Bleached but not broken: CCMI reveals impacts and future implication of record-breaking temperatures on Little Cayman’s Reefs

June 19, 2024

Little Cayman, Cayman Islands; 18th June 2024 – The summer of 2023 was the hottest on record and brought with it the longest and most extreme marine heatwave experienced in the Cayman Islands.

The Central Caribbean Marine Institute (CCMI) has been monitoring the impact of this marine heatwave throughout and just released the results of this monitoring from July 2023 to January 2024. CCMI’s 2023 Coral Bleaching Report Card shows that the coral bleaching in Little Cayman was severe and comparably more severe than other reefs in the region. This is likely to be attributed to factors including higher coral cover to start with and the presence of more susceptible species that are not present on most reefs with more stressors.

CCMI’s research found that 90% of corals in Little Cayman bleached during the marine heatwave and more than 50% subsequently died. Most of the corals that died were ‘weedy’ species, whereas many of the key reef-building, boulder-like species showed lower mortality and higher rates of recovery.

Even with such extreme bleaching, hope is not lost. Coral reefs that are protected from the added pressures of local threats such as pollution and overfishing, such as those in Little Cayman, show improved long-term recovery from disturbance.

Before the bleaching event, coral cover in Little Cayman remained at approximately 20%, compared to 10-15% regionally[1]. CCMI’s pre-bleaching 2023 Healthy Reefs monitoring showed that 90% of these reefs were in “good” to “very good” condition. This higher coral cover, along with higher species diversity and healthy fish populations, particularly herbivores, may mean that Little Cayman’s reefs show better long-term recovery than reefs in poorer health. This provides hope for the recovery of these reefs, but the next year or so will be pivotal.

Similarly, 25 years of CCMI’s monitoring data show above average health of corals, with no reefs recorded in “poor” health in 2022 or 2023, and stable levels of coral cover despite regional decline. Although no one can say for certain how these reefs will recover and fare in the future as climate change impacts intensify, we can say that historically they have showed stability while other reefs in the Caribbean have recorded decline.

Regardless, with the impacts of climate change intensifying, now, more than ever, these reefs need our help. With predictions forecasting that 2024 could be just as hot, CCMI’s research team are seeking solutions to support reef recovery and understand how we can help these reefs to survive and adapt through science-based action.

CCMI is taking a multi-faceted approach to helping reefs to survive and adapt to climate change through a combination of cutting edge-research and action. CCMI has been pioneering a resilience-based coral restoration programme in Little Cayman since 2012. This restoration programme has grown more than 1,500 corals and outplanted over 70m2 of coral on to the reefs of Little Cayman, informed by CCMI’s ongoing research in coral genetics to boost the resilience of corals to stressors such as warmer oceans and coral disease.

CCMI is also researching how mesophotic, or reefs deeper than 30 m, can help shallow water corals survive climate change. With National Science Foundation funding, CCMI’s researchers are investigating how corals may adapt to extreme environmental conditions. A recent publication by CCMI’s Director of Research, Dr Goodbody-Gringley, found that coral larvae from shallow-water reefs may be able to settle and survive on deeper reefs, offering hope that these mesophotic reefs could provide refuge for corals if shallow reefs become inhospitable.

To further support this, CCMI has been exploring and documenting previously uncharted mesophotic reefs on seamounts Pickle Bank and 12-mile Bank, off the coast of Cayman. Here, CCMI’s technical divers have found highly productive coral reefs that could provide further hope for maintaining coral biodiversity through climate extremes.

Overall, the impact of last year’s coral bleaching was extreme, not only in Little Cayman but globally, and the summer of 2024 is likely to bring further bleaching. However, the historically stable, healthy and highly diverse reefs in Little Cayman may fare better when it comes to recovery and become a site of hope and re-seeding for other reefs. CCMI is further supporting these valuable reefs through their research and conservation efforts.

As a community, everyone has a part to play in supporting these ecosystems at such a pivotal time. Small lifestyle changes such as eating less meat, switching to renewable energy sources, eating sustainable seafood and supporting environmental initiatives are powerful ways for everyone to make a difference to the future of coral reefs.


Read CCMI’s full 2023 Coral Bleaching Report Card.

Read the CCMI 2023 Healthy Reefs report card.

Learn more about CCMI’s research and Healthy Reefs campaign.

[1] (GCRMN 2020, Jackson et al 2014)” Jackson, J., Donovan, M., Cramer, K. and Lam, V., 2014. Status and trends of Caribbean coral reefs: 1970-2012. Gland, Switzerland: Global Coral Reef Monitoring Network; International Union for the Conservation of Nature (IUCN)