Жарқыраған теңіз тұрқыласы: Noctiluca scintillans

Bioluminescent, marine dinoflagellate

Noctiluca scintillans is a marine species of dinoflagellate that can exist in a green or red form, depending on the pigmentation in its vacuoles. It can be found worldwide, but its geographical distribution varies depending on whether it is green or red. This unicellular microorganism is known for its ability to bioluminesce, giving the water a bright blue glow seen at night. However, blooms of this species can be responsible for environmental hazards, such as toxic red tides. They may also be an indicator of anthropogenic eutrophication.

The name Noctiluca scintillans comes from the Latin Noctiluca, meaning "light at night" and scintillans, meaning "shining, throwing out flashes of light". This classification is still subject to discussion today and the relationship of Noctiluca to the dinoflagellates is not yet clearly demonstrated, as the results of analysis are still too variable to assert a single classification. At present, it is part of the phylum Myzozoa, which are unicellular flagellated organisms. It is then part of the class Dinophyceae, which has two flagella, the order Noctilucales, whose nucleus is not dinokaryonic in the adult, and the family Noctilucaceae, which has a globular shape with a tentacle.

Noctiluca scintillans is a single celled spheroid organism, ranging from 400 to 1500 μm in length. It moves with the current and cannot really swim. Noctiluca scintillans is a species capable of managing its buoyancy by regulating the intracellular ion concentration. To rise, the concentration of potassium will increase and to fall, it will use heavier elements such as calcium or magnesium. Because of their excessive proliferation, they attract many predators due to their very dense aggregations and frequent bioluminescence in this phase of their life. and the Red Sea. It is the transformation of chemical energy into light energy by a living being which then emits this light. Bioluminescence differs from fluorescence and phosphorescence because the latter two require contact with light to trigger the phenomenon. N. scintillans produces luminous flashes, which constitute bioluminescence, during mechanical stress. This phenomenon can therefore be observed in agitated water, i. e. when boats are passing, near the coast at wave level or after water agitation. Luciferin combines with luciferase and the two react with oxygen to form an oxidised complex. The luciferin then emits a photon. Of course, the reaction itself is not so simple, in fireflies it also requires two additional cofactors, ATP and magnesium. There are also several types of luciferin and each is associated with a specific luciferase giving different chemical reaction systems. The light is produced by mechanical stimulation due to shear stress. The deformation of the cell membrane causes an action potential across the vacuole membrane caused by Ca2+ ions released from intracellular stores. This action potential releases an influx of protons from the vacuole to the scintilla, lowering the pH from 8 to 6. This changes the conformation of luciferase making it active. Luciferin contains a binding protein that prevents it from auto oxidising in an alkaline pH. It releases it by a conformational change in acidic pH, activating luciferin. This activation then allows the enzyme to oxidise luciferin to oxyluciferin. It is this molecule that leads to the emission of photons by an unknown process. The eutrophication of the water is therefore not directly related to Noctiluca scintillans, but the fact that the dissolved oxygen concentration is already slightly low during the monsoon period shows a more consistent development of the species which worsens the situation by increasing its oxygen uptake and decreasing the amount of available dissolved oxygen. This decrease in natural dissolved oxygen is actually caused by the presence of phytoplankton brought in by the hypoxic waters of the Southern Ocean during the monsoon period. To date, this is the only explanation for the arrival of the low oxygen waters. There is still a lot of work to be done to find ways to remedy this problem, especially to understand the precise mechanisms of the interaction.

+Summary of the role of N. scintillans in the environmentPositive effectNeutral effectNegative effectIn the food chainBioluminescence (role unknown)Euthrophication, impacts on coral reefs, red tides

The phenomenon of bioluminescence is very nice to observe, but it is not found everywhere at any time. Attached is a calendar of peak abundance in different regions of the world and in different months of the year. +Calendar of N. scintillans sightingsRegionMonth of the yearJFMAMJJASONDNortheast Atlantic (Gulf of Gascony)XNorth Sea (Flemish, Zeeland and Holland coast)XXBlack Sea (central north)XBlack Sea (south)XBlack Sea (North East) XSea of MarmaraXAdriatic Sea (North)XNorth Arabian Sea (Pakistan coast)XXNorth West Arabian Sea (coast and open sea)XXXWest Arabian Sea (Gulf of Oman)XXEast Arabian Sea XRed Sea (North)XXNorth East Indian Ocean (Bay of Bengal)XXXXXXGulf of ThailandXXSouth East Australian Shelf XXNorth West Pacific Ocean (Japanese Shelf)X