1. Chapter 6 Multicellular Primary Producers: Seaweeds and Plants

2. Seaweeds -multicellular (a few exceptions), eukaryotes
-important source of food, habitat
-producers of oxygen for organisms on land and in oceans
-economic importance
-also called MACROPHYTES or MACROALGAE
-NOT PLANTS (Kingdom Protista)
-Lack true roots, stems, leaves

3. General Structure: -thallus: complete body
-blade: leaflike flattened portion
-pneumatocysts: gas-filled bladders
-stipe: stem-like structure
-holdfast: rootlike portion that attaches thallus to bottom

4. General Structure

5. Holdfast

6. 3 Major Divisions (Phyla):
-Green algae (PHYLUM CHLOROPHYTA)
-Brown algae (PHYLUM PHAEOPHYTA)
-Red algae (PHYLUM RHODOPHYTA)

7. Green Algae
CHLOROPHYTA

8. Green Algae Mostly freshwater and terrestrial environments
Also bays estuaries, rocky tide pools
Simpler thallus than red or brown algae
Pigments and food reserve (starch) same as land plants
Land plants evolved from green algae
Typically bright green (chlorophyll not masked by other pigments)

9. Genera of Green Algae Enteromorpha Ulva Valonia Caulerpa Codium
Halimeda

10. Enteromorpha
Filamentous
Thin thallus in the form of a hollow tube

11. Enteromorpha

12. Ulva Also called sea lettuce Paper-thin sheets
Shape varies according to environmental factors
Polar to tropical

13. Ulva

14. Valonia
Large spheres or clusters of spheres
Tropical and subtropical

15. Valonia

16. Caulerpa Tropical and subtropical Great variety of shapes
Thin filaments or tubes (siphons) formed by a single giant cell with many nuclei

17. Caulerpa

18. Codium “Dead man’s fingers”
Multinucleated filaments woven into a branching thallus
Tropical to temperate
Both coasts of North America

19. Codium

20. Halimeda Calcareous green alga
Numerous segments with deposits of CaCO3
Accumulation of dead, calcified segments plays an important role in the formation of coral reefs

21. Halimeda

22. Coral Reef Seaweeds- 3 major groups
Turf algae-small, filamentous, colonize vacant surfaces that cover non-living hard surfaces on the reef
Coralline algae-red algae; produce hard calcareous skeleton; hold reefs together
Macroalgae (larger in size)-together with coralline algae plays role in CaCO3 deposition

23. Coral Reef Seaweeds
Seaweeds not often regarded as components of healthy coral reefs
Reefs impacted by pollution are often overrun with seaweeds
Coral Reef Ecosystem Divison (CRED) of NOAA found that in central Pacific Ocean (subtropical northwestern Hawaiian islands), some healthy coral reefs are dominated by seaweeds rather than corals

24. Brown Algae
PHAEOPHYTA

25. Brown Algae Varies from olive green to dark brown
Contains yellow-brown pigments: FUCOXANTHIN (versus chlorophyll)
Usually temperate and rocky polar coasts
Largest & most complex seaweeds

26. Genera of Brown Algae Ectocarpus Dictyota Padina Desmarestia Fucus
Ascophyllum
Sargassum
Kelps (several genera: Laminaria, Agarum, Alaria, Postelsia, Egregia, Eisenia, Nereocystis, Pelagophycus, Macrocystis)

27. Ectocarpus
Simplest brown algae
Finely filamentous thallus

28. Ectocarpus

29. Dictyota
Flat, branched thallus
Tropical and subtropical

30. Dictyota

31. Padina
Lightly calcified
Fan-shaped
Tropical and subtropical

32. Padina

33. Desmarestia
Typically Antarctic, some species in temperate areas

34. Desmarestia

35. Ascophyllum
Knotted seaweed
Temperate Atlantic coasts

36. Ascophyllum

37. Fucus Rockweed, wracks Atlantic and Pacific Coasts
North American and other temperate shores

38. Fucus

39. Sargassum Warm waters, including Gulf of Mexico and CA
Sargasso Sea (in the Atlantic, north of West Indies)
Most species grow on rocks
2 species float offshore in huge masses

40. Sargassum

41. Sargasso Sea

42. Laminaria Agarum Alaria Postelsia Nereocystis Pelagophycus Macrocystis
Kelps
Laminaria
Agarum
Alaria
Postelsia
Nereocystis
Pelagophycus
Macrocystis

43. Laminaria Single large blade, up to 3 m in length
Blades harvested for food
May have a split or branched blade

44. Laminaria

45. Agarum
Conspicuous rib runs along the middle of a single blade

46. Agarum

47. Alaria
Like Agarum, with a conspicuous rib running down the middle of a single blade
Blades can be as long as 25 m

48. Alaria

49. Postelsia Known as sea palm because of its appearance
Grows on intertidal rocks with heavy wave action
Thick clusters from central California to British Columbia

50. Postelsia

51. Nereocystis Bull kelp Whip-like stipe up to 30 m
Large, spherical pneumatocyst at upper end

52. Nereocystis

53. Pelagophycus
Similar to the bull kelp in size
Antler-like branches

54. Pelagophycus

55. Macrocystis ***Largest of the kelps***
Massive holdfast attached to hard bottoms
Individuals as long as 100 m
Can grow 50 cm or more per day
Forms kelp beds or forest in the colder waters of the North and South Pacific
Forms some of the richest, most productive marine environments (research kelp communities)

56. Macrocystis

57. Red Algae
RHODOPHYTA

58. Red Algae
Largest group of seaweeds (more spp. than green and brown combined)
Simple structure, some are completely heterotrophic (parasites)
Most appear red; depends on exposure to light
phycobilins: red pigments

59. Gelidium, Gracilaria Found worldwide
Dense clumps common on upper levels of rocky shores exposed at low tide
Longer and flatter branches in areas less exposed to air and in deeper water

60. Gelidium

61. Gracilaria

62. Endocladia
Wiry clumps on rocky shores from Alaska to Southern California

63. Endocladia

64. Gigartina
Among the most massive red algae with blades as long as 2 m

65. Gigartina

66. Porphyra
Common on rocky shores above the lowest tide marks from polar to tropical coasts
Thallus with thin, large blades

67. Porphyra

68. Rhodymenia
Common in the North Atlantic
Blades may reach 1 m in length

69. Rhodymenia

70. Chondrus Irish moss Common in the North Atlantic
Tolerates wide range of temperatures, salinity, and light
Shapes vary in response to above factors

71. Chondrus

72. Coralline Algae Red algae that deposit CaCO3 within their cell walls
Calcified thallus takes a variety of shapes
Color of live coralline algae is reddish-pink
Dead coralline algae is white
Warm-water coralline algae involved in formation and development of coral reefs
Some in temperate and polar waters

73. Coralline Algae

74. Life History in Seaweeds
Is both asexual (a.k.a. vegetative) and sexual
Asexual: a piece of thallus can grow into a new individual (e.g. Sargassum)
Alternation of generations:
sexual stage alternates with an asexual one
gametophyte alternates with a sporophyte

75. Types of cell division:
Mitosis:
resulting cells are identical to original
chromosomes in pairs (diploid or 2n)
e.g. somatic cells
Meiosis:
resulting cells are haploid (n)
gametes contain half the number of parent’s chromosomes

76. Four types of reproduction
Type 1 (sea lettuces and kelps)
Type 2 (many red algae)
Type 3 (rockweeds)
Type 4 (some green algae)

77. Reproduction in sea lettuce (Type 1)
***Most common***
Involves 2 types of thalli (sporophyte & gametophyte)
Sporophyte generation (2n) goes through meiosis and makes haploid (n) spores
Spores divide and develop into second kind of thallus, a haploid (n) gametophyte generation
Gametophytes produce haploid gametes which unite to produce a diploid zygote
Sometimes separate male and female thalli
Sometimes male and female gametes produced in one thallus

78. Reproduction in sea lettuce (Type 1)

79. Reproduction in red algae (Type 2)
Unique to red algae
Similar to type 1, but involves a 3rd generation called carposporophyte (2n) from fusion of gametes
Carpospores are diploid spores produced by the carposporophyte which develop into sporophytes

80. Reproduction in red algae (Type 2)

81. Reproduction in rockweeds (Type 3)
Easiest to understand
Similar to reproduction in animals
NO ALTERNATION OF GENERATIONS
One thallus (2n)
Thallus produces haploid gametes by meiosis
After fertilization, zygote develops into a new diploid thallus

82. Reproduction in rockweeds (Type 3)

83. Reproduction in green algae (Type 4)
Dominant thallus is haploid and produces haploid gametes
On fertilization, gametes form a diploid zygote
Meiosis takes place in the zygote, resulting in haploid spores
Each spore develops into a haploid individual and it begins again…

84. Reproduction in green algae (Type 4)

85. Economic Importance mariculture: China, Japan, Korea
fertilizer, food additives
phycocolloids: gelatinous chemicals, used in food processing, suspensions & gels
algin: stabilizer/emulsifier in diary products
carageenan: from red algae (Irish moss/Chondrus), used as emulsifier (pudding, dairy products)
agar: used to form jellies, to protect meats in canning, as thickener, pharmaceuticals, cosmetics

86. Flowering Plants (angiosperms):
Dominant plants on land, few are marine
True leaves, stems, roots
Xylem and phloem to transport water, nutrients, food from photosynthesis
Grouped in Kingdom Plantae
Reproduction involves a dominant sporophyte with a flower as the reproductive organ

87. Seagrasses: not true grasses, closest relatives are lilies
horizontal stems (rhizomes) that grow beneath sediment
flowers are small, pollen carried by water currents
seeds dispersed by water currents, in feces of fish and other animals (!)
eelgrass (Zostera) is most widely distributed of the 60 known species of seagrass

88. Zostera Temperate and tropical regions
Shallow, well-protected coastal waters (bays, estuaries)
Flat, ribbon-like leaves
Common in oxygen-poor sediments
Zostera beds are highly productive and provide food to variety of animals

89. Zostera

90. Surfgrass Unusual seagrass
Inhabits rocky coasts exposed to wave action
May become exposed at low tide
Pacific coasts of North America
Research seagrass beds

91. Surfgrass

92. Salt-Marsh Plants: Cordgrasses are true members of grass family
Not marine species
Land plants tolerant of salt
Do not tolerate total submergence by seawater
Live in salt-marshes and soft-bottom coastal areas
Temperate regions
Habitat and breeding grounds for fish
Erosion control, natural water purification

93. Salt-Marsh Plants Leaves are always partly exposed to air
Salt glands in leaves excrete excess salt
Halophytes= salt-tolerant plants
Pickle weed (Salicornia) is another example

94. Cordgrass

95. Pickle weed

96. Mangroves:
Trees and shrubs adapted to live along tropical and subtropical shores around the world
Land plants that can tolerate salt
Muddy or sandy shores protected from waves
Include up to 80 different species of flowering plants

97. Red Mangroves
Red mangroves (tropics and subtropics)—extreme northern and southern limits of red mangrove are areas where killing frosts begin
Salt marshes replace red mangroves in areas exposed to frost

98. Red Mangrove

99. Red Mangrove Leaves are thick to reduce water loss
Seeds germinate while still attached to parent tree
Develop into seedlings as long as 30 cm before falling from the parent
Seedlings stick in muddy sediment or float in the water to new locations