Avaliação da comunidade bentônica como ferramenta para monitorar a qualidade da água: estudo de caso da bacia do rio Alegria

Abstract

The aquatic quality has been discussed and analyzed for many years by several studies, because they are extremely important environments and are increasingly suffering alterations and disturbances by the anthropic activities, thus modifying their functioning, nature and their ecological diversity. Benthic organisms provide differentiated responses in relation to physicochemical variables, since they provide information on perturbations over time. The objective of this study was to evaluate the quality of the Alegria river, in the municipality of Medianeira – PR, through physicochemical characteristics (pH, conductivity, dissolved oxygen, turbidity, temperature and total phosphorus) and benthic macroinvertebrates. Four collection points were defined, the first near the source, another near the water catchment for public supply, the next in an irregular occupation within the urban perimeter and the last at the mouth of the river. The samples were collected using a modified Petersen type dredger, where the sediment samples were washed in sieves and stored for further identification. The other analyzes were performed following Standard Methods. To analyze the aquatic organisms, the diversity index of Shannon-Weaver and the attributes of wealth and equitability were realized. Two temporal collections, in May and December of 2017, were evaluated for water and sediment quality parameters, in different seasons (autumn and summer). The result obtained by benthic fauna was sensitive to degradation of water quality. At point P1, sensitive taxa were recorded, while at point P2 and P3, resistant and pollution tolerant taxa were identified. The biomonitoring presented a satisfactory result with that observed by the physical and chemical parameters. The variation of the collected season allowed to identify the changes of the taxa in the collections.