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Marine Ecology Progress Series

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MEPS 171:303-305 (1998)  -  doi:10.3354/meps171303

Relationship between aqueous CO2 concentrations and stable carbon isotope discrimination in the diatoms Chaetoceros calcitrans and Ditylum brightwellii

Rebecca E. Korb*, John A. Raven, Andrew M. Johnston

Department of Biological Sciences, University of Dundee, Dundee DD1 4HN, Scotland, UK
*Present address: Marine Sciences Research Center, State University of New York, Stony Brook, New York 11794-5000, USA. E-mail:

ABSTRACT: Recent work has focused on a possible relationship between marine organic δ13C and the concentration of carbon dioxide dissolved in seawater [CO2(aq)]. This relationship is based on the general assumption that diffusive CO2 uptake is the main pathway of photosynthetic carbon acquisition by phytoplankton. This study found an inverse linear relationship between [CO2(aq)] and organic δ13C in the marine diatoms Chaetoceros calcitrans and Ditylum brightwellii. However, the relationship was not a function of diffusive CO2 use by these diatoms, which have previously been shown to be HCO3- users. Our findings underline the importance of understanding the mechanisms of phytoplankton carbon acquisition in interpreting carbon isotope data.

KEY WORDS: Organic δ13C · Carbon dioxide · Bicarbonate · Chaetoceros calcitrans · Ditylum brightwellii

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