Decadal variability in chlorophyll and primary production off NW Spain.

CLIMATE RESEARCH Clim Res Vol. 48: 293–305, 2011 doi: 10.3354/c 00935 Published Augus 30 1. INTRODUCTION Phy oplank onic pho osyn hesis in he ocean ab - so bs >100 Tg o ca bon daily (Beh en eld e al. 2006). This p ocess causes a subs an ial educ ion in excess a mosphe ic CO2, hus helping o mode a e global wa ming (IPCC 2007). The a ailabili y o nu ien s and ligh in he su ace laye a e he main ac o s con- olling p ima y p oduc ion. Adequa e ligh le els only each a ela i ely hin laye o he su ace ocean. Nu ien s a e apidly consumed by phy oplank on and hei eplenishmen depends mos ly on e ical mixing, mainly h ough he mal con ec ion and wind- d i en u bulence in win e , while he hea abso bed by he su ace laye s ends o ein o ce e ical s a i- ica ion. Wa ming o su ace wa e s was de ec ed a signi ican a es in almos all ocean egions (She man & Hempel 2009). The inc easing he mal g adien be ween he su ace and sub-su ace laye s may educe he inpu o nu ien s o he illumina ed eupho ic laye whe e p ima y p oduc ion occu s. As a esul , la ge a eas o he majo oceans ha e a educed abili y o cap u e CO2 h ough phy oplank- on pho osyn hesis (McClain e al. 2004, G egg e al. © In e -Resea ch 2011 · www.in - es.com*Email: [email p o ec ed] Decadal a iabili y in chlo ophyll and p ima y p oduc ion o NW Spain An onio Bode1,*, Rica do Anadón2, Xosé Anxelu G. Mo án3, En ique Noguei a3, E a Tei a4, Manuel Va ela1 1Cen o Oceanog á ico de A Co uña, Ins i u o Español de Oceanog a ía, Apdo. 130, 15080 A Co uña, Spain 2Dep o. Biología de O ganismos y Sis emas, Uni e sidad de O iedo, Campus del C is o, 33071 O iedo, Spain 3Cen o Oceanog á ico de Gijón, Ins i u o Español de Oceanog a ía, A da. P íncipe de As u ias 70b, 33212 Gijón/Xixón, Spain 4Dep o. de Ecoloxía e Bioloxía Animal, Uni e sidade de Vigo, Campus Lagoas-Ma cosende, 36210 Vigo, Spain ABSTRACT: Long- e m a iabili y o phy oplank on biomass (chlo ophyll a) and p ima y p oduc ion (ca bon ixa ion) in ela ion o changes in clima ic and oceanog aphic ac o s was analysed o oceanic and shel wa e s o he no h and no hwes Ibe ian Peninsula. Changes ela ed o s a i ica- ion in he wa e column and upwelling in ensi y we e speci ically add essed. The ime se ies include measu emen s o p ima y p oduc ion and biomass o e 19 y . Seasonally, he main mode o empo al a iabili y o he se ies is he occu ence o phy oplank on blooms du ing he win e -sp ing and sum- me -au umn ansi ion pe iods. On he no hwes e n coas (Galicia), he blooms a e mo e equen and a ain highe biomass and p oduc ion alues han on he no he n coas (Ma Can áb ico) due o he longe du a ion and highe in ensi y o upwelling in he o me egion. E en o he longes se ies he e is no signi ican long- e m end in biomass, bu p ima y p oduc ion inc eased in Galicia and dec eased in he Ma Can áb ico a nea ly equi alen a es when conside ing mon hly se ies. The lagged ela ionships be ween ex e nal ac o s and phy oplank on biomass and p oduc ion sugges non-linea in e ac ions be ween phy oplank on and clima e. Nei he he inc ease in su ace s a i ica- ion no he dec ease in upwelling in ensi y has nega i ely a ec ed p ima y p oduc ion in his egion ollowing consis en and sys ema ic pa e ns. Changes in he amoun and p opo ions o nu ien s du ing win e wa e -mass o ma ion, and an inc eased use o nu ien s emine alised in si u, a e p o- posed as he main causes o decadal a iabili y in p ima y p oduc ion in his egion. KEY WORDS: P ima y p oduc ion · Upwelling · Clima e change · Nu ien s · Remine alisa ion · NE A lan ic Resale o epublica ion no pe mi ed wi hou w i en consen o he publishe Con ibu ion o CR Special 27 ‘Clima e change in he NW Ibe ian Peninsula’ Clim Res 48: 293–305, 2011294 2005, Beh en eld e al. 2006, Van e po e & Mélin 2009). P ima y p oduc ion in la ge a eas o he oceans depends on wind-d i en upwelling o nu ien - ich deep wa e s. Such ecosys ems, loca ed a bo h sides o he equa o and on he wes e n shel es o he con i- nen s, accoun o abou 10% o oceanic new p oduc- ion, despi e ep esen ing <1% o he wo ld ocean by a ea (F éon e al. 2009). New p oduc ion elies on nu i- en s p o ided om ex e nal sou ces (new nu ien s) and allows o a ne expo o o ganic ma e o sedi- men s and uppe ophic le els o he ood web. In con- as , p oduc ion based on nu ien s emine alised in si u om o ganic ma e ( egene a ed nu ien s) only sus ains ood webs based on mic obes wi h no ne expo o o ganic ma e (Bode e al. 2004). Be cause o he di e en ial wa ming o he land and ocean, an inc ease in upwelling- a ou able winds has been p e- dic ed as a esul o global wa ming (Bakun 1990). This inc ease has been shown as a cooling o su ace wa e s in some egions (Mendelssohn & Schwing 2002, McG ego e al. 2007) and led o an augmen a ion o phy o plank on biomass in he majo upwelling egions (G egg e al. 2005, Van epo e & Mélin 2009). The upwelling ecosys em o no hwes e n A ica ex ends o e he wes e n Ibe ian Peninsula, o ming one o he wo ld’s la ge ma ine ecosys ems (Long hu s 2007), which sus ain high yields in ishe ies and aqua- cul u e (She man & Hempel 2009). High le els o p i- ma y p oduc ion a e p ima ily ela ed o he nu ien inpu s by upwelling and i s ampli ica ion by emine al- isa ion p ocesses in he coas al inle s o he Galician ias (Bode e al. 1996, Ál a ez-Salgado e al. 2002). Upwelling is less impo an o p oduc ion in he Ma Can áb ico (sou he n Bay o Biscay), whe e nu ien e i lisa ion depends mos ly on he deep con ec ion oc - cu ing du ing win e (Bo as e al. 1990). Mos s udies on he a iabili y o p ima y p oduc ion and biomass in his egion ha e ocused on he e ec s o he inpu s o new nu ien s a sho - e m and local scales (Fe nán- dez & Bode 1991, Casas e al. 1997, Llope e al. 2007) and only limi ed in o ma ion exis s on in e annual changes a he egional scale (Ál a ez-Salgado e al. 2002). In con as o o he upwelling e en s, ecen s udies ha e poin ed ou a mul idecadal dec ease in he in ensi y o upwelling (e.g. Lemos & Sansó 2006) and changes in plank on biomass and composi ion (Llope e al. 2007, Bode e al. 2009, Hue e-O ega e al. 2010, Pé ez e al. 2010). The objec i e o he p esen s udy was o analyse long- e m ends in phy oplank on biomass and p i- ma y p oduc ion in he upwelling ecosys em o NW Spain wi h emphasis on hei ela ionship o changes in la ge-scale o cing ac o s ela ed o clima e, such as hose ela ed o changing a mosphe ic p essu e ields and coas al upwelling. The wo king hypo hesis was ha he inc ease in empe a u e in su ace wa e s would enhance s a i ica ion, and in u n educe he inpu o nu ien s in o su ace wa e s. This e ec would be ampli ied by he dec easing in ensi y o up - welling, and would lead o measu able dec eases in he biomass and p oduc ion o phy o plank on. A com- pa a i e analysis o he di e en ial e ec o en i on- men al ac o s on p ima y p oduc ion on he wes e n coas (Galicia) and he no he n coas (Ma Can- áb ico) was made using ime se ies o obse a ions om sa elli e-bo ne senso s and in si u measu emen s. 2. MATERIALS AND METHODS Phy oplank on biomass was es ima ed om chlo o- phyll aconcen a ions measu ed in si u o es ima ed om sa elli e-bo ne senso s. Measu emen s a sea we e ob ained om he ime-se ies s a ions o he p o- jec RADIALES (www.se ies empo ales-ieo.ne ), in ope a ion since 1987 in NW Spain (Valdés e al. 2007). De ails o sampling and addi ional in o ma ion on hese ime se ies can be ound in Casas e al. (1997) and Llope e al. (2007). B ie ly, wa e samples we e col- lec ed mon hly a each loca ion wi h Niskin bo les a up o 8 dep hs simul aneously wi h CTD cas s (Seabi d SBE-25 o SBE-911). Fi e s a ions wi h maximum dep hs be ween 80 and 110 m and dis ibu ed along 10°W 8° 6° 4° 2° 40° 42° 44° N Vigo A Co uña Gijón San ande Cudille o OG OC Ma Can áb ico Galicia Ibe ian Peninsula Fig. 1. S udy a ea. Coas al ime-se ies si es o chlo ophyll (all si es) and p ima y-p oduc ion (only in A Co uña and Cudille o) measu emen s. Sampling si es we e cha ac e is ic o Galicia (Vigo and A Co uña) and Ma Can áb ico (Cud- ille o, Gijón and San ande ) egions. The weekly SeaWiFS sa elli e obse a ions we e a e aged o each o he coas al and oceanic a eas inside he ma ked ec angles. The 200 m isoba h is ma ked (dashed line). OG: oceanic Galicia, OC: oceanic Ma Can áb ico Bode e al.: Decadal a iabili y in chlo ophyll and p oduc ion he coas we e selec ed o he p esen s udy (Fig. 1). Chlo ophyll aconcen a ion was de e mined om sam- ples collec ed on GF/F il e s, ex ac ed in 90% ace- one o e nigh and measu ed luo ome ically (Pa sons e al. 1984). Recen samples om he se ies o A Co uña (since 2000) and Gijón (since 2001) we e ana - lysed using he spec o luo ome ic me hod (Ne eux & Pa nouse 1987). In hese cases, in e calib a ion adjus - men s be ween me hods we e made o ensu e he com- pa ibili y o he se ies. These se ies a e he la ges col- lec ion o ield measu emen s o chlo ophyll in he egion, co e ing he pe iod 1989 o 2007 wi h di e en leng hs o ime acco ding o he s a o sampling a each loca ion. Sa elli e-de i ed chlo ophyll concen a ion allowed o a mo e de ailed analysis o phy oplank on dis ibu- ion o e la ge a eas and wi h highe empo al esolu- ion han measu emen s a ixed s a ions. In he p esen s udy we collec ed 8 d a e aged su ace chlo o phyll alues es ima ed om he Sea- iewing Wide Field-o - iew Senso (SeaWiFS) a ailable o he pe iod 1998 o 2007. Da a om 9 × 9 km pixels (le el 3, ep ocess 5.2, da a accessed in June 2009, h p:// eason. gs c. nasa. go / Gio anni/) we e a e aged in di e en a eas ha a e conside ed ep esen a i e o di e en coas al and oceanic en i onmen s h ough he egion (Fig. 1). P ima y-p oduc ion measu emen s we e made only in A Co uña and Cudille o using wa e samples om 3 o 5 dep h le els dis ibu ed h ough he eupho ic zone and ob ained along wi h hose o chlo ophyll de - e mina ions. Samples we e inocula ed wi h ino ganic 14C and incuba ed in simula ed empe a u e and i a- diance condi ions equi alen o hose o he o iginal sampling dep h (Bode e al. 1996, Llope e al. 2007). Incuba ions las ed o up o 3 h a noon and he mea- su ed ca bon up ake a es we e scaled o daily p i- ma y-p oduc ion a es using he pho ope iod o each sampling da e. No co ec ions o espi a ion we e made and he es ima es we e assumed o be close o g oss p oduc ion a he han o ne p oduc ion. Fo compa a i e pu poses, and aking in o accoun ha he eupho ic zone in he shel a ied be ween 30 and 45 m (Bode e al. 2004), he chlo ophyll and p ima y- p oduc ion se ies we e in eg a ed down o 80 m (A Co uña) o 110 m (Cudille o) in he wa e column be o e s a is ical analysis. La ge-scale en i onmen al o cing was ep esen ed by he win e -a e aged (Decembe o Ma ch) and sum- me -a e aged (June o Augus ) No h A lan ic Oscilla- ion (NAO) index, measu ing he di e ence in a mos- phe ic p essu e be ween Iceland and he Azo es (Ba ns on & Li ezey 1987, Folland e al. 2009); he A lan ic Mul idecadal Oscilla ion (AMO), measu ing anomalies in sea su ace empe a u e (SST) (Delwo h & Mann 2000); and he upwelling index (UI), de i ed om Ekman anspo compu ed in a 2° × 2° g id cen- ed a 43°N, 11° W om geos ophic winds (La in e al. 2000, Pé ez e al. 2010). Local-scale ac o s we e indica ed by seawa e empe a u e, densi y (σ ) and dissol ed nu ien s. Tempe a u e and densi y we e de e mined om CTD p o iles. SST was in ended as an indica o o he local e ec o global wa ming, while he deg ee o s a i ica ion was ep esen ed by he s anda d de ia ion o empe a u e (e.g. Valdés e al. 2007) o densi y ( o accoun o eshwa e inpu s) in he uppe 50 m laye . Dissol ed nu ien s we e mea- su ed in wa e samples collec ed along wi h hose o chlo ophyll and p ima y p oduc ion using low- segmen ed colo ime ic analysis (Casas e al. 1997, Llope e al. 2007). In he p esen s udy, we employed mean annual alues o ni a e, phospha e and o al eac i e silica in eg a ed in he wa e column a each s a ion o he same dep hs as o chlo ophyll and p i- ma y p oduc ion. Annual means o he se ies we e compu ed using 8 o mo e mon hly obse a ions o a gi en yea . Missing alues we e es ima ed using linea in e pola ion. The a iabili y o he ime se ies (X) was in es iga ed using an addi i e decomposi ion me hod (e.g. No gue i a e al. 1998): X = ⎯x + b + a + ΣAicos [(2π / Ti) + θi] + φi + ε (1) whe e he a iance e ms o a gi en se ies X in ime ( ) we e ep esen ed by he clima ological mean o he ime se ies ( ⎯x), he linea end, pa ame e ised by he slope (b) and in e cep (a) o he linea eg ession, he pe iodic componen s (Ai: ampli ude, Ti: pe iod, θi: phase), he se ial dependence be ween consecu i e ime-se ies alues pa ame e ised by he au oco ela- ion co e icien s (φi ), and he unexplained esiduals (ε ). Pe io dic componen s we e ex ac ed using Fou ie ana - lysis (Poula ikas & Seely 1991) and hei signi icance was de e mined by he Fishe G- es (Swan & Sandi- lands 1995). Au oco ela ion e ms we e de e mined in he de ended and deseasonalised ime se ies using Yule-Walke equa ions (Wei 1989). Signi icance o lin- ea eg ession was de e mined by ANOVA. Co ela ion be ween phy oplank on and en i onmen al a iables was compu ed using he esiduals ob ained a e ime- se ies decomposi ion. Time-se ies analysis was i s made on he mon hly-a e aged alues o desc ibe di - e ences in seasonali y along wi h o he componen s o a iance. The long- e m ends and ela ionships wi h en i onmen al a iables we e compu ed on an nual a - e age alues o he se ies, as ends om mon hly se ies a e la gely in luenced by ex eme e en s (e.g. blooms). Annual se ies allowed o he s udy o he in luence o seasonal-scale en i onmen al a iables such as up- welling o a mosphe ic p essu e ields. 295 Clim Res 48: 293–305, 2011 3. RESULTS 3.1. Biomass a iabili y a egional scale Tempo al pa e ns o SeaWiFS chlo ophyll a ied among si es (Fig. 2). In ocean a eas, he main annual bloom (de ined as he maximum annual concen a ion) occu ed in sp ing while low concen a ions p e ailed o mos o he yea (Fig. 2a,b). Nea he coas , bloom e en s c opped up se e al imes a yea and chlo ophyll concen a ions we e highe in gene al han hose in he nea by ocean. In Galicia, blooms occu ed almos all yea ound bu pa icula ly du ing sp ing and sum- me , he season o highe upwelling ac i i y. Two di - e en egimes, howe e , we e pe cep ible in he Gali- cian shel : in he sou he n pa he e was a apid al e - nance o high and low chlo ophyll alues (Fig. 2c); in he no he n pa , blooms we e in gene al o lowe magni ude, pa icula ly du ing he sp ing (Fig. 2d). Blooms in he Ma Can áb ico we e gene ally e - s ic ed o he sp ing, al hough some seconda y blooms may appea also in au umn (Fig. 2e, ). In si u chlo ophyll se ies also showed sho - e m blooms o highe magni ude in Galicia han in he Ma Can áb ico (Fig. 3). Phy oplank on biomass concen- a ed gene ally in he su ace laye excep in win e and a he end o summe when wa e accumula ion owa ds he coas du ing he upwelling-downwelling ansi ion p oduced high chlo ophyll alues uni o mly dis ibu ed h ough he wa e column (Casas e al. 1997). Local di e ences we e appa en , despi e he di - e en leng hs o he se ies. The e was a gene al de - c easing end in maximum alues and in he e- quency o blooms om Vigo o San ande . E en o e ela i ely sho dis ances, he e we e, howe e , a ia- ions o hese pa e ns. In Gijon, o ins ance, blooms we e mo e equen han in Cudille o and wi h a di e - en e ical dis ibu ion. The 2 oceanic se ies o SeaWiFS chlo ophyll we e sig ni ican ly co ela ed ( = 0.885, p < 0.001, n = 108), and we e also co ela ed wi h hose om shel a eas in he Ma Can áb ico ( = 0.669 and 0.660 o co ela ion be ween oceanic Ma Can áb ico and Cudille o and San ande , espec i ely; p < 0.001, n = 108). In con as , he e we e no co ela ions among se ies om he Gali- cian shel , no be ween he la e and hose se ies om he ocean. These ela ionships highligh he highe impo ance o coas al upwelling o phy oplank on p o- duc ion on he wes e n coas compa ed o he no he n coas , and he in luence o local cha ac e is ics, such as he p esence o ias. Ne e heless, all chlo ophyll se ies om shel a eas used in he p esen s udy we e signi ican ly co ela ed, despi e being ob ained wi h di e en me hods and a di e en si es. Co ela ion coe icien s be ween SeaWiFS and in si u se ies we e 0.593, 0.596, 0.612 and 0.602 o Vigo, A Co uña, Cud- ille o and San ande , espec i ely (p < 0.001, n > 40). These esul s sugges ha he ends in all a eas we e easonably connec ed o consis en . 3.2. Seasonali y and long- e m ends in biomass The analysis o SeaWiFS se ies a e aged a mon hly in e als e ealed ha seasonali y accoun ed o mos o he a iance, pa icula ly in o -shel a eas (Table 1). Two main peaks cha ac e ised ocean chlo o- phyll in bo h he Galicia and Ma Can áb ico a eas, 296 1997 1999 2001 2003 2005 2007 JFMAMJ ASONDJJFMAMJ ASONDJ 1997 1999 2001 2003 2005 2007 JFMAMJ ASONDJJFMAMJ ASONDJ 1997 1999 2001 2003 2005 2007 JFMAMJ ASONDJJFMAMJ ASONDJ a c b d e 0.0 0.5 1.01.52.02.53.0 Chlo ophyll (mg m–3) Chlo ophyll (mg m–3) Chlo ophyll (mg m–3) 051015 0.0 0.51.01.5 2.02.5 3.0 Fig. 2. Tempo al a iabili y o 8 d a e aged SeaWiFS es ima es o su ace chlo ophyll concen a ion in (a) oceanic Galicia, (b) oceanic Ma Can áb ico, (c) Vigo, (d) A Co uña, (e) Cudille o and Gijón, ( ) San ande Bode e al.: Decadal a iabili y in chlo ophyll and p oduc ion wi h he la ges peak being in sp ing and he sec- onda y one in au umn (Fig. 4a). These peaks cap u ed >60% o o al se ies a iance. On he shel , seasonal- i y was s ill he main componen o o al a iance bu accoun ed o a lowe pe cen age han in oceanic a eas, eaching 46% in San ande (Table 1). The suc- cession o blooms along he se ies a ec ed he signi i- cance o pe iods ound o each a ea (Fig. 4b). In Vigo, all blooms o med one majo season o high chlo o- phyll concen a ion, ex ending om ea ly sp ing o he au umn, while in A Co uña he blooms we e g ouped in 2 main peaks o equi alen concen a ion in sp ing and au umn, espec i ely (Fig. 4b). Simila ly, in he Ma Can áb ico, he se ies o Cudille o e - ealed one main peak in ea ly sp ing while in San ande he e was also a seconda y peak in he au umn (Fig. 4b). O he ac o s cap u ed compa a- i ely smalle ac ions o o al se ies a iance a he han seasonali y. Au oco ela ion wi h 1 mo lag was ound only in he Galicia se ies, ac - coun ing o <5% o a iance, indica - ing ha mos blooms we e o sho du a ion and ha co ela i e obse a- ions in he se ies we e independen o each o he . The e we e no signi ican pe iodic componen s o he han seasonali y o any o he SeaWiFS se ies, indica ing ha he e we e no long- e m cycles in he 10 y pe iod analysed. A signi ican linea end, howe e , appea ed in he se ies o A Co uña, accoun ing o ca. 5% o o al a iance (Table 1). This long- e m end indica ed a small bu con inuous inc ease o 0.11 mg chl m–3 y –1 in su ace wa e s. Apa om his end, he ela i ely low pe cen age o a iance accoun ing o he ime-se ies decomposi ion models indica ed ha , pa icula ly in shel wa e s, chlo ophyll concen a ion was a ec ed by local, sho - e m e en s. 3.3. Biomass and p ima y p oduc ion nea he coas The longe in si u ime se ies o chlo ophyll in A Co uña and Cudi lle o compa ed o o he si es, and he simul- aneous measu emen s o p ima y p o- duc ion a hese locali ies, al lowed o a i s compa a i e analysis o he em- po al a iabili y be ween Galicia and he Ma Can áb ico. As ob ained om he analysis o he Sea WiFS se ies, in si u chlo ophyll and p ima y- p oduc ion se ies we e cha ac e ised mainly by hei seasonal cycles (Table 1). In his case bo h se ies displayed a single seasonal peak (Fig. 5a) ex ending o e mos o sp ing and summe (A Co uña) o mo e cen ed in he sp ing (Cudille o). Fo A Co uña, he single seasonal peak ob ained wi h he in si u se ies con as s wi h he double peak ound wi h he SeaWiFS se ies, which can be a ibu ed o he mo e equen sampling equency o he la - e (weekly), hus cap u ing sho -li ing blooms in au umn (e.g. Fig. 2d). Lowe sampling equency (mon hly) in he in si u se ies would also explain he low ac ion o o al a iance accoun ed o by he models (<20%) and he absence o au oco ela ion. No signi ican linea ends we e iden i ied in any o he se ies (Table 1). P ima y p oduc ion also displayed signi ican season- ali y in bo h se ies (Fig. 5b), bu in his case seasonali y 297 a b c 100 75 50 25 0 Vigo 100 75 50 25 0 A Co uña 100 75 50 25 0 Cudille o 100 75 50 25 0 Gijón 100 75 50 25 0 San ande 1990 1994 2002 2006 1998 Dep h (m) 0.0 0.5 1.0 1.5 2.0 d e Chlo ophyll (mg m –3 ) Fig. 3. Tempo al and e ical a iabili y o chlo ophyll concen a ion measu ed in si u a (a) Vigo, (b) A Co uña, (c) Cudille o, (d) Gijón, (e) San ande Clim Res 48: 293–305, 2011 accoun ed o ca. 30% o o al a iance (Table 1). In con as , chlo ophyll in he se ies o A Co uña dis- played a signi ican linea long- e m posi i e end, while he se ies o Cudille o showed a nega i e end. Bo h ends we e o simila magni ude (be ween 4 and 5 mg C m–2 d–1 y –1) and accoun ed o 5 o 7% o o al a iance, bu di e ed in sign (posi i e o nega i e al- ues) (Table 1). 3.4. Long- e m ends and en i onmen al changes The annually-a e aged se ies ollowed ends simi- la o hose desc ibed using he mon hly-a e aged se ies. As indica ed in Sec ion 3.3, no signi ican long- e m cycles we e ound and he only signi ican componen iden i ied was he linea end o p i- ma y p oduc ion a A Co uña (Table 2). This posi i e 298 Se ies Pe iod ⎯x Linea end Pe iodic componen s Au oco ela ion To al b a % a Ti(mo) AiθiTmax % a Lag (mo) Φi % a % a Chl-SeaWiFS OG 1998–2007 0.45 – – – 12 0.25 4.32 3.75 33.20 1 0.20 1.35 66.31 6 0.24 1.88 4.21 31.77 OC 1998–2007 0.40 – – – 12 0.27 4.49 3.43 40.11 – – – 61.85 6 0.20 2.14 3.95 21.74 Vigo 1998–2007 2.84 12 0.99 2.31 7.58 17.20 1 0.24 4.64 21.84 A Co uña 1998–2007 1.64 0.11 –226.14 4.76 6 0.73 3.18 2.96 11.55 1 0.24 4.71 21.01 Cudille o 1998–2007 0.59 – – – 12 0.24 5.35 1.78 31.74 – – – 31.74 and Gijón San ande 1998–2007 0.51 – – – 12 0.26 5.07 2.31 32.71 – – – 46.23 – – – 6 0.17 2.77 3.36 13.52 – – – Chl A Co uña 1989–2007 43.44 – – – 12 16.48 3.57 5.18 16.16 – – – 16.16 Cudille o 1992–2007 30.65 – – – 12 9.91 4.12 4.13 11.16 – – – 11.16 PP A Co uña 1989–2007 138.07 4.95 –9893.40 4.82 12 87.22 3.44 5.43 24.40 – – – 29.22 Cudille o 1992–2007 82.84 –4.11 8210.40 6.72 12 34.51 3.74 4.86 11.33 – – – 30.36 Table 1. Va iance decomposi ion o ime se ies o chlo ophyll and p ima y p oduc ion. Chl-SeaWiFS: SeaWiFS su ace chlo o- phyll concen a ion (mg chl m–3); Chl: wa e -column in eg a ed in si u chlo ophyll concen a ion (mg chl m–2); PP: wa e -column in eg a ed p ima y-p oduc ion a e (mg C m–2 d–1); OG: oceanic Galicia; OC: oceanic Ma Can áb ico. Va iance componen s: ⎯x: mean; b: slope; a: in e cep ; Ti: pe iod; Ai: ampli ude; θi: phase; Tmax: maximum empe a u e; Φi : au oco ela ion coe icien ; % a : ac ion o o al a iance accoun ed o by each componen ; (–): no signi ican (p ≥ 0.05) 0.0 0.2 0.4 0.6 0.8 1.0 JFMAMJJASOND Galicia Ma Can áb ico 0 1 2 3 4 5 JFMAMJJASOND Chlo ophyll (mg m –3 ) Chlo ophyll (mg m –3 ) Vigo A Co uña Cudille o and Gijón San ande ab Fig. 4. Seasonali y o SeaWiFS es ima es o su ace chlo ophyll concen a ion in (a) oceanic a eas o Galicia and Ma Can áb ico, (b) coas al a eas Bode e al.: Decadal a iabili y in chlo ophyll and p oduc ion 299 end was highly signi ican and accoun ed o 60% o o al a iance o he se ies. An appa en decadal cycle, howe e , is indica ed by he dis ibu ion o alues o bo h chlo o- phyll and p ima y-p oduc ion se ies in Cudille o (Fig. 6). This cycle is cha ac e ised by high alues in he ea ly 1990s and la e 2000s, wi h ela- i ely low alues be ween 1995 and 2002 o chlo ophyll and be ween 1996 and 2005 o p oduc ion. Tha some yea s lacked enough obse a- ions, and ha he se ies was ela- i ely sho (16 y ), may ha e caused he mul iyea cycle o end o be no signi ican in ou analysis. The main signi ican componen o he annual se ies o en i onmen al a iables was he linea end (Table 2). In he case o phospha e concen a ions and he N:P a io in A Co uña, he e was a signi ican cycle o 18 y accoun ing o ca. 60% o o al a iance. The ampli ude and phase o hese cycles was 4.97 and 0.25, espec i ely o phospha e (65.7% a iance), and 10.77 and 3.43 o he N:P a io (56.3% a iance). Wa ming o su ace wa e s was signi - ican in A Co uña (0.03°C y –1) bu no in Cudille o, and mainly o igi- na ed om he low alues measu ed in 1990 in A Co uña (Fig. 7a). S a i i- ca ion measu ed by he e ical a i- abili y in empe a u e did no show JFMAMJJASOND JFMAMJJASOND Chlo ophyll (mg m –2 ) ab 0 20 40 60 80 A Co uña Cudille o 0 100 200 300 PP (mg C m –2 d –1 ) Fig. 5. Seasonali y o wa e -column in eg a ed (a) chlo ophyll and (b) p ima y p oduc ion (PP) measu ed in si u in A Co uña and Cudille o Va iable Zone Pe iod b a % a p Chl A Co uña 1989–2007 – – – – – Cudille o 1993–2007 – – – – – PP A Co uña 1990–2007 13.71 –27397.30 60.89 0.780 <0.001 Cudille o 1993–2007 – – – – – SST A Co uña 1989–2006 0.03 –59.74 23.23 0.482 0.043 Cudille o 1989–2006 – – – – – sd A Co uña 1991–2007 – – – – – Cudille o 1993–2007 – – – – – sd σ A Co uña 1991–2007 0.01 –19.14 44.69 0.669 0.003 Cudille o 1993–2007 – – – – – N A Co uña 1989–2007 – – – – – Cudille o 1993–2007 – – – – – P A Co uña 1989–2007 – – – – – Cudille o 1993–2007 – – – – – Si A Co uña 1991–2007 3.31 –6616.08 37.60 0.613 0.009 Cudille o 1993–2007 – – – – – N:P A Co uña 1989–2007 – – – – – Cudille o 1993–2007 – – – – – N:Si A Co uña 1991–2007 –0.09 184.19 24.84 –0.498 0.042 Cudille o 1993–2007 0.05 –93.18 29.55 0.544 0.036 NAODM 1989–2007 –0.04 85.21 28.28 –0.532 0.019 NAOJJA 1989–2007 – – – – – AMO 1989–2007 0.02 –48.76 58.30 0.764 <0.001 UIAS 1989–2007 –10.18 20339.99 23.54 –0.485 0.035 Table 2. Signi ican (p < 0.05) in e annual ends indica ed by he pa ame e s o he linea eg ession be ween he sampling yea and annual mean alues o chlo ophyll concen a ion (Chl, mg m–2), p ima y-p oduc ion a e (PP, mg C m–2 d–1), ni a e concen a ion (N, mmol m–2), phospha e concen a ion (P, mmol m–2), silica e concen a ion (Si, mmol m–2), ni a e- o-phospha e (N:P) and ni- a e- o-silica e (N:Si) a ios, sea su ace empe a u e (SST), s anda d de ia ion o empe a u e (sd , °C) and s anda d de ia ion o densi y (sd σ ). All a iables excep SST we e in eg a ed o a e aged in he pho ic laye o A Co uña (40 m) and Cudille o (50 m) s a ions. Signi ican linea ends a e o he No h A lan ic Oscilla ion a e aged be ween Decembe and Ma ch (NAODM) o be ween June and Augus (NAOJJA), o he annual a e age o he A lan ic Mul idecadal Oscil- la ion (AMO) and o he upwelling index (UIAS) compu ed in a 2° × 2° cell cen- ed a 43°N, 11°W and a e aged be ween Ap il and Sep embe . b: slope, a: in- e cep , % a : pe cen o o al a iance accoun ed o by he eg ession, : co ela ion coe icien , p: signi icance; (–): no signi ican Clim Res 48: 293–305, 2011 any signi ican end in ei he se ies (Fig. 7b), while he e was a posi i e end in he e ical a iabili y o σ in A Co uña (Fig. 7c). Dissol ed nu ien s did no show linea in e annual ends, excep o an inc ease in silica e concen a ion in A Co uña (Fig. 8). The dis- ibu ion o nu ien alues sugges s he p esence o la ge cycles in se e al cases, such as he signi ican 18 y cycle o phospha e (Fig. 8b) in A Co uña accompa- nied by simila (bu non-signi ican ) a ia ions in phospha e and ni a e concen a ions in Cudille o. The ends in la ge-scale a iables we e nega i e o NAO and UI and posi i e o AMO du ing he s udy pe iod (Fig. 9, Table 2). C oss-co ela ions be ween chlo o- phyll and en i onmen al se ies indi- ca ed ha he signi ican e ec s appea ed a e a lag o se e al yea s o A Co uña bu we e immedia e in he case o Cudille o se ies (Table 3). Fo ins ance, high phospha e alues in A Co uña we e co ela ed wi h a de c ease in chlo ophyll alues 1 y la e , while he N:P a io was posi- i ely co ela ed wi h chlo ophyll in he same yea . In Cudille o, he mal s a i ica ion and upwelling we e posi i ely co ela ed wi h chlo o - phyll alues, bu no sig ni ican co e- la ions we e ound o any pa icula nu ien , no be ween chlo o phyll se ies and la ge-scale a iables. P i- ma y p oduc ion showed pa e ns o c oss-co ela ion wi h en i onmen al a iables di e en om hose o chlo ophyll (Table 3). The lags o sig - ni ican coe icien s we e la ge o A Co uña compa ed o Cudille o se ies. Only ni a e was posi i ely co ela ed wi h p ima y p oduc ion du ing he same yea . The mal s a i i ca ion was nega i ely co - ela ed wi h p ima y p oduc ion (bu no wi h chlo o- phyll) wi h a lag o 2 y . The e ec o NAO condi ions du ing he p e ious win e was posi i e on p ima y p oduc ion a A Co uña, while he e we e no signi i- can co ela ions be ween phy oplank on a iables and summe NAO. In con as , he e we e no sig - ni ican co e la ions be ween s a i ica ion o la ge- scale a iables and p ima y p oduc ion a Cudille o. The only signi ican co ela ions whe e hose o nu i- en a ios N:P and N:Si om he same yea o om he yea be o e he p ima y-p oduc ion alues we e a e aged. 300 0 100 200 300 400 500 1985 1990 1995 2000 2005 2010 PP (mg C m–2 d–1) 0 20 40 60 80 100 120 0 100 200 300 400 500 0 20 40 60 80 100 120 Chlo ophyll (mg m–2) 1985 1990 1995 2000 2005 2010 A Co uña Cudille o ab cd Fig. 6. Tempo al a iabili y o annual mean alues o wa e -column in eg a ed (a,b) chlo ophyll and (c,d) p ima y p oduc ion (PP) measu ed in si u in (a,c) A Co uña and (b,d) Cudille o. Mean alues compu ed using <8 mon hly obse a- ions (s) we e no used in he se ies analysis. S aigh line: signi ican end (see Table 2) 0.0 0.5 1.0 1.5 2.0 1985 1990 1995 2000 2005 2010 sd (ºC) 0.0 0.2 0.4 0.6 0.8 1.0 1985 1990 1995 2000 2005 2010 sd σ 12 14 16 18 1985 1990 1995 2000 2005 2010 SST (°C) A Co uña Cudille o abc Fig. 7. Tempo al a iabili y o annual mean alues o (a) sea su ace empe a u e (SST) and 2 indices o s a i ica ion: (b) he SD o empe a u e (sd ) and (c) ha o densi y (sd σ ) be ween 0 and 40 m dep h in A Co uña and Cudille o. Open symbols: mean alues compu ed using <8 mon hly obse a ions ha we e no used in he se ies analysis. S aigh line: signi ican end (see Table 2) Bode e al.: Decadal a iabili y in chlo ophyll and p oduc ion 301 4. DISCUSSION 4.1. Seasonal cycle o phy oplank on biomass and p oduc ion Ou analysis using he longes ime-se ies obse a- ions o he no he n Ibe ian coas o da e, spanning >15 y , e ealed a ma ked g adien in he seasonali y o phy oplank on biomass and p ima y p oduc ion ela ed o he p e alence o upwelling. P e ious s ud- ies using sho e se ies highligh ed some local cha ac- e is ics, such as he e ilising e ec o upwelling (e.g. Bode e al. 1996), bu he emphasis was gene ally on he seasonal cycle o a main sp ing bloom and a sec- onda y bloom in au umn, which is expec ed o a em- pe a e sea (e.g. Longhu s 2007). The p esen s udy shows ha blooms occu du ing a longe season and a e o highe in ensi y and equency on he wes e n coas (Galicia) compa ed o he no he n coas (Ma Can áb ico). Fu he mo e, he in ensi y o blooms de - c eased om sou h o no h along he Galician coas , as he p esence o la ge ias in sou he n Galicia am - pli y he e ilising e ec o upwelling by egene a - 0 50 100 150 Silica e (mmol m –2 ) 0 50 100 150 200 250 Ni a e (mmol m –2 ) 0 5 10 15 20 Phospha e (mmol m –2 ) 1985 1990 1995 2000 2005 2010 1985 1990 1995 2000 2005 2010 1985 1990 1995 2000 2005 2010 A Co uña Cudille o abc Fig. 8. Tempo al a iabili y o annual mean alues o (a) ni a e, (b) phospha e and (c) silica e in eg a ed in he wa e column in A Co uña and Cudille o. Open symbols: mean alues compu ed using <8 mon hly obse a ions ha we e no used in he se ies analysis. S aigh line: signi ican end (see Table 2) NAO NAODM NAOJJA –1.5 –1.0 –0.5 0.0 0.5 1.0 1.5 AMO (°C) –0.6 –0.4 –0.2 0.0 0.2 0.4 0.6 –100 0 100 200 300 400 500 UI (m 3 s –1 km –1 ) abc 1985 1990 1995 2000 2005 2010 1985 1990 1995 2000 2005 2010 1985 1990 1995 2000 2005 2010 Fig. 9. Tempo al a iabili y o annual mean alues o la ge-scale, clima ic a iables: (a) No h A lan ic Oscilla ion (NAO) index a - e aged be ween Decembe and Ma ch (DM) o be ween June and Augus (JJA), (b) A lan ic Mul idecadal Oscilla ion (AMO), (c) Upwelling Index (UI) compu ed om geos ophic winds in a 2° × 2° cell cen ed a 43° N, 11° W. S aigh lines: signi ican ends (see Table 2) Va iable Se ies Chl PP Lag (y ) Lag (y ) SST None – – – – sd A Co uña – – –0.489 2 Cudille o 0.575 0 – – sd σ None –– –– N A Co uña – – 0.514 0 P A Co uña –0.498 1 – – Si None – – – – N:P A Co uña 0.620 0 – – Cudille o – – 0.680 0 N:Si Cudille o – – 0.634 1 NAODM A Co uña – – 0.677 1 NAOJJA None –– –– AMO None – – – – UIAS Cudille o 0.572 0 – – Table 3. Signi ican (p < 0.05) c oss-co ela ions be ween annual mean alues o chlo ophyll (Chl, mg m–2) o p ima y p oduc ion (PP, mg C m–2 d–1) and en i onmen al a iables in Table 2. See Table 2 o abb e ia ions. Only co ela ions delayed up o 2 y we e conside ed; (–): no signi ican