http://www.cop.noaa.gov/stressors/extremeevents/hab/current/HAB_Econ.aspx
Some harmful algae produce potent toxins which cause illness or death in humans and other organisms, including endangered species. Other harmful algae are non-toxic to humans and wildlife but degrade ecosystems by forming such large blooms that they can adversely affect corals, seagrasses, and organisms living on the sea-bottom. Human health and ecosystem impacts of HABs and management responses to lessen those impacts can have significant economic and sociocultural consequences. Read more