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Coral Bleaching

Coral bleaching is an issue that causes corals and coral reefs to lose their coloration as a result of expelled algae and dinoflagellates, resulting in coral death in nearly all cases. The risk of coral bleaching has constantly increased at a rate of about 4% per year since the 1980s. Some causes for coral bleaching include warmer sea temperatures, lower oxygen levels, increased solar intensity, ocean acidification, and pollution.

Oxybenzone is one of the major pollutants and evidence suggests that elevated oxybenzone levels may contribute to sea level warming, a key contributor to coral bleaching. A 2019 study on Ultraviolet filters (oxybenzone, octyl salicylate, and octinoxate) and commercial sunscreen effect on coral health, found that oxybenzone may act as an endocrine disrupto r while the coral is developing its exoskeleton. Oxybenzone was found to induce ossification of the planula (larval form of coral) of the coral Stylophora pistillata and six other coral species, causing an increase in the levels of LC50 and deformity in EC20 (effective concentration at 20%) levels. The damage to coral reefs in their larval and skeletal developments can be damaging for the entirety of the coral and reefs development and in many cases is irreversible.

Oxybenzone toxicity to corals and coral reef health is still largely unclear, but some suspect that it is caused by the formation of tissue-damaging reactive oxygen species that have effects that are similar to increased seawater temperatures and increased light intensity. The negative effects of seawater temperature and light intensity stressors may be exasperated by the presence of oxybenzone.

Oxybenzonecite has been found to disrupt the viral lytic cycle of zooxanthellae and other algae, resulting in a decrease in the zooxanthellae and algae population on the corals. Zooxanthellae are dinoflagellates that can be found on a number of many marine organisms, including corals and coral reefs. Symbiodiniacean zooxanthellae have a symbiotic relationship with other marine invertebrates and have important photosynthetic properties that help provide nutrients to their host organisms. The zooxanthellae help the coral and reef-building corals create their calcium carbonate skeletons, fuel their issue growth, and help the metabolic processes of their hosts. The loss of these symbiotic zooxanthellae is the main component of coral bleaching.

Marine Ecosystems

A number of studies have linked oxybenzone and the decreased health of different marine organisms and the marine ecosystem. According to the National Oceanic and Atmospheric Administration (NOAA), oxybenzone and other sunscreen chemicals have adverse effects on green algae, mussels, sea urchins, fish, and dolphins as well as coral reefs and other organisms. Oxybenzone causes green algae to have challenges with growth and photosynthesis, mussels to have defects, damage sea urchins immune and reproductive systems while also causing deformities in young and juvenile sea urchins. Oxybenzone and other sunscreen chemicals have been found to gather dolphin’s tissues and that these tissues can be hereditary. Oxybenzone may decrease the reproduction characteristics and change the sex characteristics in fish. Oxybenzone has been found to be a weak estrogen, which can cause lower levels of androgen in males.

As of 2016, there was only one study of the effects of organic UV filters (oxybenzone, octyl salicylate, and octinoxate) on tropical reef fish. There have been several studies focusing on different organisms including Japanese medaka, zebrafish, and flathead minnow, which have shown some effect on the endocrine system. The effects found include disrupted brain and liver development, and decreased egg production from exposure to sunscreens containing oxybenzone. At this time, there is not a sufficient amount of research on the effects of organic UV filters on the endocrine systems of tropical reef fish.

Tourism Oxybenzone can be found in nearly 70% of all commercially sold sunscreen products in the United States. Oxybenzone is commonly used in sunscreen due to its natural UV filtering capabilities and natural availability. High rates of oxybenzone are more commonly found in tourist rich areas known for their beaches, oceans, coral reefs, marine life, and tropical environment cite. Tourist rich areas -- like Hawaii, the Caribbean, and Australia-- have been found to have increased oxybenzone levels and increased coral bleaching. Sunscreen does not always absorb or stay on the surface of the skin after being applied and exposed to water, it is estimated that about 25% of sunscreen becomes washed off within the first 20 minutes of it being underwater cite. Those who wear sunscreen containing oxybenzone have been estimated to have released 14,000 tons of sunscreen onto corals and coral reefs. High sunscreen exposed areas make up about 10% of the ocean’s corals and nearly 40% of the world’s coastal areas. These increased exposed areas are associated with many recreational activities, such as snorkeling and swimming.

Wastewater Wastewater treatment plants (WWTP) are used to treat water that has been used with humans before returning it to natural bodies of water. Several studies have found that organic UV filters, including oxybenzone, can be found in nearly all water sources across the globe. Due to the organic filters’ chemical properties, WWTP has difficulties filtering out the compounds and they are released back into the water systems.

Studies done in Korea and Switzerland have shown that there may be a seasonal component to the amount of oxybenzone found in the waterways, with a higher percentage during the warmer and summer seasons.

Discussion of effects on coral

Oxybenzone’s effect on coral reefs is a topic that is still being widely discussed and studied across the scientific community. A number of studies have shown that oxybenzone is a contributor to coral bleaching and has an effect on some marine species and the marine ecosystem. Many of these studies have been conducted in a lab setting and/or focus on a specific species, resulting in continuous discussion. The exposure to oxybenzone and other chemicals that are done in a lab setting may not represent the natural levels of exposure to sunscreen, thus may not be able to be applied.

Oxybenzone is a contributing factor to coral bleaching and can magnify the effects of other contributors such as warm water temperatures, light intensity, and ocean acidification.