Iron in Antarctic waters

Martin, John H.; Gordon, R. Michael; Fitzwater, Steve E.

doi:10.1038/345156a0

Cited by 1,000 publications

(638 citation statements)

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“…Our experimental results are supported by numerous field observations. The Southern Ocean, together with the Subartic Pacific and Equatorial Pacific, belongs to the high nutrient-low chlorophyll (HNLC) regions and it is now well accepted that iron plays a key role in the structure and functioning of these ecosystems (Martin et al, 1990;De Baar and Boyd, 2000). It is generally assumed that the smaller sized phytoplankton species, due to a large surface to volume ratio, possess an ecological advantage in terms of having a smaller nutrient (iron) requirement or a more efficient uptake of iron compared to larger species Timmermans et al, 2001).…”

Section: Fe Limitation Experimentsmentioning

confidence: 99%

Physiological responses of three species of marine pico-phytoplankton to ammonium, phosphate, iron and light limitation

Timmermans

Wagt

Veldhuis

et al. 2005

Journal of Sea Research

105

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Physiological responses of three species of marine pico-phytoplankton to ammonium, phosphate, iron and light limitation Timmermans, K.R.; Wagt, B. van der; Veldhuis, M.J.W.; Maatman, A.; de Baar, Henricus Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. AbstractExperiments were conducted with three species of marine pico-phytoplankton: Synechococcus sp. (CCMP 839), Pelagomonas calceolata (CCMP 1756) and Prasinomonas capsulatus (CCMP 1617) in order to collect physiological parameters for pico-phytoplankton to be utilised in Ocean Biogeochemical Climate Models. The main parameters to follow the effects of ammonium, phosphate, iron and light limitation were cell growth rates (A), half saturation constants for growth (K m ), N, P and Fe quota (per cell or per mol C), and photochemical quantum efficiency (F v /F m ).The nitrate and phosphate limitation experiments demonstrated that the small phytoplankton species could grow at low N and P concentrations. K m values were in the micro-molar (NH 4 + ) and sub-micro-molar (PO 4 3À ) range. N and P quota were in the femto-molar range per cell and varied from nutrient-deplete to nutrient-replete conditions. F v /F m values were only adversely affected at the lowest N and P concentrations in these experiments. In the Fe limitation experiments, it was shown that all three species were adversely affected only at extremely low Fe concentrations. Iron chelating agents had to be added to force the species in Fe limitation till ultimately growth stopped. K m values with respect to dissolved Fe were in the femto-molar range. Fe quota were in the low zepto-molar (10 À21 M) range per cell, and varied considerably from Fe limiting to Fe replete growth conditions. F v /F m values diminished only at the lowest iron concentrations. In the light limitation experiments, growth rates and photochemical quantum efficiencies were adversely affected only at irradiance levels below 10 Amol photons m À2 s À1 . These results indicate that the pico-phytoplankton species will hardly ever be completely stopped in their growth by NH 4 + , PO 4 3À, Fe or light (separately) under natural conditions. D

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Section: Fe Limitation Experimentsmentioning

confidence: 99%

Physiological responses of three species of marine pico-phytoplankton to ammonium, phosphate, iron and light limitation

Timmermans

Wagt

Veldhuis

et al. 2005

Journal of Sea Research

105

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“…This is consistent with, respectively, the lower dissolved Fe ; 0.1-0.88 nM in offshore Drake Passage waters and higher dissolved iron at ; 4.7-7.4 nM in in-Ž . shore Gerlache Strait Martin et al, 1990a . At their offshore site C, the Fe enrichment selectively stimulated the larger microplankton, as opposed to the control incubation.…”

Section: Limitation By Fe In the Remote Southern Oceanmentioning

confidence: 99%

“…and Ohman, 1991;Nolting et al, 1991 similar to inshore Gerlache Strait at the Pacific side of the Ž . Peninsula Martin et al, 1990a . In this frontal re-Ž .…”

Section: Limitation By Fe In the Remote Southern Oceanmentioning

confidence: 99%

Low dissolved Fe and the absence of diatom blooms in remote Pacific waters of the Southern Ocean

et al. 1999

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The remote waters of the Pacific region of the Southern Ocean are the furthest away from any upstream and upwind Ž continental Fe sources. This prime area for expecting Fe limitation of the plankton ecosystem was studied March-April . 1995 along a north-south transect at ; 898W. At the end of the austral summer the upper wind-mixed layers were in the order of ; 100 m deep, thus mixing the algae down into the dimly lit part of the euphotic zone where photosynthesis is severely restricted. The dissolved Fe was found at low concentrations ranging from 0.05 nM near the surface to 0.5 nM in Ž . deeper waters. Along the transect 528S-698S , the dissolved iron was enhanced in the Polar Front, as well as near the Ž . Antarctic continental margin 0.6-1.0 nM . In between, the southern ACC branch was depleted with iron; here the concentrations in surface waters were quite uniform at about 0.21 nM. This is only somewhat lower than the 0.49 nM Ž . Ž . October 1992 and 0.31 nM November 1992 averages in early spring in the southern ACC part of Atlantic 68W sections wde Baar, H.J.W., de Jong, J.T.M., Bakker, D.C.E.. Loscher, B.M., Veth, C., Bathmann, U., Smetacek, V., 1995. Importancë of iron for phytoplankton spring blooms and CO drawdown in the Southern Ocean. Nature 373, 412-415; Loscher, B.M., 2 de Jong, J.T.M., de Baar, H.J.W., Veth, C., Dehairs, F., 1997. The distribution of iron in the Antarctic Circumpolar Current.x Deep-Sea Research II 44, 143-188. . First, the lower ; 0.21 nM in March-April 1995 may partly be due to continuation of the seasonal trend where the phytoplankton growth, albeit modest, was removing Fe from the surface waters. Secondly, the 898W Pacific stations are further downstream continental or seafloor sources than the Atlantic 68W section. In the latter case, the ACC water had passed through the Drake Passage and also over the Sandwich Plateau. Indeed for Drake Passage, intermediate Fe concentrations have been reported by others. The generally somewhat lower surface water Fe at the ACC and PF at 898W is consistent with the distance from sources and the late summer. It also would explain the very low Ž . abundance of phytoplankton Chl a in the region and the conspicuous absence of plankton blooms. In the subAntarctic waters north of the Polar Front there are no diatoms, let alone diatom blooms, due to low availability of silicate. Thus, it Baar et al.r Marine Chemistry 66 1999 1-34 2 appears the biological productivity is suppressed due to iron deficiency, in combination with the severe seasonal effects of wind mixing on the light climate, as well as regional silicate limitation for diatoms. q

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“…With the ensuing oxygenation of the oceans and the atmosphere, dissolved Fe (DFe) was removed from the oceans and became a "hard to get essential" (Martin and Fitzwater, 1988), inducing the evolution of specialized Fe harvesting strategies in marine organisms (Price and Morel, 1998). In the modern marine environment, the Southern Ocean is an example where Fe, next to light and grazing, is strongly limiting primary production de Baar et al, 1990;Martin et al, 1990), thereby affecting biogeochemical cycles: notably that of carbon (de Baar and Boyd, 2000).…”

Section: Introductionmentioning

confidence: 99%

Enhancement of the reactive iron pool by marine diatoms

et al. 2008

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Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. Abstract Short term (2 days) laboratory experiments were performed to study the change in irradiance induced production of Fe(II) in seawater in the presence of two open oceanic Southern Ocean diatom species, Thalassiosira sp. and Chaetoceros brevis. Three irradiance conditions were applied: 1) UVB + UVA + VIS, 2) UVA + VIS, and 3) VIS, and Fe concentrations of 0 and 5 nM Fe were added to natural Southern Ocean seawater (containing 0.32 nM dissolved Fe and 1.69 equivalents of nM L − 1 Fe dissolved organic ligands, log K′ = 22.03). The photoproduced concentration of Fe(II) showed no relationship with the concentration of total dissolved Fe or the concentration of strongly chelated iron. During incubations with the diatoms an increase in the Fe(II) concentration during the second day suggested a modification of the Fe speciation. In the presence of Thalassiosira sp. photoreduction of Fe(III) was observed, whereas in the presence of C. brevis irradiance independent Fe(III) reduction played an important role in the Fe(II) production. Furthermore, a decrease in the strongly chelated Fe concentration, in concert with a decrease in the conditional stability constant, suggested a modification of the strongly chelated Fe fraction in the experiments with C. brevis. The chelated Fe fraction did not change in cultures with Thalassiosira sp. Overall, the presence of diatoms appeared to enhance the reactive Fe pool improving the biological availability of Fe.

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Iron in Antarctic waters

Cited by 1,000 publications

References 12 publications

Physiological responses of three species of marine pico-phytoplankton to ammonium, phosphate, iron and light limitation

Physiological responses of three species of marine pico-phytoplankton to ammonium, phosphate, iron and light limitation

Low dissolved Fe and the absence of diatom blooms in remote Pacific waters of the Southern Ocean

Enhancement of the reactive iron pool by marine diatoms

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