Observed Changes in Springtime Nutrient Flux Budget along the Korean Peninsula (2012-2021): Roles of Streamflow and Nutrient

Abstract

Through precipitation, nutrients on the surface flow along the river and flow out to the coast. In order to effectively manage coastal water quality and ecosystem, it is essential to study the changes in terrestrial nutrient discharge to the coast through streamflow. However, research on long-term on estuarial or coastal water quality and river streamflow data remains limited particularly around the Korean Peninsula where long-term data for water quality and streamflow are available. Here, this study aimed to investigate changes in inland nutrient fluxes the coastal regions around the Korean Peninsula and the contribution of changes of streamflow and water quality. The overarching question of this study is to which extent can changes in nutrient flux discharge be contributed by changes in streamflow or nutrient concentrations? First, we used observational data of rivers during the spring months (March through May) to assess changes in the nutrient fluxes over 2012–2021, which were springtime TN, TP and Chlorophyll-a nutrient fluxes from the inland to the coastal regions of the surrounding Korean Peninsula. Second, we conducted analytically a simple decomposition analysis of the relative contribution of changes in streamflow and nutrient concentration to the changes of nutrient fluxes model. Results show that the change rate of annual spring nutrient (TN, TP, Chlorophyll-a) flux was more affected by streamflow flowrate (84, 51, 91%, respectively) than nutrient concentration (19, 48, 5%, respectively). In addition, the regional analysis of the nutrient flux on the Korean Peninsula (the western, northern, and eastern sides) showed the contribution of the western side was the largest to changes the total nutrient fluxes.This study emphasized the importance of hydrological linkage between the water and nutrient cycles through an analytical approach, highlighting the potential impacts of changes of nutrient fluxes on off-shore ecological communities and aquacultural productivities.