In September 2018, when my colleague Sohan M was on a late evening beach walk in Mangalore, beachgoers observed the phenomenon of bioluminescence. Excited by this news from him, I rushed to my nearest beach, Mattu, to see if I would be lucky. My friends and I witnessed our dream sighting – the bloom was localised between the breakwater barriers, and when bigger tides disturbed them, the bioluminescence was visible!

This was observed at multiple locations for almost a week – Sasihithlu, Surathkal and Someshwara beaches in Mangalore, and Chitrapu backwaters, all treated spectators to a magical experience. According to the locals, this phenomenon occurs regularly: fishermen said that they have grown up seeing massive blooms throughout their childhood. For us, it was our first time!

Bioluminescence is due to the production and emission of light by a living organism, and a form of chemiluminescence i.e. light produced from a chemical reaction. Bioluminescence in nature occurs in many forms. From glowing fungi that grow on dead and rotting wooden substrates, to mushrooms and other aquatic creatures living in deep oceans – all exhibit bioluminescence for various reasons. Some use it for defence, while others use the light to lure prey. The bioluminescence I witnessed was probably due to the congregation of Noctiluca scintillans, a species of dinoflagellate that exhibits bioluminescence when disturbed.

In a general sense, the principal chemical reaction in bioluminescence involves some light-emitting molecule and an enzyme, generally called luciferin and luciferase respectively. Along India’s west coast, post monsoons, between July and October, when the weather turns warm and the sea has a rich supply of diatoms which the Noctilucas feed on, massive congregations are observed. The sea must be calm for them to multiply faster and congregate. But since all these factors vary and change quickly, it is difficult to predict when and where they congregate effectively.