Acute copper exposure alters respiratory physiology and upper thermal limits in green crab (Carcinus maenas) at three global capture sites.

The green crab (Carcinus maenas) is a globally invasive species, inhabiting marine environments around the world, and known for its tolerance to environmental perturbations. While the green crab is a common model species in ecotoxicology, it is critical to understand their relative sensitivities to toxicants, and how this may vary among distinct populations. Here, we use a multi-stressor approach to evaluate the influence of acute copper exposure on the upper thermal tolerance of green crabs native to the Swedish North Sea and invasive to the Canadian Pacific and Atlantic Coastlines. Throughout thermal ramping green crabs exhibited an increase in ṀO2 from the 16 °C acclimation temperature to a peak ṀO2 at 33.5-34.5 °C, followed by an abrupt decline and a subsequent collapse at their upper thermal limits. Corresponding thermal limits in green crabs decreased following both low (200 μg L-1) and high (600 μg L-1) copper exposure, exhibiting consistent reductions in upper thermal limits ~2 °C sooner, with oxygen consumption reaching a peak at 31.5-33 °C, and respiratory failure occurring between 36.5 and 36.8 °C in tested locations. We therefore suggest few notable differences between capture locations, and while acute copper exposure is unlikely to influence green crab cardiorespiratory function in temperatures ranging from 16 to 28 °C, during extreme weather events or within shallow sun exposed environments, prolonged exposure to temperatures exceeding 30 °C in combination with high Cu contamination would increase green crab susceptibility to thermal stress.