Empirical relationships between the element composition of aquatic macrophytes and their underlying sediments

A simple view of the role of rooted macrophytes in element cycling sees them as pumps retrieving buried elements from the sediment profile. To investigate the relationship between the elemental composition of plants and sediments, we analysed published data for 39 elements. The best general model explained 84% of the variance of the log of plant element concentration: LPE = - 0.81 + 0.90 Log Sediment Element (ug/g dry wt.) – 0.12 Sediment Organic Content (ug/g drt wt.) + 0.67 Atomic radius (nm) (r ² = 0.84; n = 39)This close relationship between the concentrations of an element in plant tissues and in the underlying sediment indicates that acquatic plants do not differ markedly in element composition from the sediments in which they grow. T-tests between mean residuals indicated that these aquatic plants do not discriminate between essential and nonessential elements. Model II regression analyses showed no difference between the slopes of the functional relationships for individual elements and that of the general model. When the elements were separated into three groups (alkali, transition and related metals, and halogens), Log Sediment Element accounted for 75–96% of the variation in LPE. Element physicochemical parameters were also significant independent variables explaining an additional 3–12% variation in LPE. The relative importance of the independent variables differed for the three groups of elements.Abbreviations AN Atomic number - AR Atomic radius (nm) - ELEC Electronegativity - IPD Ionization potential differential (eV: the difference in ionization potential between the used and next lower oxidation number) - IR Ionic radius (nm) - LPE Log plant element (ug/g dry wt.) - LSE Log sediment element (ug/g drt wt.) - OP Oxidation potential (eV) - ORG Sediment organic content (ug/g dry wt.)