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Phytoplankton processes. Part 2: rates of primary production and factors controlling algal growth during the Southern Ocean Iron RElease Experiment (SOIREE)


Gall, MP and Strzepek, R and Maldonado, M and Boyd, PW, Phytoplankton processes. Part 2: rates of primary production and factors controlling algal growth during the Southern Ocean Iron RElease Experiment (SOIREE), Deep-Sea Research Part 2, 48, (11-12) pp. 2571-2590. ISSN 0967-0645 (2001) [Refereed Article]

Copyright Statement

Copyright 2001 Elsevier Science Ltd.

DOI: doi:10.1016/S0967-0645(01)00009-1


The Southern Ocean Iron RElease Experiment (SOIREE) fertilised 200km2 of polar waters (mixed-layer depth, 65m) south of Australia in February 1999. During the 13-d SOIREE, iron enrichment stimulated primary production, algal growth and biogenic silica production rates. A floristic shift from small to large cells resulted in a greater contribution to community production by diatoms, which contributed >60% to community production towards the end of SOIREE. Column-integrated rates of primary production increased by more than 10-fold, and community production rates (normalised to chlorophyll) had doubled by day 4, but then declined after day 6 to initial rates. Iron enrichment increased the growth rates of the algal community from 0.02 to 0.15d−1 (based on changes in in-situ chlorophyll concentrations), from 0.02 to 0.2d−1 (based on algal carbon), and more than doubled initial rates (based on 14C) to 0.2d−1 during SOIREE. However, these iron-elevated rates were less than the maximum rates (0.69d−1) predicted for waters at 2.5C. Community biogenic silica production rates increased by 6-fold, i.e. to a lesser extent than primary production rates, resulting in a 2-fold reduction in the silicic-acid:carbon uptake ratio. Shipboard perturbation experiments indicated that iron, rather than both iron and light, limited algal growth in these waters. However, a significant increase in light attenuation in situ due to algal self-shading, suggested that light limitation of algal growth might become significant after day 13 at this locale. Limitation of algal growth by both iron (and silicic acid and/or zinc) within iron-fertilised waters after day 8 of SOIREE was not evident from the results of a shipboard experiment. A simple mathematical model of particulate organic carbon (POC) potential export during SOIREE predicted large increases in export, due to both elevated production rates and a floristic shift to large cells. However, no significant increase in POC export was observed during SOIREE.

Item Details

Item Type:Refereed Article
Keywords:phytoplankton, bloom, Southern Ocean, iron, fertilization
Research Division:Earth Sciences
Research Group:Oceanography
Research Field:Biological oceanography
Objective Division:Environmental Management
Objective Group:Management of Antarctic and Southern Ocean environments
Objective Field:Antarctic and Southern Ocean oceanic processes
UTAS Author:Strzepek, R (Dr Robert Strzepek)
UTAS Author:Boyd, PW (Professor Philip Boyd)
ID Code:147707
Year Published:2001
Web of Science® Times Cited:74
Deposited By:Australian Antarctic Program Partnership
Deposited On:2021-11-11
Last Modified:2021-12-21

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