The tide producing a fluorescent blue hue, popularly known as bioluminescence, recently made an appearance at Mumbai’s Juhu Beach and Devgad Beach in Sindhudurg, along Maharashtra’s coastline. Bioluminescence has been an annual occurrence along the west coast since 2016, especially during the months of November and December.

Why is it caused?

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 makes them release blue light.

1. Main factors for its occurrence could be eutrophication – the reduction of oxygen in the water – which makes the phytoplanktons very dominant.

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’.

1. 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.

2. 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.

3. Some species, such as the sea sparkle (Noctiluca scintillans) are not as toxic, but may have other unpleasant effects.