Fritsen, C.H., Desert Research Institute, Division of Earth and Ecosystem Sciences, Reno NV, USA, cfritsen@dri.edu
Marschall, S.M., Desert Research Institute, University of Nevada Reno, USA, sarahm@dri.edu
Stewart, F.S., Desert Research Institute, University of Nevada Reno, USA fstewart@dri.edu
Memmott, J.F., Division of Earth and Ecosystem Sciences, Reno NV, USA
The distributions and activities of sea ice microbial communities were assessed in the sea ice and water column environments of the Western Antarctic Peninsula centering around Marguerite Bay during the austral fall and winter (April 17-June 3 and July 17-September 1) of 2001. These interdisciplinary studies were conducted to determine how the stocks and dynamics of materials associated with sea ice are linked to oceanographic and atmospheric forcing. Such information is necessary for an interdisciplinary evaluation of the potential for over-wintering krill populations to utilize this over-wintering resource (see http://www.ccpo.odu.edu/Research/globec_menu.html for more information regarding the Southern Ocean GLOBEC Program).
The dynamics of the late forming ice cover (formed in Marguerite Bay during late June to early July) were dominated by the dynamic pancake ice cycle that then became strongly influenced by flooding, freezing and snow ice formation (up to 17 cm) associated with high snow deposition (> 20 cm of snow on 35 cm of flat ice). Chlorophyll a was 4 to 50-fold more concentrated (average, 1.04 ug per liter) in the late forming pack ice compared to the water column concentrations that decreased from an average of 0.25 to 0.02 ug per liter from May to July. Although chlorophyll a biomass was low in sea ice compared to other seasons (e.g., chla concentrations > 100 to 1000 ug per liter in spring and summer in the Ross Sea) the relative distribution of biomass reaffirms the seemingly ubiquitous characteristic of ice-covered oceans- that microbes and algae are much more concentrated in ice environments, regardless of season. The dynamics of flood freeze cycles are not likely to have stimulated primary production in the near-surface sea ice habitats (as evidenced by conservative behavior of macronutrients) although the general habitat warming in association with flooding processes likely stimulated heterotrophic production and release of particulate organic matter from ablating ice surfaces. Such sea ice biota and dynamics will continue to be evaluated in context of krill ecology and physiology throughout the upcoming SO GLOBEC studies.