Zonation
updated
Aug 08
Plants and
animals are NOT randomly distributed on our intertidal zone. Each
living thing is generally found in a place that best suits it. Thus
as you move from place to place on our shores, you may observe a
change in the kind of plants and animals that you see. More
about the intertidal.
Changes are quite obvious as you move further away from the shore
at low tide towards the water's edge. More about
tides.
If you visit at high tide or moderate low tides, the area may appear
bare. This is because few marine plants and animals can tolerate
being out of water for a long time. Parts of the shore that are
seldom covered in water thus have fewer plants and animals.
These zones of life are also obvious on a large boulder and on a
rocky shore. You can often see 'bands' of
particular kinds of animals or plants settling on such a boulder.
Immobile rock dwellers start life as free-swimming larvae. When
settling down, these larvae compete for the a good spot, e.g., one
that is less often exposed at low tide or is moist and shady. Each
kind of animal survives best in a spot where it does better than
its competitors. As a result, different kinds of animals are often
found in distinct zones on a rock. This happens, for example, with
barnacles.
At low tide, areas that are more often covered in water may be exposed
for a short time. Here, you might see a greater variety of plants
and animals. Some animals, in fact, function best during this window
of low tide. These include fiddler
crabs, sand
bubbler crabs and soldier
crabs. Other less hardy animals simply hunker down and wait
until the tide comes back in. Many hide under the sand, in holes
and crevices of rocks and coral rubble, or shelter in pools.
At very low spring tides, even more areas are exposed. These areas
are almost always covered with water and are thus richer in marine
life that do not tolerate being exposed out of water for long. Most
of the bigger and mobile animals would have moved into deeper waters.
But plants and immobile animals such as corals, sponges and large
sea anemones may be seen. In places where pools of water collect,
even more animals may be seen taking shelter.
The
spectrum of life: The different shore ecosystems are
found in different zones: such as mangroves, seagrasses, sandy shores,
rocky shores and corals reefs. The boundaries of each ecosystem
are not clearly marked. Overlaps occur as one ecosystem gradually
changes into adjoining ecosystems. The ecosystems impact one another
and a shore with many different ecosystems tends to be richer in
biodiversity.
Many marine creatures spend different parts of their lifecycle in
different ecosystems. For example, our favourite seafood such as
shrimps and fishes may grow up in the safety of mangroves or seagrasses,
before venturing out into the reefs as adults. They may return to
the 'nursery' of mangroves and seagrasses to lay their eggs.
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Zones are quite obvious on a rocky shore
with bands of different kinds of
plants and animals.
Different kinds of animals are found in
different niches where they do best.
Our favourite shrimps grow up in seagrasses
meadows before venturing out
as adults into other ecosystems. |
