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

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