Effects of ferrous addition to Vallisneria natans: An attempt to apply ferrous to submerged macrophyte restoration

Abstract

Restoration of submerged macrophytes is an efficient way for endogenous nutrient control and aquatic ecological restoration, but slow growth and limited reproduction of submerged macrophytes still exist. In this research, the effect of ferrous on the seed germination and growth of Vallisneria natans (V. natans) were studied through aquatic simulation experiments and its influence on the rhizosphere microbial community was also explored. The seed germination, growth, and physiological and ecological parameters of V. natans were significantly affected by the ferrous treatments. Ferrous concentration above 5.0 mg/L showed significant inhibition of seed germination of V. natans and the best concentration for germination was 0.5 mg/L. During the growth of V. natans, after ferrous was added, a brief period of stress occurred, which then promoted the growth lasting for about 19 days under one addition. The diversity and richness of the rhizospheric microbial were increased after the ferrous addition. However, the function of the rhizospheric microbial community showed no significant difference between different concentrations of ferrous adding in the overlying water. Ferrous addition affected the growth condition of plants (content of CAT, Chl a, Chl b, etc.), thus indirectly affecting the rhizospheric microbial community of V. natans. These impacts on V. natans and rhizosphere microorganisms could generalize to other submerged macrophytes in freshwater ecosystems, particularly which have similar habits. These findings would contribute to the ecological evaluation of ferrous addition or iron-containing water, and provide a reference for submerged macrophytes restoration and ecological restoration in freshwater ecosystems.