MEPS 124:307-312 (1995)  -  doi:10.3354/meps124307

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

France RL

Previous work has shown freshwater macrophytes from lake littoral zones to be 13C-enriched compared to the same species collected from fast moving rivers. It is thought that carbon fixation in aquatic plants having thicker, stagnant boundary layers, such as that which occurs within low turbulence lentic systems, will result in more positive delta13C values due to greater diffusion resistance and subsequent assimilation of otherwise normally discriminated 13C. The present study confirms this hypothesis by examining 876 algal delta13C values collected from the literature. The average delta13C value 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 delta13C value for marine phytoplankton was -22 compared to -17 for marine benthic algae. When comparisons were made on an individual study basis, differences of 10 or greater in delta13C were observed between planktonic and benthic algae in both oceans and lakes. These algal differences in delta13C were found to be substantial enough to be reflected in the delta13C values of consumers in marine coastal environments.

delta13C . Marine . Freshwater . Benthic and planktonic algae

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