Microscopic examination of marine organisms (larger than 45 µm) collected from the sea ice, brine and water column in McMurdo Sound and the Ross Sea

Large marine organisms, specifically foraminifers and copepods, were collected from the sea ice, brine and water column from thin ice north of Beaufort Island at the beginning of the warming period when the brine channels in the sea ice are widening, providing a conduit for organisms at the bottom of the ice to migrate to the top. A suit of ice cores were collected from 9 stations in sea ice varying in thickness. Eight stations were on ice that formed last winter and one station was on second year ice in which the brine channels from the previous year were closed but clearly visible.

At each station, a complete core (cut into approximately 25cm sections), a brine sample and an under-ice plankton tow was collected. Corresponding cores from each site were collected for iron and iron isotopes, gases, dimethyl sulfide, temperature (measured on the spot) and salinity, and biology (algae and bacteria). Additional samples of bottom sea ice were obtained from blocks cut in the ice near Cape Evans and off Cape Barne where there was a thick carpet of diatoms and associated biota at the bottom of the ice.