Bioluminscent algae are bathing this Australian beach in an electric blue ‘ethereal glow’
By Laura Paddison, CNN
(CNN) — A beach in Melbourne, Australia has been bathed in a “ethereal glow” at nighttime this week thanks to bioluminescent algae adding a shimmering, electric blue hue to the water and sand.
Richard Pensak first saw the algae — called Nocticula scintillan and sometimes referred to as “sea sparkle” — on Sunday morning at St. Kilda Beach, about 4 miles from the center of Melbourne, a city in southeastern Australia.
By day, the algae bloom appears as a bright pinkish-orange cloud, said Pensak, a marine ecologist and a coordinator at Earthcare St Kilda, a local environmental group. It’s at night when it transforms into a “stunning light display” lending the beach a “magical, ethereal glow,” he told CNN.
There are reports the algae has spread along the north-western coast of Melbourne, Pensak added.
The phenomenon is caused by a chemical reaction the algae produce when they are agitated or disturbed — if they are grabbed by a predator, for example, or experience a surge of movement from a wave or swimmer.
It “is likely a defence mechanism,” Pensak said, as the bioluminescence can startle predators or attract larger predators to target those consuming the algae.
The algae are not known to be toxic, but they can be hazardous to fish due to their high ammonia content and their ability to lower oxygen levels. Extensive blooms off the Indian coast have been linked to fisheries declines.
These sparkling algal blooms are a natural phenomenon, but their abundance and length have increased rapidly since the 1990s, Pensak said.
Research has linked more frequent and intense blooms to warming oceans. As the water heats up, ocean layers mix less, which in turn makes it harder for nutrients to mix properly, creating conditions that favor the algae, Pensak said. “It can be a sign of an unhealthy ocean,” he added.
Still, the algae has proved to be an extremely popular attraction. Hundreds of people have visited St. Kilda to experience it, Pensak said. “Being a city beach, we often don’t get to see phenomena like this.”
The-CNN-Wire
™ & © 2025 Cable News Network, Inc., a Warner Bros. Discovery Company. All rights reserved.
