Protections are buffering Little Cayman reefs from threats

(CNS): Little Cayman’s coral reefs are subject to the same pressures of climate change and disease as those around the world, but the latest survey of the reefs by the Central Caribbean Marine Institute (CCMI) shows that local marine protections have provided a buffer from the impact of those threats. Fish populations around the island have shown significant signs of recovery and the reefs continue to show resilience, especially within the marine protected areas (MPAs), proving the importance of legal protection.

Nevertheless, the reefs remain vulnerable as they are getting smaller and coral recruitment is decreasing. In addition, the decline in large boulder corals that create massive reef structures leaves the island more vulnerable to storms, according to CCMI researchers.

But there is cause for optimism. Specific protections put in place in 2016 to protect Nassau grouper have had a knock-on effect on other species, and CCMI researchers said they are seeing more fish, larger fish, and a greater diversity of species than in previous years.

“Major increases in 2020 and 2021 could be further influenced by COVID-19 and reduced overall activity on the reef,” a press release from CCMI said. Significantly higher biomass inside the MPAs give the reefs a buffer from environmental changes, allowing fish to thrive. The survey found that in 2021, fish biomass was 40% higher inside the protected areas than outside.

Parrotfish density increased by 47% from 1999 to 2021. This is another positive indicator of reef health as they are key herbivores that feed on algae, which competes for space on the reef with coral. The effects are reflected in the overall health of the reefs. Researchers found that 90% of surveyed reefs were classified as in a ‘good’, ‘good+’, or ‘very good’ state, based upon coral cover. This is an encouraging indicator, as fewer sites were classed as ‘fair’ than in recent years, and no sites were classed as ‘poor’, CCMI said.

However, the survey data also shows the vulnerability of corals to increasing threats of climate change and disease. Because they are slow-growing and unable to move to seek refuge from stress events, they are not able to rebound or respond quickly. Previously the reefs of Little Cayman were dominated by large boulder coral species, but this is shifting to smaller, faster-growing species, which is a trend seen throughout the Caribbean region.

The 2021 surveys recorded a 60% decrease in the size of corals surveyed. The shift to smaller species impacts the overall function of the coral reefs, as the larger boulder species build up the massive reef structure necessary for the critical wave break that protects coastlines in Little Cayman from storms, which are becoming increasingly powerful due to climate change.

The vulnerability of coral species on the reefs is compounded by an 83% decline in new recruits, or baby corals, between 2006 and 2021, and almost no boulder coral recruits. If the local adult population experiences a mortality event, such as bleaching or disease, low recruitment means that the coral reefs are unlikely to recover quickly.

Overall, the resilience of coral and fish populations is a good news story that can largely be attributed to the success of the MPAs and specific species protections, which have shielded Little Cayman from extreme pressures that are heavily impacting reefs around the globe.

CCMI’s surveys of Little Cayman’s reefs indicate that with appropriate management policies, coral
reefs may be able to recover and display resilience to regional and global threats. Investigating mechanisms of coral resiliency is crucial to understanding how corals can survive future threats and a changing climate.

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