Influence of wastewater discharge from dredging mariculture pond sediments on the food sources of two intertidal crab species

The present study δ13C, δ15N and fatty acid compositions of two dominant mangrove crabs, Tubuca arcuata and Parasesarma plicatum were compared between a mangrove site frequently receiving dredged wastewater from mariculture ponds and an adjacent reference site, to investigate the impact of wastewater discharge on their diets. A laboratory experiment was also conducted to further test how their diets changed with the wastewater input. The result showed no significant change in the δ13C while clear 15N enrichment of crabs in association with the wastewater discharge. Changes in 15N signature and fatty acid composition of the crabs due to the wastewater discharge indicated that the impact of wastewater discharge was related to crab species, being more apparent on the deposit feeder (T. arcuata) than the herbivorous P. plicatum. The results suggested that the discharge of dredged wastewater into mangroves resulted in the uptake of wastewater-derived materials and nutrients by mangrove crabs.