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If connected to the sea, however , tidal water flows in and out of the
lagoon through its inlet, the amount and intensity of the flow depending
largely on the range of the local tide. The larger the tidal range , the
greater the exchange of water between the lagoon and the open ocean.
Lagoons are best characterised as calm,shallow bodies of water with
salinities that range between brackish and hypersaline ,depending on
the local hydrology and climate. They may be vegetated by sea grasses ,
seaweeds , mangrove , or salt-marsh plants or have edges and bottoms
that are barren .
Some lagoons are pristine ,fecund environments filled with
uncontaminated , clear blue water. This is particularly true
of the
lagoons that lie at the center of pacific atolls. Because many lagoons are
,however, located at the edge of continents and large populated islands
and have relatively sluggish circulation, their water is susceptible to
pollution. Some of the most fouled lagoons ,which are tucked behind a
system of barrier islands , occur along west Africa.
Originally these lagoon waters were biologically productive and
supported important local and commercial fisheries.today residents refer
to them as « biological graveyards » .
Little marine life lives in them ,because they have been used for decades
as convenient dumping sites for municipal and industrial waste.
( source : invitation to oceanography .2006. p :424,434)
Exercises : Exercise : read the following questions and choose the
right answer :
1-the words coast and shore have the same meaning :
a-True.
b-false.
2-the coast refers to : a-the juncture between land and water.
b-to a broader zone that consists of the land beside or near the sea and
the habitats and ecosystems that are affected by processes associated
with this unique setting between land and water.
3-an estuary is a coastal habitat : a- true.