A lecture on marine algae (seaweeds)

1. ALGAE AND
ANGIOSPERMS
Alex
Slipperlimpet.co.uk

2. Why is algae so
important?

3. Carbon sink
Indicator
Fertilser
species
Weather
Food
telling
production
device
Why?
Nursery Coastal
habitat defence
Food for
Symbiotic
marine
relationships
species

4. Kingdom
• Protoctista
Characteristics
• Single celled to mutlicelled
• Autotrophic
• Form reproductive structures
• Aquatic
• Have flagellum at some point in their life
• Many contain organelles which store and synthesise starch
(pyrenoids)
Types
• Unicellular
• Colonial
• Filamentous
• multicellular

5. •7 Phylum
•Based on
•Colour
•Type of Chlorophyll
•Food Storage substance
•Cell wall composition
•Focus on Multicelled or Macroalgae
•3 Phylum
•Chlorophyta
•Phaeophyta
•Rhodophyta

8. Green Algae (Chlorophyta)
• Land based plants have arisen from evolution
of green seaweeds.
• 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

9. Examples of Green Algae
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 Man’s Fingers)
• Multinucleated
Halimeda
• Calcareous alga

10. • 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

11. Examples of 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

12. D. Red Algae (Rhodophyta)
 Mostly marine (~4000 species)
 Common in shallow water but also found in depths up to 200 metres.
 Contain accessory pigments called phycobilins (phycoerythrin, phycocyanin)
 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

13. Next session:
•Bring life cycle of Red, Green and Brown
seaweed.
•Box Justification

14. Angiosperms

15. Key Features
•Marine flowering plants
•NOT seaweeds
•Salt tolerant or able to withstand constant emersion
•Oxygen absorbed from water
•Produce rhizome roots
•Only able to photosynthesise on leaves

17. Habitats

18. Eelgrass beds