Hillmann, ER, Rivera-Monroy, VH, Nyman, JA La Peyre MK. 2020.nEstuarine submerged aquatic vegetation habitat provides organic carbon storage across a shifting landscape Science of the Total Environment
Within estuaries, submerged aquatic vegetation (SAV) thrives across the salinity gradient providing valuable ecosystem services. Within the saline portion of estuaries, seagrass areas are frequently cited as hotspots for their role in capturing and retaining organic carbon (Corg); non-seagrass SAV, located in the fresh to brackish estuarine areas, may also retain significant soil Corg, yet their role remains unquantified. Given rapidly occurring landscape and salinity changes, landscape level carbon pool estimates would benefit from estuarine SAV habitat blue carbon estimates. We assessed Corg stocks in SAV habitats from estuarine freshwater to saline habitats (interior deltaic) to saline barrier islands (Chandeleur Island) within the Mississippi River Delta Plain (MRDP), Louisiana, USA. SAV habitats contain Corg stocks (56-231 Mg Corg ha-1) equivalent to those reported for other estuarine vegetation types (seagrass, salt marsh, mangrove). Interior deltaic SAV Corg stocks (231.6 ± 19.5 Mg Corg ha-1) were similar across the salinity gradient, and significantly higher than at barrier island sites (56.6 ± 10.4 Mg Corg ha-1). Within the MRDP, shallow water SAV habitat covers up to an estimated 26, 500 ha, indicating that soil Corg storage is potentially 6.1 ± 0.1 Tg representing an unaccounted Corg pool. Extrapolated across Louisiana, and the Gulf of Mexico, this represents a major soil Corg storage.