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Primary productivity, bacterial productivity and nitrogen uptake in response to iron enrichment during the SEEDS II

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Title: Primary productivity, bacterial productivity and nitrogen uptake in response to iron enrichment during the SEEDS II
Authors: Kudo, Isao Browse this author →KAKEN DB
Noiri, Yoshifumi Browse this author
Cochlan, William P. Browse this author
Suzuki, Koji Browse this author
Aramaki, Takafumi Browse this author
Ono, Tsuneo Browse this author
Nojiri, Yukihiro Browse this author
Keywords: Phytoplankton
Heterotrophic bacteria
Carbon budget
Subarctic pacific ocean
Fe enrichment
Chlorophyll-α
Issue Date: 15-Dec-2009
Publisher: Elsevier Ltd.
Journal Title: Deep Sea Research Part II: Topical Studies in Oceanography
Volume: 56
Issue: 26
Start Page: 2755
End Page: 2766
Publisher DOI: 10.1016/j.dsr2.2009.06.003
Abstract: Primary productivity (PP), bacterial productivity (BP) and the uptake rates of nitrate and ammonium were measured using isotopic methods (13C, 3H, 15N) during a mesoscale iron (Fe)-enrichment experiment conducted in the western subarctic Pacific Ocean in 2004 (SEEDS II). PP increased following Fe enrichment, reached maximal rates 12 days after the enrichment, and then declined to the initial level on day 17. During the 23-d observation period, we observed the development and decline of the Fe-induced bloom. The surface mixed layer (SML) integrated PP increased by 3-fold, but was smaller than the 5-fold increase observed in the previous Fe-enrichment experiment conducted at almost the same location and season during 2001 (SEEDS). Nitrate uptake rates were enhanced by Fe-enrichment but decreased after day 5, and became lower than ammonium uptake rates after day 17. The total nitrogenous nutrient uptake rate declined after the peak of the bloom, and accumulation of ammonium was obvious in the euphotic layer. Nitrate utilization accounted for all the requirements of N for the massive bloom development during SEEDS, whereas during SEEDS II, nitrate accounted for >90% of total N utilization on day 5, declining to 40% by the end of the observation period. The SML integrated BP increased after day 2 and peaked twice on days 8 and 21. Ammonium accumulation and the delayed heterotrophic activity suggested active regeneration occurred after the peak of the bloom. The SML integrated PP between days 0 and day 23 was 19.0g Cm^[-2]. The SML integrated BP during the same period was 2.6 g C m^[-2], which was 14% of the SML integrated PP. Carbon budget calculation for the whole experimental period indicated that 33% of the whole (particulate plus dissolved) PP (21.5 gCm^[-2]) was exported below the SML and 18% was transferred to the meso-zooplankton (growth). The bacterial carbon consumption (43% of the whole PP) was supported by DOC or POC release from phytoplankton, zooplankton, protozoa and viruses. More than a half (56%) of the whole PP in the Fe patch was consumed within the SML by respiration of heterotrophic organisms and returned to CO2.
Type: article (author version)
URI: http://hdl.handle.net/2115/42553
Appears in Collections:水産科学院・水産科学研究院 (Graduate School of Fisheries Sciences / Faculty of Fisheries Sciences) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 工藤 勲

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