Sydney’s Northern Beaches are iconic, with golden sands, crisp surf, and a deep connection
to the ocean that defines our way of life. We depend on flourishing marine ecosystems for everything – from local businesses and recreational tourism to the mental and physical wellbeing that comes from a morning swim or coastal walk.
Our underwater neighbours are just as iconic: whales breaching offshore, dolphins cruising in the shallows, and Port Jackson sharks weaving through unique kelp forests and rocky reefs. But there’s something else. Something unexpected. Something tropical this way comes.
Branching corals – more commonly found on the Great Barrier Reef – have taken up
residence in Sydney’s waters.
One species in particular, Pocillopora aliciae, the Cauliflower coral, has been quietly flourishing on our rocky reefs. First detected about 10 years ago around Cabbage Tree Bay to North Head, this coral isn’t just surviving – it’s thriving, creating new habitat for tropical fish and adding complexity to areas once dominated by bare rock. It’s a sign of change. And a story we’re only just beginning to understand.
A tropical coral in a temperate sea
As oceans warm, many marine species are shifting their ranges, moving south in search of cooler, more stable conditions. While this global trend often spells trouble for ecosystems, Sydney’s coastline may be offering something rare: refuge.
Pocillopora aliciae isn’t just any coral. It’s a tropical species with robust, rounded branches that provide shelter and structure – exactly the kind of architecture reef fish love. Unlike the low-lying, encrusting native corals we’ve seen around Sydney for decades, this newcomer stands tall, transforming flat rocky reefs into miniature cities teeming with life. And unlike their northern cousins, P. aliciae in Sydney hasn’t shown signs of bleaching (yet), even during major marine heatwaves. So, is this a good news story in the making?
Refuge, or red flag?
That’s the big question. Could these corals boost biodiversity and help tropical species survive climate change? Or are they potential invaders that might outcompete native species and alter local ecosystems? Right now, we don’t know.
Despite their ecological importance, we don’t have a clear map of where corals are – or aren’t – in Sydney. Without this baseline, we can’t track changes, understand impacts, or plan effective restoration if it’s ever needed. That’s why we’ve launched the Sydney Coral Project.
Help us map Sydney’s corals
We’re building the first-ever map of coral presence and absence across Sydney’s coastline. And we need your help. Whether you’re a diver, snorkeller, fisher, ocean swimmer, or curious beachcomber, you can contribute.
Seen this coral?
Look for a chunky, dark brown-green branching coral with rounded tips. It’s most often spotted on wave-exposed rocky reefs, especially around Manly, Fairlight, and North Head.
- Snap a photo (if you can)
- Record the dive site or estimate the location
- Note the date
- Upload your observations to the Sydney Coral Project at SydneyCoralProject.com
Every sighting – but more importantly a confirmed absence – helps us build a picture
of Sydney’s changing reefscape.
Be part of the discovery
This is a moment of marine change – and discovery – happening right on our doorstep. Let’s find out what’s really going on and let’s map it together.