By Nancy Richie
Bioluminescent. A big word for tiny organisms. Each summer, a few locations in the Marco Island canals glimmer and twinkle in the night. Boat wakes, fish movement and jelly fish paths sparkle as the bioluminescent organisms are agitated in the water. Not just the fireworks were lighting up our Island on the 4th of July, but there was a bloom of bioluminescent algae that doubled the pleasure of the fireworks for a few residents. Studies at Scripps concluded that bioluminescent dinoflagelletes thrive in calm waters which most likely results from their extreme flow sensitivity that triggers luminescence.
These glimmering organisms, vary in size and shape but are generally very small, unicellular phytoplankton (micro algae), called dinoflagelletes, and are found worldwide in warm subtropical and tropical waters. About two thousand species of dinoflagelletes are found in marine waters and it has been estimated that about 30% of these species are bioluminescent. They typically have two “tails” called flagella that are used to propel the single cell algae organism through the water. Dinoflagelletes species are food sources for larger marine animals but they can also live symbiotically with other species. One the best known symbiotic relationship of a dinoflagellete exists with coral in reefs. The zoosanthellae dinoflagellete, a micro algae species, for protection lives within a coral polyp. It symbiotically photosynthesizes food for both themselves and the coral and at the same time gives the coral its beautiful colors.
So how does this single cell algae light up? The light is not absorbed and radiated but is a chemical reaction created within the organism itself. Similar to when a “glow stick” is bent and shaken, a chemical reaction occurs. In the case of dinoflagelletes it is a reaction of a substance called luciferin and the enzyme luciferase in the present of oxygen creates light energy within the dinoflagellete.
Bioluminescence is a widely distributed phenomenon in other marine species; from fish to squid, crustaceans, worms, jellyfish, shellfish, and bacteria. Some of this may be due to ingesting the dinoflagelletes, but many times the bioluminescence is creating within the species and used for offensive (illuminate, stun and distract prey) and defensive (startle, distract, use as a “smoke screen” and warn predators) measures. It could also be used to attract mates.
Marine bacteria species that create bioluminescent show a different display of light. While dinoflagelletes spark and glimmer when agitated by boat wakes, waves crashing or fish movement, the bioluminescent bacteria species, when at very high concentrations, can give a continuous glow causing, what sailors call, a “milky sea”. This situation has been recorded by mariners for centuries.
Some species of dinoflagelletes are known to be quite dangerous in the right conditions. Locally, we know Karenia brevis, or Red Tide, a dinoflagellete species that blooms can cause upper respiratory discomfort, fish kills and discolored waters. This species is not bioluminescent. Scientists study these blooms to understand the causes, possible prevention and life cycles of dinoflagelletes. They also study bioluminescent single-cell dinoflagelletes to help explain how all cells can be affected by the complexities of flow in their fluid environment. There are also studies to explore how dinoflagelletes can be used in microscopic flow sensors, which in the future, could be used to develop safer artificial hearts by ensuring the shear of blood flow is not too high or low.
Just look in a canal nearby and you may see the twinkling and glimmering show of bioluminescent dinoflagelletes this summer! Another extraordinary and beautiful reason to live on Marco Island is summed up by resident Burt Robbins the morning after 4th of July as he states, “After the fireworks last night I was really surprised to see an even greater light show. Our canal was packed with bioluminescent organisms. I could not believe how bright and reactive they were.”
If you need additional information or have any questions and/or comments, please contact the City of Marco Island at 239-389-5003 (office), 239-825-0579 (mobile) or firstname.lastname@example.org. Nancy Richie is a long time Island resident and Marine Biologist.