2001 Indicator Study

One of the most important environmental issues in the Pacific Northwest is saving the salmon. Poor water quality makes it difficult for salmon to spawn. A goal for many of the stakeholders in the Clover Creek Watershed and surrounding area, is to strive for a better water quality in order bring back some of these salmon populations. The lack of salmon in an area that was once populated with these fish is definitely a sign that water conditions are hurting. A more useful method of indicating the watershed’s health is focussing on benthic macroinvertebrates (BMI). BMIs, unlike salmon, have a relatively short lifecycle. Assessing the effects of pollutants on a salmon it would take several years. Certain taxa of BMI are tolerant to degraded areas that have high turbidity, increased temperatures, or the presence of toxins. Other BMI’s however, are very sensitive and will not be present in such water conditions. BMIs are great indicators because they show a long term picture of the streams health. Measuring stream characteristic on their own, like looking for toxins, will only tell what pollutant is present at that moment. A chemical spill may have occurred several days prior to testing, but was quickly flushed out by the stream. If BMIs were sampled in this case, the lack of sensitive benthic macroinvertebrates would indicate that some damaging event occurred. BMI sampling prevents harmful changes to the stream from being unnoticed because it shows long term effects.

Sampling for BMIs is somewhat easy and very inexpesive. To collect, several methods can be used like kick seines, surber samplers, and dip nets. Sorting the different taxa can be done using a dichotomous key like the one in the Streamkeepers Field Guide. Using the pollution tolerance index (PTI) is an easy way to quantify the streams health. In order to calculate PTI, samples from each site must consistent in terms of number of tests run and area sampled. Calculating the PTI is found in the Field Guide for Water Quality Monitoring. PTI gives a rating based on the types taxa that are present at a sample site.

In order to sample for BMIs the sample site must be shallow and relatively slow because the collector has to be in the stream. Consistency is crucial when sampling for BMI. It is very important that the same amount of area is sampled at each site and the same type of methods are applied.