Marine Biology "2001) 138: 679±686 Ó Springer-Verlag 2001

E. Aguirre-von-Wobeser á F. L. Figueroa A. Cabello-Pasini Photosynthesis and growth of red and green morphotypes of Kappaphycus alvarezii Rhodophyta) from the Philippines

Received: 19 June 2000 / Accepted: 28 November 2000

Abstract The e€ect of photosynthetic available radia- white light. Short exposure to high levels of solar radia- tion "PAR) levels, light quality, ultraviolet "UV) radia- tion "UV-A + UV-B + PAR), and ®ltered solar tion, and temperature on photosynthesis, growth, and radiation "UV-A + PAR or PAR) decreased e€ective chlorophyll ¯uorescence was evaluated in red and green quantum yield "DF/Fm¢) in both morphotypes. The morphotypes of the rhodophyte Kappaphycus alvarezii reduction of DF/Fm¢ values in the red and green mor- "Doty) Doty under controlled conditions. Chlorophyll a photypes was accounted for by high levels of PAR and and phycoerythrin "PE) levels were similar in the red and not by the UV-A + UV-B + PAR and UV-A + PAR green morphotypes cultured under the same conditions, treatments. Photoinhibition caused by UV-A, UV-B, or but phycocyanin "PC) and allophycocyanin "APC) levels PAR was completely reversed within 30 h after incuba- were 2-fold greater in the green than in the red tions. Recovery rates from photoinhibition, however, morphotype. Pigment characterization indicated that the were signi®cantly reduced in the green morphotype when overexpression of PC and APC masked the red incubated with UV-B radiation. The results here suggest pigmentation in the green morphotype. Maximum that the overexpression of pigments do not necessarily photosynthesis and photosynthetic eciency were similar increase photosynthesis and growth in these morpho- between the two morphotypes assayed at a wide tem- types. perature range, which was re¯ected in the similar growth rates observed in outdoor culture systems. In the green morphotype, photosynthetic eciency increased 2-fold Introduction relative to the red morphotype when assayed with red light "k > 600 nm), indicating that photosynthetic Kappaphycus alvarezii has been exploited in Asia for characteristics are modi®ed as a result of pigment varia- severaldecades and is one of the most important sources tion in these morphotypes. Such increase in photosyn- of carrageenan in the world "Doty and Norris 1985; thetic eciency in the green morphotype, however, did Doty et al. 1987). Natural populations of K. alvarezii, not result in greater growth rates when cultured under however, have decreased drastically as a result of over- harvesting "Doty et al. 1987). Presently, most of the K. alvarezii harvested in the Philippines comes from small private farms, which produce more than 30,000 Communicated by M. Horn, Fullerton/ O. Kinne, Oldendorf/Luhe tons annually "Doty et al. 1987). Despite the great eco- E. Aguirre-von-Wobeser nomic importance of this species as a carrageenan Facultad de Ciencias Marinas, source, there are few studies that relate its physiology to Universidad Auto noma de Baja California, the wide ¯uctuations of irradiance and temperature A.P. 453, Ensenada, Baja California 22800, Mexico observed in the culture systems "Wu et al. 1989; Gan- F. L. Figueroa zon-Fortes et al. 1993; Hurtado-Ponce 1995). Departamento de Ecologõ a, Facultad de Ciencias, The existence of morphotypes of K. alvarezii with Universidad de Ma laga, Campus Universitario Teatinos, 29071 Ma laga, Spain varied pigmentation in the ®eld and culture systems has been reported in the literature for decades "Doty et al. A. Cabello-Pasini "&) Instituto de Investigaciones Oceanolo gicas, 1987; Hurtado-Ponce 1995). These morphotypes gener- Universidad Auto noma de Baja California, ally show di€erences in their photosynthetic character- A.P. 453, Ensenada, Baja California 22800, Mexico istics and levels of carrageenan. Similarly, it has been e-mail: [email protected] shown that growth rates of green morphotypes are Tel.: +52-6-1744601; Fax: +52-6-1745303 slightly lower than growth rates of red and brown 680 morphotypes "Dawes et al. 1994; Hurtado-Ponce 1995). Incident irradiance reached approximately 2,000 lmolpho- Such di€erences in photosynthetic characteristics and tons á m)2 s)1 at midday throughout the experiment, and water temperature averaged 24 °C initially and increased to approxi- growth rates could be critical for the selection of mor- mately 29 °C at the end of the experimentalperiod. Seawater was photypes of K. alvarezii with rapid growth rates in changed twice weekly and NaNO3 supplied to a ®nal concentration commercialseaweed cultures.Despite these important of 100 lM. Ten individuals of the red and green morphotypes of physiological di€erences, there are no studies that relate K. alvarezii of approximately 5 g FW were tagged individually and the percentage and frequency of the red and green the increase in fresh weight was determined twice weekly. Plants were gently blotted with paper towels and fresh weight determined morphotypes of K. alvarezii in the ®eld. with an electronic balance. Daily growth rates "G;%á day)1) Light is absorbed di€erentially by the di€erent pho- were determined using the following equation: G % Á day)1)=  1=tà tosynthetic pigments of algae and vascular plants "Kursar Wt=W0† Á 100, where Wt is tissue weight after an incubation et al. 1983). As a consequence, the photosynthetic and period "t) and W0 is the initialtissue weight. growth response to di€erent light qualities can vary in algae with di€erent pigment composition "Dawes 1992). Pigment and protein analysis Although phycoerythrin "PE) levels can be lower in the Chlorophyll was extracted from approximately 0.1 g of tissue in green morphotype than in the red morphotype of K. al- 5 mlof 90% acetone "v/v) using a glasstissue homogenizer. The varezii "Dawes 1992), little is known about the in¯uence homogenate was centrifuged at approximately 2,000 g for 15 min of pigment variations on photosynthesis and growth of and chlorophyll a levels were determined following the equations either morphotype. It would be expected that the pho- described by Je€rey and Humphrey "1975). PE, PC and allophyc- tosynthetic and growth eciency would be reduced in ocyanin "APC) were extracted in 5 mlof 0.1- M phosphate bu€er "pH 6.9), 1 mM EDTA, and 1 mM dithiothreitol"DTT) using a morphotypes with lower pigment levels per unit biomass glass tissue homogenizer. The homogenate was centrifuged at ap- and as a consequence be selected against in nature. proximately 2,000 g for 15 min and biliprotein levels were deter- It has been demonstrated that a reduction of PE and mined using the equations described by Kursar et al. "1983). phycocyanin "PC) levels, as a consequence of exposure Total protein levels were evaluated by disrupting approximately 0.1 g of tissue with 3 mlof extraction bu€er "0.1- M phosphate to ultraviolet "UV) radiation, is correlated to a decrease bu€er "pH 6.9), 1 mM EDTA, 1% "w/v) PVP, and 1 mM DTT) in of optimal quantum yield in red algae "Figueroa et al. a glass tissue homogenizer. Protein concentration of the extracts 1997). The e€ect of UV radiation on morphotypes of was estimated as described by Bradford "1976) and standardized K. alvarezii with low biliprotein levels, however, is not against bovine serum albumin. known. In this study we have examined growth and photosynthesis of red and green morphotypes of Photosynthesis versus irradiance relationships K. alvarezii as a function of light levels and tempera- ture under both natural and controlled laboratory Photosynthetic response and dark respiration were evaluated in the red and green morphotypes of K. alvarezii maintained under lab- conditions. We also investigated the e€ect of UV and oratory conditions. Photosynthetic and respiratory rates were photosynthetically available radiation "PAR) on the evaluated polarographically on tissue segments. Lamps with halo- photoinhibition of photosynthesis of this species. These gen bulbs "500 W, quartzline) were used as light sources and experiments will further our understanding of the impact photosynthetic photon ¯ux "PPF) was varied using neutral-density ®lters from 0 to 650 lmolphotons á m)2 s)1. All measurements of environmentalfactors such as temperature and in- were conducted in 5-mljacketed chambers at speci®c temperatures creasing UV radiation on the physiology of natural and between 8 °C and 37 °C using a temperature-controlled water bath. cultured populations of marine algae. Maximum oxygenic photosynthesis "Pmax), respiration "R), pho- tosynthetic eciency "a), and the threshold for irradiance-saturated photosynthesis "Ik) were determined by a non-linear direct ®tting algorithm "Sigma Plot, Jandel Scienti®c) of the data to the expo- nentialequation described by Webb et al."1974). Materials and methods The e€ect of red light "k > 600 nm) on photosynthesis was evaluated at 25 °C on the red and green morphotypes of K. al- Plant material varezii. The photosynthetic response to increasing red light was evaluated by placing a red ®lter "HT026, Lee Filter, England) di- Red-pigmented and green-pigmented morphotypes of Kappaphycus rectly in front of the light path so that only k > 600 nm reached alvarezii were collected in seaweed farms from the Philippines and the incubation chambers. Lamps with halogen bulbs "500 W, transported at ambient temperature in dark containers to a labo- quartzline) were used as light sources and PPF was varied using ratory facility in Ensenada, Baja California, Me xico. Prior to the neutral-density ®lters from 0 to 650 lmolphotons á m)2 s)1. experiments, approximately 30 individuals of the red and green Controls were evaluated using white light "without red ®lters) and morphotypes were maintained in the laboratory for approximately photosynthesis was evaluated as described above. 1 year in 30-lcontainers at approximately25 °C. Individuals were kept on a 16:8 light:dark photoperiod with approximately 100 lmol photons á m)2 s)1 from wide-spectrum cool¯uorescent bulbs. In vivo ¯uorescence Water was changed once weekly, enriched with 250 lM NaNO3, and kept under constant aeration. All experiments were conducted Photoinhibition of photosynthesis was determined by evaluating on morphotypes maintained under laboratory conditions. in vivo chlorophyll ¯uorescence with a pulse amplitude-modulated ¯uorometer "PAM 2000, Waltz, E€eltrich, Germany) as described by Schreiber and Neubauer "1990). E€ective quantum yield "DF/Fm¢ ) Growth from tissue exposed to di€erent light treatments is a measurement of the actualquantum yieldfor photosynthesis at the experimental Growth experiments were conducted from Aprilto July1997 using irradiance, and its decrease at high experimentalirradiances can be 100-loutdoor tanks under naturalirradiance and temperature. used as a measure of photoinhibition "Genty et al. 1989; Krause 681 and Weis 1991). Values of e€ective quantum yield were calculated 0 0 0 0 as DF/Fm where DF ˆ Fm ) Ft , Fm is the maximal¯uorescence and 0 0 0 Ft is the basalsteady-state ¯uorescence. Valuesof Ft and Fm in the tissue were determined at very low-intensity pulse of red light )2 )1 0 "650 nm, 0.3 lmolphotons á m s ), and Fm was induced with a saturating white light pulses "0.4 s, approx. 9,000 lmolpho- tons á m)2 s)1). E€ective quantum yield was determined in the al- gae submerged in seawater under white ¯uorescent light "Osram DL, 20W) at an irradiance of 50 lmolphotons á m)2 s)1. Tissue from K. alvarezii was placed horizontally in a seawater cuvette with a cooling jacket "Walz, Germany) and fastened at a distance of 2 mm from the ®ber optic of the ¯uorometer.

E€ect of UV light on photoinhibition of photosynthesis

The e€ect of UV radiation on photoinhibition of the red and green morphotypes was determined by evaluating chlorophyll ¯uores- 0 cence. Values of DF/Fm were determined in both morphotypes prior to the experiments and then after a 1-h incubation period at noon under PAR + UV-A + UV-B "Ultraphan, Digrefa GmbH, Ger- many, k > 295 nm), PAR + UV-A "Folex 320 nm, Folex GmbH, Germany), and PAR alone "Ultraphan k > 395). The transmission spectra of the ®lters have been previously reported by Figueroa et al. "1997). After the experimental treatment, the algae were Fig. 1 Absorbance spectra of chlorophyll a "Chl a), organic soluble transported in a black container with seawater "17 °C) to the lab- pigments, phycoerythrin "PE), phycocyanin "PC), and allophycocy- oratory nearby and chlorophyll ¯uorescence was determined within anin "APC) in the red and green morphotypes of Kappaphycus 0 alvarezii 2 min of collection. It has been demonstrated that DF/Fm values do not vary within 10 min of collection of the algae from the ®eld "VinÄ egla 2000). Levels of PAR were approximately 2,000 lmol photons á m)2 s)1,53Wá m)2 UV-A, and approximately 2- to 3-fold greater than PC and APC peaks in the red 1.5 W á m)2 UV-B during the incubation period. Incident PAR morphotype. However, absorbance peaks of PE, PC, and levels were determined with a LI±190SA 2p quantum sensor at- APC were relatively similar in the green morphotype. tached to a LI-COR data logger. Ultraviolet A and B radiation Biomass-normalized pigment levels also varied be- levels were determined using UV sensors connected to a RM-11 tween the red and green morphotypes of K. alvarezii radiometer "GrobelInstruments, Germany). Valuesof UV radia- tion were corrected against an Optronic 752 double monochro- "Table 1). Chlorophyll a levels were statistically similar mator spectroradiometer "Optronic Labs, Florida, USA). After the in the two morphotypes, which is inconsistent with ob- incubation period, the individuals were placed in an incubator at servations by Dawes "1992). In general, the levels of PE approximately 10 lmolphotons á m)2 s)1 PAR and 17 °C, and the 0 were approximately 2-fold greater "P < 0.05) than PC recovery of DF/Fm was followed for 30 h in both morphotypes. Measurements were conducted on a minimum of six individuals. and APC levels in the red morphotype, which is con- sistent with observations made in other rhodophytes. In contrast, the levels of PE, PC, and APC were similar in Statisticalanalysis the green morphotype "P > 0.05). Levels of PE were Statistical di€erences in the pigment and protein levels between the statistically similar in the red and green morphotypes of red and green morphotypes of K. alvarezii were evaluated using K. alvarezii. However, PC levels were approximately 3- Student t-tests. The statisticaldi€erence of growth rates and the fold greater in the green morphotype than in the red e€ect of UV radiation in both morphotypes was evaluated with morphotype. Similarly, APC levels were 2-fold greater in one-way analysis of variance "ANOVA) after testing for homo- scedasticity and normality of the data "Sokal and Rohlf 1981). the green morphotype than in the red morphotype. Speci®c di€erences were determined using Tukey's multiple com- Protein levels were signi®cantly greater in the green than parison test. Slope di€erences were evaluated through an analysis in the red morphotype of K. alvarezii. Biliprotein levels of covariance "ANCOVA). Minimum signi®cance level was estab- lished at P < 0.05. Table 1 Chlorophyll a, phycoerythrin, phycocyanin, allophyco- cyanin, and protein concentration and statisticalsigni®cance in the red and green morphotypes of Kappaphycus alvarezii. Values in Results parentheses indicate 1 SD. Degrees of freedom "df), statistical t value "t), probability value "P) Pigments and protein Pigment Morphotype df t P level The absorption spectra of some pigments varied in the mg gFW)1 Red Green red and green morphotypes of Kappaphycus alvarezii "Fig. 1). The chlorophyll and PE spectra showed similar Chlorophyll a 0.061 "0.010) 0.062 "0.009) 5 0.91 n.s. absorbance patterns in the red and green morphotypes; Phycoerythrin 0.238 "0.037) 0.203 "0.019) 6 1.62 n.s. Phycocyanin 0.077 "0.012) 0.195 "0.016) 6 11.99 <0.001 the absorbance from PC and APC in the green mor- Allophycocyanin 0.103 "0.015) 0.213 "0.046) 6 4.58 <0.01 photype, however, was approximately 2-fold greater than Totalproteins 0.66 "0.11) 0.76 "0.11) 22 2.11 <0.05 that of the red morphotype. As expected, PE peaks were 682 accounted for approximately 63% of total proteins in the red morphotype and approximately 80% in the green morphotype.

Growth and photosynthesis

Although there were statistical di€erences "P < 0.05) in growth rates at speci®c sampling times, in general, rel- ative growth rates did not di€er between the red and green morphotypes of K. alvarezii throughout the incu- bation period "Fig. 2). Plants lost weight for approxi- mately 1±2 weeks after the laboratory-maintained individuals were transferred to the outdoor culture sys- tem, after which growth rates increased in both mor- photypes. Initially, the red morphotype had 2-fold greater "P < 0.05) growth rates than the green mor- photype; however, growth rates for both morphotypes reached maximum values "approximately 4% á day)1) after 30 days in the outdoor culture tanks. Growth rates in both morphotypes declined for the next 60 days until )1 they stabilized at approximately 0.1% á day . The de- Fig. 3 Photosynthesis versus irradiance response of the red and green cline in growth rates in both morphotypes coincided morphotypes of K. alvarezii incubated at 20 °C. The photosynthetic with an increase of approximately 5 °C in seasonalwater response characteristics of these curves are representative of curves at temperature in the culture tanks. other temperatures. Symbols represent average "n >6)anderror bars Photosynthesis versus irradiance curves were relatively represent one standard deviation similar for the red and green morphotypes at any speci®c temperature "Fig. 3). As a consequence, photosynthetic parameter values covaried as a function of increasing temperature in both morphotypes. Maximum photo- synthesis "Pmax) reached maximum values "0.2 lmol )1 )1 O2 á gFW min ) in both morphotypes at 30 °C "P < 0.05), after which Pmax declined to values observed at 8 °C "Fig. 4A). Values of a in both morphotypes were

Fig. 2 Growth rates "% á day)1) under naturalirradiance of the red Fig. 4 Maximum photosynthesis "A), photosynthetic eciency "B), and green morphotypes of K. alvarezii in outdoor culture systems. and respiration "C) values of K. alvarezii as a function of temperature. Symbols represent average "n ³ 10) and error bars represent one Symbols represent average "n ˆ 6) and error bars represent one standard deviation. Error bars not seen are smaller than symbol size standard deviation. Error bars not seen are smaller than symbols 683 greatest "P < 0.05) at 15 °C and signi®cantly declined as the green morphotype were 2-fold greater "P < 0.05) temperature increased "Fig. 4B). In contrast, Ik increased when incubated under red light, relative to the white "P < 0.05) to similar values in both morphotypes at light control "Fig. 5B). Values of a did not vary 30 °C and signi®cantly declined at 37 °C "data not "P > 0.05) in the red morphotype when incubated in shown). Respiration did not show a clear pattern red light, relative to the white light control. throughout the experimentaltemperature range for either of the two morphotypes "Fig. 4C). In the red morpho- type, respiration was greatest at 15 °C and 30 °C; how- E€ect of UV light on photoinhibition ever, respiration values were highest at 30 °C in the green 0 morphotype. In general, respiration represented ap- Values of DF/Fm decreased in the red and green mor- proximately 30±40% of Pmax values. photypes when exposed to high levels of UV-A, UV-B, 0 or PAR. Values of DF/Fm in both morphotypes signi®- cantly declined "P < 0.05) to approximately 30% of E€ect of light quality on photosynthesis pretreatment levels after treatments with UV-A + UV-B + PAR, UV-A + PAR and to approximately The e€ect of red light "k > 600 nm) on photosynthesis 40% after treatments with PAR "Fig. 6). However, the 0 showed di€erent trends in the red and green morpho- decrease of DF/Fm was not signi®cantly di€erent types of K. alvarezii. Values of Pmax decreased "P > 0.05) among treatments. Complete recovery of 0 "P < 0.05) in the red morphotype when incubated in DF/Fm was observed in the red and green morphotypes red light, relative to the white light control "Fig. 5A). In and all treatments after a 30-h incubation under no UV contrast, the photosynthetic response did not vary in the green morphotype when incubated in red light relative to the white light control. In contrast to Pmax, a values in

0 Fig. 6A±C Relative values DF/Fm in the red and green morphotypes of K. alvarezii incubated under UV-A + UV-B + PAR, Fig. 5 Maximum photosynthesis "Pmax, A) and photosynthetic UV-A + PAR, and PAR. First data point represents pretreatment eciency "Alpha, B) of the red and green morphotypes of K. alvarezii values followed by a 1-h light quality treatment "second data point). incubated under red light treatment "k > 600 nm) and white light Photoinhibition recovery was determined after individuals were controls. Bars represent average "n ˆ 6) and error bars one standard transferred to a low PAR and no UV radiation environment. Symbols deviation represent average "n ˆ 6) and error bars one standard deviation 684 radiation and low photosynthetic photon ¯ux. Initial incubated under white light. Furthermore, there is a 0 recovery slope of DF/Fm under all treatments was similar greater photoinhibition of the green morphotype when "P > 0.05) in the red morphotype, but the recovery of exposed to UV-B radiation compared to the red mor- 0 DF/Fm in the green morphotype treated with UV-B ra- photype. diation showed signi®cantly lower "P < 0.05) values The green pigmentation in the green morphotype of than those treated under UV-A or PAR "Fig. 7). K. alvarezii has been assumed to be the result of low PE levels "Doty et al. 1987). Our results indicate rather, that the green pigmentation is the result of an overexpression of PC and APC in the green morphotype. Such elevated Discussion concentrations of PC and APC in the green morphotype mask the characteristic red coloration of this rhodo- The evaluation of the physiological characteristics phyte. Since proteins can be an important nitrogen re- among mutants from algae and vascular plants has serve, it has been suggested that low levels of PE and proved criticalfor understanding photosynthesis, pig- other biliproteins are responsible for the lower ability of ment synthesis, and other autotrophic metabolic path- the green morphotype of K. alvarezii to store nitrogen, ways "Schmidt and Lyman 1974; Russell and Dra€an relative to the red morphotype "Dawes 1992). The in- 1978; Lam et al. 1995). Marine algae lacking chlorophyll crease in protein levels in the green morphotype here was or with varied concentrations of biliproteins are known accounted for by the increase in PC and APC levels, to occur in nature or have been mutagenized by chemical suggesting an increase of nitrogen reserves in the green treatments "Russell and Dra€an 1978; Kursar et al. morphotype relative to the red morphotype. 1983; Hurtado-Ponce 1995). Kappaphycus alvarezii is The lack of expression or the overexpression of some one of the most important sources of carrageenan in the pigments in some species has been shown to be meta- world and the presence of green-pigmented morpho- bolically disadvantageous for the mutant morphotypes types has been reported. It is not known, however, if when compared to the wild-natural morphotypes "Rus- such pigmentation provides a physiological advantage/ sell and Dra€an 1978; Kursar et al. 1983; Dawes 1992). disadvantage relative to the red-pigmented morphotype Although there was a lag response in growth rates for "Doty et al. 1987; Dawes 1992; Hurtado-Ponce 1995). approximately 1±2 weeks as a result of transferring the Here we characterized the photosynthetic response of individuals to the outdoor culture system, growth rates red and green morphotypes of K. alvarezii under labo- increased rapidly afterwards and maintained similar ratory conditions. Our results clearly show that the values in both the green and red morphotypes pigment composition di€ers in the red and green mor- throughout the study period. Similarly to growth, P photypes of K. alvarezii, but photosynthesis and growth max and a values showed comparable responses in the green are relatively similar in the two morphotypes when and red morphotypes of K. alvarezii exposed to white light. This is in agreement with results observed by Hurtado-Ponce "1995) and Dawes "1992) and suggests that in culture systems or in the wild, the light require- ments for maximum photosynthesis are ful®lled by the light-harvesting scheme of the red morphotype. In con- trast to this study, relative growth rates under labora- tory conditions have been reported to be generally greater in the red than in the green morphotype "Dawes et al. 1994); however, the pigment compositions of the morphotypes were not reported and are dicult to compare with results here. The results here also show that the overexpression of PC and APC does not impart a photosynthetic advantage to the green K. alvarezii morphotype when incubated in white light. This is consistent with results from other studies that demon- strate that an increase in pigment levels in rhodophytes does not always result in an increase of photosynthetic activity "Talarico 1996). Phycobilisomes are structured with an internalcore of APC, severalintermediate packets of PC, and an external layer of PE "Talarico 1996). As a consequence, the energy transfer in phyco- bilisomes is from PE to PC to APC. The lack of an increase in photosynthetic eciency "a) in the green Fig. 7 Recovery rates of DF/F 0 values in the red and green m morphotype, compared to the red one, suggests that PC morphotypes of K. alvarezii after a 1-h treatment under UV-A + UV-B + PAR, UV-A + PAR, and PAR. Bars represent and APC energy absorbance is much lower than that of average "n ˆ 6) and error bars one standard deviation PE and chlorophyll. 685

Values of Pmax in both morphotypes were maximalat throughout the year as observed in other studies "Dawes approximately 30 °C, which is consistent with the ob- et al. 1994). The low Pmax and a values observed for served optimum growth rate temperature for K. alvarezii both morphotypes at 8 °C and 37 °C are probably the in culture systems "Wu et al. 1989; Ohno et al. 1994). result of extreme experimental temperatures that would Maximum growth rates, however, were not maintained not be observed in the ®eld under normal conditions. for prolonged periods in the culture systems here once The similar photoinhibitory e€ect of UV-A, UV-B, 0 temperature approached 30 °C. In contrast to Pmax, a and PAR irradiance on DF/Fm of photosystem II in both values were optimal at lower incubation temperatures morphotypes suggests that high levels of PAR account here. Such ¯uctuations in photosynthetic characteristics for most of the photoinhibition in K. alvarezii under the are consistent with results observed in other species experimentalconditions used here. These resultsare "Davison 1987) and probably contribute to the ability of consistent with those observed in the red alga Palmaria K. alvarezii to maximize growth rates over a wide tem- palmata and other species where PAR, and not UV ra- perature range. Additionally, temperature in culture diation, accounted for most of the photoinhibition systems where K. alvarezii is grown ¯uctuates from ap- "Lorenz et al. 1997; Aguirre-von-Wobeser et al. 2000). proximately 15 °C to above 30 °C "Wu et al. 1989; Photoinhibition in marine algae generally follows a di- 0 Ohno et al. 1994), indicating that seasonal temperature urnalpattern, with high DF/Fm values in the morning changes might regulate the photosynthetic and growth and afternoon and low photosynthetic activity at noon metabolism of this species. "HaÈ der et al. 1996, 1997; Cabello-Pasini et al. 2000). As Morphological and physiological changes, including K. alvarezii grows or is cultured in shallow water col- pigment levels and composition, have been observed in umns "Doty et al. 1987), it is likely that both morpho- red algae incubated under red and blue light "Talarico types exhibit photoinhibition, particularly during 1996). Relative to white light controls, light-saturated maximum irradiance levels at noon. The relatively high photosynthesis decreased in the red morphotype when inhibition observed here after 1-h incubation at natural incubated under long wavelength light. At k > 600 nm, irradiance levels suggests that K. alvarezii might grow light absorbance by PS II is absorbed mainly by PC and better at depths where elevated photon ¯ux is reduced, APC "Kursar et al. 1983). As a consequence, the de- as observed for other species "Figueroa et al. 1997). 0 crease in Pmax in the red morphotype is probably the However, the complete recovery of DF/Fm values after a result of insucient levels of PC and APC to harvest the few hours at low irradiances suggests an e€ective incident red light. mechanism of photosystem repair that might provide an The greater a values observed in the green K. alvarezii advantage over other species to inhabit environments morphotype incubated under red light ">600 nm) here with elevated UV and PAR levels. are consistent with its greater levels of APC and PC The ability to recover from photoinhibition was compared to the red morphotype. As PE absorbs at lowered when individuals were treated with UV-B, as wavelengths lower than 600 nm "Kursar et al. 1983; observed for other rhodophytes "Figueroa et al. 1997; Lorenz et al. 1997), the overexpression of PC and APC Lorenz et al. 1997). Hanelt et al. "1992) found that red "absorbance >600 nm) in the green morphotype prob- seaweeds exposed to full solar radiation could have ably results in an increase of photosynthetic eciency permanent photodamage after photoinhibition. Our re- when incubated with k > 600 nm. However, the de- sults suggest that K. alvarezii has a high rate of photo- crease of Pmax values of the red morphotype incubated system repair that is criticalfor maintaining rapid with red light, relative to those incubated in white light, growth rates in environments with elevated irradiance indicates that short wavelengths are more eciently used levels, such as those experienced in natural populations during photosynthesis, as observed in other species or culture systems. "Forster and Dring 1994). In the red treatment where PE These experiments provide the ®rst evidence of the is not absorbing, the increase of Pmax values in the green e€ect of light quality on the physiology and pigment morphotype is explained by the overexpression of PC composition of the red and green morphotypes of and APC, and the increased capacity for the absorbance K. alvarezii from the Philippines. The results here sug- of photons relative to the red morphotype. It is clear gest that photosynthesis and growth are not a€ected by that photosynthetic characteristics vary as a function of an overexpression of PC and APC in red algae if PE pigment composition in K. alvarezii, but PE absorbance levels remain constant. Although marked physiological appears to saturate growth in both morphotypes grown di€erences between the two morphotypes are described under white light in the ®eld or culture systems. This here, there are no studies describing the frequency of might explain why the green morphotype of K. alvarezii these morphotypes in the wild. More investigations are has not been selected for/against in nature. also necessary to determine the possible advantage and The comparable photosynthetic response between the the subsistence of the green morphotype of K. alvarezii red and green morphotypes throughout the experimental in the naturalenvironment. temperatures is consistent with the similar growth rates observed in the culture tanks. These results suggest that Acknowledgements We thank Dr. Jose Zertuche for providing the survivalof the green morphotype in the ®eldis the the red and green morphotypes of Kappaphycus alvarezii, and result of similar photosynthetic and growth patterns Dr. David Chapman and Dr. Alejandro Buschmann for reviewing 686 the originalmanuscript. We thank Dr. D.-P. Ha È der for the cali- HaÈ der DP, Lebert M, Flores-Moya A, Jimenez C, Mercado J, bration of the UV sensors. This work was supported by grants Salles S, Aguilera J, Figueroa FL "1997) E€ects of solar from the University of Baja California "UABC/IIO 4023, UABC radiation on the photosynthetic activity of the red alga Coral- 4078-30) and Consejo Nacionalde Ciencia y Tecnologõ  a "I26655- lina elongata Ellis et Soland. J Photochem Photobiol 37: 196± N). All experiments conducted within this study comply with the 202 current laws of Mexico. Hanelt D "1992) Photoinhibition of photosynthesis in marine macrophytes of the south Chinese Sea. Mar EcolProg Ser 82: 199±206 Hurtado-Ponce AQ "1995) Carrageenan properties and proximate composition of three morphotypes of Kappaphycus alvarezii References Doty "Gigartinales, Rhodophyta) grown at two depths. 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