Sediment Requirements For The Growth And Anchorage Of Three Submerged Macrophytes

Submerged macrophytes play a critical role as the primary producers in lake ecosystems.Among all aquatic plant groups,submerged macrophytes have the closest relationship with the water environment.They occupy the interface between water and sediment,maintaining water biodiversity,improving water quality,and inhibiting algae growth to ensure the stability of lakes.However,the area,biomass,and species richness of submerged macrophytes have been declining in lakes due to factors such as eutrophication,water level changes caused by water conservancy projects,and overstocking of herbivorous animals.This decline in submerged macrophytes often leads to the degradation of the lake ecosystem’s structure,function,and ecosystem service value.Consequently,the restoration of submerged vegetation has become an important aspect of lake ecological restoration.Sediment serves as the medium for the growth and anchorage of submerged macrophytes,and its quality is a key determinant of successful restoration.Evaluating the suitability of sediment for submerged macrophyte growth and anchorage holds great significance.In this study,we conducted experimental analyses on the distribution depth of submerged macrophyte roots in sediments to determine the range of sediment depth that affects macrophyte growth and anchorage.Initially,the range of physical and chemical parameters of sediment for the growth and anchorage of Hydrilla verticillata,Potamogeton maackianus,and Myriophyllum spicatum was determined based on literature data.Subsequently,controlled experiments were conducted to verify and expand upon these findings,and they were compared and validated with field survey data.The objective was to provide preliminary data on sediment conditions for the design of submerged macrophyte restoration projects and offer references for similar research involving other commonly used submerged macrophytes in ecological restoration.This study contributes to the knowledge necessary for the protection and recovery of submerged macrophytes.The main findings of this study are as follows:(1)The root biomass of the three submerged macrophytes declined as sediment depth increased.The sediment depth range of 0-10 cm supported root biomass of over55%for all three macrophytes.Among them,P.maackianus exhibited the highest root biomass in the sediment depth range of 0-10 cm,surpassing 85%.M.spicatum and H.verticillata followed with root biomasses of 65%and 56%,respectively.Therefore,it is recommended to collect sediment at a depth of 10 cm for outdoor experiments and field investigations involving these three submerged macrophytes.(2)A comprehensive analysis of literature,outdoor experiments,and field investigations revealed that H.verticillata exhibited adaptability to a wide range of sediment conditions.The species could survive within sediment organic matter content ranging from 0.16%to 38.36%,sediment density from 1.08 to 2.06 g/cm~3,sediment water content from 19.80%to 78.14%,and silt and clay percentage from11.62%to 99.89%.Optimal sediment conditions for the growth of H.verticillata were determined to be within the ranges of 0.64%to 21.84%for organic matter content,1.07 to 2.06 g/cm3 for sediment density,25.32%to 73.80%for sediment water content,and 20.30%to 94.00%for silt and clay percentage.H.verticillata was found to successfully root within the ranges of 0.29%to 18.30%for organic matter content,1.16 to 2.06 g/cm~3for sediment density,19.80%to 72.17%for sediment water content,and 11.62%to 99.89%for silt and clay percentage.(3)A comprehensive analysis of literature,outdoor experiments,and field investigations revealed that P.maackianus exhibited adaptability to a wide range of sediment conditions.The species could survive within sediment organic matter content ranging from 0.80%to 13.33%,sediment density from 1.10 to 2.06 g/cm~3,sediment water content from 19.80%to 75.42%,and silt and clay percentage from11.62%to 99.89%.Optimal sediment conditions for the growth of P.maackianus were found to be within the ranges of 1.86%to 10.76%for organic matter content,1.08 to 1.82 g/cm~3for sediment density,25.28%to 77.22%for sediment water content,and 19.75%to 97.77%for silt and clay percentage.P.maackianus was observed to successfully root within the ranges of 1.44%to 10.84%for organic matter content,1.47 to 2.06 g/cm3 for sediment density,19.80%to 72.17%for sediment water content,and 11.62%to 99.89%for silt and clay percentage.(4)The summary of the literature,outdoor experiments,and field investigations demonstrated that M.spicatum displayed adaptability to a range of sediment conditions.The species could survive within sediment organic matter content ranging from 0.29%to 29.64%,sediment density from 1.05 to 1.65 g/cm~3,sediment water content from 25.20%to 76.94%,and silt and clay percentage from 34.26%to 94.21%.Optimal sediment conditions for the growth of M.spicatum were identified within the ranges of 0.41%to 26.33%for organic matter content,1.05 to 1.64 g/cm~3for sediment density,24.59%to 77.48%for sediment water content,and 30.27%to94.02%for silt and clay percentage.M.spicatum could successfully root within the ranges of 0.29%to 18.30%for organic matter content,1.16 to 1.64 g/cm~3for sediment density,and 24.59%to 61.87%for sediment water content.