Australian photographer Toby Schrapel had an unforgettable experience on Christmas night in 2024. That night, seawater washing onto a beach on Tasmania Island glowed teal in neon. When a stone was thrown, the fluorescence splashed like sparks. It was just like a scene from the movie "Avatar."
A research team led by Wil Srubar, a professor in the Department of Civil, Environmental and Architectural Engineering at the University of Colorado, said on the 6th (local time) that it had developed a technology that can emit light without electricity for 25 minutes at a time for up to four weeks using the microorganisms that light up beaches at night, and published the findings in the international journal Science Advances.
◇ Using microalgae that shine when shaken
The neon that lit the beach was produced by Pyrocystis lunula, a single-celled organism that lives in the sea. The University of Colorado team said it succeeded in keeping the light switch continuously on by putting Pyrocystis into a hydrogel, a jelly-like, water-rich substance, and using a simple chemical solution.
Pyrocystis in seawater emits light when it receives physical stimulation as waves crash. Inside the organism, a substance called luciferin is oxidized by an enzyme called luciferase, releasing energy as light. This is bioluminescence. Fireflies use the same principle to glow when they seek mates.
When waves crash or passing boats cause shaking, bioluminescence occurs in Pyrocystis. But the light lasts only a few milliseconds. The researchers thought they could extend the emission time by providing continuous physical stimulation. Contrary to expectations, even when they kept pressing the hydrogel containing the microorganisms to give continuous mechanical stimulation, there was little change in light emission.
Instead, the University of Colorado team found a chemical switch. They poured solutions with different acidity (pH) and tracked changes in bioluminescence. They exposed the system to an acidic solution of pH 4, similar to tomato juice, and an alkaline solution of pH 10, similar to mild soap. Both induced bioluminescence, but the light behaved differently. Under acidic conditions, bright light lasted up to 25 minutes. Under alkaline conditions, the emission time was shorter and the light was diffuse and faint.
◇ Use as a light source in extreme exploration
The researchers put the luminescent microorganisms into hydrogel and used it as ink in a 3D printer to produce various shapes. The hydrogel structures glowed blue when exposed to acidic or alkaline solutions. The microorganisms survived for weeks within the hydrogel structures. Results were best under acidic conditions in particular. Even after four weeks, the microorganisms maintained 75% of their initial brightness in the hydrogel structures.
The team said luminescent microorganism materials can be used in a variety of places. In the deep sea, where sunlight does not reach, 90% of organisms produce their own light. For example, deep-sea anglerfish emit light from a protrusion on the forehead to lure prey. In the same way, robots exploring the deep sea or space could use them as light sources.
They could also be made into sensors to monitor marine pollution. The team is studying whether the luminescent microorganisms respond to other chemicals. If the microorganisms can be made to glow when they encounter pollutants, they could be used for water-quality monitoring.
Luminescent microorganism sensors not only use no energy but also help curb warming. The researchers said Pyrocystis is photosynthetic and can remove carbon dioxide, a greenhouse gas. Srubar said, "Other light sources emit carbon to illuminate spaces, but microorganisms store carbon while emitting light."
◇ Also causing marine pollution due to warming
Pyrocystis is classified as a dinoflagellate because it moves by rotating like a vortex with a whip-like tail. There is another dinoflagellate that lights up beaches at night: Noctiluca scintillans, known as sea sparkle. The genus name Noctiluca means it glows at night. But sea sparkle itself can also cause marine pollution.
The two bioluminescent marine microorganisms differ in many ways. Pyrocystis is crescent-shaped, while Noctiluca is apple-shaped. Pyrocystis also produces its own nutrients through photosynthesis, like plants, but sea sparkle is a predator that feeds on plankton. For this reason, a sudden increase in sea sparkle threatens marine ecosystems. When Noctiluca blooms all at once, a red tide occurs.
When a red tide occurs, seawater turns red in daylight as if splashed with ketchup because of the red pigment inside sea sparkle. A sudden surge in sea sparkle consumes the diatoms that krill, a crustacean, feed on, disrupting the ecosystem. It also depletes dissolved oxygen, killing fish.
For these reasons, scientists cannot simply enjoy beaches glowing at night. Scientists at the Commonwealth Scientific and Industrial Research Organisation (CSIRO) in Australia published findings in 2012 that nighttime glowing beaches in Tasmania are evidence that global warming is intensifying. Until 1994, there was no sea sparkle in Tasmania. CSIRO scientists explained that as global warming worsened, ocean currents shifted and warm seawater inhabited by sea sparkle flowed into Tasmania.
References
Science Advances (2026), DOI: https://doi.org/10.1126/sciadv.aee3907
Journal of Plankton Research (2012), DOI: https://doi.org/10.1093/plankt/fbr112