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 1 st survey, whereas during the 2 nd survey the range of the cells was recorded from 8,000to 12,500 cells ml 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.