1. Ch. 6: Multicellular Primary Producers

2. Ch. 6: Multicellular Primary Producers: Seaweeds and Plants
When we think of photosynthesizers we think of plants
But in the ocean they are photosynthetic bacteria, unicellular algae (from Ch. 5) and seaweeds!
They are considered plant-like because they are all primary producers
They can photosynthesize

3. Seaweeds
A type of Algae
Play an important role in coastal environments
Use solar energy to produce organic matter for food webs
Organisms live on or in their tissues
Produce oxygen for organisms in the ocean and on land
Can Photosynthesize

4. 6.1 Multicellular Algae: The Seaweeds
The most familiar types of marine algae are seaweeds
They’re not weeds, so some biologists called them macrophytes or macroalgae
They are multicellular and eukaryotic
More complex structure and reproduction than unicellular algae
less complex than plants
Kingdom Protista

5. General Structure Don’t have roots, stems or leaves like plants
The body is known as the thallus
The leaf-like structures
are blades
Large, flat surface for photosynthesis

6. Gas-filled bladders called pneumatocysts keep it near the surface to get more sunlight
The stipe is like a stem; it provides support
The holdfast attaches the thallus (body) to the bottom
Cannot anchor in sand, needs a hard bottom
Water and nutrients are absorbed across the surface of the whole alga

7. Three types: green, brown & red
B. Types of Seaweeds
Three types:
green, brown & red
Turn paper to the back and make 3 columns labeled green, brown, and red

8. 1. Green Algae – -phylum Chlorophyta
LEAST COMPLEX!!!
Only 10% of 7,000 species are marine
Found in freshwater, terrestrial, and marine habitats
Simple thallus
Same pigments and food reserves as plants; thought to have evolved into land plants

9. Green Cont. Common on rocks in shallow water and tide pools
Different sea lettuce (genus Ulva) species are widespread; from polar to tropical waters
Halimeda is a calcareous green alga that has deposits of calcium carbonate in its thallus
As they die and accumulate they help build coral reefs

10. Green Seaweed (Algae)

11. Brown Algae – phylum Heterokontophyta, class Phaeophyta
Color varies from olive green to dark brown
Has more yellow- brown pigments, like fucoxanthin, than chlorophyll
Almost all 1,500 species are marine

12. Brown Algae Cont.
Dominant primary producers on temperate and polar rocky coasts
The largest and most complex seaweeds
Rockweeds (genus Fucus) is found on Atlantic and Pacific coasts of N. America

13. Brown Algae Cont.
In warm waters (Gulfs of Mexico and California) Sargasso weed (Sargassum) are found
Pneumatocysts keep the blades afloat
Some grow on rocks, some float offshore in huge masses
The Sargasso Sea gets name from it

14. Brown Cont.
The kelps are the largest and most complex of the brown algae
Most found below the tide level in temperate and sub- polar regions
Huge forests grow providing food and shelter for many organisms
Laminaria consists of a single large blade up to 10 ft long
¨ Harvested for food in several parts of the world

15. The blade of Alaria can be 80 ft. long
Bull kelp, Nereocystis, has a 90 ft. long stipe with a large
pneumatocysts and several blades at the top
Macrocystis is the largest of the kelp
¨ Massive holdfast is attached to hard bottoms
¨ Several long stipes and long blades
¨ A pneumatocysts at the base of each blade
¨ Have been found over 300 ft tall!
¨ Can grow 20 inches per day
Kelp beds or kelp forests are among

16. Kelp beds or kelp forests are among the most productive marine environments
¨ Found in the colder waters of the
North and South Pacific
¨ The tops are chopped off to harvest
food and several other natural products

17. Red Algae – phylum Rhodophyta
Almost all of the 4000 species are marine
More species than all green and brown combined
Have red pigments called phycobilins, which mask the green chlorophyll
Inhabit most shallow-water marine environments
Some are parasites of other seaweeds
Some have no chlorophyll and depend solely on their host

19. Red Algae Cont.
Can grow as dense clumps in upper tidal areas or long, flat branches in deeper
water
Coralline algae deposit calcium carbonate within their cell walls
Encrusting grows on rocks or branched (articulated) like a plant
Their secretions help form coral reefs by cementing it together

20. STOP WRITING ON CHART!! CONTINUE NOTES Seaweed Life Cycle
Seaweed produces in two ways:
Asexual (vegetative reproduction) is common and more important than sexual reproduction
Thallus fragments of Sargassum can grow into new individuals
Spores are resistant cells that can disperse to new locations
Zoospores have flagella for movement
In sexual reproduction gametes from different parents fuse to recombine the genetic information
Each generation shows genetic variation
Cells divide and multiply by mitosis; gametes are
formed by meiosis

21. During a seaweed’s life cycle they may exist as one of four different types
One type of thallus is a diploid sporophyte will
produce haploid spores
The spores divide and grow into another type of
thallus, a haploid gametophyte
The gametophyte produces haploid gametes
The gametes fuse to form a diploid zygote that
grows into a sporophyte
This type of life cycle is called alternation of generations
Sometimes the sporophyte looks just like the gametophyte, sometimes the gametophyte is much smaller

23. Economic Importance
People around the world harvest seaweed for many uses
Mostly as a food source
Also used for fertilizer, animal feed, and wound dressing
Mariculture, the farming of seaweed, is big business in China, Japan & Korea
Seaweeds produce gelatinous phycocolloids used in foods
They produce viscous gels

24. Algin
– used as a stabilizer and emulsifier in dairy products like ice cream & cheese
¨ It gives it a smooth texture
¨ Keeps frosting and pies from becoming dry
¨ Also found in shampoo, shaving cream, plastics, rubber, paper, paints, cosmetics, and pesticides
¨ The giant brown kelp, Macrocystis, is a major crop for algin
¨ Harvesting ships off the California coast cut stipes and fronds (blades) to a depth of six feet below the surface

25. Carrageenan – used as an emulsifier
¨ Obtained from red algae
¨ Gives body to dairy products and pudding
Agar – used for its ability to form jellies
¨ Protects ham, fish, and meats during canning
¨ Used in low-calorie foods, since it is not digestible by humans
¨ Used as a thickener, in laxatives, and in cosmetics
¨ Used by biologists to grow bacteria in Petri dishes

26. 6.2 Flowering Plants
Of the 250,000 species of plants only a few live in the ocean
They are more evolved than algae, and have true leaves, stems and roots with tissues to transport water and nutrients

27. Seagrasses Not really grass, evolved from land
plants (the lily family)
About 60 species
Live mostly submerged in shallow waters, such as bays and estuaries

28. B. Salt-Marsh Plants Cordgrasses are members of the grass family
Not marine, but can tolerate high salt areas (halophyte)
Salt marshes and coastal mudflats
Salt glands in the leaves excrete excess salt

29. Mangroves Adapted to life along tropical and subtropical shores
Land plants that can tolerate salt
Like muddy or sandy shores protected by waves
Include about 80 mostly unrelated species of trees and shrubs

30. Mangroves Cont.
Have adapted to an environment where salinity is high, water loss from leaves is high, and sediments are soft and poor in oxygen
Thick leaves reduce water loss
Seeds germinate while still attached to the parent
Foot-long seedlings fall and stick into the soft ground like a knife or float in the water to disperse to new locations