Orbicella

Orbicella is a genus of massive stony corals belonging to the family Merulinidae. These corals are a major component of coral reefs in the Caribbean Sea and the western Atlantic Ocean. Characterized by their large, boulder-like or columnar shapes, Orbicella colonies can grow to substantial sizes over many years, often forming the structural foundation of reef ecosystems.

Orbicella corals are zooxanthellate, meaning they harbor symbiotic algae (zooxanthellae) within their tissues. These algae provide the coral with energy through photosynthesis, which is vital for coral growth and survival. The corals, in turn, provide the algae with protection and access to nutrients.

Three species were previously recognized within the genus Orbicella: Orbicella annularis, Orbicella faveolata, and Orbicella franksi. However, genetic analyses have indicated that these are distinct species that likely arose through hybridization and subsequent independent evolution. This reclassification is significant for understanding coral biodiversity and conservation efforts.

Orbicella corals are susceptible to various threats, including ocean acidification, rising sea temperatures (leading to coral bleaching), disease, and pollution. Their slow growth rates and sensitivity to environmental stressors make them particularly vulnerable. Conservation efforts are focused on mitigating these threats and promoting reef resilience. The decline of Orbicella populations poses a significant risk to the health and stability of Caribbean coral reef ecosystems.