Stable carbon isotope evidence for atmospheric CO2 uptake by cyanobacterial surface scums in a eutrophic lake

Abstract

The carbon isotope composition of photosynthetic organisms reflects the δ13C of their inorganic carbon sources. The large difference between δ13C in cyanobacterial surface scums (-25 to -18‰) and subsurface blooms (-34 to -30‰) in a subarctic lake indicates direct atmospheric CO2 fixation by the scums.