A novel approach to measuring chlorophyll uptake by cultivated oysters

Worms on the Cape: An integrative survey of polydorid infestation in wild and cultivated oysters (Crassostrea virginica) from Massachusetts, USA

Haemocytic and humoral activities of eastern and Pacific oysters following challenge by the protozoan Perkinsus marinus

Vibrio tubiashii is reported to be a bacterial pathogen of larval Eastern oysters (Crassostrea virginica) and Pacific oysters (Crassostrea gigas) and has been associated with major hatchery crashes, causing shortages in seed oysters for commercial shellfish producers. Another bacterium, Vibrio coralliilyticus, a well-known coral pathogen, has recently been shown to elicit mortality in fish and shellfish. Several strains of V. coralliilyticus, such as ATCC 19105 and Pacific isolates RE22 and RE98, were misidentified as V. tubiashii until recently. We compared the mortalities caused by two V. tubiashii and four V. coralliilyticus strains in Eastern and Pacific oyster larvae. The 50% lethal dose (LD50) of V. coralliilyticus in Eastern oysters (defined here as the dose required to kill 50% of the population in 6 days) ranged from 1.1 × 10(4) to 3.0 × 10(4) CFU/ml seawater; strains RE98 and RE22 were the most virulent. This study shows that V. coralliilyticus causes mortality in Eastern oyster larvae. Results for Pacific oysters were similar, with LD50s between 1.2 × 10(4) and 4.0 × 10(4) CFU/ml. Vibrio tubiashii ATCC 19106 and ATCC 19109 were highly infectious toward Eastern oyster larvae but were essentially nonpathogenic toward healthy Pacific oyster larvae at dosages of ≥1.1 × 10(4) CFU/ml. These data, coupled with the fact that several isolates originally thought to be V. tubiashii are actually V. coralliilyticus, suggest that V. coralliilyticus has been a more significant pathogen for larval bivalve shellfish than V. tubiashii, particularly on the U.S. West Coast, contributing to substantial hatchery-associated morbidity and mortality in recent years.

Suspended versus bottom oyster culture in eastern Canada: Comparing stocking densities and clearance rates

Molecular impacts of dietary exposure to nanoplastics combined with arsenic in Canadian oysters (Crassostrea virginica) and bioaccumulation comparison with Caribbean oysters (Isognomon alatus)

Wild oysters (Crassostrea virginica) contained cholesterol, 24‐methyl‐cholesta‐5, 22‐dienol, 24‐methylenecholesterol, 22‐dehydrocholesterol, 24‐methylcholesterol, 24‐ethylcholesterol, 24‐norcholesta‐5, 22‐dienol, 24‐ethylcholesta‐5, 22‐dienol and fucosterol. The same species was cultivated on a defined diet ofThalassiosira pseudonana andIsochrysis sp. The dietary algae were cultured and their sterol compositions were analyzed by gas chromatography and mass spectroscopy.T. pseudonana andIsochrysis sp. had 24‐methylenecholesterol and 24‐methyl‐cholesta‐5, 22‐dienol as their major sterols. The sterol composition of the cultivated oysters revealed the predominance of cholesterol (19%), 24‐methyl‐cholesta‐5, 22‐dienol (21%) and 24‐methylenecholesterol (46%). Therefore, oysters must be able to bioconvert phytosterols to cholesterol, concentrate dietary cholesterol, or synthesize cholesterol de novo.

An investigation of mercury-resistant bacteria was undertaken to determine their role in the accumulation of mercury in a simplified food chain. Oysters (Crassostrea virginica) were maintained in a closed system, sealed aquarium with stirred, aerated water containing 10 mug of 203-HgCl2 per liter. Uptake of 203-Hg by oysters held under control conditions was compared with that of 203-Hg uptake by oysters under similar conditions except that mercury-accumulating and mercury-metabolizing species of Pseudomonas, isolated from Chesapeake Bay, were added to the experimental oysters. After incubation for 4 days, the major portion ofthe 203-Hg in the water column was found to be associated with the microparticulate fraction, corresponding to a rise in total viable count. Mercury accumulation in the oysters was significantly higher in the gill and visceral tissue than other tissue. Mercury concentrations were 200 times greater in tissue fractions of oysters dosed with mercury-metabolizing bacteria compared with the oysters held under control conditions without mercury-metabolizing bacteria.

Modeling oyster populations. V. Declining phytoplankton stocks and the population dynamics of American oyster ( Crassostrea virginica) populations

Restoration of foundation species promises to reverse environmental degradation and return lost ecosystem services, but a lack of standardized evaluation across projects limits understanding of recovery, especially in marine systems. Oyster reefs are restored to reverse massive global declines and reclaim valuable ecosystem services, but the success of these projects has not been systematically and comprehensively quantified. We synthesized data on ecosystem services associated with oyster restoration from 245 pairs of restored and degraded reefs and 136 pairs of restored and reference reefs across 3500km of U.S. Gulf of Mexico and Atlantic coastlines. On average, restoration was associated with a 21-fold increase in oyster production (mean log response ratio=3.08 [95% confidence interval: 2.58-3.58]), 34-97% enhancement of habitat provisioning (mean community abundance=0.51 [0.41-0.61], mean richness=0.29 [0.19-0.39], and mean biomass=0.69 [0.39-0.99]), 54% more nitrogen removal (mean=0.43 [0.13-0.73]), and 89-95% greater sediment nutrients (mean=0.67 [0.27-1.07]) and organic matter (mean=0.64 [0.44-0.84]) relative to degraded habitats. Moreover, restored reefs matched reference reefs for these ecosystem services. Our results support the continued and expanded use of oyster restoration to enhance ecosystem services of degraded coastal systems and match many functions provided by reference reefs.

Feeding ability during settlement and metamorphosis in the oyster Crassostrea virginica (Gmelin, 1791) and the effects of hypoxia on post-settlement ingestion rates

The heritability of oyster (Crassostrea virginica) larval growth rate was estimated to be in the range of 0.25 to 0.50 and a significant part of this genetic variation is of the additive type. Larval growth rate and spat growth rate were found to be highly correlated. These results suggest that a selection program for faster growing larvae and spat would be successful.

Estuarine circulation and predicted oyster larval dispersal among a network of reserves

Eastern oysters (Crassostrea virginica) often undergo epizootics of MSX (Multinucleated Spore Unknown) disease, which is caused by the protozoan pathogen, Haplosporidium nelsoni. The disease has been present in oyster populations in the mid-Atlantic United States since the 1950s. During the 1980s and 1990s, it became established further north along the east coast of the United States. To investigate the factors underlying the northward progression of MSX disease, a model that simulates the host-parasite-environmental interactions was used. The model is physiologically-based and is structured around the transmission, proliferation and death rates of the parasite. Environmental conditions of temperature, salinity and oyster food supply provide the external forcing that results in variations in the biological rates. For this study, environmental data sets, both average and extreme, were obtained at a site in upper Chesapeake Bay for 1986 through 1995. This site is in the middle of one of the most productive oyster growing regions on the east coast of the United States; thus, both short-and long-term changes in the environment measured here realistically reflect conditions experienced by important oyster populations. The effect of short-term high-salinity (drought) or low-salinity (wet) conditions on MSX disease prevalence and intensity was relatively small because the average salinity regime already favors maximum parasite activity at this site. Even the extreme low salinity events were not low enough to significantly inhibit the parasite. Similarly, simulations using short-term high-temperature extremes for the same site showed only minor deviations from the average pattern because average temperatures were already high enough to support parasite development. In contrast, the measured low temperature conditions, applied for a single year, caused a dramatic reduction in parasite activity, which extended over a 2-year period. Additional simulations show that overall food supply to the host is of little consequence in determining the basic disease pattern; however, the timing of maximum food supply provided to the host, relative to specific times in the parasite life cycle, is important in determining whether or not the parasite attempts sporulation or undergoes density-independent growth. Simulations that test a sequence of changing environmental conditions show that when a year with cold winter temperatures (less than 3 °C) is followed by a year of low salinity (less than 15 ppt), prevalences and intensities of MSX disease are greatly reduced, with the disease becoming almost absent in the oyster populations; however, the disease returns when average environmental conditions return. Simulations using progressive cooling or warming conditions indicate that winter temperatures consistently lower than 3 °C limit the long-term development of MSX disease. These simulations support the suggestion that climate warming is a contributing factor to the northward spread of MSX disease.

Brevetoxin metabolism and elimination in the Eastern oyster ( Crassostrea virginica) after controlled exposures to Karenia brevis

Legare, B. and Mace, C., 2017. Mapping and classifying Eastern Oyster (Crassostrea virginica) habitat in Copano Bay, Texas, by coupling acoustic technologies. The Texas coast is characterized by an extensive array of shallow turbid embayments containing expansive oyster habitats and is home to a large Eastern Oyster (Crassostrea virginica) fishery. Mapping habitats in shallow (1–10 m), turbid environments is challenging, since direct visual access to the habitats limited. To quantify the extent of habitats, the integration of remote sensing and GIS technologies is used. The Texas Parks and Wildlife Department coupled two acoustic technologies (sidescan sonar and echosounder) to map habitats within Copano Bay, a 181-km2 shallow water embayment along the mid-Texas coast. Data were collected during 17 days from September 2013 to February 2014 and resulted in 159 km2 of sidescan imagery and 375 km of single beam echosounder data. Individual echosounder transmissions were segmented and processed in Ar...