Nickerson Fellowship Research Abstract
Quantifying Greenhouse Gas Emissions from Seagrass Meadows over a Nutrient Gradient in the Cape Cod National Seashore
Seagrass meadows provide important ecosystem services in coastal and estuarine systems, including carbon (C) sequestration and storage. Mcleod et al. (2011) estimate that worldwide seagrass ecosystems bury 138 (± 38) g C m-2 yr-1– an amount 10x greater than that buried in temperate forest soils. Current estimates of C sequestration in seagrass ecosystems however, do not consider pathways of C release that could offset the benefits of C storage and contribute to atmospheric warming. Specifically, sediment microbial processes could stimulate the release of the potent greenhouse gases, carbon dioxide (CO2) and methane (CH4). Further, eelgrass meadows are in decline due to anthropogenic disturbance caused by excess nitrogen (N) loading. The stress of excess N could enhance CO2 and CH4 release thereby offsetting eelgrass C storage. For example, methanogenesis occurs in anoxic environments like those present in heavily N loaded systems. Without measurements of CO2 and CH4 release from sediment in seagrass meadows, the actual value of C-sequestration in these systems remains largely unconstrained. In this study I propose to 1) quantify CO2 and CH4 fluxes and 2) determine the impact of N loading on these C emissions in four Cape Cod National Seashore eelgrass (Zostera marina) meadows over an N loading gradient: Pleasant Bay, East Harbor, Wellfleet Harbor, and Cape Cod Bay (high to low N loading, respectively).