Résumé
Distributions of arsenic species, iron and manganese were studied in the oxidizing and reducing waters of a small, well-stratified crater lake in the Massif Central Range (France). The concentrations versus depth of the arsenic species were found not to reflect the expected thermodynamic equilibria indicating that the response to redox conditions is slow and incomplete. Arsenic species were found to be transported on particulates and phytoplanktonic organisms.