Puget Sound Stream Benthos

Kimball Creek Water Quality Improvement Project, Snoqualmie Tribe

To sample the benthic macroinvertebrate community in Kimball Creek, Coal Creek, and Fisher Creek, we used a 0.09 sq. meter Surber sampler with 500 micron mesh and a 3.5 inch cod-end with portholes. We adapted our sampling method from Barbour et al. (1999). We selected the best riffles present in each reach that we wanted to sample. We could not sample at site KC2 as desired because of the prevalence of ironoxidizing bacteria on the substrate, which would have clogged the sampler. We attempted to avoid bridges (and their corresponding effects on stream ecology) but found that the best riffle downstream of KC2 was near a bridge at sampling site KCX (SE 80th St), so we sampled as far downstream from the bridge as possible while still being in the required habitat. For lower Kimball Creek, below its confluence with Fisher Creek, the only riffle was at sampling site KC5, under Hwy. 202, so that was the only choice for a sample location. All sampling was conducted at base flows on August 5th and 6th, 2010.

For each site, we attempted to obtain 500 individual macroinvertebrates in 3 reps. If we were not confident that 500 individuals were obtained in 3 reps, we performed additional reps until we were confident that we had reached or exceeded the desired number. A rep consisted of placing the Surber sampler in the riffle tight to the substrate and cleaning all the large rocks within the frame with a scrub brush so that all organisms were dislodged into the sampler net. Then we agitated the substrate with a “weed fork” within the sampler frame to a depth of 10 cm for 60 seconds. Additional reps were always performed upstream of earlier reps.

We used stream water, splashed from the outside of the netting so as not to introduce new organisms into the sample, to rinse all the organisms and material that were stuck to the inside of the mesh into the cod-end. We rinsed all the organisms and material from the sampler cod-end into 1-liter polyethylene bottles with 99% isopropyl alcohol, then filled the bottles with sufficient alcohol to cover all the material within, and labeled the bottles. All samples were keyed and scored by EcoAnalysts Inc. to level III, lowest level practical (typically to species) in accordance with the Puget Lowland B-IBI for wadeable streams.

Contact Name: Matt Baerwalde, mattb@snoqualmietribe.us, 425.292.0249 x2101