Differential processing of anthropogenic carbon and nitrogen in benthic food webs of A Coruña (NW Spain) traced by stable isotopes

Au ho 's Accep ed Manusc ip Di e en ial p ocessing o an h opogenic ca - bon and ni ogen in ben hic ood webs o A Co uña (NW Spain) aced by s able iso opes An onio Bode, Consolación Fe nández, Ca men Mompeán, San iago Pa a, Fe nando Rozada, Joaquín Valencia-Vila, Inés G. Viana PII: S0967-0645(13)00374-3 DOI: h p://dx.doi.o g/10.1016/j.ds 2.2013.09.033 Re e ence: DSRII3520 To appea in: Deep-Sea Resea ch II Ci e his a icle as: An onio Bode, Consolación Fe nández, Ca men Mompeán, San iago Pa a, Fe nando Rozada, Joaquín Valencia-Vila, Inés G. Viana, Di e en ial p ocessing o an h opogenic ca bon and ni ogen in ben hic ood webs o A Co uña (NW Spain) aced by s able iso opes, Deep-Sea Resea ch II, h p://dx.doi.o g/10.1016/j.ds 2.2013.09.033 This is a PDF ile o an unedi ed manusc ip ha has been accep ed o publica ion. As a se ice o ou cus ome s we a e p o iding his ea ly e sion o he manusc ip . The manusc ip will unde go copyedi ing, ypese ing, and e iew o he esul ing galley p oo be o e i is published in i s inal ci able o m. Please no e ha du ing he p oduc ion p ocess e o s may be disco e ed which could a ec he con en , and all legal disclaime s ha apply o he jou nal pe ain. www.else ie .com/loca e/ds 2 1  Di e en ial p ocessing o an h opogenic ca bon and ni ogen in ben hic ood webs o A Co uña (NW Spain) aced by s able iso opes An onio Bode*1, Consolación Fe nández2, Ca men Mompeán1, San iago Pa a1, Fe nando Rozada1,3, Joaquín Valencia-Vila1 and Inés G. Viana1 * e-mail: an onio.bod[email p o ec ed] 1 Ins i u o Español de Oceanog a ía. Cen o Oceanog á ico de A Co uña. Apdo. 130. 15080 A Co uña, Spain 2 Unidad de Ecología. Depa amen o de Biología de O ganismos y Sis emas. Uni e sidad de O iedo. 33071 O iedo, Spain 3 P esen add ess: Ins i u o de Ganade ía de Mon aña, CSIC-Uni e sidad de León, Finca Ma zanas, C a. G ulle os, 24346 León, Spain Abs ac In his s udy he e ec o inpu s o o ganic ma e and an h opogenic ni ogen a small spa ial scales we e in es iga ed in he ben hos o he Ria o A Co uña (NW Spain) using s able ca bon and ni ogen iso opes. This ia is cha ac e is ically en iched in nu ien s p o ided ei he by ma ine p ocesses (as coas al upwelling) o by u ban and ag icul u al was e. S able iso ope composi ion in ophic guilds o in aunal ben hos e ealed spa ial di e ences ela ed o hei nu ien inpu s. The main di e ence was he p esence o an addi ional chemoau o ophic ood web a he si e wi h a la ge accumula ion o o ganic ma e . The en ichmen in hea y ni ogen iso opes obse ed in mos compa men s sugges s he in luence o sewage-de i ed ni ogen, despi e la ge inpu s o ma ine ni ogen. Mac oalgae (Fucus esiculosus) esul ed signi ican ly en iched a he si e in luenced by es ua ine wa e s. In con as , no di e ences we e ound in mussels (My ilus gallop o incialis), hus sugges ing a majo dependence on ma ine nu ien sou ces o his species. Howe e , he es ima ions o an h opogenic in luence we e la gely dependen on assump ions equi ed o model he di e en con ibu ions o sou ces. The 2  measu emen o s able iso ope signa u es in a ious compa men s e ealed ha , despi e an h opogenic nu ien s a e eadily inco po a ed in o local ood webs, a majo in luence o na u al ma ine nu ien sou ces canno be disca ded. Keywo ds: δ15N, δ13C, sub idal, in e idal, was ewa e , upwelling, chemoau o ophy 1. In oduc ion Coas al ood webs a e inc easingly al e ed by p essu es om eu ophica ion and pollu ion as mos o he human popula ion concen a es nea he coas . An h opogenic nu ien s, as hose de i ed om u ban and ag icul u al was ewa e s ha e been iden i ied as one o he main causes o changes in he s uc u e and composi ion o ood webs because o hei impac in he nu ien cycles (McClelland and Valiela, 1998; Cas o e al., 2007). The excess nu ien s may lead o la ge inc eases in p ima y p oduc ion and clea signs o eu ophica ion, including hypoxia when he emine alisa ion o he p oduced o ganic ma e exhaus s he oxygen in he wa e , bu o en he changes emain unno iced because some coas al ecosys ems a e al eady highly p oduc i e. Es ua ies, o ins ance, display enhanced p oduc ion and speci ic ood webs ela ed o hei di e se inpu s o nu ien s om ma ine and e es ial sou ces. Simila ly, coas al upwelling causes ele a ed le els o p ima y p oduc ion by he inpu o signi ican amoun s o nu ien s om deep wa e s. The Galician coas (NW Spain) is one pa adigma ic egion o s udy he e ec s o he an h opogenic and na u al sou ces o nu ien s. I is loca ed a he no he n limi o he eas e n bounda y upwelling sys em o he N A lan ic and cha ac e ised by high p ima y p oduc ion due o he inpu o nu ien - ich deep ocean wa e s nea he coas (Al a ez-Salgado e al., 2002). The e ilising e ec o he upwelling is ampli ied by he ias and bays ha e ain and exchange wa e wi h he shel and a ou apid mine alisa ion o he p oduced o ganic ma e (Al a ez- Salgado e al., 1997). Es ua ine zones in he ias a e gene ally small because o he low low o mos i e s in his egion (Rio Ba ja and Rod iguez Les egás, 1996) and upwelling dynamics 3  domina e nu ien luxes (Noguei a e al., 1997). Howe e , mos o he u ban and indus ial popula ion o Galicia concen a es nea he ias. Nea 57% o a o al popula ion o 1.5 million inhabi an s li es in he wo majo u ban a eas o Vigo and A Co uña (P ecedo Ledo e al., 2008) loca ed inside wo o he main ias. The Ria o A Co uña is o med by a bay o 15.7 km2 and a small es ua ine zone (Ria do Bu go) in he mou h o he i e Me o (Cosme de A ilés and P ego, 1995). The i e basin d ains 385 km2 bu i s mean annual low is only 6.6 m s-1. The ma ine in luence is high in he bay (Cabanas e al., 1987) e lec ing he nu ien dynamics d i en by he win e mixing and summe upwelling in he nea by shel (Casas e al., 1997; Bode e al., 2004a, b). The in luence o es ua ine wa e s is es ic ed o he inne bay whe e he e was also an e ec o he ha bou in as uc u es causing enhanced nu ien and phy oplank on concen a ions (Va ela e al., 1994; Va ela and P ego, 2003). U ban popula ion nea he ia amoun s ca. 250,000 inhabi an s acco ding o he Spanish O icial Popula ion Census (h p://www.ine.es/inebase) hus ha ing a la ge po en ial impac on nu ien inpu s o coas al wa e s. U ban and indus ial de elopmen s in he a ea collec and ea was ewa e in a wa e ea men plan ecen ly imp o ed wi h seconda y and e ia y ea men (h p://augasdegalicia.xun a.es/es/eda s/ACOR.h ml). This plan is designed o a popula ion o up o 600,000 inhabi an s and he ea ed wa e s each he open ocean h ough a subma ine ou all loca ed ou side and 7.5 km wes o he mou h o he bay. Ne e heless he possible in luence o di use inpu s o nu ien s o he ia by local poin sou ces, occasional leaks in he sani a ion sys em o o e lows du ing s o ms is no known. Disc imina ion be ween nu ien sou ces o species o ood webs can be made by measu ing he na u al abundance o s able iso opes. As ligh iso opes a e mobilised as e in chemical eac ions han hea y ones, each molecule has a cha ac e is ic iso opic signa u e e lec ing he pa hways ollowed in i s o ma ion. The eac an s a e p og essi ely en iched in hea y iso opes while he p oduc s a e ela i ely deple ed. The iso ope en ichmen o he eac an (ε) is cha ac e is ic o each eac ion (Ma io i e al., 1981; Ruby e al., 1987; Wasse e al., 1998; Needoba e al., 2004) and allows o a di e en ia ion o nu ien s wi h di e en o igins (Hea on, 1986). Ni ogen om 4  u ban and ag icul u al was ewa e s is gene ally en iched in hea y iso opes because o he la ge ac iona ion associa ed wi h ni i ica ion (Ma io i e al., 1981). This ea u e was employed in nume ous s udies o de e mine he in luence o was ewa e in coas al sys ems (McClelland and Valiela, 1998; Sa age and Elmg en, 2004; Cas o e al., 2007; Bode e al., 2011; Viana e al., 2011; Viana and Bode, 2013). Simila ly ca bon iso opic signa u es e lec he o igin o he o ganic ma e in ma ine ood webs (Spi o e al., 1986; Ci uen es e al., 1988; Dando and Spi o, 1993; Machas e al., 2003; Ma ineau e al., 2004; Bode e al., 2006; Male e al., 2008; Sakamaki and Richa dson, 2008; Bode e al., 2011). Howe e , p e ious s udies ocus on a ew species o ben hic compa men s, hus limi ing he gene alisa ion o hei conclusions o he whole ecosys em. The objec i e o he p esen s udy is o de e mine he e ec o inpu s o o ganic ma e and an h opogenic ni ogen a small spa ial scales in he Bay o A Co uña (NW Spain). Fo his pu pose he na u al abundance o s able ca bon and ni ogen iso opes was examined in di e en compa men s, including wa e , ses on, sub idal sedimen s and in auna and in e idal o ganisms. Each compa men was selec ed as ep esen a i e o nu ien e ec s a ins an aneous (su ace wa e ) o longe ime-scales (sedimen s and ben hic o ganisms). In e idal ben hos was chosen as indica o o he con ibu ion o di e en nu ien sou ces in su ace wa e , while sub idal in auna was in ended o e lec nu ien sou ces nea he sedimen . The seasonal a iabili y was aken in o accoun by sampling ac oss annual seasons and he es ima ions o an h opogenic con ibu ions included a ia ions in iso opic ac iona ion. 2. Me hods 2.1 Sub idal sedimen s and in auna Samples o sub idal sedimen s and in auna we e collec ed bimon hly (Janua y 2010 o No embe 2011) a s a ions B2 (9 m dep h) and DB (17 m dep h) using R/V Lu a (Fig. 1). These s a ions we ep esen a i e o he spa ial a iabili y o in aunal ben hos in he a ea (López- Jama and Meju o, 1985). A each sampling da e i e box-co e samples (Bouma- ype box-co e , 5  sampling a ea = 0.0175 m2) we e pooled o ob ain ep esen a i e es ima es o in aunal species composi ion and biomass (López-Jama e al., 1986). The uppe 2 cm o he co e sample sedimen s we e analysed o o al o ganic ma e con en (ash- ee d y weigh ) and g anulome ic cha ac e is ics (Buchanan, 1984). In addi ion pa icula e o ganic ca bon and ni ogen concen a ions (POC and PON) and s able iso ope abundance we e de e mined in subsamples o hese sedimen s. The in aunal samples we e sie ed h ough a 0.5 mm mesh, anaes he ized wi h magnesium chlo ide (7% w/ ), and hen p ese ed in 5% bu e ed o maldehyde p e iously con aining Rose Bengal as a s aining agen o acili a e he so ing o o ganisms. Specimens in ended o s able iso ope de e mina ions we e ob ained om addi ional box-co e samples, so ed immedia ely a e sampling in he labo a o y and kep o 24 h in small aqua ia con aining il e ed seawa e o acili a e e acua ion o gu con en s. Fo ophic analysis species we e classi ied in ophic guilds ( il e eede s, deposi eede s, omni o es and ca ni o es) om he in o ma ion p o ided in he li e a u e. 2.2. Wa e Tempe a u e, salini y and chlo ophyll- luo escence p o iles o wa e abo e each sub idal sedimen s a ions we e ob ained a each sampling da e using a CTD SBE-25. Fluo escence was con e ed o chlo ophyll-a concen a ions a e calib a ion wi h ace onic ex ac s o disc e e wa e samples collec ed wi h Niskin bo les. In addi ion, su ace wa e nu ien s we e de e mined in samples collec ed mon hly du ing 2011 a s a ions W1 and W2, loca ed nea he sedimen s a ions and, acco ding o p e ious s udies (Cabanas e al., 1987; Va ela e al., 1994; Va ela and P ego, 2003), ep esen a i e o ma ine and es ua ine end-membe s, espec i ely (Fig. 1). Addi ional wa e samples we e collec ed nea he coas concu en ly wi h samples o in e idal o ganisms. Dissol ed ni a e, ni i e and ammonium concen a ions we e de e mined by segmen ed- low analysis (Casas e al., 1997). 6  2.3. In e idal ben hos Samples o he b own alga Fucus esiculosus and he mussel My ilus gallop o incialis we e collec ed mon hly du ing 2010 and 2011 a wo in e idal si es (Fig. 1). Me a was loca ed a he ou e bay in he less u banized pa o he s udy a ea. In con as , Ria do Bu go was loca ed in he a ea o di ec es ua ine in luence and hea y u ban popula ion. Algal samples o s able iso ope de e mina ions we e collec ed om he apical 2 cm o he hallus o 25-35 cm long specimens, while mussel samples we e collec ed om he adduc o muscle o 40-50 cm (shell leng h) indi iduals a bo h si es. 2.4. S able iso ope analysis Sedimen and biological samples o s able iso ope de e mina ion we e d ied (50 ⁰C, 24 h), g ound o a ine powde and weigh ed (± 0.002 mg). The iso opic composi ion o o al ni a e (NO3 -+NO2 -) was de e mined by p e ious con e sion in o ammonium and la e eco e y o ammonium on a solid phase (Ahad e al., 2006). The p ocedu e is an adap a ion o he di usion me hod (Sigman e al., 1997) in ol ing he incuba ion o samples in wo s eps. Fi s , aliquo s o he samples we e incuba ed (50 °C, 1 week) in he same collec ing lask wi hou cap o educe he olume and concen a e ni a e. Ashed MgO was added o aise pH abo e 9.7 o emo e ammonia by ola iliza ion. In he second s ep (50 °C, 2 weeks), ashed De a da´s alloy was added o he educed olume sample o con e ni a e and ni i e in o ammonium. The high pH (>11) o he mix u e ensu ed also he con e sion o ammonium in o ammonia gas ha was collec ed on a s e ilized glass- ib e disk (Wha man, GF/F), acidi ied wi h 0.5 ml o 0.25N H2SO4 and hooked on a needle ixed o he inne side o he lask (Slawyk and Raimbaul , 1995). A e he incuba ion, he disk il e s con aining ammonium sulpha e we e d ied and p epa ed o iso opic analysis. The s able iso ope composi ion o ammonium was de e mined in ano he aliquo o he wa e samples by an adap a ion o he di usion me hod (Holmes e al., 1998). This me hod in ol es gas-phase di usion as desc ibed o he second s ep o he o al 7  ni a e ex ac ion. In all cases co ec ions o iso opic ac iona ion du ing he whole incuba ion and di usion s eps we e made (Holmes e al., 1998). Samples we e placed in in capsules and in oduced in o an iso ope- a io mass spec ome e (The mo Finnigan Ma Del a Plus) ia an elemen analyse (Ca lo E ba CHNSO 1108). Iso opic esul s a e exp essed in del a no a ion (δ15N o δ13C) ela i e o a mosphe ic N o VPDB ( Bode e al., 2011). P ecision (SE o 5 eplica es) was be e han 0.05 ‰ o ei he δ15N o δ13C. The coe icien o a ia ion o iplica e sample aliquo s was always <2%. P ecision o δ15N de e mina ions in bo h ni a e and ammonium was be e han 0.4 ‰. The con ibu ions o an h opogenic ( a) and ma ine (1- a) sou ces o ni ogen composi ion o p ima y p oduce s (δ15NP) we e es ima ed using a mixing model o wo end membe s: δ15NP = a δ15Na + (1- a) δ15Nm - ε whe e δ15NP is he iso opic composi ion o phy oplank on, mic ophy oben hos o mac oalgae, es ima ed om he analysis o ses on, su ace sedimen s o F. esiculosus, espec i ely. The iso opic composi ion o ni ogen sou ces was ep esen ed by he mean alue o o al ni a e in su ace ma ine wa e s (δ15Nm) o an h opogenic ni ogen (δ15Na). As i was di icul o ob ain ep esen a i e samples om he di use sou ces o an h opogenic ni ogen in he s udy a ea, we used a mean δ15Na alue ob ained om measu emen s in samples o u ban was ewa e eleased om se e al wa e ea men plan s in he s udy egion (17.8±0.6‰ se, n=7). The model included an iso opic en ichmen ac o (ε) be ween he sou ce (ni a e) and he p oduc (p ima y p oduce ni ogen). Se e al alues o ε we e employed o cons ain he es ima ed con ibu ions. 2.5. S a is ical analysis Di e ences be ween s a ions in he alues o he en i onmen al a iables we e de e mined using non pa ame ic ANOVA (Mann-Whi ney U) while di e ences in iso opic composi ion among ophic guilds we e analysed using pa ame ic ANOVA and a pos e io i es s (Dunne C). As he main objec i e o his s udy is o compa e di e en loca ions in he s udy a ea, all alues 8  om he same sampling si e we e a e aged. The species composi ion o he in aunal communi ies in sub idal sedimen s was analysed using a clus e analysis (B ay-Cu is dis ance, g oup a e age me hod) on log- ans o med species biomass o each sampling da e. Only species con ibu ing >0.1% o o al biomass we e selec ed o his analysis. The con ibu ion o species o simila i y wi hin each s a ion was de e mined using he p ocedu e SIMPER o PRIMER s a is ical package (Cla ke and Wa wick, 2001). 3. Resul s 3.1. Wa e and sedimen s Su ace wa e om he s a ion W2 was signi ican ly less saline han wa e om W1 bu o he wise bo h s a ions ha e simila mean alues o SST, ni ogenous nu ien s o chlo ophyll (Table 1). The in luence o he es ua ine wa e s was mo e e iden in he ses on composi ion, as POC and PON alues a W2 wa e s we e ca. 2.5 imes highe han hose o W1, ha ing also an excess o ca bon as indica ed by he C:N a io. Howe e , he e we e no signi ican di e ences in he a e age iso opic composi ion o ses on o wa e a bo h s a ions. The wa e collec ed a bo h in e idal sampling si es did no show ei he di e ences in he wa e a iables analysed, excep in he δ15N alues o ni a e ha we e signi ican ly lowe a he es ua ine si e (Table 1). Simila esul s we e ound when compa ing wa e cha ac e is ics abo e bo h in auna sampling s a ions, as bo h ha e equi alen empe a u e, salini y, and in eg a ed chlo ophyll alues (Table 2). The only signi ican di e ence was in he a e age amoun o ligh eaching he sedimen su ace (21% a S . B2 and 7% a S . DB). Despi e he simila i ies in wa e -column p ope ies, he e we e la ge di e ences in sedimen s om he in aunal s a ions (Table 3). Sedimen s om S . DB showed a mix u e o sands bu we e cha ac e ised mainly by a la ge ac ion o mud and o ganic ma e han hose om S . B2. To al o ganic ma e (%AFDW), ca bon (%C o al) and ni ogen con en a S . DB we e >5, 15  Ni a e de i ed om was ewa e s and manu e is cha ac e is ically en iched in 15N because o he la ge ac iona ion associa ed wi h ni i ica ion and dini i ica ion p ocesses (Ma io i e al., 1981) wi h bo h ni a e and ammonium δ15N gene ally abo e 10‰ (Tucke e al., 1999; Sa age and Elmg en, 2004). The alue assumed o δ15Na is compa able wi h ha ound in was ewa e s om o he a eas e en i exceeded ou measu emen s in he wa e , sedimen s o bio a. This would indica e ha he e we e no la ge inpu s om u ban o ag icul u al was ewa e s o he bay, despi e o he la ge u ban popula ion. This is suppo ed by he small en ichmen in 15N (<2‰) ound be ween ni a e, ses on and su ace sedimen s (Tables 1 and 3). Howe e , he e we e ela i ely high en ichmen s in some guilds (e.g. DF) o species (F. esiculosus), sugges ing he po en ial impac o ni ogen om was ewa e , a leas in he inne zone o he bay. The en ichmen could be explained by he accumula ion o hea y ni ogen in s uc u al issues wi h low u no e a es while ligh ni ogen is apidly exchanged wi h he wa e , as ound in o he s udies (Sa age and Elmg en, 2004). In addi ion, di use sou ces o hea y ni ogen may a ec ben hic o ganisms a small spa ial scales. Recen measu emen s o δ15N in ni a e om in e s i ial wa e s in uppe 10 cm o sedimen s om he inne es ua y (unpub. esul s) p oduced alues (mean±se 17.2±0.9‰, n=3) which we e close o hose ound in was ewa e s. This sugges s ha es ua ine sedimen s play a majo ole o in he emine alisa ion o di use inpu s o was ewa e ni ogen. Ou es ima ions indica e an a e age low inpu o was ewa e (an h opogenic) ni ogen o ses on o sedimen s, and e en o F. esiculosus in he es ua ine zone, bu hese es ima ions we e la gely dependen on he iso opic ac iona ion employed. Assimila ion o ni a e is gene ally associa ed wi h iso opic ac iona ion ac o s be ween 0- 20‰, bo h in phy oplank on (Wase e al., 1998; Needoba e al., 2004) and mac oalgae (Naldi and Wheele , 2002) bu mos es ima es a e nea 5‰. In con as assimila ion o ammonium is assumed o ha e almos no ac iona ion a he low ambien concen a ions no mally ound in ma ine wa e s (Wase e al., 1998). The e o e he use o a mean ac iona ion ac o o 3‰ in ou es ima es o an h opogenic ni ogen inpu s ep esen s a conse a i e comp omise be ween he assimila ion o bo h ni a e and ammonium by phy oplank on and mac oalgae. No wi hs anding he upwelling pulses o ni a e in he s udy a ea, s udies wi h iso opic ace s 16  indica ed ha a leas phy oplank on uses equi alen amoun s o ni a e and ammonium a seasonal ime scales (Bode e al., 2004a). The esul ing low in luence o an h opogenic ni ogen is consis en wi h p e ious s udies in he Galician coas (Bode e al., 2006; 2011; Viana e al., 2011; Viana and Bode, 2013). Howe e , he la ge in luence o he alue o he iso opic ac iona ion ac o employed in he es ima ed con ibu ion o di e en ni ogen sou ces is no gene ally acknowledged in pollu ion s udies (Sa age and Elmg en, 2004; Lamb e al., 2012) and ou esul s add o he g owing e idence ha δ15N alues alone do no p o ide an unequi ocal p oo o a majo in luence o an h opogenic ni ogen on coas al ecosys ems. Acknowledgemen s We a e g a e ul o he c ew o R/V Lu a o hei collabo a ion du ing wa e and sedimen sampling. Nu ien concen a ions we e de e mined by R. Ca ballo and sedimen cha ac e is ics by J. F. Feijoo. We also acknowledge he pa icipa ion o A.F. Lamas in sample collec ion and p epa a ion o s able iso ope analysis and o M.C. Vázquez in he analysis o in aunal species. S able iso ope de e mina ions we e made by he Se icio de Apoyo a la In es igación o he Uni e sidad de A Co uña (Spain). This esea ch was unded by p ojec s ANILE (CTM2009- 08396 and CTM2010-08804-E) o he Plan Nacional de I+D+i (Spain), and RADIALES o he Ins i u o Español de Oceanog a ía (IEO, Spain). C.M. and I.G.V. we e suppo ed by FPI ellowships om IEO and om Minis e io de Economía y Compe i idad (Spain), espec i ely. Re e ences Ahad, J., Ganesh am, R., Spence , R., Uhe , G., Gulli e , P., B yan , C., 2006. E idence o an h opogenic 14C-en ichmen in es ua ine wa e s adjacen o he No h Sea. Geophysical Resea ch Le e s 33(8), doi: 10.1029/2006GL025991. Al a ez-Salgado, X.A., Cas o, C.G., Pé ez, F.F., F aga, F., 1997. Nu ien mine aliza ion pa e ns in shel wa e s o he Wes e n Ibe ian upwelling. Con inen al Shel Resea ch 17, 1247-1270. 17  Al a ez-Salgado, X.A., Beloso, S., Join , I., Noguei a, E., Chou, L., Pé ez, F.F., G oom, S., Cabanas, J.M., Rees, A.P., Elskens, M., 2002. New p oduc ion o he NW Ibe ian shel du ing he upwelling season o e he pe iod 1982-1999. Deep Sea Resea ch 49(10), 1725- 1739. 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Measu emen o δ15N in mac oalgae s o ed in an en i onmen al specimen bank o egional scale moni o ing o eu ophica ion in coas al a eas. Ecological Indica o s 11, 888-895. Viana, I.G., Bode, A., 2013. S able ni ogen iso opes in coas al mac oalgae: geog aphic and an h opogenic a iabili y. Science o he To al En i onmen 443, 887-895. 22  Wase , N.A., Yin, K.D., Yu, Z.M., Tada, K., Ha ison, P.J., Tu pin, D.H., Cal e , S.E., 1998. Ni ogen iso ope ac iona ion du ing ni a e, ammonium and u ea up ake by ma ine dia oms and coccoli hopho es unde a ious condi ions o N a ailabili y. Ma ine Ecology P og ess Se ies 169, 29-41. 23  8.44° 8.40° 8.36° 8.32° 43.32° 43.36° 43.40° Me a Ria do Bu go DB B2 W1 W2 A Co uña 8° 4° 0° 36° 40° 44° 48° Ibe ian Peninsula Figu e 1. Loca ion o sampling s a ions o sub idal in auna (DB and B2), in e idal ben hos (Me a and Ria do Bu go) and su ace wa e p ope ies (W1 and W2) in he Bay o A Co uña (NW Spain). 24  G oup a e age DB DB DB DB DB DB B2 B2 B2 B2 B2 B2 Sam p les 100 80 60 40 20 0 Simila i y T ans o m: Log(X+1) Resemblance: S17 B ay Cu is simila i y S . DB S . B2 Figu e 2. Clus e o in aunal samples (g oup a e age me hod) compu ed om B ay-Cu is simila i y index on log- ans o med biomass alues o species con ibu ing a leas 0.1% o o al biomass. 31  SSS 30.4 2.4 34.0 0.6 n.s. NO3 - 38.62 33.77 14.21 10.65 n.s. NO2 - 0.76 0.15 0.53 0.11 n.s. NH4 + 4.72 1.13 3.51 1.32 n.s. δ15NNH4 0.2 0.7 0.2 0.7 n.s. δ15NNO3 3.1 0.2 4.2 0.3 0.007 Table 2. Mean (se: s anda d e o ) alues o a iables measu ed in he wa e column abo e in auna s a ions (B2 and DB). SST: sea su ace empe a u e (°C), SSS: sea su ace salini y, bo om: empe a u e 1 m abo e he bo om (°C), Chlain : wa e column in eg a ed chlo ophyll-a, %PARbo om: pe cen o su ace i adiance (PAR) a he bo om. numbe o samples = 12. P: signi icance o Mann-Whi ney U o di e ences be ween s a ions. n.s.: P>0.05 B2 DB mean se mean se P SST 14.95 0.49 14.65 0.52 n.s. SSS 33.82 0.51 34.43 0.59 n.s. bo om 14.82 0.34 14.34 0.28 n.s. Chlain 16.01 5.46 45.17 13.96 n.s. %PARbo om 20.81 3.13 6.66 1.37 0.001 Table 3. Mean (se: s anda d e o ) alues o sedimen a iables measu ed a he in auna s a ions. Q50 φ: median o he dis ibu ion o pa icle diame e (φ = log2(mm)), S0: selec ion coe icien , %Coa se sand: pe cen o >500 µm diame e pa icles (by weigh ), %Fine sand: pe cen o 62- 500 µm diame e pa icles (by weigh ), %Mud: pe cen o <62 µm diame e pa icles (by weigh ), %AFDW: pe cen ash- ee d y weigh , %C o al: pe cen o al ca bon (including 32  ca bona es), %N: pe cen ni ogen, C:N: mola C:N a io, δ13C o al: na u al abundance o 13C (including ca bona es), δ13Co g: na u al abundance o 13C (o ganic ma e ), δ15N: na u al abundance o 15N. numbe o samples = 9. P: signi icance o Mann-Whi ney U o di e ences be ween s a ions. n.s.: P>0.05. S a ion B2 DB mean se mean se P Q50 φ 2.95 0.01 3.62 0.08 0.000 S0 1.44 0.01 2.06 0.03 0.000 %Coa se sand 1.02 0.14 3.20 0.37 0.000 %Fine sand 91.19 0.46 56.61 1.74 0.000 %Mud 7.79 0.39 40.19 1.90 0.000 %AFDW 2.07 0.18 10.30 0.55 0.000 %C o al 1.90 0.16 4.60 0.12 0.000 %N 0.03 0.00 0.20 0.01 0.000 C:N 76.86 7.97 27.41 1.14 0.001 δ13C o al -2.8 0.3 -13.4 0.3 0.000 δ13Co g -25.3 0.1 -24.9 0.1 n.s. δ15N 5.2 0.1 5.1 0.1 n.s. Table 4. Mean (se: s anda d e o ) alues o δ13C, δ15N and biomass (B, mg esh weigh m-2) o selec ed in aunal species a s a ions B2 and DB. The axonomic g oup (all species) and ophic guild (only species analysed o s able iso opes) a e indica ed. %sim: pe cen con ibu ion o species o B ay-Cu iss simila i y o each s a ion (SIMPER analysis, Cla ke and Wa wick, 2001). n: numbe o samples (o indi iduals o s able iso opes). FF: il e eede , FFs: il e eede wi h symbion s, DF: deposi eede , O: omni o e, P: p eda o . 33  δ13C δ15N B2 DB G oup species Gui ld me an s e me an s e n %si m mea n se n %si m mea n se n Mollusca Pha us legumen FF - 15. 5 0. 17.7 0. 29 16. 8 760 6.2 529 2.4 6 --- --- --- - - - Polychae a Pa adoneis a ma a --- --- -- - --- -- - - - - 11. 1 416. 8 61.2 6 --- --- --- - - - Mollusca Chamelea gallina FF - 17. 4 0. 37.3 0. 2 1 29.0 228 9.3 138 8.0 5 --- 2.6 --- 1 O he s Neme ea --- --- -- - --- -- - - - -8.3 293. 4 215. 7 7 --- 251 6.3 227 1.3 6 Polychae a Magelona ili o mis --- --- -- - --- -- - - - - 7.3 80.5 23.7 6 --- --- --- - - - Mollusca My ea spini e a FFs - 27. 5 0. 5 - 1.9 0. 5 1 8 --- --- --- - - - 10. 4 177 5.0 574. 5 6 Polychae a No omas us la e iceus DF - 17. 5 0. 58.3 0. 4 9 --- 75.5 74.3 4 8.8 435. 1 115. 8 7 Polychae a Euclymene oe s edi DF - 18. 1 0. 38.7 0. 4 7 --- --- --- - - -8.3 528. 5 233. 6 7 34  Polychae a Chae ozone gibbe DF - 19. 3 0. 47.6 0. 3 8 --- 0.3 --- 1 8.0 792. 6 213. 4 7 Mollusca Nucula sp. --- --- -- - --- -- - - - - --- 69.7 68.9 2 7.4 455. 8 131. 1 6 Polychae a Chae ozone se osa --- --- -- - --- -- - - - - --- --- --- 0 7.2 100 6.5 808. 8 7 Echinode ma a Lep osynap a be gensis DF - 16. 6 0. 3 11. 8 1. 5 4 --- 155. 1 91.8 6 --- 75.7 28.8 5 Echinode ma a Lep osynap a inhae ens DF - 16. 7 0. 4 10. 8 0. 0 3 --- 99.8 --- 1 --- 362. 8 337. 0 2 Mollusca Ab a ni ida DF - 18. 1 -- - 6.6 -- - 1--- 0.9 0.64--- 131. 7 71.2 3 Mollusca Co bula gibba FF - 16. 9 0. 27.1 0. 2 8 --- --- --- - - ---- 560. 6 367. 1 3 Mollusca Mac a s ul o um FF - 15. 9 0. 17.9 0. 2 7 --- 581 7.6 324 1.4 5 --- 237 9.2 --- 1 Mollusca Nassa ius e icula us O - 16. 5 0. 4 10. 8 0. 3 1 4--- 412 5.4 363. 3 2 --- 100 0.0 465. 5 4 35  Mollusca Thyasi a lexuosa FFs - 28. 5 0. 3 - 6.3 0. 7 5 --- 0.3 --- 1 --- 112. 1 32.3 6 Polychae a Diopa a neapoli ana C - 17. 3 0. 3 10. 6 0. 4 5 --- 569. 2 354. 7 3 --- --- --- - - - Polychae a Glyce a sp. C - 17. 5 0. 2 11. 3 0. 6 6 --- 3.7 3.0 3 --- 369. 9 58.5 2 Polychae a Neph ys hombe gii C - 16. 7 0. 49.2 0. 6 6 --- 384. 3 285. 6 6 --- 15.0 11.7 4