Wildfire ashes: evaluating threats on the Pantanal wetland reserve (Mato Grosso, Brazil) using ecotoxicological tests.

In 2020, the largest continuous wetland area on the planet, the Brazilian Pantanal, experienced an unprecedented fire that affected the entire ecosystem. Our goal was to elucidate the effects of ash presence following the fire events. We quantified the impact of ashes, collected in four Conservation Units, on soil, water, and atmosphere. On the edaphic system, we tested the impact through behavioral and acute toxicity tests using annelids exposed to contaminated soil at different ash concentrations. We assessed the effect of ash on the flux of soil greenhouse gases. In the water, we examined the impact through tests with the Daphnia similis Claus, 1876. On the edaphic system, Eisenia andrei (Bouché, 1972) exhibited reduced average mortality rates and negative sublethal responses, including behavioral and morphological changes. Annelids displayed rejection responses to the ash substrate, suggesting potential damage to soil function. D. similis showed high mortality rates. We noted an increase in carbon dioxide emissions after ash addition. Changes in soil characteristics were also observed, mainly an increase in minerals. Considering the escalating frequency and intensity of fires in tropical areas due to climate change and deforestation, our findings contribute to understanding the potential ecotoxicological impact of ash in wetlands.