Bioavailability and Biogeochemical Processes of Trace Metals in … · 2014. 3. 11. · trace...

subtropical North Pacific (Young et al.1991). However, the dissolution process oftrace metals in atmospheric aerosols suchas the Asian dust, which is a main supplyprocess of micronutrients to the surfaceseawater, has not been fully elucidated.Biologically-important trace metals, suchas iron, zinc and copper, are known to ex-ist mostly in the form of an organic com-plex with natural organic ligands inseawater, and thus their biological avail-ability, as well as their chemical reactiv-ity, may dynamically change by the pho-tochemical processes and biochemical re-duction in the surface water (Morel andPrice 2003). Therefore, in order to under-stand the chemical reactivity of trace met-als which are released from the atmos-pheric aerosols to the surface seawater, thebiological uptake of these elements bymicrobes, and the scavenging processes ofthese elements within the water column, itis necessary to conduct a study that con-siders interactions between the chemicalspeciation of trace elements and the bio-logical processes.

In the context of the foregoing scien-tific background, the Surface Ocean-Lower Atmosphere Study (SOLAS) has

Bioavailability and Biogeochemical Processes of TraceMetals in the Surface Ocean

S. Takeda1*, H. Obata2, A. Okubo2, M. Sato3 and Y. Kondo3

1Faculty of Fisheries, Nagasaki University, Bunkyo-machi 1-14, Nagasaki 852-8521, Japan2Atmosphere and Ocean Research Institute, The University of Tokyo, Kashiwanoha 5-1-5, Kashiwa, Chiba 277-8564, Japan3Graduate School of Agricultural and Life Sciences, The University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113-8657, Japan*E-mail: [email protected]

Keywords: Asian Dust; Trace Metals; Iron; Chemical Speciation; Phytoplankton

Introduction

Natural, or anthropogenic, forces on cli-mate change and global elemental cyclescould have significant influences on theatmospheric deposition of aerosols, includ-ing essential trace elements such as iron,to the surface ocean. As a result, inducedchanges in the structures of primary pro-duction, and the marine plankton food web,may affect the distribution of carbon be-tween the atmosphere and ocean, as wellas the production of the biogenic gasessuch as DMS, which lead to the feedbackreaction to the global climate (Jickells etal. 2005). An elucidation of the stimula-tion effects of biological activity by thetrace elements in aerosols is a key for abetter understanding of a series of theseprocesses.

In the subarctic western North Pacific,a deficiency of iron, and other trace met-als, in seawater has been shown to be animportant l imiting factor for aphytoplankton growth, and controls pri-mary production (Takeda and Tsuda 2005).In addition, a temporal increase in the pri-mary productivity, after the depositionevent of Asian dust, was reported in the

Western Pacific Air-Sea Interaction Study,Eds. M. Uematsu, Y. Yokouchi, Y. W. Watanabe, S. Takeda, and Y. Yamanaka, pp. 163–176.© by TERRAPUB 2014.

doi:10.5047/w-pass.a03.001

164 S. TAKEDA et al.

been established as one of the core projectsunder the International Geosphere Bio-sphere Programme (IGBP), and the eluci-dation of the dissolution process of traceelements derived from atmospheric aero-sols to the seawater, and its biological uti-lization in the pelagic ecosystem, is oneof the important topics. In contrast to re-cent activities investigating the influenceof dust, derived from the Sahara, on ma-rine biogeochemical cycles in the AtlanticOcean, the promotion of an integratedstudy, based on the latest knowledge ofatmospheric chemistry, chemical oceanog-raphy and biological oceanography, wasstrongly needed in the western North Pa-cific, where a large quantity of atmosphericdeposition occurs by Asian dust events.

In this study, we have investigated thebiogeochemical processes of trace metals,which are supplied through the depositionof atmospheric aerosols such as Asian dust,and its bioavailability for phytoplanktongrowth in the surface waters of the west-ern North Pacific Ocean, from the view-point of the following three questions forthe purpose of clarifying how essentialtrace elements, such as iron, are suppliedin a form available for phytoplankton fromthe aerosols which are deposited in thewestern North Pacific:

(1) What is the major factor control-ling the solubility of trace elements in theaerosols?

(2) What is the dominant chemical formof trace elements that are released from theaerosols into the seawater?

(3) What kind of chemical form of thetrace elements can the phytoplankton usefor their growth in the surface ocean?The purpose of this study has been to quan-titatively evaluate the relationship betweenthe supply of trace elements from the at-mosphere and changes in the biologicalproductivity in the surface waters, consid-ering not only the supply flux, but also thephysical and chemical speciation of traceelements in the seawater. New knowledge

obtained by this study could make a sig-nificant contribution to a better under-standing of the elemental cycles and theroles of the biological carbon pump in theocean, and, consequently, the prediction ofthe response of the marine ecosystem tofuture climate change.

Methods

In addition to the oceanographic obser-vations in the subarctic and subtropicalwestern North Pacific, on-board cultureexperiments, and atmospheric sampling onland stations, were conducted togetherwith aerosol dissolution experiments andphytoplankton culture experiments in thelaboratory.

Solubility of trace elements in aerosolsTotal deposition samples were col-

lected at three stations (Hedo in Okinawa,Kushiro in Hokkaido and Otsuchi in Iwate)in Japan during the high dust season, whenChinese Loess (Kosa) frequently reachesJapan. We determined the total and solu-ble fractions of trace elements in the totaldeposition samples and the solubility byusing a high-resolution inductively-cou-pled plasma (ICP) mass spectrometer(Finnigan Element2, Thermo ElectronCo.), and investigated the effects of anthro-pogenic substances on the solubility.

Speciation of trace elements derived fromaerosol in seawater

We have established a sensitive methodof determining Fe(II) in seawater, and wehave investigated the distributions ofFe(II) in surface seawater. To understandthe scavenging processes of trace metalsin seawater by biogenic particles, producedduring phytoplankton blooms,biogeochemical cycles of rare earth ele-ments in surface waters were investigatedduring the iron fertilization experiment inthe western subarctic North Pacific(SEEDS-II).

Biogeochemical Processes of Trace Metals 165

Chemical form of trace element used forphytoplankton growth

On-board culture experiments wereconducted using surface waters with anatural phytoplankton assemblage in thesubarctic and subtropical western NorthPacific by adding atmospheric dry/wetdeposition samples collected at the Japa-nese coast and the sea. Increases inphytoplankton biomass and changes indominant phytoplankton groups were ex-amined during the incubation. In addition,laboratory culture experiments were car-ried out using a diatom culture strain iso-lated from the subarctic western NorthPacific to evaluate the biologically-avail-able fraction of iron included in the atmos-pheric deposition samples.

Based on the results obtained fromthese studies, the atmospheric depositionfluxes of trace elements, in a form avail-able for phytoplankton growth, were esti-mated, and a main process that controls thebioavailability of trace elements originat-ing from atmospheric deposition, was ex-tracted to evaluate the role of trace ele-ments in the interaction of the atmosphereand ocean.

Results and Discussion

What is the major factor controlling thesolubility of trace elements in the aerosols?(1) Dissolution process of iron from theAsian dust particle

The dissolution of iron from the Asiandust standard particle (CJ-2) was examinedby a dissolution experiment using a flow-through system with artificial seawater.Iron concentration in the eluted seawatershowed two peaks just after the initiationof the seawater permeate and after sevenhours (Fig. 1). This result suggests that thedissolution of highly-reactive iron oc-curred at the surface of the dust particles,and also the flush out of small colloidaliron occurred during the initial phase ofthe contact of seawater with the CJ-2 par-

ticles. Less reactive iron was then slowlyreleased in the dissolved and colloidal frac-tions from the CJ-2 particles. Ooki et al.(2009) reported that the dissolution rate ofiron in the Asian dust strongly dependedon the particle size, and, therefore, furtherstudy is needed to elucidate the magnitudeand time-scale of changes in the particlesize of Asian dust after deposition into thesurface seawater.

The addition of the model iron-complexing organic ligand, DFB, to theseawater did not stimulate the dissolutionof iron from the Asian dust particles within24 hours, and there was no clear differencein the solubility of dust iron between theartificial seawater and the filtered surfaceseawater, which contained natural organicligands, collected from the subarctic west-ern North Pacific. Therefore, the existenceof iron-complexing organic ligands at con-centrations usually observed in the surfacewater (a few nM) may not strongly accel-erate the dissolution of iron from the dustparticles within a timescale of a few days.However, considering the residence timeof dust particles in the surface mixed layer,which had been estimated to be severalweeks, it cannot be excluded that the iron-complexing organic ligands are playing animportant role in maintaining the iron in adissolved form after the release from dustparticles on a longer timescale.

Fig. 1. Changes in the iron concentra-tion in the artificial seawater eluted fromthe Asian dust standard particle (CJ-2).


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(2) Solubility and origin of trace metals inatmospheric deposition samples

The averaged atmospheric depositionof Al was the highest among the trace met-als at Cape Hedo (Okinawa), Kushiro(Hokkaido) and Otsuchi (Iwate) in 2008,which was consistent with the crustalabundance. The total deposition flux ofiron was 194 mg/m2/day in Kushiro.

The percentages of particulate fractionsto total fractions were higher for scandium,aluminum and iron, than those for manga-

nese, cobalt, copper, zinc, cadmium andlead. The percentages were lower at lowerpH conditions for most trace metals (Fig.2). The enrichment factors, calculated fromaluminum concentrations, indicated thatiron, titanium and scandium were derivedfrom the crust, but others were influencedby human activities (Fig. 3). For example,Mn, Co and Th, which showed relatively-high enrichment factors, were highly cor-related with other components other thanthe crustal component, which probably

Fig. 3. Al-normalized enrichment factors of trace metals at KU and HE stations.

Fig. 4. Relationship between particulate/total (%) and enrichment factor values for Mn, Zn,Cd, and Pb at HE station.


pogenic substances, were more easily dis-solved than those in the samples collectedat the Kosa event (Fig. 4). The soluble frac-tions of iron were about 6% collected inCape Hedo, which was 4 times higher thanthose at the Kosa event. The anthropogenicsubstances largely affect the solubility oftrace metals by lowering the pH of aero-sol (Hsu et al. 2010), which is an impor-

Fig. 5. Horizontal distribution of dissolved iron (nM) in the surface water observed in thesubarctic (top) and the subtropical (bottom) western North Pacific Ocean.

indicates the effect of anthropogenic emis-sions. However, Al in the total depositionsamples collected in Cape Hedo might bepartially derived from anthropogenic sub-stances. We noted that scandium is morerepresentative for crustal substances thanis aluminum in this case.

Generally, trace metals in the totaldeposition samples, influenced by anthro-


tant process for the supply of dissolvedfractions of trace metals to the sea surfaces.

What is the dominant chemical form oftrace elements that are released from theaerosols into the seawater?(1) Horizontal distribution of trace met-als in the oceanic surface waters

Continuous sampling of the surfacewater along several transects were con-ducted in the subarctic and the subtropicalwestern North Pacific using a trace-metalclean Fish sampling system (Fig. 5). Re-gardless of some variations in thephytoplankton abundance, the dissolved

iron concentration was extremely lowthroughout the observation area in thesubarctic waters. It seems that the rapiduptake of dissolved iron by aphytoplankton assemblage under condi-tions of iron deficiency can suppress pos-sible changes in the dissolved iron concen-tration by the atmospheric deposition ofmineral dust or anthropogenic aerosols. Onthe other hand, there was a west-east gra-dient in the dissolved iron concentrationin accordance with the change in the depo-sition flux of Asian dust in the subtropicalwaters from the East China Sea to the west-ern North Pacific. Observed high dissolved

Fig. 6. Conceptual diagram of the analytical system for detecting Fe(II) in seawater.

Fig. 7. Time variation of temperature and Fe(II) in surface waters of the western subarcticNorth Pacific.


iron concentrations in the western regionssuggest that dissolved iron in the surfacewater was mostly complexed by naturalorganic ligands.(2) Fe(II) in surface waters

In seawater, trace metals exist in vari-ous chemical forms, such as organic com-plexes, and inorganic forms. Availabilityof the trace metals in seawater byphytoplankton depends on the chemicalforms of the trace metals. For Fe, Fe(II) isan important inorganic form in seawaterbecause Fe(II) is an easily-available formfor marine phytoplankton.

We have investigated a sensitive ana-lytical method of detecting Fe(II) inseawater based on an existing chemilumi-nescence method (Hansard and Landing2009). The conceptual diagram of the flowanalytical system is shown in Fig. 6.

Using this system, the detection limitof Fe(II) in seawater was 5–13 pM onboardthe ship. In the western subarctic NorthPacific, the Fe(II) concentrations in sur-face waters were 5~43 pM (Fig. 7), whichwas almost the same level as reported in aprevious study (Roy et al. 2008).

Based on previous studies, Fe(II) isproduced, as expected, by photoreductionin surface waters. However, we could notobserve a clear relationship between Fe(II)and the light intensity. For more than 12hours, about 20 pM of Fe(II) was kept insurface waters. In polar regions, it isknown that oxidation rates of Fe(II) be-come slower at a lower temperature (Crootet al. 2001). Also in the western subarcticNorth Pacific, Fe(II), produced by photore-duction, might be kept for a relatively longtime. We performed UV-irradiation experi-ments to decompose naturally-occurringorganic matter in seawater. After the UV-irradiation, the oxidation rates of Fe(II)become faster, which indicates that thenaturally-occurring organic matter inseawater affects the oxidation rate of Fe(II)in seawater.

(3) Rare earth elements in seawater dur-ing the phytoplankton bloom induced byan iron fertilization experiment

During the iron fertilization experimentin the western subarctic North Pacific(SEEDS-II), we investigated rare earth el-ements (REE) in seawater. After thephytoplankton bloom, dissolved REE rap-idly decreased, though total REE concen-trations (including particulate fractions)were almost constant in seawater (Fig. 8).Decreases of light REE were more remark-able than those of heavy REE. Light REEare more easily complexed with organicligands on the surface of biogenic parti-cles (Sholkovitz et al. 1994), which is con-sistent with the observed trend of REEduring the phytoplankton bloom. The scav-

Fig. 8. North-Pacific-Deep-Water nor-malized patterns of REE in surface watersduring the Fe fertilization experiment(SEEDS-II). D-REE: REE concentrations indissolved fraction (0.2-mm pore size); AS-REE: REE concentrations in acid-solublefraction.


enging process of REE could be applica-ble for other trace metals, indicating thatthe REE are suitable tracers for particle-reactive trace metals in seawater.

What kind of chemical form of trace ele-ments can the phytoplankton use for theirgrowth in the surface ocean?(1) Biological availability of iron releasedfrom the Asian dust

On-board culture experiments wereconducted using surface waters collected

Fig. 9. Relationship between the dissolved iron concentration increased by the addition ofatmospheric dust samples, and the specific growth rate of the diatom culture strain. Atmos-pheric dust samples collected in Hedo, Otsuchi or Kushiro was added to the culture media toobtain the same final concentration of total iron at 5 nM. The red line in the figure indicates thegrowth rate of the diatom cultured with iron sulfate spiked at the corresponding dissolved ironconcentration.

Fig. 10. Increase reply of the phytoplankton crowd of the North Pacific subarctic zone areato addition of an atmosphere descent thing and the rainwater.

from the subarctic Oyashio waters by add-ing the Asian dust standard particle (CJ-2)or inorganic iron sulfate, and the growthresponse of the phytoplankton assemblagewere monitored for 5 days. Although sig-nificant growth stimulation of diatoms,such as Chaetoceros spp., by inorganiciron addition suggested that thephytoplankton were under iron stress, theobserved growth response to the CJ-2 ad-dition was relatively small. The biologi-cal availability of iron in the atmospheric


Fig. 11. Cell density (top) and relative intensity of cellular chlorophyll fluorescence (bottom)of each phytoplankton group observed after 24 hours during enrichment experiments con-ducted in the East China Sea (top) and the subtropical western North Pacific (bottom). Addi-tions to the surface water were made with 1 nM CuSO4, 1 nM FeSO4, 100 nM iron-complexingorganic ligand (DFB), 4, 40 and 400 mg/L Asian dust collected in Nagasaki, 0.6 mM NaNO3, 0.6mM NH4Cl, 0.1 mM NaHPO4, or 3% (v/v) rain water collected at the western North Pacificduring the cruise.

deposition samples collected at the coastalareas in Japan was examined by laboratoryculture experiments using a diatom culturestrain isolated from the subarctic North

Pacific. The growth rate of iron-limiteddiatom cells showed a clear correlationwith iron concentration in the dissolvedphase (Fig. 9), suggesting that most of the


iron remaining in the particle phase wasnot available for phytoplankton growth.(2) Enhancement of phytoplankton growthin the surface water by the addition of at-mospheric deposition samples

Atmospheric deposition samples col-lected at Kushiro in spring, rain water, andatmospheric aerosols collected at the sea,were added to the surface water obtainedfrom the high-nitrate, low-chlorophyll re-gion of the subarctic western North Pacific,and the water samples with an ambientphytoplankton assemblage were incubatedon board for 6 days. The addition of at-mospheric deposition samples stimulatedthe phytoplankton growth mainly in largediatom species (Fig. 10). There was a sig-nificant relationship between the magni-tude of phytoplankton growth response andthe amount of added iron in the dissolvedfraction. The atmospheric deposition sam-ples affected by anthropogenic sourcestended to have a higher amount of biologi-cally-available iron compared to thosewithout such influences.

Since atmospheric aerosols of an an-thropogenic origin sometime contain highconcentrations of trace elements having atoxicity to marine microbes, such as cop-

per and cadmium, the inhibition ofphytoplankton production by atmosphericdeposition has been discussed (Paytan etal. 2009). However, inhibition of algalgrowth was not observed in our incubationexperiments using atmospheric depositionsamples affected by anthropogenic activi-ties, suggesting that contamination of at-mospheric aerosols by toxic heavy metalsover the western North Pacific is not sohigh at present. It is possible that excessorganic ligands in the surface water areplaying a role in reducing the toxicity ofdeposited heavy metals by forming lessreactive organic complexes. Another ex-periment conducted in the East China Seashowed that the plankton assemblage re-leased copper-complexing organic ligandsin response to the addition of inorganiccopper sulfate. Therefore, it is necessaryto consider the biological responses to theatmospheric deposition, which may alterthe chemical speciation of released metalions and their biological availability in thesurface water.

In the oligotrophic surface waters of thesubtropical western North Pacific and thesoutheastern East China Sea, growthstimulation of phytoplankton (e.g.

Fig. 12. Changes in dissolved iron, chlorophyll a and nutrient concentrations in the surfacewater along the E-W cruise track at 48∞N in the subarctic western North Pacific. The area of thevolcanic ash deposition is indicated by a red arrow.


Synechococcus) by the addition of Asiandust, and rain water samples, was observedmainly due to an increase in inorganic ni-trogen concentration together with the sup-ply of micronutrients such as iron (Fig. 11).The results also indicated that physiologi-cal activity of unicellular nano-sizecyanobacteria, which might bediazotrophic, was enhanced by the supplyof ammonium ions and dissolved iron.Other incubation experiments conducted inthe Indian Ocean revealed that small-sizephytoplankton could respond to the addi-tion of rain water within 1 day, while ittook about 3 days for large-sizephytoplankton to respond.(3) Possible influences on phytoplanktonproductivity by volcanic ash deposited inthe subarctic North Pacific during summer

During the subarctic North Pacificcruise in August, 2008, we encountered anatmospheric deposition event of volcanicash which had been transported from Mt.Okmok in the Aleutian Islands. Four daysafter the volcanic ash deposition, we ob-served a growth response of the residentphytoplankton assemblage in the depositedwaters (Fig. 12), and chlorophyll a con-centrations in the surface waters increasedto approximately 3 times compared withits value just before the volcanic ash depo-sition event. Improvement of photosyn-thetic activity of the residentphytoplankton was also confirmed in thesewaters, where pennate diatoms andprymnesiophytes dominated in thephytoplankton communities.

There were unusually many volcaniceruptions at the Aleutian Islands, and theKamchatka Peninsula, during the summerof 2008, when we observed a growthstimulation of the phytoplankton assem-blage in the subarctic western North Pa-cific. In the same year, similar increasesin sea-surface chlorophyll a concentrationswere observed over wide areas of the east-ern subarctic North Pacific, and its rela-tion to the volcanic ash deposition was

considered (Hamme et al. 2010). It hasbeen reported that 35–107 nmol iron couldbe released from 1 g of volcanic ash within1 hour, when the ash is suspended inseawater in a ratio of 1:400 (Olgun et al.2011). Reactions of ash particles withacidic fog during the atmospheric transpor-tation process may enhance the solubilityof iron, and other trace elements, in thevolcanic ash, and thus volcanic ash couldbe one of the important sources of traceelements in the subarctic North Pacific.

Conclusions

In the surface waters of the westernNorth Pacific Ocean, we investigatedbiogeochemical processes of trace metals,which were supplied through the deposi-tion of atmospheric aerosols, such as Asiandust, and its bioavailabili ty forphytoplankton growth. Atmospheric aero-sols influenced by anthropogenic sources,during transport from the Asian continentto the North Pacific, showed a relativelyhigh trace-metal solubility. Our resultsshowed that 1–20% of iron in the atmos-pheric aerosols deposited in the westernNorth Pacific became a dissolved formwhich was available for phytoplankton inthe surface water. However, the solubilityof Asian dust varied significantly due toinfluences of the mixing with anthropo-genic aerosols, as well as the low pH ow-ing to reactions with nitric acid and sul-phuric acid in the urban atmosphere, andit is difficult to apply a single averagevalue as the solubility of Asian dust inseawater. Deposited dust particles maycontinuously supply dissolved iron tophytoplankton, if these particles remainsuspended in the euphotic zone. A detailedstudy is needed to understand the behav-iour of deposited aerosol particles in thewater column. Regarding the trace metalsother than iron, we observed a high solu-bility (20–80%) for manganese, zinc andcopper, in which the contribution of an-


thropogenic sources were significant.However, atmospheric deposition fluxes ofthese elements were not so large comparedwith ambient concentrations in the surfacewater, suggesting that atmospheric aero-sols played a minor role in thebiogeochemical cycles of these element inthe surface ocean.

Volcanic ash depositions were found toinitiate phytoplankton blooms in the high-nitrate, low-chlorophyll waters of thesubarctic North Pacific, where the ambi-ent phytoplankton assemblage was undera strong iron-limitation stress. Asian dusthas been considered as an important ironsource for the subarctic phytoplanktoncommunities, but the peak of the Asiandust deposition event usually occurs inspring, when deep mixing of the surfacewater prevents phytoplankton growth bylight limitation. On the other hand, vol-canic eruption could happen throughoutthe year, and, thus, iron supply from vol-canic ash may have a strong impact onphytoplankton productivity during thestratified summer. Although the futuredesertification of the Asian continent mayresult in a lengthening of the high-dustseason, our findings support the conclu-sion that volcanic ash is playing an impor-tant role as a source of limiting trace ele-ments in controlling phytoplankton pro-ductivity in the subarctic North Pacificwhich is surrounded by a lot of active vol-canoes.

Along with the ongoing economic de-velopment of East Asia, the atmosphericdeposition of anthropogenic materials willcontinuously increase in the western NorthPacific (Duce et al. 2008). Therefore, therelative importance of atmospheric nutri-ent supply in the biogeochemical processeswithin the surface ocean will increase inthe future. Our findings relating tophytoplankton responses to the atmos-pheric supply of trace elements could beintroduced into global physical-ecosystemmodels that describe the interaction be-tween the atmosphere and ocean. Throughsuch scientific efforts, this study wouldcontribute to a better prediction of futureclimate changes and the global impact ofhuman activities on marine ecosystems.

Acknowledgements

We would like to express our gratitude to Dr. Ono,Dr. Nishioka, Dr. Fukuda, and Dr. Furutani, for theirhelp in collecting the samples. We owe our samplingto the Atmosphere and Aerosol Monitoring Stationat Cape Hedo (NIES). We would like to thank Mr.Jinyoung for his help in the ion analysis usingUematsu laboratory’s ion chromatography system atORI. We are grateful to the Directors, researchers,captains, and the crews, of the R/V Hakuho Marufor their help. This study was financially supportedby the Ministry of Education, Culture, Sports, Sci-ence and Technology, Japan, the Grant-in-Aid forScientific Research in Priority Areas “Western Pa-cific Air-Sea Interaction Study (W-PASS)” (GrantNo. 18067006). This research is a contribution tothe Surface Ocean-Lower Atmosphere Study(SOLAS) Core Project of the InternationalGeosphere-Biosphere Programme (IGBP).

References

Croot PL, Bowie AR, Frew RD, Maldonado MT, Hall JA, Safi KA, La Roche J, Boyd PW, Law CS (2001)Retention of dissolved iron and FeII in an iron induced Southern Ocean phytoplankton bloom.Geophys. Res. Lett. 28, 3425–3428.

Duce RA, LaRoche J, Altieri K, Arrigo KR, Baker AR, Capone DG, Cornell S, Dentener F, Galloway J,Ganeshram RS, Geider RJ, Jickells T, Kuypers MM, Langlois R, Liss PS, Liu SM, Middelburg JJ, MooreCM, Nickovic S, Oschlies A, Pedersen T, Prospero J, Schlitzer R, Seitzinger S, Sorensen LL, UematsuM, Ulloa O, Voss M, Ward B, Zamora L (2008) Impacts of atmospheric anthropogenic nitrogen onthe open ocean. Science 320, 893–897.

Hamme RC, Webley PW, Crawford WR, Whitney FA, DeGrandpre MD, Emerson SR, Eriksen CC,


Giesbrecht KE, Gower JFR, Kavanaugh MT, Peña MA, Sabine CL, Batten SD, Coogan LA, GrundleDS, Lockwood D (2010) Volcanic ash fuels anomalous plankton bloom in subarctic northeast Pa-cific. Geophys. Res. Lett. 37, L19604, doi:10.1029/2010GL044629.

Hansard SP, Landing WM (2009) Determination of iron(II) in acidified seawater samples by luminolchemiluminescence. Limnol. Oceanogr. Method 7, 222–234.

Hsu S-C, Liu SC, Arimoto R, Shiah F-K, Gong G-C, Huang Y-T, Kao S-J, Chen J-P, Lin F-J, Lin C-Y, HuangJ-C, Tsai F, Lung S-CC (2010) Effects of acidic processing, transport history, and dust and sea saltloadings on the dissolution of iron from Asian dust. J. Geophys. Res. 115, D19313, doi:10.1029/2009JD013442.

Jickells TD, An ZS, Andersen KK, Baker AR, Bergametti G, Brooks N, Cao JJ, Boyd PW, Duce RA, HunterKA, Kawahata H, Kubilay N, LaRoche J, Liss PS, Mahowald N, Prospero JM, Ridgwell AJ, Tegen I,Torres R (2005) Global iron connections between desert dust, ocean biogeochemistry, and cli-mate. Science 308, 67–71.

Morel FMM, Price NM (2003) The Biogeochemical cycles of trace metals in the oceans. Science 300,944–947.

Olgun N, Duggen S, Croot PL, Delmelle P, Dietze H, Schacht U, Óskarsson N, Siebe C, Auer A, Garbe-Schönberg D (2011) Surface ocean iron fertilization: The role of airborne volcanic ash from sub-duction zone and hotspot volcanoes and related iron-fluxes into the Pacific Ocean. GlobalBiogeochem. Cycles, doi:10.1029/2009GB003761 (in press).

Ooki A, Nishioka J, Ono T, Noriki S (2009) Size dependence of iron solubility of Asian mineral dustparticles. J. Geophys. Res. 114, D03202, doi:10.1029/2008JD010804.

Paytan A, Mackey KRM, Chen Y, Lima ID, Doney SC, Mahowald N, Labiosa R, Post AF (2009) Toxicityof atmospheric aerosols on marine phytoplankton. PNAS 106, 4601–4605.

Roy EG, Wells ML, King DW (2008) Persistence of iron(II) in surface waters of the western subarcticPacific. Limnol. Oceanogr. 53, 89–98.

Sholkovitz ER, Landing WM, Lewis BL (1994) Ocean particle chemistry: The fractionation of rare earthelements between suspended particles and seawater. Geochim. Cosmochim. Acta 58, 1567–1580.

Takeda S, Tsuda A (2005) An in situ iron-enrichment in the western subarctic Pacific (SEEDS): introduc-tion and summary. Prog. Oceanogr. 64, 95–109.

Young RW, Carder KL, Betzer PR, Costello DK, Duce RA, DiTullio GR, Tindale NW, Laws EA, UematsuM, Merrill JT, Feely RA (1991) Atmospheric iron inputs and primary productivity: Phytoplanktonresponses in the North Pacific. Global Biogeochem. Cycles 5, 119–134.

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