Carbon draw-down potential by the native eelgrass Zostera marina in Puget Sound and implications for ocean acidification management

Thesis (Master's)--University of Washington, 2013In 2012, the Washington State Blue Ribbon Panel on Ocean Acidification recommended actions to address local impacts of ocean acidification. At least two of these actions included a focus on seagrasses. Recognizing the ability of the native seagrasses <italic>Z. marina</italic> to remove carbon from seawater, the panel identified the need to “ preserve Washington's existing native seagrass and kelp populations and, where possible, restore these populations ” and to “ develop vegetation-based systems of remediation for use in upland habitats and in shellfish areas ”. In this research I take the first steps to evaluate the potential utility of the native eelgrass <italic>Z. marina</italic> as a tool for mitigation of ocean acidification in Puget Sound. Using estimates of eelgrass abundance and distribution and regional estimates of net primary productivity, I estimated at relatively coarse scales the annual amount of carbon that could be removed from seawater by eelgrass via photosynthetic assimilation of carbon. I did not estimate long-term sequestration or burial. I applied a simple model to estimate the potential for carbon removal from seawater at several locations where eelgrass is present. At the basin level, rates of carbon removal by <italic>Z. marina</italic> are on the order of 10 <super>10 </super> gC y <super>-1 </super> for the Puget Sound Basin, and range from 10 <super>8 </super> to 10 <super>10 </super> gC y <super>-1 </super> for individual sub-basins. Initial estimates suggest that at most of the selected sites, the change in dissolved inorganic carbon (DIC) resulting from seagrass carbon assimilation may not be sufficient to cause a pronounced shift in carbonate chemistry. This first estimate of carbon draw-down potential suggests that <italic>Z. marina</italic> has limited ability to serve as a tool to ameliorate effects of ocean acidification in Puget Sound