Does inflow of water river shape the nutrient content of lake sediments?

This study evaluated the influence of the Symsarna River on the spatial distribution of organic matter, Kjeldahl nitrogen (NK) and total phosphorus in the surface layer of bottom sediments. The analyzed site was Symsar Lake in the Olsztyn Lakeland (north-eastern Poland) and the inflows. The results of this study indicate that the lake’s morphology and inflowing streams were largely responsible for the variations in the nutrient content of bottom deposits in the flow-through Symsar Lake. The NK content was significantly correlated with the lake’s depth, whereas TOC levels were determined mainly by the location in the lake. The surface layers of bottom sediments in Lake Symsar were characterized by an average organic matter content of 171.2 g kg-1 and near-neutral pH (6.78-7.77). The average contents of components in the analyzed sediments were determined at 62.01 gTOC kg-1 d.m., 6.08 gNK kg-1d.m. and 2.18 gTP kg-1d.m. Converted to fresh mass, the above contents expressed per square meter of the lake’s sediment reached 3.95 kgTOC m-2 f.m., 0.42 kgNK m-2 f.m. and 0.18 kgTP m-2 f.m. In turn, the average concentrations of components in sediments from the streams, likewise per square meter, equalled 12.4 gTOC m-2 d.m., 0.93 gNK m-2 d.m. and 0.9 gTP m-2 d.m. The highest contents of the analyzed components were observed in bottom sediments near the outflow of a river from the lake and in the lake’s region intersected by the river. The Symsarna River was responsible for the transport of and variability in the deposition of mineral fractions, and for the nutrient accumulation in the surface layer of bottom sediments. A flow-through water body in a river-lake system can contribute to retention in periods when it exerts a negative impact on the trophic status of a lake. From a broader, ecological viewpoint, it can inhibit the transport of pollutants outside the catchment.