Bri Groves
Organisms are fascinated by light, but as the sun goes down, light is a rare commodity. To brighten the night, some organisms produce their own pseudo flashlights. These creatures are labelled as bioluminescent. Bioluminescence refers to an organism’s ability to produce its own light through a chemical reaction. Fireflies are prominent bioluminescence producers, but Boothbay harbors several others worth looking at. Many marine organisms rely on bioluminescence to attract prey, confuse predators, and entice mates. Humans usually see bioluminescence induced by physical disturbances, such as water movement, that trigger creatures to illuminate themselves. While this false alarm may be energetically costly for the organism, humans can enjoy the accidental performance.
Nature’s Light Show
Bioluminescence is found in a variety of marine organisms including (but certainly not limited to) algae, bacteria, crustaceans, jellyfish, worms, seastars, fish, and sharks. For Boothbay residents, small organisms provide a grand show. Many minute planktonic surface dwellers, like dinoflagellates, are bioluminescent. At dusk, a biological clock prompts light production, but collisions are essential for admittance. For optimal viewing, go out to the ocean on a cloudy calm night. Use your hand or grab a stick to disturb the surface water. Watch for blue and white lights as you skim the liquid. Some areas may provide more glow than others. Look for patches of algae growth, hydroids, or particularly shallow regions. These locations are perfect for dinoflagellate accumulation and some of the surrounding organisms may even emit their own light. Keep an eye out for rarer sightings such as glowing jellyfish, ctenophores, and fish.
Making Light
Bioluminescence requires a chemical reaction to produce light within an organism’s body. The key to lighting up is luciferin, a molecule that, in the presence of oxygen, emits a flashing glow. Not all luciferin is made equal. Bioluminescent species have a wide range of luciferin types, and this diversity leads to a plethora of luminescing varieties. Physiological differences in chemistry, enzymes, and regulation have led to a multiplicity of unique light patterns, colors, and intensities. The vast numbers of bioluminescent organisms and their patterns suggest that bioluminescence may have evolved separately over 40 times.
The Benefits of Bioluminescence
Bioluminescence has a variety of purposes. For some organisms, bioluminescence is a way to lure prey, for others, bioluminescence has the opposite effect. Some organisms emit light when they are being eaten or attacked. This light show serves as a last resort burglar alarm. The light may attract larger predators to come and eat the current feeding predator. This light serves as a communication source between species, but light is also used for interactions and courting within the same species. Arguably one of the most elaborate applications of bioluminescence is counterillumination. Counterillumination is a process through which light can be used to help camouflage organisms from prey. In some neritic animals, photophores on the bottom of their bodies can be used to match the light shining down from the surface water. This process allows bioluminescent swimmers to blend in and makes it harder for predators to identify prey from below.
Bri Groves is a Mount Holyoke College student in Bigelow Laboratory for Ocean Science’s Research Experience for Undergraduates program. This intensive experience provides an immersion in ocean research with an emphasis on hands-on, state-of-the-art methods and technologies.