Diversity of aquatic arthropods on Eichhornia crassipes (Mart.) Solms roots before and after removal of bottom sediment in a reservoir in southern Brazil

Abstract

The objective of this study was to determine the influence of substrate removal on the diversity, composition and trophic structure of aquatic arthropods found on Eichhornia crassipes roots. Because many arthropods are intimately associated with their substrate, its removal might result in increased richness and diversity for the aquatic arthropods on E. crassipes roots. The study was performed in the Lajeado da Cruz River in Cruz Alta-RS, where the identification of the aquatic arthropods captured during eight samplings between August 2008 and May 2011 was performed. Four samples were collected prior to removal of the substrate and four were collected afterward. A total of 8,894 exemplars and 55 families of aquatic arthropods were sampled. The families Palaemonidae and Chironomidae were the most abundant. The diversity indices indicated increases in both diversity and richness after substrate removal. Values of the water quality parameters of turbidity, color, iron and aluminum were found to be outside the norms, which indicated a need for caution with regard to water quality. The removal of the substrate triggered changes in the community and its trophic structure as well as an increase in the diversity of arthropods on the water hyacinth roots.