Course:EOSC270/2022/Impacts of sunscreen and skin care products on coral reefs

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Partially bleached coral reefs on Molasses reef. What's the cause?

What is the problem?

Coral reefs are unique and biodiverse ecosystems made up of colonies of diverse organisms found in nutrient-poor marine seas.  These ecosystems are in a constant state of equilibria and are extremely sensitive to changes in environmental conditions which may be caused directly or indirectly by humans. It is estimated that in the past 20 years over half of all coral reefs have become threatened by coral bleaching, resulting in a “domino effect” on other marine life and one of the leading causes is sunscreen concentrations in the ocean[1].

Coral reefs are one of the most visited tourist attractions around the world and there are currently seven such destinations, including Hawaii, that have banned certain sunscreens 4. These particular sunscreens contain various harmful ingredients, some of which are oxybenzone and octinoxate. Oxybenzone and octinoxate are used in approximately 70-80% of sunscreens and also a variety of personal care products such as body fragrances, hair‐styling products, skin care products, insect repellents, and cosmetics. These two specific ingredients as well as Benzophenone-1, Benzophenone-8, OD-PABA, 4-Methylbenzylidene camphor, 3-Benzylidene camphor, zinc and Octocrylene have been shown to have adverse effects on marine ecosystems, specifically coral reefs and their surrounding organisms[2].

Figure 1: Obtained from the Danvero et al study which shows the impact on sunscreen of members of four different species of Coral. Only 10 microliter per lite amount of sunscreen is used (which is very small!) however bleaching is still observed within 96 hours.

Coral bleaching is the visible indicator that an organism is in distress or in danger. Through photosynthesis, zooxanthellae, which are symbiotic algae that dwell in healthy coral tissue, offer nourishment and stunning colors to corals. When zooxanthellae die or leave the reef, the corals lose their color, their protective skeletons are revealed, and the corals become incredibly weakened while still being alive but it can also eventually lead to death[3].

So, how do we know that the chemicals in sunscreen, such as oxybenzone and octinoxate, contribute to coral bleaching? There have been multiple studies that report the association between sunscreen and coral toxicity. It has been found that such chemicals found in sunscreen induce a viral lytic cycle in the zooxanthellae causing their deaths and thereby coral bleaching[4].

One finding reports that upon exposure to UV light, octinoxate degrades rapidly and forms several photoproducts, and that the cellular toxicities of these photoproducts were found to be significantly toxic to cells even at extremely low concentrations[5].

This potential influence of sunscreen components on hard corals has also been tested on different species of the genus Acropora, Stylophora pistillata, and Millepora complanata, with various doses of sunscreens. These studies took place in several parts of the world between 2003 and 2007, including the Celebes Sea, the Caribbean Sea, the Andaman Sea, and the Red Sea. Using colometry analysis to quantify coral bleaching, they found that sunscreen addition, even in very small concentrations (i.e., 10 uL/L), led to the production of substantial volumes of coral mucous (composed of zooxanthellae and coral tissue) within 18–48 hr in all replicates and at all sampling sites, and found full bleaching of hard corals by 96 hr[4] (Figure 1). This result is particularly alarming when we consider that as of 2017, it was estimated that anywhere from 8000 to 16000 tons of sunscreen enters the coral reefs each year, and shows how widespread and critical this issue is[6].

How does this problem impact marine ecosystems?

Rising levels of sunscreen in marine environments[7] causes different scales of impacts, ranging from damaging individual animals to disrupting processes within the greater coral reef ecosystem.

Individual effects

Figure 2: Coral reef ecosystems are composed of multiple dimensions and diversity, allowing them to support various species. Image by Francesco Ungaro retrieved from Unsplash.

Sunscreen can harm coral individuals by bleaching, altering DNA, lessening their ability to reproduce, and lowering survival at different stages of life. First, corals face negative effects when zooxanthellae are released or damaged from bleaching, because they lose an important source of fixed carbon, oxygen, and nutrients that they usually gain from the algae’s photosynthesis[8][9]. This can be in very high volumes, such as up to 95% of the algae’s photosynthetic products[10]. Without this, coral may not be able to grow or develop successfully, and can face death. Second, some very concerning sunscreen ingredients, like oxybenzone, can damage coral genetics by changing their DNA[11]. This problem can affect the animal's ability to produce the next generation of corals, or its survival[11]. This may be especially serious if DNA damage occurs when the coral is young[12]. Third, sunscreen can affect coral larvae by impeding their swimming, modifying their shape, and lead to death[11]. Over a longer term, concerns for the health of young corals now may affect their recruitment and future population sizes[12].

Ecosystem effects

These smaller-scale impacts can transition to a larger-scale when looking at the effect of sunscreen on the marine ecosystem more broadly. This includes how complex the habitat grows to be and the animals found there, changing how energy is distributed and transferred in the food web, plus the ecosystem's resilience to other threats.

First, the lost relationship with zooxanthellae affects the growth of reef-building corals, called Scleractinian[13]. These corals act as ecosystem-engineers by building multidimensional habitats (Figure 2) that can be used by many different organisms living in the ocean[13][14]. Creatures ranging from algae to fish may use reef environments as residence or feeding grounds[14]. So, the loss of reef-building corals could have consequences for an ecosystem's level of complexity and the availability of key habitat for some marine animals.

Second, the creation and movement of energy in the form of food is impacted by sunscreen. As an algae, zooxanthellae photosynthesize and contribute to primary production- which supports the whole reef food web[15]. If lost, even organisms at a higher trophic level than corals could be affected. When tested, organisms representing the reef environment had less population growth when water contained sunscreen[16]. Lost food resources can have an effect on the diversity in an environment[16].

Third, previous problems could have implications for the reef ecosystem’s vulnerability to other threats. When ecosystems are diverse- in the species that live there, energy levels, and habitat structures- its ecological complexity rises[17]. This can help determine how a species or environment will respond to something that could shift its state[18]. This may be important to consider in coral recovery, as climate change is one threat like this.

What is the extent of the problem?

Threat status

Despite covering less than 0.1% of the ocean floor, coral reefs are home to more than 25% of all marine species including sponges, fish, molluscs, cnidarians, crustaceans and plenty more[19]. Today, 75% of these reefs are already threatened by anthropogenic impacts such as carbon emissions and pollution[19]. A large portion of this harmful pollution comes from sunscreen and skin products entering the ocean. With volumes up to 16000 tons of sunscreen entering the world's oceans per year, an amount as small as 62 parts per trillion (the size of a raindrop in an Olympic swimming pool) is enough to cause toxic levels[12]. This puts at least 10% of coral reefs, and up to 40% in coastal regions, at risk of exposure to the harmful chemicals that can be found in these products[12].

In 2021, Hawaii passed a ban on two ingredients common in sunscreen: oxybenzone and octinoxate[1]. The ban came after a study done exhibiting the extent to which these ingredients can act to bleach coral. Pieces of coral from various world oceans were incubated with a diluted sunscreen solution for 62 hours and their colors were compared before and after. The results of the study showed all species to be completely bleached[4]. This was enough for the legislature of the State of Hawaii to pass the ban although the study has since been criticized for being in vitro and thus potentially not demonstrating accurately the effects of sunscreen on corals in the ocean.

Figure 3: Before and after images of an area in the Great Barrier Reef that has been damaged due to coral bleaching. Provided by UNESCO.[20]

Implications for the future

Another study in 2021 found that there has been a 50% decrease in area covered by coral reefs since 1950[21]. Of the remaining 50%, three quarters of the reefs are currently in a threatened status. Up to 100% of reefs could be exposed to harmful sunscreen chemicals by 2050 if we do not begin to take action now[21]. The loss of coral reefs would not only be devastating to marine diversity, but would also threaten the lives and livelihoods of over 200 million people. Many communities that live along coasts rely on coral reefs to absorb some of the energy of waves battering the land[22] [16]. Reefs can reduce wave energy by 97%, providing a natural barrier to flooding and erosion. Coral reefs are also a major source of food for an even larger portion of the Earth’s population. Loss of coral reefs would mean the reduction of 20 - 25% of the fish caught in developing countries[16]. It would also result in a decrease of around $36 billion in the global economy per year as a result of jobs created by fishing, processing and transporting these fish[16].

Given the impact, what are the solutions?

Since the effect of certain chemicals found in sunscreens and other cosmetic products has negative consequences for coral reefs, it is essential that action is taken to mitigate them. However, there are a number of limitations facing the execution of solutions to this sunscreen problem. First, sunscreens are a component of sun-safety, since they can help to avoid skin cancer. Second, there has been some resistance to changing formula ingredients due to a potential research deficit. While acknowledging these issues, there are some solutions that can be employed.

Ingredient bans

An effective way to reduce the impact of the harmful substances in sunscreens and cosmetics is to jurisdictionally ban them[1]. This ensures that products containing the ingredients that have been found to be bad for coral reef health do not get sold and/or it is illegal to possess these products where the ban is in place. This has been done in Hawaii, Key West in Florida, Bonaire and Aruba, the US Virgin Islands, Palau, and some places in Mexico[23]. While ingredient bans can be effective, the process to get the ban put in place is slow and is generally done chemical-by-chemical and so while one toxic chemical may be banned, others could still be allowed and harm the reefs anyway so other solutions should be explored alongside this one.

Alternative products

Products that do not contain the chemicals known to be harmful can be used to reduce the amount of toxic chemicals entering the ocean. Some examples are rash guards to physically block UV rays from touching the skin, and using ‘reef-safe’ sunscreens with alternative ingredients to those that are toxic to coral reefs.

Figure 4: Proposed way to systematically  test the effect of chemicals on corals[13]

Further research on harmful substances and alternatives

Although there is evidence of the negative impacts of specific substances on coral reefs, some researchers, health organizations, and cosmetic companies claim there is not enough viable data to prove these findings[24][13][1]. There is pressure for more standardized testing to be done and researchers have suggestions for how to do so, outlined in Figure 4.  Emerging research suggests testing substances across corals’ life-stages, to see their short- and long-term effects would be highly beneficial [24]. Having more standardized research procedures would help to identify more chemicals that could be toxic in the ocean, as well as to provide better data to make informed decisions from and understand the full extent of how harmful and how many toxic substances are entering the ocean[13].

Research is also being done on alternative products that could replace the harmful sunscreens. One study is exploring biotechnology from the ocean that uses marine organisms’ natural protection from UV rays[25]. The substances of interest are mycosporine-like amino acids which can absorb the high-energy UV radiation through their bonds and dissipate the energy as heat[25]. Presently the research needs to confirm the effectiveness of the substances against UV rays, and whether they are safe to use for people and the environment.

References

  1. ↑ 1.0 1.1 1.2 1.3 "Raffa, R. B., Pergolizzi, J. V., Taylor, R., & Kitzen, J. M. (2018). Sunscreen bans: Coral reefs and skin cancer". Journal of Clinical Pharmacy and Therapeutics, 44(1), 134–139.
  2. ↑ "Coral Reef Alliance. (2021, September 28). Sunscreen 101: Protecting Your Skin and Coral Reefs. Coral Reef Alliance".
  3. ↑ "Tibbetts, J. (2008). Bleached, But Not by the Sun: Sunscreen Linked to Coral Damage". Environmental Health Perspectives, 116(4).
  4. ↑ 4.0 4.1 4.2 "Danovaro, R., Bongiorni, L., Corinaldesi, C., Giovannelli, D., Damiani, E., Astolfi, P., Greci, L., & Pusceddu, A. (2008). Sunscreens Cause Coral Bleaching by Promoting Viral Infections". Environmental Health Perspectives, 116(4), 441–447.
  5. ↑ "Stein, H. V., Berg, C. J., Maung, J. N., O'Connor, L. E., Pagano, A. E., MacManus-Spencer, L. A., & Paulick, M. G. (2017). Photolysis and cellular toxicities of the organic ultraviolet filter chemical octyl methoxycinnamate and its photoproducts". Environmental Science: Processes & Impacts, 19(6), 851–860.
  6. ↑ "DiNardo, J. C., & Downs, C. A. (2017). Dermatological and environmental toxicological impact of the sunscreen ingredient oxybenzone/benzophenone-3". Journal of Cosmetic Dermatology, 17(1), 15–19.
  7. ↑ "Corinaldesi, C., Marcellini, F., Nepote, E., Damiani, E., & Danovaro, R. (2018). Impact of inorganic UV filters contained in sunscreen products on tropical stony corals (Acropora spp.)" Check |url= value (help). The Science of the Total Environment, 637-638, 1279-1285. no-break space character in |url= at position 49 (help)
  8. ↑ "Kühl, M., Cohen, Y., Dalsgaard, T., Jørgensen, B. B., & Revsbech, N. P. (1995). Microenvironment and photosynthesis of zooxanthellae in scleractinian corals studied with microsensors for O₂, pH and light". Marine Ecology, 117(1/3), 159-172.
  9. ↑ "Douglas, A. E. (2003). Coral bleaching––how and why?". Elsevier, 385-392.
  10. ↑ "Smith, D. J., Suggett, D. J., & Baker, N. R. (2005). Is photoinhibition of zooxanthellae photosynthesis the primary cause of thermal bleaching in corals?". Global Change Biology, 11(1), 1-11.
  11. ↑ 11.0 11.1 11.2 "Wood, E. (2018). Impacts of Sunscreens on Coral Reefs. International Coral Reef Initiative".
  12. ↑ 12.0 12.1 12.2 12.3 "Downs, C. A., Kramarsky-Winter, E., Segal, R., Fauth, J., Knutson, S., Bronstein, O., Ciner, F. R., Jeger, R., Lichtenfeld, Y., Woodley, C. M., Pennington, P., Cadenas, K., Kushmaro, A., & Loya, Y. (2015;2016;). Toxicopathological effects of the sunscreen UV filter, oxybenzone (benzophenone-3), on coral planulae and cultured primary cells and its environmental contamination in hawaii and the U.S. virgin islands". Archives of Environmental Contamination and Toxicology, 70(2), 265-288.
  13. ↑ 13.0 13.1 13.2 13.3 13.4 "Moeller, M., Pawlowski, S., Petersen-Thiery, M., Miller, I. B., Nietzer, S., Heisel-Sure, Y., Kellermann, M. Y., & Schupp, P. J. (2021). Challenges in current coral reef protection – possible impacts of UV filters used in sunscreens, a critical review". Frontiers in Marine Science, 8, 1-17.
  14. ↑ 14.0 14.1 "Adjeroud, M., Kayal, M., & Penin, L. (2017). Importance of recruitment processes in the dynamics and resilience of coral reef assemblages. In S. Rossi, L. Bramanti, A. Gori, & C. Orejas (Eds.), Marine Animal Forests: The ecology of benthic biodiversity hotspots (pp. 549-569)". Springer.
  15. ↑ Hatcher, B. G. (1988). Coral reef primary productivity: A beggar's banquet. Elsevier Ltd. https://doi.org/10.1016/0169-5347(88)90117-6
  16. ↑ 16.0 16.1 16.2 16.3 16.4 "McCoshum, S. M., Schlarb, A. M., & Baum, K. A. (2016). Direct and indirect effects of sunscreen exposure for reef biota". Hydrobiologia, 776(1), 139-146.
  17. ↑ "Obura, D., & Grimsditch, G. (2009) Coral Reefs, Climate Change and Resilience - An agenda for action from the IUCN World Conservation Congress". October 6-9 2008. 1-48.
  18. ↑ "Hughes, T. P., Baird, A. H., Bellwood, D. R., Card, M., Connolly, S. R., Folke, C., Grosberg, R., Hoegh-Guldberg, O., Jackson, J. B. C., Kleypas, J., Lough, J. M., Marshall, P., Nystrom, M., Palumbi, S. R., Pandolfi, J. M., Rosen, B., & Roughgarden, J. (2003). Climate change, human impacts, and the resilience of coral reefs". Science, 301(5635), 929-933.
  19. ↑ 19.0 19.1 "Mulhall, M. (2009). Saving the rainforests of the sea: An analysis of international efforts to conserve coral reefs". Duke Environmental Law & Policy Forum, 19(2), 321.
  20. ↑ "Bethesda Green".
  21. ↑ 21.0 21.1 "Miller, I. B., Pawlowski, S., Kellermann, M. Y., Petersen-Thiery, M., Moeller, M., Nietzer, S., & Schupp, P. J. (2021). Toxic effects of UV filters from sunscreens on coral reefs revisited: Regulatory aspects for "reef safe" products". Environmental Sciences Europe, 33(1).
  22. ↑ "Elliff, C. I., & Silva, I. R. (2017). Coral reefs as the first line of defense: Shoreline protection in face of climate change". Marine Environmental Research, 127, 148-154.
  23. ↑ Levine, A. (2020). Sunscreen use and awareness of chemical toxicity among beach goers in Hawaii prior to a ban on the sale of sunscreens containing ingredients found to be toxic to coral reef ecosystems. Marine Policy, 117, 103875. https://doi.org/10.1016/j.marpol.2020.103875
  24. ↑ 24.0 24.1 Levine, A. (2021). Reducing the prevalence of chemical UV filters from sunscreen in aquatic environments: Regulatory, public awareness, and other considerations. Integrated Environmental Assessment and Management, 17(5), 982–988. https://doi.org/10.1002/ieam.4432
  25. ↑ 25.0 25.1 Pandika, M. (2018). Looking to Nature for New Sunscreens. ACS Central Science, 4(7), 788–790. https://doi.org/10.1021/acscentsci.8b00433
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