Noctiluca scintillans is a marine species of dinoflagellate that can exist in a green or red form, depending on the pigmentation in its vacuoles.

This unicellular microorganism is known for its ability to bioluminesce, giving the water a bright blue glow seen at night.

This remained the case until 1920 when Charles Atwood Kofoid finally placed it in the order Noctilucales following certain observations.

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.

[citation needed] Noctiluca scintillans is a single-celled spheroid organism, ranging from 400 to 1500 μm in length.

N. scintillans has a long cytoplasmic expansion that hangs at the base of a deep groove, close to which is the nucleus.

Another identifying feature are the fine striae that start from the central nucleus and extend towards the periphery of the cell.

[4][5] 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.

[6] Because of their excessive proliferation, they attract many predators due to their very dense aggregations and frequent bioluminescence in this phase of their life.

[citation needed] Noctiluca scintillans is a heterotrophic dinoflagellate that causes toxic red tides.

As gametogenesis progresses, there is a condensation of chromosomes within the different nuclear divisions which darkens the colour of the cell.

During further development they become rounder, and two distinct flagella are formed, one longer and one shorter, and finally only one is left.

The result is a miniature trophont with a tentacle through which it absorbs food to eat by means of viscous materials to which the algae cling.

The population varies according to sunlight, current, the presence of nutrients (especially nitrate, ammonium and urea), water salinity, temperature and trophic stress.

[7] The two forms overlap in the western, eastern and northern Arabian Sea with a seasonal difference in abundance.

He named the two substances luciferase, a thermolabile enzyme, and luciferin, which is preserved by hot water but is present in limited quantities in organisms.

There are also several types of luciferin and each is associated with a specific luciferase giving different chemical reaction systems.

[10] In the case of Noctiluca scintillans, the chemical reaction occurs in organelles called scintillons.

This action potential releases an influx of protons from the vacuole to the scintilla, lowering the pH from 8 to 6.

Bioluminescence is therefore influenced by cell sensitivity to stimulation, specific response, time, physiology and environmental factors.

[1] The proliferation of N. scintillans can be toxic, and has been linked to massive mortality of fish and marine invertebrates.

It is actually because of the accumulation of ammonium in excessive quantities and the reduction of dissolved oxygen in the direct ecosystem during its proliferation that N. scintillans is harmful to other species of fish and invertebrates that experience high mortality.

[1] When the concentration of individuals exceeds one and a half million per litre, the water turns pink or orange, hence the name of the red tide phenomenon.

Since then, winter dissolved oxygen concentrations in the upper euphotic zone have remained low.

This allows the species to grow faster and thus creates waves of green Noctiluca scintillans blooms in the Arabian Sea every winter.

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.

[12] Another interesting detail is that Noctiluca scintillans produces large amounts of phosphorus and nitrogen in its excretions.

[4] The bloom of the species has often been linked to mass mortalities of marine invertebrates and fish but in reality it does not produce toxins, it accumulates lethal amounts of ammonium which is then excreted into the environment.

[13] 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.