We examined the horizontal distribution of salinity and the concentrations of DIN and DIP after heavy rainfall events in coastal areas of South Korea from Yeoja Bay to Narodo and from Gwangyang Bay to Geomodo to determine whether fresh water actually flows into areas of Cochlodinium polykrikoides red tides and to observe its effect on the growth of this organism after heavy rainfall. Following heavy rainfall (155 mm) in the Yeosu and Suncheon regions, the average salinity was 21 and 29 psu at Yeoja Bay and in the coastal waters of Narodo, respectively. After 126 mm of rainfall, the values were 19 and 25 psu in the coastal waters of Yeosu and Geomodo, respectively. This may have been caused by an influx of fresh water, after the rainfall event, into the open sea coastal areas around Narodo and Geomodo from the Dong and Seomjin Rivers, which are about 3540 km away. After the rainfall, the concentrations of NH4-N, NO2-N, and PO4-P were slightly increased; however, the concentration of NO3-N was greatly increased and diffused throughout the coastal areas of Narodo and Geomodo, which frequently experience C. polykrikoides blooms. The influence of NH4-N, NO2-N, and PO4-P on the occurrence of C. polykrikoidesred tides in coastal areas around Narodo and Geomodo after heavy rainfall does not appear to be great. Instead, the occurrence C. polykrikoides red tides in the coastal areas of Narodo and Geomodo seems to be facilitated by NO3-N.

Variations in phytoplankton concentrations result from changes of the ocean color caused by phytoplankton pigments. Thus, ocean spectral reflectance for low chlorophyll waters are blue and high chlorophyll waters tend to have green reflectance. In the Korea region, clear waters and the open sea in the Kuroshio regions of the East China Sea have low chlorophyll. As one moves even closer to the northwestern part of the East China Sea, the situation becomes much more optically complicated, with contributions not only from higher concentrations of phytoplankton, but also from sediments and dissolved materials from terrestrial and sea bottom sources. The color often approaches yellow-brown in the turbidity waters (Case Ⅱ waters). To verify satellite ocean color retrievals, or to develop new algorithms for complex case Ⅱ regions requires ship-based studies. In this study, we compared the chlorophyll retrievals from NASA's SeaWiFS sensor with chlorophyll values determined with standard fluorometric methods during two cruises on Korean NFRDI ships. For the SeaWiFS data, we used the standard NASA SeaWiFS algorithm to estimate the chlorophyll a distribution around the Korean waters using Orbview/ SeaWiFS satellite data acquired by our HPRT station at NFRDI. We studied to find out the relationship between the measured chlorophyll a from the ship and the estimated chlorophyll a from the SeaWiFS satellite data around the northern part of the East China Sea, in February, and May, 2000. The relationship between the measured chlorophyll_a and the SeaWiFS chlorophyll_a shows following the equations (1) in the northern part of the East China Sea. Chlorophyll_a=0.121Ln(X) + 0.504, R2 = 0.73 (1) We also determined total suspended sediment mass (SS) and compared it with SeaWiFS spectral band ratio. A suspended solid algorithm was composed of in-situ data and the ratio (LWN(490 nm)/LWN(555 nm)) of the SeaWiFS wavelength bands. The relationship between the measured suspended solid and the SeaWiFS band ratio shows following the equation (2) in the northern part of the East China Sea. SS=-0.703 Ln(X) + 2.237, R2 = 0.62 (2) In the near future, NFRDI will develop algorithms for quantifying the ocean color properties around the Korean waters, with the data from regular ocean observations using its own research vessels and from three satellites, KOMPSAT/OSMI, Terra/MODIS and Orbview/SeaWiFS.

Identified 7 species of the genus Prorocentrum which have been obtained from the southern coast area for 4 years from 1990 to 1994 can be summarized as followed. P.balticum is rare species, causing a red tide, and P.dentatum, P.micans, P.minimum, P.triestinum are cosmopolitan species often causing a red tide in the study area. P.gracile and P. lima are very rarely showed up, the former is recorded at first in domestic and later is benthic attached species which has diarrheic shellfish poison.