De novo transcriptome profiling reveals the bioeffect of the clam (Cyclina sinensis) to graded extremely low-frequency electromagnetic fields (ELF-EMF, 50 Hz) exposure.

The rapid expansion of offshore and onshore wind farms has raised concerns regarding the potential ecological impacts of extremely low-frequency electromagnetic fields (ELF-EMF) on benthic organisms. In this study, we investigated the intensity-dependent effects of ELF-EMF exposure on the bivalve Cyclina sinensis, a dominant species inhabiting in coastal mudflats. Individuals were exposed to two intensities of ELF-EMF (50 Hz) for 14 days: a low-intensity group at (5 ± 1) μT and a high-intensity group at (15 ± 1) μT, alongside a control group maintained under ambient magnetic field conditions without additional ELF-EMF sources. Results showed that high-intensity exposure reduced survival rates and induced oxidative stress, as evidenced by increased activities of superoxide dismutase (SOD), catalase (CAT), and elevated malondialdehyde (MDA) levels in the hepatopancreas. Transcriptomic analysis identified 1,509 and 4,936 differentially expressed genes (DEGs) in the low- and high-intensity groups, respectively, indicating an intensity-dependent molecular response. KEGG enrichment analysis revealed significant disruptions in the 'protein processing in endoplasmic reticulum' and 'oxidative phosphorylation' pathways under high-intensity ELF-EMF. Key genes involved in endoplasmic reticulum stress (e.g., OS9, ATF6, EDEM) were upregulated, whereas genes critical for mitochondrial energy metabolism (e.g., ND4, COX3/1, CYTB) were downregulated. These findings suggest that high-intensity ELF-EMF disrupts proteostasis and impairs ATP synthesis, ultimately leading to physiological stress in C. sinensis. This study provides important molecular insights into the ecological risks posed by ELF-EMF from offshore wind infrastructure, and offers a scientific basis for establishing biosafety standards to support sustainable marine energy development.