A comparison of stream bioassessment in Quebec (Canada) using six European and North American diatom-based indices
The purpose of this study was to first present different approaches used for developing diatom-based indices and second, to evaluate the ecological integrity of eastern Canadian streams (Québec) using these different approaches. Six indices from Europe (TDI, IPS, IBD, SLA) and North America (IBI, IDEC) were employed. The results from this study confirmed that, as a general trend, most of the common riverine taxa have similar ecological preferences throughout Europe and North America. The comparison of the six diatom-based indices illustrated the similarity of results and robustness of diatom-based monitoring no matter what indices were used. All indices effectively scored river health across most of the environmental gradient, although variations in scores were observed at both tails of the integrity spectrum with the greatest range in index scores at the heavily impacted end of the gradient. The use of sub-indices to account for ecoregion characteristics and natural pH variations improves regional index performance, especially at the extremes (i.e. in reference and heavily impacted rivers). Regionally derived indices are more sensitive and preferred, although we recognize the utility of using larger gradient indices excluding ecoregion or geological considerations for broader national and international applications.