The devastation of coral bleaching

This was the part of the workshop that I was most looking forward to, as the idea of diving in the Seychelles was very exciting. I had envisaged this underwater paradise with biodiversity and colour a-plenty. Unfortunately, the reality was quite different.

I found out that I would be accompanying Dr Obura on his trip to the Seychelles to assist him with a training workshop at relatively short notice. I therefore didn’t have the time to get excited about the trip, despite everyone constantly reminding me how lucky I was. I didn’t bother to picture what the place would be like beforehand, and so just landed with a more or less open-mind, ready to take it all in.

The workshop was to be held on Mahe Island, and although it is the most ‘developed’ of the Seychelles islands, it was one of the greenest places I have ever been to. On my first morning I was pleasantly surprised to see a mangrove swamp in what I believed to be the middle of a residential area. Mahe has a hilly inland, and I was thrilled to see that it was still covered in forest. Even the most touristy part of the island had a line of trees at the beach’s edge, providing much needed shade to locals and tourists. Hotels also retained the trees by the beach, which is a stark difference to Kenya, where developers try and grab every possible inch of land right up until the beach, many times illegally.

The workshop was a training exercise on coral reef monitoring for the Island Conservation Society, a local Seychelles NGO that are mandated to conserve the nature around several Seychelles’ islands. As part of a UNDP funded project, four outer-islands will have new marine parks established, and CORDIO was consulted to develop a coral reef monitoring protocol and management plan for each of the islands. During the 5-day workshop, we had organised 6 dives for participants to practice the new methods. This was the part of the workshop that I was most looking forward to, as the idea of diving in the Seychelles was very exciting. I had envisaged this underwater paradise with biodiversity and colour a-plenty. Unfortunately, the reality was quite different.

I was shocked to see the skeletons of coral colonies all around, but instead of healthy living tissue surrounding the skeletons, it was algae. There were large areas of branching and tabular corals, forming a complex three-dimensional reef, spreading for 100s of meters….but all dead! And it wasn’t just at one site, but all 6 dive sites that we visited. Before each dive we hoped for different conditions, but at each site we were met with the same sad reality. After speaking with Pierre (a local scientist) and the boat captain, they confirmed that in fact most of the mortality occurred last year. The consensus was clear … the reefs around Mahe had been severely impacted by coral bleaching in 2016!

I spent most of 2016 gathering coral bleaching records from across the region, and knew from the data that the reefs around Seychelles were some of the worst hit. But seeing what ‘severe mortality’ looked like first-hand was something totally different. Coral bleaching is a phenomenon that occurs when corals are stressed and expel their symbiotic nutrient-providing algae. If they remain in this ‘bleached’ condition for too long they die. In 2016, globally warm conditions and a positive El Niño caused record-high sea temperatures leading to mass coral bleaching throughout the Western Indian Ocean, as well as other regions across the world.

On each of his previous visits to the Seychelles, Dr Obura had watched the coral reefs steadily recover after the devastating bleaching of 1998. National monitoring records show that by 2016 reefs had just recovered to their pre-1998 hard coral cover levels. To see 18 years of recovery destroyed so quickly was difficult. It is unlikely that the reefs will have another 18 years to recover before the next major bleaching event. This is because climate change is accelerating, and extreme climatic events such as El Niños are likely to occur more frequently, resulting in more frequent bleaching.

It’s not all doom and gloom however, as although over 90% of the coral is now dead, the structure created by the skeletons of branching Acropora and Pocillopora colonies, and the steadfast massive colonies, has held firm in most places, providing suitable habitat for several fish species. The algae growing on the skeletons also provides an abundant food source for some herbivorous fish, leading to short-term population increases in these groups. Therefore for the casual recreational diver there are still plenty of marine animals to observe, and we saw spotted eagle rays, a porcupine ray, green turtles, octopi and a large diversity of reef fish.

On one of the dives I remained still at 12m and looked around at the reef, trying to imagine what it would have looked like had the corals been alive … I’m sure it would have been spectacular! This thought saddened me, and I couldn’t help but wonder whether this would be the fate of most coral reefs around the world in the near future. Without swift and decisive action to limit greenhouse gas emissions, it may well be. But with a history of fighting back and naturally recovering from similar events, combined with local and international conservation efforts, there is still some hope that the reefs of Seychelles and of the world can survive.

Mishal Gudka

Large areas of dead branching coral

A rare healthy hard coral

A coral recruit struggling to survive in the hostile environment