Limitation of Algal Growth by Iron Deficiency in the Australian Subantarctic Region

• Published in: Geophysical Research Letters
• Main Authors: Sedwick, Peter N., DiTullio, Giacomo R., Hutchins, David A., Boyd, Philip W., Griffiths, F. Brian, Crossley, A. Clive, Trull, Thomas W., Queguiner, Bernard
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: ODU Digital Commons 1999
• Subjects: Phytoplankton growth; Limitation; Iron deficiency; Tasmania; Subantarctic; Subtropical Convergence Zone; Silicic acid; Mineral aerosol; Biogeochemistry; Biology; Oceanography; Southern Ocean
• Online Access: https://digitalcommons.odu.edu/oeas_fac_pubs/94; https://doi.org/10.1029/1998GL002284; https://digitalcommons.odu.edu/context/oeas_fac_pubs/article/1101/viewcontent/Sedwick_1999_Limitation_of_algal_growth_by_iro.pdf

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 (∼42°S, 142°E), silicic acid concentrations were low (< 1.5μM) 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 (∼46.8°S, 142°E), low concentrations of dissolved iron (0.05-0.11nM) and silicic acid (< 1μM) 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.