On March 29, the whole of Xiamen was swept away by "blue tears", and a fluorescent sea of light appeared in the local Yundang Lake and Huandao Road in Xiamen! When you walk on the shore of the night, the waves of the sea shimmering blue fluorescence come in, which is comparable to a fairy tale scene, but it is real in the real world.
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Surprised by the blue tears of Xiamen
In fact, these blue fluorescences are formed by some glowing marine creatures, in fact, not only in the coast, but also in the deep sea there are many luminous creatures, in the middle of the night, they make the dark and silent ocean become vibrant.
"Blue Tears" with Milky Seas
Long ago, coastal fishermen witnessed the blue fluorescent waves, which they called "sea fires", but now more people call them "blue tears".
In addition to the "blue tears", the phenomenon of the sea glowing is also the phenomenon of the "milky white ocean". We know that in English, the milky way is called The milky way, and the "milky sea" is called Milky seas in English. In 1995, the ship Lima, which witnessed it, reported on the Milky Seas, "as if the ship were sailing on a patch of snow and as if it were moving through the clouds."
Luminous in the deep sea
In addition to the waves of the coast, there are many creatures that emit light in the deep sea, which cannot be penetrated by light. Many crustaceans, starfish, algae, jellyfish and even fish have the ability to emit light, from luminous algae with a diameter of only a few millimeters to armored sharks with a body length of more than a meter. The reasons for their ability to emit light are varied, and the luminescence mechanism of many species remains an unsolved mystery.
Luminous algae with a diameter of only 0.2-2.0 mm
Recently, researchers in New Zealand have discovered that armored sharks can emit light
In short, whether it is the creatures that create the "blue tears" or the creatures that glow in the deep sea, together they make the whole ocean more colorful. And next, we'll explore their illuminated codes together.
Light up the "cold light"
Step 1: Filament
Most luminous creatures live in the ocean, and there are almost no luminous creatures in freshwater. At the same time, the fluorescence emitted by living beings is a kind of "cold light", and less than 20% of this light produces thermal radiation and heat. Simply put, when this biofluorescence hits us, we don't feel as warm as the sun's rays.
If bioluminescence is like the process of lighting a light bulb, then the chemicals it requires are like the filament of that light bulb. So, what is the filament needed to light up the "cold light"?
A cigar Dharma shark that emits a "cold light"
From a chemical point of view, the chemical reaction that produces bioluminescence requires two unique chemicals, namely luciferin and luciferase or photoprotein. After a complex physiological process, the difference in the color of the light emitted by the final organism is the result of the different arrangements of fluorescein molecules.
Luciferin/luciferase luminescence principle
At the same time, the ways in which living beings make themselves glow are also different. Some organisms emit light by producing their own luciferin, such as the luminous organism Dinoflagellus; while some organisms cannot synthesize luciferin themselves, but can absorb fluorescein by eating other organisms or coexisting with them, such as squid, and the luminous bacteria in their light organs that symbiosis with them can make them glow.
Hawaiian short-tailed squid that symbiotes with luminous bacteria
Step 2: Switch
We liken a chemical that makes bioluminescence to a filament in a light bulb; then the biological behavior or ecological conditions that cause the organism to eventually emit light are equivalent to the switches that light the bulb. We have already introduced the chemicals that illuminate the "cold light", so what are the biological behavior and ecological conditions that can act as switches?
In general, we can roughly divide it into two types: one is that organisms spontaneously emit light; the other is that organisms emit light due to the influence of the environment.
In the ocean, creatures spontaneously fluoresce out of instinct to prey, find a mate, or defend. Let's give you a few interesting little examples.
The ugly-looking sturgeon actually has a very small and beautiful "little lantern", which we also call bait. Seeing the name of this "little lantern", I think everyone has already guessed its role. The trout with "little lanterns" can often lure some weak creatures, although these creatures see the glimmer on the top of the sturgeon's head, but they do not see the danger below, so they become the belly food of the squid.
At the same time, we often think that squid spew out black juice that traps predators in the dark. But many of the squids that live in the deep sea spew out not black sap. For example, the vampire squid, which actually spews out glowing mucus, and uses this to confuse predators and buy themselves time to escape. There are also sea snakes that are able to emit light and, when encountering predators, are able to separate some of the glowing parts of their bodies to distract predators.
A glowing sea snake
In addition, many creatures also use luminescence to hide themselves in the ocean. When many sharks hunt, they look above them, and the light casts a shadow on the creatures, which sharks use to find their prey. Some creatures "eliminate" their shadows by emitting light, in order to achieve a hidden effect, which we can call "counter-illumination" (counter-illumination), and some people call it "luminous extinction".
Of course, there are many luminescent phenomena in the ocean that adapt to the environment. For example, most marine life can only recognize blue-green light, and they cannot recognize yellow, red, or purple. For example, the protective light of ctenophores can make it ingested by translucent predators, causing these predators to glow, exposing them to more advanced predators, and this protective light is also known as the "sacrifice label".
A ctenophore that emits rainbow light
In addition to spontaneously emitting light from organisms, some organisms also emit fluorescence after being stimulated.
For example, a drop in salinity can force some algae that can emit light to emit light. When they glow, they look like pink or green dots of light in the dark ocean, and this luminous phenomenon is also called spark-type luminescence.
Another type of luminescence that we call flash type is a phenomenon that emits light after being stimulated by some large animals such as jellyfish.
Glowing jellyfish
And the Milky seas that we mentioned at the beginning are a phenomenon in which the ocean emits a continuous stream of light, which we also call diffuse luminescence. Scientists believe that this is most likely due to the glowing bacteria on the surface of the ocean. Of course, the conditions for the formation of this phenomenon are very harsh, and while millions of bacteria must be present, other conditions must also be very suitable. At the same time, Milky seas can also be observed by satellites, and the blue glow spots in this photo are nearly 300 km long, covering an area as large as the Hawaiian Islands!
Milky seas in satellite photos
A glowing ocean near the late ruler
From our human perspective, the most intuitive effect of glowing marine life on us is of course a visual feast. The dreamy scene of the sea fire seems to be a fairy tale in the world, and whenever they appear, they will quickly appear on the news and attract people's attention - the stars falling into the sea are no longer words, but real romance. The closest time and space to us is the "Blue Tears" that appeared in Xiamen's Yundang Lake and Music Square on March 29, 2021.
"Blue Tears" under the lens of Xiamen netizens
But on the other hand, the conditions for producing "blue tears" can be very harsh, similar to Milky seas, which requires a fairly high concentration of luminous organisms and is accompanied by some conditions such as seawater surge, which also brings us ecological and environmental hazards. Some theories suggest that the appearance of "blue tears" is likely to mean that the content of some nutrient factors in the seawater has risen, causing the number of luminous organisms to rise significantly, in other words, it may be a precursor to the occurrence of red tide.
For academic research, luminous marine life also guides scientists to continue to grope forward in the field of bioluminescence, just like the green light that Gatsby believes in in "The Great Gatsby" constantly flashes, dragging scientists to sail against the current and travel to the haunting place. When scientists studied luminous jellyfish, they miraculously discovered another substance, which is what academia knows today as green fluorescent protein (GFP).
Green fluorescent protein
As you may recall, the green fluorescent mouse in the biology textbook that only emits light is the product of the introduction of the green fluorescent protein gene. The use of green fluorescent protein in academia is so widespread that when members of the 2008 Nobel Prize in Chemistry committee commented on it, they affectionately called it "illuminating the future of biological research."
Can you believe it? There is an old legend in Norse mythology that says that if a person sees a green light in his lifetime, his wish will come true. A lot of people think, that must be the Aurora Borealis. But I think, relative to the sky, the glimmer of life in the ocean is not the green light we expect in life?
bibliography
[1]https://www.nationalgeographic.org/encyclopedia/bioluminescence/
[2]http://blog.sciencenet.cn/blog-3500-620374.html
[3]http://www.ngchina.com.cn/animals/facts/10045.html
[4]https://post.smzdm.com/p/ag87r6x3/
[5]https://www.bbcearth.com/blog/?article=the-mystery-of-the-milky-sea
Source: Marine Media Lab