Oyster Weight Research Articles

Short communication: The boring sponge (Pione vastifica, Hancock, 1849) induces oxidative stress in the Pacific oyster (Magallana gigas, Thunberg, 1793)

Boring sponge infection affects growth, development and reduces the soft tissue weight of oysters. In this study, we investigated the effects of boring sponge on the activity of three antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GP)) in the mantle, and the production of reactive oxygen species (ROS) and potential genotoxicity in hemocytes of the Pacific oyster Magallana gigas. Our results showed a significant increase in ROS production and DNA damage in hemocytes. Notably, the activity of SOD, CAT, and GP in the mantle was not significantly affected by boring sponge infection. Collectively, these results suggest that sponge invasion may cause oxidative stress in Pacific oyster hemocytes through ROS overproduction.

Microplastic accumulation in oysters: Insights from aquaculture and laboratory conditions

Microplastics, emerging pollutants, are present in seafood and pose a potential health risk to consumers. The objective of this study was to assess microplastic concentrations in the surface water, sediments, and oysters of the Cha Va River, an aquaculture production area in southern Vietnam. Laboratory experiments were also conducted to examine rates of ingestion by and bioconcentration of microplastics in oysters. Microparticles including microplastics were measured in all samples collected from the field, and presented 9–27 items m−3 in surface water, 3300–8000 items kg−1 dry weight in sediments, and 0.67–8.33 items ind−1 or 0.02–0.33 items g−1 wet weight in oysters. Fibre shapes and blue colour were the most common while polypropylene, polyester, polyethylene, and polyethylene terephthalate acrylate, alkyd were identified. The presence of microparticles in surface water and sediment was influenced by the complex vertical motion characteristic of tidal environments whereas the microparticles in natural oysters seemed to be closer related to those in sediment than in the surface water. Laboratory experiments showed that oysters incubated in 10 and 1000 microplastics L−1 tanks accumulated 4.1 ± 2.0 and 19.0 ± 11.0 microplastics per individual, respectively. However, bioconcentration of microplastics in oysters was higher (12.37 ± 6.95) in tanks with lower microplastic concentrations than in tanks with higher microplastic concentrations (0.62 ± 0.35). It is a high potential human health risk to the local oyster-consumers because of the annually microparticle ingestion from 657 to 3942 items per person. We suggested further studies on the severity of this potential health risk and policies for minimising microplastic emissions into the environment in Vietnam.

Use of recirculation and settling chamber in synbiotic multi‐trophic culture of Crassostrea sp. with Litopenaeus vannamei

The objective of this work was to evaluate the use of recirculation and settling chamber in synbiotic multi-trophic culture of Crassostrea sp. with Litopenaeus vannamei. Four treatments were tested: MONO (shrimp monoculture); integrated multi-trophic aquaculture (IMTA) (shrimp and oysters in the same tank); IMTA-R (shrimp and oysters in adjacent tanks with recirculation) and IMTA-RS (shrimp and oysters in adjacent tanks with recirculation using settling chamber). Shrimp post-larvae (pL10) and oyster juveniles (3.12 cm) were stocked at a density of 3000 pL m−3 and 200 oysters m−2, respectively, for 42 days. The IMTA treatments showed lower values of settleable solids, when compared to monoculture. However, the excessive removal in the IMTA-RS increased the levels of TAN (1.15 mg L−1) and nitrite-N (3.47 mg L−1). The weight and yield of shrimp (1.59 g and 4.63 kg m−3) and the weight of oysters (18.05 g) was significantly higher in the IMTA. Regarding the planktonic community analysis, significant difference was observed on abundance in relation to time and among treatments, where the initial samples and IMTA treatments, with lower values, differed from the 21st and 42nd days and MONO respectively. The results indicate the benefits of the integrated multi-trophic culture application with the two species in the same productive unit for better water quality and greater shrimp growth.

Growth of oyster (Crassostrea sp.) with different stocking density in Alue Naga waters, Banda Aceh Indonesia

Oyster (Crassostrea sp.) is one of the potential bivalves that have big potency to increase Indonesian economic income. This study aimed to investigate the growth of oysters (Crassostrea sp.) with different densities, and to determine the effect of different stocking densities on growth and survival in the submerged raft method in oyster aquaculture in Alue Naga district, Indonesia. A completely randomized design model (CRD) was used with three treatments and triplications. There were three different stocking densities namely 25, 30, and 35 ind/1500 cm2. The results showed that the absolute length and weight of oysters with a density of 25, 30 and 35ind/1500 cm2 were ranged from9.49 mm and 10.60 grams, 4.83 mm and 9.13 grams and 4.62 mm and 5.76 grams respectively. It is concluded that the best growth oyster in this study was at 25 ind / 1500 cm2 stocking densities.

Heavy metals bioconcentration in Crassostrea rhizophorae: A site-to-site transplant experiment at the Potengi estuary, Rio Grande do Norte, Brazil

In this study, we analyzed the bioconcentration of Cd, Cr, Cu, Pb, Ni, and Zn in the soft tissue of transplanted oysters in two sites in the Potengi estuary for six months. Native oysters collected before and after the transplantation experiment provided the background for statistical analyses. Cd, Cr, and Ni showed a strong inverse correlation with oyster weight in both sites. Transplantation upstream of the estuary presented increasing concentrations of Zn, Cu, and Pb and condition index (CI) and decreasing trends for Cd and Ni, whereas Cr oscillated significantly. In the downstream transplantation, Cu, Pb, and Zn and the CI tended to decrease, whereas for Ni, Cd, and Cr, the concentrations increased. Spatiotemporal principal component analysis correlated these results mainly with proximity to the polluting source, seasonality, and previous exposure to heavy metals. These results helped interpret the responses provided by these biomonitors to environmental changes, whether they are natural or anthropogenic.

Remote Sensing-Driven Pacific Oyster (Crassostrea gigas) Growth Modeling to Inform Offshore Aquaculture Site Selection

Aquaculture increasingly contributes to global seafood production, requiring new farm sites for continued growth. In France, oyster cultivation has conventionally taken place in the intertidal zone, where there is little or no further room for expansion. Despite interest in moving production further offshore, more information is needed regarding the biological potential for offshore oyster growth, including its spatial and temporal variability. This study shows the use of remotely-sensed chlorophyll-a and total suspended matter concentrations retrieved from the Medium Resolution Imaging Spectrometer (MERIS), and sea surface temperature from the Advanced Very High Resolution Radiometer (AVHRR), all validated using in situ matchup measurements, as input to run a Dynamic Energy Budget (DEB) Pacific oyster growth model for a study site along the French Atlantic coast (Bourgneuf Bay, France). Resulting oyster growth maps were calibrated and validated using in situ measurements of total oyster weight made throughout two growing seasons, from the intertidal zone, where cultivation currently takes place, and from experimental offshore sites, for both spat (R-2 = 0.91; RMSE = 1.60 g) and adults (R-2 = 0.95; RMSE = 4.34 g). Oyster growth time series are further digested into industry-relevant indicators, such as time to achieve market weight and quality index, elaborated in consultation with local producers and industry professionals, and which are also mapped. Offshore growth is found to be feasible and to be as much as two times faster than in the intertidal zone (p < 0.001). However, the potential for growth is also revealed to be highly variable across the investigated area. Mapping reveals a clear spatial gradient in production potential in the offshore environment, with the northeastern segment of the bay far better suited than the southwestern. Results also highlight the added value of spatiotemporal data, such as satellite image time series, to drive modeling in support of marine spatial planning. The current work demonstrates the feasibility and benefit of such a coupled remote sensing-modeling approach within a shellfish farming context, responding to real and current interests of oyster producers.

Influence of some ecological factors on the filtration intensity of the oyster (ostrea edulis l.)

The quantitative regularities of filtration of the Black Sea oyster are studied depending on a number of environmental factors. The influence of food concentration on the filtration activity of mollusks is considered. The dependences of the filtration rate on the body weight of oysters for different temperature regimes were determined, and seasonal changes in its intensity in the Kerch Strait and the Donuzlav estuary were characterized. The influence of water salinity on the filtration activity of this type of mollusks has been established.

Futuristic Ocean Acidification Levels Reduce Growth and Reproductive Viability in the Pacific Oyster (&lt;i&gt;Crassostrea gigas&lt;/i&gt;)

In this study, we investigated the effects of futuristic pH because of climate change on the growth and reproductive viability of the Pacific oysters. The futuristic pH levels to which adult oysters were exposed are 7.5 and 7.8 (as extreme case) and 8.1 (as moderate case), with pH 8.2 serving as the control. We monitored growth and reproductive viability over a four-week exposure period. The reproductive viability of the oysters exposed to each pH level were assessed based on the sperm motility and egg viability. Throughout the exposure period, the induced acidified nature of each treatment aquaria was maintained. Data obtained from this investigation revealed significant decrease in weight of oysters exposed to pH 7.5 and 7.8 compared to the groups exposed to pH levels 8.1 and 8.2 (p &lt; 0.05). Groups of oysters exposed to pH 7.5 recorded as much as 10.49% decrease in weight, with specific growth rate (SGR) of -0.4 %/day. Reproductive viability was significantly compromised in groups exposed to pH 7.5 and 7.8 as evident with reduced sperm motility and percentage of ruptured eggs in these groups of oysters. We therefore postulate that climate change will have significant impact on the recruitment of oysters in coastal waters as growth and reproduction will be impaired at extreme levels of futuristic ocean acidification.Keywords: Ocean acidification, climate change, growth, reproductive viability, Crassostrea gigas

Phenotype plasticity, local adaptation, and biofouling influence on growth of the pearl oyster Pinctada margaritifera: A common garden approach

The purpose of our study is to investigate (1) the influence of phenotype plasticity and local adaptation on pearl-oyster physiology by testing the persistence of growth differentiation of two pearl oyster populations (Arutua and Mangareva) in common garden experiment; (2) to quantify the influence of biofouling development on the growth of each pearl oyster population. According to our observations, the growth rate in terms of total oyster weight suggested better growth performance of the pearl oyster Pinctada margaritifera in Mangareva (0.21–0.24 ± 0.01 g.day−1) than Arutua (0.14–0.15 ± 0.01 g.day−1). However, similar growth performances are observed at the Vairao common garden site for oyster stocks from Mangareva (0.07 ± 0.01 mm.day−1 or 0.15 ± 0.01 g.day−1) and Arutua (0.07 ± 0.01 mm.day−1 or 0.13 ± 0.01 g.day−1). Our results suggest that growth performance variability observed at the pearl farming sites of Arutua and Mangareva is due more to phenotypic plasticity than to local adaptation. This result thus accords a major importance to site selection for the pearl farming optimization process.Biofouling dynamics on Pinctada margaritifera shells differed radically between Arutua and Mangareva sites. In Arutua, biofouling colonization was relatively slow (0.016 g.oyster−1.month−1) and was mainly composed of sponges and bivalves. On Mangareva, the colonization process appeared faster and more continuous over the study period (0.15–0.18 g.oyster−1.month−1) and the biofouling community was dominated by tunicates. On the basis of our results obtained on growth performance between cleaned and uncleaned stock in Arutua and Mangareva, biofouling development after 14–15 months of colonization does not appear to have any negative effect on P. margaritifera growth. Due to the high cost of biofouling management in pearl farming facilities, our results suggest once more that reconsideration of the pearl farming management process is needed.

Response to selection for growth in three selected strains of the Pacific oyster Crassostrea gigas

Applying successive high selection pressures in fecund aquatic animals can easily lead to high increases in inbreeding and, consequently, to reductions in fitness and long-term genetic progress. The Pacific oyster Crassostrea gigas is one of the most commercially important aquaculture species worldwide. C. gigas from three cultured stocks in China, Japan and Korea were used to establish three mass-selected strains for fast growth, and a positive response to selection for fast growth was observed in the first two generations of these strains. To determine whether continuous progress can be achieved by selection for growth, we evaluated response to selection for the eighth to tenth generations of the three breeding strains. At grow-out stage, a genetic gain of 8.8–15.2%, selection response of 0.506–0.786 and realized heritability of 0.275–0.420 for shell height were observed in the selective breeding strains after seven to nine generations of selection. For body weight of oysters at grow-out stage, an average of 8.12–12.47% in genetic gains and 0.358–0.706 in selection responses were also obtained in the three mass-selected strains. The current response to selection for growth obtained in the eighth- to tenth-generation selection strains suggests that a large amount of genetic variance still remains in the selected strains and there is a potential for sustained genetic improvement in growth-related traits in these strains through selective breeding. The results obtained in this study provides important information for future breeding programmes for C. gigas.

Alga diet formulation – An attempt to reduce oxidative stress during broodstock conditioning of Pacific oysters

The Pacific oyster Crassostrea gigas is among the most frequently cultured aquaculture species worldwide. In bivalve aquaculture, some environmental factors may induce the production of Reactive Species of Oxygen (ROS) that besides causing injuries to several vital cellular components, may lead to inflammatory processes. Usually, antioxidant enzymes of bivalves defense systems have an important role in the diminution of harmful effects of ROS. However sometimes it is not enough to restore the oxidative balance, being required an additional action of external antioxidant compounds.Knowing that biochemical composition of the diets may influence the physiology of bivalves, the aim of this study was to evaluate the effects of different ratios of microalgae and macroalgae on the oxidative stress responses during broodstock conditioning of C. gigas.Seven hundred and twenty oysters were divided in four dietary groups (3 tanks/diet; 60 oysters/tank). Each group was fed with one of the following diets: 100% macroalgae (Ulva rigida) (Diet 1); 50% macroalgae +50% live microalgae blend (Diet 2); 25% macroalgae +75% microalgae blend (Diet 3); or 100% microalgae blend (Diet 4). The microalgae blend comprised 33% Tisochrysis lutea and 66% diatoms (75% Skeletonema costatum + 25% Chaetoceros calcitrans). To assess diets effectiveness in the reduction of oysters oxidative stress, antioxidant capacity of the diets and the oxidative stress responses of the oysters were determined. The ABTS+, DPPH, ORAC, O2− and −NO assays were performed on diets to characterize their antioxidant capacity; Moreover, a possible anti-inflammatory effect of diets was assessed via human red blood cell (HRBC) membrane stabilization by heat induced assay. Catalase, lipid peroxidation, glutathione S-transferase and total and oxidized glutathione were quantified in the oysters to evaluate the dietary effects on the oxidative stress responses. Flesh weight of oysters fed Diet 3 and 4 was significantly higher than oysters fed with diets 1 and 2 (P ≤ .001). Results revealed that a 25% macroalgae and 75% microalgae blend (Diet 3) was the most effective dietary formulation in decreasing the oxidative stress, in terms of TG levels during the broodstock conditioning of the Pacific oysters, and in terms of NO and O2−; also exhibiting a potential anti-inflammatory effect. An additional advantage in supplementing 25% of Ulva rigida is the reduction of microalgae production costs during the broodstock conditioning of Pacific oysters.

Culture site dependence on pearl size realization in Pinctada margaritifera in relation to recipient oyster growth and mantle graft biomineralization gene expression using the same donor phenotype

Size is the most important and valuable quality of the cultured black-lip pearl, Pinctada margaritifera. As this pearl aquaculture is carried out at numerous grow-out sites, this study analyzes the environmental influence on pearl size parameters (nacre weight and thickness) in relation to the recipient oyster biometric parameters (shell thickness, height, width, and oyster weight) at harvest time. Toward this end, an experimental graft was designed by using a homogeneous donor oyster phenotype. The recipient oysters were randomly and equally transferred and reared in five commercial and contrasting grow-out locations. Overall inter-site comparisons revealed that the cultured pearl size (N = 2168) and the biometric parameters of the recipient oysters were highest for sites with warmer temperatures with low seasonal variation in comparison to the southern latitude sites. These results were supported by positive correlations between pearl nacre thickness and recipient oyster shell thickness, height, and width. In parallel, the biomineralization potential of the mantle graft was screened through four genes encoding aragonite (Pif 177, MSI60) and calcite (shematrin 9, aspein). As the gene expression levels were the same among all the donor oysters, this finding demonstrates that: 1) the pearl sac that originated from the mantle graft was not isolated from environmental variations during the culture period and 2) the phenotypic expressions of the two biomineralizing tissues in the recipient oyster were consistent (shell and pearl). In the near future, this knowledge will be helpful at the production sites of genetically selected donor oyster lines for growth produced in hatchery systems.

Partitioning behavior of perfluorinated compounds between sediment and biota in the Pearl River Delta of South China

Surface sediment and biota were collected from 12 sampling sites – seven along the Pearl River Delta and five along the Hong Kong coastline. Perfluorinated compound (PFC) concentrations were detected using a high-performance-liquid-chromatogram–tandem-mass-spectrometry system. Analytical results indicated that the total PFC concentrations were in the range of 0.15–3.11ng/g dry weight in sediments, while the total PFC concentrations in oyster and mussel samples were between 0.46–1.96 and 0.66–3.43ng/g wet weight, respectively. The major types of PFCs detected in the sediment samples were perfluorooctanesulfonic acid (PFOS) and perfluorobutanoic acid (PFBA), with concentrations ranging from low limits of quantification to 0.86±0.12ng/g dry weight and 1.50±0.26ng/g dry weight, respectively. In bivalve samples, PFOS was the dominant contaminant with concentrations ranging from 0.25±0.09 to 0.83±0.12ng/g wet weight in oysters and 0.41±0.14 to 1.47±0.25ng/g wet weight in mussels. An increase in PFC concentration was found to be correlated with increased human population density in the study areas.

Accumulation profile and seasonal variations of polychlorinated biphenyls (PCBs) in bivalves Crassostrea tulipa (oysters) and Anadara senilis (mussels) at three different aquatic habitats in two seasons in Ghana

Research has shown that some polychlorinated biphenyl congeners degrade slowly in the environment and build up in the food chain, causing a wide range of possible adverse effects to humans. In order to ascertain the nature of the situation in Ghana, polychlorinated biphenyls congener residues in Crassostrea tulipa (oysters) and Anadara senilis (mussels) at Narkwa, Ada and Anyanui in the coastal region of Ghana were determined. At Narkwa, both bivalves’ species were collected; at Ada only Anadara senilis were collected while at Anyanui, only Crassotrea tulipa were collected. The number of each bivalve species collected from each site was 80 (n=80), making up a total of 320 for the dry and the wet seasons. The PCBs were extracted with (1:1) hexane-acetone mixture and analyzed with a gas chromatogram equipped with 65Ni electron capture detector, model CP 3800 using the mixed PCBs standard of the ICES 7. Total PCBs in the bivalves ranged from 5.55 to 6.37μg/kg wet weight in mussels and 2.95–11.41μg/kg wet weight in oysters, respectively. The composition of the PCB homologues in the bivalves was dominated by tri-, hepta- and hexa-PCBs in descending order. Risk assessments conducted on the samples indicated that edible bivalves from Narkwa, Ada and Anyanui in Ghana might pose some health risk to the consumers.

Epidemiology of Bonamia ostreae infecting European flat oysters Ostrea edulis from Lake Grevelingen, The Netherlands

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 409:131-142 (2010) - DOI: https://doi.org/10.3354/meps08594 Epidemiology of Bonamia ostreae infecting European flat oysters Ostrea edulis from Lake Grevelingen, The Netherlands Marc Y. Engelsma1,*, Sonja Kerkhoff1,4, Ineke Roozenburg1, Olga L. M. Haenen1, Ad van Gool2, Wil Sistermans3, Sander Wijnhoven3, Herman Hummel3 1Central Veterinary Institute of Wageningen UR, PO Box 65, 8200 AB, Lelystad, The Netherlands 2Institute for Marine Resources and Ecosystem Studies (IMARES), PO Box 77, 4400 AB, Yerseke, The Netherlands 3Monitor Taskforce, Centre for Estuarine and Marine Ecology (NIOO-CEME), PO Box 140, 4400 AC, Yerseke, The Netherlands 4Present address: Pepscan Therapeutics BV, Zuidersluisweg 2, 8243 RC Lelystad, The Netherlands *Email: marc.engelsma@wur.nl ABSTRACT: Production of European flat oysters Ostrea edulis in the Netherlands has been hampered by the presence of the haplosporidian parasite Bonamia ostreae, which is now an enzootic species following its establishment after 1980. We analyzed histopathological data from annual shellfish disease monitoring from 1988 to 2006 to quantify prevalence of B. ostreae in flat oyster stocks of the marine Lake Grevelingen. In addition, we estimated prevalence of B. ostreae on a monthly basis with field surveys in 2003. The parasite was detected with PCR, using specific primers for B. ostreae. Prevalence of B. ostreae was analyzed relative to O. edulis density, biomass and a range of environmental parameters. B. ostreae was detected in flat oysters throughout the year with a higher prevalence in spring than in autumn, possibly due to termination of spawning and the onset of oyster growth in autumn. Although B. ostreae was detected in all oyster weight classes, prevalence was highest in the largest oysters in spring and declined disproportionately in autumn, possibly due to high mortality of large oysters before autumn, suggesting that prevalence depends on oyster age. Parasite prevalence was independent of oyster density and total biomass, but appeared to be higher after a warm autumn. Abundance of the flat oyster (infected or non-infected with B. ostreae) was negatively related to the temperature of the preceding period, suggesting that mortality in flat oysters increased at higher water temperatures. Furthermore, O. edulis appeared to be more susceptible to B. ostreae after years with lower food availability and lower salinities (<29.5). B. ostreae may weaken the competitive ability of O. edulis relative to the introduced Pacific oyster Crassostrea gigas, particularly in years with high water temperatures. KEY WORDS: Bonamia ostreae · Ostrea edulis · Oyster · Disease · Population dynamics · Environmental factors Full text in pdf format PreviousNextCite this article as: Engelsma MY, Kerkhoff S, Roozenburg I, Haenen OLM and others (2010) Epidemiology of Bonamia ostreae infecting European flat oysters Ostrea edulis from Lake Grevelingen, The Netherlands. Mar Ecol Prog Ser 409:131-142. https://doi.org/10.3354/meps08594 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 409. Online publication date: June 23, 2010 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2010 Inter-Research.

Anesthesia in Pacific oyster,Crassostrea gigas

A reliable anaesthesia and sampling protocol for Pacific oysters will enable experiments to be conducted without sacrificing animals and will facilitate successive sampling of individuals for gametogenesis studies. As no such techniques were available for Crassostrea gigas, the present study aimed to define suitable anaesthetic conditions for use with this species. Three groups of ten oysters (mean weight ± SD, 32.1±9.0 g) were anaesthetised in 5 L containers. Among different chemicals: benzocaine, eugenol and three different types of magnesium chloride (a laboratory one - Flucka - and two designed for agriculture - DEUSA International and Dead Sea Works) and concentrations tested, one laboratory (concentration: 72 g L −1 ) and one agricultural (Dead Sea Works 50 g L −1 ) type of magnesium chloride were the most effective, respectively inducing anaesthesia in 73 ± 3% and 80 ± 3% after three hours. Lower oyster weight and a two day period of starving prior to treatment significantly increased the number of anaesthetised animals. Using this protocol, losses of 0 to 10% of oysters were observed one week after anaesthesia. Increasing anaesthesia duration from 3 to 16 h resulted in a significant increase in the number of anaesthetised oysters (from 50 ± 10 to 97 ± 7%) but no increase in mortality (7 ± 11%). On the other hand, reducing water temperature from 19.5 ◦ Ct o 15.3 ◦ C, resulted in a significant decrease in anaesthesia efficacy. A reliable anaesthesia protocol was developed: 100% of Pacific oysters are anaesthetised using 50 g L −1 MgCl2 Dead Sea Work for a 16 h duration. This long duration facilitates tissue sampling and does not increase the working time needed. This protocol was validated by monthly anaesthesia and gonad sampling during a three month period with the loss of only a single oyster. It can thus be used for routine applications.

Monthly variation of condition index, energy reserves and antibacterial activity in Pacific oysters, Crassostrea gigas, in Stansbury (South Australia)

This paper investigates the temporal responses of 2-year old Crassostrea gigas to environmental changes in Stansbury, South Australia from September 2005 to October 2006. A total of 360 oysters were grown in one-line baskets on the farm using six replicates that were sampled monthly. A range of environmental parameters were assessed and correlated against biological indicators for oyster condition, metabolism and antimicrobial activity. Food availability by chlorophyll a, was low throughout the study period (0.5–1.5 µg L − 1 ) and was significantly correlated to phosphorus concentrations. The condition index and shell weight of oysters significantly increased over the year, with the condition index dropping after spawning but then recovering within one month. Significant temporal variation in energy storage and utilization were observed in different tissues over the year. Glycogen in the mantle tissue was influenced by reproduction and correlated to chlorophyll a levels, but not in the gill or adductor muscle. The mantle glycogen and gill protein reached the lowest level in February when spawning occurred and presented evidence for seasonal variation in oyster metabolic activity. However, mantle and adductor muscle proteins did not drop after spawning indicating that these proteins contribute little to gametogenesis. Hemolymph protein was negatively correlated to water temperature and chlorophyll a, reaching the lowest level during summer. Hemolymph antibacterial activity significantly decreased after spawning, implying that the period of post-spawning is critical for oyster health. This study revealed trade-offs in the energy budget between immune resistance, growth, and reproduction. The results indicate that in a lean water environment, spawning events significantly regulate metabolic and immune capacities of oysters and a second year of rearing increased meat and shell weight but not the shell length. These findings are applicable to the management and development of oyster aquaculture within temperate southern hemisphere.

INTRAPOPULATIONAL VARIATION IN CRASSOSTREA VIRGINICA (GMELIN 1971) IS ASSOCIATED WITH THE HOST SIZE BUT NOT WITH DISEASE STATUS OR DEVELOPMENTAL STABILITY

Vibrio vulnificus is an important human pathogen, which occurs naturally in estuarine waters and in large numbers in oysters. The levels of V. vulnificus in shellfish vary greatly, and the causes of this variation are not well understood. A protozoan parasite, Perkinsus marinus, is a pathogen of oysters, which was earlier suggested to increase susceptibility of oysters to bacterial infections. A goal of our study is to determine whether the presence of P. marinus plays a role in determining the incidence or magnitude of V. vulnificus infection in oysters. We also used fluctuating asymmetry (FA) of shell weight as an indicator of developmental instability and thus of microbially-induced physiological stress in oysters. We harvested 155 adult oysters (Crassostrea virginica) from a small environmentally homogeneous site in North Carolina, and examined them for V. vulnificus and P. marinus infections. V. vulnificus and P. marinus were detected in 88% and 73% of the oysters, respectively. The incidence of the two pathogens in these oysters was independent, with no greater tendency to infection by V. vulnificus in oysters infected by P. marinus and vice versa. V. vulnificus loads per g tissue weight varied by over four orders of magnitude in oysters of the same size, weight and age, which were harvested from this single habitat. V. vulnificus loads were found to be unaffected by age of oysters (and thus by the length of exposure to this pathogen). On the contrary, there was a significant decrease in both incidence of V. vulnificus infection and tissue loads of this bacterium with the host weight, possibly indicating growth dilution. Infection with V. vulnificus or P. marinus did not affect FA of shell weight in oysters. Overall, our findings suggest that infection by P. marinus does not predict V. vulnificus loads in C. virginica, nor did oysters infected with either of these pathogens exhibit physiological stress that results in developmental instability.

Evaluation of Two Off-Bottom Oyster, Crassostrea virginica, Culture Methods for Use in Oyster Gardening in Alabama

Three sample sites on the north side of Dauphin Island, Alabama, were used to evaluate two different types of floats, Taylor (surface area of 0.74 m2) and Eastfields (surface area of 0.35 m2), for the culture of oysters, Crassostrea virginica, for oyster gardening. Three replicated treatments containing 1,014, 676, or 338 oysters/m2 were stocked into Taylor and Eastfields floats. Growth and survival of oysters in each float type were compared and correlated with water quality parameters (temperature, dissolved oxygen, and salinity) for 36 weeks. Oysters in the Eastfields floats demonstrated greater total growth at all densities than oysters in Taylor floats. Survival of oysters was similar in each float type. Average survival of oysters ranged from 30.1% to 56.4% among the three treatments and two float types. There was a very weak positive correlation (r = 0.30) between temperature and mortality, and a moderate positive correlation (r = 0.70) between temperature and growth in both types of floats. The Eastfields floats required more maintenance and were less durable than Taylor floats. However, the Taylor floats were cumbersome and became too heavy to lift without mechanical assistance due to biofouling and the weight of oysters. Modifications and a new cage design have been developed (www.mobilebaynep.com) as a result of these design disadvantages in Eastfields and Taylor floats.

Identification of a new type of ecological hazard of chemicals: inhibition of processes of ecological remediation.

Some approaches to solving the problem of environ-mental pollution are based on bioremediation and phy-toremediation of contaminated aquatic ecosystems.Many ecological processes causing self-purification ofwater in ecosystems were reviewed in the precedingworks [1, 2]. The aggregate of these processes consti-tutes a system of remediation (self-purification). To acertain extent, the importance of the processes of eco-logical remediation in natural ecosystems is compara-ble with that of the processes of repair, which take placeat the molecular genetic level. Indeed, the processes ofthe two types facilitate stabilization of biological sys-tems. The aggregate of natural processes of ecologicalremediation includes water filtration by hydrobionts,activity of microbial destructors of pollutants, and otherphenomena [1, 2].There are many publications on the identification,analysis, and classification of dangerous anthropogenicimpacts on organisms, populations, ecosystems, andthe biosphere [3–11].The goal of this work was to identify and character-ize essential elements of a new type of ecological haz-ard of chemical pollution of water, which includes inhi-bition of important processes of ecological remediationof ecosystems (water filtration by hydrobionts). Thefirst steps in this direction were made in [1, 7, 8].The effects of some synthetic washing mixtures(SWMs) on the filtration activity of various bivalvemollusks were studied in this work to provide a deeperinsight into the mechanisms of anthropogenic impact ofmixed chemical preparations.Experiments were performed using mollusks (oys-ters), Crassostrea gigas Thunberg, and a cell suspen-sion of Saccharomyces cerevisiae [7]. Mollusks wereobtained from the Department of Mariculture, Instituteof Biology of Southern Seas, National Academy of Sci-ences of Ukraine. The experimental procedure wasdescribed in more detail in [7]. The SWM Lanza-Automat was tested. This washing mixture includessurfactants, water softeners, enzymes, optical bleachpowder, and odorants. Lanza-Automat is produced byBenckiser.Mollusks were incubated in water at 23.4 ° C. Theoptical density (OD) of the cell suspension was simul-taneously measured in three variants (A, B, and C).Two variants (B and C) were control. The cells of S. cerevisiae were uptaken from water by mollusks dur-ing biological filtration. This caused a decrease in ODof the suspension of algae in the experimental tank con-taining mussels. The initial concentration of the S. cer-evisiae cells added to all tanks (A, B, and C) was thesame (100 mg dry weight per l). The volume of seawa-ter (from the Bay of Sevastopol, the Black Sea) in eachtank was 500 ml. Mollusks were placed in tanks A andB (ten specimens in each). The overall wet weight ofoysters (with shell) in tanks A and B was 52.6 and49.0 g, respectively. The mean weight of one specimenin tanks A and B was 5.26 and 4.9 g, respectively. TankA contained mollusks, cells of S. cerevisiae , and SWM(20 mg/l). Tank B contained mollusks and a suspensionof the S. cerevisiae cells but did not contain SWM. TankC contained only the suspension of S. cerevisiae with-out oysters and SWM. Optical density was measured at550 nm (optical path length, 10 mm) using an SF-26LOMO spectrophotometer. Spectrophotometric read-ings were rounded off to the second decimal place.During the experiment, the process of water filtra-tion by oysters caused a decrease in the value of OD invariant A (in the presence of SWM) from 0.27 to 0.15(Table 1). Under otherwise identical conditions in vari-ant B (with mollusks but without SWM; control 1),there was a decrease in the value of OD from 0.18 to0.08. Therefore, the rate of medium turbidity decreasein the presence of SWM in the incubation medium wassignificantly lower than in control 1 (variant B). In theabsence of mollusks (variant C), the optical density ofthe cell suspension remained almost invariable duringthe experiment (variant C (control 2) in Table 1).The value of the effect on elimination efficiency(EEE) was calculated to obtain quantitative estimatesof the extent of influence of chemicals on the rate of fil-tration and elimination of particles from water [7]. Thevalue of EEE depended on the experiment duration and