The health of coral reefs worldwide is a growing concern, with these vibrant underwater ecosystems facing numerous threats. Among these, the potential impact of common personal care products, specifically sunscreens, on coral vitality has emerged as a significant area of inquiry. This raises an important question: does sunscreen contribute to coral bleaching?
What is Coral Bleaching?
Coral are tiny animals called polyps, living in colonies. Most reef-building corals form a mutually beneficial relationship with microscopic algae called zooxanthellae, which reside within their tissues. These algae perform photosynthesis, providing the coral with energy and giving coral its vibrant colors.
Coral bleaching occurs when corals expel these symbiotic algae, turning white. This expulsion is a stress response to environmental changes. While a bleached coral is not immediately dead, it becomes more vulnerable to starvation, disease, and death if conditions persist. Primary causes of mass coral bleaching events include rising ocean temperatures and ocean acidification, often exacerbated by climate change. Other factors like changes in salinity, increased solar irradiance, and pollution can also induce bleaching.
How Sunscreen Affects Coral
Sunscreen chemicals can enter marine environments when people swim or shower and impact coral health. The chemical components in sunscreens can disrupt several biological processes in corals. Certain sunscreen ingredients can damage coral DNA, which can hinder their ability to reproduce and recover from environmental stressors.
Sunscreen chemicals may also interfere with coral’s ability to cope with heat stress, potentially making them more susceptible to bleaching in warming waters. Some research suggests that these chemicals can promote viral infections in the symbiotic zooxanthellae, leading to their expulsion and subsequent coral bleaching. Furthermore, certain ingredients can cause deformities in developing coral larvae and abnormal skeletal growth in juvenile corals.
Key Sunscreen Ingredients to Avoid
Oxybenzone, also known as Benzophenone-3, is a widely used UV filter toxic to corals. Oxybenzone can disrupt coral reproduction, cause DNA damage, and lead to abnormal skeletal growth in juvenile corals. It is also linked to increased susceptibility to bleaching.
Another problematic ingredient is Octinoxate, or Octylmethoxycinnamate. This chemical can negatively affect coral larvae and has been shown to degrade into other compounds that may pose risks.
Given the evidence of harm, several regions have taken legislative action. Hawaii, for example, implemented Act 104 (Senate Bill 2571), which banned the sale and distribution of sunscreens containing oxybenzone and octinoxate, effective January 1, 2021. Other locations worldwide have followed suit, restricting the use of these chemicals to protect their marine ecosystems.
Choosing Ocean-Friendly Sunscreen
To minimize impact on coral reefs, choose sunscreens that utilize mineral-based active ingredients. Non-nano zinc oxide and non-nano titanium dioxide are better alternatives to chemical UV filters. These minerals create a physical barrier on the skin, reflecting UV rays rather than absorbing them. The “non-nano” designation is important, as it means the particles are larger than 100 nanometers and are less likely to be ingested by marine life or interfere with their biological processes.
Beyond sunscreen choice, other sun protection strategies can further reduce environmental impact. Wearing UPF (Ultraviolet Protection Factor) clothing, such as long-sleeved shirts and rash guards, provides effective sun protection by physically blocking UV radiation. Seeking shade during peak sun hours and planning outdoor activities for earlier or later in the day also reduces the need for extensive sunscreen application.