北海道大学 · 地球惑星科学
西岡淳教授の研究室では、北太平洋の亜寒帯域における鉄の供給メカニズムとその生物地球化学的影響を、海洋化学的・物理的プロセスの観点から解明しています。特に、オホーツク海中層水や北太平洋中層水を介した鉄の輸送と、それが表層の栄養塩豊富な水域を維持する役割に注目しています。鉄の供給が春のプランクトンブloomを制御する仕組みや、鉄の形態（溶解・粒子状・ラビリス型）の変化が生態系に与える影響について、長期観測と実験的アプローチを組み合わせて研究しています。
Figures are computed from collected data and may differ slightly.
Iron is an essential nutrient and plays an important role in the control of phytoplankton growth (Martin et al., 1989). Atmospheric dust has been thought to be the most important source of iron, supporting annual biological production in the western subarctic Pacific (WSP) (Duce and Tindale, 1991; Moore et al., 2002). We argue here for another source of iron to the WSP. We found extremely high concentrations of dissolved and particulate iron in the Okhotsk Sea Intermediate Water (OSIW) and the N
The mechanism by which nutrients in the deep ocean are uplifted to maintain nutrient-rich surface waters in the subarctic Pacific has not been properly described. The iron (Fe) supply processes that control biological production in the nutrient-rich waters are also still under debate. Here, we report the processes that determine the chemical properties of intermediate water and the uplift of Fe and nutrients to the main thermocline, which eventually maintains surface biological productivity. Ext
Abstract It is well known that phytoplankton growth is broadly limited by iron (Fe) availability in the subarctic Pacific. To investigate which Fe sources control the amplitude of seasonal variation in biogeochemical parameters in the subarctic Pacific, we examined the spatial variation in the west‐to‐east distribution of dissolved Fe (DFe) across the western and central subarctic Pacific through the Japanese GEOTRACES program. The vertical section profile of the western subarctic Pacific gyre s
Comparison of vertical profiles of size‐fractionated iron between the western and eastern subarctic North Pacific clearly showed higher labile particulate iron concentrations towards the west and this result strongly supports the higher iron supply in the western region. Additionally, the results of the SEEDS experiment, the first meso‐scale iron enrichment experiment in the subarctic North Pacific, clearly showed that artificially enriched iron in the dissolved fraction (mainly in colloidal fra
time series observations along the A line provided information on the temporal variability of the dissolved iron (diss-Fe) concentration in the Oyashio region of the western subarctic Pacific, and the data indicated that there was an annual cycle in the concentration of surface diss-Fe occurring every year. Diss-Fe was supplied into the surface water in this region every winter and supports the spring phytoplankton bloom after development of the thermocline. The diss-Fe concentration was drawn d
Abstract The subarctic Pacific is a high‐nutrient low‐chlorophyll (HNLC) region in which phytoplankton growth is broadly limited by iron (Fe) availability. However, even with Fe limitation, the western subarctic Pacific (WSP) has significant phytoplankton growth and greater seasonal variability in lower trophic levels than the eastern subarctic Pacific. Therefore, differences in Fe supply must explain the west‐to‐east decrease in seasonal phytoplankton growth. The Fe flux to the euphotic zone in
Abstract One of the most important breakthroughs in oceanography in the last 30 years was the discovery that iron (Fe) controls biological production as a micronutrient, and our understanding of Fe and nutrient biogeochemical dynamics in the ocean has significantly advanced. In this review, we looked back both previous and updated knowledge of the natural Fe supply processes and nutrient dynamics in the subarctic Pacific and its impact on biological production. Although atmospheric dust has been
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