Legacies of recent environmental change in the benthic commu

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TitleLegacies of recent environmental change in the benthic communities of Lake Joyce, a perennially ice-covered Antarctic lakeAbstractMany Antarctic lakes provide habitat for extensive microbial mats that respond on various timescales to environmental change. Lake Joyce contains calcifying microbialites and provides a natural laboratory to constrain how environmental changes influence microbialite development. In Lake Joyce, depth-specific distributions of calcitic microbialites, organic carbon, photosynthetic pigments and photosynthetic potential cannot be explained by current growth conditions, but are a legacy of a 7-m lake level rise between 1973 and 2009. In the well-illuminated margins of the lake, photosynthetically active benthic communities colonised surfaces submerged for just a few years. However, observed increases in accumulated organic material with depth from 5 to 20m (2-40mg ash-free dry weightcm -2) and the presence of decimetre-scale calcite microbialites at 20-22m depth, apparently related to in situ photosynthetic growth, are inconsistent with the current distributions of irradiance, photosynthetic pigments and mat photosynthetic potential (as revealed by pulse-amplitude-modulated fluorometry). The microbialites appeared photosynthetically active in 1986 and 1997, but were outside the depth zone where significant phototrophic growth was possible and were weakly photosynthetically competent in 2009. These complex microbial structures have persisted after growth has ceased, demonstrating how fluctuating environmental conditions and the hysteresis between environmental change, biological response and microbialite development can be important factors to consider when interpreting modern, and by inference ancient, microbially mediated structures. Copyright 2011 Blackwell Publishing Ltd.AcknowledgementsThis research was supported by NASAÅ› Exobiology Programme (NNZ09AE77A) and the New Zealand Foundation for Research, Science and Technology (C01X0306). The US National Science Foundation Office of Polar Programmes provided logistic support. We thank all of our field colleagues for support throughout, Mark Gall and Chris Cunningham (NIWA, New Zealand) for assistance with HPLC and colleagues and reviewers for assistance with various stages of this manuscript.

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TypeArticleCitationHawes, I.Sumner, D.Andersen, D.Mackey, T. (2011). Legacies of recent environmental change in the benthic communities of Lake Joyce, a perennially ice-covered Antarctic lake. Geobiology, 9(5): 394-410