The Contributions of Sea Ice Algae to Antarctic Marine Primary Production

SYNOPSIS. The seasonally ice-covered regions of the Southern Ocean have dis- tinctive ecological systems due to the growth of microalgae in sea ice. Although sea ice microalgal production is exceeded by phytoplankton production on an an- nual basis in most offshore regions of the Southern Ocean, blooms of sea ice algae differ considerably from the phytoplankton in terms of timing and distribution. Thus sea ice algae provide food resources for higher trophic level organisms in seasons and regions where water column biological production is low or negligible. A flux of biogenic material from sea ice to the water column and benthos follows ice melt, and some of the algal species are known to occur in ensuing phytoplankton blooms. A review of algal species in pack ice and offshore plankton showed that dominance is common for three species: Phaeocystis antarctica, Fragilariopsis cy- lindrus and Fragilariopsis curta. The degree to which dominance by these species is a product of successional processes in sea ice communities could be an important in determining their biogeochemical contribution to the Southern Ocean and their ability to seed blooms in marginal ice zones.