The occurrence and risks of microplastic pollutants to wintering Whooper Swans (Cygnus cygnus) in Swan Lake, North China
By Changjun Li, Wenchan Liang, Zihan Yuan, Lixin Zhu, Xin Hou and Xuri Dong
Marine plastic and microplastic (MP) pollution is widely recognized as an emerging issue that poses significant risks to marine organisms, particularly birds. However, little is known about MP exposure in migratory birds at their wintering grounds. This study, conducted at Swan Lake in Rongcheng city, China, is the first to investigate the occurrence of MPs in feces of migratory Whooper Swans, and assess the associated ecological risks.
Whooper swan (Cygnus cygnus) coming into land by Juha Soininen / WWT
The mean abundance of MPs in fecal samples was 0.40 ± 0.40 items/g, with an overall detection rate of 76.67%. Fragment-shaped MPs were the predominant form in sediment and fecal samples, primarily composed of polypropylene (PP) and polyethylene (PE). Conversely, fibrous MPs, predominantly polyethylene terephthalate (PET), were the most abundant type in water. Principal Coordinate Analysis (PCoA) revealed that fecal MP composition overlapped with surrounding water and sediment.
Our findings suggest that Whooper Swans may function as reliable bioindicators for monitoring environmental MP pollution within their wintering habitats. Evaluations using the Pollution Load Index (PLI), Polymer Hazard Index (PHI), and Potential Ecological Risk Index (PERI) collectively indicated that the overall ecological risk associated with MP abundance to wintering Whooper Swans remains low. Nevertheless, the presence of high-toxicity plastic polymers, such as polyacrylonitrile and polyurethane, were identified in specific regions of the lake. Source attribution analyses revealed that the predominant contributors to MP pollution in Swan Lake are linked to local fishery operations (e.g. linear PP, PE), small-scale runoff inputs (e.g. fibrous PET), and coastal beach tourism activities (e.g. fragmented PP, PE). Taken together, these findings offer essential scientific insights that support the conservation of Whooper Swans and inform the formulation of management strategies aimed at mitigating plastic and MP pollution in the wintering habitats for key migratory birds.
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