SBMP) is essential. This program will deliver benthic habitat maps and their associated inventory reports to NPS managers in a consistent, servicewide format to support informed management and protection of 3 million acres of submerged National Park System natural and cultural resources. The NPS and the U.S. Geological Survey (USGS) convened a workshop June 3-5, 2008, in Lakewood, Colo., to discuss the goals and develop the design of the NPS SBMP with an assembly of experts (Moses and others, 2010) who identified park needs and suggested best practices for inventory and mapping of bathymetry, benthic cover, geology, geomorphology, and some water-column properties. The recommended SBMP protocols include servicewide standards (such as gap analysis, minimum accuracy, final products) as well as standards that can be adapted to fit network and park unit needs (for example, minimum mapping unit, mapping priorities). SBMP Mapping Process. The SBMP calls for a multi-step mapping process for each park, beginning with a gap assessment and data mining to determine data resources and needs. An interagency announcement of intent to acquire new data will provide opportunities to leverage partnerships. Prior to new data acquisition, all involved parties should be included in a scoping meeting held at network scale. Data collection will be followed by processing and interpretation, and finally expert review and publication. After publication, all digital materials will be archived in a common format. SBMP Classification Scheme. The SBMP will map using the Coastal and Marine Ecological Classification Standard (CMECS) that is being modified to include all NPS needs, such as lacustrine ecosystems and submerged cultural resources. CMECS Version III (Madden and others, 2010) includes components for water column, biotic cover, surface geology, sub-benthic, and geoform. SBMP Data Archiving. The SBMP calls for the storage of all raw data and final products in common-use data formats. The concept of 'collect once, use often' is essential to efficient use of mapping resources. Data should also be shared with other agencies and the public through various digital clearing houses, such as Geospatial One-Stop (http://gos2.geodata.gov/wps/portal/gos). To be most useful for managing submerged resources, the SBMP advocates the inventory and mapping of the five components of marine ecosystems: surface geology, biotic cover, geoform, sub-benthic, and water column. A complete benthic inventory of a park would include maps of bathymetry and the five components of CMECS. The completion of mapping for any set of components, such as bathymetry and surface geology, or a particular theme (for example, submerged aquatic vegetation) should also include a printed report.

Moses, Christopher S.; Nayegandhi, Amar; Beavers, Rebecca; Brock, John

2010-01-01

207

Application of Multiple Index Development Approaches to Benthic Invertebrate Data from the Virginian Biogeographic Province (SETAC NA)  

EPA Science Inventory

Benthic invertebrate indices have commonly been utilized to assess benthic invertebrate communities. These indices have been constructed using different techniques, but have shown different levels of application success. For example, the EMAP Virginian Province Index did not pe...

208

Ecological periodic tables for benthic macrofaunal usage of estuarine habitats : Insights from a case study in Tillamook bay, Oregon, USA  

EPA Science Inventory

This study validates the ecological relevance of estuarine habitat types to the benthic macrofaunal community and, together with previous similar studies, suggests they can serve as elements in ecological periodic tables of benthic macrofaunal usage in the bioregion. We compared...

209

Disturbance, colonization and development of Antarctic benthic communities  

PubMed Central

A decade has yielded much progress in understanding polar disturbance and community recovery—mainly through quantifying ice scour rates, other disturbance levels, larval abundance and diversity, colonization rates and response of benthos to predicted climate change. The continental shelf around Antarctica is clearly subject to massive disturbance, but remarkably across so many scales. In summer, millions of icebergs from sizes smaller than cars to larger than countries ground out and gouge the sea floor and crush the benthic communities there, while the highest wind speeds create the highest waves to pound the coast. In winter, the calm associated with the sea surface freezing creates the clearest marine water in the world. But in winter, an ice foot encases coastal life and anchor ice rips benthos from the sea floor. Over tens and hundreds of thousands of years, glaciations have done the same on continental scales—ice sheets have bulldozed the seabed and the zoobenthos to edge of shelves. We detail and rank modern disturbance levels (from most to least): ice; asteroid impacts; sediment instability; wind/wave action; pollution; UV irradiation; volcanism; trawling; non-indigenous species; freshwater inundation; and temperature stress. Benthic organisms have had to recolonize local scourings and continental shelves repeatedly, yet a decade of studies have demonstrated that they have (compared with lower latitudes) slow tempos of reproduction, colonization and growth. Despite massive disturbance levels and slow recolonization potential, the Antarctic shelf has a much richer fauna than would be expected for its area. Now, West Antarctica is among the fastest warming regions and its organisms face new rapid changes. In the next century, temperature stress and non-indigenous species will drastically rise to become dominant disturbances to the Antarctic life. Here, we describe the potential for benthic organisms to respond to disturbance, focusing particularly on what we know now that we did not a decade ago. PMID:17405206

Barnes, David K.A; Conlan, Kathleen E

2006-01-01

210

Calibration of Multiple Trace Metal Proxies in Benthic Foraminifera  

NASA Astrophysics Data System (ADS)

Paleoceanographic reconstructions of deep ocean conditions rely almost entirely on the chemistry of benthic foraminifera. In order to accurately utilize paleoceanographic proxies it is necessary to understand the biogeochemical behavior of their incorporation into the shells of benthic foraminifera. We examine modern or near-modern benthic foraminifera picked from a set of 38 multi-core casts from the Dry Tortugas and Great Bahama Bank regions (Florida Straits), collected during R/V Knorr cruise 166-2. Multi-core sites span temperature, salinity, and carbonate ion concentration ranges of 15°C, 1.9 psu, and 120 ?mol/kg respectively, as determined from in situ seawater sampling and nearby CTD casts. We present new calibrations of Mg/Ca (temperature), Cd/Ca (labile nutrient), and Zn/Ca (refractory nutrient). Possible uses of U/Ca and Li/Ca as proxies for carbonate ion concentration are also discussed. Here we focus on the cosmopolitan species Cibicidoides pachyderma and Uvigerina peregrina. Data presented here significantly expand upon the existing calibrations of Mg/Ca in C. pachyderma, which rely heavily on data from Little Bahama Bank. Previous calibrations have used an exponential equation to explain the Mg/Ca - temperature relationship. This new dataset, which includes nine multi-core sites warmer than 15°C, indicates that a linear equation may be a better fit. Warm-water Mg/Ca values, measured by both ICP-MS and SIMS, are notably lower than previous measurements from Little Bahama Bank. This new calibration may call for a reexamination of paleotemperature reconstructions that employ Cibicidoides Mg/Ca. Existing Uvigerina Mg/Ca calibrations differ significantly; an independent calibration of Uvigerina would be exceedingly beneficial to studies in regions where Cibicidoides are uncommon.

Bryan, S. P.; Marchitto, T. M.; Curry, W. B.

2005-12-01

211

Benthic macroinvertebrate richness along Sausal Creek, Oakland, California  

NASA Astrophysics Data System (ADS)

Sausal Creek, 5.0 km long, is one of the principal watercourses in Oakland, California. The headwaters of Sausal Creek arise in the Oakland Hills and the creek flows southwestward through the city, discharging into the tidal canal that separates the island of Alameda from Oakland; the creek ultimately flows into San Francisco Bay. Due to the presence of rainbow trout, the stream health of Sausal Creek is a local conservation priority. In the present study, a survey of benthic macroinvertebrates in the creek was conducted and possible correlations between environmental variables and taxonomic richness were analyzed. Three stations along the creek were sampled using a 30.5cm 500 micron aquatic d-net, and temperature, pH and dissolved oxygen levels were measured in creek samples obtained at each station. Temperature, pH and dissolved oxygen levels remained constant along the creek. Taxonomic richness was highest at the upstream site of Palo Seco, located in an eastern section of the creek, and furthest downstream at Dimond Park, in the western portion of the creek. The Monterrey site, just west of Palo Seco was found to be significantly low in benthic macroinvertebrates. The Palo Seco and Monterrey sites are separated by Highway 13 and storm drain inputs may bring contaminants into the creek at this site. At the Monterrey site Sausal Creek follows the Hayward Fault, gas emissions or change in substrate may also affect the local population of benthic invertebrates. Further research will be conducted to determine what factors are contributing to this local anomaly.

Lara, D.; Ahumada, E.; Leon, Y.; Bracho, H.; Telles, C.

2012-12-01

212

Benthic buffers and boosters of ocean acidification on coral reefs  

NASA Astrophysics Data System (ADS)

Ocean acidification is a threat to marine ecosystems globally. In shallow-water systems, however, ocean acidification can be masked by benthic carbon fluxes, depending on community composition, seawater residence time, and the magnitude and balance of net community production (pn) and calcification (gn). Here, we examine how six benthic groups from a coral reef environment on Heron Reef (Great Barrier Reef, Australia) contribute to changes in seawater aragonite saturation state (?a). Results of flume studies showed a hierarchy of responses across groups, depending on CO2 level, time of day and water flow. At low CO2 (350-450 ?atm), macroalgae (Chnoospora implexa), turfs and sand elevated ?a of the flume water by around 0.10 to 1.20 h-1 - normalised to contributions from 1 m2 of benthos to a 1 m deep water column. The rate of ?a increase in these groups was doubled under acidification (560-700 ?atm) and high flow (35 compared to 8 cm s-1). In contrast, branching corals (Acropora aspera) increased ?a by 0.25 h-1 at ambient CO2 (350-450 ?atm) during the day, but reduced ?a under acidification and high flow. Nighttime changes in ?a by corals were highly negative (0.6-0.8 h-1) and exacerbated by acidification. Calcifying macroalgae (Halimeda spp.) raised ?a by day (by around 0.13 h-1), but lowered ?a by a similar or higher amount at night. Analyses of carbon flux contributions from four different benthic compositions to the reef water carbon chemistry across Heron Reef flat and lagoon indicated that the net lowering of ?a by coral-dominated areas can to some extent be countered by long water residence times in neighbouring areas dominated by turfs, macroalgae and potentially sand.

Anthony, K. R. N.; Diaz-Pulido, G.; Verlinden, N.; Tilbrook, B.; Andersson, A. J.

2013-02-01

213

Larger benthic foraminifera of the Paleogene Promina Beds (Croatia)  

NASA Astrophysics Data System (ADS)

In order to add more information about complex origin of Promina Beds (traditionally interpreted as Paleogene molasse of Dinarides), two sections (Lišani Ostrova?ki and Ostrovica, Central Dalmatia, Croatia) have been studied in detail. Sampled carbonate sequences contain predominantly coralline red algae, larger benthic foraminifera and corals. Based on sedimentary textures, nummulitid (Nummulites s.str and Asterigerina sp.) test shapes and the associated skeletal components, altogether three types of the Middle Eocene (Lutetian to Bartonian) facies were recognized. The Ostrovica section is composed of alternating couples of marly limestones and marls, several decimeters thick with great lateral continuity. Two facies which vertically alternate are recognized as Nummulites - Asterigerina facies, where patchily dispersed large, robust and party reworked larger benthic foraminifera constitute 20% and small bioclasts (fomaniniferal fragments and whole tests less than 3 mm in diameters) 10% of rock volume and, Coral - Red algal facies with coral fragments of solitary and colonial taxa up to 1 cm in size constitute 5 - 40%, red algae 15 - 60% and lager benthic foraminifera up to 5% of rock volume. The textural and compositional differences among the facies suggest rhythmic exchanges of conditions that characterize shallower part of the mesophotic zone with abundant nummulithoclasts with deeper mesophotic, lime mud-dominated settings where nummulitids with the flat tests, coralline red algae and scleractinian corals are common. The scleractinian corals (comprising up to 20% of rock volume) encrusted by foraminifera (Acervulina, Haddonia and nubeculariids) or coralline red algae and foraminiferal assemblage made of orthophragminid and nummulitid tests scattered in matrix, are distributed uniformly throughout the studied Lišani Ostrova?ki section. In the central part of section, wavy to smooth thin (< 1 mm) crusts (laminas) alternating with encrusted corals occur. The characteristics of associated fauna and spatial relationship between corals and laminations indicate that this facies originated in a mid-ramp (shelf) setting.

Cosovic, V.; Mrinjek, E.; Drobne, K.

2012-04-01

214

Disturbance, colonization and development of Antarctic benthic communities.  

PubMed

A decade has yielded much progress in understanding polar disturbance and community recovery-mainly through quantifying ice scour rates, other disturbance levels, larval abundance and diversity, colonization rates and response of benthos to predicted climate change. The continental shelf around Antarctica is clearly subject to massive disturbance, but remarkably across so many scales. In summer, millions of icebergs from sizes smaller than cars to larger than countries ground out and gouge the sea floor and crush the benthic communities there, while the highest wind speeds create the highest waves to pound the coast. In winter, the calm associated with the sea surface freezing creates the clearest marine water in the world. But in winter, an ice foot encases coastal life and anchor ice rips benthos from the sea floor. Over tens and hundreds of thousands of years, glaciations have done the same on continental scales-ice sheets have bulldozed the seabed and the zoobenthos to edge of shelves. We detail and rank modern disturbance levels (from most to least): ice; asteroid impacts; sediment instability; wind/wave action; pollution; UV irradiation; volcanism; trawling; non-indigenous species; freshwater inundation; and temperature stress. Benthic organisms have had to recolonize local scourings and continental shelves repeatedly, yet a decade of studies have demonstrated that they have (compared with lower latitudes) slow tempos of reproduction, colonization and growth. Despite massive disturbance levels and slow recolonization potential, the Antarctic shelf has a much richer fauna than would be expected for its area. Now, West Antarctica is among the fastest warming regions and its organisms face new rapid changes. In the next century, temperature stress and non-indigenous species will drastically rise to become dominant disturbances to the Antarctic life. Here, we describe the potential for benthic organisms to respond to disturbance, focusing particularly on what we know now that we did not a decade ago. PMID:17405206

Barnes, David K A; Conlan, Kathleen E

2007-01-29

215

Deep-sea benthic footprint of the deepwater horizon blowout.  

PubMed

The Deepwater Horizon (DWH) accident in the northern Gulf of Mexico occurred on April 20, 2010 at a water depth of 1525 meters, and a deep-sea plume was detected within one month. Oil contacted and persisted in parts of the bottom of the deep-sea in the Gulf of Mexico. As part of the response to the accident, monitoring cruises were deployed in fall 2010 to measure potential impacts on the two main soft-bottom benthic invertebrate groups: macrofauna and meiofauna. Sediment was collected using a multicorer so that samples for chemical, physical and biological analyses could be taken simultaneously and analyzed using multivariate methods. The footprint of the oil spill was identified by creating a new variable with principal components analysis where the first factor was indicative of the oil spill impacts and this new variable mapped in a geographic information system to identify the area of the oil spill footprint. The most severe relative reduction of faunal abundance and diversity extended to 3 km from the wellhead in all directions covering an area about 24 km(2). Moderate impacts were observed up to 17 km towards the southwest and 8.5 km towards the northeast of the wellhead, covering an area 148 km(2). Benthic effects were correlated to total petroleum hydrocarbon, polycyclic aromatic hydrocarbons and barium concentrations, and distance to the wellhead; but not distance to hydrocarbon seeps. Thus, benthic effects are more likely due to the oil spill, and not natural hydrocarbon seepage. Recovery rates in the deep sea are likely to be slow, on the order of decades or longer. PMID:23950956

Montagna, Paul A; Baguley, Jeffrey G; Cooksey, Cynthia; Hartwell, Ian; Hyde, Larry J; Hyland, Jeffrey L; Kalke, Richard D; Kracker, Laura M; Reuscher, Michael; Rhodes, Adelaide C E

2013-01-01

216

Flow enhances photosynthesis in marine benthic autotrophs by increasing the efflux of oxygen from the organism to the water  

PubMed Central

Worldwide, many marine coastal habitats are facing rapid deterioration due in part to human-driven changes in habitat characteristics, including changes in flow patterns, a factor known to greatly affect primary production in corals, algae, and seagrasses. The effect of flow traditionally is attributed to enhanced influx of nutrients and dissolved inorganic carbon (DIC) across the benthic boundary layer from the water to the organism however, here we report that the organism’s photosynthetic response to changes in the flow is nearly instantaneous, and that neither nutrients nor DIC limits this rapid response. Using microelectrodes, dual-pulse amplitude-modulated fluorometry, particle image velocimetry, and real time mass-spectrometry with the common scleractinian coral Favia veroni, the alga Gracilaria cornea, and the seagrass Halophila stipulacea, we show that this augmented photosynthesis is due to flow-driven enhancement of oxygen efflux from the organism to the water, which increases the affinity of the RuBisCO to CO2. No augmentation of photosynthesis was found in the absence of flow or when flow occurred, but the ambient concentration of oxygen was artificially elevated. We suggest that water motion should be considered a fundamental factor, equivalent to light and nutrients, in determining photosynthesis rates in marine benthic autotrophs. PMID:20133799

Mass, Tali; Genin, Amatzia; Shavit, Uri; Grinstein, Mor; Tchernov, Dan

2010-01-01

217

Flow enhances photosynthesis in marine benthic autotrophs by increasing the efflux of oxygen from the organism to the water.  

PubMed

Worldwide, many marine coastal habitats are facing rapid deterioration due in part to human-driven changes in habitat characteristics, including changes in flow patterns, a factor known to greatly affect primary production in corals, algae, and seagrasses. The effect of flow traditionally is attributed to enhanced influx of nutrients and dissolved inorganic carbon (DIC) across the benthic boundary layer from the water to the organism however, here we report that the organism's photosynthetic response to changes in the flow is nearly instantaneous, and that neither nutrients nor DIC limits this rapid response. Using microelectrodes, dual-pulse amplitude-modulated fluorometry, particle image velocimetry, and real time mass-spectrometry with the common scleractinian coral Favia veroni, the alga Gracilaria cornea, and the seagrass Halophila stipulacea, we show that this augmented photosynthesis is due to flow-driven enhancement of oxygen efflux from the organism to the water, which increases the affinity of the RuBisCO to CO(2). No augmentation of photosynthesis was found in the absence of flow or when flow occurred, but the ambient concentration of oxygen was artificially elevated. We suggest that water motion should be considered a fundamental factor, equivalent to light and nutrients, in determining photosynthesis rates in marine benthic autotrophs. PMID:20133799

Mass, Tali; Genin, Amatzia; Shavit, Uri; Grinstein, Mor; Tchernov, Dan

2010-02-01

218

Benthic Marine Algal Herbarium of L.I. Sound  

NSDL National Science Digital Library

The University of Connecticut has a tremendous collection of algae from the Long Island Sound, and back in 2001 they went ahead and photographed the original herbarium sheets featuring the preserved algae specimens. The archive is quite comprehensive, as it features all of the benthic marine macroalgal species in the Long Island Sound. All told, there are over 299 images here, and visitors are encouraged to peruse the collection by phylum, family, or name. The site also contains a list of definitions, a regional map, and information about the team that worked to make this collection a possibility.

219

Intertidal benthic resources of the Copper River Delta, Alaska, USA  

NASA Astrophysics Data System (ADS)

The Copper River Delta, Alaska is the largest contiguous coastal wetland system along the West Coast of North America. Vast expanses of tidal mud flats formed by sediments carried by the suspended load of the Copper River serve as a connection between the Gulf of Alaska and the extensive network of wetlands, rivers and sloughs of the delta system. In addition to providing habitat for resident fish, shrimp and crabs, these tidal flats serve as critical feeding grounds for up to 5 million migratory shorebirds as well as an entry and exit corridor for three species of commercially fished salmonids. Here we report the first description of the benthic community of these intertidal flats. Between April and September 2000, we conducted three samplings on the Copper River Delta in which we quantified benthic macro-invertebrates inhabiting silt-clay sediments, the dominant substrate in the system, over a range of tidal inundation. Specifically, sampling was performed in two areas on the delta: near the outflows of the Eyak River and Pete Dahl Slough. Pore-water salinity of surficial sediment ranged from 4 psu during peak summer flow of the Copper River to 14 psu in April prior to increased riverine input. Sediment temperatures corresponded to ambient air temperatures with lowest temperatures during the April-September observation period recorded in April (4°C) and warmest in August (16°C). The benthic community of the delta's tidal flats was characterised by low species diversity and was dominated by the tellinid bivalve Macoma balthica, which reached densities greater than 4000 m -2. Age-length relationship of M. balthica indicated slow growth and longevity of up to 8 years. Polychaete densities, primarily the phyllodocid Eteone longa, were low throughout the study period, reaching a maximum of only 700 m -2 in August. Amphipod densities, primarily the corophid amphipod Corophium salmonis, were high (up to 7000 m -2) only during the August sampling. Spatial patterns of benthic invertebrate abundance were best explained by differences in tidal inundation with longer inundation corresponding to greater invertebrate densities. Temporal changes in abundance of polychaetes, amphipods, and M. balthica recruits corresponded to increases in sediment temperatures. Natural or human-induced changes to M. balthica populations could impact the food web of the delta, which could cascade to larger geographic impacts because of the importance of the delta to migratory species.

Powers, Sean P.; Bishop, Mary Anne; Grabowski, Jonathan H.; Peterson, Charles H.

2002-02-01

220

Effect of organic carbon flux and dissolved oxygen on the benthic foraminiferal oxygen index (BFOI)  

Microsoft Academic Search

Variations in oceanic primary productivity, flux of organic carbon to the sediments, and dissolved-oxygen levels in the water column are thought to be important in the control of benthic foraminiferal test size, wall thickness, morphology, and species composition of assemblages by many foraminiferal paleontologists. Aspects of these processes should be reflected by the benthic foraminiferal oxygen index (BFOI) based on

Kunio Kaiho

1999-01-01

221

Development of a National-Scale Indicator of Benthic Condition for the National Coastal Condition Assessment.  

EPA Science Inventory

The US EPA has evaluated the application of a national-scale indicator of estuarine benthic condition for the National Coastal Condition Assessment (NCCA). Historically, in the National Coastal Condition Reports (NCCR I-IV), estuarine benthic condition was assessed by applying m...

222

Human exploitation and benthic community structure on a tropical intertidal flat  

Microsoft Academic Search

Human exploitation of intertidal marine invertebrates is known to alter benthic community structure. This study describes the impact that harvesting by women and children has on the intertidal community structure of the mudflats of the Saco on Inhaca Island, Mozambique, by comparing the benthic communities of exploited and unexploited areas. Sampling was done using two different methods: a standard core

W. F. de Boer; H. H. T. Prins

2002-01-01

223

Effects of pentachlorophenol on field- and laboratory-developed estuarine benthic communities  

Microsoft Academic Search

A study of the response of benthic communities exposed to pentachlorophenol (PCP) was conducted to obtain additional information on the effects of this widely used chemical on the estuarine environment and to compare its effect on estuarine benthic communities developed in the field and in the laboratory. PCP is used as a wood preservative, an insecticide, a fungicide and a

M. E. Tagatz; J. M. Ivey; N. R. Gregory; J. L. Oglesby

1981-01-01

224

Assessing acid stress in Swedish boreal and alpine streams using benthic macroinvertebrates  

Microsoft Academic Search

Sixty streams in northern Sweden were sampled for benthic macroinvertebrates in spring and autumn of 2000 as part of the European Union project AQEM (the Development and Testing of an Integrated Assessment System for the Ecological Quality of Streams and Rivers throughout Europe using Benthic Macroinvertebrates). Samples were taken using a harmonised multi-habitat sampling procedure and a large number of

Leonard Sandin; Joakim Dahl; Richard K. Johnson

2004-01-01

225

IMPORTANCE OF PHYSICAL SCALING FACTORS TO BENTHIC MARINE INVERTEBRATE RECOLONIZATION OF LABORATORY MICROCOSMS  

EPA Science Inventory

Five laboratory studies of benthic macroinvertebrate recolonization were conducted for 6-wk periods to evaluate the effects of physical factors (i.e., microcosm size, seawater flow rates and sediment depth) on benthic community structure. esign variables included4 open-faced acry...

226

Nutrient exchange and ventilation of benthic gases across the continental shelf break  

E-print Network

Nutrient exchange and ventilation of benthic gases across the continental shelf break S. A (2011), Nutrient exchange and ventilation of benthic gases across the continental shelf break, J] observed a large nutrient flux onto the southeastern U.S. continental shelf from shelf break upwelling

Mahadevan, Amala

227

Benthic organic carbon influences denitrification in streams with high nitrate concentration  

Microsoft Academic Search

SUMMARY 1. Anthropogenic activities have increased reactive nitrogen availability, and now many streams carry large nitrate loads to coastal ecosystems. Denitrification is potentially an important nitrogen sink, but few studies have investigated the influence of benthic organic carbon on denitrification in nitrate-rich streams. 2. Using the acetylene-block assay, we measured denitrification rates associated with benthic substrata having different proportions of

CLAY P. A RANGO; L. T ANK; J AMIE L. S CHALLER; TODD V. R OYER

2007-01-01

228

Efficiencies of benthic and pelagic trophic pathways in a subalpine lake  

Microsoft Academic Search

Although the study of lakes has traditionally focused on pelagic production pathways, recent stable isotope and diet evidence indicates that benthic algal production is an important contributor to fish production. This has led to the suggestion that energy may be more efficiently passed along benthic food chains relative to their pelagic counter- parts. To test this idea, we combined stable

M. Jake Vander Zanden; Sudeep Chandra; Sang-Kyu Park; Yvonne Vadeboncoeur; Charles R. Goldman

2006-01-01

229

Spatial variation of benthic macroinvertebrates and the environmental factors influencing their distribution in Lake Victoria, Kenya  

Microsoft Academic Search

Benthic macroinvertebrates in the Kenyan waters of Lake Victoria were sampled on a monthly basis from March 1994 to March 1995. Ekman grab samples were obtained from 10 stations representing all the major ecological zones of the lake. The aim of the study was to estimate the abundance and diversity of benthos.The highest mean (± standard error) benthic density was

Jones R. Muli

2005-01-01

230

Selenium in sediments, pore waters and benthic infauna of Lake Macquarie, New South Wales,  

E-print Network

Selenium in sediments, pore waters and benthic infauna of Lake Macquarie, New South Wales December 1998 Abstract Measurements of selenium in sediments and benthic infauna of Lake Macquarie, an estuary on the east coast of Australia, indicate that sediments are a signi®cant source of selenium

Canberra, University of

231

Bioturbation, sediment fluxes and benthic community structure around a salmon cage farm in Loch Creran, Scotland  

Microsoft Academic Search

This study examined bioturbation along an organic carbon gradient away from an Atlantic salmon farm and sought to determine relationships between benthic fluxes, mixing intensity and the infaunal community structure. Macrofaunal community structure, abundance and biomass were examined at stations with varying quantities and qualities of organic matter input. In situ benthic chambers were used to determine oxygen and nutrient

Lois A Nickell; Kenneth D Black; David J Hughes; Julian Overnell; Tim Brand; Thomas D Nickell; Eric Breuer; S Martyn Harvey

2003-01-01

232

DEVELOPING AND INDEX OF BENTHIC CONDITION FOR THE ACADIAN BIOGEOGRAPHIC PROVINCE  

EPA Science Inventory

The National Coastal Assessment has sampled benthic assemblages each summer since 2000 in coastal areas of the U.S. Acadian Biogeographic Province (tip of Cape Cod to Canadian border). We are developing a multimetric index to be used as an indicator of benthic condition. During...

233

DEVELOPMENT OF AN INDEX OF BENTHIC CONDITION FOR COASTAL AREAS OF THE GULF OF MAINE  

EPA Science Inventory

The National Coastal Assessment has sampled benthic assemblages each summer since 2000 in coastal areas of the U.S. Gulf of Maine. We are developing a multimetric index to be used as an indicator of benthic condition for both spatial comparisons of condition along the coast and f...

234

Interspecific Comparisons and the Potential Importance of Nutrient Excretion by Benthic Fishes in a Large Reservoir  

Microsoft Academic Search

Fishes can provide an important link between benthic and pelagic habitats by removing nutrients from sediments and excreting them into the water column. The relative importance of nutrients excreted by fishes to ecosystem productivity may vary among species and with abiotic conditions. I measured excretion rates of three benthic feeding fishes, gizzard shad Dorosoma cepedianum, smallmouth buffalo Ictiobus bubalus, and

Keith B. Gido

2002-01-01

235

To what extent does upright sessile epifauna affect benthic biodiversity and community composition?  

Microsoft Academic Search

Small-scale habitat complexity, including that caused by biological structures, is an important factor in structuring benthic communities and also sometimes in increasing biodiversity. The aim of this study was to determine if hydroid colonies have an effect on the composition of benthic communities in the Irish Sea, and if so, which components of the fauna are affected. Forty-six seabed core

C. Bradshaw; P. Collins; A. R. Brand

2003-01-01

236

Benthic foraminiferal faunal and isotopic changes as recorded in Holocene sediments of the northwest Indian Ocean  

Microsoft Academic Search

Historically, the Holocene has been considered an interval of relatively stable climate. However, recent studies from the northern Arabian Sea (Netherlands Indian Ocean Program 905) suggested high-amplitude climate shifts in the early and middle Holocene based on faunal and benthic isotopic proxy records. We examined benthic foraminiferal faunal and stable isotopic data from Ocean Drilling Program (ODP) Site 723 and

Anil K. Gupta; Moumita Das; Steven C. Clemens; Baidehi Mukherjee

2008-01-01

237

An algal carbon budget for pelagic-benthic coupling in Lake Michigan  

Microsoft Academic Search

A budget for algal carbon was constructed to quantify the magnitude and major pathways of pelagic- benthic coupling at a site in southeastern Lake Michigan. The flux of algal C to the benthos and the rate of carbon burial were estimated from sediment traps and dated sediment cores, respectively. Assimilation and respiration rates of Diporeia sp., an abundant benthic amphipod,

SHARON A. FITZGERALD; WAYNE S. GARDNER

1993-01-01

238

Abundance and Distribution of Benthic Invertebrates, with Emphasis on Diporeia, along the Keweenaw Peninsula, Lake Superior  

Microsoft Academic Search

The benthic invertebrate community in Lake Superior is an important component in the fisheries food web. Among the Great Lakes, only Lake Superior contains populations of Diporeia spp. that have not been reduced or extirpated in the last 20 years. The objectives of this study were to determine the abundance and distribution of benthic invertebrates along the Keweenaw coast, and

Nancy A. Auer; Jason E. Kahn

2004-01-01

239

Diversity as a measure of benthic macroinvertebrate community response to water pollution  

Microsoft Academic Search

The assumption that water pollution causes a depression in the diversity of benthic macroinvertebrates as measured by the Shannon index and similar diversity indices is questioned. An interpretation of the community response of benthic macroinvertebrates to pollution in the Millers River, Massachusetts is developed from species presence-absence and abundance data in conjunction with published information on the species' environmental tolerances

Paul J. Godfrey

1978-01-01

240

The benthic biological submodel in the European regional seas ecosystem model  

Microsoft Academic Search

The submodel describing benthic biology including a bioturbation module as incorporated in the European Regional Seas Ecosystem Model (ERSEM) is discussed. It is linked to a nutrient dynamic model. The structure of the benthic model food web is presented. There are four macrobenthic functional groups, meiobenthos and aerobic and anaerobic bacteria. The modelling uses ‘standard organisms’ as basic building blocks.

W. Ebenhöh; C. Kohlmeier; P. J. Radford

1995-01-01

241

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

Microsoft Academic Search

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, Virginia. Benthic detritus loadings per sample did not change after LWD addi- tions, but large increases in pool habitats created by LWD increased

A. Dennis Lemly; Robert H. Hilderbrand

2000-01-01

242

Sea-level and deep water temperature changes derived from benthic foraminifera isotopic records  

Microsoft Academic Search

We show that robust regressions can be established between relative sea-level (RSL) data and benthic foraminifera oxygen isotopic ratios from the North Atlantic and Equatorial Pacific Ocean over the last climatic cycle. We then apply these regressions to long benthic isotopic records retrieved at one North Atlantic and one Equatorial Pacific site to build a composite RSL curve, as well

C. Waelbroeck; L. Labeyrie; E. Michel; J. C. Duplessy; J. F. McManus; K. Lambeck; E. Balbon; M. Labracherie

2002-01-01

243

Comparison of benthic algal composition developed on different substrata in Lake Donghu, Wuhan  

Microsoft Academic Search

Biomass (Chl.a) of benthic algae colonized and developed mature community on different artificial substrata was determined in eutrophic lake Donghu, and species composed and structure characteristic of mature diatom communities on artificial and natural substratum were analysed qualitatively. Biomass variance of benthic algae was compared on four different artificial substratum, granite stone, glass, plastic (PVC) and pine wood during the

PEI Guofeng; LIU Meifang

244

Support of benthic invertebrates by detrital resources and current autochthonous primary production: results  

E-print Network

Support of benthic invertebrates by detrital resources and current autochthonous primary production of Ecosystem Studies, Millbrook, NY, U.S.A. SUMMARY 1. Secondary production of benthic invertebrates in lakes sources including phytoplankton, periphyton or macro- phytes. Furthermore, OM from any of these sources

Pace, Michael L.

245

Benthic macro-invertebrate community composition within a mangrove\\/seagrass estuary in northern New Zealand  

Microsoft Academic Search

In the tropics and sub-tropics, estuarine environments with mangrove and seagrass habitats provide important structures and resources for diverse communities of benthic organisms. However, temperate estuarine habitats, especially in mangrove areas, may differ significantly in their community associations and interactions. The community composition of benthic macro-fauna was investigated within temperate Matapouri Estuary, northern New Zealand. The density and distribution of

Andrea C. Alfaro

2006-01-01

246

Sequential sampling: A cost-effective approach for monitoring benthic macroinvertebrates in environmental impact assessments  

Microsoft Academic Search

Sequential sampling is a method for monitoring benthic macroinvertebrates that can significantly reduce the number of samples required to reach a decision, and consequently, decrease the cost of benthic sampling in environmental impact assessments. Rather than depending on a fixed number of samples, this analysis cumulatively compares measured parameter values (for example, density, community diversity) from individual samples, with thresholds

Vincent H. Resh; Donald G. Price

1984-01-01

247

MIDDLE REACH OF THE SNAKE RIVER: WATER QUALITY AND BENTHIC BIOMONITORING  

EPA Science Inventory

This study examined spatial and temporal trends in water quality, sestonic and benthic algal concentrations, and benthic macroinvertebrate taxa richness, population density, and biomass at nine stations along the Middle Snake River from Pillar Falls to Upper Salmon Falls Dam. Pri...

248

Cumulative impacts of seabed trawl disturbance on benthic biomass, production, and species richness in different habitats  

Microsoft Academic Search

Bottom trawling causes widespread disturbance of sediments in shelf seas and can have a negative impact on benthic fauna. We conducted a large-scale assessment of bottom trawl fishing of benthic fauna in different habitats, using a theoretical, size-based model that included habitat features. Species richness was estimated based on a generalized body mass versus species richness relationship. The model was

J. G. Hiddink; S. Jennings; M. J. Kaiser; A. M. Queiros; D. E. Duplisea; G. J. Piet

2006-01-01

249

Identifying cold-water coral ecosystem by using benthic foraminiferal indicators: from active reefs to the geological record  

NASA Astrophysics Data System (ADS)

Cold-water coral ecosystems dominated by the species Lophelia pertusa and Madrepora oculata, as well as cold-water coral carbonate mounds (fossils and/or active) occur worldwide and are especially developed along the European margin, from northern Norway to the Gulf of Cadiz and into the Alboran Sea. Their discovery is a major achievement of the last few decades and their widespread occurrence presents a challenge to understand their development, preservation and possible importance in the geologic record. On the Norwegian shelf active/living reefs are developed on elevated hard substrata. Along the Irish margin L. pertusa builds large fossil and/or active carbonate mounds. In the Gulf of Cadiz and in the Alboran Sea buried reefs and patch reefs are generally found in association with mud volcanoes. In modern oceans, they provide important ecological niches for the marine benthic fauna in the deep-sea. In comparison to the macrofauna the microfauna, particularly the foraminifera associated to these systems, are poorly known. We present here a detailed study based on quantitative analyses of benthic and planktonic foraminifera together with the statistical treatment of assemblage data collected along the Norwegian margin, in the Porcupine-Rockall region and in the Alboran Sea. The three regions were and/or are site of cold-water coral ecosystems settlements. Our study reveals that in the Porcupine/Rockall region benthic foraminiferal assemblages are strictly related to the distribution of facies. On the Norwegian margin, benthic foraminiferal habitats are weakly defined and grade one into the other preventing the sharp facies separation observed along the Irish margin (Margreth et al., 2009). In the Alboran Sea cold-water coral ecosystems and cold-water carbonate mounds are presently buried and corals are generally fragmented. However, benthic assemblages from coral-rich layers in the Alboran Sea and those from Porcupine/Rockall and Norway show remarkable similarities. In particular, epifaunal-attached species such as Discanomalina coronata, Cibicides refulgens, and Lobatula lobatula dominate the assemblages with D. coronata restricted to living cold-water coral reefs facies only and/or in co-occurrence with coral fragments. In conclusion, our data suggest that although cold-water coral ecosystems occur at different latitudes, the associated foraminiferal assemblages are consistent from Norway to the Western Mediterranean. Thus they can be used to identify these ecosystems even in the geologic record, when the corals are often strongly dissolved like in the Alboran Sea. References: Margreth, S., Rüggeberg, A. and Spezzaferri, S., 2009. Benthic foraminifera as bioindicator for cold-water coral reef ecosystems along the Irish margin. Deep Sea Res. Part I, 56: 2216-2234. This study is funded by the Swiss National Foundation Projects 200020-117928 and 200021-111694.

Margreth, Stephan; Rüggeberg, Andres; Gennari, Giordana; Spezzaferri, Silvia

2010-05-01

250

Continued disappearance of the benthic amphipod Diporeia spp. in Lake Michigan: is there evidence for food limitation?  

Microsoft Academic Search

Benthic surveys were conducted in the southern basin of Lake Michigan and throughout the lake to assess trends in benthic populations, emphasizing recent changes in densities of the benthic amphipod Diporeia spp. and dreissenid mussels. In the southern basin, Diporeia populations declined 89%, 91%, and 45% between 1993 and 2002 at sites <30, 31-50, and 51-90 m, respectively. Lakewide, the

Thomas F. Nalepa; David L. Fanslow; Andrew J. Foley III; Gregory A. Lang; Brian J. Eadie; Michael A. Quigley

2006-01-01

251

Benthic metabolism and nitrogen cycling in a subtropical east Australian estuary (Brunswick): Temporal variability and controlling factors  

Microsoft Academic Search

We examined temporal variability in benthic metabolism and nitrogen (N) cycling in the subtropical Brunswick Estuary, Australia from December 2000 to December 2002. Benthic metabolism was tightly coupled to the pro- duction of labile carbon (C) in the water column (phytodetritus) and temperature, both of which increased in summer, resulting in increased rates of benthic metabolism and a shift to

Bradley D. Eyre; Angus J. P. Ferguson

2005-01-01

252

Biological control of trace metal and organometal benthic fluxes in a eutrophic lagoon (Thau Lagoon, Mediterranean Sea, France)  

Microsoft Academic Search

In situ benthic chamber experiments were conducted in the Thau Lagoon that allowed the simultaneous determination of the benthic exchanges of trace metals (Cd, Co, Cu, Mn, Pb and U) and mercury species (iHg and MMHg). Fluxes of organotin compounds (MBT, DBT and TBT) were also investigated for the first time. The benthic incubations were performed during two campaigns at

M. Monperrus; E. Tessier; D. Amouroux; L. Chauvaud; G. Thouzeau; F. Jean; E. Amice; J. Grall; A. Leynaert; J. Clavier; O. F. X. Donard

2007-01-01

253

Carbon and oxygen isotope geochemistry of live (stained) benthic foraminifera from the Aleutian Margin and the Southern Australian Margin  

E-print Network

Carbon and oxygen isotope geochemistry of live (stained) benthic foraminifera from the Aleutian October 2008 Accepted 4 November 2008 Keywords: stable isotopes benthic foraminifera 13C 18O deep sea-water geochemistry and stable isotopic values of the tests of living (stained) calcareous benthic foraminifera from

Levin, Lisa

254

Multivariate benthic ecosystem functioning in the Arctic - benthic fluxes explained by environmental parameters in the southeastern Beaufort Sea  

NASA Astrophysics Data System (ADS)

The effects of climate change on Arctic marine ecosystems and their biogeochemical cycles are difficult to predict given the complex physical, biological and chemical interactions among the ecosystem components. We studied benthic biogeochemical fluxes in the Arctic and the influence of short-term (seasonal to annual), long-term (annual to decadal) and other environmental variability on their spatial distribution to provide a baseline for estimates of the impact of future changes. In summer 2009, we measured fluxes of dissolved oxygen, nitrate, nitrite, ammonia, soluble reactive phosphate and silicic acid at the sediment-water interface at eight sites in the southeastern Beaufort Sea at water depths from 45 to 580 m. The spatial pattern of the measured benthic boundary fluxes was heterogeneous. Multivariate analysis of flux data showed that no single or reduced combination of fluxes could explain the majority of spatial variation, indicating that oxygen flux is not representative of other nutrient sink-source dynamics. We tested the influence of eight environmental parameters on single benthic fluxes. Short-term environmental parameters (sinking flux of particulate organic carbon above the bottom, sediment surface Chl a) were most important for explaining oxygen, ammonium and nitrate fluxes. Long-term parameters (porosity, surface manganese and iron concentration, bottom water oxygen concentrations) together with ?13Corg signature explained most of the spatial variation in phosphate, nitrate and nitrite fluxes. Variation in pigments at the sediment surface was most important to explain variation in fluxes of silicic acid. In a model including all fluxes synchronously, the overall spatial distribution could be best explained (57%) by the combination of sediment Chl a, phaeopigments, ?13Corg, surficial manganese and bottom water oxygen concentration. We conclude that it is necessary to consider long-term environmental variability along with rapidly ongoing environmental changes to predict the flux of oxygen and nutrients across Arctic sediments even at short timescales. Our results contribute to improve ecological models predicting the impact of climate change on the functioning of marine ecosystems.

Link, H.; Chaillou, G.; Forest, A.; Piepenburg, D.; Archambault, P.

2013-09-01

255

Benthic control freaks: Effects of the tubiculous amphipod Haploops nirae on the specific diversity and functional structure of benthic communities  

NASA Astrophysics Data System (ADS)

Haploops nirae is a gregarious tubiculous amphipod which extended its habitat over thousands of hectares in shallow waters of South Brittany bays (Bay of Biscay, Atlantic) over the last decades and created uniquely large and dense tube mats. In the bay of Concarneau, we investigated the specific diversity (i.e. species richness and species composition) and the functional structure (using biological traits) of the macrofauna associated with this Haploops community as a comparison with several surrounding soft-sediment communities to determine the effect of this engineer species on ecosystem functions. We showed that the occurrence of Haploops tubes and individuals significantly modifies sediment features (e.g. change in sediment grain size, increase in C and N organic content) but also largely affect species diversity and benthic composition. The species richness was significantly higher in Haploops community but the species assemblage associated with Haploops habitat was very homogeneous compared to the neighboring habitats and unique with 33% of all species exclusively found in this community. Multivariate analysis (dbRDA) revealed that Haploops density was by far the factor explaining the variation in species composition of benthic communities. No differences in species diversity and assemblage were detected in relationship to Haploops density. A biological trait analysis performed on the whole ecosystem (Haploops included) revealed that Haploops largely dominates the functional structure of the Haploops community by its own functional traits. When performed on selected traits of the associated fauna only (Haploops excluded) the functional structure of the Haploops community was characterized by a greatly reduced proportion of small to medium long lived, sensitive to disturbance, free living or burrowing/tube-building filter-feeding species. H. nirae appears to be a bioengineer and a foundation species that largely modifies its hydro-sedimentary features, controlling diversity and abundances of associated species, and creating a complex set of positive and negative interactions so that a unique benthic assemblage is found in sediments they colonized.

Rigolet, Carinne; Dubois, Stanislas F.; Thiébaut, Eric

2014-01-01

256

Seasonal enhancement of submarine groundwater discharge (SGD)-derived nitrate loading into the Ria Formosa coastal lagoon assessed by 1-D modeling of benthic NO3- profiles  

NASA Astrophysics Data System (ADS)

The role of benthic sandy ecosystems in mitigating NO3- loads carried by Submarine Groundwater Discharge (SGD) to coastal marine ecosystems is uncertain. Benthic biogeochemical mediation of NO3--rich submarine groundwater discharge was studied at the seepage face of a barrier island site in the Ria Formosa coastal lagoon (Southern Portugal). Preliminary analysis of NO3- porewater distributions at the seepage face during discharge indicated that benthic biogeochemical processes could significantly affect the fluxes of groundwater-borne NO3- into the lagoon. In order to discriminate between the relative contribution of transport and reaction processes to shape and concentration range evidenced by in-situ porewater NO3- gradients, an advection-dispersion-reaction (ADR) model of NO3- diagenesis was applied to describe NO3- porewater profiles obtained in March, June, September and December 2006. Good agreement between modeled and measured profiles was obtained. Model-derived apparent benthic nitrification and NO3- reduction rates ranged from 0.01 to 5.2 mmol m-2 h-1, sufficient to explain gross observed changes in NO3- fluxes arriving at the seepage face (up to 70% within the surficial 20 cm depth layer). Results of the analysis indicated that the upper limit of the seepage face promoted mitigation of NO3- fluxes to the lagoon throughout the year. In contrast, the lower limit of the seepage area promoted net amplification of the NO3- fluxes into the lagoon in June and September. These results will help constrain further work aiming to clarify the role of permeable sediments in mitigating nitrogen loading of coastal ecosystems.

Ibánhez, J. Severino P.; Leote, Catarina; Rocha, Carlos

2013-11-01

257

Spatially-explicit hydrologic controls on benthic invertebrate habitat suitability  

NASA Astrophysics Data System (ADS)

Streamflow variability is a major determinant of basin-scale distribution of benthic invertebrates. Here we present a probabilistic approach for a spatially explicit quantitative assessment of benthic invertebrate abundance as derived from near-bed flow variability throughout an entire stream network. We consider aquatic invertebrates as these are widely employed as sensitive indicators of fluvial ecosystem health and human-induced perturbations. Moving from the analytical characterization of site-specific probability distribution functions of streamflow and bottom shear stress, we achieve a spatial extension to a stream network ranging up to 5th order. Bottom shear stress distributions, coupled with habitat suitability curves derived from field studies, are then used to produce maps of invertebrate habitat suitability based on shear stress conditions. The proposed framework allows to inspect the possible impacts of human-induced perturbations of streamflow variability on river ecology. We apply our approach to an Austrian river network, for which rainfall and streamflow time series, river network hydraulic properties and local information on invertebrate abundance for a limited number of sites are available. This allows a comparison between observed species density versus modeled habitat suitability based on shear stress. Although the proposed strategy neglects ecological determinants other than hydraulic ones and thus represents an ecological minimal model, it allows derivation of important implications of water resource management and fluvial ecosystem protection for basin-scale distribution patterns of organisms.

Ceola, Serena; Bertuzzo, Enrico; Singer, Gabriel; Battin, Tom; Montanari, Alberto; Rinaldo, Andrea

2014-05-01

258

Hydrologic controls on basin-scale distribution of benthic invertebrates  

NASA Astrophysics Data System (ADS)

variability is a major determinant of basin-scale distributions of benthic invertebrates. Here we present a novel procedure based on a probabilistic approach aiming at a spatially explicit quantitative assessment of benthic invertebrate abundance as derived from near-bed flow variability. Although the proposed approach neglects ecological determinants other than hydraulic ones, it is nevertheless relevant in view of its implications on the predictability of basin-scale patterns of organisms. In the present context, aquatic invertebrates are considered, given that they are widely employed as sensitive indicators of fluvial ecosystem health and human-induced perturbations. Moving from the analytical characterization of site-specific probability distribution functions of streamflow and bottom shear stress, we achieve a spatial extension to an entire stream network. Bottom shear stress distributions, coupled with habitat suitability curves derived from field studies, are used to produce maps of invertebrate suitability to shear stress conditions. Therefore, the proposed framework allows one to inspect the possible impacts on river ecology of human-induced perturbations of streamflow variability. We apply this framework to an Austrian river network for which rainfall and streamflow time series, river network hydraulic properties, and local information on invertebrate abundance for a limited number of sites are available. A comparison between observed species density versus modeled suitability to shear stress is also presented. Although the proposed strategy focuses on a single controlling factor and thus represents an ecological minimal model, it allows derivation of important implications for water resource management and fluvial ecosystem protection.

Ceola, Serena; Bertuzzo, Enrico; Singer, Gabriel; Battin, Tom J.; Montanari, Alberto; Rinaldo, Andrea

2014-04-01

259

Anabaenolysins, Novel Cytolytic Lipopeptides from Benthic Anabaena Cyanobacteria  

PubMed Central

Two novel cyclic lipopeptides, anabaenolysin A and anabaenolysin B, were isolated from two benthic cyanobacterial strains of the genus Anabaena. This novel class of cyanobacterial lipopeptides has a general structure of a small peptide ring consisting of four amino acids from which two are proteinogenic and two unusual; glycine1, glycine2, 2-(3-amino-5-oxytetrahydrofuran-2-yl)-2-hydroxyacetic acid3 and a long unsaturated C18 ?-amino acid4 with a conjugated triene structure. They are distinguished by the presence of a conjugated dienic structure in the C18 ?-amino acid present in anabaenolysin A but not in anabaenolysin B. Conjugated triene structure generates a typical UV spectrum for anabaenolysins for easy recognition. Anabaenolysin A constituted up to 400 ppm of the cyanobacterial dry weight. We found evidence of thirteen variants of anabaenolysins in one cyanobacterial strain. This suggests that the anabaenolysins are an important class of secondary metabolites in benthic Anabaena cyanobacteria. Both anabaenolysin A and B had cytolytic activity on a number of mammalian cell lines. PMID:22829929

Jokela, Jouni; Oftedal, Linn; Herfindal, Lars; Permi, Perttu; Wahlsten, Matti; D?skeland, Stein Ove; Sivonen, Kaarina

2012-01-01

260

Benthic flux sampling device. Operations, methods, and procedures. Final report  

SciTech Connect

As part of the Navy's clean up program, the Installation Restoration (IR) Program, methods are evaluated to better assess suitable remediation and restoration strategies for sites that contain sediments contaminated with toxic compounds. Toward this goal, we have developed a Benthic Flux Sampling Device (BFSD) to quantify mobility of toxicants from contaminated sediments. The BFSD is a remote instrument for in-situ measurement of toxicant flux rates from sediments. A flux out of or into the sediment is measured by isolating a volume of water above the sediment, drawing off samples from this volume over time, and analyzing these samples for increase or decrease in toxicant concentration. Increasing concentrations indicate that the toxicant is fluxing out of the sediment. Decreasing concentrations indicate that the toxicant is fluxing into the sediment. Initial tests carried out in conjunction with Scripps Institution of Oceanography and the Environmental Protection Agency's Environmental Research Laboratory (Newport, OR) show that the system is capable of measuring a variety of contaminant and nutrient fluxes.... Marine chemistry, Benthic flux.

Chadwick, D.B.; Stanley, S.D.

1993-02-01

261

Deep-sea benthic boundary layer communities and food supply: A long-term monitoring strategy  

Microsoft Academic Search

Long-term monitoring of deep-ocean processes is essential for understanding the potential impacts of climate variation on the deep sea. A suite of autonomous and cabled instrumentation has been developed to allow continuous measurements of food supply availability, species composition and abundance, and organism activity. A sedimentation sensor combines a traditional sediment trap configuration with a digital-imaging system and fluorometer to

Alana D. Sherman; K. L. Smith Jr.

2009-01-01

262

BLIPS: A SYSTEM FOR STUDYING BENTHIC BOUNDARY LAYER DYNAMICS. (R825513C001)  

EPA Science Inventory

The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

263

Using benthic macroinvertebrate and fish communities as bioindicators of the Tanshui River basin around the greater Taipei area - multivariate analysis of spatial variation related to levels of water pollution.  

PubMed

After decades of strict pollution control and municipal sewage treatment, the water quality of the Tanshui River increased significantly after pollution mitigation as indicated by the River Pollution Index (RPI). The pollution level of the estuarine region decreased from severe pollution to mostly moderately impaired. The most polluted waters are presently restricted to a flow track length between 15-35 km relative to the river mouth. From July 2011 to September 2012, four surveys of fish and benthic macroinvertebrates were conducted at 45 sampling sites around the Tanshui River basin. The pollution level of all the study area indicated by the RPI could also be explained by the Family Biotic Index (FBI) and Biotic Index (BI) from the benthic macroinvertebrate community, and the Index of Biotic Integrity (IBI) of the fish community. The result of canonical correlation analysis between aquatic environmental factors and community structure indicated that the community structure was closely related to the level of water pollution. Fish species richness in the estuarine area has increased significantly in recent years. Some catadromous fish and crustaceans could cross the moderate polluted water into the upstream freshwater, and have re-colonized their populations. The benthic macroinvertebrate community relying on the benthic substrate of the estuarine region is still very poor, and the water layer was still moderately polluted. PMID:25026081

Young, Shuh-Sen; Yang, Hsi-Nan; Huang, Da-Ji; Liu, Su-Miao; Huang, Yueh-Han; Chiang, Chung-Ting; Liu, Jin-Wei

2014-07-01

264

Ecological periodic tables for benthic macrofaunal usage of estuarine habitats in the US Pacific Northwest  

NASA Astrophysics Data System (ADS)

This study shows that spatially and temporally recurring benthic macrofauna-habitat patterns validate the ecological relevance of habitat types to benthic macrofauna and suggest they can serve as elements in ecological periodic tables of benthic macrofaunal usage. We discovered patterns across nine habitat types (intertidal eelgrass [ Zostera marina], dwarf eelgrass [ Zostera japonica], oyster [ Crassostrea gigas] ground culture, burrowing mud shrimp [ Upogebia pugettensis], burrowing ghost shrimp [ Neotrypaea californiensis], shell, sand, mud, and subtidal) on a variety of benthic macrofaunal community state variables in Grays Harbor, Washington, USA and compared them to those in Willapa Bay, Washington, USA. There were nominal differences in benthic macrofaunal Bray-Curtis similarity between all the habitats investigated except eelgrass and oyster in both estuaries. Across-habitat patterns on mean benthic macrofaunal species richness, abundance, biomass, abundance of deposit, suspension and facultative feeders, a dominance and a diversity index for the five habitats common to both studies were the same on a rank measurement scale: eelgrass ? oyster > mud shrimp > ghost shrimp ? subtidal. The patterns for most of the habitats and benthic macrofaunal measures were the same on a ratio measurement scale.

Ferraro, Steven P.; Cole, Faith A.

2011-07-01

265

Importance of allochthonous material in benthic macrofaunal community functioning in estuarine salt marshes  

NASA Astrophysics Data System (ADS)

Allochthonous input provides important food and spatial resources for estuarine benthic fauna. While it is known that autochthonous materials are important for fauna occupying small marshes, here, we present the significance of allochthonous materials for benthic fauna inhabiting a large salt marsh. To assess the effects of allochthonous input on benthic macrofaunal communities in estuarine salt marshes, we determined the source of substrate sediments and food resource utilisation patterns of benthic invertebrates in 2 temperate estuaries (the Tama River and the Obitsu River estuarine outlets into Tokyo Bay) by using stable carbon and nitrogen isotope analyses. In the Tama River estuary, which has small patches of marsh vegetation upstream of the river mouth, there was an input of sedimentary organic matter from autochthonous sources (i.e. common reed and microphytobenthos). In the Obitsu River estuary salt marsh, which is situated immediately upstream of the river mouth and is well connected to the sea, sediment consists of allochthonous sources (i.e. imported phytoplankton), along with microphytobenthos. Isotope analysis indicated that most benthic invertebrates in the Tama River estuary depend on benthic microalgae (autochthonous) as a food resource, whereas the macrofauna in the Obitsu River estuary are supported by drift macroalgae (allochthonous), in addition to microphytobenthos or phytoplankton. Our results indicated that allochthonous material provides a food resource and potential habitat for benthic macrofauna in extensive salt marshes that have a strong connection to the sea but is not substantial in smaller marshes with limited connectivity to coastal water.

Kon, Koetsu; Hoshino, Yukihiro; Kanou, Kouki; Okazaki, Daisuke; Nakayama, Satoko; Kohno, Hiroshi

2012-01-01

266

Benthic nitrogen cycling traversing the capitalize peruvian oxygen minimum zone  

NASA Astrophysics Data System (ADS)

Benthic nitrogen (N) cycling was investigated at six stations along a transect traversing the Peruvian oxygen minimum zone (OMZ) at 11°S. An extensive dataset including porewater concentration profiles and in situ benthic fluxes of nitrate (NO 3-), nitrite (NO 2-) and ammonium (NH 4+) was used to constrain a 1-D reaction-transport model designed to simulate and interpret the measured data at each station. Simulated rates of nitrification, denitrification, anammox and dissimilatory nitrate reduction to ammonium (DNRA) by filamentous large sulfur bacteria (e.g. Beggiatoa and Thioploca) were highly variable throughout the OMZ yet clear trends were discernible. On the shelf and upper slope (80-260 m water depth) where extensive areas of bacterial mats were present, DNRA dominated total N turnover (?2.9 mmol N m -2 d -1) and accounted for ?65% of NO 3- + NO 2- uptake by the sediments from the bottom water. Nonetheless, these sediments did not represent a major sink for dissolved inorganic nitrogen (DIN = NO 3- + NO 2- + NH 4+) since DNRA reduces NO 3- and, potentially NO 2-, to NH 4+. Consequently, the shelf and upper slope sediments were recycling sites for DIN due to relatively low rates of denitrification and high rates of ammonium release from DNRA and ammonification of organic matter. This finding contrasts with the current opinion that sediments underlying OMZs are a strong sink for DIN. Only at greater water depths (300-1000 m) did the sediments become a net sink for DIN. Here, denitrification was the major process (?2 mmol N m -2 d -1) and removed 55-73% of NO 3- and NO 2- taken up by the sediments, with DNRA and anammox accounting for the remaining fraction. Anammox was of minor importance on the shelf and upper slope yet contributed up to 62% to total N 2 production at the 1000 m station. The results indicate that the partitioning of oxidized N (NO 3-, NO 2-) into DNRA or denitrification is a key factor determining the role of marine sediments as DIN sinks or recycling sites. Consequently, high measured benthic uptake rates of oxidized N within OMZs do not necessarily indicate a loss of fixed N from the marine environment.

Bohlen, L.; Dale, A. W.; Sommer, S.; Mosch, T.; Hensen, C.; Noffke, A.; Scholz, F.; Wallmann, K.

2011-10-01

267

Development and evaluation of sediment quality guidelines based on benthic macrofauna responses.  

PubMed

Toxicity-based sediment quality guidelines (SQGs) are often used to assess the potential of sediment contamination to adversely affect benthic macrofauna, yet the correspondence of these guidelines to benthic community condition is poorly documented. This study compares the performance of 5 toxicity-based SQG approaches to a new benthos-based SQG approach relative to changes in benthic community condition. Four of the toxicity-based SQG approaches--effects range median, logistic regression modeling (LRM), sediment quality guideline quotient 1 (SQGQ1), and consensus--were derived in previous national studies in the United States, and one was developed as a regional variation of LRM calibrated to California data. The new benthos-based SQG approach, chemical score index, was derived from Southern California benthic community data. The chemical-specific guidelines for each approach were applied to matched chemical concentration, amphipod mortality, and benthic macrofauna abundance data for Southern California. Respective results for each SQG approach were then combined into a summary metric describing the overall contamination magnitude (e.g., mean quotient) and assessed in accordance with a set of thresholds in order to classify stations into 4 categories of expected biological effect. Results for each SQG approach were significantly correlated with changes in sediment toxicity and benthic community condition. Cumulative frequency plots and effect category thresholds for toxicity and benthic community condition were similar, indicating that both types of effect measures had similar sensitivity and specificity of response to contamination level. In terms of discriminating among multiple levels of benthic community condition, the toxicity-based SQG indices illustrated moderate capabilities, similar to those for multiple levels of toxicity. The National LRM, California LRM, and the chemical score index had the highest overall agreement with benthic categories. However, only the benthos-based chemical score index was consistently among the highest performing SQG indices for all measures of association (correlation, percent agreement, and weighted kappa) for both toxicity and benthos. PMID:22275113

Ritter, Kerry J; Bay, Steven M; Smith, Robert W; Vidal-Dorsch, Doris E; Field, L Jay

2012-10-01

268

Antarctic Benthic Fauna in the Global Climate Change  

NASA Astrophysics Data System (ADS)

In the last 50 years a significant climatic shift has been observed along the Antarctic Peninsula (air and seawater temperature rise, glacial retreat, localized instances of lowered shallow waters salinities). Many Antarctic marine benthic invertebrates are adapted to specific environmental conditions (e.g. low stable temperatures, high salinity and oxygen content). Changes caused by global climate changes and subsequent glacial melting can be expected to have significant impacts on species physiology and distribution. The rise of sea water temperature coupled with such additional stress factors as melt water run-off, increased ice disturbance, disruption of food webs or invasion of alien species can be a serious problem for their long-term survival.

Kidawa, Anna; Janecki, Tomasz

2011-01-01

269

Benthic foraminifera of the Panamanian Province: distribution and origins.  

USGS Publications Warehouse

Two hundred twenty-nine species of benthic foraminifera have been identified from 96 stations representing 33 localities on the eastern Pacific inner continental shelf, ranging from southern Peru to northern Baja California. Their distributions mark nearshore provincial boundaries that are nearly identical with those previously documented from the distribution of ostracodes and molluscs. Thirteen species are characteristic of the Panamanian Province, one is characteristic of the Chilean-Peruvian Province, and one is characteristic of the newly proposed Sonoran Subprovince. Seventeen species (7%) appear to be endemic to the eastern Pacific. Fifty-eight (25%) of the species recognized are disjunct from population centers in the western Pacific, 134 species (59%) are disjunct from modern assemblages of the Atlanto-Carribean region, and 40 species (17%) are disjunct from both the western Pacific and the Atlanto-Caribbean. The distribution of the remaining 57 species (25%) is poorly documented; we classify them as of unknown origin. -Authors

Crouch, R.W.; Poag, C.W.

1987-01-01

270

Benthic foraminifera and environmental changes in Long Island Sound  

USGS Publications Warehouse

Benthic foraminiferal faunas in Long Island Sound (LIS) in the 1940s and 1960s were of low diversity, and dominated by species of the genus Elphidium, mainly Elphidium excavatum clavatum, with common Buccella frigida and Eggerella advena. The distribution of these species was dominantly correlated with depth, but it was not clear which depth-related environmental variable was most important. Differences between faunas collected in 1996 and 1997, and in the 1940s and 1960s include a strong decrease in relative abundance of Eggerella advena over all LIS, an increase in relative abundance of Ammonia beccarii in western LIS, and a decrease in species diversity. The decreased diversity suggests that environmental stress caused the faunal changes. Oxygen isotope data for E. excavatum clavatum indicate that a change in salinity is not a probable cause. Carbon isotope data suggest that the supply of organic matter to the benthos increased since the early 1960s, with a stronger increase in western LIS where algal blooms have occurred since the early 1970s, possibly as a result of nutrient input by waste water treatment plants. These blooms or the resulting episodes of anoxia/hypoxia may have played a role in the increased relative abundance of A. beccarii. There is no clear explanation for the decreased abundance of E. advena, but changes in the phytoplankton composition (thus food supply) are a possible cause. Benthic foraminiferal faunal and stable isotope data have excellent potential as indicators of physicochemical environmental changes and their effects on the biota in LIS.

Thomas, E.; Gapotchenko, T.; Varekamp, J.C.; Mecray, E.I.; Buchholtz ten Brink, M. R.

2000-01-01

271

Benthic nutrient sources to hypereutrophic Upper Klamath Lake, Oregon, USA  

USGS Publications Warehouse

Three collecting trips were coordinated in April, May, and August 2006 to sample the water column and benthos of hypereutrophic Upper Klamath Lake (OR, USA) through the annual cyanophyte bloom of Aphanizomenon flos-aquae. A porewater profiler was designed and fabricated to obtain the first high-resolution (centimeter-scale) estimates of the vertical, concentration gradients of macro- and micronutrients for diffusive-flux determinations. A consistently positive benthic flux for soluble reactive phosphorus (SRP) was observed with solute release from the sediment, ranging between 0.4 and 6.1 mg/m2/d. The mass flux over an approximate 200-km2 lake area was comparable in magnitude to riverine inputs. An additional concern, related to fish toxicity was identified when dissolved ammonium also displayed consistently positive benthic fluxes of 4 to 134 mg/m2/d, again, comparable to riverine inputs. Although phosphorus was a logical initial choice by water quality managers for the limiting nutrient when nitrogen-fixing cyanophytes dominate, initial trace-element results from the lake and major inflowing tributaries suggested that the role of iron limitation on primary productivity should be investigated. Dissolved iron became depleted in the lake water column during the course of the algal bloom, while dissolved ammonium and SRP increased. Elevated macroinvertebrate densities, at least of the order of 104 individuals/m2, suggested, that the diffusive-flux estimates may be significantly enhanced, by bioturbation. In addition, heat-flux modeling indicated that groundwater advection of nutrients could also significantly contribute to internal nutrient loading. Accurate environmental assessments of lentic systems and reasonable expectations for point-source management require quantitative consideration of internal solute sources ?? 2009 SETAC.

Kuwabara, J.S.; Topping, B.R.; Lynch, D.D.; Carter, J.L.; Essaid, H.I.

2009-01-01

272

Anthropogenic and natural disturbances to marine benthic communities in Antarctica  

SciTech Connect

Sampling and field experiments were conducted from 1975 to 1990 to test how the structure of marine benthic communities around McMurdo Station, Antarctica varied with levels of anthropogenic contaminants in marine sediments. The structure of communities (e.g., infauna density, species composition, and life history characteristics) in contaminated and uncontaminated areas were compared with the structure of communities influenced by two large-scale natural disturbances, anchor ice formation and uplift or iceberg scour. Benthic communities changed radically along a steep spatial gradient of anthropogenic hydrocarbon, metal, and PCB contamination around McMurdo Station. The heavily contaminated end of the gradient, Winter Quarters Bay, was low in infaunal and epifaunal abundance and was dominated by a few opportunistic species of polychaete worms. The edge of the heavily contaminated bay, the transition area, contained several motile polychaete species with less opportunistic life histories. Uncontaminated sedimentary habitats harbored dense tube mats of infaunal animals numerically dominated by populations of polychaete worms, crustaceans, and a large suspension feeding bivalve. These species are generally large and relatively sessile, except for several crustacean species living among the tubes. Although the community patterns around anthropogenic and natural disturbances were similar, particularly motile and opportunistic species at heavily disturbed and marginal areas, the natural disturbances cover much greater areas of the sea floor about the entire Antarctic continent. On the other hand, recovery from chemical contamination is likely to take many more decades than recovery from natural disturbances as contaminant degradation is a slow process. 77 refs., 6 figs., 5 tabs.

Lenihan, H.; Oliver, J.S. [Moss Landing Marine Labs., CA (United States)

1995-05-01

273

Water conditions and geochemistry in northern Adriatic anoxia-prone areas and response of benthic faunas to oxygen deficiencies  

NASA Astrophysics Data System (ADS)

One predicted effect of global climate change, specifically global warming, is the increase in the temperatures and stratification of shallow coastal and estuarine systems. This, coupled with ongoing anthropogenic eutrophication, will exacerbate hypoxia and benthic mortalities, significantly damaging these critical marine ecosystems. These phenomena are particularly severe on sublitoral soft-bottoms such as the poorly sorted silty sands at the study site in the northern Adriatic Sea. We deployed a specially developed underwater chamber to artificially induce anoxia in situ. Our Experimental Anoxia Generating Unit (EAGU) is a large plexiglass chamber that combines a digital camera with oxygen/hydrogen sulphide/pH sensors along with flashes and battery packs. The unit can be deployed for up to five days to autonomously generate oxygen crises and quantify both physico-chemical parameters and benthic responses. The system is initially positioned in an "open" configuration (open-sided aluminium frame) over the benthic fauna ("control" experiment). After 24 h the EAGU is switched to its "closed" configuration (plexiglass enclosure) and repositioned over the same assemblage. In this contribution, we focus on the natural oxygen content, temperature and pH of bottom waters during summer, the course of oxygen decrease during our experiments and the onset of H2S development. Oxygen content of the bottom water, a few centimetres above the sediment-water interface, ranges from ~3.5-8 but is mostly between 4-6 ml l-1 during July to September of the study periods (2005 and 2006) and decreases to zero within ~1-3 days after initiation of our experiments. In parallel, H2S starts to develop at the onset of anoxia. Water temperatures at the bottom were stable during experiments and ranged from 18.5°C to 21.4°C, but pH decreased from 8.3 to 8.1 at the beginning to 7.9 to 7.7 at the end of the experiments. Sediment profiling indicates that the diffusive benthic boundary layer is approximately 2.5 mm thick and that oxygen values decrease from ~2 ml l-1 3.5 mm above the sediment water interface to virtually zero at the interface. PH-values in 2 mm depth decrease from 8.15 to 7.6 within the first 10 h of the experiment. This indicates that the most reactive organic matter is decomposing in the uppermost few mm of the sediment. These data can be related to behavioural responses and mortality sequences of benthic faunas, including echinoids, crustaceans, molluscs and anemones. Beginning hypoxia (?2.0 ml l-1 DO) elicited escape patterns such as increased horizontal and vertical locomotion of animals. Moderate hypoxia (?1.0 ml l-1 DO) triggered species-specific sublethal effects such as arm-tipping in ophiuroids or extension from the sediment in sea anemones. At severe hypoxia (?0.5 ml l-1 DO) infaunal organisms began to emerge and first mortalities occurred. Some crustaceans and echinoderms are among the first to die, but sea anemones and large gastropods can even survive the onset of hydrogen sulfide.

Zuschin, Martin; Riedel, Bettina; Stachowitsch, Michael; Cermelj, Branko

2010-05-01

274

A cross-continental comparison of the effects of flow intermittence on benthic invertebrate assemblages  

EPA Science Inventory

Although temporary rivers are widespread freshwater systems, they have been poorly studied by ecologists and are largely ignored in water management plans, practices and policies. If the effects of dry events on benthic invertebrates have been reported individually from different...

275

ENVIRONMENTAL INFLUENCES ON BENTHIC COMMUNITY STRUCTURE IN A GREAT LAKES EMBAYMENT  

EPA Science Inventory

An Intensified Environmental Monitoring and Assessment Program (EMAP) sampling grid in the St. Louis River estuary of western Lake Superior was used toassess the relationship between surficial sediment characteristics and benthic community structure. Ninety sites within two habit...

276

RESPONSES OF ESTUARINE BENTHIC INVERTEBRATES TO SEDIMENT BURIAL: THE IMPORTANCE OF MOBILITY AND ADAPTATION  

EPA Science Inventory

Estuarine benthic organisms are frequently subjected to disturbance events caused by hydrodynamic processes that disrupt and move the sediment in which the animals reside, however the mechanisms by which physical disturbance processes affect infaunal and epifaunal populations and...

277

THE EFFECTSOF CIRCULATION" LARVAL PLANKTONIC PERIOD.ADULT DISTRIBUTION AND POLLUTION ON BENTHIC RECRUITMENT IN  

E-print Network

THE EFFECTSOF CIRCULATION" LARVAL PLANKTONIC PERIOD.ADULT DISTRIBUTION AND POLLUTION ON BENTHIC pollution (estuariesandharbors)alongthe southern shoreof Oahu. The resultsindicatethat the SandIsland sewageoutfall did not havea negativeeffect on the ratesand speciescompositionsof larval recruitment. The sewage

Luther, Douglas S.

278

St. Johns Estuary: Estuarine Benthic Macroinvertebrates Phase 2 Final Report. Special Publication SJ2012-SP4.  

National Technical Information Service (NTIS)

Benthic macrofaunal communities can be strongly influenced by changes in freshwater inflows in an estuary. Macrofauna are affected by changes in estuarine condition (including nutrient concentrations, sediment supply and salinity) caused by variation in f...

J. B. Pollack, P. A. Montagna, T. A. Palmer

2011-01-01

279

Coral reef condition and benthic sedimentation threat in four regions of south Puerto Rico  

EPA Science Inventory

Scleractinian corals, gorgonian octocorals, sponges and fishes were assessed near the cities of LaParguera, Guánica, Guayanilla, and Jobos along the southern coast of Puerto Rico in November – December 2010. Survey sites were targeted near areas with varying benthic...

280

Benthic community and sediment quality assessment of Port Hope Harbour, Lake Ontario  

SciTech Connect

Sediments in Port Hope Harbour, Lake Ontario, have been heavily contaminated by radionuclides and heavy metals from a radium recovery plant, a uranium refinery, and other industrial activities. Spatial patterns in surficial sediment contamination, benthic community structure, and bioaccumulation of contaminants were assessed to determine possible relationships and potential environmental hazards in the event of dredging. Benthic community differences in species composition and density between inner and outer harbour areas corresponded with both habitat and sediment quality differences. Sediment loss-on-ignition, nitrogen, iron, copper, lead, chromium, zinc, and nickel concentrations in the inner harbour exceeded provincial guidelines for open water disposal of dredged spoils. Only iron exceeded those guidelines in the other harbour. Tissue levels of radionuclides and heavy metals in benthic invertebrates were greatest at the most heavily contaminated stations in the inner harbour. Reduced benthic densities and maximum sediment contamination occurred near a refinery cooling water discharge. 59 references, 3 figures, 5 tables.

Hart, D.R.; McKee, P.M.; Burt, A.J.; Goffin, M.J.

1986-01-01

281

BENTHIC MICROBIAL RESPIRATION IN APPALACHIAN MOUNTAIN, PIEDMONT, AND COASTAL PLAINS, STREAMS OF THE EASTERN USA  

EPA Science Inventory

Our study had two objectives. First, in order to quantify the potential underestimation of community respiration caused by the exclusion of anaerobic processes, we compared benthic microbial respiration measured as 02 consumption with estimated based on DHA. Second, our previous ...

282

In Situ Monitoring of the Effects of Water Quality on Benthic Detrital Decomposition.  

National Technical Information Service (NTIS)

Detrital decomposition is an important marine benthic process which contributes to the fertility of seas, particularly in estuarian and coastal waters. The process involves a complex community of microorganisms and small animals which interact with each o...

J. J. Lee, C. Mastropaolo, M. McEnery, J. H. Tietjen, J. Garrison

1978-01-01

283

DISCRIMINATING THE BENTHIC EFFECTS OF ANTHROPOGENIC POINT SOURCES FROM SALINITY AND NITROGEN LOADING  

EPA Science Inventory

To evaluate the influence of anthropogenic point sources on estuarine systems, environmental managers must be able to discern the level and effects of significant natural factors and nonpoint source inputs. We compared benthic community state, salinity and dissolved inorganic nit...

284

POTENTIAL USE OF BENTHIC ALGAE AS HYDROLOGIC INDICATORS FOR HEADWATER STREAMS: SOME DATA EXPLORATION  

EPA Science Inventory

Benthic algae were sampled to determine the utility of algal communities as indicators of hydrologic regime as part of a national survey involving habitat measurements and community assessments. Streams from four forests near Cincinnati were classified according to hydrologic pe...

285

Recruitment of Benthic Animals as a Function of Petroleum Hydrocarbon Concentrations in the Sediment.  

National Technical Information Service (NTIS)

Three separate field installations, consisting of clean and oiled sediment in fiberglass trays, were placed in the intertidal zone of Sequim Bay, Washington to determine rates of hydrocarbon depuration and recruitment of benthic organisms. Detailed chemic...

J. W. Anderson, R. G. Riley, R. M. Bean

1977-01-01

286

EVALUATION OF BENTHIC MACROINVERTEBRATE BIOMASS METHODOLOGY. PART 1. LABORATORY ANALYTICAL METHODS  

EPA Science Inventory

Evaluation of analytical methods employed for wet weight (live or preserved samples) of benthic marcoinvertebrates reveals that centrifugation at 140 x gravity for one minute yields constant biomass estimates. Duration of specimen exposure in ethanol, formalin, and formol (formal...

287

Prepared in cooperation with the U.S. Bureau of Reclamation Quantifying the Benthic Source of  

E-print Network

Prepared in cooperation with the U.S. Bureau of Reclamation Quantifying the Benthic Source of the Interior U.S. Geological Survey #12;Prepared in cooperation with the U.S. Bureau of Reclamation Quantifying

288

Effect of Organic Enrichment and Hypoxia on the Biodiversity of Benthic Communities in Narragansett Bay  

EPA Science Inventory

Excessive input of nitrogen to coastal waters leads to eutrophication and hypoxia that reduce biodiversity and impair key ecosystem services provided by benthic communities; for example, fish and shellfish production, bioturbation, nutrient cycling, and water filtration. Hypoxia ...

289

Paleontological Society New and Renamed Species of Benthic Foraminifera from the Pleistocene Santa Barbara  

E-print Network

Barbara Formation of California Author(s): R. Timothy Patterson Source: Journal of Paleontology, Vol. 64 FROM THE PLEISTOCENESANTA BARBARA FORMATION OF CALIFORNIA R. TIMOTHY PATTERSON Ottawa, Patterson et al. (1990) examined quantitatively the benthic and planktonic foraminiferal populations

Patterson, Timothy

290

Ecological periodic tables for benthic macrofaunal usage of estuarine habitats in the US Pacific Northwest  

EPA Science Inventory

Estuary-wide benthic macrofauna-habitat associations were determined for 9 habitats (intertidal eelgrass [Zostera marina], dwarf eelgrass [Zostera japonica], oyster [Crassostrea gigas], mud shrimp [Upogebia pugettensis], ghost shrimp [Neotrypaea californiensis], shell, sand, mud,...

291

Ecological periodic tables for nekton and benthic macrofaunal community usage of estuarine habitats Slides  

EPA Science Inventory

Ecological periodic tables for nekton and benthic macrofaunal community usage of estuarine habitats Steven P. Ferraro, U.S. Environmental Protection Agency, Newport, OR Background/Questions/Methods The chemical periodic table, the Linnaean system of classification, and the Her...

292

ABUNDANCE AND DISTRIBUTION OF INDIGENOUS, NONINDIGENOUS, AND CRYPTOGENIC BENTHIC MACROFAUNA IN WILLAPA BAY, WASHINGTON, USA  

EPA Science Inventory

Benthic macrofaunal samples were collected in Willapa Bay, WA, in four habitats [eelgrass (Zostera marina), Atlantic cordgrass (Spartina alterniflora), mud shrimp (Upogebia pugettensis), ghost shrimp (Neotrypaea californiensis)] in 1996 and in seven habitats (Zostera, Spartina, U...

293

Seasonal variation of benthic macro invertebrates from Tons River of Garhwal Himalaya Uttarakhand.  

PubMed

Present investigation was carried out to assess the seasonal variation of benthic macro-invertebrates from the Tons river, a tributary of Yamuna River in Garhwal Himalaya, Uttrakhand during December, 2007 to November, 2009. The seasonal benthic diversity was correlated with various physic-chemical parameters which documented that the macrobenthic diversity is mostly regulated by the dissolved oxygen in the water while temperature and free CO2 were found to be inversely correlated with the benthic fauna. Maximum diversity of benthos was reported at the upstream site ('H' 0.204) during the winter season while it was recorded minimum during the rainy season at all the sites. Maximum diversity is reported during the winter season at all the sites. The benthic fauna is represented by three phylum, 4 classes and 10 orders with Insecta emerging as the most dominant class. Maximum genera were reported from midstream site as it acts as ecotone between upstream and downstream. PMID:24511693

Negi, R K; Mamgain, Sheetal

2013-11-15

294

Recruitment of benthic organisms onto a planned artificial reef: shifts in community  

E-print Network

, Israel (Red Sea), and compare them to its adjacent NR. Visual surveys of macro-invertebrates were for settlement of benthic invertebrates and fish. This type of AR is common worldwide and can be considered

Benayahu, Yehuda

295

PROCEDURES FOR DERIVING EQUILIBRIUM PARTITIONING SEDIMENT BENCHMARKS (ESBS) FOR THE PROTECTION OF BENTHIC ORGANISMS: DIELDRIN  

EPA Science Inventory

This equilibrium partitioning sediment benchmark (ESB) document describes procedures to derive concentrations of the insecticide dieldrin in sediment which are protective of the presence of benthic organisms. The equilibrium partitioning (EqP) approach was chosen because it acco...

296

Distribution, thickness and origin of Heinrich layer 3 in the Labrador Sea  

NASA Astrophysics Data System (ADS)

The presence of Heinrich layer 3 (HL-3) in the northwest Labrador Sea has been debated in the literature. Calypso giant piston core MD99-2233, five new standard piston cores, and re-interpretation of 34 cores from previous cruises confirm the presence of HL-3 in the Labrador Sea. It is identified by high total carbonate concentration (up to 45%), an increase in coarse fraction content, and lighter ? 18O values in polar species planktonic foraminifer Neogloboquadrina pachyderma (left-coiling) as low as 3.1‰. The age of HL-3 of ˜27 ka was bracketed in the various cores by about 50 14C-accelerator mass spectrometer dates. Where it is present in ice-proximal regions, it consists of nepheloid-flow deposits at the base and mud turbidites at the top. The thickness of HL-3 varies between 4.8 m (proximal to Hudson Strait) and 0.9 m (distal), decreasing rapidly seaward. On the upper continental slope, HL-3 was too deeply buried to be sampled. Elsewhere, HL-3 is absent in some cores, probably due to slumping or erosion associated with sandy turbidity currents or debris flows.

Rashid, Harunur; Hesse, Reinhard; Piper, David J. W.

2003-01-01

297

Stimulation of microbial nitrogen cycling in aquatic ecosystems by benthic macrofauna: mechanisms and environmental implications  

NASA Astrophysics Data System (ADS)

Invertebrate animals that live at the bottom of aquatic ecosystems (i.e., benthic macrofauna) are important mediators between nutrients in the water column and microbes in the benthos. The presence of benthic macrofauna stimulates microbial nutrient dynamics through different types of animal-microbe interactions, which potentially affect the trophic status of aquatic ecosystems. This review contrasts three types of animal-microbe interactions in the benthos of aquatic ecosystems: (i) ecosystem engineering, (ii) grazing, and (iii) symbiosis. Their specific contributions to the turnover of fixed nitrogen (mainly nitrate and ammonium) and the emission of the greenhouse gas nitrous oxide are evaluated. Published data indicate that ecosystem engineering by sediment-burrowing macrofauna stimulates benthic nitrification and denitrification, which together allows fixed nitrogen removal. However, the release of ammonium from sediments is enhanced more strongly than the sedimentary uptake of nitrate. Ecosystem engineering by reef-building macrofauna increases nitrogen retention and ammonium concentrations in shallow aquatic ecosystems, but allows organic nitrogen removal through harvesting. Grazing by macrofauna on benthic microbes apparently has small or neutral effects on nitrogen cycling. Animal-microbe symbioses provide abundant and distinct benthic compartments for a multitude of nitrogen-cycle pathways. Recent studies reveal that ecosystem engineering, grazing, and symbioses of benthic macrofauna significantly enhance nitrous oxide emission from shallow aquatic ecosystems. The beneficial effect of benthic macrofauna on fixed nitrogen removal through coupled nitrification-denitrification can thus be offset by the concurrent release of (i) ammonium that stimulates aquatic primary production and (ii) nitrous oxide that contributes to global warming. Overall, benthic macrofauna intensifies the coupling between benthos, pelagial, and atmosphere through enhanced turnover and transport of nitrogen.

Stief, P.

2013-12-01

298

Stimulation of microbial nitrogen cycling in aquatic ecosystems by benthic macrofauna: mechanisms and environmental implications  

NASA Astrophysics Data System (ADS)

Invertebrate animals that live at the bottom of aquatic ecosystems (i.e., benthic macrofauna) are important mediators between nutrients in the water column and microbes in the benthos. The presence of benthic macrofauna stimulates microbial nutrient dynamics through different types of animal-microbe interactions, which potentially affect the trophic status of aquatic ecosystems. This review contrasts three types of animal-microbe interactions in the benthos of aquatic ecosystems: (i) ecosystem engineering, (ii) grazing, and (iii) symbiosis. Their specific contributions to the turnover of fixed nitrogen (mainly nitrate and ammonium) and the emission of the greenhouse gas nitrous oxide are evaluated. Published data indicate that ecosystem engineering by sediment-burrowing macrofauna stimulates benthic nitrification and denitrification, which together allows fixed nitrogen removal. However, the release of ammonium from sediments often is enhanced even more than the sedimentary uptake of nitrate. Ecosystem engineering by reef-building macrofauna increases nitrogen retention and ammonium concentrations in shallow aquatic ecosystems, but allows organic nitrogen removal through harvesting. Grazing by macrofauna on benthic microbes apparently has small or neutral effects on nitrogen cycling. Animal-microbe symbioses provide abundant and distinct benthic compartments for a multitude of nitrogen-cycle pathways. Recent studies revealed that ecosystem engineering, grazing, and symbioses of benthic macrofauna significantly enhance nitrous oxide emission from shallow aquatic ecosystems. The beneficial effect of benthic macrofauna on fixed nitrogen removal through coupled nitrification-denitrification can thus be offset by the concurrent release of (i) ammonium that stimulates aquatic primary production and (ii) nitrous oxide that contributes to global warming. Overall, benthic macrofauna intensifies the coupling between benthos, pelagial, and atmosphere through enhanced turnover and transport of nitrogen.

Stief, P.

2013-07-01

299

Responses of benthic macroinvertebrate communities to natural geothermal discharges in Yellowstone National Park, USA  

Microsoft Academic Search

We examined responses of benthic macroinvertebrate communities to natural geothermal discharges in 32 streams in Yellowstone\\u000a National Park (YNP), USA. Geothermal discharges played a major role in structuring benthic communities in YNP, as downstream\\u000a communities were characterized by low species richness, reduced abundance of EPT taxa and increased abundance of tolerant\\u000a caddisflies (Trichoptera), chironomids and non-insects. While some taxa were

William H. ClementsJeffrey; Jeffrey L. Arnold; Todd M. Koel; Rob Daley; Cathie Jean

2011-01-01

300

Effect of seaweed proliferation on benthic habitat quality assessed by Sediment Profile Imaging  

NASA Astrophysics Data System (ADS)

Changes in sediment quality, with special reference to benthic habitat conditions resulting from macroalgae overgrowth, were studied in the Venice Lagoon, Italy. Data were collected biweekly in spring and summer from 1993 to 1998 and from 2001 to 2002, as part of the macroalgae growth control strategies managed by the Venice Water Authority-Consorzio Venezia Nuova. Benthic habitat conditions were studied by means of Sediment Profile Imaging, which allowed the collection of several variables: aRPD (apparent redox potential discontinuity), prism penetration depth, presence of anoxia on the surface of the sediment, presence of reduced gas bubbles, stage of benthic colonization. All these variables led to the calculation of an environmental index (Organism-Sediment Index, OSI), which was then related to physical variables and macroalgae abundance. Until 1996, the overall benthic habitat of the Venice Lagoon showed almost stressed conditions; from 1997, the seaweed biomass rapidly declined and the OSI increased significantly. The OSI seemed to be affected by seaweed biomass, sediment compactness and water depth. Macroalgae biomass greater than 4.5 kg/m 2 led to the complete disappearance of stage III of benthic colonization; values as low as 0.70 kg m 2 already had a severe impact on recolonization. SPI attributes indicated the main mechanisms that could have contributed to the benthic quality: seaweed proliferation is often followed by rapid decay of macroalgae biomass, especially when present in large amounts. The decrease in seaweed biomass often results in oxygen depletion in the water column and thus in the sediment, preventing complete benthic colonization. This research confirms the importance of in situ rapid reconnaissance surveys to assess the impact of eutrophication on the benthic habitat.

Bona, Francesca

2006-10-01

301

An estuarine benthic index of biotic integrity (B-IBI) for Chesapeake Bay  

Microsoft Academic Search

A multimetric benthic index of biotic integrity (B-IBI) was developed using data from five Chesapeake Bay sampling programs\\u000a conducted between 1972 and 1991. Attributes of the index were selected by comparing the response of 17 candidate measures\\u000a of benthic condition (metrics) between a set of minimally affected reference sites and at all other sites for which data were\\u000a available. This

Stephen B. Weisberg; J. Ananda Ranasinghe; Daniel M. Dauer; Linda C. Schaffner; Robert J. Diaz; Jeffrey B. Frithsen

1997-01-01

302

Consequences of Increasing Hypoxic Disturbance on Benthic Communities and Ecosystem Functioning  

PubMed Central

Disturbance-mediated species loss has prompted research considering how ecosystem functions are changed when biota is impaired. However, there is still limited empirical evidence from natural environments evaluating the direct and indirect (i.e. via biota) effects of disturbance on ecosystem functioning. Oxygen deficiency is a widespread threat to coastal and estuarine communities. While the negative impacts of hypoxia on benthic communities are well known, few studies have assessed in situ how benthic communities subjected to different degrees of hypoxic stress alter their contribution to ecosystem functioning. We studied changes in sediment ecosystem function (i.e. oxygen and nutrient fluxes across the sediment water-interface) by artificially inducing hypoxia of different durations (0, 3, 7 and 48 days) in a subtidal sandy habitat. Benthic chamber incubations were used for measuring responses in sediment oxygen and nutrient fluxes. Changes in benthic species richness, structure and traits were quantified, while stress-induced behavioral changes were documented by observing bivalve reburial rates. The initial change in faunal behavior was followed by non-linear degradation in benthic parameters (abundance, biomass, bioturbation potential), gradually impairing the structural and functional composition of the benthic community. In terms of ecosystem function, the increasing duration of hypoxia altered sediment oxygen consumption and enhanced sediment effluxes of NH4+ and dissolved Si. Although effluxes of PO43? were not altered significantly, changes were observed in sediment PO43? sorption capability. The duration of hypoxia (i.e. number of days of stress) explained a minor part of the changes in ecosystem function. Instead, the benthic community and disturbance-driven changes within the benthos explained a larger proportion of the variability in sediment oxygen- and nutrient fluxes. Our results emphasize that the level of stress to the benthic habitat matters, and that the link between biodiversity and ecosystem function is likely to be affected by a range of factors in complex, natural environments. PMID:23091592

Villnas, Anna; Norkko, Joanna; Lukkari, Kaarina; Hewitt, Judi; Norkko, Alf

2012-01-01

303

Benthic–pelagic coupling on coral reefs: Feeding and growth of Caribbean sponges  

Microsoft Academic Search

Benthic–pelagic coupling and the role of bottom-up versus top-down processes are recognized as having a major impact on the community structure of intertidal and shallow subtidal marine communities. Bottom-up processes, however, are still viewed as principally affecting the outcome of top-down processes. Sponges on coral reefs are important members of the benthic community and provide a crucial coupling between water-column

Michael P. Lesser

2006-01-01

304

Trace metals, PCBs, and PAHs in benthic (epipelic) diatoms from intertidal sediments; a pilot study  

SciTech Connect

Intertidal sediments in many estuaries around the world have a history of contamination resulting from long term discharges of industrial, agricultural and domestic waste effluents. These contaminated sediments are now regarded as a major source of toxicants for bottom-related organisms which, in turn, may pass on certain contaminants (e.g. methylmercury, polychlorinated biphenyls (PCBs)) to organisms higher in the foodchain. Many studies have been conducted on the contamination of benthic macrofauna, estuarine fish and birds, but to our knowledge no research has yet been carried out on benthic diatoms which form the lowest trophic level of an intertidal ecosystem. Research on the effects of micro-contaminants on primary producers in marine ecosystems is mainly performed with phytoplankton. In the estuaries of temperate regions, benthic diatoms make a significant contribution to primary production in the ecosystem and are predated especially by deposit feeding Polychaete and Mollusca. Knowledge of the level of contamination in benthic diatoms is of major importance to recognize possible effects on growth rate and species composition of the benthic diatom populations and to understand the accumulation of toxicants into the foodchain. For chemical analysis it is difficult to obtain [open quote]pure[close quote] samples of benthic diatoms because they form part of the sediment. A similar problem occurs with the sampling of phytoplankton in turbid estuarine waters. The aim of this pilot study was (a) to improve a trap technique to collect pure samples of benthic diatoms of at least 2 gram dry weight for analysis of trace metals, PCBs and polyaromatic hydrocarbons (PAHs) and (b) to compare the concentrations in benthic diatoms with levels in sediment and some bottom-related organisms. 16 refs., 2 figs., 2 tabs.

Stronkhorst, J.; Misdorp, R. (National Institute for Marine and Coastal Management, The Hague (Netherlands)); Vos, P.C. (Geological Survey of the Netherlands, Oosterwolde (Netherlands))

1994-06-01

305

Effects of coral reef benthic primary producers on dissolved organic carbon and microbial activity.  

PubMed

Benthic primary producers in marine ecosystems may significantly alter biogeochemical cycling and microbial processes in their surrounding environment. To examine these interactions, we studied dissolved organic matter release by dominant benthic taxa and subsequent microbial remineralization in the lagoonal reefs of Moorea, French Polynesia. Rates of photosynthesis, respiration, and dissolved organic carbon (DOC) release were assessed for several common benthic reef organisms from the backreef habitat. We assessed microbial community response to dissolved exudates of each benthic producer by measuring bacterioplankton growth, respiration, and DOC drawdown in two-day dark dilution culture incubations. Experiments were conducted for six benthic producers: three species of macroalgae (each representing a different algal phylum: Turbinaria ornata--Ochrophyta; Amansia rhodantha--Rhodophyta; Halimeda opuntia--Chlorophyta), a mixed assemblage of turf algae, a species of crustose coralline algae (Hydrolithon reinboldii) and a dominant hermatypic coral (Porites lobata). Our results show that all five types of algae, but not the coral, exuded significant amounts of labile DOC into their surrounding environment. In general, primary producers with the highest rates of photosynthesis released the most DOC and yielded the greatest bacterioplankton growth; turf algae produced nearly twice as much DOC per unit surface area than the other benthic producers (14.0±2.8 µmol h?¹ dm?²), stimulating rapid bacterioplankton growth (0.044±0.002 log10 cells h?¹) and concomitant oxygen drawdown (0.16±0.05 µmol L?¹ h?¹ dm?²). Our results demonstrate that benthic reef algae can release a significant fraction of their photosynthetically-fixed carbon as DOC, these release rates vary by species, and this DOC is available to and consumed by reef associated microbes. These data provide compelling evidence that benthic primary producers differentially influence reef microbial dynamics and biogeochemical parameters (i.e., DOC and oxygen availability, bacterial abundance and metabolism) in coral reef communities. PMID:22125645

Haas, Andreas F; Nelson, Craig E; Wegley Kelly, Linda; Carlson, Craig A; Rohwer, Forest; Leichter, James J; Wyatt, Alex; Smith, Jennifer E

2011-01-01

306

Assessment of the benthic environment following offshore placer gold mining in the northeastern Bering Sea  

Microsoft Academic Search

The effects of offshore placer gold mining on benthic invertebrates were assessed on ‘sand’ and ‘cobble’ substrates in Norton Sound, northeastern Bering Sea. Mining with a bucket-line dredge occurred nearshore in 9–20 m during June to November 1986–90. Sampling nearly a year subsequent to mining demonstrated minor alteration of substrate granulometry with no clear trends. However, benthic macrofaunal community parameters

S. C. Jewett; H. M. Feder; A. Blanchard

1999-01-01

307

Benthic community re-adjustment following dredging of a muddy-maerl matrix  

Microsoft Academic Search

Changes in the benthic infaunal community structure at a location in south-west Ireland subject to dredging impacts were studied. Dredging of a muddy-maerl matrix takes place with a seasonally varying frequency of 2–5 times per month. The benthic infauna at a currently dredged site was compared to a fallowed portion of the area, at which extraction ceased 6 months prior

S De Grave; A Whitaker

1999-01-01

308

Spatial Variability of Benthic-Pelagic Coupling in an Estuary Ecosystem: Consequences for Microphytobenthos Resuspension Phenomenon  

PubMed Central

The high degree of physical factors in intertidal estuarine ecosystem increases material processing between benthic and pelagic compartments. In these ecosystems, microphytobenthos resuspension is a major phenomenon since its contribution to higher trophic levels can be highly significant. Understanding the sediment and associated microphytobenthos resuspension and its fate in the water column is indispensable for measuring the food available to benthic and pelagic food webs. To identify and hierarchize the physical/biological factors potentially involved in MPB resuspension, the entire intertidal area and surrounding water column of an estuarine ecosystem, the Bay des Veys, was sampled during ebb tide. A wide range of physical parameters (hydrodynamic regime, grain size of the sediment, and suspended matter) and biological parameters (flora and fauna assemblages, chlorophyll) were analyzed to characterize benthic-pelagic coupling at the bay scale. Samples were collected in two contrasted periods, spring and late summer, to assess the impact of forcing variables on benthic-pelagic coupling. A mapping approach using kriging interpolation enabled us to overlay benthic and pelagic maps of physical and biological variables, for both hydrological conditions and trophic indicators. Pelagic Chl a concentration was the best predictor explaining the suspension-feeders spatial distribution. Our results also suggest a perennial spatio-temporal structure of both benthic and pelagic compartments in the ecosystem, at least when the system is not imposed to intense wind, with MPB distribution controlled by both grain size and bathymetry. The benthic component appeared to control the pelagic one via resuspension phenomena at the scale of the bay. Co-inertia analysis showed closer benthic-pelagic coupling between the variables in spring. The higher MPB biomass observed in summer suggests a higher contribution to filter-feeders diets, indicating a higher resuspension effect in summer than in spring, in turn suggesting an important role of macrofauna bioturbation and filter feeding (Cerastoderma edule). PMID:22952910

Ubertini, Martin; Lefebvre, Sébastien; Gangnery, Aline; Grangeré, Karine; Le Gendre, Romain; Orvain, Francis

2012-01-01

309

Polychlorinated biphenyls (PCBs) in a benthic ecosystem in Gwangyang Bay, South Korea  

Microsoft Academic Search

Benthic ecosystem in Gwangyang Bay, a fast developing industrial area with steel production, port container handling, petroleum and other chemical processing in South Korea was studied. The average levels of polychlorinated biphenyls (?PCB) in the benthic components were: seawater 2.99±0.13 (ng\\/L); sediment 294±118 (ng\\/g TOC); [biota=ng\\/g lipid] starfish 92; prawn 131±2; mussels 127±22; crab 182±114; clam 187; polychaeta 215; sea

Sang Hee Hong; Narayanan Kannan; Un Hyuk Yim; Jin-Woo Choi; Won Joon Shim

310

Turnover and paleoenvironmental changes across the Cretaceous/Paleogene boundary at the Galanderud section (Northern Alborz, Iran) based on benthic foraminifera  

NASA Astrophysics Data System (ADS)

A high-resolution quantitative study of benthic foraminifera across the expanded and continuous Cretaceous/Paleogene (K/Pg) boundary at the Galanderud section in northern Iran provides an excellent record of the K/Pg event. The benthic foraminiferal assemblages, in contrast to the planktic foraminifers, did not suffer mass extinction at the K/Pg boundary. Uppermost Maastrichtian assemblages are well preserved and highly diverse. Only ~3% of the benthic species became extinct, including Bolivinoides draco, Eouvigerina subsculptura, Neoflabellina sp. and Praebulimina reussi. Other species are temporarily absent for a short interval after the K/Pg boundary. Benthic foraminifera indicate outer neritic-uppermost bathyal depths during the Plummerita hantkeninoides Zone until 70 cm below the K/Pg boundary. This interval contains abundant species of Bolivinoides draco, Gaudryina pyramidata, Cibicidoides hyphalus, P. reussi, and Sitella cushmani. The paleodepth decreased to outer neritic in the uppermost Maastrichtian based on the dominance of Stensioeina excolata, G. pyramidata, Cibicidoides pseudoacutus, and Coryphostoma incrassata forma gigantea. On the other hand, some species such as P. reussi and C. hyphalus, which are normally found at bathyal depths, decreased in their abundances. These data suggest a sea-level fall at the end of Maastrichtian. Additional evidence for sea-level fall is a decrease of planktic/benthic ratio from ~60% to ~40% in the uppermost Maastrichtian. The K/Pg clay layer is characterized by a high abundance of opportunistic species such as Cibicidoides spp., C. pseudoacutus, and Tappanina selemensis. The drastic change of benthic foraminiferal assemblages coincides with a sharp drop in magnetic susceptibility and %CaCO3, mass extinction of planktic foraminifera, a sharp enrichment in Ir, and a 2.25‰ negative excursion in ?13C at the K/Pg boundary, which is largely compatible with the catastrophic effects of an asteroid impact on Earth that briefly, but severely destabilized the oceanic phytoplankton food webs. Isothermal Remanent Magnetization (IRM) curves treated by the cumulative log-Gaussian function shows that hematite (or goethite) and magnetite are the main magnetic minerals in the K/Pg clay layer, whereas large and small magnetite characterize the Maastrichtian and the Danian sediments, respectively. The dominance of hematite over magnetite at the K/Pg boundary explains the lack of the characteristic positive magnetic susceptibility peak observed in other sections suggesting higher oxidation state of the Galanderud depositional environment during the impact. The presence of three calcareous dinoflagellate chalk layers and large excursions in O- and C-isotopic compositions in basal Danian Zone P0 highlight the instability of the ecosystem immediately following the K/Pg boundary. In the Parvularugoglobigerina eugubina and Parasubbotina pseudobulloides Zones, there is an increase in both diversity and infaunal morphogroups, and a slight decrease of the epifaunal morphogroups; some deeper species increase in abundance including Gyroidinoides globosus and Marssonella oxycona. These changes might indicate a sea level rise and uppermost bathyal paleodepths in the early Danian, but it might also indicate improved conditions at the seafloor including greater flux of organic matter. These abrupt paleoenvironmental changes at the K/Pg boundary are correlated in age to the Chicxulub impact event and to the Deccan Phase 2; the contribution of each event is currently under study.

Asgharianrostami, Masoud; Leckie, R. Mark; Font, Eric; Frontalini, Fabrizio; Koeberl, Christian

2014-05-01

311

Associations between degraded benthic communities and contaminated sediments: Sabine Lake, Lake Pontchartrain, and Choctawhatchee Bay  

SciTech Connect

The Environmental Monitoring and Assessment Program for Estuaries (EMAP-E) in the Gulf of Mexico supplements its base sampling effort each year with localized, intensive spatial sampling in selected large estuarine systems. By selecting random locations within 70 km{sup 2} hexagonal areas, individual estuaries were sampled using EMAP methods but at four times the density as base sampling. In 1992, 19 sites were sampled in Lake Pontchartrain, Louisiana. In 1 993, 18 sites were sampled in Sabine Lake, Texas and 12 sites were sampled in Choctawhatchee Bay, Florida. At all sites, sediment grabs were taken and analyzed for benthic species composition and abundance, for toxicity to Ampelisca, and for organic and inorganic sediment contaminants. An indicator of biotic integrity, the benthic index, was calculated to represent the status of benthic communities. A series of statistical techniques, such as stepwise regression analysis, were employed to determine whether the variation in the benthic index could be associated with variation in sediment contaminants, sediment toxicity, or levels of dissolved oxygen. Spatial distributions of these parameters were examined to determine the geographical co-occurrence of degraded benthic communities and environmental stressors. In Lake Pontchartrain, for example, 85% of the variation in the benthic index was associated with decreased levels of dissolved oxygen, and increased concentrations of PCBs, alkanes, copper, tin, and zinc in the sediments.

Engle, V.D. [Avanti Corp., Gulf Breeze, FL (United States); Summers, J.K.; Macauley, J.M. [Environmental Protection Agency, Gulf Breeze, FL (United States). Environmental Research Lab.

1994-12-31

312

Preliminary estimates of benthic fluxes of dissolved metals in Coeur d'Alene Lake, Idaho  

USGS Publications Warehouse

This report presents porewater and selected water column data collected from Coeur d'Alene Lake in September of 1992. Despite probable oxidation of the porewater samples during collection and handling, these data are used to calculate molecular diffusive fluxes of dissolved metals (that is, Zn, Pb, Cu, and Mn) across the sediment-water interface. While these data and calculations provide preliminary information on benthic metal fluxes in Coeur d'Alene Lake, further work is needed to verify their direction and magnitude. The benthic flux calculations indicate that the sediment is generally a source of dissolved Zn, Cu, Mn, and, possibly, Pb to the overlying water column. These benthic fluxes are compared with two other major sources of metals to Coeur d'Alene Lake-the Coeur d'Alene and St. Joe Rivers. Comparisons indicate that benthic fluxes of Zn, Pb, and Cu are generally less than half of the fluxes of these metals into the lake from the Coeur d'Alene River. However, in a few cases, the calculated benthic metal fluxes exceed the Coeur d'Alene River fluxes. Benthic fluxes of Zn and, possibly, Pb may be greater than the corresponding metal fluxes from the St. Joe River. These results have implications for changes in the relative importance of metal sources to the lake as remediation activities in the Coeur d'Alene River basin proceed.

Balistrieri, L.S.

1998-01-01

313

Explosive diversification following a benthic to pelagic shift in freshwater fishes  

PubMed Central

Background Interspecific divergence along a benthic to pelagic habitat axis is ubiquitous in freshwater fishes inhabiting lentic environments. In this study, we examined the influence of this habitat axis on the macroevolution of a diverse, lotic radiation using mtDNA and nDNA phylogenies for eastern North America’s most species-rich freshwater fish clade, the open posterior myodome (OPM) cyprinids. We used ancestral state reconstruction to identify the earliest benthic to pelagic transition in this group and generated fossil-calibrated estimates of when this shift occurred. This transition could have represented evolution into a novel adaptive zone, and therefore, we tested for a period of accelerated lineage accumulation after this historical habitat shift. Results Ancestral state reconstructions inferred a similar and concordant region of our mtDNA and nDNA based gene trees as representing the shift from benthic to pelagic habitats in the OPM clade. Two independent tests conducted on each gene tree suggested an increased diversification rate after this inferred habitat transition. Furthermore, lineage through time analyses indicated rapid early cladogenesis in the clade arising after the benthic to pelagic shift. Conclusions A burst of diversification followed the earliest benthic to pelagic transition during the radiation of OPM cyprinids in eastern North America. As such, the benthic/pelagic habitat axis has likely influenced the generation of biodiversity across disparate freshwater ecosystems. PMID:24341464

2013-01-01

314

Concentrations of selected heavy metals in benthic diatoms and sediment in the Westerschelde Estuary  

SciTech Connect

In recent years considerable data have been compiled on heavy metal levels in biota in marine and estuarine environments. With respect to the fauna, much information is available on accumulation and effects of heavy metals in birds, fish and benthic macrofauna. Accumulation of heavy metals in aquatic flora has been studied mostly in benthic macroalgae, in particular in relation to the use as a biological monitor. The response of planktonic algal species to heavy metals has been studied extensively in cultured populations. Also. heavy metal concentrations in natural plankton have been studied. As far as we know, very few data are available on the concentrations of heavy metals in the lowest benthic trophic level, the benthic microflora. It is a major food supply for numerous intertidal species, so it is obvious that microflora might play an important role in the accumulation of contaminants through coastal food chains. The aim of this research was to adjust a recently developed collection technique for benthic diatoms so that it is suitable for large-scale field studies. The method was then used to assess the concentration of the heavy metals Cd, Cu, Pb and Zn in benthic diatoms and sediments along an estuarine gradient. 18 refs., 2 figs., 1 tab.

Absil, M.C.P.; Scheppingen, Y. van [Netherlands Inst. of Ecology, Vierstraat (Netherlands)] [Netherlands Inst. of Ecology, Vierstraat (Netherlands)

1996-12-31

315

Effects of contrasting upwelling downwelling on benthic foraminiferal distribution in the Ría de Vigo (NW Spain)  

NASA Astrophysics Data System (ADS)

Live benthic foraminifera in the superficial sediments from the muddy central axis of the Ría de Vigo were examined under two contrasting hydrographic conditions: downwelling and upwelling. During downwelling conditions the abundance of benthic foraminifera does not show large differences between sites with different organic carbon contents. The arrival of labile organic carbon to the seafloor delivered during upwelling events causes an increase in the abundance of the most significant species and the appearance of new species in the life assemblage. This suggests that benthic foraminiferal faunas strongly depend on high quality organic carbon supply and the sedimentary organic carbon is not a good indicator of food availability to benthic foraminifera. The response of benthic foraminifera to phytoplankton blooms differs between outer and inner sites. In outer and middle areas benthic foraminiferal assemblages show quick population growth in reaction to phytoplankton blooms (r-strategists), whereas in inner sites the most abundant species displays both growth and reproduction (k-strategists). It is suggested that r-strategy results of adaptation to perturbations on short time-scales (downwelling/upwelling cycles) under favourable microenvironmental conditions, while the k-strategy represents the adaptation to long term perturbations, such as relatively low oxygen concentrations and/or reducing microenvironmental conditions in the sediment.

Diz, Paula; Francés, Guillermo; Rosón, Gabriel

2006-04-01

316

Classifying Deep Water Benthic Habitats around Tutuila, American Samoa  

E-print Network

Coral reef ecosystems are the most varied on Earth. These valuable ecosystems see danger worldwide, continually facing destruction from anthropogenic effects and natural disasters. Among efforts to understand coral reef ecosystems is the Coral Reef Task Force's objective to map all U.S. coral reefs and, more specifically, to characterize priority deep water (>30m) reef systems in the U.S. and Trust Territories by 2009. This project satisfies that objective for coral reef systems around Tutuila, American Samoa, by using 3D visualization and high-resolution multibeam bathymetry, bathymetric derivatives (bathymetric position index, rugosity, and slope), acoustic backscatter imagery, and in situ visual ground-truthing in an integrated GIS to classify benthic habitats in Fagatele Bay National Marine Sanctuary, on Taema Bank, and at Coconut Point. Resulting habitat maps establish a classification scheme for American Samoa, pinpoint "hot-spots " for biodiversity, and help NOAA's Coastal Services Center develop a deep water benthic habitat mapping tool. Understanding and Monitoring Coral Reef Ecosystems Marine and coastal environments are a vast frontier for exploration. Coral reefs, along with tropical rainforests, are the most diverse ecosystems on earth. There is a need for documenting baseline information about coral reefs with long-term monitoring and for developing methods to estimate their geographic extent (Miller and Crosby 1998). In the effort to understand and protect ocean resources, several agencies and governmental organizations have been established. In the forefront of strategies and initiatives is the need for seafloor mapping. We need to know the fine-scale terrain of the seafloor in order to locate and study specific resources associated with these particular terrains. The United States Coral Reef Task Force (CRTF) was established by the National Oceanic and Atmospheric Administration (NOAA) in June 1998 as an overseer of coral reef protection. The CRTF Mapping and Information Working Group has a goal to map all United States (U.S.) coral reefs below 30 m depth by 2009 (Evans et al. 2002). The work described here is a first step in meeting that objective for coral reef systems around the

unknown authors

317

Acoustic scattering by benthic and planktonic shelled animals.  

PubMed

Acoustic backscattering measurements and associated scattering modeling were recently conducted on a type of benthic shelled animal that has a spiral form of shell (Littorina littorea). Benthic and planktonic shelled animals with this shape occur on the seafloor and in the water column, respectively, and can be a significant source of acoustic scattering in the ocean. Modeling of the scattering properties allows reverberation predictions to be made for sonar performance predictions as well as for detection and classification of animals for biological and ecological applications. The studies involved measurements over the frequency range 24 kHz to 1 MHz and all angles of orientation in as small as 1 degree increments. This substantial data set is quite revealing of the physics of the acoustic scattering by these complex shelled bodies and served as a basis for the modeling. Specifically, the resonance structure of the scattering was strongly dependent upon angle of orientation and could be traced to various types of rays (e.g., subsonic Lamb waves and rays entering the opercular opening). The data are analyzed in both the frequency and time domain (compressed pulse processing) so that dominant scattering mechanisms could be identified. Given the complexity of the animal body (irregular elastic shell with discontinuities), approximate scattering models are used with only the dominant scattering properties retained. Two models are applied to the data, both approximating the body as a deformed sphere: (1) an averaged form of the exact modal-series-based solution for the spherical shell, which is used to estimate the backscattering by a deformed shell averaged over all angles of orientation, and produces reasonably accurate predictions over all k1a(esr) (k1 is the acoustic wave number of the surrounding water and a(esr) is the equivalent spherical radius of the body), and (2) a ray-based formula which is used to estimate the scattering at fixed angle of orientation, but only for high k1a(esr). The ray-based model is an extension of a model recently developed for the shelled zooplankton Limacina retroversa that has a shape similar to that of the Littorina littorea but swims through the water [Stanton et al., J. Acoust. Soc. Am. 103, 236-253 (1998b)]. Applications of remote detection and classification of the seafloor and water column in the presence of shelled animals are discussed. PMID:10955618

Stanton, T K; Chu, D; Wiebe, P H; Eastwood, R L; Warren, J D

2000-08-01

318

Benthic foraminiferal assemblages help to understand carbonate mound evolution  

NASA Astrophysics Data System (ADS)

On- and off-mound sediment cores from Propeller Mound (Porcupine Seabight) were analysed for their benthic foraminiferal assemblages. Benthic foraminifera from the off-mound position show three different assemblages describing the Holocene, Oxygen Isotope Stage (OIS) 2 and late OIS 3. The Holocene assemblage is dominated by Uvigerina mediterranea, Trifarina angulosa, Melonis barleeanum, Hyalinea balthica, Bulimina marginata. These species are related to a higher supply of organic material. The glacial assemblage shows high abundances of Cassidulina teretis, C. reniforme, Globocassidulina subglobosa, and Cibicidoides kullenbergi, implying cold bottom waters and a reduced productivity. The lower part of late OIS 3 is dominated by Elphidium excavatum, which is displaced continuously by very high abundances of C. teretis towards the transition of OIS3/2. E. excavatum, a shallow shelf species generally reported from above 200 m water depth, and high amounts of sediment supplied to the core site points to shelf erosion related to sea level lowering (approx. 50 m). Towards OIS 2 the system returns to normal background sedimentation pattern. We transferred the established off-mound assemblages onto the on-mound core, in which the sediment sequence is incomplete characterised by numerous hiatuses. The Holocene assemblage describes almost the complete core with relative abundances of >20%, interrupted only by three sections with slightly higher amounts of the glacial assemblage, which are not comparable to abundances of >70% of the glacial assemblage found in the off-mound core. These results are in conjunction with stable oxygen isotope data indicating only interstadial values, assuming peak glacial and interglacial sediments to be removed from the mound. Another assemblage described for the on-mound core is dominated by Discanomalina coronata, Gavelinopsis translucens, Planulina ariminensis, Cibicides lobatulus and to a lower degree by Hyrrokkin sarcophaga. These species are only found or show significantly higher relative abundances in on-mound samples and are grouped to the mound assemblage. This assemblage probably indicates a higher coral growth density on Propeller Mound in an earlier period, but is less abundant during the Holocene, which indicates a declining of the mound associated with less coral growth.

Rüggeberg, A.; Dorschel, B.; Dullo, C.; Hebbeln, D.; Freiwald, A.

2003-04-01

319

Signals from the benthos: Development and evaluation of a benthic index for the nearshore Gulf of Maine  

Microsoft Academic Search

We developed a benthic index for the nearshore Gulf of Maine to provide researchers and environmental managers a way to make spatial and year-to-year comparisons of benthic condition. The data set used included 248 stations sampled for physical, chemical, and biological variables by the National Coastal Assessment in 2000–2003. We used logistic regression with 49 candidate measures of benthic species

Stephen S. Hale; James F. Heltshe

2008-01-01

320

Layered Slopes  

NASA Technical Reports Server (NTRS)

4 June 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows exposures of layered material on slopes in the south polar region near 81.9oS, 72.2oW. Layers record the history of a place, but accessing the information contained in these layers may one day require a visit by a human or robotic explorer. The south polar layers, in general, are believed to be accumulations of dust and ice that were built up in the most recent billion years or so. However, they could just as easily be sedimentary rocks from much earlier in martian history. The picture covers an area about 3 km (1.9 mi) across. The scene is illuminated by sunlight from the upper left.

2004-01-01

321

The effects of beach nourishment on benthic invertebrates in eastern Australia: impacts and variable recovery.  

PubMed

Beach erosion is likely to accelerate, driven by predicted consequences of climate change and coastal development. Erosion is increasingly combated by beach nourishment, adding sand to eroding shores. Because a range of engineering techniques exists to nourish beaches, and because these techniques differ in their environmental effects, assessments of ecological impacts need to be tailored and specific. Here we report on impacts and recovery of benthic invertebrates impacted by beach nourishment operations undertaken at Palm Beach (SE Queensland, Australia). Assessments are made based on a beyond-BACI design, where samples were taken once before nourishment and twice afterwards at the impact and two control sites. Because almost all of the sand was deposited on the upper beach and later moved with bulldozers down-shore, we specifically examined whether the effects of nourishment varied at different heights of the beach-a little-studied question which has management implications. Impacts on the fauna were massive on the upper and middle levels of the beach: samples collected two days after the conclusion of nourishment were entirely devoid of all invertebrate life ('azoic'), whereas weaker effects of nourishment were detectable on the lower shore. Recovery after five months also varied between shore levels. The sediment of the upper level near the dunes remained azoic, the fauna of the middle shore had recovered partially, and the lower level had recovered in most respects. These findings indicate that the height and position of sand placement are important. For example, rather than depositing fill sand on the intertidal beach, it could be placed in the shallow subtidal zone, followed by slow up-shore accretion driven by hydrodynamic forces. Alternatively, techniques that spread the fill sand in thin layers (to minimize mortality by burial) and leave unfilled intertidal refuge islands (to provide colonists) may minimize the ecological impacts of beach nourishment. PMID:22878101

Schlacher, Thomas A; Noriega, Rocio; Jones, Alan; Dye, Theresa

2012-10-01

322

Ecological periodic tables for benthic macrofaunal usage of estuarine habitats: Insights from a case study in Tillamook Bay, Oregon, USA  

NASA Astrophysics Data System (ADS)

This study validates the ecological relevance of estuarine habitat types to the benthic macrofaunal community and, together with previous similar studies, suggests they can serve as elements in ecological periodic tables of benthic macrofaunal usage in the bioregion. We compared benthic macrofaunal Bray-Curtis similarity and the means of eight benthic macrofaunal community measures across seven habitat types in Tillamook Bay, Oregon, USA: intertidal eelgrass (Zostera marina), dwarf eelgrass (Zostera japonica), oyster (Crassostrea gigas) ground culture, burrowing mud shrimp (Upogebia pugettensis), burrowing ghost shrimp (Neotrypaea californiensis), sand and subtidal. Benthic macrofaunal Bray-Curtis similarity differed among all the habitats except ghost shrimp and sand. The habitat rank order on mean benthic macrofaunal species richness, abundance and biomass was dwarf eelgrass ? oyster ? mud shrimp ? eelgrass > sand ? ghost shrimp ? subtidal. The benthic macrofaunal habitat usage pattern in Tillamook Bay was, with a few exceptions, similar to that in two other US Pacific Northwest estuaries. The exceptions indicate variants of eelgrass and ghost shrimp habitat that differ in benthic macrofaunal usage perhaps due to differences in the coarseness of the sand fraction of the sediments in which they live. The similarities indicate periodic benthic macrofaunal usage patterns across the other habitat types extend over a wider geographic scale and range of environmental conditions than previously known.

Ferraro, Steven P.; Cole, Faith A.

2012-05-01

323

Assessment of toxicity thresholds in aquatic environments: does benthic growth of diatoms affect their exposure and sensitivity to herbicides?  

PubMed

Benthic diatoms evolved in a biofilm structure, at the interface between water and substrata. Biofilms can adsorb toxicants, such as herbicides, but little is known about the exposure of biofilm organisms, such as benthic diatoms, to these adsorbed herbicides. We assessed the sensitivity of 11 benthic diatoms species to 6 herbicides under both planktonic and benthic conditions using single-species bioassays. The concentration that reduced the growth rate of the population by 10% (EC10) and 50% (EC50), respectively, varied depending on the species, the herbicides, and the growth forms involved. As a general trend, the more hydrophobic the herbicide, the more species were found to be sensitive under benthic growth conditions. Statistical differences (alpha<5%) were observed between the sensitivities under planktonic and benthic growth conditions for many hydrophobic herbicides. A protective effect of the biofilm against herbicides was observed, and this tended to decrease (at both the EC10 and EC50 levels) with increasing hydrophobicity. The biofilm matrix appeared to control exposure to herbicides, and consequently their toxicity towards benthic diatoms. For metolachlor, terbutryn and irgarol, benthic thresholds derived from species sensitivity distributions were more protective than planktonic thresholds. For hydrophobic herbicides, deriving sensitivity thresholds from data obtained under benthic growth seems to offer a promising alternative. PMID:23831793

Larras, Floriane; Montuelle, Bernard; Bouchez, Agnès

2013-10-01

324

Quantitative benthic habitat characterization at Heceta Bank, Oregon  

NASA Astrophysics Data System (ADS)

Recent studies have highlighted the shortcomings of regional trawl surveys for quantifying abundance of demersal fishes in rugged habitats. Many species show strong affinities to areas of high topographic relief and rugosity, therefore precluding sampling by bottom trawl gears. Consequently, advanced survey technologies such as submersibles and camera sleds have been utilized to survey demersal fishes in situ. One prerequisite in extrapolating densities of demersal fishes observed in situ is the mapping of benthic habitats beyond the observational extent of submersibles. Habitat characteristics observed from submersible and ROV dives in the late 1980s, 2000, and 2001 were used to establish habitat classes that have been statistically shown to correlate with demersal fish distributions. Those habitat characteristics were then extrapolated over the extent of a multibeam sonar survey conducted in 1998 using quantitative parameters derived from high-resolution bathymetric and acoustic backscatter data. The resultant map predicts the coverage of four lithologic habitat classes: mud (unconsolidated), sand (unconsolidated), boulder/cobble (high acoustic reflectivity), and rock outcrop (high vertical relief). Those four habitat classes will facilitate the extrapolation of fish densities to the larger spatial scales at which resident fish populations and physiographic provinces occur.

Whitmire, Curt E.; Wakefield, W. Waldo; Embley, Robert W.; Merle, Susan G.; Tissot, Brian N.; Puniwai, Noelani

2004-10-01

325

Oil from the tropical marine benthic-diatom Navicula sp.  

PubMed

The potential of the tropical marine benthic-diatom Navicula sp. for biodiesel feedstock was investigated. Growth profiles were analyzed by changing nutrient compositions in three different media (Walne, plain seawater, and modified seawater) and irradiance intensities. Navicula sp. cells showed significant growth in Walne and modified seawater medium but not in plain seawater medium. The microalgae grew well in a pH range of 7.8-8.4, and the cells were very sensitive to the intensity of direct sunlight exposure. The average cell concentration obtained from the cultures in plain seawater, Walne, and modified seawater media at the beginning of the stationary phase was 0.70, 2.17, and 2.54 g/L, respectively. Electron spray ionization-ion trap-mass spectrometry showed that the triacylglycerols of the algae oil were identified as POP (palmitic-oleic-palmitic), POO (palmitic-oleic-oleic), and OOLn (oleic-oleic-linoleic). The oil productivity of Navicula sp. cultivated in Walne and modified seawater media was 90 and 124 ?L L(-1) culture d(-1). The Navicula sp. biodiesel exhibited a kinematic viscosity of 1.299 mm(2)/s, density of 0.8347 g/mL, and internal energy of 0.90 kJ/mL. PMID:22926527

Nurachman, Zeily; Brataningtyas, Dewi Susan; Hartati; Panggabean, Lily Maria Goretty

2012-11-01

326

Seaweed-assisted, benthic gravel transport by tidal currents  

NASA Astrophysics Data System (ADS)

Traction transport of pebbles and cobbles occurs subtidally at current velocities below 0.5 m s- 1 when seaweed attached to clasts provides additional lift and drag to the clast. In the Juan de Fuca Strait, British Columbia, Canada, the seaweed Cymanthere triplicata commonly attaches to pebbles and provides sufficient additional surface area for tidal currents to drag the clast along the seafloor. Using in situ measurements of current velocities at 13 m water depth, the threshold for initiation of motion of a 30 mm pebble with attached seaweed is 0.3 m s- 1. This is approximately one order of magnitude less than the activation velocity for a 30 mm pebble without attached seaweed. In addition to kelp-rafted (floated) gravel, seaweed-assisted, benthic gravel transport is possible in marine settings where unidirectional currents (e.g., tidal currents, storm-induced bottom currents) are sufficient to transport pebbles alongshore, and into and across the offshore (below fairweather wave base). If preserved in the rock record, deposits of algal-enhanced gravel deposited via unidirectional, subtidal currents will likely appear as isolated gravel clasts encased in sandstone, reflecting the similar current velocities required to transport these two clast groups.

Frey, Shannon E.; Dashtgard, Shahin E.

2012-07-01

327

Sensitivity of heterogeneous marine benthic habitats to subtle stressors.  

PubMed

It is important to understand the consequences of low level disturbances on the functioning of ecological communities because of the pervasiveness and frequency of this type of environmental change. In this study we investigated the response of a heterogeneous, subtidal, soft-sediment habitat to small experimental additions of organic matter and calcium carbonate to examine the sensitivity of benthic ecosystem functioning to changes in sediment characteristics that relate to the environmental threats of coastal eutrophication and ocean acidification. Our results documented significant changes between key biogeochemical and sedimentary variables such as gross primary production, ammonium uptake and dissolved reactive phosphorus flux following treatment additions. Moreover, the application of treatments affected relationships between macrofauna communities, sediment characteristics (e.g., chlorophyll a content) and biogeochemical processes (oxygen and nutrient fluxes). In this experiment organic matter and calcium carbonate showed persistent opposing effects on sedimentary processes, and we demonstrated that highly heterogeneous sediment habitats can be surprisingly sensitive to subtle perturbations. Our results have important biological implications in a world with relentless anthropogenic inputs of atmospheric CO2 and nutrients in coastal waters. PMID:24312332

Rodil, Iván F; Lohrer, Andrew M; Thrush, Simon F

2013-01-01

328

Sensitivity of Heterogeneous Marine Benthic Habitats to Subtle Stressors  

PubMed Central

It is important to understand the consequences of low level disturbances on the functioning of ecological communities because of the pervasiveness and frequency of this type of environmental change. In this study we investigated the response of a heterogeneous, subtidal, soft-sediment habitat to small experimental additions of organic matter and calcium carbonate to examine the sensitivity of benthic ecosystem functioning to changes in sediment characteristics that relate to the environmental threats of coastal eutrophication and ocean acidification. Our results documented significant changes between key biogeochemical and sedimentary variables such as gross primary production, ammonium uptake and dissolved reactive phosphorus flux following treatment additions. Moreover, the application of treatments affected relationships between macrofauna communities, sediment characteristics (e.g., chlorophyll a content) and biogeochemical processes (oxygen and nutrient fluxes). In this experiment organic matter and calcium carbonate showed persistent opposing effects on sedimentary processes, and we demonstrated that highly heterogeneous sediment habitats can be surprisingly sensitive to subtle perturbations. Our results have important biological implications in a world with relentless anthropogenic inputs of atmospheric CO2 and nutrients in coastal waters. PMID:24312332

Rodil, Ivan F.; Lohrer, Andrew M.; Thrush, Simon F.

2013-01-01

329

Recent benthic ostracoda of Pahang River Delta, Pahang Darul Makmur  

NASA Astrophysics Data System (ADS)

A study on the distribution of recent benthic Ostracoda in marine sediment was carried out around Pahang River Delta, Pahang Darul Makmur. A total of 24 surface sediments were taken from the sampling stations between latitude 3°20' and 3°39'N and longitude 103°26' and 103°35'E. From this study, 71 species of ostracods belonging to 17 families and 42 genera were identified. The abundant and dominant species is Pontocypris virdis with 326 specimens obtained. The dominant family is Trachyleberididae (16 species, 585 specimens). The distribution of ostracoda is from 13 to 637 specimens. The species diversity is from 6 to 29 species. The diversity index, H(s) is in the range of 1.71 to 3.08. There are five common species (Hemicytheridea cancellata, Parakrithella australis, Propontocypris rostrata, Loxoconcha paiki and Lankacythere coralloides) in the study area. A comparison showed that a total of 53 species identified had been previously recorded in Malacca Straits, South China Sea and Java Sea. Five species are newly recorded in Malaysians waters. The species are Papillatabairdia elongata. Mimicocythere pseudomelobesoides, Kotoracythere doratus, Xestoleberis maculanitida and Bosasella profunda.

Noraswana, N. F.; Ramlan, O.

2014-09-01

330

Spatial-temporal feeding dynamics of benthic communities in an estuary-marine gradient  

NASA Astrophysics Data System (ADS)

We investigated the fluctuations of carbon and nitrogen stable isotope ratios in benthic consumers and their potential food sources to determine the spatial and temporal variations in the utilization of available organic matter, indicating the origin and pathways of energy from Yura Estuary to Tango Sea, Japan. Field samplings were conducted from the upper estuary to offshore with sampling frequency of twice per season from April (spring) 2006 to February (winter) 2007. The ?13C signatures of the upper and lower estuary benthos showed depleted and in wide range (-28.9‰ to -13.5‰) compared to the enriched and within narrow range signatures of marine benthos (-20.6‰ to -14.0‰) in all seasons. On the contrary, the ?15N signatures of benthic communities showed decreasing trend seaward and summer values were different from the other seasons. Using the dual isotope and multisource mixing models, we estimated the relative contributions of potential food sources to the benthos diet. River POM played an important source of energy for the estuarine benthos, especially in winter when river discharge was high. Marine POM served as an important alternative food for the estuarine benthos from spring to autumn when seawater intruded the bottom estuary. Benthic microalgae were the major food source at the shallow coast throughout the year, while marine POM fueled the deep coast and offshore benthic food webs. Spatial and temporal feeding variations in estuarine benthic communities were driven by the hydrology of the estuary, whereas primary production and transport of food source dictated diet variations of marine benthic communities. The elucidation of the dynamic energy subsidy among aquatic systems highlights the importance of the land-sea transition zones that is crucial for benthic secondary productions.

Antonio, Emily S.; Kasai, Akihide; Ueno, Masahiro; Ishihi, Yuka; Yokoyama, Hisashi; Yamashita, Yoh

2012-10-01

331

Determining the relative sensitivity of benthic diatoms to atrazine using rapid toxicity testing: a novel method.  

PubMed

Herbicides pose a potential threat to aquatic ecosystems, especially to phototrophic organisms such as benthic diatoms. Benthic diatoms may be a valuable indicator of the toxic impacts of herbicides in aquatic systems. However, this requires information on the herbicide sensitivity of a wide range of freshwater benthic diatom taxa. Unfortunately this information is only available for a limited number of species as current methods of developing new algae toxicity tests on individual taxa are lengthy and costly. To address this issue, we developed a new rapid toxicity test method to test natural benthic communities, from which the relative herbicide sensitivity of many individual taxa can be derived. This involved the collection of natural benthic communities from rocks in situ, which were placed directly into laboratory toxicity tests. Sensitivity data for several diatom genera in a 48 hour exposure toxicity test were produced, without the need for cultures or multiple site visits. After exposure to the highest treatment of atrazine (500 ?g L(-1)) there were significant declines of healthy cells in the most sensitive genera: Gomphonema declined by 74%, Amphora by 62%, Cymbella by 54% and Ulnaria by 34% compared to control levels. In contrast, the genera, Eunotia, Achnanthidium and Navicula, had no statistically significant decline in cell health. This method can identify the diatom taxa most at risk of herbicide toxicity within the natural benthic diatom community. The rapid toxicity testing method presented is a simple and effective method to obtain sensitivity data for multiple taxa within a natural benthic diatom community in a relatively short period of time. PMID:24742551

Wood, Rebecca J; Mitrovic, Simon M; Kefford, Ben J

2014-07-01

332

Seasonal Changes in Quality and Quantity of Food Available for Benthic Suspension-feeders in the Golfo Marconi (North-western Mediterranean)  

NASA Astrophysics Data System (ADS)

Suspended particulate matter was collected, from the water layer at 10 cm above the sediments, over a period of 13 months in the Golfo Marconi (Ligurian Sea, NW Mediterranean). Measurements of seston concentration as well as the elemental (particulate organic carbon and nitrogen; POC and PON, respectively) and biochemical composition (lipids, proteins, carbohydrates, DNA) of particulate organic matter were carried out to assess quality and quantity of food potentially available to benthic suspension-feeders. Particulate organic matter showed wide qualitative and quantitative variations during the sampling year. Seston concentrations and POC did not reflect the quantity and quality of the food available to benthic suspension-feeders. The biopolymeric fraction of particulate matter (C-BPF, i.e. the sum of lipid, protein and carbohydrate carbon) was mostly composed of phytoplankton (which accounted for about 60% of C-BPF). The ratio of C-BPF to POC was utilized as a measure of the fraction which had the potential to be more readily available to consumers. Suspended organic matter showed higher values of the C-BPF:POC ratio during spring, and lower values in summer and autumn-winter. Quantitative estimates of the energy content of the suspended particulate matter were obtained from its biochemical composition. Bacterial dynamics were significantly related to changes in phytoplankton biomass. Bacteria accounted for a significant fraction of the biopolymeric carbon pool (annual average about 15%) and of the total particulate DNA (21·5%), thus enhancing the nutritional value of the particulate organic matter. The results achieved in this study indicate that the biochemical composition of the particulate matter provides additional information on the origin, quality and characteristics of the seston more readily available to benthic suspension-feeders.

Danovaro, R.; Fabiano, M.

1997-06-01

333

Multispecies Record of Benthic Foraminiferal Shell Weight in Santa Barbara Basin: A Deglacial Environmental Record  

NASA Astrophysics Data System (ADS)

There exists increasing interest in resolving the effect of environmental parameters on foraminiferal test weight. We utilize a high-resolution core, MV0811-15JC (34°36.930' N, 119°12.920' W; 418m water depth; 3-15 ka; sedimentation rate ~100cm/ka) from the Santa Barbara Basin (SBB) to examine a multispecies record of benthic foraminiferal weight and test wall thickness. We compare these findings to records of benthic ecosystem, oxygenation and ?18O change during and since the last deglaciation. Ongoing work in SBB has characterized drastic changes in benthic communities over the past 15 kyr in response to climate and dissolved oxygen concentrations. Records of the average test weight in the >250 ?m size fraction of Uvigerina peregrina covary with changes in the benthic community in response to oxygenation events and may represent a record of average maximum growth size. Average test weight, constrained by a narrow size fraction (within < 55 ?m difference in mesh size), is sometimes treated alone or with additional size correction as a proxy for test wall thickness. Narrow fraction test weights show significantly less variability in both Uvigerina peregrina and Bolivinia argentea between samples. We further analyze average test wall thickness in these samples, to develop an understanding of controls on shell weight and ongoing work seeks, to identify ideal benthic target species and to best understand shell weight as a proxy for carbonate ion (pH) of seawater.

Davis, K. V.; Hill, T. M.; Moffitt, S. E.; Downing, S.

2012-12-01

334

Calibration of ?18O of cultured benthic foraminiferal calcite as a function of temperature  

NASA Astrophysics Data System (ADS)

The geochemical composition of deep-sea benthic foraminiferal calcite is widely used to reconstruct sea floor paleoenvironments. The calibration of the applied proxy methods has until now been based on field observations in complex natural ecosystems where multiple factors are interfering. However, laboratory experiments with stable physico-chemical conditions appear to be the ideal way to evaluate the influence of a single parameter. In this paper, we present the oxygen isotopic composition of deep-sea benthic foraminiferal shells entirely calcified under controlled experimental conditions over a large temperature range (4 to 19 °C). The new laboratory protocols developed for this study allowed us to produce large quantities of shells in stable conditions, so that also the shell size effect could be investigated. It appears that when considering a narrow test size range, the curve describing the temperature dependency of ?18O in Bulimina marginata is parallel to the thermodynamically determined curve observed in inorganically precipitated calcite (-0.22‰ °C-1). This observation validates the use of ?18O of this benthic species in paleoceanographical studies. Over the studied size range (50 to 300 ?m), the effect of test size was 0.0014‰ ?m-1, confirming previous suggestions of a substantial test size effect on ?18O of benthic foraminifera. This study opens new perspectives for future proxy calibrations in laboratory set-ups with deep-sea benthic foraminifera (e.g. quantification of the influence of the carbonate chemistry).

Barras, C.; Duplessy, J.-C.; Geslin, E.; Michel, E.; Jorissen, F. J.

2010-04-01

335

Ecological health monitoring of the Mekong River by using benthic algae in 2003-2004  

NASA Astrophysics Data System (ADS)

The monitoring of ecological health of the Mekong River by using benthic algae was carried out from 2003 - 2004. Thirty sampling sites along the Mekong River and its tributaries were selected in Laos, Thailand, Cambodia and Veitnam. In this investigation, the distribution of some species of benthic algae in different environments revealed that there was a significant relationship in the presence of them to the water quality, and these species could be used as a potential biomonitor of water quality in the Mekong River. One hundred and eighty six species of benthic diatoms and 46 species of macroalgae were found. Some dominant species of benthic algae could be used as biomonitors to assess water quality. Hydrodictyon recticulatum and Microspora floccosa and indicated clean-moderate water quality; Audouinella cylindrica, Cladophora glomerata, Achnanthes inflate and Cymbella turgidula indicated moderate water quality; Stigeoclonium flagelliforum, Aulacoseira granulata and Cymbella tumida indicated moderate-polluted water quality and Caloglossa leprieurii, Gomphonema parvulum and Nitzschia clausii indicated polluted water quality. The ecological health assessment of the Mekong River by using the species of benthic algae as biomonitors reveled that in the upstream and tributaries revealed moderate water quality. In contrast, some sites in the lower Mekong showed moderate-polluted to polluted water quality.

Kunpradid, T.

2005-05-01

336

Contrasting effects of hydrological stability and flow extremes on benthic and hyporheic invertebrate communities  

NASA Astrophysics Data System (ADS)

In lotic ecosystems, the most common disturbance events occur at the extremes of the hydrological continuum, i.e. spates and streambed drying. During spates, high flow velocities can mobilise sediments and displace invertebrates, and during streambed drying, loss of free water can cause mass mortality of many aquatic taxa. In both cases, invertebrates inhabiting the surface sediments are subject to a greater frequency and magnitude of disturbance than those in the hyporheic zone, and this habitat may therefore act as a refugium. Between extreme events, stable hydrological conditions allow competitive species to thrive, which can cause biotic interactions to increase. We compared the effects of flow extremes and hydrological stability on benthic and hyporheic invertebrate communities. Hydrological conditions included spates, flow recession, and localised streambed drying. During flow recession, competitive benthic taxa, particularly Gammarus pulex (Amphipoda) increased in abundance in surface sediments, causing community diversity to decline. A concurrent increase in the hyporheic abundance of G. pulex indicated that the hyporheic zone may act as a refugium from increasing biotic pressures in the benthic sediments. In contrast, spate events caused severe reductions in both benthic and hyporheic invertebrate abundance, and declines in G. pulex abundance were particularly pronounced; spate events were therefore important in increasing both benthic and hyporheic community diversity.

Stubbington, Rachel; Wood, Paul J.; Reid, Ian

2010-05-01

337

Benthic substrate classification map: Gulf Islands National Seashore  

USGS Publications Warehouse

The 2005 hurricane season was devastating for the Mississippi Gulf Coast. Hurricane Katrina caused significant degradation of the barrier islands that compose the Gulf Islands National Seashore (GUIS). Because of the ability of coastal barrier islands to help mitigate hurricane damage to the mainland, restoring these habitats prior to the onset of future storms will help protect the islands themselves and the surrounding habitats. During Hurricane Katrina, coastal barrier islands reduced storm surge by approximately 10 percent and moderated wave heights (Wamsley and others, 2009). Islands protected the mainland by preventing ocean waves from maintaining their size as they approached the mainland. In addition to storm protection, it is advantageous to restore these islands to preserve the cultural heritage present there (for example, Fort Massachusetts) and because of the influence that these islands have on marine ecology. For example, these islands help maintain a salinity regime favorable to oysters in the Mississippi Sound and provide critical habitats for many migratory birds and endangered species such as sea turtles (Chelonia mydas, Caretta caretta, and Dermochelys coriacea), Gulf sturgeon (Acipenser oxyrinchus desotoi), and piping plovers (Charadrius melodus) (U.S. Army Corps of Engineers, 2009a). As land manager for the GUIS, the National Park Service (NPS) has been working with the State of Mississippi and the Mobile District of the U.S. Army Corps of Engineers to provide a set of recommendations to the Mississippi Coastal Improvements Program (MsCIP) that will guide restoration planning. The final set of recommendations includes directly renourishing both West Ship Island (to protect Fort Massachusetts) and East Ship Island (to restore the French Warehouse archaeological site); filling Camille Cut to recreate a continuous Ship Island; and restoring natural regional sediment transport processes by placing sand in the littoral zone just east of Petit Bois Island. Prevailing sediment transport processes will provide natural renourishment of the westward islands in the barrier system (U.S. Army Corps of Engineers, 2009b). One difficulty in developing the final recommendations is that few data are available to incorporate into restoration plans related to bathymetry, sediment type, and biota. For example, the most recent bathymetry available dates to when East and West Ship Islands were a single continuous island (1917). As a result, the MsCIP program has encouraged post-hurricane bathymetric data collection for future reference. Furthermore, managing a complex environment such as this barrier island system for habitat conservation and best resource usage requires significant knowledge about those habitats and resources. To effectively address these issues, a complete and comprehensive understanding of the type, geographic extent, and condition of marine resources included within the GUIS is required. However, the data related to the GUIS marine resources are limited either spatially or temporally. Specifically, there is limited knowledge and information about the distribution of benthic habitats and the characteristics of the offshore region of the GUIS, even though these are the habitats that will be most affected by habitat restoration. The goal of this project is to develop a comprehensive map of the benthic marine habitats within the GUIS to give park managers the ability to develop strategies for coastal and ocean-resource management and to aid decisionmakers in evaluating conservation priorities.

Lavoie, Dawn; Flocks, James; Twichell, Dave; Rose, Kate

2013-01-01

338

Benthic foraminiferal assemblages reveal the history of the Burdigalian Seaway  

NASA Astrophysics Data System (ADS)

The opening and closure of seaways have immanent paleoclimatic, paleoceanographic and paleobiogeographic consequences as they determine the exchange of water masses. During the Oligocene to Miocene severe alterations of marine gateway configuration shaped the evolution of the Mediterranean - Paratethys region. From early to middle Burdigalian (20.4-17.5 Myrs) the Burdigalian Seaway connected the western Mediterranean Sea with the Central Paratethys Sea via the North Alpine Foreland Basin (NAFB). Its evolution resulted in profound paleoceanograpic and -geographic changes, and initiated a wave of faunal immigration from the Atlantic and Mediterranean into the Paratethys that had a severe impact on marine ecosystems. A detailed Early Miocene proxy record integrating seismic images, microfossil assemblages and geochemical analyses has been recently established for the Puchkirchen Basin (PB) as part of the NAFB. Herein, we exemplarily show the reconstruction of the dynamic early to middle Burdigalian paleoenvironment based on a quantitative evaluation of benthic foraminiferal assemblages from drill-sites and outcrops. Four major phases in PB development are distinguished, and new stratigraphic constraints allow discussing the results in the context of the evolution of the Burdigalian Seaway: 1. The global early Burdigalian sea-level rise initiated a marine transgression in the NAFB. In the PB, a long-lived basin-axial channel system was reactivated resulting in turbiditic and mass-flow deposition. The unstable upper bathyal environment is reflected in a low diverse autochthonous benthic foraminiferal fauna mainly composed of Bathysiphon filiformis. 2. The perpetuating transgression flooded large shelf areas and established the Burdigalian Seaway. The channel belt was cut off from its sediment sources and shut down. Subsequently, sedimentation was controlled by episodic turbidites from the southern basin margin, and large NE prograding delta fans. High sedimentation rates and strong terrestrial input led to the development of diverse foraminiferal faunas that are largely composed of agglutinated species. The encountered astrorhizids, ammodiscids and textualriids are adapted to high organic matter input and suboxic bottom-waters. Assemblages dominated by Bathysiphon filiformis occur in phases of turbidite deposition. 3. At ~19 Ma the Burdigalian Seaway became a vast shelf sea when increasing sedimentation rates led to the upfill of the PB. At the same time marine sedimentation reached its maximum extent in the NAFB. Characteristic hyaline shelf faunas composed of Lenticulina, Amphicoryna, Melonis, Cibcidoides and Ammonia developed along the inner-outer neritic shelf environments. 4. The beginning of a regression at ~18 Ma heralded the closure of the Burdigalian Seaway. Biofacies distribution shows a prograding tide-influenced shelf and widespread shallow water environments largely dominated by Ammonia, Elphidium and Cibicidoides developed. The closure of the Burdigalian Seaway initiated a major paleogeographic reorganization resulting in the final retreat of the Central Paratethys towards the east.

Piller, W. E.; Grunert, P.; Harzhauser, M.

2013-12-01

339

Lava Layering  

NSDL National Science Digital Library

This is a lesson about geologic history. Learners will work together to create models of volcanic lava flows and analyze the layers that form on a planet's surface. They will sequence lava flows produced by multiple eruptions. Students will be asked to observe where the flows travel, make a model, and interpret the stratigraphy. Students will use their volcanic layering model to demonstrate the relative dating and geologic mapping principles to later be applied to satellite imagery. The lesson models scientific inquiry using the 5E instructional model and includes teacher notes and vocabulary.

340

Benthic invertebrate bioassays with toxic sediment and pore water  

USGS Publications Warehouse

The relative sensitivities of bioassays to determine the toxicity of sediments were investigated and three methods of making the sample dilutions required to generate dose-response relationships were compared. The assays studied were: (a) Microtox(R), a 15-min assay of Photobacterium phosphoreum bioluminescence inhibition by pore water; (b) 48-h Daphnia magna lethality test in pore water; (c) 10-d subchronic assay of lethality to and reduction of weight gain by Chironomus tentans performed in either whole sediment or pore water; (d) 168-h acute lethality assay of Hexagenia limbata in either whole sediment or pore water. The three methods of diluting sediments were: (a) extracting pore water from the toxic location and dilution with pore water from the control station; (b) diluting whole sediment from the toxic location with control whole sediment from a reference location, then extracting pore water; and (c) diluting toxic, whole sediment with whole sediment from a reference location, then using the whole sediment in bioassays. Based on lethality, H. limbata was the most sensitive organism to the toxicity of Detroit River sediment. Lethality of D. magna was similar to that of H. limbata in whole sediment and can be used to predict effects of whole sediment toxicity to H. limbata. The concentration required to cause a 50% reduction in C. tentans growth (10-d EC50) was approximately that which caused 50% lethality of D. magna (48-h LC50) and was similar to the toxicity that restricts benthic invertebrate colonization of contaminated sediments. While the three dilution techniques gave similar results with some assays, they gave very different results in other assays. The dose-response relationships determined by the three dilution techniques would be expected to vary with sediment, toxicant and bioassay type, and the dose-response relationship derived from each technique needs to be interpreted accordingly.

Giesy, John P.; Rosiu, Cornell J.; Graney, Robert L.; Henry, Mary G.

1990-01-01

341

Biological vs. physical mixing effects on benthic food web dynamics.  

PubMed

Biological particle mixing (bioturbation) and solute transfer (bio-irrigation) contribute extensively to ecosystem functioning in sediments where physical mixing is low. Macrobenthos transports oxygen and organic matter deeper into the sediment, thereby likely providing favourable niches to lower trophic levels (i.e., smaller benthic animals such as meiofauna and bacteria) and thus stimulating mineralisation. Whether this biological transport facilitates fresh organic matter assimilation by the metazoan lower part of the food web through niche establishment (i.e., ecosystem engineering) or rather deprives them from food sources, is so far unclear. We investigated the effects of the ecosystem engineers Lanice conchilega (bio-irrigator) and Abra alba (bioturbator) compared to abiotic physical mixing events on survival and food uptake of nematodes after a simulated phytoplankton bloom. The (13)C labelled diatom Skeletonema costatum was added to 4 treatments: (1) microcosms containing the bioturbator, (2) microcosms containing the bio-irrigator, (3) control microcosms and (4) microcosms with abiotic manual surface mixing. Nematode survival and subsurface peaks in nematode density profiles were most pronounced in the bio-irrigator treatment. However, nematode specific uptake (??(13)C) of the added diatoms was highest in the physical mixing treatment, where macrobenthos was absent and the diatom (13)C was homogenised. Overall, nematodes fed preferentially on bulk sedimentary organic material rather than the added diatoms. The total C budget (µg C m(-2)), which included TO(13)C remaining in the sediment, respiration, nematode and macrobenthic uptake, highlighted the limited assimilation by the metazoan benthos and the major role of bacterial respiration. In summary, bioturbation and especially bio-irrigation facilitated the lower trophic levels mainly over the long-term through niche establishment. Since the freshly added diatoms represented only a limited food source for nematodes, the macrobenthic effect was more pronounced in niche establishment than the negative structuring effects such as competition. PMID:21455308

Braeckman, Ulrike; Provoost, Pieter; Moens, Tom; Soetaert, Karline; Middelburg, Jack J; Vincx, Magda; Vanaverbeke, Jan

2011-01-01

342

Benthic foraminifera from polluted marine environment of Sulaibikhat Bay (Kuwait).  

PubMed

Quantitative analyses of recent benthic foraminiferal assemblages (living and dead) were carried out on the surface sediments of Sulaibikhat Bay. Marked contrast in foraminiferal assemblages between the shallow tidal mudflats and the deep tidal channel and their relation to the extent of pollution were observed. Cluster analysis of quantitative data on the distribution of foraminiferal tests revealed three assemblages that depend mainly on the intensity of pollution; (1) a highly polluted tidal flat assemblage, (2) normal (or less polluted) mud flat assemblage and, (3) tidal channel and subtidal assemblage. The highly polluted assemblage characterized by a drop in species densities (< 100 tests/20 cm(3) sediment) but with high average diversity (5.8 Yule-Simpson Index). The microfauna of the less polluted flat displays relatively lower diversity (4.6) but high density of tests (47.2% of the total picked tests). The most abundant species of this assemblage is Ammonia tepida, displays its maximum density in this assemblage. Ammonia tepida drops in density from 17.12% to 3.07% in the polluted assemblage. Tidal channel foraminiferal assemblages should normally display lower diversities than those of tidal flats, because tidal current in the channels tend to wash away most nutrient materials. However, this is not the case of the present study area which could be due to environmental setting of the Sulaibikhat Bay in which tidal currents bring in exceptionally high amounts of nutrients from Shatt Al-Arab Estuary and in which the tidal flats are strongly and adversely polluted. PMID:18389379

Al-Zamel, A Z; Al-Sarawi, M A; Khader, S R; Al-Rifaiy, I A

2009-02-01

343

Maximum ecological potential of tropical reservoirs and benthic invertebrate communities.  

PubMed

The Reference Condition Approach (RCA) is now widely adopted as a basis for the evaluation of the ecological quality of water bodies. In accordance with the RCA, the integrity of communities found in a given location should be analyzed according to their deviation from the communities that would be expected in the absence of anthropogenic disturbances. The RCA was used here with the aim of defining the Maximum Ecological Potential (MEP) of tropical reservoirs located in the hydrographical basin of the Paraopeba River in the state of Minas Gerais, Brazil. Among the reservoirs, Serra Azul is used as a water supply and is located in a core area of environmental protection where tourism is not allowed and the native vegetation is conserved. The benthic macroinvertebrate communities at 90 sites located in three reservoirs were analyzed and sampled every 3 months over 2 years. The temporal patterns of the communities in the three reservoirs were analyzed (2nd-STAGE MDS and ANOSIM) and were not significantly related to seasonal fluctuations in temperature and precipitation. Twenty-eight sites belonging to the Serra Azul reservoir were selected to define the MEP of these reservoirs because these sites had the lowest human disturbance levels. The macroinvertebrate taxa present in the selected MEP sites are similar to those of natural lakes and different from the communities of disturbed sites. The biological classification of these sites revealed two groups with distinct macroinvertebrate communities. This distinction was related to climatic variables, bottom substrate type, the presence of gravel/boulders, coarse sand, silt, clay or muck, depth, and the shoreline substrate zone. These two subsets of biological communities and respective environmental conditions can serve as a basis for the future implementation of ecological quality monitoring programs for tropical reservoirs in the study area. This approach can also, however, be implemented in other geographic areas with artificial or heavily modified water bodies. PMID:23288597

Molozzi, Joseline; Feio, Maria João; Salas, Fuensanta; Marques, João Carlos; Callisto, Marcos

2013-08-01

344

Leaky Layers  

NSDL National Science Digital Library

Figure from the Nature Geoscience article, Geodynamics: Layer cake or plum pudding? by Paul Tackley (Nature Geoscience 1, 157 - 158 (2008)). The figure shows the current understanding of the interaction between the 660 km discontinuity, the core-mantle boundary, downgoing slabs, upwelling plumes.

Tackley, Paul J.; Geoscience, Nature

345

Methods for collecting benthic invertebrate samples as part of the National Water-Quality Assessment Program  

USGS Publications Warehouse

Benthic invertebrate communities are evaluated as part of the ecological survey component of the U.S. Geological Survey's National Water-Quality Assessment Program. These biological data are collected along with physical and chemical data to assess water-quality conditions and to develop an understanding of the factors that affect water-quality conditions locally, regionally, and nationally. The objectives of benthic invertebrate community characterizations are to (1) develop for each site a list of tax a within the associated stream reach and (2) determine the structure of benthic invertebrate communities within selected habitats of that reach. A nationally consistent approach is used to achieve these objectives. This approach provides guidance on site, reach, and habitat selection and methods and equipment for qualitative multihabitat sampling and semi-quantitative single habitat sampling. Appropriate quality-assurance and quality-control guidelines are used to maximize the ability to analyze data within and among study units.

Cuffney, Thomas F.; Gurtz, Martin E.; Meador, Michael R.

1993-01-01

346

Effects of hypoxia on benthic organisms in Tokyo Bay, Japan: a review.  

PubMed

Bottom hypoxia (dissolved oxygen concentration ?2 ml l(-1)) from anthropogenic eutrophication is a growing global concern. Here, we summarized characteristics of hypoxia and its effects on benthic organisms in Tokyo Bay. Despite recent decreases in nutrient inputs, hypoxia has been increasing in duration and spatial extent, suggesting that the substantial loss of tidal flats from reclamation is contributing to a decrease in the ability of Tokyo Bay to recycle nutrients. Hypoxia develops in the central to northern part of the bay and persists from spring to autumn, causing defaunation of benthic organisms. After the abatement of hypoxia in autumn, the defaunated area is recolonized, either through migration or larval settlement. Some megabenthic species with a spawning peak in spring and summer experience failure of larval settlement, which is probably due to hypoxia. The adverse effects of hypoxia are an impediment to recovery of benthic organisms in Tokyo Bay. PMID:21561630

Kodama, Keita; Horiguchi, Toshihiro

2011-01-01

347

Long-term benthic monitoring programs for the mesohaline Chesapeake Bay. Interim report  

SciTech Connect

This report presents a summary of data collected and an updated progress report for a long-term benthic study conducted to measure the long-term effects of power plant operations on benthic populations and to identify long-term trends and annual cycles in these populations. Benthic organisms and the physical/chemical characteristics of sediments and water were sampled between July 1981 and May 1982 in the mesohaline portion of the Chesapeake Bay and the Potomac estuary. The surveys were concentrated near the Morgantown and Calvert Cliffs, Maryland power plant. Salinities during 1981-1982 were high relative to long-term salinity records with the deviation from average salinities being larger in the Potomac than the mainstem of the Bay.

Hiegel, M.H.; Fisher, K.; Johnson, G.F.

1982-04-01

348

Benthic foraminifera show some resilience to ocean acidification in the northern Gulf of California, Mexico.  

PubMed

Extensive CO2 vents have been discovered in the Wagner Basin, northern Gulf of California, where they create large areas with lowered seawater pH. Such areas are suitable for investigations of long-term biological effects of ocean acidification and effects of CO2 leakage from subsea carbon capture storage. Here, we show responses of benthic foraminifera to seawater pH gradients at 74-207m water depth. Living (rose Bengal stained) benthic foraminifera included Nonionella basispinata, Epistominella bradyana and Bulimina marginata. Studies on foraminifera at CO2 vents in the Mediterranean and off Papua New Guinea have shown dramatic long-term effects of acidified seawater. We found living calcareous benthic foraminifera in low pH conditions in the northern Gulf of California, although there was an impoverished species assemblage and evidence of post-mortem test dissolution. PMID:23473095

Pettit, L R; Hart, M B; Medina-Sánchez, A N; Smart, C W; Rodolfo-Metalpa, R; Hall-Spencer, J M; Prol-Ledesma, R M

2013-08-30

349

Factors regulating benthic food chains in tropical river deltas and adjacent shelf areas  

NASA Astrophysics Data System (ADS)

Benthic food chains of the Amazon (Brazil) and Fly (Papua New Guinea) river deltas and adjacent shelves are compared. Abundance patterns of the major trophic groups (bacteria, meiofauna, and macroinfauna) are similar between regions, with very low densities, or the absence of benthos, within and near the deltas. For muds in the more quiescent areas, benthic abundance and productivity are highest, commonly coinciding with maximum pelagic primary production. Episodes of physical disturbance, erratic food supply, and dilution of river-derived, particulate organic matter foster the development of opportunistic benthic communities of variable diversity and low biomass, dominated by bacteria. These pioneering assemblages are the main food of penaeid shrimp, which dominate the demersal trawl fisheries of both fluvial-dominated regions.

Alongi, D. M.; Robertson, A. I.

1995-09-01

350

Sequential sampling: A cost-effective approach for monitoring benthic macroinvertebrates in environmental impact assessments  

NASA Astrophysics Data System (ADS)

Sequential sampling is a method for monitoring benthic macroinvertebrates that can significantly reduce the number of samples required to reach a decision, and consequently, decrease the cost of benthic sampling in environmental impact assessments. Rather than depending on a fixed number of samples, this analysis cumulatively compares measured parameter values (for example, density, community diversity) from individual samples, with thresholds that are based on specified degrees of precision. In addition to reducing sample size, a monitoring program based on sequential sampling can provide clear-cut decisions as to whether a priori-defined changes in the measured parameter(s) have or have not occurred. As examples, sequential sampling programs have been developed to evaluate the impact of geothermal energy development on benthic macroinvertebrate diversity at The Geysers, California, and for monitoring the impact of crude oil contamination on chironomid midge [ Cricotopus bicinctus (Meigen) and C. mackenziensis Oliver] population densities in the Trail River, Northwest Territories, Canada.

Resh, Vincent H.; Price, Donald G.

1984-01-01

351

Marine Benthic Communities of Block Island and Rhode Island Sounds and What they're Good For  

EPA Science Inventory

The benthic invertebrates of Block Island and Rhode Island Sounds include those adapted to near-shore habitats with variable temperature and salinity, mid-shelf species with narrower requirements, and boreal species that avoid elevated temperatures. Studies of benthic fauna in th...

352

CHANGES IN THE FRESHWATER BENTHIC COMMUNITY OF LAKE ONTARIO SINCE THE INVASION OF DREISSENA 1972-1997  

EPA Science Inventory

Population changes of three major benthic taxa are discussed in relation to Dreissena spp. Lake Ontario was sampled pre-invasion (1972) and post-invasion (1994, 1997) for abundance of benthic organisms. In offshore sediments of Lake Ontario, neither species composition nor abunda...

353

Bacteria and Foraminifera: key players in a short-term deep-sea benthic response to phytodetritus  

Microsoft Academic Search

The deep-sea floor has long been considered a 'food desert' but recent observations suggest that episodic inputs of relatively fresh organic matter (phytodetritus) occur and that benthic processing of this material may be rapid. Although the responses of the total community in terms of oxygen consumption and of some individual benthic groups have been identified, the quantitative role of the

L. Moodley; J. J. Middelburg; H. T. S. Boschker; GCA Duineveld; R. Pel; P. M. J. Herman; C. H. R. Heip

2002-01-01

354

Comparison of seasonal dynamics of the essential PUFA contents in benthic invertebrates and grayling Thymallus arcticus in the Yenisei river  

Microsoft Academic Search

Seasonal dynamics of contents of essential polyunsaturated fatty acids (PUFA) in dominant groups of benthic invertebrates: gammarids (Gammaridae, Amphipoda), oligochaetes (Oligochaeta), chironomid larvae (Chironomidae, Diptera) and caddisfly larvae (Trichoptera), and dominant benthivorous fish, Siberian grayling Thymallus arcticus, have been studied in ecosystem of the large Siberian river. During the year of the study most benthic invertebrate taxa showed significant variations

N. N. Sushchik; M. I. Gladyshev; G. S. Kalachova; O. N. Makhutova; A. V. Ageev

2006-01-01

355

Spatial variation in organic matter utilization by benthic communities from Yura River-Estuary to offshore of Tango Sea, Japan  

NASA Astrophysics Data System (ADS)

We investigated the distribution of ? 13C and ? 15N of organic matter among benthic communities from the upper estuary of Yura River to offshore of Tango Sea, Japan, to determine spatial variation in utilization of organic matter by benthic communities. The ? 13C values of benthic animals ranged from -27 to -15‰ in the upper estuary, -21 to -15‰ in the lower estuary, -20 to -16‰ in the shallow coast (5-10 m depths), -18 to -16‰ in the deep coast (30-60 m depths) and -19 to -15‰ in offshore (100-150 m depths) stations. Adapting the dual isotope values to mixing models, we estimated the relative contributions of potential food sources to the benthos diet. Phytoplankton and macroalgae that intruded the estuary in summer were utilized as alternative food aside from the terrestrial-origin organic matter assimilated by the estuarine benthic consumers. Resuspended benthic microalgae were important source of energy in the shallow coastal stations, while abundant supply of phytodetritus fueled the deep coastal and offshore benthic food webs. Spatial difference in the diet of benthic communities depends largely on the shifts in the primary carbon source. Thus, benthic communities are important link of autochthonous/allochthonous production and secondary production in the continuous river-estuary-marine system.

Antonio, Emily S.; Kasai, Akihide; Ueno, Masahiro; Won, Nam-il; Ishihi, Yuka; Yokoyama, Hisashi; Yamashita, Yoh

2010-01-01

356

A conceptual model for the growth, persistence, and blooming behavior of the benthic mat-forming diatom Didymosphenia geminata (Invited)  

Microsoft Academic Search

The nuisance diatom Didymosphenia geminata (didymo) presents an ecological paradox. How can this benthic algae produce such large amounts of biomass in cold, fast flowing, low nutrient streams? The aim of this paper is to present a conceptual model for the growth, persistence, and blooming behavior of this benthic mat-forming diatom that may help to explain this paradox. The conceptual

J. D. Cullis; C. Gillis; M. Bothwell; C. Kilroy; A. I. Packman; M. A. Hassan

2010-01-01

357

Recent changes in benthic macroinvertebrate populations in Lake Huron and impact on the diet of lake whitefish (coregonus clupeaformis)  

Microsoft Academic Search

Surveys of the benthic macroinvertebrate community were conducted in the main basin of Lake Huron in 2000 and 2003, and corresponding studies of lake whitefish diets were conducted in 2002-2004. Populations of three major benthic taxa, Diporeia spp., Sphaeriidae, and Chironomidae, declined dramatically between 2000 and 2003, with densities declining 57%, 74%, and 75% over this 3-year period. By 2003,

Thomas F. Nalepa; Steven A. Pothoven; David L. Fanslow

2009-01-01

358

Effects of Management Legacies on Stream Fish and Aquatic Benthic Macroinvertebrate Assemblages  

NASA Astrophysics Data System (ADS)

Fish and benthic macroinvertebrate assemblages often provide insight on ecological conditions for guiding management actions. Unfortunately, land use and management legacies can constrain the structure of biotic communities such that they fail to reflect habitat quality. The purpose of this study was to describe patterns in fish and benthic macroinvertebrate assemblage structure, and evaluate relationships between biota and habitat characteristics in the Chariton River system of south-central Iowa, a system likely influenced by various potential management legacies (e.g., dams, chemical removal of fishes). We sampled fishes, benthic macroinvertebrates, and physical habitat from a total of 38 stream reaches in the Chariton River watershed during 2002-2005. Fish and benthic macroinvertebrate assemblages were dominated by generalist species tolerant of poor habitat quality; assemblages failed to show any apparent patterns with regard to stream size or longitudinal location within the watershed. Metrics used to summarize fish assemblages and populations [e.g., presence-absence, relative abundance, Index of Biotic Integrity for fish (IBIF)] were not related to habitat characteristics, except that catch rates of piscivores were positively related to the depth and the amount of large wood. In contrast, family richness of benthic macroinvertebrates, richness of Ephemeroptera, Trichoptera, and Plecoptera taxa, and IBI values for benthic macroinvertebrates (IBIBM) were positively correlated with the amount of overhanging vegetation and inversely related to the percentage of fine substrate. A long history of habitat alteration by row-crop agriculture and management legacies associated with reservoir construction has likely resulted in a fish assemblage dominated by tolerant species. Intolerant and sensitive fish species have not recolonized streams due to downstream movement barriers (i.e., dams). In contrast, aquatic insect assemblages reflected aquatic habitat, particularly the amount of overhanging vegetation and fine sediment. This research illustrates the importance of using multiple taxa for biological assessments and the need to consider management legacies when investigating responses to management and conservation actions.

Quist, Michael C.; Schultz, Randall D.

2014-09-01

359

Benthic foraminifera as indicators of pollution in high latitude marine environments  

NASA Astrophysics Data System (ADS)

An increasing number of studies demonstrate the potential of benthic foraminifera to characterize ecological status. However, the use of benthic foraminifera as bio-indicators has previously not been tested in high latitudes. This research contributes to the development of foraminifera as a bio-monitoring technique for the Arctic region, as industrial activities in this region will increase in the coming years. Surface sediments (0-1 cm) from sites close to gas fields in the SW Barents Sea were studied. In addition, to elucidate the range from less to very affected, surface sediments from the harbor of the town of Hammerfest (70° N) were studied. At least 300 living benthic foraminifera from the size fraction 100 µm-1 mm were counted and identified at species level. Pollution levels (heavy metals and persistent organic pollutants) and sediment properties (grainsize and TOC) were also analyzed. Pollution levels at the sea floor in the SW Barents Sea are of background to good level (level I-II) according to the definitions by the Water Framework Directorate (WFD). Benthic foraminiferal assemblages are influenced by natural environmental parameters such as water mass properties, water depth, nutrient availability, bottom current strength, and grain size. Surface sediments from the Hammerfest harbor are of moderate environmental status (WFD level II-III) based on heavy metal concentrations and of bad environmental status (WFD IV-V) based on persistent organic pollutant concentrations. Opportunistic benthic foraminifera are dominating the assemblages. The most polluted areas in the harbor are barren for foraminifera or have high amounts of deformed shells. In both environments the foraminiferal diversity of the samples, does not correspond to expected environmental status based on the pollution levels of the sediments. Environmental status classes, based on benthic foraminifera instead of macrofauna, would allow rapid analyses of the environmental impact of pollution.

Dijkstra, N.; Junttila, J.; Husum, K.; Carroll, J.; Klitgaard-Kristensen, D.; Hald, M.

2012-04-01

360

Multiscale patterns in the diversity and organization of benthic intertidal fauna among French Atlantic estuaries  

NASA Astrophysics Data System (ADS)

Based on a parallel sampling conducted during autumn 2008, a comparative study of the intertidal benthic macrofauna among 10 estuarine systems located along the Channel and Atlantic coasts of France was performed in order to assess the level of fauna similarity among these sites and to identify possible environmental factors involved in the observed pattern at both large (among sites) and smaller (benthic assemblages) scales. More precisely this study focused on unraveling the observed pattern of intertidal benthic fauna composition and diversity observed at among-site scale by exploring both biotic and abiotic factors acting at the among- and within-site scales. Results showed a limited level of similarity at the among-site level in terms of intertidal benthic fauna composition and diversity. The observed pattern did not fit with existing transitional water classification methods based on fish or benthic assemblages developed in the frame of the European Water Framework Directive (WFD). More particularly, the coastal plain estuaries displayed higher among-site similarity compared to ria systems. These coastal plain estuaries were characterized by higher influence of river discharge, lower communication with the ocean and high suspended particulate matter levels. On the other hand, the ria-type systems were more dissimilar and different from the coastal plain estuaries. The level of similarity among estuaries was mainly linked to the relative extent of the intertidal “Scrobicularia plana-Cerastoderma edule” and “Tellina tenuis” or “Venus” communities as a possible consequence of salinity regime, suspended matter concentrations and fine particles supply with consequences on the trophic functioning, structure and organization of benthic fauna. Despite biogeographical patterns, the results also suggest that, in the context of the WFD, these estuaries should only be compared on the basis of the most common intertidal habitat occurring throughout all estuarine systems and that the EUNIS biotope classification might be used for this purpose. In addition, an original inverse relation between ?-diversity and area was shown; however, its relevance might be questioned.

Blanchet, Hugues; Gouillieux, Benoît; Alizier, Sandrine; Amouroux, Jean-Michel; Bachelet, Guy; Barillé, Anne-Laure; Dauvin, Jean-Claude; de Montaudouin, Xavier; Derolez, Valérie; Desroy, Nicolas; Grall, Jacques; Grémare, Antoine; Hacquebart, Pascal; Jourde, Jérôme; Labrune, Céline; Lavesque, Nicolas; Meirland, Alain; Nebout, Thiebaut; Olivier, Frédéric; Pelaprat, Corine; Ruellet, Thierry; Sauriau, Pierre-Guy; Thorin, Sébastien

2014-07-01

361

Benthic community and food web structure on the continental shelf of the Bay of Biscay (North Eastern Atlantic) revealed by stable isotopes analysis  

Microsoft Academic Search

The North Bay of Biscay continental shelf is a major French demersal fishery, but little was known on the trophic food web of its benthic communities. In order to determine the benthic trophic web, the objectives of this study are to describe the macro- and megafaunal benthic community structure (species richness, abundance and biomass) and to establish the trophic pathways

François Le Loc'h; Christian Hily; Jacques Grall

2008-01-01

362

Correspondence of stream benthic invertebrate assemblages to regional classification schemes in Missouri  

USGS Publications Warehouse

Benthic invertebrates from 44 reference streams throughout the state of Missouri were examined for their concordance with established regionalization systems, both aquatic and terrestrial. Invertebrate assemblages coincided nicely with Pflieger's established aquatic faunal regions system, expanding its generality to more than fish assemblages. Our benthic invertebrate and Pflieger's fish assemblages coincided well with both Bailey's ecological sections and Omernik's ecoregions. Subregionalization using Pflieger's subregions and Bailey's subsections further reduced unexplained variation and is recommended for use wherever possible. The concordance of the aquatic fauna and terrestrial features implies the possibility of coordinated regional management among different natural resource disciplines.

Rabeni, C.F.; Doisy, K.E.

2000-01-01

363

Effects of gut sediment contents on measurements of metal levels in benthic invertebrates - a cautionary note  

SciTech Connect

Studies of heavy metal levels in benthic organisms typically do not correct for gut sediment metal levels other than by allowing a period of depuration in clean water. The effectiveness of depuration has recently been questioned in British Columbia in the particular case of the marine clam Yoldia. In light of this controversy, it appears appropriate to present data from a study of heavy metal levels in sediments and benthic organisms in the Lower Fraser River, BC, regarding the effects of gut sediment contents.

Chapman, P.M.

1985-09-01

364

Assessment of sediment contaminants, toxicity, and benthic community structure in Massachusetts bass  

SciTech Connect

Sediments samples were collected during July 1993 at 12 stations in Massachusetts and Cape Cod Bays along the Massachusetts coastline. The stations consisted of foursites from shallow subtidal depths in each of three harbor systems: Wellfleet Harbor, Boston Harbor, and Salem/Beverly Harbors. Synoptic measurements were made of pollutant concentrations, sediment/porewater toxicity, and benthic community structure as a basis for examining potential linkages between sediment contamination and adverse impacts on living benthic resources of the Massachusetts Bay/Cape Cod Bay nearshore ecosystem. Results from this application of the Sediment Quality Triad approach will be presented.

Hyland, J. [NOAA/NOS, Charleston, SC (United States). Carolinean Province Office; Costa, H. [Arthur D. Little, Inc., Cambridge, MA (United States)

1994-12-31

365

Benthic infaunal community structuring in an acidified tropical estuarine system  

PubMed Central

Background Recent studies suggest that increasing ocean acidification (OA) should have strong direct and indirect influences on marine invertebrates. While most theory and application for OA is based on relatively physically-stable oceanic ecological systems, less is known about the effects of acidification on nearshore and estuarine systems. Here, we investigated the structuring of a benthic infaunal community in a tropical estuarine system, along a steep salinity and pH gradient, arising largely from acid-sulphate groundwater inflows (Sungai Brunei Estuary, Borneo, July 2011- June 2012). Results Preliminary data indicate that sediment pore-water salinity (range: 8.07 - 29.6 psu) declined towards the mainland in correspondence with the above-sediment estuarine water salinity (range: 3.58 – 31.2 psu), whereas the pore-water pH (range: 6.47- 7.72) was generally lower and less variable than the estuarine water pH (range: 5.78- 8.3), along the estuary. Of the thirty six species (taxa) recorded, the polychaetes Neanthes sp., Onuphis conchylega, Nereididae sp. and the amphipod Corophiidae sp., were numerically dominant. Calcified microcrustaceans (e.g., Cyclopoida sp. and Corophiidae sp.) were abundant at all stations and there was no clear distinction in distribution pattern along the estuarine between calcified and non-calcified groups. Species richness increased seawards, though abundance (density) showed no distinct directional trend. Diversity indices were generally positively correlated (Spearman’s rank correlation) with salinity and pH (p <0.05) and negatively with clay and organic matter, except for evenness values (p >0.05). Three faunistic assemblages were distinguished: (1) nereid-cyclopoid-sabellid, (2) corophiid-capitellid and (3) onuphid- nereid-capitellid. These respectively associated with lower salinity/pH and a muddy bottom, low salinity/pH and a sandy bottom, and high salinity/pH and a sandy bottom. However, CCA suggested that species distribution and community structuring is more strongly influenced by sediment particle characteristics than by the chemical properties of the water (pH and salinity). Conclusions Infaunal estuarine communities, which are typically adapted to survive relatively acidic conditions, may be less exposed, less sensitive, and less vulnerable than epibenthic or pelagic communities to further acidification of above-sediment waters. These data question the extent to which all marine infaunal communities, including oceanic communities, are likely to be affected by future global CO2-driven acidification.

2014-01-01

366

Do bottom mixed layers influence 234Th dynamics in the abyssal near-bottom water column?  

Microsoft Academic Search

Dynamics of the natural radioactive particle tracer 234Th (half-life: 24.1 days) within the abyssal water column up to 1000m above bottom and within surface sediments of the northeast Atlantic (Porcupine Abyssal Plain; depth: ?4845m) were investigated. Distributions of transmissometer voltages and potential temperature indicated a subdivision of the near-bottom water column into a benthic mixed layer (BML; thickness: ?10–65m) and

Robert Turnewitsch; Barbara M Springer

2001-01-01

367

Fatty acid profiles of marine benthic microorganisms isolated from the continental slope of bay of bengal: a possible implications in the benthic Food web  

Microsoft Academic Search

Marine bacteria, actinomycetes and fungal strains were isolated from continental slope sediment of the Bay of Bengal and studied\\u000a for fatty acid profile to investigate their involvement in the benthic food-web. Fifteen different saturated and unsaturated\\u000a fatty acids from bacterial isolates, 14 from actinomycetes and fungal isolates were detected. The total unsaturated fatty\\u000a acids in bacterial isolates ranged from 11.85

Surajit Das; P. S. Lyla; S. Ajmal Khan

2007-01-01

368

JULY 2002 2113M O U M E T A L . 2002 American Meteorological Society  

E-print Network

that fluid there must be replenished. Intermediate nepheloid layers detected optically contained fluid with ­S properties distinct from their sur- roundings. It is suggested that intermediate nepheloid layers are interior signitures of the boundary layer de- tachment required by the near-bottom flux divergance. 1

Kurapov, Alexander

369

NOAA Technical Report ERL 417-PMEL 35 Suspended Particulate Matter  

E-print Network

and Duwamish River runoff in winter, 2) a uniform mid-depth minimum-SPM zone, and 3) a bottom nepheloid layer nepheloid layer in Elliott Bay. iv #12;Suspended Particulate Matter in Elliott Bay Edward T. Baker 1) a thin «5 m) surface layer of variable SPM concentration dominated by phytoplankton growth in summer

370

PIV measurements in the bottom boundary layer of the coastal ocean W.A.M. Nimmo Smith, P. Atsavapranee, J. Katz, T.R. Osborn  

E-print Network

digital cameras, operating simultaneously. Optical fibers were used to transmit light from a surface velocity components, but it cannot scan the boundary layer. The BASS system (benthic acoustic stress sensor measurements have been performed using several devices. Doppler shift based methods include the acoustic

371

Modelling COD and N removal in the water and in the benthic biofilm for the River Wupper in Germany.  

PubMed

The River Wupper, a tributary of the River Rhine, is at several locations influenced by anthropogenous nitrogen input, hydraulic structures, and influents from other tributaries. These influences have an impact both on the water quality and on the hydrodynamic conditions. The model approaches used for this article are based on work of Rauch et al. and the River Water Quality Model No. 1; they allow the simulation of the nitrogen conversion in the River Wupper. They are compatible with the activated sludge models and can thus be used also for integrated approaches. The calibration and validation of the model was realized using actual data of the River Wupper over a length of 60 km with one dam, 10 weirs, three wastewater treatment plants and 11 tributaries. The model considers the nitrogen conversion and COD removal and has a strong focus on biofilm processes in the benthic zone. Additional information is given about the sedimentation processes, the physical oxygen input processes, biofilm detachment processes, molecular diffusion, the influence of the laminar border layer and the changing of COD fractions and biofilm densities. PMID:16838700

Wichern, M; Kehl, O; Erbe, V; Luebken, M; Wilderer, P A

2006-01-01

372

Relationship between the pore density in benthic foraminifera and bottom-water oxygen content  

NASA Astrophysics Data System (ADS)

Reliable estimates of bottom-water oxygen contents are crucial to understand the formation of past oxygen-depleted environments. Here, we investigate the relationship between pore density in calcareous benthic foraminiferal (BF) tests and measured oxygen concentrations of the surrounding bottom-waters (BW-O2) in living (Rose Bengal stained) specimens of the shallow-infaunal species Bolivina pacifica, and the three deep-infaunal species Fursenkoina mexicana, Globobulimina turgida, and Chilostomella oolina. Used samples span a wide oxygen-gradient across oxygen minimum zones (OMZ) off Namibia and Pakistan. Bolivina pacifica, F. mexicana and G. turgida display a significant negative exponential correlation between the pore density and BW-O2, indicating a morphological response of the foraminifers to decreasing oxygenation. Supporting previous results, we suggest that an increasing number of pores improves the ability of oxygen uptake in low-oxygen environments. This morphological response can be used to establish an independent proxy for BW-O2. The inter-specific comparison of the dependency of pore density and BW-O2 reveals a steeper gradient for B. pacifica than for F. mexicana, and G. turgida. We hypothesize that the inter-specific pore density-BW-O2-relationship may reflect their species-specific microhabitat preferences. The shallow-infaunal species B. pacifica is probably stronger affected by oxygen depletions than the two deep-infaunal species F. mexicana, and G. turgida. Our results for the deep-infaunal species C. oolina show no significant relationship between pore density and BW-O2. This suggests that C. oolina has another life-strategy to survive sustained low-oxic conditions than increasing its pore density. Overall, we propose that the pore density of individual BF species provides a valuable independent proxy to reconstruct ancient bottom-water oxygenation. To test the application of this proxy in fossil assemblages, we used the organic-carbon rich sapropel layer S1 in two cores from the North Agean Sea to illustrate the decrease in BW-O2 before and during the sapropel formation as well as the BW-O2 increase afterwards.

Kuhnt, T.; Friedrich, O.; Schmiedl, G.; Milker, Y.; Mackensen, A.; Schiebel, R.

2012-04-01

373

The respiration of common benthic invertebrate species from the shallow littoral zone of Lake Esrom, Denmark  

Microsoft Academic Search

To enable estimation of the total assimilation of benthic populations, we measured the oxygen consumption of macroinvertebrates from the littoral zone of a eutrophic lake. The animals were collected all the year round, and their respiration was measured at field temperatures using a closed-bottle method. Multiple regressions relating the rate of oxygen consumption to temperature and body size were established

Kirsten Hamburger; Peter C. Dall

1990-01-01

374

The effect of seamount induced oceanographic retention on the structure of seamount benthic communities  

Microsoft Academic Search

Processes structuring seamount benthic communities are poorly understood. However, despite limited seamount species inventories, biogeographical examination of accumulated data suggest that communities may vary in composition and structure at local and regional scales, that they may contain high endemicity, and are potential centers of speciation in the deep-sea. Theoretically, drivers of these patterns are in part, related to reduced seamount

P. E. Brewin; K. I. Stocks; D. B. Haidvogel

2006-01-01

375

BENTHIC AND WATER COLUMN PROCESSES IN A SUBTROPICAL ESTUARY: EFFECTS OF LIGHT ON OXYGEN FLUXES  

EPA Science Inventory

Murrell, M.C., J.D. Hagy, J.G. Campbell and J.M. Caffrey. In press. Benthic and Water Column Processes in a Subtropical Estuary: Effects of Light on Oxygen Fluxes (Abstract). To be presented at the ASLO 2004 Summer Meeting: The Changing Landscapes of Oceans and Freshwater, 13-18 ...

376

A PROBABILISTIC ASSESSMENT OF BENTHIC CONDITION OF CALIFORNIA ESTUARIES: RESULTS FROM THE NATIONAL COASTAL ASSESSMENT 1999  

EPA Science Inventory

As part of the National Coastal Assessment, the Environmental Monitoring and Assessment Program of EPA is conducting a three year evaluation of benthic habitat condition of California estuaries. In 1999, probabilistic sampling for a variety of biotic and abiotic condition indica...

377

A comparative study of benthic nematodes in two Chinese lakes with contrasting sources of primary production  

Microsoft Academic Search

Ecological studies on benthic nematodes were conducted in two small, shallow lakes in the middle Yangtze basin, China; Lake Houhu, where the main source of primary production is phytoplankton and Lake Biandantang where it is predominantly macrophytic in origin. Monthly sampling was carried out from April 1996 to March 1997. A total of 36 species of nematodes was found in

Jihua Wu; Yanling Liang

1999-01-01

378

BenthicDispersalof CaribbeanSpinyLobstersamong InsularHabitats:Implicationsfor theConservationof  

E-print Network

, ubereas islands surrounded by sand and rubble bad skeuted clistri- butions dominated b1 adult lobsters. Rubblefields appeared tofunction as a barrier to benthic dispersalfor all lobsters except adults. Vege- tated.bitats es nece- sario para desamollar una estrategia efectiua de conserua.ci6n. Durante su compleja bistoria

Acosta, Charles A.

379

Movers and shakers: nutrient subsidies and benthic disturbance predict biofilm biomass and stable isotope  

E-print Network

Movers and shakers: nutrient subsidies and benthic disturbance predict biofilm biomass and stable. gorbuscha) and chum (O. keta) salmon on stream biofilm. Biofilm is a mix of algae, fungi and bacteria that provides food and habitat and forms the base of these aquatic food webs. 2. We collected rock biofilm

Reynolds, John D.

380

Longitudinal and Seasonal Distribution of Benthic Invertebrates in the Little Lost River, Idaho  

Microsoft Academic Search

A yearlong investigation of the Little Lost River, Idaho (five sites) was conducted to determine the environmental conditions and benthic invertebrate community composition of the stream and to discover factors responsible for distribution of the benthos. All chemical constituents measured showed a tendency to increase from headwaters to mouth. Stream temperatures ranged from 0-15 C near the headwaters and 0

Douglas A. Andrews; G. Wayne Minshall

1979-01-01

381

Effects of PredatorPrey Interactions and Benthic Habitat Complexity on Selectivity of a Foraging Generalist  

E-print Network

strategies, affecting the preferences and consumption patterns of predators. Yellow perch Perca flavescens compared the prey selection of yellow perch (230­311 mm) foraging on common Great Lakes prey species--in simple and complex benthic habitats. Yellow perch selected alewives in both simple and complex habitats

382

Nutritional value of different food sources for the benthic Daphnidae Simocephalus vetulus : role of fatty acids  

Microsoft Academic Search

In this experimental study, growth, survival and fecundity of the benthic Cladoceran Simocephalus vetulus were measured when feeding on Cryptomonas ovata, Paraphysomonas vestita, Cyclidium glaucoma and particulate amorphous organic matter to investigate the nutritional value of these food sources. Cladocerans fed Cr. ovata (autotrophic flagellate) exhibited the highest fecundity and growth. Par- ticulate organic matter (POM, mainly composed of detrital

Alexandre Bec; Christian Desvilettes; Aurelie Véra; Dominique Fontvieille; Gilles Bourdier

2003-01-01

383

RELATIONSHIPS BETWEEN SEAGRASSES, BENTHIC MACROALGAE AND NUTRIENTS IN A PACIFIC NORTHWEST ESTUARY  

EPA Science Inventory

Pacific Northwest estuaries are characterized by large tidal ranges (2-3 m) that routinely expose submerged aquatic vegetation (SAV) such as seagrass and benthic macroalgae. The dominant native seagrass in PNW estuaries is the eelgrass Zostera marina. However, in recent decades...

384

SPATIAL PATTERNS AND ECOLOGICAL DETERMINANTS OF BENTHIC ALGAL ASSEMBLAGES IN MID-ATLANTIC STREAMS, USA  

EPA Science Inventory

We attempted to identify spatial patterns and determinants for benthic algal assemblages in Mid-Atlantic streams. Periphyton, water chemistry, stream physical habitat, riparian conditions, and land cover/use in watersheds were characterized at 89 randomly selected stream sites i...

385

An overview of the assessment of aquatic ecosystem health using benthic invertebrates  

Microsoft Academic Search

Community structure or species composition of benthic invertebrates has frequently been used in environmental monitoring and assessment of aquatic systems. Three general approaches have been taken: the ‘saprobic’ approach, which requires detailed knowledge of taxonomy and is most effective in measuring impacts from sewage effluents; diversity indices, which do not require detailed knowledge of species requirements but ignore information provided

Trefor B. Reynoldson; Janice L. Metcalfe-Smith

1992-01-01

386

Relationships among observed metal concentrations, criteria, and benthic community structural responses in 15 streams  

Microsoft Academic Search

Physical, chemical, and biological data were collected summer and fall, 1980, from 15 river systems impacted by publicly owned treatment works. Elevated metal concentrations in these polluted streams were compared to federally recommended aquatic life criteria and to resident macro-invertebrate communities above and below pollutant sources. In those rivers limited to metal problems benthic invertebrate fauna were predictable indicators of

T. W. LaPoint; S. M. Melancon; M. K. Morris

1984-01-01

387

Spatial scale and the diversity of benthic cyanobacteria and diatoms in a salina  

Microsoft Academic Search

We characterized the richness of benthic cyanobacteria and diatoms in a salina system using traditional and molecular biological methods. After determining the different morphotypes and 16S rRNA genes present in various localities within this hypersaline system, an analysis of the increase of organismal richness as a function of numbers of samples considered was carried out. We found that the spatial

U. Nuebel; F. Garcia-Pichel; M. Kuehl; G. Muyzer

1999-01-01

388

Development of Bacteria and Benthic Total Maximum Daily Loads: A Case Study, Linville Creek, Virginia  

Microsoft Academic Search

quality in approximately 22.5% of the state's free-flow- ing streams and rivers for which sufficient data were Two total maximum daily load (TMDL) studies were performed available to assess at least some designated uses. Of the for Linville Creek in Rockingham County, Virginia, to address bacte- approximately 31 076 km (19 310 miles) assessed, some rial and benthic impairments. The

Brian L. Benham; Kevin M. Brannan; Gene Yagow; Rebecca W. Zeckoski; Theo A. Dillaha; Saied Mostaghimi; Jeff W. Wynn

389

Diagenesis of carbon and nutrients and benthic exchange in sediments of the Northern Adriatic Sea  

Microsoft Academic Search

The characteristics of diagenesis and benthic biogeochemical cycling were studied at six stations in the Northern Adriatic during September, 1988. The objectives of this work were to quantify the mechanisms responsible for mass transport and to establish the stoichiometry of reactions involving carbon and nutrients. Stations were chosen to include sites near the Po delta that have rapid sediment accumulation,

D. E Hammond; P Giordani; W. M Berelson; R Poletti

1999-01-01

390

The role of bacteria in nutrient recycling in tropical mangrove and other coastal benthic ecosystems  

Microsoft Academic Search

Sedimentary bacteria have generally been recognized as an essential food for protists and invertebrates, forming the base of benthic food webs. This trophic role has been well documented, but bacteria play an equally important role as mineralizers of organic detritus and recyclers of essential nutrients. Recent evidence suggests that this latter role is more important than their trophic function in

Daniel M. Alongi; Townsville MC

1994-01-01

391

Habitat-Specific variation in eyespot size of a benthic cladoceran  

Microsoft Academic Search

Pigmented eyespot size of the benthic cladoceran Simocephalus exspinosus was measured in individuals sampled from four freshwater ponds that differed in the extent of visually-oriented predation. In ponds with such predation (from fish, salamander larvae, and dragonfly nymphs), eyespot size was found to be significantly smaller, relative to body size, than in a pond without visually-oriented predation. Reduction in pigmented

Michael J. Konecny; Carmine A. Lanciani; Charles P. White

1982-01-01

392

Recent benthic foraminiferal associations and ecology of the Scotia Sea and Argentine Basin  

Microsoft Academic Search

We investigated 88 surface sediment samples taken with a multiple corer from the southwestern South Atlantic Ocean for their live (Rose Bengal stained) and dead benthic foraminiferal content. Using Q-Mode Principal Component Analysis six live and six dead associations are differentiated. Live and dead association distributions correspond fairly well; differences are mainly caused by downslope transport and selective test destruction.

J. Harloff; A. Mackensen

1997-01-01

393

Development of Benthic Indicators for Nearshore Coastal Waters of New Jersey - A REMAP Project  

EPA Science Inventory

EPA's National Coastal Assessment (NCA) is providing the first complete, consistent dataset on the condition of benthic communities in the nation's estuaries. Prior to NCA, New Jersey based its evaluation of the ecological condition of its coastal waters solely on dissolved oxyg...

394

COMPARATIVE PERFORMANCE OF SIX DIFFERENT BENTHIC MACROINVERTEBRATE SAMPLING METHODS FOR RIVERINE ECOSYSTEMS  

EPA Science Inventory

At each of 60 sites, we collected benthic macroinvertebrates using six different protocols (including the EMAP methods for non-wadeable rivers) and physical habitat data using the USEPA-EMAP-SW protocols for non-wadeable rivers. We used PCA with physical habitat data and DCA wit...

395

A Palaeozoic open shelf benthic assemblage in a protected marine environment1 Muriel Vidala,  

E-print Network

)16 17 18 ABSTRACT19 20 A Late Ordovician benthic assemblage containing trilobites (Colpocoryphe and diploporids is found in the SF1 and SF2.27 In SF1, fossils are randomly scattered in sediments (taphofacies 1: Barrier-lagoon environments; taphonomy; facies analysis; Katian (Ordovician);48 Armorican Massif.49 50 1

Boyer, Edmond

396

A diverse benthic assemblage 100 km from open water under the Amery Ice Shelf, Antarctica  

Microsoft Academic Search

A hot water drill was used to penetrate 480 m of ice to reveal a diverse benthic assemblage, dominated by suspension-feeding invertebrates, under the Amery Ice Shelf (East Antarctica) at a location 100 km from open water and at a depth of 775 m below sea level (840 m below the ice shelf surface). This is the first record of

M. J. Riddle; M. Craven; P. M. Goldsworthy; F. Carsey

2007-01-01

397

High Resolution Multibeam Sonar Mapping of the Lost City Hydrothermal Site with the Autonomous Benthic Explorer  

Microsoft Academic Search

The Autonomous Benthic Explorer (ABE) of the Woods Hole Oceanographic Institution (WHOI) collected high-resolution multibeam sonar bathymetry of the Atlantis Massif and the Lost City vent site in May 2003. A Simrad Mesotech SM 2000 multibeam sonar has been fully integrated into the vehicle for this purpose. The challenging topography of the Lost City site demanded careful AUV survey planning,

M. V. Jakuba; D. R. Yoerger; A. M. Bradley; D. S. Kelley; J. A. Karson

2003-01-01

398

Upward cascading effects of nutrients: shifts in a benthic microalgal community and a negative herbivore response  

Microsoft Academic Search

We evaluated the effects of nutrient addition on interactions between the benthic microalgal community and a dominant herbivorous gastropod, Cerithidea californica (California horn snail), on tidal flats in Mugu Lagoon, southern California, USA. We crossed snail and nutrient (N and P) addition treatments in enclosures on two tidal flats varying from 71 to 92% sand content in a temporally replicated

Anna R. Armitage; Peggy Fong

2004-01-01

399

Assessing estuarine benthic quality conditions in Chesapeake Bay: A comparison of three indices  

Microsoft Academic Search

Legislation in US and Europe has been adopted to determine the ecological integrity of estuarine and coastal waters, including, as one of the most relevant elements, the benthic macroinvertebrate communities. It has been recommended that greater emphasis should be placed on evaluating the suitability of existing indices prior to developing new ones. This study compares twowidely used measures of ecological

A. Borja; D. Dauer; R. Diaz; R. J. Llansod; I. Muxika; J. G. Rodriguez; L. Schaffner

2007-01-01

400

Application of Multiple Index Development Approaches to Benthic Invertebrate Data from the Virginian Biogeographic Province, USA  

EPA Science Inventory

Previous work had indicated that the Virginian Province Index did not perform well in a smaller estuarine complex. While it was hoped that the existing Chesapeake Bay Benthic Index of Biotic Integrity, with its greater number of metrics and habitat separation would be more adapt...

401

IMPERVIOUS SURFACE AREA AND BENTHIC MACROINVERTEBRATE RESPONSE AS INDEX OF IMPACT FROM URBANIZATION ON FRESHWATER WETLANDS  

EPA Science Inventory

The use of benthic macroinvertebrates to monitor water quality and ecological integrity is not as well established for wetlands as it is for rivers, streams and lakes where this form of biomonitoring is now a formalized procedure. he impact to wetlands from urbanization (as measu...

402

Benthic and pelagic food resources for zooplankton in shallow high-latitude lakes and ponds  

E-print Network

Benthic and pelagic food resources for zooplankton in shallow high-latitude lakes and ponds MILLA. 2. In this study we quantified zooplankton food sources and feeding rates in the shallow waters polar desert (Resolute, Nunavut). Five substrate types were tested (beads, bacteria, picophytoplankton

Vincent, Warwick F.

403

Alterations in the energy budget of Arctic benthic species exposed to oil-related compounds  

Microsoft Academic Search

We studied cellular energy allocation (CEA) in three Arctic benthic species (Gammarus setosus (Amphipoda), Onisimus litoralis (Amphipoda), and Liocyma fluctuosa (Bivalvia)) exposed to oil-related compounds. The CEA biomarker measures the energy budget of organisms by biochemically assessing changes in energy available (carbohydrates, protein and lipid content) and the integrated energy consumption (electron transport system activity (ETS) as the cellular aspect

Gro Harlaug Olsen; Eirin Sva; JoLynn Carroll; Lionel Camus; Wim De Coen; Roel Smolders; Helene Øveraas; Ketil Hylland

2007-01-01

404

Benthic indices and ecological quality of shallow Algeria fine sand community  

Microsoft Academic Search

This study applies six macrozoobenthos-based biotic indices in the shallow coastal waters along the Algerian coast (southern Mediterranean Sea) to establish a reference situation for future use. These shallow fine sand communities were sampled in seven bays along the Algerian coast during the 1980s and the beginning of the 1990s. For the first time, some of the benthic indices used

A. Bakalem; T. Ruellet; J. C. Dauvin

2009-01-01

405

DOWNSTREAM BENTHIC RESPONSES TO SMALL DAM REMOVAL IN A COLDWATER STREAM  

E-print Network

DOWNSTREAM BENTHIC RESPONSES TO SMALL DAM REMOVAL IN A COLDWATER STREAM CAILIN H. ORR,* STEVE J with an aging dam infrastructure has led to an increase in dam removals. However, ecological responses removals on downstream periphyton and macroinvertebrates in Boulder Creek, WI (USA). The dams were 180 m

Stanley, Emily

406

Sources and Sinks of Escherichia coli in Benthic and Pelagic Fish  

Microsoft Academic Search

Escherichia coli and fecal coliform bacteria were isolated from five benthic and four pelagic fish species to determine their role in the fecal contamination of recreational waters. All fish were collected during fall 2006 from Southworth Marsh in the Duluth-Superior Harbor, a public beach that is commonly posted to minimize water contact due to high E. coli levels. Although fecal

Dennis L. Hansen; John J. Clark; Satoshi Ishii; Michael J. Sadowsky; Randall E. Hicks

2008-01-01

407

In situ monitoring of the effects of water quality on benthic detrital decomposition  

Microsoft Academic Search

Detrital decomposition is an important marine benthic process which contributes to the fertility of seas, particularly in estuarian and coastal waters. The process involves a complex community of microorganisms and small animals which interact with each other in a manner similar to that which occurs in forest litter and in composts. Plastic chambers for measuring decomposition rates of Spartina alterniflora

J. J. Lee; C. Mastropaolo; M. McEnery; J. H. Tietjen; J. Garrison

1978-01-01

408

Structural and functional responses of benthic invertebrates to imidacloprid in outdoor stream mesocosms  

Microsoft Academic Search

Structural and functional responses of a benthic macroinvertebrate assemblage to pulses of the insecticide imidacloprid were assessed in outdoor stream mesocosms. Imidacloprid pulses reduced invertebrate abundance and community diversity in imidacloprid-dosed streams compared to control streams. These results correlated well with effects of imidacloprid on leaf litter decomposition and feeding rates of Pteronarcys comstocki, a stonefly, in artificial streams. Reductions

J. L. T. Pestana; A. C. Alexander; J. M. Culp; D. J. Baird; A. J. Cessna; A. M. V. M. Soares

2009-01-01

409

Benthic foraminiferal dissolved-oxygen index and dissolved-oxygen levels in the modern ocean  

Microsoft Academic Search

Changes in oxygen concentrations at the sediment-water interface play a major role in controlling benthic foraminiferal assemblages and morphologic characteristics; such changes are reflected in size, wall thickness, porosity, and also taxa (genera and species) of foraminifera present. These morphologic and taxonomic differences have been quantified as a dissolved-oxygen index. This paper demonstrates that the foraminiferal oxygen index derived from

Kunio Kaiho

1994-01-01

410

Benthic diatom composition in wet and dry isolated forested wetlands: implications for monitoring and assessment  

EPA Science Inventory

The development of bioindicators for wetlands, especially ephemerally hydrated depressional and isolated wetlands, can be problematic because of seasonal changes in hydrology and target organism biology. To determine if benthic diatoms could be used as a year-round biological ind...

411

Benthic diatom composition in isolated forested wetlands subject to drying: implications for monitoring and assessment  

EPA Science Inventory

The development of bioindicators for wetlands, especially ephemerally hydrated depressional and isolated wetlands, can be problematic because of seasonal hydrology and target organism biology. To determine if benthic diatoms could be used as a year-round biological indicator of w...

412

Cd in planktonic and benthic foraminiferal shells determined by thermal ionization mass spectrometry  

SciTech Connect

A highly sensitive method for Cd determination in foraminiferal shells by isotope-dilution TIMS has been developed and applied to (1) a more detailed reconstruction of seawater Cd depth profiles for the North Atlantic in the Holocene and at the Last Glacial Maximum (LGM); (2) the analysis of Cd/Ca in individual benthic foraminifera shells; and (3) determination of Cd/Ca in Holocene and glacial planktonic foraminifera. Although Ca has a high first ionization potential, through chemical separation of Cd from the Ca and optimization of the loading technique, it is possible to analyze routine sized samples (10 benthics) with a reproducibility in Cd/Ca of {+-}0.0025 {micro}mol/mol between replicate picks from a single sample. The blank of the method is 1.1 pg, permitting analysis of individual benthics and of planktonic foraminifera. The seawater Cd reconstruction for the LGM is consistent with previous work, but also suggests that depths >2,500 m were ventilated by a northern source of nutrient depleted deep water on the western side of the Mid Atlantic Ridge. Individual benthic Cd/Ca ratios show interspecimen variability which is averaged in routine analysis of multiple specimens. Planktonic Cd/Ca from N. Atlantic cores shows interspecific differences between Globigerina bulloides and Neogloboquadrina pachyderma and Holocene-LGM contrasts which offers potential for use of planktonic Cd/Ca as a palaeochemical tracer.

Rickaby, R.E.M.; Greaves, M.J.; Elderfield, H.

2000-04-01

413

Change in biomass of benthic and planktonic algae along a disturbance gradient for 24 Great  

E-print Network

Change in biomass of benthic and planktonic algae along a disturbance gradient for 24 Great Lakes. The PC1 site score was significantly related to both periphyton and phytoplankton biomass, respectively accounted for 18% of the variation in epiphyton biomass. Periphytic and epiphytic biomass were negatively

McMaster University

414

VQ6. Earth Surface, Snow/Ice and Shallow Water Benthic  

E-print Network

VQ6. Earth Surface, Snow/Ice and Shallow Water Benthic Composition What is the land surface soil's polar regions? · How can measurements of rock and soil composition be used to understand and mitigate terrestrial surface? · Science Issue ­ The composition and distribution of the exposed rock and soil substrate

Christian, Eric

415

The benthic invertebrates of the Salton Sea: distribution and seasonal dynamics  

Microsoft Academic Search

The Salton Sea, California's largest inland water body, is an athalassic saline lake with an invertebrate fauna dominated by marine species. The distribution and seasonal dynamics of the benthic macroinvertebrate populations of the Salton Sea were investigated during 1999 in the first survey of the benthos since 1956. Invertebrates were sampled from sediments at depths of 2–12 m, shallow water

P. M. Detwiler; Marie F. Coe; Deborah M. Dexter

2002-01-01

416

Tolerances of five benthic invertebrates to hydrogen ions and metals (Cd, Pb, Al)  

Microsoft Academic Search

96-hr LC50 static bioassays were carried out to determine if the hydrogen ion content and the levels of cadmium, lead, and aluminum characteristic of lakes in the Muskoka District, Ontario, are lethal to benthic macroinvertebrates in four functional groups. The results show that cadmium is the most toxic of the three metals tested to all four functional groups (filter feeders,

G. L. Mackie

1989-01-01

417

Structure, dynamics and production of the benthic fauna in Lake Manitoba  

Microsoft Academic Search

The structure and diversity, including seasonal variation, and the energy budget of the benthic fauna in southern Lake Manitoba were studied and related to physical and chemical properties of the water and sediment. A total of 47 taxa were identified but 90 percent of individuals were represented by seven taxa (Candona rawsoni, Cytheromorpha fuscata, Pisidium spp., Amnicola limosa, Harnischia curtilamellata,

Claudiu Tudorancea; Roger H. Green; Judith Huebner

1979-01-01

418

Using Benthic Marcoinvertebrates Captured by Rock Baskets to Determine Biodiversity in a River.  

NSDL National Science Digital Library

In this ecology investigation, students will build and place rock baskets to collect benthic macroinvertebrates in a local waterway. They will observe and identify their macroinvertebrates and use the data to determine the pollution tolerance index for various areas of a river.

Meyer, Amanda

419

Relationship between the location of chemosynthetic benthic communities and geologic structure on the Cascadia subduction zone  

Microsoft Academic Search

Chemosynthetic benthic communities, which live symbiotically with microbes capable of metabolizing nutrients dissolved in water seeping out of the seafloor, are widespread along the Cascadia subduction zone. These seeps and vents are therefore indicative of one mode of fluid migration out of the subduction zone sediments. The authors have used deep-towed seismic methods, including hydrophones mounted on Alvin, to examine

Brian T. R. Lewis; Guy C. Cochrane

1990-01-01

420

Relationship between the location of chemosynthetic benthic communities and geologic structure on the Cascadia subduction zone  

Microsoft Academic Search

Chemosynthetic benthic communities, which live symbiotically with microbes capable of metabolizing nutrients dissolved in water seeping out of the seafloor, are widespread along the Cascadia subduction zone. These seeps and vents are therefore indicative of one mode of fluid migration out of the subduction zone sediments. We have used deep-towed seismic methods, including hydrophones mounted on Alvin, to examine the

Briant T. R. Lewis; Guy C. Cochrane

1990-01-01

421

TOXICITY OF CLAY FLOCCULATION OF RED TIDE ORGANISMS ON BENTHIC ORGANISMS ERF 2001  

EPA Science Inventory

Toxicity of Clay Flocculation of Red Tide Organisms on Benthic Organisms (Abstract). To be presented at the16th Biennial Conference of the Estuarine Research Foundation, ERF 2001: An Estuarine Odyssey, 4-8 November 2001, St. Pete Beach, FL. 1 p. (ERL,GB R854). We have eva...

422

Proposed sediment quality criteria for the protection of benthic organisms: Dieldrin  

SciTech Connect

The criteria presented in the document are the EPA's best recommendation of the concentrations of a substance in sediment that will not unacceptably affect benthic organisms. These criteria are applicable to a variety of freshwater and marine sediments because they are based on the biologically available concentration of dieldrin in sediments.

Hansen, D.J.; Berry, W.J.; Di Toro, D.M.; Paquin, P.; Davanzo, L.

1991-11-01

423

Proposed sediment quality criteria for the protection of benthic organisms: Fluoranthene  

SciTech Connect

The criteria presented in the document are the EPA's best recommendation of the concentrations of a substance in sediment that will not unacceptably affect benthic organisms. These criteria are applicable to a variety of freshwater and marine sediments because they are based on the biologically available concentration of fluoranthene in sediments.

Not Available

1991-11-01

424

Structural responses of benthic macroinvertebrate communities from different stream orders to zinc  

SciTech Connect

It is well established that benthic invertebrate community structure and function shift in a predictable fashion along longitudinal stream gradients as a result of variation in environmental conditions. The authors research is concerned with experimentally testing whether this shift in community structure influences the response of benthic macroinvertebrates to heavy metals. Using artificial streams, they compared effects of Zn on natural assemblages of benthic macroinvertebrates communities collected from Little Beaver Creek (LBC; a third-order stream) and the Big South Fork of the Cache la Poudre, Colorado, catchment. Organisms collected from LBC and SFP were exposed to 0 or 130 [mu]g/L Zn in indoor experimental streams for 7 d. In general, similar taxa were found at both sites, but densities were generally higher at SFP than at LBC. They observed significant effects at the community and population level as a result of Zn, stream order, and the interaction between Zn and stream order. Specifically, mayflies from both sides were sensitive to Zn, but the magnitude of the response varied between sites. The results indicate that benthic macroinvertebrate communities from different stream order may vary in sensitivity to Zn.

Kiffney, P.M.; Clements, W.H. (Colorado State Univ., Fort Collins, CO (United States). Dept. of Fishery and Wildlife Biology)

1994-03-01

425

Effects of heavy metals on benthic macroinvertebrate communities in New Zealand streams  

SciTech Connect

The authors performed chemical analyses of heavy metals in water and periphyton, toxicity tests with Daphnia magna and an indigenous mayfly (Deleatidium sp.), and field surveys of benthic macroinvertebrates to estimate the degree of metal pollution in three catchments in the Coromandel Peninsula of New Zealand. Good agreement was found between toxicity tests and measures of benthic community structure, particularly at stations with the highest metal levels. Responses of benthic communities at stations with low or moderate levels of metal contamination were variable and were probably confounded by factors other than heavy metals. Effects of heavy metals on benthic communities in New Zealand streams were similar to those reported for metal-polluted streams in North America and Europe, suggesting that responses to metal contamination are predictable. Abundance and species richness of mayflies, number of taxa in the orders Ephemeroptera, Plecoptera, and Trichoptera, and total taxonomic richness were the best indicators of heavy metals in New Zealand streams. In contrast, the quantitative macroinvertebrate community index (QMCI), a biotic index proposed for assessing effects of organic enrichment in New Zealand streams, could not distinguish between reference and metal-polluted streams. The poor performance of the QMCI was primarily due to incorrect tolerance scores for some taxa to heavy metals. Because of concerns regarding the subjective assignment of tolerance values to species, the authors recommend that tolerance values for dominant species in New Zealand streams should be verified experimentally in stream microcosms.

Hickey, C.W. [National Inst. of Water and Atmospheric Research, Hamilton (New Zealand); Clements, W.H. [Colorado State Univ., Fort Collins, CO (United States). Dept. of Fishery and Wildlife Biology

1998-11-01

426

Proposed sediment quality criteria for the protection of benthic organisms: Endrin  

SciTech Connect

The criteria presented in the document are the EPA's best recommendation of the concentrations of a substance in sediment that will not unacceptably affect benthic organisms. These criteria are applicable to a variety of freshwater and marine sediments because they are based on the biologically available concentration of endrin in sediments.

Not Available

1991-11-01

427

Proposed sediment quality criteria for the protection of benthic organisms: Acenaphthene  

SciTech Connect

The criteria presented in the document are the EPA's best recommendation of the concentrations of a substance in sediment that will not unacceptably affect benthic organisms. These criteria are applicable to a variety of freshwater and marine sediments because they are based on the biologically available concentration of acenaphthene in sediments.

Hansen, D.J.; Berry, W.J.; Di Toro, D.M.; Paquin, P.; Davanzo, L.

1991-11-01

428

Development of an Ecological Model Incorporating Benthic Processes in an Unsteady Framework  

E-print Network

dissolved oxygen (sec" ). p * is the stoichiometry coefficients of benthic algaealgae-water column interactions that Smith (1978) included, they take the following forms for phosphate phosphorus, ammonia nitrogen, nitrate nitrogen, and dissolved oxygen:algae (BA) with a constant mass flux (mass/time) of nutrient (nitrate) to the river. Temperature and dissolved oxygen (

Breithaupt, Stephen A; King, Ian P; Orlob, Gerald T

1995-01-01

429

Drift and benthic invertebrate responses to stepwise and abrupt increases in non-scouring flow  

Microsoft Academic Search

We conducted two experiments to assess drift and benthic invertebrate responses to stepwise and abrupt changes in non-scouring flow in gravel-bed experimental streams. Intuitively, a stepwise flow increase should allow aquatic invertebrates more time to seek refuges than would an abrupt increase. We hypothesized that abrupt flow increases would result in larger increases in taxon richness and in the number

J. Bosco Imbert; James A. Perry

2000-01-01

430

Protein synthesis in a solitary benthic cephalopod, the Southern dumpling squid (Euprymna tasmanica)  

E-print Network

Protein synthesis in a solitary benthic cephalopod, the Southern dumpling squid (Euprymna tasmanica-history Protein synthesis Squid Tissue protein synthesis Rates of protein synthesis were measured in the whole body and tissues of southern dumpling squid Eu- prymna tasmanica to validate the use of a flooding

McFall-Ngai, Margaret

431

Diet effects on lipid composition, somatic growth potential, and survival of the benthic amphipod Diporeia spp  

Microsoft Academic Search

The benthic amphipod Diporeia represents a crucial trophic link that conveys vital nutrients and energy to predators at higher trophic levels. The current decline of Diporeia populations, mostly in the North American Great Lakes, may, in part, be related to concurrent declines in food quantity and\\/or quality. We hypothesized that somatic growth and survival of Diporeia would be positively related

Martin J. Kainz; Ora E. Johannsson; Michael T. Arts

2010-01-01

432

Benthic microbial fuel cells: long-term power sources for wireless marine sensor networks  

Microsoft Academic Search

Wireless marine sensor networks support an assortment of services in industries ranging from national security and defense to communications and environmental stewardship. Expansion of marine sensor networks has been inhibited by the limited availability and high cost of long-term power sources. Benthic Microbial Fuel Cells (BMFCs) are a novel form of energy harvesting for marine environments. Through research conducted in-lab

Juan J. Guzman; Keegan G. Cooke; Marcus O. Gay; Sage E. Radachowsky; Peter R. Girguis; Michael A. Chiu

2010-01-01

433

Spatial Patterns of Benthic Macroinvertebrates in Intertidal Areas of a Southern European Estuary: The Tagus, Portugal  

Microsoft Academic Search

This study characterizes the composition and spatial distribution patterns of the benthic macrofauna in the intertidal mudflats of the Tagus estuary, western Portugal. A total of 68 species, more than 226,000 specimens with a total wet weight biomass of approximately 1170 g were identified in 380 sites. The species Streblospio shrubsolii, Cyathura carinata, Tharyx sp., Hydrobia ulvae and Tubificids were the

Ana Maria Rodrigues; Sónia Meireles; Teresa Pereira; Alice Gama; Victor Quintino

2006-01-01

434

Response of benthic foraminifera to heavy metal contamination in marine sediments (Sicilian coasts, Mediterranean Sea)  

Microsoft Academic Search

To examine the suitability of benthic foraminifera and their test deformations as bioindicators of pollution in coastal marine environments, we studied foraminifera and metal concentrations in 72 marine sediment samples, collected from the inner shelf along the Sicilian coast (Gulfs of Palermo and Termini) and on the south-eastern coast of Lampedusa Island. These areas are characterised by different environmental conditions.

Antonio Caruso; Claudia Cosentino; Luigi Tranchina; Maria Brai

2011-01-01

435

Periphyton As A Source Of Bioavailable Cd and Cu To Invertebrate Benthic Grazers  

Microsoft Academic Search

High metal body burdens observed in invertebrate benthic grazers suggest that periphyton is an important source of bioavailable metals. We conducted comparative studies among five species of stream insects (the mayflies Nixe sp., Epeorus albertae, E. longimanus, Serratella tibialis, and Drunella flavilinea) to quantify dietary and dissolved cadmium (Cd) and copper (Cu) bioaccumulation kinetics as a means of characterizing exposure

D. Cain; M. Croteau; S. N. Luoma

2009-01-01

436

Foraging modes of stream benthic fishes in relation to their predation effects on local prey density  

Microsoft Academic Search

Habitat use and foraging behavior of two benthic insectivorous gobies, Rhinogobius sp. CO (cobalt type) and Rhinogobius sp. DA (dark type), were examined in relation to their predation effects on local prey density in a small coastal stream in southwestern Shikoku, Japan. Correlations among the foraging range, frequency of foraging attempts and current velocity indicated that individuals using fast-current habitats

Mikio Inoue; Masanobu Miyayoshi; Shin Sone

2005-01-01

437

Structure and function of a benthic invertebrate stream community as influenced by beaver ( Castor canadensis )  

Microsoft Academic Search

Beaver (Castor canadensis) affect the benthic invertebrate community of small woodland streams in Quebec through habitat modifications. Their activities influence community structure through the replacement of lotic taxa by lentic forms and community function by increasing the absolute importance of collectors and predators while decreasing the relative importance of shredders and scrapers in impounded sites. At our study site during

Donald M. McDowell; Robert J. Naiman

1986-01-01

438

OPTIMUM BENTHIC MACROFAUNAL SAMPLING PROTOCOL FOR DETECTING DIFFERENCES BETWEEN FOUR HABITATS IN WILLAPA BAY, WASHINGTON, USA  

EPA Science Inventory

Abstract -- As part of an effort to estimate estuarine habitat values with respect to ecological indicators of benthic macrofaunal community condition, an optimal (effective and least costly) sampling protocol (sample unit size [area 3 depth], sieve mesh size, and sample number [...

439

A Comparison of the Influences of Urbanization in Contrasting Environmental Settings on Stream Benthic Algal Assemblages  

Microsoft Academic Search

Patterns of stream benthic algal assemblages along urbanization gradients were investi- gated in three metropolitan areas—Boston (BOS), Massachusetts; Birmingham (BIR), Alabama; and Salt Lake City (SLC), Utah. An index of urban intensity derived from socioeconomic, infrastruc- ture, and land-use characteristics was used as a measure of urbanization. Of the various attributes of the algal assemblages, species composition changed along gradients

MARINA P OTAPOVA; ELISE M. P. GIDDINGS; HUMBERT ZAPPIA

2005-01-01

440

Acute toxicity of four heavy metals to Benthic fish food organisms from the River Khan, Ujjain  

Microsoft Academic Search

The acute toxicity of four heavy metals (Hg, Zn, Cd and Pb) to two benthic invertebrates viz. Tubifex tubifex and 4th instar larvae of chironomous sp. from the River Khan (Ujjain) have been determined by static bioassay experiments. Although both Tubifex tubifex and chironomous larvae have been found to be resistant to heavy metals (Hg, Zn, Cd and Pb), the

S. A. Qureshi; A. B. Saksena; V. P. Singh

1980-01-01

441

BENTHIC COMMUNITY STRUCTURE OF THE GREEN AND COLORADO RIVERS THROUGH CANYONLANDS NATIONAL PARK, UTAH, USA  

Microsoft Academic Search

We sampled the aquatic benthos at 6 remote sites on the Colorado and Green rivers through Canyonlands National Park, Utah, USA. This study provides the first published description of benthic standing mass, invertebrate community composition, and primary carbon source for this portion of the Colorado River system. High suspended sediment concentrations prohibited growth of primary producers. The primary carbon source

G. ALLEN HADEN; JOSEPH P. S HANNON; K EVIN P. W ILSON; DEAN W. BLINN

442

Effect of acidification on leaf litter decomposition in benthic and hyporheic zones of woodland streams.  

PubMed

Anthropogenic acidification has deleterious effects on both structure and functioning of surface water ecosystems. This study examined how it may affect the leaf decomposition rate and the community structure and activity of decomposers in both benthic and hyporheic zones of five headwater streams along an acidification gradient from highly acidic (pH 4.6) to circumneutral (pH 7.4). Overall, responses to acidification in hyporheic zones were less pronounced, but followed the same pattern as in their benthic counterparts. Leaf decomposition was much faster in the circumneutral stream, both in the hyporheic and benthic zones (k = 0.0068 and 0.0534 d(-1), respectively), than in the most acidic one (k = 0.0016 and 0.0055 d(-1), respectively), and correlated well with the acidic gradient in both compartments. Interestingly, leaf litter decomposition was less affected by acidification in hyporheic compared to benthic compartments, likely due to the relatively low sensitivity of fungi, which were the main decomposers of buried coarse particulate organic matter. These results argue in favour of conserving hyporheic habitats in acidified streams as they can maintain matter and species fluxes that are essential to the ecosystem. PMID:23069077

Cornut, Julien; Clivot, Hugues; Chauvet, Eric; Elger, Arnaud; Pagnout, Christophe; Guérold, François

2012-12-01

443

Terrestrial and benthic foods in the diet of the shortjawed kokopu, Galaxias postvectis Clarke (Teleostei: Galaxiidae)  

Microsoft Academic Search

Shortjawed kokopu from diverse localities feed extensively on several species of cased caddisflies from the stream benthos and on diverse terrestrial invertebrates from the surface. Small caddisflies often dominate the diet numerically and are selected for, whereas other often abundant benthic insects, such as Chironomidae and the mayfly Deleatidium, are avoided. We hypothesise that this selectivity indicates that caddisflies are

R. M. McDowall; M. R. Main; D. W. West; G. L. Lyon

1996-01-01

444

Effects of large woody debris placement on stream channels and benthic  

E-print Network

Effects of large woody debris placement on stream channels and benthic macroinvertebrates Robert H. Hilderbrand, A. Dennis Lemly, C. Andrew Dolloff, and Kelly L. Harpster Abstract: Large woody debris (LWD] Introduction The importance of large woody debris (LWD) is well docu- mented in temperate stream ecosystems

Hilderbrand, Robert H.

445

A COMPARISON OF BENTHIC MACROINVERTEBRATE SAMPLING METHODS ON SELECTED LARGE RIVER TRIBUTARIES TO THE MISSISSIPPI  

EPA Science Inventory

We compared three benthic macroinvertebrate sampling methods on the St. Croix, Wisconsin and Scioto Rivers in summer 2004 and 2005. EPA's newly developed, multi-habitat Large River Bioassessment Protocol (LR-BP) was compared to the multi-habitat method of the Minnesota Pollution...

446

ROV observations of benthic fishes in the Northwind and Canada Basins, Arctic Ocean  

Microsoft Academic Search

Abyssal and midslope Arctic benthic fishes were sampled nonquantitatively by still photography and videography from a remotely operated vehicle (ROV) between 13 August and 7 September 2002. Species diversity was low: only six putative species were seen, including Lycodes frigidus Collett 1879, Lycodes sp., Rhodichthys regina Collett 1879, Paraliparis bathybius (Collett 1879), Raja (Amblyraja) hyperborea Collett 1879, and Cottunculus species

David L. Stein; James D. Felley; Michael Vecchione