Weber State University      Department of Botany

                                                    BOTANY  LS1203 - PLANT  BIOLOGY

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ALGAE 

Kingdom Protista

includes
    animal-like organisms:    
        euglenoids, protozoa
    fungal-like organisms:    
        myxomycota (plasmodial slime molds)
        oomycota (water molds, like potato blight)
    plant-like organisms:  
        green algae (Chlorophyta) 
        stoneworts (Charophyta)
        red algae (Rhodophyta)
        brown algae (Phaeophyceae in the Chromophyta)
        diatoms (Bacillariophyceae in the Chromophyta)
        dinoflagellates (Dinophyta)
       

heterotrophs (internal digestion, external digestion) and photosynthetic autotrophs
all three types of life cycles (gametic, zygotic, sporic) as well as a three generation variation of the sporic life cycle in the red algae (one gametophyte generation and two sporophyte generations)

photosynthetic pigments
primary for plants, algae, and cyanobacteria:  chl a
Accessory pigments:    chl b, chl c, phycobilins
            carotenoids:  carotenes, xanthophylls  (examples:  β-carotene, lutein, fucoxanthin)

Green  Algae (Phylum Chlorophyta)

> 5,000 species ==> second largest group of algae

multicellular, unicellular, filamentous, colonial

life cycles: gametic, zygotic, sporic

mostly found in fresh water, but a fair number are marine or terrestrial (soil, tree bark)

with fungi, can form lichens

chl a, chl b, and same carotenoids  as in land plants; store starch
only the green algae store food (starch) in the chloroplasts; all the rest of the algae store their carbohydrate reserve outside of chloroplasts

some have cell walls of cellulose; some also have hemi-cellulose and pectin

Stoneworts (Phylum Charophyta) 

include Chara and other stoneworts; considered by some to be in the Chlorophyta (green algae) as their pigmentation and other chloroplast/photosynthesis features are the same as the green algae
some have the same process to divide cell contents (cytokinesis) as the land plants; plasmodesmata, apical growth, nodes and internodes 
apparently share a common ancestor with the land plants

Red  Algae (Phylum Rhodophyta)

among the oldest eukaryotic fossils known, > 2 billion years old

> 5,000  species

mostly marine, especially in warm, tropical waters

generally grow attached to something; some are free,

filamentous, or unicellular

chloroplast pigments:  chl a, phycobilins (phycocyanin, phycoerythrin), carotenoids
    These pigments allow the red algae to live in deeper water than  the other types of algae; deeper water is found beyond the tidal zone, so it is a more stable water environment

store floridean starch

cell walls:  cellulose, agar, carrageenan

coralline algae have calcium carbonate in their walls
build coral reefs, even more than corals do.  Also serve as food for reef inhabitants (so do diatoms).

Brown  Algae   (Phaeophyceae in the Phylum Chromophyta)

mostly marine; predominantly in temperate and cold oceans

> 1,500 species known

large species have distinct structures analogous to structures of vascular plants:  holdfast (for anchorage to a substrate), stipe (a stem-like structure that sometimes has rudimentary conducting tissue), and a blade (leaf-like).  Air bladders for buoyancy are also sometimes present.  No unicellular or colonial brown algae are known.

store laminarin (made of glucose and mannitol)

cell walls of cellulose and alginic acid (algin, alginates)

chloroplasts have chl a, chl c, and carotenoids (esp. fucoxanthin)

shoreline:  find Laminaria
open ocean: Sargassum
kelps generally up to 70 m long (longest = 274 m)

Diatoms   (Bacillariophyceae in the Phylum Chromophyta)

largest group of algae; ~20,000 described species; actual number could be ~100,000

major producer in aquatic systems

estimates put them at providing c. 25% of the total primary production on earth  (in cooler marine environments ==>  phytoplankton)

fresh and marine forms; mostly unicellular

chl a, chl c, carotenoids (esp. fucoxanthin)

store chrysolaminarin

cell walls contain silica  ==>  diatomaceous earth (diatomite)
The silica walls of diatoms have a lot of surface area and are highly absorptive.  This property means that scarce minerals stick to diatoms.
Also, a silica wall requires less energy to make compared to a cellulose wall (only c. 10%).

Dinoflagellates  (Phylum Dinophyta)

important producers in warm, tropical oceans

mostly unicellular

chl a, chl c, brownish xanthophylls (esp. peridinin)

outer covering of cellulosic plates

some are heterotrophic, living as parasites on fish and other protists

some are bioluminescent

cause most red tides (not necessarily red:  brown, yellow, green, etc.; not necessarily toxic); not all dinoflagellates form red tides
predominant cause of red tides off the Gulf coast and the coast of central California 
some dinoflagellates produce neurotoxins; shellfish and fish can contain the toxins. The concentration of the toxins increases as you go up the food chain; the toxicity decreases once the bloom is over.  Humans can get sick from eating contaminated fish (ciguatera) or shellfish (paralytic shellfish poisoning).
cause of the blooms:  increased mineral nutrients (runoff, upwelling of oceans); source of the dinoflagellates for the bloom:  cysts in sediments
______________

Algal blooms in general
increased P in water (from runoff) increases algal growth
the algae die; decomposition uses up O₂ in water; fish die
_____________

Uses  of  algae

Food algae of Japan:
Kombu (Laminaria, a brown alga)  
Nori (Porphyra, a red alga)    Nori has been cultivated in Japan for >300 years on submerged rope beds.
Wakambe (Undaria, a brown alga)

Limu (Hawaii):  uses many genera, including Ulva (a green alga, also known as sea lettuce)

Ireland:  Irish moss (Chondrus crispus, a red alga):  carrageenan, blanc mange

Cell Wall Products:

alginic acid (from Laminaria, Macrocystis):  ice cream and other dairy products, shaving cream, paint, to thicken dye pastes in the textile industry, for making dental impressions

carrageenan:      stabilizing and thickening agent for  paints, cosmetics, dairy products (like sour cream, ice cream, egg nog, and chocolate milk), instant pudding,  toothpaste, creamed soups

agar:  to gel growth media for microorganisms (bacteria, fungi) and plant tissue culture
    used in mayonnaise, pudding, lotions

Algal harvests for wall products:
Chondrus crispus (Irish moss) = harvested in Ireland as a source of carrageenan
Eucheumu = grown in the Philippines for carrageenan
Gracililaria = agar
Macrocystis, a kelp harvested off the Pacific coast of North America for alginic acid.  It is cut several times a year, ~ 3 m below the water surface.
Diatoms:  diatomaceous earth is used as a filtering agent, for insulation, as a mild abrasive.  1 cm³ = 4.6 million diatom shells.  Essentially insoluble and extremely heat resistant.

Algae  of  Local  Interest

Dunaliella

D. salina = grows in GSL; harvested as a source of β-carotene
To live in a saline environment than can be up to 10x saltier than sea water, D. salina  stores carbohydrates as glycerol (not starch) which will help the alga maintain its water balance.  The glycerol can make up as much as 30% of a cell’s dry weight.  Under stress conditions, the alga makes large amounts of β-carotene; the  β-carotene can account for up to 20% of a cell's dry weight.

Other species of Dunaliella grow in extreme environments other than saline lakes, like acid hot springs.
Dunaliella acidophila
Cyanidium caldarium
Galdieria sulphuraria - can grown in the rocks  around the hot spring
Within the rocks,  the upper layers of the alga near the rock’s surface are the  primary producers, and the algal layers further into the rock are consumers dependent on the surface cells.  


Pink  Snow  (Watermelon  Snow)

Noticeable in the summer in lingering snow banks at high elevation (like Snowbird)
Has been observed for centuries, with cause unknown.  Observations:
different shades of red in a single snow patch
if you compress the snow, it gets redder
the falling snow isn't red

turns out to be unicellular green algae.  
About 60 species have been observed in the western US.  The red color comes from carotenoid pigments (which are also responsible for the pink color of flamingo feathers).  (other animal associated algae:  sloths, polar bears)
The algae might live up to 25 cm (10 inches) deep in the snow.
1 tsp of melted snow can have > 1 million algal cells

The algae in pink snow are the producers for a very small ecosystem:
bacteria and fungi breakdown windblown detritus, pollen, dead algae and insects
algae do photosynthesis
algae feed protozoa, nematodes, snow worms, rotifers
these organisms feed mites, spiders, and insects
these organisms feed birds

REVIEW

Kingdom Protista ==> home of the algae
Be familiar with the six groups of algae covered in class.
Be able to distinguish the six groups on the basis of:  accessory pigments (particularly chlorophylls/phycobilins) for photosynthesis, cell wall molecules, food storage molecules, habitats, and diversity of growth forms and numbers of species  that are found.  Most likely, your best approach for organizing the information would be to make a table and fill it in.

All of the algae, and land plants organize their photosynthetic pigments into collections called photosystems.  Why is chlorophyll a important in all of these organisms?  How do the accessory pigments fit in?

What organisms are responsible for most red tides?  What environmental conditions promote the development of the red tides?  Why is fishing usually prohibited during red tides?  

Be familiar with the algal foods of island countries/states.  Which red alga has been cultivated in Japan for over 300 years?  What are the sources of other algae that are used for food or preparation of wall materials?
Be familiar with algal wall materials and their uses in the US.  Know the algae used as sources for these materials.

How can Dunaliella salina live in the Great Salt Lake?  What type of alga is D. salina?  Why does it turn deep orange/red?   Why is D. salina harvested from the GSL?
Which  algae are responsible for pink snow?  
What is the importance of D. salina and the snow algae to their ecosystems?

LINKS

Uses of Seaweeds   (The Seaweed Site, maintained by Michael Guiry of the National University of Ireland, Galway)

Algae: The Forgotten Treasure of Tidepools  lots of pictures of green, red, and brown algae  (Biology Department, Sonoma State University)

Kingdom Protista   (by Steven Wolf at California State University Stanislaus)

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Revised 14 November 2004.  Links checked 14 November 2004.