81
Consequence of organic discharge to sea :
Organic waste , particularly sewage , may be discharged to sea aby
pipeline or dumped from barges at designated dump sites. Although
theses direct discharges have been much reduced or stopped in many
areas , organic industrial wastes discharged by pipeline and oily drill
cuttings dumped on the seabed at offshore oil platforms have similar
effects, which depend on the
hydrography of the area where the
discharge is made.
Sewage dumped in the sea has a direct effect on the benthic fauna ,
which is exposed to the sedimentation of particulate matter rich in
nutrients and bacteria . Smoothering by the particulate matter and
reduction of the oxygen concentration because of enhanced bacterial
activity excludes the most sensitive species , but the more toleratnt
species flourish because of the input of extra nutrients to the system.
The result is a reduction in diversity but an increase in the abundance
of organisms.
(source : marine pollution .2001. p : 17, 51)
Exercise : fill in the gaps with the right words
1- The environmental impact of substances discarded by humans in
oceans varies from …………………………to the other
and depends
also on ……………………………..of the efffluent .
2- The degree of ………………………to pollutants , ………………………….of
marine organisms determine the impact of pollution on marine
organisms that in extreme cases results in ……………….
3- Toxicity
states
……………………..to
which
something
is
…………………….and ……………………….required to kill an organism.
4- LT50 refers
to ………………………………is the time for death
for………………of organisms exposed to a toxin.
5- The lethal time depends on ………………………..of the toxin to which
an organism is subjected to and ………………………of the organism.