Carbon-13 enrichment in benthic compared to planktonic algae: foodweb implications

Abstract

Confirms the hypothesis that carbon fixation in aquatic plants having thicker, stagnant boundary layers, will result in more positive δ13C values due to greater diffusion resistance and subsequent assimilation of otherwise normally discriminated 13C. The average δ13C value found in the literature for benthic algae in lakes was 26‰, whereas that for riverine benthic algae was -29‰. The greater water turbulence to which planktonic algae are exposed is known to dramatically reduce boundary layer thickness and was found to cause even more severe 13C depletion, resulting in an average value of -32‰. This same effect also operates in coastal environments where the average δ13C value for marine phytoplankton was -22‰ compared to -17‰ for marine benthic algae. -from Author