Review of benthic invertebrates and epilithic algae at long-term monitoring sites in the Bow River /

Water for Life: Alberta' s Strategy for Sustainability (Government of Alberta 2003) requires regular monitoring, évaluation, and reporting of aquatic ecosystem health.Although comprehensive water quality information is generated annually as part of Alberta Environment' s Long-term River Network (LTRN), comparable, current information on sédiment quality and biological communities is not available.In 2006 benthic invertebrates and epilithic algae were collected from the Bow River in order to:1 .Fill knowledge and information gaps identified by North South Consulting Inc. et al. (2007) with current data for Bow River LTRN sites.2. Compare various benthic invertebrate sampling techniques for long-term river monitoring sites in Alberta and provide recommendations for future monitoring at these sites.3. Evaluate temporal changes and longitudinal trends in benthic invertebrate and epilithic algal communities, particularly as they relate to nutrient management in the Bow River.After comparing the relative merits of data collected with a Neill cylinder sampler and kick nets of varying mesh sizes, the former was selected for further monitoring at LTRN sites.This decision was based on several considérations.Maintaining continuity with Alberta Environment' s historical database was viewed as important.Neill cylinder samples are quantitative and replicated, and hence lend themselves easily to statistical différence testing of population densities.Furthermore, Neill cylinder samples reflect a greater taxonomie diversity than kick samples.Nevertheless, kick samples could be appropriate in other contexts even though they only provide qualitative information.Benthic invertebrate data from 2006 show evidence of perturbation at Cochrane, most likely due to sharp diurnal fluctuations in discharge (and stage) caused by the operation of an upstream hydro-electric dam.As well, Didymosphenia geminata, a colonial diatom which forms dense cotton-like mats on the rocks contributes further to the inhospitable nature of the physical habitat at this site.Zoobenthic and epilithic algal communities provide clear evidence of nutrient enrichment at Stier's Ranch and Carseland downstream of Calgary.Algal and invertebrate abundances are lower at Cluny, but a diverse community including sensitive taxa is supported.The fauna at Ronalane, near the mouth of the Bow River, is characteristic of a depositional area with a sédiment bottom, macrophytes, and potentially lower dissolved oxygen levels.Longitudinal changes in benthic invertebrate communities are similar in erosional and depositional areas, although signs of stress, such as lower diversity indices, are apparent in depositional areas of Stier's Ranch and Carseland.There is a gap of thirteen years between the current data and the last zoobenthic samples collected from the Bow River.Based on this limited record, it appears that while the City An Assessment of Benthic Invertebrates and Epilithic Algae at Long-term Monitoring i Sites in the Bow River (Fall 2006)of Calgary's nutrient removal program led to some improvements reflected in the river' s benthic invertebrate and epilithic algal communities, the degree of impairment may again be increasing.These conclusions may be biased by differing annual flow régimes; in the future, a more consistent sampling schedule should be adhered to so that such variation can be better accounted for.Evaluating these biomonitoring data along with sédiment and water quality chemistry will help to further define current conditions and past changes in the Bow River.The development of indicators and perhaps even a prédictive model for aquatic ecosystem health should follow.Again, this work would be of most value if supported by a regular and consistent sampling schedule.An Assessment of Benthic Invertebrates and Epilithic Algae at Long-term Monitoring Sites in the Bow River (Fall 2006)

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