Oxybenzone and Coral Bleaching: Sunscreen in the Environment
Coral Reefs and Oxybenzone
Coral reefs are extremely valuable ecosystems. The National Oceanic and Atmospheric Administration (NOAA) says that a million or more species may live in and around coral reefs, including about 4000 species of fish and 800 species of hard corals. Hard or stony corals are the organisms that make the coral reef. Researchers have found evidence that oxybenzone, a common ingredient in sunscreens, may damage coral reefs even when it's present in a low concentration. The chemical enters the ocean when we swim with sunscreen on our skin and when wastewater drains from our homes after we have washed ourselves.
Biologically, humans are animals. In fact, about 98.4% of our DNA (our genetic material) is identical to that in chimpanzees. Researchers are finding more and more similarities between chimpanzee and human behaviour. Nevertheless, the small percentage of DNA that is unique to humans has given us the most advanced brain on the planet and some comparatively impressive abilities. In my opinion, it has also given us the responsibility to preserve the Earth not only for ourselves but also for other life forms. These life forms include corals and the creatures that depend on them. We are failing woefully in our task.
The Coral Reef
The protective calcium carbonate (or limestone) coverings built by colonial hard corals make a reef. The reef starts near the shore and may extend as far as tens or even hundreds of miles into the ocean.
Importance of Coral Reefs
Coral reefs have many benefits for both the ocean environment and humans. Some of the key ones are described below.
- Coral reefs provide a habitat or a feeding area for a diverse collection of sea creatures and are an important part of the ocean ecosystem.
- Reefs act as a buffer that protects shorelines from erosion. They also reduce the chance of wave damage to shoreline habitats, businesses, and property and decrease the loss of human life from wave action.
- Coral reefs are often important to the local economy. Tourists, divers, photographers, people who want to fish for food, and those who want to collect natural sponges are all attracted to coral reefs. (Any harvesting of coral creatures should be sustainable, which is another topic of concern.)
- An important reason for maintaining biodiversity on Earth is that living things provide us with new medicines. Researchers are finding chemicals in coral that may be useful in treating human diseases.
Coral reefs are some of the most diverse and valuable ecosystems on Earth.— NOAA
What Are Corals?
Corals are small animals whose body consists of a soft polyp. The polyp is tubular and has a mouth surrounded by tentacles at its upper end and a cavity in the middle that acts as a stomach. Each polyp secretes a calcium carbonate covering to protect itself. This covering is often referred to as a skeleton. The coral can extend its body out of its skeleton and retract into it as necessary.
The skeletons of the different polyps in a colonial coral stick together. When old or injured polyps die, new ones grow on top of the dead ones' skeletons. This process slowly builds a coral reef.
A layer of soft tissue called the cenosarc (or coenosarc) connects one polyp to another over the surface of the reef. This enables the members of the colony to communicate with each other.
The Importance of Zooxanthellae in Reef Corals
The corals that make up a coral reef normally have tiny, one-celled creatures in their tissues. These creatures are referred to as zooxanthellae and are a type of dinoflagellate. Dinoflagellates are often classified as algae.
The zooxanthellae are found near the surface of a polyp. They absorb light and carry out photosynthesis. In this process, a carbohydrate food source is made from simple molecules with the aid of light energy.
Zooxanthellae and corals have a mutualistic relationship. The zooxanthellae receive protection as well as the carbon dioxide and water needed for photosynthesis. The corals absorb some of the food and oxygen made by the zooxanthellae. Coral tentacles do have stinging cells that can trap small animals, but 80% to 90% of a reef coral's food comes from its zooxanthellae.
A Time Lapse Video of the Great Barrier Reef
What Is El Niño?
El Niño is believed to play a role in coral bleaching. It's a phenomenon in which there are unusually warm temperatures in the Pacific Ocean around the equator. Since the ocean temperature affects the air above the water and movements of air in the atmosphere contribute to our weather, El Niño can influence weather patterns.
In addition to providing the coral's main food source, zooxanthellae give a coral its colour. When corals are stressed in some way, they release their zooxanthellae into the surrounding seawater and become white in colour. This process is known as coral bleaching.
The main cause of coral bleaching seems to be a rise in water temperature due to an increased concentration of carbon dioxide in the atmosphere. Bleaching in coral reefs near shorelines can be caused by pollution runoff from the land. Our personal care products may contribute to this pollution. Exposure to sunlight in shallow water and to air during very low tides can also contribute to bleaching. There may be other triggers for zooxanthellae release that are presently unknown. The process of coral bleaching isn't completely understood.
Corals can sometimes recover from a temporary bleaching event. Some polyps may be able to obtain enough food on their own and some may be able to obtain new zooxanthellae. Survival is a struggle after bleaching, however. The longer bleaching lasts, the less likely a coral is to recover. We have already lost large areas of coral reef due to bleaching.
Locally produced threats to coral, such as pollution from the land and unsustainable fishing practices, stress the health of corals and decrease the likelihood that corals can either resist bleaching or recover from it,— Jennifer Koss, NOAA Coral Reef Conservation Program
A Theory to Explain Zooxanthellae Release
The Third Global Coral Bleaching Event
According to NOAA, the third global coral bleaching event began in 2014. What is so worrying about this event is that it lasted until 2017. In June 2017, NOAA announced that the global bleaching had "likely" ended, although a further six months of observations would be needed to be certain. The bleaching was still bad in some areas but had improved in others, so although it still existed it could no longer be considered a global occurrence. The cause of the three-year event is believed to have been warmer water due to climate change and the damaging effects of a severe El Niño in 2015-2016.
Global warming is taking place due to an increased level of carbon dioxide in the atmosphere. Carbon dioxide is one of the greenhouse gases. It traps heat above the Earth's surface. Some of the carbon dioxide in the air enters the ocean, causing it to become more acidic. The average temperature of the oceans and atmosphere and the acidity of the oceans are all increasing. The powerful video below shows the possible and final result of increased atmospheric carbon dioxide on the world's coral reefs. I don't consider it to be an exaggeration.
While carbon dioxide in the atmosphere is a very important topic to consider with respect to coral health, it's also important to consider other factors that weaken coral. Research suggests that oxybenzone is one of these factors.
Coral Reefs and Climate Change: A Possible Outcome
What Is Oxybenzone?
Oxybenzone is also known as benzophenone-3. It's a white solid that has the interesting ability to absorb ultraviolet light. Oxybenzone is a broad-spectrum sunscreen that absorbs both UVA and UVB light rays. It's produced synthetically by a chemical reaction.
Oxybenzone is added to many commercial sunscreens as well as some cosmetics and hairsprays because of its ability to stop UV damage to the skin and hair. It's also added to some food packaging to prevent the breakdown of the package when it's exposed to light.
There is a lot of controversy about the safety of oxybenzone for humans. It causes contact dermatitis in some people. It can be absorbed through the skin and has been found in the urine of most people who have been tested. There have been claims that it's an endocrine (hormone) disruptor. Not everyone agrees with this last idea, though. Some researchers say there is no reliable evidence that oxybenzone is harmful to humans, apart from its ability to irritate the skin of sensitive people.
Oxybenzone or benzophenone-3 belongs to a family of sunscreen chemicals known as the benzophenones. The American Contact Dermatitis Society gave benzophenones the Allergen of the Year award in 2014.
Effects of Oxybenzone on Coral Reefs
A recent study focused on the effects of oxybenzone on a coral named Stylophora pistillata. The results were published in 2015. The research team looked at the effect of oxybenzone on coral larvae and adults. They made the following discoveries, which were published in the Environmental Contamination and Toxicology journal.
- Under lab conditions, oxybenzone transformed the coral larvae, or planulae, from a motile state to a deformed and sessile state.
- The chemical caused the coral to make an enlarged skeleton and to become encased in it. The researchers stated that oxybenzone is "a skeletal endocrine disruptor" in coral.
- Oxybenzone also damaged the coral DNA.
- As the concentration of oxybenzone increased, the degree of coral bleaching increased.
- Although oxybenzone was harmful under all light conditions, it exerted stronger effects in the light than in the dark.
- The oxybenzone concentration around coral reefs in Hawaii and the U.S. Virgin Islands was found to be in similar or even larger than that used in the experiments.
Effects of Benzophenone-2 on Coral
We need to be careful when assessing results produced by only one researcher or only one research team. Accidental errors in procedure are always possible. Scientists who are not involved in an experiment often note new discoveries with interest and then look for confirmation in a second experiment. There is evidence that doesn't confirm the results of the latest discoveries about oxybenzone but does suggest that they are accurate, however.
In 2013, NOAA scientists explored the ways in which a chemical called benzophenone-2 affects corals. Benzophenone-2 is a relative of benzophenone-3 (or oxybenzone). Like benzophenone-3, it blocks ultraviolet light. It's not approved for use as a sunscreen in the United States, however. Benzophenone-2 is used in soaps, fragrances, and cosmetics instead of sunscreen. This means that it can reach the ocean in wastewater from homes after we wash ourselves.
Sometimes a small change is chemical structure can produce a big change in a chemical's properties. Still, it's interesting to note that the NOAA scientists found that like benzophenone-3, benzophenone-2 causes coral bleaching and damages coral DNA.
Viral Activation and Zooxanthellae Release
An experiment reported in 2008 showed that four chemicals commonly found in sunscreen could damage coral. One of the four chemicals was simply identified as "benzophenone". The corals were surrounded by a plastic bag so that the sunscreen ingredient being tested didn't contaminate the local seawater. While this act was commendable, it prevented the normal dilution of chemicals created by water movement around reefs and may have affected the results.
The researchers said that the sunscreen ingredients activated dormant viruses within the zooxanthellae in the coral, destroying them. This may be one of the causes of coral bleaching. As far as I know, however, the claim hasn't been confirmed.
There is no doubt that we need to protect our skin from the sun in order to reduce the chance of developing skin cancer. Although protective clothing, a wide-brimmed hat, sunglasses, and staying indoors around the middle of the day are useful, sunscreen may be needed.
Dermatologists and health agencies say that we should be wearing sunscreen all year round to protect us from both premature skin aging and skin cancer. It's therefore very important that we choose a safe product to apply to our skin for both our sake and the environment's.
People with pigment loss due to vitiligo must keep the skin areas without pigment away from the sun by clothing or sunscreen. Melanin is a pigment in skin of any colour that absorbs radiation from the skin and gives us some protection from the sun's radiation. Melanin is never a suitable substitute for sunscreen or sun protection, though. In vitiligo, areas of skin lose their ability to make melanin.
Sunscreen and Coral Reef Safety
So far, there is no evidence that mineral sunscreens harm coral. Mineral sunscreens contain zinc oxide or titanium dioxide, which exist naturally in the Earth. They are often considered to be the healthiest sunscreen for humans as well as coral reefs.
Unfortunately, mineral sunscreens give a white, pasty appearance to the skin. Reducing the minerals to tiny nanoparticle size eliminates or greatly reduces this whiteness. There are concerns about whether or not these nanoparticles can penetrate the skin and about whether or not they are harmful if they do so. Still, mineral sunscreens—especially those containing zinc oxide—seem to be the safest option for humans and the environment that is available today.
The ultimate decision about whether to buy a chemical or a mineral sunscreen and about which brand to buy is up to the individual. I urge people to consider coral reef safety when choosing a sunscreen, however. This is especially true when sunscreen is worn regularly and reapplied frequently, as health agencies tell us to do.
Consumer research is very worthwhile in order to find a sunscreen that fulfills three very important goals. These goals are the prevention of skin damage from UV light, the avoidance of damage to other parts of the body, and the prevention of damage to coral reefs and the rest of the environment. While climate change seems to be a major cause of coral destruction, other factors may be making the situation worse. Even if we aren't actively working to save ocean life, we can help coral reefs and the environment by ensuring that our cosmetics—including our sunscreens—don't contribute to ocean pollution.
Global coral bleaching event likely ending: An announcement by NOAA on June 19th, 2017
Oxybenzone and coral reefs from the online version of The Guardian newspaper
Toxic effects of benzophone-2 on a coral species from the NIH (National Institutes of Health)
Sunscreen and coral from National Geographic
Questions & Answers
© 2015 Linda Crampton