Variation in Carbon Sediment Storage Across Salish Sea Eelgrass Habitats

Abstract

Seagrasses are marine flowering plants that are found globally in coastal habitats. Seagrass meadows serve as valuable carbon sink habitats by trapping and storing carbon within the sediment. The ability of these habitats to store sediment is variable region to region. It is unclear what biotic or abiotic factors contribute to the success of carbon burial in these habitats within the Salish Sea. This study assesses sediments stored in Z. marina meadows and unvegetated sites within two distinct estuaries located in the Salish Sea. The two study sites represent estuaries located within an active delta and an inactive delta. I evaluated the carbon stock and isotopic signatures of these sites to understand how vegetation and location can affect the origin and amount of carbon stored in these habitats. I found that carbon stock did not significantly differ between sites regardless of estuary type or presence of Z. marina. This may indicate that physical processes may be the primary driver of carbon storage instead of the presence of Z. marina within these sites. The total carbon stock integrated over the top 50cm of sediment was lower than other published estimates with an average of 8.30 Mg ha-1 within an active delta and 11.62 Mg ha-1 within an inactive delta. Isotopic signatures of carbon and nitrogen were statistically significantly depending on site vegetation and location. At the current Californian market price of carbon, the mean value of all sites in this study equates to $229,214 per square mile within the top 50cm of sediment. I conclude that there is a need for more information to determine the abiotic influences on carbon sediment storage variability across the Salish Sea.