Lake Chelan is the longest and deepest natural lake in Washington, formed by glacial retreat at the end of the last Ice Age. Based on water quality data collected in the 1980s, and more recent data collected by the Institute for Watershed Studies from 2024-2025, it is considered an oligotrophic lake and has some of the clearest waters in the state. Because the lake is an important recreational destination and drinking water source there are concerns about the growth of algae in nearshore areas. One species of note is the invasive diatom Didymosphenia geminata (“Didymo”), which was collected in the Chelan River and multiple nearshore areas in the lake. The goal of this project was to provide information about algae found along the shoreline of Lake Chelan. The linked reports include summaries of the algal taxa found along the lakeshore and near the outflow into the Chelan River. An online key is available for researchers interested in identifying the common algae found in Lake Chelan.
Image copyright Robin Matthews, Western Washington University.