『Abstract
The spatial and temporal changes in vertical distribution of
soluble Fe (＜200 kDa or ＜0.03μm) and small colloidal Fe (200 kDa-0.2μm,
200 kDa-0.1μm, 0.03-0.2μm or 0.03-0.1μm) were studied during September
1997, June and September 1998, and February 1999 along a transect
extending from southern Vancouver Island to Ocean Station Papa
(OSP). At OSP, vertical profiles of soluble Fe exhibited nutrient-like
distribution. In June and September, concentrations of soluble
Fe were low in the surface mixed layer (0.05-0.07 nM) and increased
below 300 m depth with temporal variation (0.17-0.42 nM, 300-600
m depth). The concentrations of small colloidal Fe were generally
low in the surface mixed layer (0.01-0.06 nM) with higher concentrations
below 200 m depth. From 200 to 600 m depth, small colloidal Fe
represented 13-50％ of dissolved Fe (＜0.2μm) and it has temporal
variation. Concentrations of soluble Fe (0.20-0.57 nM) were higher
in February 1999 than those in June and September 1997-1998. Concentrations
of small colloidal Fe from 200 to 1000 m depth were also higher
in February 1999 (0.17-0.37 nM) than those in June and September
1997-1998. These results suggest that, in OSP, a substantial portion
of small colloidal Fe exists in the dissolved Fe fraction (＜0.2μm)
and that there are temporal changes in soluble and small colloidal
Fe concentration in OSP seawater. Meanwhile, vertical profiles
of Fe at stations near Vancouver Island did not show nutrient-like
distributions. High concentrations of small colloidal Fe and large
labile particulate Fe (＞0.2μm, labile at pH 3.2) were observed
in deep water at coastal stations both in September 1998 and February
1999. These results suggest that soluble and small colloidal Fe
vary spatially and temporally. Particularly, in our observation,
the soluble Fe has temporal changes in open ocean seawater while
the small colloidal and large labile particulate Fe has spatial
changes at coastal area. Thus, we need to consider the existence
of small colloidal Fe in the dissolved Fe fraction (＜0.2μm) in
seawater to better understand the Fe dynamics in the ocean.
Keywords: Iron; Size-fraction; Spatially variation; Temporally
variation』
1. Introduction
2. Study area
3. Materials and method
3.1. Sample collection
3.2. Size-fractionation and analysis for Fe
3.2.1. Filters
3.2.2. Sample treatment during each cruise
3.2.3. Onboard clean filtration method and Fe analysis
3.2.4. Confirmation of the onboard clean filtration method
3.2.5. Definition of size-fraction in this study
4. Result
4.1. Total acid-labile and size-fractionated Fe vertical
distributions at OSP
4.2. Total acid-labile and size-fractioned Fe distributions along
line P and three extra stations (September 1997, 1998 and February
1999)
5. Discussion
5.1. Vertical distribution of total acid-labile and size-fractionated
Fe at OSP
5.2. Temporal change in dissolved Fe at OSP
5.3. Temporal change in size-fractionated Fe at OSP
5.4. Spatial change in total acid-labile and size-fractionated
Fe
6. Conclusions
Acknowledgements
References