Article (Scientific journals)
Export production in the Bay of Biscay as estimated from barium - barite in settling material: a comparison with new production
Dehairs, F.; Fagel, Nathalie; Antia, A. et al.
2000In Deep-Sea Research. Part I, Oceanographic Research Papers, 47 (4), p. 583-601
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Keywords :
Ba-proxy; carbon export; margin system
Abstract :
[en] We present barium data for sediment traps deployed in a northeast Atlantic margin environment (Bay of Biscay). Fluxes of excess barium were measured with the objective of calculating carbon export production rates from the surface mixed layer and thus contribute to the understanding of organic carbon transport in a margin environment. Therefore, it was necessary to properly understand the different processes that affected the barium fluxes in this margin environment. Seasonal variability of POC/Ba flux ratios and decrease of barium solubilisation in the trap cups with increasing depth in the water column probably indicate that the efficiency of barite formation in the organic micro-environment varies with season and that the process is relatively slow and not yet completed in the upper 600 m of water column. Thus barite presence in biogenic aggregates will significantly depend on water column transit time of these aggregates. Furthermore, it was observed that significant lateral input of excess-Ba can occur, probably associated with residual currents leaving the margin. This advected excess-Ba affected especially the recorded fluxes in the deeper traps (>1000 m) of the outer slope region. We have attempted to correct for this advected excess-Ba component, using Th (reported by others for the same samples) as an indicator of enhanced lateral flux and assigning a characteristic Ba/Th ratio to advected material, Using transfer functions relating excess-Ba flux with export production characteristic of margin areas, observed Ba fluxes indicate an export production between 7 and 18 g C m(-2) yr(-1). Such values are 3-7 times lower than estimates based on N-nutrient uptake and nutrient mass balances, but larger and more realistic than is obtained when a transfer function characteristic of open ocean systems is applied. The discrepancy between export production estimates based on excess-Ba fluxes and nutrient uptake could be resolved if part of the carbon is exported as dissolved organic matter. Results suggest that margin systems function differently from open ocean systems, and therefore Ba-proxy rationales developed for open ocean sites might not be applicable in margin areas. (C) 2000 Elsevier Science Ltd. All rights reserved.
Disciplines :
Earth sciences & physical geography
Author, co-author :
Dehairs, F.
Fagel, Nathalie  ;  Université de Liège - ULiège > Département de géologie > Argiles, géochimie et environnements sédimentaires
Antia, A.
Peinert, R.
Elskens, M.
Goeyens, L.
Language :
English
Title :
Export production in the Bay of Biscay as estimated from barium - barite in settling material: a comparison with new production
Publication date :
2000
Journal title :
Deep-Sea Research. Part I, Oceanographic Research Papers
ISSN :
0967-0637
eISSN :
1879-0119
Publisher :
Pergamon Press - An Imprint of Elsevier Science, Oxford, United Kingdom
Volume :
47
Issue :
4
Pages :
583-601
Peer reviewed :
Peer Reviewed verified by ORBi
Name of the research project :
OMEX
Funders :
EU - European Commission
Available on ORBi :
since 19 May 2010

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