Copyright © 1990 Kluwer Academic Publishers. Printed in Belgium.Manometric studies were conducted on Pterocladia capillacea, Gelidium latifolium and Gelidium spinulosum from the Azores, Portugal to determine optimal values of temperature, light and salinity for growth. Physiological responses were considered in relation to vertical distribution patterns of these species commonly observed throughout the Azores. Optimal parameters for the growth of Pterocladia capillacea, Gelidium latifolium and G. spinulosum were 17 to 25 ºC, a photon flux density between 200 and 300 umol m -2 s -1 and salinities of 25 to 35 per thousand

Baldwin, Heather P.

Fralick, Richard A.

Hehre, Edward

Neto, Ana I.

Repositório da Universidade dos Açores

Hydrobiologia 204/205 : 479-482, 1990 .S. C. Lindstrom and P . W. Gabrielson (eds), Thirteenth International Seaweed Symposium .	479© 1990 Kluwer Academic Publishers. Printed in Belgium .Physiological responses of Pterocladia and Gelidium (Gelidiales,Rhodophyta) from the Azores, PortugalRichard A . Fralick 1 , H . P. Baldwin 2 , A. I. Neto 3 & E. J. Hehre 2'Natural Science Dept., Plymouth State College of the University System of New Hampshire, Plymouth,NH 03264, USA ; 'Dept. of Botany and Plant Pathology, University of New Hampshire, Plymouth, NH03824, USA ; 'Dept. of Biology, University of the Azores, Rua Mae de Deus, Ponta Delgada, Sao Miguel,Azores, PortugalKey words : Gelidium, photosynthesis, physiological responses, Pterocladia, RhodophytaAbstractManometric studies were conducted on Pterocladia capillacea, Gelidium latifolium and Gelidium spinulosumfrom the Azores, Portugal to determine optimal values of temperature, light and salinity for growth .Physiological responses were considered in relation to vertical distribution patterns of these speciescommonly observed throughout the Azores . Optimal parameters for the growth of Pterocladia capillacea,Gelidium latifolium and G. spinulosum were 17 to 25 'C, a photon flux density between 200 and 300 pmolm -2 s -1 and salinities of 25 to 35% . .IntroductionNumerous authors have studied the geographicand vertical distribution of the Gelidiales . Muchof this work has been summarized by Santelices(1974) ; however, literature is lacking in informa-tion on the physiological-ecology of gelidioidspecies from the Azores, Portugal . Two of threespecies of Gelidium and one species of Pterocladiawere included in this study : Gelidium spinulosum(Agardh) J. Agardh, Gelidium latifolium (Grey .)Bornet et Thuret and Pterocladia capillacea (S .Gmelin) Bornet et Thuret. Each of the speciesoccupies a different vertical niche with only mini-mal overlap occurring between G. latifolium andP. capillacea (Fig. 1) .Several reasons combine to make this projectof interest . First, there are few published data toaccount for intertidal benthic macroalgal distribu-tions in the Azores ; second, there is potentialeconomic value in these species for two existingFig . 1 . Zonation profile for Pterocladiaand Gelidium spp .from the Azores, Portugal .agar-producing plants, and third, there is a needto determine optimal growth parameters for thesespecies in anticipation of a proposed aquaculturepilot study . Harvesting impacts of Azores Ptero-cladia over the past decade have created a need480for additional knowledge of gelidioid species inthe area, which are required to sustain a decliningindustry .Pterocladia capillacea is the sole source of rawmaterial for the agar factories . Another species,Gelidium spinulosum, referred to locally as`Cabalhao' has reportedly been used to improvethe gel strength of agar-agar extracted fromPterocladia . Our personal observations on theislands of Terceira and Sao Miguel indicate thatsmall amounts of G. spinulosum are collected,dried, kept separate from Pterocladia collectionsand when necessary used specifically for this gel- .enhancing purpose .The purpose of this work was to obtain afundamental understanding of the optimalphysiological parameters for growth of Azoresgelidioid algae . In addition, we were interested, intheir physiological tolerances to temperaturechanges in relation to their intertidal distributionpatterns .Materials and methodsSpecimens of Pterocladia and Gelidium were col-lected in the intertidal zone of the Island of Faial,Azores, Portugal during June, 1988. Additionalmaterial was collected on the island of SaoMiguel, Azores in January, 1989 . Specimens wereplaced in a cooler with ice and transported within12 h to Plymouth, New Hampshire, USA andstored under conditions of 10 : 14 (LD) at84 tmolM-2s - ' and 10 'C. The thalli weremaintained in a culture media made from UVfiltered seawater enriched with alga-grow nutrientconcentrate from Carolina Biological Supply Co .The media was changed every 10 days throughoutthe study . Apparent photosynthesis rates wererecorded in a Gilson Differential Respirometerequipped with a series of 50 Watt incandescentlight bulbs . Light intensities (Fig . 2) were variedusing a rheostat and were measured with aLI-COR (Li 185 B) Quantum/Radiometer/Photometer . Respiration experiments were un-dertaken in a darkened room. All fronds were equil-ibrated for a minimum of 30 min prior to eachEra85 .063 .3O N-.	41 .720 .0M5aFig . 2 . Apparent photosynthesis for Pterocladia and Gelidiumspp . a t different light intensities .trial ; each experiment had 10 replicates . Ingeneral, the methodology for these experimentsfollowed those of Fralick & Mathieson (1975),Dawes (1981) and Mathieson & Dawes (1986) .ResultsPhotosynthesis and lightOptimal photosynthesis for Pterocladia capillaceaoccurred at 177 µmol m- ' s - ' and for Gelidiumspinulosum and G. latifolium at 225 µcool m - 2S- 1(Fig. 2). Oxygen production values for P. capil-lacea remained high up to 320 ymol, but wereminimal at light levels of 125 tmol and beyond385 pmol. The optimal ranges for G. spinulosumand G. latifolium were similar with higher valuesoccurring between 250 tmol and 385 tmol . Mini-mal ranges for oxygen production for bothGelidium species occurred at 120 ymol .Photosynthesis and temperatureMinimal oxygen evolution values were recordedfor all species at temperatures below 10 ° C(Fig. 3) . Optimal values for Pterocladia capillaceawere recorded between 15 and 25 'C. Beyondthis P. capillacea showed some degree of tempera-I'03 .7;6 .33 .0070 .046 .723 .30 .00Temperature (`c)Fig. 3 . Apparent photosynthesis of Pterocladia and Gelidiumspp. at different temperatures .Lure tolerance up to about 30 'C, but the valuesdeclined substantially at that point .Apparent photosynthesis for Gelidium spinu-losum increased in a linear manner from 5 to15 'C. Optimal values were exhibited between 15and 30 'C . Gelidium latifolium values also in-creased in a linear manner from 5 to 15 ° C andremained constant to 30 'C. The rates of photo-synthesis declined beyond 30 °C for thesespecies .Photosynthesis and salinityApparent photosynthesis for Pterocladia capil-lacea, Gelidium spinulosum and G . latifolium along40.020 .0	30.0Salinity ( .)Fig . 4 . Apparent photosynthesis of Pterocladia and Gelidiumspp. atdifferent salinities.0 .00 10 .048 1Fig . 5 . Respiration values for Pterocladia and Gelidium spp.at different temperatures .a salinity gradient at 15 ° C is seen in Fig . 4 . Thevalues were nearly constant for each of the speciesat salinities of 15% 0 and greater with the exceptionof G. latifolium, which showed an unusual in-crease at 20%0 . A slight increase in optimal salinityat 35% 0 was observed for G. spinulosum .Respiration and temperatureRespiration values for Pterocladia capillacea,Gelidium spinulosum and G . latifolium at differenttemperatures are shown in Fig . 5. The lowestvalues for all three species occurred at 15 'C . Therate of respiration for P. capillacea increasedrapidly at temperatures above 15 ° C and con-tinued to increase up to 30 ° C but remainedsteady beyond this temperature. The rate ofincrease in respiration differed for the twoGelidium species with increases continuing up to30 ° C and then also remaining steady from 35 to40 ° C for G. spinulosum .DiscussionPhotosynthesis was reduced at temperaturesabove 25 ° C and 30 ° C for Pterocladia and bothGelidium species, respectively . This suggests thattemperatures above 25 °C may stress Pterocladiaplants and restrict their distribution in the upper482intertidal zone . Tolerance to temperatures from25 ° C to 30 ° C for both Gelidium species mayprovide the plants with a means for survival inboth the upper intertidal for G. spinulosum and inthe lower intertidal for G. latifolium.Respiration rates show a lower temperaturetolerance for Pterocladia and a slightly highertolerance for both Gelidium species. Minimalrespiratory stress for all three species occurred at15 'C. No stress-related values were recorded forPterocladia or Gelidium at salinities below 15% ° .However, all species showed a slight decrease inphotosynthesis at salinities of 40%° .Temperature may be a significant factor amongothers influencing the vertical distribution ofP. capillacea, G. latifolium and G. spinulosum inthe intertidal zone of the Azores . However, morelong-term field data is necessary to clearly under-stand the influence of other variables on verticaldistribution . Such variables as herbivory, tem-perature and porosity of the substratum, exposureto sunlight and high energy wave action should beconsidered on a seasonal basis and comparedwith manometric results to clarify intertidal algalstratification .AcknowledgementsThis work was supported by a faculty develop-ment grant from Plymouth State College and bythe Biology Department of the University of theAzores. We also acknowledge the assistance,from Dean Theodora Kalikow, April O'Keefeand Chris Boland .ReferencesDawes, C. J ., 1981 . Marine Botany . Wiley-Interscience, NewYork, USA, 628 pp .Fralick, R. A. & A. C . Mathieson, 1975 . Physiologicalecology of four Polysiphonia species (Rhodophyta,Ceramiales) . Mar. Biol . 29 : 29-36 .Mathieson, A . C. & C. J . Dawes, 1986. Photosyntheticresponse of Florida seaweeds to light and temperature :physiological survey . Bull . mar. Sci . 38 :-512-514 .Santelices, B ., 1974 . Gelidioid algae, a brief resume of thepertinent literature. Tech. Rpt . No . 1 U .S . Sea Grant Pro-gram, University of Hawaii, 111 pp .

Physiological responses of Pterocladia and Gelidium (Gelidiales, Rhodophyta) from the Azores, Portugal

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Physiological responses of Pterocladia and Gelidium (Gelidiales, Rhodophyta) from the Azores, Portugal

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