Cascading effects of offshore wind farm construction: sediment disturbance-pollutant transport responses in marine environment and biological populations

With the rapid development of offshore wind power, the ecological impacts of sediment disturbance during construction have attracted growing attention. Thus, we detected the concentrations of ${\mathrm{P}\mathrm{O}}_4^{3-}$, petroleum hydrocarbons, and heavy metals in the waters of the nearshore area and offshore wind farm in Yangjiang, the levels of heavy metals in sediments, as well as the quality of organisms across three phases: pre-construction, pile foundation construction, and submarine cable laying. The results show: 1) Construction activities significantly changed local water quality and benthic characteristics, with ${\mathrm{P}\mathrm{O}}_4^{3-}$ concentrations increasing by 82.12% after cable installation. 2) Sediment disturbance exacerbated the reducing conditions in the marine environment, where S²⁻ combined with Pb²⁺ to form PbS precipitates, which were later re-released under oxidizing conditions. Meanwhile, As was preferentially reduced to toxic As³⁺, posing increased ecological risks to phytoplankton and benthic communities. 3) Distinct patterns of heavy metal accumulation emerged between fish and crustaceans, while the bioaccumulation of total petroleum hydrocarbons revealed construction-induced shifts in trophic pathways. Notably, these disturbances disproportionately affected the early life stages of fish (Eggs and larvae), impairing population resilience and forming spatiotemporally heterogeneous ecological risk networks. By clarifying the cascade mechanism of sediment disturbance-pollutant migration-ecological response, the research highlights the ecological risks arising from habitat reconstruction, food web decoupling, and pollutant reactivation. The results establish critical benchmarks for environmental risk assessment and provide actionable insights for pollution control strategies during the development of offshore wind farms.