Last week saw the yearly spectacle of the Great Barrier Reef’s coral spawning event! The time of year where all corals get busy making babies happens usually just once a year and this year was special as always but for more reasons than normal. Researchers and Marine Biologists from around the world jumped into the waters of the biggest reef in the world to witness this spectacle and, as always, ground breaking science occurred…
So what is coral spawning and why do marine biologists treat this yearly event like the marine equivalent of Christmas?
Coral spawning, also known as broadcast spawning, is how most corals around the world reproduce. Although a small percentage of corals reproduce through brooding, literally popping out a mini but fully formed coral polyp that is ready to settle, the other 83% spawn. Two to six nights after the full moon, usually in November here on the Great Barrier Reef, all our broadcasting corals release bundles of sperm and egg into the water at the same time. The genetic material then floats to the surface where it can mingle, swiping right on the other bundles of eggs and sperm that are floating around with them, and from there, form coral larvae.
The coral larvae will settle on the reef in anything from a few days to a couple of weeks. To settle down, they look for a pink algae called Coralline algae. Its still unknown as to why they choose this algae exactly but there are many different theories floating around on the wide world of the internet. What is known though is that some species of coral can even work out the different species of Coralline algae and choose their favourite, pretty amazing right?
Now the most amazing part of the coral spawning event is that we’ve only known about spawning for around 40 years. This means it is still very new for science, especially as we can only really study it once every year! So there is much we don’t know and every spawning event is a chance to find out something new about their reproduction and resilience.
This year was special. Why you may ask? Well…
Over the last few years, many places on the Great Barrier Reef have been growing species of fast-growing coral to see just how they grow and how they are reacting to changes in the climate. This year marks a very special year as it is the first year that out planted corals have spawned! On Fitzroy Island, just off the coast of Cairns, corals that were planted out from growing frames just 4 short years ago, have grown big enough to now reproduce themselves! This is very exciting moment for science as it shows the resilience of these corals and how we can potentially help them in the future.
So what can we take away from this years spawning event? Well, the biggest thing is it shows that despite all the pressures that are facing reefs around the world, the Great Barrier Reef is still big, beautiful and resilient. Resilient enough in fact that the corals are still showing off their reproductive strength in their masses, all the way along the reef through the biggest spawning event on the planet (not something I would suggest you try at home, showing off your own reproductive strength like corals is a little frowned upon in polite society!).
Now if that’s not a positive takeaway from this whole thing, I don’t know what is!
Abby Seymour
