This issue contains, as part of a focus on diatoms, some of the contributions presented at the 34th Symposium of the Association des Diatomistes de Langue Française (ADLaF) held in Bordeaux. This French-speaking society, funded in 1980, promotes diatom research and facilitates, through its annual symposium and its website (http:// adlaf.free.fr/), the exchange of information between diatom experts from diverse origins: academic research, water management and consultancy. In 2015, about 60 participants attended the ADLaF symposium, presenting a total of 38 communications (posters and lectures).