Impactos das mudanças globais nos ecossistemas aquáticos: uma análise das respostas de microrganismos sob diferentes estressores ambientais.

Abstract

Environmental changes occur at a global level and are enhanced by human activities, with significant impacts on natural ecosystems by affecting the temperature, nutrient load and input of organic debris in freshwater bodies or aquatic systems. In the first section, we investigated the impacts of increased temperature, nutrient input, predation by fish and a reduction in organic detritus on the community of testate amoebae, rotifers and periphytic cladocerans over 49 experimental days. The second section analyzed the effects of increased temperature, nutrient input and reduced organic detritus on the testate amoeba community during 160 experimental days. The experiments were carried out in mesocosms with three temperature conditions: control (referring to the ambient temperature), constant increase of +4°C and fluctuation between 2°C and 6°C above the control, with and without enrichment by nitrogen and phosphorus, and reduction of organic detritus, controlled by previous additions of this detritus. In relation to the results of the first section, the density of the groups analyzed was significantly impacted by the increase in temperature, while the other stressors explored in this work did not represent a significant influence on the abundance of the communities. As for community composition, the presence of nutrients had a more predominant impact on community structure, although specific species distribution patterns were not identified. For the second section, it was evident that warming resulted in a reduction in species diversity (demonstrated by the Shannon index), with a tendency for species richness to decrease in the face of this stressor. On the other hand, nutrient enrichment was responsible for an increase in richness, with time being a relevant factor in this context. As for changes in community density, nutrients and time emerged as the main factors influencing these changes. Analysis of species diversity using the Shannon index revealed greater diversity in the temperature control treatments, with time exerting a significant influence on community structure throughout the experiment. For species composition, the βtotal diversity analysis highlighted the importance of temperature, presence of detritus and time. The βrepl and βrich components were notably affected by temperature and time, indicating changes in species identity.