Showing papers on "Oyster published in 2005"

Introduction of Non-Native Oysters: Ecosystem Effects and Restoration Implications

Abstract: ▪ Abstract Oysters have been introduced worldwide to 73 countries, but the ecological consequences of the introductions are not fully understood. Economically, introduced oysters compose a majority of oyster harvests in many areas. Oysters are ecosystem engineers that influence many ecological processes, such as maintenance of biodiversity, population and food web dynamics, and nutrient cycling. Consequently, both their loss, through interaction of overharvest, habitat degradation, disease, poor water quality, and detrimental species interactions, and their gain, through introductions, can cause complex changes in coastal ecosystems. Introductions can greatly enhance oyster population abundance and production, as well as populations of associated native species. However, introduced oysters are also vectors for non-native species, including disease-causing organisms. Thus, substantial population, community, and habitat changes have accompanied new oysters. In contrast, ecosystem-level consequences of oyste...

Outbreak of Vibrio parahaemolyticus gastroenteritis associated with Alaskan oysters.

Abstract: background Vibrio parahaemolyticus, the leading cause of seafood-associated gastroenteritis in the United States, typically is associated with the consumption of raw oysters gathered from warm-water estuaries We describe a recognized outbreak of V parahaemolyticus infection associated with the consumption of seafood from Alaska methods After we received reports of the occurrence of gastroenteritis on a cruise ship, we conducted a retrospective cohort study among passengers, as well as active surveillance throughout Alaska to identify additional cases, and an environmental study to identify sources of V parahaemolyticus and contributors to the outbreak results Of 189 passengers, 132 (70 percent) were interviewed; 22 of the interviewees (17 percent) met our case definition of gastroenteritis In our multiple logistic-regression analysis, consumption of raw oysters was the only significant predictor of illness; the attack rate among people who consumed oysters was 29 percent Active surveillance identified a total of 62 patients with gastroenteritis V parahaemolyticus serotype O6:K18 was isolated from the majority of patients tested and from environmental samples of oysters Patterns on pulsed-field gel electrophoresis were highly related across clinical and oyster isolates All oysters associated with the outbreak were harvested when mean daily water temperatures exceeded 150°C (the theorized threshold for the risk of V parahaemolyticus illness from the consumption of raw oysters) Since 1997, mean water temperatures in July and August at the implicated oyster farm increased 021°C per year (P<0001 by linear regression); 2004 was the only year during which mean daily temperatures in July and August at the shellfish farm did not drop below 150°C conclusions This investigation extends by 1000 km the northernmost documented source of oysters that caused illness due to V parahaemolyticus Rising temperatures of ocean water seem to have contributed to one of the largest known outbreaks of V parahaemolyticus in the United States

The Potential for Created Oyster Shell Reefs as a Sustainable Shoreline Protection Strategy in Louisiana

Abstract: Coastal protection remains a global priority. Protection and maintenance of shoreline integrity is often a goal of many coastal protection programs. Typically, shorelines are protected by armoring them with hard, non-native, and nonsustainable materials such as limestone. This study investigated the potential shoreline protection role of created, three-dimensional Eastern oyster (Crassostrea virginica) shell reefs fringing eroding marsh shorelines in Louisiana. Experimental reefs (25 × 1.0 × 0.7 m; intertidal) were created in June 2002 at both high and low wave energy shorelines. Six 25-m study sites (three cultched and three control noncultched) were established at each shoreline in June 2002, for a total of 12 sites. Shoreline retreat was reduced in cultched low-energy shorelines as compared to the control low-energy shorelines (analysis of variance; p < 0.001) but was not significantly different between cultched and noncultched sites in high-energy environments. Spat set increased from 0.5 ± 0.1 spat/shell in July 2002 to a peak of 9.5 ± 0.4 spat/shell in October 2002. On average, oyster spat grew at a rate of 0.05 mm/day through the duration of the study. Recruitment and growth rates of oyster spat suggested potential reef sustainability over time. Small fringing reefs may be a useful tool in protecting shorelines in low-energy environments. However, their usefulness may be limited in high-energy environments.

Introduced Pacific oysters (Crassostrea gigas) in the northern Wadden Sea: Invasion accelerated by warm summers?

Abstract: Among the increasing number of species introduced to coastal regions by man, only a few are able to establish themselves and spread in their new environments. We will show that the Pacific oyster (Crassostrea gigas) took 17 years before a large population of several million oysters became established on natural mussel beds in the vicinity of an oyster farm near the island of Sylt (northern Wadden Sea, eastern North Sea). The first oyster, which had dispersed as a larva and settled on a mussel bed, was discovered 5 years after oyster farming had commenced. Data on abundance and size-frequency distribution of oysters on intertidal mussel beds around the island indicate that recruitment was patchy and occurred only in 6 out of 18 years. Significant proportions of these cohorts survived for at least 5 years. The population slowly expanded its range from intertidal to subtidal locations as well as from Sylt north- and southwards along the coastline. Abundances of more than 300 oysters m−2 on mussel beds were observed in 2003, only after two consecutive spatfalls in 2001 and 2002. Analyses of mean monthly water temperatures indicate that recruitment coincided with above-average temperatures in July and August when spawning and planktonic dispersal occurs. We conclude that the further invasion of C. gigas in the northern Wadden Sea will depend on high late-summer water temperatures.

Herpes virus in juvenile Pacific oysters Crassostrea gigas from Tomales Bay, California, coincides with summer mortality episodes

Abstract: Pacific Crassostrea gigas and eastern C. virginica oysters were examined between June 2002 and April 2003 from 8 locations along the east, west and south USA coasts for oyster herpes virus (OsHV) infections using the A primer set in a previously developed PCR test. Only surviving Pacific oysters from a mortality event in Tomales Bay, California, USA, where annual losses of oysters have occurred each summer since 1993, were infected with a herpes-like virus in 2002. PCR examination using template amounts of both 50 and 500 ng were essential for OsHV detection. Sequence analysis indicated that the Tomales Bay OsHV was similar to that identified in France with the exception of a single base pair substitution in a 917 bp fragment of the viral genome. However, unlike the French OsHV-1, the Tomales Bay OsHV did not amplify with the primer pair of a second OsHV-1 PCR assay, suggesting that further characterization of these viruses is warranted. No evidence of Cowdry type A viral infections characteristic of herpes virus infections or other pathogens were observed in OsHV-infected oysters. Hemocytosis, diapedesis and hemocyte degeneration characterized by nuclear pycnosis and fragmentation were observed in infected oysters, which is consistent with previous observations of OsHV infections in France. Together these data suggest that OsHV may be associated with the annual summer Pacific oyster seed mortality observed in Tomales Bay, but establishment of a causal relationship warrants further investigation.

The comparative roles of suspension-feeders in ecosystems

Abstract: Modeling particle selection efficiency of bivalve suspension feeders.- Field measurements on the variability in biodeposition and estimates of grazing pressure of suspension-feeding bivalves in the northern Baltic Sea.- Can bivalve suspension-feeders affect pelagic food web structure?- Motile suspension-feeders in estuarine and marine ecosystems.- Impact of suspension-feeding nekton in freshwater ecosystems: patterns and mechanisms.- Influence of eastern oysters on nitrogen and phosphorous regeneration in Chesapeake Bay, USA.- How does estimation of environmental carrying capacity for bivalve culture depend upon spatial and temporal scales?- Impact of increased mineral particle concentration on Acartia clausi (Copepoda) behaviour, suspension feeding and reproduction.- Suspension-feeders as factors influencing water quality in aquatic ecosystems.- Neoplasia in estuarine bivalves: effect of feeding behaviour and pollution in the Gulf of Gdansk (The Baltic Sea, Poland).- Bivalves as biofilters and valuable by-products in land-based aquaculture systems.- Significance of suspension feeder systems on different spatial and temporal scales.- Invaders in suspension-feeding systems: variations along the regional environmental gradient and similarities between large basins.- Contrasting distribution and impacts of two freshwater exotic suspension-feeders, Dreissena polymorpha and Corbiculafluminea.- Functional changes in benthic freshwater communities after Dreissena polymorpha (Pallas) invasion and consequences for filtration.- Does the introduction of the Pacific oyster Crassostrea gigas lead to species shifts in the Wadden Sea?- One estuary, one invasion, two responses: phytoplankton and benthic community dynamics determine the effect of an estuarine invasive suspension-feeder.- Development of human impact on suspension-feeding bivalves in coastal soft-bottom ecosystems.- Oyster reefs as complex ecological systems.- Synthesis/Conclusions.- Index .

Prevalence of Salmonella spp. in oysters in the United States.

Abstract: Food-borne diseases such as salmonellosis can be attributed, in part, to the consumption of raw oysters. To determine the prevalence of Salmonella spp. in oysters, oysters harvested from 36 U.S. bays (12 each from the West, East, and Gulf coasts in the summer of 2002, and 12 bays, four per coast, in the winter of 2002-2003) were tested. Salmonella was isolated from oysters from each coast of the United States, and 7.4% of all oysters tested contained Salmonella. Isolation tended to be bay specific, with some bays having a high prevalence of Salmonella, while other bays had none. Differences in the percentage of oysters from which Salmonella was isolated were observed between the summer and winter months, with winter numbers much lower probably due to a variety of weather-related events. The vast majority (78/101) of Salmonella isolates from oysters were Salmonella enterica serovar Newport, a major human pathogen, confirming the human health hazard of raw oyster consumption. Contrary to previous findings, no relationship was found between the isolation of fecal coliforms and Salmonella from oysters, indicating a necessity for specific monitoring for Salmonella and other pathogens rather than the current reliance on fecal coliform testing.

Oyster Reef Habitat Restoration: Relationships Between Oyster Abundance and Community Development based on Two Studies in Virginia and South Carolina

Abstract: Most Atlantic and Gulf coast U.S. states with an oyster fishery have operated some form of oyster reef enhancement program over the past 50 years. Although programs were initially only directed at oyster fisheries augmentation, recent emphasis has shifted to include the restoration of their ecological functions. Furthermore, many of these programs are managed by environmental organizations or state agencies not traditionally involved in fisheries management or research, but rather in ecological restoration, monitoring, and/or environmental education. A simple assessment of shellfish meetings over the past five years, including the inaugural Restore America's Estuaries meeting from which this paper is derived revealed more than 300 presentations related to oyster restoration, with fewer than 25% focused solely on oyster fishery restoration. Unfortunately, many of those efforts lacked well-defined success criteria, with progress often judged using fisheries-based metrics such as market-sized (generally 75 mm or 3) oysters. Here we discuss our findings as they relate to the value of alternative restoration metrics and associated success criteria using data from two very different systems and approaches: one conducted in Virginia's lower Chesapeake Bay (Rappahannock River), based on data from a two-year program utilizing subtidally constructed reefs of different reef scale, and the other a long-term study in South Carolina focusing on intertidal reefs. For each system, we compared newly created reef structures, relating oyster abundance and size to resident species abundance and biodiversity over time. Our results revealed positive correlations between several community descriptors and the size and density of oysters on the reefs. Of the 15 significant (and 5 marginally insignificant) correlations observed out of a total of 78 examined across both studies, all but one were positive. The exception was for epifaunal invertebrate diversity vs. oyster biomass on the Rappahannock reefs. Despite these numerous positive correlations, none indicated that market-sized oysters are a prerequisite for supporting an abundant and diverse community. For example, intertidal oysters >75 mm in South Carolina typically make up of all reef oysters, with a maximum of 18%. Finally, until we have a more thorough understanding of the interactions between individual species and the mechanisms linking oyster populations and reef community attributes, we propose that oyster abundance/size structure be used for assessments. Future studies need to develop and evaluate restoration progress using a combination of standardized criteria that can be applied to reef success over a wide geographical range and surrogate or indirect ecological measures (e.g., filtering, habitat use).

One-year monitoring survey of organic compounds (PAHs, PCBs, TBT), heavy metals and biomarkers in blue mussels from the Arcachon Bay, France

Abstract: Marine mussels Mytilus sp. were transplanted on a monthly basis in cages over one year to oyster farms and harbours in the Arcachon Bay (France) in order to assess the water quality of the bay. Contaminant levels (organotin compounds, trace metals, PCBs and PAHs) were measured in tissues of transplanted mussels and mussels from a reference station, along with physiological parameters of the mussels (condition indexes, lipid content and dry weight). Four biomarkers (AChE: acetylcholinesterase activity, GST: gluthathione S-transferase activity, CAT: catalase activity and TBARS: thiobarbituric acid-reactive substance content) were also monitored. The remote stations monitored (oyster parks) exhibited no accumulation pattern of pollutants. Their respective concentrations therefore constitute a background level of the contamination in the bay ([TBT] = 30 ng Sn g−1 dw, [ΣHAPs] = 100 ng g−1 dw, [ΣPCBs] = 35 ng g−1 dw). The elevated chemical contamination of the largest harbour of the bay, the Arcachon harbour, can be interpreted in terms of persistence of organotin compounds ([ΣOTs] = 1500–2000 ng Sn g−1 dw) and PAHs ([ΣHAPs] = 4500–5000 ng g−1 dw) in sediments and, to a lesser extent, of direct inputs of copper ([Cu] = 20 μg g−1 dw in harbours versus 7 in oyster parks) and petrogenic PAHs ([methylphenanthrenes] = 1600 ng g−1 dw in the dockyard versus 170 at the gas stations), related to the use of copper-based antifouling paints and to dockyard activity, respectively. However, the Arcachon Bay presents a low contamination level by PCBs and metals, including harbour stations. Furthermore, higher levels of other PAHs (particularly alkyl PAHs such as methylphenanthrenes/1600 ng g−1 dw) not included in the 16 PAHs from the EPA priority list (usually studied in biomonitoring programmes/1500 ng g−1 dw) in the Arcachon harbour underline the need to integrate these compounds in biomonitoring of highly PAH-polluted areas such as harbours in order to avoid misinterpretation of the biological responses observed. Biomarker responses were not able to discriminate the different chemical contamination levels recorded in the Arcachon Bay and rather reflected changes in environmental factors. Furthermore, the strong intraspecies variability of biological responses could be due to genetic differences of mussels from the Arcachon Bay. It is the first time that such an integrated monitoring is performed in the Arcachon Bay, also taking into account seasonal variations of chemical contents and biomarkers levels in mussel tissues.

Response of a benthic suspension feeder (Crassostrea virginica Gmelin) to three centuries of anthropogenic eutrophication in Chesapeake Bay

Abstract: Biogenic reefs built by oysters and other suspension feeders are vital components of estuarine ecosystems. By consuming phytoplankton, suspension feeders act to suppress accumulation of organic matter in the water column. Nutrient loading increases the rate of primary production, thereby causing eutrophication. As suspension feeders consume more organic matter from increasing abundance of phytoplankton, their rate of growth should also increase if they are food limited. We show here that the eastern oyster, Crassostrea virginica (Gmelin), from St. Mary's and Patuxent rivers, Chesapeake Bay, grew faster during anthropogenic eutrophication relative to C. virginica before eutrophication. Growth of shell height, shell thickness and adductor muscle increased after eutrophication began in the late 18th century. After 1860, growth decreased, perhaps reflecting the negative effects of hypoxia, harmful algal blooms, disease and fishing on oyster growth. These results are consistent with the view that an increasing supply of phytoplankton resulting from eutrophication enhanced growth of C. virginica between 1760 and 1860, before oyster reefs were degraded by destructive fishing practices between 1870 and 1930. Alternative factors, such as changes in water temperature, salinity, and fishing are less likely to be responsible for this pattern. These results have implications for restoration of oyster reefs in order to mitigate the effects of eutrophication in estuaries, as well as the paleoecological relationship between suspension feeders and paleoproductivity.

Removal of phosphate by adsorption onto oyster shell powder: kinetic studies

Abstract: Kinetic studies on the removal of phosphate by adsorption onto oyster shell powder have been investigated at 24 °C. The results showed that the equilibrium occurred in 10 min and the equilibrium data followed the Freundlich isotherm. Freundlich constants were found to be kf, 1.4 × 10−2, and n, 0.71. The phosphate removal was not influenced by pH over the range 5.0–10.5. Continuous agitation studies at 24 °C and 530 rpm reached equilibrium after 7.7 days, when 24 g dm−3 of oyster shell powder reduced the phosphate concentration from 50 to 7.0 mg dm−3. The Lagergren rate constant for the slow adsorption process was observed to be 3.81 × 10−4 dm3 min−1. Comparison with calcium carbonate, GR grade, showed that oyster shell powder and CaCO3 behave more or less in the same way. Copyright © 2004 Society of Chemical Industry

Seasonal variability of infaunal community structures in three areas of the North Sea under different environmental conditions

Abstract: Infaunal communities were studied on a monthly scale from September 2000 until May 2002 in order to investigate their seasonal variability in different areas of the North Sea: the German Bight, the Oyster Ground and the Dogger Bank. The stations were chosen to reflect a gradient in the hydrographic regime, temperature and organic matter supply. The seasonal variability in mean abundance, diversity and community structure of the infauna was mainly caused by recruitment in spring and summer. It was found to be highest in the German Bight, where fluctuations in environmental parameters were higher than in the Oyster Ground and at the Dogger Bank. Despite the dominant role of recruitment, the seasonal variability of the benthic communities seems to be a result of synergistic effects of numerous factors such as food availability, water temperature, predation and hydrodynamical stress. Among these effects, the input of high quality food to the benthic system seems to be of major importance for the seasonal variability of the benthic communities, since the faunal patterns in the German Bight and the Oyster Ground were correlated significantly with sediment parameters indicating inputs of fresh nitrogen rich organic matter, such as chlorophyll a and C/N ratio (German Bight) and fucoxanthin (Oyster Ground). This role of food quality might be intensified by high bottom water temperatures in areas such as the German Bight, where a mixed water column results in an increase of macrofauna abundance during summer, in contrast to a moderate increase of macrofauna in the Oyster Ground and the Dogger Bank which have a stratified water column. Low water temperatures in winter did not affect the mortality of the juvenile benthic fauna. It is suggested that food limitation and predation pressure caused the decrease in abundance. Thus, depending on the season, a shift from a bottom-up controlled community to a top-down controlled community might be the result at least for the juvenile macrofauna.

Factors Affecting Survival and Growth of Juvenile Freshwater Mussels Cultured in Recirculating Aquaculture Systems

Abstract: Seasonal differences in glochidial maturity, substrate, and diet were studied to determine how these factors affect the survival and growth of juvenile freshwater mussels. Comparisons were made between juveniles produced in the fall and spring of the year; cultured in sediment, sand, or without substrate; and fed either of two species of small (5–10-μm) green algae. The survival and growth of endangered juveniles of oyster mussel Epioblasma capsaeformis were compared with those of a common, seemingly more robust species, the rainbow mussel Villosa iris. The growth of rainbow mussel juveniles was significantly greater than that of oyster mussel juveniles (P < 0.001). The survival and growth of oyster mussel juveniles were significantly greater when propagated in the spring, that is, when glochidia were mature and would normally be released, than in fall (P < 0.001). Survival and growth of juveniles of both species were significantly greater when they were cultured in a sediment substratum rather t...

Occurrence of Vibrio parahaemolyticus in Two Oregon Oyster-growing Bays

Abstract: ahaemolyticus ahaemolyticus ahaemolyticus was detected in 15.0% of o was detected in 15.0% of o was detected in 15.0% of o was detected in 15.0% of o was detected in 15.0% of oyster, 20.0% of seawater of seawater of seawater of seawater of seawater, and 47.5% of sediment samples with v , and 47.5% of sediment samples with v , and 47.5% of sediment samples with v , and 47.5% of sediment samples with v , and 47.5% of sediment samples with very low levels of pathogenic str els of pathogenic str els of pathogenic str els of pathogenic str els of pathogenic strains being detected in o es ( es ( es ( es (P < 0.01), with < 0.01), with < 0.01), with < 0.01), with < 0.01), with higher densities in samples being detected in summer higher densities in samples being detected in summer higher densities in samples being detected in summer higher densities in samples being detected in summer higher densities in samples being detected in summer, especially J , especially J , especially J , especially J

Spatio-temporal variations in biological performances and summer mortality of the Pacific oyster Crassostrea gigas in Normandy (France)

Abstract: Mortality and biological performances of half-grown Crassostrea gigas were studied from spring 2000 to autumn 2001 at six instrumented stations located in two areas (Gefosse and Grandcamp) of the Bay of Veys (Normandy). Shell and meat growth, condition indexes and a macroscopic maturity index were determined on oysters deployed at the six stations in order to assess spatial variability in the influence of environmental conditions. In addition, histological and biochemical analyses were performed in order to determine the sex and establish the reproductive cycle (at all six sites) and the biochemical composition (at four stations). The data set including monthly mean temperatures and data provided by examination of 2,837 oysters were analysed by Principal Component Analysis and a Hierarchical Ascending Clustering which resulted in the formation of four clusters. The highest station on the shoreline belonged to a cluster characterized notably by low total weight due to a short immersion/feeding period, whereas all other stations belonged to another single cluster. Nevertheless, various biological differences were found between these stations, e.g. the reproductive cycle was generally synchronized throughout the bay but some differences relative to spawning occurrence were observed. In 2000, oyster mortality was higher at Gefosse than at Grandcamp, the latter being a more marine area. In 2001, oyster mortalities were significantly higher and all stations were strongly affected. In the Bay of Veys, oyster biological performances and mortality thus showed spatio-temporal variations which were worthy to be discussed.

Morphological characterization via light and electron microscopy of the hemocytes of two cultured bivalves: a comparison study between the hard clam (Meretrix lusoria) and Pacific oyster (Crassostrea gigas).

Abstract: In this study, the circulating hemocytes of the hard clam (Meretrix lusoria) were characterized by light and electron microscopic observations and simultaneously compared with those of the Pacific oyster (Crassostrea gigas). First, two cell types, granulocytes and agranulocytes, were identified based on the existence of cytoplasmic granules under light microscopy. The hemocytes were then stained and the granulocytes subclassifed into eosinophilic and basophilic granulocytes. In the oyster, three types of granulocytes were observed: eosinophilic, basophilic and an intermix. Conversely, the main type of granulocyte in the hard clam was eosinophilic granulocytes, and distinctive small and large granules were recognized. Agranulocytes in the hard clam could be subdivided into hyalinocytes and blast-like cells. Another cell type, vesicular cells, was observed in the oyster as unclassified cells. To further characterize hemocyte populations in both species, transmission electron microscopic observations were carried out. In hard clam granulocytes, abundant electron-dense cytoplasmic granules of two distinctive sizes were observed as recognized in light microscopy. However, two granulocyte types with either electron-dense or electron-lucent granules were found in the oyster, with the latter likely being basophilic granulocytes, which were seldom found in the hard clam. In addition, hemocytes with few or no cytoplasmic granules, and possessing few organelles such as mitochondria, Golgi complexes, and endoplasmic reticula, were found in the agranulocytes of both species. Blast-like cells, however, were particular in the hard clam in that they were small and had a high nucleus: cytoplasm ratio, while lacking most organelles, except mitochondria.

Assessment of Recent Habitat Conditions of Eastern Oyster Crassostrea virginica Bars in Mesohaline Chesapeake Bay

Abstract: Eastern oysters Crassostrea virginica in Chesapeake Bay, USA, have been subjected to intense harvest pressure since about 1850 and to disease epizootics since the 1950s. Combined, these processes have degraded the once extensive eastern oyster bottom; the remaining oyster shells, which are required as substrate for successful larval oyster settlement, are thus rendered increasingly susceptible to siltation. Between 1999 and 2001, we used an acoustic seabed classification system and underwater videography to assess oyster habitat conditions throughout Maryland's portion of Chesapeake Bay relative to eastern oyster recruitment and habitat restoration activities. We performed 16 surveys that covered a total of 39 km2 of bottom that were classified in 1911 as supporting productive oyster populations. Over 90% of this area has degraded from productive oyster bottom to mud, sand, or heavily sedimented oyster shell. Seventy percent of the locations we identified as containing unsedimented shell came fro...