CHAPTER 6
Multicellular Primary Producers:
Seaweeds and Plants
BBC films
 http://www.youtube.com/watch?v=n45x2Ek-jAk

SEAWEEDS
 NOT
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PLANTS! (or weeds)
Eukaryotic
Multicellular algae
Primary producers
No roots, stems, leaves
Difference reproductive
mechanisms than plants
 More
accurately,
MACROPHYTES or
 MACROALGAE

SEAWEED STRUCTURE
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Thallus – the entire body
Blades – flattened, leaf-like
portion; large area for
photosynthesis (NOT leaves)
Pneumatocysts (floats) – gasfilled bladders (usually carbon
monoxide) that keep blades close
to surface
Stipe – stem-like structure used
for support; not used for transport
of water or nutrients
Holdfast – attaches the thallus to
the bottom (not used in transport)
Thallus – entire body
TYPES OF SEAWEEDS
TYPES OF SEAWEEDS

Classified based upon their pigments
Revealed upon chemical analysis
 Green (phylum Chlorophyta)
 Brown (phylum Heterokontophyta; Class Phaeophyta)
 Red (phylum Rhodophyta)

GREEN ALGAE - CHLOROPHYTA
Only 10% of species (around 700) are marine
 Most marine species are unicelluar
 More dominant in estuarine and tide pool areas

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Tolerate salinity variation
Land plants believed to have evolved from them
 Examples:
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Enteromorpha
Ulva
Caulerpa
Codium
Halimeda
ENTEROMORPHA
Filamentous
 Thallus is tube shaped.
 Common in bays, estuaries, exposed coastlines.
 Re-colonizers that can tolerate polluted areas

Photo: Enteromorpha prolifera – Elkhorm
Slough, CA by Judith Connor
Photo: Enteromorpha intertinalis -- Stillwater
Cove, Pebble Beach CA
ULVA
Sea lettuce
 Not a distinct genera from Enteromorpha
 Forms sheets but only in the presence of bacteria
or other algal species
 Widespread, first-colonizers on new substrate

© 2006 Jan Holmes
CAULERPA
Composed of multiple think tubes (siphons)
 Multinucleated
 Proliferative, especially in marine aquariums
 Tropical/subtropical

Caulerpa sp.
Caulerpa racemosa
CODIUM
“Multinucleated filaments woven into a spongy,
branching thallus”
 Eaten by sea slugs


Chloroplasts of the algae can remain alive inside
these animals
HALIMEDA
Calcareous green alga
 Play an important role in the build up of tropical
reefs.

BROWN ALGAE - PHAEOPHYTA
Almost all 1,500 species are marine
 Can dominate temperate and polar rocky coasts
 Vary in complexity (few celled to kelps)
 Color varies: olive green to dark brown
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Due to presence of yellow-brown pigment, fucoxanthin
Examples:
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Ectocarpus
Dictyota
Fucus
Sargassum
Laminaria
Nereocystis
Macrocystis
ECTOCARPUS
branching, filamentous
 May exist attached to substrate or free-floating
 widespread

DICTYOTA
Fan-shaped
 Lightly calcified
 Now widespread, but originally from Northeast
North America and Mediterranean.

FUCUS

Known as a ‘rockweed’ or ‘wracks’ along coastlines
Have gas-filled floats (pneumatocysts)
 Leathery thalli often covered with mucus to withstand
prolonged air exposure
 Strong disk-shaped holdfasts to endure intertidal zone

SARGASSUM
Have many gas-filled bladders
 Can grow on rocks or in huge floating masses
 Common in the Gulf of Mexico & Sargasso Sea
 Important for nursery and transport communities
 http://www.youtube.com/watch?v=np01gswinmI

LAMINARIA
Sea palms, feather boa kelps, etc.
 Up to 3m in length
 Single or small group of large blades attached to
a single stipe.
 Important food source

NEREOCYSTIS
Bull kelps
 Whip-like stipe that is up to 30m long
 Large spherical pneumatocyst at one end

MACROCYSTIS
Giant kelps
 Enormous holdfasts that anchor multiple stipes
 Elongate blades branch from stipes, each with a
gas-filled (CO) pneumatocyst
 Grow up to 100m (up to 20 cm/day)
 Form dense forests or ‘kelp beds’
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Among most productive marine ecosystems
Are harvested for several natural products
RED ALGAE - RHODOPHYTA
Most numerous (~4,000 species) in marine
environment
 Contain a red pigment (phycobilins)
 Harvested for food and other natural products
 Most are filamentous
 Some are heterotrophic and parasitic on other algae
 Examples:
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Ceramium
Chondrus
Nemalion
Porphyra
Corallina
CERAMIUM
Small, filamentous algae
 Epiphytic
 Produce chemicals that make them distasteful

CHONDRUS
Irish moss
 Ranges across the North Atlantic
 Shape varies with changes in temperature,
salinity, and light availability

NEMALION
Grows as a branched ‘worm’ on rocks in the
intertidal zone.
 Softly cartilaginous

PORPHYRA
Common on rocky shores
 Polar to tropical distribution

CORALLINA
Coralline algae
 Deposit calcium carbonate within their cell walls

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Can be an important reef building species in tropical
waters
Can grow branching or encrusting
LIFE HISTORY
Refers to the series of growth, metamorphoses,
and reproductive stages in an organism’s
generation.
 A little review:
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Sexual vs. asexual reproduction
Diploid vs. haploid
Gametes
Mitosis vs. Meiosis
What’s a spore?
ALGAL GENERATIONS
Sporophyte – diploid (2n) , spore producing
generation
 Gametophyte – haploid (n), gamete producing
generation
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Alternation of generations – life histories in which
two generations, a sporophyte and a
gametophyte, exist

Can take four basic patterns
LIFE HISTORIES OF VARIOUS SEAWEEDS
HALIMEDA LIFE HISTORY
Economic Importance of Seaweeds
Harvested for food (mariculture)
 Produce phycocolloids
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used in food processing & manufacturing as
thickeners or gels
Algin
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produced from giant kelp (Macrocystis) and bull
kelp (Laminaria)
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Stabilizer and emulsifier in dairy products
Prevents drying of frostings and toppings
Pharmaceuticals
Shampoo
Plastics
Pesticides
Used in textiles as a thickener for printing paste
SPHERICAL MANGO RAVIOLI
Algin
Blend the Citras with 250g of water, add the
and blend once more.
Bring to a boil, allow to cool and mix with the mango puree. Blend 1000g of water with Calcic.
Pour the contents of a dosing spoon full of the mango and Algin mixture into this
Calcic bath, leave for 2 minutes and wash in cold water. Repeat until all of the ravioli are made.
Carageenan

Produced from red algae such as Chondrus
Used as an emulsifier especially in dairy products,
soy milk, processed foods, and puddings
 Toothpastes and other beauty products
 Used in vaccines against HPV and other sexually
transmitted Link

Ingredients: skim milk, partially hydrogenated soybean oil, disodium phosphate,
carrageenan, Vitamin A Palmitate, and Vitamin D3
Agar
Extracted from several red algae including
(Gelidium, Gelidiella, and Pterocladiella)
 Uses:
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protect meats during canning
low-calorie (diet) foods
thickener
laxatives, cosmetics, and pharmaceuticals
as a medium for bacteria and mold growth
Sugar Coated Pills: Each sugar coated pill contains: sennosides USP 15 mg. Nonmedicinal
alginic acid
ingredients: acacia,
, calcium phosphate, carnauba wax, cellulose, iron
oxide, magnesium stearate, sodium benzoate, sodium lauryl sulfate, starch, stearic acid,
sucrose, talc and titanium dioxide. Blister packs, boxes of 10, 30 and 60.
FLOWERING PLANTS
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Have true leaves, stems, and roots
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Structures to transport water, nutrients, and food
Reproduce sexually with the production of spores in
flowers
 Three types of marine plants;

Seagrasses – completely submerged in seawater
 Salt-marsh plants – roots only covered at high tide
 Mangroves – trees and shrubs that live along shores, roots
adapted to salt

SALT MARSHES, MANGROVES
AND SEAGRASSES….OH MY!
MARSH METAPHORS
SALT-MARSH GRASSES
Cordgrasses are true members of the grass family
 Not marine species; land plants tolerant of salt –
cannot tolerate complete submergence in seawater
 Inhabit soft-bottom, coastal areas partially submerged
by sea water at high tide – leaves are always partially
exposed to air
 Salt glands in their leaves excrete excess salt

MANGROVES
Trees and shrubs adapted to live along tropical
shores
 Salty environment means water loss from leaves
is high and soil sediment is poor in oxygen

Leaves are thick to reduce water loss
 Seeds germinate while on parent tree and begin to
grow before falling to soft sediment

SEAGRASSES
o
o
o
o
o
Truly marine and spend their lives
entirely submerged by water
Not grass; more closely related to the
lily family
Horizontal stems call rhizomes that
grow under sediment; roots and shoots
grow from stem
Small flowers (no need to attract
pollinators)
Examples:
o Eelgrass – widely distributed in
temperate and tropical water;
inhabits shallow, well protected
coastal waters
o Surf grass – inhabit rocky coasts
exposed to heavy wave action
http://www.chesapeakebay.net/videos/clip/bay_grasses
DO WE HAVE SEAGRASS BEDS IN THE
CHESAPEAKE BAY?