Microplastics accumulate in all major organs of the mediterranean loggerhead sea turtle (Caretta caretta).

Microplastics (MPs) are a pervasive marine environmental pollutant, posing a serious threat to marine ecosystems and organisms at all trophic levels. Plastic ingestion is well documented in marine turtles, and loggerhead sea turtles (Caretta caretta) have been identified as an indicator species to monitor MP pollution globally. Our understanding of the translocation and bioaccumulation potential of MPs beyond the gastrointestinal tract is, however, limited. Here we demonstrate that MP translocation occurs in these marine reptiles and present a comprehensive analysis of MP accumulation in body tissues of 10 stranded Mediterranean loggerhead turtles including the kidney, liver, spleen, heart, skeletal muscle, subcutaneous fat, stomach, intestine, and reproductive organs. Foreign microparticles were identified in 98.8 % of all samples (∼70 % being MPs) and were significantly concentrated in the reproductive organs followed by the heart. Raman spectroscopy revealed that polypropylene, cotton fibres, and polyethylene were the most common microparticle types, and optical photothermal infrared (O-PTIR) spectroscopy provided direct visualisation of cotton microfibres embedded in loggerhead heart tissue. Future studies should determine the biological impact of MP bioaccumulation in sea turtle organs, to fully appreciate the impacts of these anthropogenic pollutants on protected and vulnerable populations worldwide.