Efeito de técnicas de mitigação de lagos eutrofizados sobre assembleias de macroinvertebrados bentônicos

Abstract

Coagulant application and the removal of bentivorous fish are two techniques of water quality management of eutrophic lakes, which decrease or increase the internal phosphorus of sediments to a water column and mitigate the effects of eutrophication. However, the selected and combined effects of these two management techniques on the structure and skills of aquatic communities are little used. Coagulant application increases the flow of organic matter from the sediment water column, reduces the availability of debris to benthic invertebrates, while the removal of bentiva fish reduces competition pressure and / or predation on benthic invertebrates. Therefore, increased debris availability may affect a stronger positive effect on benthic macroinvertebrates that affect the presence of debris bentivorous fish, and is therefore considered a synergistic effect of both techniques on population and the same types of use. To test this hypothesis, a field experiment with a 2 x 2 factorial design was carried out, combining the application or not of the PAC with the presence and absence of the Prochilodus brevis bentivore fish. The experiment was carried out during 8 weeks in 20 6 m3 mesocosms inserted in a tropical semiarid lake and the 4 treatments randomly allocated in the mesocosms. Sediment samples were collected at each mesocosm at the beginning, middle and end of the experiment. Benthic macroinvertebrates were identified and quantified in each sample and the density data of these organisms were used by a Kruskal-Wallis. As water quality management techniques and interaction between them are not effects on macroinvertebrate benthic. Therefore, the results refuted the research hypothesis and suggested that the high availability of organic matter, the typical eutrophic environments, do not influence the assembly of macroinvertebrate benthic plants.