1. Multicellular Primary Producers
Chapter 7
Multicellular Primary Producers

2. Plankton Phytoplankton – Plants Zooplankton – Animals
Most are microscopic
Can not swim against currents and waves
Meroplankton – Live part of their lives as plankton
Holoplankton – Remain plankton their entire lives

3. Multicellular Algae Major groups: Red algae (phylum Rhodophyta)
Brown algae (phylum Phaeophyta)
Green algae (phylum Chlorophyta)

4. Multicellular Algae Economy of coastal seas:
Produce 3 habitat for other marine organisms
Consumed by an array of animals

5. Distribution of Seaweeds
Most are Benthic:
Growing on rock, sand, mud, corals and other hard substrata
Distribution is governed by Light and Temperature

6. Distribution of Seaweeds
Effects of Temperature
Diversity greatest in Tropical waters
Many colder-water algae are perennials (living more than 2 years)
Only part of the alga survives colder seasons
Freezing and ice scouring can eliminate seaweeds in high latitudes
Intertidal algae can be killed if temperatures become too hot or cold

7. Structure of Seaweeds Thallus: Body
When flattened, called a frond or blade
Holdfast: Attaching the thallus to a surface
Stipe: A stem-like region between the holdfast and blade
Lack vascular tissue, roots, stems, leaves and flowers

8. Biochemistry of Seaweeds
Photosynthetic pigments
Chlorophylls absorb blue/red wavelengths of light
Accessory pigments absorb various colors

9. Biochemistry of Seaweeds
Cell walls
Primarily cellulose
Maybe with calcium carbonate
Many secrete slimy mucilage as a protective covering
Holds moisture, and may prevent desiccation
Can be sloughed off to remove organisms
Some have a protective cuticle - a multi-layered protein covering

10. Biochemistry of Seaweeds
Nature of food reserves
Unique sugars and alcohols may be used as antifreeze during cold weather

11. Reproduction in Seaweeds
Fragmentation: Asexual reproduction
Drift algae: huge accumulations of seaweeds formed by fragmentation, e.g., some sargassum weeds
Asexual reproduction through Spore formation

12. Reproduction in Seaweeds
Sexual reproduction
Alteration of generations: The possession of 2 or more separate multicellular stages in succession

13. Green Algae (Phylum: Chlorophyta)
Most are unicellular or small multicellular filaments, tubes or sheets
There is a large diversity of forms among green algae

14. Green Algae
Herbivory
Tolerance: Rapid growth and release of huge numbers of spores and zygotes
Avoidance: Small size allows them to occupy out-of-reach crevices
Deterrence:
Calcium carbonate deposits require herbivores with strong jaws and fill stomachs with non-nutrient minerals
Many produce repulsive toxins

15. Red Algae (Phylum: Rhodophyta)
Primarily marine and mostly benthic
Highest diversity among seaweeds
Red color comes from phycoerythrins
Thalli can be many colors, yellow to black
Structure - Almost all are multicellular

16. Red Algae
Seasonal food for sea urchins, fish, molluscs and crustaceans
Herbivory
Less edible by calcium carbonate
Avoiding by growing in crevices

17. Red Algae
Human uses
Phycocolloids are valued for stiffening properties
e.g. agar, carrageenan
Irish moss is eaten in a pudding
Porphyra are used in oriental cuisines
e.g. sushi, soups, seasonings
Cultivated for animal feed or fertilizer in parts of Asia

18. Brown Algae (Phylum: Phaeophyta)
Familiar examples:
Rockweeds
Kelps
Sargassum weed
99.7% of species are marine, mostly benthic (sargassum – not benthic)
Olive-brown color

19. Brown Algae Distribution
More diverse and abundant along the coastlines of high latitudes
Most are temperate
Sargassum weeds are tropical

20. Brown Algae
Structure
Most have thalli that are well differentiated into holdfast, stipe and blade
Bladders - gas-filled structures used to help buoy the blade and maximize light

21. Brown Algae Kelp house many marine animals
Habitat
Kelp house many marine animals
Sargassum weeds of the Sargasso Sea provide a home for unique organisms
Human uses:
Thickening agents
Once used as an iodine source
Food (especially in Asia)
Cattle feed in some coastal countries

22. Marine Flowering Plants
Seagrasses, Marsh Plants, Mangroves
Halophytes, meaning they are salt-tolerant

23. Seagrasses Generally beneath the water Structure
3 basic parts: stems, roots and leaves

24. Seagrasses (Structure)
Stems
Rhizomes—horizontal stems
usually lying in sand or mud
Vertical stems - grow upward toward the sediment surface
Roots
From nodes of stems and anchor plants
Usually bear root hairs
Absorb mineral nutrients

25. Seagrasses Reproduction
some use fragmentation, drifting and re-rooting and do not flower

26. Seagrasses Primary producers Depositing and stabilizing sediments
contribute to food webs through fragmentation and loss of leaves
Depositing and stabilizing sediments
blades reduce water velocity
decay of plant parts contributes organic matter
help stabilize the bottom
reduce turbidity—cloudiness of the water

27. Seagrasses (Ecological Roles)
Habitat
other organisms can settle, hide, graze or crawl
Nursery for commercial species of fish and shellfish
Human uses:
Indirect – fisheries
Direct – for food, medicine and industrial application

28. Salt Marsh Plants Must be exposed to air by ebbing tide
well developed along the low slopes of river deltas and shores of lagoons and bays in temperate regions

29. Salt Marsh Plants Structure flowers are pollinated by the wind
seeds drop to sediment or are dispersed by water currents

30. Salt Marsh Plants Adaptations
Facultative halophytes—tolerate salty as well as fresh water
Leaves covered by a thick cuticle to retard water loss
Well-developed vascular tissues
Spartina alterniflora have salt glands

31. Salt Marsh Plants Ecological roles of
Contribute to detrital food chains
Stabilize coastal sediments and prevent shoreline erosion
Serve as refuge, feeding ground and nursery
Remove excess nutrients from runoff
Consumed by crabs and terrestrial animals (e.g. insects)

32. Mangroves Classification Red mangrove (Rhizophora mangle)
Black mangrove (Avicennia germinans)
White mangroves and Buttonwood

33. Mangroves (Distribution)
Tropical shores with limited wave action, low slope, high rates of sedimentation, and soils that are waterlogged, anoxic, and high in salts

34. Mangroves Structure Trees with simple leaves, complex root systems
Roots: many are aerial (above ground)
Prop roots of the red mangrove arise high on the trunk

35. Mangroves (Structure)
Pneumatophores: grow out of sediments and into water or air
Act as ventilation system for black mangrove

36. Mangroves (Structure)
Leaves
Simple, oval, leathery and thick, succulent like marsh plants, never submerged
Salt is eliminated through salt glands (black mangroves) or by concentrating salt in old leaves that shed

37. Mangroves Reproduction Propagule: grows an elongated cigar-shaped stem
Falls from parent tree and may drift in currents for as long as 100 days

38. Mangroves Ecological roles Root systems stabilize sediments
Epiphytes live on aerial roots
Canopy is a home for insects and birds
Nursery and refuge
Mangrove leaves, fruit and propagules are consumed by animals
Contribute to detrital food chains