Seasonal and dirunal variation of chlorophyll distribution off the east coast of Korea (East/Japan Sea), 2011

Abstract

The time evolution data of the biogeochemical and physical properties of the water column in coastal area (East/Japan Sea) located off the east coast of Korea is obtained by the coastal monitoring buoy station (ESROB, East Sea Realtime Ocean Buoy), equipped with chlorophyll a fluorometer (WQM), current meter (ADCP), PAR sensors, and Dissolved Oxygen and temperature. In April 2011, the optically-derived fluorescence sensor was installed into the buoy station within upper layer (about 1 m water depth) with highly resolved time resolution (10 min.) to examine the variability of various timespan spectrum, which has periods from diurnal to monthly variation, on the chlorophyll a fluorescence. The fluorescence time-series data showed distinct low-frequency (spring and fall blooms which is a typical characteristic in East/Japan Sea) fluctuations ranging from 0.2 μg/l to 3.8 μg/l, including abnormal summer surface bloom event in the coastal region. The high chlorophyll concentration within upper layer in summer may be attributed to surface thin low salinity water with the relatively rich nutrients flowing along the east coast of Korea through Korea Strait. Surface chlorophyll a fluorescence estimated from WQM sensor well correspond to the chlorophyll concentration derived from in situ water samples, showing a relatively high correlation coefficient (r=0.78).