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Limnological properties of Antarctic ponds during winter freezing

Published online by Cambridge University Press:  14 May 2004

S. Schmidt
Affiliation:
Greenpeace Antarctic Expedition, Private Bag, Auckland, New Zealand
W. Moskal
Affiliation:
Greenpeace Antarctic Expedition, Private Bag, Auckland, New Zealand
S. J. De Mora
Affiliation:
Chemistry Department, University of Auckland, New Zealand
C. Howard-Williams
Affiliation:
Taupo Research Laboratory, DSIR Marine & Freshwater, Taupo, New Zealand
W. F. Vincent
Affiliation:
Taupo Research Laboratory, DSIR Marine & Freshwater, Taupo, New Zealand Permanent address: Départment de Biologie, Université Laval, Québec G1K 7P4, Canada

Abstract

Two shallow ponds at Cape Evans, Ross Island, were sampled at 1–2 week intervals, during winter freezing throughout the winter and during the subsequent melt period, to examine the physical and chemical conditions imposed on the biota during the year. Liquid water was first detected at the base of the ponds in late December. During the main summer melt period conductivities were less than 10 mS cm−1 with maximum daily temperatures around 5°C. The bottom waters became increasingly saline during freezing and water temperatures decreased below 0°C; by June the remaining water overlying the sediments had conductivities >150 mS cm−1 and temperatures of −13°C. Calcium carbonate, then sodium sulphate precipitated out of solution during early freezing. The dominant nitrogen species was dissolved organic-N which reached 12 g m−3 in Pond 1 just prior to final freeze up. The organic and inorganic forms of nitrogen and dissolved reactive phosphorus increased with increasing conductivity in the ponds. The behaviour of particulate-N and particulate-P mirrored that of chlorophyll a with a peak in March-April and a second higher peak just before final freeze-up. This study provides clear evidence that organisms which persist throughout the year in Antarctic coastal ponds must be capable of surviving much more severe osmotic, pH, temperature and redox conditions than those measured during the summer melt. Deoxygenation, pH decline and H2S production, however, point to continued respiratory activity well into the dark winter months.

Type
Papers—Life Sciences and Oceanography
Copyright
© Antarctic Science Ltd 1991

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