| 1. |
- Bishop, K., et al.
(författare)
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Aqua Incognita: the unknown headwaters
- 2008
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Ingår i: Hydological Processes. - : Wiley. - 0885-6087 .- 1099-1085. ; 22, s. 1239–1242-
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Tidskriftsartikel (refereegranskat)abstract
- Running water comprises just over one millionth of the world’s water. The importance of those streams and rivers as a resource for human welfare and biodiversity, however, is far out of proportion to that minuscule fraction. This explains why protecting running waters (the flow regimes, water quality and biota) is such a vital concern for society. Yet for all the focus and concern, how much do we actually know about these running waters, and the lotic habitat they comprise?
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| 2. |
- Köhler, S.J., et al.
(författare)
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Climate's control of intra-annual and interannual variability of total organic carbon concentration and flux in two contrasting boreal landscape elements
- 2008
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Ingår i: Journal of Geophysical Research - Biogeosciences. - : American Geophysical Union (AGU). - 2169-8953 .- 2169-8961. ; 113:G3
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Tidskriftsartikel (refereegranskat)abstract
- [1] Large spatial and temporal variations in stream total organic carbon (TOC) concentration and export occurred during an 11-year observation period (1993-2003) in a boreal headwater catchment. TOC flux and concentration patterns from mire- and forest-dominated subcatchments differed ( mean annual flux 8.2 g m(-2)a(-1) versus 5.8 g m(-2) a(-1)). Temporal variations in stream TOC concentrations in both landscape types were primarily driven by variations in streamflow, with the mire stream generally diluting by half with increased runoff during spring flood and TOC from the forested landscape increasing during runoff peaks irrespective of season. Average TOC concentration in the mire stream in the snow-free season increased with increased seasonal precipitation from around 20 to 40 mg L-1 but then dropped to around 35 mg L-1 during very wet years. Average snow-free season TOC concentration at the forested site remained stable when summer precipitation was below average but then increased from 10 to around 25 mg L-1 during exceptionally wet years. For both the forested subcatchment and the whole catchment, TOC concentrations increased during the warm summer months during wet years, but no such increase occurred during dry years. Interannual variations in TOC flux were primarily driven by variations during the snow-free period. Wet years decreased the relative TOC export from the mire and favored the relative export of TOC from areas dominated by forest, an observation that also held true on a larger scale when similar landscape types were considered. Predicted climate change in rainfall and temperature patterns will affect the amount and character of TOC exported downstream from boreal landscapes with a mix of forest and mire.
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| 4. |
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| 5. |
- Serrano, Ignacio, et al.
(författare)
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Thresholds for survival of brown trout during the spring flood acid pulse in streams high in dissolved organic carbon
- 2008
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Ingår i: Transactions of the American Fisheries Society. ; 137, s. 1363-1377
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Tidskriftsartikel (refereegranskat)abstract
- The survival of brown trout Salmo trutta embryos and first-year juveniles was studied using in situ bioassays during the snowmelt-driven spring flood in 12 streams in northern Sweden. Unlike in most previous studies on the impact of acidity on brown trout, the streams in this study were high in dissolved organic carbon (DOC), and as a result organic acids play a primary role in controlling pH. During the spring flood period DOC concentrations increased strongly in most streams and, in combination with dilution of acid-neutralizing capacity, resulted in a decrease in pH and an increase in total and inorganic monomeric aluminum. High mortality of brown trout juveniles occurred during the spring flood and was best correlated to the high H+ concentration. No toxic effect could be directly attributed to measured inorganic aluminum concentrations. An empirical model to predict juvenile brown trout mortality in DOC-rich streams was developed, and based on these predictions a critical chemical threshold of pH 4.8–5.4 is proposed for first-year juveniles. There was high embryo and yolk sac fry survival during the spring flood, even at sites with pH as low as 4.0, suggesting that the pH threshold in DOC-rich waters is lower than the previously established threshold for low-DOC systems. We discuss the complex role that DOC has in humic-rich surface waters, where it both causes a pH decrease and protects against aluminum toxicity in fish. The results suggest that first-year juveniles are likely to be the stage most vulnerable to the effects of episodic pH depression associated with the snowmelt period in northern boreal systems. This results from asynchrony in the seasonality of the spring flood acid pulse and the seasonality of trout embryo development, which is slow in cold northern waters.
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| 6. |
- Temnerud, Johan, et al.
(författare)
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Can the distribution of headwater stream chemistry be predicted from downstream observations?
- 2010
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Ingår i: Hydrological Processes. - : Wiley. - 0885-6087 .- 1099-1085. ; 24:16, s. 2269-2276
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Tidskriftsartikel (refereegranskat)abstract
- Small streams with catchment areas <2 km(2) make up the majority of all stream length and are of great ecological importance. Surveys of first and second order streams reveal great spatial and temporal variability in the water chemistry of these headwaters, but their assessment presents a serious challenge since systematic, representative data are usually only collected in larger streams and rivers. Using low flow synoptic survey data from seven mesoscale Swedish catchments, this study tests the hypothesis that downstream monitoring data can be used to predict key features of the distribution of chemistry in headwater streams [median and interquartile range (IQR)]. Three ecologically relevant analytes were tested: pH, acid neutralizing capacity (ANC) and total organic carbon (TOC). For all seven catchments, the outlets (36-127 km(2)) were considerably less acid with lower TOC than the median of the headwaters (<2 km(2), N = 19-45). Among catchments, headwater median and IQR were positively correlated with the value at the outlet, for all three analytes. A univariate general linear model (GLM) was used to predict the headwater chemistry distribution for each catchment from its outlet chemistry, using the relationship established with the other six catchments. Headwater median pH and IQR of ANC were well predicted by a single downstream sample [median adj. R-2 similar to 0.7, normalized root mean squared error (NRMSE) <0.7]. Other response variables were not as well predicted, with median adj. R-2 ranging from 0.08 to 0.48, and NRMSE up to 1.1. A minority of models were significant at alpha = 0.05, in part due to the limited availability of catchments with such extensive survey data. However, the clear trends observed suggest that with additional model development, downstream chemistry could ultimately provide a valuable tool for characterizing the range of chemistry in the contributing headwaters. Copyright (C) 2010 John Wiley & Sons, Ltd.
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| 7. |
- Ågren, Annelie, et al.
(författare)
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Importance of seasonality and small streams for the landscape regulation of dissolved organic carbon export
- 2007
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Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 112, s. Art. No. G03003-
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Tidskriftsartikel (refereegranskat)abstract
- The regulation of the spatial and seasonal variation in terrestrial dissolved organic carbon (DOC) exports was studied in a 68 km2 boreal stream system in northern Sweden. A total of 1213 DOC samples were collected in 15 subcatchments over a 3 year period (2003–2005). The mean annual DOC exports from the 15 subcatchments (0.03–21.72 km2) ranged from 14.8 to 99.1 kg ha−1 yr−1. Many catchment characteristics determined the spatial variation in DOC exports. The relative importance of the different catchment characteristics varied greatly between seasons because of differing hydrological conditions. During winter base flow the spatial variation was linked to patterns in wetland coverage. During snowmelt in spring the spatial variation was connected to characteristics describing size and location, i.e., median stream size, silty sediment distribution, stream order, altitude, and proportion of catchment above highest postglacial coastline (HC). During the snow-free season the spatial variation in DOC exports was regulated by the amount of wetlands and forests, particularly forests made up of Norway spruce (Picea abies). Median stream size also influenced the exports during this season. A striking result in this study was the effect of size implying that small headwaters may be the largest contributor to the terrestrial DOC export, per unit area.
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