Bioluminescent Beasties Light Up California Beaches

SCIENCE

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Discussion Ideas

Why are waves turning electric blue when crashing into California beaches?
- Miles of Southern California beaches are experiencing a “red tide”—a rapid, dense accumulation of plankton.
  - The plankton causing bioluminescent red tides in Southern California are dinoflagellates. Dinoflagellates are microscopic marine organisms (protists) that float near the ocean surface. Click here to learn more about dinoflagellates from the good folks at the University of California Museum of Paleontology (one of our favorite resources).
    - Dinoflagellate-driven red tides can sometimes contribute to harmful algal blooms, which threaten aquatic environments by reducing the amount of oxygen in the water, blocking sunlight, or releasing toxic chemicals.
    - Most dinoflagellate-driven red tides are sporadic, hard to predict, and harmless. Red tides like the one in Southern California can last from a few days to a few months. “But in some areas,” the good folks at Scripps remind us, “such as the so-called bioluminescent bays of Puerto Rico, brilliant bioluminescence persists throughout the year and makes for an amazing personal experience as you kayak or swim through the warm water.” Those bioluminescent bays were disturbed by Hurricane Maria, but are well on their way to recovery.

Why do dinoflagellates glow?
- Not all of them do. The dinoflagellate species responsible for the glowing waves is Lingulodinium polyedra. (L. polyedra just got a new name this year. Read all about it here.)
- The glowing dinoflagellates are bioluminescent, meaning chemical reactions within the organism itself can produce the organism’s own “living light.” The flashes of bioluminescence in the Southern California dinoflagellates are triggered by mechanical stress or agitation; even slight movement in the water around them can cause these creatures to glow.
  - Take a look at this video of surfers agitating millions of dinoflagellates in the coolest special effect you’ll see today.
- Bioluminescence in dinoflagellates is a defense mechanism. “Dinoflagellate flashes cause a startle response in their predators, disrupting their feeding behavior and resulting in a decrease in grazing rate by reducing the number of dinoflagellates consumed. Dinoflagellate bioluminescence is also thought to act as a ‘burglar alarm’ to attract a secondary predator that threatens to eat the primary predator.”

How do dinoflagellates glow? Browse our reference resource for some help—we even have a short section on dinoflagellates.
- The chemical reaction that results in dinoflagellate bioluminescence requires two unique chemicals: luciferin and luciferase.
  - Luciferin is called the base or substrate. Dinoflagellates’ blue-green bioluminescent color is a result of the arrangement of luciferin molecules.
  - Luciferase is an enzyme. An enzyme is a chemical (called a catalyst) that interacts with a substrate to affect the rate of a chemical reaction.
  - Through an exchange of protons in cell structures called scintillons, the luciferin-luciferase reaction creates a flash of light.

OK, but if the bioluminescence is blue-green, why is the phenomenon called a red tide?
- The dinoflagellates are not bioluminescent all the time, and the bioluminescence is really best visible at night.
- During daylight, the mass of organisms appears reddish. That’s also when the red tide is most active and visible. (Click here to take a look at a red tide during the day.) “At midday, the photosynthetic organisms swim upward toward the light, creating a thin, dense layer near the surface. Circulation patterns create dense groups of the red tide organisms over the troughs of the waves.”

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