Occurrence of photoprotective mycosporine-like amino acid compounds (MAAs) in marine red macroalgae from temperate Australian waters

7 Pages·2000·3.1 MB·

by  U Karsten

Occurrence of Photoprotective Mycosporine-like
Amino Acid Compounds (MAAs) in Marine Red
Macroalgae from Temperate Australian Waters
Ulf Karsten
University ofRostock, DepartmentofBiology, Institute ofAquatic Ecology,
Freiligrathstrasse 7/8, D-18051 Rostock, Germany
Karsten,U. (2000). Occurrenceofphotoprotectivemycosporine-likeaminoacidcompounds
(MAAs) in marine red macroalgae from temperateAustralianwaters. Proceedings ofthe
LinneanSocietyofNewSouthWales122, 123-129.
UV-absorbingmycosporine-likeaminoacidcompounds(MAAs)wereidentifiedand
quantified in 35 red macroalgal species (Rhodophyta) collected from the rocky shores of
SoutheasternNewSouthWalesandSouthernVictoria, Australia.Withinalltaxainvestigated
5distinctcompoundswerefound,whichwereidentifiedasshinorine,porphyra-334,palythine,
asterina-330andpalythinol.WhilesublittoralspeciescontainedonlytraceamountsofMAAs
orevenlackthesesubstances,intertidalplantsalwaysexhibitedhighconcentrations.Thedata
suggest that the biosynthesis and accumulation ofMAAs may represent a natural defence
systemagainstexposuretobiologicallyharmfulUV-radiation.
Manuscriptreceived25August2000,acceptedforpublication22November2000.
KEYWORDS:mycosporine-likeaminoacidcompounds,MAAs,macroalgae,UV-radiation
INTRODUCTION
Due to a decrease in stratospheric ozone, levels of ultraviolet B (UVB, 280-320
nm)reachingtheEarth'ssurfacehadincreasedby>50%inAntarcticaunderspring"ozone
hole" conditions (Madronich et al. 1998). This depleted ozone layer does usually not
extend as far north as Australia, but stratospheric winds can occasionally carry ozone-
depletedairmassestowardsAustraliacausingashorttermrise inUVB values.Although
the relative rise in UVB has been most pronounced in the polar regions over the last
decade (Kerr 1994), high ambient doses of UV-radiation are characteristic of tropical/
subtropical continents such as Australia even under normal stratospheric ozone
concentrations (Fleischmann 1989). In these regions, the lightpath for solarradiation is
short and the usually clear, oligotrophic water column exhibits a high transparency for
UVB (Smith and Baker 1979). Consequently, many phototrophic organisms in aquatic
ecosystems may be affectedby this spectral waveband (Franklin and Forster 1997).
MultipleharmfuleffectsofUVB onmarineprimaryproducershavebeenreported,
andincludethedirectinfluencesonmoleculartargets such as nucleic acids andproteins,
onphysiologicalprocesses suchasphotosynthesis, growthandoncommunity structures
(Smith et al. 1992; Buma et al. 1995; Davidson et al. 1996; Franklin and Forster 1997;
Aquilera et al. 1999). Of major interest is the identification ofrepair and/or protective
mechanisms that allow phototrophic organisms living in high-light habitats to survive
andreproduce.
Proc.Linn.Soc.n.s.w., 122.2000
124 MAAsINREDMACROALGAE
AnimportantphysiochemicalmechanismagainstbiologicallyharmfulUV-radiation
involves the biosynthesis and accumulation of photoprotective sunscreens. Typically
absorbingintheUVA(320-400nm)andUVB,thesecompoundswereinvokedtofunction
as passive shielding substances by dissipating the absorbed radiation energy in form of
harmless heat without generating photochemical reactions (Bandaranayake 1998).
The most common substances with a potential role as UV-sunscreens in marine
organisms are the mycosporine-like amino acids (MAAs), a suite ofchemically closely
related, water-solublecompounds. MAAshavebeenidentifiedintaxonomically diverse
marineorganismsincludingbacteria,cyanobacteria,micro-andmacroalgae,invertebrates
and fish (Dunlap and Shick 1998). Their function as intracellular screening agents has
beeninferredfromadecreaseinconcentrationwithincreasingdepthasobservedincorals
(Dunlapet al. 1986) andmacroalgae (Karsten etal. 1999). In addition, macroalgae from
MAA
South Europe contain up to 2-fold higher contents compared to similar species
fromhigherlatitudesindicatingapositiverelationshipwiththenaturalsolarUV-radiation
ofthe respective biogeographic region, i.e. the higher the UV-dose the more MAAs are
formed and accumulated (Karsten et al. 1998a). In more recent studies on microalgae,
Riegger and Robinson (1997) calculated sunscreen factors forAntarctic phytoplankton
duetothepresenceofMAAsofupto0.72,i.e. 72%ofharmfulUVquantawereabsorbed
beforehittingintracellularmoleculartargets. Inthered-tidedinoflagellateGymnodinium
sanguineum Hirasaka, MAAs prevent, at least partially, UV-induced inhibition of
photosynthesis (Neale et al. 1998).
AlthoughMAAs arewidelypresentinvarioustypesofmarineorganisms,fewdata
existoftheirtypeandquantityinmacroalgae(Nakamuraetal. 1982; Karentzetal. 1991;
Karsten et al. 1998a,b), in particular from high-radiation coasts such as inAustralia. In
the present investigation a qualitative and quantitative inventory was made ofMAAs in
red macroalgae collected from the rocky shore in southeastern New South Wales and
southern Victoria.
MATERIALS AND METHODS
ThelocationsofcollectioninsoutheasternNewSouthWalesandsouthernVictoria
are shown in Figure 1 and the red macroalgal species studied are listed in Table 1. All
plants were sampledduringafieldtripinMarch 1999 directly fromtheshoreas attached
ordriftmaterial,orbysnorkeling.Afterwardsthealgaewereair-driedinthesunfollowed
by storage in sealed plastic bags undercool, dry and dark conditions until analysis.
Thalliofabout 10-20mgdryweight(DW)wereextractedfor2hin screw-capped
centrifugevialsfilledwith 1 mL25%aqueousmethanol(v/v)andincubatedinawaterbath
at 45°C. After centrifugation at 5000 g for 5 min, 700 |jL of the supernatants were
evaporatedtodrynessundervacuum(SpeedVacConcentratorSVC lOOH).Driedextracts
werere-dissolvedin700|iL 100% methanolandvortexedfor30s.Afterpassingthrough
a0.2|im membranefilter, sampleswere analysedwithaWatersHPLC systemaccording
to the method ofKarsten et al. (1998a), modified as follows. MAAs were separatedon a
mm
stainless-steel Phenomenex SpherecloneRP-8column(5 |im, 250x4 I.D.)protected
withaRP-8guardcartridge(20x4mmI.D.).Themobilephasewas5%aqueousmethanol
(v/vj plus 0.1% acetic acid (v/v) in water, run isocratically at a flow rate of0.7 ml min'.
MAAsweredetectedat330nmandabsorption spectra(290-400nm)wererecordedeach
seconddirectlyontheHPLC-separatedpeaks. Identificationwasdonebyspectra,retention
timeandbyco-chromatography with standardsextractedfromthemarineredmacroalgae
ChondruscrispusStackhouse(Karstenetal., 1998a)andPorphyraumbilicalis(Linnaeus)
Kutzing,aswell asfromocularlensesofthecoraltroutPlectropomusleopardus(Lacepede,
1802). kindly sentby Dr. David Bcllwood,JamesCook University,Townsville,Australia.
Quantification was made using the following molar extinction coefficients: shinorine:
e334=44.700(Tsujinoetal. 1980),palythine:e320=36,200(Takanoetal. 1978),palythinol:
e332=43,500 (Dunlap et al. 1986), porphyra-334: e334=43,300 (Takano et al. 1978),
Proc.Linn.Soc.n.s.w., 122.2000
U. KARSTEN 125
asterina-330: e330=43,500(Gleason 1993).Allamountsaregivenasmeanof4replicates
(±SD) based on separate extracts from separate algae, randomly collected from the
respective habitatandexpressed as concentration on a dry weightbasis.
J
_
New SouthWales
V
^
Sydney
34°-
^Batemans Bay
Victoria 36°-
Melbourne
4^^ —
^ 38°-
Warrnambool S
Pacific Ocean
Lonsdale
142° 146° 150° 154° Er
1 .._j 1
HGURELEGENDS
Figure 1.MapshowingcollectinglocationinsoutheasternNewSouthWalesandsouthernVictoria,Australia.
RESULTS
TheMAAsextractedfromthedriedredalgalsampleswerecharacterisedbyHPLC,
and identified and quantified according to their retention times, absorption spectra, co-
chromatography with standards and molar extinction coefficients (see Materials and
Methods). FivedifferentMAAs couldbe detectedwithinthe samplesinvestigated, allof
whichwereidentifiedas shinorine, porphyra-334, palythine, asterina-330andpalythinol
(Table 1). The sum ofall MAAs ranged in all macroalgae analysed from (no trace) to
5.5 mg g'' DW. While typical subtidal species such as Ballia callitrichia, Hypnea
episcopalis,Nizymeniaaustralis andPhacelocarpusalatuscontainedno MAAs atall or
tracesonly, intertidalspeciessuchasBangiaatropurpurea, Capreolia implexa, Gelidium
MAA
australe and Porphyra columbina exhibited high concentrations between
palpapryoexdiamamtienloyr2.r5olaenads5i.n5dmicgatge'dDbyWl(oTwabmlaex1)i.mQuuamntciotnacteinvterlaytaisotnesrionfa0-.33380amngdpga'lyDthWinoals
detected in Laurencia elata. While palythine showed high contents ofup to 1.7 mg g '
DW MAA
inonlyfewspeciessuchasL. elata, shinorinewasthequantitativelydominant
in most species containing this compound. The maximum amounts ofshinorine reached
up to 3.9 mgg"' DW. Porphyra-334 occurred in highconcentrations between 1.5 and 2.5
mg g ' DWinBangiaatropurpurea, Laurencia rigida andPorphyra columbina (Table 1).
Proc.Linn. Soc.n.s.w., 122.2000
126 MAAsINREDMACROALGAE
TO o g-
if"
TO g-7
2S<;.w-O^sC<o?
"§•§ o
>3 3-
tJ»>nZT3O'
^ « « SS'^ ^ ooS^ooooo*- Ei « 3
s-s" -,.-_p_p-a_g S,g3grl3rg3S3g3S §t-§3gt|~3pS|33t~pS53|3 a=JO.•0^c oo2
<<< z*z^<< << o< 5z2 n< n< <n<o o<n<n<^zn<^zo<^z o<:f^<<n 2 ;5 iS z fSf ^3"n
oo o o— o
O K>O —
•oC-D^ ouC-j>^ •^p—i aUC^)D op<~>~ o o 5a-3<;o2..
3 o ^
or- r* r- 3 P >
• £8
— ^ — — o — — o o OS o= o3
o1taj+\J 1o^^+ 1o0<*7i+^.^1oQ^+01oOt+oO3r» 1o<^—-+ft o1o.o+— o1^No+io1o(•-+—TiooiQ—T 1oHoo+- 1o—oo+ 1oovo+o o oo o o 9 "
to o o to o ^ O Lftop o oo o to — ^ b> g 3
1+ §
sp. 3p
o = o— o_ o
D.oo
o >— o\ — CI.
3 —
D.
gsg UUJ) tc^o oo oooo p -a ^
s s Sii p p p p p p re St'
*>.^LnL»JC2ooo
g_3
Proc.Linn.Soc.n.s.w., 122. 2000
U. KARSTEN 127
DISCUSSION
ThisstudyprovidesthefirstcomprehensivesurveyofthequaUtativeandquantitative
occurrence ofMAAs in red macroalgae from temperateAustraha. In contrast to brown
and green macroalgae, UV-absorbing substances have been widely observed in many
speciesoftheRhodophyta(Sivalingametal. 1974;SivalingamandNisizawa 1990;Wood
1989; Karentzetal. 1991; Maegawaetal. 1993; MolinaandMontecino 1996; Karstenet
al. 1998 a,b). Inthepresentstudy, theMAAconcentrationsmeasuredintypicalintertidal
algae such as Bangia atropurpurea and Capreolia implexa are approximately >20-fold
highercomparedtosublittoralspeciessuchasBalliacallitrichia.Thisisingoodagreement
with earlierreports on RhodophytafromArctic to warm-temperate localities (Maegawa
et al. 1993; Karsten et al. 1998a) which indicate that species from deeper water exhibit
only trace amounts oreven lackthese compounds.
Theredalgaecantolerateawiderrange ofradiation levels than any othergroupof
macroalgae. The deepest known plant is a coralline-like species found at 268 m offthe
Bahamasthatgrows at<0.1 |umolphotonsm -^ s ' (Littleretal. 1985). Othermembers of
thegroup wellreproduce and survive in theupperintertidal zone, often fully exposedto
bright sunlight at >2200 |amol photons m - s ' (Pedroche et al. 1995). Between these
extremes theradiation quality andquantity reaching different species in differentdepths
is highly variable due to the inherent optical properties ofthe water column, sun angle,
latitude, seasonandweatherconditions. However, sublittoralredalgaeareadaptedtothe
generallylowunder-waterradiationclimateandhencearecharacterisedas 'shade-plants'
(Raven et al. 1979; Liining 1990). These species usually exhibit a lower photosynthetic
capacity andrateofdarkrespirationthan 'sun-plants', as well asoptimumgrowthatlow
photon flux densities. Moreover, photosynthesis ofmacroalgae from deeper waters was
showntobeparticularly sensitivetoUVradiation(Bischofetal. 1998). Since sublittoral
plants are generallyneverexposedtohigh irradiances includingUV, atleastnotforlong
periods, there is no physiological need to synthesise and accumulate metabolically
expensive MAAs as indicated in the data presented. This in turn would save energy to
better support other essential pathways such as, for example, light-harvesting
phycobilisomes.
IthadbeenrecentlyreportedfromMalagainsouthernSpain(36.6°N-similarlatitude
as the locations in this study) that the depth distribution of brown macroalgae on the
shoreis controlledbytheincidentUV-radiation due tothe species-specific sensitivity of
sporesagainstthisshortwavelengths(sporesfromshallowwaterspeciesaremoreresistant
than spores from species collected at greater depths). This means that one specific
developmental stage ofthe life history is the main target ofUV-radiation and this may
affectzonation (Wiencke at al. 2000).
Compared to sublittoral red algae, intertidal species are known to contain high
contentsofMAAs(Maegawaetal. 1993;Karstenetal. 1998a),whichisingoodagreement
with the results shown. While mostplants growing in this regularly exposed habitat are
abletoflexiblysynthesiseandaccumulatethesecompoundsinresponsetotherespective
radiation climate, some taxa such as Bangia atropurpurea exhibit always ahigh steady-
state concentration. In this particular species cells seem to be loaded-up with the
photoprotective substances, whichisconsistentwiththe typicaloccurrence very highon
the shore.
Besides the depthzonation, thebiogeographic distribution ofmacroalgae seems to
MAA
beanotherimportantfactorcontrollingthe concentrations,sincespeciesfromlower,
high-solar latitudes always exhibit more MAAs than species from higher, low-solar
latitudes (Karsten et al. 1998a). These observations indicate that the higher the natural
solarUV-radiationoftherespectivehabitatthemoreMAAsareformedandaccumulated
in these plants.
MAAs are one ofnature's sunscreens, with 19 structurally distinct compounds so
MAA
far identified in marine organisms (Dunlap and Shick 1998). Although levels in
Proc.Linn. Soc.n.s.w., 122.2000
. .
128 MAAsINREDMACROALGAE
macroalgae show a decline in concentration with increasing growth depth and are in
general positively correlated with natural doses ofUV-radiation (Karsten et al. 1998b),
experimental evidence for the role of MAAs as UV-protectants in these plants is still
MAA
circumstantial. Nevertheless, the presence of increasing contents in the red alga
Devaleraearamentaceawithdecreasingdepthstronglycorrelatedwithamoreinsensitive
photosynthetic capacity under UV exposure (Karsten et al. 1999). Photosynthetic
experimentsontheunicellularmicroalgaeGymnodiniumsanguineumprovedthatMAAs
indeedactasspectrallyspecificUV-sunscreens(Nealeetal. 1998).Inmarineinvertebrates
the function of MAAs as intracellular photon screening agents has been inferred from
UV-induceddelaysinthefirstdivisionofseaurchinembryoshavinglowconcentrations
ofMAAs compared to embryos with high MAA contents (Adams and Shick 1996). In
anotherstudy,Dionisio-Seseetal. (1997)showedthatthepresenceofMAAsinthesurface
tunic of the colonial ascidian Lissoclinum patella protect its photosynthetic symbiont,
Prochlownsp.,fromUV-inducedphotodamage.Moreover,Ishikuraetal. (1997)measured
maximum MAA concentrations in the outermost surface layerofthe siphonal mantle of
thegiantclam Thdacna crocea. TheoccurrenceofMAAs intheanimaltissueprevented
aninhibition ofphotosynthesis ofits zooxanthellaeSymbiodinium sp., whichoutsidethe
protecting animal tissue responded very sensitively to UV radiation. These authors
calculated that the sunscreen capacity ofthe measured MAAs were sufficient to absorb
87% of310-nmradiation and90% of320-nmradiationbeforereaching 0.2mmdepthin
the siphonal mantle. All recent publications on marine algae and invertebrates strongly
support the photobiological function ofMAAs as a cellular defenCe system againstthe
harmful effects ofUV-radiation (Dunlap and Shick 1998).
Therefore it is concluded thatthephysiological capability ofintertidalredalgae to
MAA
synthesise and accumulate high concentrations plays a vital role as biochemical
adaptation ensuring survival underthe environmental extremes in thehabitat.
ACKNOWLEDGEMENTS
ThisprojectwasfinanciallysupportedbytheAlexandervonHumboldtFoundationviathePost-Contact-
ProgrammeandtheDeutscheForschungsgemeinschaft(Ka899/3-2/3).TheauthorlikestothankLindaFranklin,
HeikeLippert,AlanMillar,MonicaSchoenwaelder,JohnWestandJoeZuccarellofortechnicalsupport,aswell
asfortheidentificationofthespecies.
REFERENCES
Adams, N.L., and Shick, J.M. (1996). Mycosporine-like amino acids provide protection againstultraviolet
radiation in eggs of the green sea urchin Strongylocentrotus dwebachiensis. Photochemistry and
Photobiolog\64, \49-l5S.
Aguilera.J., Karsten, U., Lippert, H., Philip, E., Vogele, B., Hanelt, D., andWiencke,C. (1999). Effectsof
solarradiationongrowth,photosynthesisandrespirationofmarinemacroalgaefromtheArctic.Marine
EcologyProgressSeries 191, 109-119.
Bandaranayake.W.M.(1998).Mycosporines:aretheynature'ssunscreens?NaturalProductReports15, 159-
172.
Bischof, K., Hanelt, D.. and Wiencke, C. (1998). UV-radiation can effect depth-zonation ofAntarctic
macroalgae. MarineBiology 131,597-605.
Buma,uAl.tGr.aJv.io,lVeatn-B-Hianndnuceend,DE.NJ.A,'dRaozmaa,geL.i,nVienlddihvuiidsua,lMd.iJa.tWo.m,caenlldsGbiyesikmemsu,noWf.lWu.oCr.esc(e1n99t5)t.hyMmoinnietodriimnegr
Davidsodnet,ecAt.iTo.n,.MJaorucrhnaanlt,ofHP.hJ.y,coalnodgyde31la,3M1ar4e-3,2W1.K. (1996). Natural UVB exposure changes the species
composition ofAntarctic phytopjankton in mixedculture.AquaticMicrobialEcology 10, 299-305.
Dionisio-Sese, M.L.. ishikura, M., Maruyama, T., and Miyachi, S. (1997). UV-absorbing substances in the
tunic of a colonial ascidian protect its symbiont, Prochloron sp., from damage by UV-B radiation.
MarineBiology 128,455-461
Proc.Lln.n.Soc..N.S.W., 122.2000
U. KARSTEN 129
Dunlap, W.C., Chalker, B.E., and Oliver, J.K. (1986). Bathymetric adaptions ofthe reef-building corals at
DaviesReef,GreatBarrierReef,Australia.III. UV-B absorbingcompounds.JournalofExperimental
MarineBiologyandEcology 104,239-248.
Dunlap,W.C.,andShick,J.M.(1998).Ultravioletradiation-absorbingmycosporine-likeaminoacidsincoral
reeforganisms: abiochemical andenvironmentalperspective.JournalofPhycology34,418-430.
Fleischmann, E.M. (1989). The measurement and penetration of ultraviolet radiation into tropical marine
water.LimnologyandOceanography34, 1623-1629.
Franklin, L.A., and Forster, R.M. (1997). The changing irradiance environment: consequences for marine
macrophytephysiology,productivityandecology.EuropeanJournalofPhycology32,207-232.
Gleason,D.F.(1993).DifferentialeffectsofultravioletradiationongreenandbrownmorphsoftheCarribean
coralPoritesastreoides.LimnologyandOceanography38, 1452-1463.
Ishikura, M., Kato, C, and Maruyama, T. (1997). UV-absorbing substances in zooxanthellate and
azooxanthellateclams.MarineBiology 128,649-655.
Karentz,D.,McEuen,F.S.,Land,M.C.,andDunlap,W.C. (1991). Surveyof mycosporine-like amino acid
compounds in Antarctic organisms: potential protection from ultraviolet exposure. Marine Biology
108, 157-166.
Karsten,U.,Sawall,T,Hanelt,D.,Bischof,K.,Figueroa,F.L.,Flores-Moya,A.,andWiencke,C.(1998a).An
inventoryofUV-absorbingmycosporine-likeaminoacidsinmacroalgaefrompolartowarm-temperate
regions.BotanicaMarina41,443-453.
Karsten, U., Franklin, L.A., Liining , K. and Wiencke, C. (1998b). Natural ultraviolet and photosynthetic
activeradiationinduceformationofmycosporine-likeaminoacidsinthemarinemacroalgaChondrus
crispus(Rhodophyta). Planta205,257-262.
Karsten, U., Bischof, K., Hanelt, D.,Tiig, H. and Wiencke, C. (1999).Theeffectofultravioletradiation on
photosynthesis and ultraviolet-absorbing substances in the endemic Arctic macroalga Devaleraea
ramentacea(Rhodophyta).PhysiologiaPlantarum 105,58-66.
Kerr,J.B. (1994). Decreasingozonecauseshealthconcern.EnvironmentalScienceandTechnologv28,514-
518.
Littler,M.M.,Littler,D.S.,Blair,S.M.,andNorris,J.N.(1985).Deepestknownplantdiscoveredonanuncharted
seamount.Science227,57-59.
Liining, K. (1990). ,Seaweeds: theirenvironment, biogeography, and ecophysiology'. John Wiley & Sons:
NewYork.
Madronich,S.(1993).TheatmosphereandUV-Bradiationatgroundlevel.In'EnvironmentalUVPhotobiology'
(EdsA.R.Young,L.O.Bjorn,J.MoanandW. Nultsch)PR l-40.(PlenumPress: NewYork).
Maegawa,M.,Kunieda,M.,andKida,W.(1993).DifferenceoftheamountofUVabsorbingsubstancebetween
shallow-anddeep-waterredalgae.JapaneaseJournalofPhycology41, 351-354.
Molina,X.,andMontecino,V.(1996).AcclimationtoUVirradianceinGracilariachilensisBird,McLachlan
&Oliveira(Gigartinales,Rhodophyta).Hydrobiologia2>16I2>21,414-420.
Nakamura, H., Kobayashi, J., andHirata,Y. (1982). Separationofmycosporine-like amino acids in marine
organismsusingreversed-phasehigh-performanceliquidchromatography.JournalofChromatography
250,113-118.
Neale, P.J., Banaszak, A.T., and Jarriel, C.R. (1998). Ultraviolet sunscreens in Gymnodinium sanguineum
(Dinophyceae): mycosporine-likeaminoacidsprotectagainstinhibitionofphotosynthesis.Journalof
Phycology34,928-938.
Pedroche, F.F., West, J.A., Zuccarello, G.C., Senties, A., and Karsten, U. (1995). Marine red algae ofthe
mangrovesinSouthern PacificMexicoandPacificGuatemala.BotanicaMarina38. 111-119.
Raven,J.A., Smith,F.A., andGlidewell, S.M. (1979). Photosyntheticcapacitiesandbiological strategiesof
giant-celledandsmall-celledmacroalgae.NewPhytologist83, 299-309.
Riegger,L.,andRobinson,D. (1997). PhotoinductionofUV-absorbingcompoundsinAntarcticdiatomsand
Phaeocystisantarctica.MarineEcologyProgressSeries 160, 13-25.
Smith, R.C., and Baker, K.S. (1979). Penetration ofUV-B and biologically effective dose-rates in natural
waters. PhotochemistryandPhotobiology29, 311-23.
Smith,R.C.,Prezelin,B.B.,Baker,K.S.,Bidigare,R.R.,Boucher,N.R,Coley,T.,Karentz,D.,Macintyre,S.,
Matlick,H.A.,Menzies,D.,Ondrusek,M.,Wan,Z.,andWaters,K.J.(1992).Ozonedepletion:ultraviolet
radiationandphytoplanktonbiologyinAntarcticwaters.Science255,952-959.
Takano,S.,Uemura,D.,andHirata,Y.(1978).Isolationandstructureofanewaminoacid,palythine,fromthe
zoanthidPalythoatuberculosa. TetrahedronLetters26,2299-2300.
Tsujino,I.,Yabe,K.,andSekekawa,I.(1980).Isolationandstructureofanewaminoacid,shinorine,fromthe
redalgaChondrusyendoiYamadaetMikami.BotanicaMarina23,65-68.
Wiencke,C,Gomez,I,Pakker, H.,Flores-Moya,A.,Alttamirano.M.,Hanelt,D.,Bischof, K.andFigueroa,
F.(2000).ImpactofUVradiationonviability,photosyntheticcharacteristicsandDNAofbrownalgal
zoospores: implicationsfordepthzonation.MarineEcologyProgressSeries 197,217-229.
Proc.Linn. Soc.n.s.w., 122.2000