Structure and robustness to species loss in Arctic and Antarctic ice-shelf meta-ecosystem webs

Abstract

While changes in the structure and dynamics of food-webs associated with sea-ice in polar regions will be among the most pronounced ecosystem-level changes on the planet that will occur with warming temperatures, little is known about how the loss of sea-ice will affect energy flow in polar food webs or whether Arctic and Antarctic sea-ice associated food-webs will respond similarly to species loss. Sea-ice ecosystems are unique from a global warming perspective as increasing temperature will result in the reduction of actual habitat substrate in addition to the air and water warming that will affect most other ecosystems. Over the next century sea-ice declines are predicted to range from 3–67% in the northern hemisphere and 8–64% in the southern hemisphere. We assembled meta-ecosystem food webs for Arctic and Antarctic sea-ice ecosystems for terrestrial and marine species that are dependent on the sea-ice to compare their topological structure and structural robustness to species loss. While the Arctic and Antarctic webs generally showed similar topology, a number of differences between the webs were identified including higher trophic species richness in the Antarctic, a right shifted trophic position distribution, and greater generality. Arctic webs had higher looping, clustering, and diet discontinuity suggesting the presence of stronger sub-webs and compartmentalization. Both the Arctic and Antarctic webs showed low robustness to the loss of low trophic position species and highly connected species, with 50% species loss occurring after the removal of ∼8% of species. The Arctic web was 33% less robust to deletions when ordered from lowest to highest trophic position than the Antarctic web. Our results suggest that food webs in the Arctic webs may be more sensitive to species loss as might occur due to sea-ice declines than Antarctic food webs.