ASSESSMENT OF BENTHIC MACROINVERTEBRATES AS BIOINDICATORS OF ON WATER QUALITY IN RIVER NAKA, CHUKA

Abstract

Freshwater ecosystems worldwide have been progressively deteriorating leading to a decrease in aquatic biodiversity. Conventionally, evaluation of water quality uses single physical-chemical parameters which may be insufficient to fully assess the quality of freshwaters. This study used bio-indicators to assess water quality River Naka in Tharaka-Nithi, Kenya. Fluvial ecosystems support rich and diverse assemblages, making them vulnerable to possible alterations in the habitat. The study assessed the diversity and abundance of benthic macroinvertebrate communities and use as bioindicators of water quality. Grab sampling was used to collect water samples, a kick sampler and D-frame aquatic net was used to collect 121 benthic macroinvertebrates from three selected sites and determined using EPT Index (Ephemeroptera, Plecoptera and Trichoptera group). The data obtained was used to determine the index of the sampling sites. Physico-chemical factors were analyzed in-situ (temperature, turbidity and pH) and (nitrates and phosphates) in the laboratory. The highest EPT index values at the upstream corresponded to good water quality, while the slightly low values at the midstream indicated moderate water quality and the lowest values recorded at the downstream showed fair water quality. The water quality parameters downstream exceeded the World Health Organization standards posing health hazard to water users. Continuous bio-assessment based on EPT biotic indicators of rivers should be conducted oftenly to develop long-term profile of water quality status and ecological integrity of rivers.