Seasonal dynamics of phytoplankton in the Antarctic Polar Front region at 170°W

• Main Authors: Landry, Michael R., Selph, Karen E., Brown, Susan L., Abbott, Mark R., Measures, Christopher I., Vink, Suzanna, Allen, Colleen B., Calbet, Albert, Christensen, Stephanie, Nolla, Hector
• Other Authors: National Science Foundation (US)
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Pergamon Press 2002
• Subjects: Antarctic; Southern Ocean; The Antarctic; Austral; Antarc*
• Online Access: http://hdl.handle.net/10261/180998; https://doi.org/10.1016/S0967-0645(02)00015-2; https://doi.org/10.13039/100000001

Special issue The Southern Ocean I: Climatic Changes in the Cycle of Carbon in the Southern Ocean (3RD SO-JGOFS).-- 23 pages, 13 figures [EN] Phytoplankton dynamics in the region of 55-70°S, 170°W were investigated using Sea-viewing Wide Field-of-View Sensor satellite imagery, shipboard sampling and experimental rate assessments during austral spring and summer, 1997-1998. We used image-analysis microscopy to characterize community biomass and composition, and dilution experiments to estimate growth and microzooplankton grazing rates. Iron concentrations were determined by flow-injection analysis. The phytoplankton increase began slowly with the onset of stratification at the Polar Front (PF) (60-61°S) in early November. Seasonally enhanced levels of chlorophyll were found as far north as 58°S, but mixed-layer phytoplankton standing stock was highest, approaching 200 mg C m-3, in the region between the receding ice edge and a strong silicate gradient, which migrated from ∼62°S to 65°S during the study period. The most southern stations sampled on four cruises were characterized by small pennate diatoms and Phaeocystis. From the PF to the Southern Antarctic circumpolar current front (∼65°S), this ice margin assemblage was seasonally replaced by a community dominated by large diatoms. The large diatom community developed only in waters where measured iron concentrations were initially high (≥0.2nM), and crashed when dissolved silicate was depleted to low levels. Phytoplankton growth rates were highest (0.5-0.6 d-1) between the PF and silicate front (60°S and 63°S) in December. In January, growth rates were lowest (0.1 d-1) near the PF, and the highest rates (0.3-0.4 d-1) were found in experiments between 64.8°S and 67.8°S. Phytoplankton production estimates were highest south of the PF through December and January, averaging 2.2-2.4 mmol C m-3 d-1 and reaching levels of 5 mmol C m-3 d-1 (64.8°S and 67.8°S in January). Microzooplankton grazers consumed 54-95% of production for experiments conducted on four AESOPS ...