Coral reefs are among the most diverse and valuable ecosystems on Earth, providing food, shelter, and livelihoods for millions of people.
However, they are also under threat from global warming, which causes coral bleaching, a phenomenon that can lead to coral death and reef degradation.
What is coral bleaching and why is it a problem?
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Coral bleaching is the loss of symbiotic algae that live inside the coral tissues and provide them with energy and nutrients, as per Phys.org.
These algae also give corals their vibrant colors, so when they are expelled or die, the corals turn white or pale.
Coral bleaching can be triggered by various environmental stressors, such as high or low temperatures, changes in salinity, pollution, or disease.
However, the main cause of coral bleaching is the rise in sea surface temperature due to climate change.
When the water temperature exceeds the optimal range for corals, they become stressed and release reactive oxygen species (ROS), which damage their cells and DNA.
This leads to the breakdown of the symbiosis between corals and algae, resulting in bleaching. Bleached corals are not dead, but they are weakened and more susceptible to infections and mortality. If the stress persists or recurs frequently, the corals may not be able to recover and re-establish their symbiosis.
Coral bleaching has become a global problem in recent decades, affecting most of the world's major coral reefs, such as the Great Barrier Reef in Australia, the Coral Triangle in Southeast Asia, and the Caribbean Sea.
According to the Intergovernmental Panel on Climate Change (IPCC), coral reefs are projected to decline by 70-90% if global warming reaches 1.5°C above pre-industrial levels, and by more than 99% if it reaches 2°C.
This would have devastating consequences for marine biodiversity, ecosystem services, coastal protection, and human well-being.
How can curcumin help protect corals from bleaching?
Curcumin is a natural compound that is extracted from the rhizomes of turmeric (Curcuma longa), a plant native to India and Southeast Asia, as per SciTechDaily.
Curcumin has been used for centuries in traditional medicine and cuisine for its anti-inflammatory, antioxidant, anticancer, and antimicrobial properties.
Recently, researchers from the Italian Institute of Technology (IIT) and the University of Milan-Bicocca, in cooperation with Genoa Aquarium in Italy, have discovered that curcumin can also protect corals from bleaching.
The researchers developed a biodegradable biomaterial based on zein, a protein derived from maize, to deliver curcumin to the corals in a controlled manner without causing harm to the surrounding marine environment.
The biomaterial forms a thin film that covers the coral surface and releases curcumin gradually over time.
The curcumin acts as an antioxidant agent that scavenges ROS and reduces oxidative stress in the coral cells. This helps maintain the symbiosis between corals and algae and prevents bleaching.
The researchers tested their technique on a coral species (Stylophora pistillata) typical of the tropical Indian Ocean, which is included in the IUCN Red List of endangered species.
They simulated overheating conditions in tropical seas by raising the water temperature up to 33°C for 10 days.
Under these conditions, all untreated corals were affected by bleaching as would occur in nature. However, all specimens treated with curcumin showed no signs of bleaching or stress response.
The researchers published their findings in ACS Applied Materials & Interfaces, where they also reported that their technique did not affect the growth or calcification of the corals or alter their microbiome composition.
They also filed a patent application for their technology and plan to test it in nature and on a large scale.
"This technology is the subject of a patent application that has been filed, and in fact the next steps of this research will focus on its application in nature and on a large scale," said Marco Contardi, first author of the study.
