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1. A
Seaweed
Divided

2. What touches each of our
lives on land, determines
the destiny of millions of
aquatic organisms, and
is estimated to be worth
over a million dollars a
year per square mile?

3. What if we said they may
thrust skyward from the sea
floor forming canopies
where assorted seabirds
vie for perches, carpet
rocks in intertidal zones,
fortify coral reefs, or,
dislodged and washed up
on a beach, form a wrack
line for beachcombers and
a buffet for small
crustaceans?
Image ID: Giant Kelp, NOAA's Restoration Center Collection
Location: Baja, California

4. Neither plants nor
animals, seaweeds
are classified into
three major groups —
the red algae, green
algae and brown
algae — distinctions
which are not always
obvious by their
apparent color.

5. Seaweed
Some Points for Discussion
• Food
• Oxygen
• Some live on tissues of other seaweeds
• Multicellular algae
• Macrophytes or macroalgae
• Eukaryotes
• Pigments
• Highly variable
• Nutrient rich
• Produce phycocolloids – algin –
stabilizer; emulsifier in dairy products;
carrageenan (Chondrus); agar

6. General Structure
• Blades – leaf-like, broad surface
• Stipe — stemlike support structure
• No transport system in stem or leaf
• Holdfast – not involved in absorption of
water, lack transport tissues
• Thallus – complete body
• Question: How do they differ from land
plants?

7. Green Algae
• Phylum Chlorophyta – green algae
• Mostly freshwater, 10% estuaries
• Many unicellular, Halimeda (calcareous
green algae)
Three Types of Seaweed

8. Green Algae
Growing on a rock in
the shallows of the
Patuxent River
Green Algae
Image ID: line2273, NOAA's America's
Coastlines Collection
Location: Patuxent River, Maryland
Photo Date: 2001 November
Photographer: Mary Hollinger, NODC
biologist, NOAA

9. Brown Algae
• Phylum Heterokontophyta – brown algae,
olive to dark brown, fucoxanthin
• 1,500 species, all marine
• Kelps (largest)
• Temperate and polar rocky coasts
• Rockweeds, wrack, sargassum

10. Brown Algae
Pelagic brown algae in
the genus Sargassum.
The berry-like
structures are gas-filled
bladders known as
pneumatocysts, which
provide buoyancy to
the plant.
NOAA’s Estuary to Abyss Expedition 2004
Brown Algae
Image ID: expl1137, Voyage To Inner Space - Exploring the Seas With NOAA
Collect
Photographer: Image courtesy of H. Scott Meister, SCDNR
Credit: Estuary to Abyss 2004. NOAA Office of Ocean Exploration.

11. Red Algae
• Phylum Rhodophyta – Red algae phycobilins
• Marine, shallow waters, largest group
• Some may be parasitic
• Some are calcareous (have a skeleton) –
important in coral reef habitats
• Food for humans – Gracilaria

12. Red Algae
North Inlet -
Winyah Bay
National Estuarine
Research Reserve.
Seaweeds like this
red algae are
important
producers in
estuaries,
especially during
winter months.
Red Algae
Image ID: nerr0319, NOAA's Estuarine Research Reserve Collection
Location: Vicinity of Georgetown, South Carolina

13. Economic Importance
• Mariculture – Japan, China, Korea
• Nori, ogo, dulse, Irish moss
• Source of salts, trace elements,
fiber, iodine
• 3 oz of dried seaweed = more
vitamin A, B-1, B-2, half
requirement vitamin C
• Carrageenan – thickener,
smoother, emulsifier (puddings)

14. Food for Thought
• Algin – cell wall of brown algae (kelp), thickening,
suspending, emulsifying such products as polishes,
shampoos, cosmetics, ice cream; preventing frostings
and pies from drying; thickening printer paste (sharper
prints)
• Agar – jellylike from Gelidium – substitute for gelatin and
as an anti-drying agent for foods like cheese, ice cream,
and canned meats. Lab gels. Indigestible (laxatives,
pharmaceuticals)
• Ash – burned seaweeds containing Na and KOH
(potash) used in manufacturing glass and soap
• Fertilizers
• Fuel
• Question: Have you used something with seaweed
today?

15. What are the limiting factors for
algal growth?
Numerous types of
algae are visible in
this image. Although
over 50 meters deep,
the light penetrates
through the very clear
water in this area of
the Gulf of Mexico.

16. How would you classify this
specimen?
Image ID: line1320, NOAA's
America's Coastlines Collection
Location: Maine, Cousins Island
Photographer: Mr. William Folsom,
NOAA, NMFS

17. A Case Study
A sea change, taking place in the Baltic Sea, worries scientists, fishermen, politicians
and citizens. Something is happening in the Baltic Sea’s underwater forests. A new kind
of seaweed that is less ideal for fish, crustaceans, barnacles and other organisms is
spreading over hundreds of miles in the north. Extensive algal blooms caused by
eutrophication and vast “dead zones” have formed on the sea bottom. Seven of the
world’s ten biggest dead zones, where nothing can survive due to lack of oxygen, are
found in the Baltic Sea.

18. A Seaweed
Divided
Illustration Patterson Clark, The Washington Post
What is the impact
of salinity changes
on the growth of
seaweed in the
Baltic Sea?

19. Narrow Wrack — Super Female Clone
Baltic Sea Offshoot
Encroaches
on a
Vital Counterpart

21. • What has concerned scientists
since the discovery of the
narrow wrack in the Baltic
Sea?
• How is salinity related to the
reproductive cycle of the
bladder wrack and the narrow
wrack seaweed?

22. • What threats exist for all
seaweed?
• What are the benefits of
seaweed?

23. For more information about the
bladder wrack and narrow wrack, read
The Washington Post Science page
article, “A Seaweed Divided Against
Itself Upsets Oceanic Order.” This
August 3, 2009, article may be found
in The Post NIE program online
curriculum guide:
The Sea — Rich and Strange.
Download at no cost at
www.washingtonpost.com/nie; select
lesson plans, September 10, 2009.