Impact of changing hydrology on nutrient uptake in high arctic rivers

Despite the importance of river nutrient retention in regulating downstream water quality and the potential alterations to nutrient fluxes associated with climate-induced changes in Arctic hydrology, current understanding of nutrient cycling in Arctic river systems is limited. This study adopted an experimental approach to quantify conceptual water source contributions (meltwater, groundwater), environmental conditions and uptake of NO3−, NH4+, PO43− and acetate at 12 headwater rivers in Svalbard and so determine the role of changing hydrology on nutrient uptake in these Arctic river systems. Most rivers exhibited low demand for NO3− and PO43−, but demand for NH4+ and acetate was more variable and in several rivers comparable with that measured in sub-Arctic regions. The proportion of meltwater contributing to river flow was not significantly related to nutrient uptake. However, NH4+ uptake was associated positively with algal biomass, water temperature and transient storage area, whereas acetate uptake was associated positively with more stable river channels. Mean demand for NH4+ increased when added with acetate, suggesting NH4+ retention may be facilitated by labile dissolved organic carbon availability in these rivers. Consequently, nutrient export from Arctic river systems could be influenced in future by changes in hydrological and environmental process interactions associated with forecasted climate warming.