Hydrodynamic-driven changes in the source and composition of sedimentary organic matter via grain size distribution in shallow lakes

Sediment organic matter (SOM) differs in composition and function in different size fractions in relation to material and energy flows. The hydrodynamic effects on a lake’s autochthonous (terrestrial plants) and allochthonous (microalgae, aquatic plants and bacteria) inputs and transformation, and the components of SOM are still far from clear. To elucidate the SOM composition as driven by the hydrodynamic conditions associated with sedimentary grain size, we performed an ecosystem-level investigation in the shallow lake Izunuma, Japan, measuring source-specific fatty acids and the current velocity. High organic matter concentrations occurred in the finer fractions. Bacteria were dominant in the <32 µm fraction, microalgae were mainly present in the <32 and 63-125 µm fractions, aquatic plants appeared to be evenly distributed in all size fractions and terrestrial plants mainly comprised the >125 µm fraction. Although the linear correlation between current velocity and sedimenta...