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Primary, new and export production in the NW Pacific subarctic gyre during the vertigo K2 experiments

Citation

Elsken, M and Brion, N and Buesseler, K and Van Mooy, BAS and Boyd, P and Dehairs, F and Savoye, N and Baeyens, W, Primary, new and export production in the NW Pacific subarctic gyre during the vertigo K2 experiments, Deep-Sea Research Part, 55, (14-15) pp. 1594-1604. ISSN 0967-0645 (2008) [Refereed Article]

Copyright Statement

Copyright 2008 Elsevier

DOI: doi:10.1016/j.dsr2.2008.04.013

Abstract

This paper presents results on tracer experiments using 13C and 15N to estimate uptake rates of dissolved inorganic carbon (DIC) and nitrogen (DIN). Experiments were carried out at station K2 (47°N, 161°E) in the NW Pacific subarctic gyre during July–August 2005. Our goal was to investigate relationships between new and export production. New production was inferred from the tracer experiments using the f ratio concept (0–50 m); while export production was assessed with neutrally buoyant sediment traps (NBSTs) and the e ratio concept (at 150 m). During trap deployments, K2 was characterized both by changes in primary production (523–404 mg C m−2 d−1), new production (119–67 mg C m−2 d−1), export production (68–24 mg C m−2 d−1) and phytoplankton composition (high to low proportion of diatoms). The data indicate that 17–23% of primary production is exportable to deeper layers (f ratio) but only 6–13% collected as a sinking particle flux at 150 m (e ratio). Accordingly, >80% of the carbon fixed by phytoplankton would be mineralized in the upper 50 m (1–f), while <11% would be within 50–150 m (f–e). DIN uptake flux amounted to 0.5 mM m−2 h−1, which was equivalent to about 95% particulate nitrogen (PN) remineralized and/or grazed within the upper 150 m. Most of the shallow PN remineralization occurred just above the depth of the deep chlorophyll maximum (DCM), where a net ammonium production was measured. Below the DCM, while nitrate uptake rates became negligible because of light limitation, ammonium uptake did continue to be significant. The uptake of ammonium by heterotrophic bacteria was estimated to be 14–17% of the DIN assimilation. Less clear are the consequences of this uptake on the phytoplankton community and biogeochemical processes, e.g. new production. It was suggested that competition for ammonium could select for small cells and may force large diatoms to use nitrate. This implies that under Fe stress as observed here, ammonium uptake is preferred and new production progressively suppressed despite the surplus of nitrate.

Item Details

Item Type:Refereed Article
Keywords:f ratio, new production, e ratio, export production, carbon and nitrogen budget
Research Division:Environmental Sciences
Research Group:Ecological Applications
Research Field:Ecological Impacts of Climate Change
Objective Division:Environment
Objective Group:Climate and Climate Change
Objective Field:Ecosystem Adaptation to Climate Change
Author:Boyd, P (Professor Philip Boyd)
ID Code:95535
Year Published:2008
Web of Science® Times Cited:24
Deposited By:IMAS Research and Education Centre
Deposited On:2014-10-03
Last Modified:2014-11-11
Downloads:0

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