Offshore wind farm disturbance alters ecological thresholds and reshapes niche distribution patterns of nekton communities: Insights from indicator species.

Construction and operation of offshore wind farms can generate ecological disturbances that reshape coastal nekton habitats and affect marine biodiversity. To evaluate these effects, fixed-station surveys of nekton communities and environmental variables were conducted from 2021 to 2024 in a wind power area and an adjacent control area in the coastal waters off Cangnan, China. Shannon-Wiener diversity, β-diversity, Mantel tests, Threshold Indicator Taxa Analysis (TITAN), and niche metrics were applied to characterize diversity patterns, identify environmental response thresholds, and quantify niche dynamics under wind farm disturbance. Niche characteristics were further incorporated to interpret the response mechanisms of TITAN indicator species and clarify community responses to environmental stress. β-Diversity was mainly driven by species turnover. Shannon-Wiener diversity was higher in the control area than in the wind power area; diversity-based assessment indicated that the overall ecological condition remained relatively good. Mantel tests identified water depth, salinity, dissolved oxygen, and inorganic nitrogen as key factors shaping nekton distribution. TITAN revealed distinct differences between areas in indicator species composition, response direction, and threshold ranges along these gradients. Species in the wind power area generally exhibited narrower threshold ranges, suggesting modified ecological filtering by environmental gradients. Compared with the control area, major indicator species in the wind power area showed reduced average niche breadth and increased interspecific niche overlap. By integrating static community patterns with dynamic ecological processes, this study elucidates how offshore wind farms impact nekton assemblages and establishes a framework to assess ecological thresholds and niche variations in coastal waters.