Coastal ecosystems are experiencing changes in nutrient loading and species composition much higher than previously measured, undoubtedly affecting productivity and sustainability of coastal regions. Predicting the impacts of these changes is important in salt marshes because marshes are among the most biologically productive areas in the world and provide critical ecosystem services, such as nursery areas for fisheries, removal of nitrogen, and shoreline storm buffering. This project addresses a critical question: What are the effects of increased nutrients and species change on ecosystem services provided by salt marsh ecosystems? The project is the first to use whole-ecosystem experiments that alter nutrient loading and reduce fish populations to understand the effects on nutrient cycling, species diversity, food webs and the long-term sustainability of salt marshes.
The damage by Hurricane Katrina due to degradation of coastal wetlands is one example of the importance of salt marshes to society. A growing appreciation of this role for marshes has led to estuaries becoming the focus of large-scale restoration programs. This project will provide information essential for developing water quality standards and providing perspective for multi-million dollar coastal management decisions, such as construction of sewage treatment facilities, regulation of fishing, or rebuilding of lost marshes.
Final Project Report This grant was in collaboration with a more extensive project "Interacting Controls on Ecosystem Function" (Principle Investigator L. Deegan, Marine Biological Laboratory). This larger grant was to follow the long-term impact of fertilization on a salt marsh ecosystem. The primary goal of Middlebury's RUI grant proposal was to involve undergraduate students in research. Our undergraduates helped 1) maintain the large fertilization study which involved moving fertilizers to platforms in the marsh every two days, 2) quantify fertilizer effects on various components of the ecosystem (for example they collected fish by night time netting of fish during the highest tides each month, or clipping salt marsh grasses) and 3) to carry out Middlebury-specific research concentrating on the effects of fertilization primarily on the algal component of the system, although one student studied the animals in the creek channels. Six undergraduates stayed at the research site and worked throughout the project, maintaining the larger experiment and worked on independent projects. Another eight Middlebury undergraduates traveled from Vermont to the site at least once to set up our algal experiments. Measuring the effects of fertilizer on algal growth was harder than expected, because the algae are very patchy in this system. Within a single place there was both no algae on creek walls and dense algae. We developed a technique to make creek walls more uniform in algal cover. Often plant biomass is used to measure plant growth, however other things are changing in the system, e.g. shrimp may be eating algae, so algal growth may be under counted. We developed a technique to measure the amount of photosynthesis of the algae. Finally, we found a way to grow algae on creek walls and keep the animals that might be feeding them away using cages. The results were surprising. Adding fertilizer had no effect on to salt marsh creek algae, although in one of the creeks, small animals appeared to be eating the algae making it hard to measure direct fertilizer effects. A total of 14 undergraduates were involved in the research. Two of these students carried out independent honors research in this system. Of these two, one is enrolled in a PhD program in biology and the other is currently applying to graduate school in environmental engineering.
