Phosphorus sorption experiments and the potential for internal phosphorus loading in littoral areas of a stratified lake

The exchange of phosphorus (P) during the resuspension of sediments into shallow (oxic) waters of deep stratified lakes is regulated by equilibrium dynamics. In this study, we compared the P-sorption characteristics of sediments from 17 shallow and deep littoral sites in an oligo-mesotrophic lake. Zero Equilibrium P Concentration (EPC0) ranged from 0.2 to 5 μg P L−1. EPC0 did not vary with sediment characteristics, but increased with increasing sediment-to-water ratios (SWR). Buffering capacity also increased with increasing SWR up to 1 g L−1, at which point P concentrations were buffered almost perfectly. Therefore, internal P loading in littoral areas may depend primarily on the intensity and duration of sediment resuspension instead of sediment composition, and is expected to be spatially and temporally patchy. Maximum P-sorption capacity (Smax) varied with chemical composition of the sediments, but was generally low, indicating a limited capacity of littoral sediments to retain external inputs of P.