Placing temporary shade on vulnerable Caribbean corals could partly reverse bleaching caused by marine heatwaves
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Around the world, climate change is the biggest threat to coral reef survival. As land temperatures rise, so do ocean temperatures, causing a ‘bleaching’ effect as corals turn pale white. The impact of coral bleaching is vast: it destroys the foundation of marine ecosystems, strips coastlines of natural protection, and threatens global food security.
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Now, scientists believe they have found a way to protect some especially vulnerable Caribbean corals from coral bleaching: umbrella-like underwater shades.
These shades don’t cool the water; instead, they prevent UV and irradiance damage, which can worsen heat damage to corals.
In their study, scientists set up 20 custom-made shades across 10 colonies of two brain coral species in the Florida Keys, and selected 20 matching corals as controls. Umbrella-like shades, constructed of nylon cloths attached to pipes, were temporarily fixed to the seabed and floated over the coral. Divers came every two weeks to track colour changes and take tissue biopsies from the corals.
They found shaded corals lost less colour than expected, with some even recovering partial colour after shades were installed. No dead coral were reported, even under the most intense periods of thermal stress.
‘Scaling is the big limitation of this study; shading is not a cure-all for coral reefs, and its use would require hard decisions about what corals are worth saving,’ said Dr Karen Neely of Nova Southeastern University, lead author of the article published in Frontiers in Marine Science.
‘We found it was effective on two highly susceptible coral species, so it is likely to be useful for most others, but additional studies would be needed to confirm that. It is also likely that thermal stress would reach a point at which no amount of shading could help a coral, but only future experimentation would be able to define the bounds of that.’
How else can coral reefs be protected?
Effectively enforcing Marine Protected Areas (MPAs) can be a great way of allowing corals to regrow. In doing so, fish populations can be restored, reef structures can become more stable, and biodiversity can be boosted.
However, just six per cent of coral reefs globally are situated within effectively managed MPAs, leaving around 66 million acres of coral reefs unprotected.
Better wastewater management can also help protect these ecosystems, as runoff from cities, farms, and sewage systems can suffocate coral and fuel algal blooms. To do this, interventions such as upgrading wastewater systems, managing stormwater and restoring coastal vegetation can be implemented.
In addition, global collaboration between locals, governments, NGOs and industries is also a solution to conserving coral reefs.
