Coral Spawning Phenomenon Captivates Cuba's Coastal Waters

This Sunday, the underwater realm of Cuba's coastal platform becomes the stage for a remarkable marine event: the synchronized spawning of hermatypic corals. This massive reproductive event plays a crucial role in maintaining the health of the nation's coral reefs.

A diverse team of scientists, students, and volunteers have embarked on a mission led by the Marine Research Center (CIM) at the University of Havana, in collaboration with the National Aquarium of Cuba and the Marine Section of the Cuban Zoological Society, as reported by the Cuban News Agency (ACN).

The main goal of the 2026 expedition is an ambitious one: to refine the national coral spawning calendar. This scientific tool is vital for planning future restoration efforts of Cuba's coral ecosystems, according to the organizers.

Prior to the dive, CIM hosted lectures last Friday by specialists Patricia González Díaz and Marileidy Albertus, who delved into the challenges of sexual reproduction in coral reefs. "The 2026 mission is ambitious: refining the national coral spawning calendar, a task demanding scientific rigor and unwavering passion for conservation," the experts emphasized.

Hermatypic corals, the stars of this event, are key players in reef construction, contributing calcium carbonate from their skeletons, and acting as the primary architects of these ecosystems.

Understanding Coral Spawning

Coral spawning involves entire colonies releasing millions of gametes—eggs and sperm—into the water simultaneously in one night. This creates what scientists term a "biological snowstorm" of rising white bubbles. This sexual reproduction process is essential for generating genetic diversity, making reefs more resilient to bleaching and climate change.

The observation and documentation of this natural spawning are part of a broader scientific strategy within the CoralCarib reef restoration project. This project, backed by €10.8 million from Germany's International Climate Initiative, covers 1,871 hectares of priority reefs in Cuba, the Dominican Republic, Jamaica, and Haiti.

The project combines asexual reproduction through coral fragments and assisted sexual reproduction with gamete collection and larva cultivation, complementing fragmentation nurseries with genetically unique individuals.

Efforts to Revive Coral Reefs

In Guanahacabibes, techniques were employed to propagate Acropora cervicornis corals, and by August 2022, 11 monitored colonies had spawned as part of these assisted reproduction techniques.

The urgency of these initiatives is underscored by mounting threats. In 2024, a mass coral mortality event was confirmed at Desembarco del Granma National Park, where Acropora palmata species suffered significant losses, documented by the Eastern Center for Ecosystems and Biodiversity in Santiago de Cuba.

Adding to the challenges, invasive species have emerged: in September 2022, the first sighting of the white coral Unomia stolonifera in Cuba was reported at Bacuranao Bay, east of Havana, and subsequently eradicated in 2023. In June 2025, the decomposition of sargassum posed a threat to marine biodiversity in coastal areas such as Baitiquirí Bay, Guantánamo.

Despite these pressures, Cuban reefs are considered among the best-preserved in the Caribbean. Dorka Cobián Rojas, the lead investigator for the monitoring program in Guanahacabibes, highlighted Cuba's efforts to rescue reefs damaged by overfishing and global warming, noting that "reefs have been seriously affected in recent years."

Established in 1970, CIM stands as a leading scientific institution in marine research in Cuba, fostering international collaborations for coral ecosystem monitoring.