Benthic Field Study

1. Benthic Field Study Taken from Citizen’s Environment Watch 2002

2. Introduction • Benthic macroinvertebrates are widely used to monitor environmental quality in streams. • They are animals found on the bottom of a waterbody that are large enough to be seen with the naked eye, and lack a backbone and internal skeleton. • They are relatively sedentary and widespread with varying tolerances to changes in water and sediment quality.

3. When to Sample • Sampling is possible anytime beginning in early spring (Apr.) and ending in late fall (Oct.). • The most important consideration relates to safety, where periods of high flow associated with spring floods and storm events should be avoided.

4. Where to Sample • The choice of where to sample will also be limited by health and safety considerations. • Choose sampling sites where water conditions do not pose any known or potential risks (e.g. pollution, high water levels). Otherwise, the choice of a sampling site will largely depend on the monitoring goals of each group. For example, some community groups may be concerned with fish populations and may wish to assess the effects of habitat loss due to sedimentation. • Construction sites are one possible source of increased sedimentation. In this case, a sampling site should include both a reference site upstream and a site downstream of construction site. A similar approach would be used for any suspected negative impact on stream quality (e.g. stormwater outfalls, major roads).

5. Collecting Your Sample • Begin sampling at your downstream limit (i.e. first transect) and at a point as close to the bank as possible. • Place the net firmly against the stream bottom, making sure that no macroinvertebrates can pass beneath the net. • Hold the net so that the current is flowing into the net. • Scoop up a continuous sample in a straight line across your transect. You will need to keep emptying your sample into a filtering device as you proceed. • Pick up unembedded rocks along the transect and carefully rub their surface to dislodge any attached bugs and collect them in the net. • Place sample into a white tray for sorting • Avoid entering the stream prior to sampling. Any additional sampling (e.g. biological, chemical) or site survey should be carried out after the macroinvertebrate sampling has been completed.

6. Sort your sample • Carefully disturb the contents of the tray and look for moving and resting water bugs. • Look carefully for smaller bugs (<3mm) and under/on the surface of remaining small debris, twigs, small rocks, etc. • Be sure not to pick only the largest and/or least mobile macroinvertebrates. • As a rule, once a bug is spotted, it must be picked, regardless of size or movement. • Use magnifying glasses and your identification chart to identify your sample. When a macroinvertebrate is discovered place a line on your data collection sheet.

7. Sketch your site • This should be completed for each of your transects on the sheet provided. • Make it to scale • You are welcome to use symbols

8. Final Notes • We are going to complete three data collections (transects) • Upstream, midstream and downstream • From each data source (transect) collect a raw sample to bring back in a sample bag. • Complete your package and hand it in.