A Seaweed Divided

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?

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

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.

SeaweedSome 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

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?

Green Algae

• Phylum Chlorophyta – green algae• Mostly freshwater, 10% estuaries• Many unicellular, Halimeda (calcareous

green algae)

Three Types of Seaweed

Green AlgaeGrowing on a rock in

the shallows of the Patuxent River

Green AlgaeImage ID: line2273, NOAA's America's Coastlines Collection Location: Patuxent River, MarylandPhoto Date: 2001 NovemberPhotographer: Mary Hollinger, NODC biologist, NOAA

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

Brown AlgaePelagic 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 2004Brown AlgaeImage ID: expl1137, Voyage To Inner Space - Exploring the Seas With NOAA CollectPhotographer: Image courtesy of H. Scott Meister, SCDNRCredit: Estuary to Abyss 2004. NOAA Office of Ocean Exploration.

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

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 AlgaeImage ID: nerr0319, NOAA's Estuarine Research Reserve Collection Location: Vicinity of Georgetown, South Carolina

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)

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?

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.

How would you classify this specimen?

Image ID: line1320, NOAA's America's Coastlines Collection Location: Maine, Cousins IslandPhotographer: Mr. William Folsom,

NOAA, NMFS

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.

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?

Narrow Wrack — Super Female Clone

Baltic Sea Offshoot Encroaches

on a

Vital Counterpart

• 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?

• What threats exist for all seaweed?

• What are the benefits of seaweed?

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.