California Department of Water Resources scientists have begun their annual summer monitoring program for harmful algal blooms at Lake Oroville, the Thermalito Forebay and the Thermalito Afterbay, with early results showing no toxins detected in monitored recreation areas. Environmental scientists began collecting weekly water samples in May from recreation areas throughout the Oroville-Thermalito Complex. The samples are sent to a laboratory for analysis to determine whether toxin-producing cyanobacteria, commonly known as blue-green algae, are present. DWR scientists collect samples weekly during the recreation season, which runs from Memorial Day through Labor Day, to monitor potential health risks.