Mercury (Hg) contamination in Manado Bay, North Sulawesi, Indonesia

Artisanal gold minings, which are situated in the highlands of the northern part of Sulawesi Island, use mercury (Hg) to extract gold and discharge theirs tailings into rivers; one of the rivers (Bailang River) is connected to Manado Bay. This could cause Hg contamination into the bay. This study aimed to assess the contamination of Hg in the aquatic ecosystem of the bay. For the assessment, the bay was divided into 2 parts, namely the North and the South, and the contamination was assessed by measuring the total Hg concentration in sediments and fishes. Determination of Hg concentration refers to the Indonesian National Standard (SNI) 01- 2896-1992 and Guidance of Balai Riset dan Standarisasi Industri Manado. The results showed that the range of Hg concentrations in fish varied by species; in the northern part of the bay: Holocentridae (0.1144-0.1151 ppm), Siganidae (0.0020-0.0034 ppm), Apogonidae (0.0461-0.050 ppm), and <i>Nemipterus</i> (0.0142-0.0144 ppm ). While in the southern part of the bay: Holocentridae (0.1090-0.1104 ppm), Siganidae (0.160-0.164 ppm), Apogonidae (0.1280-0.1291 ppm), <i>Nemipterus</i> (0.0522-0.0530 ppm), and <i>Priacanthus</i> sp. (0.0194-0.0210 ppm). The average concentration of Hg in sediments of the bay around river mouths varied based on location, i.e. Bailang River was 0.0502 ppm, Sario River was 0.0270 ppm, Bahu River was 0.0615 ppm, and Malalayang River was 0.0143 ppm.