The benthic community of stream riffles in Newfoundland, Canada and its relationship to selected physical and chemical parameters

The benthic macroinvertebrate communities of riffle habitats in 20 streams of Newfoundland, Canada were surveyed for density, biomass and diversity. These measures were compared to physical and chemical parameters of each stream. Population measures showed no patterns with regard to stream acidity with two exceptions. Gastropods and the ephemeropteran Heptagenia were absent from streams where the pH was below 6.1. Macroinvertebrate density and diversity were not significantly related to any of the parameters measured, although diversity was positively correlated with dissolved organic carbon and negatively correlated with nitrate concentration. Macroinvertebrate biomass (B) however, was significantly related to the concentration of organic anions (p = 0.017) and 46% of the variance in biomass was explained by the equation B = -241 + 3.91 (org) +33.7 (temp). This significant (p = 0.005) relationship suggests that the production of these communities is controlled by the amount of allochthonous material entering the stream.