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Folic acid in Rogoznica lake and in seawater in northern Adriatic , Croatia

Folic acid has been determined by electrochemical method of cathodic stripping voltammetry. Folic acid (FA), belongs to B-group vitamins and has been recognized as possible nutrient for some phytoplankton species (a diatom Phaeodactylum tricornutum). The FA concentration was over the range of 0.1&#8211; 13.5 nM in the oxic part of Rogoznica Lake, and 0.1&#8211; 22 nM in the northern Adriatic. A weak but statistically significant correlation was established between photosynthetic pigment zeaxanthin, a characteristic biomarker of cyanobacteria, and FA in the oxic layer of the Rogoznica Lake (r2 = 0.3967 ; n = 29 ; P < 0.01), indicating cyanobacteria as a possible source of FA in this ecosystem. A statistically significant correlation (r2 = 0.36 ; n = 18 ; P < 0.01) between the two parameters was also found for the surface layer of the northern Adriatic (0 m). However, a low contribution of cyanobacteria to the total photosynthetic biomass in the northern Adriatic, and a lack of correlation between FA and zeaxanthin in the deeper layers of the water column, suggested that cyanobacteria were probably not the main source of FA in these waters. Due to the widespread use of FA it could pose a problem to enclosed coastal areas and lakes.

folic acid; cathodic stripping voltammetry; Rogoznica lake; the Northern Adriatic

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