ABSTRACT
This book allows us to have a complete view of the state of the art in the field of tolerance to environmental contaminants, considering (1) the frequency of occurrence of this phenomenon in different taxa exposed to many classes of chemicals, (2) the mechanisms of defence and the acquisition of tolerance to chemical stress, and (3) the ecological and ecophysiological consequences of being tolerant. In this concluding chapter, the large body of knowledge presented earlier can be brought together to respond to a number of very important questions:
Does tolerance occur in all taxa exposed to any chemical contaminant in • their environment under chronic or subchronic exposure? How does tolerance work?• What are the main mechanisms involved in tolerance?• What are the efficiency limits of tolerance?•
17.1 Is Tolerance a Widespread Phenomenon? ..................................................... 410 17.2 How Does Tolerance Work? ......................................................................... 412
17.2.1 Tolerance at Different Levels of Biological Organisation ................ 412 17.2.2 Genetic Adaptation versus Physiological Acclimation ..................... 413
17.3 What Are the Main Mechanisms Involved in Tolerance? ............................ 415 17.4 What Are the Efficiency Limits of Tolerance? ............................................. 416
17.4.1 Interferences between Chemical Stress and Other Stressors ........... 416 17.4.2 Cotolerance ....................................................................................... 417 17.4.3 Saturation of Defence Mechanisms .................................................. 418
17.5 Consequences of Tolerance for Organisms and Their Environment ............ 419 17.5.1 Consequences at the Individual Level .............................................. 419 17.5.2 Consequences for Biodiversity and Ecosystem Functioning ............ 421 17.5.3 Human Health and Well-Being ......................................................... 421
17.6 Operational Consequences of Tolerance ......................................................424 17.6.1 The Role of Biomarkers in Assessing Environmental Quality ........424 17.6.2 Ecotoxicity Tests ............................................................................... 425 17.6.3 Safety Factors ................................................................................... 427 17.6.4 Concurrent Use of Sensitive and Tolerant Species ........................... 427
References .............................................................................................................. 429
What are the consequences of tolerance for organisms in their environment, • and for the assessment of environmental health and environmental quality using ecotoxicological tools?
