Blue carbon storage and variability in Clayoquot Sound, British Columbia

Seagrass habitats store substantial amounts of organic carbon, known as 'blue carbon', We took sediment cores from the intertidal and subtidal zones of three eelgrass (Zostera marina) meadows on the Pacific Coast of British Columbia, to assess carbon storage and accumulation rates. Sediment carbon concentrations did not exceed 1.30 %Corg, and carbon accumulation rates averaged 10.8 ± 5.2 g Corg m-2 yr-1. While sediment carbon stocks were generally higher in the eelgrass meadows relative to non-vegetated reference sites, carbon stocks averaged 1343 ± 482 g Corg m-2, substantially less than global averages. Our carbon estimates are in line with results from other Z. marina meadows; Z. marina’s shallow root system may contribute to lower carbon storage. Sandy sediment, nutrient limitation, and low sediment input may also contribute to low carbon values. The larger, more marine influenced meadows with cooler temperatures resulted in larger total carbon stock. By improving the quantification of site-specific carbon dynamics, eelgrass' role in climate change mitigation and conservation can be assessed.