Puget Sound Stream Benthos

Ambient Monitoring Project, King County - DNRP

King County Water and Land Resources Division collects annual benthic macroinvertebrate samples from approximately 150 stream locations within the Greater Lake Washington (WRIA 8) and Green-Duwamish River watersheds (WRIA 9). Starting in 2014 we are adding up to 40 stream locations within the Snoqualmie watershed (WRIA 7). This sampling helps to characterize existing aquatic macroinvertebrate conditions, detect differences in biological condition between sub-basins, and identify changing trends over time. A random, probabilistic sampling design was used for site selection.

Sample collection methods are based on the recommended sampling protocols outlined by Karr and Chu (1999) with some minor modifications. At each location, a Surber sampler (500 micron mesh, 1 sq ft frame) is used to collect eight samples. With this method, two samples are taken from 4 different riffles starting downstream and working upstream to get a total sample size of 8 square feet. Prior to 2012, the protocol was to sample 1 square feet in 3 separate riffles for a total sample size of 3 square feet. Changing to the 8 square foot protocol provides a more representative sample of the overall benthic community, and also allows us to coordinate our methods with other agencies.

All large materials (e.g., large gravel and large wood) within the one square foot sampling area are washed clean of any invertebrates or detritus into the 500 micron Surber net. A “weed tool” is used to vigorously agitate the substrate within the perimeter of the Surber frame to a depth of approximately 10 cm, for 60 seconds. The eight composited samples are then condensed and transferred to a sample container and preserved in the field with 90-95% ethanol (EtOH). Samples are then sent to a private lab for taxonomic identification. Prior to 2012, Chironomids were identified to family level, Acari to subclass, and Oligochaeta to class, and all other taxa were identified to the lowest practical level. Beginning in 2012, all samples were identified to a finer resolution matching Washington Department of Ecology's requirements so that chironomids, Acari, and oligochaetes are all identified to lowest practical level (standards generally match the 'fine' resolution summarized on the Taxonomic Effort web page: http://pugetsoundstreambenthos.org/Standard-Taxonomic-Effort.aspx).

Sampling is conducted annually between early August and mid September, if possible. QC replicates are sampled at 10% of locations annually to address intra-site variability.

Contact Person: Jo Wilhelm, jo.wilhelm@kingcounty.gov, 206-477-4849; Deb Lester, deborah.lester@kingcounty.gov, 206-477-4752 or Kate Macneale, kate.macneale@kingcounty.gov, 206-477-4769.

General macroinvertebrate information: http://www.kingcounty.gov/environment/data-and-trends/monitoring-data/stream-bugs.aspx

Reports and Sampling and Analysis plans: http://www.kingcounty.gov/environment/data-and-trends/monitoring-data/stream-bugs/stream-data.aspx