Microplastics in Turkish Coastal Lagoons: Unveiling the Hidden Threat to Wetland Ecosystems

<title>Abstract</title> Transitional ecosystems like coastal lagoons provide numerous ecosystem services. However, they are increasingly threatened by plastic pollution, particularly microplastics (MPs). Despite growing concerns, the occurrence and distribution of MPs in Türkiye’s lagoon systems remain largely unknown. This study aims to assess the abundance, composition, and seasonal variability of MPs in the surface water and sediments of five lagoons located in the northeastern Mediterranean region of Türkiye. Additionally, potential MP sources and their environmental implications are addressed. Water and sediment samples were collected from Akyatan, Tuzla, Ağyatan, Çamlık, and Yelkoma Lagoons during the November and June periods. MPs were extracted using density separation and digestion techniques, quantified via stereo microscopy, and characterized through µ-Raman spectroscopy to identify polymer composition. A total of 15,526 MPs were recovered, with significantly higher concentrations in water (47.5 ± 4.02 MPs/L) during November compared to June (17.0 ± 2.57 MPs/L; p &lt; 0.05). MP concentrations varied among lagoons, with Yelkoma and Tuzla exhibiting the highest levels in water, while Akyatan showed the highest sediment contamination. Fibers were the dominant MP type, followed by fragments and films. polymer analysis identified polyethylene (PE), polypropylene (PP), and polyester (PES) as the most common polymers, indicating agricultural runoff, fishing activities, and mismanaged plastic waste as primary MP sources. This study provides the first comprehensive assessment of MP pollution in Turkish lagoons, highlighting seasonal and spatial differences in contamination levels. The results highlight the pressing need for improved waste management policies and conservation strategies to mitigate MP pollution in these ecologically and economically significant coastal systems.