Freshwater Harmful Algal Blooms: Causes, Challenges, and Policy Considerations [Updated July 8, 2020] [open pdf - 1MB]
From the Summary: "Scientific research indicates that in recent years, the frequency and geographic distribution of harmful algal blooms (HABs) have been increasing nationally and globally. Because the impacts of HABs can be severe and widespread--often with interstate implications--these issues have been a perennial interest for Congress. While algal communities are natural components of healthy aquatic ecosystems, under certain conditions (e.g., increased temperatures and nutrient concentrations), algae may grow excessively, or 'bloom,' and produce toxins that can harm human health, animals, aquatic ecosystems, and the economy."
CRS Report for Congress, R44871
Congressional Research Service: https://crsreports.congress.gov/