Settlement and survival of the oyster Crassostrea virginica on created oyster reef habitats in Chesapeake Bay

Efforts to restore Crassostrea virginica oyster reef habitats in Chesapeake Bay typically begin with the placement of hard substrata, such as oyster shell, in the form ofthreedimensional mounds on the seabed to serve as a base for oyster recruitment and growth. A shortage of sufficient volumes of oyster shell for creating large-scale reefs has led to widespread use of other materials, such as surf clam (Spisula solidissima) shell, as a substitute for oyster shell. We monitored oyster recruitment, survival, and growth on intertidal and subtidal reefs constructed shucked oyster and surf clam shell. Results indicate that oyster settlement occurred on both substrate types throughout the monitoring period but high levels of postsettlement mortality occurred on clam shell mounds. On the subtidal clam shell mound, the quality of the substrate material varied with reef elevation with large shell fragments and intact valves scattered around the reef base and small, tightly packed shell fragments paving the crest and flank of the reef mound. The abundance of oysters on this reef reflected this distribution where oysters were more abundant and larger at the reef base and less abundant and smaller on the crest of the reef. Oyster shell reefs supported greater oyster growth and survival and offered the highest degree of structural complexity. We suggest that the availability of interstitial space and appropriate settlement surfaces account for the observed differences in oyster abundance across the reef systems. The patterns observed give context to the importance of substrate selection in similar restoration activities

Ecological functions of constructed oyster reefs along an environmental gradient in Chesapeake Bay: Final Report

Oyster reef habitat restoration within the Chesapeake Bay has as its objectives not only the enhancement of the commercially important oyster stocks, but also the restoration of associated assemblages of organisms and, most importantly, the restoration of ecological functions associated with natural reef communities. Despite our efforts to date, many uncertainties still exist with respect to achieving these restoration goals. These include long-term information on the temporal sequence of community development on new reef substrate, evaluating oyster recruitment patterns (a) across restored reef systems and (b) in relation to resident brood stocks. In this study we sought to characterize the development of resident assemblages on and transient visitors to a variety of constructed reef bases. This study provided a means with which to examine a variety of inter/intra-system processes by coupling the monitoring of resident reef assemblages with characterizations of the transient assemblages (particularly higher trophic levels) in different reef systems. Models of oyster reef community interactions can be generated by synthesizing oyster population data and trophic information over small (system wide) and large (regional) geographic scales

Field Validation of Multi-Species Laboratory Test Systems for Estuarine Benthic Communities

The aim of this project was to evaluate the validity of using multi-species laboratory systems to assess the response of eatuarine benthic communities to an introduced stress. Over a 5- year period experiments in Apalachicola Bay, Florida, and the York River, Virginia, sought to (1) develop criteria for microcosm tests for evaluating the capacity of microcosms to model natural communities in the presence and absence of a pollution-induced stress, and (2) assess the validity of extrapolating test results from one location to another. Procedures for constructing, maintaining and sampling microcosms were tested and refined over the study period. A large number of laboratory and field tests were conducted synoptically over this period, including experiments in which microcosms and field sites were dosed with toxicants (mixed hydrocarbons in some and pentachlorophenol in others). We have investigated various methodologies for analysing and interpreting data derived from microcosm tests

Filtration by oysters : interactive effects of water flow, seston composition and filtration rate

Filtration by suspension-feeding bivalves affects water quality and the postulated impacts include increased light penetration and enhanced benthic primary production. Such system-level predictions are extrapolated fiom still water experiments which neglect the effects of flow, seston composition, turbulent mixing and refiltration by oysters within groups. Flume experiments were used to investigate the effects of varying flow speed and seston composition on filtration capacity of oysters. Six groups of 90 oysters were used in treatments which varied concentrations of the algae Ekalassiosira weisj70grgrsie parately and in combination with inorganics; four sets of shell only controls were used to evaluate hydrodynamic effects. The results indicate the importance of morphological differences in bed structure on turbulence and particle redistribution which may obscure biological effects and of the importance of the physiological condition of oysters on filtration capacity. Field transplants of eelgrass, Zostera marina, and American oysters, Crassostrea virgmica, were used to evaluate interactions between oyster filtration, water quality and plant survival in the field. Abnormally poor water quality forced the early termination of these experiments, but in conjunction with the flume results they indicate a strong effect of physical forces on seston distribution against which impacts of suspension feeders must judged

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

Lessons Learned From Efforts To Restore Oyster Populations In Maryland And Virginia, 1990 To 2007

A century-long decline of the fishery for the Eastern oyster Crassostrea virginica (Gmelin, 1791) in Maryland and Virginia stimulated numerous efforts by federal, state, and nongovernmental agencies to restore oyster populations, with limited success. To learn from recent efforts, we analyzed records of restoration and monitoring activities undertaken between 1990 and 2007 by 12 such agencies. Of the 1,037 oyster bars (reefs, beds, or grounds) for which we obtained data, 43% experienced both restoration and monitoring, with the remaining experiencing either restoration or monitoring only. Restoration activities involved adding substrate (shell), transplanting hatchery or wild seed (juvenile oysters), bar cleaning, and bagless dredging. Of these, substrate addition and transplanting seed were common actions, with bar cleaning and bagless dredging relatively uncommon. Limited monitoring efforts, a lack of replicated postrestoration sampling, and the effects of harvest on some restored bars hinders evaluations of the effectiveness of restoration activities. Future restoration activities should have clearly articulated objectives and be coordinated among agencies and across bars, which should also be off limits to fishing. To evaluate restoration efforts, experimental designs should include replication, quantitative sampling, and robust sample sizes, supplemented by pre- and postrestoration monitoring

The spatiotemporal expression of multiple coho salmon ovarian connexin genes and their hormonal regulation in vitro during oogenesis

BACKGROUND: Throughout oogenesis, cell-cell communication via gap junctions (GJs) between oocytes and surrounding follicle cells (theca and granulosa cells), and/or amongst follicle cells is required for successful follicular development. To gain a fundamental understanding of ovarian GJs in teleosts, gene transcripts encoding GJ proteins, connexins (cx), were identified in the coho salmon, Oncorhynchus kisutch, ovary. The spatiotemporal expression of four ovarian cx transcripts was assessed, as well as their potential regulation by follicle-stimulating hormone (FSH), luteinizing hormone (LH) and insulin-like growth factor 1 (IGF1). METHODS: Salmonid ovarian transcriptomes were mined for cx genes. Four gene transcripts designated cx30.9, cx34.3, cx43.2, and cx44.9 were identified. Changes in gene expression across major stages of oogenesis were determined with real-time, quantitative RT-PCR (qPCR) and cx transcripts were localized to specific ovary cell-types by in situ hybridization. Further, salmon ovarian follicles were cultured with various concentrations of FSH, LH and IGF1 and effects of each hormone on cx gene expression were determined by qPCR. RESULTS: Transcripts for cx30.9 and cx44.9 were highly expressed at the perinucleolus (PN)-stage and decreased thereafter. In contrast, transcripts for cx34.3 and cx43.2 were low at the PN-stage and increased during later stages of oogenesis, peaking at the mid vitellogenic (VIT)-stage and maturing (MAT)-stage, respectively. In situ hybridization revealed that transcripts for cx34.3 were only detected in granulosa cells, but other cx transcripts were detected in both oocytes and follicle cells. Transcripts for cx30.9 and cx44.9 were down-regulated by FSH and IGF1 at the lipid droplet (LD)-stage, whereas transcripts for cx34.3 were up-regulated by FSH and IGF1 at the LD-stage, and LH and IGF1 at the late VIT-stage. Transcripts for cx43.2 were down-regulated by IGF1 at the late VIT-stage and showed no response to gonadotropins. CONCLUSION: Our findings demonstrate the presence and hormonal regulation of four different cx transcripts in the salmon ovary. Differences in the spatiotemporal expression profile and hormonal regulation of these cx transcripts likely relate to their different roles during ovarian follicle differentiation and development

Restoration of seagrass habitat leads to rapid recovery of coastal ecosystem services

There have been increasing attempts to reverse habitat degradation through active restoration, but few largescale successes are reported to guide these efforts. Here, we report outcomes from a unique and very successful seagrass restoration project: Since 1999, over 70 million seeds of a marine angiosperm, eelgrass (Zostera marina), have been broadcast into mid-western Atlantic coastal lagoons, leading to recovery of 3612 ha of seagrass. Well-developed meadows now foster productive and diverse animal communities, sequester substantial stocks of carbon and nitrogen, and have prompted a parallel restoration for bay scallops (Argopecten irradians). Restored ecosystem services are approaching historic levels, but we also note that managers value services differently today than they did nine decades ago, emphasizing regulating in addition to provisioning services. Thus, this study serves as a blueprint for restoring and maintaining healthy ecosystems to safeguard multiple benefits, including co-benefits that may emerge as management priorities over time

Millennial-scale sustainability of the Chesapeake Bay Native American oyster fishery

Estuaries around the world are in a state of decline following decades or more of overfishing, pollution, and climate change. Oysters (Ostreidae), ecosystem engineers in many estuaries, influence water quality, construct habitat, and provide food for humans and wildlife. In North America\u27s Chesapeake Bay, once-thriving eastern oyster (Crassostrea virginica) populations have declined dramatically, making their restoration and conservation extremely challenging. Here we present data on oyster size and human harvest from Chesapeake Bay archaeological sites spanning similar to 3,500 y of Native American, colonial, and historical occupation. We compare oysters from archaeological sites with Pleistocene oyster reefs that existed before human harvest, modern oyster reefs, and other records of human oyster harvest from around the world. Native American fisheries were focused on nearshore oysters and were likely harvested at a rate that was sustainable over centuries to millennia, despite changing Holocene climatic conditions and sea-level rise. These data document resilience in oyster populations under long-term Native American harvest, sea-level rise, and climate change; provide context for managing modern oyster fisheries in the Chesapeake Bay and elsewhere around the world; and demonstrate an interdisciplinary approach that can be applied broadly to other fisheries