PHYTOPLANKTON DIVERSITY

I. What are algae?
    A. Phylogenetic diversity
    B. Characteristics
        1. photosynthesis
            a. some are secondarily colorless (heterotrophic) or partially heterotrophic
            b. chlorophyll a is common to all
        2. simple structure (compared to higher vascular plants)
            a. unicellular
            b. multicellular
                1) colonial
                    a) indefinite number of cells per colony - reproduce by fragmentation
                    b) fixed number of cell per colony
                2) filamentous
            c. not much division of labor
        3. reproduction -- sexual and asexual - many unique modes of reproduction
            a. unicellular algae - the organisms themselves may function as gametes or will produce gametes or may divide asexually
            b. multicellular
                1) unicellular gametangia
                2) multicellular gametangia with every cell fertile
            c. for some algae the haploid form (1N) is the dominant lifestage, for others the diploid form (2N) is dominant
    C. Classification -- Algal divisions (equivalent to animal phyla) based on:
        1. Biochemical criteria
            a. pigments --
                1) (primary) chlorophyll a, b, c (fat soluble)
                2) (secondary) carotenoids – carotenes and xanthophylls (fat soluble);
                                                             phycobilins – phycocyanin and phycoerythrin (water soluble)
            b. storage products -- starch, chrysolaminarin, fats, oils
            c. composition of cell walls – cellulose, pectins, mineral deposits (CaCO3, SiO2), naked, scaled
        2. Morphological criteria
            a. flagellated or not;
            b. types of flagella: #, insertion, length, fine structure
            c. fine structure of chromatophores
        3. Genetic differences
    D. Categories

    E. Special adaptations
        1. flagellae
        2. gas vacuoles - can adjust their buoyancy, position in the water column
        3. mixotrophy
        4. many can survive desiccation for years or have resting stages that can do so

II. Taxonomic survey
    A. Cyanophyta (cyanobacteria; blue-green algae)
        1. Ancient group -- stromatolites -- fossils that are 3 by old
        2. Distinguishing characteristics
            a. They are prokaryotic --
            b. pigments
                1) chlorophyll a
                2) secondary pigments - phycobilins
                    a) phycoerythrin - red (marine red tides)
                    b) phycocyanin - blue -- gives the blue-green color
            c. storage product - glycogen-like substances
            d. cell wall - mucopolysaccharide with unique amino acids
            e. no flagella
        3. Some are nitrogen fixers
            a. use the enzyme nitrogenase
            b. some have heterocysts, specialized thick-walled cells in which N2 fixation occurs
        4. Have another type of specialized cell - akinete - dormant cell
        5. Some are toxic -- kill cattle, dogs
            a. Examples:
                1) Microcystis aeruginosa
                2) Aphanizomenon flos aquae
                3) Anabaena flos aquae
            b. Toxins  hepatotoxins, neurotoxins
        6. Common genera
            a. Oscillatoria – filaments with short vegetative cells; no heterocysts; an indicator of beginning eutrophication;
                                        tolerant of low light
            b. Lyngbia
            c. Anabaena - heterocysts and akinetes
            d. Chroococcus
            e. Microcystis -- commonly in high abundance in eutrophic lakes and can reach nuisance bloom proportions
            f. Aphanizomenon - parallel filaments in bundles; N fixer
            g. Spirulina -- common in health food stores as a high protein food; grows in saline ponds; eaten by flamingoes
            h. Gleotrichia - often occur as 'puff ball' colonies with heterocysts on the inside
            i. Nostoc

        The rest of the divisions are eukaryotic

    B. Chlorophyta (green algae)
        1. Distinguishing characteristics
            a. eukaryotic
            b. pigments
                1) chlorophyll a
                2) chlorophyll b
            c. storage product - starch
            d. cell wall - cellulose
            e. may have flagella (0-8)
        2. Pigments and storage products lead many scientists to believe that some ancient members of the chlorophyta
                were the ancestors of higher plants
        3. Common genera
            a. Spirogyra - spiral chloroplast
            b. Pediastrum; Hydrodictyon - autocolony formation – each cell forms a whole new colony
            c. Chlamydomonas/Gonium/Pandorina/Volvox- (order Volvocales) from a single cell with 2 equal length flagella
                            to multicellular forms with colonies of different sizes
            d. Closterium (desmid -- 2 half cells with mirror images) also Staurastrum and Microasterias, Cosmarium
                           desmids are common in low pH waters
            e. Scenedesmus
    C. Cryptophyta (cryptomonads)
        1. Distinguishing characteristics
            a. eukaryotic
            b. pigments
                1) chlorophylls a and c
                2) many secondary pigments; carotenes and unique xanthophylls -- can be different colors from green, blue, brown, olive, red
            c. storage - starch
            d. no cell walls - naked
            e. biflagellate
        2. Unicellular
        3. Are generally small and good/preferred food for zooplankton
        4. Common genera
            a. Cryptomonas - capable of mixotrophy -- will ingest bacteria
    D. Chrysophyta (golden algae; yellow-green algae; diatoms)
        1. Distinguishing characteristics
            a. eukaryotic
            b. pigments
                1) chlorophylls a and c
                2) carotenoids (e.g., b-carotene); fucoxanthin
            c. storage product - chrysolaminarin (beta 1-5 glucan); oils
            d. cell wall
                1) naked
                2) cellulose
                3) silica frustule (diatoms)
            e. may or may not have flagella - 1 or 2 if present
        2. Groups
            a. Class Chrysophyceae (Golden Algae)
                1) Ochromonas – single celled
                2) Synura - cluster of cells, each with 2 flagellae; golden brown color; no division of labor between cells
                3) Mallomonas - has silica plates, each with a spicule; these spicules increase the effective size of the cell
                                            and make it harder for some zooplankton to ingest it
                4) Dinobryon - makes a lorica out of cellulose; has a diploid zygote that is a resting stage
                                        (can survive for years in the sediments)
            b. Class Bacillariophyceae (Diatoms)
                1) Have frustules made of silica with 2 valves -- fit together with 2 intercalary bands
                                                        valve view; girdle view; epitheca and hypotheca
                2) Unicellular or colonial
                3) Diatomaceous earth – diatom frustules in sediments
                4) Opal is the mineralized form of diatoms in sediments
                5) Reproduction:
                        a) the two valves subdivide
                        b) each always makes a hypotheca
                        c) progressive decrease in size
                        d) sexual reproduction occurs and restores the original size --
                                zygote known as an auxospore
                6) Orders
                    a) Centrales -- radially symmetrical in valve view(mostly marine and pelagic)
                        i. Aulacosira (Melosira) - colonial
                        ii. Stephanodiscus
                        iii. Cyclotella
                    b) Pennales - bilaterally symmetrical (mostly freshwater); some groups have a raphe (split in frustule)
                            through which organic material is released that allows them some 'gliding' motility on surfaces --
                            'pennate diatoms'
                        i. Synedra
                        ii. Fragillaria
                        iii. Asterionella - never seen auxospores or gametes, but assume that they occur because the cells undergo
                                                    the same size decrease and then increase
                        iv. Tabellaria
                        v. Navicula - has a raphe
                        vi. Cocconeis - often found on rocks in streams
    E. Pyrrophyta (dinoflagellates)
        1. Distinguishing characteristics
            a. eukaryotic
            b. pigments
                1) chlorophylls a and c
                2) xanthophylls
            c. storage product - starch
            d. cell wall -- cellulose; some may be armored theca
            e. flagella -- typically biflagellate in equatorial and longitudinal grooves
        2. Common
            a. Ceratium - armored dinoflagellate; covered with cellulose plates
            b. Peridinium
            c. Gymnodinium - non-loricate (related to endosymbionts in corals)
        3. Interesting facts
            a. red tides
            b. Pfisteria outbreaks (non-photosynthetic dinoflagellate)
            c. Biolumninescence -- Noctoluca
            d. Some may have extremely complicated lifecycles with amoeboid, predatory or parasitic stages --
                active area of controversy and research
    F. Euglenophyta
        1. Distinguishing characteristics
            a. eukaryotic
            b. pigments
                1) chlorophylls a and b
                2) carotenoids
            c. storage product – paramylon (polymer of glucose)
            d. cell wall – typically no cell walls; have pellicles (strips of protein) within the cell membrane
            e. flagella – typically 2, often with hairs
        2. Common
            a. Euglena
            b. Phacus
        3. Interesting facts
            a. Can take up dissolved organic molecules from the water
            b. Have an eyespot
    G. Rhodophyta
        1. Distinguishing characteristics
            a. eukaryotic
            b. pigments
                1) chlorophylls a and d
                2) phycobilins, especially phycoerythrin
            c. storage product – starch
            d. cell wall – cellulose
            e. no flagellated cells
        2. Common – found mostly in well oxygenated cold streams
            a. Audouinella (Rhodochorton) –  small, tufted
            b. Batrachospermum – ‘frog eggs’
        3. Interesting facts
            a. Mostly marine
            b. Marine species are often used as food emulsifiers (agar, carageenan)
 

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