Marine Biology 5 1, 289-294 (1979) MARINE BIOLOGY ;).rf1·~ © by Sp ringer-Verla g 1979

~~ti'1~ Acclimation Responses to Salinity of Three Estuarine Red Algae from New Jersey

C. Yarlsh- , P. Edwards l * and S. Casey2 153 6 / 1Department of Botany, Rutgers, The State University ; New Brunswick, New Jer sey, USA and

2Depart ment of Statistics, Rutgers, The State University ; New Brunswick, New Je rsey, USA

Abstract

The e ffe c ts o f sal i n ity a nd a cc limation time on t he net p hotosyn t het i c r esponses o f 3 e stuarine r ed a lgae, Bostrychia r adicans Mont . , Caloglossa leprieurii (Mont. ) J. Ag., and Polysiphoni a subtili ssima Mont., from Gr e at Ba y Estuary, New Jer sey , USA, were in­ve s t igate d . Th e a lgae we r e c u l t ured in a s erie s o f s ynthetic s eawate r media o f 5 , 15, 25 and 3 5~ S for a cclimation pe r iod s o f 0, 2, 4, 8 , and 16 d ays prior t o de­te rmining the ir p ho tosyn t he t ic responses. All spe cies were e uryha l ine , a nd d emon­strated phot osynthesis at all the above salinities. B. r adican s, whi ch was more c om­mon t owards the mouth o f the e stua ry , had a ma ximum photosynthet i c r ate a t 2 5~ S , whils t C. l eprieurii a nd P . sub tili s sima , wh i ch were more c ommon towards t he he a d of the estuary, had pho t o s y ntheti c ma x ima betwee n 15 and 2 5%, and at 1 5 ~, res pective­l y. The c u r ve s r elat ing net p ho tos ynthes is t o s a lini ty wer e usually similar wi t h i n a species at d i ff e r ent acc l im a t i on p e riod s , although stat i stical ly significant diff e r ence s were s omet i mes noted . The a cc l i mat ion period s prod uc i ng ma ximal net photo s yn t h es i s we re 0, 2 and 4 days f or B. radi cans, and 4 day s f or c . leprieurii, whils t fo r p . s ub tilissima there was no s igni f i c a n t dif ference in res ponse f o r a ny a cclimation pe r iod o ve r the range o f salinities studied.

Introduct ion

Previous i nv e s t ig a t ion s on the e f f e c t o f s alinity on the net photosyn t hes i s o f benthic marine a l g a e have revealed a varie t y of responses whi ch sugg es t that the interactions are c omple x . The in­abi lity to d e f ine gene r a l t rends stems i n part from on e or mor e o f t he fo l low­ing: a lack o f suffici e nt r eplication which is necessar y with p l a n t material that may be heterogeneous; the ability o f different species of s eaweeds t o thrive in a restricted (s t en oha l i n e spe­cies ) o r in a wi d e (euryha l i ne s p ecies ) salinity range; d if f e r e n c e s in experi­mental tec hn i q u e s , p a r t i c u la r ly wi th re­gar d t o the accl imat ion o f t he plant ma­te r i al p r io r t o r unn i ng an e xp e r i men t .

Fromageot (1 923 ) r e por ted t ha t t he highest rate s o f photosynthesis in sev ­eral g ree n algae o ccurred in full­s trength seawater and that deviations in s alinity in e i t her direction cause d a

*Pr e sent address : Agricultural an d Food Engineer­ing Division, Asian Insti tute of Technology, P.O. Box 2754 , Ba ngkok, Tha iland.

decline in t h e rate of pho tosynthesis. This r esponse s uggests a r elatively stenohaline group o f a l g a e . In c ontrast, t he e uryha l i n e s pec i e s Ul va lac t uc a, Fucus virs oide s, Por phyra l euc osticta and Wrange l ia penicillata fr om the Adriatic Sea, studied by Zavodn ick (197 5) , wer e able t o photo­synthesiz e over a wide range o f salini­tie s, fr om a t o 4 2~ S .

However, there are reports in the literature that a r e more difficult t o interpret. Legendre ( 1 9 2 1) found that, in a r e duced salinity o f a bout 2 2~ S, the photosynthetic r ates o f Ul va l actuca and Fucus ser ratus g r a dua l ly increased t o more tha n do ub l e the rate in f u l l ­strength seawater. Nellen (1966) studied sal inity i n f luence s on photo syn t hes i s in Delesseria s an guine a and F. s erra tus and var­i ed both the s alinity and exposure time. Some of her r e sults indicate that changes in salinity c a us e d a subsequen t stimulation in p erformance, foll owed by a d e pression due to t he detrimen tal e f ­fects of the salinity change, b u t t hat this was not always s o.

Another potential source of variation in t he respons e o f algae to salinity

00'25·3162179/0051/0289/$01 .20

290 c. Yarish et al.: Salinity Responses of Estuarine Algae

changes is the period of time the plant material is acclimated to the salinity in question. Many investigators used no acclimation period (Ogata and Matsui, 1965; Gessner, 1969; Zavodnick, 1975), so that responses measured may result from shock on being transferred to a to­tally different regime; other workers apparently chose arbitrary acclimation times (Druehl, 1967, 5 days; Mathieson and Dawes, 1974, 4 days; Fralick and Mathieson, 1975, 4 days; Dawes et al., 1976, 3 days).

The present study was designed to study the net photosynthetic responses of laboratory cultured material of 3 es­tuarine red algae, Bostrychia radicans Mont. , Caloglossa leprieurii (Mont.) J.Ag., and Polysiphonia subtilissima Mont., to varia­tions in salinity as a function of ac­climation periods ranging from 0 to 16 days. The observed photosynthetic re­sponses to salinity variations are cor­related with the horizontal or local distribution of the algae in their estu­arine environment.

Materials and Methods

The unialgal cultures of benthic algae used in the study were isolated from the Great Bay Estuary, New Jersey, USA. The habitats, locations and dates of collec­tion of each isolate are as follows: Bos­trychia radicans Mont., upper euli ttoral zone, wooden pilings, Marine Biology Station, 17 July, 1973; Cal og l o s s a lepri­eurii (Mont.) J.Ag., mid-eulittoral zone, wooden pilings, Parkway Bridge, 13 July, 1973; Polysiphonia subtilissima Mont., lower eulittoral zone, woode~ pilings, Parkway Bridge, 30 July, 1974. stock cultures were maintained in von Stosch's enriched seawater media (as cited by Ott, 1966), at 2 5~ S for B. radians and at 15~ S for C. leprieurii and P. subtilissima. The tanks containing the algae were maintained un­der an illumination of 2252 ± 269 lux at 25 0C. Female plants of one clone each of B. radicans and C. leprieurii and a vegeta­tive clone of P. subtilissima were grown from excised branch tips in 15 1 plastic tanks containing 12 1 of the enriched seawater media. Each tank was aerated with compressed air to avoid C02 deple­tion (Emerson and Green, 1934; Tseng and Sweeny, 1946), enhance growth (Colinvaux et al., 1965; Ogata et al., 1972) and pro­vide circulation. The air was passed through two deionized water filters to minimize the chance of contamination. Cloned plants were used to reduce genet­ic variability and ensure that reproduc­tion would not take place. Thus, all ex­periments for each species were conducted

on a single genotype in the vegetative state.

A preliminary experiment was carried out in which the net photosynthesis of each species was determined at salini­ties of 0, 5, 15, 25 and 35 ~ without prior acclimation. A series of experi­ments was then conducted to investigate the effect of acclimation periods of 0, 2, 4, 8 and 16 days (in a Sherer Dual Jet Incubator, Model RT46 B-SE, Marshall, Michigan, USA) in a given salinity re­gime on the net photosynthesis of each isolate. A synthetic seawater medium (Ott, 1965) containing 5, 15, 25 and 35 ~ total salt was used to insure the avail­ability of C02 (Ogata and Matsui, 1965; Hammer, 1968). This medium also contained NaHC03. The concentration of carbonate buffers in the artificial seawater was the same in all salinities. The pH of the media was 7.5 to 8.0, regardless of salinity. Net photosynthesis was mea­sured by the azide modification of the Winkler Method (Rand et al., 1976) and ex­pressed as mg 02 g-l dry weight h-l. Each experiment consisted of 4 repli­cates with an incubation time of 3 h. The light intensity and temperature in the Sherer Incubators were held constant at 2252 ± 269 lux and 26 0 c ± 1 Co. The data were analyzed by one- and two-way ANOVA's, and Tukey's multiple comparison of the means (= Tukey's w-procedure, Miller, 1966), and were tested for sig­nificant differences at the 5% level.

Results

The net photosynthesis of Bostrychia radi­c an s prevLous Ly cultured at and there­fore acclimated to a salinity of 25~,

was uniform (P <0 . 0 5 ) over a salinity range of 15 to 35 ~ (Fig. 1). A decrease in net photosynthesis occurred at salin­ities less than 15~, and no net photo­synthesis was recorded at O~ S. During acclimation experiments, all plants died after 3.5 days immersion in a salinity of O~. The effects of acclimation time on net photosynthesis at different sa­linities are shown in Fig. 2, and a sta­tistical analysis of the trends is pre­sented in Table 1. There was no signifi­cant difference (P <0.05) between accli­mation regimes of 0, 2 and 4 days over a wide range of salinities. Acclimation periods of 8 and 16 days, however, led to statistically significant reductions in the net photosynthetic rate compared to the acclimation periods of 0, 2, and 4 days. The optimal rate of net photo­synthesis in all acclimation regimes was at 25 ~ s. There were marked declines in

----

291 c. Ya rish et al.: Salinity Resp o nses o f Estuarine Al gae

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Fig. 1. Bostrychia radi cans (Tuk e y 's w = 2 .73) , Cal ogl os s a l eprieurii (w = 1. 55), and Polys ipho ­nia subtilissima (w = 1. 49). Net photosynthetic rate s after 3 h incubation a t various s ali nities. Each point is based o n 4 replicates. The a l gae had not been pre viously a c climated to the vari­o u s s a l i n i t i e s . B. radicans was cul t ur ed at 25%; S, C. lepri eurii and P. s ub t i l issi ma at IS%; S

Table 1. Bostrychia radicans, Cal ogl ossa lepri­eurii and Polysiphonia sUbtilissima. St a t istical s ummar i es of net photosynthetic r esponses of clone s t o v a r i ations in s alinity wi t h di f f e rent acclimation times. Analyses b y TUkey' s multi ple compa r ison of mean s at t he 5% l e ve l. Values un­der s core d by same line are not significantly d if f e r e n t f rom e ach o t her . Magni t ude of photo­s y n t h e t i c respon ses are ranked f rom s ma l l e s t to largest, l eft t o r igh t

Sp ec ies Treatment Salini t y (?&, ) Acclimation times

(d ays)

B. r ad i can s 5 35 15 25 8 16 2 4:::,o_-=---:. C. l epr i e uri i :::.3:::.5_~5 15 25 16 8 2 0 4

P. s ub t i l i s s i ma 35 5 25 15 2 0 4 16 8

net photosynthesis after 8 and 16 days acclimation at 35 % S .

The net photosynthesis of Caloglossa leprieurii previously cultured at and therefore acclimated to a sal inity of

10 BOSTRYCHIA

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Fig. 2 . Bostrychia radi cans. Net p hotosyn t he t i c rate wi t h acc lima tion p e riod s o f 0, 2, 4, 8 a nd 16 day s i n sal inities o f 5, 15, 25 and 35%; (w = 2.75) . Ea c h poin t is bas ed o n 4 replicate s

15 ?&, was uniform (P <0 .0 5 ) over a salini­ty range o f 5 to 25 ?&, (Fig. 1). A decrease in net p ho to s y n t he s i s occurred at salin­ities greater than 25 %;, and n o net photo­s ynthesis wa s r ecorded at a?&' S. The effects of acclimation time at different salinities are shown in Fig. 3, and a statistical anal­ysis of the trends are given in Table 1. The opt i ma l acclimation period o v e r a broad range o f sal inities was 4 days (Table 1, P <0 .0 5) . A significant de­cline in net photosynthesis occurred in both 8- and 16-day acclimation regimes at 5?&, S. The o p timal rate o f n et photo­s ynthesis in all acclimation regimes oc­c u r r e d b e t we e n 15 and 25 %; S (P <0 . 0 5 ) •

The optimal rate of net ph o t osy n t he ­sis o f Pol ysi phoni a s ubtilissim a pr e v i o u s ly cultured at and therefore acclimated t o a salinity of 15%;, occurred at 15%; S (Fig. 1). A decline in net p h ot o s y n t he ­sis was apparent at salinities greater than o r less than the optimum, and lit­tle photosynthesis was recorded at 0% S (P <0 . 05) . All p l a n t s died after 1. 5 days immersion in a salinity o f 0%. The effects of acclimation time on net pho­

292 C. Yari s h et al. : Salinity Resp onses of Estuarine Algae

tosynthesis at different salinities are shown in Fig . 4 , and a statistical anal­ysis of the t r ends is p r e s e n t e d in Ta­ble 1. There was no significant differ­enc e in response between acclimation times over the whole range of salinities tested (P <0 . 0 5 ) . The optimal rate of net photosynthesis i n all acclimation reg imes was at 15 % S (P <0 . 0 5 ) . A dis­tinct increase in net photosynthesis o c­c urred at 35% S after 8 days acclimation.

Discussion

The patterns o f net photos yn the t i c rates as a funct ion of salinity variations differed for the 3 estuarine species of red algae studied, although all s pecies were very e ur y ha l i ne . Bostrychia r adican s photosynthesized between 15 and 35% S (Fig s. 1, 2 ) wi th a statistically sig­nificant maximum rate at 25% S (Fig. 2, Table 1). Calogl os s a l eprieurii had a rela­tively high photosynthetic rat e at all s a l i n i t i e s tested (Figs. 1, 3 ) , with a statistically significant maximum rate between 15 and 25 % S (Table 1 ) . Polysi­phonia subtilissima demonstrated a l ess broad response to salinity than the two preceding species, and had a d ist inct maximum rate at 15 % S. All 3 species oc­c ur r e d throughout the estuary (Yarish and Edwa r d s , 1976 ), with B. radi ca n s be­ing more abundant at the mouth (salin­ity range 2 3 to 31~) and C. lep rieurii and P. subt i l issima being more common t owa r d s t he head (salinity rang e at the Parkway Bridge 5 t o 19 ~). Thus, there is a gen­era l correlat i on be tween the horizontal or local distribution of these algae in the Great Bay Estuary System i n New Jer­sey a nd their net p h o t o syn t he t i c re­s p on ses t o salinity v a r i a t i ons in the laboratory.

None of the species occurred i n fresh water, and this correlated with their limited survival time o f 1.5 t o 3 . 5 d a y s in fresh water. More diff i cult t o ex­plain is t he absence of the species from the r elativ e l y h igh e r salinity r e gime of the open coast of New Jersey (monthly range for nearby Atlantic City on the o pen coast i s 27 to 35 ~ S, U. S . Co a s t and Geodetic Survey, 19 65) . All 3 spe­cies s how e d con siderable p hotosynthetic activ i ty at 3 5~ S. However, Bostr ychia radi can s showed a large decline in activ­ity at this s a l i n i t y after 8- and 16-day acclimation p e r i od s , and Pol ys i phoni a s ub ­til issi ma after 16 days. Surprisingly however, the photosyntheti c rate of p .

s ubtili s sima at 3 5% after an 8-day accli­mation period, was the highest among all acclimation p e r i od s . The r eduction o f the photosynthetic rate could h ave been

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Fig. 3 . Cal oglossa l eprieuri i. Ne t photo s ynthet­ic rate with ac climation periods of 0, 2 , 4 , 8 and 16 d a ys in sa l i n i t i e s of 5, 15, 25 and 35% (w = 1 .48) . Eac h point is base d on 4 r e pli cate s

POLYSIPHONIA

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Fig. 4 . Pol ysi ph on i a s ub t i li ssima . Net photosyn ­thetic r ate with acclimation p e r iod s of 0, 2 , 4 8 and 16 days in sa l i n i t i e s o f 5, 15, 25 and 35 % (w = 2 .33) . Each po i n t is b ased on 4 replicates

10

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293 C. Yari sh e t al. : Sa l ini ty Re s p o nses of Estuarin e Al gae

due to the long acclimation period in artificial seawater, which ma y not be an a dequ a t e substitute f or natural s eawa­ter. Certainly, th e respons es of all 3 s pecie s i n enriched seawater media were similar t o the responses o f mat erial ac­cl imated in a r ti f icial media for up t o 4 days, but plants were not acclimated in enriched seawater me d i a .

However, the possibility cannot ye t be ruled out that a salinity o f 35~ is too high for these species. This is also suppor ted by Fralick and Math i e s on ( 1975), who re ported a decrease in the photos yn­thetic r ate of Pol ysiphoni a s ubtil iss ima at salinities greater than 3 0~. On the oth­er hand, Mathieson a nd Dawes (1 97 5 ) have recorded e , s ub t il i s s i ma in Florida on the open coast in a salinity range o f from 3 7 to 42 ~. Suc h distribution diff erences might be due to ecotypic or physiologi­ca l ra ce v a riation s .

There are c onflicting reports in the literature on the ef fect o f acclimating plants t o a given salinity before deter­mining their pho t osyn t he tic rate. Kj e l d ­son (1967) and Ogata and Schramm (1971) r e ported tha t the r ate s o f p ho t o syn t he ­sis o f non- acclimated plants in a given salinity were a l wa y s higher than i n p l a n t s acclimated to that salinity. Montfort (19 31 ) stated t ha t it may not be pos s i b l e to e s t ab l i s h a definite re­lationship between the photosynthetic rate o f a given species and salinity, since t he ra te va r i e s according to bo t h sal inity and exposure t ime, result ing in an almos t unlimited number o f curves. However, for each s pecies in the p r e s ­e n t study, the c urve s relating net pho­tosynthesis with s alinity were similar for different acclimation pe r i od s , and mos t c an be corr e l a t e d wi th the horizon­tal distribution o f the species in the estuary. Assuming that a maximal net photosynthetic rate implies that a spe­cies is f u l ly acc limated, a 4-day accli­mation per i od wou l d a ppe ar to be the best one to use for the 3 species stud­ied (Table 1) . Therefore, i t would b e wise t o d o p r e l i mi na ry a cclimation s tud­ies to ide nti fy a v a lid t i me per iod , since this study indicates that such an acclimation pe r i od would not b e a pp r o ­priate for all species.

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