• Seagrass plastispheres host taxonomically distinct but functionally overlapping microbiomes. • Microbially-driven C and S metabolisms on plastisphere were more significantly distinct from the other habitats. • Organic N assimilation and thiosulfate disproportionation were major but previously overlooked pathways on plastisphere. • Silicimonas and Erythrobacter were keystone taxa driving the coupled cycling of C, N and S on plastisphere. • Plastisphere potentially elevated risks of CO 2 /N 2 O emissions, H 2 S accumulation and eutrophication. Seagrass meadow, a crucial blue carbon ecosystem, is increasingly threatened by plastic pollution. Plastic debris in this sensitive ecosystem creates a new microbial habitat known as “plastisphere”. However, the functional role of plastisphere, particularly in driving the cycling of key biogenic elements, remains poorly understood. This knowledge gap raises concerns over potential disruptions to elemental fluxes and subsequent ecological consequences. Here, metagenomic analysis was employed to investigate the metabolic profile of in-situ plastisphere in seagrass meadow, with particular focus on carbon (C), nitrogen (N), phosphorus (P), and sulfur (S) biotransformation. The obtained results revealed that plastisphere microbes were taxonomically distinct from those in natural environments of the seagrass meadow, and these inhabitants were capable of driving diverse metabolic pathways. However, >75% functional gene similarity indicated a significant functional overlap between the plastisphere and natural environments. This niche enriched genes related to heterotrophic organic C degradation (27.71% ± 3.28%) and oxidation (17.86% ± 2.04%) pathways, organic N metabolism (62.18% ± 8.57%) mainly through GS-GOGAT pathways and denitrification (8.70% ± 4.06%), polyphosphate degradation (22.89% ± 2.20%) and organic P mineralization (17.50% ± 1.70%), as well as assimilatory/ dissimilatory sulfate reduction (30.60% ± 3.49%) and thiosulfate disproportionation (13.57% ± 2.89%) metabolic pathways. Metabolic linkage within seagrass plastisphere was facilitated by highly connected taxa including Silicimonas and Erythrobacter , which linked electron-donating processes (including organic C degradation and S oxidation) to electron-accepting pathways ( e.g. , sulfate/nitrate reduction, C fixation). These interactions established the plastisphere as a potential biogeochemical hotspot, potentially amplifying the risks of CO 2 /N 2 O emission, H 2 S accumulation, nutrient competition with seagrass and potential eutrophication from imbalanced P mobilization, ultimately threatening the health and stability of seagrass ecosystem.
Wu et al. (Fri,) studied this question.