Urbanized Tributary Causes Loss of Biodiversity in a Neotropical River Segment

We used the community of benthic macroinvertebrates, alongside physical and chemical characteristics of the water, to verify the influence of an urbanized tributary on a Neotropical river. Specifically, our hypothesis is that urbanized tributaries are potentially able to simplify the biological diversity of the rivers where they flow. The collections were sampled in six sites every 2 weeks from April 2013 to March 2014, using artificial substrates. In conjunction with the benthic macroinvertebrate collections, the temperature, pH, and dissolved oxygen were measured using portable devices, as well as ammonia, total nitrogen, total phosphorus, and biochemical oxygen demand (BOD) in the laboratory. Rainfall values were also obtained. We observed a marked fall in the number of taxa and the values of richness, diversity equitability at the point located below the tributary mouth, with predominance of Chironomidae and Annelida . The high capture rates of a few groups considered tolerant and the high concentrations of total nitrogen, total phosphorus, and BOD confirm the alteration of the quality of the water at the sampling point located below the tributary mouth, leading to a local process of ecological simplification.