Impact of fires on eutrophication in rivers (the Simmy River, the Bolon Nature Reserve)

Compared to research on eutrophication in lakes, our understanding of eutrophication in rivers remains extremely limited. This is especially true of the impact of fires, which have become much more frequent in recent decades. Since the risks of eutrophication in rivers as a result of fires increase, it is important to timely assess the impact of fires on the state of rivers draining fire-prone territories. The aim of the study is to select and evaluate the reliability of criteria for impact of fires on eutrophication in stream on the example of the Simmi River (Bolon Nature Reserve, Far East, Russia). The tasks of the work are to assess the fire-prone of the territory from remote sensing data and and to identify markers of the impact of fires on the Simmi River. The fire-prone of the river watershed was estimated by the fire repeatability. The in situ study dealt with river bottom sediments. The sampling was carried out in in three month and the third year after the fire. To assess the impact of fires on eutrophication in the Simmi River, we used the P content in bottom sediments as a marker of the nutrient loading. The obtained results indicate high fire-prone and repeatability of fires the river watershed. In the first months after the fire, the response of the river system is the sequestration of P soluble compounds as a result of the binding of phosphate ions to vivianite. Vivianite is formed on the surface of clay microaggregates, which are removed by the stream over time. In three years after fire, vivianite-clay microaggregates were not detected. Flushing in flow system tends to reduce the scale of the fire impact.