Bioluminescence [UPSC Notes]

In April 2023, on a moonless night, a group of M.Tech students noticed something unusual while riding along the coast of Visakhapatnam. They saw waves of blue light ebb and flow by the shore. The mystery behind the blue waves of Visakhapatnam’s beaches is bioluminescence. What is bioluminescence? What causes bioluminescence? Know the answers to these questions in this article. This topic is relevant for the IAS exam environment and ecology segment.

What is Bioluminescence?

• The glow of the waves is caused by tiny marine organisms called phytoplankton, which emit light on the ocean surface at night. This phenomenon is known as bioluminescence.
• This has been attracting visitors to the beaches along Visakhapatnam, including photographers, marine researchers, and nature enthusiasts.

Source: Sciencenews

What causes Bioluminescence?

• Bioluminescence is a natural phenomenon that occurs when certain marine organisms, such as phytoplankton, emit light on the ocean surface at night.
• Phytoplankton is a microscopic plant-like organism that is an essential part of the marine food chain, and they are responsible for producing almost half of the world’s oxygen. 
• Bioluminescent phytoplankton uses light as a way to communicate, defend themselves from predators, and attract prey. 
• They have a pigment called luciferin and an enzyme called luciferase. When luciferin reacts with luciferase in the presence of oxygen, it produces light, creating a spectacular display on the ocean’s surface.

The Occurrence of Bioluminescence in Visakhapatnam:

• The recent occurrence of bioluminescence in Visakhapatnam is the result of an algal bloom of the dinoflagellate species of noctiluca and ceratium. 
• These organisms emit light when disturbed by breaking waves. This unique phenomenon has been visible on some other beaches in India, including Havelock Island in the Andamans, Thiruvanmiyur Beach in Chennai, Mattu Beach in Karnataka, and Bangaram Island in Lakshadweep. 
• According to M Ram Murthy, a marine biologist, bioluminescence is not new to Visakhapatnam and has occurred on several occasions in the past. However, what makes the recent experience different is the scale, making it a visual spectacle.

Environmental Changes and Bioluminescence:

• While phytoplankton blooms that result in bioluminescence are not rare and are widely reported across coasts worldwide and in India, marine biologists say that it is a likely indication of environmental changes in seawater in the region of its occurrence.
•  “It may not be harmful to humans, but any kind of algal bloom can affect the marine ecosystem as phytoplankton are consumed by fish,” says Vinod Malayilethu, Associate Director of the marine conservation programme, WWF-India. 
• The impact of these noctiluca blooms off the Visakhapatnam coast on marine species is less reported and explored and needs to be studied. 
• A possible reason behind the rapid algal growth of noctiluca on the Visakhapatnam coast could be environmental changes like sudden low salinity or disturbance by pollutants.
• It also gets affected by ocean acidification which is on the rise due to climate change.
• While bioluminescence is not harmful to humans, any kind of algal bloom can affect the marine ecosystem, and it needs to be studied to understand its environmental impacts.
• It is essential to protect our oceans and their inhabitants by reducing pollution and maintaining the delicate balance of the marine ecosystem.

Ocean Acidification and Bioluminescence:

•  As the pH of the ocean decreases due to climate change, some bioluminescent organisms might get brighter, while others see their lights dim, according to the Society for Integrative and Comparative Biology. 
• Bioluminescence is a common trait in many marine organisms, and its chemical structures vary widely, making it difficult to predict the effects of changes in pH levels. 
• The team of scientists gathered 49 studies on bioluminescence across nine different phyla to understand how bioluminescence might be affected by the predicted decrease in ocean pH. 
• The study found that as pH drops, the bioluminescent chemicals in some species increase light production, while others have a modest increase or a decrease in light production. 
• For example, the sea firefly, which uses glowing trails to attract mates, could benefit from a small increase in light production, while the firefly squid might not be able to communicate effectively with low pH levels and less light. Further testing is necessary to understand the impact of bioluminescence changes on marine organisms that rely on this ability.

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