What if nanoparticles could save the coral reefs?

Coraux et nanomatériaux

Coral reefs are critically endangered

Global warming is a terrible threat to biodiversity. The effects on coral reefs and countless other organisms are already considerable. Coral reefs are veritable hotspots of marine biodiversity, and climate change is a direct and immediate threat to them. Rising ocean temperatures are already adversely affecting them. Oceanologists see the extent to which they are undeniably shrinking year after year, and scientists work every day to find ways to combat this phenomenon.

Coral reefs account for 1% of the surface area of the ocean floor, but they host around 1 million species and almost a quarter of the world’s fish.

These reefs also play a crucial role in curbing erosion caused by tropical storms and in stemming inevitably rising sea levels.

What we know now is disturbing. A UNESCO report explains that within one to three decades, rising water temperatures caused by global warming will exceed those survivable by coral reefs at the majority of World Heritage-listed sites (https://whc.unesco.org/en/news/1676/).

So how exactly does global warming affect coral reefs?

Corals live in symbiosis with microalgae. These microalgae live within the tissues of the coral — an environment that is both protected and relatively stable (these microalgae are often zooxanthellae). In return, the microalgae provide the coral with energy and nutrients produced by photosynthesis.

Photosynthesis allows the microalgae to transform sunlight into chemical energy, producing carbohydrates and other organic compounds necessary for the coral’s survival. By feeding on these, the coral then produces the carbon, nitrogen, and phosphorus needed by the microalgae.

Unfortunately, global warming harms the delicate symbiosis between microalgae and corals. Higher water temperatures create thermal stress in zooxanthellae, which affects their metabolic processes. This results in a reduction in their ability to photosynthesise. Furthermore, when corals are exposed to high temperatures for too long, they are prone to expelling algae from their tissues, resulting in what’s known as coral bleaching. This significantly weakens them.

Global warming is also leading to increased carbon dioxide uptake in the oceans, which leads to a phenomenon known as ocean acidification. This directly impacts both the growth of ocean species and the symbiotic relationships between them.

How could nanoparticles turn the tide?

An innovative solution to this immense challenge could be around the corner: nanoparticles. In a recent article published in One Earth (July 2023) called “Nanobiotech engineering for future coral reefs”, researchers put forward a promising approach. They have discovered that cerium dioxide nanoparticles, when functionalised with polyacrylic acid, could provide protection for the microalgae that live symbiotically with corals.

How does this work? The nanoparticles protect the microalgae by acting like a shield against harmful UV radiation. They also help regulate photosynthesis, which reduces oxidative stress in the microalgae. Corals could then also benefit as a result.

These exciting discoveries are just the beginning. Further in situ research is needed to verify both the effectiveness of this approach and its safety for marine flora and fauna.

We at SON are particularly excited about how nanomaterials can benefit our ecosystem and the environment.