28
The Last Resource
in relatively large quantities. On the land, the soil acts as the mineral
storehouse for growing plants but in the marine world the sea itself
provides the vital soup of nutrients.
The most conspicuous marine plants are the tangles of seaweeds
which fringe rocky shores all over the world. But they are of little
importance in the food cycle of the sea when compared with the
much smaller plants, many of them no more than a single cell, which
drift in the surface waters—the phytoplankton. As long as the sun—
light continues to reach it, the phytoplankton ourishes—a cup
lled from the surface water would contain countless thousands of
these simple plants all of which belong to the group known as algae.
This group includes both large and small marine plants. However,
it is the microscopic algae such as diatoms with their curious silicon
cell walls which form the hub of life in the sea; they provide grazing
for countless small animals in the zooplankton zone—up
to 30 or 40
feet below the surface. The grazing members of the zooplankton
provide food for carnivorous ones which in turn are preyed upon by
other marine animals including some of the fish eaten by man. The
most important members of the zooplankton are the copepods.
Some 70 per cent of zooplankton consists of these small crusta—
ceans: they are the ‘insects’ of the sea and some sh feed almost
entirely on them.
This sequence of events by which energy is transferred from the
primary producer (the phytoplankton) to the herbivores and then to
carnivores is usually described as a food chain, but in nature such
a simple sequence is rarely if ever found. Instead ecologists talk in
terms of a web. Each linking point in its mesh is occupied by a single
or group of species all having in common the way they feed and the
way they are preyed upon by animals at a higher level. At each of
these points, energy ‘changes hands’ and in the process probably as
much as 90 per cent of it is lost. In other words 1,000 pounds of
plants will support 100 pounds of vegetarians which in turn will
support 10 pounds of carnivores—a yield of one per cent! Even this
is probably an optimistic gure.
Much remains to be learned about these fundamental equations
but, ultimately, the energy passing through the marine food web
depends upon the state of the phytoplankton. Anything which affects
the growth of marine plants causes repercussions throughout the
marine life dependent upon it. While the phytoplankton ourishes
all is well. Unfortunately the initial spring ‘owering’ of the
The Last Resource
in relatively large quantities. On the land, the soil acts as the mineral
storehouse for growing plants but in the marine world the sea itself
provides the vital soup of nutrients.
The most conspicuous marine plants are the tangles of seaweeds
which fringe rocky shores all over the world. But they are of little
importance in the food cycle of the sea when compared with the
much smaller plants, many of them no more than a single cell, which
drift in the surface waters—the phytoplankton. As long as the sun—
light continues to reach it, the phytoplankton ourishes—a cup
lled from the surface water would contain countless thousands of
these simple plants all of which belong to the group known as algae.
This group includes both large and small marine plants. However,
it is the microscopic algae such as diatoms with their curious silicon
cell walls which form the hub of life in the sea; they provide grazing
for countless small animals in the zooplankton zone—up
to 30 or 40
feet below the surface. The grazing members of the zooplankton
provide food for carnivorous ones which in turn are preyed upon by
other marine animals including some of the fish eaten by man. The
most important members of the zooplankton are the copepods.
Some 70 per cent of zooplankton consists of these small crusta—
ceans: they are the ‘insects’ of the sea and some sh feed almost
entirely on them.
This sequence of events by which energy is transferred from the
primary producer (the phytoplankton) to the herbivores and then to
carnivores is usually described as a food chain, but in nature such
a simple sequence is rarely if ever found. Instead ecologists talk in
terms of a web. Each linking point in its mesh is occupied by a single
or group of species all having in common the way they feed and the
way they are preyed upon by animals at a higher level. At each of
these points, energy ‘changes hands’ and in the process probably as
much as 90 per cent of it is lost. In other words 1,000 pounds of
plants will support 100 pounds of vegetarians which in turn will
support 10 pounds of carnivores—a yield of one per cent! Even this
is probably an optimistic gure.
Much remains to be learned about these fundamental equations
but, ultimately, the energy passing through the marine food web
depends upon the state of the phytoplankton. Anything which affects
the growth of marine plants causes repercussions throughout the
marine life dependent upon it. While the phytoplankton ourishes
all is well. Unfortunately the initial spring ‘owering’ of the