Saharan input of phosphate to the oligotrophic water of the open western Mediterranean Sea

Ridame, Céline; Guieu, Cécile

doi:10.4319/lo.2002.47.3.0856

Cited by 213 publications

(209 citation statements)

References 55 publications

(66 reference statements)

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“…Thus, the response of the Z treatment (N limited) after 48 h as somewhat lower than ZN (P limited) for both variables and was significantly lower than the response of the ZNA treatment where the added limiting nutrient P concentration was 40 times higher than Z and ZN (Figures 2, 3). This confirms that the dust provided a bioavailable (leachable) source of N and P as found in other studies (Herut et al, , 2002Migon et al, 2001;Ridame and Guieu, 2002) and relieved the phytoplankton community of N and P co-limitation (Kress et al, 2005;Krom et al, 2005;Pitta et al, 2005;Tanaka et al, 2011).…”

Section: Discussionsupporting

confidence: 76%

Response of the Eastern Mediterranean Microbial Ecosystem to Dust and Dust Affected by Acid Processing in the Atmosphere

et al. 2016

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Acid processes in the atmosphere, particularly those caused by anthropogenic acid gases, increase the amount of bioavailable P in dust and hence are predicted to increase microbial biomass and primary productivity when supplied to oceanic surface waters. This is likely to be particularly important in the Eastern Mediterranean Sea (EMS), which is P limited during the winter bloom and N&P co-limited for phytoplankton in summer. However, it is not clear how the acid processes acting on Saharan dust will affect the microbial biomass and primary productivity in the EMS. Here, we carried out bioassay manipulations on EMS surface water on which Saharan dust was added as dust (Z), acid treated dust (ZA), dust plus excess N (ZN), and acid treated dust with excess N (ZNA) during springtime (May 2012) and measured bacterioplankton biomass, metabolic, and other relevant chemical and biological parameters. We show that acid treatment of Saharan dust increased the amount of bioavailable P supplied by a factor of ∼40 compared to non-acidified dust (18.4 vs. 0.45 nmoles P mg −1 dust, respectively). The increase in chlorophyll, primary, and bacterial productivity for treatments Z and ZA were controlled by the amount of N added with the dust while those for treatments ZN and ZNA (in which excessive N was added) were controlled by the amount of P added. These results confirm that the surface waters were N&P co-limited for phytoplankton during springtime. However, total chlorophyll and primary productivity in the acid treated dust additions (ZA and ZNA) were less than predicted from that calculated from the amount of the potentially limiting nutrient added. This biological inhibition was interpreted as being due to labile trace metals being added with the acidified dust. A probable cause for this biological inhibition was the addition of dissolved Al, which forms potentially toxic Al Krom et al.Acidified Dust to E. Med. Microcosm nanoparticles when added to seawater. Thus, the effect of anthropogenic acid processes in the atmosphere, while increasing the flux of bioavailable P from dust to the surface ocean, may also add toxic trace metals such as Al, which moderate the fertilizing effect of the added nutrients.

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Section: Discussionsupporting

confidence: 76%

Response of the Eastern Mediterranean Microbial Ecosystem to Dust and Dust Affected by Acid Processing in the Atmosphere

et al. 2016

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“…Chen et al [2006] extracted aerosol samples in pure water for 30 min with sonication and obtained slightly higher SRP yields than with samples extracted in low-nutrient seawater (LNSW). Ridame and Guieu [2002] also observed greater SPR yields in pure water than in LNSW for gently stirred solutions containing Saharan soil particles. However, Nehring [1976] found that although the extraction rate of P from Saharan dust was slower in seawater than in pure water, the amount of extractable P was similar when longer extraction times were used.…”

Section: Sample and Data Analysismentioning

confidence: 90%

“…It is unclear whether Chen et al [2006] would have obtained different results if they had employed a longer extraction time. Also, neither Chen et al [2006] nor Ridame and Guieu [2002] used buffered pure water for their extractions.…”

Section: Sample and Data Analysismentioning

confidence: 99%

Atmospheric P deposition to the subtropical North Atlantic: sources, properties, and relationship to N deposition

et al. 2013

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[1] Biogeochemical studies show that the surface waters of the subtropical North Atlantic are highly phosphorus (P) stressed. Human activity may exacerbate phosphorus stress by enhancing atmospheric nitrogen (N) deposition and raising N/P ratios in deposition. However, the magnitude of this effect is unclear, in part, because atmospherically deposited phosphorus sources are not well known, particularly the contribution from organic phosphorus. Here we report measurements of phosphorus in aerosols and wet deposition at Miami and Barbados. African dust is the major aerosol P source at both Miami and Barbados, containing~880 ppm total phosphorus and~70 ppm soluble reactive phosphorus (SRP). Organic compounds contribute, on average, 28%-44% of soluble phosphorus in precipitation. Because of dust transport seasonality, phosphorus inputs to the North Atlantic are expected to be highly variable with 2-10 times more P deposition during summer than winter. Pollution is also an important contributor to total and soluble phosphorus in Miami aerosols and deposition. Estimated SRP deposition in Barbados and Miami is 0.21 and 0.13 mmol m À2 d À1 phosphorus, respectively. Inorganic nitrogen in excess of Redfield ratio expectations in deposition was very different between the sites, totaling 21-30 and 127-132 mmol m À2 d À1 nitrogen in Barbados and Miami, respectively; the high deposition rates at Miami are linked to pollutants. Including soluble organic nitrogen and phosphorus halved the estimates of excess nitrogen in Barbados wet deposition. Thus, the organic phosphorus fraction is important in the assessment of the magnitude of biogeochemical change of the North Atlantic caused by atmospheric deposition.Citation: Zamora, L. M., J. M. Prospero, D. A. Hansell, and J. M. Trapp (2013), Atmospheric P deposition to the subtropical North Atlantic: sources, properties, and relationship to N deposition,

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“…Two exposure durations were chosen to simulate natural conditions: 24 hours and 7 days. These exposure durations were assumed to be representative of the contact time between the atmospheric particles and seawater [Ridame and Guieu, 2002]. During incubations, the flasks were stirred every 12 hours.…”

Section: Methodsmentioning

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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Saharan input of phosphate to the oligotrophic water of the open western Mediterranean Sea

Abstract: A Saharan soil, considered as a proxy for Saharan aerosols, was used to perform a series of dissolution experiments: various amounts of Saharan soil were exposed to ultrapure water and seawater for varying lengths of time.

Cited by 213 publications

References 55 publications

Response of the Eastern Mediterranean Microbial Ecosystem to Dust and Dust Affected by Acid Processing in the Atmosphere

Response of the Eastern Mediterranean Microbial Ecosystem to Dust and Dust Affected by Acid Processing in the Atmosphere

Atmospheric P deposition to the subtropical North Atlantic: sources, properties, and relationship to N deposition

Dissolution of atmospheric iron in seawater

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