Ecotoxicity assessment of burned sediments from dry lagoons in amphibian larvae: hazards in post-fire wetland reflooded

The aim of this study was to evaluate the survival, metabolism and swimming behavior of <i>Rhinella arenarum</i> tadpoles exposed to burned sediments from dry lagoons located in the "Los Sapos" Island (Santa Fe Province, Argentina), with different fire events over one year: no fire events (NF), two fire events (TF) and multiple fire events (MF). The physicochemical parameters of the sediments were analyzed. A sediment test was performed using 25, 50 and 100% dilutions of each sediment sample at a microcosm scale for 48 h. Tadpole survival and swimming behavior, as well as acetylcholinesterase (AChE) and glutathione S-Transferase (GST) activities (markers of neurotoxicity and oxidative stress), were analyzed. The burned sediments showed high conductivity (<1000 μS/cm2) and proton activity with presence of carbonates. The treatments with sediments from TF and MF led to mass tadpole mortality (100%). Diluted 25 and 50%, these treatments also resulted in a significant decrease (30%) in the activities of AChE and GST as well as in the swimming speed (60%) and total distance moved (40%) respect to the NF treatment (ANOVA and Tukey's test, <i>p</i> < 0.05). These results highlight the high ecological risks faced by tadpole reproductive sites that have been affected by fires.