Multicellular Primary ProducersSeaweeds and Plants

Chapter 6

All photosynthetic?

Most are photosynthetic but of course there are exceptions

Some are not photosynthetic and are actually parasites of other seaweeds!

The role of seaweeds

• Transform solar every to chemical energy in the form of organic matter– Energy is then available for consumption

• Habitat• Oxygen producers

Structure of seaweeds

• Seaweeds are eukaryotic

• Seaweeds still lack the specialized structures and reproductive mechanisms characteristic of terrestrial plants

• Wide range of variation among seaweeds

Variation

• Rocky shore- small and sturdy to withstand waves– Some delicate ones live on other seaweeds

• Kelps- found offshore in cold waters (giants)

General Structure

• Seaweeds lack true leaves, stems, and roots of plants.

• Thallus- Complete body• Blades- Leaf-like flattened portions of the thallus, large

surface area, photosynthesis• Pneumatocysts- Gas-filled bladders that can keep

blades close to sea surface• Stipe- Stem-like structure for support, blades originate • Holdfast- Attaches the thallus to the bottom and well

developed in kelps

Structure

Types of Seaweeds

• Three types• 1) Green• 2) Brown• 3) Red

Green Algae

• Most are freshwater and terrestrial• 10% of the 7,000 species are marine• Most have a simple thallus compared to the

other 2 groups• Thought that land plants evolved from green

algae– Pigments and food reserve are the same

Where do green algae live?

• Common on rocks in shallow water • Rocky shore tide pools

Types of green seaweeds

• Filamentous types may be branched or unbranched • Enteromorpha- thin thallus in the form of a hollow

tube• Ulva- Sea lettuce is paper thin• Valonia- forms large spheres or curious spherical

clusters.• Caulerpa- Single giant cell with many nuclei• Codium- Deadman’s fingers• Halimeda- Calcareous green algae (coral reefs)

Enteromorpha

Ulva

Valonia

Caulerpa

Codium

Halimeda

Brown Algae

• Coloration – varies from olive green to dark brown– Fucoxanthin over chlorophyll

• Almost all of the 1500 species are marine• Often the dominant primary producers on

temperate and polar rocky coasts.• Largest and structurally most complex (Include

the kelps)

Types of Brown Algae

• Ectocarpus- Finely filamentous thallus • Dictyota – thallus is flat and branched• Padina- Fan-shaped and lightly calcified• Desmaretia- branched

• Some are exposed at low tides at the middle and upper levels of rocky shores

• Gas-filled floats – rockweeds or wracks

Sargassum

• Brown algae found in warm waters (Gulfs of Mexico and California)

• Sargasso weed has spherical air bladders to keep small leaf like blades afloat

• Most grow on rocks• Offshore in huge masses• Sargasso Sea– Area in Atlantic

Sargasso Sea

Sargassum Sea

• http://www.youtube.com/watch?v=JFxhlyJ3U4Q

Kelps

• Most complex and largest of all brown algae• Great importance – provide food and shelter for many

organisms. • Laminaria- species of kelp where a single large blade can be

up to 10 ft• Agarum and Alaria – Rib runs along the middle of a single

blade• Egregia- Feather boa kelp• Eisenia- Southern sea palm• Nereocystis- Bull kelp• Pelagophycus- Antler like branches

Brown Algaes

• kelp.gifkelp.gif

Ectocarpus

Dictyota

Padina

Desmarestia

Laninaria

Agarum

Alaria

Egregia

Nereocystis

PelagophycusEisnia

Macrocystis

• Largest of kelps• Massive holdfast attaches to the bottom• At the base of each blade a gas-filled

pneumatocyst• Can grow 20 in per day in optimal conditions• Form kelp beds or forests– Among the richest, most productive environments

in the marine world

Kelp Forest

• http://www.youtube.com/watch?v=GcbU4bfkDA4

• What coast of North America can they be found?

• What do kelps consist of?• What do young kelp compete for?• What do fish use the kelp forest for?• Why does the canopy make a good nursery

environment?

Red Algae

• More red algae that green and brown combined

• Red pigments known as phycobilins• Essentially marine– Of the 4000 species, only a few are fresh water or

soil• Live in most shallow-water marine

environments

Structure of Reds

• Simplified in structure by becoming parasites of other seaweeds

• A few have lost all chlorophyll and are heterotophs

• Most are filamentous – Thickness, width, arrangement of filaments varies

Types of Reds

• Gelidium • Gracilaria• Endocladia – wirey clumps on rocky shores from Alaska

to S. Ca.• Gigartina- Most massive of the red algae• Porphyra-Common on rocky shores above the lowest

tide mark• Rhodymenia –Common in North Atlantic• Chondrus –Irish moss and can tolerate wide ranges in

temp, light and salinity

Red Algae

• en

Gelidium Gracilaria

Endocladia

Gigartina

Porphyra

Rhodymenia

Chondrus

Coralline Algae (Corallina)

• Red algae that deposit calcium carbonate in their cell walls

• Important in several marine environments • Calcified thallus takes a variety of shapes• Color varies from light to intense reddish-pink• Warm-water coralline algae are actively

involved in formation and development of coral reefs

Bingo• Thallus• Blades• Pneumatocysts• Stipe• Holdfast • Green algae• Red algae• Brown algae• Enteromorpha• Ulva• Valonia• Caulerpa• Halimeda• Gigartina• Chondrus

• Fucoxanthin• Ectocarpus• Dictyota• Padina• Desmarestia• Rockweeds• Sargasso Sea• Laminaria• Nereocystis• Pelagophycus• Macrocystis• Kelp forest• Phycobilins• Coralline algae• Gracilaria• Porphyra