The Arctic Plant Aboveground Biomass Synthesis Dataset.

Plant biomass is a fundamental ecosystem attribute that is sensitive to rapid climatic changes occurring in the Arctic. Nevertheless, measuring plant biomass in the Arctic is logistically challenging and resource intensive. Lack of accessible field data hinders efforts to understand the amount, composition, distribution, and changes in plant biomass in these northern ecosystems.

Aquatic biomass is a major source to particulate organic matter export in large Arctic rivers.

Arctic rivers provide an integrated signature of the changing landscape and transmit signals of change to the ocean. Here, we use a decade of particulate organic matter (POM) compositional data to deconvolute multiple allochthonous and autochthonous pan-Arctic and watershed-specific sources. Constraints from carbon-to-nitrogen ratios (C:N), δC, and ΔC signatures reveal a large, hitherto overlooked contribution from aquatic biomass.

Multidecadal declines in particulate mercury and sediment export from Russian rivers in the pan-Arctic basin.

SignificanceRussian rivers are the predominant source of riverine mercury to the Arctic Ocean, where methylmercury biomagnifies to high levels in food webs. Pollution controls are thought to have decreased late-20th-century mercury loading to Arctic watersheds, but there are no published long-term observations on mercury in Russian rivers. Here, we present a unique hydrochemistry dataset to determine trends in Russian river particulate mercury concentrations and fluxes in recent decades.

Stream Dissolved Organic Matter in Permafrost Regions Shows Surprising Compositional Similarities but Negative Priming and Nutrient Effects.

Permafrost degradation is delivering bioavailable dissolved organic matter (DOM) and inorganic nutrients to surface water networks. While these permafrost subsidies represent a small portion of total fluvial DOM and nutrient fluxes, they could influence food webs and net ecosystem carbon balance via priming or nutrient effects that destabilize background DOM. We investigated how addition of biolabile carbon (acetate) and inorganic nutrients (nitrogen and phosphorus) affected DOM decomposition with 28-day incubations.

An Abrupt Aging of Dissolved Organic Carbon in Large Arctic Rivers.

Permafrost thaw in Arctic watersheds threatens to mobilize hitherto sequestered carbon. We examine the radiocarbon activity (FC) of dissolved organic carbon (DOC) in the northern Mackenzie River basin. From 2003-2017, DOC-FC signatures (1.

Mercury Export from Arctic Great Rivers.

Land-ocean linkages are strong across the circumpolar north, where the Arctic Ocean accounts for 1% of the global ocean volume and receives more than 10% of the global river discharge. Yet estimates of Arctic riverine mercury (Hg) export constrained from direct Hg measurements remain sparse. Here, we report results from a coordinated, year-round sampling program that focused on the six major Arctic rivers to establish a contemporary (2012-2017) benchmark of riverine Hg export.

Increasing Alkalinity Export from Large Russian Arctic Rivers.

Riverine carbonate alkalinity (HCO and CO) sourced from chemical weathering represents a significant sink for atmospheric CO. Alkalinity flux from Arctic rivers is partly determined by precipitation, permafrost extent, groundwater flow paths, and surface vegetation, all of which are changing under a warming climate. Here we show that over the past three and half decades, the export of alkalinity from the Yenisei and Ob' Rivers increased from 225 to 642 Geq yr (+185%) and from 201 to 470 Geq yr (+134%); an average rate of 11.

Temporal and Longitudinal Mercury Trends in Burbot (Lota lota) in the Russian Arctic.

Current understanding of mercury (Hg) dynamics in the Arctic is hampered by a lack of data in the Russian Arctic region, which comprises about half of the entire Arctic watershed. This study quantified temporal and longitudinal trends in total mercury (THg) concentrations in burbot (Lota lota) in eight rivers of the Russian Arctic between 1980 and 2001, encompassing an expanse of 118 degrees of longitude. Burbot THg concentrations declined by an average of 2.

Utilization of ancient permafrost carbon in headwaters of Arctic fluvial networks.

Northern high-latitude rivers are major conduits of carbon from land to coastal seas and the Arctic Ocean. Arctic warming is promoting terrestrial permafrost thaw and shifting hydrologic flowpaths, leading to fluvial mobilization of ancient carbon stores. Here we describe (14)C and (13)C characteristics of dissolved organic carbon from fluvial networks across the Kolyma River Basin (Siberia), and isotopic changes during bioincubation experiments.

Molecular mapping of sorbent selectivities with respect to isolation of Arctic dissolved organic matter as measured by Fourier transform mass spectrometry.

The objectives of this study were to identify molecular features characteristic to arctic DOM from the Kolyma River basin and to elucidate structural imprints induced by a choice of the sorption technique. To achieve this goal, DOM was isolated from the Kolyma River basin with a use of three nonionic sorbents: Amberlite XAD-8 resin, PPL- and C18 - SPE cartridges, and one anion exchanging resin-diethylaminoethyl (DEAE) -cellulose. The structural studies were conducted with a use of electrospray ionization Fourier Transform Ion Cyclotron Resonance (ESI FT-ICR) mass spectrometry and liquid state (1)H NMR spectroscopy.

Low and declining mercury in arctic Russian rivers.

Mercury (Hg) dynamics in the Arctic is receiving increasing attention, but further understanding is limited by a lack of studies in Russia, which encompasses the majority of the pan-Arctic watershed. This study reports Hg concentrations and trends in burbot (Lota lota) from the Lena and Mezen Rivers in the Russian Arctic, and assesses the extent to which they differ from those found in burbot in arctic rivers elsewhere. Mercury concentrations in burbot in the Lena and Mezen Rivers were found to be generally lower than in 23 other locations, most of which are in the Mackenzie River Basin (Canada).

Evidence for key enzymatic controls on metabolism of Arctic river organic matter.

Permafrost thaw in the Arctic driven by climate change is mobilizing ancient terrigenous organic carbon (OC) into fluvial networks. Understanding the controls on metabolism of this OC is imperative for assessing its role with respect to climate feedbacks. In this study, we examined the effect of inorganic nutrient supply and dissolved organic matter (DOM) composition on aquatic extracellular enzyme activities (EEAs) in waters draining the Kolyma River Basin (Siberia), including permafrost-derived OC.

Circumpolar synchrony in big river bacterioplankton.

Natural bacterial communities are extremely diverse and highly dynamic, but evidence is mounting that the compositions of these communities follow predictable temporal patterns. We investigated these patterns with a 3-year, circumpolar study of bacterioplankton communities in the six largest rivers of the pan-arctic watershed (Ob', Yenisey, Lena, Kolyma, Yukon, and Mackenzie), five of which are among Earth's 25 largest rivers. Communities in the six rivers shifted synchronously over time, correlating with seasonal shifts in hydrology and biogeochemistry and clustering into three groups: winter/spring, spring freshet, and summer/fall.

Measurements of Cd, Cu, Pb and Zn in the lower reaches of major Eurasian arctic rivers using trace metal clean techniques.

Concentrations of dissolved and particulate Cd, Cu, Pb and Zn were determined in samples collected in summer 1998 from the lower reaches of six major Eurasian arctic rivers: the Onega, Severnaya Dvina, Mezen, Pechora, Ob and Yenisey. These data comprise some of the earliest measurements of trace metals in Eurasian arctic rivers above the estuaries using recognized clean techniques. Significant (alpha = 0.

Trajectory shifts in the Arctic and subarctic freshwater cycle.

Manifold changes in the freshwater cycle of high-latitude lands and oceans have been reported in the past few years. A synthesis of these changes in freshwater sources and in ocean freshwater storage illustrates the complementary and synoptic temporal pattern and magnitude of these changes over the past 50 years. Increasing river discharge anomalies and excess net precipitation on the ocean contributed approximately 20,000 cubic kilometers of fresh water to the Arctic and high-latitude North Atlantic oceans from lows in the 1960s to highs in the 1990s.

Increasing river discharge to the Arctic Ocean.

Synthesis of river-monitoring data reveals that the average annual discharge of fresh water from the six largest Eurasian rivers to the Arctic Ocean increased by 7% from 1936 to 1999. The average annual rate of increase was 2.0 +/- 0.