Iron deficiency in micro-sized diatoms in the Oyashio region of the Western subarctic Pacific during spring |
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| Authors: | Ai Hattori-Saito Jun Nishioka Tsuneo Ono R Michael L McKay Koji Suzuki |
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| Institution: | (1) Frontier Research System for Global Change, Showa-machi, Kanazawa-ku, Yokohama, Kanagawa, 236-0001, Japan;(2) Hokkaido National Fisheries Research Institute, Katsurakoi, Kushiro, Hokkaido, 085-0802, Japan;(3) Japan Meteorological Agency, Otemachi, Chiyoda-ku, Tokyo, 100-8122, Japan;(4) Hydrospheric Atmospheric Research Center, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, 464-8601, Japan |
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| Abstract: | In order to detect iron (Fe) stress in micro-sized (20–200 μm) diatoms in the Oyashio region, western subarctic Pacific during
spring, immunological ferredoxin/flavodoxin assays were applied to samples collected from the surface layer in May 2005. Concomitantly,
the community composition of the micro-sized phytoplankton and hydrographic conditions, including dissolved Fe and macronutrient
concentrations, were also examined. Chlorophyll (Chl) a concentrations were <2 mg m−3 at all sampling stations, except at a station where the Chl a level was 9.0 mg m−3 and a micro-sized diatom bloom occurred. A high abundance of ferredoxin in micro-sized diatoms was detected only at a rather
near-shore station where dissolved Fe and macronutrient concentrations were higher, indicating that the micro-sized diatoms
did not suffer from iron deficiency. On the other hand, flavodoxin in micro-sized diatoms was often observed at the other
stations, including the bloom station, where macronutrients were replete but dissolved Fe concentration was low (0.31 nM).
A significant amount of chlorophyllide a, a degradation product of Chl a, was also observed at the bloom station, suggesting a decline of the diatom bloom. The micro-sized phytoplankton species
at all the stations were mainly composed of the diatoms Thalassiosira, Chaetoceros, and Fragilariopsis spp. Our study indicates that micro-sized diatoms were stressed by Fe bioavailability during the spring season in the Oyashio
region |
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