Crowds defying stay-at-home orders gathered along Carlsbad State Beach on Saturday night to catch a glimpse of neon blue bioluminescence caused by a red tide.
Carlsbad Police attempted to enforce physical distancing and verbally warned numerous drivers not to park along the beach.
Police said officers from the California Highway Patrol and and California State Parks would assist with crowd control if necessary on Sunday night.
Scientists at Scripps Institution of Oceanography said the red tide is due to a concentration of the phytoplankton Lingulodinium polyedra, a species known for its dazzling displays.
On sunny days, the organisms concentrate on the surface, coloring the water a reddish brown. When the phytoplankton are agitated by waves, they emit a neon blue glow that is visible at night.
The phenomenon has attracted crowds to many local beaches over the past week.
Scripps said it’s unknown how long the current red tide will last, but previous ones have persisted anywhere from one week to a month or more.