Effects of initial operation phase of Wailuo Offshore Wind Farm in Zhanjiang on benthic biotic communities

To assess the coupled effects of offshore wind farm operation and seasonal environmental changes, we conducted sediment and benthic organism surveys at 18 stations (9 near-turbine area, NO; 9 far-from-turbine area, FO) in Wailuo offshore wind farm in Zhanjiang during autumn and winter. By integrating diversity indices, Mantel tests, and niche analysis, we examined the effects of the initial operational phase on benthic environmental quality and elucidated the ecological adaptation mechanisms of benthic communities to operational disturbances. The results indicate that the initial operation did not adversely affect sediment quality, with overall favorable conditions and no significant differences in pH, organic carbon, or heavy metal contents between areas (p<0.05). Elevated petroleum hydrocarbons in the wind farm area may be attributed to residual ship activities during construction. However, benthic community responses showed distinct seasonal coupling effects. In autumn, although species richness was lower in the NO area, the community structure remained stable, with comparable Shannon diversity indexes between areas (e.g., 1.34±0.73 vs. 1.34±0.71 in Q2). Broadly adaptable filter-feeding species such as Cadella narutoensis also exhibited significantly increased biomass near foundations. In winter, the NO area experienced a sharp decline in species richness and biomass, with the Shannon index dropping to 0.50±0.67, and the community shifted toward dominance by small-sized, tolerant opportunistic species such as Oliva plana. Niche analysis reveals that broad-niche species like Nassarius terefiusculas sustained community function through efficient resource utilization. The study demonstrates that the impact of the initial wind farm operation on benthic communities varies significantly with season, with winter operational disturbances and natural stressors leading to reduced biomass near turbines and driving the community toward opportunist-dominated evolution.