~---------------------------------------------~
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100:
I
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,
-'
,
,
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,
Laomedea loveni
/i
-- ------;,.J- 25
,
,
1
,
/1
/
60 :
- --------,'- 20
E
I
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o 1
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-------,--15 _\
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U 20 ~~: _____ ,k:.....-.....,,k:..:=::;===::::;f:::.===;l~-------. . . ~ 10 0'lt
/
/
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7.5
10
125
15
11.5
20
Temperature
Fig. 61. Experimental animals react differently to poisons, depending on the ecological conditions under which they have been kept. The diagram shows the cadmium concentration at which
half the number of polyps in a colony of hydroid polyps (Laomedea loveni) is reduced, after
7 experimental days (7 d LCso). At below 20 I1GJI, cadmium is most poisonous at high temperatures and low salinity (Theede et al. 1979b)
Table 25. Different populations of an animal species can
be immune to the poisonous effect of heavy metals to
different degrees. Depending on the geological formation
and mining activity in the vicinity, the sediment in the
estuaries of southwest England has a different heavy
metal content (see Fig. 67). As a measuring unit for the
sensitivity of the Nereis diversicolor polychaet vis-a-vis
copper and zinc, the concentration of poison is indicated at which half of the experimental animals died in
the course of a 4-day experiment (96 h LCso). Animals
from Restronguet Creek, which has a high heavy metal
content, are more resistant than animals from the Avon
Estuary which is not influenced by heavy metals (Bryan
1974)
Origin of the animals
Restronguet Creek
Avon Estuary
122
96 h LCso
Copper
Zinc
2.3 mg/l
0.5 mg/l
94 mg/l
5 mgtl