Post-drainage changes in the structure of the benthic macroinvertebrate community

in a floodplain palustrine wetland in the South of Brazil

MALTCHIK¹, L., TEIXEIRA¹, R.R. & STENERT¹, C

¹ Laboratório de Ecologia e Conservação de Ecossistemas Aquáticos – UNISINOS. Av. Unisinos, 950, CEP 93022-000, São Leopoldo, RS, Brasil.

e-mail: maltchick@unisinos.br

 ABSTRACT: The drainage of wetlands for agricultural irrigation was the principal responsible for the destruction of wetlands in the South of Brazil. The objective of this study was to analyze the effects of a drainage event on the richness, density and composition of the benthic macroinvertebrate community in a floodplain palustrine wetland in the South of Brazil. Twelve monthly macroinvertebrate collections were carried out from April 2003 to March 2004. In each collection five macroinvertebrate samples were collected at random along the whole area of the studied palustrine wetland. The studied period was characterized by two hydrological phases: before and after the drainage event. A total of 48 taxons and 1,930 macroinvertebrates were sampled. Ephydridae was the single taxon observed in all collections. Tubificidae and Glossiphoniidae were present in 91% of collections. The mean number of taxons and the mean density of benthic macroinvertebrates were lower after the drainage event than before it and the macroinvertebrate composition varied between the two hydrological phases. The structure of the macroinvertebrate community changed with the decrease in the water level over the drainage succession in the studied palustrine wetland, where typically aquatic taxons were replaced by taxons either adjusted or resistant to the land condition. In this sense, programs aimed at the conservation of wetland biodiversity in the South of Brazil should be a priority, mainly when 90% of the wetlands in this area have disappeared along the last century.

Key-words: drainage, floodplain, wetland, macroinvertebrate, conservation.