Abstract:

The chlorophyll a concentrations and oceanographic conditions under sea ice near Zhongshan Station(69°22′24″S,76°22′40″E) ,east Antarctica was monitored from April 12 to December 30 in 1992.The biomass measured as chlorophyll a were lower than 0.5mg/m 3 during wintertime,and even lower than 0.1mg/m 3 from July to September.The concentrations began to rise during spring and reached its maximum value of 21.40mg/m 3 in mid December in the water surface following the ice algal bloom,and then decreased quickly again.The ratios of nanoplankton(<20μm) biomass to the total phytoplankton biomass were commonly higher than 50% in winter but decreased following the increasing biomass in spring,the ratio in the water shrface was only 3.2% during the phytoplanton bloom. The nutrients were sufficent to support the growth of phytoplankton,but the concentrations decreased apparently during spring,and reached its lowest values of PO 4 P:0.32,SiO 3 Si:26.47,and NO 3 N:1.41(μmol/L) during phytoplankton bloom.The irradiance might be the prodominant factor to limit the phytoplankton biomass in water column under sea ice. Comparison of biomass in water column and sea ice shows that the phytoplankton biomass was less important when the sea surface was covered with sea ice. Because the primary production were mostly distributed in the bottom of ice and the surface water,the role of ice water interface in the ecosystem was very important.