An aquatic toxicology primer for the experimental biologist and guidance for conducting robust stressor exposures

The field of aquatic toxicology has undergone a paradigm shift in recent decades. The movement away from observational data detailing the concentrations that produce deleterious effects and towards a mechanistic understanding of how toxicants affect organismal physiology has significant advantages for the field. This mechanistic approach allows for the prediction of toxicant effects across species and among toxicants with similar modes of action. Critically, knowledge of the pathways by which toxicants exert their impacts can provide insight into how environmental factors such as temperature, salinity, dissolved oxygen, pH, alkalinity, dissolved organic carbon, major ions and co-occurring toxicants interact to modify toxicity, providing a more nuanced understanding of toxicity in natural settings. This mechanism-based approach has driven changes in the regulatory environment, through the incorporation of predictive modelling tools that can determine, on a site-specific basis, safe thresholds for concentrations of toxicants in aquatic settings. This represents an exemplar of how fundamental experimental biology translates into real-world application. However, we argue that while mechanistic aquatic toxicology is an important subfield of experimental biology, there are a number of factors that make it unique. In this Commentary, we outline best practices for the experimental biologist conducting research into toxicant effects on aquatic biota, provide examples of the utility of mechanistic approaches to the field of aquatic toxicology and outline how future advances in aquatic toxicology could benefit from experimental biology approaches.