Every few years, a bloom of microscopic organisms called dinoflagellates transform coasts around the world by endowing breaking waves with an eerie blue glow. This year's spectacular bloom in southern California was a particularly striking example.

 

 

Scientists have long wondered how these tiny organisms produce this stunning blue light. The new study published on Monday in the Physical Review Letters answered this question.

 

 

An international team led by researchers from the University of Cambridge developed unique experimental tools based on micromanipulation and high-speed imaging to visualize light production on the single-cell level. They showed how a single-celled organism of the species Pyrocystis lunula produces a flash of light when its cell wall is deformed by mechanical forces. Through systematic experimentation, they found that the brightness of the flash depends both on the depth of the deformation and the rate at which it is imposed.

 

 

 

Known as a 'viscoelastic' response, this behavior is found in many complex materials such as fluids with suspended polymers. In the case of organisms like Pyrocystis lunula, this mechanism is most likely related to ion channels, which are specialized proteins distributed on the cell membrane. When the membrane is stressed, these channels open up, allowing calcium to move between compartments in the cell, triggering a biochemical cascade that produces light.

 

 

Bioluminescence has been of interest to humankind for thousands of years, as it is visible as the glow of night-time breaking waves in the ocean. Many authors and philosophers have written about bioluminescence, from Aristotle to Shakespeare, who in Hamlet wrote about the 'ineffectual fire' of the glow-worm: a reference to the production of light without heat.

 

 

In a report published on the website of the University of California, senior author professor Raymond Goldstein said: "Despite decades of scientific research, primarily within the field of biochemistry, the physical mechanism by which fluid flow triggers light production has remained unclear.”

 

 

“Our findings reveal the physical mechanism by which the fluid flow triggers light production."