MEPS 554:51-69 (2016)  -  DOI: https://doi.org/10.3354/meps11803

Increasing CO2 changes community composition of pico- and nano-sized protists and prokaryotes at a coastal Antarctic site

Paul G. Thomson1,2,*, Andrew T. Davidson2,3, Lynsey Maher

1School of Civil, Environmental and Mining Engineering and The UWA Oceans Institute, The University of Western Australia, Mailstop M470, 35 Stirling Highway, Crawley, Western Australia 6009, Australia
2Department of Sustainability, Environment, Water, Population & Communities, Australian Antarctic Division, Channel Highway, Kingston, Tasmania 7050, Australia
3Antarctic Climate and Ecosystems Cooperative Research Centre (ACECRC), University of Tasmania, Private Bag 80, Hobart, Tasmania 7001, Australia
*Corresponding author:

ABSTRACT: Ocean acidification is a globally recognised phenomenon, but little is known of its impacts on Antarctic marine microbes. Here we report on the community response of pico- and nanophytoplankton, heterotrophic nanoflagellates (HNF) and prokaryotes (Archaea and Bacteria) to elevated CO2 during 3 minicosm experiments over the 2008/2009 summer at Davis Station, Antarctica. Coastal seawater was incubated in 650 l minicosms (n = 6) for ≤12 d at CO2 concentrations ranging from preindustrial levels to those predicted for 2100 and beyond. The abundance of pico- and nano-sized protists and prokaryotes were determined by flow cytometry, using chlorophyll autofluorescence to discriminate the phytoplankton, SYBR-Green to stain the prokaryotes and LysoTracker Green stain to discriminate the HNF. While the effects on nanophytoplankton abundance were inconclusive, our results show that increasing CO2 can alter the composition of the microbial community in Antarctic coastal waters. Our 3 experiments consistently showed lower concentrations of HNF and higher abundances of picophytoplankton and prokaryotes in treatments exposed to elevated CO2. While the mechanism remains to be confirmed, our study suggests that CO2 may reduce the mortality of picoplankton by HNF grazing. Our results indicate that changes in the composition of Antarctic microbial communities may occur within the concentration range of 750 to 1118 ppm CO2, potentially impacting the Antarctic food web through reduced food availability.


KEY WORDS: Ocean acidification · Minicosms · CO2 · Flow cytometry · Picophytoplankton · Nanophytoplankton · Heterotrophic nanoflagellates · Bacteria · Archaea


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Cite this article as: Thomson PG, Davidson AT, Maher L (2016) Increasing CO2 changes community composition of pico- and nano-sized protists and prokaryotes at a coastal Antarctic site. Mar Ecol Prog Ser 554:51-69. https://doi.org/10.3354/meps11803

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