‘Blue tide’, a rare occurrence when luminescent marine life colours the sea in a deep shade of blue, was witnessed for the second time this year near Juhu. The natural phenomena, that has been seen for the last two nights, will be on display for the next two nights, said marine scientists.
The Central Marine Fisheries Research Institute (CMFRI) confirmed that the occurrence of bioluminescence – emission of light by marine organisms - has been observed at several coastal areas this year. Earlier in January, the phenomenon was observed at the same location by students of Bhavan’s College, Andheri.
The spectacle occurs when phytoplanktons (microscopic marine plants), commonly known as dinoflagellates, produces light through chemical reactions in proteins, said researchers. The sight has been observed across India’s coast as well as the coastline of many beaches in the world such as Maldives, Vietnam, Indonesia, USA, Australia and many other countries.
“This can be due to several factors for the occurrence but one of the main factors could be eutrophication – the reduction of oxygen in the water, which makes the phytoplanktons pretty dominant. A sample of the water needs to be analysed to check the exact cause of the blue tide. This has been spotted along the Indian coast with increasing frequency,” said E Vivekanandan, consultant and scientist, CMFRI.
On Tuesday and Wednesday night, about nine students from Bhavan’s College, Andheri along with their professor spotted the blue tide from 10.15pm onwards to well beyond 1am (see pic) at the shoreline behind Holy Family Church, Juhu Koliwada. The students will be visiting the site again on Thursday and Friday to recapture similar images.
“Microorganisms called dinoflagellates are related to amoeba and paramecium. They have enzymes in their body with which break down certain organic substrates and this gets emitted into light,” said Dr Parvish Pandya, vice-principal and associate professor, zoology, Bhavan’s College. “The light is produced when the organisms are churned or mechanically stimulated, for example the light spreads further when waves surf up along the rocks.”
He added that there are two main theories for this phenomenon. “The first being that this helps these organisms gather together and make colonies and second being that the light helps dissuade or alert predators,” said Pandya. “People need to try their luck in the coming days as there is a good chance that it might occur again.”
A student witnessing it for the first time said it was a spectacular show of light. “As the waves crashed onto the shore of the jetty, I was speechless watching scores of microscopic marine organisms, capable of such wonder,” said Vikrant Choursiya, student and resident of Andheri.
Locals from Juhu Koliwada said they call the fluorescent occurrence as ‘neeli machli’ (blue fish). “I have been observing this phenomenon from a young age and even my father has told me stories about it from nearly 30 years ago when this used to be spotted. It is not harmful and if one puts their hand into the water, it starts glowing,” said Hardik Mangela, resident of Juhu Koliwada.
“Marine biologists said it was a rare sight to be observed twice in the same year along Mumbai’s coast. “Only a water sample can confirm whether the occurrence was due to phytoplanktons or bacterial microorganisms. The latter too increase in large numbers and blue colour is seen when nutrients and temperatures are high. They have shown bioluminescence at fish ponds as well,” said Vinay Deshmukh, former scientist, CMFRI adding that there needs to be a study to check whether the phenomenon is caused by bacteria.
Red tide, the harmful algal bloom
Similar to the blue tide, there exists another such phenomenon called red tide or harmful algal blooms that emits red light. It is rare occurrence caused by colonies of algae—simple plants that live in the sea and freshwater—grow out of control while producing toxic or harmful effects on people, fish, shellfish, marine mammals, and birds
“While making the light this organism secretes a chemical which is toxic and kills fish in the area the light emerges and are known to occur near the Florida gulf coast. However, in Mumbai’s case, the blue light is not toxic and has maximum transmission in water that helps reach maximum distance,” said Dr Parvish Pandya, vice-principal and associate professor, Zoology, Bhavan’s College.
Where to locate the blue hue at Juhu?
19°05’14.8”N 72°49’34.8”E - Paste this on Google Map or Safari on Apple phones to access the exact location during the next two days.