Biologist Maria Sinetova about a beautiful and sometimes dangerous phenomenon of glowing of dinoflagellates
In the picture, you can see the bioluminescent glow of plankton organisms. These could be copepods or jellyfish, but the most widespread are dinoflagellates. Dinoflagellates glow while moving in the water column and the glow is stronger when they experience mechanical impact or stress — for example when a boat or a predator comes around.
Generally, one could say that dinophytes feel rather comfortable in the water column — there is enough sun and food, nitrogen, phosphorus, and there are no substances that are harmful to them. The better the conditions, the brighter the glow of the organisms experiencing mechanical impact.
The chemistry of bioluminescence has been understood only recently, but today the ability of organisms to produce light is widely used in science. Japanese scientist Osama Shimomura received the Nobel Prize for his discovery of bioluminescence (in jellyfish) and GFP protein.
The protein binding substrate luciferin dissociates from the protein under external influence, and then an enzyme called luciferase acts upon it. Oxygen also takes part in this reaction, and the electrical impulse serves as a signal for its initiation. As a result, the cell membrane potential changes and the cell starts to glow.Bioluminescence of dinoflagellates may be beautiful, but it may also be a signal of danger. Many of the species in this group are toxic. If dinoflagellates reproduce rapidly, they may cause so-called ‘red tides’. During this period all the animals (molluscs, fish, etc.) that feed on dinoflagellates also become toxic due to the accumulation of high amounts of toxins from dinoflagellates. It is dangerous to eat such sea animals because the toxins that are contained in them may have various unpleasant effects: some merely irritate the bowel and cause food poisoning, whereas others, being neurotoxins, may even have an effect on memory.
Some species, such as the sea sparkle (Noctiluca scintillans) are not as toxic, but may have other unpleasant effects.