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Export production in the Bay of Biscay as estimated from barium-barite in settling material: a comparison with new production
Dehairs, F.A.; Fagel, N.; Antia, A.N.; Peinert, R.; Elskens, M.; Goeyens, L. (2000). Export production in the Bay of Biscay as estimated from barium-barite in settling material: a comparison with new production. Deep-Sea Res., Part 1, Oceanogr. Res. Pap. 47(4): 583-601. dx.doi.org/10.1016/S0967-0637(99)00072-2
In: Deep-Sea Research, Part I. Oceanographic Research Papers. Elsevier: Oxford. ISSN 0967-0637; e-ISSN 1879-0119
Peer reviewed article  
Available in  Authors 
    Vlaams Instituut voor de Zee: Open Marine Archive 100985 [ download pdf ]
Keywords
    Biological production
    Biological production > Primary production
    Chemical compounds > Alkaline earth metal compounds > Barium compounds
    Materials > Biogenic material
    Minerals > Sulphate minerals > Barite
    Organic matter > Particulates > Particulate organic matter > Organic carbon > Particulate organic carbon
    Sedimentation
    Transport processes > Advection
    ANE, Biscay Bay [Marine Regions]
    Marine/Coastal
Author keywords
    Ba-proxy; carbon export; margin system
Authors  Top 
  • Dehairs, F.A.
  • Fagel, N.
  • Antia, A.N.
  • Peinert, R.
  • Elskens, M.
  • Goeyens, L.
Abstract
    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.
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