Sea anemones and coral turn a common sunscreen ingredient into a toxin activated by light
|According to a study, oxybenzone, a common ingredient found in sunscreens, can be converted into a fatal poison by corals and sea anemones, posing a threat to coral reefs. |
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One common sunscreen ingredient has the potential to harm coral reefs. Scientists have figured out why.
Sea anemones and mushroom coral, both closely related to corals, can convert oxybenzone, a molecule that protects people from ultraviolet radiation, into a lethal toxin that is activated by light. The good news is that algae living alongside the organisms can absorb the poison and reduce its effects, according to a study published in Science on May 6.
However, coral reefs that have been bleached and are devoid of algae may be more sensitive to death. Corals and anemones that are overheated can eject beneficial algae that supply oxygen and eliminate waste, turning reefs white. As a result of climate change, such bleaching is becoming more common (SN: 4/7/20).
According to Craig Downs, the findings suggest that sunscreen pollution and climate change may pose bigger harm to coral reefs and other marine habitats when combined. He is a forensic ecotoxicologist at the nonprofit Haereticus Environmental Laboratory in Amherst, Virginia, but was not involved in the research.
Oxybenzone has been shown in the past to kill baby corals and inhibit older corals from recovering following tissue damage. As a result, oxybenzone-containing sunscreens have been banned in various places, including Hawaii and Thailand.
Glass anemones (Exaiptasia pallida) exposed to oxybenzone and UV radiation adds sugars to the chemical, according to a recent study by Stanford University environmental chemist Djordje Vuckovic and colleagues. Rather than helping organisms detoxify toxins and remove them from the body, the oxybenzone-sugar combination acts as a poison that is activated by light.
The team demonstrated that anemones exposed to either simulated sunlight or oxybenzone alone survived the entire experiment, which lasted 21 days. However, all anemones that were subjected to simulated sunshine while submerged in water containing the drug died after 17 days.
|According to a study, algae can absorb oxybenzone and its hazardous by-products. When subjected to oxybenzone and UV light, sea anemones without algae (white) died faster than those with algae (brown). |
CHRISTIAN RENICKE AND DJORDJE VUCKOVIC
The algal companions of the anemones absorbed a large portion of the oxybenzone and toxin that the animals were exposed to in the lab. Anemones without algae died days before anemones that had algae.
Similar research found that algae living inside mushroom coral (Discosoma sp.) absorbed the toxin as well, indicating that algal connections protect against the toxin's detrimental effects. The coral's algae appear to be particularly protective: after being exposed to oxybenzone and simulated sunshine for eight days, no mushroom corals died.
It's yet unknown how much oxybenzone is harmful to coral reefs in the wild. Another unanswered concern, according to Downs, is if other sunscreen ingredients with comparable structures to oxybenzone have the same impacts. Researchers may be able to develop better, reef-safe sunscreens if this information is gathered.
D. Vuckovic et al. Conversion of oxybenzone sunscreen to phototoxic glucoside conjugates by sea anemones and corals. Science. Vol. 376, May 6, 2022, p. 644. DOI: 10.1126/science.abn2600.