5
Excessive nutrient inputs
into a water body induce biological,
chemical and physical
changes in aquatic plant and animal
communities, often leading
to oxygen depletion, especially
in deeper waters.
Greenish, murky water is
typically the first sign of eutrophication
as microscopic plants and
algae grow profusely, consuming the
surplus nutrients. But
algae are short-lived, and when they die
they sink to the bottom of
the sea, where their decomposition
uses up oxygen.
The worst affected areas
can become completely anoxic. In the
absence of oxygen,
decomposition can release toxic hydrogen
sulphide, poisoning organisms and
making the sea-bed lifeless.