Transcript Chap06

Chapter 6
Multi-cellular
Primary Producers:
Seaweeds and
Plants
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Seaweeds
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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)
Seaweed Morphology
[Insert Fig. 6.1 of 10th ed. here]
Seaweeds
• Sexual reproduction by many seaweeds
involve complex life cycles often consisting
of different generations (see Fig. 6.11).
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
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
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.
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.
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)
Coralline alga (Corallina)
[Insert Fig. 6.10 of
the 10th ed. here]
Seaweeds
• Some seaweeds are commercially important
• Algin, obtained from kelps, is used as a
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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.
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.
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.
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.
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
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)
Marine Flowering Plants
• Seeds of mangroves germinate while still
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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.
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.
Most Important Characteristics
of Seaweeds and Marine Plants
[Insert Table 6.1 of
10th ed. here]