King County Benthic Macroinvertebrate Monitoring Program
What do we do?
Each summer a team of scientists, the “Stream Team”, visits the approximately 170 sampling sites in King County to collect benthic macroinvertebrate samples and habitat data to assess stream health. Summer is the best time to collect samples because in most areas, water flow is deep and swift enough to effectively use the sampling equipment, but not too deep and swift that being in streams and rivers becomes dangerous for staff. The King County Stream Team visits sites throughout the County, from wadable rivers like the Tolt and forks of the Snoqualmie, to the smallest backyard streams. Keep an eye out during the summer season, you may even see the Stream Team in your neighborhood!
The Stream Team collects benthic macroinvertebrates and information about the stream habitat.
Habitat Data Collection
Scientists survey the stream habitat because those observations help them understand why they see the kinds and numbers of benthic macroinvertebrates that they see in their samples. For example, some macroinvertebrates thrive in bigger, deeper streams whereas other prefer small, shaded streams.
Our Stream Team gathers a variety of different types of data using specialized equipment. They take measurements to determine how much shade a stream is getting, the stream width and depth, and the speed that the water is moving. They also conduct a survey called a Wolman pebble count, which captures what the stream bottom is like-- sandy, lots of boulders, or something in between. In some streams, we deploy temperature loggers that collect continuous temperature data throughout the year.
Benthic Macroinvertebrate Collecting
The primary tool we use to collect benthic macroinvertebrates is a Surber sampler - a sort of underwater butterfly net. It consists of a 1 square foot metal frame attached to a long mesh net with a collection cup on the end. To collect a sample, we position the Surber sampler on the bottom of the stream within a riffle. A riffle is the shallow, highly oxygenated, and fast-moving area within a stream. We then stir up the bottom sediment and rocks within the metal frame of the Surber sampler which dislodges the macroinvertebrates up out of the benthos (stream bottom) and into the net. We repeat this action 8 times in several different riffles. The contents of the net represent a single sample collected from an 8 square-foot area.
The macroinvertebrates and the contents of the net are carefully removed and placed in sample bottles. The sample bottles are then sent off to a laboratory, where they are identified and counted.