Recent changes in nitrate and dissolved organic carbon export from the upper Kuparuk River, North Slope, Alaska

McClelland, J. W.; Stieglitz, Marc; Pan, Feifei; Holmes, Robert M.; Peterson, Bruce J.

doi:10.1029/2006jg000371

Cited by 120 publications

(119 citation statements)

References 75 publications

(89 reference statements)

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“…These are not significantly different (p = 5.01; ANCOVA) from slope and y-intercept values of ?14.1 and ?458 in 1980 (p \ 0.0001;Peterson et al 1986). These findings are consistent with the analysis of McClelland et al (2007), who showed that, although DOC export from the Kuparuk watershed decreased in the 1990s, this was largely attributable to lower spring discharge rather than a change in discharge-specific concentrations.…”

Section: Changes In C and N Flux In The Kuparuk Riversupporting

confidence: 82%

Seasonal and hydrologic drivers of dissolved organic matter and nutrients in the upper Kuparuk River, Alaskan Arctic

et al. 2010

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As the planet warms, widespread changes in Arctic hydrology and biogeochemistry have been documented and these changes are expected to accelerate in the future. Improved understanding of the behavior of water-borne constituents in Arctic rivers with varying hydrologic conditions, including seasonal variations in discharge-concentration relationships, will improve our ability to anticipate future changes in biogeochemical budgets due to changing hydrology. We studied the relationship between seasonal water discharge and dissolved organic carbon and nitrogen (DOC and DON) and nutrient concentrations in the upper Kuparuk River, Arctic Alaska. Fluxes of most constituents were highest during initial snowmelt runoff in spring, indicating that this historically under-studied period contributes significantly to total annual export. In particular, the initial snowmelt period (the stream is completely frozen during the winter) accounted for upwards of 35% of total export of DOC and DON estimated for the entire study period. DOC and DON concentrations were positively correlated with discharge whereas nitrate (NO 3 -) and silicate were negatively correlated with discharge throughout the study. However, discharge-specific DOC and DON concentrations (i.e. concentrations compared at the same discharge level) decreased over the summer whereas discharge-specific concentrations of NO 3 -and silicate increased. Soluble reactive phosphorus (SRP) and ammonium (NH 4 ? ) were negatively correlated with discharge during the spring thaw, but were less predictable with respect to discharge thereafter. These data provide valuable information on how Arctic watershed biogeochemistry will be affected by future changes in temperature, snowfall, and rainfall in the Arctic. In particular, our results add to a growing body of research showing that nutrient export per unit of stream discharge, particularly NO 3 -, is increasing in the Arctic.

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Section: Changes In C and N Flux In The Kuparuk Riversupporting

confidence: 82%

Seasonal and hydrologic drivers of dissolved organic matter and nutrients in the upper Kuparuk River, Alaskan Arctic

et al. 2010

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“…We interpret this change in DIC to be a result of an increased contribution of deeper groundwater, like those indicated by the detailed generic simulations of Frampton et al (2011) of permafrost thawing effects on flow and flow pathways under long-term climate change, rather than to changes in external inputs (e.g., Sjöberg et al, 2013). There is not a concomitant decrease in DOC as has been observed from several studies from other permafrost influenced watersheds (Striegl et al 2005;Walvoord and Striegl, 2007;McClelland et al, 2007). Such a decrease has been attributed to increase in hydrological residence time and microbial breakdown of DOC that would otherwise be released to streams (Striegl et al, 2005).…”

Section: The Role Of Shifting Flow Pathways For Dic and Doc Concentramentioning

confidence: 63%

Catchment-scale dissolved carbon concentrations and export estimates across six subarctic streams in northern Sweden

et al. 2014

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Abstract. Climatic change is currently enhancing permafrost thawing and the flow of water through the landscape in subarctic and arctic catchments, with major consequences for the carbon export to aquatic ecosystems. We studied stream water carbon export in several tundra-dominated catchments in northern Sweden. There were clear seasonal differences in both dissolved organic carbon (DOC) and dissolved inorganic carbon (DIC) concentrations. The highest DOC concentrations occurred during the spring freshet while the highest DIC concentrations were always observed during winter baseflow conditions for the six catchments considered in this study. Long-term trends for the period 1982 to 2010 for one of the streams showed that DIC concentrations has increased by 9 % during the 28 yr of measurement while no clear trend was found for DOC. Similar increasing trends were also found for conductivity, Ca and Mg. When trends were discretized into individual months, we found a significant linear increase in DIC concentrations with time for September, November and December. In these subarctic catchments, the annual mass of C exported as DIC was in the same order of magnitude as DOC; the average proportion of DIC to the total dissolved C exported was 61 % for the six streams. Furthermore, there was a direct relationship between total runoff and annual dissolved carbon fluxes for these six catchments. These relationships were more prevalent for annual DIC exports than annual DOC exports in this region. Our results also highlight that both DOC and DIC can be important in highlatitude ecosystems. This is particularly relevant in environments where thawing permafrost and changes to subsurface ice due to global warming can influence stream water fluxes of C. The large proportion of stream water DIC flux also has implications on regional C budgets and needs to be considered in order to understand climate-induced feedback mechanisms across the landscape.

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“…Slumping of permafrost soils into Alaskan streams increases their inorganic and organic concentrations (Bowden et al, 2008), but phosphorus adsorption onto clays may decrease SRP concentrations in some mineral permafrost environments (Breton et al, 2009). Nitrate export from the Kuparuk River catchment on the Alaska North Slope increased 5-fold between the late 1970s and early 2000s and may have been related to permafrost soil and vegetation effects (McClelland et al, 2007). These processes may also operate in the peatland permafrost sites studied here.…”

Section: Nutrient Enrichmentmentioning

confidence: 81%

Bacterial production in subarctic peatland lakes enriched by thawing permafrost

et al. 2016

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Abstract. Peatlands extend over vast areas of the northern landscape. Within some of these areas, lakes and ponds are changing in size as a result of permafrost thawing and erosion, resulting in mobilization of the carbon-rich peatland soils. Our aims in the present study were to characterize the particle, carbon and nutrient regime of a set of thermokarst (thaw) lakes and their adjacent peatland permafrost soils in a rapidly degrading landscape in subarctic Québec, Canada, and by way of fluorescence microscopy, flow cytometry, production measurements and an in situ enrichment experiment, determine the bacterial characteristics of these waters relative to other thaw lakes and rock-basin lakes in the region. The soil active layer in a degrading palsa (peatland permafrost mound) adjacent to one of the lakes contained an elevated carbon content (51 % of dry weight), high C : N ratios (17 : 1 by mass), and large stocks of other elements including N (3 % of dry weight), Fe (0.6 %), S (0.5 %), Ca (0.5 %) and P (0.05 %). Two permafrost cores were obtained to a depth of 2.77 m in the palsa, and computerized tomography scans of the cores confirmed that they contained high concentrations (> 80 %) of ice. Upon thawing, the cores released nitrate and dissolved organic carbon (from all core depths sampled), and soluble reactive phosphorus (from bottom depths), at concentrations well above those in the adjacent lake waters. The active layer soil showed a range of particle sizes with a peak at 229 µm, and this was similar to the distribution of particles in the upper permafrost cores. The particle spectrum for the lake water overlapped with those for the soil, but extended to larger (surface water) or finer (bottom water) particles. On average, more than 50 % of the bacterial cells and bacterial production was associated with particles > 3 µm. This relatively low contribution of free-living cells (operationally defined as the < 1 µm fraction) to bacterial production was a general feature of all of the northern lakes sampled, including other thaw lakes and shallow rock-basin lakes (average ± SE of 25 ± 6 %). However, a distinguishing feature of the peatland thaw lakes was significantly higher bacterial specific growth rates, which averaged 4 to 7 times higher values than in the other lake types. The in situ enrichment experiment showed no difference between organic carbon or phosphorus enrichment treatments at day 5 relative to the control, however there was an apparent increase in bacterial growth rates between days 1 and 5 in the soil and the carbon plus phosphorus enrichments. Collectively these results indicate that particles, nutrients and carbon are released by degrading permafrost peatland soils into their associated thermokarst lakes, creating favorable conditions for production by particle-based as well as free-living aquatic bacterial communities. The reduced bacterial concentrations despite high cellular growth rates imply that there is control of their population size by loss-related factors such as grazing and vira...

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Recent changes in nitrate and dissolved organic carbon export from the upper Kuparuk River, North Slope, Alaska

Cited by 120 publications

References 75 publications

Seasonal and hydrologic drivers of dissolved organic matter and nutrients in the upper Kuparuk River, Alaskan Arctic

Seasonal and hydrologic drivers of dissolved organic matter and nutrients in the upper Kuparuk River, Alaskan Arctic

Catchment-scale dissolved carbon concentrations and export estimates across six subarctic streams in northern Sweden

Bacterial production in subarctic peatland lakes enriched by thawing permafrost

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