Carbon Uptake in Aquatic Plants Deduced from Their Natural 13C and 14C Content

Abstract

delta-13C and 14C activity measurements were made on terrestrial, marsh and aquatic plants growing in their natural habitat of the Plitvice Lakes in northwest Yugoslavia. delta-13C values were ca -47 per mil for aquatic mosses, which indicate that the carbon source was dissolved inorganic carbon (DIC) from alkaline karst waters, following a C3 pathway, and ca -25 per mil for marsh plants, indicating the carbon source was atmospheric CO2. 14C activity of true aquatic plants and submerged parts of helophytes was close to 14C activity of DIC, whereas that of emergent parts of helophytes and terrestrial plants was similar to atmospheric CO2 activity. Aquatic plants which use DIC in freshwater for their photosynthesis are not suitable for 14C dating, unless the initial activity of incorporated carbon is known. delta-13C values of plant material also depend on the carbon source and cannot be used for 14C age correction.