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Whales
and Food Webs
A simple Antarctic food chain and the secret
of the success of the baleen whales - keep the chain short and transfer as much
energy as possible as efficiently as possible.
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Words
Plankton: organisms that live in the top layers
of water whether sea, lake, river, stream etc. Plankton are at the mercy
of the currents and movement of the water. Some plankton dwellers can
move about within the water column, up and down, but generally drift
where the tides and currents take them.
Phytoplankton: Phyto - plant, Plankton
- see above. These are the tiny plants that capture the energy of the
sun and turn it into food, these are the Producers of the Antarctic
food web.
Producer: Organism that produces food. Usually
a green plant, anything from a tree to microscopic algae. The raw materials
are sunlight for energy and carbon dioxide and water. Producers drive
all food webs and chains. At each step along the chain energy is lost,
usually around only 10% or much less is passed on.
Zooplankton; Zoo - animal, Plankton
- see above. These are the tiny (and not so tiny) animals that feed
directly on the phytoplankton
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Whales are the largest animals ever to have lived, larger even
than the largest dinosaurs. There are two reasons that they have managed to
attain such enormous size - well over a hundred tonnes for the largest blue whales
and nearing this amount for some other whale species.
 | 1/ They live in the oceans and so the buoyancy
of the water can support their great bulk without having to
be supported and moved on land by legs and muscles. Like most other
animals, the density of a whale is very close to that of water. |
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| 2/ They feed very close to the bottom of the
food chain. Energy for the vast majority of life on earth comes
in from the sun and is captured by plants. These plants are fed
on by animals, that are in turn fed on by other animals. At each
step of this food chain energy is lost and so less energy is available
to animals higher up the chain. |
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The consequence of this is that the higher up a food chain you
get, the lower the biomass of animals (that is number of animals multiplied by their
weight).
As whales tap the food chain low down - close to the producers,
relatively little energy is lost and so more is available to the whales, so they
are able to grow to enormous sizes.
Antarctic Ocean Food Web
The Antarctic Food Web is relatively simple compared to ecosystems
in other parts of the world. There are fewer different species, but greater
numbers of them. The second most numerous large mammal in the world (after man)
is the crab-eater seal, an archetypal Antarctic animal.
A key part of the Antarctic food web are
krill small shrimp-like crustaceans that the great majority
of Antarctic animals, seal, whales, penguins and other birds, fish etc. feed upon.
The
whaling gallery is a collection of images from a
whole range of sources. It is intended to inform
and illustrate a now (thankfully) vanished occupation and way of life that for the men
so engaged was hard and often
dangerous. It is intended for historical interest rather than a commentary on the ethics of whaling. |
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