94
Cadmium :
Cadmium is not an essential element for organism although , for
unknown reason , it enhances phytoplankton photosynthesis and growth
at concentrations up to 100 ppm.
Zooplankton in the surface layers of the ocean evidently have high
cadmium levels. Molluscs accumulate large
concentrations
of
cadmium.
There are no well-authenticated reports of cadmium contamination of
seafood causing lasting damage . High concentrations of cadmium
(173ppm) and zinc (57600ppm) in oysters caused nausea and vomiting
in people that consumed them , but there were no further effects.
Cooper :
Cooper is an essential element for animals , and the higher
concenttrations are found in decapod crustaceans , gastropods and
cephalopods.
Cooper does not generally accumulate in the food chain , despite the
existence of a number of detoxifying and storage systems for cooper , it
is the most toxic metal , after mercury and silver .
Lead :
Lead aerosols are carried to earth in rain and snow and are widely
scattered. The start of the industrial revolution marks the first major
increase
in the deposition rate ; the growth in the number of
automobiles using leaded petrol since 1940 is reflected in a second
marked acceleration in deposition rates.
Compared with other metals , lead in the sea is not particularly toxic ,
high concentrations of lead can be accumulated by some animals
without apparent harm .
(source : marine pollution.2001.p : 99,105,110,117)
Exercise : Fill in the gaps with the right words :
1- Metals in the marine environment are the result of either
………………..activities or …………………………processes .
Marine