Presentation on theme: "Biology of Seaweeds What are algae?"— Presentation transcript:
1 Biology of Seaweeds What are algae? Algae are a diverse group of mostly photosynthetic organisms that share afew characteristics, but which lack the structural complexity associated withhigher plants…Phycology - The study of algae (also referred by some as algology)Algal classification:Algae are subdivided into a number of distinct evolutionary lines. Themajor groupings of algae are in form of divisions, a term parallel tophyla in case of animals…Algal divisions are based on the following features:1. Light-harvesting pigments for photosynthesis2. Polysaccharide reserve3. Cellular organization4. Morphology5. Ecology
2 Review of Photosynthesis What is photosynthesis?The ability to use light to convert inorganic molecules into organicmolecules.H2O + CO2 ==== light == sugar + O2Sugar can then be used to make other required molecules, or it can bebroken down as a source of energy… O2 is simply a biproduct of photo-synthesis… almost all the O2 in the earth’s atmosphere comes fromphotosynthesis.
3 Photosyntesis – Pigments The first step of photosynthesis involves using pigments to capture light.The range of visible light used forphotosynthesis is from about400 to 750 nanometer wavelengthsof electromagnetic radiation…this range is referred to as PAR –Photosynthetically Active Radiation.Although chlorophyll is the primarypigment used by plants (it’s what makesplants green…), other pigments such ascarotenoids and phycocyanin are alsoused… why do you think this is? Whymay this be of particular interest inalgal systems?
4 Photosyntesis – Effects of varying light levels In marine systems, light can be a limiting factor to photosynthesis… The success ofDifferent algae at different depths/conditions may be a function of their ability toEfficiently capture light and photosynthesize…P: photosynthesisPmax: maximum photosynthesisPg : gross photosynthesisPn : net photosynthesisR : respirationIK : saturating irradiance
5 Biology of Seaweeds – Algal Divisions Will cover on future lectures (on phytoplanktons):Bacillariophyta (=Diatomophyceae) – DiatomsPhotosynthetic pigments: Chlorophyll a, c ; CarotenioidsMajor storage products: Chrysolaminarin, oilMajor cell wall component: Silica, PectinPyrophyta (=Dinophyta) - DinoflagellatesPhotosynthetic pigments: Chlorophyll a, c ; CarotenioidsMajor storage products: Starch, oilMajor cell wall component: CelluloseNote that some researchers will classify diatoms into their own division, whereasothers will put diatoms into the class bacillariophyceae, under the division chrysophyta,which would include a number of different algae, including all the different brown algaeoff our coast…
6 Biology of Seaweeds – Brown Algae Division Phaeophyta (=Fucophyta) - Brown algaePhotosynthetic pigments: Chlorophyll a, c ; Carotenioids (includingfucoxanthin which give the brown coloration)Major storage products: Laminarin, oilMajor cell wall component: CelluloseBrown algae are extremely common off the coast of California; here are some examples:
7 Biology of Seaweeds – Brown Algae Brown algae are often the dominant primary producers in temperate and polarregions… The brown algae often do best in these cold, nutrient-rich waters, andsome kelp have the capacity to grow as much as two to three feet per day!!The complete algal body is known as the thallus; make sure you can identify allthe individual body parts and know what each of their functions are…
8 Biology of Seaweeds – Brown Algae One more picture of the stype, pneumatocysts, and blades.
9 Biology of Seaweeds – Brown Algae Distribution of kelp is very dependent on water temperature and is therefore afunction of both latitude and oceanic circulation…In many of these areas, kelp (and other brown, red, and green algae) are harvestedfor the resources they provide… more on this later…
10 Biology of Seaweeds – Red Algae Division Rhodophyta – Red algaePhotosynthetic pigments: Chlorophyll a; Phycobilins [includingphycoerythrin (red in color) and phycocyanin(blue in color)]Major storage products: StarchMajor cell wall component: Cellulose, Agar, Carrageenanand in case of coralline algae, CarbonatesSome examples of red algae from the California coast:
11 Biology of Seaweeds – Red Algae Many red algae show calcification throughout their thallus (some in fact grow as anencrusting layer over rocks), whereas others do not…What do you think may be the reason for the calcification in some of these species?What may be the advantages and/or disadvantages of having a calcified body?Structural? …. Protection from intense sunlight? …. Protection from grazing?
12 Biology of Seaweeds – Green Algae Division Chlorophyta – Green algaePhotosynthetic pigments: Chlorophyll a, b; CarotenioidsMajor storage products: starchMajor cell wall component: Cellulosebut also carbonates in some coralline forms…The similarity of photosynthetic pigments, storage products, and cell wallcomponents of green algae with higher plants suggest that higher land plantsprobably evolved from a green algal type ancestor…Some examples of typical green algae from the California coast:
13 Biology of Seaweeds – Economic Implications Seaweeds have a wide range of potential uses:Food – The most obvious use of seaweeds is in form of various foods prepareddirectly or indirectly from algae or algal products…Phycocolloids – used in food processing, they have the ability to form viscoussuspensions and gels…Algin and carrageenen for example are often used as a stabilizers andemulsifiers in dairy products, the baking industry, and for makingof shampoos and toothpastes, etc.Agar, another phycocolloid, is used in canning of hams, fish, meats, etc.,because of its ability to form jellies… this helps with protectingthe canned material… Other uses of agar include production ofvarious forms of pharmaceuticals, and even research media…Seaweeds may also be used as a source of fertilizer, food additives in animalfeeds, etc., etc., etc.,… Big industry!!!!!
14 Biology of Seaweeds – One more type of algae to consider!! Division Cyanophyta – Blue green algae (=cyanobacteria)Photosynthetic pigments: Chlorophyll a; PhycobilinsMajor storage products: Cyanophycean starch; Cyanophycin (protein)Major cell wall component: Chains of amino sugars and amino acidsThese bacteria (yes they are prokaryotes!) are some of the most primitiveplant-like organisms on earth… They are thought to have been among thefirst photosynthetic organisms on earth, and as such played an importantrole not only in the evolution of algae and plants, but also in the processof the initial accumulation of oxygen in our atmosphere…Many species are very eurythermal and euryhaline …Make up much of the slime on tropical, submerged rocks…
15 Biology of Seaweeds – The Sea Grasses Tracheophyta – Vascular plants(The classification of tracheophyts will vary depending on whom you talkto… many researchers cannot even agree on if algae and vascular plantsshould be in the same kingdom or not… same issues need to be consideredwhen studying cyanobacteria)Photosynthetic pigments: Chlorophyll a, b ; Carotenioids [includingCarotene (orange in color), and Xanthophyll (yellowin color)]Major storage products: StarchMajor cell wall component: Cellulose
16 Biology of Seaweeds – The Sea Grasses As vascular plants, sea grasses have flow tubes called xylem and phloem.Xylem – tube like hollow vessels that transport water and minerals invascular plants.Phloem – a tissue that conducts food material (i.e. photosynthates) in vascularplants…The sea grasses do not look like yourtypical “land plants”… whatadaptations do you think they havefor life in their shallow subtidal /intertidal marine habitats?
17 Biology of Seaweeds – The Kelp Forest More on this, next lecture…