The biotic community in and on the sea ice is amazingly diverse. Every organism within it plays its own unique – and often indispensable – part. Microscopic bacteria and archaea change the structure of the sea ice by producing gelatinous biopolymers. With an effect similar to that of antifreeze, these polymers prevent the formation of large ice crystals, keeping the porous spaces and channels within the ice open and liquid. Within these channels and on the underside of the ice, a veritable armada of tiny ice algae uses sunlight and photosynthesis to produce energy-rich biomass. In this way, the algae provide the central basis that all higher levels of the food web depend on. The algae are eaten by rotifers, nematodes and copepods, which in the water below the ice are in turn prey for fish larvae and juvenile fish. And the levels of the food web only go up from there – from penguins (Arctic), ringed seals and walruses (Arctic), to polar bears (Arctic) and whales.
Here we’ll introduce you to the most important sea-ice organisms in the Arctic and Arctic – from microscopic to massive – and highlight their key functions in the polar ecosystem.