Download Red Algae

-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
-thallus: complete body
-blade: leaflike flattened portion
-pneumatocysts: gas-filled bladders
-stipe: stem-like structure
-holdfast: rootlike portion that attaches thallus to bottom
General Structure
Holdfast
-Green algae (PHYLUM CHLOROPHYTA)
-Brown algae (PHYLUM PHAEOPHYTA)
-Red algae (PHYLUM RHODOPHYTA)
CHLOROPHYTA
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)
Genera of Green Algae
 Enteromorpha
 Ulva
 Valonia
 Caulerpa
 Codium
 Halimeda
Enteromorpha
 Filamentous
 Thin thallus in the form of a hollow tube
Enteromorpha
Ulva
 Also called sea lettuce
 Paper-thin sheets
 Shape varies according to environmental factors
 Polar to tropical
Ulva
Valonia
 Large spheres or clusters of spheres
 Tropical and subtropical
Valonia
Caulerpa
 Tropical and subtropical
 Great variety of shapes
 Thin filaments or tubes (siphons) formed by a single
giant cell with many nuclei
Caulerpa
Codium
 “Dead man’s fingers”
 Multinucleated filaments woven into a branching
thallus
 Tropical to temperate
 Both coasts of North America
Codium
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
Halimeda
Coral Reef Seaweeds3 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
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
PHAEOPHYTA
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
Genera of Brown Algae
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Ectocarpus
Dictyota
Padina
Desmarestia
Fucus
Ascophyllum
Sargassum
Kelps (several genera: Laminaria, Agarum, Alaria,
Postelsia, Egregia, Eisenia, Nereocystis, Pelagophycus,
Macrocystis)
Ectocarpus
 Simplest brown algae
 Finely filamentous thallus
Ectocarpus
Dictyota
 Flat, branched thallus
 Tropical and subtropical
Dictyota
Padina
 Lightly calcified
 Fan-shaped
 Tropical and subtropical
Padina
Desmarestia
 Typically Antarctic, some species in temperate areas
Desmarestia
Ascophyllum
 Knotted seaweed
 Temperate Atlantic coasts
Ascophyllum
Fucus
 Rockweed, wracks
 Atlantic and Pacific Coasts
 North American and other temperate shores
Fucus
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
Sargassum
Sargasso Sea
Laminaria
Agarum
Alaria
Postelsia
Nereocystis
Pelagophycus
Macrocystis
Laminaria
 Single large blade, up to 3 m in length
 Blades harvested for food
 May have a split or branched blade
Laminaria
Agarum
 Conspicuous rib runs along the middle of a single
blade
Agarum
Alaria
 Like Agarum, with a conspicuous rib running down
the middle of a single blade
 Blades can be as long as 25 m
Alaria
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
Postelsia
Nereocystis
 Bull kelp
 Whip-like stipe up to 30 m
 Large, spherical pneumatocyst at upper end
Nereocystis
Pelagophycus
 Similar to the bull kelp in size
 Antler-like branches
Pelagophycus
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)
Macrocystis
RHODOPHYTA
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
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
Gelidium
Gracilaria
Endocladia
 Wiry clumps on rocky shores from Alaska to Southern
California
Endocladia
Gigartina
 Among the most massive red algae with blades as long
as 2 m
Gigartina
Porphyra
 Common on rocky shores above the lowest tide marks
from polar to tropical coasts
 Thallus with thin, large blades
Porphyra
Rhodymenia
 Common in the North Atlantic
 Blades may reach 1 m in length
Rhodymenia
Chondrus
 Irish moss
 Common in the North Atlantic
 Tolerates wide range of temperatures, salinity, and
light
 Shapes vary in response to above factors
Chondrus
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
Coralline Algae
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
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
Four types of reproduction
 Type 1 (sea lettuces and kelps)
 Type 2 (many red algae)
 Type 3 (rockweeds)
 Type 4 (some green algae)
Reproduction in sea lettuce
(Type 1)
 ***Most common***
 Involves 2 types of thalli (sporophyte & gametophyte)
 Sporophyte generation (2n) goes through meiosis and
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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
Reproduction in sea lettuce
(Type 1)
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
Reproduction in red algae (Type 2)
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
Reproduction in rockweeds
(Type 3)
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…
Reproduction in green algae
(Type 4)
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
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
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
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
Zostera
Surfgrass
 Unusual seagrass
 Inhabits rocky coasts exposed to wave action
 May become exposed at low tide
 Pacific coasts of North America
 Research seagrass beds
Surfgrass
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
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
Cordgrass
Pickle weed
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
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
Red Mangrove
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