Red tides, a type of harmful algal bloom, colour the water rusty orange along the coast of British Columbia in Canada.
Photograph by Julian Nieman, Alamy
Filter-feeders, like clams and mussels, accumulate toxins produced by microscopic algae in their bodies. A shellfish farmer in Massachusetts, Peggy Jennings, couldn't harvest shellfish in 2005 because of a red tide.
Photograph by Jodi Hilton, The New York Times, Redux
Notices are posted along the coast where red tides force closures to shellfish fishing, seen in June 2005.
Photograph by Jodi Hilton, The New York Times, Redux
Here, blooms of microscopic algae give a red tint to water along the coast of China in November 2014.
Photograph by Xinhua News Agency, Eyevine, Redux
