High vulnerability of jellyfish ephyras (Aurelia aurita) and copepods (Calanoids) to understudied organic UV filters: A multi-trophic ecotoxicological assessment.

Organic ultraviolet filters have become a growing concern in coastal environments, yet our understanding of their toxicity remains surprisingly uneven. While some compounds like benzophenone have been studied extensively, others that are increasingly used in sunscreens such as octisalate (EHS) and ethylhexyl triazone (EHT) have received little attention. Even less is known about how these substances affect marine species that are not part of standard toxicity testing. To address these gaps, this work combined a systematic review following the PRISMA approach with a series of acute toxicity tests across five marine species: the microalga Phaeodactylum tricornutum, the crustaceans Artemia franciscana, Calanoids sp. and Gammarus sp., and ephyras of the jellyfish Aurelia aurita and five organic UV filters were tested (avobenzone, octocrylene, octisalate, ethylhexyl triazone, and UV-326) along with three commercial sunscreen formulations. The literature review confirmed that research has been heavily skewed toward benzophenone and inorganic filters, while EHS and EHT together account for only 13% of the studies. The experimental results revealed that these understudied compounds are far from harmless. Octisalate proved to be highly toxic to both A. aurita (EC50 48 h = 2.1 mg/L) and Calanoids sp. (EC50 48 h = 4.3 mg/L). Octocrylene also showed considerable toxicity, particularly in A. franciscana (EC50 48 h = 23.8 mg/L), and caused noticeable behavioural issues in jellyfish ephyras, which struggled to pulse normally. Interestingly, the jellyfish ephyras were by far the most sensitive organisms we tested, more so than the standard crustacean models. When we tested commercial sunscreens, they generally turned out to be less toxic than the pure compounds, suggesting that the other ingredients in these formulations might limit how much of the UV filters are available to cause harm. The one exception was a sunscreen that combined octocrylene and octisalate, which was significantly toxic to copepods. The microalga, in contrast, showed little sensitivity to any of the treatments. Taken together, these findings suggest that octisalate and octocrylene pose a greater threat to marine zooplankton and jellyfish than the current literature would lead us to believe. We hope these data will help fill some of the existing knowledge gaps and support more informed regulatory decisions that consider a wider range of marine organisms.