Beneath the Surface: How Sunscreens Impact Marine Ecosystems

In recent decades, tourism in the Canary Islands has experienced exponential growth, with over 15 million visitors in 2019 and a projected global increase of 179% by 2035 (UNEP, 2020). The extraordinary biodiversity, volcanic landscapes, and pleasant year-round climate have made the archipelago one of the most popular destinations, especially for European tourists. However, this massive influx has brought with it a series of significant environmental impacts, including marine and coastal pollution, the destruction of sensitive habitats, and beach erosion.

Intensive use of sunscreens

Each year, enormous quantities of sunscreen are released into the waters, this adds to the input of products and UV filters introduced into the sea through wastewater discharges. Sunscreens, while essential for protecting the skin from UV damage, contain a range of chemical compounds that, once released into the environment, present a threat to marine ecosystems. Many studies have demonstrated the impact of sunscreens on coral reefs and raised significant concerns; the mechanisms causing the bleaching of tropical coral have also been studied and identified. Although the Canary Islands do not host large coral reefs, there are many other ecosystems worthy of preservation:
volcanic rocky barriers, deep-sea corals, gorgonian forests, sponges, coralline algae, pelagic fish schools, and megafauna. A growing body of scientific evidence now documents that sunscreens pose a threat to the biodiversity of the islands, which are subjected to multiple anthropogenic impacts.

Primary responsible ingredients

The primary ingredients responsible for pollution are organic UV filters, which persist in the marine environment for decades and have been detected in freshwater, wastewater, and marine waters at concentrations reaching up to 1 mg/L. In a study conducted by Rodríguez et al. (2015), eight organic UV filters were identified in the coastal waters of Gran Canaria, including diethylamino hydroxybenzoyl hexyl benzoate (DHHB), diethylhexyl butamido triazone (DBT), and methylene bis-benzotriazolyl tetramethylbutylphenol (MBBT), with potential long-term impacts on the health of marine ecosystems. In addition to UV filters, sunscreens contain other chemicals such as emollients, emulsifiers, and fragrances, which can have significant impacts on marine ecosystems. Among these, triethanolamine, used as an emulsifier, is poorly biodegradable and may accumulate over time, causing persistent damage. Moreover, sunscreens have been identified as a significant source of inorganic nutrients such as phosphate (PO4³⁻), which can promote excessive algal growth in oligotrophic waters, leading to eutrophication. This contributes to the deterioration of water quality and the health of corals and other marine organisms.

Threatened species

Sunscreens can accumulate in the roots of Posidonia oceanica, which protects coastlines from erosion. Even Mytilus galloprovincialis, our common mussel, can be threatened by sunscreens, as UV filters like butyl methoxydibenzoylmethane (avobenzone) can harm the reproduction of these mollusks. Another threatened species is the loggerhead sea turtle Caretta caretta, which can bioaccumulate sunscreen filters with various negative effects. Among the various marine species that can be exposed to the impact of sunscreens, we also find the sea urchin Paracentrotus lividus, frequently encountered in the coastal area most intensely affected by beach tourism. This species is also known as an “ecosystem engineer”. Due to its sensitivity, the sea urchin is also considered an excellent model for assessing the impact of contaminants, including heavy metals, pharmaceuticals, and personal care products. This species allows us to study the effects of different substances on its early embryonic and larval development stages, providing key information on the potential vulnerability of many species to various pollutants. Sea urchins are at the base of the trophic network and control the balance of algal populations they feed on during their activity: a decrease in the population of these echinoderms can lead to an overgrowth of autotrophic organisms, just as their overpopulation can lead to unfertile sea-beds with a consequent loss of biodiversity.

Paracentrotus lividus – Case Study

Paracentrotus lividus is a relatively large sea urchin, with a test diameter (excluding spines) reaching up to 7.5 cm. It is distributed along the Atlantic coast from Ireland to Morocco, including the Canary Islands, the Azores, and the entire Mediterranean Sea. It commonly inhabits shallow subtidal rocky areas and Posidonia oceanica beds, where it is often found among the rhizomes.
Due to its rapid development, P. lividus has been widely used since the early 20th century in embryonic development and ecotoxicology studies. Its gametes and embryos allow researchers to assess the toxicity of various contaminants. The synchronized fertilization and development of its eggs in laboratory settings enable immediate detection of anomalies, classified as reversible or irreversible. Experiments have revealed abnormalities due to heavy metal exposure, sensitivity to persistent organic pollutants, reduced mitotic activity caused by ZnO, and impaired calcification due to zinc ions.
The impact of sunscreens on early sea urchin development varies depending on the formulation. For example, benzophenone-3 causes severe skeletal abnormalities, preventing larvae from reaching adulthood. In contrast, sunscreens containing “next-generation” filters, such as diethylamino hydroxybenzoyl hexyl benzoate (DHHB), methylene bis-benzotriazolyl tetramethylbutylphenol (MBBT), ethylhexyl triazone (EHT), and bis-ethylhexyloxyphenol methoxyphenyl triazine (BEMT), have shown much milder or negligible effects. Recent studies indicate that new formulations containing these advanced filters, which are progressively replacing oxybenzone and octinoxate (already banned in several countries), are more eco-friendly. However, formulations with ethylhexyl salicylate continue to cause skeletal deformities and molecular stress in sea urchin larvae, sometimes leading to death. Additionally, while UV filters are often blamed for harming marine life, other sunscreen ingredients—such as emollients, texturizing agents, preservatives, and fragrances—can also have detrimental effects. Simply removing harmful UV filters is not enough to define an eco-friendly formulation. Furthermore, in silico evaluations of individual ingredients do not always predict real-world impacts, as combined chemicals may interact in unexpected ways, with effects varying based on concentration, species, developmental stage, and health status. Developing truly sustainable sunscreens requires rigorous laboratory and in-situ testing on model organisms.

Preserving the Canary Islands’ Marine Ecosystems

Given that marine life is already under stress from pollution and climate change, a precautionary approach is essential until the full impact of these substances is understood. Scientific evidence shows that it is possible to create eco-friendly sunscreens that effectively protect human skin while minimizing harm to marine ecosystems.
Sunscreen pollution in the Canary Islands threatens marine biodiversity and disrupts fragile ecosystems. Sustainable tourism management is key to preserving the islands’ natural heritage, requiring stricter regulations and the promotion of eco-friendly alternatives. While tourism remains an economic pillar, long-term sustainability depends on balancing economic growth with environmental protection. Strengthening regulations and integrating sustainable practices are essential to safeguarding the archipelago’s unique ecosystems for future generations