Photoacclimation and photoregulation strategies of Corallina (Corallinales, Rhodophyta) across the NE Atlantic

Full Te ms & Condi ions o access and use can be ound a h p://www. and online.com/ac ion/jou nalIn o ma ion?jou nalCode= ejp20 Eu opean Jou nal o Phycology ISSN: 0967-0262 (P in ) 1469-4433 (Online) Jou nal homepage: h p://www. and online.com/loi/ ejp20 Pho oacclima ion and pho o egula ion s a egies o Co allina (Co allinales, Rhodophy a) ac oss he NE A lan ic Ch is ophe J. Williamson, Rupe Pe kins, Ma ian L. Yallop, Césa Pe ei o, Noemí Sanchez, Ka l Gunna sson, Maggie Gamble & Julie B odie To ci e his a icle: Ch is ophe J. Williamson, Rupe Pe kins, Ma ian L. Yallop, Césa Pe ei o, Noemí Sanchez, Ka l Gunna sson, Maggie Gamble & Julie B odie (2018) Pho oacclima ion and pho o egula ion s a egies o Co allina (Co allinales, Rhodophy a) ac oss he NE A lan ic, Eu opean Jou nal o Phycology, 53:3, 290-306, DOI: 10.1080/09670262.2018.1442586 To link o his a icle: h ps://doi.o g/10.1080/09670262.2018.1442586 © 2018 The Au ho (s). Published by In o ma UK Limi ed, ading as Taylo & F ancis G oup. View supplemen a y ma e ial Published online: 17 May 2018. Submi you a icle o his jou nal A icle iews: 161 View C ossma k da a Pho oacclima ion and pho o egula ion s a egies o Co allina (Co allinales, Rhodophy a) ac oss he NE A lan ic Ch is ophe J. Williamson a,b , Rupe Pe kins c , Ma ian L. Yallop b , Césa Pe ei o d , Noemí Sanchez e , Ka l Gunna sson , Maggie Gamble b and Julie B odie a a The Na u al His o y Museum, Depa men o Li e Sciences, C omwell Road, London SW7 5BD, UK; b School o Biological Sciences, Li e Sciences Building, Uni e si y o B is ol, 24 Tyndall A enue, B is ol BS8 1TQ, UK; c School o Ea h and Ocean Sciences, Ca di Uni e si y, Ca di CF10 3AT, Glamo gan, UK; d Ins i u o Español de Oceanog a ia (IEO), Cen o Oceanog á ico de San ande , P omon o io de San Ma ín, 39004 San ande , Spain; e Uni e si a de Gi ona (UdG), Facul a de Ciències, Campus de Mon ili i s/n., 17071 Gi ona, Spain; Ma ine Resea ch Ins i u e, Skúlaga a 4, PO Box1390, 121 Reykja ik, Iceland ABSTRACT This s udy cha ac e izes he pho oacclima ion and pho o egula ion mechanisms ha allow calci ied mac oalgae o he genus Co allina (Co allinales, Rhodophy a) o domina e ock pool habi a s ac oss he NE A lan ic despi e he highly a iable i adiance egimes expe ienced. Rapid ligh cu es (RLCs) we e pe o med wi h pulse ampli ude modula ion (PAM) luo ome y in si u ac oss a ull seasonal cycle in he UK in e idal wi h C. o icinalis and C. caespi osa. La i udinal compa isons we e pe o med ac oss he ull ex en o C. o icinalis’ ange in he NE A lan ic (Iceland–no he n Spain), and o C. caespi osa in no he n Spain. Ex si u RLCs wi h da k eco e y we e u he employed o assess he op imal, as compa ed wi h ac ual, pho ophysiology ac oss seasons and la i udes. Co allina species we e shown o pho oacclima e a seasonal imescales o changing i adiance, inc easing ligh -ha es ing du ing low-ligh au umn/win e pe iods and p o ec ing pho osys ems du ing high-ligh summe condi ions. Seasonal pho oacclima ion was achie ed h ough al e a ion in he numbe o pho osys em (PS) uni s (PSII and ligh ha es ing an ennae) o e ime. Non-pho ochemical quenching (NPQ) se ed as an impo an pho o egula ion mechanism u ilized by Co allina o p e en o minimize pho oinhibi ion o e sho e ime scales (seconds–hou s), hough he e iciency o NPQ was dependen on he seasonal-acclima ed s a e. Wi h inc easing la i ude he e iciency o pho o egula ion dec eased, ep esen ing po en ial di e en ial pho oadap a ion o Co allina ac oss species anges in he NE A lan ic. In con as , highly conse ed in e -speci ic pa e ns in pho ophysiolo- gical esponses o i adiance we e appa en . This s udy demons a es he pho ophysiological mechanisms allowing Co allina o op imize use o he a iable i adiance condi ions appa en in ock pool en i onmen s, when and how hey a e employed, and hei limi a ions. ARTICLE HISTORY Recei ed 18 Sep embe 2017; e ised 15 Janua y 2018; accep ed 19 Janua y 2018 KEY WORDS Co allina; NE A lan ic; NPQ; pho oacclima ion; pho o egula ion; apid ligh cu e In oduc ion I adiance is an essen ial, ye highly a iable, esou ce o mac oalgal g ow h and su i al (Henley & Ramus, 1989). In he in e idal, luc ua ions in i adiance occu o e a a ie y o ime scales, anging om seconds o less, o diu nal and seasonal-scale a ia ions ha a e bo h p edic able (changes in dayleng h and sola angle) and unp edic able (cloudiness, u bidi y and un-o ) (De a & Go don, 1968; Henley & Ramus, 1989; Lobban &Ha ison,1994). In e idal species mus cope wi h la ge g adien s in i adiance ha depend on bo h he daily cou se o sola i adiance, and he idal ange and empo al coincidence o maximum i adiance a mid- day wi h he iming o low ide (Goss & Jakob, 2010). Fo a ben hic mac oalga in a ixed posi ion in he in e idal zone, he challenge is he e o e o op imize he use o he a iable i adiance egime expe ienced (Henley & Ramus, 1989). To complica e his u he , he quan i y o pho o- syn he ically ac i e adia ion (PAR, c. 400–700 nm) expe ienced by in e idal mac oalgae is o en in excess o ha needed o sa u a e pho osyn hesis, pa icula ly du ing summe pe iods (F anklin & Fo s e , 1997). In mos in e idal mac oalgae, he pho ochemical appa a- us ope a es o op imize pho osyn hesis a low ligh le els associa ed wi h imme sion, wi h he esul ha eme sed plan s a e exposed o a la ge excess o ligh ene gy (Da ison & Pea son, 1996). An excess o abso bed ligh ene gy can esul in pho o-damage o he pho osyn he ic appa a us (Hänel e al., 1993), leading o pho o-oxida i e damage ia inc eased p o- duc ion o eac i e oxygen species, which in ex eme cases can cause pigmen bleaching and dea h (Mülle e al., 2001). As such, in e idal mac oalgae mus espond o changes in i adiance in a manne ha bo h op imizes pho osyn hesis and g ow h, whils con- olling o po en ial s ess (Mülle e al., 2001). Th ee gene al p ocesses allow algae o manage p e- ailing i adiance condi ions: adap a ion, acclima ion and egula ion (Huo & Babin, 2011). Pho oadap a ion CONTACT Ch is ophe J. Williamson [email p o ec ed] EUROPEAN JOURNAL OF PHYCOLOGY, 2018 VOL. 53, NO. 3, 290–306 h ps://doi.o g/10.1080/09670262.2018.1442586 © 2018 The Au ho (s). Published by In o ma UK Limi ed, ading as Taylo & F ancis G oup. This is an Open Access a icle dis ibu ed unde he e ms o he C ea i e Commons A ibu ion License (h p://c ea i ecommons.o g/licenses/by/4.0/), which pe mi s un es ic ed use, dis ibu ion, and ep oduc ion in any medium, p o ided he o iginal wo k is p ope ly ci ed. Published online 17 May 2018 is a long- e m selec ion p ocess in esponse o i adi- ance, ul ima ely esul ing in gene ically di e en eco- ypes (Huo & Babin, 2011;Bee e al., 2014). In con as , pho oacclima ion e e s o a pheno ypic plas- ic esponse o a change in i adiance (Huo & Babin, 2011;Bee e al., 2014). This is ypically achie ed by ei he an al e a ion o he size o numbe o pho o- syn he ic uni s (pho osys em II (PSII) and associa ed an ennae pigmen s) (Falkowski & LaRoche, 1991; Mülle e al., 2001;Bee e al., 2014). Du ing sho - e m (seconds o hou s) i adiance luc ua ions, pho o- egula ion u he se es o p o ide a pho o-p o ec i e ne wo k ha allows pho osyn he ic e iciency o be apidly uned by sa ely dissipa ing excess abso bed ligh ene gy as hea and/o he exci a ion ene gy o be balanced wi hin PSs o p e en o lowe po en ial damage (Huo & Babin, 2011; La aud & Lepe i , 2013). Non-pho ochemical quenching (NPQ) is one mechan- ism o pho o egula ion ha quenches pho ochemis y h ough non-pho ochemical p ocesses, e.g. con e sion o many o he exci a ions in he an ennae complex o hea (Consal ey e al., 2005). Du ing NPQ, he ligh - d i en de-epoxida ion o speci ic xan hophyll pig- men s ( ypically iolaxan hin, an he axan hin and zeaxan hin) and he da k eco e y o he ini ial pool, e med he xan hophyll cycle, is associa ed wi h he - mal ene gy dissipa ion (Demmig-Adams & Adams, 1996; Es eban e al., 2009; Goss & Jakob, 2010). This s udy add esses he pho ophysiology o wo in e idal mac oalgae o he genus Co allina (Co allinales, Rhodophy a) ac oss he NE A lan ic, namely Co allina o icinalis Linnaeus and Co allina caespi osa Walke , B odie & I ine. These calci ied, genicula e (a icula ed) species o m ex ensi e u s ha co e la ge a eas o he in e idal and p o ide subs a um, habi a and e ugia o a numbe o impo an ma ine o ganisms (Johansen, 1981; Coull &Wells,1983;Kelahe ,2002,2003;Ho manne al., 2012;Pe kinse al., 2016). Howe e , hey a e p edic ed o be signi ican ly ulne able o u u e an h opogenic change, including wa ming seawa e empe a u es and ocean acidi ica ion (Ho mann e al., 2012; Egilsdo i e al., 2013;Noise ee al., 2013). As such, much ecen esea ch has been aimed a gaining a be e unde - s anding o Co allina ecophysiology, pa icula ly in he NE A lan ic (e.g. B odie e al., 2013,2016; Williamson e al., 2014a,2014b,2015,2017; Pe kins e al., 2016). The aim o his s udy was o build on he ini ial wo k o Williamson e al.(2014b) in o de o iden i y he sui e o pho oacclima ion and pho o egula ion mechanisms ha allow Co allina o op imize ligh use in he a iable in e idal en i onmen , hus con- ibu ing o hei dominance o NE A lan ic ock pools, and o cha ac e ize he use o hese mechanisms in space and ime. Pho ophysiological assessmen s we e pe o med in si u ac oss a ull seasonal cycle in he UK in e idal, and complemen ed wi h ex si u echniques unde labo a o y condi ions. La i udinal compa isons we e u he pe o med o C. o icinalis ac oss he ull ex en o he species’ ange in he NE A lan ic (Iceland–no he n Spain, Williamson e al., 2015), and o C. caespi osa in no he n Spain. Me hods Sampling si es Seasonali y in C. o icinalis and C. caespi osa pho o- physiology was assessed in si u using apid ligh esponse cu es (RLCs, Pe kins e al.,2006) ac oss a comple e annual cycle a Combe Ma in (CM), No h De on, UK (Table 1,Fig. 3), and complemen ed wi h ex si u RLC wi h da k eco e y assessmen s. Combe Ma in lies wi hin he middle o C. o icinalis’ ange in he NE A lan ic (Iceland–no he n Spain), hough is compa a i ely close o he cu en ly known no h- e n edge (no he n England) o C. caespi osa (Williamson e al., 2015). Williamson e al.(2014b) p e iously assessed he pho ophysiology o bo h spe- cies in ela ion o idal eme sion in his si e, and as such, idal assessmen was no epea ed he e. Combe Ma in is a no h-wes acing ocky in e idal si e, posi ioned wi hin a ela i ely shel e ed bay. Co allina caespi osa inhabi s a na ow zone (c. 2 cm Table 1. Si e and sampling in o ma ion. Si e Combe Ma in UK Þo lákshö n ICE Comillas NSP Loca ion 51°12’13N 4°2’19W 63°53’36N 21°23’45W 43°23’18N 4°17’21W Tidal Range MHWS–MLWS MHWS–MLWS MHWS–MLWS 9.2–0.68 (8.52) 3–0.2 (2.8) 4.7–0.2 (4.5) MHWN–MLWN MHWN–MLWN MHWN–MLWN 6.9–3.1 (3.8) 2.3–1 (2.2) 3.2–1.4 (1.8) Sampling Da es Win e 27.01.12 Sp ing 10.03.12 Summe 20.06.12 17.07.12 13.08.13 Au umn 03.09.12 05.09.13 19.10.12 Species sampled C. o icinalis C. o icinalis C. o icinalis* C. caespi osa C. caespi osa Sho e heigh s sampled Uppe (5.5) Lowe (1.5) Uppe (3.0) *Co allina o icinalis is accessible only du ing summe in NSP. EUROPEAN JOURNAL OF PHYCOLOGY 291 deep) a he uppe wa e line o la ge (c. 40 m 3 , 0.5 m dep h) uppe sho e ock pools c ea ed by a man- made walkway, wi h C. o icinalis domina ing below (Fig. 4). Ac oss he lowe in e idal, C. o icinalis domina es ock pools and d ainage channels, whils C. caespi osa is absen . La i udinal pa e ns in Co allina pho ophysiology we e u he examined ac oss he species’ anges in he NE A lan ic, including si es in Iceland and no h- e n Spain (Fig. 3). In si u assessmen s o pho ophy- siology we e conduc ed o C. o icinalis in Þo lákshö n, SW Iceland (ICE, Fig. 1), du ing sum- me and au umn (Table 1), a he s a , middle and end o day ime idal eme sion, wi h ex si u analyses pe o med in all sampling mon hs. Co allina o icinalis is he sole Co allina species ound in Icelandic ock pools, and is p esen as a well-de el- oped u in ock pools a Þo lákshö n (Figs 1,2). In Comillas, no he n Spain (NSP, Fig. 5), an exposed no h- acing ocky sho e is co e ed by a well-de el- oped Co allina and Ellisolandia assemblage. Co allina caespi osa occupies e y shallow (c. 2 cm deep) wa e co e ed a eas o he in e idal whe eas C. o icinalis is a ypically sub idal species, es ic ed o he in e idal in la ge ock pools (c. >1 m deep), ound only in small pa ches accessible on sp ing ides (Fig. 5). In si u pho ophysiology assessmen s we e he e o e con- duc ed o bo h species a hei espec i e posi ions on sho e du ing summe in NSP (Table 1), hough o only C. caespi osa du ing au umn, as C. o icinalis Figs. 1–5. Sampling si es, loca ions and species, showing: Fig. 1. in e idal ock pools a Þo lákshö n, Iceland, domina ed by Fig. 2. u s o C. o icinalis,Fig. 3. he loca ions o sampling si es ac oss he NE A lan ic, Fig. 4. he uppe laye o C. caespi osa (black a ow) in in e idal ock pools a Combe Ma in, UK, wi h C. o icinalis ( ed a ow) below, and Fig. 5. he well-de eloped u ing assemblage o co allines ac oss he in e idal a Comillas, no he n Spain. 292 C. J. WILLIAMSON was no accessible. In si u assessmen s we e made ac oss day ime idal eme sion and complemen ed wi h ex si u assessmen s. In si u pho ophysiology In he UK, RLCs we e pe o med on n=5 andomly selec ed Co allina onds o each species immedia ely a he s a o idal eme sion pe iods. Gi en idal impac s o Co allina pho ophysiology demons a ed p e iously a his loca ion (Williamson e al.2014a), RLCs we e pe o med a he s a o idal eme sion pe iods o minimize in luences on seasonal pa e ns. The o de o RLC de e mina ion was u he ando- mized ac oss species o minimize po en ial diu nal e ec s. Fo pho ophysiology assessmen in ICE, RLCs we e pe o med a e Williamson e al.(2014a)onn= 3 onds andomly selec ed om each o h ee uppe sho e ock pools, a he s a , middle and end o day- ime idal eme sion. S a and end eme sion pe iods we e de ined as being wi hin 1.5 h o idal isola ion (s a ) and idal econnec ion (end) o he ock pool o he main idal wa e mass. Middle eme sion was he midway be ween hese ime poin s. In NSP, RLCs we e pe o med on n= 3 onds o C. caespi osa a he s a , middle and end o idal eme sion, and n= 3 onds o C. o icinalis a he s a and middle o eme sion only, gi en he sho e du a ion o access o C. o icinalis a i s lowe posi ion on sho e a his la i ude. In all cases, RLCs we e pe o med on apical ond egions o a oid po en ially sel -shaded egions (Pe kins e al., 2016), and on he side o onds acing di ec sunligh , as he unde side o onds p obably demon- s a e di e en s a es o pho oacclima ion. RLCs we e pe o med using a Walz Wa e -PAM luo ome e using a sa u a ing pulse o c. 8600 μmol pho ons m –2 s –1 , o 800 ms du a ion, and wi h nine 30 s inc emen ally inc easing ligh s eps om 0 o 1944 μmol pho ons m –2 s –1 . Ligh s ep du a ion was selec ed o balance po en ial pho o egula ion occu ing du ing longe ligh s eps (60 s), wi h e o s associa ed wi h sho e ligh s eps (10 s) when samples ha e been exposed o high i adiance (Pe kins e al., 2006). Ambien pho o- syn he ically ac i e adia ion (PAR, μmol pho ons m –2 s –1 ) and ock pool wa e empe a u es we e moni o ed in pa allel o in si u RLCs a 30 min in e als using a 2- pi LI-COR cosine-co ec ed quan um senso posi ioned c. 5 cm abo e he su ace o ock pools, and a digi al he mome e (accu acy ±0.1°C), espec i ely. Fo each PAR measu emen , a 15 s a e age was aken using an au oma ed unc ion on he senso . Ex si u pho ophysiology assessmen Ex si u assessmen o Co allina pho ophysiology was pe o med du ing he p esen s udy o allow de e mi- na ion o pho oacclima ion and pho o egula ion dynamics unde educed in luence o in si u abio ic condi ions, acili a ing iden i ica ion o longe - e m seasonal, la i udinal and in e -speci ic pa e ns in pho ochemis y. Ex si u RLCs wi h da k eco e y phase we e pe o med o n=3C. o icinalis and C. caespi osa samples om CM du ing win e , summe and au umn, and o n= 3 samples o all species p esen a ICE and NSP du ing summe and au umn (Table 1). In all cases, 3 disc e e samples o each Co allina species we e sampled by hand om he in e idal a he end o idal eme sion. Samples we e placed sepa a ely in o 1 l con aine s con aining si e seawa e ob ained om ock pools a he ime o sampling and anspo ed immedia ely in da kness o nea by labo a o y acili ies. In he labo a o y, sam- ples we e le subme ged in si e seawa e in 1 l aqua- ia o a u he 1 h in da kness o allow e-oxida ion o Q A , elaxa ion o NPQ and PSII epai (Ralph & Gademann, 2005); seawa e was eplenished e e y 0.5 h o main ain ae a ion and ambien si e empe a- u es (Table 3). Following he 1 h da k adap a ion pe iod, ex si u RLCs wi h eco e y we e pe o med on an apical ond egion o each sample. RLCs we e pe o med as in si u, wi h eco e y o pho ochemis y subsequen ly acked o e a 17.5 min pe iod o da k- ness using he Walz Wa e -PAM inbuil p og amme o eco e y phase, wi h quan um e iciency measu e- men s a 10, 40, 100, 160, 460 and 1060 s. Da a ea men To a oid long pe iods o da k-adap a ion p io o in si u RLCs, which would lead o modi ica ion o he pho oacclima ion s a e o he cells in es iga ed (Ralph & Gademann, 2005; Pe kins e al., 2010), he max- imum ligh u iliza ion e iciency o in si u RLCs (F / F m ) was calcula ed om F m and F o alues ob ained du ing he ini ial RLC s ep o 30 s da kness (see Table 2 o luo escence pa ame e de ini ions and de i a ions). Fo ex si u RLCs, ull da k adap a ion was appa en , hough F /F m was also calcula ed as abo e. Elec on anspo h ough PSII was calcula ed om all RLCs in ela i e uni s ( ETR), assuming an equal di ision o PAR be ween PSI and PSII. Analysis o all RLCs ( ETR s. PAR) ollowed Pe kins e al. (2006), wi h i e a i e cu e i ing using he ‘nls’ unc ion o R base package (R Co e Team, 2014) and calcula ion o he ela i e maximum elec on ans e a e ( ETR max ), he maximum ligh u iliza- ion coe icien (α) and he ligh sa u a ion coe icien (E k ) ollowing Eile s & Pee e s (1988). Down- egula- ion in he o m o S e n–Volme non-pho ochemical quenching (NPQ) was calcula ed om he quenching o he maximum luo escence yield (i.e. he educ ion om he da k-adap ed maximum yield, F m , o he ope a ional maximum yields in he ligh , F m ’). Gi en he sho da k-adap a ion pe iod applied EUROPEAN JOURNAL OF PHYCOLOGY 293 du ing in si u RLCs (30 s), luo escence quenching was obse ed in he da k-adap ed s a e (i.e. F m ’> F m ) and hus in si u NPQ was calcula ed using he maximum F m ’ alue (F m ’ m ) a e Se ôdio e al.(2005). Two NPQ pa ame e s we e subsequen ly calcula ed o each in si u RLC; NPQ a he ini ial RLC s ep (NPQ RESID ), ep esen ing esidual NPQ due o in si u i adiance, and NPQ a he inal RLC s ep (NPQ INDUC ) ep esen ing he amoun o NPQ induced by he RLC i sel . Gi en he long da k-adap- a ion pe iod p io o ex si u RLCs, luo escence quenching in he da k-adap ed s a e was no obse ed and hus ypical S e n–Volme NPQ was calcula ed using F m . Quan um e iciency as a p opo ion o F / F m ( he ela i e quan um e iciency, RQE) was calcu- la ed o each ex si u RLC s ep and da k eco e y measu emen o allow compa ison o induc ion and eco e y dynamics ac oss seasons, species and la i udes. Da a analysis All s a is ical analyses and plo ing o da a we e pe - o med using R .3.0.2 (R Co e Team, 2014). P io o all analyses, no mali y o da a was es ed using he Shapi o–Wilk es and examina ion o equency his- og ams. I da a we e no no mally dis ibu ed, Box– Cox powe ans o ma ion was applied using he boxcox unc ion o he MASS package (Venables & Ripley, 2002), and no mali y e-checked. Following he applica ion o models o da a, model assump ions we e alida ed by examina ion o model c i icism plo s. S a is ical compa isons o RLC (and eco e y) pa ame e s be ween independen a iables we e pe - o med whe e app op ia e using ei he - es , analysis o a iance (ANOVA), o linea mixed-e ec s models (LMER) wi h es ic ed maximum likelihood (REML) c i e ion (Ba es e al., 2013), as de ailed below. Seasonal pho ophysiology in he UK Di e ences in ambien i adiance and wa e em- pe a u e be ween sampling mon hs a CM (Table 1) we e analysed by 1-way ANOVA wi h he ac o mon h (4 le els). Seasonal and in e speci- ic di e ences in in si u pho ophysiological pa a- me e s we e analysed using 2-way ANOVA wi h he ac o s mon h (4 le els) and species (2 le els), and in e ac ion e m. Ex si u pho ophysiology was analysed using 1-way ANOVA wi h he ac o sea- son o C. o icinalis (3 le els), and - es analysis wi h he ac o season (2 le els) o C. caespi osa. ICE and NSP la i udinal compa isons Fo ICE da a, di e ences in ambien i adiance be ween seasons and o e idal eme sion pe iods we e examined using 2-way ANOVA wi h he ac- o s season (2 le els) and ide (3 le els), and in e - ac ion e m. Rock pool wa e empe a u es and in si u pho ophysiological pa ame e s om ICE we e analysed using LMER wi h he ixed ac o s season (2 le els) and ide (3 le els), and ock pool (3 le els) as andom e m. Ex si u pho ophysiology was analysed using - es compa isons o pa a- me e s in ela ion o season (2 le els). Fo NSP da a, i adiance and wa e empe a u e we e exam- ined using 2-way ANOVA wi h he ac o s season (2 le els) and ide (3 le els), and in e ac ion e m. Co allina caespi osa in si u pho ophysiology was analysed using 2-way ANOVA wi h he ac o s season (2 le els) and ide (3 le els) and in e ac ion, and in e speci ic compa isons wi h C. o icinalis a s a and middle summe idal eme sion achie ed wi h 1-way ANOVA wi h he ac o species (2 le els), and ide as andom e m (2 le els). NSP C. caespi osa ex si u pho ophysiological pa ame e s we e examined be ween seasons using - es wi h he ac o season (2 le els). Resul s Seasonal pho ochemis y o UK Co allina Ambien i adiance and ock pool wa e empe a- u es anged om 270±16 o 1143±124 μmol pho ons m –2 s –1 , and 7.7±0.4 o 19.2±0.9°C du ing sampling a Combe Ma in (CM), espec i ely, wi h signi ican ly Table 2. Fluo escence pa ame e s, de ini ions and de i a ions (a e Cosg o e & Bo owi zka, 2011). Pa ame e De ini ion De i a ion F o Minimum luo escence yield (da k adap ed, all RCIIs open) F m Maximum luo escence yield (da k adap ed, all RCIIs open wi h no NPQ) F Maximum a iable luo escence F m –F o F /F m Maximum quan um e iciency (da k adap ed) (F m –F o )/F m F’Fluo escence yield in ac inic ligh F m ’Maximum luo escence yield in ac inic ligh F m ’ m The maximum alue o F m ’ F q ’Fluo escence quenched in ac inic ligh F m ’–F’ F q ’/F m ’E ec i e quan um e iciency in ac inic ligh (F m ’–F’)–F m ’ RQE Rela i e quan um e iciency (F q ’/F m ’)/(F /F m ) × 100 ETR Rela i e elec on anspo a e ( h ough PSII) F q ’/F m ’× PAR × 0.5 NPQ (S e n–Volme ) Non-pho ochemical quenching (F m –F m ’)/F m ’ Non-pho ochemical quenching calcula ed wi h he maximum alue o F m ’(F m ’ m ) a e Se ôdio e al.(2005)(F m ’ m –F m ’)/F m ’ All pa ame e s a e dimensionless (PAR = pho osyn he ically ac i e adia ion). 294 C. J. WILLIAMSON inc eased i adiance (F 3,16 = 116.06, P< 0.01) and wa e empe a u e (F 3,16 = 42.04, P< 0.001) appa en du ing June and Sep embe as compa ed wi h Janua y and Ma ch, and no di e ence be ween espec i e pai s o mon hs (Table 3). S ong seasonali y in RLCs and de i ed pa ame e s was appa en o bo h C. o icinalis and C. caespi osa ac oss sampling mon hs a CM (Figs 6,7, Supplemen a y able 1). F om Janua y o June, declines in C. o icinalis F /F m , ETR max and α, e lec ed inc eased pho o-s ess and co esponding supp ession o pho ochemis y, wi h some eco e y in Sep embe . Highly compa able pa e ns we e also obse ed o C. caespi osa, hough a mo e ab up shi in pa ame e s was e iden be ween Ma ch and June in compa ison wi h C. o icinalis (Fig. 7). Al hough a iable, E k did no di e signi ican ly be ween sam- pling mon hs o ei he species. Ambien i adiance was less han E k du ing Janua y and Ma ch, sugges - ing ligh -limi a ion o pho osyn hesis. Con e sely, ambien i adiance was c. 2.4- and 1.8- imes E k du - ing June, and 3.6- and 2.5- imes E k du ing Sep embe , o C. o icinalis and C. caespi osa, espec i ely, sug- ges ing sa u a ion and hence po en ial o induce pho o-s ess. No in e speci ic di e ences in F /F m , ETR max ,αo E k we e obse ed du ing any sampling mon h. Non-pho ochemical quenching (NPQ) a ied be ween seasons o bo h C. o icinalis and C. caespi- osa (Fig. 7, Supplemen a y able 1). NPQ induced unde in si u condi ions was g ea es du ing summe / au umn as demons a ed by inc eased NPQ RESID , wi h minimal NPQ INDUC appa en a he end o sum- me /au umn RLCs. The opposi e ends we e obse ed du ing win e , demons a ing minimal ac i e NPQ unde in si u condi ions, bu induc ion o NPQ by RLC i adiance. No signi ican in e spe- ci ic di e ences in NPQ pa ame e s we e e iden ac oss mon hs (Supplemen a y able 1). In con as o in si u pho ophysiology, no signi ican di e ence in C. o icinalis o C. caespi osa ETR max ,αo E k was e iden be ween seasons as de e mined by ex si u RLCs wi h da k eco e y (Fig. 8,Table 4, Fig. 6. In si u apid ligh esponse cu es (RLCs) o C. o icinalis (ci cles and solid lines) and C. caespi osa ( iangles and dashed lines) pe o med a Combe Ma in, UK, du ing Janua y, Ma ch, June and Sep embe , showing (a–d) ela i e elec on anspo a es ( ETR) and (e–h) non-pho ochemical quenching (NPQ) ac oss RLCs (mean ± SE, n= 5). Do ed e ical lines ep esen he a e age ambien i adiance eco ded in si u a he ime o RLC de e mina ion. Table 3. Mean (± SE) wa e empe a u e and i adiance measu ed a si es du ing RLC pho ophysiology assessmen s. Si e Da e Season Tidal pe iod Wa e empe a u e (°C) Ambien i adiance (μmol pho ons m –2 s –1 ) Combe Ma in, UK 27.01.12 Win e S 7.87±0.07 311±42 10.03.12 Sp ing S 7.72±0.41 270±16 20.06.12 Summe S 17.30±2.80 1111±267 03.09.12 Au umn S 19.24±0.91 1143±124 Þo lákshö n, Iceland 17.07.12 Summe S 15.05±0.03 712±83 M 15.25±0.03 630±60 E 15.57±0.07 616±66 05.09.13 Au umn S 9.66±0.08 861±76 M 10.20±0.14 1152±63 E 11.20±0.11 1215±70 Comillas, no he n Spain 13.08.13 Summe S 20.94±0.27 1160±59 M 22.68±0.19 1568±142 E 23.67±0.11 1405±344 19.10.12 Au umn S 18.68±0.07 500±29 M 18.90±0.04 510±48 E 18.94±0.04 264±24 S = s a , M = middle and E = end idal eme sion. EUROPEAN JOURNAL OF PHYCOLOGY 295 Supplemen a y able 2). F /F m and NPQ INDUC we e signi ican ly lowe in summe as compa ed wi h au umn and win e o C. o icinalis. Un o una ely, ins umen a ion ailu e p e en ed ex si u pho ophysiol- ogy assessmen o C. caespi osa du ing summe . Rela i e quan um e iciency (RQE) dec eased o 14.7 ±1.5% in C. o icinalis and 14.9±0.9% in C. caespi osa a he end o ex si u RLCs, wi h no seasonal di e ence appa en o ei he species. The magni ude o da k eco e y in RQE was g ea es du ing summe (87.3 ±9.3%) and au umn (88.3±3.2%) in compa ison wi h win e (60.1±6.8%) o C. o icinalis, and du ing au umn (91.5±6.9%) in compa ison wi h win e (55.9 ±6.1%) o C. caespi osa. NPQ elaxa ion du ing da k eco e y was as es du ing summe (160 s), hen au umn (460 s), wi h slowes elaxa ion in win e (17.5 min) o C. o icinalis. NPQ elaxa ion was as e o e all o C. caespi osa, wi h simila seasonal dynamics (160 s in au umn, 460 s in win e ). Icelandic Co allina pho ophysiology I adiance was signi ican ly lowe du ing summe in ICE as compa ed wi h au umn, wi h no signi ican change in i adiance appa en o e idal eme sion pe iods du ing ei he season (F 1,24 = 50.80, P< 0.001) (Table 3). Rock pool wa e empe a u es we e signi ican ly inc eased du ing summe as compa ed wi h au umn (F 1,24 = 6973.01, P< 0.001), and sig- ni ican ly inc eased a he end o idal eme sion du - ing bo h seasons (F 2,24 = 86.55, P< 0.001). Fig. 7. Pa ame e s de e mined om in si u apid ligh esponse cu es o Co allina o icinalis (unshaded ba s) and C. caespi osa (shaded ba s) a Combe Ma in, UK, du ing Janua y (Jan), Ma ch (Ma ), June (Jun) and Sep embe (Sep), showing: he maximum quan um e iciency in he da k adap ed s a e (F /Fm), he ela i e maximum a e o elec on anspo ( ETRmax), he ligh u iliza ion e iciency (α), he ligh u iliza ion coe icien (Ek), and non-pho ochemical quenching (NPQ) a he s a - and end- o RLCs (mean ± SE, n= 5). Lowe -case le e s deno e Tukey’s HSD homogeneous subse s in ela ion o sampling mon h. 296 C. J. WILLIAMSON Fig. 8. Ex si u apid ligh esponse cu es (RLCs) wi h eco e y o Co allina o icinalis (le hand panels) and C. caespi osa ( igh hand panels) du ing summe (ci cles and solid lines), au umn ( iangles and dashed lines) and win e (squa es and do ed lines), om Combe Ma in, UK. Showing (a & b) ela i e elec on anspo a es ( ETR) o e he induc ion phase o RLCs, and (c & d) ela i e quan um e iciency (RQE) and (e & ) non-pho ochemical quenching (NPQ) o e he induc ion (whi e backg ound) and da k eco e y (g ey backg ound) phases (mean ± SE, n= 3). EUROPEAN JOURNAL OF PHYCOLOGY 297 Addi ional o seasonal a iabili y, he p esen s udy u he indica es la i udinal pa e ns in he pho o egula ion capaci y o Co allina ac oss he NE A lan ic. The as e NPQ e u ns o 0 in da k- ness is an indica o o a plan ’s ole ance o high ligh (Ralph & Gademann, 2005). By moni o ing elaxa ion kine ics a e ex si u RLCs i was hus possible o examine eco e y om ligh exposu e, allowing he a ious componen s o NPQ o be dis inguished. The componen o NPQ which elaxes quickly (seconds–minu es) is associa ed wi h he emo al o ene gy-dependen NPQ (qE), and is linked o elaxa ion o he p o on g adien ac oss he hylakoid memb ane (Ralph & Gademann, 2005). In con as , a slowe elaxa ion o NPQ (>10 min, up o hou s), is associa ed wi h pho oinhibi ion (qI) and changes in ene gy dis i- bu ion in a ou o PSII (Ralph & Gademann, 2005). qE was shown he e o be he majo com- ponen o Co allina NPQ, wi h apid elaxa ion o 0 by a maximum o 160 s o da kness obse ed du ing summe and au umn in he UK and no h- e n Spain o bo h Co allina species. In con as , qI was iden i ied o Icelandic C. o icinalis du ing bo h summe and au umn, gi en he pe sis ence o NPQ ollowing 17.5 min o da kness. Reco e y o quan um e iciency by he end o da k pe iods u he showed la i udinal g adien s, wi h he g ea es eco e y obse ed in lowe ela i e o highe la i udes, in all seasons. Co allina popula- ions hus demons a ed an inc eased suscep ibil- i y o pho os ess, and educed capaci y o pho o egula ion, wi h inc easing la i ude ac oss he NE A lan ic. Species wi h an ex ended la i udinal dis ibu ion can be exposed o high en i onmen al a iabili y ha may p omo e pheno ypic plas ici y and/o eco ype di e en ia ion as an adap i e esponse o empo al and spa ial a ia ion (Lynch & Gab iel, 1987). Gi en ha he ne amoun o sola adia ion eaching he ea h’s su ace dec eases wi h inc easing la i ude (Beaug and, 2014), da a may e lec low-ligh pho o- acclima ion (o pho oadap a ion) o highe la i ude Co allina popula ions ac oss he NE A lan ic, wi h consequen inc eases in sensi i i y o pho os ess ela i e o lowe la i ude popula ions. This may be u he exace ba ed by low empe a u e es ic ions on enzyma ic eco e y p ocesses a highe la i udes, which can mimic he impac s o high-ligh s ess (Ensminge e al., 2006; Hune e al., 1996). In his espec , he capaci y o NE A lan ic Co allina popu- la ions o e ec i ely pho o egula e may dec ease wi h inc easing la i ude due o di e en ial pho oacclima- ion coupled wi h low- empe a u e es ic ions o physiology. In e speci ic di e ences in pho ochemis y Da a highligh ed highly conse ed pho ophysiology be ween C. o icinalis and C. caespi osa, consis en wi h he indings o Williamson e al.(2014b). Fo example, seasonal pa e ns in in si u pho ophysiology in he UK we e almos iden ical be ween he wo species, wi h no signi ican di e ence in F /F m , ETR max ,αo E k obse ed. Fu he mo e, whe e in e - speci ic di e ences we e appa en in si u, hese e lec ed local esponses o di e en ial abio ic s ess gi en hei espec i e posi ions on he sho e (Va ela e al., 2006), and we e absen wi h emo al o ex si u analyses o pho ochemis y. Known di e ences in he global dis ibu ions o he Co allina species s udied he e (Williamson e al., 2015) do no , he e o e, appea o ela e o di e en ial capaci y o pho o- chemis y. As such, u he esea ch is equi ed o examine he physiological mechanisms unde lying in e speci ic di e ences wi hin he genus Co allina. Disclosu e s a emen No po en ial con lic o in e es was epo ed by he au ho s. Funding This wo k was unded by he NERC g an (NE/H025677/1). Au ho con ibu ions C. Williamson, R. Pe kins, M Yallop and J. B odie: o iginal concep and s udy design; All au ho s: ield suppo , ield sampling and manusc ip p epa a ion. Supplemen a y in o ma ion The ollowing supplemen a y ma e ial is accessible ia he Supplemen a y Con en ab on he a icle’s online page a h ps://doi.o g/10.1080/09670262.2018.1442586. Supplemen a y able 1. Analysis o a iance o UK C. o icinalis and C. caespi osa seasonal pho ophysiology. Supplemen a y able 2. Analysis o a iance and - es analysis o UK C. o icinalis and C. caespi osa ex-si u pho o- physiology pa ame e s in ela ion o he ac o ‘season’. Supplemen a y ig. 1.Ex-si u apid ligh esponse cu es wi h eco e y o C. o icinalis du ing summe and au umn a Þo lákshö n, Iceland, showing (a) ela i e elec on ans- po a es ( ETR) o e he induc ion phase o RLCs, and (b) ela i e quan um e iciency (RQE) and (c) non-pho o- chemical quenching (NPQ) o e he induc ion and da k eco e y phases. Supplemen a y ig. 2.Ex-si u apid ligh esponse cu es wi h eco e y o C. caespi osa du ing summe and au umn a Comillas, no he n Spain, showing (a) ela i e elec on 304 C. J. WILLIAMSON anspo a es ( ETR) o e he induc ion phase o RLCs, and (b) ela i e quan um e iciency (RQE) and (c) non- pho ochemical quenching (NPQ) o e he induc ion and da k eco e y phases. Supplemen a y ig. 3.Ex-si u apid ligh esponse cu es wi h eco e y o C. o icinalis du ing summe a Comillas, no he n Spain, showing (a) ela i e elec on anspo a es ( ETR) o e he induc ion phase o RLCs, and (b) ela i e quan um e iciency (RQE) and (c) non-pho oche- mical quenching (NPQ) o e he induc ion and da k eco - e y phases. ORCID Césa Pe ei o h p://o cid.o g/0000-0003-0698-3573 Re e ences Alga a, P., Dela ina, G. & Niell, J. (1991). E ec s o ligh quali y and i adiance le el in e ac ions on sho - e m pigmen esponse o he ed alga Co allina elonga a. Ma ine Ecology P og ess Se ies,74:27–32. Ba es, D., Maechle , M., Bolke , B. & Walke , S. (2013). lme4: Linea mixed-e ec s models using Eigen and S4. R package. Beaug and, G. (2014). Ma ine Biodi e si y, Clima ic Va iabili y and Global Change. Rou ledge, Abingdon. Bee , S., Bjo k, M. & Bea dall, J. (2014). Pho osyn hesis in he Ma ine En i onmen . Wiley-Blackwell, Ames, IA. B odie, J., Walke , R.H., Williamson, C. & I ine, L.M. (2013). Epi ypi ica ion and edesc ip ion o Co allina o icinalis L., he ype o he genus, and C. elonga a Ellis e Solande (Co allinales, Rhodophy a). C yp ogamie, Algologie,34:49–56. B odie, J., Williamson, C.J., Ba ke , G., Walke , R.H., B iscoe, A., & Yallop, M. (2016). Cha ac e ising he mic obiome o Co allina o icinalis, a dominan calci ied in e idal ed Alga. FEMS Mic obiology Ecology 92: iw110. Consal ey, M., Pe kins, R.G., Pa e son, D.M. & Unde wood, G.J.C. (2005). PAM Fluo escence: a begin- ne s guide o ben hic dia omis s. Dia om Resea ch,20: 1–22. Cosg o e, J. & Bo owi zka, M.A. (2011) Chlo ophyll luo - escence e minology: an in oduc ion. In Chlo ophyll a Fluo escence in Aqua ic Sciences: Me hods and Applica ions (Sugge , D.J., P ášil, O. & Bo owi zka, M. A., edi o s), 1–17. Sp inge , Do d ech . Coull, B.C. & Wells, J.B.J. (1983). Re uges om ish p eda ion –expe imen s wi h phy al meio auna om he New Zealand ocky in e idal. Ecology,64: 1599–1609. Da ison, I. & Pea son, G. (1996). S ess ole ance in in e - idal seaweeds. Jou nal o Phycology,32: 197–211. Demmig-Adams, B. & Adams, W.W. (1996). Xan hophyll cycle and ligh s ess in na u e: uni o m esponse o excess di ec sunligh among highe plan species. Plan a,198:460–470. De a, J. & Go don, H.R. (1968). Ligh ield luc ua ions in pho ic zone. Limnology and Oceanog aphy,13: 697–699. Egilsdo i , H., Noise e, F., Noël, L.M.-L.J., Ola sson, J. &Ma in,S.(2013). E ec s o pCO 2 on physiology and skele al mine alogy in a idal pool co alline alga Co allina elonga a. Ma ine Biology,160: 2103–2112. Eile s, P.H.C. & Pee e s, J.C.H. (1988). A model o he ela- ionship be ween ligh in ensi y and he a e o pho osyn h- esis in phy oplank on. Ecological Modelling,42: 199–215. Ensminge , I., Busch, F. & Hune , N.P.A. (2006). Pho os asis and cold acclima ion: sensing low empe a u e h ough pho osyn hesis. Physiologia Plan a um,126:28–44. Es eban, R., Ma ínez, B., Fe nández-Ma ín, B., Bece il, J. M. & Ga cía-Plazaola, J.I. (2009). Ca o enoid composi- ion in Rhodophy a: insigh s in o xan hophyll egula ion in Co allina elonga a. Eu opean Jou nal o Phycology,44: 221–230. Falkowski, P.G. & LaRoche, J. (1991). Acclima ion o spec- al i adiance in algae. Jou nal o Phycology,27:8–14. F anklin, L.A. & Fo s e , R.M. (1997). The changing i a- diance en i onmen : consequences o ma ine mac o- phy e physiology, p oduc i i y and ecology. Eu opean Jou nal o Phycology,32: 207–232. Goss, R. & Jakob, T. (2010). Regula ion and unc ion o xan hophyll cycle-dependen pho op o ec ion in algae. Pho osyn hesis Resea ch,106: 103–122. Häde , D-P., Lebe , M., Flo es-Moya, A., Jiménez, C., Me cado, J., Salles, S., Aguile a, J. & Figue oa, F.L. (1997). E ec s o sola adia ion on he pho osyn he ic ac i i y o he ed alga Co allina elonga a Ellis e Soland. Jou nal o Pho ochemis y and Pho obiology B: Biology,37: 116–202. Häde , D-P., Lebe , M, & Helbling E.W. (2003). E ec s o sola adia ion on he Pa agonian Rhodophy e Co allina o icinalis (L.). Pho osyn hesis Resea ch,78: 119–132. Hänel , D., Huppe z. K & Nul sch, W. (1993). Daily cou se o pho osyn hesis and pho oinhibi ion in ma ine mac oalgae in es iga ed in he labo a o y and ield. Ma ine Ecology P og ess Se ies,97:31–37. Henley, W.J. & Ramus, J. (1989). Time cou se o physiolo- gical esponse o Ul a o unda a o g ow h i adiance ansi ions. Ma ine Ecology P og ess Se ies,54: 171–177. Ho mann, L., Yildiz, G., Hanel , D. & Bischo , K. (2012). Physiological esponses o he calci ying hodophy e, Co allina o icinalis (L.), o u u e CO 2 le els. Ma ine Biology,159: 783–792. Hune , N.P.A., Maxwell, D.P., G ay, G.R., Sa i ch, L.V., K ol, M., I ano , A.G. & Falk, S. (1996). Sensing en i - onmen al change: PSII exci a ion p essu e and edox signalling. Physiologia Plan a um,98: 358–364. Huo , Y. & Babin, M. (2011). O e iew o luo escence p o ocols: heo y, basic concep s and p ac ice. In Chlo ophyll a Fluo escence in Aqua ic Sciences: Me hods and Applica ions (Sugge , D.J., P ášil, O. & Bo owi zka, M.A., edi o s), 31–74. Sp inge , Do d ech . Johansen, H.W. (1981). Co alline Algae: A Fi s Syn hesis. CRC P ess, Boca Ra on, FL. Kelahe , B.P. (2002). In luence o physical cha ac e is ics o co alline u on associa ed mac o aunal assemblages. Ma ine Ecology P og ess Se ies,232: 141–148. Kelahe , B.P. (2003). Changes in habi a complexi y nega- i ely a ec di e se gas opod assemblages in co alline algal u . Oecologia,135: 431–441. Kim, J.H., Lam, S.M.N. & Kim, K.Y. (2013). Pho oacclima ion s a egies o he empe a e co alline alga Co allina o icinalis: a pe spec i e on pho osyn h- esis, calci ica ion, pho osyn he ic pigmen con en s and g ow h. Algae,28: 355–363. La aud, J. & Lepe i , B. (2013). An explana ion o he in e -species a iabili y o he pho op o ec i e non- pho ochemical chlo ophyll luo escence quenching in dia oms. Biochimica e Biophysica Ac a –Bioene ge ics, 1827: 294–302. EUROPEAN JOURNAL OF PHYCOLOGY 305 Lobban, C.S. & Ha ison, P.J. (1994). Seaweed Ecology and Physiology. Camb idge Uni e si y P ess, New Yo k, NY. Lynch, M. & Gab iel, W. (1987). En i onmen al ole ance. Ame ican Na u alis ,129: 203–208. Maxwell, K. & Johnson, G.N. (2000). Chlo ophyll luo es- cence –a p ac ical guide. Jou nal o Expe imen al Bo any,51: 659–668. Mülle , P., Xiao-ping, L & Niyogi, K.K. (2001). Upda e on pho osyn hesis non-pho ochemical quenching: a esponse o excess ligh ene gy. Plan Physiology,125:1558–1566. Noise e, F., Egilsdo i , H., Da oul , D. & Ma in, S. (2013). Physiological esponses o h ee empe a e co al- line algae om con as ing habi a s o nea - u u e ocean acidi ica ion. Jou nal o Expe imen al Ma ine Biology and Ecology,448: 179–187. Pe kins, R.G., Mouge . J-L., Le eb e, S. & La aud, J. (2006). Ligh esponse cu e me hodology and possible implica ions in he applica ion o chlo ophyll luo es- cence o ben hic dia oms. Ma ine Biology,149: 703–712. Pe kins, R.G., K omkamp, J.C., Se ôdio, J., La aud, J., Jesus, B., Mouge , J.L., Le eb e, S. & Fo s e , R.M. (2010). The applica ion o a iable chlo ophyll luo es- cence o mic ophy oben hic bio ilms. In Chlo ophyll a Fluo escence in Aqua ic Sciences: Me hods and Applica ions (Sugge , D.J., P ášil, O. & Bo owi zka, M. A., edi o s), 237–275. Sp inge , Do d ech . Pe kins, R.G., Williamson, C.J., B odie, J., Ba ille, L., Launeau, P., La aud, J., Yallop, M.L. & Jesus, B. (2016). Mic ospa ial a iabili y in communi y s uc u e and pho ophysiology o calci ied mac oalgal mic obiomes e ealed by coupling o hype spec al and high- esolu- ion luo escence imaging. Scien i ic Repo s,6: 22343. R Co e Team (2014). R: A Language and En i onmen o S a is ical Compu ing. R Founda ion o S a is ical Compu ing, Vienna. Ralph, P.J. & Gademann, R. (2005). Rapid ligh cu es: a powe ul ool o assess pho osyn he ic ac i i y. Aqua ic Bo any,82: 222–237. Ramus, J. (1981). The cap u e and ansduc ion o ligh ene gy. In The Biology o Seaweeds (Lobban, C.S. & Wynee, M.J., edi o s), 458–492. Blackwell Scien i ic, Ox o d. Richa dson, K., Bea dall, J. & Ra en, J.A. (1983). Adap a ion o unicellula algae o i adiance –an analy- sis o s a egies. New Phy ologis ,93: 157–191. Se ôdio, J., C uz, S., Viei a, S. & B o as, V. (2005). Non- pho ochemical quenching o chlo ophyll luo escence and ope a ion o he xan hophyll cycle in es ua ine mic ophy oben hos. Jou nal o Expe imen al Ma ine Biology and Ecology,326: 157–169. Va ela, D.A., San elices, B., Co ea, J.A. & A oyo, M.K. (2006). Spa ial and empo al a ia ion o pho osyn hesis in in e idal Mazzaella lamina ioides (Bo y) F ede icq (Rhodophy a, Giga inales). Jou nal o Applied Phycology,18: 827–838. Venables, W.N. & Ripley, B.D. (2002). Mode n Applied S a is ics wi h S. 4 h ed. Sp inge , New Yo k, NY. Williamson, C.J., Najo ka, J., Pe kins, R., Yallop, M.L. & B odie, J. (2014a). Skele al mine alogy o genicula e co - allines: p o iding con ex o clima e change and ocean acidi ica ion esea ch. Ma ine Ecology P og ess Se ies, 513:71–84. Williamson, C.J., B odie, J., Goss, B., Yallop, M.L., Lee, S. & Pe kins, R. (2014b). Co allina and Ellisolandia (Co allinales, Rhodophy a) pho ophysiology o e day- ligh idal eme sion: in e ac ions wi h i adiance, em- pe a u e and ca bona e chemis y. Ma ine Biology, 161: 2051–2068. Williamson, C.J., Walke , R.H., Robba, L., Yesson, C., Russell, S., I ine, L.M. & B odie, J. (2015). Towa d esolu ion o species di e si y and dis ibu ion in he calci ied ed algal gene a Co allina and Ellisolandia (Co allinales, Rhodophy a). Phycologia,54:2–11. Williamson, C.J., Pe kins, R., Volle , M., Yallop, M.L. & B odie, J. (2017). The egula ion o co alline algal physiol- ogy, an in-si u s udy o Co allina o icinalis (Co allinales, Rhodophy a). Biogeosciences,14:4485–4498. 306 C. J. WILLIAMSON