Monterey Bay Aquarium Research Institute
Marine Botany

Phytoplankton Blooms

A "red-tide" bloom of the bioluminescent dinoflagellate, Noctiluca, off 

the coast of California; the object at the mid-left is a ship, for scale. 

(photo used with permission by owner, Dr. PJS Franks)

When conditions are just right, phytoplankton populations can increase their numbers at an incredible rate - this population explosion is known as a bloom.  Often, you can witness blooms yourself because the water is so thick with single-celled plants that it gives the water an unusual color - often called red tides.  

A bloom of the coccolithophorid, Emiliana huxleyi, off the coast of Newfoundland, 21st July 1999. ( photo used with permission by owner: SeaWiFS/ORBIMAGE)

What are good conditions for a bloom?

Just like house plants, phytoplankton need nutrients, light, and to be within a certain temperature range to grow well.  Along the California coast, the most common times for phytoplankton blooms are in the spring, after winter storms have mixed nutrients into the surface layer of the ocean and when daylight is becoming longer.  There are often blooms later in the summer or early fall, as well. 

An oceanographic vessel motors through a cyanobacterial bloom, perhaps of Synechocystis, a common bloom producer; photograph taken from the air (by the Finnish Frontierguards) during the 1997 summer bloom of cyanobacteria.  (photo used with permission by owner:

Finnish Institute of Marine Research, Helsinki)

What types of phytoplankton produce blooms? 

All of the groups covered in these web pages can produce blooms: cyanobacteria, silicoflagellates, coccolithophorids, diatoms and dinoflagellates.  

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