Algae. 2000; 15(2): 89-98.

Water Quality and Phytoplankton Communities in Yeoja Bay of Korea

Jin Hwan Lee, Su Mi Youn

In order to find out the water quality, dynamics and structure of phytoplankton communities and red-tides, the present study was carried out on a monthly basis from July to September 1988 at 21 stations in the Yeoja Bay. Water temperature varied from 22.5℃ to 28.1℃ and the salinity ranged from 7.1‰ to 29.0‰. Concentrations of nutrients such as nitrogen and phosphate were high in the inner Bay. Phytoplankton were composed of 2 divisions, 3 classes, 7 order, 5 suborder, 18 families, 3 subfamilies, 34 genera, 75 species, 5 varieties, 5 forms and 2 unknown species. These taxa were composed of 70 diatoms, 15 dinoflagellates, and 2 silicoflagellates. Phytoplankton standing crops varied from minimum of 4.8×10 supper(3) cells·l supper(-1) (Aug., St. 18) to maximum of 2.8×10 supper(6) cells·l supper(-1) (July, St. 17), showing red tide in July and average standing crops of 1.6×10 supper(6) cells·l supper(-1). The leading causative organisms of red tide were Thalassiosira weissflogii in the inner Bay, Chaetoceros decipiens and C. curvisetus were in the mouth and in the middle part of the Bay. It can be assumed that red tide due to T. weissflogii in July was caused by high concentration of nutrients and low salinity brought on by surface runoff.