Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | , σ Fe of 56

Open Access δ 0.98 ‰ (2 ± 1.90 to 0.00 ‰ − Discussions set of chiton teeth 1.47 ff − , and erent species from the ff 1,4 Biogeosciences Fe of 56 δ erent locations in the Atlantic and ff , A. Matthews 3 erent organisms. ff 5534 5533 , J. Vinther 2 Fe), probably reflecting a combination of geograph- 56 δ 2 , 3 specimens), while Mopalia muscosa, which feeds primarily on σ erent feeding habits but collected from the same location, we infer a ff Fe (relative to IRMM-014) in chiton teeth range from , J. A. Schuessler 1 56 ) uncertainty in δ σ 0.26 ‰ (2 ± ective tracer of ambient oceanic conditions and biogeochemical cycling. Here, in a 0.05 ‰ (2 Values of 0.65 ff This discussion paper is/has beenPlease under refer review to for the the corresponding journal final Biogeosciences paper (BG). in BG if available. Institute of Earth Sciences, TheGerman Hebrew Research University Centre of for Jerusalem, Geosciences Jerusalem, GFZ, Israel Sect. 3.4, EarthSchool Surface Geochemistry, of Earth Sciences, UniversityNational of Natural Bristol, History Bristol, Collections, UK Institute of Earth Sciences, Hebrew University of ± topic signatures. Tonicella lineata,− which feeds ongreen red algae, shows algae, lighter has5 isotopic a specimens). values Although with mean a chitonsisotopic mean are signature, not these simple preliminary recorders resultstion of suggest concerning the that Fe Fe ambient biogeochemical isotopes seawaterused cycling provide Fe to in informa- probe near sources shore of environments, Fe and in the might diets be of di ( ical control andsurface biological seawater fractionation Fe processes. isotopeFe Comparison data isotope with shows compositions relative published a tosame consistent local seawater. locality Strikingly, negative two in o di the North Pacific (Puget Sound, Washington, USA) have distinct iso- e pilot study to measurein Fe modern isotopes marine in chitonPacific marine oceans radula invertebrates, to collected we assess examine fromisotopic the Fe di signatures range isotopes reflect of isotopic seawaterthat values, have values. very and Furthermore, di to bypossible test comparing link whether between two or diet species not and Fe the isotopic signatures. Chitons (Mollusca) aretongue) marine containing invertebrates high thatbearing concentrations minerals. produce of As radula biomineralizedbiological Fe (teeth fractionation, magnetite isotope or Fe signatures and isotopes rasping are other in influenced chiton iron radula by might redox be processes expected and to provide an Abstract Iron isotope fractionation in marine invertebrates in near shore environments S. Emmanuel 1 2 Potsdam, Germany 3 4 Jerusalem, Jerusalem, Israel Received: 27 February 2014 – Accepted: 27Correspondence March to: 2014 S. – Emmanuel Published: ([email protected]) 11 AprilPublished 2014 by Copernicus Publications on behalf of the European Geosciences Union. Biogeosciences Discuss., 11, 5533–5555, 2014 www.biogeosciences-discuss.net/11/5533/2014/ doi:10.5194/bgd-11-5533-2014 © Author(s) 2014. CC Attribution 3.0 License. F. von Blanckenburg 5 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | erent feeding , aerosols, hy- ff ff erent species that ff 5536 5535 erent sources, including continental runo ff attempt to isolate the potential impact of diet on metal isotopic erent locations around the world. However, in this preliminary study first ff erent locations in the Atlantic and Pacific oceans to determine the range ff Here, in a preliminary study, we examine Fe isotopes in modern marine chitons col- However, a number of factors may influence the isotopic composition of Fe accumu- While studies have examined isotopic variations of Fe in marine rocks (e.g., specimens from di such an approach was not feasible, and instead samples were selected from the col- habits, we make a signatures. While our findingsthe are possible not pathways definitive, of the Fe biogeochemicallighting small cycling important new in new dataset near-shore directions sheds environments, for high- light future research. on 2 Methods Ideally, chiton samples would have been obtained from a field campaign that collected lected from di of isotopic values thatnatures might reflect be seawater values. encountered, Furthermore,were and by collected whether comparing from or two di not the these same isotopic geographical sig- location but have very di light magnetite during dissimilatory microbialson reduction et of al., Fe(III) 2005); oxyhydroxidescould (John- other also fractionate organisms, Fe such isotopesFe as as isotope a algae signatures result and of in biomineralizationBlanckenburg, even higher processes. 2002; the organisms Although Hotz, have chitons been 2011), themselves, of studied little metal (e.g., is isotopes Walczyk currently in andand known marine von environmental about invertebrates, factors, or the such the as naturalsignatures. influence geographical variation location that and biological diet, fractionation may have on those drothermal fluids, and oceanic crust alteration2007; Johnson (Sharma et et al., al., 2008; 2001; Homoky Anbarbrate et and teeth al., Rouxel, could 2012), therefore the change isotopic value withmarine recorded geographical organisms in location. inverte- and In addition, associated utilizationrole biological by in fractionation determining may also Fe play isotope an compositions. important Bacteria are known to form isotopically the relative contributions of di As the isotopic composition of Fe in seawater can vary spatially due to variations in ment using radula (orand rasping other tongue) iron made bearing upLowenstam, minerals, such of 1962a; as teeth Towe ferrihydrite, and impregnated goethite,Lowenstam with Lowenstam, and and Weiner, magnetite 1967; lepidocrocite 1989). (e.g., Due Lowenstam totopic and their signature Kirschvink, high of level 1996; of modern ironenvironments. chiton accumulation, radula the might Fe iso- be expected to reflect ambientlated oceanic in chiton teethnutrients at from any marine given algae, location. which Being in primarily turn herbivorous, absorb they nutrients extract directly from seawater. Matthews et al., 2004;ganisms Staubwasser that et accumulate al., significant 2006;ronmental amounts Severmann recorders. et of One al., Fe group could 2006), of(Fig. also marine marine 1a prove molluscs or- and to that b). might be Belonging fulfillon good to this the envi- the role class surface is Polyplacophora, of chitons these rocks molluscs graze and on other algae hard substrates in the near shore coastal environ- in the isotopic signatureredox state, of chemical iron. bonding Changesorganic-ligand environment, to bonding adsorption processes Fe properties, (e.g., isotope and MatthewsBeard ratios microbial et et al., occur and 2001, al., due 2008; 2003a,Johnson to Zhu et et b; shifts al., al., Brantley in 2005; 2002; et Teutschments et of al., al., these 2005; 2004; isotopes Crosby could Croalconditions et yield et in vital al., information both 2007), al., about present and geochemical 2004; day precise and and Welch measure- ecological past et environments. al., 2003; Iron plays a critical role1990; in De controlling Baar biological productivity et in al.,cycling the 1995; oceans Coale of (Martin et Fe et al., al., 1996), istentially and rewarding therefore understanding way the key to biogeochemical in reconstruct reconstructing past the marine conditions history is of to life examine on variations Earth. One po- 1 Introduction 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ESI and cient ffi Fe value from New Fe during 56 and an 58 δ Fe, matching erent species ff 1 − Ni on Fe were monitored 58 58 Tonicella lineata multi collector inductively Ni on Fe and 58 54 Tonicella marmorea PFA nebuliser for sample introduc- Cr on amplifier, H cones) of the bracketing 1 Fe and erent species – 54 − Ω ff 54 11 cient separation of Cr and Ni from Fe was 16), which is identical with the unprocessed and diluted to about 2 µgml ffi 5538 5537 Cr on Neptune Plus Jet Interface Pump 3 = Fe; 10 50 µLmin 7600) to resolve all Fe isotopes from polyatomic 54 n 56 ∼ > ect of prolonged exposure of Fe oxides to formalin ff Thermo Scientific Neptune 20 V on 0.02 (2SE, ∼ (5 %, 95 %) ± Ni, and corrections to Fe isotope ratios were made according m 60 ∆ 0.03 that feed on predominantly green algae and red algae respectively – − m/ Cr and 52 erent geographical locations were selected for analysis. A summary of the ff desolvating system with a After separation, the radula were then processed in a clean room facility, where they The protocol for sample preparation involved dissection of the chitons to extract the at masses to the method described in Schoenberg and von Blanckenburg (2005). In this study set of 18 chiton samplescoupled using plasma a mass spectrometermass (MC-ICP-MS) spectrometer at is GFZ equipped PotsdamApex-Q with in a Germany. The tion. Iron isotope analysesresolving were power performed in “medium”interferences mass (mainly resolution ArO, mode ArOH, (mass tails). and Potential ArN, interferences see from Weyer and of Schwieters, 2003, for de- for IRMM-014 of IRMM-014, within thesamples external were uncertainty dissolved of in thethe 0.3 M ion method. beam HNO Prior intensitiesstandard to ( (IRMM-014) isotope within 10 analysis, %. The Fe isotopic analyses were performed on a total by inductively coupled plasma-mass spectrometryPurity (ICP-MS; Agilent of 7500cx) analyses. Fefor analyte accurate solutions Fe isotope was analysesvon found using Blanckenburg, to the 2005). method be described Noteworthy,achieved, better e below eliminating (Schoenberg than and spectral 99 %, interferencesmass of which spectrometric measurements is of Fe su isotopeby ratios. The processing procedure was the also tested referencematographic separation material protocol IRMM-014 as repeatedly the through samples. the This same method yielded chro- a were digested using ultrapure concentratedremove HCl; hydrogen any peroxide residual was also organic addedon material. to a The hot digested plate sample andcolumns re-dissolved solution to in was isolate 6 evaporated M Feand HCl (Zhu quantitative and et recovery then al., passed of 2002; through iron Archer chromatographic after and the Vance, column 2004). Purity separation procedure of samples was verified radula sac containing thewas magnetite-capped used to teeth; separate atwo the magnetic symmetric radula separation from rows technique theradula of can organic teeth vary matter. depending (Fig. A onresents single 1a). the a radula The homogenised species. is sample Here, total comprising each madevidual all number isotopic of specimen. teeth analysis and of Due (Table a 1) to size complete rep- Brunswick, the radula of small the for teeth size each teeth indi- of of from theto each 8 produce radula one for individual isotopic specimens measurement.duplicate, One were and sample a combined (YPM12739-16) total was and of processed homogenized 18 in values are reported here. tide line leading toately periodic below dry the and eulittoral floodthe zone periods. seafloor and The is in sublittoral permanently the zonewithin underwater. starts eulittoral the Sunlight immedi- zone photic penetrates zone. so to that both the eulittoral and sublittoral zones are samples is given inOcean, Table 1. chitons To from represent Bermuda highPacific and and Ocean, New low samples Brunswick, latitude from Canada, sitesaddition, Panama were from and from sampled; the Washington from the Atlantic State, the USA,Mopalia Washington muscosa were locality, selected. two In di were selected for comparison. Ofeulittoral the (intertidal) 5 zone, species investigated whiletoral in 2 zone this are is study, characterised 3 found by inhabit in tidal the activity the and sublittoral extends (neritic from the zone). low The tide line eulit- to the high were collected in the earlyantimicrobial 1900’s and agent; preserved although in the formalin, e whichis primarily not acts as known, an wethe samples. assume A no total of mineralogicalfrom 24 or 4 individual isotopic di chiton specimens changes representing to 5 di have occurred in lections at the Peabody Museum of Natural History at Yale University. The samples 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Fe Fe val- and 56 58 ) and , with δ δ n σ , yield- 1.90 ‰ 0.32 ‰ Ni/ i √ − x ± 58 / erent loca- ), and from ff replicates is σ SD 0.23 · n t − erent inputs and Fe values in the 0.05 ‰ (2 = 2 standard devia- = ff ± 56 = δ Tonicella lineata Fe 91 measured from the sub-tropical σ 0.08 ‰ (2 from the south Pacific 56 = Fe values ranged from 0.13 ‰ to 0.27 ‰ have 0.005 ‰ and -value of th chiton sample having i δ ± 56 j − ), respectively, δ < n δ σ Σ replicate analyses ), while 1.82 ‰ at a depth of 900 m. Fe 0.39 erent locations in the Pacific σ i − + 54 ff 0.05 ‰ (2 erent depths too within the wa- 0.10 ‰ have also been reported the north-eastern coast of North ff , for the Fe values are ± + Cr/ } ff Fe values reported for dissolved Fe 57 Fe, respectively. Hence, the overall 54 ) agrees well with the mass spectro- 0.98 ‰ (2 Fe of δ 1)] 56 σ 57 0.03 ± δ 57 − δ Chiton stokessi from the North Atlantic (Grand Manan − 0.44 ‰ (2 j δ , i = ± Chiton tuberculatus n ( from Student’s t-distribution at 95 % proba- 1.47 0.90 ‰ to Σ Fe and − Fe n [ − 5540 5539 / 56 1.09 56 ] Fe and 0.08 ‰ (2 1.10 ‰. 2 determined from δ − δ 59) and ) erent oceans. Isotopically heavy values in 56 ± − 1000. (1) ff = ) and δ σ × n mean mean , 0.30 ‰ to 0.71 ‰ have been reported in some studies 0.04 − − ! j σ j + ) for 1 − x x σ − = − i Fe value of 0.23 ‰ have been reported for the Atlantic Section of the x Tonicella marmorea Fe ( + 0.26 ‰ (2 56 Σ 57 [ δ ± sample { Fe] δ 0.08 (2 0.05 ‰ (2 0 ‰) were independently processed through the same chromato- ± √ 54 0.58 ‰ have been measured at di ± · Fe] / from the north Pacific (Puget Sound, Washington) possess mean ≡ + 0.65 54 − Fe / Fe 0.27 erent regions cluster reasonably close together, with each chiton group 56 ) and 0.14 ‰ to ff [ Fe 56 ), respectively. σ − δ 56 σ = + [ 0.45 µm) in seawater in di

Fe Fe values measured in the samples cover a wide range, varying from < 0.01 ‰ to = 56 56 + 0.05 (2 δ δ ± ), while the value for Fe values varying between Fe values of Fe correction factor for small numbers of Such large variation in isotopic signatures between the chitons in the di 0.5 %. The sample-standard bracketing method was used for mass bias correction σ 0.08 ‰ (2 56 56 56 = tures is generally thought to be due to changes in the balance of di 0.00 ‰ at theLarge surface variations to have extremely also negativerange been values from reported of inSouthern the Ocean Atlantic (Lacan Ocean: etbeen al., measured 2008, in 2010), the whileδ South values of East Atlantic(John (Lacan and et Adkins, 2010; al., Lacan 2010);America et isotopic in al., signatures 2010), the in while the North o (Rouxel range Atlantic and Auro, 2010). Such geographical dependence of seawater isotopic signa- (filtered from Ocean (Lacan et al.,ter 2010; column, Radic significant variations et in al.,Pacific Fe Ocean: 2011). isotope in compositions At the have di been San reported Pedro in Basin the in the North Pacific, north Atlantic (Bermuda) has(2 a mean Fe isotope signatureIsland, of New Brunswick, Canada)(Panama) has is a mean Mopalia muscosa δ tions might be expected given the widely varying The to 0.00 ‰ (Fig. 2).each Although of the overall the range di ispossessing quite large, a the distinct chiton isotopic specimens from composition: 3 Results and discussion uncertainty estimates in the± reported and isotope analysis of IRMM-14tion with of the mean) and metric repeatability estimated overwith the course of thisthe study dataset from of the HanFe theues) standard according 18 to 2 investigated chitona mean teeth isotope samples composition ( ing bility). For data quality control,repeated measurement analyses accuracy of and precision an was in-housecontrol assessed working standard) by in standard each (HanFe: analytical pureIRMM-014 session, Fe ( and solution four used aliquots as ofgraphic the separation reference material protocol as the samples. The reproducibility of the Fe separation notation: δ Between 4 and 8formed in repeat 2 measurements or ofreported 3 independent in each analytical Table purified 1 sessions; samplet together the with solution mean the were 95 % per- confidence interval (2SE due to the low< impurity levels of(using Cr IRMM-014 and as bracketing Ni,and standard), i.e., data following acceptance criteria the of theare Schoenberg measurement reported and procedure von relative Blanckenburg to (2005), the and results international reference material IRMM-014 using the delta corrections made to the data are insignificant compared to the analytical uncertainty, 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 0.45 ‰ does in- 0.4 ‰ in − + , have less ) at the dif- Fe values as Fe values ob- erences might 56 ff 56 δ δ erences between Fe values ranging ff Fe values between citontheeth 0.83 ‰ to is much higher than erence could be the 56 − ff 56 M. muscosa δ Fe ) were found for the 3 δ M. muscosa 56 σ δ and − is from predominantely feeds on red al- M. muscosa erence in 0.98 ‰, 2 ff seawater erent isotopic signatures could also ± T. lineata ff Fe 56 Fe of dissolved Fe in surface seawater δ 1.47 56 erent isotopic compositions. Furthermore, − = ff δ M. muscosa = 5542 5541 Tonicella lineata Fe values in the eulittoral zone and heavier iso- chiton Fe − 56 Fe signature for 56 δ sw ); in contrast, more negative 56 δ σ flux (Anbar and Rouxel, 2007), while positive values δ erence between Fe (Fig. 2). As one of the important di ff ff 56 ∆ which would seem to be consistent with the observation 0.1 ‰ (2SD) (Beard et al., 2003). Modern marine sediments, Fe value, with variations of less than 0.3 ‰ (e.g., Beard et al., 0.26 ‰, y ± 56 ± δ has a diet more rich in green algae (Boolootian, 1964; Demopulos, 0.94 ‰ (mean − 0.65 T. lineata, − ects. As photo-reduction is a dynamic process, such di Mopalia muscosa = ff ective in the eulittoral zone than in the deeper sublittoral zone due to light erent isotopic signature to green algae. In near-surface coastal seawater, T. lineata Fe ff ff 56 δ 1.90 ‰ to − Fe (e.g, Beard et al., 2003; Poitrasson and Freydier, 2005) with an average igneous ect the chiton teeth (Lowenstam and Kirschvink, 1996). The Fe isotope composition Assuming that the isotopic di Biological fractionation could also explain the isotopic values measured in the two Seawater samples taken at the same site and time of chiton sampling were not avail- 56 ff produce biovailable Fe(II) with light have a di dissolved bioavailable Fe(II) is thought tonanoparticles be and produced by complexes the (e.g.,beau, photo-reduction Johnson 2006; of Fan, Fe(III) et 2008). al., Experimentsoxides 1994; have produces shown Barbeau that isotopically et the light al.,2010) reductive and dissolution 2000; Fe(II) bioavailable of Fe(II) Bar- (e.g., Fe- in seawater Wiederholda might result et also of possess al., the negative UV-induced 2006;be reduction. more Beard However, e photo-reduction et ofattenuation al., Fe(III) to e Fe(II) may the variance for that chitons from thespecific eulittoral feeding zone habits, (intertidal often ingesting zone), both such red as and green algaedeed (Boolootian, reflect 1964). their contrasting diets, it is interesting to consider why red algae would tained from 5 individual(mean specimens of from specimens of the two species is theirgae, contrasting while diets ( 1975), food sources could account forthe the variance di associated with the derived from rocky subtrates iswe unlikely measured, to although account confirming forbeyond this the the would constraints very have of light required this Fe in prelimary isotope situ study. values sampling that was chiton species from Puget Sound (Washington, USA). The range in neous Fe-isotope composition found in loess and aerosols (Zhu et al., 2000). Thus, Fe 2003; Rouxel et al., 2003; Fantle and DePaolo, 2004), consistent with the homoge- result of biological fractionationdirect from ingestion the of seawater Fe from Fe rockya pool. substrates We with note di hereof though that crustal igneous rocksδ is relatively restricted,rock ranging compostion from of about 0.1 0such ‰ as to terrigenous sediments, turbiditeoceanic clays, cust, and also volcanoclastites, have as a well restrictedthe as range average altered of igneous Fe isotope compositions clustered around the south Altlantic, andis the more north positive Pacific), thanseawater the and chiton Fe theeth inferent ( chiton locations teeth: ranges the fromseem 0.28 di ‰ to to be isotopically 1.14 ‰. lighter Thus, than overall Fe Fe in seawater, in and chiton such teeth a would di shallow or surface seawater, whichto play suggests an that important biological role fractionation in is determining also the likely isotopicable composition. for Fe isotope analyses insessment this of preliminary biological study. However, to fractionation allowdata during a with Fe first-order published as- uptake data for from Fe seawater,ter isotopes we measured of compare at dissolved Fe locations our from as surfacethe close or three as shallow regions possible seawa- for to which the seawater chiton Fe sampling isotope sites values (Fig. are 2). reported For (the north Atlantic, 2011). Negative seawater valueslocal could flux be from due continental tohave runo dissimilatory been iron interpreted reduction aset or indicative al., high 2011). of However, non some ofsignificantly reductive the more dissolution Fe negative isotope of compared values sediments of to (Radic chiton the teeth global reported range here reported are for dissolved Fe in the influence of utilisation of Fe as a nutrient by marine organisms (e.g, Radic et al., 5 5 25 15 20 10 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Fe er- ff 56 , and erent δ ff ff ect. As ff Tonicella erently or ff Fe signal. How- 56 δ -FeOOH), and ferrihydrite γ ), chiton radula contain other 4 O 3 erent algal types would help determine ff orts in materials science to better under- ff 5544 5543 -FeOOH), lepidocrocite ( α erences between seawater and chiton teeth are likely ff erence measured between phytoplankton and seawater, ff erent phases using new techniques such as laser ablation MC- erent locations, suggesting that the isotopic compositions may ff ff erent isotopic ratios in the two species may simply reflect relatively high 0.25 ‰ was suggested (Bergquist and Boyle, 2006; Radic et al., 2011). O) (see Brooker and Shaw, 2012, and references therein). To form these ff 2 + erent species analysed from Puget Sound, USA, suggest that Fe isotopes ff 0.5H · feeds. 3 O 2 erent values could indicate that the algae either fractionate Fe isotopes di Clearly the dataset presented in the current study possesses a number of limitations. In Fig. 3, a schematic summary is presented of the primary pathways control- However, isotopic fractionation could also occur during the uptake of Fe by the di ff Firstly, the number of chitons in our study is relatively small, a fact that complicates in the relative balance of inputsnon from reductive dissimilatory dissolution iron reduction, of continental sediments. runo the However, the two distinct di signatures recordedcould from also be dietthe controlled. sublittoral As zone one while ofdi the the other chiton eats species mainly eatsthat green primarily the algae red dissolved in bioavailable algae Fe the in the varies eulittoral shore. significantly zone, in the their isotopic composition near 4 Concluding remarks In this paper,marine we locations report in the the Pacific andvalues Fe Atlantic between oceans. isotopic the We di found composition ain large of part variation be in chiton controlled by radula variations from in the di local isotopic source signature due to changes undetermined. However, this transformationmineral must (ferrihydrite) involve to a achanges transition mineral in that from redox state contains an can both causetope Fe(III) Fe Fe(II) signature isotope could and fractionation, change Fe(III) it during is (magnetite). theof possible formation Fe As that of isotopes the magnetite. in Fe Precise the iso- measurements di ICP-MS will help determine will help determine whether or not this is the case. rior epithelial cells of thetransferred to radula sac an (Shaw organic et matrixBrooker al., where et 2009). it al., At is 2003). astand deposited Despite later Fe as biomineralization stage, the ferrihydrite (e.g, the recent (Kim Weaver ferritin et e mechanism et is al., al., 2010; by Xiao 1989; which and Yang, the 2012), the ferrihydrite precise precursor is transformed to magnetite remains Fe minerals, iron originates as ferritin in the haemolymph and is delivered to the supe- (Fe where an isotopic fractionationton favouring light of isotopes about during uptakeThus, into the phytoplank- observed isotopicto di be at least partially controlled by algal-mediated fractionation. ling Fe isotope fractionationand biological in fractionation, chiton biomineralization mechanisms teeth.play within an Importantly, the chitons in important may addition role. also Fe to In minerals, including addition food goethite to sources ( magnetite (Fe Fe(II) concentrations in thetoral eulittoral zone. zone While and isotopic lowwhich analyses Fe(II) mechanisms concentrations can of account in the for theavailable di for the sublit- analysis chitons’ in isotopic the signatures, currentsupported study. samples However, by a were an biological not Fe fractionation isotope by di algae is itate photochemical redox cyclingknown (e.g., to Amin produce et strong2009; al., fractionations Guelke-Stelling in 2009). and von terrestrial Uptake Blanckenburg,the plants mechanisms 2012), light (von are and isotope Blanckenburg if may et enough beever, if preferentially Fe(II) al., Fe(II) occurs absorbed, is in producing available, low a concentrations,as little light the fractionation might algae be attempt expected toinheriting to occur the absorb Fe as isotope mucha signature Fe result as of the possible di the from source their due surroundings, to thus so called reservoir e lineata ent kinds of algae. AlgaeCasal are known et to al., contain high 2007),Fe(II) concentrations having from of developed Fe low (e.g., a solubility García- range Fe(III) of species, strategies including for the creating use bioavailable of siderophores that facil- topic values in the deeper sublittoral zone, where red algae dominate and 5 5 25 15 20 10 25 20 10 15 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | er- ff : Mollusca: Polyplacophora), Mar. Biol., 5546 5545 Acanthopleura echinata ett, J.: Laboratory and field studies of colloidal iron oxide dissolution as SE would like to thank the German Israel Foundation for Scientific Re- ff culties associated with identifying Fe-biominerals in the fossil record ffi Despite the limited dataset, the present study nevertheless yields a number of im- mineralisation in chiton teeth ( 142, 447–454, 2003. evolution of magnetite biomineralization, Annu. Rev. Earth Planet. Sci., 17, 169–195, 1989. Monica Bay Helgoland, Mar. Res., 11, 186–199, 1964. in: Advanced Topics in Biomineralization, edited by: Seto, J., 65–84, 2012. Planet. Sc. Lett., 295, 241–250, 2010. transport signatures, Earth Planet. Sc. Lett., 248, 39–53, 2006. on Fe cycling and2003a. mass balance in the oxygenated earth’s oceans, Geology,of 31, Fe 629–632, isotopes to87–118, tracing 2003b. the geochemical and biological cyclingson, of C. Fe, Chem. M.: Geol., Iron 195, isotope fractionation between aqueous ferrous iron and goethite, Earth mediated by phagotrophy and photolysis, Limnol. Oceanogr., 45, 827–835, 2000. Planet. Sci., 35, 717–746, 2007. tochem. Photobiol., 82, 1505–1516, 2006. tolysis of iron–siderophore chelates promotes106, bacterial–algal 17071–17076., mutualism, 2009. P. Natl. Acad. Sci., Brooker, L. R., Lee, A. P., Macey, D. J., van Bronswijk, W.,Chang, and S. Webb, R. J.: and Multiple-front Kirschvink, iron- J. L.: Magnetofossils, the magnetization of sediments, and the Brooker, L. R. and Shaw, J. A.: The chiton radula: a unique model for biomineralization studies, Boolootian, R. A.: On growth, feeding and reproduction in the chiton Mopalia muscosa of Santa Bergquist, B. A. and Boyle, E. A.: Iron isotopes in the Amazon River system: weathering and Beard, B. L., Handler, R. M., Scherer, M. M., Wu, L., Czaja, A. D., Heimann, A., and John- Beard, B. L., Johnson, C. M., Von Damm, K. L., andBeard, Poulson, B. R. L., L.:. Johnson, Iron C. isotope M., constraints Skulan, J. L., Nealson, K. H., Cox, L., and Sun, H.: Application Barbeau, K. and Mo Barbeau, K.: Photochemistry of organic iron(III) complexing ligands in oceanic systems, Pho- Anbar, A. D. and Rouxel, O. M.: Metal stable isotopes in paleoceanography, Annu. Rev. Earth Amin, S. H., Green, D. H., Hart, M. C., Küpper, F. C., Sunda, W. G., and Carrano, C. J.: Pho- References ent organisms, serving asAlthough an the additional di tool(Chang with and which Kirschvink, 1989) to currently probe limitpast ecological their conditions, potential systems. usefulness further in documentation reconstructing organisms of is Fe expected isotopes tomarine in help environments. seawater, algae, track and the higher present-day pathways and sources of Fe in (polyplacophora) and even limpets (archeogastropods)goethite (Lowenstam, – 1962b) which – have could still teethFe, record and containing the provide signature information of concerning dissolvedronments. bioavailable Fe Furthermore, biogeochemical in cycling a in similarcould near way shore be to envi- used oxygen to and distinguish nitrogen isotopes, between Fe the isotopes primary sources of Fe in the diets of di of Fe isotope fractionationisotope in fractionation marine mechanisms invertebrates, are andsignificance therefore our of preliminary. findings To the regarding determine pathways thesampling the controlling campaign Fe relative – Fe involving isotopic in-situand signatures, measurements chitons a of – water, would far rock be more substrates, necessary. algae, extensive portant conclusions. Although thenot results necessarily suggest record that oceanic Fe-isotopes in values, iron-concentrating bio-minerals do organisms such as chitons values for seawater exists, no Fe isotopethe data exact are available locations for algae from andif seawater which values from the were chiton to specimenswould be be obtained were for for collected; the the samples moreover, inconstraints, present even this day, our study it study that is were must unclear collected be decades how ago. relevant regarded In such view as data of a such first attempt to tackle the complexities the interpretation of the results. In addition, although a dataset of published Fe isotope Acknowledgements. search and Development forIn generous addition, financial we supportPeabody are via Museum grateful invertebrate their zoological to Young collection. Scientists’ Eric Program. 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W.: Iron isotopes in the seawater of the equatorial Pacific Poitrasson, F. and Freydier, R.: Heavy iron isotope composition of granites determined by high 5 5 30 15 25 10 20 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | n 0.08 ‰ ± ) and σ Fe ‰ 2SE ‰ 0.40 0.07 5 0.540.40 0.03 6 0.04 8 1.54 0.09 4 1.89 0.06 4 1.03 0.07 5 1.86 0.03 6 1.63 0.05 6 1.61 0.06 5 1.39 0.04 5 2.332.81 0.06 0.03 5 6 1.22 0.06 4 0.82 0.07 5 0.83 0.05 5 1.07 0.07 4 0.84 0.07 4 57 0.05 ‰ (2 replicate analyses of the ± − − − − − − − − − − − − − − − δ − − n Fe ‰ 2SE ‰ a radula sac containing the 0.28 0.05 0.38 0.01 0.28 0.02 1.06 0.05 1.29 0.06 0.73 0.04 1.26 0.01 1.11 0.03 1.10 0.05 0.94 0.04 1.581.90 0.04 0.02 0.83 0.05 0.54 0.04 0.56 0.05 0.73 0.05 0.57 0.04 56 − − − − − − − − − − − − − − − δ − − correction factor from Student’s t-distribution at 95 % (b) = t , with n √ / SD · t YPM-12739-17 YPM-12739-16b YPM-5176-14 YPM-5176-13 YPM-5176-12 YPM-12718-08 YPM-12720-05 YPM-12720-04 YPM-12716-03 = 5552 5551 green algae YPM-12739-16a 0.00 0.05 0.00 0.09 4 green algae YPM-5176-11 green algae YPM-12718-07 red algae YPM-12716-02 in the eulittoral zone, and Fe associated with the entire Fe isotope analytical procedure are estimated to be 57 δ Fe and 56 New Brunswick, Canada red algae δ Chiton tuberculatus 3 Bermuda Eulittoral, YPM-12739-15 5 Panama Eulittoral, YPM-5176-10 8 Grand Manan Island, Sublittoral, YPM-12760-09 3 Puget Sound, WA, USA Eulittoral, YPM-12718-06 specimens 5 Puget Sound, WA, USA Sublittoral, YPM-12716-01 Summary of analysed chiton samples. ), respectively (see text). σ tuberculatus Chiton stokessi marmorea Chiton Tonicella muscosa Mopalia lineata Species IndividualTonicella Locality Ecology Specimen ID Iron isotope data are reportedsame as analyte permil solution deviation are relative reported to with the their international 95 % reference confidence material(2 intervals IRMM-014. (2SE Mean values of probability). Uncertainties in magnetite-capped teeth, indicated by the arrow. Fig. 1. (a) Table 1. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | from Vineyard (a) Tonicella marmorea the north-eastern coast of North Waquoit Bay on Cape Cod, Mas- ff (b) 0.3 ‰; sampled near Bermuda, John and + ( 0.82 ‰); − (d) 5554 5553 Connecticut River estuary in Long Island Sound, Connecticut, (c) 0.55 ‰); − (0.00 ‰; John and Adkins, 2010) are compared with the Puget Sound chiton (e) 0.04 ‰). Data for the North Atlantic Caption on next page. Fe isotope signatures of 18 chiton teeth analyses (grey circles). Analytical uncertainties + Fe are smaller than the symbols. Data points encircled by the red dashed lines indicate 56 75 m depth) seawater (Lacan et al., 2008, 2010; John and Adkins, 2010; Rouxel and Auro, δ < Grand Manan Island representsthe the average average for of igneousthe rocks 8 range (Beard homogenized of et Fe specimens. isotope al., For( values 2003) comparison, reported is in the indicated literature2010; by for Radic the dissolved Fe et vertical in grey al.,are surface line, and 2011) published shallow while local is coastal representedby surface by seawater Rouxel the isotope and solid analyses Auro, of blue (2010) dissolved band are Fe. at Data for the reported three bottom. sites Blue squares located o Fig. 2. in chitons with a red-algae richalgae diet, diet. while Note green dotted thatclose lines the together; indicate values by a contrast, for predominantly chitons thea blue-green from larger chitons the variance same with and location a a with lighter red-algae a isotopic diet diet signature. of from The blue-green single Washington algae value have cluster for America (about 500 km south of the chiton sampling site at Grand Manan Island): sampling site. sachusetts, USA ( USA ( Adkins, 2010) are comparedPedro with Basin the Bermuda chiton sampling site, while data from the San Sound on Cape Cod, Massachusetts, USA ( Fig. 2. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | erent ff biomineralization processes within the reductive dissolution of Fe complexes and (c) (a) 5555 erent pathways. ff uptake by algae; or (b) Schematic pathways for Fe isotope fractionation between Fe in seawater and di chitons. The mechanismscould are reflect not a combination mutually of exclusive di and the signatures in the chiton teeth Fig. 3. chiton species. Fractionation could occurnanoparticles during in seawater;