Harmful algal blooms are proliferations of microscopic algae that harm the environment and humans by producing toxins that accumulate in shellfish and fish, pollute drinking and swimming water, and contaminate coastal air. Increases in the number, frequency, and type of harmful algal blooms have become a critical issue in near shore marine waters and freshwater environments globally. This image of harmful algal blooms near South Bass Island in Lake Erie was taken August 4, 2006.