This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).
Overfishing is emerging as one of the greatest threats to the integrity of marine ecosystems and the societal services they provide. Though the consequences of predator depletion are increasingly appreciated for a few well-studied coastal habitats including kelp forests and coral reefs, the risks of overfishing to other valuable marine ecosystems including salt marshes remain uncertain and controversial. For over two decades, die-offs of salt marsh vegetation have been spreading across the Western Atlantic, threatening the critical nursery ground, nutrient filtering and storm barrier ecosystem services that marshes provide coastal environments. This project is based on the premise that recently described salt marsh die-offs on Cape Cod, Massachusetts are being driven by the native herbivorous crab, Sesarma reticulatum, and that these die-offs are an extensive and actively expanding threat to the near shore marine ecosystems throughout the surrounding region. The investigators outline a research program to examine the general hypothesis that overfishing of pelagic marine predators is releasing Sesarma populations from predator control and triggering herbivore-driven die-off and the degradation of Northeastern US salt marshes by exploring the following questions: 1) Is regional depletion of predators causing the die-off of Northeastern US salt marshes by releasing herbivorous Sesarma populations from predator control? Large-scale, regional surveys of crab and predator abundance and marsh die-off and experimental assays of predation pressure and crab herbivory will be conducted. 2) Is local fishing pressure triggering and intensifying salt marsh die-off? Impacts of predation and herbivory in heavily fished and nearby marine conservation areas will be quantified to explore preliminary data suggesting a strong causal relationship between local fishing pressure, crab herbivore pressure and creek bank die-off. 3) How are creek bank die-offs influencing the structure of Northeastern US salt marshes and their ability to provide ecosystem services? The investigators will map and follow the fate of die-offs throughout the region to develop a predictive understanding of the ontogeny and trajectory of crab-driven die-offs and their effect on the ecosystem services provided by salt marshes.
This work has conservation implications since it links the management of predators (commercially and recreationally harvested crabs and fish) that may control marsh plant consumers with the health and long-term persistence of coastal wetlands, and will provide a mechanistic understanding of these systems necessary for their management and continued provision of ecosystem services. The research will be complemented by a strong undergraduate and graduate educational focus and a community outreach component.
