Abstract: The invasion of Spartina alterniflora (SA) has led to significant hydrogen sulfide (H₂S) production in coastal wetlands. The phytotoxic S²⁻ plays a critical role in elemental biogeochemistry and may contribute to the successful invasion of SA in areas contaminated with heavy metals. To explore how H₂S influences nutrient uptake and energy utilization in SA and the native Phragmites australis (PA) under cadmium (Cd) stress, and to uncover the mechanisms by which H₂S facilitates SA invasion, a hydroponic experiment was conducted. This experiment included three Cd concentrations (0, 1 and 2 mg Cd L⁻¹) and three H₂S treatments (inhibiting H₂S synthesis, simulating an external H₂S source and untreated control). Results revealed that H₂S plays a crucial role in balancing the uptake of Mg, Mn, Ca and Zn in SA, mitigating Cd-induced damage to the photosynthetic system and enhancing nutrient and energy accumulation under Cd stress. In contrast, H₂S was toxic to PA, increasing lipid peroxidation, inhibiting growth, and disrupting mineral uptake, particularly of Ca. This exacerbated the detrimental effects of Cd on the photosynthetic system and nutrient accumulation in PA. These results highlight that irrespective of Cd treatment, H₂S enhanced energy accumulation, mineral uptake, and growth in SA compared to PA, which could support the ecological niche competition within the coastal wetlands during the invasion of SA into PA habitats. Consequently, inhibiting endogenous H₂S synthesis in SA may offer a potential strategy for controlling its invasion.

Key words: Spartina alternifora, Phragmites australis, hydrogen sulfde, cadmium, invasion plant