Occurrence of microplastics across tissues in North Atlantic fin whales (Balaenoptera physalus)

As long-lived filter-feeders, baleen whales integrate and reflect changes in ocean contamination, including exposure to microplastics (MPs). This study reports the occurrence of MPs in multiple tissues of North Atlantic fin whales ( Balaenoptera physalus ) collected off southwestern Iceland in 2023. Five tissues (blubber, muscle, liver, lung, and kidney) from eight individuals were analyzed using the Micro-FTIR and Micro-Raman spectroscopy under strict contamination control. MPs occurred in 32.5% of the samples (13/40; n = 16 particles), predominantly as blue fragments (75%) with an average length of 67.2 ± 33.8 μm. Polyester, polyethylene, and polypropylene were the most common polymers. Although overall tissue differences were minimal, blubber contained the highest MP abundance and longer average particles than other tissues. These findings provide evidence of MP tissue-specific accumulation within a mysticete species and highlight the need to clarify the mechanisms and implications of MP accumulation in marine megafauna. • Microplastics (MPs) were detected across multiple tissues of fin whales • Sixteen MPs were confirmed across five internal tissues. • Blubber showed the highest number and longest MP particles. • Most particles were blue fragments made of PES, PE and PP. • Findings support systemic MP translocation in fin whales.