2002-2003 Science Planning Summary

Biology & Medicine

Dr. Polly Penhale
Program Manager


NSF/OPP 00-88000
Station: McMurdo Station
RPSC POC: Steve Alexander
Research Site(s): Wohlschlag Bay, Granite Harbor

Function and chemical nature of ice-active substances associated with sea ice diatoms
Dr. James A. Raymond
University of Nevada Las Vegas
Department of Biological Science 4004

Deploying Team Members: Michael G Janech . Michael Kuiper . James A Raymond
Research Objectives: Sea ice diatoms -- a class of algae -- are plentiful in McMurdo Sound in the ice platelet layer and congelation ice. Previous work suggests these particular diatoms produce certain extracellular ice-active substances (IASs) -- molecules with large molecular weights that appear to be glycoproteins. They are widely distributed in the Southern Ocean, occur in both summer and winter sea ice, are associated with many, if not all, of the diatoms found in sea ice, and are apparent as darkly stained areas in the sea ice. Because similar molecules have not been found in temperate water diatoms, they apparently have a function related to cold or icy environments.

The IASs represent a novel type of ice-binding molecule that is distinct from the antifreeze proteins and glycoproteins found in some fish species. Since they are ubiquitous in antarctic sea-ice communities but absent in warmer regions, they would appear to have an important role in polar communities.

Although different in structure, the IASs do share some properties with fish antifreezes, and so understanding their ice-binding properties and chemical structure will make it possible to better understand how this family of molecules interacts with ice. Finally, unlike the fish antifreezes, the IASs are produced in large quantities in nature. Perhaps they could be used in other applications.

The objective of this project is to characterize the chemical nature and function of the ice-active substances produced by sea ice diatoms. During the 2002-2003 season they will travel to locations in McMurdo Sound to collect darkly-stained sea ice. In the lab at they will (1) purify the IASs (reducing large quantities of ice to small volumes), (2) test the ability of the IASs to protect sea ice diatoms from cell damage during the freeze-thaw process, (3) experiment with a new technique for purification, and (4) examine the effect of the IAS on brine pocket formation in sea ice.

Field Season Overview:
Team members will take ice samples between Hut Point and Inaccessible Island. They will collect brown ice from Botany Bay and from the UCSG icegreaker near the ice edge and in the channel.

In Crary Laboratory researchers will purify and analyze ice active substances to test their ability to protect sea ice diatoms from cell damage during the freeze-thaw process. They will also examine the effect of the ice active substances on brine pocket formation in sea ice. Some ice and diatom samples will be returned to their home institution for further analyses.