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Subantarctic zone oceanography - SAZ Project 1997-1998 - Iron Related DataEntry ID: ASAC_2256_Iron
Abstract: Oceanographic processes in the subantarctic region contribute crucially to the physical and biogeochemical aspects of the global climate system. To explore and quantify these contributions, the Antarctic Cooperative Research Centre (CRC) organised the SAZ Project, a multidisciplinary, multiship investigation carried out south of Australia in the austral summer of 1997-1998.
Taken from the ... abstracts of the referenced papers:
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 degrees S, 142 degrees E), silicic acid concentrations were low (less than 1.5 micro-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 (-46.8 degrees S, 142 degrees E), low concentrations of dissolved iron (0.05-0.11 nM) and silicic acid (less than 1 micro-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.
The importance of resource limitation in controlling bacterial growth in the high-nutrient, low-chlorophyll (HNLC) region of the Southern Ocean was experimentally determined during February and March 1998. Organic- and inorganic-nutrient enrichment experiments were performed between 42 degrees S and 55 degrees S along 141 degrees E.
Bacterial abundance, mean cell volume, and [3H]thymidine and [3H]leucine incorporation were measured during 4- to 5-day incubations. Bacterial biomass, production, and rates of growth all responded to organic enrichments in three of the four experiments. These results indicate that bacterial growth was constrained primarily by the availability of dissolved organic matter. Bacterial growth in the subtropical front, subantarctic zone, and subantarctic front responded most favourably to additions of dissolved free amino acids or glucose plus ammonium. Bacterial growth in these regions may be limited by input of both organic matter and reduced nitrogen. Unlike similar experimental results in other HNLC regions (subarctic and equatorial Pacific), growth stimulation of bacteria in the Southern Ocean resulted in significant biomass accumulation, apparently by stimulating bacterial growth in excess of removal processes. Bacterial growth was relatively unchanged by additions of iron alone; however, additions of glucose plus iron resulted in substantial increases in rates of bacterial growth and biomass accumulation. These results imply that bacterial growth efficiency and nitrogen utilisation may be partly constrained by iron availability in the HNLC Southern Ocean.
The download file also contains three excel spreadsheets of iron data from the project. The file Sedwick_A9706_Fe_data contains water-column dissolved Fe and total-dissolvable Fe data from cruise A9706, which is presented in Sedwick et al. (1999) and Sedwick et al. (2008).
The files Sedwick_A9706_ProcessStn1_Exp_data and Sedwick_A9706_ProcessStn2_Exp_data present data from shipboard experiments conducted during cruise A9706 at Process Stations 1 and 2, respectively, as reported in Sedwick et al. (1999).
This data set description is a member of a collection. The collection is described in
Start Date: 1997-09-01Stop Date: 1998-03-31
ISO Topic Category
Quality See the referenced papers for more information.
Access Constraints Copies of the referenced publications are available for download from the provided URL to AAD staff only.
Use Constraints This data set conforms to the PICCCBY Attribution License
Please follow instructions listed in the citation reference provided at http://data.aad.gov.au/aadc/metadata/citation.cfm?entry_id=ASAC_225... when using these data.
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Distribution Media: HTTP
Distribution Size: 682 kb
Distribution Format: pdf
Distribution Media: HTTP
Distribution Size: 126 kb
Distribution Format: Excel, csv
Role: TECHNICAL CONTACT
Phone: (757) 683-4936
Fax: (757) 683-5303
Email: psedwick at odu.edu
4600 Elkhorn Ave
Province or State: VA
Postal Code: 23529
Phone: +61 3 6226 2988
Fax: +61 3 6226 2973
Email: tom.trull at utas.edu.au
GPO BOX 252-80 Antarctic CRC University of Tasmania
Province or State: Tasmania
Postal Code: 7001
Role: DIF AUTHOR
Phone: +61 3 6232 3244
Fax: +61 3 6232 3351
Email: dave.connell at aad.gov.au
Australian Antarctic Division 203 Channel Highway
Province or State: Tasmania
Postal Code: 7050
Sedwick P.N., DiTullio G.R., Hutchins D.A., Boyd P.W., Griffiths F.B., Crossley A.C., Trull T.W., Queguiner B. (1999), Limitation of algal growth by iron deficiency in the Australian Subantarctic region, Geophysical Research Letters, 26, 2865
Church M.J., Hutchins D.A., Ducklow H.W. (2000), Limitation of bacterial growth by dissolved organic matter and iron in the Southern Ocean, Applied and Environmental Microbiology, 66, 2, 455-466
Sedwick, P. N., A. R. Bowie, and T. W. Trull (2008), Dissolved iron in the Australian sector of the Southern Ocean (CLIVAR-SR3 section): meridional and seasonal trends, Deep-Sea Research I, doi:doi:10.1016/j.dsr.2008.03.011
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Creation and Review Dates
DIF Creation Date: 2012-01-17
Last DIF Revision Date: 2014-01-10