The Xiamen Symposium on Marine Environmental Sciences (XMAS 2025)

Coastal sediment cores serve as valuable archives documenting historical land-based antibiotic deposition in marine ecosystems. This study focused on sediment cores obtained from the seriously polluted Hangzhou Bay (HB) in the East China Sea (ECS) at a depth of approximately 50 cm. A time series of sediment cores covering the period from 1980 to 2020 was established utilizing 210Pbex dating. Due to natural or anthropogenic disturbances in the study area, there was a mismatch in sediment layer depth and age. Anthropogenic disturbances in the form of land-based wastewater treatment facilities has significantly reduced the release of antibiotics into the sea, resulting in lower antibiotic concentrations between 2003 and 2020 compared to the period from 1980 to 2001. Over a 40-year timeframe, twenty-seven antibiotics were identified, with enrofloxacin (ERFX) and nadifloxacin (NDFX) exhibiting the highest average concentrations of 84.9 and 83.4 ng/g, respectively. The significance of Quinolones (QNs) in sediment samples has been highlighted, and they showed strong co-occurrence and similar distribution patterns driven by similar K_d values. Further, QNs were selected as a key indicator of total antibiotics due to their consistent dominance and significant positive correlation with overall antibiotic levels. We propose a multi-dimensional evaluation of the environmental risks of antibiotics, encompassing ecological risk and antimicrobial resistance assessments, which complement each other. The evaluation outcomes identified priority antibiotics with varying types of environmental risks: sulfacetamide (SCM) and clindamycin (CLIN) exhibited high ecological risks to mysid, while ERFX, ciprofloxacin (CFX), norfloxacin (NFX), gatifloxacin (GTFX), moxifloxacin (MXFX), and marbofloxacin (MBFX) presented high antimicrobial resistance.

Antibiotics; Antimicrobial resistance risks; Coastal sediment cores; Ecological risks; Historical distribution