Biological Quality Elements (BQE)

For the implementation of the Water Framework Directive, the assessment of ecological status of water bodies is based on biological indicators from several groups of organisms known as biological quality elements (BQE). For inland surface waters the BQE's are:

• Phytoplankton
• Macrophytes and phytobenthos
• Benthic Invertebrates
• Fish

The indicators may be related to the composition, abundance and diversity of species, as well as the presence or absence of some disturbance-sensitive species.

The evaluation of the status of the water bodies may be complemented with Hydromorphological Quality Elements (see next section) and/or physicochemical quality elements.

Each BQE is indicated below as a separate Category. Click on it to see the corresponding list of case studies.