Anthropogenic impacts on zooplankton communities: distribution of non-native species and effects of wildfire ash deposition in freshwater ecosystems

Abstract

Anthropogenic pressures on freshwater ecosystems were investigated in this Master thesis through two complementary approaches focused on zooplankton communities: i) a systematic review focused on the global distribution and factors related to the establishment of non-native copepod species in freshwater and brackish ecosystems, and ii) a mesocosm experimental study on the impacts caused by wildfires near water bodies in the Mato Grosso Pantanal. In the first study, our systematic review encompassing 151 studies published between 1991 and 2025 identified the occurrence of 67 non-native copepod species distributed across 44 countries, revealing that East Asia and the Ponto-Caspian region act as the main propagule donors to North America and Europe. Introduction vectors are primarily associated with aquaculture (32.5%) and aquatic transport, with establishment success conditioned by specific physiological traits such as euryhalinity (22.5%) in Eurytemora affinis, and the thermal tolerance and adaptation to eutrophic environments observed in non-native cyclopoids. Our second study demonstrated that the input of wildfire ash in the Pantanal acts as an environmental filter, promoting immediate alkalinization and a drastic increase in water electrical conductivity. These changes initially resulted in a collapse of richness and density, and in the total suppression of microcrustaceans (cladocerans and copepods). However, over the following days, a subsidy-stress effect was observed, characterized by temporary outbreaks in rotifer density, which benefited from reduced competition with other planktonic organisms. These results suggest that anthropogenic stressors, at both global and local scales, converged toward the simplification of food webs and the loss of functional resilience in the studied aquatic ecosystems.