- A new lab-based study found that coral can convert oxybenzone, a common component of sunscreens, into toxic chemicals.
- Toxins can be particularly harmful to bleached corals that have expelled symbiotic algae as a result of stressors such as elevated seawater temperatures.
- However, the results are controversial as they may not reflect the actual situation.
- Oxybenzone in the seawater of coral reefs may not reach harmfully high concentrations.
Coral reefs around the world face an uncertain future as a result of climate change.
Many tourists who swim in coral reefs use sunscreen to protect their skin from the ultraviolet rays (UV) that can cause skin cancer.
According to new research, exposure of corals to oxybenzone, the active ingredient in many sunscreens, can make them even more vulnerable to rising seawater temperatures.
The study is published at Chemistry..
However, coral experts question whether new discoveries, including exposure of corals and sea anemones to oxybenzone in the laboratory, accurately reflect real-world situations.
Over the last few decades, rising seawater temperatures have increased the frequency of massive bleaching events that occur when coral polyps expel algae that are dependent on their survival.
Corals and algae work together in what biologists call a “symbiotic” relationship.
“These microscopic symbiotic algae give the corals color, and most importantly, the nutrients they need very much,” said Dr. Victor Weltas., Researcher at the ARC Center of Excellence for Coral Reef Studies, part of James Cook University in Townsville, Australia.
“When the algae symbiont is expelled by coral, the colonies appear bright white because the clear coral tissue exposes the calcified skeleton that supports it,” said Dr. Huertas, who was not involved in the new study. rice field.
Bleaching is usually a response to high temperature stress, but other causes are possible.
“While bleached, corals can survive for up to several weeks, but some corals tolerate more heat stress than others,” Dr. Huertas said. Today’s medical news..
The sale of sunscreens containing oxybenzone is banned at popular eco-tourist destinations such as Hawaii in the United States and Key West, Florida.
Scientists were uncertain about the possible mechanism, but the ban followed previous studies that chemicals were involved in coral bleaching.
MeIn a new study, scientists at Stanford University in Stanford, California, found that oxybenzones are converted from UV blockers to “phototoxins” in the cells of anemones and corals.
Photoxin is a chemical that becomes toxic when exposed to sunlight.
Their experiments also suggest that coral-dwelling algae provide some protection against toxins. This may mean that bleached corals are more vulnerable to chemicals.
Researchers argue that in warmer climates, sunscreens containing oxybenzone can accelerate damage to coral reefs and prevent their recovery.
“”[T]He found that oxybenzone sunscreens are more toxic to these bleached sea anemones, which are also more toxic to bleached corals and actually have these adverse effects of warming. It may indicate that it will make it worse. .D. Candidates for Djordje Vuckovic Chemistry Podcast.
Vuckovic and his colleagues hope that their research will help guide the development of UV blockers that are unlikely to be converted to phototoxin.
Researchers studied sea anemones Iptasia And mushroom coral Discosoma..
In the laboratory, sea anemones were exposed to oxybenzone at a concentration of 2 milligrams per liter of seawater at 27 ° C.
All sea anemones died within 17 days under artificial sunlight, including UV light.
In contrast, when scientists exposed animals to simulated sunlight without oxybenzone, or to oxybenzone in the absence of UV light, mortality after 21 days was negligible.
Researchers report that while oxybenzone protects tissues from the harmful effects of UV light, both sea anemones and corals have converted it into other molecules that are potent phototoxins.
However, the symbiotic algae that live inside the sea anemones appeared to protect the sea anemones by storing or “quarantining” these phototoxins.
Sea anemones lacking algae showed higher mortality in the presence of oxybenzone, and their tissues contained higher concentrations of phototoxin.
Scientists have discovered algae inside Discosoma Corals were even more effective in isolating phototoxin.
In their dissertation, they conclude that:
“If coral symbiotic algae … protect the coral from the toxic effects of oxybenzone metabolites, then the coral becomes more sensitive when the coral is extensively bleached in response to rising sea temperatures … this is recreational swimming and tanning. Coral reefs that use stops are likely to be a practical problem. “
However, coral experts have expressed skepticism about these conclusions.
“The 17-day laboratory exposure does not mimic how sunscreen leaves the skin of coral reef tourists and is rapidly diluted,” said Professor Emeritus and former director of the ARC Coral Reef Research Center. Dr. Terry Hughes said.
“The concentration in the lab is much higher than in previous measurements in the field,” he said. MNT..
Professor Hughes said previous bleaching events on the Great Barrier Reef in Australia closely matched where the water was the longest and hottest.
“Even the most remote coral reefs in the world are now bleached far from any airport,” he added.
“If tourists want to save coral reefs, they need to consider carbon dioxide emissions and who to vote for, rather than avoiding sunscreen,” he said.
Professor Hughes wrote about the Oxybenzone controversy conversationCancer experts added that they are warning about the dangers of public health if people stop using sunscreen.
“”[W]I do not disagree with the author’s findings, but note that their work is based on experimental work done in the laboratory, “says Dr. Huertas.
“Things can change a lot in the ocean, especially when ocean currents are working,” he said. MNT..
A study in Bermuda found this to be the case, he added.
Dr. Beth Goldstein, co-founder of Modern Ritual in Chapel Hill, North Carolina and President of Central Dermatology, said:
She recommended a mineral-based sunscreen instead of one containing a similar chemical called oxybenzone or octinoxate. However, she emphasized that scientists have not proven that other ingredients such as preservatives and emulsifiers are safe for reefs.
For example, on a recent family holiday, her family chose UV swimwear. MNT..
“These have proven to be effective for long seizures in the sun, without fear of” missing a spot “when diving for hours at a time,” she said.
