Mercer Island Project, King County - DNRP

King County Water and Land Resources Division collected annual benthic macroinvertebrate samples from 1999 to 2008 with the exception of 2004 and 2007 from up to six small watersheds on Mercer Island. This sampling was part of a larger, ongoing stormwater monitoring project for the City of Mercer Island to assess the effectiveness of drainage basin improvements and supports the municipal stormwater NPDES permit application. In addition to benthic macroinvertebrate sampling, this program measures conventional water quality parameters, nutrients, bacteria, dissolved metals, herbicides, pesticides, sediment metals, and sediment hydrocarbons.

Contact Person for Mercer Bug program: Jo Wilhelm, jo.wilhelm@kingcounty.gov; 206-263-6556

Contact Person for overall Mercer water quality sampling: Debra Bouchard, debra.bouchard@kingcounty.gov; 206-263-6343

SAP: Followed the same protocols as the King County ambient monitoring program, which is 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) was used to collect three samples along the midline of three separate riffles or non-depositional habitat starting downstream and working upstream. All large materials (e.g., large gravel and large wood) within the sampling area were scrubbed by hand and examined before being placed downstream. A “weed tool” was used to vigorously agitate the substrate within the perimeter of the frame to a depth of approximately 10 cm, for 60 seconds. The three composited samples were condensed and transferred to a sample container and preserved in the field with 90-95% ethanol (EtOH). Samples were then sent to a private lab for taxonomic identification. Chironomids were identified to family level; other taxa were identified to the lowest practical level. Sampling was conducted between the last week of July and mid September each year.