Pelagic processes and vertical flux of particles: an overview of a long-term comparative study in the Norwegian Sea and Greenland Sea

Abstract

Pelagic processes and their relation to vertical flux have been studied in the Norwegian and Greenland Seas since 1986. Results of long-term sediment trap deployments and adjoining process studies are presented, and the underlying methodological and conceptional background is discussed. Recent extension of these investigations at the Barents Sea continental slope are also presented. With similar conditions of input irradiation and nutrient conditions, the Norwegian and Greenland Seas exhibit comparable mean annual rates of new and total production. Major differences can be found between these regions, however, in the hydrographic conditions constraining primary production and in the composition and seasonal development of the plankton. This is reflected in differences in the temporal patterns of vertical particle flux in relation to new production in the euphotic zone, the composition of particles exported and in different processes leading to their modification in the mid-water layers.In the Norwegian Sea heavy grazing pressure during early spring retards the accumulation of phytoplankton stocks and thus a mass sedimentation of diatoms that is often associated with spring blooms. This, in conjunction with the further seasonal development of zooplankton populations, serves to delay the annual peak in sedimentation to summer or autumn. Carbonate sedimentation in the Norwegian Sea, however, is significantly higher than in the Greenland Sea, where physical factors exert a greater control on phytoplankton development and the sedimentation of opal is of greater importance. In addition to these comparative long-term A. A n t i a • E. B a u e r f e i n d -O. H a u p t • W. K o e v e E. M a c h a d o • I. P e e k e n -R. Peinert ( [ ] ) -S. R e i t m e i e r C. T h o m s e n • M. W u n s c h • U. Zeller • B. Zeitzschel Institut for M e e r e s k u n d e , D t i s t e r n b r o o k e r W e g 20, D-24105 Kiel, G e r m a n y email: rpeinert@IFM.uni-kiel.d400.de B. yon B o d u n g e n • M. Voss Institut far Ostseeforschung, Seestrasse 15, D-18119 W a r n e m t i n d e , G e r m a n ystudies a case study has been carried out at the continental slope of the Barents Sea, where an emphasis was laid on the influence of resuspension and across-slope lateral transport with an analysis of suspended and sedimented material.

Fluxes of carbon and nutrients to the Iceland Sea surface layer and inferred primary productivity and stoichiometry

“…Earlier estimates of new production in the Norwegian Sea (70 • N, 0 • E) are in the range 21-29 g C m −2 yr −1 (Bodungen et al, 1995). These values agree with estimates of NCP, based on oxygen fluxes in the Norwegian Sea, of ∼ 24-32 g C m −2 yr −1 (Skjelvan et al, 2001).…”

Pigment specific in vivo light absorption of phytoplankton from estuarine, coastal and oceanic waters

“…The annual nutrient loading into the Greenland Sea was estimated from measurements of annual new production (ca. 27 g C m -2 ; Bodungen et al 1995) and an assumed C:N ratio of 6. In the Sound and the Greenland Sea, samples were taken at the surface (2 to 5 m) and in deeper layers at the chl a maximum.…”

Northwest African upwelling and its effect on offshore organic carbon export to the deep sea

“…Organic carbon fluxes must be regarded as conservative values owing to some decomposition and remineralization of organic matter in the sample cups [Fischer et al, 2000;Fischer and Wefer, 1991]. Measurements of, for example, dissolved silica in the supernatant water of the collector cups reveal near-saturation concentrations, which can comprise a substantial amount of the total sedimented particulate organic silica during low silica sedimentation [Fischer and Wefer, 1991;von Bodungen et al, 1995]. Laboratory experiments with samples from short term traps show 20% loss of particulate organic carbon for shallow traps (100-300 m) and 5% loss for deep traps (1000-3000 m) [von Bodungen et al, 1995].…”

“…Measurements of, for example, dissolved silica in the supernatant water of the collector cups reveal near-saturation concentrations, which can comprise a substantial amount of the total sedimented particulate organic silica during low silica sedimentation [Fischer and Wefer, 1991;von Bodungen et al, 1995]. Laboratory experiments with samples from short term traps show 20% loss of particulate organic carbon for shallow traps (100-300 m) and 5% loss for deep traps (1000-3000 m) [von Bodungen et al, 1995]. At our deployment depth (3580 m) most of the labile material is likely already respired.…”