BIOGEOCHEMISTRY OF ANTARCTIC SEA ICE

Abstract

Antarctic sea ice at its maximum extent in winter covers 40% of the Southern Ocean in a frozen layer, on average, 1 m thick. Sea ice is not solid, rather it is an ice crystal matrix permeated by a labyrinth of brine filled channels and pores in which life thrives. Organisms are constrained by a set of physicochemical factors quite unlike anything they encounter in the plankton from where they are recruited. Because sea ice is increasingly viewed as a suitable proxy for life in previous periods of the Earth's history, and even for astrobiology, it is pertinent that the physicochemical constraints acting upon sea-ice biology are better understood. The, largely microbial, network that develops in the ice itself imparts a unique chemistry that influ- ences the nature and chemical composition of biogenic material released from the ice. This chemistry can result in the export of material to the sediments with distinctive chemical signa- tures that are useful tools for reconstructing past sea-ice cover of the oceans. This review synthesises information on inorganic nutrient, dissolved organic matter and dissolved gases from a variety of Antarctic ice habitats.