Food web background (taken from Castro, pg. 204-205)
"The flow of energy and matter through an ecosystem can be traced
by observing the food, or trophic, relationships among its organisms:
who makes the food and who eats it. The organisms can be divided
into two broad components: primary producers, the autotrophs that
make the food, and consumers, the heterotrophs that eat it. Not
all consumers feed directly on producers. Many animals eat other
animals rather than primary producers. Thus, the transfer of energy
through the system usually takes place in several steps known as
a food chain. Each of the steps in the food chain is known as a
Most ecosystems have a number of different primary producers. Furthermore,
many animals eat more than just one kind of food, and many change
their diet as they get older and larger. For these reasons, trophic
structure is usually a complex, interwoven food web instead of a
simple, straight-line food chain. Such food webs are often difficult
for biologists to unravel and understand, but their complexity is
one reason for the tremendous diversity of life." (additional material
can be found in Castro, pg. 205-212)
(taken from http://seawifs.gsfc.nasa.gov/OCEAN_PLANET/HTML/education_lesson1.html)
Although fish and other seafood products make delicious, healthy
meals for people all over the world, many American children would
not mind if they never had to eat tuna casserole again. But they
would mind if suddenly there were no more cheese and chocolate milk,
peanut butter and pudding, frozen desserts and fruit drinks. What
could such different foods have in common? Along with hundreds of
other common foods and household items, they contain the aquatic
autotroph known as seaweed.
Many kinds of seaweed are edible and rich in vitamins and iodine.
They are as common in many Asian countries as green beans and carrots
are in the United States. But until more people here develop a taste
for sea vegetables, it is alginates, carrageenan, and beta carotene
-- seaweed derivatives that act as stabilizers, thickeners, and
colorants -- that end up on our dining room tables.
Seaweeds are not really weeds but large forms of marine algae that
grow in the coastal ocean waters of many countries. They include
thousands of species ranging from microscopic algaes called phytoplankton
to giant floating or anchored varieties.
The three main groups of seaweed are brown, red, and green algae,
each providing important ingredients for the manufacture of food
and other products. Carrageenan is a generic term for compounds
extracted from species of red algae. Carrageenans are used in stabilizing
and gelling foods, cosmetics, pharmaceuticals, and industrial products.
From brown algae come alginates. They make water-based products
thicker, creamier, and more stable over extreme differences in temperature,
pH, and time. For example, alginates prevent ice crystals from forming
in ice cream. Beta Carotene, a natural pigment derived from green
algae, is used as a yellow-orange food coloring and may help prevent
certain types of cancers.
These seaweed derivatives represent only a small part of the many
living and nonliving products we derive from ocean algaes, animals,
minerals, and sea water. Together, they provide an important reason
to protect the oceans."