BREAKING NEWS: KILLER SUNSCREEN MURDERS INFANT CORALS IN COLD BLOOD!

During my somewhat shameful evening routine of trawling through Daily Mail online, I came across a rather dramatic article on how sunscreen lotions are “killing off” coral reefs. Having previously explored the impacts of recreational tourist activity on coral reefs this immediately caught my attention. My initial thoughts were pretty sceptical – the language was highly sensationalist (posing sun lotions as an “existential threat”), and after all, it is the Daily Mail. But I eventually found the original, much more academic (and, I must say, rather dense) article that has since received heavy press coverage. Hence, not only am I able to further use my blog to name-and-shame tourism for killing off corals, but I was presented with a tantalising opportunity to compare the Daily Mail’s (and other news outlets) translation of hard academic science to, well, chain-procrastinators like me.

Oxybenzone is an chemical ingredient that shields against ultraviolet radiation, often present in sunscreen lotions. The specific oxybenzone studied in the article is benzophenone-3 (BP-3). An estimated 6 thousand - 14 thousand tonnes of sunscreen is released into areas surrounding coral reefs annually, both directly through swimmers, and indirectly through wastewater discharges from coastal development, e.g. hotel sewerage systems. Many of these lotions contain 1-10% BP-3, putting roughly 40% of coral reefs at exposure.

The experimental results of the study identified several toxicity mechanisms resulting from exposure of juvenile corals to BP-3, including DNA damage to coral larvae, reducing juvenile survival and resilience to other stressors, such as rising sea-surface temperatures under climate change. This changed the larvae of the coral species Stylophora pistillata from being healthy and mobile, to deformed and sessile - as shown in Figure 2. Furthermore, corals exhibited increased susceptibility to bleach at lower temperatures with rising concentrations of oxybenzone. 

Figure 2. Panel A is a healthy juvenile planula, approxiamtely 5 mm in length. Panel B is a sessile deformed, sessile coral exposed to oxybenzone for 8 hours. Source (although originally used from Source₁).

The study identified 62 parts per trillion of BP-3 as (arguably) the lowest concentration required to see any toxicity effect on corals. Worryingly, many popular coastal tourist areas far exceed this amount, for example 1.4 parts per million were detected in Trunk Bay of the Virgin Islands National Park.

Having read both the original paper and numerous related press articles, besides the significant dramatizing of language in media outlets (damage to juvenile corals became “fatal to baby coral” in this expressive Guardian article), I noticed that a lot of them failed to mention a key part of the experimental study – that different coral species responded differently to BP-3 exposure. In other words, each of the 7 tested coral species exhibited differing levels of tolerance. For this study, slower growing coral species were naturally more tolerant than faster growing species. In fact the species Porites astreoides was about 38 x more tolerant to DP-3 than the most sensitive species, suggesting that not all coral species are being “killed off” by sunscreen lotions - in fact some may be more tolerant than we’d expect.

Nevertheless, given the results of the study, I would still argue that reducing coral exposure to BP-3 is critical for sustaining the resilience of coral reefs, especially given the global coral bleaching event predicted with this year’s El Nino. Even with varying tolerance levels, exposure would still encourage a community shift to a less diverse and thus less resilient coral community. Furthermore, being a photo-toxicant, Oxybenzone's toxicity is exacerbated in strong light, making tropical regions where coral loss is already in a critical state even more vulnerable. With shocking figures such as at least 80% of all corals reefs already lost in the Caribbean, we really can’t afford to lose anymore from these places whose economies depend on tourist-income from coral reefs. Already, concerns in some areas have resulted in banning of products containing oxybenzone in managed marine areas. In Akumal Bay for example, the study site discussed in my previous post, visitors are encouraged to use either no sunscreen or sunscreen without BP-3. Furthermore, public relations campaigns such as “Protect Yourself, Protect the Reef!” have been set up specifically to reduce chemical contamination by suncreen-wearing swimmers in high-tourism areas.

Downs, the leader of the original paper’s research team, stated:

“Any small effort to reduce oxybenzone pollution could mean that a coral reef survives a long, hot summer, or that a degraded areas recovers. Everyone wants to build coral nurseries for reef restoration, but this will achieve little if the factors that originally killed off the reef remain or intensify in the environment.”

Downs makes two important points in this quote. Firstly, that coral reefs experience numerous stressors, both anthropogenic (e.g. trampling, climate change) and natural (ENSO events). Oxybenzone in your sun lotions may not seem like too big a problem, but it reduces the resilience of coral reefs to much more acute large-scale stressors, such as ENSO events that cause mass, global-scale coral bleaching events. Secondly, instead of trying to fix the problem through technical schemes (such as breeding “super corals” (!), perhaps we should firstly try and reduce our destruction of corals reefs in the first place.

So, in reply to the Daily Mail article’s questioning title ‘Is your sunscreen killing off coral reefs?’ we can turn to one of the aptly put answers of the avid commenter ‘BirdMail’: “Along with all the other crap we put in our oceans, yes, yes it is.”

One Guardian article states that oxybenzone is present in ~3500 brands of sunscreen worldwide, including Coopertone and L’Oreal. As conscious consumers, we should read the product labels and opt for coral reef-safe sunscreen, as well as wearing rash guards/scuba wetsuits rather than sunscreen.