Very small dams change benthic community in rocky rivers

Gilmar Perbiche-Neves, Sidnei Pressinate-Jr., Larissa Kruger, Ana Lúcia Suriani, Letícia Mattos


The construction of dams on rivers has been widely debated, because of the many impacts caused by them. But studies suggest that smaller dams have little impact because they present minor changes in river morphology. In the present study we analyzed the basic ecological attributes of the benthic community in a stretch of the Jordão River (Paraná State, Brazil) under the influence of a dam of a meter in height, forming a small reservoir type run-of-river. Sediment samples were taken at three different periods and in three points: upstream from the dam (site 1), close to the dam (site 2) and downstream from the the dam (site 3). The particle size analysis indicated that the sites 1 and 2 are dominated by fine sediments, in contrast to site 3, composed of medium and coarse sediments. There were found 23 taxa of benthic macroinvertebrate groups and 31 genera of Chironomidae. There was also a significant difference of richness and abundance between sampling sites. There was a spatial trend of increasing richness and abundance towards downstream, explained by the sediment composition and the originally lotic conditions in site 3, confirmed by all statistical analysis used. There was a richness decrease in the site located in the dam (site 2). Therefore, it can be seen that even very small dams as the present study alter the environmental attributes of benthic macroinvertebrates, and may have potentiated in a shallow rocky river.


Benthos; Brazil; Chironomidae; Jordão River; Paraná State.

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