Seafood resistome across trophic levels: Tissue patterns, drivers, and potential dietary exposure

Antibiotic resistance genes (ARGs) are recognized as emerging contaminants relevant to human exposure. They are widespread in seafood, but their distribution across trophic levels and tissues remains unclear. We analyzed 43 metagenomes covering five marine trophic levels, from seawater plankton to obligate piscivores, and examined muscle, gill, and viscera samples. Multidrug, tetracycline, bacitracin, and β-lactam genes together accounted for about 70% of total relative ARG abundance. ARG richness, diversity, and abundance increased with trophic level. In higher trophic taxa, edible muscle contributed a larger share of the total ARG signal, indicating greater relevance to dietary exposure. Procrustes and variation partitioning showed that ARG composition was mainly associated with microbial community structure and mobile genetic elements (MGEs). Contig analysis further showed co-occurrence of ARGs and MGE markers, suggesting mobility potential. A composite risk index that integrates abundance, mobility proxies, and host or pathogen association also increased with trophic position. These results show clear trophic and tissue patterns of ARGs in marine foods and support priority monitoring of high trophic taxa, edible tissues, microbiome and MGE features along seafood supply chains.