Antarctic Science

Special Issue: The Latitudinal Gradient Project (LGP)

Comparison of the microalgal community within fast ice at two sites along the Ross Sea coast, Antarctica

K.G. Ryan a1c1, E.N. Hegseth a2, A. Martin a1, S.K. Davy a1, R. O'Toole a1, P.J. Ralph a3, A. McMinn a4 and C.J. Thorn a1
a1 Victoria University of Wellington, PO Box 600, Wellington, New Zealand
a2 The Norwegian College of Fishery Science, University of Tromsø, 9037 Tromsø, Norway
a3 Research Institute for Water and Environmental Resource Management, Department of Environmental Sciences, University of Technology, Sydney, PO Box 123 Broadway, Sydney, NSW 2007, Australia
a4 Institute of Antarctic and Southern Ocean Studies, University of Tasmania, Box 252-77 Hobart, TAS 7001, Australia

Article author query
ryan kg   [PubMed][Google Scholar] 
hegseth en   [PubMed][Google Scholar] 
martin a   [PubMed][Google Scholar] 
davy sk   [PubMed][Google Scholar] 
o'toole r   [PubMed][Google Scholar] 
ralph pj   [PubMed][Google Scholar] 
mcminn a   [PubMed][Google Scholar] 
thorn cj   [PubMed][Google Scholar] 


Diverse microbial communities survive within the sea ice matrix and are integral to the energy base of the Southern Ocean. Here we describe initial findings of a four season survey (between 1999–2004) of community structure and biomass of microalgae within the sea ice and in the underlying water column at Cape Evans and Cape Hallett, in the Ross Sea, Antarctica as part of the Latitudinal Gradient Project. At Cape Evans, bottom-ice chlorophyll a levels ranged from 4.4 to 173 mg Chl a m−2. Dominant species were Nitzschia stellata, N. lecointei, and Entomoneis kjellmanii, while the proportion of Berkeleya adeliensis increased steadily during spring. Despite being obtained later in the season, the Cape Hallett data show considerably lower standing stocks of chlorophyll ranging from 0.11 to 36.8 mg Chl a m−2. This difference was attributed to a strong current, which may have ablated much of the bottom ice biomass and provided biomass to the water below. This loss of algae from the bottom of the ice may explain why the ice community contributed only 2% of the standing stock in the total water column. Dominant species at Cape Hallett were Nitzschia stellata, Fragilariopsis curta and Cylindrotheca closterium. The low biomass at Cape Hallett and the prevalence of smaller-celled diatoms in the bottom ice community indicate that the ice here is more typical of pack ice than fast ice. Further data will allow us to quantify and model the extent to which ice-driven dynamics control the structure and function of the sea ice ecosystem and to assess its resilience to changing sea ice conditions.

(Published Online November 14 2006)
(Received February 2 2006)
(Accepted June 12 2006)

Key Words: biomass; Cape Evans; Cape Hallett; Latitudinal Gradient Project; pack ice; primary production; Victoria Land.