Mesophotic Coral Ecosystems and Associated Biodiversity

Mesophotic coral ecosystems occupy the twilight zone of tropical and subtropical reefs between approximately 30 and 150 metres depth. They form a complex interface between shallow reef assemblages and the deep sea, characterised by reduced light availability, cooler and more stable temperatures, and unique oceanographic regimes. Unlike shallow reefs, mesophotic communities are dominated by specialised corals, algae and invertebrates adapted to low‐light conditions, often hosting high levels of endemism and phylogenetic novelty. These deeper reefs provide critical habitat for diverse fish and benthic communities, contribute to regional biodiversity and may serve as reservoirs for genetic and reproductive refugia as shallow reefs degrade. Recent advances in technical diving, remotely operated vehicles and genomic sequencing have revealed steep ecological gradients with depth, shifts in species composition and functional traits, and complex patterns of connectivity both within mesophotic strata and with adjacent habitats. However, their potential as thermal or reproductive refuges is context dependent, as mesophotic reefs can experience episodic bleaching and stress driven by thermocline dynamics. Mesophotic ecosystems also face mounting threats from climate change, fishing, pollution and emerging deep-sea industries. Integrating knowledge of their biodiversity, connectivity and environmental drivers is vital to inform conservation planning and management at a global scale.

Research from Nature Portfolio

Recent findings have demonstrated that mesophotic corals are not immune to bleaching, with documented events at depths of 90 metres linked to persistent thermocline deepening and internal wave activity, underscoring the importance of detailed oceanographic monitoring in predicting stress events. A separate investigation into mesophotic black coral forests revealed that these key habitat engineers substantially alter both the taxonomic and functional composition of fish assemblages. Although mesophotic fish richness may match shallow communities, the identity of dominant species and trait evenness diverge markedly, highlighting the need for tailored conservation strategies to preserve the unique ecological functions of mesophotic strata.

Mesophotic Coral Ecosystems and Associated Biodiversity publication trend

The graph below shows the total number of articles in mesophotic coral ecosystems and associated biodiversity across all publications each year (not limited to Nature Index journals).

Technical terms

Mesophotic Coral Ecosystem: A coral community inhabiting depths of approximately 30–150 metres characterised by low-light conditions.

Thermocline: A subsurface layer in the ocean where temperature changes rapidly with depth, influencing coral thermal stress.

Functional Diversity: Variation in ecological roles and traits among species within a community, affecting ecosystem functioning.

Genetic Connectivity: The exchange of genes among populations through larval dispersal, shaping biodiversity patterns and resilience.

Refugia: Habitats that provide stability and protection from environmental extremes, potentially aiding species persistence.

References

1. Mesophotic coral bleaching associated with changes in thermocline depth. Nature Communications (2023).
2. Black coral forests enhance taxonomic and functional distinctiveness of mesophotic fishes in an oceanic island: implications for biodiversity conservation. Scientific Reports (2023).
3. Climate change impacts on mesophotic regions of the Great Barrier Reef. Proceedings of the National Academy of Sciences of the United States of America (2024).
4. Trait-based approaches reveal that deep reef ecosystems in the Western Indian Ocean are functionally distinct. The Science of The Total Environment (2023).
5. Global phylogenomic assessment of Leptoseris and Agaricia reveals substantial undescribed diversity at mesophotic depths. BMC Biology (2023).