Limitation of algal growth by iron deficiency in the Australian Subantarctic region

• Published in: Geophysical Research Letters
• Main Authors: Sedwick, PN, DiTullio, GR, Hutchins, DA, Boyd, PW, Griffiths, FB, Crossley, AC, Trull, T, Queguiner, B
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Geophysical Union 1999
• Subjects: Biological Sciences; Ecology; Marine and Estuarine Ecology (incl. Marine Ichthyology); Southern Ocean
• Online Access: https://doi.org/10.1029/1998GL002284; http://ecite.utas.edu.au/17093

In March 1998 we measured iron in the upper water column and conducted iron- and nutrient-enrichment bottle-incubation experiments in the open-ocean Subantarctic region southwest of Tasmania, Australia. In the Subtropical Convergence Zone (42S, 142E), silicic acid concentrations were low (< 1.5 M) in the upper water column, whereas pronounced vertical gradients in dissolved iron concentration (0.12-0.84 nM) were observed, presumably reflecting the interleaving of Subtropical and Subantarctic waters, and mineral aerosol input. Results of a bottle-incubation experiment performed at this location indicate that phytoplankton growth rates were limited by iron deficiency within the iron-poor layer of the euphotic zone. In the Subantarctic water mass (46.8S, 142E), low concentrations of dissolved iron (0.05-0.11 nM) and silicic acid (< 1 M) were measured throughout the upper water column, and our experimental results indicate that algal growth was limited by iron deficiency. These observations suggest that availability of dissolved iron is a primary factor limiting phytoplankton growth over much of the Subantarctic Southern Ocean in the late summer and autumn. Copyright 1999 by the American Geophysical Union.