Decoupling physicochemical-biological dynamics in marine oil spills: early adaptive microbial response to...

Oil spills involve complex interactions of physicochemical and biological factors. The coupled physicochemical and biological behavior in the early stages significantly complicates the transport and transformation processes of oil at sea. Here, we conducted a comprehensive assessment of the early-stage environmental impacts of "A Symphony", China's largest recent oil spill, using first-hand data from satellite and drone monitoring, as well as navigation surveys across nine sites (R1→R9). The spilled oil rapidly dispersed under the influence of wind and current (vector velocity, 4 m/s), covering an area of 1.24 × 10³ km² within 30 days. In this region, organic carbon, and nutrient levels (e.g., nitrogen and phosphorus) exhibited irregular fluctuations. The concentration of total petroleum hydrocarbons (TPH) was significantly negatively correlated with the diffusion distance (R²=0.414). Early adaptive changes in the microbial community were observed in three distinct regions, correlating with oil concentrations. Multiple linear stepwise regression and structural equation modeling confirmed that wind and current vector velocity, oil dispersion distance, and oil concentrations significantly influence the microbial community and the abundance of oil-degrading bacteria (R² > 0.66, P > 0.85). These physicochemical and biological factors collectively determine the initial environmental behavior of oil spills. Notably, a discernible threshold distance exists for the effects of an oil spill, beyond which disruptions to the marine environment decrease markedly. Based on the migration and transformation characteristics of oil spills, as well as the diverse responses of physical, chemical, and biological factors at specific distances, early-stage impact zones were categorized into high-, medium-, and mild-impact zones. This framework is pertinent to the ASOS and has the potential for application in other oil spill events. This study provides a theoretical foundation for effective long-term management and mitigation of the environmental consequences of global oil spills.