1. Multi-cellular Primary Producers: Seaweeds and Plants
Chapter 6
Multi-cellular Primary Producers: Seaweeds and Plants
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2. Seaweeds Important primary producers
Often called marine algae or macroalgae
Eukaryotic, mostly multicellular
Lack leaves, stem, and roots of plants:
Thallus – body of seaweed
Blades – leaf-like structures
Stipes – stem-like structures
Holdfast – root-like structures
(these structures lack the conducting tissues [“veins”] of plants)

3. Seaweed Morphology
[Insert Fig. 6.1 of 10th ed. here]

4. Seaweeds
Sexual reproduction by many seaweeds involve complex life cycles often consisting of different generations (see Fig. 6.11).

5. Types of Seaweeds Green Seaweeds (Green Algae)
About 7,000 species, mostly marine
Microscopic to macroscopic
Photosynthetic pigments: chlorophylls a and b as well as carotenoids (same as in true plants)
Store excess energy as starch (as in plants)
Cellulose in cell walls (as in plants)
Calcareous green algae – thallus with calcium carbonate

6. Types of Seaweeds Brown Seaweeds (Brown Algae)
About 1,500 species, almost all marine
Some microscopic, most larger (up to more than 100 m [300 ft.])
Prefer shallow, cold waters
Contain chlorophyll a, c, and fucoxanthin (brown photosynthetic pigment)
Examples: kelps, rockweeds (Fucus), Sargassum

7. Brown Seaweeds (Brown Algae)
Kelps: found in temperate and polar locations; the largest of the seaweeds
In some species, like the giant kelp, each individual can be hundreds of feet in length
Kelp forests (discussed in Ch. 13) are among the most productive (and richest) marine communities.
High biodiversity of organisms associated with kelp forests.

9. Brown Seaweeds (Brown Algae)
Sargassum is a brown seaweed that forms massive floating mats in the Sargasso Sea, a section of the Atlantic Ocean north of the West Indies.

10. Red Seaweeds (Red Algae)
About 4,000 species, almost all marine
Contain chlorophyll a, phycobilins, and other red photosynthetic pigments
Most species are found in warm or cold shallow water, but some can be found in relatively deep water
Coralline algae – thallus accumulate calcium carbonate (Ex: Corallina)

11. Coralline alga (Corallina)
[Insert Fig of the 10th ed. here]

12. Seaweeds Some seaweeds are commercially important
Algin, obtained from kelps, is used as a emulsifier in many food items and in the making of many products.
Carrageenan, harvested from red seaweeds, is used as a thickening agent in dairy products such as yogurt and milkshakes.
Agar from red seaweeds is used to culture microorganisms in the healthcare industry, as a thickener in foods, filler in pharmaceuticals and cosmetics and to protect canned meats.

13. Marine Flowering Plants
Flowering plants, or angiosperms, are true plants, all having true leaves, stems, roots, and conducting tissues.
Over 250,000 species exist worldwide, but only a few are truly marine.
Must be adapted to live in seawater.

14. Marine Flowering Plants
Seagrasses
About 60 species in mostly tropical waters; some are temperate in distribution
Flowers are small and inconspicuous in most species.
Pollen (containing sperm) is carried by water currents.
Tiny seeds, the result of fertilization. are also carried by water currents or in the feces of animals that consume the seagrasses.

15. Marine Flowering Plants
Seagrasses
Seagrasses form highly productive seagrass meadows, or beds, that provide a habitat to many organisms that hide among the leaves
Eelgrass (Zostera) is the most widely distributed of the seagrasses, common in shallow water in temperate waters around the world
The significance of seagrass meadows in the marine environment is discussed in more detail in Chapter 13.

17. Marine Flowering Plants
Salt-Marsh Plants - plants bordering shallow bays and estuaries at the mouth of rivers.
Cordgrass (Spartina) is the dominant salt-marsh plant in many salt marshes.
Exposed to saltwater at high tide; salt glands help deal with excess salt.
Important as habitat to many marine animals including juvenile invertebrates and fishes.
Detritus from cordgrass is a nutrient for countless organisms.
Other halophytes (salt-tolerant plants) grow in areas of higher elevation than cordgrass.
The ecological significance of salt marshes and the impact of humans are discussed in more detail in Chapter 12

18. Marine Flowering Plants
Mangroves
About 80 species of mangroves live only in tropical and subtropical areas of the world.
They cannot withstand freezing temperatures.
Only tolerate partial salt water submergence.
Many mangroves have prop roots that are exposed at low tide (see Fig. 6.16)

19. Marine Flowering Plants
Seeds of mangroves germinate while still attached to the parent plant and develop into seedlings before falling into the water.
Seedlings drop into nearby soft sediments or are carried by water currents to new locations.

20. Marine Flowering Plants
Mangrove forests, or mangals, are highly productive communities that provide habitat to many marine and land organisms
Tropical equivalent of salt marshes.

21. Most Important Characteristics of Seaweeds and Marine Plants
[Insert Table 6.1 of 10th ed. here]