A Novel Testing Paradigm to Identify and Manage Multiple Stressor Impacts on Wildlife

Biodiversity is declining at an alarming rate. Multiple stressors are driving many of these declines with freshwater (FW) ecosystems particularly impacted. Ephemeral FWs (e.g. marshes, ponds) are exceptionally biodiverse and highly exposed to varied environmental stressors but are generally overlooked within academia and regulation. Amphibians have been a major faunal component of these habitats for at least 350 million years, being highly evolved to these ecosystems. Amphibians and wetlands are some of the most highly threatened Phyla/ecosystems globally, with wetland health key to the climate crisis, due to the high methane levels emitted from human impacted systems. Using both field and laboratory approaches, here we will investigate the environmental stressor combinations driving negative impacts in amphibians (common frog, Rana temporaria) and seek to develop a biomonitoring approach to assess the health of these vital ecosystems. As amphibians are the most highly threatened vertebrate Phyla, this project is highly relevant to conservation priorities. General health, disease status, stress markers and global gene expression in wild and caged tadpoles will be measured. The use of toxicogenomics and alterations to physiology to assess impacts on tadpoles allows both the anchoring of molecular initiating events to downstream physiological endpoints and resulting adversity, as well as mapping these responses to stressor combinations. This mapping presents a highly novel approach, allowing the identification of specific stressors and their combinations that are driving negative impacts, and is widely applicable across biota. Catchment-scale eco-epidemiological studies between wild taxa and the presence/severity of stressors often rank pollution as amongst the most important variables driving negative effects in FWs. However, studies on effects of pollution at environmentally relevant levels and mixture combinations are scarce, particularly in the context of multiple stressors. Here pollutant mixture formulations will be based directly on measured levels in ephemeral FWs and combined with other ubiquitous stressors (salinity, heat wave and/or invasive crayfish - Pacifasticus leniusculus cue), all at environmentally relevant levels and combinations. These laboratory exposures will be highly novel and of vital importance to understand the true impacts of multiple stressors on iconic amphibian biota that inhabit vital ephemeral FWs. It will be tested how best to utilise data from single stressor exposures, to predict effects using theoretical models. For this, we will apply novel theoretical paradigms to the data - dominance (few stressors contribute disproportionately to observed effects) and burden (total stressor load determines effects) - which have huge potential for wide applicability for multi-stressor science. In contrast to the single-endpoint approach, here we propose to use ecological modelling to investigate effects on whole organisms and their populations in order to drastically improve the utility of these data for conservation. Finally, by transplanting spawn and sampling both caged and native tadpoles, the utility of naïve/locally adapted tadpoles as a biomonitoring tool to assess the health of FW wetlands will be assessed. This work will address an important gap in the literature between field-based catchment-level evidence demonstrating the importance of multiple stressors and the current limited laboratory-based evidence/understanding; as well as developing a new testing paradigm with practical application for conservation. The research team combines excellence in FW ecotoxicology, multiple stressors/mixture effect biology, FW ecology, ecological modelling, bioinformatics and chemistry needed for this project. In addition, the project partners and supporting organisations comprise a range of stakeholders that are focused on the health of FW ecosystems and reducing the impacts of pollution.