Distribution shifts of marine taxa in the Pacific Arctic under contemporary climate changes

Aim: To investigate the species-specific exposure and distributional responses of marine fish and invertebrate taxa to rapidly shifting climate in the Pacific Arctic, characterized by warming and cooling episodes, over the last 24years. Location: Pacific Arctic region, eastern Bering Sea and Chukchi Sea. Methods: We examined the variations in the summer (June-July) habitat patterns of 21 marine fish and invertebrate taxa in the eastern Bering Sea using multimodel ensemble predictions of species distribution between 1993 and 2016. Using ensemble model outputs, we examined the rates of predicted (biotic velocities) and expected (bioclimatic velocities) distribution shifts across taxa under four consecutive time periods of distinct climatic regimes. We then compared these species-specific velocity metrics to the rates of local climatic shifts (climatic velocities) and quantified the potential lags in distributional responses relative to changes in climate across taxa and transitions. Results: Our analyses showed that individual taxa responded to climatic fluctuations at different paces and generally exhibited lags in their predicted distributional responses. Subarctic species revealed higher habitat sensitivity and exposure to climatic changes than Arctic taxa, as they expand their habitat ranges into suitable regions emerging in the north under warmer conditions. Importantly, the actual rates of climate shifts (climatic velocities) were poorly correlated with both the expected and observed shifts in species distributions across taxa. Main conclusions: Our findings underpin the importance of incorporating species-specific climatic sensitivity and exposure to changes in climatic conditions when predicting range shift responses and evaluating species vulnerability. These insights are critical for conservation and management of fisheries resources in the region.