Iron(III) hydroxide solubility and humic-type fluorescent organic matter in the deep water column of the Okhotsk Sea and the northwestern North Pacific Ocean

Tani, Heihachiro; Nishioka, Jun; Kuma, Kenshi; Takata, Hyoe; Yamashita, Youhei; Tanoue, Eiichiro; Midorikawa, Takashi

doi:10.1016/s0967-0637(03)00098-0

Cited by 65 publications

(97 citation statements)

References 38 publications

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“…In the present study, the fluorescence intensity of FDOM M in the subtropical western North Pacific was always low in surface waters, increased with depth, and was almost constant around 1000 m ( Figure 5). These profiles are comparable with those observed in various open oceans, such as the subtropical and subarctic North Pacific [Hayase et al, 1988;Chen and Bada, 1992;Tani et al, 2003;Yamashita and Tanoue, 2008], equatorial Pacific [Chen and Bada, 1992;Hayase and Shinozuka, 1995], Southern Ocean [Wedborg et al, 1998;Yamashita et al, 2007] and Sargasso Sea [Mopper et al, 1991;Chen and Bada, 1992;Mopper and Schultz, 1993].…”

Section: Fluorescence Intensity Of Fdom M In Pelagic Areasupporting

confidence: 85%

Relationship between the seasonal change in fluorescent dissolved organic matter and mixed layer depth in the subtropical western North Pacific

Omori

Hama

Ishii³

et al. 2010

J. Geophys. Res.

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[1] Spatial and temporal distributions of marine humic-like fluorescent dissolved organic matter (FDOM M ) were determined in the subtropical western North Pacific to evaluate the controlling factors of FDOM M behaviors. The observations were conducted at 4 stations (15-30°N) along 137°E in a subtropical area between January 2006 and April 2007. The florescence intensity of FDOM M was low (0.14-0.25 quinine sulfate units (QSU)) in the surface layer probably due to photodegradation, and increased with depth (0.90-1.10 QSU at 1000 m), irrespective of season and station. In the surface layer, the thickness of the water mass with low fluorescence intensity (<0.3 QSU) showed the seasonal change by being deeper in winter and shallower in summer, depending on the mixed layer depth (MLD). The average fluorescence intensity within the mixed layer also varied seasonally at midlatitudes; the intensity in summer was 40.8-53.8% of that in winter. Since the MLD was very much shallower in summer than in winter, FDOM M in the mixed layer would be kept within a shallow depth during the summer where intensive photodegradation could occur. The concentration of total organic carbon (TOC) was at its maximum at the water surface and decreased with depth, being adverse to FDOM M . Thus, the ratio of fluorescence intensity to TOC concentration was lowest (0.002-0.003) in surface water, which implies that FDOM M is not quantitatively important to the dissolved organic carbon pool. However, considering the possible difference in the stabilities of FDOM M against photochemical and microbial degradation, it is conceivable that photobleached FDOM M is one of the important organic groups constituting marine dissolved organic matter.Citation: Omori, Y., T. Hama, M. Ishii, and S. Saito (2010), Relationship between the seasonal change in fluorescent dissolved organic matter and mixed layer depth in the subtropical western North Pacific,

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Section: Fluorescence Intensity Of Fdom M In Pelagic Areasupporting

confidence: 85%

Relationship between the seasonal change in fluorescent dissolved organic matter and mixed layer depth in the subtropical western North Pacific

Omori

Hama

Ishii³

et al. 2010

J. Geophys. Res.

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“…[46,47] A considerable body of work, particularly by Kuma and associates, on the solubility of Fe III in seawater points towards the important role of natural organic matter in controlling the solubility of iron in surface and deep waters by forming complexes with Fe III , and the potential generation of ligands from oxidation of organic material in deep waters. [48][49][50][51][52][53][54][55] In addition, several direct measurements of the complexation of Fe III by organic matter in seawater have been reported, mainly as a result of electrochemical titration measurements. These measurement methods and results have been recently reviewed by Bruland and Rue.…”

Section: Iron In Seawatermentioning

confidence: 99%

Iron-binding ligands and their role in the ocean biogeochemistry of iron

2007

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Environmental context. It is now well accepted that iron is an essential micronutrient for phytoplankton growth in many areas of the global ocean, even though this element is present in seawater in extremely low abundance. It is also known that most of the iron in seawater is present as complexes formed with ligands of natural organic matter whose nature and origin remain largely unknown. Here we consider how these iron-complexing ligands might have evolved during geological time, what factors may have given rise to their presence and the possible roles that they play in iron biogeochemistry.Abstract. Current knowledge about the role of iron-binding organic ligands in the ocean and their role in determining the biogeochemistry of this biologically active element has been summarised. Some electrochemical measurements suggest the presence of at least two ligand types, a strong binding ligand L 1 found mainly in the mixed layer and a weaker ligand L 2 found mainly in deep water. Speciation of Fe III is dominated by L 1 in the mixed layer and L 2 in the deep ocean. There is some evidence that L 1 is siderophore-like and is specifically generated by marine microbes (i.e. heterotropic bacteria and cyanobacteria). We suggest that this is a specific biological mechanism for sequestering iron in the mixed layer that developed early in the ocean's history (Archaean period, 2500-3500 million years BP), whereas the more ubiquitous L 2 ligand only arose at the close of the Proterozoic (500-2500 million years BP) when eukaryotic organisms evolved to switch on the ocean's biological pump, allowing L 2 ligands to form from the oxidation of sinking biological particles. This development coincided with the complete oxygenation of the ocean's interior which removed the iron-binding sulfide ion and allowed maintenance of the ocean's iron inventory. These speculations are accompanied by various suggestions about avenues for future research to better understand iron biogeochemistry.

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“…This uncertainty should be solved with further measurements of inorganic Fe solubility that are made across a spectrum of temperatures from high (, 40uC) to low (the freezing point) for each single sample of UV-irradiated seawater. Another Kuma et al (1996; gray squares) and Tani et al (2003;gray circles). The long-dashed line shows the inorganic Fe solubility in the samples at measurement temperature (20uC and pH 7.8 < 0.155 nmol L 21 ; Liu andMillero 1999, 2002).…”

Section: Discussionmentioning

confidence: 99%

Solubility of iron in the Southern Ocean

Schlösser¹,

Rocha²,

Streu³

et al. 2012

Limnology & Oceanography

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Iron solubility (cFe S ) ranged from 0.4 to 1.5 nmol L 21 , decreasing from south to north in three different Southern Ocean zones (the Coastal Zone, the Antarctic Zone, and the Polar Frontal Zone plus the Subantarctic Zone). This decrease was at times correlated with an increase in temperature. Organic Fe solubility (cFe S,org ), which was obtained by subtracting from total measured Fe solubility the solubility of inorganic species of iron (Fe) at the measurement temperature (20uC), ranged from 0.3 to 1.3 nmol L 21 , representing an average of 32 6 14% of the concentration of ligands in the dissolved size fraction as determined via competitive ligand exchangeabsorptive cathodic stripping voltammetry (barring a handful of extremely high values from a transect run to the east of Prydz Bay). Values of cFe S were mainly lower than the predicted value for inorganic Fe solubility at the in situ temperature. Total in situ Fe solubility (cFe S,adj ) was therefore estimated by adjusting for inorganic Fe solubility at in situ temperatures (between 22uC and +18uC). Because in situ temperatures in the Antarctic Circumpolar Current were mostly lower than +3uC, such cFe S,adj values, ranging from 0.5 to 1.8 nmol L 21 , were roughly twice as large as cFe S,org . The adjustment relies heavily on model calculations of inorganic Fe solubility but, if correct, indicates that the bulk of the solubility of Fe in the cold waters of the Southern Ocean is tied to the solubility of inorganic Fe rather than to Fe ligands in the soluble size fraction.

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Iron(III) hydroxide solubility and humic-type fluorescent organic matter in the deep water column of the Okhotsk Sea and the northwestern North Pacific Ocean

Cited by 65 publications

References 38 publications

Relationship between the seasonal change in fluorescent dissolved organic matter and mixed layer depth in the subtropical western North Pacific

Relationship between the seasonal change in fluorescent dissolved organic matter and mixed layer depth in the subtropical western North Pacific

Iron-binding ligands and their role in the ocean biogeochemistry of iron

Solubility of iron in the Southern Ocean

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