Sex, Corals & The Ocean

Happy May everyone!

I hope all your ocean adventures have been splendid this month. Here on Thailands gulf things have been just beautiful with calm crystal clear oceans, clear blue sky’s filled with endless sun, and beautiful starry nights; my absolute favourite.

Something pretty spectacular happened this month. A rare occasion, one that occurs only a handful of times each year; and even so, most ocean lovers might be lucky to see it happening once in their lifetime. I am speaking of CORAL SPAWNING. Wowzas. Exciting!

Before joining the New Heaven Reef Conservation Program I had never heard of this event. And my thoughts about it went something along these lines:

‘Spawning? Like, jizzing...? Underwater though? By corals? Isn’t that kind of a weird thing to get excited over?

Well, yes. I guess it is at first. Although once I understood how interesting this part of corals life cycles is, I realised that it really isn’t such a strange thing to get excited over, and in fact many people only hope to be lucky enough to witness it!

During this event mature coral colonies will release their gametes over the span of a single evening with the hope that they will fertilize with the gametes of another colony within the same genus. It is one of the most beautiful events I have been lucky enough to lay my eyes on. I consider myself an incredibly fortunate young human, who has been lucky enough to travel abundantly and seen a beautiful assortment of some of nature’s best. But seriously, this is one of the coolest things, ever.

It’s got a lot to do with the moon, as at certain times of year (post full moon) corals collectively decide it’s that time to sexually reproduce. For the most part corals reproduce asexually (making clones of themselves) and this is how large coral structures are built- we talk about this in detail in some of 2017’s blog posts. I mentioned just moment ago that it’s amazing, because all the corals know to release their gametes on the same night. While this is true, the specifics of this event are a lot cooler.

Each genus will literally release their eggs and sperm at the same time, within an hour of each other usually. This means the gametes of each genus are more likely to actually meet and fertilize. This is amazing, especially if we ask ourselves; ‘how the heck do coral colonies- which are often spread over quite large geographic ranges actually organise themselves to spawn at precisely the same time? Well well, great question! And the answer is; we don’t know! Corals are just incredible animals which have been evolving over millennia and even though us humans like to think we know a lot, we actually know very little. Corals really showed us up on this one. Damn cool right?

Scientific Name: Acropora

So, what is it like? Remarkable; although I think I have already communicated that. It looks a lot like upside down snow, with the flakes coming out of each polyp of coral colonies. Coral eggs are tiny- and are actually released as egg ‘bundles’; round balls that are easy enough for us to see. The sperm is released in clouds of white- as we’d expect. However the eggs vary significantly in colour, some being white, others yellow, orange, and we even saw many table and branching corals spitting out hot pink coloured bundles. It was pure magic.

This year we got particularly lucky. Usually we see about 5-6 genera spawn. This time however we tried a new spot and a different night and saw an additional 8-10 genera. This provided us with extra information new genera and their spawning times (as each year they will spawn at the same time); in case we want to expand our conservation efforts into working more with improving genetic variability during these special times of year (previously we had done this work, but only with one genus of coral).

The water column was full of life during this evening. Everything from tiny invertebrate worms to the large butterfly fish hung around to get their mouths around some of the juicy and nutritious gametes that were being released. If we take a moment to think about it, the survivability of any one of these eggs and sperm are very low. Straight off the bat they are prey for anything and everything, then they need to hope to float to the surface (they are positively buoyant) to hopefully be fertilized, and then flow with the currents while beginning the first part of their development before they (hopefully) find appropriate substrate to settle and grow onto. The seemingly simple task of surviving is becoming ever more difficult as we add anthropogenic stressors to the mix; such as warming oceans and ocean acidification. It all seems quite difficult for these little eggs.

To improve rates of survival and therefore the ability for coral reefs to thrive, we need to make conscious choices and chose to support governments that are willing to support our life support system; the ocean. I realise I say this most month, and I do so because it’s just so damn important for us to prioritise.

I hope each of you might get the opportunity to see this extraordinary marvel of nature in your lives.

See you next month!


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