Written by: Alli Jin '25
Edited by: Ashley Nee '22
What is the first thing we do when we go to the beach? For most of us, it would be to apply sunscreen. Whether it’s SPF 40, 50, or 100, sunscreen is used to prevent UV ray exposure to minimize the chances of skin burns and skin cancer. However, the same ingredients that protect human skin simultaneously harm the coral reef ecosystem. This biome supports fish, invertebrates, plants, and thousands of other species; therefore, the health of the wildlife depends on the health of the coral reef. Since scientists have now discovered sunscreen ingredients like oxybenzone and octinoxate are detrimental to coral health , they also know how the coral is affected and what steps need to be taken to prevent this decay.
Across the world, from the Bahamas to the Philippines, coral reefs need to be protected. In fact, some scientists from the Reef World Foundation believe all coral reefs will die within just thirty years . If action is not taken, thousands of species risk losing their habitat. Furthermore, coral reefs also serve as a protective barrier for the coastline against the effects of natural disasters. The extinction of coral reefs would correspondingly leave coastlines more vulnerable to hurricanes, cyclones, earthquakes, etc.  Additionally, there is a large economic dependency on reefs whether it be for fishing industries or tourism . Due to the countless benefits of coral reefs, it is critical that their health stays at optimal levels compared to the current, rapid decline.
Before learning how coral reefs are affected, it is important to understand what they are and how they function. Known as the “rainforests of the sea” because of the diversity within them, coral reefs are “large underwater structures composed of the skeletons of colonial marine invertebrates.”  An exoskeleton made of calcium carbonate protects their softer, inner body . Coral start off as a polyp–a single coral–but these polyps combine their exoskeletons to create an extensive colony of coral all over the ocean floor . This range can stretch for miles on end; the longest coral reef system in the world is the Great Barrier Reef in Australia which is about 1,429 miles long . When looking at coral beyond its physical structure, miniscule cells called zooxanthellae live inside the tissue of the polyp. Zooxanthellae and coral have a symbiotic relationship; since the coral provides a habitat, the zooxanthellae provides the food through algae photosynthesis .
Since the coral rely on the zooxanthellae for their health, it is critical that this algae stays alive. However, the specific ingredients in sunscreen known as oxybenzone and octinoxate harm coral by targeting zooxanthellae. Unfortunately, most sunscreens on the market today contain those ingredients, encouraging consumers to use the product without knowing its harm to the ocean. Another cause is that though people are aware of the toxicity of certain sunscreens, they continue to use it because the issue does not affect them enough. Dr. Arielle Levine, a professor and researcher at San Diego State University conducted a survey in which she was able to learn about the public’s awareness of sunscreen effects on coral reefs. Her sample was 1,325 beach-goers–both tourists and Hawaiian residents–at four beaches in Hawaii: Hanauma Bay, Waikiki Beach, Kahalu’u Beach Park, and Waialea Bay. Of her sample, 75.4% of respondents were aware of the sunscreen chemical issue but still 27.1% of the same respondents were using sunscreen which contained toxic chemicals.  This survey shows that though there is awareness on the topic, there is still a percentage of people who are unaware or are not doing anything about the crisis so that coral reefs continue to drastically decay.
If these ingredients are so toxic and even banned in Hawaii, why are they still commonly found in the ingredient lists of popular sunscreens? Oxybenzone and octinoxate are included in sunscreens because they form soluble crystals that block UV rays. These ingredients, found in about 32% of all sunscreens sold, harm coral reefs by bleaching and mutating DNA which correspondingly hinders reproduction and causes physical defects . Even at the smallest concentration of 10 μL/L, there are adverse effects. However, a study conducted at Haereticus Environmental Laboratory in 2019 measured the waters at Kahaluu Bay, Hawaii for oxybenzone and found the “chemical’s concentration was found in amounts 262 times greater than levels considered high-risk by the U.S. Environmental Protection Agency.”  Since the concentration of these toxic chemicals are already at high-risk levels, the effects will only be more difficult to reverse.
However, coral reef decay is not only limited to toxic ingredients found in sunscreens - several other factors come into play. Causes include climate change, pollution, overfishing, destructive fishing, and careless tourism. Thankfully, some of these factors are controllable. Therefore, learning the significance of sunscreens containing harmful ingredients oxybenzone and octinoxate is one step people can take to prevent the rapidly decaying coral reef ecosystem.
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[Image Citation] Coral bleaching at Heron Island Feb 2016_credit The Ocean Agency / XL Catlin Seaview Survey / Richard Vevers https://www.flickr.com/photos/stopadani/33675818851