Does sunscreen kill marine life? New research shows how quickly it can become toxic in the ocean.

Sunscreen is essential to protect humans from UV rays which can lead to skin cancer and other problems. But while it has been proven to save people, in many cases it also kills coral reefs. Now, new research shows just how deadly sunscreen can be to marine life.

It has been known for years that sunscreens containing oxybenzone are the likely culprits of the damage to coral reefs. The chemical is very effective at blocking UV rays from human skin, but once it’s in the ocean it’s no longer harmless to other life forms, a fact that led to the ban of certain sunscreen formulas in reef-dense areas, such as Hawai’i, the US Virgin Islands, Palau, and Bonaire.

But what wasn’t known was how this chemical ended up being so toxic to the marine environment, and without that information, there’s no guarantee that sunscreen alternatives would be safer.

It is the lack of information that a new study, published Thursday in the journal Science, sought to fill.

They placed 21 anemones in seawater under a bulb that emits full spectrum sunlight, with five of the animals covered in a box that blocks UV light that typically interacts with oxybenzone. The animals were then exposed to 2 mg of oxybenzone per liter of seawater.

“Anemones, like corals, have a translucent surface, so if oxybenzone acted as a phototoxin, UV rays hitting the light group would trigger a chemical reaction and kill the animals – while the dark group would survive,” the researchers said. researchers in an article. they wrote to explain their findings.

And that’s exactly what happened.

It took only six days for the first anemone that had been exposed to oxybenzone and left in the UV light to die. Ten days later, all anemones covered in light were dead, while all anemones that had not been hit by UV light were alive.

The researchers found that the anemones’ bodies automatically treated oxybenzone as a foreign substance, triggering metabolic processes that altered the chemical composition of oxybenzone. This is a common process that plants and animals use to make foreign substances less toxic, but in the case of this particular chemical, it simply made the foreign substance deadly.

“It traps the energy it absorbs from UV light and sets off a series of rapid chemical reactions that damage cells. Rather than converting sunscreen into a harmless, easy-to-excrete molecule, anemones convert oxybenzone into a powerful sunlight-activated toxin,” the researchers said.

Some forms of marine life have built-in protection, the researchers found. When they repeated their mushroom coral experiment, they discovered that these phototoxins were stored in the algae that live in the coral. Without this algae, it is suspected that the coral would have suffered the same fate as the anemones tested.

In fact, when the scientists ran the test again on anemones that had no algae, they died about twice as fast and had almost three times as much phototoxin in their cells as the anemones that had algae. .

While seeing the protection algae can provide offers some hope, the research also comes at a time when bleaching is devastating coral reefs around the world. When coral bleaching occurs, algae are expelled from the coral in which they reside, leaving marine animals without their primary food source and more susceptible to disease.

As the Earth approaches 1.5°C global warmingthe researchers warned that more than 90% coral reefs will suffer from an “intolerable level of heat stress” as extreme heat events – a cause of coral bleaching – become more frequent and intense.

This means that without better sunscreen formulas, a summer swim in the ocean could only make life worse for vital coral reef ecosystems, especially given how much sunscreen gets into the waters of the ocean. ocean.

Each year, between 4,000 and 6,000 tons of sunscreen enter coral reefs, according to the National Park Service. With 90% of snorkeling and diving tourists exploring the waters on 10% of the world’s reefs, according to the service, it’s the most popular and beautiful underwater scenes on the planet that bear the brunt of toxicity.

“It would be a sad irony if ecotourism aimed at protecting coral reefs actually worsened their decline,” study lead author Djordje Vuckovic said in a statement.

Today, many alternative sunscreen formulas considered safer for marine life contain chemicals similar to oxybenzone, which means they could simply be adding to the problem rather than solving it. But the latest research provides an essential piece of the information puzzle, and with summer approaching and efforts to mitigate the effects of climate change, the researchers’ findings could help create a sunscreen formula that protects and remains harmless to all forms of life.

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