Phytoplankton in the Antarctic marginal ice zone

Phytoplankton cells from discrete water samples from 73 stations near the marginal ice-edge zones during all seasons were counted to gain quantitative information on the composition, abundance, distribution, and condition of the phytoplankton.; The prymnesiophyte, Phaeocystis sp. and the diatom species. Fragilariopsis cylindrus were the predominant phytoplankton in the ice-edge zone. Phaeocystis sp. attained the highest mean integrated values in the studied depths throughout the euphotic zone during summer the ice-free period in Prydz Bay with 2.4 {dollar}times{dollar} 10{dollar}sp{lcub}11{rcub}{dollar} cells m{dollar}sp{lcub}-2{rcub}.{dollar} During winter in the Weddell Sea, the time of maximum ice extent, Phaeocystis sp. showed the lowest numbers with 2.5 {dollar}times{dollar} 10{dollar}sp8{dollar} cells m{dollar}sp{lcub}-2{rcub}.{dollar} The relative abundance of Phaeocystis sp. to total phytoplankton cells ranged from 24% in autumn in the Weddell Sea to 80% in early spring in the Bellingshausen Sea. Fragilariopsis cylindrus accounted for more than 17% of total phytoplankton during summer in Prydz Bay and autumn and winter in the Weddell Sea. During early spring and late spring, F. cylindrus was less abundant than Phaeocystis sp., accounting for 3.8% and 6.7% of total phytoplankton, respectively. As Phaeocystis sp. showed, the highest mean integrated numbers of F. cylindrus were found during the summer cruise in Prydz Bay with 7.9 {dollar}times{dollar} 10{dollar}sp{lcub}10{rcub}{dollar} cells m{dollar}sp{lcub}-2{rcub}{dollar} and the lowest numbers were found farther west during the winter cruise with 1.1 {dollar}times{dollar} 10{dollar}sp8{dollar} cells m{dollar}sp{lcub}-2{rcub}.{dollar}; There were seasonal and regional differences in abundance between Phaeocystis sp. and total diatom species. Phaeocystis sp. cells were higher than total diatoms in early spring, but total diatoms were higher than Phaeocystis sp. in autumn. During late spring, summer, and winter there was no significant difference between Phaeocystis sp. and total diatoms. The overall spatial pattern of Phaeocystis sp. and diatom species near the marginal ice-edge zones during the five seasonal cruises was different. Diatom species were generally observed in highest numbers in the open water seaward of the ice edge, while Phaeocystis sp. dominated under the ice and near the ice-edge stations.; The regression analysis suggests that both Phaeocystis sp. and diatom species are important contributors for phytoplankton increases in the marginal ice zones in different regions such as under ice, near ice, and open water and seasons.