Antarctic phytoplankton down-regulate their carbon-concentrating mechanisms under high CO2 with no change in growth rates

Abstract

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 532:13-28 (2015) - DOI: https://doi.org/10.3354/meps11336 Antarctic phytoplankton down-regulate their carbon-concentrating mechanisms under high CO2 with no change in growth rates Jodi N. Young1,*, Sven A. Kranz1,4, Johanna A. L. Goldman1, Philippe D. Tortell2,3, François M. M. Morel1 1Department of Geosciences, Princeton University, Princeton, NJ 08544, USA 2Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, BC V6T 1Z4, Canada 3Department of Botany, University of British Columbia, Vancouver, BC V6T 1Z4, Canada 4Present address: Department of Earth, Ocean and Atmospheric Sciences, Florida State University, Tallahassee, Fl 32306, USA *Corresponding author: jny@princeton.edu ABSTRACT: High-latitude oceans, in particular the coastal Western Antarctic Peninsula (WAP) region of the Southern Ocean, are experiencing a rapidly changing environment due to rising surface ocean temperatures and CO2 concentrations. However, the direct effect of increasing CO2 on polar ocean primary production is unclear, with a number of experiments showing conflicting results. It has been hypothesized that increased CO2 may cause a reduction of the energy-intensive carbon concentrating mechanism (CCM) in phytoplankton, and these energy savings may lead to increased productivity. To test this hypothesis, we incubated natural phytoplankton communities in the WAP under high (800 ppm), current (400 ppm) and low (100 ppm) CO2 for 2 to 3 wk during the austral spring-summer of 2012/2013. In 2 incubations with diatom-dominated phytoplankton assemblages, high CO2 led to a clear down-regulation of CCM activity, as evidenced by an increase in half-saturation constants for CO2, a decrease in external carbonic anhydrase activity and a higher biological fractionation of stable carbon isotopes. In a third incubation, there was no observable regulation of the CCM, possibly because HCO3- served as the major inorganic carbon source in all treatments for this phytoplankton assemblage. We did not observe a significant effect of CO2 on growth rates or community composition in the diatom-dominated communities. The lack of a measureable effect on growth despite CCM down-regulation is likely explained by a very small energetic requirement to concentrate CO2 and saturate Rubisco at low temperatures. KEY WORDS: Phytoplankton · CO2 · Antarctic · CCM · Growth Full text in pdf format Supplementary material PreviousNextCite this article as: Young JN, Kranz SA, Goldman JAL, Tortell PD, Morel FMM (2015) Antarctic phytoplankton down-regulate their carbon-concentrating mechanisms under high CO2 with no change in growth rates. Mar Ecol Prog Ser 532:13-28. https://doi.org/10.3354/meps11336 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 532. Online publication date: July 21, 2015 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2015 Inter-Research.