A stunning natural phenomenon called "blue tears" drew crowds of tourists and photographers to the waters off the coast of Pingtan City, east China's Fujian Province, on Friday night. 

The blue tears are actually the result of a chemical reaction called bioluminescence that occurs when "sea sparkles," also known as noctiluca scientillans, are disturbed in turbulent water. This explains why the sea radiates when people hit it.

According to local residents, the sea sparkle blooms can be seen in many waters off the coast of Fujian, and they usually occur between May and October. Friday night's appearance was a little early.

There are usually two types of one-celled organisms that have bioluminescent emission, noctiluca scientillans and cypridina, which generally appears in the summer when the water temperature is over 25 degrees Celsius, according to Chen Chun, a senior engineer at the Island Research Center (IRC). 

"The location of Pingtan is relatively special, which causes some currents and tides to gather here. And the blue tears over here are the joint result of local oceanography and meteorology," said Chen.

He warned that a large sea sparkle bloom could lead to a red tide, which depletes oxygen in the water and releases toxins that may be harmful to marine life and humans.  

According to the latest monitoring of the sea area of Pingtan, the density of the sea sparkles is not high.

To prevent a red tide from happening, Fujian's marine and fishery department monitors the sea twice a month from April to June each year.

(Cover image via VCG)

(If you want to contribute and have specific expertise, please contact us at nature@cgtn.com.)