Potential Effects of Endocrine Disrupting Compounds on Bivalve Populations in Chesapeake Bay: A Review of Current Knowledge and Assessment of Research Needs

Numerous compounds in the environment interfere with normal endocrine function in humans and other animals. These compounds, which include heavy metals, a wide variety of anthropogenic organic compounds, steroids and steroid-mimicking compounds, are collectively termed endocrine disrupting compounds (EDCs). Over the past 20 years, research on the impacts of EDC exposure has identified a range of effects on growth, development, and reproduction in humans and wildlife

Settlement Of Oyster (Crassostrea-Virginica) Larvae - Effects Of Water-Flow And A Water-Soluble Chemical Cue

Although previous evidence indicates that larvae of benthic marine invertebrates can respond to waterborne cues in still water, the importance of waterborne cues in mediating natural settlement out of flowing water has been questioned. Here, we summarize the results of flume experiments demonstrating enhanced settlement of oyster larvae in small target wells (circles of 7-cm diam) with the release of a waterborne settlement cue compared to identical substrates without the cue. In concurrent still-water experiments, more oyster larvae settled in solutions of waterborne cue than in seawater controls. Velocity and electrochemical measurements of a conservative tracer verified that at low flow velocities (2 and 6 cm s(-1)) with U* value

Settlement Of Crassostrea Ariakensis Larvae: Effects Of Substrate, Biofilms, Sediment And Adult Chemical Cues

The Suminoe oyster (Crassostrea ariakensis) is being considered for introduction into the Chesapeake Bay. However, our current understanding of the biology and ecology of C. ariakensis is insufficient to predict whether an introduction will be successful, provide desired benefits, or have adverse impacts. Behavior of native Eastern oyster (C. virginica) pediveligers has been studied for many years and it is well established that they use a variety of habitat characteristics when selecting a site for colonization. Perhaps the most important of these are chemical cues emitted by adult conspecifics, which can lead to gregarious larval settlement and dense, persistent reef communities. Conversely, almost nothing is known about the mechanisms that regulate larval settlement and metamorphosis for C. ariakensis or how pediveligers might respond to conditions found in Chesapeake Bay. In a comparative study with C. virginica, we examined how environmental factors such as substrate type, natural biofilms, sediment and waterborne chemical cues influence larval settlement for two C. ariakensis strains (‘‘south China’’ and ‘‘west coast’’). Our results demonstrate many similarities but also potentially important differences. Both species and strains of larvae greatly prefer natural substrates (e.g., shell) covered with biofilms for colonization but the west coast strain of C. ariakensis exhibited greater attachment onto manmade substrates (e.g., fiberglass) than C. virginica. Waterborne chemical cues emitted by adult oysters were also found to enhance substrate attachment for all larval forms but cues do not appear to be species specific. These results provide critical insight to the ability of C. ariakensis larvae to identify and colonize suitable substrates in the Chesapeake Bay, which will have a large impact on recruitment success and their ability to establish self-sustaining populations

A Comparative Field Study Of Crassostrea ariakensis (Fujita 1913) And Crassostrea virginica (Gmelin 1791) In Relation To Salinity In Virginia

We examined survival, growth, and disease susceptibility of triploid Crassostrea ariakensis (= rivularis) and compared results with that of diploid Crassostrea virginica. Two hundred and fifty oysters (age = 2 yr, mean shell height = 60-64 mm) of each species were deployed at duplicate sites, (Chesapeake Bay, and the Atlantic Coast of Virginia) within low, medium, and high salinity regimes respectively (\u3c 15%, 15-25%, \u3e 25%). Over the course of the study, from June 1998 to September 1999, C. virginica exhibited low survival, modest growth and high disease susceptibility. In contrast, C. ariakensis exhibited high survival, high growth rate, and low disease susceptibility. At low salinity sites, final mean cumulative mortality of C. virginica (81%) was significantly higher than that of C. ariakensis (14%). At medium and high salinity sites, all C. virginica died before the end of the study whereas final mean cumulative mortality in C ariakensis was 13 to 16%. After 1 year of deployment, mean shell height of C. virginica at low, moderate, and high salinity sites was respectively 70, 80 and 73 mm. In comparison, mean shell height of C. ariakensis was respectively 93, 121 and 137 mm. At low salinity sites, mean growth rate of C virginica was not significantly different from that of C ariakensis. At medium and high salinity sites, mean growth rate of C virginica was significantly lower than that of C ariakensis. Prevalence and intensity of Perkinsus marinus infections were significantly higher in C. virginica than in C. arlakensis. During the second summer of disease exposure, prevalence in C. virginica was 100% at all sites whereas in C ariakensis it ranged from 0 to 28%. Heavy intensity of infections were prevalent in C. virginica whereas infections in C. ariakensis were limited to light intensity. Haplosporidium nelsoni (MSX) was present in C. virginica, but absent in C. ariakensis. Mud worms (Polydora spp.) were present in both oyster species, but infestations were low and did not appear to affect condition or growth. In summary, wide salinity tolerance and low disease susceptibility were associated with high survival and growth of C. ariakensis in Chesapeake Bay and the Atlantic Coast of Virginia

A Comparative Field Study of Crassostrea ariakensis and Crassostrea virginica in Relation to Salinity in Virginia

In accordance with the Rational Plan for Testing Application of Non-Native Oyster Species (VIMS 1996) we conducted a field experiment to examine survival, growth and disease susceptibility of Crassostrea ariakensis (=rivularis) in relation to salinity in Virginia. The performance of triploid C. ariakensis in comparison with that of diploid C. virginica, (n = 250, age = 2 years, mean shell height = 60- 64 mm) was evaluated at replicate sites within low, medium, and high salinity regimes (respectively, \u3c 15‰, 15-25‰, \u3e 25‰) in Chesapeake Bay and the Atlantic Coast. During the course of this study, from June 1998 to September 1999, there was a severe oyster disease epizootic prevailing in Chesapeake Bay. At the end of the study C. ariakensis exhibited lower disease prevalence and intensity and superior survival and growth than C. virginica. At low salinity sites cumulative mortality in C. ariakensis (14%) was significantly lower than that in C. virginica (81%). At medium and high salinity sites, cumulative mortality in C. ariakensis was less than 16% whereas all C. virginica were dead by the end of the experiment. After one year of deployment, mean shell height of C. ariakensis at low, moderate, and high salinity sites, was respectively 96 mm, 125 mm, and 140 mm. In comparison, mean shell height of C. virginica was respectively 72 mm, 85 mm, and 75 mm. Prevalence and intensity of Perkinsus marinus infections were significantly lower in C. ariakensis than in C. virginica. During the second summer of disease exposure, prevalence in C. ariakensis ranged form 0-28% whereas prevalence in C. virginica was 100% at all sites. Only light infections were present in C. ariakensis whereas heavy infections were found in C. virginica. MSX was absent in C. ariakensis and present in C. virginica. Mud worms were present in both oyster species but infestations were low and did not appear to affect condition or growth. In summary, wide salinity tolerance and low disease susceptibility were associated with high survival and growth of C. ariakensis in Chesapeake Bay and the Atlantic Coast of Virginia

Linking structural and functional characteristics of restored oyster reefs : A Restoration Project in the Virginia Coast Reserve

Eighteen native oyster reefs (16-m2 each) were restored using six oyster densities (0, 10, 25, 50, 100 and 250 adult oysters m-2) with three replicates of each density at an intertidal site in The Nature Conservancy’s Virginia Coast Reserve. Reef construction was successful and continues to provide a range of oyster biomass densities useful for exploring relationships between oyster reef structural and functional parameters. Between April 2012 and July 2013, a science-based monitoring program explored quantitative relationships between structural and functional characteristics of these restored reefs. Structural parameters examined included oyster abundance, oyster size/biomass, surface shell volume, reef topographic complexity and sediment characteristics. Functional parameters included denitrification rates and macrofaunal abundance and biomass. Relationships between reef structural parameters and functional parameters were complex and variable. As of July 2014, these reefs continue to serves as a platform for continued studies of the relationships between reef structural and functional characteristics

Oyster Reef Restoration: Convergence Of Harvest And Conservation Strategies

Oyster reef restoration, protection, and construction are important to meeting harvest, water quality, and fish habitat goals. However, the strategies needed to achieve harvest and conservation goals have often been considered to be at odds. We argue that these goals are. in fact, compatible and that the same strategies will promote a sustainable harvest of the resource, increased filtration of estuarine waters, and increased provision of structured habitat for finfish, crabs, and other organisms that utilize oyster reefs or receive benefit indirectly from them. Creation or designations of unharvested sites (refuge sites) are key components of these strategies. Unharvested reefs have the potential to provide vertical relief, which is typically destroyed by harvest practices, to act as a source of larvae, which potentially increases the supply of harvestable oysters, and to protect those individuals most likely to have some resistance to disease. Furthermore. proper monitoring and design of refuge and restoration efforts are critical to providing information needed to improve the success of future restoration efforts, and will simultaneously enhance the basic information needed to understand the ecology of oysters and their role in estuarine and coastal systems

A Comparison Of Crassostrea Virginica And C. Ariakensis In Chesapeake Bay: Does Oyster Species Affect Habitat Function?

We examined the possibility that a nonnative oyster species would provide an ecologically functional equivalent of the native oyster species if introduced into the Chesapeake Bay. Habitat complexity and associated benthic communities of experimental triploid Crassostrea virginica and Crassostrea ariakensis reefs were investigated at 4 sites of varying salinity, tidal regime, water depth, predation intensity, and disease pressure in the Chesapeake Bay region (Maryland and Virginia). Four experimental treatments were established at each site: C. virginica, C. ariakensis, 50:50 of C. virginica and C. ariakensis, and shell only. Abundance, biomass, species richness, evenness, dominance, and diversity of reef-associated fauna were evaluated in relation to habitat location and oyster species. Although habitat complexity varied with location, no differences among complexity were associated with oyster species. Similarly, differences in faunal assemblages were more pronounced between sites than within sites. Our results show functional equivalency between oyster species with respect to habitat at the intertidal site and the low-salinity subtidal location. At subtidal sites of higher salinity, however, the numbers of organisms associated with C. virginica reefs per unit of oyster biomass were significantly greater than the numbers of organisms associated with C. ariakensis reefs. Multivariate analyses of data from subtidal high-salinity sites revealed unique communities associated with C. virginica treatments, whereas mixed-oyster species assemblages were functionally equivalent to monospecific C. ariakensis experimental treatments. Our study represents the first effort to quantify the potential habitat function of C. ariakensis, which has been proposed for an intentional introduction into Chesapeake Bay, and provides evidence of species-specific similarities and differences in reef-associated communities