CO2‐concentrating mechanisms in three southern hemisphere strains of Emiliania huxleyi. Issue 4 (15th May 2013)

• Record Type: Journal Article
• Authors: Stojkovic, Slobodanka; Beardall, John; Matear, Richard; Lin, S.
• Is Part Of: Journal of phycology. Volume 49:Issue 4(2013:Aug.)
• Page Start: 670
• Page End: 679
• Publication Date: 2013-05-15
• Subjects: Algae -- Periodicals; 579.8
• DOI: 10.1111/jpy.12074
• Languages: English
• ISSNs: 0022-3646

Abstract

<abstract abstract-type="main" id="jpy12074-abs-0001"> <title> <x xml:space="preserve">Abstract</x> </title> <p>Rising global CO<sub>2</sub> is changing the carbonate chemistry of seawater, which is expected to influence the way phytoplankton acquire inorganic carbon. All phytoplankton rely on ribulose‐bisphosphate carboxylase oxygenase (RUBISCO) for assimilation of inorganic carbon in photosynthesis, but this enzyme is inefficient at present day CO<sub>2</sub> levels. Many algae have developed a range of energy demanding mechanisms, referred to as carbon concentrating mechanisms (CCMs), which increase the efficiency of carbon acquisition. We investigated CCM activity in three southern hemisphere strains of the coccolithophorid <italic>Emiliania huxleyi</italic> W. W. Hay & H. P. Mohler. Both calcifying and non‐calcifying strains showed strong CCM activity, with HCO<sub>3</sub><sup>−</sup> as a preferred source of photosynthetic carbon in the non‐calcifying strain, but a higher preference for CO<sub>2</sub> in the calcifying strains. All three strains were characterized by the presence of pyrenoids, external carbonic anhydrase (CA) and high affinity for CO<sub>2</sub> in photosynthesis, indicative of active CCMs. We postulate that under higher CO<sub>2</sub> levels cocco‐lithophorids will be able to down‐regulate their CCMs, and re‐direct some of the metabolic energy to processes such as calcification. Due to the expected rise in CO<sub>2</sub> levels, photosynthesis in calcifying strains is expected to benefit most, due to their use of CO<sub>2</sub> for carbon uptake. The non‐calcifying strain, on the other hand, will experience only a 10% increase in HCO<sub>3</sub><sup>−</sup>, thus making it less responsive to changes in carbonate chemistry of water.</p> </abstract>