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

Abstract

In 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.