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Climate δ Sciences Sciences Dynamics Chemistry using of the Past Solid Earth Techniques Geoscientific Methods and and Physics and Atmospheric Atmospheric Atmospheric Data Systems Geoscientific C indicating growth oc- Earth System Earth System Measurement ◦ Instrumentation Hydrology and Ocean Science Annales Biogeosciences The Cryosphere Natural Hazards Natural Hazards and Earth System and Earth Model Development Geophysicae , H. W. van der Veer in Dutch coastal waters, assess- 1 culty of interpreting externally visible ffi 4304 4303 Open Access Open Access Open Access Open Access Open Access Open Access Open Access Open Access Open Access Open Access Open Access Open Access Open Access (Conrad, 1843) (also known as

C may be the threshold temperature for growth. , R. Witbaard ◦ Ensis directus 1 6 Ensis directus ∼ ´ edicas Abel Salazar, Laboratorio de Fisiologia Aplicada, C). Climate Sciences Sciences 13 Dynamics Chemistry δ of the Past Solid Earth Techniques Geoscientific Methods and and Physics and Advances in Atmospheric Atmospheric Atmospheric Data Systems Geoscientific Geosciences Ensis directus Earth System Earth System Measurement Instrumentation Hydrology and Ocean Science Biogeosciences The Cryosphere Natural Hazards Natural Hazards ˆ encias Biom , G. Nieuwland O and EGU Journal Logos (RGB) EGU Journal Logos and Earth System and Earth 18 1,2 Model Development δ C) suggests that ◦ 2,3 O values in the shell coincided with growth marks on the external surface 18 δ C values and annual growth lines. Although counting external annual growth lines High 13 This discussion paper is/has been under review for the journal Biogeosciences (BG). Please refer to the corresponding final paper in BG if available. NIOZ – Royal Netherlands Institute for Sea Research, P.O. BoxCIIMAR/CIMAR 59, – 1790 Interdisciplinary AB Centre Den of Burg Marine Texel, and Environmental Research,ICBAS University – Instituto de Ci pean waters, it was first observedbeen in introduced the in German Europe Bight in shortly 1979 before and by it larval is thought transport to in have ballast waters of ships analysing acetate peels oflines and cross-sections disturbance to lines. support the distinction between annual 1 Introduction The American razor clam Binney, 1870) is aNorth America suspension-feeding from bivalve, Labrador (in common Canada) to along Florida the (Abbot and Atlantic Morris, 2001). coast In Euro- of Nevertheless, most of the reconstructedcurred values fell mainly above 14.5 in thelowed a summer more at or less relativelyδ seasonal high cycle temperatures. but no Shell directled relationship to could be a made correct between estimation of age and consequently of growth rates, we recommend growth lines. In theline present formation paper, using we visualisotope aimed techniques analyses in ( at combination validating with the stable seasonality oxygen in andof growth carbon the valve andples in were acetate assigned peels tosamples of the were retrieved the months indicating shell’s June thattemperature the cross to (6.1 shell September. section. did From Most not November grow. shell The to lowest March reconstructed no To evaluate the role ofment the and razor understanding clam its populationture dynamics of is the important. population Asshells such, forms is the not a age always key straightforward struc- due parameter. to Accurate the age di determination in bivalve Abstract Biogeosciences Discuss., 10, 4303–4330, 2013 www.biogeosciences-discuss.net/10/4303/2013/ doi:10.5194/bgd-10-4303-2013 © Author(s) 2013. CC Attribution 3.0 License. Growth increment periodicity in theof shell the razor clam Universidade de Porto, Rua de Jorge Viterbo FerreiraReceived: 228, 18 4050–313 February Porto, 2013 Portugal – Accepted: 19Correspondence February to: 2013 J. – F. M. Published: F. 6 Cardoso March ([email protected]) Published 2013 by Copernicus Publications on behalf of the European Geosciences Union. stable isotopes as a methodage to validate J. F. M. F. Cardoso J. P. Machado 1 the Netherlands 2 of Porto, Rua dos3 Bragas 289, P 4050–123 Porto, Portugal 5 25 15 20 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | O O) the 18 18 δ O and originat- 18 along the δ 2 ¨ has spread uhlenhardt- E. ensis , although it C (Mook and 13 and δ O (enriched in O) to higher temper- E. directus C in the shell (Lorrain 18 18 E. directus E. directus 13 δ δ ects of water temperature E. siliqua ff , ´ ee et al., 1994; Armonies and O ratios (Wefer and Berger, 1991). ´ on et al., 2004), following the growth E. macha O (depleted in 18 δ 18 δ 4306 4305 is not only a commercially important species to assess if the analysis of these lines gives an in Dutch coastal waters, studying population dy- C) ratios in carbonate shell materials are influenced ney 2001; Fahy et al., 2001; Palmer 2004; Cardoso 13 ff δ ¨ one and Giere, 2005; Mannino et al., 2008; Versteegh is the most dominant bivalve species in the Dutch coastal E. directus ´ E. directus on et al., 2004). Alternative methods used for the validation C) along the longitudinal profile of shells. The ratio of stable E. directus 12 C/ O) in the shell reflects the combined e 13 18 , externally visible growth lines (marks) have often been used to δ E. directus O and C in the shell usually reflects seasonal variation of water 16 13 δ O/ E. directus 18 In the present paper, we aim to validate the seasonality in external and internal To evaluate the role of Vogel, 1968; Killingley and Berger, 1979;ing Arthur from et food metabolism al., may 1983), mask respiratory the CO seasonal variation of latter co-varying with salinitysalinity (Gillikin, are generally 2005). constant In during therecord environments lifetime mainly where of an changes water organism, in changescorresponds in water to shell temperature, lower temperatures whereby and higher lower atures. Carbon stable isotope ( by metabolic factors andbon environmental isotope conditions, and, ratios in therefore,Although the shells profiles are of less car- clear than growth lines in the shellaccurate of estimation of age. Forratios that, ( we determined stable oxygenoxygen and isotopes carbon ( isotope and water isotopic composition (Epstein et al., 1953; Grossman and Ku, 1986), the also be validated. Theto use of make isotope the sclerochronologyhas distinction provides never between an been objective annual used method tohas and verify been disturbance the widely periodicity used growth of toKrantz lines. growth study et This lines growth al., and in method 1984; validate2001; Jones growth and Keller lines Quitmyer, et in 1996; other al.,et Witbaard bivalves 2002; al., et (e.g. 2010; Sch al., Santos 1994; et Goodwin al., et 2012; al., Cardoso et al., 2013). of this periodicity include marking experimentsof (Bar cohorts with time (Beukemalines and visible Dekker, in 1995; cross-sections Palmer, of 2004) theson, and shell 1994; analysing (Gaspar Palmer, et growth 2004). al., However, disturbance 1994;Commens-Carson, lines Henderson often 2008), and extent Richard- and internally therefore, (Haag the and periodicity of internal growth lines should and Richardson, 1994; Bar to the presence of lines formed by non-annual events (Gaspar et al., 1994; Henderson growth cessation (Swennen etand al., Reise, 1985; 1999; Robinson Fahyet and and al., Ga Richardson 2009). 1998;months, In Armonies due temperate to areas, low the foodin temperature availability cessation or and food of low conditions, temperatures. growthto spawning, However, and coincides sudden a other changes with temporary stressing factors thegrowing cessation may season. also winter of lead Such growth, growth marksof causing externally may deposition visible cause lines. of errors Inestimation growth in razor clams, age of marks such determination the as during on age the basis from external growth lines was found to be very unreliable due namics is important. Inpatterns this from respect, age which iscluding productivity required of to a establish growthdetermine population and individual can mortality age, be whereby derived. they were In considered razor to clams, correspond in- to a period of Reise, 1999), this speciesters has (Dekker managed and to Waasdorp, 2007; build Perdon2010). up and Presently, Goudswaard, a 2007; strong Goudswaard population etzone, al., in with Dutch a wa- total(Goudswaard et estimated al., biomass 2010). of(Wijsman around et 479 al., 2006), millionand but kg references also therein). fresh a Considering weightDutch food the in coast, item increasing competition 2010 for numbers with of fish native species and cannot sea be ducks ruled (Tulp out. et al., 2010 along the Wadden Seaway, and Britain and North the Sea west coast coasts,therein; of and Sweden Hopkins, (Beukema is and 2001; now Dekker, 1995 Minchin foundDespite and from and the references France frequent Eno, to events 2002; Nor- ofSiegel Palmer, mass et 2004; mortality al., Dauvin and 1983; et variable recruitment Beukema al., (M and 2007). Dekker, 1995; Cad that crossed the Atlantic (Von Cosel et al., 1982). Since then, 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 23 ◦ the coast, shell 2 at ff . To this end, we have determined E. directus 4308 4307 , and (3) the analysis of external and internal shell preserve seasonal environmental records as variation the coast of Egmond aan Zee, The Netherlands (52 E. directus ff E). Shell 1 was collected at about 7 km o E. directus 0 36 ◦ C, (2) isotope records confirm the periodicity of band formation and can –4 0 13 δ 18 ◦ N, 4 0 O and 18 38 ◦ δ Internal annual lines on the acetate peel were defined as thin dark lines which could For each shell, the number of macroscopically visible annual lines on the external Isotope ratio profiles can, therefore, be used to validate whether or not identified Sampling was done along(175 µm the around external the side growth of lines the identified valve externally in as equally being annual spaced and intervals 300 µm in tion of the internal andrecord. external lines which were confirmed to be annual by2.2 the isotope Isotopic composition The concave side ofvalve the and right-hand valves enable was drillingder filled with of was epoxy the sampled resincroMill, valve to using New convex reinforce Wave a the (outer) Research) micro side. and equipped sampler Calcium with carbonate attached a pow- to small dental a drill binocular (bit size microscope 80 µm). (Mi- increments were registered and comparedisotope with profiles. the external reading and later with the be seen in themargin hinge of the (Fig. valve 1b) (Fig. and 1c). Annual followed growth along rates the were determined shell based section on until the posi- the external no scratches were visible.about Polished 20 s shell and sections rinsed were withshell distilled submerged surface water. in Acetate with peels 1 drops vol% werecellulose prepared HCl of acetate. by With for acetone covering this the and method,served making the and organic a the parts carbonate copy of parts withcross-section, the are a carbonate which dissolved, matrix 0.1 resulting is mm are in then con- thick aon transferred relief sheet microscope to on slides of the the and surface acetateing of photographs composite sheet. the were pictures, Acetate taken the number under peels and a were position microscope. put of In the internal the growth result- lines and growth valves were placedin with epoxy the resin concave (Poly(1985). side Service, Once down hardened, THV-500 the in epoxyhars blocksgrowing and a were edge sectioned Harder plastic longitudinally (Fig. 355), from mould 1a), following theest and in umbo Ropes to to embedded the the the form umbo of was slices ground of flat about under 5 successively mm finer thick. grit The and surface wet clos- polished until to remove adhering sediment, rinsed with distilled water and left to air dry. Left hand the shell surface occurringgitudinally parallel along to the the shell growing until edge, the which umbo could (Fig. be 1a). followed Shells lon- were scrubbed with a brush program “Buiding with Naturetional (BwN)” Institute for and Waterways the andand monitoring Public the Works programme Environment) of “LaMER” the o 52 (Na- Dutch Ministry of Infrastructure about 5 km and shells 3 and 4 at aboutside 2 of km the (Supplement, valve Fig. was S1). sal recorded to and the shell ventral length margin) (defined was as measured. the Annual distance lines from were the defined dor- as dark bands on 2 Materials and methods 2.1 Analysis of growth lines For the analysis ofwere growth increments, selected. four They live were bivalves without collected damage in on April the valve 2010, in the framework of the research in further interpretationidentify of the the growth patterns visible in lines.whether: the (1) This shell shells of approach of wasin used in thisbe study used to to estimate age of lines gives a reliable estimate of age. Poulain et al., 2010). Nevertheless,and since food metabolism conditions, is which mostlypattern in related for to temperate this temperature habitats isotope vary is expected in as an well. annual cycle,growth a bands in seasonal the shell of bivalves are formed at regular (annual) intervals and help et al., 2004; Geist et al., 2005; McConnaughey and Gillikin, 2008; Lartaud et al., 2010; 5 5 25 15 20 10 20 25 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | O N, 18 0 val- δ C or T S 0.1‰ 18 13 ◦ ). O (‰) us- δ E) were ≤ O 0 18 18 W δ δ 03 O ◦ T 18 δ ciently large car- N, 04 values). Then the 0 ffi S 32 ◦ O by first matching peaks 18 δ S O C in the shell could not be 0.001) (4) O of the seawater (VSMOW). 18 13 ). Daily temperature data were ) (relative to VSMOW – Vienna δ 18 S δ ) using the relationship between p < δ O S values: 18 S δ 0.77, O = 18 2 δ r (‰) is the ) values were compared to predicted values (‰) and daily reconstructed ) (2) is the fractionation factor between water and S C and environmental parameters were avail- 4310 4309 W has an aragonitic shell (Kahler et al., 1976), W S O 13 O α O O C, respectively. δ 18 18 0.72) ( 18 18 13 δ O of the shell ( δ ± 30.91 (3) δ δ δ 18 + + δ E) for shells 3 and 4 and “Noordwijk 10 km” (52 0 0.715 (1) with predicted values, a time scale was assigned to the E. directus VPDB O and + 7.9456( S O shell ( 24 (1000 ) ◦ O − 18 / O 2 18 ) δ 18 S − δ 18 · δ values) and troughs (most negative T http://live.waterbase.nl/waterbase δ (‰) is the · N, 4 6 0 S described by Santos et al. (2012): O 15 record was shifted horizontally and matched to predicted values as 0.02) Aragonite ◦ W 18 values are usually reported relative to VPDB (Vienna Pee Dee belem- ± S O O δ S O Aragonite 18 18 1.03091 O values calculated in terms of VSMOW were converted to VPDB using the 2.559(10 O 18 δ δ = 18 S δ = 18 + δ ) is temperature in Kelvin and O δ 0.2333( α was inferred from instrumental salinity data ( 18 T = 0.05‰ (1 SD) for δ E) for shells 1 and 2 (Fig. S1 in Supplement). Because no data on water W W VSMOW 0 ≤ (1000 O O O To determine the temperature at which shell growth started and ceased, Observed sea surface temperature and salinity nearby the sampled area were ob- To align measured In total 238–330 transects were drilled in each shell from the ventral margin to as 18 = C) were derived from measured 18 18 18 ◦ ◦ ( ing Eq. (1) solved for temperature, with the suggestion of Dettman et al. (1999) for tained via Waterbase ( delimit the beginning andcalendar end of year, each dates calendar were year.(most assigned For all to positive growth the records measured andmeasured each closely as possible, maintaining themeasured and temporal predicted sequence. values The was goodness then of determined fit using between aues linear regression. recorded in the shells were used to reconstruct water temperatures ( δ salinity and δ able for the sampledcompared. area, measured and predicted individual data points of themargin shell to isotopic each record. For drilled that, line the was distance measured. from Identified the annual dorsal growth lines were used to not available for thefrom 2001–2010 sampled for the area station andtaken “IJmuiden munitiestortplaats” period. (Fig. (52 S1 Therefore, in meansame Supplement). daily station, Since temperatures mean noordwijk annual recent 2 salinity km” salinity from (52 data4 2001–2010 was was available taken fromreliable for the relationships the between station water “No- δ aragonite described by the equation: α whereby Standard Mean Ocean Water) and Because nite), equation of Coplen et al. (1983): et al. (1999) was used to calculate predicted 1000ln( where close as possible tosampling the transect umbo. near Shells could thebonate samples. not umbo When be the was sampled amount oftenwas of completely not calcium too because enough carbonate for small powder the isotope from to determination,was a the pooled. single yield powder drill Measured from su line two neighbouring(determined transects on basis of temperaturelibrium and salinity fractionation. data) Since assuming agreementthe with equation equi- for biogenic aragonite by Grossman and Ku (1986) updated by Dettman der (20–80 µg) was analyseda for Thermo stable Finnigan oxygen and MAT253 mass carbonration spectrometer isotopic coupled device. composition to Reproducibility using a of Kieland IV the carbonate external prepa- standard NBS 19 amounted to between) and following the concentric external growth lines. Calcium carbonate pow- 5 5 25 15 20 10 25 20 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | S S C ◦ C O 13 18 δ 0.001, δ values) S p < O values were 18 C and 18.8 S ◦ δ C 13 δ (ANOVA, S C O of the water (SMOW) 13 18 C in shell 4 (Table 1). ◦ δ δ C in shell 1, 6.1 ◦ samples were assigned to the and is the S S O O W δ 18 18 C and 21.8 δ δ ◦ C and 19.2 ◦ samples assigned to the months April/May. 4312 4311 (Table 1) and showed similar profiles (Fig. 2). values, the shell did not grow. Therefore, no S S values showed a very good fit with the curve of S O C S S O 18 0.01). 13 O O δ 18 δ = δ 18 18 2 δ δ r ) (5) and W δ S C in shell 3, and 6.2 ◦ − O 0.05, S 18 O of the shell (VPDB) and O = δ observed between 6.5 and 7.0 cm) (Fig. 2, left panel). In all shells, 18 18 p O VSMOW values to the VPDB scale: S δ δ 18 O (Table 2). During part of the year (November–March), which includes δ 18 S δ C and 20.4 4.34( is the ◦ O − S 0.11) while shell 4 showed a very weak positive relationship between values corresponded with the lines assigned to be annual by visual analysis 18 (ANOVA, O δ S < S records also showed a truncated sinusoidal pattern, with sections of increase 18 O 2 C 20.6 S records showed a truncated sinusoidal pattern. All four shells had a section with δ 18 13 C = S > r δ δ 13 O O Reconstructed seawater temperatures (calculated from measured δ For each shell, isotope profiles were matched with the number and position of the 18 18 δ annual by analysis of theAge valve estimation and took acetate into peel, account and validated that by all the shells isotope were record. collected in April 2010 and that closely resembled the observedstructed temperatures field ranged temperatures between 8.4 (Fig.in S2 shell 2, in 9.7 Supplement). Recon- 3.3 Age estimation and growth Age of each shell was determined based on the growth lines which were assigned as predicted the period ofisotope highest samples predicted could be retrieved fromis the shell completely and lacking the from respective temperature theand range shell acetate record. peel Annual corresponded growth to lines identified on the valve exhibited a weak negative relationship between 0.05 and 3.2 Measured vs. predicted By matching measured andmonths April predicted to values, October, althoughSeptember most (Fig. samples 3). were Measured assigned to the months June to in values followed by aseen decrease (Fig. on 2, or right around panel).were Although the also low identified measured annualprofiles in growth and lines, between identified patterns these annual of growth annual lines peaks lines. could and not A troughs be relationship established. Shells between 1, 2 and 3 valve were not considered asthe shell. being These annual were because not they seen could in not the be acetate followed peels. along lines observed on thehad similar external ranges shell of surfaceδ and on the acetatea peel. steep All decrease four inmargin) shells values followed (e.g. by in slow(more positive shell decrease 1 (between between 3.5high 3.0 and and 6.5 cm) 3.5 cm andof from the a external the surface steep of dorsal increase the valve and the acetate peel. Some dark lines visible on the 2, five lines weas considered annual. to Although be theedge, annual most there while recent was growth in clear line shellwas shell in 4 considered growth shell have only after occurred 6 one in this was line 2009. line. observed was Therefore, close the classified to last the period of growth 3 Results 3.1 Inspection of growth lines andExternal isotope and profiles internal growth lineswere were visually considered analysed in to each be shell.also The clearly annual lines visible which by in visualfour the annual inspection acetate lines of peel were of the considered the surface by cross-section of analysis (Fig. the of 1). valve the In were shells valve and 1 and acetate 3, peel. In shell correcting water T where minus 0.27 ‰ (Hut, 1987). 5 5 25 15 20 10 25 20 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | 1 − ecting ff C. In the ◦ E. directus C to 22 ◦ , somatic growth starts C (Witbaard et al., 2012; ◦ E. directus ´ ee and Hegeman, 2002; Witbaard values revealed that the most neg- C and that growth stop occurs in au- S ◦ , with a maximum mean of 0.22 mmd O C. This suggests that a temperature of values and by observations in the field 1 ◦ 18 − C (Fig. S3 in Supplement) confirming that S ◦ δ O 1.6 18 4314 4313 ± δ data could be collected from calcium carbonate C (around June). In 2011, highest shell growth was ◦ S O values). This illustrates that growth rates are highest 18 data retrieved in some years covered almost the whole S δ O S , the onset of growth is thought to be mainly determined by O 18 C (Fig. S2 in Supplement). However, observations near the ◦ δ 18 δ concentration in the seawater (Cad A. islandica O and growth a in the area occurred mainly between July and August (Fig. S3 in Supple- C and 19.1 18 ◦ δ shore). Growth rates in the following years were higher in shells 1 and 2 ff records showed truncated sinusoidal patterns suggesting seasonality in shell S O E. directus C may be the threshold for growth start. Nevertheless, most of the reconstructed The fact that shell growth occurs well above 6 Comparison of measured and predicted Length-at-age and growth rate values varied among shells and mean yearly growth ◦ 18 and energy allocation to reproduction. in chlorophyll et al., 2012). Gametogenesis startset earlier al., in 2012) the together yearAken, with (Cardoso 2008; the et Witbaard, al., increase 2012). 2009; in Shellning Witbaard growth, seawater of however, temperature occurs summer) after mainly and, later themisaligned (in therefore, winter in the growth time. (Van begin- Shell of growth soft seems(around tissue to May) start and suggesting only that shell after the carbonateused the energy for end growth shell used of are growth. the in Shell main spring growthwhile spawning in for shell autumn reproduction may growth is be in hampered afterwards by spring low may food conditions, be hampered by a combination of low temperatures Fig. S3 in Supplement) suggestsshell that growth. temperature In alone is notthe seasonal the cycle only in factor primary a sonal production cycle which in is, temperature in (Witbaard turn,in et closely al., regulated March/April 1994). by (Cardoso In the sea- et al., 2009; Witbaard et al., 2012), along with the increase tures in February can6 be as low asvalues fell 3.8 in the rangeobserved above 14.5 in July at temperaturesshell around 17 growth occurs mainlycan in grow the at summer low temperatures at but relatively the high growth temperatures. rate istumn extremely when low. near bottom temperatures are usually above 10 some shells, however, predicted range. Reconstructed temperaturesyears ranged 2001–2010, from mean about daily 6 between sea 5.5 surface temperatures measuredsea in floor the in field 2011 varied and 2012 (Witbaard, personal observation) revealed that tempera- temperatures) where generally not all represented in the shell carbonate samples. In ative values (corresponding to theshell highest carbonate. temperatures) were The well most represented in (predicted) the positive values (corresponding to the lowest growth rates. Mostwhich detailed was deposited duringobserved the and months predicted Juneduring to this September period (estimated (average growth by 0.15observed mmd in matching June). Field data collectedof in 2011 showed that thement) increase supporting in our shell findings length that growth is fastest during the summer. 4 Discussion 4.1 Shell δ occurred in 2009 and shell 2 was aged 6 yrrate old decreased (year with class age 2004). (Table 3).in Growth shells rates 3 during and the 4further first (closest year to o of the life coast) werethan than higher in in shells shell 1 3. andcomparison. Because 2 shell (collected 4 from a has location only one growth line, it could not be used in this by matching measured and(Cardoso predicted et al., 2007; Witbaard5 et yr al., old 2012). (year Shells 1the class and most 2005) 3 recent and were growth considered shell lineshell as in 4 growth being shell was after 2 aged was this observed 2 line. yr close Therefore, old to the the (year last edge, class there period 2008). was of clear Although growth was considered have significant shell growth in the field does not start before early summer, as confirmed 5 5 25 15 20 10 20 25 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | ects. ff values E. direc- S O 18 δ O in these shells. ). Higher tempera- erence in alignment 18 ff δ C). Maximum observed ) and kinetic (acting on ◦ C in the shell of 2 profiles and the presence 13 S are formed due to a growth δ C erent from the 10-yr average ff 13 δ C vs. 19.1 ◦ E. directus values seem to follow a more or less si- S values observed between the last growth C S 13 4316 4315 δ O in the Wadden Sea, the first around May and , C and 21.8 18 ◦ δ http://live.waterbase.nl/waterbase C; ◦ values although other factors play a role as well. values, growth lines were confirmed to be annual. Fast values were observed in 2008 and 2009 during periods values showed a good fit with predicted values, following S E. directus ects, can contribute to marine bivalve shell carbonate and E. directus values. This resulted in higher reconstructed temperatures S S S ff C profiles relative to the position of the growth lines, reflecting O S O O 13 S O ) e 18 18 18 δ S O δ δ δ 18 C δ values coincided with the growth lines visible on both the external 18 variation. This decoupling might explain the di C and 19.9 13 was very weak suggesting the presence of little or no kinetic e δ ◦ S S δ S O C C O 18 13 and 13 18 δ δ and S δ δ set between soft tissue growth and shell growth processes. cult to understand, the decoupling between tissue growth, shell growth and S C ects, i.e. metabolic (resulting from respiratory CO ff ffi ff O 13 and 18 δ δ S are di C Since shells were sampled in April and growth starts in late spring (Cardoso et al., Vital e An interesting fact is that, in 2007, the period with lowest predicted Overall, measured 13 stopped around October–November (asNovember revealed until by March/April, the no isotope carbonatenot was record). grow. It deposited From is in about not thecorresponding until shell to shell and growth the the resumes preceding shell in periodsults did the of thus following slow growing suggest growth season that becomes thatcessation annual clearly a which visible. growth line starts The lines in re- in autumn. 2009; Fig. S3line in and Supplement), the all shell edge were considered to belong to the growing season of 2009. The highest surface of the valvesured and and in predicted thegrowth acetate occurred peel between of June the and cross-section. September, By slowing matching down mea- after that until growth Although the mechanisms controlling thetus incorporation of gametogenesis (Witbaard et al., 2012)intra-annual suggests that metabolism may play aof role in the the a phase o 4.3 Validation of growth lines and age both could result in a deviation from1986; isotopic Klein equilibrium et with al., the 1996; environment2006, McConnaughey (Tanaka et et 2007; al., al., Goewert 1997; Lorrain etδ et al., al., 2004; 2007). Gillikin In et al., the analysed shells, the relationship between influences variation in 4.2 Shell For shell building,(respired) carbon, both mainly environmental derivedet from al., dissolved 1997). carbon In inorganic in thenusoidal the shell carbon trend of diet, although are and a direct usedof metabolic relationship (McConnaughey annual between growth lines could not be established. This suggests that temperature partly periods were observed in the second around August (Armonies,event 1996; in Cardoso combination et with al., highstop 2009). summer An temperatures in extra could August spawning be in acaused reason by 2007. for short-term However, the events a growth such disruption as storms. in shell growth could have also been sea surface temperatures in(respectively 2008/09 18.7 were nottures very near di the coastUnfortunately, could no temperature have data influenced from thegestion. these incorporation stations is of available to support our sug- (corresponding to the highest observedbonate temperatures) records. was not This representedstrained in suggests the during that car- a in short this period year of time shell (around growth August). might In have some been years two con- spawning a seasonal pattern. Insured shells and 3 predicted and 4of (closer lowest predicted to thethan coast), the deviations observed between 10-yr mea- mean (20.4 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 | 2 − ˆ encia erent leads ff erences in 184indm ff shows large ∼ C in summer; ◦ ˜ ao para a Ci E. directus was 7 yr old (Armonies E. directus erences in growth. Density- ff cient accuracy. Nevertheless, to C in winter and 20 ). This suggests that di ◦ ffi E. directus shore. During their first year of life, ff 4318 4317 8, 10 and 12 cm at respectively an age of 2, erences in growth between locations could be ∼ ff . was suggested for the English coast (Palmer, 2004). in the Wadden Sea; Beukema and Dekker, 1995; Wit- 2 − E. directus The authors would like to thank Evaline van Weerlee for helping with the 10indm http://live.waterbase.nl/waterbase ; < ” funded by the “Monitoring and Evaluation Programme Sandmining” of the Na- from the Dutch Wadden Sea reached an average size of 6.4 cm (Beukema Based on our results, we conclude that counting annual growth lines on the exter- Growth rates calculated using isotope sclerochronology were similar to those calcu- In the Wadden Sea, maximum reported age of sequently growth rates cansupport be the determined identification withthe of su cross-section annual as lines well. weenvironmental When conditions, recommend analysing this analysing populations type acetaterochronology. of from analysis peels areas should with of be very combined di with isotope scle- Supplementary material related to thishttp://www.biogeosciences-discuss.net/10/4303/2013/ article is available online at: bgd-10-4303-2013-supplement.pdf Acknowledgements. isotope analysis and Valeskapart Borges for of preparing the theEnsis project shells directus “Determination for analysis. oftional This Dynamic Institute research Energy was for BudgetEnvironment Waterways and (RWS) (DEB) Public and model Worksresearch the parameters programs of LaMER for “Building the Foundation. withment” Dutch Analysed Nature, (LM-006588/LM-10092). program Ministry shells Joana NTW.3.1.” Cardoso were for and wase “RWS-LaMer Infrastructure collected partly a Long funded and within Tecnologia Deploy- (FCT, by Portugal) the Fundac¸ and34773/2007). Fundo Social Europeu (POPH/FSE) (grant nr. SFRH/BPD/ Goudswaard, 2006), the observeda di reflexion of density-dependent growth. nal side of theto valve an as accurate well estimation as of the in number the of cross-section annual of winter the lines. shell Hence, of age and con- inter-annual variability in growth (Dekker, 2011; Daan and Mulder, 2006; Perdon and The mean annual temperature patternNorth between Sea the coast Dutch is Wadden similar Seahttp://www.nioz.nl (varying and between the about Dutch 5 coast (in shells 3lower and than 4). observed However, shell inserved growth the observed in Dutch for the Wadden the Sea, German3 following being Wadden and years more Sea was 4 similar ( yr towas old; in the general growth Swennen higher ob- et than al., the one 1985). observed In in contrast, the English shell east growth coast in (Palmer, 2004). the present study due to higher densities, causing lower food availability. Since is required to support this suggestion. lated by analysis ofduring external the shell first lines year andobserved of acetate in life peels. the were following The higher years,while fact suggests closer conditions that that to for growth juvenile the growth rates growthE. of coast is directus adults and better are near that the better theand coast o opposite Dekker, was 1995), a similar growth rate to the one observed in this study near the food conditions between areas may causedependent the growth observed of di Average densities near stations 3 andties 4 observed of by this Beukema study and were Dekker alsoat (1995) much in the higher the than Dutch coast densi- Wadden vs. Seabaard ( et al., 2012). Therefore, the lower growth observed at the Dutch coast could be counted (5 yr old for shells 1 and 3, 6and yr Reise, for 1999) shell although 2 andthan it 2–4 2 is yr yr considered old (Armonies that and for Reise,along shell most 1999; the 4). individuals Cardoso Dutch et do coast al., seems not 2009). to become Life be span older higher, of although this an species analysis of a larger sample size Therefore, shells were considered to be one year older than the number of lines 5 5 10 15 20 15 20 10 25 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | O: En- 18 Ensis Ensis δ op de ) bed at , and phytoplankton, Ensis directus Ensis siliqua DIC : validation of the sea- C 13 δ (Annelida : Polychaeta) and ects of dredging on shell formation ff (Molina, 1782), Sci. Mar., 68, 211–217, er, N., Stokes, D., Carroll, J., and Han- ff Macoma balthica , J. Mar. Biol. Ass. UK, 75, 351–362, 1995. 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C.: Isotopic equilibrium between shells and their environment, Sci- Minchin, D. and Eno, C.: Exotics of coastal and inland waters of Ireland and Britain, in: 5 5 15 10 30 25 20 15 10 Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | O values in the 18 δ C) ◦ value 0.001 0.001 0.001 0.001 O. p < < < < 18 δ 2 r C Reconstructed 13 δ 2.2811.2412.544 6.1 0.5031.396 14.2 2.846 9.7 20.4 1.352 16.3 6.2 15.8 2.3160.1211.169 8.4 19.2 15.6 0.0424 18.8 − − − − − − − − − − − measured 0.02 0.85 0.050.10 0.89 0.83 0.08 0.86 = + + − − 4326 4325 y O x x x x · · · · 18 C and reconstructed temperature data retrieved from 0.69 O, δ 0.783 1.386 1.709 0.424 0.327 13 − 18 δ − − − − − 0.91 0.87 0.95 1.01 δ = = = = O, y y y y 18 δ predicted MaxNMeanSD 2.247 0.382 Max 278N 0.531Mean SD 1.092 278 0.477Max 237NMean 0.48SD 1.889 237 0.409 278 2.3 0.0216 221 0.595 221 0.444 237 2.1 21.8 221 2.6 MaxNMeanSD 1.706 0.0493 311 0.495 311 0.465 311 2.1 Basic Shell Equation 1 2 3 4 = x 3 Min 4 Min 2 Min Shell statistics (‰) (‰) temperature ( 1 Min shell. shells. Results of the linear regression between measured and predicted Summary statistics of E. directus E. directus Table 2. four Table 1. each Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | SD) 0.78) 0.45) 0.51) 0.47) ± ± ± ± ± valve with lines iden- shells. (a) SD) ( 0.90)0.68)0.67)0.99) 5.27 ( 3.65 ( 1.49 ( 1.31 ( shells: ± ± ± ± ± E. directus acetate peel of the hinge showing internal E. directus (b) 4328 4327 acetate peel of the valve with two annual growth lines. (c) Shell 1 Shell 2 Shell 3 Shell 4 ( Length-at-age (cm) and growth of each age class of Photographs of valve and cross-sections of 1 5.06 4.30 5.26 6.48 5.27 ( Age2 Length-at-age (cm)345 9.2 10.77 12.24 Mean length-at-age 7.84 9.80 11.48 Mean yearly growth 8.53 9.48 10.27 12.56 10.02 11.33 ( ( 8.52 ( 12.56 1.08 tified externally as annual growth lines (arrows), Fig. 1. annual growth lines, and Table 3. Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | Discussion Paper | shells. Line repre- E. directus C, right panel) isotope profiles along 13 δ O values in 18 δ 4330 4329 shells. Vertical dotted lines represent annual growth lines observed O, left panel) and carbon ( 18 δ O values according to Eq. (1) (see text), open circles represent measured 18 E. directus δ Stable oxygen ( Comparison of measured and predicted Fig. 3. sents predicted values sampled along theon valve. the Vertical surface dotted of lines the represent shell and annual in growth the lines acetate observed peels. Fig. 2. the valve of four on the surface of the shell and in the acetate peels.