Mechanisms of growth regulation and environmental effects of ambient nutrients on Vallisneria natans in eutrophic lakes

Eutrophication poses a significant global environmental challenge for freshwater lakes today, often leading to the substantial decline of Vallisneria natans , a key submerged macrophyte vital for maintaining lake clarity and stability. While previous studies have explored the physiological impacts of aquatic environmental nutrients on V. natans (e.g., variations in biomass), the mechanisms by which nutrient levels influence its growth and ecological effects remain largely unexplained. In this study, we regulated nutrient levels in both sediment and the water columns through two mesocosm experiments to evaluate the influence of aquatic environmental nutrients on the growth and metabolic products of V. natans biomass. We developed the first multiple linear regression models with interaction term for V. natans growth in response to aquatic environmental nutrients, thereby quantifying the nutrient-mediated processes of its growth and decline. Furthermore, we discovered that aquatic environmental nutrients modulate gene expression within five key metabolic pathways in V. natans : photosynthesis, MAPK signaling, phytohormones, carbohydrate metabolism, and the sulfur cycle, identifying 47 key differentially expressed genes (DEGs) that regulate these pathways. Our results demonstrate that moderate aquatic nutrient enrichment significantly upregulates genes associated with Photosystems I and II, as well as key enzymes including sulfur transporters (SULTR) and ATP sulfurylase (ATPS), thereby promoting carbohydrate accumulation and odorant (dimethyl sulfide, DMS) synthesis. These findings provide a scientific basis for optimizing the use of submerged macrophytes in eutrophic lake restoration and odorant control, offering critical insights for the ecological recovery of V. natans within lake ecosystems.