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Coral reef surveys after Typhoon Odette (Rai)
No scuba diver wants to see his or her diving holiday interrupted or ended by a typhoon. However, typhoons are annual weather phenomena in the tropics and subtropics and it is important to understand how coral reefs are damaged by such storms and how they recover. Dr. Klaus M. Stiefel tells us in sequence about his experiences and observations with the life in the coral reef after the typhoon.
Odette in Dauin
Typhoon Odette (Rai) cost over 400 lives in the Philippines, caused about a billion euros in damage and also damaged many coral reefs.
It would be very risky to dive during a typhoon, but I had the opportunity to dive in Negros in the Philippines in December 2021 just two days after Typhoon Odette and see how the storm had broken the reef. I have lived in the Philippines for several years and had spent the night of the storm sleepless but safe in our house not far from the well-known diving destination of Dauin due to the extreme wind noise. Interestingly, typhoons get a new name as soon as they reach the Philippines, as if to nationalise them. Odette's international name was "Rai". As soon as conditions were safe again, my dive buddy Matt and I grabbed two tanks and inspected the damage Odette had done. As we were in the middle of the pandemic, there was no one but us on what is normally a very popular dive spot in Dauin.
What we noticed immediately and most of all was the poor visibility underwater; this of course was not really surprising. The storm had carried a large amount of sand and soil onto the corals. Interestingly, the corals were covered in sediment to a depth of 22 metres - deeper than I would have expected!
Some of the beautiful large table corals had turned over. Odette had also broken off pieces of many of the staghorn corals. The reef in Dauin where we dived at that time is next to an area without corals, a stagnant area with only scattered anemones and stones. This is one of the areas where you can enjoy "muck diving", searching for seahorses, ghost pipefish, unusual scorpionfish like the Ambon and Rhinopias scorpionfish and similar rare marine life. Some of the broken fragments of staghorn coral Odette had carried over a hundred metres into this sandy plain!
The sand on the corals was gone again after about two weeks. The relatively strong currents in the region, which usually run parallel to the coast, have contributed to this. Also, coral polyps themselves are able to rid themselves of sediment, and even the crabs that live between the coral fingers, popular with underwater photographers, also contribute to the removal of sediment.
Now, 18 months after Odette, the reef in Dauin looks very attractive again. Some of the table corals are still crooked, but have survived; and even parts of the coral fragments that have blown into the sandy plain are surprisingly still alive. The fact that this reef is in a protected area has certainly contributed to its rapid recovery. And the diving tourism and the income generated by it have certainly contributed to the fact that this protected area continues to be respected and does not only exist on paper.
The island of Apo
Not far from my place of residence is the island of Apo, one of the most famous diving destinations in the Philippines. The island's reefs have been at least partially protected since the 1980s due to the efforts of the highly deserving Filipino marine biologist Prof. Angel Alcala, who recently passed away at an advanced age. In 2011 and 2012, typhoons Sendong and Pablo took a heavy toll on Apo's coral reefs, and the east side of the island was particularly hard hit. To allow the corals to recover as much as possible, part of the east side of the island has been declared a protected area where both fishing and diving are prohibited.
I have had the chance to dive there with my friend and colleague Dr. Rene Abesamis for the last 3 years with a special permit to continuously measure the recovery of the reefs. In the years after the typhoons, the faster growing soft corals came back first. Gradually, these were then displaced by hard corals, mostly the relatively fast-growing Acropora staghorn corals. In 2022, 10 years after the typhoons had caused so much damage, the coral reef on the east side of Apo had already recovered to such an extent that for the first time more hard corals than soft corals could be seen. In the deeper regions, deeper than 30 metres, I still saw large amounts of coral rubble, i.e. pieces of dead coral skeletons that had slid down like an avalanche during and after the typhoons.
An attempt to fix the coral fragments broken off by the typhoons with plastic nets so that new corals can grow more easily went wrong, and the nets are still devoid of any hard coral after 10 years. Fortunately, these nets were only put up in a small area.
Healthy reefs recover
What is clear in both Dauin and Apo is that healthy reefs recover faster! Algae-eating fish play a big role in this. Filamentous algae and corals compete for space on the reef; the more algae-eating fish like surgeonfish there are, the more the balance tilts to the side of the corals. This dynamic is especially important when a coral reef is recovering from storm damage. Overfished reefs then naturally have a harder time. Interestingly, parrotfish, which also eat algae, are not involved in this dynamic because they specialise in eating algae that grow in dead coral pieces and in the rock matrix, but not the filamentous algae that compete with the corals.
It is realistic to assume that tropical storms will become more frequent and intense with human-induced climate change (1). The increasing energy in the atmosphere due to its rising temperature will be discharged through typhoons. Each of these storms will damage coral reefs. It will then be even more important to keep other damage such as water pollution and overfishing away from these reefs to give them a chance to recover as quickly as possible.
(1) Emanuel, K. A. (2013). Downscaling CMIP5 climate models shows increased tropical cyclone activity over the 21st century. Proceedings of the National Academy of Sciences, 110(30), 12219-12224.
About the author
Biologist and diving instructor Dr. Klaus M. Stiefel lives and dives on Negros Island in the Philippines. In his book "Gehirn Extrem" [Editors note: Brain Extreme] (Hübner Verlag) he deals, among other things, with the processes in the human brain during nitrogen narcosis and apnoea diving. Klaus is represented on various social media under "Pacificklaus" & on youTube @pacificklaus8189 with underwater photos and videos.
Video channel Klaus: https://www.youtube.com/@pacificklaus8189
More information on the typhoon Odette: Super typhoon Rai (Odette) brings incredible destruction