WILLEMSTAD - The Caribbean Research & Management of Biodiversity (Carmabi) Foundation has observed the occurrence of a coral bleaching event on our coral reefs this year. This phenomenon was detected about 16 weeks ago and is currently past its peak.
Carmabi has been monitoring and researching the coral reef around Curaçao since 1955. As the water temperature is starting to decrease again, it appears that the corals around Curaçao have weathered this period with warmer-than-normal water well. This positive development marks a notable contrast to previous years when coral bleaching was a worrisome issue in Curaçao, and this is also in comparison to other reefs in the Caribbean.
Due to El Niño and ongoing climate change, the seawater in the Caribbean this year is warmer than ever before. In Curaçao, the seawater has never been so warm in the past three months, reaching 31 degrees in October. The land temperature has also been scorching, and many people have been complaining about it in recent months. Prolonged heat, as experienced this year, is not only a problem for humans. Other animals can also suffer from higher-than-normal temperatures, and corals are a prime example.
Microscopic algae that occur in the tissue of reef-building corals usually provide their host (the coral) with food through photosynthesis, but they begin producing toxic substances when the seawater becomes warmer than 29 degrees Celsius. Corals then expel these algae into the surrounding water. Since these algae give corals their typical green/brown color, corals appear to bleach when the algae are expelled. The coral tissue itself is transparent, revealing the underlying white coral skeleton. Therefore, this phenomenon is called 'coral bleaching.'
If the seawater cools sufficiently after a few weeks, the algae return to the coral, and everything returns to normal. However, if the seawater remains warm for too long, some coral species may starve because they depend on these algae for food. If the water remains warm for an extended period, as it has this year, many coral colonies begin to die from starvation after a month. The temperature of the seawater and how long it stays above 29 degrees ultimately determine how many corals will die from bleaching.
In 1998, 2005, and 2010, the seawater was also very warm (though not as warm as this year). In these years, 80 percent of all coral colonies bleached in some areas of the Caribbean, and up to 60 percent local mortality occurred. Coral bleaching is often considered one of the key phenomena contributing to the global decline of coral reefs. However, coral bleaching is not something that can be fought because it is a symptom of an underlying problem: the increasingly warm sea caused by excessive emissions of, among other things, CO2.
This year, between August and November, the seawater around Curaçao has been warmer than 29 degrees Celsius for the first time for 16 weeks, and in some Caribbean locations (such as the Florida Keys), coral mortality is significant. Somewhat to the surprise of coral researchers, the damage on Curaçao seems to be relatively limited so far. Many corals are currently bleached, but despite the historically prolonged period of elevated seawater temperatures, and unlike previous bleaching events on the island, many species are still alive. As the seawater is currently (end of November) dropping below 29 degrees, there is hope that many of the corals currently bleached will soon reabsorb their algae from the surrounding water, and the previously anticipated massive mortality may be avoided. The reason for this is currently unknown, but it is suspected that some corals may slowly adapt to the warming water or switch to other food sources such as plankton. It will only become clear in a month or longer whether the currently bleached corals on Curaçao will ultimately survive or whether the incurred damage is already significant enough for many colonies to die in the near future.
In the coming period, Carmabi will draw attention to this phenomenon through various channels. The research institute under Carmabi continues to monitor the situation and experiments with possibilities to restore the coral reef, involving its own researchers and guest researchers.
Carmabi emphasizes the crucial role of such research in understanding and preserving the biodiversity of the coral reef. Monitoring these events contributes to developing effective strategies for the conservation of this precious ecosystem. The foundation remains committed to the protection and sustainable management of biodiversity around Curaçao, focusing on future challenges and the preservation of the unique marine life in the region.