第六講海洋底棲藻類生態(tài)近海底棲植物區(qū)系Benthos海底生物（包括底棲動、植物）近海底棲植物包括：

redalgae,brownalgae,greenalgae,blue-greenalgae,diatoms,

seagrass,mangroves,marshgrass海洋底棲植物生存于陸地與大洋之間的交界地帶，具有高生產(chǎn)力、棲息地類型多變、人類和動物影響大等特點。海洋底棲植物分布范圍：上限：Thisregionextendontothelanduntiltheeffectofseawaterisnegligibleandthefloraindistinguishablefromthatoftypicalfreshwaterhabitats.下限：Thelowermostpointseawardmustbethepointbelowwhichgrowthofbenthicfloraceasesduetolackoflightforphotosynthesis,andthismaybeclosetolandonsteepslopeandoutonthecontinentalshelfongentleslope.

底棲植物分布的下限會隨著季節(jié)和水體混濁度的變化而變化，這些都和水體中陽光的透射強度變化有關(guān)。底棲植物區(qū)系通常都是lightlimited（光限制）,由于浮游藻類、海草甚至陸源植物的遮蔭作用，導(dǎo)致水體的光線透射率降低；例如，如果大型海藻密集生長，其葉狀體（algalfrond）就會形成一個遮蓬，阻擋光線透射下去，對于小型底棲藻類而言，光就成為限制其生長的關(guān)鍵因子；海流、波浪運動、陸地徑流輸入、動物活動等，都會增加水體混濁度，甚至翻起的泥沙會覆蓋藻體，造成光線不足，限制底棲植物生長；

Estuarinewaterscarryhighconcentrationsofsiltinsuspensionandthismayrestrictlightpenetrationtosuchandextentthatphytoplanktonandbenthicproductionisseverelyreduced.底質(zhì)為底棲植物提供了適宜的附著場所；沉積物及豐富的異養(yǎng)生物（動物、微生物等），使得底層水體具有豐富的營養(yǎng)鹽，一般認為，與外海浮游植物的營養(yǎng)鹽限制相比較，近海底棲植物區(qū)系受到營養(yǎng)鹽限制的可能性比較??；淺海水體中，波浪運動、海流和上升流等都能產(chǎn)生攪動，阻止水體的熱力學(xué)分層（exceptforbriefperiodatleastinthetemperatezone），因此，營養(yǎng)鹽很少能成為底棲植物生長的限制因子，與外海相比較，近岸具有更高的生產(chǎn)力。陸源徑流輸入和水體中營養(yǎng)鹽再循環(huán)，使得近海水體中營養(yǎng)鹽含量豐富?？臻g的競爭

Indenselypopulatedbenthiccommunity,competitionforspaceislikelytobesevere,andbioticinteractionsamongalgae,andbetweenalgaeandothergroupsoforganismslikebacteria,fungi,seagrasses,grazinganimalsaremorecomplex.Spores(孢子)ofseaweedsgerminates（萌發(fā)）onlywhentheyadherestosubstrate.Crowdingleadshadingandcompetitionfornutrientsandthereisaninverserelationshipbetweendensityandindividualsize.兩種不同的底棲環(huán)境Intertidalzone潮間帶inwhichorganismsaresubjectatintervalstodesiccation(干燥),directsolarheat,rain,snow,freshwaterrunoff,wind,frost,etc.Subtidalzone潮下帶whichisstrictlyaquaticandmoreuniform,buthasneverthelessmarkedvariablesoflightintensityandquality.Thealgaegrowinginintertidalzonemustbeabletowithstandandrecoverrapidlyfromthesechangesthansubtidalalgae.Fullsunlightseverlyinhibitphotosynthesisinphytoplanktons,butphotosynthesisversuslightintensitycurveofbenthicdiatomshasabroadoptimum,saturatingatfairlylowlightintensitieswithonlyslightinhibitionunderfullsunlight.兩種主要的沉積物基質(zhì)Solidrock礁石Particulatesandormud沙、泥Ingeneral,onrockyshores,thegreatestamountofsolidsubstratumistobefoundbetweentidemarks,withaprogressivechangethroughsandtomudindeepwater.Thestabilityofsubstratumisobviouslyimportantforgrowthofseaweeds.Thegreatestgrowthofseaweedsoccurwherethereisarocksurfaceforattachment.Thetopography（地形）ofrockyshorealsoaffectsthetypeofflora.Onsteeprockysurface,silt（泥沙）doesn’taccumulateandonlyepilithic

（長在石頭上的）floragrow.Butachangeinthefloraoccurwheresufficientsiltofsandcollectonflatrockysurface.Someepilithicalgae:Laminaria

海帶

Porphyra

紫菜Themovingpebbles(鵝卵石)orgravel(砂礫)cannotmaintainanepilithicflora,yetsimilarsizedpebbledinaprotectedhabitatarecolonizedbygenerasuchasEnteromorpha(滸苔),Ectocarpus（水云）ofevenFucus（墨角藻）.Inareasofsandmovement,thespeciesdiversityislowandthespeciestendtobetoughandwiry.Mostoftheseaweedsfoundonsandyshorearetornloosefromtheirholdfast（固著器）andwashedontoshore.第一節(jié)微型底棲藻類Typesofbenthicmicroalgae

底棲微藻的類群1)Blue-greenalgae藍綠藻2)Diatom硅藻3)Dinoflagellates

甲藻1）Blue-greenalgaeInmarinehabitats,blue-greenalgaearerelativelyinconspicuousascomparedtootheralgae.Thegrowthofblue-greenalgaeoftengivesablackappearancetothesubstratum.Blue-greenalgaeliveinallpartsofthelightedmarinebenthicenvironmentandmaybedredgedfromwaterdepthmorethan30munderverydimillumination.Blue-greenalgaeonmud-flatsmakeasignificantcontributiontothenitrogenbalanceandalsoexertaprofoundstabilizinginfluenceonthesubstratum.

藍綠藻的固氮作用，將氮氣直接轉(zhuǎn)化為可為植物直接利用的氮鹽。一些常見的近海藍綠藻（Fig.）2)DiatomThemostubiquitous（普遍存在的）ofallbenthicmarinealgaearediatoms.Theyareeitherattachedtoorlielooseontherocky,sandyormuddysurface.Thephysicalnatureoftheshorehasaprofoundinfluenceontheflora.海灘的物理環(huán)境對植物區(qū)系有重要影響

Oncoarsesandybeaches,motilediatomspeciesseemstobeabsentandonlythoselikeAchnanthes（曲殼藻）andCocconeis（卵形藻）whichareattachedtosandparticlesaremostlyfound,whereasonfinesandoronsiltymud,thespeciesofNitzschia（菱形藻）,Navicula（舟形藻）,Pleurosigma（斜紋藻）,Amphora（雙眉藻）,Caloneis（美壁藻）,Diploneis（雙壁藻）,etc.whichlielooseonthesurfaceoftenfromabrowncolorationduringstableperiod.底棲硅藻的垂直移動Benthicdiatomfloralyinglooseonthesurfaceshowsdiurnalverticalmovement,theydisappearfromthesurfacewhencoveredbytideandreappearwhenexposedduringlowtideprovidedthatlightissufficient.Thisisprobablyamechanismtoavoidwash-outandabrasion(磨損)damageinthedisturbedsurfacelayersathightide,howevermanybenthicdiatomswillbeputintosuspensionbyincomingtide.Insublittoral(近海灘的)zone,thenumberofdiatomsfallpresumablybecauseofdecreaseinlightintensitywithdepth.3）DinoflagellatesPatchesofdinoflagellatesoccuronsandybeachesandcauseagreenishbrowndiscoloration(變色、污點)ofthesand.Thediscolorationofsanddisappearsshortlybeforeitbecomescoveredbytherisingtideandreappearswhenthesandisagainexposed.Allofthesesand-inhabitingformsareflatandgenerallyverymobile.第二節(jié)大型底棲藻類Whatareseaweeds?Seaweedsareclassifiedasalgae:photosyntheticorganismswhich,incontrasttotheplantsgrowingonland,arenon-floweringanddonothaveroots,leafyshootsorsophisticatedtissuesfortransportingwater,sugarsandnutrients.大型綠藻、褐藻、紅藻通過固著器或者假根固著生在在巖石基質(zhì)上；Theygrowextensivelyextendingverticallyfromtheupperlimittowhichwavesplashreaches,downwardthroughtheintertidaltothesubtidaluptothelowerlimitofphoticzone.分布的上限為潮流與波浪能到達的地方，下限為真光層的下限；Mixedwithseaweedsarealsopresentlargenumberofmicroscopicbenthicblue-greenalgaeanddiatoms.Seaweedsaremostlyconfinedtopermanentrockyshoresandareusuallyabsentoflessfrequentfromshoresofshiftingsand,gravelandcobbles(鵝卵石),becausetheycannotordinarilysurvivethemovementofcurrentandsurgewithoutsecureattachmenttosubstratum.Holdingfast固著

Rootsarenotneededforseaweedssincenutrientssuchasnitrogen,phosphorusandtraceelementsaredissolvedintheseawater.Thenutrientscanbetakenupandexchangedbydiffusionandactivetransportdirectlyacrossallthesurfacesoftheseaweed(carbondioxideandoxygenarealsoassimilatedandreleasedinthisway).Thereforeitisonlythemechanicalfeaturesofarootsystemthatwouldbebeneficialfortheseaweeds,holdingthemsteadynomatterhowturbulentthewatermovementis.Someseaweeds,suchastheconchocelisphase(殼孢子世代)ofPorphyra,obtainafootholdusingamoreaggressiveapproach.Theysecreteacidthichdissolvesthecalciumcarbonate(碳酸鈣)ofshellsandcoralskeletonssothatfinerhizoidsandfilamentscangrow.Thecalciumandbicarbonatethatarereleasedbytheacidificationofthecalciumcarbonatestructuresalsoprovidealocalizedsourceofnutrientsfortheseaweed.ThequestforlightIncloudycoastalwatersfullofplanktonandsuspendedparticleswashedinfromthelandandbroughtdownbyrivers,lightmaynotpenetratefurtherthanafewmeters.Thereareseveralstructuralfeatures,commontomanyspeciesofseaweed,thathelptoaddressthisproblem.(1)thestipe(柄)Thestipeofaseaweedcanbeverylongindeed.Thepurposeistosupportthebulk(主要部分)ofthephotosynthetictissueatthesurfaceofthewaterwhereincidentlightisatitsmaximumintensity.

例如：Nereocystis

luetkeana（腔囊藻）的柄長可達30m,可支撐超過100張葉片，每張葉片幾米長，長柄可使得葉片盡量獲取更多的光能進行光合作用。(2)Buoyancyaids增加浮力的構(gòu)造—氣囊

Largegas-filledbladderensuresthatthebladesarefloatingasclosetothesurfaceofthewateraspossible.

例如：Macrocystis

pyrifera

(巨藻)的每張葉片上都有氣囊，有助于整棵植物體能懸浮在水體中，盡量獲得更多的光線。Inspiteofsuperficialresemblanceofkelpholdfaststotherootsofvascularplants,thereisnoevidencethattheyaresupplyingnutrientstootherpartsoftheplant.Thewholethallus(葉狀體)ofseaweedsperformsphotosyntheticandabsorptivefunctions.Large,long-livedthallusofseaweedsenablethemtostorenutrients,whichextendtheirgrowingperiodsandrepresentasurvivalstrategynotavailabletomicroscopicalgae.Typeofseaweeds1)Greenseaweeds2)Brownseaweeds3)Redseaweeds1)GreenseaweedsGreenalgaearerelativelyofminoroccurrenceinseaascomparedwiththeiroverwhelmingdominanceinfreshwaters,andunlikeinfreshwaters,marinegreenalgaeareprimarilymacroscopicforms.2)BrownseaweedsTheyoccurinbulkinnearlyalltemperateandhigh-latitudewaters,wheretheydominantthevegetationofcoastalwaters,buttheyaremuchsmallerinnumberandsizeintropicalcoastalwater.Sargassum(馬尾藻)isaclassicexampleofanabundantfree-floatingbrownalgainSargassosea.Brownalgae