Microplastic pollution in the surface water of Lake Singkarak, Indonesia

Abstract Microplastic pollution is already at an “alarming” level in Indonesia’s marine and freshwater ecosystems. However, to the best of our knowledge, no study has reported the microplastic occurrence in the lake ecosystem in Indonesia. Lake Singkarak, a big tectonic lake, has been considered one of the priority lakes to be restored. The lake receives a high influx of plastic waste from rivers and catchment runoff. Controlling the outflow through the hydropower dam and the sluice in the main lake outlet may prevent the microplastic’s outflux. The study’s objective was to determine the microplastic first occurrence and abundance in the lake’s surface water. Water samples were collected from three sites in the lake inlet area, one in the intake area of the hydropower dam and one in the outlet area, by performing four parallel trawls in each site using a modified plankton net. The most abundant microplastics in the lake’s surface water were 9 particles/m 3 in the lake inlet area, which received a high plastic waste input from the river. The lowest abundance was 2 particles/m 3 in the main lake outlet area. Foams and fragments, white and clear in color, size of 300 μm, were the dominant types of microplastics observed. Our preliminary study suggests that the lake could act as a sink of microplastics. Therefore, ceasing the input sources of plastic waste from the river should be prioritized to prevent further microplastic pollution of Lake Singkarak.