Sediment accumulation and retention in the littoral zone of lakes

Submerged macrophyte beds provide a secondary realm of accumulation in lakes. Particles otherwise destined to reside in the deep-water profundal zone are intercepted by nearshore macrophyte communities that attenuate wave and current energy. The microenvironment found inside submerged macrophyte beds can be substantially more quiescent than that of the open-water, allowing for fine particles to be deposited out of the water column. Together with larger, eroded inorganic sediments and coarse organic particles, these materials comprise the sediments underlying macrophyte communities.Thirty-four littoral sites were sampled in Lake Memphremagog (Quebec-Vermont) to quantify the role of morphometry (littoral slope and site exposure) and macrophyte beds (mean biomass and biomass density) on the accumulation of sediments. An established historical marker, stable Pb, was used to date the sediments (approx. 110 years) and calculate rates of accumulation (SARs). Identifiable stable Pb profiles were obtained at two-thirds of the sites confirming the utility and robustness of littoral sediment core analysis. Multiple regression analyses showed that macrophyte parameters were the best predictors of SARs. Macrophyte mean biomass and biomass density were clearly most important in predicting the volume (total SAR) and organic content (organic SAR) of the sediments ($R sp2=0.57 rm to 0.76$, $P