Showing papers on "Oyster published in 2012"

The oyster genome reveals stress adaptation and complexity of shell formation

Abstract: The Pacific oyster Crassostrea gigas belongs to one of the most species-rich but genomically poorly explored phyla, the Mollusca. Here we report the sequencing and assembly of the oyster genome using short reads and a fosmid-pooling strategy, along with transcriptomes of development and stress response and the proteome of the shell. The oyster genome is highly polymorphic and rich in repetitive sequences, with some transposable elements still actively shaping variation. Transcriptome studies reveal an extensive set of genes responding to environmental stress. The expansion of genes coding for heat shock protein 70 and inhibitors of apoptosis is probably central to the oyster's adaptation to sessile life in the highly stressful intertidal zone. Our analyses also show that shell formation in molluscs is more complex than currently understood and involves extensive participation of cells and their exosomes. The oyster genome sequence fills a void in our understanding of the Lophotrochozoa.

The Pacific oyster, Crassostrea gigas, shows negative correlation to naturally elevated carbon dioxide levels: Implications for near-term ocean acidification effects

Abstract: We report results from an oyster hatchery on the Oregon coast, where intake waters experienced variable carbonate chemistry (aragonite saturation state , 0.8 to . 3.2; pH , 7.6 to . 8.2) in the early summer of 2009. Both larval production and midstage growth (, 120 to , 150 mm) of the oyster Crassostrea gigas were significantly negatively correlated with the aragonite saturation state of waters in which larval oysters were spawned and reared for the first 48 h of life. The effects of the initial spawning conditions did not have a significant effect on early-stage growth (growth from D-hinge stage to , 120 mm), suggesting a delayed effect of water chemistry on larval development.

Economic Valuation of Ecosystem Services Provided by Oyster Reefs

Abstract: Valuation of ecosystem services can provide evidence of the importance of sustaining and enhancing those resources and the ecosystems that provide them. Long appreciated only as a commercial source of oysters, oyster reefs are now acknowledged for the other services they provide, such as enhancing water quality and stabilizing shorelines. We develop a framework to assess the value of these services. We conservatively estimate that the economic value of oyster reef services, excluding oyster harvesting, is between $5500 and $99,000 per hectare per year and that reefs recover their median restoration costs in 2–14 years. In contrast, when oyster reefs are subjected to destructive oyster harvesting, they do not recover the costs of restoration. Shoreline stabilization is the most valuable potential service, although this value varies greatly by reef location. Quantifying the economic values of ecosystem services provides guidance about when oyster reef restoration is a good use of funds.

Historical ecology with real numbers: past and present extent and biomass of an imperilled estuarine habitat

Abstract: Historic baselines are important in developing our understanding of ecosystems in the face of rapid global change. While a number of studies have sought to determine changes in extent of exploited habitats over historic timescales, few have quantified such changes prior to late twentieth century baselines. Here, we present, to our knowledge, the first ever large-scale quantitative assessment of the extent and biomass of marine habitat-forming species over a 100-year time frame. We examined records of wild native oyster abundance in the United States from a historic, yet already exploited, baseline between 1878 and 1935 (predominantly 1885–1915), and a current baseline between 1968 and 2010 (predominantly 2000–2010). We quantified the extent of oyster grounds in 39 estuaries historically and 51 estuaries from recent times. Data from 24 estuaries allowed comparison of historic to present extent and biomass. We found evidence for a 64 per cent decline in the spatial extent of oyster habitat and an 88 per cent decline in oyster biomass over time. The difference between these two numbers illustrates that current areal extent measures may be masking significant loss of habitat through degradation.

Analysis of stomach and gut microbiomes of the eastern oyster (Crassostrea virginica) from coastal Louisiana, USA.

Abstract: We used high throughput pyrosequencing to characterize stomach and gut content microbiomes of Crassostrea virginica, the Easter oyster, obtained from two sites, one in Barataria Bay (Hackberry Bay) and the other in Terrebonne Bay (Lake Caillou), Louisiana, USA. Stomach microbiomes in oysters from Hackberry Bay were overwhelmingly dominated by Mollicutes most closely related to Mycoplasma; a more rich community dominated by Planctomyctes occurred in Lake Caillou oyster stomachs. Gut communities for oysters from both sites differed from stomach communities, and harbored a relatively diverse assemblage of phylotypes. Phylotypes most closely related to Shewanella and a Chloroflexi strain dominated the Lake Caillou and Hackberry Bay gut microbiota, respectively. While many members of the stomach and gut microbiomes appeared to be transients or opportunists, a putative core microbiome was identified based on phylotypes that occurred in all stomach or gut samples only. The putative core stomach microbiome comprised 5 OTUs in 3 phyla, while the putative core gut microbiome contained 44 OTUs in 12 phyla. These results collectively revealed novel microbial communities within the oyster digestive system, the functions of the oyster microbiome are largely unknown. A comparison of microbiomes from Louisiana oysters with bacterial communities reported for other marine invertebrates and fish indicated that molluscan microbiomes were more similar to each other than to microbiomes of polychaetes, decapods and fish.

Persistent carry‐over effects of planktonic exposure to ocean acidification in the Olympia oyster

Abstract: Predicting impacts of global environmental change is challenging due to the complex life cycles that characterize many terrestrial and aquatic taxa. Different life stages often interact with the physical environment in distinct ways, and a growing body of work suggests that stresses experienced during one life stage can “carry over” to influence subsequent stages. Assessments of population responses to environmental perturbation must therefore consider how effects might propagate across life-history transitions. We investigated consequences of ocean acidification (decreased pH and carbonate saturation) for early life stages of the Olympia oyster (Ostrea lurida), a foundation species in estuaries along the Pacific coast of North America. We reared oysters at three levels of seawater pH, including a control (8.0) and two additional levels (7.9 and 7.8). Oysters were cultured through their planktonic larval period to metamorphosis and into early juvenile life. Larvae reared under pH 7.8 exhibited a 15% decre...

Characterization of calcium carbonate obtained from oyster and mussel shells and incorporation in polypropylene

Abstract: There is a high content of calcium carbonate in mussel and oyster shells, which can be used in the formulation of medicine, in construction or as filler in polymer materials. This work has as its main objective to obtain calcium carbonate from mussel and oyster shells and used as filler in polypropylene compared their properties with polypropylene and commercial calcium carbonate composites. The shellfish was milling and heated at 500 oC for 2 hours. The powder obtained from shellfish were characterized by scanning electron microscopy (SEM), X-ray fluorescence, particle size distribution and abrasiveness and compared with commercial CaCO3 and mixed with polypropylene. The thermal and mechanical properties of polypropylene with CaCO3 obtained from oyster and mussel shells and with commercial CaCO3 were analysed. The results showed that CaCO3­ can be obtained from oyster and mussel shell and is technically possible to replace the commercial CaCO3 for that obtained from the shells of shellfish in polypropylene composites.

Hepatitis E virus genotype 3 in shellfish, United Kingdom.

Abstract: To the Editor: Bivalve mollusks (shellfish), such as mussels and oysters, are filter feeders; they concentrate microorganisms of human and animal origin (up to 100×) from the surrounding environment. Several recent reports have linked the incidence of human infection with hepatitis E virus (HEV) to consumption of undercooked pork, game products, and shellfish (1,2). Infectious HEV has been found in swine manure and wastewater (3); therefore, application of manure to land and subsequent runoff could contaminate coastal water, leading to contamination of shellfish and, subsequently, possible human infection. Because they are filter feeders, bivalve mollusks are biologically relevant sentinels and can indicate potential pathogens that are contaminating the environment. It is essential to ensure that this sustainable resource of coastal areas, where mussels and oysters are farmed or collected wild, is not subjected to environmental contamination that could lead to public health risks. Risk management for bivalve mollusks, aimed at control of fecal pollution, relies heavily on the use of Escherichia coli as an indicator of fecal (sewage) contamination and is enacted under European food regulations (Regulation 854/2004, www.cefas.co.uk/media/455777/extract_reg_no_854_2004.pdf). However, although these regulations probably reduce the number of infections, especially bacterial infections, they are not viewed as adequately controlling the risk for viral infections. Specific risks are posed by the robustness of viruses in the environment and the different behavior of viruses within bivalve mollusks compared with behavior within bacterial fecal indicators. HEV is deemed to be inactivated during processing procedures used to prepare mussels for consumption; however, HEV is only 50% inactivated at 56°C and 96% at 60°C for 1 hour, it is stable when exposed to trifluorotrichloroethane, and it is resistant to inactivation by acidic and alkaline conditions (4). Most shellfish are usually eaten raw, but viable virus can also pose a risk to public health in shellfish that are lightly steamed or preserved by smoking and/or in acetic acid. Indeed, a recent study by the Food Standards Agency, in which >800 oyster samples from 39 growing beds in the United Kingdom were collected and screened during 2009–2011, found norovirus at low levels in at least 76% of oysters (5). Other studies identified hepatitis A virus and norovirus in shellfish production areas and in ready-to-eat products in the United Kingdom (1,6). In fact, depuration experiments demonstrated no decrease in titers against hepatitis A virus over a 23-hour cleansing period (7). In addition, acute HEV infection attributed to consumption of shellfish was diagnosed for 33 passengers who recently returned from a cruise (2). However, data have been restricted to questionnaires implicating consumption of shellfish as a source of transmission; no follow-up analyses of the contaminated foodstuff have been conducted. Thus, possible transmission routes for HEV remain poorly studied in the United Kingdom (2). To determine whether HEV is present in mussels collected locally for human consumption, we examined 48 mussels from 5 tidal locations in Scotland. We collected closed mussels from the west coast of Scotland (11 at Lunderston Bay and 28 at Ardrossan) and the east coast of Scotland (9 at Stannergate, Dundee; Ferryden, Montrose; and the Ythan Estuary at Newburgh). The site at Ardrossan was near a slaughterhouse and a meat preparation purification plant that processes pigs. The plant was considered a potential source of contamination, and mussels were collected in a 10-m2 area around an outfall (drain/sewage pipe) directly in line with the processing plant. A total of 36 (92%) of the 39 mussels from the west coast were positive by PCR for HEV, and 5 (55%) of the 9 from the east coast were positive. The mean value of HEV RNA detected in the samples was 4.25 log10 IU/mL (range 3.73–5.2 log10 IU/mL), and the assay was validated by using the current candidate HEV World Health Organization standard (http://whqlibdoc.who.int/hq/2011/WHO_BS_2011.2175_eng.pdf). Phylogenetic analysis showed that most bivalve mollusk sequences clustered with HEV genotype 3 from humans and swine (Figure; Technical Appendix). Also, HEV sequences isolated specifically from a UK human source corresponded with sequences isolated from the bivalve mollusks. The presence of a swine-like HEV genotype 3 in freshwater bivalve mollusks has also been reported in Japan and South Korea (1,9). Figure Phylogenetic analysis of HEV open reading frame 2 sequences isolated from Mytilus spp. RNA was isolated from 50–100 mg of digestive gland or gill. Tissue was homogenized in 300 μL phosphate-buffered saline, and viral RNA was isolated by ... Worldwide, an estimated 40,000 persons die and another 40,000 experience long-term disability as a result of consuming raw or undercooked shellfish (10). This study, demonstrating the presence of HEV in mussels collected locally in Scotland for human consumption, raises concern as to whether these shellfish are a potential source of infection, as reported (2). The association between environmental contamination with HEV and possible transmission by eating shellfish warrants investigation. Technical Appendix: ClustalW alignment of sequences used to generate the phylogenetic tree in the Figure. Click here to view.(218K, pdf)

Identification of genes potentially related to biomineralization and immunity by transcriptome analysis of pearl sac in pearl oyster Pinctada martensii.

Abstract: Pearl oyster Pinctada martensii is cultured for production of pearl in China. It needs to implant a mantle graft cut from a donor oyster and a seed nucleus into the gonad of the host oyster to produce a pearl. Pearl sac surrounding the nucleus is formed by the proliferation of the implanted mantle graft from the outer mantle epithelial cells in the host oyster. The pearl sac is responsible for production of a cultured pearl. A comprehensive transcriptome analysis on pearl sac will help to understand the mechanism on pearl formation and immune response of host oyster after nucleus implantation. In the present study, 39,400,004 reads were produced from the pearl sac using RNA-sequence technology and then assembled into 102,762 unigenes. More than 22.4% of these unigenes were possibly involved in approximately 219 known signaling pathways. A total of 37,188 unigenes were annotated based on sequences similarities with known proteins. Fifty-one biomineralization-related unigenes and 268 immune-related unigenes were not previously detected in P. martensii. The un-annotated unigenes may be some genes specifically existed in P. martensii. These annotated or un-annotated unigenes in the present studies were valuable for the future investigation on molecular mechanism of pearl formation and immune response of the species.

Benthic flow environments affect recruitment of Crassostrea virginica larvae to an intertidal oyster reef

Abstract: Restoration efforts to enhance Crassostrea virginica oyster populations along the Vir- ginia, USA, coastline focus on creating benthic habitat suitable for larval recruitment, survival, and growth. To determine how benthic flow processes affect larval recruitment, velocity and tur- bulence we collected data over multiple intertidal benthic surfaces including a mud bed, a C. vir- ginica oyster reef, and 2 restoration sites comprised of deposited C. virginica oyster shell or the relatively larger Busycotypus canaliculatus whelk shell. Mean estimates of the drag coefficient, CD, used as a measure of hydrodynamic roughness over the C. virginica reef were found to be 2 times greater than over the restoration sites and 5 times greater than over the mud bed. Enhanced fluid shear increased both peak Reynolds stresses and vertical momentum transport above the reef, but within the interstitial areas between individual oysters, velocities and turbulence were reduced. Larval settlement plates of varying triangular-shaped benthic roughness were used to mimic the natural topographic variability found along oyster reefs. The greatest larval recruitment occurred along interstitial regions between high-roughness topography, where shear stresses, which act to dislodge larvae, were found to be up to 20 times smaller than along exposed surfaces. Greater recruitment was also found on the more hydrodynamically rough whelk shell compared to the oyster shell restoration site. Results suggests that restoration efforts should consider creat- ing 3-dimensional benthic topography similar to established oyster reefs to provide hydrodynamic conditions and settlement surfaces that promote larval recruitment, prevent burial by sediment, and provide refuge from predation.

The Antimicrobial Defense of the Pacific Oyster, Crassostrea gigas. How Diversity may Compensate for Scarcity in the Regulation of Resident/Pathogenic Microflora

Abstract: Healthy oysters are inhabited by abundant microbial communities that vary with environmental conditions and coexist with immunocompetent cells in the circulatory system. In Crassostrea gigas oysters, the antimicrobial response, which is believed to control pathogens and commensals, relies on potent oxygen-dependent reactions and on antimicrobial peptides/proteins (AMPs) produced at low concentrations by epithelial cells and/or circulating hemocytes. In non-diseased oysters, hemocytes express basal levels of defensins (Cg-Defs) and proline-rich peptides (Cg-Prps). When the bacterial load dramatically increases in oyster tissues, both AMP families are driven to sites of infection by major hemocyte movements, together with bactericidal permeability/increasing proteins (Cg-BPIs) and given forms of big defensins (Cg-BigDef), whose expression in hemocytes is induced by infection. Co-localization of AMPs at sites of infection could be determinant in limiting invasion as synergies take place between peptide families, a phenomenon which is potentiated by the considerable diversity of AMP sequences. Besides, diversity occurs at the level of oyster AMP mechanisms of action, which range from membrane lysis for Cg-BPI to inhibition of metabolic pathways for Cg-Defs. The combination of such different mechanisms of action may account for the synergistic activities observed and compensate for the low peptide concentrations in C. gigas cells and tissues. To overcome the oyster antimicrobial response, oyster pathogens have developed subtle mechanisms of resistance and evasion. Thus, some Vibrio strains pathogenic for oysters are equipped with AMP-sensing systems that trigger resistance. More generally, the known oyster pathogenic vibrios have evolved strategies to evade intracellular killing through phagocytosis and the associated oxidative burst.

Reactive Oxygen Species in Unstimulated Hemocytes of the Pacific Oyster Crassostrea gigas: A Mitochondrial Involvement

Abstract: The Pacific oyster Crassostrea gigas is a sessile bivalve mollusc whose homeostasis relies, at least partially, upon cells circulating in hemolymph and referred to as hemocytes. Oyster's hemocytes have been reported to produce reactive oxygen species (ROS), even in absence of stimulation. Although ROS production in bivalve molluscs is mostly studied for its defence involvement, ROS may also be involved in cellular and tissue homeostasis. ROS sources have not yet been described in oyster hemocytes. The objective of the present work was to characterize the ROS sources in unstimulated hemocytes. We studied the effects of chemical inhibitors on the ROS production and the mitochondrial membrane potential (Δψ(m)) of hemocytes. First, this work confirmed the specificity of JC-10 probe to measure Δψ(m) in oyster hemocytes, without being affected by ΔpH, as reported in mammalian cells. Second, results show that ROS production in unstimulated hemocytes does not originate from cytoplasmic NADPH-oxidase, nitric oxide synthase or myeloperoxidase, but from mitochondria. In contrast to mammalian cells, incubation of hemocytes with rotenone (complex I inhibitor) had no effect on ROS production. Incubation with antimycin A (complex III inhibitor) resulted in a dose-dependent ROS production decrease while an over-production is usually reported in vertebrates. In hemocytes of C. gigas, the production of ROS seems similarly dependent on both Δψ(m) and ΔpH. These findings point out differences between mammalian models and bivalve cells, which warrant further investigation about the fine characterization of the electron transfer chain and the respective involvement of mitochondrial complexes in ROS production in hemocytes of bivalve molluscs.

Molecular Analysis of Bacterial Microbiota Associated with Oysters ( Crassostrea gigas and Crassostrea corteziensis ) in Different Growth Phases at Two Cultivation Sites

Abstract: Microbiota presumably plays an essential role in inhibiting pathogen colonization and in the maintenance of health in oysters, but limited data exist concerning their different growth phases and conditions. We analyzed the bacterial microbiota composition of two commercial oysters: Crassostrea gigas and Crassostrea corteziensis. Differences in microbiota were assayed in three growth phases: post-larvae at the hatchery, juvenile, and adult at two grow-out cultivation sites. Variations in the microbiota were assessed by PCR analysis of the 16S rRNA gene in DNA extracted from depurated oysters. Restriction fragment length polymorphism (RFLP) profiles were studied using Dice’s similarity coefficient (Cs) and statistical principal component analysis (PCA). The microbiota composition was determined by sequencing temperature gradient gel electrophoresis (TGGE) bands. The RFLP analysis of post-larvae revealed homology in the microbiota of both oyster species (Cs > 88 %). Dice and PCA analyses of C. corteziensis but not C. gigas showed differences in the microbiota according to the cultivation sites. The sequencing analysis revealed low bacterial diversity (primarily β-Proteobacteria, Firmicutes, and Spirochaetes), with Burkholderia cepacia being the most abundant bacteria in both oyster species. This study provides the first description of the microbiota in C. corteziensis, which was shown to be influenced by cultivation site conditions. During early growth, we observed that B. cepacia colonized and remained strongly associated with the two oysters, probably in a symbiotic host–bacteria relationship. This association was maintained in the three growth phases and was not altered by environmental conditions or the management of the oysters at the grow-out site.

Molecular analysis of the bacterial communities in the live Pacific oyster (Crassostrea gigas) and the influence of postharvest temperature on its structure.

Abstract: Aims: To evaluate the effect of postharvest temperature on bacterial communities in live Pacific oysters (Crassostrea gigas) using nonculture-based methods. Methods and Results: Live oysters were compared before and after storage at 4, 6, 15, 20 and 30°C using terminal restriction fragment length polymorphism (T-RFLP). Bacterial communities in freshly harvested (control) vs stored oysters were significantly different. Changes in bacterial communities at 4, 15 and 30°C observed by T-RFLP were further investigated by clone library analysis. Members of the Proteobacteria predominated (43·0–57·0% of clones) in control oysters, while storage altered the bacterial profile. At 4°C, Psychrilyobacter spp. (phylum Fusobacteria) predominated (43·8% of clones), while at 15 and 30°C, members of the phylum Bacteroidetes represented 63·0 and 60·2% of clones, respectively. High microbial diversity in oysters was observed, with at least 73 different genera-related clones among all samples. Conclusions: Changes in the overall bacterial community of Pacific oysters were influenced by storage temperature and would likely not be detected by standard culture-based methods currently used to assess oyster quality. Certain dominant genera, such as Psychrilyobacter, Polynucleobacter and a bacterial group related to Alkaliflexus, should be further studied as possible indicators for postharvest temperature control. Significance and Impact of the Study: This work is the first report describing the effect of different storage temperatures on bacterial diversity in postharvest live Pacific oysters using molecular-based methods.

Triploid Oysters in the Chesapeake Bay: Comparison of Diploid and Triploid Crassostrea virginica

Abstract: Diploid and triploid Eastern oysters, Crassostrea virginica, were tested at 3 sites characterized by low or moderate salinity regimes in the Virginia part of the Chesapeake Bay from November 2005 through October 2007. Both diploid and triploid cultures were replicated 3 times by producing separate spawns from different broodstock. Ploidy had a generally consistent effect on the performance of C. virginica at the 3 test sites. At the end of the study, in October 2007, and across all sites, triploid oysters had lower cumulative mortality than diploids (-34%), and greater shell height (+25%), whole weight (+88%), and yield (+152%). as well as a higher proportion of market-size oysters (+114%) than diploids. Both diploids and triploids were similarly infected by Perkinsus marinus and, to a lesser extent, by Haplosporidium nelsoni. In a closer look, growth parameters (shell height growth, whole weight, yield, and percentage of marketable oysters) were always higher in triploids than in diploids regard...

Gametogenesis in the Pacific oyster Crassostrea gigas: a microarrays-based analysis identifies sex and stage specific genes.

Abstract: BACKGROUND: The Pacific oyster Crassostrea gigas (Mollusca, Lophotrochozoa) is an alternative and irregular protandrous hermaphrodite: most individuals mature first as males and then change sex several times. Little is known about genetic and phenotypic basis of sex differentiation in oysters, and little more about the molecular pathways regulating reproduction. We have recently developed and validated a microarray containing 31,918 oligomers (Dheilly et al., 2011) representing the oyster transcriptome. The application of this microarray to the study of mollusk gametogenesis should provide a better understanding of the key factors involved in sex differentiation and the regulation of oyster reproduction. METHODOLOGY/PRINCIPAL FINDINGS: Gene expression was studied in gonads of oysters cultured over a yearly reproductive cycle. Principal component analysis and hierarchical clustering showed a significant divergence in gene expression patterns of males and females coinciding with the start of gonial mitosis. ANOVA analysis of the data revealed 2,482 genes differentially expressed during the course of males and/or females gametogenesis. The expression of 434 genes could be localized in either germ cells or somatic cells of the gonad by comparing the transcriptome of female gonads to the transcriptome of stripped oocytes and somatic tissues. Analysis of the annotated genes revealed conserved molecular mechanisms between mollusks and mammals: genes involved in chromatin condensation, DNA replication and repair, mitosis and meiosis regulation, transcription, translation and apoptosis were expressed in both male and female gonads. Most interestingly, early expressed male-specific genes included bindin and a dpy-30 homolog and female-specific genes included foxL2, nanos homolog 3, a pancreatic lipase related protein, cd63 and vitellogenin. Further functional analyses are now required in order to investigate their role in sex differentiation in oysters. CONCLUSIONS/SIGNIFICANCE: This study allowed us to identify potential markers of early sex differentiation in the oyster C. gigas, an alternative hermaphrodite mollusk. We also provided new highly valuable information on genes specifically expressed by mature spermatozoids and mature oocytes.

The Rise and Fall of Crassostrea Virginica Oyster Reefs: The Role of Disease and Fishing in Their Demise and a Vignette on Their Management

Abstract: We describe a model designed to simulate the shell carbonate budget of an oyster reef. We identify five parameters descriptive of basic characteristics of the shell carbonate budget of a reef that limit simulation accuracy. Two describe the TAZ (taphonomically-active zone) and the distribution of shell carbonate within it. One is the taphonomic rate in the TAZ. Two determine the volume contribution of shell carbonate and the taphonomic loss rate within the reef framework. For Mid-Atlantic estuaries, model simulations suggest that reef accretion only occurs if oyster abundance is near carrying capacity. Simulations further suggest that reef accretion is infeasible for any estuarine reach where dermo is a controlling influence on population dynamics. We forecast that the oyster disease dermo is a principal antagonist of reef persistence through its ability to limit shell addition. Model simulations suggest that reefs with inadequate shell addition ‘protect themselves’ by limiting the volumetric content of shell carbonate in the TAZ. Thus, a dominant process is the transient expansion and contraction of the shell resource, otherwise termed cultch, within the TAZ, rarely expanding enough to generate reef accretion, yet rarely contracting enough to foster erosion of the reef framework. The loss of framework carbonate thusly is curtailed during periods when the surficial shell layer deteriorates. Stasis, a reef neither accreting nor eroding, is a preferred state. Reef recession requires an inordinately unbalanced shell carbonate budget. Results strongly argue for expanded focus on the dynamics of the shell resource within the TAZ, as this likely fosters a feedback loop with abundance through recruitment, serves as the protective layer for the reef during periods of reef stasis, and establishes the threshold conditions for reef accretion and recession. Model simulations suggest that attaining maximum sustainable yield and maintaining a biomass capable of supporting sufficient shell production for reef accretion are irreconcilable goals over a large component of the oyster’s range. Reef stasis would appear to be the only achievable restoration goal in Mid-Atlantic estuarine reaches where dermo holds sway. Exploitation rates much above 5% of the fishable stock per year restrict availability of surficial shell and foster reef erosion. In contrast, in the Gulf of Mexico at the high-productivity end of the oyster’s range, an enhanced fishery and reef accretion may be compatible goals. 1. Rutgers University, Institute of Marine and Coastal Sciences and The New Jersey Agricultural Experiment Station, Haskin Shellfish Research Laboratory, Port Norris, New Jersey, 08349, U.S.A. 2. Corresponding author. email: eric@hsrl.rutgers.edu 3. Center for Coastal Physical Oceanography, Department of Ocean, Earth and Atmospheric Sciences, Old Dominion University, Norfolk, Virginia, 23508, U.S.A.

Quality Characteristics of Bread Made from Wheat and Nigerian Oyster Mushroom (Pleurotus plumonarius) Powder

Abstract: Bread containing graded levels of Mushroom Powder (MP) were produced by replacement of Wheat Flour (WF) with 0, 5, 10, 15, 20 and 25% MP. Effect of MP supplementation on the bread making properties, proximate composition and sensory qualities were evaluated. Water absorption was significantly (p<0.05) increased as MP level increased in all dough, however, loaf volume, specific volume, crumb grain and loaf quality decreased. Supplementation of WF with MP from 0-25% increased the crude protein content significantly from 7.96-14.62%, ash from 0.90-2.64% and crude fiber 0.51-2.48%. Sensory evaluation based on appearance, crust color, crumb color, crumb texture, taste, chew ability, flavor and overall acceptability showed there were no significant (p>0.05) difference between 5% MP fortified bread and 100% WF bread (control) in all the attributes evaluated. Equally, 10% MP fortified bread did not differ significantly in crust color, taste, chew ability and overall acceptability, it compared favorably well with control bread in these attributes. Bread with 15% MP though had significantly (p<0.05) lower rating compared to the control, was also acceptable to the panelist. Mushroom powder therefore could be added to wheat flour up to 10% without any observed detrimental effect on bread sensory properties. This could be used to improve the nutritional quality of bread especially in developing countries were malnutrition is prevalent.