Charles-Henri Delogne (1834-1901) was a Belgian naturalist and diatomist who amassed a collection of several hundreds of sam-ples from the region around Brussels and the Semois Valley in southern Belgium. Several of his samples were used by famous diatomists such as Albert Grunow and Henri Van Heurck, who described a considerable number of new species from this mate-rial, such as Cymbella subaequalis Grunow (now in the genus Cymbopleura), Fragilaria brevistriata, transferred to the genus Pseudostaurosira, and Nitzschia palea var. tenuirostris Grunow in Van Heurck, now known by its new name N. saprobionta (Van de Vijver & de Zwart 2023), although the taxon was long consid-ered a synonym of N. capitellata Hustedt.
Probably more important than these samples used to describe new species, Delogne gathered from 1876 to 1878 a collection of more than 700 samples from various water bodies (fountains, ba-sins, lakes, natural pools, ponds) in the Brussels area. These sam-ples provide a magnificent overview of the Brussels diatom flora at that time in the suburbs of Brussels (Saint-Josse, Laeken, Uccle), before the complete urbanisation of the current city of Brussels. Most of these samples represent large collections of sed-iment or algal material and can still be used to prepare new slides for a thorough analysis using both light (LM) and scanning elec-tron microscopy (SEM) observations.
In this presentation, we will present Delogne's material, his dia-toms, and the water quality we were able to calculate from the diatom community counts. Most of the samples studied were dominated by mesotrophic, or even more often eutrophic, taxa, such as Nitzschia palea, Gomphonema parvulum, and Melosira varians. These diatom compositions are reflected in the calcu-lated water quality indices.
In addition to the historical samples, several new samples were collected from locations where Delogne also sampled, such as the Fontaine des Naïades in the old Jardin Brus-sels Botany or the Sainte-Anne spring in Laeken.