this thesis investigates freshwater lake classification in northwestern ontario, canada. the research is based on a case study of cloud lake, 40km south of thunder bay ontario, canada. complaints of decreasing water quality brought attention to the need for a detailed assessment of the current conditions on cloud lake. the purpose of this thesis was to determine cloud lake’s present trophic state based on two currently implemented trophic state indexing (tsi) methods, (carlson’s tsi, and the ontario ministry of the environment and climate changes). this thesis provides biological, chemical, and physical evidence that cloud lake’s water quality is a serious concern. cloud lake is a mesotrophic lake with confirmed occurrences of toxin producing cyanobacteria. the results underlie a misconception within current monitoring of inland lakes located within northwestern ontario that environmental conditions are pristine. therefore, lakes in the geographic region should all be oligotrophic. despite the absence of significant anthropogenic inputs (i.e. agricultural or urban development) cloud lake demonstrates a number of symptoms associated with eutrophication in larger, more developed lakes that relate to internal loading being a dynamic factor. the thesis provides recommendations for future monitoring and research to better understand the complex causes of eutrophication in cloud lake.