Do floods of brief duration affect the aquatic macroinvertebrate community in a floodplain oxbow lake in the South of Brazil?

Abstract

The effects of floods of brief and very brief duration on the number of taxons, density and composition of macroinvertebrates were recorded in a floodplain oxbow lake in the South of Brazil over a year. Twelve collections were distributed in two hydrological phases (with floods and without floods). The oxbow lake experienced three flood events. A total of 1,225 macroinvertebrates representing 50 taxons was sampled. The majority of the macroinvertebrate taxons corresponded to aquatic insects (67.3%). Tubificidae, Glossiphoniidae and Ephydridae represented the dominant macroinvertebrate families. The number of taxons and density of macroinvertebrates did not change after the flood events of brief and very brief duration and the recurrence of the floods did not diminished the resistance of the dominant macroinvertebrate families. The macroinvertebrate composition varied along the hydrological phases. The first and the second axes of DCA explained 48.2% of the variance in the macroinvertebrate composition. Sphaeriidae, Tubificidae and Glossiphoniidae families were more associated to the phase with floods and Hydracarina, Curculionidae and Dytiscidae taxons were more associated to the phase without floods.

Key words: macroinvertebrates, floods, duration, frequency, resistance.