Impact of the natural Fe-fertilization on the magnitude, stoichiometry and efficiency of particulate biogenic silica, nitrogen and iron export fluxes

Lemaitre, Nolwenn; Planquette, Hélène; Dehairs, Frank; Merwe, Pier van der; Trull, Thomas W.; Laurenceau-Cornec, E. C.; Davies, Diana M.; Bollinger, Claire; Goff, Manon Le; Grossteffan, Emilie; Planchon, F.

doi:10.1016/j.dsr.2016.09.002

Cited by 10 publications

(13 citation statements)

References 96 publications

(120 reference statements)

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“…As shown in Figure S3 and Table S1, >53µm concentrations vary between elements, with values ranging from 10 -6 to 10 1 nmol/L in the suite of Cd, Co < Cu, Mn, Ni, Ti, Zn < Fe < Al, P. Similarly to p 234 Th activities, concentrations and distributions also vary significantly for each pTE along the transect, like those of the lithogenic, authigenic and biogenic phases. Overall, our >53µm pTE concentrations are comparable with those of the world ocean literature 31,36,86 . If we compare more closely to data from the GA03 cruise, which also took place in the North Atlantic (GEOTRACES IDP2017 87 ), our concentrations of pP are slightly higher, reaching 24 nmol/L during GEOVIDE (4.7 nmol/L during GA03), likely because of the higher productivity observed in the subpolar compared to the subtropical North Atlantic.…”

Section: Activities Of P 234supporting

confidence: 84%

“…Despite an increasing number of studies addressing TE export, this process remains still poorly understood 23,26,35,36,[27][28][29][30][31][32][33][34] . Besides the strong temporal and spatial variability, another reason likely resides in the difficulty in measuring particulate trace element (pTE) fluxes, as TEs are present at very low concentrations in the ocean and are easily prone to contamination.…”

Section: Introductionmentioning

confidence: 99%

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Particulate Trace Element Export in the North Atlantic (GEOTRACES GA01 Transect, GEOVIDE Cruise)

Lemaitre

Planquette

Dehairs

et al. 2020

ACS Earth Space Chem.

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Vertical export of particulate trace elements (pTEs) is a critically underconstrained aspect of their biogeochemistry. Here, we combine elemental analyses on large (>53 μm) particles and 234Th measurements to determine downward export fluxes from the upper layers (40-110 m) of pTEs (Al, Cd, Co, Cu, Fe, Mn, Ni, P, Ti, V, Zn) and mineral phases (lithogenic, Fe-and Mn-oxides, calcium carbonate, and opal) in the North Atlantic along the GEOVIDE transect (Portugal-Greenland-Canada; GEOTRACES GA01 cruise). The role of lithogenic particles in controlling TE fluxes is obvious at proximity of the Iberian margin where the highest pTE export fluxes were estimated (up to 3912 μg/m2/d for pFe). However, high lithogenic and pTE fluxes are also observed up to 1700 km off this margin in the west European and Icelandic basins (up to 931 μg/m2/d for pFe). The lowest pTE export fluxes are determined in the Labrador Sea (as low as 501 μg/m2/d for pFe). High Mnand Fe-oxide fluxes are estimated at the open ocean stations, suggesting that authigenic particles are an important vector of pTEs. All along the transect, biogenic particles also drive the pTE export fluxes, as shown by the similar pTE/POC ratios between exports and phytoplankton quotas. The shortest residence times (dissolved + particulate) are generally observed where lithogenic particles control the pTE fluxes (as low as 2 days for Fe) whereas pTEs seem to be longer retained when the contribution of biogenic particles become greater (residence times up to 147 days for Fe).

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Section: Activities Of P 234supporting

confidence: 84%

Section: Introductionmentioning

confidence: 99%

Particulate Trace Element Export in the North Atlantic (GEOTRACES GA01 Transect, GEOVIDE Cruise)

Lemaitre

Planquette

Dehairs

et al. 2020

ACS Earth Space Chem.

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“…Where sediment traps were used, the Fe inventories have been calculated from surface to the trap depth and the residence times determined accordingly. At a couple of locations (e.g., Bowie et al, 2015; Lemaitre et al, 2016), the traps were located below the inventory measurements (e.g., mixed layer inventory measured to 123 m and sediment trap deployed at 200 m), and the measured inventories were extrapolated to cover unquantified inventory gap.…”

Section: Methodsmentioning

confidence: 99%

Ironing Out Fe Residence Time in the Dynamic Upper Ocean

Black

Kienast

Lemaitre³

et al. 2020

Global Biogeochemical Cycles

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Although iron availability has been shown to limit ocean productivity and influence marine carbon cycling, the rates of processes driving iron's removal and retention in the upper ocean are poorly constrained. Using 234 Th-and sediment-trap data, most of which were collected through international GEOTRACES efforts, we perform an unprecedented observation-based assessment of iron export from and residence time in the upper ocean. The majority of these new residence time estimates for total iron in the surface ocean (0-250 m) fall between 10 and 100 days. The upper ocean residence time of dissolved iron, on the other hand, varies and cycles on sub-annual to annual timescales. Collectively, these residence times are shorter than previously thought, and the rates and timescales presented here will contribute to ongoing efforts to integrate iron into global biogeochemical models predicting climate and carbon dioxide sequestration in the ocean in the 21st century and beyond. Plain Language Summary Iron is a key micronutrient for organisms living in the upper ocean, and thus, its availability is one of the key factors controlling the removal of carbon dioxide via phytoplankton growth in much of the global ocean. Until very recently, measurements of internal iron cycling were scarce. This includes estimates of how much iron leaves the surface ocean via sinking particles. Due to the lack of observations, models struggle to reproduce observed patterns in global surface iron distributions. For the first time, we constrain the rate of iron loss from the upper ocean along three basin-wide transects and bring together all preexisting estimates to determine the timescales on which different forms of iron are retained in the upper ocean. Overall, our findings suggest that iron cycles more rapidly between the surface and the subsurface ocean than previously estimated, and we encourage the modeling community to utilize the wealth of data presented here to explore the global consequences of these findings.

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“…A deficit or excess of 234 Th relative to its parent is used with the ratio of an element or component to 234 Th on sinking particles at a given depth to determine a flux of that element (Buesseler et al, 1992(Buesseler et al, , 2006. While only a few studies to date have applied the 234 Th method to estimate particulate TM fluxes, these efforts have provided some of the first constraints on Fe and Pb cycling near the North American coastline (Smith et al, 2014;Weinstein & Moran, 2005) and on Fe budgets in island-influenced regions of the Southern Ocean (Lemaitre et al, 2016;Planquette et al, 2011). inputs from productive coastal waters and upwelling can supply Cd to the global ocean's gyres, dust is not thought to be a substantial source of Cd to the surface ocean (Bruland et al, 1994).…”

Section: Constraining the Particulate Export Of Trace Metalsmentioning

confidence: 99%

Insights From the²³⁸U‐²³⁴Th Method Into the Coupling of Biological Export and the Cycling of Cadmium, Cobalt, and Manganese in the Southeast Pacific Ocean

Black

Lam

Lee

et al. 2019

Global Biogeochemical Cycles

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Better constraints on the magnitude of particulate export and the residence times of trace elements are required to understand marine food web dynamics, track the transport of anthropogenic trace metals in the ocean, and improve global climate models. While prior studies have been successful in constructing basin‐scale budgets of elements like carbon in the upper ocean, the cycling of particulate trace metals is poorly understood. The 238U‐234Th method is used here with data from the GP‐16 GEOTRACES transect to investigate the upper ocean processes controlling the particulate export of cadmium, cobalt, and manganese in the southeastern Pacific. Patterns in the flux data indicated that particulate cadmium and cobalt behave similarly to particulate phosphorus and organic carbon, with the highest export in the productive coastal region and decreasing flux with depth due to remineralization. The export of manganese was influenced by redox conditions at the low oxygen coastal stations and by precipitation and/or scavenging elsewhere. Residence times with respect to export (total inventory divided by particulate flux) for phosphorus, cadmium, cobalt, and manganese in the upper 100 and 200 m were determined to be on the order of months to years. These GEOTRACES‐based synthesis efforts, combining a host of concentration and tracer data with unprecedented resolution, will help to close the oceanic budgets of trace metals.

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Impact of the natural Fe-fertilization on the magnitude, stoichiometry and efficiency of particulate biogenic silica, nitrogen and iron export fluxes

Cited by 10 publications

References 96 publications

Particulate Trace Element Export in the North Atlantic (GEOTRACES GA01 Transect, GEOVIDE Cruise)

Particulate Trace Element Export in the North Atlantic (GEOTRACES GA01 Transect, GEOVIDE Cruise)

Ironing Out Fe Residence Time in the Dynamic Upper Ocean

Insights From the²³⁸U‐²³⁴Th Method Into the Coupling of Biological Export and the Cycling of Cadmium, Cobalt, and Manganese in the Southeast Pacific Ocean

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Impact of the natural Fe-fertilization on the magnitude, stoichiometry and efficiency of particulate biogenic silica, nitrogen and iron export fluxes

Cited by 10 publications

References 96 publications

Particulate Trace Element Export in the North Atlantic (GEOTRACES GA01 Transect, GEOVIDE Cruise)

Particulate Trace Element Export in the North Atlantic (GEOTRACES GA01 Transect, GEOVIDE Cruise)

Ironing Out Fe Residence Time in the Dynamic Upper Ocean

Insights From the238U‐234Th Method Into the Coupling of Biological Export and the Cycling of Cadmium, Cobalt, and Manganese in the Southeast Pacific Ocean

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Product

Resources

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Insights From the²³⁸U‐²³⁴Th Method Into the Coupling of Biological Export and the Cycling of Cadmium, Cobalt, and Manganese in the Southeast Pacific Ocean