Recently, Maharashtra has witnessed the spectacle of a fluorescent bluish glow when the waves hit the shoreline. Bioluminescence or light-emitting tide made an appearance on state’s coastline.
• Bioluminescence is the property of a living organism to produce and emit light. Animals, plants, fungi and bacteria show bioluminescence.
• An extraordinary diversity of marine animals and microbes are able to produce their own light. It is found in many marine organisms such as bacteria, algae, jellyfish, worms, crustaceans, sea stars, fish and sharks.
• Luminescence is generally higher in deep-living and planktonic organisms than in shallow species.
Why did the waves appear blue?
The spectacle blue colour 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.
It is cited as an anti-predatory response. Bioluminescence is assumed to startle predators, causing them to hesitate, in a form of predator intimidation. Another explanation is that bioluminescence helps these organisms gather together and make colonies.
This can be due to several factors for the occurrence but one of the main factors could be eutrophication – the reduction of oxygen in the water, which makes the phytoplanktons pretty dominant.
Bioluminescent waves in India
Bioluminescence has been an annual occurrence along the west coast since 2016 during the months of November and December.
The sight was observed at Juhu and at Devgad and Velas beaches in Ratnagiri. Recently, the ‘blue tide’ was witnessed along Dakshina Kannada-Udupi coast.
While bioluminescence is not common in India, there are several tourist places across the world, which are famous for this phenomenon for instance-the Blue Grotto in Malta is one of nine caves near the island of Filfa that produces a phosphorescent glow. Similar to the Blue Grotto is Bioluminescent Bay in Puerto Rico, San Diego in California, Navarre Beach in Florida, and Toyama Bay in Japan.
Impacts of Blue Tide
While smaller blooms may be harmless, slow-moving larger blooms may have an impact on deep-sea fishing.
According to marine experts, the phenomenon is an indicator of climate change. Factors such as the pattern of the wind and the temperature of the ocean also determine the occurrence of bioluminescent waves.
It is a believed that it is spectacle but in reality, it is an ecological indicator of degraded water quality.
The phytoplankton shows up where seawater has low dissolved oxygen and high presence of Nitrogen. The bioluminescence could have been caused by heavy rain, fertilizers run off, discharge of sewage into the ocean.