Empco Algaculture
Marine Microalgal Bioluminescence
What is bioluminescence?
Marine bioluminescence has been misunderstood throughout history by some of the world's most famous scientists, including Aristotle, Boyle, Hooke, and Newton. At present, scientific knowledge of marine algal bioluminescence remains rudimentary, at best.
Bioluminescence (not to be confused with fluorescence or phosphorescence) is the production and emission of light by a living organism as the result of a chemical reaction during which chemical energy is converted to light energy (Wikipedia.org).
Terrestrial and aquatic organisms alike exhibit bioluminescence. In a marine system, bioluminescent emissions are in the approximate wavelength range of 450 to 490 nm (blue light). Blue light travels further through water than other wavelengths of the visible spectrum, making it the ideal emission color for marine bioluminescent organisms. The ocean surface waters contain two predominant sources of bioluminescence: bacteria and algae. Beneath the epipelagic zone (200 m), bioluminescence becomes very common.
What does microalgal bioluminescence look like?
Click here to view Empco's bioluminescence photo/video collection.
How does bioluminescence relate to phytoplankton?
The only known phenomenon of algal bioluminescence occurs in a few species from the phylum Dinoflagellata. In fact, very few epipelagic organisms are capable of bioluminescence. But those equipped with it are likely advantaged. Bioluminescence requires ATP. Evolution therefore selects for the bioluminescence gene(s) because it aids in species survival. Although the purpose of bioluminescence is well documented in sub-epipelagic organisms (camouflage, attraction, repulsion), the purpose of bioluminescence in dinoflagellates is unknown. Bioluminescence is theorized to act as a defense mechanism against predators. Schantz (1971) proposed that bioluminescence acts as mimetic aposematic coloration, providing a false warning to predators of toxins that dinoflagellates do not actually have. Esaias and Curl (1972) hypothesized that the bright bioluminescent flashes startle predators, increasing the chance of dinoflagellate survival. Burkenroad (1943) proposed the most widespread dinoflagellate bioluminescence theory: the burglar alarm theory, which proposes that bioluminescence illuminates the grazers of dinoflagellates, thus attracting predators of the grazers. Although investigations on the validity of the burglar alarm theory have been conducted, no conclusive results have yet been obtained. Challenges often arise in simulating an accurate ecosystem in which to conduct such an investigation.
The Greek philosopher Aniximenes was the first to document marine dinoflagellate bioluminescence, in the sixth century (Harvey 1957). An oar he struck into the water produced dazzling blue light. This mysterious dinoflagellate bioluminesce has since captivated the attention of famous philosophers and scientists, including Aristotle, Boyle, Hooke, and Newton (Harvey 1957). Undercover naval vessels, SEALs, and torpedos have been exposed by mechanosensitive bioluminescence as well. Prior to many naval missions, bioluminescent-sensitive photometers must be used to determine if unsafe dinoflagellate blooms are present. In fact, the last sinking of a German U-boat in WWI occurred in 1918, when dinoflagellate bioluminescence revealed its location (Tarasov 1956).
Today in the twenty-first century, the mechanism of dinoflagellate bioluminescence remains a mystery, understood only in outline. Mechanical forces trigger an unidentified mechanoreceptor in the lipid bilayer to permit the entry of extracellular calcium into the cytoplasm. The influx of calcium propagates an action potential across the membranes of hydrogen ion storing vacuoles. The released hydrogen ions lower the pH of scintillons, activating the pigment luciferin, which is oxidized by the enzyme luciferase, releasing light in the wavelength of 475 nm as a product. (Cussatlegras and Le Gal 2007).
luciferin + O2 ––luciferase–– > oxyluciferin + light
Many cellular functions in dinoflagellates, such as bioluminescence, are controlled by a circadian rhythm. A clock biologist, Sweeney (1958), first discovered rhythms of oxygen release in the bioluminescent dinoflagellate, Gonyaulax polyedra. Subsequent studies revealed that bioluminescent output is 40 to 60 times greater in cells during the night compared to during the day. Although the phase of the rhythm can be shifted by changes in intensity and duration of light, the 24 hour rhythm persists even when cells are placed in constant light or dark.
The Phytoplankton Culture Collection of Empco (PCCE) offers three strains of bioluminescent marine dinoflagellates: Pyrocystis fusiformis, Pyrocystis lunula, and Pyrocystis noctiluca.
For recent news and updates regarding bioluminescence, visit The UCSB Bioluminescence Web Page.
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Scripps/UCSD: Glow with the flow