Showing papers on "Oyster published in 2009"
TL;DR: The results suggest that temperate estuarine and coastal ecosystems are vulnerable to the expected changes in water chemistry due to elevated atmospheric CO2 and that biological responses to acidification, especially calcifying biota, will be species-specific and therefore much more variable and complex than reported previously.
Abstract: Background: Human activities have increased atmospheric concentrations of carbon dioxide by 36% during the past 200 years. One third of all anthropogenic CO2 has been absorbed by the oceans, reducing pH by about 0.1 of a unit and significantly altering their carbonate chemistry. There is widespread concern that these changes are altering marine habitats severely, but little or no attention has been given to the biota of estuarine and coastal settings, ecosystems that are less pH buffered because of naturally reduced alkalinity. Methodology/Principal Findings: To address CO2-induced changes to estuarine calcification, veliger larvae of two oyster species, the Eastern oyster (Crassostrea virginica), and the Suminoe oyster (Crassostrea ariakensis) were grown in estuarine water under four pCO2 regimes, 280, 380, 560 and 800 matm, to simulate atmospheric conditions in the pre-industrial era, present, and projected future concentrations in 50 and 100 years respectively. CO2 manipulations were made using an automated negative feedback control system that allowed continuous and precise control over the pCO2 in experimental aquaria. Larval growth was measured using image analysis, and calcification was measured by chemical analysis of calcium in their shells. C. virginica experienced a 16% decrease in shell area and a 42% reduction in calcium content when preindustrial and end of 21 st century pCO2 treatments were compared. C. ariakensis showed no change to either growth or calcification. Both species demonstrated net calcification and growth, even when aragonite was undersaturated, a result that runs counter to previous expectations for invertebrate larvae that produce aragonite shells. Conclusions and Significance: Our results suggest that temperate estuarine and coastal ecosystems are vulnerable to the expected changes in water chemistry due to elevated atmospheric CO2 and that biological responses to acidification, especially calcifying biota, will be species-specific and therefore much more variable and complex than reported previously.
353 citations
TL;DR: Results indicate oyster shell waste combusted at high temperature can be reused in biodiesel production as a catalyst and yield was more than 70% with high biodiesel purity.
322 citations
TL;DR: Field evidence is presented of a successful restoration of a large metapopulation of native oysters in the Great Wicomico River, a tributary on the western shore of the Chesapeake Bay, that is the largest of any native oyster worldwide and validates ecological restoration ofnative oyster species.
Abstract: Native oyster species were once vital ecosystem engineers, but their populations have collapsed worldwide because of overfishing and habitat destruction. In 2004, we initiated a vast (35-hectare) field experiment by constructing native oyster reefs of three types (high-relief, low-relief, and unrestored) in nine protected sanctuaries throughout the Great Wicomico River in Virginia, United States. Upon sampling in 2007 and 2009, we found a thriving metapopulation comprising 185 million oysters of various age classes. Oyster density was fourfold greater on high-relief than on low-relief reefs, explaining the failure of past attempts. Juvenile recruitment and reef accretion correlated with oyster density, facilitating reef development and population persistence. This reestablished metapopulation is the largest of any native oyster worldwide and validates ecological restoration of native oyster species.
294 citations
TL;DR: The assessment reveals that the introduction and spread of pest species are potentially important but often overlooked consequences of oyster cultivation, and the spread of pests by aquaculture activities can occur at regional scales, potentially leading to ecologically significant and irreversible changes to coastal ecosystems.
202 citations
TL;DR: Assessment of the role of live oysters in providing habitat, community metrics of resident fishes and decapod crustaceans were compared and there was little evidence to suggest that any of the decapods or fishes present were specifically selecting habitat with living oysters present.
Abstract: To assess the role of live oysters in providing habitat, community metrics of resident fishes and decapod crustaceans were compared among 3 habitat treatments: live oyster clusters; cleaned, articulated shell and sand bottom. Sampling was conducted during three seasonally wet and three seasonally dry months using 1-m2 lift nets deployed on an intertidal oyster reef in the Caloosahatchee estuary, Florida. Metrics used to assess relative habitat value included organism density, biomass and species richness. Species-specific comparisons were also made. Results indicate that organism density, biomass and richness were all greater for treatments with shell (live oyster clusters or cleaned, articulated shell) compared with the sand-bottom (no-shell) treatment. Two patterns emerged from species-specific comparisons: (1) species found in live and articulated shell (e.g., flatback mud crab, green porcelain crab) might require shelter; and (2) species found in association with articulated, cleaned shell (i...
193 citations
TL;DR: In this article, a survey of 94 oyster reefs (88 constructed, 6 natural) within 11 no-harvest sanctuaries in estuaries of central and northern North Carolina, USA, was conducted to evaluate the success of oyster reef conservation.
Abstract: Dramatic declines in populations of the eastern oyster Crassostrea virginica are a symp- tom of degradation in many US Atlantic and Gulf of Mexico estuaries. We sampled 94 oyster reefs (88 constructed, 6 natural) within 11 no-harvest sanctuaries in estuaries of central and northern North Carolina, USA, to evaluate the success of oyster sanctuaries as a conservation tool. The sanctuaries have been in existence from 3 to 30 yr; 10 sanctuaries protect constructed ('restored') oyster reefs and 1 sanctuary protects natural reefs. Measurements of vertical relief, live oyster density, recruitment, abundance of market-sized oysters, and biomass as well as disease prevalence and severity indicated that 7 of the 11 sanctuaries met criteria for minimal success by having vertical relief >20 cm in height, living oysters (>10 oysters m -2 ), and evidence of recent recruitment in 1 of 2 yr of the survey. Most reefs within the 7 sanctuaries far surpassed these relatively low benchmarks. For reefs that failed, burial by sedimentation appeared to be the primary cause in 2 sanctuaries, poor water quality (low dissolved oxygen) in 1, and poor oyster recruitment in another. All intertidal reefs were successful and had significantly higher densities of all size categories of live oysters (spat, adult, marketable size) than subtidal oyster reefs. Disease prevalence and severity were low in sanctuary reefs despite high oyster densities and increased longevity of oysters on these reefs. Pronouncements that restora- tion of the native eastern oyster is a failure prove incorrect when a decade-long history of oyster reef sanctuaries is evaluated. The proposed introduction of a non-native oyster into the US Atlantic coast estuaries cannot be justified by claiming failure of native oyster restoration in light of promising suc- cesses within sanctuaries.
183 citations
TL;DR: Larval development could be divided into an initial mixotrophic period with a lower and constant ingestion over the first days followed by an exotrophic phase characterized by a sharp increase in ingestion and a third period for larvae ≥ 300 µm during which ingestion decreased suddenly because of metamorphosis.
147 citations
TL;DR: This paper is intended to summarize potential approaches for small-scale restoration projects, including some emerging methods, and highlight the logistical benefits and limitations of these approaches.
Abstract: Reefs and beds formed by oysters such as the Eastern oyster, Crassostrea virginica and the Olympia oyster, Ostrea lurida Carpenter 1864† were dominant features in many estuaries throughout their native ranges. Many of these estuaries no longer have healthy, productive reefs because of impacts from destructive fishing, sediment accumulation, pollution, and parasites. Once valued primarily as a fishery resource, increasing attention is being focused today on the array of other ecosystem services that oysters and the reefs they form provide in United States coastal bays and estuaries. Since the early 1990s efforts to restore subtidal and intertidal oyster reefs have increased significantly, with particular interest in small-scale community-based projects initiated most often by nongovernmental organizations (NGOs). To date, such projects have been undertaken in at least 15 US states, for both species of dominant native oysters along the United States coast. Community-based restoration practitioners ...
136 citations
TL;DR: Results demonstrate that causes of C. gigas mortality are multifactorial and water quality and increased temperatures may contribute to the complex causes of significant mortalities.
115 citations
TL;DR: France is now the top producer and consumer of oysters in Europe, producing around 120,000 t of the cupped oyster C. gigas annually, and an additional 15001 of the flat oyster O. edulis, and research is making innovative contributions (selection and polyploids).
Abstract: The history of French oyster culture consists of a succession of developmental phases using different species, followed by collapses caused by diseases. The indigenous species Ostrea edulis was replaced first with Crassostrea angulata, then C. gigas. France is now the top producer and consumer of oysters in Europe, producing around 120,000 t of the cupped oyster C. gigas annually, and an additional 15001 of the flat oyster O. edulis. Cupped oysters are produced all along the French coast from natural and hatchery spat. Various structures are used to collect spat from the wild. After a growing-on period, oysters are cultivated by three main methods: (1) on-bottom culture in the intertidal zone or in deep water, (2) off-bottom culture in plastic mesh bags in the intertidal zone, or (3) suspended culture on ropes in the open sea. The main recent development is the increasing use of hatchery oyster spat, especially triploids. Almost all oyster production is sold fresh and eaten raw straight from the ...
112 citations
TL;DR: The contribution of PAH intake via oyster consumption to carcinogenic risks in humans seems to be low, and no correlation between sediment and oyster concentrations at the same sites was found.
TL;DR: While temperature regulated the time and speed of gametogenesis, results suggest that the intensity was influenced by the quantity of available food but may need further research.
Abstract: The progress of gametogenesis was studied in oysters Crassostrea gigas having the same origin (Tremblade), but cultured during 1 year in two distinctive French marine areas, the Baie des Veys and Marennes-Oleron. We assessed seasonal changes in the reproduction cycle on the basis of stereological techniques to estimate reproductive investment and measurement of gonad evolution area by quantitative histology. From a qualitative point of view, both oyster groups presented typical reproductive stages, but showed differential timing, in particular during the sequence of spawning and duration of the re-absorption stage. Oysters in Baie des Veys had a single partial spawning in August and a re-absorption stage that extended until winter. Oysters in Merennes-Oleron had a partial spawning in July and massive release of gametes during August. Spawnings in both the areas were related to maximum temperature (19°C). The quantitative analysis showed, on an annual basis, a higher reproductive investment by oysters from Baie des Veys, 86% against 53% in the other group. Larger gonads, higher gamete production, and more intensive spawning were the characteristics of oysters in Baie des Veys. Recently, the reproduction pattern and investment has been related with summer mortalities; therefore, a quantitative understanding of reproductive processes becomes necessary for C. gigas. Environmental conditions at each site may explain differences in the progress and intensity of gametogenesis. While temperature regulated the time and speed of gametogenesis, results suggest that the intensity was influenced by the quantity of available food but may need further research. However, nutrient recycling from unreleased gametes in the gonads of oysters from Baie des Vey is a factor to be considered in the results of this study.
TL;DR: Oyvlg appears to be essential for germ cell development in Crassostrea’gigas, particularly for mitotic proliferation and early meiosis, and is demonstrated for the first time that in’vivo RNA interference works efficiently in a bivalve species.
Abstract: This study investigated the potential of RNA interference, which is technically challenging in bivalve mollusc species, to assess gene function in the oyster Crassostrea gigas. We designed dsRNA targeting the oyster vasa-like gene (Oyvlg), specifically expressed in oyster germ cells. In vivo injection of oyvl-dsRNA into the gonad provokes a knockdown phenotype corresponding to germ cell underproliferation and prematurely arrested meiosis througout the organ. The most severe phenotype observed is sterile. This knockdown phenotype is associated with a decrease in Oyvlg mRNA level of between 39% and 87%, and a strong reduction in OYVLG protein, to an undetectable level. Therefore, Oyvlg appears to be essential for germ cell development in Crassostrea gigas, particularly for mitotic proliferation and early meiosis. Our results demonstrate for the first time that in vivo RNA interference works efficiently in a bivalve species, opening major perspectives for functional genetic studies.
TL;DR: Investigation of immunological activities and morphology of hemocytes of the Suminoe oyster using flow cytometry and light microscopy revealed that the granulocytes are most active in the cell phagocytosis and spontaneous reactive oxygen species (ROS) production.
TL;DR: The biologic and genomic resources available for the Pacific oyster are unparalleled by resources for any other bivalve mollusc or marine invertebrate and will be greatly leveraged by having a draft genome sequence.
Abstract: An international community of biologists presents the Pacific oyster Crassostrea gigas as a candidate for genome sequencing This oyster has global distribution and for the past several years the highest annual production of any freshwater or marine organism (42 million metric tons, worth $35 billion US) Economic and cultural importance of oysters motivates a great deal of biologic research, which provides a compelling rationale for sequencing an oyster genome Strong rationales for sequencing the oyster genome also come from contrasts to other genomes: membership in the Lophotrochozoa, an understudied branch of the Eukaryotes and high fecundity, with concomitantly high DNA sequence polymorphism and a population biology that is more like plants than any of the model animals whose genomes have been sequenced to date Finally, oysters play an important, sentinel role in the estuarine and coastal marine habitats, where most humans live, environmental degradation is substantial, and oysters suffer
TL;DR: The oyster-DEB model presented here reproduced the growth and reproduction of C. gigas very accurately and the next step will be to validate the model under contrasting coastal environmental conditions so as to confirm the accuracy of phytoplankton enumeration as a way of representing the available food that sustains oyster growth.
TL;DR: Testing the hypothesis that oyster families that had high or low survival of heat shock differ in their transcriptional responses to stress found that transcription after heat shock increased for genes putatively encoding heat shock proteins and genes for proteins that synthesize lipids, protect against bacterial infection, and regulate spawning, whereas transcription decreased for genes that mobilize lipids and detoxify reactive oxygen species.
Abstract: Sessile inhabitants of marine intertidal environments commonly face heat stress, an important component of summer mortality syndrome in the Pacific oyster Crassostrea gigas. Marker-aided selection programs would be useful for developing oyster strains that resist summer mortality; however, there is currently a need to identify candidate genes associated with stress tolerance and to develop molecular markers associated with those genes. To identify candidate genes for further study, we used cDNA microarrays to test the hypothesis that oyster families that had high (>64%) or low (<29%) survival of heat shock (43°C, 1 h) differ in their transcriptional responses to stress. Based upon data generated by the microarray and by real-time quantitative PCR, we found that transcription after heat shock increased for genes putatively encoding heat shock proteins and genes for proteins that synthesize lipids, protect against bacterial infection, and regulate spawning, whereas transcription decreased for genes for proteins that mobilize lipids and detoxify reactive oxygen species. RNAs putatively identified as heat shock protein 27, collagen, peroxinectin, S-crystallin, and two genes with no match in Genbank had higher transcript concentrations in low-surviving families than in high-surviving families, whereas concentration of putative cystatin B mRNA was greater in high-surviving families. These ESTs should be studied further for use in marker-aided selection programs. Low survival of heat shock could result from a complex interaction of cell damage, opportunistic infection, and metabolic exhaustion.
TL;DR: It is demonstrated that the invasive whelk’s distribution is causally related to a large-scale pattern of oyster mortality and the mismatch of evolutionarily based strategies among predators and prey may lead to further losses of critical habitat that support marine biodiversity and ecosystem function.
Abstract: Although invasive species often resemble their native counterparts, differences in their foraging and anti-predator strategies may disrupt native food webs. In a California estuary, we showed that regions dominated by native crabs and native whelks have low mortality of native oysters (the basal prey), while regions dominated by invasive crabs and invasive whelks have high oyster mortality and are consequently losing a biologically diverse habitat. Using field experiments, we demonstrated that the invasive whelk’s distribution is causally related to a large-scale pattern of oyster mortality. To determine whether predator–prey interactions between crabs (top predators) and whelks (intermediate consumers) indirectly control the pattern of oyster mortality, we manipulated the presence and invasion status of the intermediate and top trophic levels in laboratory mesocosms. Our results show that native crabs indirectly maintain a portion of the estuary’s oyster habitat by both consuming native whelks (density-mediated trophic cascade) and altering their foraging behavior (trait-mediated trophic cascade). In contrast, invasive whelks are naive to crab predators and fail to avoid them, thereby inhibiting trait-mediated cascades and their invasion into areas with native crabs. Similarly, when native crabs are replaced with invasive crabs, the naive foraging strategy and smaller size of invasive crabs prevents them from efficiently consuming adult whelks, thereby inhibiting strong density-mediated cascades. Thus, while trophic cascades allow native crabs, whelks, and oysters to locally co-exist, the replacement of native crabs and whelks by functionally similar invasive species results in severe depletion of native oysters. As coastal systems become increasingly invaded, the mismatch of evolutionarily based strategies among predators and prey may lead to further losses of critical habitat that support marine biodiversity and ecosystem function.
TL;DR: Observations of sediment redox potential, organic content, and ammonium release did not support hypotheses that these parameters were alone responsible for the observed differences in mortality events, and suggested a direct effect of the mud on the biologic performance of oysters cultured on the bottom.
Abstract: The purpose of this study is to investigate summer mortality of the cupped oyster, Crassostrea gigas, in relation to culture practices in the traditional oyster production region of Marennes-Oleron (France). Four oyster rearing conditions, varying culture location ("on-" or "off-bottom"), and site depth (65% to 80% daily immersion termed "deep" or 45% to 65%, termed "shallow") were studied to compare biologic performance and maturation status of oysters, in relation to sediment and water column parameters. The most severe mortality occurred in June to July in "on-bottom" reared oysters (25%), as compared with 10% mortality in "off-bottom" cultured oysters. Oysters (shell and meat) grew significantly better when reared "off-bottom" than "on-bottom." Reproductive effort was almost double in "off-bottom" reared oysters, compared with those "on-bottom"; thus, reproduction cannot be directly related to mortality in this summer mortality event. Low glycogen content recorded for both "on" and "off-bottom" reared oysters in summer, confirmed the probable lack of food and/or the overstocking in the Marennes-Oleron Bay, but did not discriminated among culture conditions. Whatever the immersion depth ("deep" or "shallow" conditions), "on-bottom" cultured oysters were adversely affected in growth, reproductive effort, and survival suggesting a direct effect of the mud (the so called "mud effect") on the biologic performance of oysters cultured on the bottom. Data from monitoring of sediment redox potential, organic content, and ammonium release did not support hypotheses that these parameters were alone responsible for the observed differences in mortality events.
TL;DR: The high concentrations of NoV in plankton samples compared to water and oyster samples were unexpected and provide new insights into the presence and distribution of human norovirus in the water environment.
Abstract: Human norovirus (NoV) has been studied extensively as an important cause of gastroenteritis outbreaks worldwide While oysters are a primary vehicle for infection, few studies have examined the wider distribution of NoV in the estuarine environment Active shellfish-harvesting areas in Georgia were examined for the prevalence, genotype diversity, and concentrations of NoV in a variety of estuarine sample types over the course of 1 year Of the 225 samples (9 oyster, 72 water, 72 63- to 200-μm plankton, and 72 >200-μm plankton) collected from 12 stations across two estuaries, 21 samples (93%) tested positive for NoV By sample type, 550% (5/9) of oysters, 83% (6/72) of water samples, 111% (8/72) of 63- to 200-μm plankton samples, and 28% (2/72) of >200-μm plankton samples were positive for human NoV The two NoV-positive >200-μm plankton samples, which contained mainly zooplankton, had the greatest quantity of NoV genomes (35 × 1013 and 17 × 1015 genomes g−1) of any sample tested The majority, 905% (19/21), of the samples tested positive for genogroup I NoV, and only 95% (2/21) of the samples tested positive for genogroup II The high concentrations of NoV in plankton samples compared to water and oyster samples were unexpected and provide new insights into the presence and distribution of human NoV in the water environment
TL;DR: Comparison of PCR assay reproducibility according to the complexity of samples revealed that seawater samples gave more reproducible quantification measures than samples from oyster homogenate, with precision of measured Ct values inferior to 0.4 and 0.6 respectively at 99% confidence.
TL;DR: Based on microbiological analysis, biochemical indices determination and sensory evaluation, shelf-life of oysters stored at 5+/-1 degrees C was determined and data showed that chitosan treatment extended the shelf- life of oyster from 8-9 days to 14-15 days.
TL;DR: An application of a 3D sediment transport model to predict the wind-induced sediment transport in Apalachicola Bay is described and indicates active sediment resuspension and transport near areas of highly productive oyster beds.
Abstract: Sediment is an important environmental factor for aquatic ecosystem and oyster productivities of Apalachicola Bay located in Florida, USA. Based on the data analysis in this study, surface wind speed is highly correlated to the turbidity of water column, which results from sediment resuspension and transport in the Apalachicola Bay. In this paper, an application of a 3D sediment transport model to predict the wind-induced sediment transport in Apalachicola Bay is described. The sediment model is coupled with a 3D hydrodynamic module in the Environmental Fluid Dynamics Code (EFDC) model that provides information on estuarine circulation and salinity transport under normal temperature conditions. The hydrodynamic model was calibrated with field observations of water levels and salinity. The sediment transport model solves the transport equation with sources and sinks terms to describe sediment deposition and resuspension. The coupled hydrodynamic and sediment transport models were used to investigate wind-induced total suspended sediments (TSS) resuspension and transport in the bay. For the period June 1-July 30, 2005 two storm events with strong winds gave model results of TSS concentrations that compared well with the field observations. Model simulations reasonably reproduce the sudden increase of sediment concentrations during the storm events. Maximum sediment concentrations in the bay during the two storm events were 10 times or more than those in the pre-storm conditions. Spatial sediment transport from model simulations indicate active sediment resuspension and transport near areas of highly productive oyster beds. The model predictions of TSS and salinity can be used as inputs to an oyster dynamic model (Wang, H., Huang, W., Harwell, M., Edmiston, L., Johnson, E., Hsieh, P., Milla, K., Christensen, J., Stewart, J., Liu, X., 2008. Modeling eastern oyster population dynamics in response to changing environment in Apalachicola Bay, Florida. Journal of Ecological Modeling 211, 77-89) to support the ecological study of oyster growth and mortality in the aquatic ecosystem of Apalachicola Bay.
TL;DR: Oyster population trends in the James River, VA from 1993 through 2006 are described using quantitative fishery independent survey data collected using a stratified random design to demonstrate remarkable stability as either high shell density + high population density associations (high:high) or low shell density - low population density Associations (low:low).
Abstract: We describe oyster population trends in the James River, VA from 1993 through 2006 using quantitative fishery independent survey data collected using a stratified random design. The 23 reefs contained in the study area cover a total of 2.41 × 107 m2 and vary in individual size from 1.26 × 104 m2 to 4.98 × 106 m2. There is a marked pattern in density of oysters among the reefs: during the study period a small group of reefs comprising 5.4% of the total area consistently contained between 25.7 and 55.5% by number and 35.8 and 54.8% by biomass of the total oyster population. The highest density reefs exhibit, with very few exceptions, mean densities well in excess of 200 oysters m-2, typically between 300 and 500 m-2, with a single maximum value of 773 oysters m-2 in 2002 coincident with the highest annual recruitment observed during the study period. Recruitment events were usually followed by very high mortality with very small percentages of the population reaching ages ≥3 y of age. A strong stoc...
TL;DR: This study confirms the presence of lectins in mucus that covers the feeding organs of oysters and suggests a new concept with regard to particle processing by suspension-feeding bivalves: specific interactions between carbohydrates on the surface of particles and lectins within the mucus mediate the selection and rejection processes.
Abstract: Despite advances in the study of particle selection in suspension-feeding bivalves, the mechanisms upon which bivalves rely to discriminate among particles have not been elucidated. We hypothesized that particle sorting in suspen- sion-feeding bivalves could be based, in part, on a biochemical recognition mechanism mediated by lectins within the mucus that covers the feeding organs. Using Crassostrea virginica, the Eastern oyster, our investigations demonstrated that lectins from oyster mucus can specifically bind several microalgal species as well as different types of red blood cells (RBC), triggering their agglutination. Agglutination of microalgal spe- cies and RBC varied with the source of mucus (gills vs. labial palps). Hemagglutination and hemagglutination inhibition as- says emphasized that mucus contains several lectins. In feed- ing experiments, Nitzschia closterium and Tetraselmis macu- lata were separately incubated with mucus before being fed to oysters. Results showed that pre-treating these microalgae with mucus significantly alters the ability of oysters to sort particles. In another experiment, oysters were fed a mixture of micro- spheres coated with either bovine serum albumin (BSA) or glucosamide-BSA. Results show that oysters preferentially ingest microspheres with bound carbohydrates, highlighting probable interactions between lectins and carbohydrates in the mechanisms of microalgae recognition. This study confirms the presence of lectins in mucus that covers the feeding organs of oysters and suggests a new concept with regard to particle processing by suspension-feeding bivalves: specific interac- tions between carbohydrates on the surface of particles and
TL;DR: In this article, the effects of pulsed freshwater events (freshet) of different magnitude, duration, and rate of change on oyster resources were examined using controlled laboratory experiments in combination with a field study.
Abstract: In coastal Louisiana, the development of large-scale freshwater diversion projects has led to controversy over their effects on oyster resources. Using controlled laboratory experiments in combination with a field study, we examined the effects of pulsed freshwater events (freshet) of different magnitude, duration, and rate of change on oyster resources. Laboratory and field evidence indicate that low salinity events (<5 psu) decreased Perkinsus marinus infection intensities. Furthermore, when salinity was low (<5 psu), parasite infection intensities continued to decrease even as temperatures exceeded 20°C. At the same time, oyster growth was positively correlated with salinity. To maximize oyster production, data indicate that both low and high salinity events will be necessary.
TL;DR: Recovery of the remnant population of O. lurida is indicated that recovery has been hampered by the removal of dense subtidal native oyster shell accumulations during exploitation, by direct competition from exotic species, and by the appearance of novel introduced Oyster shell settlement substrate in the intertidal zone.
Abstract: The Olympia oyster, Ostrea lurida Carpenter 1864,† in estuaries along the Pacific coast of North America, experienced overexploitation throughout its range in the late 1800s, resulting in commercial extinction before 1930. Significant harvest restrictions and marine reserves were established in Washington State by 1897 to protect new recruits, and harvest pressure has been negligible for the past 80 y. Nevertheless, O. lurida remains locally rare. This study focuses on the contemporary dynamics of the remnant population of O. lurida in Willapa Bay, Washington, historically home to the largest native oyster fishery on the coast, with a broad focus on factors preventing recovery. Failed recovery could be because of reproductive limitation, or to poor postrecruitment performance. In this case, reproductive limitation seems unlikely, because historical (1947 to 1983) and modern (2002 to 2006) records reveal 5-fold higher annual spatfall for O. lurida than introduced Pacific oysters (Crassostrea gigas...
TL;DR: It is concluded that crushed oyster shell can be an effective amendment to remediate organically enriched sediments in eutrophic coastal seas.
TL;DR: It is concluded that bed area is still expanding while decrease of the fraction live animals may indicate adjustment of the stock size to the local conditions.
Abstract: The Pacific oyster Crassostrea gigas was first introduced as an exotic species by oyster farmers in 1964 in the Oosterschelde estuary (SW Netherlands). The initial phase is not well documented but first natural spatfall was recorded in 1975. Excessive spatfall occurred in 1976 and this is considered the start of the expansion phase of the wild oysters. Oyster beds in intertidal and subtidal areas of the Oosterschelde estuary have been growing since. The development in the intertidal area has been reconstructed by using aerial photography, validated by ground truth in 2000–2002. In the subtidal areas extensive oyster beds have been detected by using side scan sonar; on hard substrates along the dikes coverage with oysters up to 90% locally has been recorded by scuba diving surveys. Expansion has also occurred into adjacent water bodies including the Wadden Sea. By forming resistant reefs the oysters induce structural changes in the ecosystem. It is concluded that bed area is still expanding while decrease of the fraction live animals may indicate adjustment of the stock size to the local conditions.
TL;DR: Depuration of oysters at 22 degrees C had limited effects on reducing V. parahaemolyticus or V. vulnificus in the oysters, and decreasing water temperature to 15 degrees C increased the efficacy of depuration in reducing Vibrio spp.
Abstract: This study investigated temperature effects on depuration for reducing Vibrio parahaemolyticus and Vibrio vulnificus in American oyster (Crassostrea virginica). Raw oysters were inoculated with 5-strain cocktail of V. parahaemolyticus or V. vulnificus to levels of 10(4) to 10(5) MPN (most probable number)/g and depurated in artificial seawater (ASW) at 22, 15, 10, and 5 degrees C. Depuration of oysters at 22 degrees C had limited effects on reducing V. parahaemolyticus or V. vulnificus in the oysters. Populations of V. parahaemolyticus and V. vulnificus were reduced by 1.2 and 2.0 log MPN/g, respectively, after 48 h of depuration at 22 degrees C. Decreasing water temperature to 15 degrees C increased the efficacy of depuration in reducing V. parahaemolyticus and V. vulnificus in oysters. Reductions of V. parahaemolyticus and V. vulnificus in oysters increased to 2.1 and 2.9 log MPN/g, respectively, after 48 h of depuration at 15 degrees C. However, depurations at 10 and 5 degrees C were less effective than at 15 degrees C in reducing the Vibrio spp. in oysters. Extended depuration at 15 degrees C for 96 h increased reductions of V. parahaemolyticus and V. vulnificus in oysters to 2.6 and 3.3 log MPN/g, respectively.