Bioaccumulation in a Changing Climate: Temperature-Driven Toxicokinetics in Aquatic and Terrestrial Ectotherms

Chemical pollution and climate change are major threats towards ecosystem integrity and biodiversity. While both stressors already exceed their individual planetary boundaries, they act on ecosystems simultaneously. However, the current chemical risk assessment including bioaccumulation studies is still focused on a single optimum temperature. Bioaccumulation describes the enrichment of chemicals in biota compared to their environment and is driven by toxicokinetic (e.g. uptake, elimination, transformation, and internal distribution) processes. Toxicokinetics in ectotherms (thermally conforming organisms), are described by rate constants that depend exponentially on external temperature. Thus, a few degrees of warming can already significantly alter these processes, thus potentially increase bioaccumulation. In this perspective, we synthesize recent mechanistic work on ectothermic aquatic and terrestrial sentinel species, including fish, amphipods, earthworms, and collembolans. We compare the different physiology, exposure routes and dynamics of these model organisms and provide a walk through how temperature modulates the toxicokinetics of four chemically distinct contaminant classes (organic lipophilic chemicals, per- and polyfluoroalkyl substances (PFAS), pesticides binding to specific receptors, and metals). The present work demonstrates the importance of understanding the interaction of different stressors and calls for a climate-aware risk assessment.