Abstract
Identifying the landscape and climate factors that control nutrient export by rivers in high latitude regions is one of the main challenges for understanding the Arctic Ocean response to ongoing climate change. This is especially true for Western Siberian rivers, which are responsible for a significant part of freshwater and solutes delivery to the Arctic Ocean and are draining vast permafrost-affected areas most vulnerable to thaw. Forty-nine small- and medium-sized rivers (10–100,000 km2) were sampled along a 1700 km long N–S transect including both permafrost-affected and permafrost-free zones of the Western Siberian Lowland (WSL) in June and August 2015. The N, P, dissolved organic and inorganic carbon (DOC and DIC, respectively), particular organic carbon (POC), Si, Ca, K, Fe, and Mn were analyzed to assess the role of environmental parameters, such as temperature, runoff, latitude, permafrost, bogs, lake, and forest coverage on nutrient concentration. The size of the watershed had no influence on nutrient concentrations in the rivers. Bogs and lakes retained nutrients whereas forests supplied P, Si, K, Ca, DIC, and Mn to rivers. The river water temperature was negatively correlated with Si and positively correlated with Fe in permafrost-free rivers. In permafrost-bearing rivers, the decrease in T northward was coupled with significant increases in PO4, Ptot, NH4, pH, DIC, Si, Ca, and Mn. North of the permafrost boundary (61° N), there was no difference in nutrient concentrations among permafrost zones (isolated, sporadic, discontinuous, and continuous). The climate warming in Western Siberia may lead to a permafrost boundary shift northward. Using a substituting space for time scenario, this may decrease or maintain the current levels of N, P, Si, K, Ca, DIC, and DOC concentrations in rivers of continuous permafrost zones compared to the present state. As a result, the export flux of nutrients by the small- and medium-sized rivers of the Western Siberian subarctic to the Arctic Ocean coastal zone may remain constant, or even decrease.
Highlights
IntroductionPrediction of the macro- and micro-nutrient export from the land to the ocean under various climate change scenarios is among the major scientific challenges of aquatic biogeochemistry [1,2,3,4,5]
Prediction of the macro- and micro-nutrient export from the land to the ocean under various climate change scenarios is among the major scientific challenges of aquatic biogeochemistry [1,2,3,4,5].This is true for high latitude regions, which exhibit large variation in soil properties, plant communities, and the distribution of aquatic systems
Considering permafrost-free and permafrost-bearing watersheds separately, the correlation between nutrients and other solutes was mostly pronounced in rivers located south of the permafrost boundary (Table S2 of the Supplementary Information)
Summary
Prediction of the macro- and micro-nutrient export from the land to the ocean under various climate change scenarios is among the major scientific challenges of aquatic biogeochemistry [1,2,3,4,5] This is true for high latitude regions, which exhibit large variation in soil properties, plant communities, and the distribution of aquatic systems. In this regard, Siberian watersheds draining both peatlands and mountain regions are at the forefront of scientific efforts because of their important role in element (C and nutrients) delivery to the Arctic Ocean [6,7,8,9]. Increased transport of Corg , P, and N may significantly change primary productivity in riverine [15,16], estuarine [15,17,18], and ocean ecosystems [19], making predictions of climate change impact on Arctic terrestrial-aquatic ecosystems a major concern
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