This last month we witnessed one of the most miraculous events in nature- coral reproduction. Corals have no brain, eyes, ears, or cell phones; yet they perfectly synchronize the release of millions of egg and sperm bundles (called gametes) into the water for just 15 minutes each year in an event called mass spawning. Pretty amazing since most of us can’t even manage to show up to meetings all at the same time.
Observing this event truly is magical, some describe it as an ‘upside down snow storm’ while others relate it to the view on StarTrek when they go into light speed. We didn’t just go to observe this event, we went to utilize it to further our goals of restoring and increasing the resilience of the reefs around Koh Tao. Although it is our fourth year doing this work, it never ceases to keep amazing and inspiring us. Over the year, we track the corals health and fecundity (reproductive ability), so that we can predict what month they will spawn. Based on our observations, we decide what colonies of coral we want to use as our parent populations, and choose a few reproductively isolated populations in different parts of the same bay from which to collect from.
Then it is up to our amazing team to go out every night around our predicted spawning time and wait for signs of spawning. Once we know that the corals are ‘in the right mood,’ then we all hop in with nets and jars and get ready for the event to occur. During the 15 or so minutes that the corals release their gamete bundles we collect as much as we can and then head back to the boat. There we fertilize the eggs according to our theories of selective breeding and genetic outsourcing. The fertilized embryos are then transplanting to our land based tanks where we keep them in good growing conditions away from all the predators of the sea. After we have allowed them to settle on artificial substrate and get anchored down securely we transplant them to our in-sea coral nurseries. At the nurseries, we look after the developing coral colonies for 2-4 years before then transplanting them to the natural reefs or artificial reefs. In this way we can produce genetically unique corals for our restoration activities that don’t require us to use donor colonies. The methods we use are scientifically based and cutting edge, and have been locally developed together with Dr. James True of CBiPT, Hat Yai.
This year was made extra special for several reasons, the first being that the spawning night happened on Easter. Adding to that, was the big team of amazing people we had to help us, and the fact that we observed several genera of coral spawning for which we had no prior data or information on. In all, we witnessed corals from Galaxea, Symphilia, Goneastrea, Platygyra, Diploastrea, Fungia, and Acropora a few nights later. Probably the most startling was the Diploastrea Heliopora, which released all of its eggs and sperm within 3-4 minutes, filling the entire water column with gametes and bringing the visibility down from about 9 meters to just 0.5 meters. It was even stranger if you didn’t see the gametes coming out of the coral, and just suddenly found yourself in a soup of coral reproductive matter.
Now the job requires much more patience, as we begin the long 2-4 years wait for them to get big enough to move out. Each year we see greater success in the number of colonies produced, as we refine and improve our techniques and methods. This year will be extra exciting as we wait to see how many different genera of corals we end up with on our artificial substrates.
Our team of 27 divers did an incredible job this year, and we are so proud to have had the opportunity to share such an event with them. We owe a big thank you to all those who came, and also our sympathy for those who came to the nights we waited but saw nothing, and had to leave before the spawning occurred. Better luck next year 🙂
Truly coral spawning is one of the most amazing sites you can see in your life, and an amazing project that we look forward to every year.