Abundance, community composition, and site structure of lotic assemblages in Gatineau Park streams and streams in the Ottawa-Gatineau Region

Abstract

Sixty-seven sample sites in 45 streams across the National Capital Region and Gatineau Park were sampled between the summers of 2001 and 2008 in order to describe communities within the Park and assess differences in stream fish and invertebrate assemblages along a gradient of urbanization. Additionally the relationships between nutrient concentration and biomass of algae, invertebrates, and fish were quantified, and changes in the size distribution of benthic invertebrates and fish along a gradient of nutrient and anthropogenic impacts were described. Principal Component Analyses indicated that urban and agricultural sites were easily distinguished from forested sites using water quality parameters. Invertebrate and fish assemblages did not differ as clearly among site categories. There were increased nutrient levels in agricultural and urbanized watersheds, however the biomass of primary producers did not proportionally track the increase in nutrients. Slopes of the relationships between biomass and nutrient concentration declined with increasing trophic level, indicating a reduction of the efficiency of energy transfer in more eutrophic systems. Size spectra from nitrogen enriched streams had elevated intercepts and increased residual variance was noted in perturbed watersheds. The current study has provided baseline data for stream communities within and outside of Gatineau Park and in doing so it is clear that Gatineau Park streams are in good, but variable health. In order to monitor change, protect diversity within the Park, and mitigate further stress to these streams, it may be useful to use aspects of the size spectra such as normalized density and the residual variance.