Rapid assessment of ecological integrity in urban streams of the Corumbá watershed in the Midwest of Brazil

Abstract

A major consequence of urbanization in Brazil is the production of large amounts of partially treated domestic effluents dumped into rivers, causing ecological damage to aquatic ecosystems. In order to assess the ecological integrity of urban streams in the Cerrado region of Central Brazil, this study selected four sampling points, based upon the level of human influence to which they are submitted, and the physical and chemical parameters of water, land-use map and benthic macroinvertebrates were analyzed. Samples were collected in July 2015, and electrical conductivity, water temperature, pH, dissolved oxygen, turbidity, stream width and length and current velocity were measured in situ. Samples of seston, periphyton, benthic macroinvertebrates and deposited sediment were collected soon after. The “Reference” sample point showed a lower abundance of Chironomus larvae (Chironomidae: Diptera), and greater taxonomic richness and greater abundance of taxonomic groups Ephemeroptera, Plecoptera and Trichoptera, proving to be the most undamaged ecosystem. The sub-basin delimited to this point showed a higher percentage of remaining native areas (51%). Sample points where domestic effluents were present (“ETE” and “Jusante”) showed higher values of electrical conductivity, turbidity, greater abundance of Chironomus larvae and a low richness, showing high impact due to urban activities. A rapid assessment of the composition of the benthic community and the physical and chemical variables of the water was sufficient to identify the changes in the ecological integrity caused by human influence in the watershed of the Corumbá River.