Human activities in rivers and watersheds have altered enormously the timing, magnitude and nature of inputs of materials such as water, sediments, nutrients and organic matter to estuaries. An important but neglected linkage between land and coastal waters is the input of dissolved and particulate organic carbon and organic nitrogen. This long term ecological research (LTER) in land/ocean margin ecosystems will focuses on the question-How will trophic structure and primary and secondary productivity in estuaries be affected by changes in organic matter, nutrient and water fluxes caused by changing land cover, climate and sea level? The project examines this question through 1) short and long term measurements of the fluxes of dissolved and particulate organic carbon and organic nitrogen entering estuaries from land, marshes and the ocean, 2) short and long term manipulative experiments to determine the effects of nutrient and organic matter interactions on the flow of C and N through pelagic and benthic food webs, and 3) modeling the effects of land use changes on food web transformations. The proposed research integrates estuarine biogeochernistry with studies of food webs and population biology of higher trophic levels. The research program will create a legacy of well designed and documented ecological experiments and observations. A data base of research results will be accessible (WWW) to the scientific community. The study builds on the existing long term research record at Plum Island Sound, MA, and at the North Inlet, SC and Wells, ME National Estuarine Research Reserves. Intensive work will take place at Plum Island Sound, and specific comparative studies at North Inlet and Wells. The research is designed to take advantage of natural differences between these systems to determine the importance of inorganic and organic matter interactions in controlling trophic structure, production and efficiency. The project will make a unique contribution to our understanding of land margin ecosystems by determining how changing nutrient supply interacts with the quality and quantity of organic matter to affect estuarine trophic structure. It will also develop modeling methods to link highly variable physical drivers, here tides, long term sea level rise, river inflow, and water circulation, with the understanding of ecological processes. The dynamic models developed will be useful in a variety of ways for predicting effects of various coastal management options. For example, the spatially explicit models to be developed can be used to predict the effects of changing land use on eutrophication and fish production.
