Assessment of the ecological status of the Kinyankonge River (Burundi), using a Biotic Integrity Index of zooplankton (BII-zooplankton)

This study aimed at assessing the ecological status of the Kinyankonge River using a zooplankton-based Biotic Integrity Index (BII-zooplankton). This was achieved through monthly collections of zooplankton from four stations along the river over 18 months (from July 2015 to June 2016, then from January 2017 to June 2017). Chemical parameters of the water were also measured using the AFNOR and APHA methods. Organic loads of water samples were assessed using Leclercq’s Organic Pollution Index. Zooplankton levels of disturbance were evaluated by Karr’s Biological Integrity Index. From this study, it was calculated that the Organic Pollution Index had two levels of pollution: strong organic pollution and very high organic pollution for upstream and downstream stations, respectively. Zooplankton populations were more disturbed during dry season than rainy season. The calculated Biotic Integrity Index highlighted a degradation of the ecological quality, especially in the upstream stations along the Kinyankonge River. Based on the zooplankton species diversity as an indicator of the ecological status of the river, the Biotic Integrity Index revealed a spatio-temporal variation highlighting four states of ecological quality of the Kinyankonge River: bad, moderate, good and very good, where Microcyclops sp. indicates bad ecological status, Brachionus angularis and Tropocyclops sp. indicate moderate ecological status, whereas Rotaria sp. indicates very good ecological status. No species was identified as indicator of good ecological status. Therefore, the BII-zooplankton can be used as an indicator of the ecological health of the Kinyankonge River, and extended to other aquatic ecosystems in Burundi.