Survival and aerobic performance of the northern shrimp are threatened by exposure to combined ocean global change drivers.

Environmental changes can influence species development, growth, size, distribution, and abundance, and when having a negative impact, they can potentially lead to a species' decline, and ultimately its local extinction. Consequently, evaluating the impacts of ocean global change drivers, in isolation and in combination, is particularly relevant for ecologically and economically important species which guarantee food security and income for coastal communities. This study aimed to determine the physiological responses of the northern shrimp Pandalus borealis to different combinations of ocean warming (OW), acidification (OA) and hypoxia at multiple levels of its biological organization (i.e. from the whole-organism to the cell), to help in predicting with greater accuracy the fate of this species in a rapidly changing ocean. To do so, shrimp were exposed for 30 d to different combinations of seawater temperature (2, 6 or 10°C), pH (7.75 or 7.40 pHT) and oxygen (100 or 35% relative to air saturation), and their survival, whole-organism aerobic performance, and cellular energetic capacity were characterized. Our results show that shrimp were overall tolerant to the isolated effects of OW, OA and hypoxia, but when exposed to combined drivers their survival and whole-organism aerobic performance severely decreased. Isolated and combined drivers had overall no effect on enzyme activity, suggesting a low capacity for metabolic reorganization. Nonetheless, under combined drivers, we observed an adjustment of the mitochondrial enzyme stoichiometry that might help cells to maintain their energy production efficiency. Overall, the northern shrimp's physiological status is compromised under combined ocean global change drivers, which together with the high mortality levels observed, point to a potential risk for local commercial collapse. Our results will be useful to refine mechanistic modelling for future abundance and distribution, in order to improve stock assessments, management and conservation of the northern shrimp under ongoing global changes.