Original Ma Xiaoya
Gifts and warnings of the sea
- "Blue Tears"
Author/Ma Xiaoya
State Key Laboratory of Offshore Marine Environmental Science, Xiamen University
Why does the sea emit blue fluorescence? Why does the fantastic fluorescent sea arrive every year in late spring and early summer? Today, let's unveil the mystery of this "blue tear".
01. Why does the sea shed "blue tears"
"Blue Tears" is actually a poetic description of the luminescence phenomenon of marine organisms, and the real cause of "blue tears" is the large number of plankton in the ocean - luminous algae and sea fireflies, which can also be called red tide.
Luminous algae is one of the main algae species that occur in China where the phenomenon of "blue tears" occurs. It is a cold-water algae, and its breeding peak is mostly in April and May in late spring and early summer, and luminous algae red tides rarely occur in the hot summer. When the red tide of luminous algae erupts, the sea surface at night emits a beautiful "blue fluorescence", and as the waves rise and fall, it is like the sea shed crystal clear blue tears.
Of course, since it is a red tide, no matter how beautiful the fluorescence emitted at night, it is still dull during the day.
"Blue Tears" fluorescent coast in the Pingtan sea area of Fujian Province
02. Decipher the luminous principle of "blue tears"
In addition to luminous algae, there are many other luminous organisms that can form "blue tears", such as a plankton called the Heath's curved-throated sea firefly. The "blue tears" of different causes also have slightly different luminous mechanisms. Here is the example of luminous algae.
Microscopic luminous algae cells are chubby and up to 2 mm in diameter. The center of the cell has a small nucleus, the inside of the cell is filled with many large vacuoles, and the cytoplasmic filaments radiate from the center of the cell to the edge of the cell, forming a network. Except for a very small number of luminous algae that do not emit light, luminous algae cells contain thousands of particles containing fluorescein and luciferase, cytoplasmic filaments string these particles together like beads, when the luminous algae is strongly disturbed by waves, rowing, etc., luciferase catalyzes the reaction of luciferin with oxygen, producing oxygen-containing luciferin with energy, and producing light blue cold light in the process of releasing energy.
When the density of luminous algae in the sea is very high, the light blue light converges to form a "blue tear" visible to the naked eye!
Cytoplasmic filament structure of red luminous algae [quoted from a paper published by Yasuhiro Fukuda] where n refers to the nucleus and cy refers to the cytoplasmic filament
03. Can I take "Blue Tears" home?
Seeing the beautiful "Blue Tears", there may be many people who want to take them home to watch carefully. Theoretically, as long as they can be equipped with a comfortable "nest", they can start the breeding mode.
Taking luminous algae as an example, luminous algae is divided into two nutritional methods: heterotrophic and mixed nutrition, which are divided into red luminous algae and green luminous algae according to their different colors. Red luminous algae have no pigment body, for complete heterotrophic plankton, can not directly photosynthesis for self-replenishment nutrition, can only eat other phytoplankton, bacteria, etc. to obtain nutrients, so food is particularly important for red luminous algae. This means that we need to first allocate the right temperature of seawater, add nutritional salts, and raise the creatures that luminous algae like to eat, in order to successfully feed the red luminous algae baby.
The green luminous algae has symbiotic green algae in the body, which makes the cells appear green. Although symbiotic green algae can photosynthesize to help the green luminous algae survive urgently when food is scarce, swallowing other plankton when food is plentiful is still an important way for luminous algae to obtain nutrition, so feeding luminous algae babies is still a difficult task.
Green Luminous Algae (Top) and Red Luminous Algae (Bottom) [Quoted from a paper published by K. Fuuruya]
04. Is it a gift or a warning?
Originally, "Blue Tears" was just a beautiful natural phenomenon, a beautiful gift from nature. However, in recent years, as human damage to the natural environment has gradually intensified, the appearance of "blue tears" has gradually changed its meaning - the appearance of red tide often means that there have been some abnormal changes in the local marine environment, which may be the eutrophication of seawater, or changes in wind direction and rainfall conditions.
Although the luminous algae that causes "blue tears" do not release toxins like other toxic red tide algae, dense plankton not only reduce the oxygen exchange between air and seawater, but also consume a large amount of oxygen in the water, making it impossible for other organisms to breathe, so that the "blue tears" that have not disappeared for one or two months in a row will become a nightmare for aerobic organisms in the local sea.
In recent years, the red tides we have captured in Fujian waters include The East China Sea Proto-Dinoflagellates, Kailun Algae (genus), Shi's algae (genus), and Knee Groove Algae (genus). With the complexity of the ecological environment, mixed red tides, that is, red tides caused by non-single species, also have an increasing trend, and more and more complex red tides have also brought certain difficulties for researchers to explore the mechanism of red tide outbreaks, but scientists are still making unremitting efforts to explore the ecological mysteries buried in small marine organisms.
Toxic red tide causes mass deaths of farmed seabream (Lianjiang, Fujian/Yuan Huatao)
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