Preliminary evidence for the microbial loop in Antarctic sea

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TitlePreliminary evidence for the microbial loop in Antarctic sea ice using microcosm simulationsAbstractSea ice microalgae actively contribute to the pool of dissolved organic matter (DOM) available for bacterial metabolism, but this link has historically relied on bulk correlations between chlorophyll a (a surrogate for algal biomass) and bacterial abundance. We incubated microbes from both the bottom (congelation layer) and surface brine region of Antarctic fast ice for nine days. Algal-derived DOM was manipulated by varying the duration of irradiance, restricting photosynthesis with 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) or incubating in the dark. The bacterial response to changes in DOM availability was examined by performing cell counts, quantifying bacterial metabolic activity and examining community composition with denaturing gradient gel electrophoresis. The percentage of metabolically active bacteria was relatively low in the surface brine microcosm (10-20% of the bacterial community), the treatment with DCMU indirectly restricted bacterial growth and there was some evidence for changes in community structure. Metabolic activity was higher (35-69%) in the bottom ice microcosm, and while there was no variation in community structure, bacterial growth was restricted in the treatment with DCMU compared to the light/dark treatment. These results are considered preliminary, but provide a useful illustration of sea ice microbial dynamics beyond the use of 'snapshot' biomass correlations. © Copyright Antarctic Science Ltd 2012.AcknowledgementsWe acknowledge the logistical support of Antarctica New Zealand and in particular S. Gordon, project manager of the Latitudinal Gradient Project (LGP). A. Martin was supported by a Victoria University of Wellington Postgraduate Scholarship for PhD Study and also thanks the Trans Antarctic Association for support in funding this research. K. Ryan acknowledges the support of the Foundation of Research, Science & Technology contract no. VICX0706. We extend our thanks to the anonymous reviewers whose comments significantly improved the manuscript.

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1st AuthorMartin, A.AuthorMartin, A.Mcminn, A.Davy, S.Anderson, M.Miller, H.Hall, J.Ryan, K.Year2012JournalAntarctic ScienceVolume24Number6Pages547-553DOI10.1017/S0954102012000491URLhttps://www.scopus.com/inward/recor.....348ca23e42c01e8032569ed91Keywordsabundancebacteriumbiomasscommunity compositiondissolved organic mattergrowth ratemetabolismmicroalgamicrobial activitymicrobial communitymicrocosmnumerical modelphotosynthesissea ice, Southern Ocean, algaeBacteriaAuthor KeywordsbacteriaDGGEmicroalgae

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TypeArticleCitationMartin, A., Mcminn, A., Davy, S., Anderson, M., Miller, H., Hall, J. and Ryan, K. (2012). Preliminary evidence for the microbial loop in Antarctic sea ice using microcosm simulations. Antarctic Science, 24(6): 547-553 doi:10.1017/S0954102012000491 IdentifierMartin2012bRelevancerank5