Giant Kelp (Macrocystis Integrifolia)
So What is Seaweed?
Seaweed is algae.
Algae, a group of structurally simple organisms that carry out oxygen-evolving
photosynthesis. Although most algae are microscopic, some as small as 1 to 2
micrometers in diameter (a micrometer is 0.000001 meter, or 0.00004 in), many
are conspicuous in the form of pond scum, seaweeds, red tide, blue-green discoloration
of aquarium walls, the green coating on trees, and red snow.
Macroscopic forms of algae are usually attached to a firm surface and grow abundantly
as seaweeds in intertidal and subtidal zones as deep as 268 m (879 ft), the
depth depending on light penetration. Macroscopic algae also grow on rocks in
flowing and standing fresh water, frequently becoming detached and floating
as pond scum. Microscopic forms of algae, which are mostly unicellular and planktonic
(free-floating or motile that is, capable of movement), are an essential
part of the food chain in all aquatic habitats.
Seaweed, any of the larger, multicellular forms of algae living in fresh
and salt water, especially along marine coastlines. The three main phyla, or
divisions, are the brown algae, such as the kelps; the red algae, such
as Irish moss; and the green algae, such as the sea lettuces, all of which are
commonly seen at low tide along rocky shores of northern seas. Seaweeds differ
from plants in that they lack the true stems, leaves, roots, and vascular systems
of higher plants. Instead, they anchor themselves to solid objects by holdfasts
and absorb nutrients directly from the water, manufacturing their food by photosynthesis.
The pigments of red and brown algae mask the predominant green photosynthetic
pigment, chlorophyll, and probably aid in photosynthetic metabolism by absorbing
and transferring light energy to the chlorophyll.
Seaweeds abound in shallow waters from the midtide line down to depths of 50
m (165 ft). Along damp cold-water shores, they are able to withstand several
hours of exposure to the sun, and they cover rocks high into the intertidal
zone. In the Tropics, seaweeds are confined to the zone between the low-tide
line and a depth of about 200 m (about 660 ft); red algae predominate, especially
in lagoons and around coral reefs.
Kelp, (Sea Spray is a Brown Algae / Giant Kelp)
common name for large, leafy brown algae, known as seaweed, that grow along
colder coastlines. The principal genera of kelp are the true kelps, found in
most cool seas, and the giant kelps and bladder kelps, both of which are restricted
to the northern Pacific. The giant kelps grow as long as 65 m (213 ft). The
kelp plant has a rootlike holdfast that fixes to rocky surfaces; a long, slender
stalk, or stipe; and long, leaflike blades that manufacture food by photosynthesis.
Kelps, like ferns, reproduce by alternation of generations.
Once a major source of iodine and soda, kelp is now used to manufacture algin
(alginic acid) which has wide industrial uses. It can be made into a silklike
thread or a plastic material, insoluble in water, that is used to make films,
gels, rubber, and linoleum, and as a colloid in cosmetics, car polishes, and
paints. Organic derivatives of alginates are used as food gums in making ice
cream, puddings, and processed cheeses. Brown algae have been used for centuries
as fertilizer and as an ingredient for livestock meal.