Impact/Purpose:

The States and EPA Regions will use the products of this research when setting ecologically relevant nutrient criteria for estuaries, in support of 305b reporting and TMDL development. This research develops models for predicting the response of estuarine aquatic vegetation to nutrient loads (N and P) to provide a sound scientific basis for establishment of nutrient criteria that would protect these important habitats from degradation or loss, and aid in restoration efforts. This research also provides a compendium of important species of aquatic vegetation and their habitat requirements, and develops a classification scheme for setting nutrient criteria in estuaries where historical data are lacking. The benefits of this research will be a reduction in the uncertainty associated with setting vegetation-based nutrient criteria and TMDLs for the nation's receiving waters.

Description:

This research aims to understand the relationship between SAV loss and nutrient loading (N and P). A set of models will be developed and used to examine how nutrients interact with the physical and biological components to affect the health of SAV populations. First, a literature review and compilation of scientific literature focusing on evaluating SAV-nutrient relationships and other factors limiting seagrass growth will be conducted. Where existing nutrient-SAV community data are available, this will include the compilation and analysis of data. We will then develop models of how SAV communities and nutrients interact with various environmental parameters to result in decreased survival or production in this important habitat. These models may be regionally or species specific because of the inherent differences; however, we will seek to make them as broadly applicable as possible. A classification scheme for coastal receiving waters that groups these waters according to their sensitivity to SAV loss in response to excess nutrient loadings will be proposed. We will use knowledge of species-specific requirements and develop models that include the effects of light, nutrients, and sediment geochemistry on seagrass physiology. We also will seek to link the response models with models of water column chlorophyll a-light absorption/attenuation to provide a basis for setting nutrient criteria for coastal receiving waters where protection or restoration of SAV is needed. Methods, parameters and measurement endpoints for SAV response to excess nutrients will be selected so that data and models are interchangeable across regions. The final step of this research is a verification that tests the model's prediction and our classification scheme against the actual endpoint response.

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