Abstract
The Castelhano Stream Hydrographic Basin, located in the city of Venancio Aires, RS, Brazil, shows an area of 675.3 km2, highlighting the Castelhano Stream as their main water course. The stream is the main responsiblity for the local water supply; however, there are no published studies in the literature regarding their water quality. In this context, the present research aimed to assess the water quality of Castelhano Stream in terms of organic pollution and eutrophication, applying the Biological Water Quality Index (BWQI), which uses epilithic diatoms communities as bioindicators. Biological samples were collected at three sampling stations along the stream in the months of September, November and December 2012. The results showed 81 identified species, distributed in 30 genera. The water pollution levels detected ranged from “strong” (66.7%) and “very strong” (33.3%), with differences in species composition between sampling stations. The sampling station S1 in the upper reaches was characterized by the presence of indicative species of acidophilus and lentic environments with large amounts of organic matter. The sampling stations S2 and S3, in the intermediate and lower reaches, respectively, showed a substitution of species in the community, with the presence of highly tolerant taxa to organic pollution and eutrophication. The high pollution levels detected along the basin are related to the nutrients and high organic load originating from livestock, domestic and industrial waste, as well as excess fertilizers and agricultural inputs used in farming. The results demonstrate the necessity to implement mitigation measures to contain the processes of organic pollution and eutrophication detected due to the dangers offered to public health and the environment.
Highlights
IntroductionAt highly industrialized regions in which water demand has increased, most part of domestic and industrial effluents, as well as chemical fertilizers and pesticides used in agriculture, are dumped directly into water bodies, reducing further the possibility of use water resources and drastically modifying the characteristics of aquatic ecosystems
At highly industrialized regions in which water demand has increased, most part of domestic and industrial effluents, as well as chemical fertilizers and pesticides used in agriculture, are dumped directly into water bodies, reducing further the possibility of use water resources and drastically modifying the characteristics of aquatic ecosystems. This damage has been demonstrated in two ways: through the introduction of toxic substances into groundwater and through the phenomenon of artificial eutrophication that, besides reducing the water quality, produces significant changes in the metabolism of whole ecosystem [1]
In relation to epilithic diatom composition, 81 species were identified belonging to 30 genera, 27 taxa, distributed in 17 genera were considered abundant
Summary
At highly industrialized regions in which water demand has increased, most part of domestic and industrial effluents, as well as chemical fertilizers and pesticides used in agriculture, are dumped directly into water bodies, reducing further the possibility of use water resources and drastically modifying the characteristics of aquatic ecosystems. This damage has been demonstrated in two ways: through the introduction of toxic substances into groundwater and through the phenomenon of artificial eutrophication that, besides reducing the water quality, produces significant changes in the metabolism of whole ecosystem [1].
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