Spatiotemporal variation in the ingestion of microplastics in aquatic and terrestrial salamanders endemic to Türkiye

• Microplastic (MP) pollution in aquatic and terrestrial salamanders was investigated. • MPs were detected in 79 out of the 232 salamanders. • Aquatic and terrestrial species ingested plastics at similar percentages (29% vs. 37%). • Juveniles had higher concentrations of MPs in their digestive systems than adults. • The most observed MPs had the following features: fiber, ethylene–vinyl acetate, blue and < 300 μm. Microplastics (MPs), small plastic particles measuring less than 5 mm in size, have pervaded whole ecosystems globally, posing a significant threat to both aquatic and terrestrial organisms due to their ingestion and subsequent bioaccumulation, which can result in various health effects. Do salamanders living in terrestrial habitats ingest more microplastics compared to those living in aquatic habitats? To answer this question, two endemic model organisms—one aquatic: Anatolia newt, Neurergus strauchii sensu lato, and the other terrestrial, Atıf’s Lycian salamander, Lyciasalamandra atifi —were chosen to examine microplastic accumulation in both aquatic and terrestrial species in southern and eastern Türkiye. Our hypothesis is that salamanders living in terrestrial habitats may ingest more microplastics due to the fact that plastics are primarily produced and used on land before entering aquatic ecosystems. Using FTIR stereoscopy and stereomicroscopy, a total of 31 MPs were found in 14 (78 %) of the 18 locations studied for the aquatic salamander species. In contrast, 12 (86 %) of the 14 locations examined for the terrestrial salamander species contained 48 MPs. Although the number of MPs detected per individual in the terrestrial species showed an increasing trend over the 10 years, such a trend was not observed in the aquatic species. In terrestrial species, MPs abundance and salamander body size were significantly correlated in a positive way. On the other hand, in aquatic species, a significant and positive relationship was observed between MPs abundance and specimen weight. In the age/sex-based evaluation, more MPs were found in the gastrointestinal tracts of the juveniles (0.39 MPs/indiv.) compared to females (0.34 items/indiv.) and males (0.32 MPs/indiv.). The levels of microplastics found in terrestrial and aquatic salamanders highlight the potential threat posed by human-induced plastic pollution to terrestrial and aquatic ecosystems. To the best of our knowledge, the present study was a pioneer in reporting the variations in microplastic accumulation in aquatic and terrestrial salamanders.