Sea ice is a key driver of Southern Ocean ecosystem functions and biogeochemical cycles. Long-term monitoring in the West Antarctic Peninsula area has shown how a decline in sea-ice coverage has impacted marine food webs across multiple levels and affected biogeochemical fluxes in intricate ways. Ice extent around Antarctica has recently plummeted to record lows and is predicted to continue declining over the coming decades. This work synthesizes recent advances in understanding how sea ice affects Southern Ocean lower-trophic-level ecosystem and biogeochemical processes, and provides an assessment on how changing Antarctic sea-ice-scapes, as predicted by Earth System Models (ESMs), will impact these processes at the end of the 21st century. Despite large uncertainties in these assessments, there is high likelihood for disruptive changes with regards to atmosphere-ice-ocean gas exchange, primary production and food-web dynamics across the Southern Ocean marginal ice, interior pack-ice and coastal landfast sea-ice zones. The study also highlights uncertainties in these assessments, thereby identifying key knowledge gaps in Southern Ocean ice-covered ecosystem research.