Nonnative Oysters in the Chesapeake Bay (2004) / Chapter Skim
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2. Introduction and Overview
2. Introduction and Overview
Pages 15-27
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From page 15... ...
estimates that oysters could filter the water of the bay every 3.3 days. In addition to filtering algae and particulates from the water column, the Eastern oyster forms three-dimensional reefs that provide habitat for other species in the bay (Wells, 1961; Bahr and Lanier, 1981; Dame and Patten, 1981; Mann et al., 1991; Coen and Luckenbach, 2000; Lenihan et al., 2001; Newell et al., 2002~.
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6 0O use ~ in' -.
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This is perhaps best documented in the paleological record from sediment cores taken across the Chesapeake Bay near the mouth of the Choptank River (Cooper and Brush, 1991, 1993~. For the bay, enhanced sedimentation and eutrophication have translated into increased phytoplankton biomass, reduced water transparency, loss of submerged aquatic vegetation, and expansion of hypoxic conditions in the stratified waters of the estuary during the summer (Harding et al., in Malone, 1999~.
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This is to be achieved through continued improvements to bay water quality, reduced oyster fishing pressure in selected areas, shell deposition to rebuild the reef structure, and continued development of disease-resistant oyster strains. Past restoration efforts, dating back to the 1920s, were directed toward maintaining the oyster fishery.
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Nonnative species introduced by accident over the years have already altered the bay's ecological balance, and several previous experiences with exotic species invasions (e.g., mute swans, nutria, kudzu, zebra mussels, and gypsy moths) argue against unregulated introduction of species that have the potential to spread throughout ecosystems (see Carlton, 2001; Moser, 2002, and references therein)
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ariakensis because of the possibility of introducing reproductively capable populations over the long term, even with current triploid technology and production methods. The goal of this study was to examine the ecological and socioeconomic risks and benefits of open-water aquaculture or direct introduction of the nonnative oyster, C
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The remainder of Chapter 2 describes major features of the Chesapeake Bay ecosystem, highlighting the sources of change that may contribute to the current depleted status of the native oyster population. Chapter 3 provides a review of invasive species science and presents case studies of introductions of nonnative oysters around the world.
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Finally, Chapter 10 presents the committee's conclusions and suggestions for research that would enable decision making for future use of nonnative oysters in aquaculture or to establish another oyster species for harvest in the Chesapeake Bay and neighboring waters. CHESAPEAKE BAY LIMNOLOGY AND OCEANOGRAPHY Physical Description The Chesapeake Bay is a long, narrow, relatively shallow estuary (see Figure 2.2 and Table 2.1)
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The Chesapeake Bay plume propagates more rapidly to the south during moderate-to-weak southeastward winds (downwelling favorable conditions)
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Based on factors such as bottom topography, nutrient input, and water clarity, the bay is often divided into upper, middle, and lower regions, each with distinct characteristics (Kemp et al., 1999~. The upper bay (above 39°N latitude)
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The rest is comprised of urban and suburban development, pasture, and cropland (Seagle et al., 1999~. Despite the gradual recovery of forested lands in the bay's watershed, continued human population growth, greater fertilizer use, atmospheric deposition from fossil fuel combustion (especially coal)
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(2001) provide excellent historical overviews of how the synergistic effects of human activities have led to degraded water quality, loss of oyster populations, and decreased submerged aquatic vegetation in the Chesapeake Bay.
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Nutrient levels computed using actual water quality data collected between 1985 and 1998 at these stations showed no statistically significant trends in either total nitrogen or total phosphorus loads at six of the nine stations. Some of the difference is attributable to high streamflows, which can lead to higher nutrient loads even if nutrient concentrations have maintained status quo or declined.
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