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TIDE: Trophic cascade and Interacting control processes in a Detritus-based aquatic Ecosystem. National Science Foundation, Division of Environmental Biology. C.T. Friedrichs, VIMS Principal Investigator. (Marine Biological Laboratory Lead PI: Linda Deegan.)
Proposal Summary
Human activity is changing local and global environments at unprecedented rates. Some of the most significant changes involve widespread nutrient enrichment and biotic impoverishment as well as global warming and sea level rise. Predicting the impacts of these multiple stresses on the biosphere is one of the most challenging and urgent problems in environmental science and is the first step toward sustainable management. It is particularly important in coastal salt marsh estuaries because they are among the most biologically productive areas in the world and are heavily used by humans for a variety of purposes. These areas are now experiencing changes in nutrient loading, species composition and sea level rise 5-10 fold higher than measured over the last century that are undoubtedly affecting the productivity and sustainability of coastal regions. Over the long run, how will an increase in nutrients interact with changes in species composition to alter the outcome of the race between sea level rise and marsh accretion and change ecosystem structure and function?
Despite the urgency of the problem, ecological theory cannot predict the response of salt marshes to nutrient enrichment and biotic impoverishment. The theory describing the relative importance of nutrients (bottom-up) or species composition (top-down) on ecosystem function has never been tested in detritus-based aquatic systems. Salt marshes exemplify detritus-based aquatic ecosystems in which the foodweb is based on the consumption of non-living organic matter (detritus). Detritus is also important in creating the physical structure of the system by the formation of peat. The combined effects of nutrient enrichment and biotic impoverishment will have more effect on ecosystem function and sustainability than either stress alone because of non-linear feed-backs among components of the ecosystem.
The research will advance our scientific knowledge in two ways. First, the research will broaden our understanding of all ecosystems by conducting experiments that identify biotic and abiotic controls in detritus-based aquatic ecosystems and comparing this to similar work done in other systems. Second, the research will address a general problem in environmental science: What is the relevant amount of detail, including the resolution of physical space and biotic processes, that must be incorporated in models to capture the marsh landscape response?
We will use an integrated field experiment and modeling approach that will link biogeochemical and biotic controls to sediment dynamics to predict the sustainability of coastal ecosystems. Whole salt marsh ecosystems will be altered by addition of nutrients in flooding waters and by removal of a key fish species, the mummichog and 15N tracers added to test bottom-up/top-down controls. The experiments will be used to test a new model that incorporates the spatially complex physical, chemical and biological interactions that characterize salt marshes. The model will be used to predict the marsh ecosystem response to changes in nutrients and species over decades.
This project will contribute to improving scientific infrastructure and will address societal
concerns about the environment. The proposal includes a diversity of scientific expertise, mixing senior full-time researchers with early-career scientists in traditional tenure-track (Virginia Institute of Marine Science) and full-time research positions (Marine Biological Laboratory) and includes faculty from a non-Ph.D. granting institution (Connecticut College) and a university in an EPSCoR state (Louisiana State University). The inclusion of science writers and high school students, in addition to the traditional undergraduate (4-6 per yr.) and graduate students (4 per yr.), will enhance dissemination of the results beyond traditional scientific forums. And finally, the research addresses a pressing environmental concern by conducting research that will predict the consequences of eutrophication and biotic impoverishment on vulnerable coastal ecosystems of particular importance to humans.
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