Coral Reefs Are Dying: Climate Change and Sunscreen Pollution

By Rachel Laderman

Hānau ka ‘Uku-ko‘ako‘a, hānau kana, he ‘Ako‘ako‘a, puka

Born was the coral polyp, born was the coral, came forth

In the Kumulipo, the Hawaiian creation chant, ko‘a (the coral polyp) was the very first organism on the earth, followed by others of increasing complexity.

The humble coral polyp is a powerful ecosystem engineer. Coral reefs protect shorelines from storms, nurture a tremendous amount of sea life, produce much of the oxygen in the atmosphere, and create soft sandy beaches. Yet for all their incalculable services, our actions are assaulting the coral and causing a serious die-back.

Damage to coral is most obvious when it looks bleached. Snorkelers and divers in Hawai‘i and around the world are alarmed at the whitening of the coral at their favorite spots.

Coral bleaching occurs when conditions are so stressful that the algae that live symbiotically within the coral are expelled. Algae provide the coral polyps with energy from the sun. The coral use this energy to grow their calcium shells and reproduce. Without their colorful algae, the coral not only look bleached, but are literally sapped of their strength. The coral are not dead; however, they are very weakened.

Smothering brown algae then cover the weakened coral, making it even harder for them to recapture their beneficial, symbiotic algae. “There has been mass bleaching even in the far northwest Hawaiian islands in the last few years,” says John Burns, PhD, a University of Hawai‘i at Hilo professor and researcher for the National Oceanic and Atmospheric Administration. The bleaching corresponds with record high ocean temperatures. “The level of alarm I have is higher than I thought it would ever be,” says Burns.

To do the work of reef-building, corals need particular conditions. They require a water temperate range between 22.7°–28.8° Celsius (that’s 73°–84° Fahrenheit). They need clean, clear water, free of sediment and pollution, so their algae can get sunlight to photosynthesize.

All it takes for serious coral bleaching to occur is a stretch of four to six weeks of temperatures just 1°C (around 2°F) higher than normal warm-weather temperatures.

“Occasional mass bleaching isn’t a bad thing,” says Craig Downs, PhD, Executive Director of Haereticus Environmental Laboratory. “Ecologically, it is analogous to a forest fire that happens every 8–12 years.” It encourages healthy diversity in the coral ecosystem, allowing different species to grow.

However, many coral reefs are not recovering after bleaching. Consistently warmer waters are a big part of the problem. Downs says another reason, especially along populated coasts, is the presence of hormone-mimicking chemicals from personal care products in the water. These pollutants keep not only coral but also many key fish species from reproducing.

Sunscreen: One More Stress for Coral Reefs

Ever notice the scum of oil that rises around your body when you enter the water? The chemicals we use to protect our skin unfortunately can damage sea life, including the beautiful coral that is often the very reason we have plunged underwater.

One of the most commonly used ingredients in sunscreen is oxybenzone. It is added as a UV filter and product stabilizer to thousands of personal care products. The chemical enters the ocean not just through sunscreen on swimmers but also through wastewater treatment plants, from products used inland and washed down the drain.

In a 2016 study, Downs showed that oxybenzone harms coral in several ways: it damages their DNA, is toxic to the larvae, and causes deformities in the coral. Oxybenzone lowers the temperature at which coral will bleach. Damage can occur at miniscule concentrations—62 parts per trillion.

“Oxybenzone reduces corals’ resilience to heat stress,” says Downs. “Almost all coral species will bleach around 30.5° Celsius (86.9° Fahrenheit). If corals are bleaching or paling at lower temperatures, it is highly probable that other stress factors are impacting the coral.”

What About Banning Oxybenzone?

In a presentation to the Hawai‘i legislature in 2017, Downs showed how in water polluted with oxybenzone, coral have fewer symbiotic algae than coral in clean water at the same temperature. He showed examples of extensive degradation in Hanauma Bay, a hugely popular snorkeling site on O‘ahu. He showed a series of slides of Carysfort Reef in Florida, once an amazingly beautiful and heavily visited reef that is now bleached and not recovering.

Downs’ research caught the attention of the legislature, which proposed thirteen bills regarding banning oxybenzone and octinoxate (another harmful sunscreen chemical) in 2017.

Hawai‘i State Senator Will Espero sponsored a bill to ban most oxybenzone and octinoxate from sale in Hawai‘i and from use on Hawaiian beaches. Espero’s bill, cosponsored by Democrats and Republicans, made it through the House and Senate but then died before being voted on. He explains that lobbyists for the sunscreen industry fought back hard due to Hawai‘i being the most lucrative market for sunscreen in the US.

On the bright side, “The bill has attracted positive international attention, and the cosmetic industry is reacting positively,” Espero says. All the major brands now make an oxybenzone-free sunscreen. He hopes legislation will pass in 2018.

The amount of sunscreen that comes off of swimmers is staggering—many thousands of tons a year. In many of Mexico’s marine and freshwater destinations such as Cancun and Xcaret, sunscreens with ingredients toxic to aquatic life are confiscated as visitors enter the facilities.

As Espero says, “It would be great to see Hawai‘i be the first to pass legislation banning oxybenzone.”

Fish that Taste like Sunscreen?

At an October 2017 hearing of the Maui County Council to ban oxybenzone and octinoxate, a subsistence fisherwoman testified that the limu (seaweed) and sea life she gathers tastes like sunscreen. It is becoming a common anecdote.

“The limu tastes like sunscreen. I’m a hunter, fisher, diver, I depend on the ‘āina (land), I depend on the resources, and I have to go far now. I used to be able to walk 10 minutes from my house and collect ‘opihi (limpets), ‘ōpae (shrimp), different types of limu and ogo (seaweeds). I can’t do that anymore, it’s not good to eat. The medicines that were medicines in the ocean are not medicine any more…I have to go far now because all of the food and the medicine, it tastes like sunscreen.”

As Downs explains, “Fish that taste like coconut is from coumarin, if they taste like jasmine it’s from the jasmonic acid,” both ingredients commonly labeled “fragrance” on sunscreen and cosmetics. “The issue is the reefs are dying. It’s going to hurt tourism. It’s going to hurt the GDP. It’s already hurting the culture.”

Minimize Your Impact

You can reduce your use of sunscreen through simple actions:

Cover your skin with clothing—wear rash guards, long sleeves, and wide-brimmed hats. Applying sunscreen only to the neck, face, feet and back of hands reduces use by 90 percent.

Find shade.

Plan to be on the beach and in the water when the sun is not at its peak.

Choosing a Safer Sunscreen

There are safer alternatives to toxic sunscreen ingredients.

Look for sunscreen with zinc oxide or titanium dioxide, minerals that protect your skin by physically reflecting ultraviolet radiation.

Avoid “nano” zinc or titanium oxide; nanoparticles are also toxic to sea life. In addition to avoiding oxybenzone, watch out for octinoxate, homosalate, octocrylene, and avobenzone—all have been shown to be bad for sea creatures; many are also toxic to humans.

Or simply check the label and if the list of chemicals is long and hard to pronounce—avoid it!

Do not use aerosol spray sunscreens. In addition to being harmful to those who breathe them in (i.e., the person getting spritzed plus everyone downwind), the spray lands on the sand, and then gets washed into the ocean.

While not all labels that claim “reef friendly” actually are, there are several guides to choosing safe sunscreens:

Unfortunately, we can’t just shop our way to a healthier reef. Mineral-based sunscreen (using zinc oxide or titanium dioxide) is better for the reef and better for us, but oxybenzone and its cousins are only a piece of the problem.

The overarching problem causing bleaching of coral reefs is rising ocean temperatures due to climate change. However, every added stress impacts corals’ ability to adapt. Ocean acidification, overfishing, invasive species, sedimentation, and pollution all take their toll. The last thing coral reefs need to top it off is the added stress from toxic chemicals in sunscreens. ❖

Reference: Rachel Laderman, Lynker Technologies Marine Science Division/NOAA Affiliate, Hawai‘i Island