C-13/C-12 fractionation by marine diatoms

The C-13/C-12 distributions in plants record the integrated pattern of photosynthetic carbon acquisition. Most planktonic marine algae are small, relatively rare and hard to separate from background particles, so that very few investigations have used delta(13)C to study algal photosynthesis in the sea. Diatoms are perhaps the best studied group among the marine microalgae, and this review summarizes current knowledge of effects of temperature, salinity, pH, growth rate and CO2 concentrations on diatom gamma(13)C. External CO2 concentrations have the strongest effect demonstrated thus far on C-13/C-12 distributions and isotope fractionation, with the largest isotopic discriminations found in high CO2 conditions, Both models and culture studies suggest that delta(13)C values record the balance between algal growth demand versus supply of inorganic carbon in seawater, and that carbon isotope studies can be used to probe the diversity of algal carbon acquisition strategies in the sea.