A diatom-based index for the biological assessment of eastern Canadian rivers: an application of correspondence analysis (CA)

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We developed a diatom-based index that integrates the effects of multiple stresses on streams and provides information related to the "distance" from the nonimpacted state. The Eastern Canadian Diatom Index (IDEC) was based on a correspondence analysis (CA) to develop a chemistry-free index where the position of the sites along the gradient of maximum variance (first axis) is strictly determined by diatom community structure and is therefore independent of measured environmental variables. The index value indicates the distance of each diatom community from its specific reference community. A high index value represents a non- or less-impacted site, while a low index value represents a more heavily impacted site. Two sub-indices were developed based on two sets of reference communities. The IDEC-circumneutral includes the sites that have reference communities characteristic of slightly acidic or neutral environments. The IDEC-alkaline includes the sites that have reference communities characteristic of environments where pH values are naturally higher than 7.5. The distinction between the two sub-indices is fundamental to make sure that each stream has the potential to reach a high IDEC value following complete restoration of its ecosystem.

Nous avons mis au point un indice basé sur les diatomées qui intègre les effets des nombreux stress sur les cours d'eau et qui fournit des renseignements sur la « distance » avec une état non perturbé. L'Indice Diatomées de l'Est du Canada (IDEC) est construit à partir d'une analyse des correspondances (AC) de manière à ce que la position des sites sur le gradient de variance maximale (premier axe) soit uniquement déterminée à partir de la structure des communautés de diatomées et qu'elle soit indépendante des variables environnementales. L'échelle de l'indice indique la distance entre une communauté de diatomées et sa communauté de référence spécifique. Une valeur élevée de l'indice indique une bonne intégrité écologique alors qu'une valeur faible est associée à une communauté perturbée. Deux sous-indices furent développés à partir de deux séries de communautés de référence. L'IDEC circumneutre inclut les communautés de référence des milieux légèrement acides ou neutres. L'IDEC alcalin, pour sa part, inclut les communautés de référence des milieux ayant un pH qui est naturellement supérieur à 7,5. La distinction entre les deux sous-indices est fondamentale, puisqu'elle assure que toute rivière ait le potentiel d'atteindre des valeurs indicielles élevées, advenant la restauration de son écosystème.

Document Type: Research Article

Publication date: August 1, 2006

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  • Published continuously since 1901 (under various titles), this monthly journal is the primary publishing vehicle for the multidisciplinary field of aquatic sciences. It publishes perspectives (syntheses, critiques, and re-evaluations), discussions (comments and replies), articles, and rapid communications, relating to current research on cells, organisms, populations, ecosystems, or processes that affect aquatic systems. The journal seeks to amplify, modify, question, or redirect accumulated knowledge in the field of fisheries and aquatic science. Occasional supplements are dedicated to single topics or to proceedings of international symposia.
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