Abstract:

Knowledge of how biota can be used to monitor ecosystem health and assess impacts by human alterations such as land use and
management measures taken at different spatial scales is critical for improving the ecological quality of aquatic ecosystems.
This knowledge in Uganda is very limited or unavailable yet it is needed to better understand the relationship between
environmental factors at different spatial scales, assemblage structure and taxon richness of aquatic ecosystems. In this study,
benthic invertebrate community patterns were sampled between June 2001 and April 2002 and analysed in relation to water
quality and catchment land use patterns from three shallow near-shore bays characterized by three major land uses patterns:
urban (Murchison Bay); semi-urban (Fielding Bay); rural (Hannington Bay). Variations in density and guild composition of
benthic macro-invertebrates communities were evaluated using GIS techniques along an urban-rural gradient of land use and
differences in community composition were related to dissolved oxygen and conductivity variation. Based on numerical
abundance and tolerance values, Hilsenhoff's Biotic Index ofthe invertebrates was determined in order to evaluate the relative
importance of water quality in the three bays. Murchison Bay supported a relatively taxa-poor invertebrate assemblage mainly
comprising stenotopic and eurytopic populations of pollution-tolerant groups such as worms and Chironomus sp. with an
overall depression in species diversity.