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Benthic Invertebrate Assessment of Streams in the Georgia Basin Using the Reference Condition Approach: Expansion of the Fraser River Invertebrate Monitoring Program 1998-2002


Intensive urban development and agricultural activity in the Georgia Basin of British Columbia, Canada, are a concern with regard to their effect on the stream quality. Benthic macroinvertebrates were used to assess the current biological quality of streams in the Georgia Basin . The assessment was based on a biomonitoring program developed for the Fraser River Basin which used the Reference Condition Approach and the BEAST (BEnthic Assessment of SedimenT) assessment method. The reference condition database developed for the Fraser River Basin was expanded to include 55 streams in the Georgia Basin , including areas in the Lower Fraser Valley , streams draining into the Strait of Georgia from Eastern Vancouver Island and watersheds adjacent to the Fraser River Basin . As a result, the Fraser River assessment model was modified and the new Fraser/Georgia Basin model was used to assess 46 streams exposed to urban and agricultural activities.

BEAST assessments were accompanied by other commonly used bioassessment tools such as observed to expected taxa ratios and bioassessment metrics, which are often part of a benthic index of biological integrity. Together, these tools provided a clear description of the benthic invertebrate community and how it was different from what was expected when compared to an appropriate reference condition. Ninety per cent of the streams sampled in urban and agricultural areas were possibly stressed or worse based on the BEAST assessments. Two thirds of the test sites fell outside of the 99% confidence ellipse indicating that they were stressed or severely stressed . Grab sample measurements of water quality were inadequate to identify causative stressors. The invertebrate communities may have been affected by a series of events or a single event not captured by grab samples since the communities reflect cumulative effects integrated over time. A detailed water chemistry study should be conducted at these sites.

With the development of the Canadian Aquatic Biomonitoring Network (CABIN) and online resources and a predictive model specific to the Georgia Basin , biomonitoring can be easily incorporated into water monitoring and assessment programs, possibly in cooperation with stewardship groups, in this region.

Full copy of report available by request at


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