Artificial seagrass demonstrates the role of physical trapping in seagrass carbon storage

Seagrass beds store carbon through a combination of localized primary production and trapping of fine particles. The relative contribution of these two processes is difficult to determine in natural seagrass beds, but artificial beds can be used to separate these processes. In this project, two 3m x 3m artificial seagrass beds (one sparse and one dense) were deployed near the edge of a restored seagrass meadow behind a newly forming inlet to a shallow coastal lagoon. Measurements of sediment organic content, grain size, benthic chlorophyll, temperature and light were made for 15 months in the artificial beds, the adjacent bed and an adjacent bare area. As the inlet formed, all plots accumulated between 6.9 and 8.8 cm of sediment and sediment organic content decreased. However, the decrease in organic content was smaller for the dense artificial bed than any other plot and the dense artificial bed accumulated more carbon than the natural seagrass bed during this time period. This finding indicates that the primary mechanism for carbon storage by seagrass beds is physical trapping. Artificial seagrass beds may be a viable mechanism to both enhance restoration and speed the carbon sequestration of seagrass beds.