Blue carbon dynamics within the temperate subtidal eelgrass (Zostera marina) meadows of Portage Inlet, British Columbia

Seagrass meadows are categorized as blue carbon ecosystems as they are coastal marine environments that contribute immensely to atmospheric carbon dioxide reduction. Despite the importance of their ecosystem services, the carbon stock of many local seagrass meadows and the mechanisms behind their superior sequestration abilities are unknown. This study was the first sediment carbon stock assessment conducted within the subtidal seagrass (Zostera marina) meadows of Portage Inlet, Victoria. I projected how the potential loss of the meadows could impact the underlying sediment carbon stock by comparing the seagrass carbon stock to the adjacent unvegetated subtidal mudflat. I modeled the relationship between sediment carbon stock and the productivity measures (in terms of percent coverage, leaf area index and shoot density) of the eelgrass meadows as well as other physical-chemical measures (salinity, temperature, turbidity and wave motion) to determine what factors impacted the sediment carbon stock of the inlet. Data analysis revealed that the loss of the meadows would have little to no impact on the carbon stock of the inlet given that the stock of the meadows (39.4 ± 5.71 Mg C/ha) was statistically comparable to the unvegetated subtidal mudflat (38.9 ± 3.39 Mg C/ha). Model analysis revealed that eelgrass productivity measures could not statistically explain the variation in the carbon stock within the inlet. However, individual models of salinity, temperature and turbidity were more likely to explain the observed variation in sediment carbon stocks. Future studies should continue to analyze the interaction of biological, chemical and physical components in seagrass environments to obtain a more comprehensive understanding of local blue carbon dynamics for restoration and management purposes.