physiology and environmental factors. n. scintillans is less prone to predation when in this 'phase' of bioluminescence, so this may be one of the functions of bioluminescence. the function of bioluminescence has not yet been proven, it is only a theoretical concept. however, it seems to act as a defence against predators, for oxygen, camouflage and seduction. n. scintillans is not the only species capable of bioluminescence; pyrocystis lunula, a dinobiont, or certain bacteria are also capable of it. risks red tides the proliferation of n. scintillans can be toxic, and has been linked to massive mortality of fish and marine invertebrates. however, this species does not produce toxins, which are often the cause of the harmful effect of these tides when they are caused by other organisms. 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. 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. in 1970, concentrations of 2,400,000 n. scintillans per litre were found. this phenomenon is not always red. the colour depends on the pigment in the vacuole of the organism and can be green. (there is a picture in the morphology section). other species can also cause red tides, such as species of dinobionts, which are single-celled organisms with 2 flagella. it is necessary to check under the microscope whether the red tide is indeed caused by noctiluca scintillans or not. eutrophication noctiluca scintillans was first discovered in the arabian sea in the 2000s, according to a recent study, which was also the first time that the sea water was undersaturated with oxygen. since then, winter dissolved oxygen concentrations in the upper euphotic zone have remained low. it has been shown that the species grows best in an environment with abundant light (for the green genus) and with a lower dissolved oxygen concentration, this increases oxygen uptake in the species and further decreases oxygen levels. this allows the species to grow faster and thus creates waves of green noctiluca scintillans blooms in the arabian sea every winter. 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. another interesting detail is that noctiluca scintillans produces large amounts of phosphorus and nitrogen in its excretions. 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. it is during toxic red tides, that the red genus excretes these lethal amounts to the animals around it. impact on coral reefs coral reefs have been in severe decline in recent decades. according to a study conducted in 2019 in the gulf of mannar (south india), hypoxic conditions caused by algal blooms are causing massive mortality of coral reefs. in this study, it is shown that noctiluca scintillans causes the death of these corals significantly by overgrowth, as their reproduction causes a decrease in dissolved oxygen of 2 mg/l. this causes lethal hypoxia for corals of the genus acropora, montipora and pocillopora. this phenomenon will only increase with climate change, which will increase the frequency and intensity of blooms. more and more corals will be affected. 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. corals are home to 25% of the earth's marine life. so there is a lot at stake in understanding this. role in the environment summary of the role of n. scintillans in the environment positive effect neutral effect negative effect in the food chain bioluminescence (role unknown) euthrophication, impacts on coral reefs, red tides calendar 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 sightings region month of the year j f m a m j j a s o n d northeast atlantic (gulf of gascony) x north sea (flemish, zeeland and holland coast) x x black sea (central north) x black sea (south) x black sea (north-east) x sea of marmara x adriatic sea (north) x north arabian sea (pakistan coast) x x north west arabian sea (coast and open sea) x x x west arabian sea (gulf of oman) x x east arabian sea x red sea (north) x x north east indian ocean (bay of bengal) x x x x x x gulf of thailand x x south east australian shelf x x north west pacific ocean (japanese shelf) x