Microplastics in stratified reservoirs of the Ceyhan River Basin: vertical distribution, environmental correlates, and the role of dams in contamination

Official URL: https://dx.doi.org/10.1088/2515-7620/ae51fb

This study presents the first comprehensive, depth-integrated investigation of microplastic (MP) pollution across four major dam reservoirs—Kandil, Menzelet, Sır, and Aslantaş—along the Ceyhan River Basin in southeastern Türkiye. MPs were detected ubiquitously, at all stations and depths, with mean water-column concentrations ranging from 10.3 to 14.6 MP l−1. The reservoirs were ranked in descending order of mean concentration: Kandil (14.6 MP l−1), Sır (13.6 MP l−1), Aslantaş (13.0 MP l−1), and Menzelet (10.3 MP l−1). A striking vertical distribution pattern was observed: MP concentrations significantly increased with depth, with accumulation in pelagic and bottom layers, challenging surface-centric monitoring views. Fragments and fibers were the dominant types, primarily observed in blue, black, and transparent colors. Polymer identification revealed that polyethylene (21.5%), polyethylene terephthalate (16.7%), and polypropylene (10.1%) were the most common polymers, reflecting inputs from packaging and synthetic textiles. Statistical analyses revealed strong positive correlations between high MP abundance and nutrient parameters (e.g., total phosphorus and chlorophyll-a), suggesting shared anthropogenic sources (wastewater/runoff) and the likely role of biofouling in MP sedimentation and downward flux. This study provides a crucial baseline, underscoring the urgent need for depth-integrated monitoring and targeted mitigation strategies to safeguard the ecological integrity of these vital dammed freshwater ecosystems.