Carbon Sequestration and Carbonate Preservation within Northeast Pacific Seagrass Beds

Our ongoing research aims to understand the long and short-term storage of carbon within seagrass environments in Northern California. The objective of this sedimentological research is to link long-term carbon storage of seagrass beds with short-term modifications of water chemistry in an environment that is central to ongoing ocean acidification research. Thus far, our monitoring has targeted seagrass beds of various sizes and shoot densities, as well as seasonal differences, in two estuaries (Tomales Bay and Bodega Harbor, CA). In this project, we paired automated sensor deployments and discrete bottle sampling (for pH, pCO₂, O₂, Temperature, Salinity) with biomass investigations and collection of push cores in and around seagrass meadows. We analyzed the push cores for grain size, carbonate content, total organic matter, and microfossils. Preliminary data from one seagrass ecosystem in Tomales Bay indicate that the sandy substrate within seagrass beds contains between 1-6% organic matter and 2-7% carbonate sediments. We found that the finer sediments outside the seagrass beds contain somewhat higher organic matter and carbonate concentrations. Long-term objectives are to repeat this study in four different seagrass ecosystems over the next year. Although initial results suggest that smaller grain size is linked with lower carbon sequestration in seagrass beds further data from other sites are needed to explore these relationships.