Cyanobacterial occurrence and geosmin dynamics in Paldang Lake watershed, South Korea

Abstract

AbstractWe investigated the relationship between cyanobacteria and geosmin occurrence in the Paldang Lake watershed, South Korea, by examining samples from the Bukhan and Namhan Rivers weekly from 2011 to 2015. Cyanobacteria were detected in summer, when water temperatures reached 20°C or more. Merismopedia, non‐nitrogen‐fixing cyanobacteria, dominated the Namhan River, which had high nitrogen concentrations. In the Bukhan River, Dolichospermum, nitrogen‐fixing cyanobacteria, was dominant. Temporary nitrogen inflow into the Bukhan River due to rainfall transformed the cyanobacterial community from one dominated by nitrogen‐fixing cyanobacteria (Dolichospermum) to one dominated by non‐nitrogen‐fixing cyanobacteria (Microcystis). Geosmin was highly correlated with Dolichospermum in the Bukhan River (r = 0.947, P < 0.01) and its concentration changed in accordance with Dolichospermum cell counts. In the Merismopedia‐dominated Namhan River, geosmin concentrations were low, suggesting that the cyanobacterial community composition affects geosmin levels.