Coral Bleaching and Oxybenzone: Sunscreen in the Environment

Coral Reef Bleaching 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 4,000 species of fish and 800 species of hard corals. Hard or stony corals are the organisms that make the 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. It also enters the ocean when wastewater drains from our homes after we have washed ourselves while wearing sunscreen.

Responsibility to Preserve the Reefs

Biologically, humans are animals. In fact, according to the Swiss Institute of Bioinformatics and University of Lausanne researchers, about 99% of our genome (our genetic material) is identical to that in chimpanzees. Some scientists think that this number may be slightly too high, but all of the estimates that I’ve seen have put the percentage in the high nineties.

Researchers are finding more and more similarities between chimpanzee and human behavior. 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 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 the 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 bodies consist 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 part of its body out of the 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 and living tissue called the cenosarc (or coenosarc) connects one polyp to another over the surface of the reef. The connection enables the members of the colony to communicate with each other.

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Emily Dickinson's "There is a morn by men unseen"

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 provided by the coral 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 for food, but researchers have discovered that 80% to 90% of a reef coral's food comes from its zooxanthellae.

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

Coral Bleaching Facts

In addition to providing the coral's main food source, zooxanthellae give a coral its color. When corals are stressed in some way, they release their zooxanthellae into the surrounding seawater and become white in color. This process is known as coral bleaching. The bleaching process isn't completely understood, but researchers strongly suspect that the following factors are involved.

Temperature, Pollution, and Sunlight Effects

• 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.

The Probable Role of El Niño

El Niño is defined as a specific weather pattern. It's a phenomenon in which there are unusually warm temperatures in the Pacific Ocean around the equator. The increased ocean temperature increases the temperature of the air above the water. The resulting movements of air in the atmosphere affect the weather over a large part of the Earth. These factors are believed to stimulate or at least play a role in coral bleaching.

A Chance of Coral Recovery

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 zooxanthellae loss, however. The longer the bleaching event lasts, the less likely a coral is to recover. We have already lost large areas of coral reef due to the loss of zooxanthellae.

Researchers noted that while bleached coral is stressed, it still is alive and has the potential of recovering. Severely bleached corals have higher mortality rates, whereas low or moderately bleached corals have higher likelihoods of recovering.

— Tori B. Powell, CBS News

A 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. At that time, 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.

As mentioned above, the major cause of global warming is believed to be 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.

It's important to note that although the global coral bleaching event appears to be over, that doesn't mean that local bleaching isn't occurring. In 2022, researchers announced that 91% of the parts of the Great Barrier Reef that had been surveyed had recently been affected by bleaching.