Assessment of ecological water quality along a rural to urban land use gradient using benthic macroinvertebrate-based indexes

Abstract

Agricultural practices such as livestock grazing and tilling can result in soil erosion and runoff of fine sediments, nutrients (e.g. nitrogen, phosphorus, potassium) and pesticides, leading to degradation of aquatic environments. Urbanization is also responsible for a variety of impacts on fluvial ecosystems, including pollution by heavy metals, oil, domestic sewage and garbage. In this study, we evaluate the impact of land use on stream health of the Uberabinha river catchment. Overall, rural streams presented better ecological conditions than urban streams. Both species composition and abundance of benthic communities showed significant differences between rural and urban streams. Urban streams presented a higher dominance of Oligochaeta, Hirudinea and Gastropoda, bioindicators of poor water quality. Rural streams presented significantly greater richness and diversity. Compared to urban streams, rural streams presented a significantly higher number of Ephemeroptera, Plecoptera, Trichoptera, Odonata and Hemiptera taxa. Our analyses also showed congruence (high correlation) among the classical biodiversity metrics (Shannon-Wiener index - H', Pielou's measure of eveness - J) and monitoring parameters (% Ephemeroptera, Plecoptera and Trichoptera - EPT, Biological Monitoring Work Party - BMWP, bioindicator approach and Rapid Assessment Protocol - RAP, a habitat-based approach). Five from seven rural streams presented good water quality according to both BMWP and RAP and none of the urban streams presented good water quality. Our results show that the urban streams of Uberlândia municipality are poor ecosystems, and require improved management actions by environmental authorities. We also encourage that the riparian forest restoration and management carried out in the upper portion of Uberabinha River catchment to be extended to the urban area of the municipality.