| 1. |
- Kothawala, Dolly N., et al.
(författare)
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Selective loss and preservation of lake water dissolved organic matter fluorescenceduring long-term dark incubations
- 2012
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 433, s. 238-246
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Tidskriftsartikel (refereegranskat)abstract
- The biogeochemical processing of dissolved organic matter (DOM) in inland waters is inherently related to its molecular structure and ecological function. Controlled bioassays are a valuable tool to analyze these relationships, but are seldom conducted and compared at temporal scales that typically prevail in natural inland waters. Here we incubated water from six boreal lakes in the dark and examined changes to the initial fluorescence and absorbance after 3.5 years. We identified five fluorescence components with parallel factor (PARAFAC) analysis (CC, CM, CA, CX and CT) and found a consistent change in the relative intensity of two dominant PARAFAC components (increase in CA:CC, corresponding to Peak A:Peak C), commonly found in lake water, that represent terrestrially-derived DOM. Surprisingly, we only found minor changes to specific absorbance (SUVA), and did not find any changes to other spectral indexes including the fluorescence index, humification index and freshness index. By incorporating lakes spanning a wide range of initial total organic carbon concentrations (3.7 to 32.5 mg L− 1), water residence times, and spectral characteristics (e.g. SUVA 1.13 to 3.77 L·mg C− 1·m− 1), we found that the relative intensities of two humic-like peaks were the most revealing of changes to DOM structure during dark incubations. We also verified that inner filter effects were adequately corrected within the concentration range of incubated samples. Thus, the processing of DOM under dark conditions, including microbial decomposition and flocculation, may have a greater influence on the humic-like peaks, particularly CC (Peak C), with negligible changes to more commonly used spectral indexes.
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| 2. |
- Köhler, Birgit, et al.
(författare)
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Reactivity continuum of dissolved organic carbon decomposition in lake water
- 2012
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Ingår i: Journal of Geophysical Research. - 0148-0227 .- 2156-2202. ; 117, s. G01024-
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Tidskriftsartikel (refereegranskat)abstract
- We determined microbial decomposition of dissolved organic carbon (DOC) over 3.7-year long dark bioassays of six Swedish lake waters. The overall lost DOC fraction was similar in clearwater lakes (34.8 {plus minus} 2.4%) and brownwater lakes (37.8 {plus minus} 1.9%). Reactivity continuum modeling revealed that the most labile DOC fraction, degrading at rates >0.01 day-1, was larger in the clearwater (11.1 {plus minus} 1.2%) than the brownwater lakes (0.8 {plus minus} 0.1%). The initial apparent first-order decay coefficients k was fivefold larger in the clearwater (0.0043 {plus minus} 0.0012 day-1) than the brownwater lakes (0.0009 {plus minus} 0.0003 day-1). Over time, k decreased more steeply in the clearwater than the brownwater lakes, reaching the k of the brownwater lakes within five months. Finally, k averaged 0.0001 day-1 in both lake categories. In the brownwater lakes, CDOM absorption decayed with an initial k twice as large (0.0018 {plus minus} 0.0008 day-1) as that of DOC. The initial k was inversely correlated with initial specific UV absorption and colored dissolved organic matter (CDOM) absorption, and positively correlated with initial tryptophan-like fluorescence as proxy for autochthonous DOC. Exposure to simulated sunlight at the end of the incubations caused loss of color in the clearwater lakes and loss of DOC in the brownwater lakes, where subsequent mineralization was also stimulated. The DOC lost in the absence of photochemical processes fell below previously reported watershed-scale losses in Sweden by 25% at most. This suggests that a major part of the in situ DOC loss could potentially be attributed to dark reactions alone.
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| 3. |
- Premke, Katrin, et al.
(författare)
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Stable isotope analysis of benthic fauna and their food sources in boreal lakes
- 2010
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Ingår i: Journal of The North American Benthological Society. - : University of Chicago Press. - 0887-3593 .- 1937-237X. ; 29:4, s. 1339-1348
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Tidskriftsartikel (refereegranskat)abstract
- The origin of organic C supporting zoobenthic communities in 8 boreal lakes with different concentrations of dissolved organic C (DOC) was assessed by stable-isotope analysis. Profundal zoobenthos was depleted in C-13 compared to littoral zoobenthos, and this difference increased with decreasing DOC concentration. The delta C-13 of littoral zoobenthos suggested reliance on benthic algae, whereas depleted C-13 of profundal zoobenthos could be explained by contributions from allochthonous and autochthonous C sources. In deeper lakes, profundal zoobenthos diets also included C processed by methanotrophic bacteria. Littoral zoobenthos delta C-13 decreased with increasing DOC concentration in the lake water. Our results suggest that littoral benthic fauna are mainly supported by benthic algae in low-DOC lakes and by phytoplankton and allochthonous organic C in high-DOC lakes and that this difference is a result of light absorbance and energy supply by allochthonous organic C. Increasing allochthonous DOC inputs, as expected in a warmer and wetter climate, might reduce benthic algal production and alter the organic C base for benthic food webs in lake ecosystems.
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| 4. |
- Tranvik, Lena, et al.
(författare)
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Reglerad mångfald
- 2014
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Ingår i: Älvräddaren. - 0282-1354. ; 2014, s. 17-19
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Tidskriftsartikel (populärvet., debatt m.m.)abstract
- Ingress: Vattendrag med opåverkade flöden och stränder har stora förutsättningar för höga naturvärden. Vattnets dynamik skapar variation i både strandstruktur och bottensubstrat och därmed förutsättningar för variationsrika livsmiljöer.
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| 5. |
- von Wachenfeldt, Eddie
(författare)
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Trendövervakning av kvicksilver, Kadmium och cesium-137 i abborre : I Gosjön,Redsjösjön och Tansen i Gävleborgs län
- 2010
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Kvicksilver, kadmium och cesium-137 har analyserats i abborre från tre sjöar i Gävleborgslän. Avsaknaden av trend för koncentrationer av kvicksilver och kadmium var tydlig förutomi en sjö där koncentrationen av kadmium verkar minska. Cesium-137 visade en tydligtminskande trend i två av sjöarna. Samtliga ämnen som ingår i studien har en negativ påverkanpå både miljö och människor. Det är därför angeläget med en uppföljning under 2013-2014för att utröna om koncentrationerna av samtliga tre ämnen förändras över tid.
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