▎ WuXi AppTec content team editor
I don't know if the rich and colorful landscape of coral reefs has left a shocking impression on you. Corals are not only beautiful, but also an important part of the marine ecosystem, providing habitat for other marine life and protecting coastlines from wave erosion. But in the context of global warming, corals around the world are facing a severe existential crisis.
Now, a new study explains to us: Corals are threatened not only by the climate, but also by the sunscreens that people use.
In a cover paper in the journal Science this week, a team led by Professor William Mitch of Stanford University pointed out that many sunscreens contain a common ingredient that metabolizes in corals, forming phototoxins that endanger coral survival and accelerate the disappearance of these endangered ecosystems. This research will guide people to design and use more coral-friendly sunscreens.
According to the National Park Service, 6,000 tons of sunscreen are discharged each year into U.S. coral habitats alone. Previous studies have found that the sunscreen component oxybenzophenone contained in many sunscreen skin care products can cause damage to corals. As a result, some coasts around the world have banned the use of products containing oxybenzone.
However, the mechanism by which oxybenzophenone damages corals remains a mystery. If the exact mechanism cannot be identified, it is also unknown whether other sunscreens as alternatives are safe.
In the latest study, the research team conducted research on curved mushroom corals (commonly known as mushroom corals) and sea anemones. In artificial seawater and simulated sunshine, all anemones exposed to oxybenzophenone die within 17 days, while in the absence of sun, sea anemones survive even in the presence of oxybenzophenone.
▲Under simulated light, oxybenzophenone produced phototoxins to sea anemones (Image source: Reference[1])
Subsequently, Professor Mitch's team uncovered the mechanism by which oxybenzophenone reacts in corals and anemones. From the principle of sun protection, after absorbing ultraviolet rays, oxybenzophenone converts light energy into heat release, thereby avoiding sunburn. For anemones and corals, under sunlight, oxybenzophenone metabolizes and forms phototoxic conjugated compounds with glucoside, damaging anemones and corals.
The team also found that the corals themselves have a way of defending against the damage caused by oxybenzophenone. The symbiotic algae in corals appear to protect corals: they absorb large amounts of toxins produced by corals. But in the context of global warming, corals are gradually losing these symbiotic algae, and the ability of these "bleached" corals to resist phototoxins is also weakening.
The research team points out that in addition to oxybenzophenone, there may be other sunscreen ingredients that need to be vigilant. This metabolic pathway that converts oxybenzophenone into phototoxins is equally likely to work with other common sunscreen ingredients that are chemically similar in structure.
Therefore, the research team also plans to conduct further studies to test whether these compounds and some sunscreens with metal components such as zinc and titanium, which claim to be safe for corals, are safe enough. It is believed that based on these studies, in the future, while we can enjoy the beautiful scenery safely and healthily by the sea, the coral ecosystem not far away can also continue to flourish.
Resources:
[1] Djordje Vuckovic et al., Conversion of oxybenzone sunscreen to phototoxic glucoside conjugates by sea anemones and corals. Science (2022). DOI: 10.1126/science.abn2600
[2] Understanding how sunscreens damage coral. Retrieved May 5th, 2022 from https://www.eurekalert.org/news-releases/951489
More recommendations
Click "Watching" and go again