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MEPS 238:1-13 (2002)
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Abstract
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Particulate organic matter in Antarctic summer sea ice: concentration and stable isotopic composition
H. Kennedy1,*, D. N. Thomas1, G. Kattner2, C. Haas2, G. S. Dieckmann2
1School of Ocean Sciences, University of Wales, Bangor, Menai Bridge, Anglesey LL59 5EY, Wales, UK
2Alfred Wegener Institute for Polar and Marine Research, Am Handelshafen 12, 27515 Bremerhaven, Germany
*E-mail: h.a.kennedy@bangor.ac.uk
ABSTRACT: The chemical and isotopic data from sea ice collected over a wide area of the Weddell Sea, Antarctica, during the austral summer/early autumn illustrate the range of environmental conditions under which ice algae grow. A range of ice types and
features were sampled including intact and layered ice floes and surface ponds. Sea ice communities were found in all these environments but the highest biomasses were found either at the base of ice floes, or in the interior of layered floes with
quasi-continuous horizontal gaps at or shortly below the water level. In the layered floes, particulate organic carbon (POC) measured in the ice layer immediately overlying the gap water (280 to 6014 µmol dm-3) was in excess of what would be
predicted if algal growth had occurred in a closed environment. The chemical composition of the gap water was strongly affected by biological activity in the overlying ice, which acts as a physical support for the algae retained within its matrix. The
lowest range of POC (27 to 739 µmol dm-3) conformed to predictions of algal growth in a closed system and samples were collected from the interior of ice floes where there was essentially no potential for nutrient exchange. The surface ponds
displayed nitrate (NO3-) exhaustion and total dissolved inorganic carbon (ΣCO2) reductions consistent with nutrient limited algal growth. The stable carbon isotopic composition of the particulate organic
matter
(POM) across all habitat types sampled (d13CPOC -10.0 to -27.3‰) displayed a wide range but was much less variable than the range of POC concentrations might have implied. The assumption that the
highest
biomass of algae in sea ice will result in the most positive d13CPOC values cannot be generally applied. The isotopic composition of dissolved inorganic carbon (d13CΣCO2) in gap waters and surface ponds varied from 0.15 to 3.0‰ and was shown to be commensurate with the changes predicted from NO3- deficits caused by algal growth.
KEY WORDS: POM · Antarctic sea ice · Ice macroalgae · Carbon isotopic composition
Full text in pdf format
Published in MEPS Vol.
238
(2002) on August 8
Print ISSN: 0171-8630; Online ISSN: 1616-1599.
Copyright © Inter-Research, Oldendorf/Luhe, 2002
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