Feeding Bivalves Research Articles

Microalgal Cell Surface Carbohydrates as Recognition Sites for Particle Sorting in Suspension-Feeding Bivalves

Cell surface carbohydrates play important roles in cell recognition mechanisms. Recently, we provided evidence that particle selection by suspension-feeding bivalves can be mediated by interactions between carbohydrates associated with the particle surface and lectins present in mucus covering bivalve feeding organs. In this study, we used lectins tagged with fluorescein isothiocyanate (FITC) to characterize carbohydrate moieties on the surface of microalgal species and evaluate the effect of oyster mucus on lectin binding. These analyses revealed that concanavalin A (Con A), one of six lectins tested, bound to Isochrysis sp., while Nitzschia closterium reacted with Pisum sativum agglutinin (PNA) and peanut agglutinin (PEA). The cell surface of Rhodomonas salina bound with PNA and Con A, and Tetraselmis maculata cell surface was characterized by binding with PNA, PEA, and Con A. Pre-incubation of microalgae with oyster pallial mucus significantly decreased the binding of FITC-labeled lectins, revealing that lectins present in mucus competitively blocked binding sites. This decrease was reversed by washing mucus-coated microalgae with specific carbohydrates. These results were used to design a feeding experiment to evaluate the effect of lectins on sorting of microalgae by oysters. Crassostrea virginica fed with an equal ratio of Con A-labeled Isochrysis sp. and unlabeled Isochrysis sp. produced pseudofeces that were significantly enriched in Con A-labeled Isochrysis sp. and depleted in unlabeled microalgae. Selection occurred even though two physical-chemical surface characteristics of the cells in each treatment did not differ significantly. This work confirms the involvement of carbohydrate-lectin interaction in the particle sorting mechanism in oysters, and provides insights into the carbohydrate specificity of lectins implicated in the selection of microalgal species.

Relationships between reproduction in suspension-feeding hard clams Mercenaria mercenaria and phytoplankton community structure

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 387:179-196 (2009) - DOI: https://doi.org/10.3354/meps08083 Relationships between reproduction in suspension-feeding hard clams Mercenaria mercenaria and phytoplankton community structure Roger I. E. Newell1,*, Stephen T. Tettelbach2, Christopher J. Gobler3, David G. Kimmel4 1Horn Point Laboratory, University of Maryland Center for Environmental Science, PO Box 775, Cambridge, Maryland 21613, USA 2Biology Department, Long Island University, Brookville, New York 11548, USA 3School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, New York 11794-5000, USA 4Department of Biology/Institute for Coastal Science and Policy, East Carolina University, Greenville, North Carolina 27858, USA *Email: rnewell@hpl.umces.edu ABSTRACT: We hypothesized that the decline in hard clam Mercenaria mercenaria populations since the 1970s in many of the south shore bays of Long Island, New York, USA, was due to changes in reproduction caused by variations in phytoplankton available as a food resource. We measured in 2000 and 2001 the reproductive condition of female clams from 5 sites in south shore bays of Long Island and from 2 sites in New Jersey. Phytoplankton composition was measured as the concentration of total and size-fractionated chlorophyll a (chl a), particulate organic carbon (POC), and nitrogen (PON), and the abundance of the harmful picoplankter Aureococcus anophagefferens. Timing of peak hard clam reproduction was nearly identical across sites, and was the same as in archived samples of clams collected in 1978 and 1979. Hard clam condition index differed between sites, with poorest condition being exhibited at the 3 Great South Bay (GSB) sites. There were also appreciable differences in relative reproductive output between locations, with clams again from the 3 GSB sites having the lowest estimated egg production. The central and eastern GSB had the highest levels of total chl a, POC, and PON, however, of any south shore bay, although this was mainly contributed by cells <2 µm, which have low nutritional value for adult hard clams. In addition, the 3 sites in GSB suffered brown tide blooms during 2000 and 2001, which are known to inhibit bivalve feeding. We conclude that changes in the composition of the phytoplankton community at some locations may be reducing hard clam reproductive output. KEY WORDS: Hard clam · Phytoplankton composition · Brown tide · Reproduction · Aureococcus anophagefferens · Mercenaria mercenaria Full text in pdf format Supplementary material PreviousNextCite this article as: Newell RIE, Tettelbach ST, Gobler CJ, Kimmel DG (2009) Relationships between reproduction in suspension-feeding hard clams Mercenaria mercenaria and phytoplankton community structure. Mar Ecol Prog Ser 387:179-196. https://doi.org/10.3354/meps08083Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 387. Online publication date: July 28, 2009 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2009 Inter-Research.

Introduction

AB Aquatic Biology Contact the journal Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AB 6:175-180 (2009) - DOI: https://doi.org/10.3354/ab00133 Theme Section: Directions in bivalve feeding Directions in bivalve feeding: Introduction Peter G. Beninger* Laboratoire de Biologie Marine, Faculté des Sciences, Université de Nantes, 44322 Nantes, France *Email: peter.beninger@univ-nantes.fr ABSTRACT: Manuscripts dealing with bivalve feeding and submitted to the Inter-Research journal Aquatic Biology over the course of 2008 were peer-reviewed in the standard manner, and the successful papers compiled for a Theme Issue entitled ‘Directions in bivalve feeding’. The historical progression of research in this field is summarized, and the directions of current research highlighted in view of the compiled papers. Some suggestions for future work are presented. KEY WORDS: Bivalve biology · Suspension feeding · Bivalve diet · Trophic ecology · Mechanisms · Measurements · Perspectives Full text in pdf format PreviousNextCite this article as: Beninger PG (2009) Directions in bivalve feeding: Introduction. Aquat Biol 6:175-180. https://doi.org/10.3354/ab00133Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AB Vol. 6. Online publication date: August 11, 2009 Print ISSN: 1864-7782; Online ISSN: 1864-7790 Copyright © 2009 Inter-Research.

Comparative utilization of phytoplankton and vascular plant detritus by the cockle Cerastoderma edule: digestive responses during diet acclimation

Contribution to the Theme Section 'Directions in bivalve feeding' ABSTRACT: Physiological components of food absorption (rates of particle clearance and ingestion and absorption efficiencies) were recorded in the cockles Cerastoderma edule fed variable concen- tration diets of phytoplankton (Isochrysis galbana) and detritus from salt-marsh vascular plants (Spartina maritina), after 2 and 12 d of acclimation to these diets. Corresponding digestive processes were also analysed, including determinations of gut passage time of food, gut fullness (GF) and digestive investments, the latter measured in terms of both metabolic faecal losses (MFL) and enzyme activities of the digestive glands. Digestive responses to increasing availability of phytoplankton included faster processing of food particles coupled to improved hydrolytic capacity of digestive glands that resulted in increased gut performance. Compared to phytoplankton, detritus utilization was constrained in the short-term by its refractory behaviour to digestion and the magnitude of meta- bolic faecal losses experienced by cockles fed these food materials. However, increased GF achieved during acclimation to detrital diets compensated for reduced digestibility, allowing for more food to be processed and thus cancelling out the effects of reduced passage time (and the consequent decline in absorption efficiency). Induction of the appropriate set of carbohydrases during the acclimation process resulted in increased amounts of reducing sugars released from natural substrates, with the additional benefit of diminishing the losses of endogenous materials accompanying each cycle of intracellular digestion.

Mechanisms contributing to low domoic acid uptake by oysters feeding on Pseudo-nitzschia cells. I. Filtration and pseudofeces production

AB Aquatic Biology Contact the journal Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AB 6:201-212 (2009) - DOI: https://doi.org/10.3354/ab00121 Theme Section: Directions in bivalve feeding Mechanisms contributing to low domoic acid uptake by oysters feeding on Pseudo-nitzschia cells. I. Filtration and pseudofeces production Luiz L. Mafra Jr.1,2,*, V. Monica Bricelj3, Christine Ouellette1, Claude Léger4, Stephen S. Bates4 1Institute for Marine Biosciences, National Research Council, 1411 Oxford St., Halifax, Nova Scotia B3H 3Z1, Canada 2Department of Biology, Dalhousie University, Halifax, Nova Scotia B3H 4J1, Canada 3Institute of Marine and Coastal Sciences, Rutgers University, 93 Lipman Dr., New Brunswick, New Jersey 08901, USA 4Gulf Fisheries Centre, Fisheries and Oceans Canada, PO Box 5030, Moncton, New Brunswick E1C 9B6, Canada *Email: luiz.mafra@nrc-cnrc.gc.ca ABSTRACT: Bivalve molluscs feeding on toxigenic Pseudo-nitzschia spp. are the main vector of domoic acid (DA) to humans. Although different oyster species rarely exceed the internationally adopted regulatory level for shellfish harvesting closures (20 µg g–1), these are often applied to all bivalve species in an affected area. This study examines the influence of diet composition and Pseudo-nitzschia multiseries cell size, density and toxicity on oyster feeding rates to determine potential pre-ingestive mechanisms that may lead to low DA accumulation in the oysters Crassostrea virginica. Clearance rate (CR) and pseudofeces production of juvenile oysters were quantified under varying laboratory conditions representative of natural Pseudo-nitzschia blooms. Oysters filtered increasing amounts of P. multiseries cells as cell density increased, but ingestion was limited by pseudofeces production at concentrations >10400 cells ml–1 (ca. 6 mg dry weight l–1). Oysters significantly reduced their CR when fed both toxic and non-toxic P. multiseries clones in unialgal suspensions compared to Isochrysis galbana, and this rapid grazing inhibition was not related to growth stage, cell size, or exposure time. When offered mixed suspensions containing equivalent cellular volumes of the 2 species, however, relatively high CR was restored. Therefore, we suggest that DA intake by oysters from mono-specific Pseudo-nitzschia blooms would be limited by a persistently reduced CR and rejection of cells in pseudofeces. When an alternative, good source of food is present in a mixed phytoplankton assemblage with P. multiseries, no CR inhibition is expected and DA intake will be regulated by pre-ingestive particle selection on the feeding organs, as demonstrated in Mafra et al. (2009, in this Theme Section) KEY WORDS: Pseudo-nitzschia multiseries · Domoic acid · Oyster · Crassostrea virginica · Feeding · Filtration · Pseudofeces Full text in pdf format PreviousNextCite this article as: Mafra Jr LL, Bricelj VM, Ouellette C, Léger C, Bates SS (2009) Mechanisms contributing to low domoic acid uptake by oysters feeding on Pseudo-nitzschia cells. I. Filtration and pseudofeces production. Aquat Biol 6:201-212. https://doi.org/10.3354/ab00121 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AB Vol. 6. Online publication date: March 12, 2009 Print ISSN: 1864-7782; Online ISSN: 1864-7790 Copyright © 2009 Inter-Research.

Observations on the measurement and interpretation of clearance rate variations in suspension-feeding bivalve shellfish

AB Aquatic Biology Contact the journal Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AB 6:181-190 (2009) - DOI: https://doi.org/10.3354/ab00123 Theme Section: Directions in bivalve feeding Observations on the measurement and interpretation of clearance rate variations in suspension-feeding bivalve shellfish P. L. Pascoe, H. E. Parry, A. J. S. Hawkins* Plymouth Marine Laboratory, Prospect Place, The Hoe, Plymouth PL1 3DH, UK *Corresponding author. Email: ajsh@pml.ac.uk ABSTRACT: Mussels Mytilus edulis (35 ± 2 mm shell length) were fed on cultured Isochrysis galbana in a flow-through system, and measures were undertaken to quantify separate effects of inflow cell concentration, outflow cell concentration, percentage reduction (i.e. recycling), and flow rate and/or feeding history on clearance rate measures (CR; l h–1). Findings identify the following features of physiological regulation: (1) a lag phase in the feeding response to changes in food concentration, of around 30 min; (2) a trigger level in algal cell (chlorophyll [chl] a) volume/concentration (4000 cells ml–1, 0.5 µg l–1 chl a) below which filtering in most mussels ceases; (3) saturation reduction, or satiation, resulting in reduced CR and valve closure after feeding for over 2 h at 30000 or more cells ml–1 (~6 µg l–1 chl a); and (4) at food levels between Features 2 & 3, CR increases to maximal rates (ca. 2 to 2.5 l h–1 ind.–1 or 6 to 7.5 l–1 h–1 g–1 dry weight). Our findings also help resolve uncertainties associated with the measurement and interpretation of clearance rate variations. These uncertainties are associated with: differences that result from analyses of feeding responses to different components of the available seston; whether variations in seston availability are physiologically relevent; analyses of individual shellfish as compared with average responses computed for >1 ind.; and comparisons between short-term and integrated measures. We think it is important to consider whether measures of feeding are really required per individual in real time, and we stress that population averaging and temporal integration are required for the scaling up of results when simulating ecological interrelations between shellfish populations and their environments. KEY WORDS: Filter feeding · Suspension feeding · Clearance rate · Mytilus edulis · Bivalve shellfish · Flow-through · Physiological regulation · Supply rate Full text in pdf format PreviousNextCite this article as: Pascoe PL, Parry HE, Hawkins AJS (2009) Observations on the measurement and interpretation of clearance rate variations in suspension-feeding bivalve shellfish. Aquat Biol 6:181-190. https://doi.org/10.3354/ab00123 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AB Vol. 6. Online publication date: March 12, 2009 Print ISSN: 1864-7782; Online ISSN: 1864-7790 Copyright © 2009 Inter-Research.

Feeding activity of scallops and mussels measured simultaneously in the field: Repeated measures sampling and implications for modelling

Many studies on the biology of bivalves have focused on identifying the importance of various environmental factors in regulating feeding behaviour in order to predict ingestion and growth responses in a variety of habitats. When taking into consideration the diversity of studies undertaken and the variety of methodologies employed, it is perhaps not surprising that there have been inconsistencies in both interspecific and intraspecific comparisons. In order to compare and contrast the way in which feeding activities of a mussel species ( Mytilus edulis) and a scallop species ( Placopecten magellanicus) respond to environmental factors and seston characteristics, we exposed both species simultaneously to a fluctuating assemblage of natural particles found in their local environment. Similar sizes of mussels (40–73 mm) and scallops (40–88 mm) were held in flow through chambers at two different sites in Atlantic Canada on four separate occasions, during which environmental conditions, including seston characteristics, were monitored and individual clearance rates were measured. Because the same individuals were measured over time, repeated-measures statistical procedures were used to analyze the data. Results indicate that weight standardized clearance rates of mussels were significantly higher than those of scallops only at the highest concentration tested (12.8 mg l − 1 ), which translates into almost 3 times more material being filtered. Scallops appeared to respond to fluctuations in environment parameters and suspended food particles more consistently than mussels. These data suggest that the feeding behaviour of these two species is mediated differently by the same environmental parameters. Our study also demonstrates the importance of selecting appropriate statistical tests (e.g., repeated measures) for the analyses of data obtained from repeated sampling of the same individuals over time, and the need to consider species-specific feeding responses when developing models that predict the influence of bivalve feeding on ecosystem function.

Can bivalve veligers escape feeding currents of adult bivalves?

While the stock of introduced Pacific oysters ( Crassostrea gigas) increased in the Oosterschelde estuary (SW Netherlands), so did the filtration pressure of all bivalve species together. In the same period, stocks of native bivalves declined slightly. The expansion of Pacific oysters in Dutch estuaries might be partially due to better abilities of their larvae to avoid or escape filtration, compared to larvae of native bivalves. In this context, escape and swimming abilities of Pacific oyster larvae and the larvae of the native blue mussel ( Mytilus edulis) were compared. Swimming behaviour of C. gigas larvae and larvae of M. edulis was recorded in still water and in a suction current mimicking a bivalve feeding current, in a horizontal and in a vertical plane. Larval swimming behaviour in a suction flow field was reconstructed by subtracting local water movement vectors from the total movement of larvae, yielding movement paths due to larval swimming alone. Swimming speeds and the rate of displacement in vertical direction of C. gigas and M. edulis larvae were related to larval shell length, and to the pitch of up- or downward swimming. Larvae of both species did not show escape reactions in a suction flow field. With increasing shell length, larval swimming speeds of both species increased significantly. Swimming speeds of C. gigas larvae were significantly higher than swimming speeds of M. edulis larvae, resulting in a faster vertical displacement. The ability to migrate to more favourable water layers faster may offer C. gigas an advantage over native bivalves with slower swimming larvae.

Overlap in the feeding morphology of bivalves from species-rich and species-poor intertidal flats using gill:palp ratios for comparative analyses of mollusc assemblages

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 348:213-220 (2007) - DOI: https://doi.org/10.3354/meps07067 Overlap in the feeding morphology of bivalves from species-rich and species-poor intertidal flats using gill:palp ratios for comparative analyses of mollusc assemblages Tanya J. Compton1,2,3,*, Jan Drent1, Rosemarie Kentie1,2, Grant B. Pearson3, Jaap van der Meer1, Theunis Piersma1,2 1Department of Marine Ecology and Evolution, Royal Netherlands Institute for Sea Research (NIOZ), PO Box 59, 1790 AB Den Burg, Texel, The Netherlands 2Centre for Ecological and Evolutionary Studies, University of Groningen, PO Box 14, 9750 AA Haren, The Netherlands 3Western Australian Department of Environment and Conservation, Western Australia Wildlife Research Centre, PO Box 51, Wanneroo, Western Australia 6065, Australia *Email: compton@nioz.nl ABSTRACT: Using morphological variables to describe how species coexist within morphospace, previous studies have shown that species-rich assemblages can (1) show no morphological overlap between species, and (2) occupy a larger morphospace than species-poor assemblages. To describe morphospace occupation in bivalve species from a species-rich tropical (Roebuck Bay, northwestern Australia) and a species-poor temperate (Wadden Sea, The Netherlands) intertidal flat, we used a functional trait that has a clear ecological interpretation: bivalve feeding morphology. Bivalve feeding morphology can be represented by the dimensionless log-ratio of the size of the pumping apparatus (gills) to the size of the sorting apparatus (palps). This log gill-to-palp mass ratio is tightly related to both feeding mode and environment. At both intertidal flats, the log gill-to-palp mass ratios of all species sampled fell along a continuous gradient from those typical of deposit feeders to those typical of suspension feeders. Surprisingly, the log gill-to-palp mass ratios of the species-rich assemblage at Roebuck Bay displayed greater morphological overlap within a larger total occupied morphospace than the species-poor assemblage at the Wadden Sea. The larger total morphospace at Roebuck Bay appears to reflect greater species richness and broader environmental ranges. Because gills and palps of bivalves are easily measured, we propose that they provide a basis for further morphospace comparisons among communities, e.g. along entire latitudinal, depth or productivity gradients. KEY WORDS: Morphology · Functional trait · Bivalve · Ctenidia · Labial palps · Community structure · Diversity · Morphospace Full text in pdf format PreviousNextCite this article as: Compton TJ, Drent J, Kentie R, Pearson GB, der Meer Jv, Piersma T (2007) Overlap in the feeding morphology of bivalves from species-rich and species-poor intertidal flats using gill:palp ratios for comparative analyses of mollusc assemblages. Mar Ecol Prog Ser 348:213-220. https://doi.org/10.3354/meps07067 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 348. Online publication date: October 25, 2007 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2007 Inter-Research.

Spatio-temporal variations in intertidal mudflat erodability: Marennes-Oléron Bay, western France

A portable erosion device (ERIS) was deployed in November 2000 and May 2001 to investigate the spatio-temporal variation of fine-grained sediment erosion over a transect on the intertidal mudflats of Marennes-Oléron Bay, western France. The objective was to relate changes in bed erodability over diurnal emersion periods to bioturbation, rapid changes in sediment characteristics, and microphytobenthos biomass. Macrofaunal assemblages were dominated by the bivalve, Scrobicularia plana, on the upper mudflat, and by the gastropod, Hydrobia ulvae, on the middle mudflat. A power relationship was obtained where τ cr was plotted as a function of sediment density. Results from the upper part of the mudflat deviated from this relationship due to bioturbation by S. plana. No influence of microphytobenthos (either chlorophyll a or extracellular polymeric substances (EPS) content) was found on τ cr. The bivalve feeding activities altered consolidated sediments (sediment dry mass concentration of ∼700 g l −1) so that they became resuspended easily ( τ cr<1 Pa). Fluff layer erosion was observed, with an erosion rate dependent upon the biomass of H. ulvae. It was also found that bioturbation by H. ulvae was implicated (combined with grazing activities) in chl a resuspension during the erosion of the fluff layer. Snail bioturbation stimulated the chl a enrichment of eroded material, whilst the high snail biomass produced a decrease in suspended chl a due to higher grazing rates.

PREPARATION OF LARGE BIVALVE SPECIMENS FOR SCANNING ELECTRON MICROSCOPY USING HEXAMETHYLDISILAZANE (HMDS)

Treatment with hexamethyldisilazane (HMDS) for drying specimens for Scanning Electron Microscopy (SEM) is described for relatively large (>20 mm shell height, SH) individuals of two scallop species, Placopecten magellanicus and Argopecten irradians. The traditionally used method of critical point drying (CPD) has been applied successfully for smaller specimens (~350 μm up to 15 mm SH); however, occasional rupture of the mantle occurred in these specimens. Furthermore, size limitation of the CPD chamber did not permit preparation of larger individuals. An alternative experimental protocol using HMDS was tested, which successfully preserves the morphology of the bivalve feeding organs, mantle surface and the cilia of the two scallop species with negligible shrinkage and few artifacts. Another benefit of this method is that the number of specimens and sample size is not restricted.

Organic matter pathways to zooplankton and benthos under pack ice in late winter and open water in late summer in the north-central Bering Sea

On continental shelves in arctic and subarctic seas, much of the production from spring blooms at the retreating ice edge may sink to the bottom with little grazing by zooplankton, thereby supporting abundant benthic communities. The importance of this settled phytoplankton to mac- robenthos throughout the year may partly determine effects of long-term changes in ice cover. We studied organic matter (OM) pathways to macrobenthos and macrozooplankton under ice cover in late winter (March-April) and open water in late summer (September) in the north-central Bering Sea. In late winter 2001, only a very small fraction of OM in the water column was particulate. C:N ratios, δ 13 C, and δ 15 N in suspended particulate organic matter (SPOM), and sediments indicated very little recent input of fresh ice algae or phytoplankton in ice-covered areas. For the 3 main deposit- feeding bivalves, δ 13 C and δ 15 N indicated similar diets among species, with minimal change in food quality between late summer and late winter, and between late winters with very different ice cover (1999 vs. 2001). In winter 2001, there were large increases in δ 13 C from SPOM to bulk sediments (+3.2‰) and from sediments to near-surface deposit-feeders (+1.6 to +3.0‰), but small differences in δ 15 N from SPOM to sediments (+1.2‰) and from sediments to deposit-feeders (-0.3 to +1.6‰). These values suggest that the diet of near-surface deposit-feeders during these non-bloom periods included substantial amounts of the cells or products of bacteria that had assimilated well-reworked carbon and isotopically light dissolved inorganic nitrogen (DIN). By late summer and through winter, 4 to 11 mo after the spring bloom, products of bacterial activity appeared to be an important route of OM into the benthic food web. Due to bacterial dependence on annual carbon inputs, and unique nutrient content of fresh phytoplankton for breeding invertebrates, ice-edge blooms might be an important determinant of annual variations in macrobenthic abundance.

Feeding physiology of two bivalves under laboratory and field conditions in response to variable food concentrations

In response to uncertainties about whether laboratory feeding rate measurements of bivalves reflect those occurring in situ, this study compares bivalve feeding rates experimentally determined both in the laboratory and in situ for a mussel (Mytilus chilensis) and a clam (Mulinia edulis), species exposed to a wide range of seston concentrations. Artificially prepared seston was administered in the laboratory using a mixture of Isochrysis galbana and sediment at concentrations ranging from 2 to 200 mg l -1 . Field measurements were carried out at Yaldad Bay, southern Chile, during 2 tidal cycles in March and April 1999 with naturally occurring seston ranging from 3 to 665 mg l -1 . We found that: (1) Clearance rate (CR) and selection efficiency (SE) were similar in labo- ratory and in situ conditions, but the rates of filtration (FR), ingestion (IR) and absorption (AR), and absorption efficiency (AE) were significantly higher in the laboratory than in the field. This was attributable to the greater retention efficiency and digestibility of I. galbana compared to the natu- rally occurring microalgae in the seston, and also to the greater acclimation time of specimens to the laboratory diet. (2) The responses to the changes in seston concentration (TPM) were similar under both conditions and validated previous results; CR decreased exponentially with increasing TPM while the FR, IR and AR increased. At high seston concentrations (200 mg l -1 in the laboratory and 665 mg l -1 in situ), almost all the feeding rates decreased, showing an impairment of food processing under these conditions. (3) The resuspended sediment in the intertidal zone of Yaldad Bay, especially under the influence of southerly winds and near the lowest tidal level, is an important food source for M. edulis and M. chilensis populations, allowing continued growth during the winter season when primary productivity is very low.

NETWRK을 이용한 쇄파대 생태계의 탄소수지와 네트웍 해석

A carbon budget model was constructed and analyzed for the Bangjukpo surf zone ecosystem in southern Korea by using the NETWRK. The model consists of 11 living and 1 non-living groups. Using boxes and arrows, a topological map was created to depict biomasses of each group and exchange rates between them. The system includes primary producers of phytoplankton and benthic algae, primary consumers of particle feeding zooplankton, carnivorous zooplankton, meiobenthos, malacostracans and bivalves, and top consumers of detrivorous, omnivorous, carnivorous and piscivorous fishes. The surf zone ecosystem was analyzed by means of network analysis, showing total system throughput of development capacity of ascendancy value of Finn cycling index of and internal relative ascendancy of These results were compared with similar data from other systems.

Effects of background concentrations of Aureococcus anophagefferens (brown tide) on growth and feeding in the bivalve Mercenaria mercenaria

Much research on the toxic alga Aureococcus anophagefferens (brown tide) has focused on its effects on bivalve suspension feeding, but less is known about how brown tide influences bivalve growth. This study examined the extent to which background levels, defined as concentra- tions too low for toxicity to inhibit bivalve feeding, of A. anophagefferens influenced the growth and feeding physiology of northern quahogs Mercenaria mercenaria compared to other phytoplankton common to Long Island, New York, waters. Juvenile quahogs were fed either unialgal cultures of A. anophagefferens, non brown tide species, or diets mixed with background levels of brown tide. Absorption efficiency (AE) was determined using the 14 C: 51 Cr dual-tracer method, and growth was determined by overall biomass change. Results showed that unialgal diets resulting in the highest AE, specifically Isochrysis galbana and Thalassiosira pseudonana, were associated with rapid M. mercenaria growth. Conversely, Nitzschia closterium resulted in a comparatively low AE and a loss in quahog biomass. Diets mixed with brown tide resulted in a significantly lower AE than the cor- responding unialgal diet for all phytoplankton species except N. closterium. Additionally, mixed diets exerted a small negative influence on quahog growth compared to unialgal diets. These observations suggest that quahogs may suffer subtle, chronic effects when A. anophagefferens is present in the field at background levels. Moreover, the different responses of M. mercenaria to each experimental diet have broad implications for understanding how phytoplankton community composition may influence bivalve growth patterns in the field.

Effect of oysters Crassostrea virginica and bottom shear velocity on benthic-pelagic coupling and estuarine water quality

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 271:61-75 (2004) - doi:10.3354/meps271061 Effect of oysters Crassostrea virginica and bottom shear velocity on benthic-pelagic coupling and estuarine water quality Elka T. Porter1,*, Jeffrey C. Cornwell2, Lawrence P. Sanford2 1University of Maryland Center for Environmental Science, Chesapeake Biological Laboratory, 1 Williams Street, Solomons, Maryland 20688, USA 2University of Maryland Center for Environmental Science, Horn Point Laboratory, PO Box 775, Cambridge, Maryland 21613, USA *Email: porter@cbl.umces.edu ABSTRACT: Increasing the biomass of bivalve suspensions feeders has been proposed as a means to improve water quality in eutrophic estuaries such as the Chesapeake Bay. However, water quality impacts are likely to be determined by the balance of bivalve feeding and the deposition and sediment regeneration of nutrients from particulate organic matter. In shallow-water environments, benthic and pelagic processes are closely coupled and water flow can regulate the supply of seston to the bivalves. In addition, such flow may regulate benthic-pelagic nutrient fluxes through mass transfer limitation and resuspension. We studied the interacting effects of juvenile oysters Crassostrea virginica and bottom shear velocity on phytoplankton biomass and on nutrient regeneration in a series of three 4 wk long comparative experimental ecosystem experiments. All mesocosms had a 1000 l water volume, a 1 m2 sediment surface area, and a 1 m water-column depth, and the same realistic water-column mixing (turbulence intensity 1 cm s-1). The systems included a multi-component mesocosm with moderate bottom shear velocity (0.6 cm s-1) and 2 standard cylindrical tanks with an unrealistically low bottom shear velocity (0.1 cm s-1). Oysters shifted processes to the sediments by decreasing phytoplankton biomass without stimulating additional blooms and by increasing light penetration to the bottom. Through complex and indirect relationships, the interaction of oysters and enhanced shear velocity significantly affected microphytobenthos biomass. Light, as enhanced by the oyster feeding on phytoplankton, increased microphytobenthos biomass; a moderate bottom-shear velocity eroded the biomass. Microphytobenthos biomass decreased nutrient regeneration from the sediments to the water column and may have implications for water quality in low-energy parts of shallow-water estuaries such as Chesapeake Bay. Enhanced bottom shear in more energetic parts of shallow estuaries negatively affects microphytobenthos biomass and may increase nutrient regeneration from the sediments.Erratum KEY WORDS: Benthic-pelagic coupling · Crassostrea virginica · Shear velocity · Microphytobenthos · Chesapeake Bay Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 271. Online publication date: April 28, 2004 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2004 Inter-Research.

Effect of Experience on Prey Species Selection by the Bivalve Feeder Halla Okudai (Polychaeta: Lysaretidae)

We report on the effects of previous foraging experience on prey-selection by the bivalve feeding polychaete Halla okudai, including whether there was evidence of frequency-dependent predation. Three separate batches of H. okudai were maintained for 30 days on clams, mussels, or oysters, before being offered a choice among these three prey. Initially individuals from all three treatments consumed more clams than mussels, and no oysters. As the number of clams was depleted the polychaetes shifted their diet to include a greater proportion of mussels, but even after 20 days oysters were only eaten by polychaetes that had been previously acclimated to them. Nevertheless, polychaetes from each treatment inspected significantly more of the prey species to which they had initially been acclimated, suggesting that previous experience may increase the likelihood of certain prey being detected. When individuals of H. okudai were repeatedly offered the same prey species, handling time did not decrease (and therefore prey profitability did not increase) with experience, which may be because H. okudai paralyses its prey with toxic mucus. Since repeated experience of the same prey species gives no advantage in terms of reduced handling time, we suggest this may be why this species does not show frequency-dependent prey-selection.

Revision pre-ingestive selection efficiency definition for suspension feeding bivalves: facilitating the material fluxes modelling

The importance of the particle selective feeding of bivalves becomes more evident and it is necessary to incorporate this phenomenon into ecological models in order to reflect correctly the material fluxes inside the organism and ecosystem as well. The problems related to the modelling of organic matter selection are considered in this paper and a new definition of pre-ingestive selection efficiency is proposed. It differs from the classical one in using the organic material fraction in ingested food instead of pseudofaeces. The newly defined selection efficiency exhibits an advantage in simplified shape of experimental relationship to the organic matter fraction in seston and easier derivation of formulas related to mathematical food processing formulation.

Influence of simulated bivalve biodeposition and microphytobenthos on sediment nitrogen dynamics: A laboratory study

Suspension‐feeding eastern oysters, Crassostrea virginica, were once abundant in Chesapeake Bay and may then have exerted top‐down control on phytoplankton and also reduced turbidities, thereby increasing light available to benthic plants. Alternatively, oysters may have simply recycled inorganic nutrients rapidly back to the water column, with no long‐lasting reduction in phytoplankton biomass resulting from oyster feeding activity. To help distinguish between these scenarios, we explored changes in nitrogen fluxes and denitrification in laboratory incubations of sediment cores held under oxic and anoxic conditions in response to loading by pelletized phytoplankton cells, an experimental analog for oyster feces and pseudofeces. When organics were regenerated under aerobic conditions, typical of those associated with oyster habitat, coupled nitrification‐denitrification was promoted, resulting in denitrification of ~20% of the total added nitrogen. In contrast, under anoxic conditions, typical of current summertime conditions in main‐stem Chesapeake Bay where phytoplankton is microbially degraded beneath the pycnocline, nitrogen was released solely as ammonium from the added organics. We postulate that denitrification of particulate nitrogen remaining in oyster feces and pseudofeces may enhance nitrogen removal from estuaries. In aerobic incubations with sufficient light (70 µmol m-2 s-1), a benthic microalgal/cyanobacterial community grew that not only absorbed the inorganic nitrogen released from the added organics but also fixed N2. This result suggests that an ecosystem dominated by benthic primary production may develop in shallow waters when reduced turbidity associated with bivalve feeding increases light penetration to a level that can sustain benthic microalgal production.

Differential effects of Aureococcus anophagefferens isolates ("brown tide") in unialgal and mixed suspensions on bivalve feeding

Picoplanktonic brown tides of Aureococcus anophagefferens have had devastating effects on production of commercially exploited bivalve populations in shallow, mid-Atlantic estuaries in the United States. The toxin produced by this alga has not been chemically characterized. This study develops a bioassay using juvenile mussels, Mytilus edulis, based on the inhibitory effect of brown tide on bivalve suspension-feeding, to compare the cellular toxicity of three Long Island, New York, clonal isolates of A. anophagefferens. Two recent (1995) isolates (CCMP 1707 and 1708) from Peconic Bay proved highly toxic and caused greater than 100-fold reduction in clearance rates (CR) of juvenile mussels in unialgal and mixed suspensions with a nutritious alga, Isochrysis galbana (clone T-iso), relative to controls. A third 1986 isolate from Great South Bay (CCMP 1784) showed no detectable toxicity in 24-h trials, and may have lost its initial potency over more than a decade of laboratory culture. Identification of a non-toxic strain provides a useful tool for future research. Cultures of the toxic isolate CCMP 1708 in late-stationary growth phase were significantly more toxic than those in early-exponential phase. The threshold concentration of toxic A. anophagefferens cells that inhibits clearance on co-occurring phytoplankton species was determined for juvenile (10-mm) hard clams, Mercenaria mercenaria. Relatively low concentrations (≤35×103 to 50×103 cells ml–1) of isolate CCMP 1708 were sufficient to sharply reduce clam CR of I. galbana. Calculations based on these results suggest that, at peak historical densities of M. mercenaria in Great South Bay, removal of A. anophagefferens at low cell densities by suspension-feeding benthos could provide an effective top-down grazing control mechanism to prevent the initiation of brown tide in shallow, inner bays.