1. Chapter 7: Multicellular Primary Producers

2. Most primary productivity done by phytoplankton

3. Multicellular Algae Seaweed (macroalgae) inhabit the oceans
Red, brown, and green in color
Phycologists/algologists study seaweeds and phytoplankton

4. Distribution of Seaweeds
Most are benthic
Grow on rocks, sand, mud, coral, and other organisms
Are parts of fouling communities
Plants and animals that live on pilings, bulkheads, boat hulls, moorings, and other artificial surfaces
Inhabit 2% of seafloor

5. Effects of temperature: Greatest diversity is at tropical waters
Effects of light:
Numbers vary by depth, latitude, sea conditions, and season
Red algae is at greatest depth
Green algae at shallowest depth
Brown algae is at intermediate depths
Effects of temperature:
Greatest diversity is at tropical waters
Decreases as you get farther north or south of the equator

6. Structure of Seaweeds Body is called the thallus
All but a few cells are photosynthetic
Lacks vascular tissue
No stems, roots, or leaves
Can occur in complex shapes
Holdfast attaches thallus to a surface
Stipe: stemlike region between holdfast and blade

7. Biochemistry of Seaweeds
Photosynthetic pigments
Due to wavelengths of light not absorbed by seaweed pigments
Chlorophyll absorbs blue and red wavelengths of light
Pass green light
Accessory pigments absorb different wavelengths of light
Pass energy to chlorophyll for photosynthesis
Can protect chlorophyll from damage by light

8. Cell wall composition Primarily cellulose
Many secrete a slimy gelatinous mucilage
Made of sugar polymers
Covers their cells
Can hold a great deal of water
Acts as protective covering to prevent desiccation
Can have a cuticle
Multilayered covering of protein

9. Food reserves
Excess sugars converted into polymers
Stored as starches
Unique sugars and alcohols can be used as antifreeze at high latitudes

10. Reproduction in Seaweeds
Asexual
Fragmentation: thallus breaks into pieces
Each new piece grows into new alga
Spore formation
Sexual
Fertilization of gametes to form a zygote (fertilized egg cell)

11. Green Algae (Chlorophyta)
Contain pigments like in vascular plants
Most are freshwater species
Seasonal sources of food for marine animals
Contribute to formation of coral reefs
Structure: unicellular or small multicellular filaments, tubes, or sheets

12. Response to herbivory:
Rapid growth and release of huge numbers of spores and zygotes prevent elimination of their populations by herbivores
Small size allows them to occupy crevices on rocky shores and reefs

13. Red Algae (Rhodophyta)
Primarily marine (98%)
Highest diversity among seaweeds
Mostly benthic
Are not always red

14. Almost all are multicellular Less than 1m long
Structure:
Almost all are multicellular
Less than 1m long
Thallus varies widely in shape and organization
Response to herbivory:
Food source for sea urchins, fish, mollusks, and crustaceans
Do not produce many toxins to deter herbivores
Can make thallus less edible
Can change growth patterns to make it more difficult to graze

15. Commercial uses:
Agar
Thickening agent in ice cream, pudding, and salad dressings
Source of food
Animal feed and fertilizer

16. Brown Algae (Phaeophyta)
Ex: rockweeds, kelp, sargassum weed
1500 species  marine
Range in size from microscopic and filamentous to giant
Distribution:
More diverse and abundant along coastlines of high latitudes
Less diverse in the tropics

17. Structure:
Well-defined thallus
Develop large, flat, leaflike blades
Gas-filled bladders
Help buoy the blade to get maximum sunlight exposure
Cell walls composed of cellulose

18. Habitat: found from low tide line to a depth of 10m
Commercial products:
Thickening agents in textile, dental, cosmetic, and food industries
Source of iodine
Used as food
Cattle feed

19. Marine Flowering Plants
General characteristics:
Presence of xylem (carries water) and phloem (carries nutrients)
Reproduce by seeds (protected by a fruit)
Roots, stems, and leaves

20. Invasion of the Sea by Plants
New source of habitat and food
Compete with seaweeds for light and other benthos for space
Bodies composed of polymers (cellulose, lignin) that most marine organisms cannot digest
Have few competitors

21. Seagrasses (Hydrophytes)
Live beneath the water
Only ones that are truly marine
60 species (0.02%)

22. Classification and distribution:
Not true grasses
Related to lilies and other freshwater plants
Inhabit temperate zones and higher latitudes
Others are tropical and subtropical

23. Structure:
Form from vegetative growth
Roots, stems, leaves
Aerenchyme
Gas-filled tissue
Provide buoyancy to leaves
Potential for invasion by pathogenic fungi

24. Reproduction:
Fragmentation, drifting, and plant re-rooting
Some do not flower
If they flower, they lack showy petals
Small and inconspicuous
Male or female
Hydrophilous pollination

25. Ecological roles:
Primary producers  food for herbivores
Depositing and stabilizing coastal sediments reduces turbidity
Beds provide habitats for many marine species

26. Salt Marsh Plants Less adapted to marine life
Must be exposed to air to flourish
Restricted to intertidal zone
Biological filter for terrestrial runoff on its way to the sea
Must tolerate higher sediment salinities

27. Classification and distribution:
Well developed along slopes of river deltas and shores of lagoons and bays
Distribution is limited at high and low latitudes

28. Structure:
Grows in tufts of vertical stems (culms) connected by rhizomes
Each vertical stem produces additional stems (tillers) at its base
Roots connected at culms
Plants stand as high as 3m
Well-drained nutrient-rich soils
Flowers pollinated by wind
Seeds drop to the sediment or are carried by water currents

29. Adaptations to a saline environment:
Facultative halophytes
Can tolerate salty and freshwater conditions
Tend to lose water to their environment by osmosis
Thick, water-retaining succulent parts

30. Ecological roles:
Detritus supplies nutrient needs for fish and shellfish
Shallow roots and rhizomes
Helps stabilize coastal sediments
Prevents shoreline erosion
Accumulate and stabilize sediments
Recycles phosphorous
Filter runoff from coastal areas
Removes toxic pollutants
Maintains water quality
Removes excess nutrients

31. Mangroves Trees and shrubs of tropical waters
Little is submerged by the tide

32. Classification and distribution:
54 species
Specialized roots that descend to or rise from the sediment
Thrive along protected tropical shores with limited wave action, low slope, high rates of sedimentation, and soils that are waterlogged, anoxic, and high in salts
Occur at low latitudes
Associated with saline lagoons
Found in tropical estuaries, islands, and atolls
Dominant vegetation in mangrove swamps or mangals

33. Leaves Structure: Roots
Adapted to grow in loose, shallow, anoxic, saline sediments
Many above ground (aerial)
Ability to prevent salts from entering the system from the sediment
Leaves
Simple, oval, leathery, and thick
Never submerged by flood tide
Salt glands can secrete a concentrated salt solution

34. Ecological roles:
Root systems stabilize sediments
Aerial roots aid deposition of particles
Canopy is host to many insects and birds
Nursery and refuge to many animals
Reproduction:
Simple flowers pollinated by wind or bees