Analysis of the Ecological Environment Elements in the Red Tide Generating and Vanishing Process in the Eastern Jiaozhou Bay in July, 1999

Based on the data observed in the eastern Jiaozhou Bay red tide area during July 23 to 24, 1999 and the data observed in June, July and August, 1999, the variations in ecological elements, including phytoplankton community, chlorphyll-a and nutrients in the seawater before and after the red tide occurrence were analysed. It is shown from the analysis results that this red tide is an Eucampia Zoodiacus red tide with a high total cell concentration of 1.6×10 10 cells/mL. When the red tide occurred, the chlorophyll-a ranged 28.8 mg/m 3 to 36.0 mg/m 3, the changes in temperature and salinity were not great, the DO and pH values increased; the concentrations of nuutrients, especially phosphate, decreased to result in a drastic increase in N/P value with a peak N/P value of 247, and P is considered as the limiting factor for this red tide; the NO 2-N/NO 3-N fluctuated greatly and reached an abnormally high value. When the red tide had disappeared,the above ecological elements returned to normal again.