Metabolomic response of striped marsh frog (Limnodynastes peronii) tadpoles exposed to the fire retardant Phos-Chek LC95W.

Climate change and other factors have contributed to an increased frequency and intensity of global wildfires in recent years. Ammonium-based fire retardants are widely used to suppress or delay the spread of fire and have generally been regarded as presenting a low risk of acute toxicity to fauna. However, studies have raised concerns about their potential to cause indirect or sub-lethal effects, and toxicity information regarding the potential for such impacts in aquatic species is limited. To address these knowledge gaps, we used an untargeted metabolomics approach to evaluate the sub-lethal physiological and metabolic responses of striped marsh frog (Limnodynastes peronii) tadpoles exposed to a concentration gradient of the ammonium polyphosphate (APP)-based fire retardant Phos-Chek LC95W (PC). Acute exposure (96 h) to PC significantly altered the relative abundance of 14 metabolites in whole tadpoles. The overall metabolic response pattern was consistent with effects reported for ammonia toxicity and also suggestive of energy dysregulation and osmotic stress associated with alterations to physicochemical water quality parameters in the PC treatments. Results suggest that run-off or accidental application of this formulation into waterways can have significant sub-lethal consequences on the biochemical profiles (i.e., the metabolome) of aquatic organisms and may be a concern for frog species that breed and develop in small, often ephemeral, waterbodies. Our study highlights the benefits of integrating untargeted metabolomics with other ecological and toxicological endpoints to provide a more holistic characterisation of the sub-lethal impacts associated with bushfire-fighting chemicals and with environmental contaminants more broadly.

Effects of two firefighting chemical formulations, Phos-Chek LC95W and BlazeTamer380, on striped marsh frog (Limodynastes peronii) tadpole survival, growth, development and behaviour.

Global wildfire events are projected to become more frequent and severe due to the continual threat of climate change, resulting in increasing demand for effective fire mitigation methods. Firefighting chemicals (FFCs), including retardants, foams and water enhancers, are often used to prevent the spread of wildfires. However, the impact of FFCs on wildlife and ecosystems is poorly understood. We investigated the effects of two common FFC formulations, Phos-Chek LC95W and BlazeTamer380, on tadpole survival, growth, development and swimming behaviour. Tadpoles of the striped marsh frog (Limnodynastes peronii) were exposed to two concentrations of either Phos-Chek (0.25 and 1 g/L) or BlazeTamer (0.05 and 0.2 g/L) for 16 days. The highest concentration of Phos-Chek was lethal to tadpoles, with mortalities gradually increasing over time and only 8% of animals surviving to day 16. Both FFCs influenced the growth and development of tadpoles, though effects were more severe in tadpoles exposed to the Phos-Chek formulation. Phos-Chek was found to completely stop tadpole growth and development over the 16-day exposure, whereas BlazeTamer significantly delayed growth and development in comparison to controls. Nevertheless, treatments had no apparent effect on tadpole movement patterns and swimming activity. Greater toxicity caused by the Phos-Chek treatment likely relates to the increased ammonia and altered water quality parameters. Runoff or accidental application of commonly used FFCs into small waterways may therefore have important ramifications for aquatic biota.