The European Water Framework Directive (WFD) requires the qualitative monitoring of water bodies that have been identified as requiring surveillance. To develop a new biological index based on lacustrine phytobenthos, a large-scale sampling and identification campaign of benthic diatoms was conducted on 93 French lakes from 2015 onwards.

The OFB's regional hydrobiology laboratories made a major contribution to this data collection by following an experimental method proposed by INRAE for the sampling part and the AFNOR NF T90-354 standard for the optical microscopy analysis part. Using the samples collected to draw up the floristic lists, a large number of photographic plates were produced to study the different diatom populations. Taxonomists from the Luxembourg Institute of Science and Technology and the Jardin Botanique de Meise contributed their expertise to the identifications and were able to supplement them with electron microscopy photographs.

The Atlas of diatoms in French water bodies, drawn up by OFB diatom experts, brings together in the form of taxonomic sheets the illustrations produced as part of this exceptional campaign, with the aim of providing assistance to operators responsible for implementing the Lake Diatom Biological Index (LDBI), which INRAE was able to establish in 2023 using the samples presented here.

Atlas of diatoms in French water bodies available here.