Dinophysis bloom in Norway (E. Dahl)

Residential canal in Cape Coral, FL, with blooms of the microcystin-producing blue-green algal Microcystis. Credit: M. Parsons.

Cyanobacteria bloom in Lake Erie. Photo courtesy of Tim Davis.

Aerial view of cyanobacterial bloom (NOAA, T. Davis)

Aerial photo of what is likely a blooom of Cochlodinium polykrikoides in the James River near the Monitor-Merrimack Bridge. The bloom extends from above the James River Bridge downstream into the main-stem and western branch of the Elizabeth River as well as into the Lafayette River. Photo by Wolfgang K. Vogelbein

Bloom streaks in the York River near the entrance to Mobjack Bay on July 27, 2017. Drone imagery by VIMS professor Donglai Gong.

The bloom was exceptionally dense ialong the north shore of the York River between Sarah Creek and the Perrin River. Photo by Professor Wolfgang Vogelbein.

A VIMS research vessel passes through an Alexandrium monilatum bloom near the mouth of the York River. Drone imagery by VIMS professor Donglai Gong.

Microcystis in Klamath Lake (D. Anderson)

A Noctiluca bloom in China. (M. Zhou)

A Noctiluca bloom in Hong Kong (K.C. Ho)

This massive “red tide” of the dinoflagellate Noctiluca stretched for more than 20 miles along the southern California coast. Non-toxic blooms such as these can cause extensive mortalities of plants and animals in shallow waters when the bloom biomass decays, stripping oxygen from the water. (P. Franks)

A non-toxic red tide bloom of Noctiluca scintillans in New Zealand. (M. Godfrey)

A bloom of Nodularia spummigena, a blue green algae. (W. Carmichael)

Foam following a Prorocentrum bloom in Chile. (G. Lembeye)

A freshwater red tide in the Italian Alps, species unknown. (Photo credit unknown)

Red tide in Texas (photo credit unknown)

Rhizosolenia in Hood Canal, Washington (R. Horner)

A Noctiluca bloom in the Sea of Cortez, Mexico. (M. Gaskins)

A Noctiluca bloom in Union Bay, British Columbia. (Lisa M. Holm)

A Cochlodinium bloom in the York River, Virginia. (S. Shumway)

The upper portion of photo depicts a brown tide event in an inlet along the eastern end of Long Island, New York, during Summer 1986. The blue water is Block Island Sound. (L. Cosper)

Some algal blooms are non-toxic but aesthetically unpleasant or noxious. (Photo credit unknown)

Noctiluca in B.C.

Aerial view of a red tide in Texas