Understanding the reorganization of aquatic metacommunities under agrochemical contamination

Abstract

Biodiversity on Earth is constantly reorganizing itself in face of anthropic impacts, including aquatic biodiversity. One of the greatest threats in this regard is the expansion of agriculture, including sugarcane in the state of São Paulo. In this crop it is possible to highlight the impact of pesticides and vinasse, a compound rich in nutrients from the alcohol refinement. The impacts of these contaminants are well studied at levels traditionally used in ecotoxicological studies, but in communities and metacommunities our knowledge is still incipient. One reason for this lack of knowledge is due to the high complexity of metacommunities and the greater logistical challenge in experimentation. In this sense, this project aims to use aquatic mesocosms experiments, simulating lentic ecosystems and test different hypotheses regarding the reorganization of metacommunities inserted in agricultural matrices. In metacommunities the impacts of contaminants should be closely linked to the rate of dispersal between communities, as well as to the way agricultural contaminants work. Pesticides, with toxic potential for zooplankton, should act as an unequivocal environmental filter on all species, where less abundant species should also be the ones with the highest chances of extinction. Vinasse in contrast, because it is rich in nutrients, should generate a selective filter, where species with higher fitness for more eutrophic environments should excel. In addition, in metacommunities embedded in agricultural landscape, not all local communities will be impacted. On the one hand, uncontaminated communities may be essential for the reorganization of impacted communities, since extinct species may be able to recolonize such sites. However, if the dispersion occurs from impacted to uncontaminated sites, indirect effects of contamination can be observed through the dispersal of organisms from sites with different conditions. Considering the fundamental role of zooplankton in the functioning of aquatic systems, our experiments have the potential to elucidate how this group will respond to the future pressures of agricultural expansion and how we can understand these responses through the lens of metacommunity dynamics. (AU)