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Bioassessment tools inform on environmental status

Bioassessment tools assess the status of an environment on the basis of its biological communities. The development of these techniques has required significant expansion of WFD partnership-research projects. In a natural environment, the status of the local biodiversity (both fauna and flora) provides an array of indications on the degree to which the ecosystem has been disturbed. In particular, it is possible to quantify the difference between the populations of a given group observed in situ (fish, invertebrates, algae, etc.) and those that would be found in a similar environment if the pressures did not exist. "That is the basic idea behind bioassessment tools", explains Yorick Reyjol from Onema. "The result has been the development of numerous tools to assess environments." Examples are the diatom biological index (IBD), which uses microscopic algae (diatoms) that are highly sensitive to the chemical quality of the environment, and the river fish index (IPR), which examines fish populations to determine the physical quality of rivers and aquatic habitats.


Diatomées
© Asconit Consultant

From sampling to pressure/status relations

The creation of bioassessment tools initially requires a significant amount of work in the field. Standardised sampling techniques (capture, identification and counting) must be carried out at a large number of monitoring points with different levels of degradation, plus a number of undisturbed control sites whose conditions define the "reference conditions". In parallel, work is done to collect data on pressures, both chemical and hydromorphological. "All the data are used to statistically determine the relations between anthropogenic pressures and the status of communities, and to identify the biological parameters offering the best response to a given pressure or set of pressures", notes Yorick Reyjol. This analysis work produces a set of calculation methods that can be used in fine to assign a score and an ecological status class to the assessed water body.

Key tools for the Water framework directive

Bioassessment tools have been used for many years in ecological research for all types of environments (terrestrial and aquatic), but have seen their use boosted by the WFD which has given them the "last word" in the ecological assessment of aquatic environments. European regulations now require that Member States develop several bioassessment tools, ranging from micro-algae to fish, for each type of water body (rivers, lakes, transitional waters, coastal waters). "The result has been a great R&D effort to adapt existing indices or, where necessary, to develop new tools", explains Yorick Reyjol.
In France, a large number of projects have been carried out since the founding of Onema, often in partnerships with research organisations such as Irstea and Ifremer, as well as with universities. Today, most of the tools required by the WFD are routinely used to assess water bodies in continental France and research efforts are continuing to provide the overseas territories with bioassessment tools suited to their specific environments where considerable biodiversity issues are at stake.


Perlidas, larve d’invertébré utilisée pour
l’évaluation biologique des cours d’eau
© Nicolas Poulet - Onema

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