Bioluminescence in Andaman Island

Bioluminescence in the Andaman Islands

Type	Natural phenomenon
Cause	Bioluminescent dinoflagellates (Noctiluca scintillans)
Season	November to February (peak); year-round depending on conditions
Related phenomena	Bioluminescence, Dinoflagellate

Bioluminescence in the Andaman Islands refers to the natural phenomenon in which the coastal waters of the Andaman and Nicobar Islands emit a blue-green glow at night, caused by the presence of bioluminescent microorganisms known as dinoflagellates. The phenomenon is most commonly observed in the waters around Swaraj Dweep (formerly Havelock Island), particularly at Radhanagar Beach, Elephant Beach, and the mangrove creeks of the island, as well as at Chidiya Tapu in South Andaman and the Chouldari Marine Drive area.

The glow is produced when these microscopic organisms are disturbed by movement in the water, such as waves, paddles, or even footsteps in the shallows. The phenomenon has become a significant draw for night kayaking and eco-tourism in the islands, with the Andaman and Nicobar Administration standardising night sea kayaking tours under new safety guidelines issued in February 2026.

Scientific explanation

Bioluminescence in the Andaman waters is primarily caused by microscopic marine plankton, specifically dinoflagellates such as Noctiluca scintillans. Noctiluca scintillans, commonly known as "sea sparkle", is a free-living, marine-dwelling species of dinoflagellate that exhibits bioluminescence when disturbed. The light is produced throughout the cytoplasm of this single-celled protist through a chemical reaction involving luciferin and luciferase.

In the Andaman context, these bioluminescent phytoplankton float with the current and thrive on nutrients like nitrogen, which is abundantly present in the soil of the mangroves. When disturbed by waves, paddles, or curious fish, these microorganisms emit light as a defence mechanism. Satellite data from the Ministry of Earth Sciences has confirmed spikes in chlorophyll levels along the South Andaman coast, which serve as an early sign of plankton blooms.

Beyond dinoflagellates, scientific studies have documented the presence of luminous bacteria in the coastal waters of South Andaman. A 2020 study published in the Marine Pollution Bulletin demonstrated that luminous bacteria belonging to the Harveyi clade are predominant in seawater, sediment, surfaces of marine animals and plants, and light organs of leiognathid fishes in Andaman waters. Rich biodiversity and distribution of luminous bacterial species (30% to 40%) was found in association with coral reef samples of South Andaman. Additionally, luminous polychaete larvae of Odontosyllis sp. have been recorded in South Andaman, with their luminescence attributed to the oxidation reaction of luciferin and oxygen, catalysed by an enzyme luciferase or species-specific photoprotein.

Locations

Swaraj Dweep (Havelock Island)

Swaraj Dweep, formerly known as Havelock Island, is the most prominent location for witnessing bioluminescence in the Andaman Islands. Radhanagar Beach, one of the island's most famous beaches, is a well-known spot where the water sometimes takes on a blue-green glow when the plankton in it are disturbed. Elephant Beach, another popular marine attraction on the island, has also recorded bioluminescent sightings. Night kayaking through the mangrove creeks of Havelock is a popular way to experience the phenomenon, with every stroke of the oar creating ripples of light in the dark water.

Chidiya Tapu

Chidiya Tapu, a small island at the southern tip of South Andaman approximately 25 kilometres from Port Blair, is another location where bioluminescent plankton are present in the waters. These tiny organisms emit light when disturbed, creating a natural light show at night, and swimming in these waters is described as a magical experience.

Chouldari

The Chouldari Marine Drive area in South Andaman has witnessed significant bioluminescent activity, particularly during seasonal algal blooms. In June 2025, the coastline became the stage for a rare natural phenomenon where the water shimmered a surreal shade of blue with every wave. Marine scientists attributed the glow to a bloom of Noctiluca scintillans, which thrives in tropical waters under certain seasonal conditions. Researchers from the Indian National Centre for Ocean Information Services (INCOIS) noted that ideal conditions of warm temperatures, low turbulence, and a spike in nutrients contributed to the visibility and duration of the phenomenon.

Other locations

Other areas in the Andaman and Nicobar Islands where bioluminescence has been reported include Shaheed Dweep (Neil Island) and Tsunami Island near the Middle Andaman.

Best time to visit

The dry season, roughly from November through May, is when bioluminescence is at its most active in the Andamans, as the water is clearer and calmer. Within this window, November to January typically offers the most intense and consistent glow, with dinoflagellate populations peaking during the post-monsoon months when water has settled and nutrient levels are high.

Moonless nights, particularly around the new moon, provide the best viewing conditions, as the absence of moonlight allows the bioluminescent glow to be seen more clearly. The phenomenon tends to be most striking from November to January, though it can be observed all year, weather and ocean conditions permitting. While bioluminescence does not follow a fixed season, October to May is the broader recommended travel period for the Andaman Islands.

Tourism and night kayaking

Bioluminescence has become a major draw for eco-tourism in the Andaman Islands, with night kayaking emerging as the signature experience. Kayaking tours typically operate in the mangrove creeks and bays around Havelock Island, where the calm and clear water, shallow coral reefs, and minimal water currents create ideal conditions for the phenomenon. Tours are conducted on moonless nights to maximise visibility, and participants are advised to avoid strong lights and phone flashes, which can reduce the visibility of bioluminescence and disturb wildlife.

New official safety guidelines issued in February 2026 have standardised night sea kayaking tours, making them more accessible and safer for watching bioluminescence. These guidelines include requirements for life jackets, safety briefings, and age limits, with operators typically requiring basic swimming ability or providing enhanced safety measures for non-swimmers. Kayaking supports local livelihoods while promoting conservation through education about mangroves, coral reefs, and shorebird habitats.

Ecological significance

Bioluminescence is significant in studying marine ecology, plankton dynamics, ocean productivity, and coastal ecosystem health. The presence of luminous bacteria can serve as an indicator of environmental conditions in coastal waters. However, scientists caution that prolonged or dense blooms of Noctiluca have been linked to hypoxia—a condition in which oxygen levels in the water fall dangerously low, threatening marine life. The National Institute of Oceanography categorises Noctiluca scintillans as a bio-indicator species, one that may hint at larger, less visible shifts beneath the surface.

A 2021 paper in Current Science highlighted how underreporting and lack of local ecological tracking have kept bioluminescence occurrences under the radar and called for deeper monitoring in biodiversity-rich regions like the Andaman Sea, where climate change and human activity are rapidly reshaping marine systems. A 2020 UNESCO report documented similar blooms in Southeast Asia and urged heightened surveillance of sensitive marine zones like the Andaman.

See also

• Bioluminescence
• Noctiluca scintillans
• Andaman and Nicobar Islands
• Swaraj Dweep
• Dinoflagellate

External links

• Andaman and Nicobar Administration
• Indian National Centre for Ocean Information Services (INCOIS)
• National Institute of Oceanography