1. The term biomarker refers to the physiological, biochemical, and histological changes used as indicators of exposure to chemical contaminants and/or of its effects at the suborganismal or organismal level. Recently the development of sensitive biochemical markers for monitoring environmental quality in aquatic ecosystems has raised a great deal of interest.
2. Selected biochemical markers measured in feral organisms can provide sensitive indexes, or early warning signals, of potential ecosystem degradation caused by contaminants. Compared with chemical residue analysis, biomarkers have the advantage of measuring the stress on the organism, thus being more biologically relevant.
3. Some of the most frequently used biomarkers in aquatic biomonitoring in different countries are briefly described.
4. The use of cholinesterase activity as a biomarker of pesticide exposure for biomonitoring in estuarine areas is also given as an example. Copyright © 2001 John Wiley & Sons, Ltd.