Geography
of Chek Jawa
 Chek
Jawa is on Pulau Ubin, an island off mainland Singapore in the Straits
of Johor. Pulau Ubin lies at the mouth of the Johor River.
River of Life: The mighty Johor
River is one of the most important influences on Chek Jawa. The freshwater
and nutrients that flows from the river affects the plants and animals
of Chek Jawa.
Nutrients flowing down the Johor River play affect the food chains
of Chek Jawa. For example, the seasonal increase in nutrient flow
results in 'blooms' of seaweeds that can form thick, green carpets
on the shores of Chek Jawa. These seaweeds in turn provide food for
animals. The Johor River supplies lots of freshwater, so the waters
around Chek Jawa are less salty than that around places such as the
Southern Islands.
Too Fresh? The
lower salinity of waters around Chek Jawa affects the kind of living
things found there. In most places where Carpet
anemones are found, clownfish live among their tentacles. However,
clownfish are not found with Carpet anemones on Chek Jawa. It is believed
that this is because the water is not salty enough for these fishes
which typically inhabit coral reefs. Low salinity is probably also
why there are fewer living hard corals on Chek Jawa than around the
Southern Islands.
Currents of Life and Death: Currents moving along the shore
and waves that wash ashore on Chek Jawa can change its shape and structure.
Such changes affect the plants and animals that live there. These
currents cause the sand bar on Chek Jawa to shift constantly. These
shifts change the dimentions of the lagoon that forms behind the sand
bar. Plants and animals near the sand bar may get buried over time.
This is a natural process.
Currents may also change due to human activities nearby, such as land
reclamation. If the sand bar was completely washed away, the lagoon
would disappear.
A buried coral garden:
Chek Jawa was a coral reef thousands of years ago! About 5,000 years
ago, the sea level was 3m higher and coral reefs flourished where
the lagoon is today. Subsequently, sea level fell and became too shallow
for the corals. The coral garden died and was eventually buried by
sand brought in by the waves. The sand bar
formed along the outer edge of the old coral platform, seagrasses
grew on the now sandy lagoon bottom and mangroves
took root on the inner margin. Bits and pieces of the dead coral forms
the rich coral rubble area of Chek Jawa. |
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