ECOLOGICAL-STUDIES OF PHYTOPLANKTON IN TAI TAM BAY, HONG-KONG

Of the 141 phytoplankton species found during the sampling period, the Bacillariophyceae was the most important group and included 70% of the total number of species; the Dinophyceae comprised a smaller percentage (28%) of the taxa; and only 3 chrysophyte species occurred throughout the study period. In terms of numbers of individuals, the Bacillariophyceae remained as the dominant group and contained 97% of the total numbers whereas the Dinophyceae represented only 3% of the total phytoplankton population. The most dominant diatom species was Thalassiosira allenii Takano which constituted 35% of the Bacillariophyceae group whereas the most abundant dinoflagellate was Prorocentrum gracile Schutt which represented 40% of the total Dinophyceae numbers. Chlorophyll a levels varied from 0.40 to 32.31 mg m-3 at the surface and from 0.33 to 33.91 Mg m-3 at the bottom. Seasonal trends of phytoplankton abundance and chlorophyll a concentration were observed in the survey area with generally high peaks in summer and low values during winter months. Such variations can be attributed to the interactions between, and changes of, various environmental parameters, such as temperature, salinity and nutrient availability (particularly silicate).