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DEVELOPMENT OF NITROGEN LOAD-REPONSE RELATIONSHIPS FOR ESTUARIES
Citation:
Dettmann, E H., J S. Latimer, G Cicchetti, D J. Keith, L Coiro, R A. McKinney, G B. Thursby, S Rego, M Abdelrhman, C Pesch, B J. Bergen, W Nelson, W S. Boothman, A. F. Santos, AND M Charpentier. DEVELOPMENT OF NITROGEN LOAD-REPONSE RELATIONSHIPS FOR ESTUARIES. Presented at Third International Nitrogen Conference, Najing, China, October 12-16, 2004.
Description:
A research program is currently underway to meet the United States Environmental Protection Agency's need to develop nutrient criteria for estuarine and coastal marine waters. This research is intended to develop nitrogen load-response relationships for submerged aquatic vegetation (SAV), dissolved oxygen, and food web structure in marine coastal embayments. This poster presents the overall research program, with a focus on the component that models planktonic chlorophyll based on nitrogen loading.
A simple hybrid model is being developed that combines mechanistic insights and empirical data. Empirical relationships between embayment water column chlorophyll a and total nitrogen (TN) concentrations are being added to a currently validated model that relates spatially averaged annual TN concentrations to loading. Research in Long Island Sound (northeastern USA) revealed power-law relationships between chlorophyll a and TN concentrations and provided insights into seasonal and interannual variations in these correlations, as well as their causes. Furthermore, data from other embayments are being analyzed to determine the generality of these relationships, including the degree of interannual and system-to-system variability.
This research is part of a larger effort to develop relationships between normalized nitrogen loading and several eutrophication responses in marine embayments, including spatial SAV distribution, dissolved oxygen concentrations and food web structure. Loading rates are normalized to reflect estuary volume and flushing time. Spatial extent of SAV beds and chlorophyll a concentrations in embayments are being determined by aerial photography and aircraft remote sensing of the spectral color of water, respectively. The spatial and temporal extent of anoxia is being estimated using sediment profile imagery. Benthic habitat, fish, and shellfish communities, elements of food web structure, will be monitored over broad spatial scales using video surveys. Methods for classifying marine embayment sensitivity to nutrient loading are being explored to further normalize loading, and to refine load-response relationships.