Enhancement of the reactive iron pool by marine diatoms

Rijkenberg, Micha J.A.; Gerringa, Loes J. A.; Timmermans, Klaas R.; Fischer, Astrid; Kroon, Koos J.; Buma, Anita G. J.; Wolterbeek, Bert; Baar, H. J. W. de

doi:10.1016/j.marchem.2007.12.001

Cited by 45 publications

(36 citation statements)

References 84 publications

(129 reference statements)

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“…In the UVSW without exudates the Fe(II) concentration continued decreasing exponentially reaching the detection limit after 20 min, whereas in UVSW with added diatom exudates the Fe(II) concentration remained at about 30 nmol L −1 decreasing only very slightly with time. The photochemical effect of the exudates was therefore strong enough to result in a net stabilising effect on Fe(II) after 7 min, confirming results reported by Rijkenberg et al (Rijkenberg et al, 2008) who observed irradiance dependent photoreduction of Fe(III) in the presence of the diatom Thalassiosira "sp". Total iron concentrations from the beginning and end of this experiment did not change, indicating no major loss of Fe from the system.…”

Section: Experiments 3: Effect Of Diatom Exudates and Uva/b Radiation supporting

confidence: 87%

The role of polysaccharides and diatom exudates in the redox cycling of Fe and the photoproduction of hydrogen peroxide in coastal seawaters

et al. 2010

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Abstract. The effect of artificial acidic polysaccharides (PS) and exudates of Phaeodactylum tricornutum on the half-life of Fe(II) in seawater was investigated in laboratory experiments. Strong photochemical hydrogen peroxide (H 2 O 2 ) production of 5.2 to 10.9 nM (mg C) −1 h −1 was found in the presence of PS and diatom exudates. Furthermore when illuminated with UV light the presence of algal exudates had a net stabilising effect on ferrous iron in seawater (initial value 100 nmol L −1 ) above that expected from oxidation kinetics. In the dark the PS gum xanthan showed no stabilising effect on Fe(II). The photochemical formation of superoxide (O − 2 ) in the presence of diatom exudates and its reducing effect on Fe(III) appears to result in greater than expected concentrations of Fe(II). A model of the photochemical redox cycle of iron incorporating these processes supported the observed data well. Diatom exudates seem to have the potential to play an important role for the photochemistry of iron in coastal waters.

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Section: Experiments 3: Effect Of Diatom Exudates and Uva/b Radiation supporting

confidence: 87%

The role of polysaccharides and diatom exudates in the redox cycling of Fe and the photoproduction of hydrogen peroxide in coastal seawaters

et al. 2010

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“…Also Boye et al (2003) found relatively low K 0 values in surface waters at 411N (10 20.6 -10 21 ). This indicated that the ligands presumably coming from the phytoplankton are relatively weak, supporting the conclusion of Rijkenberg et al (2008b) that phytoplankton can modify ligand characteristics. Others stated that ligands related to phytoplankton activity belong to the relatively strong ligand group (Rue and Bruland, 1997;Cullen et al, 2006;Hunter and Boyd, 2007).…”

Section: Fe-binding Ligandssupporting

confidence: 70%

Speciation of Fe in the Eastern North Atlantic Ocean

Thuroczy

Gerringa

Klunder

et al. 2010

Deep Sea Research Part I: Oceanographic Research Papers

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a b s t r a c tIn the Eastern North Atlantic Ocean iron (Fe) speciation was investigated in three size fractions: the dissolvable from unfiltered samples, the dissolved fraction (o 0.2 mm) and the fraction smaller than 1000 kDa ( o 1000 kDa). Fe concentrations were measured by flow injection analysis and the organic Fe complexation by voltammetry. In the research area the water column consisted of North Atlantic Central Water (NACW), below which Mediterranean Overflow Water (MOW) was found with the core between 800 and 1000 m depth. Below 2000 m depth the North Atlantic Deep Water (NADW) proper was recognised. Dissolved Fe and Fe in the o 1000 kDa fraction showed a nutrient like profile, depleted at the surface, increasing until 500-1000 m depth below which the concentration remained constant. Fe in unfiltered samples clearly showed the MOW with high concentrations (4 nM) compared to the overlying NACW and the underlying NADW, with 0.9 nM and 2 nM Fe, respectively. By using excess ligand (Excess L) concentrations as parameter we show a potential to bind Fe. The surface mixed layer had the highest excess ligand concentrations in all size fractions due to phytoplankton uptake and possible ligand production. The ratio of Excess L over Fe proved to be a complementary tool in revealing the relative saturation state of the ligands with Fe. In the whole water column, the organic ligands in the larger colloidal fraction (between 0.2 mm and 1000 kDa) were saturated with Fe, whereas those in the smallest fraction ( o1000 kDa) were not saturated with Fe, confirming that this fraction was the most reactive one and regulates dissolution and colloid aggregation and scavenging processes. This regulation was remarkably stable with depth since the alpha factor (product of Excess L and K 0 ), expressing the reactivity of the ligands, did not vary and was 10 13 . Whereas, in the NACW and the MOW, the ligands in the particulate (4 0.2 mm) fraction were unsaturated with Fe with respect to the dissolved fraction, thus these waters had a scavenging potential.Crown

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“…The beneficial effects of the non-lytic Alexandrium supernatant on Chaetoceros spp. may be explained by metal complexing properties of extracellular organic material, derived from phytoplankton, which can affect trace metal availability as well as seawater toxicity (Croot et al, 2000;Vasconcelos et al, 2002;Rijkenberg et al, 2008). In a laboratory study, growth of the diatom Phaeodactylum tricornutum was enhanced by algal exudates of different macro-and microalgae.…”

Section: Discussionmentioning

confidence: 99%