Some species glow in the dark in a process called
bioluminescence. These species contain a compound called
luciferin (the same compound found in fireflies). The glow
increases markedly if the algae cells are agitated, as when a
ship churns through the water. About half the species of
dinoflagellates are photosynthetic; the other half are predators
that attack bacteria, algae, and even fish. Dinoflagellate
neurotoxins can concentrate in the bodies of shellfish and fish
that eat the algal cells, in turn causing people who eat these
seafoods to come down with illnesses such as paralytic shellfish
poisoning and ciguatera (a combination of gastrointestinal,
neurological, and cardiovascular disorders.) So-called “red
tides” occur when enormous blooms of trillions of
dinoflagellates are triggered by an upwelling of nutrients from
the water’s depths during warmer seasons. The population of
dinoflagellates can jump to more than 20 million cells per liter
of sea water along some coasts during these blooms, turning the