Imagine walking along a dark beach and watching every wave break in a flash of electric blue, while your footprints in the wet sand light up as you go. It sounds like a special effect, but it is completely natural, and Australia is one of the best places in the world to see it. So why do some beaches glow blue at night, and where can you see bioluminescent beaches in Australia?
What causes bioluminescence?
The glow is called bioluminescence: light made by living things. On Australian beaches, it is usually caused by a single-celled organism called Noctiluca scintillans, better known as sea sparkle. It belongs to a group of plankton called dinoflagellates, and each one is only about half a millimetre across, so you cannot really see them individually, as Australian Geographic explains. When there are billions of them in the water, though, the effect is spectacular.
The light comes from a chemical reaction. Bioluminescent organisms contain a molecule called luciferin and an enzyme called luciferase. When luciferin reacts with oxygen, helped along by the luciferase, it releases energy as light, a cold light that produces almost no heat, as Australian Traveller explains. In sea sparkle, the luciferin is made from chlorophyll, the same green pigment plants use to capture sunlight, Australian Geographic notes.
Why it only glows when disturbed
Sea sparkle does not glow constantly. It flashes when it is disturbed: when a wave breaks, a kayak paddle moves through the water, a fish swims past, or you wade into the shallows. Scientists think the flash is a defence. As University of Tasmania marine scientist Professor Gustaaf Hallegraeff put it, imagine a tiny animal that wants to eat this plankton, and suddenly it flashes at you, according to Paste Magazine. The sudden flashes appear to startle the tiny animals that feed on sea sparkle, as Australian Geographic notes, citing researchers at the Scripps Institution of Oceanography.
By day, a dense bloom can look completely different. The same organism can turn the water a murky red or orange, which is why big blooms are sometimes called red tides. The magical blue only appears after dark.
Where to see bioluminescent beaches in Australia
Sea sparkle can turn up along much of the south-east coast, but a few places have become famous for it:
- Jervis Bay, New South Wales. About a three-hour drive south of Sydney, Jervis Bay is probably Australia’s best-known spot, and blooms there have been photographed in several recent years, including a remarkable one along the beaches of Vincentia that drew a crowd of about 60 people one evening, Australian Geographic reports. Sea sparkle can also appear further north along the New South Wales coast, as far as Lake Macquarie, according to Australian Traveller.
- The Gippsland Lakes, Victoria. This is one of the most reliable regions, about four hours’ drive from Melbourne. From December to February, spots such as Lake Victoria, Lake Tyers, Metung and Nungurner can light up when the water is disturbed by paddles or movement, according to Holidays with Kids.
- Tasmania. Some of the most spectacular displays have been in Tasmania, including Preservation Bay on the north coast, the Derwent River around the South Arm Peninsula near Hobart, and east-coast spots such as Bicheno and Coles Bay.
If you live in Queensland and want a more reliable glow, glow-worms are a good alternative; Springbrook National Park in the Gold Coast hinterland is well known for them, and they glow for a very similar chemical reason.
When to go
Bioluminescence is notoriously hard to predict, because it depends on a bloom happening in the right place at the right time. Your chances are best after a spell of rain, which washes nutrients into the sea and can trigger blooms, and on a dark, moonless night away from bright lights, as Australian Traveller advises. Blooms can happen at different times of year in different places; the Gippsland Lakes are known for summer displays, while one of Jervis Bay’s best-known blooms was in August. Because blooms come and go so quickly, the most useful tip is to follow local reports: when a bloom appears, photos usually start circulating on social media within hours, and the Bioluminescence Australia group on Facebook has thousands of members who share sightings. Once you are there, give your eyes 15 to 20 minutes to adjust to the dark, then walk along the waterline or gently splash the water to set off the glow.
Is it safe to swim in glowing water?
For people, sea sparkle is generally harmless. The algae are not considered toxic to humans, but they can cause skin irritation in some people, so it is best to rinse off afterwards and avoid swimming in dense, smelly blooms, according to Paste Magazine’s report on the Tasmanian displays. Keep children and dogs from drinking the water, as you would at any beach.
The less pretty side of sea sparkle
For marine life, big blooms are not so harmless. Sea sparkle is a voracious eater; Hallegraeff likens it to a vacuum cleaner that eats the plankton in its path, and Tasmanian shellfish farmers have complained that their shellfish were left with nothing to eat, Paste Magazine reports. As huge numbers of the cells die off, they can also release toxic amounts of ammonia, which can kill fish, according to Australian Geographic.
There is also a climate story here. Sea sparkle was first reported in Sydney Harbour in 1860, and for a long time it was a sight of warmer northern waters. It was rarely seen around Tasmania before 1994, but as the waters off south-east Australia have warmed, Tasmania has become one of the most common places in the country to see it, Australian Geographic notes, with Hallegraeff pointing to warmer oceans and shifting currents. So when a Tasmanian beach lights up, part of the reason may be that its water is warmer than it used to be.
How to photograph it
Phones have improved a lot, but bioluminescence is still tricky to capture, because it is faint and short-lived. Use a tripod, or rest the camera on something steady. Switch to your camera’s manual or night mode and use a long exposure, from a few seconds to around 20 or 30 seconds, with a high ISO and the widest aperture your lens allows. Focus manually on the waterline, because autofocus struggles in the dark. Turn off your torch and ask others nearby to do the same, since any light spoils both the photo and everyone else’s night vision. Try timing your shots for when waves break, as that is when the glow is brightest.
A light show worth chasing
Every flash of blue in a breaking wave is billions of single-celled organisms reacting to being bumped. You cannot book it in advance, and you might make the trip and see nothing, but if you keep an eye on local sightings and head out on a dark night after some rain, your odds are good. If you enjoy colourful microbes, see why is Lake Hillier pink?, and if you are already out on a dark night, my post on the Milky Way will give you something to look at overhead too.
Sources
- Australian Geographic: Sparkling seas explained
- Australian Traveller: Where to see the best bioluminescence in Australia
- Paste Magazine: Bioluminescence touches the shores of Tasmania
- Holidays with Kids: Bioluminescent beaches
- Popular Science: Tasmania’s glowing water is a sign of something sinister