AME 82:145-159 (2018)  -  DOI:

Impact of temperature, CO2, and iron on nutrient uptake by a late-season microbial community from the Ross Sea, Antarctica

Jenna L. Spackeen1,*, Rachel E. Sipler1,2, Erin M. Bertrand3,4,5, Kai Xu6,7, Jeffrey B. McQuaid4,5, Nathan G. Walworth6, David A. Hutchins6, Andrew E. Allen4,5, Deborah A. Bronk1,8

1Virginia Institute of Marine Science, College of William & Mary, PO Box 1346, Gloucester Point, VA 23062, USA
2Department of Ocean Sciences, Memorial University of Newfoundland, St. John’s, NL A1C 5S7, Canada
3Department of Biology, Dalhousie University, Halifax, NS B3H 4R2, Canada
4Microbial and Environmental Genomics, J. Craig Venter Institute, La Jolla, CA 92037, USA
5Integrative Oceanography Division, Scripps Institution of Oceanography, UC San Diego, La Jolla, CA 92037, USA
6The University of Southern California, Department of Biological Sciences, 3616 Trousdale Parkway, Los Angeles, CA 90089, USA
7State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen, Fujian 361102, PR China
8Bigelow Laboratory for Ocean Sciences, East Boothbay, ME 04544, USA
*Corresponding author:

ABSTRACT: The Southern Ocean is rapidly changing as a result of rising sea surface temperatures, elevated CO2 concentrations, and modifications to iron sources and sinks. The Southern Ocean has seasonally high rates of primary production, making it critical to determine how changes will impact biogeochemical rate processes in this important sink for CO2. During the austral summer, we measured nitrogen and carbon uptake rates by a late-season Ross Sea microbial community under different potential climate change conditions. A natural microbial assemblage was collected from the ice edge, and grown using a semi-continuous culturing followed by a continuous culturing ‘ecostat’ approach. The individual and combined impacts of temperature elevation and iron addition were tested during both approaches, and CO2 level was also manipulated during the continuous experiment. Nutrient concentrations and biomass parameters were measured throughout both experiments. During the continuous experiment we also measured uptake rates of nitrate (NO3-) and dissolved inorganic carbon (DIC) by 2 size classes (0.7-5.0 and >5.0 µm) of microorganisms. Of the parameters tested, temperature elevation had the largest impact, significantly increasing NO3- and DIC uptake rates by larger microorganisms. Iron addition was also important; however, the magnitude of its impact was greater when temperature was also changed. These results indicate that NO3- and DIC uptake rates may increase as sea surface warming occurs in the Southern Ocean, and thus have important implications for estimating new production and potential carbon uptake and eventual export to the deep sea.

KEY WORDS: Ross Sea · Temperature · CO2 · Iron · Uptake · Nitrate · DIC

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Cite this article as: Spackeen JL, Sipler RE, Bertrand EM, Xu K and others (2018) Impact of temperature, CO2, and iron on nutrient uptake by a late-season microbial community from the Ross Sea, Antarctica. Aquat Microb Ecol 82:145-159.

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