A red tide returned to La Jolla Shores this week and left the waters off Scripps Pier aglow in this image captured by UC San Diego photographer Erik Jepsen. Red tides are aggregations of phytoplankton that get their nighttime illumination from the bioluminescent dinoflagellate Lingulodinium polyedrum. When agitated, the microbes will give off a flash of blue light created by a chemical reaction within cells. When billions and billions of cells are jostled by breaking waves, the light show begins.
The last major red tide in La Jolla took place in May 2018 and lasted roughly one week. Researchers have yet to understand why or when red tides will occur or predict how long they will last.
- Bioluminescence expert Mike Latz's Answers to top 10 questions about bioluminescence.