Low stable carbon isotope fractionation by coccolithophore RubisCO

Cyanobacterial carbon concentrating mechanisms facilitate sustained CO<sub>2</sub> depletion in eutrophic lakes

“…The range of values measured in our study for both δ 13 C phyto and ε p is consistent with previous laboratory and marine field studies demonstrating shifts from diffusive to active inorganic carbon assimilation via CCM activation (Boller et al, 2011;Cassar, 2004;Erez et al, 1998;Trimborn et al, 2009). Calculated photosynthetic fractionation was lowest during blooms, which is consistent with phytoplankton CCM utilization.…”

The effect of atmospheric CO2 concentration on carbon isotope fractionation in C3 land plants

“…Both the isotopic fractionation due to diffusion and to RuBisCO (a and b within Eq. (1), respectively) are generally conceptualized as constants (Farquhar et al, 1989) and do not depend on CO 2 level (Tcherkez and Farquhar, 2005), but the values for b vary significantly between terrestrial and marine photosynthesizers, and may even vary across different species (Boller et al, 2011). The most commonly invoked values for b in higher plants range between 26 and 30& (Christeller et al, 1976;Wong et al, 1979;Farquhar et al, 1982;Roeske and O'Leary, 1984;Guy et al, 1993;Lloyd and Farquhar, 1994;Suits et al, 2005).…”

CO 2 concentrating mechanisms and environmental change

“…However, there are exceptions to the finding of more negative 13 C in deeper growing specimens of a species and, as always with natural populations, without recourse to such methods of reciprocal transplants there is the problem of distinguishing acclimation from adaptation (Marconi et al, 2011). Isotope studies on microalgae are further complicated by the observation by Boller et al (2011) that the Form ID Rubisco from the coccolithophorid (Haptophyte) E. huxleyi (and by inference maybe also that of diatoms and some dinoflagellates) shows substantially less discrimination (11.1‰) than do forms of Rubisco from other photoautotrophs (18-30.3‰). Since there is evidence from studies of the ␦ 13 C, relative to the ␦ 13 C of external CO 2 , of freshwater and marine florideophycean macroalgae lacking CCMs which suggests that their Form ID Rubisco discriminates much more than does the enzyme from E. huxleyi (MacFarlane and Raven, 1990;Maberly et al, 1992;Raven et al, 2005a;Tcherkez et al, 2006;Hepburn et al, 2011;Marconi et al, 2011;Raven and Hurd, 2012), the work of Boller et al (2011) needs to be repeated on the Form ID Rubisco from macroalgae lacking (and those that are expressing) CCMs.…”