Phytoplankton community structure in the habitat of the endemic fish species Bilih (Mystacoleucus padangensis Blkr) in Lake Singkarak, West Sumatra, Indonesia

Abstract

Bilih (Mystacoleucus padangensis Blkr.) is an endemic fish species with a high commodity value of inland fisheries in Lake Singkarak. The bilih population has declined due to over exploitation and environmental degradation. The phytoplankton community structure in the fish habitat of bilih was analyzed to assess the ecological status of the habitat and to suggest any bilih fish management measures. Phytoplankton and water quality data was collected at 12 stations, including littoral and pelagic habitats, in September 2022, May 2023 and July 2023. Water quality, such as temperature, pH, DO, turbidity, conductivity, and TDS, is suitable for fish and phytoplankton growth. We identified 52 species of phytoplankton from six divisions. Phytoplankton composition consists of Bacillariophyta, Chlorophyta, Cyanophyta, Pyrrophyta, Euglenophyta, and Cryptophyta. Cyanophyta contributing 73% to 83% characterized by high transparency was recorded in Paninggahan, Sumpur, and Ngalao stations, especially in May 2023. Based on the phytoplankton abundance range of 159 to 12200 individuals/L and the functional group of phytoplankton, the status of the bilih habitat is meso-eutrophic. The dominant phytoplankton changed during observation periods. Ulotrix sp. and Ceratium hirudinella were dominant in September 2022, while Cylindrosperopsis raciborskii and Pseudoanabaena were dominant in May 2003. The dominant phytoplankton species in July 2023 were Synedra ulna, Cylindrospermopsis raciborskii, and Merismopedia sp. The Shannon-Wiener diversity index range of 0.309 to 2.186 showed that that water quality condition was moderately polluted. The species richness index showed a wide range from 0.986 to 3.129. Monitoring water quality and phytoplankton community is important to prevent the possibility of cyanobacteria blooming. Conservation areas of bilih should be implemented in stations with a low abundance of Cyanophyta.