Growing up in Southern California, every so often there are reports in the news of a “blue tide” off of the coast. As a kid, these always intrigued me as I would venture with my family to the beach at night to watch the glowing waves crash onto the shore. Little did I know that although this phenomenon may be a rare spectacle on the seashore, it is not unlikely to be found in the deep sea.

Bioluminescence is defined as the production of light by living organisms. This occurs due to a chemical reaction that results in the creation of light energy within the organism’s body. In order for this reaction to take place, the organism must have the luciferin molecule, which reacts with oxygen to produce a light. Some organisms produce a catalyst called luciferase to help bind the luciferin to the oxygen, speeding up the reaction. Many of these bioluminescent creatures can control when they light up through regulation of brain processes and chemistry in their body. Animals that do not have the luciferin molecule may even take in bioluminescent creatures or bacteria in order to light up.

Photography by Smit Patel: bioluminescent medusa jellyfish

The color produced by the bioluminescent organism depends on the environment in which it lives. Light travels differently underwater since longer wavelengths cannot travel as far as it would through the air. Most underwater bioluminescent organisms produce blue or green light since these are shorter wavelengths that can travel and be seen in both shallow and deep water. However, even though red cannot be seen in the deep sea, some organisms are red to help with camouflage since it is like being invisible. For example, dragonfish create red light in the deep sea to see red colored prey and to communicate with other dragonfish.

Although bioluminescence is fascinating to watch, it also helps in the survival of these organisms. Lights can be used to attract and lure prey towards their mouths. The deep sea anglerfish is a popular example of this tactic. Light can also help the predator see the surrounding area better in hopes of finding prey. Additionally, bioluminescence is a helpful tactic to draw attention and hopefully attract a mate.

The Caribbean ostracod uses bioluminescent signals from its lips to attract female mates. Another useful benefit of bioluminescence is as a form of protection. A bright signal can startle and confuse the predator, scaring them away. Some animals can painlessly detach their bioluminescent arms and swim away to distract the predator. Bioluminescence can also aid for camouflage, helping the organism blend into its surrounding environment to help avoid predators. Bioluminescence is not only entertaining for those who get the chance to watch the spectacle, it is also a purposeful survival tactic for these organisms.

Thank you to volunteer Zoe Jee for her contribution. Missed a blog? Check out last week's Report from Alaska #2 and other previous blogs here.

Glowing Waters: Bioluminescence in our Oceans