Occurrence and ecological risk of microplastics in different mariculture feeds

The pollution of microplastics (MPs) in mariculture animals and its risk to human health remain a growing concern. However, although much attention has been paid to the release of MPs in mariculture facilities, few reports can be found on the occurrence of MPs in mariculture feeds consumed by mariculture animals. Therefore, the present study investigated the occurrence patterns of MPs in 23 types of mariculture feeds for different species at different life history stages, and the related ecological risks of these MPs were also assessed. MPs were prevalent with an average abundance of 5491 ± 2712 particles kg⁻¹ in all the mariculture feeds. Notably, the abundance of MPs in Stichopus japonicus (SJ) feeds was the highest, especially in adult stage feeds of SJ (19683 ± 6789 particles kg⁻¹). The majority of MPs in mariculture feeds were 20–500 μm in size (81.4%), shaped as fragments (66.2%) and fibers (23.5%), mostly transparent (58.5%) and yellow (18.3%) in color, and the polymer types were dominated by polycaprolactone (PCL), polypropylene (PP), polyethylene (PE), and cellophane (CP), which together accounted for 61.6%. More importantly, the risk index (H) indicated that MPs in Sebastes schlegelii feeds had high risk (H: 100–1000), while Litopenaeus vannamei, Penaeus monodon, Stichopus japonicus, and Larimichthys crocea feeds had medium risk (H: 10–100). These findings offer valuable information about MP contamination in mariculture feeds and establish a theoretical foundation for the safe production and use of mariculture feeds, contributing to the development of a risk assessment framework for MPs in mariculture feeds.