The Eastern Canadian Diatom Index (IDEC) Version 2.0: Including Meaningful Ecological Classes and an Expanded Coverage Area that Encompasses Additional Geological Characteristics

Abstract In 2006, the Eastern Canadian Diatom Index (IDEC: Indice Diatomées de l'Est du Canada) was developed to monitor the biological integrity of streams and rivers in Eastern Canada. The first version of the IDEC has been successfully used to evaluate the biological status of numerous sites. A new version of the index (IDEC 2.0) was recently developed to cover a larger geographic area that encompasses additional geological characteristics. IDEC 2.0 is now applicable for the biological assessment of streams in Quebec, Ontario, New Brunswick, Nova Scotia, and Prince Edward Island. Moreover, the approach used to define the biological interpretation of the index values was revised. IDEC 2.0 presents ecologically meaningful differences among biological communities (ecological thresholds or class boundaries) based on diatom biotypes, providing a more relevant interpretation of the diatom community changes along the alteration gradient.