Abstract

In the whole world, estuaries are the seat of the same paradox: they are among the most productive ecosystems while being strongly impacted by anthropogenic activities. Different stressors of potential concern are reviewed. The triad of analyses (chemistry, bioassays, community structure) classically used for environmental assessment is described, taking into account the characteristics of estuaries, which complicate its application. Other tools are recommended, including the consideration of ecosystem functioning and the use of diverse biomarkers. The debate about the concept of reference, against which most of the indicators/indices selected to characterize the health status of estuaries must be compared, is then reported. Environmental quality standards and guidelines in water, sediment, or biota are reviewed. When they are exceeded, or when risk assessment shows a degradation of environmental quality, the restoration of degraded habitats and ecosystems must be addressed. However, it is a costly procedure, with effects delayed over decades; thus, implementing preventive risk assessment is a consummation devoutly to be wished.