LTREB Renewal: Nutrients and climate as drivers of carbon sequestration and ecosystem metabolism in a nitrogen-enriched, shallow coastal ecosystem

Seagrasses provide critical habitat for many species, help maintain water quality by filtering nutrients, and store substantial quantities of carbon. In many coastal waters, seagrasses are being lost at an accelerating rate, with nutrient pollution being a major cause. This project examines the interaction of nutrient pollution with climate change on the ecology of a coastal harbor on Cape Cod, Massachusetts with extensive seagrass beds. The project studies how the seagrasses store carbon and remove nutrients in coastal marine environments, thereby reducing environmental degradation. The harbor has received high inputs of nitrogen for the past 20 years from groundwater contaminated by nearby municipal wastewater treatment. The nitrogen load to the harbor is expected to decrease over the coming years due to improved wastewater management. The project therefore measures how a seagrass-dominated ecosystem recovers from pollution. The project educates 10 to 15 undergraduate students each year who are conducting research projects. The project also shares data with the Buzzards Bay Coalition, the Town of Falmouth, and the Buzzards Bay National Estuary Program. This research informs efforts to better protect and restore seagrass habitat and water quality. This project is the second five years of a planned ten-year study that continues a set of measurements made since 2005. These measurements include: nitrogen loading; rates of primary production, ecosystem respiration, and net ecosystem production; concentrations of carbon, oxygen, nitrogen, phosphorus, sulfur, and chlorophyll in sediments, porewaters, and water column; seagrass extent and carbon, nitrogen, and phosphorus content; and exchanges of nitrogen and phosphorus with the coastal ocean. The long-term data set provided by this project is the only one globally for a nitrogen-polluted, shallow seagrass-dominated ecosystem. These data allow exploration of several fundamental questions, including whether nitrogen or phosphorus is more limiting in these types of ecosystems. Further, the project examines how climate-driven changes in ocean circulation may be altering sources of nitrogen and phosphorus. Ultimately, the research demonstrates how climate and nutrients interact to regulate the storage of organic carbon in seagrass-dominated ecosystems in the temperate zone. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.