chapter  7
24 Pages

Tolerance in Organisms Chronically Exposed to Estuarine Pollution

The importance of the variability of sensitivity to stress has been documented in numerous taxa. In freshwater microorganisms, the relative sensitivity based on the inhibition of photosynthesis (IC50) has shown that cyanobacteria are sensitive to Cd, Cu, and Zn whereas Chlorophyceae tend to have high tolerance. Within each of these taxa, inter-specific differences of IC50 can reach one (Cd, Zn) to two (Cu) orders of magnitude (Takamura et al. 1989). Among diatoms exposed to PCBs, determination of the growth rate showed that Asterionella japonica was more resistant than

7.1 Metal-Resistant Bacteria in Estuarine Mudflats ........................................... 136 7.2 Photosynthetic Activity of Microphytobenthos Exposed to Chemicals

in the Field .................................................................................................... 138 7.3 Metal Tolerance of Worms Nereis diversicolor from Clean and

Contaminated Estuaries ................................................................................ 140 7.3.1 Comparative Toxicity Tests .............................................................. 141 7.3.2 Origin of Tolerance in Nereis diversicolor ....................................... 143 7.3.3 Limits of Tolerance ........................................................................... 144

7.4 Genetic Diversity in Nereis diversicolor Populations................................... 144 7.4.1 Ecological Context and Biological Specificity ................................. 145 7.4.2 Nonfunctional Genome..................................................................... 146 7.4.3 Functional Genome ........................................................................... 148

7.5 Conclusions ................................................................................................... 150 References .............................................................................................................. 152

Ditylum brightwellii or Thalassiosira nordenskioldii (Cosper et al. 1984, 1988). In invertebrates, it is generally accepted that inter-specific variability in tolerance is linked to very important variability in adaptive strategies (limiting the influx of contaminants, storage in detoxified physicochemical form, increased elimination) (Mason and Jenkins 1995).