This study was carried out to determine the characteristics of the marine environment, including nutritional content, in order to clearly understand the outbreaks of Gonyaulax polygramma in the southern coastal areas in August, 2009. Samples were collected at 13 sites and water temperature and salinity were measured using a CTD. Field surveys were twice: the first between August 5-7, the second between August 22-24. The cell density of G. polygramma was 6,500-10,000 cells ml-1 during the 1st survey, whereas during the 2nd survey the range of the cells was recorded from 8,000 to 12,500 cells ml-1. Cochlodinium polykrikoides ranged from 0 to 105 cells l-1 during the field survey. In water environments, the majority stations during the 1st survey showed a nearly homogeneous water column below 1℃ in temperature, as well as similar profiles of salinity. However, the stratification between the surface and bottom was observed in the 2nd survey. Regarding nutrients, Dissolved Inorganic Nitrogen (DIN) in the surface ranged from 0.144 to 0.236 mg l-1 during the 1st survey, and 0.082-0.228 mg l-1 during the 2nd survey. DIP (Dissolved Inorganic Phosphorus) did not show any difference in concentration between the 1st and 2nd survey. During August of 2009, the wind speed in the southern waters remained at around ≤2 m s-1 for about 60% of time, and there was very little precipitation during the month. Irradiance of ≥10 hr was shown in the late of August. It is thought that a low level of DIN and salinity play an important role as an essential factor for rapid growth, wide distribution and longer duration of red tide in G. polygramma.

Abstract
 1. Introduction
 2. Materials and methods
 3. Results and Discussion
  3.1. Phytoplankton
  3.2. Water environment
  3.3. Nutrients
  3.4. Ocean climate
  3.5. Overview
 4. Conclusion
 References

• Eun-Seob Cho(Fishery and Ocean Information Division, NFRDI) Corresponding Author