For the first time since records began, coral bleaching has been detected in reefs across Mexico. Specialists predict mass mortality of these organisms. Although there is little that can be done to reverse the damage, researchers urged authorities to work on public policies to recognize the dangers of climate change and protect the seas.
Although in 1998, 2005, 2010, 2015 and 2020, bleaching was reported in several areas of the country, the truth is that it had not occurred in the midst of such high temperatures in the oceans. This is the first time that the phenomenon has occurred in a generalized way on all Mexican coasts.
The alarms went off at the beginning of this year, when the United States National Office of Oceanic and Atmospheric Administration (NOAA) began to give indications that 2023 would be very hot and that once again the record for being “the hottest year” would be broken.
According to the researcher at the National Autonomous University of Mexico (UNAM), Lorenzo Álvarez, the southern oscillation “El Niño” increased the temperature in the Pacific Ocean. At the same time, thermometers also rose between one and three degrees Celsius above the average in the Atlantic, the Gulf of Mexico and the Caribbean Sea, and have reached extreme levels in recent months. In fact, in places like Puerto Morelos, Quintana Roo, it increased by four degrees: it went from 30 to 34 degrees Celsius.
As if that weren't enough, the heat wave has been going on for several months. “Think about it with humans: our temperature is 37 degrees. You may have a fever and reach 41 degrees, and if it lasts a day it won't affect you as much, but if that fever lasts two months, you probably don't count it. It's the same with corals: it's not just how much the temperature has risen, but how long it has stayed above what it should be,” said the academic.
At the same time, twice as much solar radiation was detected in the middle of the year as in 2022. All this not to mention that reefs were already facing a crisis due to ocean pollution, excess wastewater, overfishing, and other factors.
“If reefs receive a lot of pollution and overfishing, they deteriorate. And it's harder for them to recover from such an extreme event. We need to improve water quality so that they have a better capacity to recover,” said Andrea Rivera-Sosa, project and outreach manager for the Coral Reef Alliance's Science for Conservation program.
Completely bleached “deer horn” coral colonies on the Puerto Morelos reef, Quintana Roo. Photo: Lorenzo Álvarez.
It was just in June when anomalies began to be reported in the reefs, up to worrying levels. They first sighted white corals in Oaxaca and then in the Caribbean.
To date, not only has bleaching been detected in all of the country's reefs: corals are already dying. In Huatulco, located in Oaxaca; in Puerto Morelos and Akumal, in Quintana Roo, what specialists such as Álvarez and Pedro Medina, from the University of Guadalajara, describe as “mass mortality” has already begun.
In fact, Baruch Figueroa, coordinator of the Coastal Ecosystems program at the Akumal Ecological Center, estimated that 70% of the corals in that town, totaling about 500 square meters in size, have already died. And they did it quickly.
“Two weeks ago we were still thinking that it wasn't going to hit us as hard as in other places. However, this week we noticed that many of the corals that are in very shallow areas less than a meter or two deep bleached very quickly and experienced mass mortality”, acknowledged the specialist.
Although the magnitude of the effects is not yet certain, given that high temperatures prevail and will end until the month of October, the truth is that when the waters begin to cool, specialists such as Álvarez estimate drastic changes in the reefs.
All the experts consulted to write this note agreed on the regrettable nature of this alarming situation, since it is serious, unprecedented and will probably result in the death of many corals throughout the country.
This fully bleached “elk-horn” coral colony on the Puerto Morelos reef is estimated to be 100 years old. Photo: Pedro Medina.
There is no solution, only palliative care
“After the child drowns, the well is plugged.” This is the analogy given by the biologist of the Healthy Reefs Initiative, Israel Muñiz, when asked about possible solutions to rescue corals that are already bleaching, or to avoid another tragedy of this size.
There are no strategies to stop bleaching, that is, the loss of corals from their symbiont algae (zooxanthellae), which give them their natural color. What does exist are possibilities to restore damaged specimens. There are projects focused on the recovery of coral colonies, through their relocation to deeper and cooler areas; others that aim to shade corals.
Precisely, coral nurseries could be key to restoring affected reefs. And a sophisticated strategy for preservation is cryogenics: keeping specimens cold to maintain their genetic diversity. “The corals were spawning in August, so all those collected gametes, which are reproductive cells, are a repository for having some material for the future, but that means taking great care of coral nurseries to be able to replant them,” explained Figueroa, from the Akumal Ecological Center.
However, the most important thing for specialists is to reduce the other factors that stress reefs, that is, that the authorities recognize the dangers of climate change and promote public policies to mitigate its effects.
They also improve the quality of ocean water by reducing tourist visits to places where there are reefs, reducing fossil fuel consumption, implementing guidelines on wastewater discharge and treatment, especially for megaprojects in tourism, and other measures.
“We have to understand the magnitude of what's happening. There are probably billions of corals affected or threatened in Mexico. It's a very large scale. So thinking of a strategy to help that universe is not humanly possible in the immediate term. This is climate change at the end of the day. We have to start as a country and society to recognize that we have a serious problem with climate change, which doesn't just affect corals, it's also affecting us with floods, hurricanes,” Álvarez said.
The specialists recalled that finally, not only are those beautiful and colorful underwater landscapes that attract tourism so much are being lost, generating significant profits with activities such as underwater tours, diving practices, among others.
In the same way, ecosystems that provide coastal protection against phenomena such as hurricanes, and that provide more than 25% of marine biodiversity, are being affected, which is why they represent the main source of income for thousands of families.
Therefore, they suggested taking some actions to try to reduce impacts locally: implementing controls on the level of use of areas with affected corals, temporarily closing access to reefs, urging citizens and companies to reduce levels of pollution and garbage.
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