Abstract: Antarctic krill (Euphausia superba) and ice krill (Euphausia crystallorophias) are key species in the Ross Sea. However, studies on the distribution and niche overlap of these two species in this region are rather limited. Given their ecological importance and the potential effects posed by ongoing climate change, we investigated the summer habitat distribution and ecological niches of these two krill species. Based on occurrence records and environmental data including chlorophyll a concentration, sea surface temperature, salinity and sea ice thickness, an ensemble model integrating four algorithms was used to analyze the summer habitats and niches of two krill species in the Ross Sea. The results showed that the two krill species had significant spatial overlap in Terra Nova Bay. However, the habitat range of Antarctic krill was broader, extending to the shelf break in the northwestern side of the Ross Sea. Moreover, the ecological niche ellipsoid of Antarctic krill fully encompassed that of ice krill, indicating the higher environmental tolerance and adaptability of Antarctic krill. By revealing the spatial distribution and niche characteristics of Antarctic krill and ice krill, our results provide scientific support for ecosystem conservation and the development of research and monitoring programs for the Ross Sea Marine Protected Area.

Key words: species distribution model, habitat, climatic adaptability, climate change, Southern Ocean, krill