Assessment of plasticizer contamination in sicklefin devil rays (Mobula tarapacana) from the remote Azores Archipelago

Plastic additives, particularly phthalic acid esters and related compounds, are pervasive pollutants in marine ecosystems; however, little is known about their accumulation in large filter-feeding megafauna. Mobulid rays, such as the critically endangered sicklefin devil ray (Mobula tarapacana), may be particularly vulnerable to chemical exposure due to their continuous filter-feeding behaviour and occurrence in plastic-polluted oceanic regions. This study aimed to assess the presence of plastic-derived chemical pollutants, specifically plasticizers, in biopsies of M. tarapacana from the Azores Archipelago, North Atlantic. An ammonium formate-modified QuEChERS extraction procedure coupled with gas chromatogrpahy-mass spectometry analysis was developed, validated, and applied to fin biopsies collected from 25 individuals. The method demonstrated excellent linearity, recovery rates between 79 and 125 %, and low matrix effects. Four plasticizers: diisobutyl phthalate, dibutyl phthalate, di(2-ethylhexyl) adipate, and di(2-ethylhexyl) phthalate (DEHP) were detected above quantification limits in 8 of the 25 analysed samples. Among them, DEHP showed the highest concentrations (185-511 ng/g wet weight). These findings provide the first empirical evidence of plasticizer accumulation in M. tarapacana, highlighting that megafauna from the open ocean are not exempt from plastic-associated chemical contamination.