Non-steady-state biological removal of atmospheric particles from Mediterranean surface waters

Buat‐Ménard, P.; Davies, Joanne; Remoudaki, E.; Miquel, Juan‐Carlos; Bergametti, Gilles; Lambert, C. E.; Ezat, Ullah; Quétel, Christophe R.; Rosa, J. La; Fowler, Scott W.

doi:10.1038/340131a0

Cited by 93 publications

(35 citation statements)

References 16 publications

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“…Both the coupling (e.g., Jickells et al, 1998;Migon et al, 2002;Ternon et al, 2010;Brust et al, 2011) and decoupling (e.g., Buat-Ménard et al, 1989;Migon et al, 2002;Ternon et al, 2010) of dust deposition and particulate export have been reported. During our experiment, only ∼ 57 and 41 % (by mass) of the lithogenic particles initially added were recovered in the sediment traps six days after the first and second seedings, respectively .…”

Section: One Dust-deposition Event Several Particle Settling Populatmentioning

confidence: 99%

“…In the open ocean, this pool of small lithogenic particles remains stored within surface layers during the stratification period until either the onset of vertical convection during winter (e.g., Migon et al, 2002), or their inclusion into faecal pellets (e.g., Buat-Ménard et al, 1989) or larger aggregates (e.g., Burd and Jackson, 2009). For this last case, POC fluxes could scavenge these slow-settling lithogenic particles from the water column and determine their flux (Passow and De La Rocha, 2006).…”

Section: One Dust-deposition Event Several Particle Settling Populatmentioning

confidence: 99%

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Quantification of the lithogenic carbon pump following a simulated dust-deposition event in large mesocosms

et al. 2014

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Abstract. Lithogenic particles, such as desert dust, have been postulated to influence particulate organic carbon (POC) export to the deep ocean by acting as mineral ballasts. However, an accurate understanding and quantification of the POC-dust association that occurs within the upper ocean is required in order to refine the "ballast hypothesis". In the framework of the DUNE (a DUst experiment in a lowNutrient, low-chlorophyll Ecosystem) project, two artificial seedings were performed seven days apart within large mesocosms. A suite of optical and biogeochemical measurements were used to quantify surface POC export following simulated dust events within a low-nutrient, low-chlorophyll ecosystem. The two successive seedings led to a 2.3-6.7-fold higher POC flux than the POC flux observed in controlled mesocosms. A simple linear regression analysis revealed that the lithogenic fluxes explained more than 85 % of the variance in POC fluxes. On the scale of a dust-deposition event, we estimated that 42-50 % of POC fluxes were strictly associated with lithogenic particles (through aggregation and most probably sorption processes). Lithogenic ballasting also likely impacted the remaining POC fraction which resulted from the fertilization effect. The observations support the "ballast hypothesis" and provide a quantitative estimation of the surface POC export abiotically triggered by dust deposition. In this work, we demonstrate that the strength of such a "lithogenic carbon pump" depends on the biogeochemical conditions of the water column at the time of deposition. Based on these observations, we suggest that this lithogenic carbon pump could represent a major component of the biological pump in oceanic areas subjected to intense atmospheric forcing.

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Section: One Dust-deposition Event Several Particle Settling Populatmentioning

confidence: 99%

Section: One Dust-deposition Event Several Particle Settling Populatmentioning

confidence: 99%

Quantification of the lithogenic carbon pump following a simulated dust-deposition event in large mesocosms

et al. 2014

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“…Although most of the particle flux is under biological control [Buat-Ménard et al, 1989], the residence time of the particles of atmospheric origin remains very long in the mixed layer because of the physical barrier created by the thermocline [Migon et al, 2002] and thus a particle residence time of at least 7 days is probably realistic. This allows the calculation of the potential DFe induced following different scenarios (from extremely low to strong Saharan events) in a 10 meter mixed layer (Table 2).…”

Section: Saharan Input Of Dfe Vs Phytoplankton Iron Requirementsmentioning

confidence: 99%

Dissolution of atmospheric iron in seawater

Bonnet¹

2004

Geophysical Research Letters

127

120

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In vitro dissolution experiments were conducted in seawater in order to quantify the partitioning between dissolved and particulate phases of iron associated to Saharan dust and urban particles. The percentage of iron released was very low (0.05 to 2.2%) depending on the particulate load, the aerosol source and the contact time. This percentage decreased with the amount of particles introduced following a power law, indicating that the process could be modeled. Indeed, these dissolution processes were a function of the lability of iron in relation to the particle source, the particle size and adsorption processes. According to these experiments, the dissolved iron induced in a 10 m mixed layer by Saharan events of various magnitudes ranges from 0.07 to 1 nM. Since these concentrations are in agreement with the natural iron requirements for the phytoplankton, such inputs can profoundly influence the primary production, especially in oligotrophic conditions.

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“…Furthermore, the mass of this dust is large at roughly one billion tonnes per year, and it has been shown that deposition of these fine particles can profoundly influence the geochemistry and sedimentology of the Mediterranean Sea (Loÿe-Pilot et al 1986;Buat-Menard et al 1989). Buat-Menard et al (1989) have demonstrated a close coupling between the large atmospheric inputs of aluminosilicates and their rapid removal from surface waters, and vertical flux to depth in the northwestern Mediterranean basin.…”

mentioning

confidence: 99%

Temporal variations in plutonium and americium inventories and their relation to vertical transport in the northwestern Mediterranean Sea

Fowler

Noshkin

et al. 2000

Limnology & Oceanography

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Vertical fluxes of 239ϩ240 Pu and 241 Am and temporal changes in their inventories in the northwestern Mediterranean Sea have been examined through high-resolution water column sampling coupled with direct measurements of the vertical flux of particle-bound transuranics using time-series sediment traps. Water column profiles of both radionuclides showed well-defined sub-surface maxima ( 239ϩ240 Pu between 100-400 m;241 Am at 100-200 m and 800 m), the depths of which are a result of the different biogeochemical scavenging behavior of the two radionuclides.Comparison of deep water column (0-2,000 m) transuranic inventories with those derived from earlier measurements demonstrate that the total 239ϩ240 Pu inventory had not substantially changed between 1976-1990 whereas 241 Am had decreased by approximately 24%. Enhanced scavenging of 241 Am and a resultant, more rapid removal from the water column relative to 239ϩ240 Pu was also supported by the observation of elevated Am/Pu activity ratios in sinking particles collected in sediment traps at depth. Direct measurements of the downward flux of particulate 239ϩ240 Pu and 241 Am compared with transuranic removal rates derived from observed total water column inventory differences over time, show that particles sinking out of deep waters (1,000-2,000 m) could account for 26-72% of the computed total annual 239ϩ240 Pu loss and virtually all of the 241 Am removal from the water column. Upper water column (0-200 m) residence times based on direct flux measurements ranged from 20-30 yr for 239ϩ240 Pu and 5-10 yr for 241 Am. The observation that 241 Am/ 239ϩ240 Pu activity ratios in unfiltered Mediterranean seawater are six times lower than those in the north Pacific suggests the existence of a specific mechanism for enhanced scavenging and removal of 241 Am from the generally oligotrophic waters of the open Mediterranean. It is proposed that atmospheric inputs of aluminosilicate particles transported by Saharan dust events which frequently occur in the Mediterranean region could enhance the geochemical scavenging and resultant removal of 241 Am to the sediments.

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Non-steady-state biological removal of atmospheric particles from Mediterranean surface waters

Cited by 93 publications

References 16 publications

Quantification of the lithogenic carbon pump following a simulated dust-deposition event in large mesocosms

Quantification of the lithogenic carbon pump following a simulated dust-deposition event in large mesocosms

Dissolution of atmospheric iron in seawater

Temporal variations in plutonium and americium inventories and their relation to vertical transport in the northwestern Mediterranean Sea

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