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GUIDELINES FOR SAMPLING BENTHIC INVERTEBRATES IN BRITISH COLUMBIA STREAMS

the addition of several other sections summarizing various sampling and analysis approaches that have come into use over the last decade. In January 2006, Chris Perrin further edited and incorporated new information to update the report for publication. The author would like to thank Ms. Fay Westcott and Mr. Chris Perrin also acknowledged as a co‐authors, for their valuable input as well as Dr. Rick Nordin and Dr. John Richardson for their expert review and comment to these guidelines. INTRODUCTION Benthic invertebrates are commonly used as indicators in the evaluation of impacts to stream ecology and entire watersheds from a variety of point and non‐point pollution sources (Barbour et al. 1999, Karr and Chu 1997, Lenat and Crawford 1994, Plafkin et al. 1989). Benthic invertebrates have been favoured in environmental effects monitoring because they are sessile or limited in their range of movement and therefore cannot avoid pollution (Gaufin 1973). They are generally abundant and can be found year round so are easily sampled. Since many aquatic species have a life span in water of approximately a year, they provide an indication of water quality conditions over that period. In other words, their life span is long relative to most short‐term environmental impacts that occur. As primary consumers in aquatic ecosystems, benthic invertebrates are an extremely important food source for many aquatic organisms including fish and are mediators in nutrient cycling in aquatic systems by the breakdown and utilization of suspended or attached organic material. As well, benthic invertebrate monitoring data provides a link between the effects of human activities on the physical and chemical properties of water and aquatic ecosystem health (Norris and Hawkins 2000). The heterogeneous or " patchy " distribution of benthic invertebrates in aquatic environments makes the task of study design, sampling and data interpretation somewhat difficult. The effects of a pollutant on a benthic community, measured by upstream/downstream or time‐series sampling, often cannot be distinguished from natural within‐site sampling variation. However, carefully defining the purpose (i.e. what is the question you are trying to answer), then selecting the appropriate study design and analytical tools for your benthic invertebrate monitoring program can overcome these limitations. There is a wealth of printed literature as well as information accessible on the internet from agencies and universities, which can provide good advice on sampling devices, analytical and statistical methods to produce more reliable and reproducible information. These guidelines are …