Mercury Accumulation in Water, Sediment, and Mud Crabs (Scylla serrata) from Kaiely Bay Along with Evaluation of Associated Histopathological Changes

This study investigated mercury (Hg) contamination in the estuarine ecosystem of Kaiely Bay, Buru Island, Indonesia, with a focus on its accumulation in environmental matrices and biological effects on Scylla serrata (mud crabs). Sampling was conducted once during the dry season from January to July 2022 across five estuarine stations: Kaiely River (St.1), Waelata River (St.2), Anahoni River (St.3), Sanleko River (St.4), and Jikumerasa River (St.5). A total of 45 samples were collected, comprising 15 water samples, 15 sediment samples, and 15 mud crab specimens (three replicates per station per matrix). Mercury concentrations were analyzed using Cold Vapor Atomic Absorption Spectrophotometry (CV-AAS). The results showed significant spatial variation, with Waelata exhibiting the highest Hg levels: 1.16 ± 0.12mg/ L in seawater, 0.43 ± 0.13mg/ Kg in sediment, and 0.27 ± 0.03mg/ Kg in crab tissues. Mercury concentrations in seawater across all stations exceeded the Indonesian marine water quality limit (0.001mg/ L) as stipulated by Government Regulation No. 22/2021. Although sediment and crab tissue values were below the FAO/WHO limit for human consumption (0.5mg/ Kg), their elevated levels raise ecological and health concerns. Histopathological and immunohistochemical analyses revealed organ-specific lesions in gills, muscles, and gonads, accompanied by varying degrees of MTF-1 expression. These findings demonstrate the bioindicator potential of S. serrata and emphasize the need for enhanced monitoring in mercury-impacted estuarine areas.