Deep Sea Research II

Marine Laboratories

Description

Niveau: Supérieur, Doctorat, Bac+8
Deep-Sea Research II 49 (2002) 3255–3273 Quantification of algal iron requirements in the Subantarctic Southern Ocean (Indian sector) S. Blaina,*, P.N. Sedwickb,1, F.B. Griffithsb,c, B. Qu!eguinerd, E. Bucciarellia, M. Fialae, P. Pondavena, P. Tr!eguera aUMR CNRS 6539, Institut Universitaire Europ!een de la Mer, Place Nicolas Copernic, 29280 Plouzan!e, France bAntarctic CRC, GPO Box 252-80, Hobart, Tasmania 7001, Australia cCSIRO Marine Laboratories, Castray Esplanade, Hobart , Tasmania 7001, Australia dCentre d'Oc!eanologie de Marseille, Parc Scientifique de Luminy, Marseille 13288, France eObservatoire Oc!eanologique, BP 11, Banyuls sur Mer 66651, France Received 9 October 2000; accepted 1 January 2002 Abstract Shipboard iron-addition incubation experiments were carried out in the Indian sector of the Subantarctic Southern Ocean during the Antares-IV campaign in late January–February 1999. The aim of these experiments was to estimate the dissolved iron requirements of the native phytoplankton community in this oceanic region, in order to improve the parameterisation of iron as a limiting nutrient in a coupled 1D physical–biogeochemical ocean model. The experiments were conducted with plankton collected from the upper water column (B20m depth) at three sites in the Crozet Basin between 43–461S and 61–651E: (1) the Polar Front Zone (PFZ, dissolved Fe=0.33 nM), (2) the confluence of the Subantarctic and

• deep-sea research


• iron has


• iron


• co-limits algal


• phytoplankton collected


• ocean


• limiting nutrient


• growth rate

Sujets

• Laboratory
• Southern
• Limiting factor
• Growth rate

Informations

• Publié par: profil-zyak-2012
• Nombre de lectures: 15
• Langue: English

Extrait

Deep-Sea Research II 49 (2002) 3255–3273

Quantification of algal iron requirements in the Subantarctic Southern Ocean (Indian sector) S. Blain a, *, P.N. Sedwick b,1 , F.B. Griffiths b,c , B. Que ! guiner d , E. Bucciarelli a , M. Fiala e , P. Pondaven a , P. Tr ! eguer a a UMR CNRS 6539, Institut Universitaire Europ ! een de la Mer, Place Nicolas Copernic, 29280 Plouzan e ! , France b Antarctic CRC, GPO Box 252-80, Hobart, Tasmania 7001, Australia c CSIRO Marine Laboratories, Castray Esplanade, Hobart , Tasmania 7001, Australia d Centre d’Oce ! anologie de Marseille, Parc Scientifique de Luminy, Marseille 13288, France e Observatoire Oce ! anologique, BP 11, Banyuls sur Mer 66651, France Received 9 October 2000; accepted 1 January 2002

Abstract Shipboard iron-addition incubation experiments were carried out in the Indian sector of the Subantarctic Southern Ocean duringthe Antares -IV campaign in late January–February 1999. The aim of these experiments was to estimate the dissolved iron requirements of the native phytoplankton community in this oceanic region, in order to improve the parameterisation of iron as a limitingnutrient in a coupled 1D physical–biogeochemical ocean model. The experiments were conducted with plankton collected from the upper water column ( B 20 m depth) at three sites in the Crozet Basin between 43–46 1 S and 61–65 1 E: (1) the Polar Front Zone (PFZ, dissolved Fe=0.33 nM), (2) the confluence of the Subantarctic and Subtropical Fronts (SAF/STF, dissolved Fe=0.29 nM), and (3) the southern Subtropical Zone (STZ, dissolved Fe=0.09 nM). Experimental results from each site indicate that algal community growth rates varied as a function of added iron concentration. Monod saturation functions fitted to the experimental data yield estimates for the community half-saturation constant for growth with respect to iron ( K m ) of 0.41–0.45 nM Fe (PFZ), 0.055–0.086 nM Fe (SAF/STF) and 0.092–0.093 nM Fe (STZ, with macronutrients added), each of which has an estimated uncertainty of 7 20%. The K m estimate for the SAF/STF site reflects the mixed algal assemblage (diatoms+nanoplankton+dino- flagellates) that grew in the experimental incubations, whereas the K m estimates for the PFZ and STZ sites probably reflect the Fe requirements of the small pennate diatoms such as Pseudo-nitzschia spp., which dominated the algal biomass produced in these experiments. The fact that there are significant differences between the K m estimates for the PFZ and STZ sites suggests that similar diatom assemblages may have quite different iron requirements, perhaps due to differences in environmental conditions (e.g., light, macronutrient levels). We also examine the sensitivity of a one- dimensional coupled physical–biogeochemical model to the choice of K m for iron, usingtime-series observations from the KERFIX station close to the Polar Front. The model was best able to simulate the KERFIX observations usinga diatom K m value of B 0.1 nM Fe, which is considerably less than our experimental estimate of B 0.4 nM Fe for the PFZ. This discrepancy probably reflects differences in the iron requirements of diatom populations immediately north and south of the Polar Front in the Kerguelen region, due to differences in diatom species composition, availability of light

*Correspondingauthor. Fax: [phone]. E-mail address: [e-mail] (S. Blain). 1 Now at Bermuda Biological Station for Research, St. George’s, GE01, Bermuda. 0967-0645/02/$ - see front matter r 2002 Elsevier Science Ltd. All rights reserved. PII: S 0 9 6 7 - 0 6 4 5 ( 0 2 ) 0 0 0 8 2 - 6