Nutrient enrichment weakens aquatic ecosystem stability via reduced species asynchrony and species richness

• Aquatic ecosystem stability is mainly maintained by the dominance effect. • Nitrate nitrogen (NO 3 -N) directly reduces aquatic ecosystem stability. • NO 3 -N weakens ecosystem stability via reduced species asynchrony and richness. Nutrient enrichment is a major factor impairing aquatic ecosystems globally. It is widely recognized that excessive inputs of nitrogen and phosphorus stimulate phytoplankton blooms and reduce aquatic biodiversity. However, the effects of nutrient enrichment on the stability of aquatic ecosystems and the underlying mechanisms remain largely unknown. To address this gap, we investigated the effects of nutrient enrichment on aquatic ecosystem stability using long-term monitoring datasets (9–34 years) from 15 diverse aquatic ecosystems. Our findings reveal that aquatic ecosystem stability is primarily maintained by the dominance effect (explanatory rate: 46 %), quantified by the stability of dominant species. Meanwhile, nitrate nitrogen (NO 3 -N), rather than phosphate phosphorus (PO 4 -P), can directly reduce aquatic ecosystem stability or indirectly reduce aquatic ecosystem stability by decreasing species asynchrony and species richness. Further analyses found that NO 3 -N reduces ecosystem stability by weakening the compensatory dynamics of dominant species. These findings indicate that nutrient enrichment affects the link between diversity, asynchrony, and stability. Given that aquatic ecosystems are increasingly affected by eutrophication caused by nutrient enrichment, we proposed that the protection of dominant species should be prioritized to mitigate the effects on the stability of aquatic ecosystems in the setting of eutrophication.