SEARCH

SEARCH BY CITATION

Keywords:

  • ecosystem;
  • dams;
  • river regulation;
  • assessment;
  • bioindicators;
  • macroinvertebrate traits;
  • macroinvertebrate metrics;
  • taxonomic composition

ABSTRACT

Damming disrupts lotic continuity, creating a lentic water body upstream of the dam and a lotic stretch downstream that is highly vulnerable to temporal fluctuations in flow and physiochemical quality depending on the operational regime of the dam. Thus, an essential part of any dam operation programme must take into account a typologically suitable environmental flow regime, in order to maintain downstream structure and function. We assessed the seasonal impact of daily flow peaking regimes on the taxonomic composition, metrics and traits of the macroinvertebrate community in the lotic section situated downstream of the Itutinga reservoir on the Rio Grande in the state of Minas Gerais in southeast Brazil. The flow manipulation experiments were carried out in both wet (January) and dry periods (July) of 2010. The samplings were carried out in two hydraulic situations (fixed flow and daily flow peaking). Benthic macroinvertebrates and sediment were collected in three habitat types (backwater, fluvial beach and running water). Water variables were measured only in the fluvial beach habitat. Both water column and sediment variables downstream were heavily influenced by the retention capacity of the reservoir rather than the daily flow peak value. The trait approach was more sensitive than abundance and metrics and could detect the effects of daily flow peaking. The benthic macroinvertebrate communities sampled downstream of the Itutinga reservoir were more influenced by the sediment composition at each of the three studied habitats, than by the tested daily flow peaking. However, given the short timescale of this study, it may be difficult to the influence of these two interrelated factors. Copyright © 2013 John Wiley & Sons, Ltd.