Short‐term sedimentation pulses recorded with a fluorescence sensor and sediment traps at 9‐m depth in the Canary basin

Fischer, Gerhard; Neuer, Susanne; Wefer, Gerold; Krause, Günther

doi:10.4319/lo.1996.41.6.1354

Cited by 35 publications

(22 citation statements)

References 14 publications

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“…This might reflect a major transport mode for tiny and heavy coccoliths (density=2.7−2.9 g cm −3 ), being densely packed within fecal pellets which are frequently found in the material collected by sediment traps (e.g. Ploug et al, 2008b;Fischer et al, 1996b). The significance of lithogenic particles for particle sinking rates could not be clarified in this study but the high values off NW Africa remain noticeable (Table 3).…”

Section: Discussionmentioning

confidence: 44%

“…These values are close to our average coccolith-associated sinking rates for the entire water column off Cape Blanc which were around 160 m d −1 (Table 3) We collected mesozooplankton fecal pellets made up to a large part of densely packed coccoliths at the ESTOC site in the Canary Current in 1992. They transported rather fresh organic detritus to greater depth providing a perfect correspondence between seasonal organic carbon and carbonate flux (Fischer et al, 1996b). In addition, we found 1000 µm long and very densely packed appendicularian pellets in the sediment trap collections at the coastal eutrophic site off Cape Blanc (CB coastal -2: 1296 m trap depth, unpubl.…”

Section: Coccolithophorid-associated Particle Sinking Ratesmentioning

confidence: 75%

“…chlorophyll derivates) very efficiently to greater depth (Fischer et al, 1996b). Fecal pellets generally have higher sinking rates (10-2700 m d −1 , Angel, 1984Angel, , 1989Fowler and Knauer, 1986;Cadée et al, 1992;Bruland and Silver, 1981;Turner, 2002) Smetacek, 1985;Billet et al, 1983;Alldredge and Gotschalk, 1989; 1-368 m d −1 from Alldredge and Silver, 1988), although the range of sinking rates for both type of larger particles overlap.…”

Section: Resultsmentioning

confidence: 99%

“…Particle sedimentation has an episodic nature (e.g. Fischer et al, 1996b), which is rarely captured by studies with optical systems because they provide only spot observations over a very short time period of the year. Particle cameras apparently record more the normal distribution of particles in the water column (e.g.…”

Section: Discussionmentioning

confidence: 99%

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Sinking rates and ballast composition of particles in the Atlantic Ocean: implications for the organic carbon fluxes to the deep ocean

2009

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Abstract. The flux of materials to the deep sea is dominated by larger, organic-rich particles with sinking rates varying between a few meters and several hundred meters per day. Mineral ballast may regulate the transfer of organic matter and other components by determining the sinking rates, e.g. via particle density. We calculated particle sinking rates from mass flux patterns and alkenone measurements applying the results of sediment trap experiments from the Atlantic Ocean. We have indication for higher particle sinking rates in carbonate-dominated production systems when considering both regional and seasonal data. During a summer coccolithophorid bloom in the Cape Blanc coastal upwelling off Mauritania, particle sinking rates reached almost 570 m per day, most probably due the fast sedimentation of densely packed zooplankton fecal pellets, which transport high amounts of organic carbon associated with coccoliths to the deep ocean despite rather low production. During the recurring winter-spring blooms off NW Africa and in opalrich production systems of the Southern Ocean, sinking rates of larger particles, most probably diatom aggregates, showed a tendency to lower values. However, there is no straightforward relationship between carbonate content and particle sinking rates. This could be due to the unknown composition of carbonate and/or the influence of particle size and shape on sinking rates. It also remains noticeable that the highest sinking rates occurred in dust-rich ocean regions off NW Africa, but this issue deserves further detailed field and laboratory investigations. We obtained increasing sinking rates with depth. By using a seven-compartment biogeochemical model, it was shown that the deep ocean organic carbon flux at a mesotrophic sediment trap site off Cape Blanc can be captured fairly well using seasonal variable particle sinking rates. Our model provides a total organic carbon flux of Correspondence to: G. Fischer (gerhard.fischer@uni-bremen.de) 0.29 Tg per year down to 3000 m off the NW African upwelling region between 5 and 35 • N. Simple parameterisations of remineralisation and sinking rates in such models, however, limit their capability in reproducing the flux variation in the water column.

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Section: Discussionmentioning

confidence: 44%

Section: Coccolithophorid-associated Particle Sinking Ratesmentioning

confidence: 75%

Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Sinking rates and ballast composition of particles in the Atlantic Ocean: implications for the organic carbon fluxes to the deep ocean

2009

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“…The organic carbon needed to support the net CO 2 production of planktonic communities in the subtropical NE Atlantic must be supplied by lateral inputs from the productive, upwelling areas in the NW African coast and atmospheric deposition. Robust evidence for the presence of significant lateral inputs of organic carbon to the subtropical NE Atlantic has been derived from the analysis of sediment trap arrays (Fisher et al 1996). Upwelling filaments, stretching offshore from the productive NW African coast to the open ocean, have been shown to be effective mechanisms to transfer organic carbon laterally to the subtropical NE Atlantic (Arís-tegui and others 1997; Barton et al 1998;Pacheco and Hernández-Guerra 1999).…”

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confidence: 99%

Evidence for a heterotrophic subtropical northeast Atlantic

Duarte

Agustı́

Arı́stegui

et al. 2001

Limnology & Oceanography

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Abstract-The mean (ϮSE) depth-integrated gross production (P) of 2,600 Ϯ 271 mg O 2 m Ϫ2 d Ϫ1 derived from a compilation of data from nine cruises conducted between 1991-2000 in the subtropical NE Atlantic was found to be significantly lower (t-test, P ϭ 0.005, N ϭ 33) than the mean (ϮSE) community respiration (R) of 3,821. Two-thirds of the stations investigated were heterotrophic, and the P/R ratio of the communities tended to increase as P increased, such that communities where P Ͻ 3,000 mg O 2 m Ϫ2 d Ϫ1 tended to be heterotrophic. The tendency for R to exceed P (P/R Ͻ 1.0) was statistically significant (Wilcoxon ranked sign test, P Ͻ 0.05) in the upper and deep layers of the photic zone, with an overall balance between P and R at intermediate depths. These results provide evidence that the subtropical NE Atlantic is a heterotrophic ecosystem, where planktonic communities respire more organic carbon than they produce, thereby acting as net sources of CO 2 .

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Mineral ballast and particle settling rates in the coastal upwelling system off NW Africa and the South Atlantic

Fischer

Karakas

Blaas³

et al. 2007

Int J Earth Sci (Geol Rundsch)

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The ocean off NW Africa is the second most important coastal upwelling system with a total annual primary production of 0.33 Gt of carbon per year (Carr in Deep Sea Res II 49:59-80, 2002). Deep ocean organic carbon fluxes measured by sediment traps are also fairly high despite low biogenic opal fluxes. Due to a low supply of dissolved silicate from subsurface waters, the ocean off NW Africa is characterized by predominantly carbonatesecreting primary producers, i.e. coccolithophorids. These algae which are key primary producers since millions of years are found in organic-and chlorophyll-rich zooplankton fecal pellets, which sink rapidly through the water column within a few days. Particle flux studies in the Mauretanian upwelling area (Cape Blanc) confirm the hypothesis of Armstrong et al. (Deep Sea Res II 49:219-236, 2002) who proposed that ballast availability, e.g. of carbonate particles, is essential to predict deep ocean organic carbon fluxes. The role of dust as ballast mineral for organic carbon, however, must be also taken into consideration in the coastal settings off NW Africa. There, high settling rates of larger particles approach 400 m day À1 , which may be due to a particular composition of mineral ballast. An assessment of particle settling rates from opal-production systems in the Southern Ocean of the Atlantic Sector, in contrast, provides lower values, consistent with the assumptions of Francois et al. (Global Biogeochem Cycles 16(4):1087. Satellite chlorophyll distributions, particle distributions and fluxes in the water column off NW Africa as well as modelling studies suggest a significant lateral flux component and export of particles from coastal shelf waters into the open ocean. These transport processes have implications for paleoreconstructions from sediment cores retrieved at continental margin settings.

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Short‐term sedimentation pulses recorded with a fluorescence sensor and sediment traps at 9‐m depth in the Canary basin

Cited by 35 publications

References 14 publications

Sinking rates and ballast composition of particles in the Atlantic Ocean: implications for the organic carbon fluxes to the deep ocean

Sinking rates and ballast composition of particles in the Atlantic Ocean: implications for the organic carbon fluxes to the deep ocean

Evidence for a heterotrophic subtropical northeast Atlantic

Mineral ballast and particle settling rates in the coastal upwelling system off NW Africa and the South Atlantic

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