Anthropogenic input of mercury (Hg) to marine environment is a great concern due to its potential impact may threat the marine ecosystem. In this paper, we evaluate Hg releases caused by mining in marine environment of Buyat Bay (BB), north Sulawesi, Indonesia, by quantifying the concentration of total mercury (THg) and methyl mercury (MeHg) in marine biota. The results showed that Hg was found in all samples and the concentration varied according to group of species. Bioaccumulation and biomagnifications occurred through the food webs in which the lowest concentration was found in the soft coral Sinularia sp. (1.3m g/kg, range 0.45-2.28) and other producers (sea grass and seaweed) and the highest was in the carnivorous fish Epinephelus merra (359m g/kg, range 211-572). As MeHg is found to accumulate in the carnivore fish sample in higher level than that in control, the methylation of inorganic Hg occurs in the marine environment of BB. That is plausible since all the Hg released from the anthropogenic sources in the region was inorganic form and there is absolutely no source of MeHg other then the spontaneous distribution.