In situ measurements of pH, temperature and dissolved oxygen were taken at different depths of lake Carheil and other lakes located upstream (lakes Sans Nom, Daviault and Perchard) using a YSI instrument. Water samples for total phosphorus analyzes were also collected at the surface of the lakes. Sediment cores were retrieved using percussion and gravity corers and long cores (30-55 cm length) were split in two. One half was subsampled at 0.5 cm intervals while the other one was analyzed using an ITRAX core scanner in order to determine its content in several chemical elements. Subsampled sediment samples were freeze-dried and loss-on-ignition analyzes were performed to examine their water and organic matter content. Diatom solutions were prepared using hydrochloric acid (HCl) and a mixture of sulphuric (H2SO4) and nitric (HNO3) acids to respectively remove carbonates and digest organic matter from the samples. They were dried onto glass coverslips and then mounted onto microscopic slides. About 300 valves per sample are currently being identified and enumerated along random transects using an optical microscope. Identification is carried out to the finest taxonomic level possible at a 1000x magnification. Grain-size and pigment analysis should also be eventually performed on the samples.