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# Why Does San Diego's Ocean Glow Blue?
- URL: https://www.cascadepbs.org/show/nature/extras/why-does-san-diegos-ocean-glow-blue/
- Published: 2024-10-23T21:00:59.000Z
- Updated: 2026-01-07T13:41:32.000Z
- Description: As the sun sets in the West, other lights come awake.
- Author: Cascade PBS Staff
- Tags: Nature, #ZZZ_Show_1b3b1a16-4d15-417c-9287-bc59a89e1201, #geo-us, #v1.7, #ZZZ_Extra_e81802e1-b872-49b0-ad0a-b3054fe1f259, #extra

Just off San Diego's shore, single-celled algae called dinoflagellates start to reproduce and if disturbed, a chemical reaction within the cell creates a tiny spark of light. When the conditions are right, the algae multiply and the coastal waters glow blue.