Bioluminescence – The Good, the Bad and the Ugly

By Ashwin Tombat
13 December 2020 11:18 IST

 

From Mumbai’s Juhu Beach to Goa’s Betalbatim, from Karnataka’s Suratkal and Mangaluru to Kerala’s Kochi, the waters of India’s west coast were dazzling with stunning blue-green flashes of light at night for the last 10 days. Now the phenomenon is rapidly fading. It’s called bioluminescence.

My fellow kayakers of The Adventure Breaks Club first noticed it on the night of Friday 27 November. Out for moonlight kayaking, the water wake passing on both sides of their kayaks as they cut through the still night sea water suddenly began to glow in a beautiful blue-green colour. Every time their paddles struck the water, it exploded in an exquisite splash of light. If they dipped their hands into the water and pulled them out, they glistened with myriad tiny blue-green beads of light for a few seconds.

What was the reason for this picturesque phenomenon? Scientists in different institutions studied this spectacle. They included the National Institute of Oceanography (NIO) in Goa, the Symbiosis International University in Pune, the Fisheries College in Mangaluru, as well as the National Centre for Coastal Research and the Dr J Jayalalitha Fisheries University, both from Chennai.

All of them quickly identified its origin. The blue colour behind the phenomenon is due to the presence of microscopic aquatic plants. These unicellular organisms are known as phytoplankton. These marine plants, also called dinoflagellates, emit these flashes of blue-green light as part of their defence mechanism against predators.

Boats or kayaks cutting through the water, splashing of water by paddles or hands, or even wave action near the beaches disturbs them, causing bioluminescence. The particular species of phytoplankton that caused this bioluminescence was mostly ‘Noctiluca Scintillans’, also known as 'sea sparkle'.  

This organism is microscopic in size and produces flashes of light as a reaction to physical disruptions. This response-to-stimulus action is termed the 'burglar alarm' effect, which is essentially a defence mechanism to dazzle a predator.

The earliest observations of bioluminescence in nature date way back in time. The Greek philosopher Aristotle reportedly noticed the light produced by dead fish in 350 BC. In the 1750s, J. Baker identified Noctiluca Scintillans as a ‘luminous animal’. In 1832, English naturalist, geologist and biologist Charles Darwin – the originator of the Theory of Evolution – wrote of “two billows of liquid phosphorus” that he saw at the prow of the Beagle, the sailing ship on which he travelled all over the world before writing his path-breaking book ‘The Origin of Species’.

According to an article by Dhriti Datta, over 1,500 species of fish sport bioluminescence, including certain sharks. Scientists are regularly discovering new bioluminescent marine creatures even today.

Bioluminescence enables marine species to communicate, to find prey, create camouflage and more. Bioluminescence also occurs on land, in certain plants and fungi. Insects such as fireflies also use bioluminescence to send out 'blinks' of light to attract mates. However, there are no known bioluminescent creatures that are native to freshwater habitats.

Freelance science writer Philip Ball says that molecules of an enzyme called Luciferin emit the light of bioluminescence. But there is not just one type of Luciferin; there are many, with diverse molecular structures.

The best known, of course, is Firefly Luciferin. Then there’s Bacterial Luciferin. Some fungi glow because they contain Hispidin, a variant. Dinoflagellates, like the phyto-plankton causing the recent bioluminescence have a Luciferin related to chlorophyll.

Different they may be, but all these Luciferins use the same basic mechanism.  The enzyme uses oxygen to oxidise the Luciferin, and sheds its excess energy by releasing a photon of light. That’s the origin of bioluminescence.

That’s why this beautiful phenomenon has an ugly side effect. Noctiluca Scintillans blooms are not good for fish. They consume oxygen dissolved in the water, which is bad for fish. Besides, they do not allow zooplankton, which is common fish food, to develop. Without zooplankton, fish have insufficient nutrition and their numbers may reduce.

Some scientists speculated that the reason for the recent bioluminescence could be sewage discharge into the sea. Considering the extensive spread of the phenomenon – from Mumbai to Kerala and, earlier, even Chennai – this seems unlikely. However, there’s another place at around the same latitudes, but on the other side of the planet, that saw this phenomenon in May 2020 for the first time in 60 years; the tourist resort of Acapulco, Mexico.

This suggests that these phytoplankton blooms may have less to do with localised causes like sewage discharge or industrial pollution, and more to do with a worldwide phenomenon like global warming. If we have many more of these blooms off our coast, the fish that are Goa’s staple diet may become scarce soon…

Disclaimer: Views expressed above are the author's own.

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Ashwin Tombat

Ashwin Tombat has been the Editor of Gomantak Times and Herald. Worked as an Associate Editor of national magazine Gentleman in Mumbai, before shifting to Goa. Loves sailing, also participates in Marathons. Has worked as an activist in students's union and trade unions in Maharashtra. Also an artist of Street Theatre during student days.

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