• Energy Research

Abstract Background Assessing the historical dynamics of key food web components is crucial to understand how climate change impacts the structure of Arctic marine ecosystems. Most retrospective stable isotopic studies to date assessed potential ecosystem shifts in the Arctic using vertebrate top predators and filter-feeding invertebrates as proxies. However, due to long life histories and specific ecologies, ecosystem shifts are not always detectable when using these taxa. Moreover, there are currently no retrospective stable isotopic studies on various other ecological and taxonomic groups of Arctic biota. To test whether climate-driven shifts in marine ecosystems are reflected in the ecology of short-living mesopredators, ontogenetic changes in stable isotope signatures in chitinous hard body structures were analysed in two abundant squids (Gonatus fabricii and Todarodes sagittatus) from the low latitude Arctic and adjacent waters, collected between 1844 and 2023. Results We detected a temporal increase in diet and habitat-use generalism (= opportunistic choice rather than specialization), trophic position and niche width in G. fabricii from the low latitude Arctic waters. These shifts in trophic ecology matched with the Atlantification of the Arctic ecosystems, which includes increased generalization of food webs and higher primary production, and the influx of boreal species from the North Atlantic as a result of climate change. The Atlantification is especially marked since the late 1990s/early 2000s. The temporal patterns we found in G. fabricii’s trophic ecology were largely unreported in previous Arctic retrospective isotopic ecology studies. Accordingly, T. sagittatus that occur nowadays in the high latitude North Atlantic have a more generalist diet than in the XIXth century. Conclusions Our results suggest that abundant opportunistic mesopredators with short life cycles (such as squids) are good candidates for retrospective ecology studies in the marine ecosystems, and to identify ecosystem shifts driven by climate change. Enhanced generalization of Arctic food webs is reflected in increased diet generalism and niche width in squids, while increased abundance of boreal piscivorous fishes is reflected in squids’ increased trophic position. These findings support opportunism and adaptability in squids, which renders them as potential winners of short-term shifts in Arctic ecosystems.

The high Arctic shelves are the particularly understudied area of the Arctic. Climate change is predicted to cause increase in primary production with cascading effect on the Arctic ecosystems, and predicted increased ship traffic through the now-ice-free areas will create anthropogenic disturbance. Thus, understanding the high Arctic shelves is required. The cephalopods are ecologically important in the area, but severely understudied. We use recent samples (2014–2019) and reuse existing literature data (1901–1998) from the Siberian and Canadian high Arctic shelves to assess distribution and ecology of cephalopods. The fauna composition of these shelves is similar, and includes two benthic octopods and two nekto-benthic bobtail squids, and two more species over the adjacent slopes. Distribution limits are updated for all shelf species, and associated environmental parameters allow for better understanding of their realised niches. The reproduction of studied cephalopods occurs from July to November, and the hatching period throughout the summer. Crustaceans are their main prey, but several more taxa are found in the stomach contents. The prey sizes range from ∼7% to ˃100% of the respective cephalopod size. Climate-driven changes in predator and prey composition are predicted to be the main drivers of the future climate change impact on cephalopods over the high Arctic shelves.