Epipelic diatom diversity as a bioindicator in River Aturukuku, Eastern Uganda

Abstract

Background: Despite their key ecological functions and application in biomonitoring, little is known about the algal flora in Uganda, especially those of lotic systems. Aim: This study related the community composition of the epipelic diatoms to environmental variables to establish the influence of rural and urban activities on water quality and on the biota on spatial and seasonal scales along River Aturukuku in Eastern Uganda. Methods: Epipelic diatoms and selected environmental variables were compared among sites: two urban, a reference site upstream, and a site downstream from the urban area, spanning the dry and wet seasons from February to October, 2018. Results: Total phosphorus and nitrogen concentrations were above the natural threshold in the river. The diatom species such as Gyrosigma attenuatum and Placoneis gastrum, tolerant of pollution, dominated in the river. Total phosphorus, pH, temperature, and bottom substrates were most related to the composition of the diatom communities. The abundances of P. gastrum and Sellaphora nyassensis correlated with increased pH at the urban sewage effluent, suggesting that they are potential indicators of this kind of polluted environment. Conclusions: The study provides baseline information on diatom community, and is relevantfor biomonitoring and biodiversity conservation in Uganda and other tropical countries. KEYWORDS: Biological integrity; catchment degradation; diatoms; ecological functions; species tolerance