Relationships between water quality and stream invertebrate assemblages of Eastern Ontario and Western Quebec.

Abstract

Forty-seven riffle zones from 21 streams of Eastern Ontario and Western Quebec were sampled in 1998 to describe how characteristics of the benthic invertebrate assemblage (abundance, taxa richness and size distribution) varied as a function of water quality parameters (conductivity, TP, SRP, TSS, NO3+NO2, NH3, TKN, Cl-, SO42-) along a gradient of watershed development. A principal components analysis on water quality parameters revealed that there were two groups of correlated water quality variables that explained the majority of the variability among sites. The first group of variables included chloride, sulfate, nitrate+nitrite and conductivity and represented a gradient of urbanization while the second group represented nutrients and included: soluble reactive phosphorus, total phosphorus, ammonia, total suspended solids and total Kjeldahl nitrogen. Simple and multiple regression models predicting invertebrate assemblage characteristics were fitted using water quality principal components scores as independent variables. Overall, invertebrate assemblage characteristics were related to both groups of water quality variables. Abundances per taxon and size classes generally increased with increased nutrients, and overall abundance and the ratio of abundances of sensitive to tolerant taxa declined with increasing chloride, sulfate, nitrate+nitrite and conductivity. Existing information suggests that the water quality gradient found in these streams is more a reflection of anthropogenic sources than the result of geological differences. Therefore, it appears that human activities affect the distribution and abundance of invertebrates in this region. However our models did not explain a good proportion of the variability. It would seem that stream invertebrates of the Ottawa valley are also affected by other parameters that have yet to be identified.