Phytoplankton pigment distributions and associated fluxes in the Bellingshausen Sea during the austral spring 1992

Pigment distribution patterns were investigated in the marginal ice zone of the Bellingshausen Sea and across the Drake Passage during the austral spr ing of November/December 1992. Elevated chlorophyll a (chl a) and fucoxanth in levels were observed at the Sub-Antarctic and Polar Fronts in the Drake Passage and at the Southern Polar Front in the Bellingshausen Sea. Investig ations at 5 stations along 85 degrees W in the Bellingshausen Sea between 7 0.5 degrees S and 67.5 degrees S revealed high concentrations of chi a (up to 24000 ng l(-1) ice melt) and fucoxanthin in hard pack ice samples and ve ry low levels of pigments in the underlying water column (< 100 ng l(-1)). At two ice melt stations, pigment concentrations in the ice were considerab ly lower and chi a in the upper mixed layer ranged from 120-250 ng l(-1), w ith increased levels of hexanoyloxyfucoxanthin and chlorophyll b (chI b). I n open water, the high chi a band at the Southern Polar Front (up to 2400 n g l(-1)) was associated with elevated fucoxanthin concentrations. Integrate d concentrations, pigment ratios and a conversion of accessory pigments to chi a equivalents indicated that diatoms (fucoxanthin) were the most import ant group in the ice (> 70%), although prymnesiophytes (hexanoyloxyfucoxant hin) and green algae (chl b) were present in smaller proportions. Diatoms d ominated at the open water stations(> 60%) and were prominent in the water column under the pack ice (52-61%). However, at the ice melt stations, prym nesiophytes (40-45%), green algae (11-13%) and, to a lesser extent, cryptop hytes (4-6%; alloxanthin) collectively contributed more to the chi a biomas s than the diatoms (37-42%). Budgeting the proportions of chloropigments in dicated an increase in chlorophyllide a and phaeopigments from the ice to t he northern open water stations, with chlorophyllide a being prominent in t he upper water column and in the ice. Export fluxes of phytoplankton-carbon and phytodetritus in the upper 100 m were estimated from chloropigment inv entories and residence times of Po-210 radionuclide reported by Shimmield e t al. (1995) [Shimmield, G.B., Ritchie, G., Fileman, T.W., 1995. The impact of marginal zone processes on the distribution of Pb-210, Po-210 and Th-23 4 and implications for new production in the Bellingshausen Sea Antarctica. Deep-Sea Res. II, 42 (1995) 1313-1335], revealing very low fluxes at the i ce stations and up to 29 mg phyto-C m(-2) day(-1) at the open water high ch lorophyll locality.