What causes dinoflagellates to glow?

Depending on how this question is interpreted, there could be a few possible answers.
Dinoflagellates glow because they are capable of bioluminescence.
Dinoflagellates glow and activate bioluminescence because they are being disturbed and stressed. A common disturbance is wave action near the shore. As the wave moves and crashes, the dinoflagellates are disturbed and glow in response to the disturbance.
Dinoflagellates glow because they produce two items that chemically react with each other and glow. Dinoflagalletes contain an organelle called a scintillon. This organelle contains luciferin and luciferase. The first is the substrate and the second is the enzyme. At certain moments, the luciferase will oxidize the luciferin to form oxyluciferin. This chemical change causes an emission of photons. In most cases, the color of light is blue.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5029497/