Microbial population responses in three stratified Antarctic

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TitleMicrobial population responses in three stratified Antarctic meltwater ponds during the autumn freezeAbstractThe planktonic microbial communities of three meltwater ponds, located on the McMurdo Ice Shelf, were investigated from the end of January 2008 to early April, during which almost the entire pond volumes froze. The ponds were comprised of an upper mixed layer overlying a salt-stabilized density gradient in which planktonic communities were primarily embedded. Plankton comprised all components of the mÌicrobial loop,Ì though carnivorous protists were rare. As the ponds froze and light became increasingly limited, it was expected conditions would induce physiological changes altering the functional role of autotrophic and heterotrophic microplankton within the ponds. The results showed that microbial groups responded to the onset of winter by declining in abundance, though an exception was the appearance of filamentous cyanobacteria in the water column in March. As freezing progressed, autotrophs declined more rapidly than heterotrophs and grazing rates and abundances of mixotrophic and heterotrophic organisms increased. Grazing pressure on bacteria and picophytoplankton also increased, in part explaining their decline over time. The results indicate that stressors imposed during freezing select for increasing heterotrophy within the remaining microbial communities, although all components of the food web eventually decline as the final freeze approaches. Copyright Copyright Antarctic Science Ltd 2012.AcknowledgementsThis research was funded by the New Zealand Foundation for Research, Science and Technology (Contracts C01 X 0708 and C01 X 0306) and Antarctica New Zealand which provided logistic support. We thank Nat Wilson who was an integral part of the field team. We also thank Dr Julie Hall for critical comments on various drafts of the manuscript, Dr Warwick Vincent, an anonymous reviewer and the editor for their comments that much improved the manuscript.

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1st AuthorSafi, K.AuthorSafi, K.Hawes, I.Sorrell, B.Year2012JournalAntarctic ScienceVolume24Number6Pages571-588DOI10.1017/S0954102012000636URLhttps://www.scopus.com/inward/recor.....0dab5bd73e18012a5a5f58525Keywordsautotrophyciliatecommunity responsedevelopmental biologyfood webgrazing pressureheterotrophymeltwatermicrobial activitymicrobial communitymicroplanktonpondpopulation declinepopulation structure, AntarcticaEast AntarcticaMcMurdo Ice Shelf, Bacteria (microorganisms)CiliophoraCyanobacteriaMastigophora (flagellates)Protista, rank5Author Keywordsbacteriaciliatesflagellate grazingfood websplanktonic communities

Other

TypeArticleCitationSandersfeld, T., Davison, W., Lamare, M., Knust, R. and Richter, C. (2015) Elevated temperature causes metabolic trade-offs at the wholeorganism level in the {Antarctic} fish {Trematomus} bernacchii. Journal of Experimental Biology, 218(15): 2373-2381 doi:10.1242/jeb.122804 IdentifierSafi2012Relevancerank5

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Hawes, I.