1. Chapter 7 Multicellular Primary Producers

2. Primary producers – those organisms that photosynthesize
Previously, we talked about phytoplankton:
Cyanobacteria
We also talked about unicellular protists that are phytoplankton (for example: dinoflagellates, diatoms, etc)
Now we will talk about the macro algae (“seaweeds”) and marine plants

3. Multicellular Algae
Most primary production in marine ecosystems takes place by phytoplankton but seaweed and flowering plants contribute especially in coastal areas
Seaweeds are multicellular algae that inhabit the oceans
Major groups of marine macroalgae:
red algae (phylum Rhodophyta)
brown algae (phylum Phaeophyta)
green algae (phylum Chlorophyta)

4. Algae – not “plants”
Red algae
Green algae
Brown algae

5. Multicellular Algae
Scientists who study seaweeds and phytoplankton are called phycologists or algologists
Seaweeds contribute to the economy of coastal seas
Produce 3 dimensional structural habitat for other marine organisms
Consumed by an array of animals, e.g., sea urchins, snails, fish

6. Distribution of Seaweeds
Most species are benthic, attaching and growing on rock, sand, mud, corals and other hard substrata in the marine environment as part of the fouling community
Benthic seaweeds define the inner continental shelf, where they provide food and shelter to the community
compensation depth: the depth at which the daily or seasonal amount of light is sufficient for photosynthesis to supply algal metabolic needs without growth
Distribution is governed primarily by light and temperature

7. Figure 7-1b ZONATION OF SEAWEEDS

8. Structure of Seaweeds
Thallus: the seaweed body, usually composed of photosynthetic cells
when flattened, called a frond or blade
Holdfast: the structure attaching the thallus to a surface
Stipe: a stem-like region between the holdfast and blade of some seaweeds
Seaweeds are not plants
Lack vascular (conductive) tissue, roots, stems, leaves and flowers

9. Figure 7-2a VARIABLE SHAPES OF SEAWEEDS.

10. Figure 7-2c VARIABLE SHAPES OF SEAWEEDS.

11. Figure 7-2d VARIABLE SHAPES OF SEAWEEDS.

12. Biochemistry of Seaweeds
Composition of cell walls
Primarily cellulose, like plants
May be impregnated with calcium carbonate in calcareous algae
Many seaweeds secrete slimy mucilage (polymers of several sugars) 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

13. Green Algae
Diverse group of microbes and multicellular organisms that contain some pigments found in vascular land plants
Structure of green algae
Most are unicellular
Unicellular ones are part of the phytoplankton
There is a large diversity of forms among green algae
Multicellular ones are seaweed

14. Figure 7-4 (c) COENOCYTIC GREEN ALGAE.

15. Red Algae Primarily marine and mostly benthic
Highest diversity among seaweeds
Red color comes from special protein-pigment complex
Thalli can be many colors, yellow to black
Structure of red algae
Almost all are multicellular
Thallus may be blade-like or composed of branching filaments or heavily calcified (may be hard)

16. Red Algae
Annual red algae are seasonal food for sea urchins, fish, molluscs and crustaceans

17. Red Algae Ecological relationships of red algae
a few smaller species are:
epiphytes—organisms that grow on algae or plants
epizoics—organisms that grow on animals
red coralline algae precipitate calcium carbonate from water and aid in consolidation of coral reefs

18. Red Algae Human uses of red algae Ice cream yogurt
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

19. Brown Algae Familiar examples:
rockweeds
kelps
sargassum weed
99.7% of species are marine, mostly benthic (sargassum – not benthic)
Olive-brown color comes form a carotenoid pigment that masks the chlorophylls

20. Figure 7-8 KELP.

21. Figure 7-9 SARGASSUM WEED.

22. Brown Algae Distribution of brown algae
more diverse and abundant along the coastlines of high latitudes
most are temperate
sargassum weeds are tropical

23. Brown Algae Structure of brown algae
most species have thalli that are well differentiated into holdfast, stipe and blade
bladders—gas-filled structures found on larger blades of brown algae, and used to help buoy the blade and maximize light

24. Figure 7-10a DIVERSITY OF SHAPE IN THE BROWN ALGAE.

25. Figure 7-10 (b) DIVERSITY OF SHAPE IN THE BROWN ALGAE.

26. Brown Algae Brown algae as habitat
kelp forests house many marine animals
sargassum weeds of the Sragasso Sea form floating masses that provide a home for unique organisms
There are species of animals that have coevolved with the sargassum and blend in (sargassum fish, sargassum seahorse)
Human uses of brown algae
thickening agents are made from alginates
once used as an iodine source
used as food (especially in Asia)
used as cattle feed in some coastal countries

27. Now we will talk about the plants of the marine environments
Most terrestrial plants are not tolerant of the marine environment, not that many plants that grow successfully in the ocean when compared to land

28. Marine Flowering Plants
Seagrasses, Marsh Plants, Mangroves
General characteristics of marine flowering plants
vascular plants are distinguished by:
phloem: vessels that carry water, minerals, and nutrients
xylem: vessels that give structural support
seed plants reproduce using seeds, structures containing dormant embryos and nutrients surrounded by a protective outer layer

29. Marine Plants 2 types of seed bearing plants:
conifers (bear seeds in cones)
flowering plants (bear seeds in fruits)
all conifers are terrestrial
marine flowering plants are called halophytes, meaning they are salt-tolerant
Examples are sea grasses, mangroves, dune plants

30. Invasion of the Sea by Plants
Flowering plants evolved on land and then adapted to estuarine and marine environments
Flowering plants compete with seaweeds for light and with other benthic organisms for space

31. Seagrasses
Seagrasses are hydrophytes (generally live and flower beneath the water)
Classification includes:
Eelgrasses
Turtle grass
Manatee grass
Shoal grass

32. Seagrasses Structure of seagrasses
vegetative growth—growth by extension and branching of horizontal stems (rhizomes) from which vertical stems and leaves arise
3 basic parts: stems, roots and leaves

33. Seagrasses Ecological roles of seagrasses
highly productive on local sale
role of seagrasses in depositing and stabilizing sediments
blades act as baffles to reduce water velocity
decay of plant parts contributes organic matter
rhizomes and roots help stabilize the bottom
reduce turbidity—cloudiness of the water

34. Seagrasses (Ecological Roles)
role of seagrasses as habitat
create 3-dimensional space with greatly increased area on which other organisms can settle, hide, graze or crawl
rhizosphere—the system of roots and rhizomes also increases complexity in surrounding sediment
the young of many commercial species of fish and shellfish live in seagrass beds
human uses of seagrass
indirect – fisheries depend on coastal seagrass meadows
direct – extracted material used for food, medicine and industrial application

35. Salt Marsh Plants
Much less adapted to marine life than seagrasses; must be exposed to air by ebbing tide
Classification and distribution of salt marsh plants
salt marshes are well developed along the low slopes of river deltas and shores of lagoons and bays in temperate regions
salt marsh plants include:
cordgrasses (true grasses)
needlerushes
various shrubs and herbs, e.g., saltwort, glassworts

36. Figure 7-17 SALT MARSH

37. Figure 7-18 PLANTS OF THE SALT MARSH.

38. Salt Marsh Plants Structure of salt marsh plants
smooth cordgrass, initiates salt marsh formation, grows in tufts of vertical stems connected by rhizomes, dominates lower marsh
flowers are pollinated by the wind
seeds drop to sediment or are dispersed by water currents

39. Salt Marsh Plants
Adaptations of salt marsh plants to a saline environment
facultative halophytes—tolerate salty as well as fresh water
leaves covered by a thick cuticle to retard water loss
well-developed vascular tissues for efficient water transport
Spartina alterniflora have salt glands, secrete salt to outside
shrubs and herbs have succulent parts

40. Salt Marsh Plants Ecological roles of salt marsh plants
contribute heavily to detrital food chains
stabilize coastal sediments and prevent shoreline erosion
serve as refuge, feeding ground and nursery for other marine organisms
rhizomes of cordgrass help recycle phosphorus through transport from bottom sediments to leaves
remove excess nutrients from runoff
are consumed by (at least in part) by crabs and terrestrial animals (e.g. insects)

41. Mangroves Classification and distribution of mangroves red mangrove
black mangrove
white mangroves

42. Figure 7-20a MANGROVES.

43. Mangroves (Distribution)
thrive along tropical shores with limited wave action, low slope, high rates of sedimentation, and soils that are waterlogged, anoxic, and high in salts
low latitudes of the Caribbean Sea, Atlantic Ocean, Indian Ocean, and western and eastern Pacific Ocean
associated with saline lagoons and tropical/subtropical estuaries

44. Mangroves Structure of mangroves
trees with simple leaves, complex root systems
plant parts help tree conserve water, supply oxygen to roots and stabilize tree in shallow, soft sediment
roots: many are aerial (above ground) stilt roots of the red mangrove arise high on the trunk (prop roots) or from the underside of branches (drop roots)

47. Mangroves (Structure)
leaves
mangrove leaves are simple, oval, leathery and thick, succulent like marsh plants, never submerged
stomata: openings in the leaves for gas exchange and water loss
salt is eliminated through salt glands (black mangroves) or by concentrating salt in old leaves that shed

48. Mangroves Ecological roles of mangroves
root systems stabilize sediments
aerial roots aid deposition of particles in sediments
epiphytes live on aerial roots
canopy is a home for insects and birds
mangals are a nursery and refuge
mangrove leaves, fruit and propagules are consumed by animals
contribute to detrital food chains