Dinoflagellates are an ecologically important group of microbial eukaryotes within
marine systems. Photosynthetic species contribute to global biogeochemical cycling
through their role as primary producers, while toxin-producing species possess the
capacity to alter food webs and impact both human and ecosystem health via the bioaccumulation
and transfer of toxins through the food web. One of the most intriguing
biochemical traits found in some species is that of bioluminescence. While they
are the only members of the phytoplankton community with the capacity to emit
visible light, they are responsible for much of the bioluminescence produced in the surface waters of the oceans (Marcinko et al. 2013). The reaction is localized to organelles
known as scintillons (DeSa and Hastings 1968), which contain the substrate
luciferin and the enzyme luciferase, and in some genera, a luciferin-binding protein
(LBP) (Schmitter et al. 1976, Johnson et al. 1985, Nicolas et al. 1991). Mechanical
stimulation of the cells creates an action potential that opens membrane channels,
allowing the rapid entrance of protons from the acidic vacuole and resulting in a
rapid and transient drop in pH within the scintillons. This pH decrease results in
enzyme activation, and the oxidation of the luciferin results in a flash of light within
the wavelength range of 472–475 nm (Hastings 1983, Widder et al. 1983, Wilson and
Hastings 1998).