Corals emit a fluorescent light at night thanks to an interaction between the fluorescent proteins present in their tissues and the blue light of the solar spectrum that they absorb during the day.
Corals often live near the surface, where the sun's ultraviolet rays strike hard. To avoid this damage, they use an original trick: the production of fluorescent pigments. These pigments act like an improvised sunscreen, absorbing ultraviolet rays and transforming them into visible light that is much less harmful. At night, even in the absence of UV, these pigments sometimes continue to emit a faint fluorescence because they release the energy accumulated during the day. This phenomenon helps to avoid excessive stress on the corals, aiding them in preserving their precious microscopic partner: the zooxanthellae, symbiotic algae essential for their survival.
The nighttime fluorescence of corals is largely due to the presence of specific proteins called fluorescent proteins. These proteins absorb ultraviolet or blue light and re-emit it at a different wavelength, in the form of visible, colored, and fluorescent light. During the day, this phenomenon is less noticeable because the intensity of sunlight masks the fluorescence. But at night, when the environment becomes darker, this light emission becomes easily visible. This mechanism occurs in special cells where fluorescent pigments capture light energy and then emit it in another, less energetic form of light, resulting in the often green or reddish fluorescent color effect. These colors mainly depend on the precise type of fluorescent pigments present in each species of coral.
The temperature of the water greatly affects coral fluorescence. For example, slightly higher temperatures often increase their fluorescence as a defensive reaction. However, if it heats up too much or for too long, that’s when it becomes problematic: prolonged thermal stress eventually weakens and bleaches the corals, ultimately reducing their ability to produce this fluorescent light.
The same goes for changes in water acidity (pH). A more acidic pH (linked to increased carbon dioxide) can temporarily intensify fluorescence, but over time, it weakens the corals.
The same applies to ambient light. Ultraviolet radiation or overly intense brightness during the day prompts corals to respond by increasing their nighttime fluorescence, serving as a kind of natural biological sunscreen.
Chemical pollution, such as the presence of certain heavy metals or chemicals in the water, also disrupts fluorescence, but often negatively: it decreases light intensity and can even completely halt the fluorescent reaction over time.
The nocturnal fluorescence of corals plays a key role in their relationships with other marine organisms, notably by attracting certain prey to the polyps with their colored light. Some species of fish and shrimp also use this fluorescence to identify their environment and locate their shelters among the reefs. Conversely, some predators instinctively avoid fluorescent areas, a potential sign of toxicity or danger. Thus, corals emit subtle and strategic visual signals that shape a whole series of ecological interactions on the reef.
The fluorescence of corals particularly interests scientists as a bioindicator to monitor the health of reefs. Essentially, the more the fluorescence changes, the more it indicates that there may be an environmental or climatic problem in the area. In medicine, fluorescent proteins derived from corals, such as the famous GFP (Green Fluorescent Protein), are used as biological markers. They make certain cells or structures visible in the laboratory, which greatly helps researchers observe diseases, study cancer cells, or even track embryonic development in certain organisms. These fluorescent proteins have thus become valuable tools for understanding how our own bodies function.
The bright colors of fluorescence can attract certain marine organisms such as small fish or crustaceans, thereby influencing nocturnal ecological interactions in coral reefs.
Each species of coral has a specific fluorescent signature; thus, divers and scientists can identify coral species simply based on their nocturnal light emission.
The fluorescence of corals allows scientists to monitor their growth and health status by detecting early signs of stress such as bleaching or disease.
The green fluorescent protein (GFP), originally isolated from a jellyfish but also found in many corals, is now widely used in medicine and biotechnology as a genetic marker.
Yes, these coral fluorescent proteins have proven to be extremely useful in medicine and biological research. They are particularly used to label cells or tissues in medical imaging studies and to visualize complex biological processes in laboratories.
Yes. Studies show that the intensity and patterns of fluorescence can provide scientists with valuable insights into the health of corals, particularly concerning their oxidative stress, potential diseases, or changes in their marine environment.
Fluorescence is not exclusive to corals. It is also found in algae, fish, jellyfish, as well as various other marine invertebrates. It serves different biological roles depending on the organisms involved.
In certain circumstances, fluorescent corals can have an ecological advantage. Fluorescence acts as a protective shield against ultraviolet rays, limits the harmful effects of excessive light radiation, promotes the attraction of symbiotic organisms, or serves as a means of communication with other marine organisms.
No. Not all corals emit fluorescent light at night. This phenomenon depends on the presence of specific fluorescent proteins that react to certain wavelengths of light, as well as the species of corals and particular environmental conditions.
Yes, with the appropriate equipment. Coral fluorescence can be easily observed at night using special lamps that emit blue or ultraviolet wavelengths, combined with suitable eye filters that reveal the bright fluorescent colors of the corals.
No one has answered this quiz yet, be the first!' :-)
Question 1/5