Increasing high latitude coexistence of Antarctic salps and krill under projected climate change

In the Southern Ocean, Antarctic krill and salps, both macroplankton species, have overlapping distributions but play contrasting roles in the food web. However, their population trajectories and interactions remain uncertain. In this study, we developed a novel 3D model to predict their changing distributions throughout the century. This model is based on an ensemble of species distribution models utilizing extensive observational databases. Our findings indicate that both species are shifting poleward, with the strongest shifts occurring under a no-mitigation climate change scenario. Projections suggest that habitat overlap will increase, particularly in areas closer to the Antarctic continent, intensifying competition for limited space and resources. A diffusion model suggests that species behavior may facilitate small-scale spatial segregation, enabling krill and salps to coexist despite limited space. The interaction between these two species in the Southern Ocean reflects a broader gelatinous-crustacean tradeoff seen in other ecosystems. The salp and krill natural redundancy is about who is better suited to a current environmental setting and the proposed increase in variability of nearshore environments under climate change scenarios may increasingly favor salps with significant consequences for high Antarctic food webs.