Getting over it? A proteomic analysis of mechanisms driving multigenerational acclimation to organic ultraviolet filters in Daphnia magna

Organic ultraviolet filters (UVFs) such as avobenzone, octocrylene and oxybenzone, are considered contaminants of concern due to their widespread occurrence in aquatic environments. Previous research has demonstrated that these UVFs are toxic to aquatic invertebrates over single generation exposures; however, data regarding long-term outcomes across generations of continuous exposure are lacking. Research performed in parallel to this manuscript (Boyd et al., 2023a) observed toxicity to novel UVF exposure, (> 40 % mortality, 46 % decreased reproduction); however, toxic effects were absent after 3 generations of continuous exposure. This study sought to identify the mechanisms behind this observed acclimation across generations through analysis of daphnid proteomes at the end of the F0, F1 and F3 generations. Impaired metabolism and immune response processes were observed in the F0 generation, with decreased abundance in > 80% of altered proteins in octocrylene and oxybenzone exposures. The impairments of these processes were gradually reversed over subsequent generations, with > 60 % of altered proteins demonstrating increased abundance by the F3 generation. An increase in chitin production that could reduce membrane permeability to xenobiotics and pathogens, along with enhanced immune response processes may allow exposed populations to negate many of the negative effects associated with UVF exposure. These results offer mechanistic insights into the gradual acclimation of continuously exposed D. magna populations that have been observed in response to a variety of contaminants, and further serve to highlight the importance of utilizing a long-term approach for studies seeking to model contamination risks in wild populations.