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“Upwelling” theory as to why 6,000 Isla Contoy coral colonies died in two weeks

Isla Contoy, Q.R. — In two weeks, more than 6,000 coral colonies of the Acropora palmata, Acropora cervicornis and Acropora prolifera species that existed in the Contoy area have died.

“It could be a new outbreak of a disease or it could be the effect of a natural event. There is no certainty of what happened,” said María del Carmen García Rivas, director of the Isla Contoy National Park.

A new phenomenon – still unknown – caused the massive death of acropora-type corals in the reefs of Isla Contoy, in Quintana Roo, which is located at the northern tip of the Mesoamerican Reef System.

Since 2017, the UNAM’s Reef Systems Unit, the Centro de Investigaciones Regional Acuícola Pesquera (Criap) and the National Commission for Protected Natural Areas (Conanp) have been working on a project to repopulate the reefs with acropores corals, whose population was devastated due to a disease called white band.

García Rivas says there are three coral nurseries in the area. However, multi-year efforts to reproduce, stock and monitor the growth of coral colonies were fizzled out in a matter of days by a sudden massive death.

According to the director, a review of the nurseries was performed on August 22, three days after the passage of Hurricane Grace.

“They were found in good condition, like the colonies already planted on the reefs,” said the biologist.

On September 3, the Isla Contoy National Park management team was notified of the bleaching of the coral colonies. Given the weather conditions and the lack of personnel, it wasn’t until September 18 that a field trip could be carried out, where a total mortality of the acropore corals was verified.

In 2018, a coral disease called white syndrome devastated more than 50 percent of the brain-corals throughout the Mexican Caribbean. However, this outbreak did not affect the branched corals, which are the ones that died en masse this time.

García Rivas said that for the moment, the cause is unknown although several hypotheses have been made. One of the possibilities is an upwelling of water from the seabed that occurred only in this area.

“Between September 1 and 10, there was possibly an upwelling since the water was green and very cold,” she explained.

Isla Contoy is a virgin island, which can only be accessed by a limited number of tourists per day. No type of real estate development is allowed.

Until now, the death of corals of this type is not known in other parts of the Mesoamerican Reef, such as Isla Mujeres, Puerto Morelos or Cozumel. Isla Contoy is part of the municipality of Isla Mujeres.