Multicellular Algae - Seaweeds

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• Multicellular Algae - Seaweeds
• Green Algae (Chlorophyta)
• Mostly freshwater species (700 marine species)
• Some species common in nearshore environments
• Structurally simple
• Many unicellular or filamentous
• Photosynthetic pigments and energy storage
  products similar to higher plants
• May have shared a common ancestor with plants
• No pigments to mask green color
• Habitat
• Many live as epiphytes
• Some species bore into calcium carbonate shells

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• Multicellular Algae - Seaweeds
• Green Algae (Chlorophyta)
• Examples
• Enteromorpha
• Often found in polluted areas Used as bioassay
  tool
• Ulva (Sea Lettuce)
• Found in areas with high nutrient levels
• Valonia (Bubble Algae)
• Tropical and subtropical
• Caulerpa
• Invasive species (C. taxifolia)
• Codium (Dead Mans Fingers)
• Multinucleated
• Halimeda
• Calcareous alga

Ulva
Caulerpa
Valonia
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Codium
Fig. 6.2 - Ulva
Halimeda
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• Multicellular Algae - Seaweeds
• Brown Algae (Phaeophyta)
• 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

Padina
Sargassum
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• Multicellular Algae - Seaweeds
• Brown Algae (Phaeophyta)
• 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

Fig. 6.5 - Fucus
Laminaria
Laminaria
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• Multicellular Algae - Seaweeds
• Brown Algae (Phaeophyta)
• 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

Fucus
Laminaria
Laminaria
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Pelagophycus
Pelagophycus
Egregia
Macrocystis
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• Multicellular Algae - Seaweeds
• Red Algae (Rhodophyta)
• 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
• Most are filamentous
• Much smaller than large brown algae
• May be heterotrophic or parasitic
• May incorporate calcium carbonate into tissues
  (Why?)
• 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

Sebdenia
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Pelagophycus
Halimeda
Porphyra
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• Multicellular Algae - Seaweeds
• Life History
• Asexual
• Fragmentation Especially in species with no
  holdfast
• Spores Resistant dispersal stages
• Zoospores Flagella permit motility
• Sexual
• Rare in unicellular algae common in
  multicellular forms
• Gametes produced by meiosis
• Two types of life stages
• Haploid (n) gametophyte generation
• Diploid (2n) sporophyte generation
• Alternation of generations between gametophyte
  and sporophyte stages
• Four basic patterns of sexual reproduction

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Fig. 6.11
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• Multicellular Algae - Seaweeds
• Economic Importance
• Food Source
• Harvested
• Mariculture
• Red algae (Porphyra, Eucheuma)
• Brown algae (Laminaria)
• Products
• Phycocolloids
• Algin (Extracted from kelp harvested with boats)
• Stabilizer, emulsifier for ice cream, cheese
• Stabilizer to keep frostings and baked goods
  moist
• Thickener, emulsifier for shampoo, shaving cream,
  plastics, rubber, paints, cosmetics, textiles
• Carrageenan (Extracted from red algae)
• Emulsifier for dairy products, toothpaste,
  puddings
• Agar (Extracted from red algae)
• Used to form jellies, thicken mixtures
• Preserves, pharmaceutical applications

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• Flowering Plants (Angiosperms)
• Flowering plants have true leaves, stems and
  roots (unlike multicellular algae)
• Contain specialized tissues that transport water,
  minerals and nutrients
• Dominant sporophyte
• Few truly marine species
• 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)
• Not true grasses (related to lilies)
• Roots, stems and shoots grow from horizontal
  rhizome
• Flowers typically small and inconspicuous (Why?)
• Pollen carried by water currents No need to
  attract pollinators

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• Flowering Plants (Angiosperms)
• Seagrasses
• Eelgrass (Zostera) Temperate Atl, Pac Tropical
  Pac
• 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
• Lives on rocky shores experience wave action
• May be exposed at low tide
• Turtle grass (Thalassia) Tropical
• Lives on muddy and sandy bottoms in calm waters
  to 10 m
• Stabilize sediments on landward sides of
  Caribbean reefs

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Fig. 6.13
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Eelgrass (Zostera marina)
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• Flowering Plants (Angiosperms)
• Seagrasses
• Eelgrass (Zostera) Temperate Atl, Pac Tropical
  Pac
• 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
• Lives on rocky shores experience wave action
• May be exposed at low tide
• Turtle grass (Thalassia) Tropical
• Lives on muddy and sandy bottoms in calm waters
  to 10 m
• Stabilize sediments on landward sides of
  Caribbean reefs

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Fig. 6.13
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Surf Grass (Phyllospadix scouleri)
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• Flowering Plants (Angiosperms)
• Seagrasses
• Eelgrass (Zostera) Temperate Atl, Pac Tropical
  Pac
• 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
• Lives on rocky shores experience wave action
• May be exposed at low tide
• Turtle grass (Thalassia) Tropical
• Lives on muddy and sandy bottoms in calm waters
  to 10 m
• Stabilize sediments on landward sides of
  Caribbean reefs

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Fig. 6.13
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Turtle Grass (Thalassia species)