Population Dynamics and the Toxin of Anabaena in the Lower Naktong River

Population dynamics of Anabaena and the anatoxin-a concentration were monitored with physicochemical parameters at 3 sites in the lower Naktong River from May to September in 2000.Total 4 species of Anabaena (A. flosaquae, A. smithii, A. ucrainica and A. mucosa) were identified with morphological characteristics.Anabaena flos-aquae was most abundant among the populations.The standing crop of Anabaena ranged from 10 to 11,220 cells • ml -1 and biomass of Anabaena more 1,000 cells • ml -1 was observed once at St. Mulgeum and St. Seonam, twice at St. Hagueon out of total 9 samplings.There were not significant correlations between the standing crop of Anabaena and other physicochemical parameters such as temperature, nitrate, total nitrogen, phosphate, total phosphorus and N/P ratios.The frequency of trichomes with akinetes was low and ranged from 0 to 4% in the total Anabaena population and A. smithii showed highest frequency of 2.8% among all species.The population at St. Seonam showed highest frequency of 1.4% among all sampling sites.The population in September showed the highest frequency of 3.0% among all sampling period.The frequency of trichomes with heterocysts was low and ranged from 1 to 87% in the total Anabaena population and A. smithii showed highest frequency of 55.1% among all species.The population at St. Mulgeum showed highest frequency of 17.6% among all sampling sites.The population in August showed the highest frequency of 21.4% among all sampling period.The frequency of trichomes with akinetes and/or heterocysts was not related to all the physicochemical parameters of temperature, nitrate, total nitrogen, phosphate, total phosphorus and N/P ratios.The anatoxin-a concentrations were determined in algal materials dominated by Microcystis and Anabaena from June though August by derivatization using 7-fluoro-4-nitro-2, 1, 3-benzoxadiazole (NBD-F) and HPLC analysis with fluorimetric detection.All the concentrations were below the detection limit of 0.1 µg • l -1 in the present study.