Algae. 2004; 19(1): 1-6.
Uptake of Carbon and Nitrogen by Microcystis Algal Assemblages in the Seonakdong River
Ok-Hee Lee, Kyung-Je Cho
Carbon (14CO2) and nitrogen (15NH4 and 15NO3) uptake were measured at two stations in the hypertrophic zone of the Seonakdong River, where Microcystis aeruginosa explosively bloomed in September 1998. Significant nitrogen limitation occurred in the period of Microcystis bloom, while phosphorus limitation was common in the river. The specific nitrogen (NH4 + NO3) uptake was 12-50 mol mg chl-a-1 hr-1 at two stations, showing substantially higher than for any other freshwaters. The specific nirtogen uptake was higher at the GAR Station of the nitrogen-limited area and this high nirtogen uptake resulted in low 14C:15Natomic ratios of algal uptake. Carbon uptake was dependent upon irradiance, decreasing gradually toward the bottom in the euphotic zone, whereas the nitrogen uptake increased slightly toward the bottom. NH4 preferable uptake against NO3 was hardly discemilble due to the fact that it exceeded the NH4 ambient concentraiton. The 14C:15N atomic ratios of algal uptake in the surface waters approached the Redfield C:N ratio.
Keywords : algal uptake; 14C and 15N ; hypertrophic water; Microcyatis; NH4 and NO3