Effects of Long-Term Anthropogenic Disturbance on the Benthic Episammic Diatom Community of an Ancient, Tropical Lake

Habitat homogenization, nutrient enrichment and loss of biodiversity are broadly recognized as the consequences of human activity in aquatic systems. Diatoms (Bacillariophyceae) are frequently used in aquatic environmental assessment and impact monitoring, but in unique habitats dominated by endemic taxa, traditional approaches may not be appropriate. We examined the impacts of long term anthropogenic impacts upon the littoral episammic diatom community around the town of Soroako, located on Lake Matano, an ancient tropical lake. Lake Matano is located on central Sulawesi Island, Indonesia, and socio-economic conditions are typical of developing nations. Although differences in nutrient concentrations were undetectable with field-based spectroscopy approaches, mean Shannon diversity was decreased in association with proximity the town-site. However, mean ß-diversity was maintained despite several decades of shoreline modification at Soroako. Elevated abundances of early-successional diatom taxa in the disturbed area drove differences between areas immediately offshore of Soroako and those farther away. These findings suggest that increased physical disturbance and TSS loads around Soroako, rather than increased nutrient loading, influenced shifts in the diatom community. These results suggest that microscopy-based biomonitoring approaches are sensitive indicators of environmental modification that could be useful in areas where access to cutting-edge analytical equipment is limited.