The role of anthropogenic influences on a tropical lake ecosystem and its surrounding catchment: a case study of Lake Sentani.

Lake Sentani is a tropical lake in Indonesia, consisting of four interconnected sub-basins of different water depths. While previous work has highlighted the impact of catchment composition on biogeochemical processes in Lake Sentani, little is currently known about the microbiological characteristics across this unique ecosystem. With recent population growth in this historically rural area, the anthropogenic impact on Lake Sentani and hence its microbial life is also increasing. Therefore, we aimed to explore the influence of environmental and anthropogenic factors on the microbial diversity of Lake Sentani. Here we present a detailed microbiological evaluation of Lake Sentani, analyzing 49 different sites across the lake, its tributary rivers and their river mouths to assess diversity and community structure using 16S rRNA gene sequencing. Our results reveal distinct communities in lake and river sediments, supporting the observed geochemical differences. Taxonomic assessment showed the potential impact of anthropogenic pressure along the northern, urbanized shore, as river and river mouth samples revealed high abundances of Bacteroidota, Firmicutes and Cyanobacteria, which could be attributed to pollution and eutriphication. In contrast, lake sediment communities were dominated by Thermodesulfovibrionia, Methanomethylicia, Bathyarchaeia and Thermoplasmata, suggesting sulfate reducing, thermophilic, acidophilic bacteria and methanogenic archaea to play an important role in tropical lake systems. This study provides novel insights into ecological functions of tropical lakes and contributes to the optimization of management strategies of Lake Sentani, ensuring its holistic preservation in the future.