Corals are vulnerable on many levels: poor water quality, climate change, overfishing, disease, invasive species, vessel damage … the list goes on.
With all these threats, it can be heartbreaking to go out to the reef here and see acropora coral colonies the size of double beds toppled by the power of the waves created by a single storm. The fastest growing corals on a reef will increase in size by around 15 cm a year, but many others are much slower, only growing at the rate of 1 or 2 cm a year, so for some corals it can take many years to reach these kinds of sizes.
You can think of a reef as being like an underwater city, so when a coral is destroyed by a storm surge, it is a bit like losing a neighbourhood apartment block. Fishes’ lives play out between the layers of these corals, and often this is the only place they call home. Some species are very territorial, and seem to remain in or around a strictly defined locale, so when the coral goes, so does their home.
Sometimes the force of the surge causes the corals to tumble over in one big piece, but often they are smashed to smithereens by other corals in the process. The space that is left behind is a raw white gash in the reef.
I’ve recorded many colonies that have gone over in one piece, though. Often these, and the space they leave behind, get quickly covered in algae before the colony can recover, or before new corals can be recruited to fill the vacant space. The colonies simply die and become part of the reef substrate or rubble.
However, sometimes there’s good news. For example, recently I (and other regular snorkellers) have noticed some of the more-complete corals regrowing, as you can see in the images below.
A close-up of the upturned acropora colony, 24 September 2020
Above left is a newly toppled acropora coral colony photographed in September 2020. I recall being captivated by the neon purples and blues (see the close ups of the same coral taken on the same day in the top image and right). What I didn’t know then was that this was a sign of extreme stress, the vivid colouration being caused by the loss its symbiotic algae – algae that is essential for the coral to sustain its own life. The Ocean Agency described this effect as being ‘chilling, beautiful and heartbreaking’, and a poignant final cry for help. Except it wasn’t the final cry, nor was it the end of this coral colony’s story.
Fast forward to 2 May 2023, and although the middle of the colony has succumbed, a wide perimeter of this large plate coral has returned to life with new growth. And it’s just wonderful to see! Below is a close up of this new, healthy growth taken on the same day as the wide shot, above right, on 5 May 2023.
Postscript
Over the last few years, much work has been done to try to help our coral reef, including allowing the wetland to reform over the last 18 months or so of heavy rain associated with the La Niña weather pattern. This wetland has been controversial on the island for many reasons, all of which I completely understand; however, I believe we are beginning to see the small seeds of improvement in the bays because of it. But before I get too excited, I will wait with interest for confirmation of these small improvements, and the next report from the coral reef health researchers.
I won’t dwell on pros and cons of the wetlands in this post, as this ecosystem is worthy of several posts in its own right. For now, let’s simply celebrate the resilience of corals!
5 May 2023, new growth is sprouting from the surviving upturned acropora coral colony