Impacts of dredging and restoration on sedimentary carbon stocks in seagrass meadows of Pari Island, Indonesia

Abstract

Abstract The effects of dredging and restoration on carbon sequestration in seagrass sediments is not well understood. Our knowledge is derived from few studies conducted in areas affected by dredging or restoration, the majority of which are from temperate regions. There is limited information available for tropical regions, where seagrass sediments can differ greatly in species composition, geomorphology, and hydrodynamic conditions. This study aims to assess the effects of dredging and seagrass restoration on sediment organic carbon concentrations and stocks at Pari Island, Indonesia. The results indicated that sediment organic carbon concentrations (%Corg) were higher in persistent seagrass meadows than in dredged, restored seagrass, and bare sand areas. Dredging at Pantai Perawan, Pari Island, led to the removal of seagrass vegetations and sediments. We found that the organic carbon concentrations in the sediment of dredged areas were 17% lower than that of persistent seagrass sediments. Although seagrass restoration has increased seagrass cover, the organic carbon concentrations in restored meadows were still lower than in persistent meadows. Therefore, we inferred that there have been no significant gains in organic carbon concentrations or stocks in sediments under the restored seagrass after 13 years. Protecting existing seagrass meadows is fundamental because restoring seagrass after disturbance and re-establishing carbon sequestration requires considerable time and resources.