Postdoctoral Fellowship: OCE-PRF: How does the increasing prevalence of weedy species alter community interactions and coastal ecosystem functioning?

College Of William & Mary Virginia Institute Of Marine Science, Gloucester Point VA

Investigators

Abstract

Coastal ecosystems provide critical benefits to society, including carbon storage, shoreline protection, and buffering against ocean acidification. Seagrass meadows are central to these services, yet many regions are experiencing shifts from long-lived structurally complex seagrasses to faster-growing, short-lived “weedy” species, alongside widespread declines in seagrass-associated bivalves. These changes may fundamentally alter how coastal ecosystems function, potentially reducing their capacity to store carbon and regulate seawater chemistry. This project improves our understanding of how changes in seagrass and bivalve communities influence ecosystem resilience to ongoing environmental stress. Field experiments that include realistic fluctuations of the natural environment are used to identify which seagrass-bivalve species combinations best support carbon sequestration and local pH regulation. Results from this project enhance conservation and restoration strategies of both seagrasses and bivalves and may be upscaled to inform global carbon budgets. As a part of this project, research and mentoring opportunities extend to undergraduate students to broaden participation in the field of ecology. This project also advances literacy in environmental sciences through the development of a K-12 lesson plan on seagrass-bivalve interactions to teach students about the role of species interactions in ecosystem health. This project investigates how reorganization of seagrass-bivalve communities affects key ecosystem processes, specifically coastal carbon sequestration and plant-mediated regulation of seawater chemistry. Many coastal regions have shifted towards dominance by opportunistic, early-successional seagrass species, yet it remains unclear how these compositional changes interact with declining bivalve populations to influence ecosystem functioning. Seagrass meadows are an ideal system for studying community effects on ecosystem function because multiple seagrass species with different life history strategies often co-exist and, as foundation species, they support and interact with other key species. Seagrass-mediated changes in dissolved inorganic carbon and total alkalinity can also impact pH-sensitive organisms living within seagrass meadows, including bivalves, and bivalves in turn interact with sediments and the water column in ways that affect both organic carbon storage and the balance of dissolved inorganic carbon and total alkalinity in the carbonate system. This project will test the hypothesis that seagrass species identity and successional strategy interact with bivalve functional traits to determine rates of carbon storage and the magnitude of pH modification in coastal waters. Specifically, this study will first assess how the strength and direction of species interactions change across seagrass species identity and bivalve functional form by evaluating seagrass and bivalve growth metrics in bivalve-addition manipulations in meadows dominated by early successional (r-selected) vs. climax (k-selected) seagrass species. Using the same experimental approach, this study will also address the impacts of seagrass-bivalve interactions on surface sediment organic carbon storage, decomposition rates, and seawater carbonate chemistry. The findings from this study will deepen understanding of the potential for seagrass facilitation of pH-sensitive organisms in natural settings and the role of faunal communities in driving seagrass meadow carbon sink capacity. This study will therefore have implications for the management and conservation of coastal ecosystems as climate change and other anthropogenic stressors increase the extent and severity of coastal acidification and continue to alter foundation species assemblages. 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.