I.
Multicellular Algae - Seaweeds
B.
Green Algae (Chlorophyta)
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•
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Mostly freshwater species (~700 marine species)
Some species common in nearshore environments
Structurally simple
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Many unicellular or filamentous
Photosynthetic pigments and energy storage products
similar to higher plants
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May have shared a common ancestor with plants
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No pigments to mask green color
Habitat
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Many live as epiphytes
Some species bore into calcium carbonate shells
I.
Multicellular Algae - Seaweeds
B.
Green Algae (Chlorophyta)
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Examples
Enteromorpha
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Often found in polluted areas; Used as bioassay tool
Ulva (Sea Lettuce)
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Found in areas with high nutrient levels
Valonia (Bubble Algae)
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Caulerpa
Ulva
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Tropical and subtropical
Caulerpa
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Invasive species (C. taxifolia)
Codium (Dead Man’s Fingers)
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Multinucleated
Halimeda
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Calcareous alga
Valonia
Codium
Fig. 6.2 - Ulva
Halimeda
I.
Multicellular Algae - Seaweeds
C.
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Brown Algae (Phaeophyta)
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Padina
Mostly marine (~1500 species)
Includes largest and most complex algae - kelps
Especially abundant on rocky coasts in temperate and polar
regions
Dominant accessory pigment is fucoxanthin
Imparts yellow-brown to brown color
Structurally simple to complex
Some with simple flat thalli (Padina)
Others with complex structures
•
Holdfast, stipe, blade, pneumatocysts
Includes fast growing species
Some kelps can grow up to 50 cm per day!
Most anchored to substrate
Some float (Sargassum – Sargasso Sea)
Common in intertidal zone
Good at withstanding mechanical stress
Tolerant of exposure and desiccation
Sargassum
I.
Multicellular Algae - Seaweeds
C.
Laminaria
Brown Algae (Phaeophyta)
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•
Fig. 6.5 - Fucus
Examples
Fucus (Rockweeds)
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Intertidal and subtidal species; Ecologically important
Laminaria (Kelp)
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Some species consist of a single blade
Commonly used for food
Postelsia (Sea Palm)
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Usually on exposed rocky shorelines
Laminaria
I.
Multicellular Algae - Seaweeds
C.
Laminaria
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Brown Algae (Phaeophyta)
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Fucus
Examples
Fucus (Rockweeds)
Intertidal and subtidal species; Ecologically important
Laminaria (Kelp)
Some species consist of a single blade
Commonly used for food
Postelsia (Sea Palm)
Usually on exposed rocky shorelines
Egregia (Feather Boa)
Common on rocky Pacific coast
Pelagophycus (Elk Kelp)
Large float
Macrocystis (Giant Kelp)
May reach 100 m and grow up to 50 cm day-1
Most common in cold water
Laminaria
Pelagophycus
Pelagophycus
Macrocystis
Egregia
I.
Multicellular Algae - Seaweeds
D.
Red Algae (Rhodophyta)
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•
Mostly marine (~4000 species)
Common in shallow water but also found in very deep
water
Contain accessory pigments called phycobilins
Structurally less complex than brown algae
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Most are filamentous
Much smaller than large brown algae
May be heterotrophic or parasitic
May incorporate calcium carbonate into tissues (Why?)
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Sebdenia
Coralline red algae
May be important in formation and cementing of coral reefs
May contribute to formation of carbonate sand
Some encrusting, others arborescent
Many are commercially important
Pelagophycus
Halimeda
Porphyra
I.
Multicellular Algae - Seaweeds
E.
Life History
1.
Asexual
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•
2.
Fragmentation – Especially in species with no holdfast
Spores – Resistant dispersal stages
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Zoospores – Flagella permit motility
Sexual
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Rare in unicellular algae; common in multicellular forms
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Gametes produced by meiosis
Two types of life stages
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Haploid (n) – gametophyte generation
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Diploid (2n) – sporophyte generation
Alternation of generations between gametophyte and
sporophyte stages
Four basic patterns of sexual reproduction
Fig. 6.11
I.
Multicellular Algae - Seaweeds
F.
1.
Economic Importance
Food Source
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•
2.
Harvested
Mariculture
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Red algae (Porphyra, Eucheuma)
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Brown algae (Laminaria)
Products
a.
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•
b.
•
Phycocolloids
Algin (Extracted from kelp; harvested with boats)
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Stabilizer, emulsifier for ice cream, cheese
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Stabilizer to keep frostings and baked goods moist
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Thickener, emulsifier for shampoo, shaving cream, plastics,
rubber, paints, cosmetics, textiles
Carrageenan (Extracted from red algae)
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Emulsifier for dairy products, toothpaste, puddings
Agar (Extracted from red algae)
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Used to form jellies, thicken mixtures
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Preserves, pharmaceutical applications
Other
Fertilizers, additives in animal feeds
II.
Flowering Plants (Angiosperms)
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Flowering plants have true leaves, stems and roots (unlike
multicellular algae)
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Contain specialized tissues that transport water, minerals and
nutrients
Dominant sporophyte
Few truly marine species
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Seagrasses entirely submerged most of the time, but other
marine angiosperms intolerant of prolonged immersion
Marine angiosperms expend considerable energy coping with
effects of salt water
Seagrasses (50-60 species)
A.
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Not true grasses (related to lilies)
Roots, stems and shoots grow from horizontal rhizome
Flowers typically small and inconspicuous (Why?)
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Pollen carried by water currents; No need to attract pollinators
II.
Flowering Plants (Angiosperms)
A.
Seagrasses
Eelgrass (Zostera) – Temperate Atl, Pac; Tropical Pac
1.
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Most widely distributed; in shallow, protected coastal waters
Common in oxygen-poor sediments
Highly productive; provides shelter for many animals
Surf grass (Phyllospadix) – Temperate Pac
2.
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Lives on rocky shores; experience wave action
May be exposed at low tide
Turtle grass (Thalassia) – Tropical
3.
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Lives on muddy and sandy bottoms in calm waters to 10 m
Stabilize sediments on landward sides of Caribbean reefs
Fig. 6.13
Eelgrass (Zostera marina)
II.
Flowering Plants (Angiosperms)
A.
Seagrasses
Eelgrass (Zostera) – Temperate Atl, Pac; Tropical Pac
1.
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Most widely distributed; in shallow, protected coastal waters
Common in oxygen-poor sediments
Highly productive; provides shelter for many animals
Surf grass (Phyllospadix) – Temperate Pac
2.
•
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Lives on rocky shores; experience wave action
May be exposed at low tide
Turtle grass (Thalassia) – Tropical
3.
•
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Lives on muddy and sandy bottoms in calm waters to 10 m
Stabilize sediments on landward sides of Caribbean reefs
Fig. 6.13
Surf Grass (Phyllospadix scouleri)
II.
Flowering Plants (Angiosperms)
A.
Seagrasses
Eelgrass (Zostera) – Temperate Atl, Pac; Tropical Pac
1.
•
•
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Most widely distributed; in shallow, protected coastal waters
Common in oxygen-poor sediments
Highly productive; provides shelter for many animals
Surf grass (Phyllospadix) – Temperate Pac
2.
•
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Lives on rocky shores; experience wave action
May be exposed at low tide
Turtle grass (Thalassia) – Tropical
3.
•
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Lives on muddy and sandy bottoms in calm waters to 10 m
Stabilize sediments on landward sides of Caribbean reefs
Fig. 6.13
Turtle Grass (Thalassia species)