| Nutrient loading to coastal waters has become one of the most pressing environmental problems in recent years. At the same time, shellfish populations have been dramatically reduced because of overharvesting and disease. The increase in nutrient loading stimulates primary production, while the decline in shellfish populations lowers grazing on phytoplankton. Together, the increase in nutrient loading and the loss of shellfish grazers has increased the risk of eutrophication in coastal waters.; In this study the ecological risks associated with nutrient loading, and the prospects for alleviating them by restoring shellfish to coastal waters was evaluated using a risk assessment framework. There were three distinct aspects to the study. First, theoretical and empirical ecology were invoked to form a conceptual model of eutrophication risk as mediated by nutrient loading and grazer activity. Second, a laboratory experiment was conducted to examine feeding selectivity and nitrogen processing by oysters fed different types of phytoplankton. Third, a nitrogen cycling model was developed and used to estimate eutrophication risks under various nutrient loading and shellfish grazing scenarios. The goal of the study was to evaluate whether, and under what circumstances, the restoration of shellfish in nutrient-enriched estuaries would reduce the likelihood of eutrophication. |
