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MULTICELLULAR PRIMARY
PRODUCERS
Chapter Outline
MULTICELLULAR ALGAE
Distribution of Seaweeds
Effects of Light on Seaweed
Distribution
Effects of Temperature on Seaweed
Distribution
Green Algae
Structure of Green Algae
Response of Green Algae to Herbivory
Reproduction in Green Algae
Human Uses of Green Algae
Red Algae
Brown Algae
Distribution of Brown Algae
Structure of Brown Algae
MARINE FLOWERING PLANTS
General Characteristics of Flowering
Plants
Invasion of the Sea by Plants
Sea Grasses
Classification and Distribution of
Classification and Distribution of Salt
Marsh Plants
Structure of Salt Marsh Plants
Adaptation of Salt Marsh Plants to a
Saline Environment
Ecological Roles of Salt Marsh Plants
Reproduction in Mangroves
Human Uses of Mangroves
KEY CONCEPTS
Chapter Objectives
• Describe the structure and characteristics of multicellular algae.
• Interpret a phylogenetic tree of marine algae.
• Identify the three different groups of marine algae.
• Describe the structure and characteristics of brown algae, green algae, red algae,
Key Terms
seaweeds
macroalga
phycologist
algologist
fouling community
frond
blade
holdfast
stipe
cuticle
fragmentation
drift algae
deterrence
red algae
nori
algal turf
carposporophyte
coralline algae
phycocolloids
agar
carrageenan
brown algae
fucoxanthin
bladders
seed
flowering plants
fruits
halophytes
sea grasses
root hairs
scale leaves
foliage leaves
sheath
blade
epidermis
senescence
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rhizosphere
culm
mangal
aerial root
nutritive roots
cable root
Chapter Summary
1. Multicellular marine algae are divided into three major groups based on the
accessory pigments they contain. Algal cells have cell walls in addition to their
2. Green algae are found in shallow coastal waters. Many marine species of green algae
exhibit a coenocytic body plan. Red algae are most widespread in the tropics. Their
3. The plants living in marine environments are vascular plants that produce seeds. All
marine plants exhibit adaptations that allow them to survive in salt water. Marine
4. Sea grasses are mainly found in shallow waters of temperate and tropical oceans.
Temperate salt marsh plants generally grow in the middle to upper intertidal zones,
Chapter Outline
I. Multicellular Algae
A. Three major groups of seaweeds: red, brown, and green.
B. Provide habitat for fishes, invertebrates, and other algae.
C. Distribution of seaweeds.
1. Fouling communities.
4. Perennial.
D. Structure of seaweeds.
1. Lack vascular tissue that characterizes higher plants.
E. Biochemistry of seaweeds.
1. Photosynthetic pigments.
a. Chlorophyll a present in all macroalgae.
F. Seaweed reproduction.
1. Fragmentation.
2. Drift algae.
G. Green algae.
1. Varied thallus forms: tubes, sheets, and filaments.
2. Coenocytic.
3. Herbivory responses.
a. Calcium carbonate in cell walls discourages predation.
4. Green algae exhibit alternation of generations.
H. Red algae.
1. Largely marine (98%) with few freshwater species. Great tropical diversity.
2. Benthic species; can be distributed to depths of 200 m in clear water.
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6. Reproduction.
a. Complex life cycles with two sporophyte phases and one gametophyte phase.
7. Ecology of red algae.
a. Epiphytes.
b. Epizoics.
8. Commercial uses of red algae.
I. Brown algae.
1. Virtually entirely marine (99.7% of 1500 species are marine), predominantly benthic.
2. More abundant and diverse in higher latitude, cooler waters than in tropics.
4. Cell walls of cellulose and alginates (similar to agar and carrageen) produce a flexible
yet sturdy thallus that can withstand wave shock.
5. Specialized conductive cells (trumpet cells) that conduct photosynthetic byproducts
(mannitol) from the blade to the rest of the thallus.
6. Reproduction.
a. Alternation of a perennial sporophyte with annual gametophyte.
7. Ecology of brown algae.
8. Commercial uses of brown algae.
II. Marine Flowering Plants
A. Vascular tissue present: phloem and xylem.
D. Sea grasses.
1. Hydrophytes; subtidal (submerged) plants.
3. Sea grass morphology.
a. Rhizomes: horizontal underground stems anchored in the sediment.
4. Sea grasses are generally found in subtidal low-wave energy environments that have
soft substrates (mud or sand) with relatively low nutrients and high light.
8. Reproduction identical to terrestrial flowering plants—hydrophilous pollination.
9. Ecology of sea grasses.
a. Require high light (except for paddle grasses, Halophila).
10. Commercial uses of sea grass.
E. Salt marsh plants.
1. Temperate intertidal communities found in areas of low water velocity with muddy
or silty substrates.
2. Salt marsh plants.
a. Cord grasses: Spartina.
3. Spartina growth form.
a. Culm: vertical cord grass stems.
4. Adaptations to saline environment.
a. Facultative halophyte.
5. Ecology of salt marsh plants.
a. Accumulate and stabilize sediments in coastal areas.
6. Commercial significance.
F. Mangroves.
1. Tropical intertidal plants found in areas of low water velocity and sandy or muddy
substrates.
2. Mangrove morphology.
a. Prop roots.
3. Mangrove reproduction.
a. Wind- or bird-pollinated flowers.
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c. Propagule.
4. Mangrove ecology.
a. Roots trap and stabilize coastal sediments, preventing sediments from washing
Suggestions for Presenting the Material
1. The Blue Planet series, “The Seasonal Seas,” shows the effects of seasonal light input
2. Use photographs and video clips to construct virtual ecosystem tours for students
3. Have students put together a summary table in which they list: primary vegetation
(list species); abiotic parameters that define the ecosystem (such as intertidal or
Classroom Discussion Ideas
1. What factors affect the location of seaweed? How likely are you to see seaweed in
the middle of the ocean? Why or why not?
2. Choose a type of plant and discuss its ecological and economic impacts.
3. What adaptations do the different types of algae exhibit to reduce herbivory?
Videos, Animations, and Websites
Videos
Deep Sea Invasion. (PBS, Nova Series)
A toxic aquarium plant is accidentally released and threatens to spread worldwide.
Animations
From Pond Scum to Power. (PBS, Nova)
In this animated primer, learn why algae and other plants make oil, and how algae oil
Websites
Provasoli-Guillard National Center for Marine Algae and Microbiota.
The NCMA is the national marine phytoplankton collection and is an integral part
National University of Iceland.
National Geographic Magazine.
Oilgae.
This site is devoted to information on converting algae into biofuel.
Suggested Answers to End of Chapter Questions
Multiple Choice
1. a. light
2. c. thallus
Matching
1. f.
2. c.
1. c.
2. b.
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Short Answer
1. What factors affect the distribution of algae in the marine environment?
Because algae are photosynthetic, their vertical depth distribution is controlled by
2. List some of the important ecological roles of marine flowering plants.
Intertidal marine plants, such as salt marsh grasses in temperate areas and
mangroves in tropical areas, trap sediments of terrestrial origin, modulate storm
3. Describe the alternation of generations that occurs in the life cycle of an alga.
Alternation of generations is an alternation of an asexually-reproducing
4. Describe the adaptations that have evolved in algae to protect against wave shock.
Algae have flexible stipes, which allow the thallus to move with the wave in a high
5. Describe the adaptations that have evolved in salt marsh plants or mangroves to help
them survive in areas where the salt content is high.
Salt marsh plants such as cordgrass (Spartina alterniflora) and mangroves have salt
Chapter 7 81
Thinking Critically
1. Salt marshes play an important role as nurseries for many commercially important
fishes and shellfish. What characteristics of salt marshes make them such ideal
nurseries?
Salt marshes provide important habitat for larval fishes and invertebrates. The
2. Predict the effects of coastal zone development on sea grass and mangrove
communities.
Coastal development negatively impacts mangrove and sea-grass ecosystems. The
mangroves trap terrestrial sediments that would increase the suspended solid load
3. One bay experiences runoff from surrounding communities with well-kept lawns.
Another has a community with failing septic systems that discharge their contents
through groundwater. How might these two bays differ in their growth of seaweeds
and sea grasses?
The bay with direct runoff from lawn care would contain excess nitrogen and
phosphorus that would stimulate algal growth in the bay. The increased algal
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4. In chapter 2 you learned that overgrazing of kelp by sea urchins led to a decline in
several other animal species associated with kelp forests. On the basis of what you
have learned in this chapter, why would a decrease in the amount of kelp affect
animals that do not feed on kelp?
A decline in the kelp biomass means a decline in the amount of habitat available
the kelp would decline.
Suggested InfoTrac® Articles
“Splendor Is a Grass: Johnson’s Seagrass, Found in Florida, Was the First Marine Plant
to be Listed as Andangered.” Daerr, E.G. National Parks, (2001).