Nutrients, sunlight, and temperature are well documented drivers of harmful algal blooms in lakes and reservoirs. However, the interactions among these drivers and other potential factors influencing HAB growth is less well understood. Lake Anna is a reservoir formed by the impoundment of the North Anna River in central Virginia. The lake is a popular vacation destination for recreation including boating, watersports, and fishing. Portions of Lake Anna have had consistent elevated cell counts of potential toxigenic species starting in the mid-summer each year since 2018, resulting in HAB advisories each year, advising the public to avoid primary contact recreation for portions of the lake. The U.S. Geological survey has partnered with Old Dominion University and Virginia Department of Environmental Quality to conduct a study which investigates the factors and processes driving HAB initiation, persistence, and decline. The focus on the poster presentation is to give an overview of the intensive and extensive monitoring programs that evaluate the hydrology, geochemistry, climate, wave-action, ecosystem metabolism, community dynamics, environmental DNA and RNA, and other new technologies, and also present preliminary results and discussion.