Summer-time episodic chlorophyll-a blooms near east coast of Korea
Abstract. We present intensive observational data of surface chlorophyll-a bloom episodes occurring over several days in the summers of 2011, 2012, and 2013, accompanying the equatorward advection of low sea-surface salinity (SSS) water near the east coast of Korea. Time-series analysis of meteorological and oceanographic (physical and biochemical) parameter data, such as chlorophyll fluorescence (CF) from surface mooring, ocean color (chlorophyll a and total suspended sediment), sea surface height (satellite-derived), and serial hydrographic data (from in-situ measurements) were used to investigate the relationship between surface bloom events and changes in seawater characteristics and currents. In the summers of the three years, a total of 10 bloom events (E01–E10) were identified where the surface CF was significantly (> 2 μg/l) enhanced over a relatively long (> 1 day) period. The bloom events in the summers of 2011 and 2012 accompanied low or decreasing SSS for several days to a week after heavy rainfalls at upstream stations and equatorward currents. Unlike the typical 8 of the 10 events (80 %), E07 was potentially derived from the onshore advection of high CF offshore water of southern origin into the coastal zone near the mooring, whereas E10 is likely prevailed by offshore advection of high CF plume water trapped by the coastal area. Contrasting with many coastal systems, these findings indicate that event-scale productivity near the east coast of Korea in summer is not controlled by local blooms triggered by either nutrients or light availability, but by the equatorward and cross-shore advections of high CF plume water.