The Influence of Phytoplankton Assemblage Composition on Biogeochemical Characteristics and Cycles in the Southern Ross Sea, Antarctica

• Main Authors: Smith, Walker O., Jr., Asper, Vernon L.
• Format: Text
• Language: unknown
• Published: The Aquila Digital Community 2001
• Subjects: phytoplankton; Antarctica; Ross Sea; polynya; nitrogen; carbon; pigments; diatoms; phaeocystis; Life Sciences; Marine Biology; Antarc*
• Online Access: https://aquila.usm.edu/fac_pubs/3987; http://logon.lynx.lib.usm.edu/login?url=http://ac.els-cdn.com/S0967063700000455/1-s2.0-S0967063700000455-main.pdf?_tid=f65605c4-9203-11e3-bc9d-00000aab0f02&acdnat=1392003326_08c9523ab6edeae386a74931561096ee

To test the hypothesis that phytoplankton assemblages dominated by different taxa have distinct biogeochemical characteristics and cycles, the temporal and spatial variations in phytoplankton biomass and composition were studied within the Ross Sea polynya, where diatoms and the haptophyte Phaeocystis antarctica are thought to have spatially distinct distributions. Two cruises were completed, with the first conducted in spring, 1994, and the second in late spring-early summer, 1995/1996. Ice concentrations decreased substantially from spring to summer. Mixed layer depths for the region decreased markedly in early spring and were relatively invariant thereafter; the strength of the stratification varied both in time and space. Mixed layers were greater in spring in assemblages dominated by diatoms (as determined by HPLC pigment concentrations) than those dominated by Phaeocystis antarctica, whereas in summer no difference was observed. Nutrient concentrations were initially high and near winter values, but decreased throughout November and December. Nitrate:phosphate removal ratios varied widely, with ratios exceeding 20 in spring but decreasing below 14 in summer. N : P removal ratios at stations dominated by diatoms were less than the Redfield ratio in both spring and summer, and at those stations dominated by P. antarctica the N : P removal ratio was ca. 19 in both seasons. Chlorophyll and particulate matter concentrations increased as nutrients decreased. Spatial and temporal variations of phytoplankton pigments occurred, with 19'-hexa-noylfucoxanthin, a pigment of P. antarctica, exceeding 3.9 mug 1(-1) during spring in the south-central polynya, and fucoxanthin, an accessory pigment of diatoms, found in concentrations > 1 mug 1-1 in the western Ross Sea. The distributions were not mutually exclusive, and concentrations of both pigments were greatest in spring. The early growth of P. antarctica appears to be related to earlier stratification and disappearance of ice from the south-central Ross Sea. Ratios ...