IRON IN MARINE SEDIMENTS FROM EXPLORERS COVE AND ADJACENT SITES IN MCMURDO SOUND, ROSS SEA, ANTARCTICA

Productivity in marine environments in Antarctica is tied to sea-ice and benthic diatom blooms during austral summer. A limiting factor for productivity is the availability of iron. Iron is known to spur growth in diatoms and enhance photosynthetic rates, but recent work on microbial planktonic communities in Antarctica suggest that with increasing temperature and an increase in iron, productivity would actually decrease, a potentially detrimental affect of global climate change. The iron content of shallow marine sediments in Antarctica is not well known and especially whether the iron content may differ among marine environments associated with glaciated and relatively unglaciated terrain (i.e., the dry valleys). We examined three different shallow (30 and 60 ft deep) sites in the McMurdo Sound, Ross Sea: Explorers Cove, located offshore of the Taylor Valley characterized by relatively unglaciated conditions and strong katabatic winds that transport sediments onto the sea ice that are eventually deposited on the sea floor; Bay of Sails, characterized by limited sediment transport onto the sea ice because of glaciated conditions; and, the Herbertson Glacier site which is intermediate between Explorers Cove and Bay of Sails, with both glaciated and partially unglaciated conditions. Results of X-Ray Fluorescence Analysis of the marine sediments revealed that Explorer’s Cove had the highest elemental iron content (30 ft: 4.03 ppm; 60 ft: 4.22 ppm). Herbertson’s Glacier had the next highest iron content (30 ft: 3.57 ppm; 60 ft: 3.44 ppm), and the least amount of iron was present at Bay of Sails (30 ft: 2.91 ppm; 60 ft: 3.02 ppm). It appears that unglaciated conditions may provide a major pathway for iron to enter the marine system, both through katabatic winds and runoff. If so, further warming of Antarctica could increase the amount of iron entering into the marine environment, with potentially large effects on the productivity of these sensitive marine habitats.