Water quality analysis of Serantangan Lake using macrozoobenthos as indicators

Illegal gold mining in West Kalimantan has led to the formation of Serantangan Lake, a post-mining void with potential for freshwater resources, tourism, and agriculture. However, mercury contamination and degraded water quality pose significant ecological and public health risks. This study evaluated the lake's water quality using macrozoobenthos as bioindicators across three stations representing varied environmental conditions. The research was conducted from December 2024 to February 2025. A total of 1,078 macrozoobenthos individuals were collected, representing 14 genera, 14 families, and 9 orders. Diversity indices revealed the highest biodiversity at Station I (H' = 1.13, E = 0.98) and the lowest at Station III (H' = 0.42, E = 0.37), which was adjacent to active mining. Dominance index (D) and Family Biotic Index (FBI) further confirmed poor ecological conditions at Station III (D = 0.41, FBI = 8.6), indicating very poor water quality. Physicochemical measurements showed elevated mercury levels (up to 0.0027 mg/L) and BOD (up to 12.6 mg/L), with transparency, mercury contamination, and hardness significantly correlated with macrozoobenthos abundance and diversity. Canonical Correspondence Analysis (CCA) and Principal Component Analysis (PCA) revealed distinct macrozoobenthos assemblages influenced by environmental parameters.