Coral Bleaching: Impact on Cousin Island

Charlotte Dale, a member of Nature Seychelles’ Reef Rescuers talks about the bleaching being seen on Cousin Island, the consequences of bleaching and what we can all do to protect corals.

Can you describe the recent coral bleaching around Cousin Island and the impacts you have observed?

The Reef Rescuers are carrying out a coral reef restoration project in Cousin Island Special Reserve. The current phase is funded by the Adaptation Fund through UNDP Mauritius and the Seychelles Government. The project was initiated in 2010 to respond to the repercussions of the 1998 coral bleaching event, which resulted in high coral mortality on Cousin Island. Multiple bleaching events have occurred in recent decades, with the current one being the fourth global coral bleaching event.

Currently, we are witnessing first-hand the devastating effects of this event. Bleaching is evident across all project sites, indicating the severity of the situation. Initial surveys indicate that 74% of the monitored coral colonies are experiencing bleaching, characterized by a pale or white appearance, signalling an alarming situation and forecasting high mortality in the coming months.
Although colonies previously transplanted from resilient sites appear to exhibit better resilience than naturally settled ones, the full extent of the devastation remains uncertain and will become clearer with time.

What mitigation measures has Nature Seychelles undertaken in Cousin?

To reduce stress on corals, all restoration operations involving coral handling have been halted. The nurseries have been relocated to lower depths to minimize exposure to high temperatures. Nature Seychelles is also building the first large-scale on-land coral nursery, called the Assisted Recovery of Corals (ARC), to create a safe environment for corals during such events, to protect species from local extinction and to create a brood stock for coral restoration. We are also pioneering the Coral Shading Initiative (CSI). During bleaching events, corals are subjected to intense light stress. So, to mitigate severe mortality, we are installing shading to reduce light stress on shallow reef corals.

Our team will continue to monitor the effects of this devastating event.

What are some of the short-term and long-term consequences of coral bleaching for marine ecosystems?

In the absence of recovery, bleached corals can die, degrading coral reef ecosystems. Coral bleaching alters ecosystem dynamics such as nutrient cycling and predator-prey interactions. Coral-dominated reefs become algae-dominated reefs.

The importance of coral reefs as vital ecosystems that provide vital ecological services cannot be overstated. Climate change in the coming decades could cause coral reefs to disappear and have profound consequences for people's livelihoods in Seychelles and in many countries.

What are some of the promising strategies or techniques being used to protect corals from bleaching?

Coral reef restoration projects such as the one we are carrying out using heat-tolerant species to enhance reef resilience and recovery are among the strategies and techniques used. Reef balls and concrete structures are being used to provide additional habitat to assist in reef regeneration. Selective breeding techniques are being used to develop coral strains that are more resilient to environmental stressors. Nature Seychelles, working with Master’s student Viktoria Sturm, is trialling the Coral Bleaching Automated Stress System (CBASS) to better understand thermal tolerances in corals in our restoration project. As mentioned, shading is used to reduce direct sunlight reaching coral reefs by placing structures and materials. Research is underway, but probiotics – introducing beneficial microbes to coral reefs to promote coral health - might improve coral reef resilience. Improving water quality, such as reducing nutrient pollution and sedimentation, can mitigate coral reef stress. Educating and involving local communities in coral conservation efforts offers hope for coral reef protection.

What can people do to prevent coral bleaching and support coral reef recovery?

Ultimately, the only way to protect coral reefs is to address the climate crisis. Coral reefs will continue to bleach unless emissions are reduced.

Individuals can help coral reefs recover by reducing their carbon footprint. There are several ways in which one can contribute to coral reef conservation, such as volunteering in local beach clean-up projects, contributing to coral restoration projects, or donating to coral reef conservation organizations. Making people aware of the crisis is also another way to get us all collectively involved in mitigating coral bleaching impacts.