
%0 Journal Article
%A Raven, John A. 
%A Johnston, Andrew M. 
%A Kübler, Janet E. 
%A Korb, Rebecca 
%A McInroy, Shona G. 
%A Handley, Linda L. 
%A Scrimgeour, Charlie M. 
%A Walker, Diana I. 
%A Beardall, John 
%A Vanderklift, Mathew 
%A Fredriksen, Stein 
%A Dunton, Kenneth H. 
%T Mechanistic interpretation of carbon isotope discrimination by marine macroalgae and seagrasses
%J Functional Plant Biology
%D 2002/03/19
%V 29
%N 3
%P 355-378
%K carbon isotope discrimination, Phaeophyceae, Rhodophyta, seagrasses, Ulvophyceae.
%R https://doi.org/10.1071/PP01201
%U https://www.publish.csiro.au/paper/PP01201 
%X The literature, and previously unpublished data from the authors&#8217; laboratories, shows that the &#948;13C of organic matter in marine macroalgae and seagrasses collected from the natural environment ranges from &#8211;3 to &#8211;35&#8240;. While some marine macroalgae have &#948;13C values ranging over more than 10&#8240; within the thallus of an individual (some brown macroalgae), in other cases the range within a species collected over a very wide geographical range is only 5&#8240; (e.g. the red alga Plocamium cartilagineum which has values between &#8211;30 and &#8211;35&#8240;). The organisms with very negative &#948;13C (lower than &#8211;30&#8240;) are mainly subtidal red algae, with some intertidal red algae and a few green algae; those with very positive &#948;13C values (higher than &#8211;10&#8240;) are mainly green macroalgae and seagrasses, with some red and brown macroalgae. The &#948;13C value correlates primarily with taxonomy and secondarily with ecology. None of the organisms with &#948;13C values lower than &#8211;30&#8240; have pyrenoids. Previous work showed a good correlation between &#948;13C values lower than &#8211;30&#8240; and the lack of CO2 concentrating mechanisms for several species of marine red algae. The extent to which the low &#948;13C values are confined to organisms with diffusive CO2 entry is discussed. Diffusive CO2 entry could also occur in organisms with higher &#948;13C values if diffusive conductance was relatively low. The photosynthesis of organisms with &#948;13C values more positive than &#8211;10&#8240; (i.e. more positive than the &#948;13C of CO2 in seawater) must involve HCO3- use. 
