Electric blue waves in San Diego: bioluminescence by Bethan Goodhead

Beautiful displays of light have always captured our attention, from firework displays which welcome the new year, to the Aurora Borealis (The Northern Lights). Of course, the development of the Aurora Borealis is a well-known natural phenomenon, whereby particles from the sun collide with Earth’s atmosphere causing electrons to move at a higher-energy state, when these return to lower-energy they produce light (release a photon). However, another natural formation of light, stemming from biology, is known as bioluminescence.

A typical example of bioluminescence is the firefly on a summer night. The light occurs due to a chemical reaction of oxidising beetle luciferin to form oxyluciferin. There are several reasons why a firefly glows: to act as a deterrent towards predators, to identify the opposite sex and to breed. Many marine organisms also light up, resulting in a glittering seascape. Take the deep sea Angler Fish as an example of this, where they have evolved so that lighted bait hangs in front of their mouths attracting prey to consume.

San Diego has seen rare beautiful displays of electric blue crashing waves which, but what species has caused this spectacle? According to Michael Latz – who is a bioluminescence researcher from The Scripps Institution of Oceanography at UC San Diego – the bioluminescence is made up of dinoflagellates. By day, due to the colour and concentration of the organisms, they turn the water red, which is commonly known as the “red tide”, but by night the coast turns into a scene from Avatar as the water turns neon blue. The red tide does not only occur in California though, there have been reports of this event occurring all over the world, lasting anywhere between a week to a year.

It is also difficult to predict unless frequent water samples are analysed because in order for a red tide to occur the environment needs four factors. Firstly is the biology, the organism must outcompete other phytoplankton in the area. The second factor is the correct chemistry, the water must have an appropriate temperature, salinity and nutrient availability. Third are the right physical conditions so that the organisms can form a concentration. The fourth component is ecology – the presence or absence of species such as marine algae may encourage a red tide.

Although this display is beautiful to behold, some red tide organisms are toxic to other members of the marine ecosystem which can result in significant losses. These are mostly fish like trout, catfish and pufferfish, but also other species such as sea lions, turtle and manatees have also been affected. An example of a hazardous compound is saxitoxin, which is a neurotoxin with a tendency to affect humans in addition to aquatic life. This is why red tides are usually a sign not to enter the water. However, according to Latz, the species involved in the latest display do not produce dangerous toxins. Additionally, even a nontoxic red tide can be damaging to the environment, in enclosed or shallow waters (as pictured) the bloom can result in the depletion of oxygen, which also can have a big impact on the ecology in the waters.

But why have the dinoflagellates evolved the quirk of bioluminescence? Scientists are not one hundred percent sure of this. A popular theory is that the light startles the organism’s main predator, which are zooplankton, so the light acts as mechanism to protect themselves from being eaten. Nevertheless, this rare spectacle is a sight to behold, even though it has the potential to be harmful to those who dare enter the waters.


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