Abstract
Submerged macrophyte restoration and in situ phosphorus (P) passivation are effective methods for the control of internal P loading from sediments. This study explored the synergistic effects of Vallisneria natans and iron (Fe)-oxidizing bacteria (IOB) on internal P loading from eutrophic freshwater lake sediments by taking into account Fe-bound P (FeP) formation and associated bacterial community structures. Sediment samples were prepared in glass tanks under four treatments, namely no V. natans planting or IOB inoculation (control), planting V. natans without IOB inoculation (Va), planting V. natans with IOB inoculation (Va-IOB), and planting V. natans with autoclaved IOB inoculation (Va-IOB[A]). Compared with the control, all three treatments with V. natans (Va, Va-IOB, and Va-IOB[A]) had significantly decreased organic matter contents and increased redox potential in sediments (p < 0.05), at the rapid growth and mature stages of V. natans. Planting V. natans with and without IOB inoculation also decreased the total P (TP) and Fe–P concentrations in sediments. Conversely, Fe3+ concentrations, Fe3+/Fe2+ ratios, and the proportions of Fe–P in TP all increased in sediments planted with V. natans, especially under the Va-IOB treatment (p < 0.05). Furthermore, bacterial community diversity increased in sediments due to the presence of V. natans. The relative abundances of IOB (including Acidovorax and Chlorobium) increased from the transplanting to the rapid growth stage of V. natans and then decreased afterwards. In the later stages, the relative abundances of IOB and their ratios to Fe-reducing bacteria were the highest under the Va-IOB treatment. Accordingly, synergistic interactions between V. natans and IOB could enhance Fe–P formation and reduce TP concentrations in eutrophic lake sediments by altering sediment physicochemical properties and Fe oxidation-related bacterial community structures.
Highlights
Eutrophication of freshwater bodies is caused primarily by excess nutrient inputs, especially phosphorus (P)
P release from surface sediments often leads to delayed recovery of freshwater from eutrophication following the reduction of external P input [3]
This study analyzed the interactive effects of V. natans planting and iron-oxidizing bacteria (IOB) inoculation on
Summary
Eutrophication of freshwater bodies is caused primarily by excess nutrient inputs, especially phosphorus (P). P is considered the key limiting nutrient in the water eutrophication process, with nitrogen (N) being the second most important element [1]. Controlling external P input has been proposed as one of the main strategies of mitigating eutrophication in lakes [2]. P release from surface sediments often leads to delayed recovery of freshwater from eutrophication following the reduction of external P input [3]. The control of internal P loading from sediments has increasingly attracted the attention of researchers and stakeholders in eutrophication management in freshwater ecosystems. Among the numerous water remediation technologies, submerged macrophyte restoration and in situ P passivation are two effective methods of controlling internal P loading
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