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Bioluminescence at night, Jervis Bay, Australia

Sydney’s seas are glowing! What’s the deal with bioluminescence?

Sydney’s shorelines are glowing blue in the dark – and it all comes down to something called ‘bioluminescence’. Here’s what that’s all about

Winnie Stubbs
Written by
Winnie Stubbs

If you’re lucky enough to have scored yourself a nighttime beach walk over the past few weeks at one of Sydney’s beautiful beaches, you might have noticed something sparkly going on in the ocean. 

That magical, luminous sea situation is known as bioluminescence: a form of light emitted by living organisms. And while bioluminescence isn’t a modern day phenomenon, it’s accurate to say there’s been a lot more of it around over the past few years, hence the influx of glowy beaches on the grid.

If you’re keen to learn more about why our oceans are lighting up with an alien-like radiance, read on.

What is bioluminescence? 

Bioluminescence refers to light emitted by certain living organisms – and while this phenomenon can appear in land-dwelling creatures such as fireflies and glow worms, it’s most commonly seen in marine environments. That scene in Life Of Pi with the airborne whale? That sea sparkle wasn’t a fantastical concept.

What is bioluminescence caused by?

While most of the light we interact with is caused by heat, bioluminescence is a form of cold light caused by a chemical reaction. In the case of ocean-based sparkle, organisms such as plankton, fish, jellyfish and bacteria become luminous when a luciferin compound is catalysed by a luciferase enzyme (science).

Bioluminescence came about due to a number of evolutionary factors: from improving food-finding capacity in dark, deep water to camouflaging closer to the sunny surface. 

The type of bioluminescence most commonly seen in New South Wales is generally omitted by a type of phytoplankton referred to as noctiluca. These ‘dinoflagellates’ form a red, slime-like substance when they appear en masse in the daytime, and by night, can emit a turquoise, otherworldly glow.

Where can I see bioluminescence in and around Sydney? 

Three hours south of Sydney, Jervis Bay (famous for its powder white sand and crystal clear water) has become known among bioluminescence enthusiasts for the glittering algal blooms that light up the waves and coat the shore. While that particularly long stretch of sand might be the most well-documented sea sparkle hotspot in NSW, it isn’t the only place you can witness the phenomenon.

Recently, bioluminescence has been spotted at various Sydney beaches, with photos from Sydney’s Northern Beaches to the harbourside corner that is Rushcutters Bay.

There’s no guarantee of coming across the sparkly phenomenon, but it’s more likely to be visible on moonless nights when the ocean is warm and still. 

Why is there more bioluminescence near Sydney this year? 

Unfortunately, the more frequent phenomenon of ocean-based bioluminescence can be largely attributed to rising sea temperatures. Warmer, more acidic oceans provide the perfect environment for ocean-dwelling algae such as the light-omitting phytoplankton to grow and increase in number.

Is bioluminescence dangerous? 

As beautiful as bioluminescence can be to witness, swimming among the sparkly stuff isn’t actively encouraged. Bioluminescent algae can be poisonous to other aquatic creatures and to humans, so park up on the sand and enjoy from a distance.


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