Mar Environ Res 2025 Oct 30;213:107670. doi: 10.1016/j.marenvres.2025.107670.

Temperature-gradient drives shifts in macrobenthic communities near nuclear power plant thermal discharges: A case study from the Sanmen bay.

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With the rapid development of the global nuclear power industry, increasing attention has been drawn to the thermal pollution effects of discharged cooling water on marine ecosystems. This study investigated the ecological impacts and adaptive responses of macrobenthos to thermal pollution from nuclear power plant operations. Focusing on the thermal discharge area of Sanmen Nuclear Power Plant, we conducted the systematic evaluation of thermal pollution effects on macrobenthos, utilizing survey data collected from 48 stations during four research cruises between 2022 and 2024. In this research, we tried to reveal the community assembly responses and indicator roles of macrobenthos to thermal discharge disturbance, using Clustering Analysis, non-metric Multidimensional Scaling (nMDS), Principal Component Analysis (PCA), Similarity Percentage analysis (SIMPER), Linear Regression, β diversity decomposition, Multiple Regression Analysis, and Indicator Species Analysis (IndVal). The results demonstrated that rising temperature is the primary environmental factor affecting macrobenthic communities in the thermal discharge area of the Nuclear Power Plant. Under middle thermal discharge impact conditions (ΔT ≤ 5.30 °C), the abundance of macrobenthos increased significantly (p < 0.05), with mollusks exhibited higher spawning efficiency and larval survival rates. However, biomass exhibited a significant decline. β diversity decomposition indicated that turnover components outweighed nestedness components, confirming that thermal discharge primarily drives community reassembly through species replacement. Three distinct thermal adaptation zones emerged along the temperature gradient: the high thermal discharge impact region (3.63 ≤ ΔT ≤ 5.30 °C) was characterized by Nassarius succinctus, Nassarius variciferus and Lumbrineris cruzensis; the middle thermal discharge impact region (0.45 ≤ ΔT ≤ 0.93 °C) by Eulima bifascialis, Raphidopus ciliatus and Typhlocarcinus nudus; and the low thermal discharge impact region (ΔT ≤ 0.2 °C) by Protankyra bidentata and Acaudina molpadioides. Indicator Species Analysis (based on an IndVal index threshold of ≥25) revealed three thermal tolerance groups: high temperature tolerant saprophagous gastropods, middle temperature tolerant small mollusks and plankton dependent crustaceans, and low temperature tolerant polychaetes. These findings provide critical insights into thermal stress responses in coastal ecosystems and establish a framework for ecological monitoring of thermal discharge impacts.

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