Estuaries are invaluable ecosystems located along the coast where
rivers meet the sea. The-mixing of the freshwater from rivers with the salty
oceanic waters results in an average salinity lower than that of the open sea.
Together with the mixing of waters is the mixing of sediments from
the rivers and from the sea. These sediments are deposited at the mouths of
estuaries as mudflats. These flats can stretch along several kilometers of
coast, especially where a great number of freshwater streams empty into the sea.
This estuarine-mudflat ecosystem lies near the mangrove forest
ecosystem. Usually, there is a gradation from the muddy substrate covered by
mangroves to the bare intertidal zone made up of sandflats and mudflats.
The main food source in the estuarine-mudflat ecosystem is the
large quantity of organic material (detritus) coming from the mangrove forest
ecosystem and usually deposited with the sediments. Primary consumers, either
living on or burrowing in the mud, feed on these organic materials. Examples of
these are barnacles, mussels, oysters, polychaetes, oligochaetes, burrowing
molluscs and other zooplanktons. Attracted to these numerous and diverse
populations present in estuaries and mudflats are secondary consumers such as
shore birds, fish and invertebrate predators like crabs, some types of shrimps
and carnivorous marine worms.
Other ecological values
Serve as nursery and breeding grounds of
commercially important fish resources.
- Stabilize shoreline.
- Aid in the moderation of water quantity and the
purification of water.
Threats to the estuarine-mudflat ecosystem
Pollution - Estuaries
receive all the wastes carried from the land by rivers. The most dangerous of
these are the non-biodegradable chemical wastes like heavy metals and
pesticides, which can accumulate in the sediments and may enter the food web
through the large number of invertebrates. Organic pollutants in great
quantities from untreated sewage from human settlements and industrial
discharges may deplete oxygen in - the water. Hence, pollution may result in
less biodiversity due to death, impairment of reproductive capability and
weakened resistance against diseases.
- Reclamation/Conversion - Estuaries are strategic locations
for ports, industrial complexes, commercial establishments and human
settlements. Reclamation for these purposes and conversion of the
estuarinemudflat areas to aquaculture ponds, salt pens and farms will lead to a
loss of an ecosystem important as a productive transition zone between rivers,