Sedentary fish Cynoglossus joyneri reveals microplastic pollution in the coastal water of Lvsi Fishing Ground

Microplastics (MPs) present a growing threat to marine ecosystems, adversely affecting organismal health and posing risks to human populations through trophic transfer. Utilizing bioindicator species can effectively assess MP pollution levels, providing crucial data for regional environmental protection. This study investigated the potential of the sedentary tonguefish Cynoglossus joyneri as a bioindicator for MP contamination in the coastal waters of Lvsi Fishing Ground. Through comparative analysis of MP characteristics in fish tissues and environmental matrices, the results showed that the predominant MP size in the region was <1 mm, with the main colors, shapes, and polymer types being blue/transparent, fragment/fiber, and polyethylene terephthalate (PET), respectively. The average abundance of MPs was 1.26 items dm⁻³ in the surface water, 1.69 items dm⁻³ in the bottom water, and 0.55 items/g in the surface sediments. In C. joyneri, the average abundance of MPs was 2.5 items ind⁻¹. in the gills and 2.1 items ind⁻¹. in the gastrointestinal tract (GIT). Additionally, a potential correlation was observed between MPs in the surface sediments and those in the GIT of C. joyneri. The species' limited mobility and sediment-associated MP patterns support its utility as a reliable bioindicator for surface sediment pollution in the targeted region. These findings establish critical baseline data for the Lvsi Fishing Ground while advancing a framework for ecosystem-based monitoring strategies targeting coastal MP hotspots.