Efeito da redução das chuvas sobre as comunidades de macroinvertebrados bentônicos do semiárido brasileiro

Abstract

The global warming expected consequences for the Brazilian semi-arid region are increased evapotranspiration and reduced precipitation, increasing the hydric deficit and prolonging drought periods. This study hypothesizes that the increase in water deficit, increases the trophic state of semi-arid reservoirs and accordingly reducing the alpha and beta diversity of benthic macroinvertebrates and increasing the susceptibility of lentic aquatic ecosystems to the elevation of trophic state. Eutrophication coupled with a negative water balance driven by climate change tends to promote cyanobacteria blooms, increase salt concentrations and the reduction of oxygen in the water column, which may reduce the complexity of lakes and benthic communities, as this phenomenon acts as an environmental filter selecting species more apt to colonize these environments. To test our hypothesis, we compared the benthic macroinvertebrate communities between two sets of reservoirs located in two neighbouring sub-basins of the Brazilian semi-arid region with contrasting precipitation regimes. The two sets of reservoirs were compared between two periods (dry and extremely dry) to evaluate the effect of drought intensity on benthic macroinvertebrates alpha and beta diversities. The results show that drought intensification increases reservoirs trophic state, especially in the sub-basin with lower annual mean precipitation. However, Contrary to what was expected for the driest basin where the reservoirs presented worse water quality there was increase in benthic macroinvertebrates beta diversity, due greater environmental heterogeneity. Deterministic mechanisms like species sorting may have been responsible structuring the communities in our study. These results imply understanding the structure of communities in climate change events of semi-arid regions.