Retention of source microbial signals in plastispheres of fibrous plastic debris after translocation

While numerous studies have explored microbial hitchhiking on aquatic plastics, the fate and interpretability of residual source signals after translocation remain unclear. Here, disposable face masks were used as model fibrous plastic debris to examine source conditioned plastisphere formation, post transfer signal retention, and mask part specific exposure history signals. Masks were conditioned in two freshwater systems and transferred to autoclaved deionized water as a simplified receiving medium to reduce source water input. Before transfer, mask surfaces developed plastispheres that differed from surrounding water in overall composition and dominant bacterial assemblages, and the two source waters produced distinguishable original plastispheres. At transfer weeks 2, 4, and 6, whole mask plastispheres remained distinguishable by their source origin; PERMANOVA explained 20.9%, 18.9%, and 19.5% of variation across Bray Curtis, Jaccard, and Aitchison CLR distances. Similarity contrast based affinity indices were further used to distinguish water-source carryover from affinity to the original plastisphere state. Whole mask water source affinity was weak and non-significant (mean = -0.0015, p = 0.728), whereas plastisphere source affinity was marginal at the whole mask scale (mean = 0.0033, p = 0.074) and significant under part matched comparisons (mean = 0.0015, p = 0.014), and source separation was clearer in inner and outer layers than ear loops. Overall, these findings indicate that source-history-associated compositional information remained detectable during post-transfer reassembly, supporting further exploration of plastisphere profiles for source tracing.