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Marine Ecology Progress Series

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MEPS 552:93-113 (2016)  -  DOI:

Enhanced CO2 concentrations change the structure of Antarctic marine microbial communities

Andrew T. Davidson1,2,3,*, John McKinlay1, Karen Westwood1,2,3, Paul G. Thomson4, Rick van den Enden1, Miguel de Salas5, Simon Wright1,2,3, Robert Johnson3, Kate Berry6

1Department of the Environment and Water Resources, Australian Antarctic Division, Channel Highway, Kingston, Tasmania 7050, Australia
2Antarctic Climate and Ecosystems Cooperative Research Centre (ACE CRC), University of Tasmania, Private Bag 80, Hobart, Tasmania 7001, Australia
3Institute of Marine and Antarctic Studies (IMAS), University of Tasmania, Private Bag 129, Hobart, Tasmania 7001, Australia
4School of Environmental Systems Engineering and The UWA Oceans Institute, The University of Western Australia, Mailstop M470, 35 Stirling Highway, Crawley, Western Australia 6009, Australia
5Tasmanian Herbarium, Tasmanian Museum and Art Gallery, College Rd., Sandy Bay, Tasmania 7005, Australia
6CSIRO Marine and Atmospheric Research (CMAR), CSIRO Marine and Atmospheric Research Laboratories, Castray Esplanade, Hobart, Tasmania 7000, Australia
*Corresponding author:

ABSTRACT: The impacts of anthropogenic enhancement of the partial pressure of carbon dioxide (pCO2) on marine organisms remain unclear, especially in Antarctic waters, which are predicted to be amongst the earliest and most severely affected by the consequent changes in ocean chemistry. Marine microbes are the base of the Antarctic food chain, and the nature of their response to elevated pCO2 is important as they are key determinants of the biogeochemical cycles that affect global climate. We studied the response of a natural community of Antarctic marine microbes from near-shore waters off Davis Station, Antarctica, to pCO2 ranging from the concentration in the water column at the time the experiment began (ambient, 84 μatm) to that predicted by the year 2300 (2423 μatm) using 6 gas-tight, environmentally controlled tanks (minicosms; 650 l) to which CO2-saturated seawater was added. The microbial community showed little difference between 84 and 643 μatm CO2 (0.2 to 1.7 times present), indicating that they can tolerate the large seasonal range in pCO2 in Antarctic coastal waters. Concentrations ≥1281 μatm reduced the accumulation rate of chlorophyll and particulate carbon, changed the microbial community, and enhanced the relative abundance of small phytoplankton. If our results are indicative of the future responses of Antarctic marine microbes, elevated CO2 could profoundly affect the structure and function of the Antarctic food web by reducing the availability of food for higher trophic levels and decreasing the efficiency of the biological pump.

KEY WORDS: Ocean acidification · Phytoplankton · Microzooplankton · Bacteria · Community structure · Abundance · Size · Biomass

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Cite this article as: Davidson AT, McKinlay J, Westwood K, Thomson PG and others (2016) Enhanced CO2 concentrations change the structure of Antarctic marine microbial communities. Mar Ecol Prog Ser 552:93-113.

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