Dinoflagellates are tiny plants which live in the sea and obtain energy from sunlight during the day. In darkness, they emit bright blue light in response to movement within the water. The phenomenon is a truly amazing experience to witness, and was recently featured in the movie "The Beach" adapted from the novel by Alex Garland.
mechanism of luminescence
The mechanism of luminescence is regulated by activity of enzymes (luciferases) upon luminescent proteins (luciferins), and requires oxygen.
The ability to produce luminescence is strictly dependent upon the day/light cycle. In a 12 hour light/12 hour dark cycle, dinoflagellates will only flash brightly during the dark phase. Light emitted is brightest after several hours of darkness. Early in the morning, glowing activity is reduced and they no longer to luminesce upon shaking. During the day, the dinoflagellates appear as ellipse shaped cells, pigmented red, indicating the presence of chlorophyll which enables photosynthesis to occur so they may harvest light from the sun.
the shock response
The luminescence is transient and the cells soon return to their resting state. Most cells flash for less than a second, however others appear to glow for 1-6 seconds. Upon repeated stimulation, light emission is much reduced and the lux-system becomes "saturated". Within about half an hour of rest, the luminescence becomes brighter again.