Extracellular organic carbon dynamics during a bottom-ice al

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TitleExtracellular organic carbon dynamics during a bottom-ice algal bloom (Antarctica)AbstractAntarctic fast ice provides a habitat for diverse microbial communities, the biomass of which is mostly dominated by diatoms capable of growing to high standing stocks, particularly at the ice-water interface. While it is known that ice algae exude organic carbon in ecologically significant quantities, the mechanisms behind its distribution and composition are not well understood. This study investigated extracellular organic carbon dynamics, microbial characteristics, and ice algal photophysiology during a bottom-ice algal bloom at McMurdo Sound, Antarctica. Over a 2 wk period (November to December 2011), ice within 15 cm from the ice-water interface was collected and sliced into 9 discrete sections. Over the observational period, the total concentrations of extracellular organic carbon components (dissolved organic carbon [DOC] and total carbohydrates [TCHO]-the sum of monosaccharides [CHOMono] and polysaccharides [CHOPoly]) increased, and were positively correlated with algal biomass. However, when normalised to chlorophyll a, the proportion of extracellular organic carbon components substantially decreased from initial measurements. Concentrations of DOC generally consisted of <20% TCHO, typically dominated by CHOMono, which decreased from initial measurements. This change was coincident with improved algal photophysiology (maximum quantum yield) and an increase in sea-ice brine volume fraction, indicating an increased capacity for fluid transport between the brine channel matrix and the underlying sea water. Our study supports the suggestion that microbial exudation of organic carbon within.AcknowledgementsWe are most grateful for the expert help and logistical support of Antarctic New Zealand and our colleagues working with us in the field and in the leadup to the expedition, particularly C. Thorn and N. Higgison (Victoria University of Wellington, New Zealand). We thank the Australian Antarctic Division (AAD) for their ongoing support and access to infrastructure. This work was made possible by the support of the Australian GovernmentÅ› Cooperative Research Centre Program through the Antarctic Climate and Ecosystems Cooperative Research Centre (ACE CRC), the Trans-Antarctic Association and the Australian Antarctic Division (AAS 4008).

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1st AuthorUgalde, S.AuthorUgalde, S.Martin, A.Meiners, K.McMinn, A.Ryan, K.Year2014JournalAquatic Microbial EcologyVolume73Number3Pages195-210DOI10.3354/ame01717URLhttps://www.scopus.com/inward/recor.....13f40f5adee8a6e7e8323f591Keywordsrank5Author KeywordsAntarcticaCarbohydratesDissolved organic carbonMicroalgaeNutrient limitationPhotophysiologySea ice

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TypeArticleCitationUgalde, S., Martin, A., Meiners, K., McMinn, A. and Ryan, K. (2014) Extracellular organic carbon dynamics during a bottom-ice algal bloom (Antarctica). Aquatic Microbial Ecology, 73(3): 195-210 doi:10.3354/ame01717 IdentifierUgalde2014Relevancerank5