Seasonal Variations of Nutrient and Organic Carbon Concentrations in the Kamchatka and Avacha Rivers, Kamchatka Peninsula, in 2023

Abstract: In 2023, during the main phases of the water regime, four expeditions were conducted to collect water samples from sources to mouths in the Kamchatka and Avacha rivers, which flow into the Kamchatka and Avacha bays of Eastern Kamchatka, respectively. In the Kamchatka River, seasonal extremes were established in the concentrations and fluxes with river flow of mineral and organic phosphorus, as well as organic carbon during the snowmelt period in the river valley and in the highlands (May–June), which was less pronounced for the Avacha River. The annual fluxes with the runoff of the Kamchatka and Avacha rivers were, respectively, 4565 and 289 t/year for P_tot, 9526 and 2006 t/year for N_tot, 60 485 and 3992 t/year for DOC. The sources and fluxes of nutrients in the catchments of the studied rivers and the potential responses of aquatic ecosystems in the receiving basins in connection with volcanism, including the eruption of the Shiveluch volcano that occurred on April 11, 2023, are discussed.