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  • 1
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    In:  Supplement to: Lammers, Richard B; Shiklomanov, Alexander I; Vörösmarty, Charles J; Fekete, Balázs M; Peterson, Bruce J (2001): Assessment of contemporary Arctic river runoff based on observational discharge records. Journal of Geophysical Research: Atmospheres, 106(D4), 3321-3334, https://doi.org/10.1029/2000JD900444
    Publication Date: 2020-01-17
    Description: We describe the contemporary hydrography of the pan-Arctic land area draining into the Arctic Ocean, northern Bering Sea, and Hudson Bay on the basis of observational records of river discharge and computed runoff. The Regional Arctic Hydrographic Network data set, R-ArcticNET, is presented, which is based on 3754 recording stations drawn from Russian, Canadian, European, and U.S. archives. R-ArcticNET represents the single largest data compendium of observed discharge in the Arctic. Approximately 73% of the nonglaciated area of the pan-Arctic is monitored by at least one river discharge gage giving a mean gage density of 168 gages per 106 km2. Average annual runoff is 212 mm yr−1 with approximately 60% of the river discharge occurring from April to July. Gridded runoff surfaces are generated for the gaged portion of the pan-Arctic region to investigate global change signals. Siberia and Alaska showed increases in winter runoff during the 1980s relative to the 1960s and 1970s during annual and seasonal periods. These changes are consistent with observations of change in the climatology of the region. Western Canada experienced decreased spring and summer runoff.
    Type: Dataset
    Format: application/octet-stream, 369.0 MBytes
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  • 2
    ISSN: 1435-0629
    Keywords: Key words: nitrogen cycling; macroinvertebrates; stream; nitrogen-15; tracer; model; detritivory; Coweeta Hydrologic Laboratory (North Carolina).
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: ABSTRACT Cycling of nitrogen (N) is commonly studied in aquatic ecosystems; however, most studies examine only parts of the N cycle, such as budgets, N uptake lengths, or oxidative transformations. To integrate conceptually and experimentally several aspects of the N cycle in a stream, we combined a N-cycling model and a tracer addition of nitrogen-15 (15N) to Hugh White Creek, a second-order forested mountain stream in North Carolina (USA). We calibrated a steady-state box model for N cycling in 5-m stream segments that included dissolved, detrital, and biotic compartments. This model was parameterized based on prior studies and used to predict the expected distribution of tracer 15N in all compartments through both time and distance downstream of the addition site. We tested the model results with a 23-day continuous addition of 15N-NH4 + to the stream. Deviations of field data from model predictions suggested areas in which we lacked understanding of the N cycle. Downstream distribution of 15N in epilithon and moss matched model predictions, indicating that our prior estimations of N uptake rates were correct. Leaves and fine detritus contained less label than predicted by the model, yet their consumers had both higher δ15N than predicted and higher δ15N than the detritus itself, suggesting selective assimilation of microbial N from ingested detritus. Splitting fine benthic organic N (FBON) into a microbial and recalcitrant pool gave better predictions of FBON and seston δ15N values relative to field data, yet overestimated invertebrate consumer δ15N possibly because our estimates of the fraction of invertebrate N derived from microbes were too high. We predicted that much of the labeled N would move downstream via FBON suspension and transport. We found that most of the 15N remained near the addition site 33 days after the addition was stopped, suggesting that the stream is highly retentive of particulate N.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-5117
    Keywords: streams ; arctic ; tundra ; epilithon ; photosynthesis ; respiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Photosynthesis and respiration by the epilithic community on cobble in an arctic tundra stream, were estimated from oxygen production and consumption in short-term (4–12 h), light and dark, chamber incubations. Chlorophyll a was estimated at the end of each incubation by quantitatively removing the epilithon from the cobble. Fertilization of the river with phosphate alone moderately increased epilithic chlorophyll a, photosynthesis, and respiration. Fertilization with ammonium sulfate and phosphate, together, greatly increased each of these variables. Generally, under both control and fertilized conditions, epilithic chlorophyll a concentrations (mg m−2), photosynthesis, and respiration (mg O2 m−2, h−1) were higher in pools than in riffles. Under all conditions, the P/R ratio was consistent at ∼ 1.8 to 2.0. The vigor of epilithic algae in riffles, estimated from assimilation coefficients (mg O2 [mg Chl a]−1 h−1) was greater than the vigor of epilithic algae in pools. However, due to the greater accumulation of epilithic chlorophyll a in pools, total production (and respiration) in pools exceeded that in riffles. The epilithic community removed both ammonium and nitrate from water in chambers. Epilithic material, scoured by high discharge in response to storm events and suspended in the water column, removed ammonium and may have increased nitrate concentrations in bulk river water. However, these changes were small compared to the changes exerted by attached epilithon.
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  • 4
    ISSN: 1573-5117
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Stream discharge and fine suspended sediment load were determined for the upper Kuparuk River, a clear-water tundra stream and tributary of the main Kuparuk River of the North Slope of Alaska. From 75 observations over 3 years we found a range of flows of 0.3 to 28.3 m3 sec−1 and a range of sediment loads of 0.4 to 35 mg liter−1. Specific water yields of 15.7, 29.7 and 33.2 cm and summer specific sediment yields of 0.5, 1.1 and 3.5 metric tons km−2 were estimated for the period 20 May through freeze-up in 1978, 1979 and 1980, respectively. The fine suspended sediment concentrations and yields for the upper Kuparuk River were less than those in many temperate streams but similar to those reported for small rivers draining the taiga of the Mackenzie Valley lowlands in subarctic Canada.
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  • 5
    ISSN: 1573-5117
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nitrogen and phosphorus concentrations were measured from May to August 1980 in the upper Kuparuk River, a tundra stream on the North Slope of Alaska. Mean values for nitrogen were 10.8 µg N 1−1 for ammonium, 21.4 µg N 1−1 for nitrate plus nitrite and 248 µg N 1−1 for dissolved organic nitrogen. Mean values for phosphorus were 8.1 µg P 1−1 for total dissolved phosphorus and 4.7 µg P 1−1 for fine particulate phosphorus. Nitrate concentrations were inversely correlated with flow whereas particulate phosphorus concentrations increased during high flows. Export of nitrogen and phosphorus from the watershed during 1980 was estimated to be 4.69, 3.25 and 91 kg km−2 yr−1 for NO3-N, NH4-N and DON-N, respectively, and 2.86 and 3.03 kg km−2 yr−1 for TDP-P and PP-P. Both the relative concentrations of N and P and the relative amounts exported suggest that phosphorus is in short supply but both nutrients are present in low concentrations comparable to those found previously in tundra ponds at Point Barrow, Alaska.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 54 (1977), S. 113-127 
    ISSN: 1573-5117
    Keywords: primary production ; phosphorus ; zooplankton phosphorus release ; phosphorus loading ; 14C uptake
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The average annual rate of carbon production in Cayuga Lake, New York, was determined by 14C uptake and by a phosphorus supply method. The rate of phosphorus supply was converted to units of carbon production using observed sestonic C : P ratios. The two methods gave good agreement and annual carbon production was estimated to be 130 gC m−2 yr−1.
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  • 7
    ISSN: 1573-515X
    Keywords: 34S ; sulfate reduction ; sulfide oxidation ; SO4 addition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract We investigated the effects of sulfate concentration on sulfate reduction and net S storage in lake sediments using34S as a tracer. The water overlying intact sediment cores from the hypolimnion of Mares Pond, MA, was replaced with two Na2 34SO4 solutions at either ambient (70 μM) or elevated (260 μM) sulfate concentrations. The δ34S of the added sulfate was 4974 ‰. Over two months, the net sulfate reduction rate in the ambient sulfate treatment was zero, while the net rate for the high sulfate treatment was 140 μmoles/m2/d. The water overlying the cores was kept under oxic conditions and the sediment received no fresh carbon inputs, thus the net rate reported may underestimate the in situ rate. Gross sulfate reduction rates calculated by isotope dilution were approximately 350 μmoles/m2/d for both treatments. While the calculation of gross sulfate reduction rates in intact sediment cores can be complicated by differential diffusion of34S and32S, isotopic fractionation, and the possible formation of ester sulfates, we believe these effects to be small. The results suggest that sulfate reduction is not strongly sulfate-limited in Mares Pond. The difference in net sulfate reduction rates between treatments resulted from a decrease in sulfide oxidation and suggests the importance of reoxidation in controlling net S storage in lake sediments. In both treatments the CRS and organic S fractions were measurably labelled in34S. Below the sediment surface, the CRS fraction was the more heavily labelled storage product for reduced sulfides.
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  • 8
    Publication Date: 2017-11-22
    Description: Author Posting. © American Geophysical Union, 2006. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 33 (2006): L06715, doi:10.1029/2006GL025753.
    Description: Several recent publications have documented changes in river discharge from arctic and subarctic watersheds. Comparison of these findings, however, has been hampered by differences in time periods and methods of analysis. Here we compare changes in discharge from different regions of the pan-arctic watershed using identical time periods and analytical methods. Discharge to the Arctic Ocean increased by 5.6 km3/y/y during 1964-2000, the net result of a large increase from Eurasia moderated by a small decrease from North America. In contrast, discharge to Hudson/James/Ungava Bays decreased by 2.5 km3/y/y during 1964-2000. While this evaluation identifies an overall increase in discharge (~120 km3/y greater discharge at the end of the time period as compared to the beginning for Hudson/James/Unvaga Bays and the Arctic Ocean combined), the contrasting regional trends also highlight the need to understand the consequences of adding/removing freshwater from particular regions of the arctic and subarctic oceans.
    Description: This work was supported by the Arctic System Science Program of the National Science Foundation (NSF-OPP-0229302, NSF-OPP-0230211, NSF-OPP-0519840) and by the National Oceanic and Atmospheric Administration (NA17RJ2612).
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 9
    Publication Date: 2017-11-22
    Description: Author Posting. © American Geophysical Union, 2005. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 110 (2005): G02013, doi:10.1029/2005JG000031.
    Description: Concentrations of dissolved organic carbon (DOC) and δ18O values have been determined following sampling of runoff from a number of major arctic rivers, including the Ob, Yenisey, Lena, Kolyma, Mackenzie and Yukon in 2003-2004. These data are considered in conjunction with marine data for DOC, δ18O values, nutrients, salinity, and fluorometric indicators of DOC that were obtained as part of the Shelf-Basin Interactions program at the continental shelf-basin boundary of the Chukchi and Beaufort Seas. These marine data indicate that the freshwater component is most likely derived from regional sources, such as the Mackenzie, the Bering Strait inflow and possibly eastern Siberian rivers, including the Kolyma, or the Lena but not rivers further west in the Eurasian arctic. Contributions of freshwater from melted sea ice to marine surface waters appeared to be insignificant over annual cycles compared to runoff, although on a seasonal basis, freshwater from melted sea ice was locally dominant following a major sea-ice retreat into the Canada Basin in 2002. DOC concentrations were correlated with the runoff fraction, with an apparent meteoric water DOC concentration of 174 ± 1 μM (standard error). This concentration is lower than the flow-weighted concentrations measured at river mouths of the five largest Arctic rivers (358 to 917 μM), indicating that removal of terrigenous DOC during transport through estuaries, shelves and in the deep basin. DOC data indicate that flow-weighted concentrations in the two largest North American arctic rivers, the Yukon (625μM) and the Mackenzie (382 μM), are lower than in the three largest Eurasian arctic rivers, the Ob (825 μM), the Yenesey (858 μM) and the Lena (917 μM). A fluorometric indicator of chromophoric dissolved organic matter (CDOM) that has provided estimates of terrigenous DOC concentrations in the Eurasian Arctic was not correlated with DOC concentrations in the Amerasian marine waters studied, except below the upper Arctic Ocean halocline. Nutrient distributions and concentrations as well as derived nutrient ratios suggest the CDOM fluorometer may be responding to the release of chromophoric materials from continental shelf sediments. Shipboard incubation experiments with undisturbed sediment cores indicate that continental shelf sediments on the Bering and Chukchi Sea shelves are likely to be a net source of DOC to the Arctic Ocean.
    Description: The PARTNERS and SBI projects have been supported by the Office of Polar Programs of the U.S. National Science Foundation.
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 10
    Publication Date: 2017-01-04
    Description: Author Posting. © Ecological Society of America, 2009. This article is posted here by permission of Ecological Society of America for personal use, not for redistribution. The definitive version was published in Ecology 90 (2009): 2535-2546, doi:10.1890/08-1051.1.
    Description: We compared processing and fate of dissolved NO3− in two New England salt marsh ecosystems, one receiving natural flood tide concentrations of 1–4 μmol NO3−/L and the other receiving experimentally fertilized flood tides containing 70–100 μmol NO3−/L. We conducted simultaneous 15NO3− (isotope) tracer additions from 23 to 28 July 2005 in the reference (8.4 ha) and fertilized (12.4 ha) systems to compare N dynamics and fate. Two full tidal cycles were intensively studied during the paired tracer additions. Resulting mass balances showed that essentially 100% (0.48–0.61 mol NO3-N·ha−1·h−1) of incoming NO3− was assimilated, dissimilated, sorbed, or sedimented (processed) within a few hours in the reference system when NO3− concentrations were 1.3–1.8 μmol/L. In contrast, only 50–60% of incoming NO3− was processed in the fertilized system when NO3− concentrations were 84–96 μmol/L; the remainder was exported in ebb tidewater. Gross NO3− processing was 40 times higher in the fertilized system at 19.34–24.67 mol NO3-N·ha−1·h−1. Dissimilatory nitrate reduction to ammonium was evident in both systems during the first 48 h of the tracer additions but 〈1% of incoming 15NO3− was exported as 15NH4+. Nitrification rates calculated by 15NO3− dilution were 6.05 and 4.46 mol·ha−1·h−1 in the fertilized system but could not be accurately calculated in the reference system due to rapid (〈4 h) NO3− turnover. Over the five-day paired tracer addition, sediments sequestered a small fraction of incoming NO3−, although the efficiency of sequestration was 3.8% in the reference system and 0.7% in the fertilized system. Gross sediment N sequestration rates were similar at 13.5 and 12.6 mol·ha−1·d−1, respectively. Macrophyte NO3− uptake efficiency, based on tracer incorporation in aboveground tissues, was considerably higher in the reference system (16.8%) than the fertilized system (2.6%), although bulk uptake of NO3− by plants was lower in the reference system (1.75 mol NO3−·ha−1·d−1) than the fertilized system (10 mol NO3−·ha−1·d−1). Nitrogen processing efficiency decreased with NO3− load in all pools, suggesting that the nutrient processing capacity of the marsh ecosystem was exceeded in the fertilized marsh.
    Description: This work was funded by National Science Foundation Grant DEB 0213767 and OCE 9726921.
    Keywords: Biogeochemistry ; Eutrophication ; New England ; USA ; Nitrogen processing efficiency ; Salt marsh ; Stable isotopes
    Repository Name: Woods Hole Open Access Server
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