Sea Ice in the Arctic: a secret world

The Arctic Ocean is the most extreme ocean in regard to the seasonality of light and its year-round existing ice cover. Arctic seas hold a multitude of unique life forms highly adapted in their life history, ecology and physiology to the extreme and seasonal conditions of this environment. In this region the impacts of climate change are strongest: effecting acidification, warming, and reduction of sea ice. The Arctic sea ice and its related biota are unique, and its year-round existence allowed the development of ice endemic species, meaning these species are not found anywhere else. The sympagic (associated to the sea-ice) community is found in the tiny (mostly <1mm diameter) network of pores and brine channels or at the ice-water interface. The organisms living within the sea ice are consequently small (<1mm), and dominated by bacteria, and unicellular plants and animals. Diatoms, a certain type of algae, are considered the most important primary producers inside the ice with more than 200 species occurring in Arctic sea ice. In addition, flagellates contribute substantially to biodiversity, as well as small protozoan and metazoan ice meiofauna, turbellarians, nematodes, crustaceans and rotifers.  In the Spring, larvae and juvenile benthic animals migrate into coastal fast ice to feed on the ice algae for a few weeks, as well as a partially endemic fauna, consisting mainly of ice-associated and pelagic crustaceans can be found in the sea ice. These are the major food sources for Arctic cod (Boreogadus saida) that occurs in close association with sea ice and acts as the major link from the ice-related food web to seals and whales. Video created by Nadjejda Espinel-Velasco.