Microbial community dynamics governed by mixed layer depth during an austral summer in Ryder Bay, Antarctica

Patrick Rozema, Tristan Biggs, Pim Sprong, Anita Buma, Hugh Venables, Claire Evans, Michael Meredith, Henk Bolhuis

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The Western Antarctic Peninsula is warming. As a result, summertime salinity stratification may occur more frequently due to enhanced glacial melt water input. The resulting changes in environmental conditions could affect the seasonal dynamics of phytoplankton and Bacteria. The aim of the present study was to examine the environmental characteristics that drive coastal Antarctic microbial community dynamics. Sampling was done at 15 m depth during the austral summer of 2010-2011 at the Rothera oceanographic and biological Time Series site (RaTS) in northern Marguerite bay, Antarctica. Environmental variables included salinity, temperature, density, irradiance, wind speed, major nutrients and δ18O, the latter indicative of fresh water origin. Phytoplankton biomass and group specific composition were followed using size fractionated Chl aand HPLC-CHEMTAX. Four different primer sets were used to study community changes using DGGE analysis: eukaryotes, diatoms, dinoflagellates and Bacteria. Salinity decrease during summer coincided with increased meteoric water input indicative of a glacial origin. Maximum Chl a values of 35 μg l-1 were found during midsummer, mainly consisting of diatoms. Analysis of DGGE patterns revealed four distinctly different periods in eukaryotic succession during the season. The Bacteria showed a delayed response to the phytoplankton community. Non-metric multidimensional scaling analysis showed that phytoplankton community dynamics were mainly directed by temperature, mixed layer depth and wind speed. The bacterioplankton community composition was mainly governed by Chl a, suggesting a link to phytoplankton community changes. Sequencing (MiSeq) results for eukaryotes and Bacteria showed a high similarity between January and February. Eukaryotic sequences were dominated by pennate diatoms in December follow by polar centric diatoms in January and February. Our results imply that the reduction of the mixed layer depth during summer, caused by melt water related surface stratification promotes a succession in diatoms rather than (nano)phytoflagellates in Ryder Bay, which may favour higher trophic levels.
Original languageEnglish
Number of pages1
Publication statusPublished - 23-Aug-2016
EventSCAR 2016: Antarctica in the global earth system: From the poles to the tropics - Kuala Lumpur, Malaysia
Duration: 22-Aug-201627-Aug-2016


ConferenceSCAR 2016
CityKuala Lumpur
Internet address

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