https://www.khanacademy.org/science/ms-biology/x0c5bb03129646fd6:organism-growth-and-reproduction/x0c5bb03129646fd6:activity-what-causes-harmful-algae-blooms/a/activty-what-causes-harmful-algae-blooms 2026-02-27T17:50:36.702607024Z Activity: What causes harmful algae blooms? Make science come alive in your classroom with this free hands-on activity aligned to middle school standards. article