Seaweed and Plants:
Multicellular
Primary Producers
Types of Algae Classes
• Chlorophyta = Green
• Phaeophyta = Brown
• Rhodophyta = Red
Seaweeds
• Seaweeds are another class of primary
producers.
• Techincally they are not weeds, but algae, and
sill eukaryotic.
• Most biologists agree that macrophyte is a
much better name.
• Some also call them macroalgae.
Seaweeds: Green algae
• Have the same pigments
as land plants (chlorophyll)
• More than 7,000 species
• Marine algae are “macro”
• Alteration of generations
Thalus
• Filamentus algae such as Ulva forms paper thin sheets.
• “Dead man’s fingers,” Codium fragile and several spp. of
Culerpa are know for there tube-like structures.
Padina (brown algae) with flat, calcified blades... advantage?
Phaeophyta
• Largest (size) and most complex of the algae
• Nearly all are marine (~1500 spp.)
• Brown color comes from accessory pigments
(fucoxanthin)
• Fucus sprialis a common brown algae can be found on
rocky shores. Unlike other algae in this category, its thallus
lacks gas bladders.
• Knotted rockweed, Ascophyllum nodosum, is common to
N. America and Europe.
Kelps!
• Kelps are the largest seaweed we encounter
in the ocean. They are also the most
complex.
• Due to this large size, many of the kelps are
harvested for food!
• Who knows where we will find seaweed
next?
Sea plam (Postelsia palmaeformis)
containsinternal support structures
that help them withstand wave
action!
It’s also eated on a regular basis as
“sea noodles.”
Macrocystis pyrifera, the largest of the kelps anchors itself to
the sea floor by use a massive holdfast. Here we can see not
only the large blades, but the extensive pneumatocysts used
for buoyancy.
Rem: Pneumatocysts
developed as a means
to maximize energy
production through
photosynthesis by
keeping the seaweed
close to the surface.
These kelp obtain huge proportions
growing as much as 0.5m/day!
These when large kelp group
together a kelp forest is develops.
Kelp forest are great for sheltering
all sorts of marine life, including
Garabaldi, scallops, seals and
sharks.
They also provide an opportunity for
selective harvesting of the upper
sections of the blades for food.
• Members of the species Rhodophyta
red algae, are more numerous than
the green and brown algae
combined (if we include aquatics).
• Although many red algae are in fact
red; due to the prescence of red
pigments known as phycobilins,
which mask chlorophyll, these algae
may display an even greater intensity
when exposed to sunlight!
Nearly 4,000 marine species exist and
many are used for food or other specialty
products.
Porphya, a “red” algae
Corallina, a coralline algae, deposits CaCO3 within its cell
walls which provides structural support and often
encrusting many surrounding surfaces.
Sexual Reproduction, or not…
• Sexual reproduction is expensive both
energetically and physiologically.
• Sometimes it’s better to reproduce by asexual
means from fragments, spores, or buds.
• Sometimes algae use both sexual and asexual
reproduction depending on environmental
conditions.
Products from Seaweed:
Phycocolloids—form gels and increase viscosity of liquids
Algin—stabilizer in ice cream (Macrocystis)
Carageenan—emulsifier (Irish Moss, Chondrus)
Agar—jellies (and of course all your plates in microbiology,
Gelidium, Pterocladiella)
Seagrasses (lillies) reproduce through rhizomes, or
horizontal stems which grow beneath the sediment.
Mangroves
Mangroves
• Mangroves thrive in salty environments
and are able to obtain freshwater from
saltwater.
• Some spp. secrete excess salt through
their leaves while other block absorption
of salt at their roots.
Magrove Impacts
• At one time, nearly 0.5 million acres of
magroves surrounded Florida’s coastal zone
contributing to ecosystem health in a variety
of ways.
-Trap and cycle organics, chemical elements, sediment
and minerals.
-Provide shelter for marine organisms.
Plate 9. Black Mangrove, Avecennia germinans.
Plate 8. Red Mangrove, Rhizophora mangle.
Red Mangrove
Plate 10. White Mangrove, Laguncularia racemosa.