‘Sea tinkle’ also known as bioluminescence enthralled the visitors of Chennai’s Eliot’s Beach on August 18.

Injambakkam beach in Chennai was abuzz on August 18 night after visitors noticed a blue shimmer on the waves. The glow was also spotted at Besant Nagar’s Eliot’s Beach, and several users took to social media to share pictures and videos of the phenomenon.

Commonly known as sea tinkle, the Noctiluca algae were behind this phenomenon. The algae exhibits the phenomenon of bioluminescence or biologically produce light when disturbed.

The light is produced by a chemical reaction in the presence of oxygen involving an enzyme called “luciferase”. Bioluminescence has been observed in fireflies, a few beetles and in marine creatures such as Anglerfish and copepods.

Though the sight that they produce is beautiful, their arrival may not be good news. Noctiluca are known to be voracious predators of planktonic organisms(diatoms), leading to disruption of the marine food chain. They also excrete large amounts of ammonia, causing massive fish mortality. These algal patches are also linked to coastal pollution and runoff from agricultural areas.

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A research paper published last year in the journal Harmful Algae highlighted that “global warming conditions” may also be responsible for their increase. The report — published last year, at a time when Mumbai’s beaches witnessed the phenomenon — noted that warming of the surface waters of the Arabian sea and reduction in the nutrient flux were the main reasons for their increase.

The function of this bio-luminescence in algae is not fully understood and various studies are being carried out to decode if it is a predator defense mechanism.

Such blooms have been reported annually in the Northern Arabian Sea since the early 2000s. Goa, Mumbai and the backwaters of Kerala have witnessed these algal blooms. Recently the magical glow featured in the Malayalam movie Kumbalangi Nights, which gained much attention.