Microplastic contamination in the gastrointestinal tracts of the Caucasian toad and its habitat at Karagöl Lake, Türkiye

Abstract Microplastics (MPs) are ubiquitous contaminants in both freshwater and terrestrial ecosystems. However, their effects on amphibian species remain poorly understood. This study investigated the presence and characteristics of MP contamination in the Caucasian toad ( Bufo verrucosissimus ) and its surrounding environment in Borçka Karagöl Lake, Türkiye. A multi-matrix sampling approach involving gastrointestinal tract analysis of the toads, as well as water and sediment sampling from the lake, was used. The MPs were identified using stereomicroscopy and Fourier-transform infrared spectroscopy. Nearly 48% of the sampled toads contained MPs, primarily ethylene-vinyl acetate fibers in blue and transparent colors, measuring tens to hundreds of micrometres. Fiber-shaped MPs were also prevalent in water (30%) and sediment (10%) samples, suggesting common sources related to recreational or textile activities. No significant correlation was found between MP presence and toad body size. This study demonstrates that protected high-altitude lacustrine environments inhabited by terrestrial amphibians are vulnerable to MP infiltration. These findings highlight the importance of expanding monitoring efforts across different amphibian life stages and exposure pathways, as well as the necessity of implementing targeted waste-capture measures at recreational entry points.