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

Abstract

The aim of this study was to evaluate the survival, metabolism and swimming behavior of Rhinella arenarum 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, p < 0.05). These results highlight the high ecological risks faced by tadpole reproductive sites that have been affected by fires.