Summer-winter transitions in Antarctic ponds II: Biological
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TitleSummer-winter transitions in Antarctic ponds II: Biological responsesAbstractAbstract We observed ice formation and water column attributes in four shallow Antarctic ponds between January and 7 April 2008. During that time ponds went from ice-free to >80 cm thick ice, near-freshwater to hypersaline, well-lit to near darkness and temperatures fell to below zero. Here we examine shifts in biological activity that accompanied these changes. During February, freeze-concentration and ongoing photosynthesis increased dissolved oxygen concentration to up to 100 mg l-1, with a near-equivalent decrease in dissolved inorganic carbon and a pH rise. Benthic photosynthesis was responsible for 99% of estimated biological oxygen production. Net oxygen accumulation ceased in late February, pH began to fall and inorganic carbon to increase, but the pool of dissolved oxygen was depleted only slowly. Anoxia had been attained in only one pond by April and there was little accumulation of indicators of anaerobic activity. The nitrogen and phosphorus balances of the ponds were dominated by organic forms, which, like DOC and CDOM, behaved conservatively. Conversely, inorganic nitrogen and phosphorus uptake was evident throughout the study period, at a molar ratio of 16N:1P in two of three ponds, consistent with uptake into biological material. We found no coupling between N and P uptake and photosynthesis. Copyright Antarctic Science Ltd 2011.AcknowledgementsThis research was funded by the New Zealand Foundation for Research, Science and Technology (Contracts C01X0708 and C01X0306) to the National Institute of Water and Atmospheric Research (NIWA). Antarctica New Zealand provided logistic support, in collaboration with the US National Science Foundation. Nat Wilson was an integral part of the field team and we are grateful to Dr Kevin Brown and Briar Wait for their contribution to the analysis of chloride. We are grateful to NIWA Christchurch for laboratory, technical and infrastructural support, particularly to Dr Clive Howard-Williams, and to two anonymous reviewers and the editor for critical comments that much improved the manuscript.
TypeArticleCitationHawes, I., Safi, K., Webster-Brown, J., Sorrell, B. and Arscott, D. (2011). Summer-winter transitions in Antarctic ponds II: Biological responses. Antarctic Science, 23(3): 243-254 IdentifierHawes2011bRelevancerank5
