Masses of glittering algae have returned to Tasmania’s coastline in a spectacular bloom of bioluminescence that experts say is the largest seen in years.

The phenomenon, known as “sea sparkles” or “red tide”, was caused by masses of noctiluca scintillans, a pink-coloured algae that experts say was beautiful to look at, but considered bad news for the environment.

Dr Lisa-ann Gershwin, a scientist and writer who runs tours of Tasmania’s naturally glowing flora and fauna, said the current algal bloom throughout Storm Bay, south-east of Hobart, was on a “truly epic” scale.

The algae was “putting on a heck of a light show”, she said. What looked like a “pink slick” during the day, emitted a “mesmerising sparkle” after dark, turning the arc of each wavelet a luminous blue that stretched as far as the eye could see.

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“It is quite an amazing spectacle. It is really an emotional experience, a very spiritual experience, to see something so awe inspiring,” she said.

Dr Jen Matthews, a marine biologist from the future reefs research group at the University of Technology Sydney, said the organism’s balloon shape allowed it to float on the surface.

“They exist in small numbers, and you might not see them, but when you get a huge abundance of them, that’s when you start to see these red tides,” she said.

The bluish glow was due to a chemical reaction in a structure called a scintillion that was triggered by movement, such as the action of the waves.

“That chemical reaction produces light and it can be really spectacular,” she said. “In the northern hemisphere, they’re making snow angels, but you could go in the water and make algal bloom angels if you waved your hands around.”

If there weren’t waves, Gershwin recommended spritzing the surface with water from a spray bottle to stimulate the sparkle, and to avoid throwing rocks which could become hazards.

While the bioluminescent light show was natural, its scale and density was a sign that something was amiss in the environment, she said. “It’s beauty and the beast.”

Gershwin said it was worrying that the algal bloom followed a pulse of salp, and that a bloom of jellyfish was beginning to arise as the noctiluca died off. These organisms in abundance were usually signs of a severely disturbed ecosystem, she said.

Noctiluca scintillans was first documented in Australia in 1860, but was considered a rare sight until the 1990s, when the algae’s range expanded and blooms became more common.

Matthews said large noctiluca blooms were usually an indication of poor ecosystem health, which usually meant there were higher nutrient levels.

Its presence could also be detrimental to marine life and aquaculture, she said, because it was a type of algae that fed on plankton in the water, sometimes even eating fish larvae and eggs.