Tasmania's southeast coast 'glows' with bioluminescent algae, pointing to imbalance in marine ecosystem

By Crystal McKay for the ABC

Seemingly out of nowhere, patches of Tasmania's southeast coastline have become streaked with red trails.

The region is a hotspot for Noctiluca scintillans - a type of bioluminescent algae that appears red in the day and glows an extraordinary blue at night - which is experiencing its biggest "bloom" in almost a decade.

It's a beautiful natural occurrence, but biologist and jellyfish expert Dr Lisa-ann Gershwin says it is also an environmental red flag.

"At night, you just get these fabulous displays of the bioluminescence that take your breath away. They're so beautiful," Gershwin said.

"But it's also a visible indicator that something is wrong. And interestingly, they are a driver of things to go even worse."

Beautiful but damaging

Gershwin estimated the invasive marine pest first appeared in Tasmanian waters in the mid-1990s.

She said there were three main ways that the blooms harmed the ecosystem.

Firstly, it consumes large quantities of plankton, which are a vital food source for other organisms. Secondly, it greatly reduces oxygen levels in the water, thereby suffocating other marine life. And lastly, it omits ammonia into the water, burning the sensitive tissues of fish and blocking their gills.

In short, the red algae could have fatal effects on sea creatures, Gershwin said.

"[It] is beautiful for us, but it's absolutely bad news for organisms that live in the water," she said.

Blooms a sign of ecosystem imbalance

Tasmania's southeast coast recently experienced blooms of small jelly-like creatures called "salps", caused by an abundance of phytoplankton from agricultural and aquacultural processes, such as fish farms.

Gershwin said the salps feed on excess nutrients in the water, but have then died off, causing the bloom event.

"As they were dying off, they create a huge pulse of nutrients that then drives the phytoplankton to bloom again," she said.

"And Noctiluca scintillans, the bioluminescent algae, is actually feeding on those phytoplankton."

The bioluminescent algae exists in Tasmania year-round, but usually in low numbers.

Gershwin said the significant bloom event was a sign of an imbalance in the ecosystem.

"It's rather scary because it's a visible indicator that something is really bad right now. But from a scientific point of view, gosh, it's fascinating."

Algae could cause 'tingly' sensation

While not toxic for humans, experts from the Derwent Estuary Program warned that swimming in the blooms could cause skin irritation.

The program's chief executive Ursula Taylor said it was generally safe to touch and swim in, but that it may make people feel "a little tingly".

"But it won't harm you in any other way," Ms Taylor said.

The heavy metal content in the River Derwent posed more of a health risk than the bloom, she said.

It is more of a problem for the fish farms, due to the fish being unable to escape should a pen be impacted by the algal bloom.

Blooms hard to predict

Tasmania's bioluminescent waters have built a strong following online, with images shared in Facebook groups.

Some of the best spots to see the blooms include Eaglehawk Neck, Port Arthur, Bellerive, Montagu Bay, Hobart's waterfront, and Bruny Island.

Gershwin said the blooms were easily identifiable by the presence of red swirls - often referred to as "pink slicks" - during the day.

But the easiest way to witness the blue bioluminescent glow was by agitating the still water at night, Gershwin said.

Despite the algae's seemingly sudden widespread arrival, she said there were too many factors to accurately predict exactly how long each bloom would last.

However, once the red algae die off and become a new source of food for other aquatic animals, Dr Gershwin said Tasmanians could expect to see a boost in jellyfish numbers.

"I think it's going to be an interesting summer," she said.

- This article was first published by the ABC