Some of the best times to observe bioluminescence in northern California’s Tomales Bay inlet are on completely dark, moonless nights in late summer or fall.
The bioluminescence is caused by tiny marine plankton known as dinoflagellates, which emit blue-green light when the water is agitated by wave action or a boat cutting through the surface. It is thought that the light emission is the dinoflagellate’s defense response to ward off predators.
There are several commercial kayak tour operators in the area that organize night time paddles in Tomales Bay to view the phenomenon. Ideal conditions for bioluminescence are total darkness, with calm waters and relatively warm surface temperatures.