Seasonal Variations in Phyto- and Zooplankton Biomass in Kagoshima Bay

Seasonal variations in size-fractionated chlorophyll a concentration were investigated at two stations located in the inner and central areas of Kagoshima Bay from April 2001 to May 2002. Chlorophyll a concentrations at the inner station were several folds higher than those at the central station. At both stations, chlorophyll a concentrations showed large seasonal fluctuations throughout the year which resulted from micro-sized phytoplankton. Vertical distributions of chlorophyll a concentrations showed slightly different patterns between the two size classes. A surface distribution was observed for pico/nano-sized phytoplankton throughout the year. A high chlorophyll a concentration of micro-sized phytoplankton was limited in the surface water during the summer, and extended downward during autumn to winter. Although they suddenly disappeared from the water column during January to February, the chlorophyll a concentration was kept high thereafter. Compared with the annual mean wet and dry weights, Zooplankton biomass in the inner area was slightly higher than that in the central area. The zooplankton biomass was high during June to July and during February to May in the central area, but an additional peak in November was observed in the inner area