The tide that produces a fluorescent blue hue—bioluminescence—made an appearance on beaches in Mumbai and Devgad beach in Sindhudurg along Maharashtra’s coastline.
Bioluminescence has been an annual occurrence along the west coast since 2016 during the months of November and December. The phenomenon 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.
What is bioluminescence?
It is the property of living organisms to produce and emit light. Animals, plants, fungi and bacteria show bioluminescence.
About blue tide
The spectacle occurs when phytoplankton (microscopic marine plants), commonly known as dinoflagellates, produce light through chemical reactions in proteins. Waves disturb these unicellular microorganisms and make them release blue light.
Why it is dangerous
The spectacle may be beautiful, but it may also be a signal of danger. Many of the species in this group are toxic. If dinoflagellates reproduce rapidly, they may cause so-called ‘red tides’.
During this period all the animals (molluscs, fish, etc.) that feed on dinoflagellates also become toxic due to the accumulation of high amounts of toxins from dinoflagellates. It is dangerous to eat such sea animals because the toxins that are contained in them may have various unpleasant effects: some merely irritate the bowel and cause food poisoning, whereas others, being neurotoxins, may even have an effect on memory. Some species, such as the sea sparkle (Noctiluca scintillans) are not as toxic, but may have other unpleasant effects.
One of the main factors for its occurrence could be eutrophication – the reduction of oxygen in the water – which makes the phytoplanktons very dominant.
This is a recurring phenomenon which is caused by a bioluminescent plankton called Noctiluca scintillans, commonly known as sea sparkle. While smaller blooms may be harmless, slow moving larger blooms may cause severe hypoxic conditions that result in fish die-offs in an area.
Known as “blue tears” in China, the phenomenon can possibly poison sea life, from fish to sea turtles. The bloom can even make humans sick.
The red tide
Similar to the blue tide, there exists another such phenomenon called red tide or harmful algal blooms that emits red light. It is a rare occurrence caused when 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.