| 1. |
- Abrahamsson, K, et al.
(författare)
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Marine algae - a source of trichloroethylene and perchloroethylene
- 1995
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Ingår i: Limnology and Oceanography. - 0024-3590 .- 1939-5590. ; 40:7, s. 1321-1326
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Tidskriftsartikel (refereegranskat)abstract
- Our results show the natural production of two olefins, trichloroethylene and perchloroethylene, by various marine macroalgae and a microalga. We found significant difference in the ability of the algae to produce these compounds. The production rates for trichloroethylenevaried between 0.022 and 3,400 ng g-l fresh wt (FW)h-l and were generally higher than those for perchloroethylene(0.0026-8.2 ng g-l FW h-l). The two subtropicalalgae, Asparagopsis taxiformis and Falkenbergia hillebrandii,showed the highest formation rates. One axenicmarine red microalga, Porphyridium purpureum, was alsotested and it could also produce trichloroethylene and perchloroethylene.The measured rates suggest that the emissionof trichloroethylene and perchloroethylene from theoceans to the atmosphere may be of such a magnitude thatit cannot be neglected in the global atmospheric chlorinebudget.
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| 2. |
- Adrian, Rita, et al.
(författare)
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Lakes as sentinels of climate change
- 2009
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Ingår i: Limnology and Oceanography. - : Wiley. - 0024-3590 .- 1939-5590. ; 54:6(2), s. 2283-2297
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Tidskriftsartikel (refereegranskat)abstract
- While there is a general sense that lakes can act as sentinels of climate change, their efficacy has not been thoroughly analyzed. We identified the key response variables within a lake that act as indicators of the effects of climate change on both the lake and the catchment. These variables reflect a wide range of physical, chemical, and biological responses to climate. However, the efficacy of the different indicators is affected by regional response to climate change, characteristics of the catchment, and lake mixing regimes. Thus, particular indicators or combinations of indicators are more effective for different lake types and geographic regions. The extraction of climate signals can be further complicated by the influence of other environmental changes, such as eutrophication or acidification, and the equivalent reverse phenomena, in addition to other land-use influences. In many cases, however, confounding factors can be addressed through analytical tools such as detrending or filtering. Lakes are effective sentinels for climate change because they are sensitive to climate, respond rapidly to change, and integrate information about changes in the catchment.
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| 3. |
- Ahlgren, Joakim, et al.
(författare)
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Degradation of organic phosphorus compounds in anoxic Baltic Sea sediments : A P-31 nuclear magnetic resonance study
- 2006
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Ingår i: Limnology and Oceanography. - Uppsala Univ, Dept Ecol & Evolut, Evolutionary Biol Ctr, S-75236 Uppsala, Sweden. Uppsala Univ, Dept Chem, S-75124 Uppsala, Sweden. Univ So Denmark, Inst Biol, DK-5230 Odense, Denmark.. - 0024-3590 .- 1939-5590. ; 51:5, s. 2341-2348
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Tidskriftsartikel (refereegranskat)abstract
- The composition and abundance of phosphorus extracted by NaOH-ethylenediaminetetraacetic acid from anoxic Northwest Baltic Sea sediment was characterized and quantified using solution P-31 nuclear magnetic resonance. Extracts from sediment depths down to 55 cm, representing 85 yr of deposition, contained 18.5 g m(-2) orthophosphate. Orthophosphate monoesters, teichoic acid P, microbial P lipids, DNA P, and pyrophosphate corresponded to 6.7, 0.3, 1.1, 3.0, and 0.03 g P m(-2), respectively. The degradability of these compound groups was estimated by their decline in concentration with sediment depth. Pyrophosphate had the shortest half-life (3 yr), followed by microbial P lipids with a half-life of 5 yr, DNA P (8 yr), and orthophosphate monoesters (16 yr). No decline in concentration with sediment depth was observed for orthophosphate or teichoic acid P.
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| 4. |
- Allesson, Lina, et al.
(författare)
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The role of photomineralization for CO2 emissions in boreal lakes along a gradient of dissolved organic matter
- 2021
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Ingår i: Limnology and Oceanography. - : John Wiley & Sons. - 0024-3590 .- 1939-5590. ; 66:1, s. 158-170
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Tidskriftsartikel (refereegranskat)abstract
- Many boreal lakes are experiencing an increase in concentrations of terrestrially derived dissolved organic matter (DOM)-a process commonly labeled "browning." Browning affects microbial and photochemical mineralization of DOM, and causes increased light attenuation and hence reduced photosynthesis. Consequently, browning regulates lake heterotrophy and net CO2-efflux to the atmosphere. Climate and environmental change makes ecological forecasting and global carbon cycle modeling increasingly important. A proper understanding of the magnitude and relative contribution from CO2-generating processes for lakes ranging in dissolve organic carbon (DOC) concentrations is therefore crucial for constraining models and forecasts. Here, we aim to study the relative contribution of photomineralization to total CO(2)production in 70 Scandinavian lakes along an ecosystem gradient of DOC concentration. We combined spectral data from the lakes with regression estimates between optical parameters and wavelength specific photochemical reactivity to estimate rates of photochemical DOC mineralization. Further, we estimated total in-lake CO2-production and efflux from lake chemical and physical data. Photochemical mineralization corresponded on average to 9% +/- 1% of the total CO2-evasion, with the highest contribution in clear lakes. The calculated relative contribution of photochemical mineralization to total in-lake CO2-production was about 3% +/- 0.2% in all lakes. Although lakes differed substantially in color, depth-integrated photomineralization estimates were similar in all lakes, regardless of DOC concentrations. DOC concentrations were positively related to CO2-efflux and total in-lake CO2-production but negatively related to primary production. We conclude that enhanced rates of photochemical mineralization will be a minor contributor to increased heterotrophy under increased browning.
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| 5. |
- Attermeyer, Katrin, et al.
(författare)
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Potential terrestrial influence on transparent exopolymer particle (TEP) concentrations in boreal freshwaters
- 2019
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Ingår i: Journal of limnology. - : Wiley. - 1129-5767 .- 1723-8633. ; 64:6, s. 2455-2466
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Tidskriftsartikel (refereegranskat)abstract
- Transparent exopolymer particles (TEP) are ubiquitous in aquatic ecosystems and contribute, for example, to sedimentation of organic matter in oceans and freshwaters. Earlier studies indicate that the formation of TEP is related to the in situ activity of phytoplankton or bacteria. However, terrestrial sources of TEP and TEP precursors are usually not considered. We investigated TEP concentration and its driving factors in boreal freshwaters, hypoth- esizing that TEP and TEP precursors can enter freshwaters via terrestrial inputs. In a field survey, we measured TEP concentrations and other environmental factors across 30 aquatic ecosystems in Sweden. In a mesocosm experi- ment, we further investigated TEP dynamics over time after manipulating terrestrial organic matter input and light conditions. The TEP concentrations in boreal freshwaters ranged from 83 to 4940 μg Gum Xanthan equivalent L−1, which is comparable to other studies in freshwaters. The carbon fraction in TEP in the sampled boreal freshwaters is much higher than the phytoplanktonic carbon, in contrast to previous studies in northern temperate and Medi- terranean regions. Boreal TEP concentrations were mostly related to particulate organic carbon, dissolved organic carbon, and optical indices of terrestrial influence but less influenced by bacterial abundance, bacterial production, and chlorophyll a. Hence, our results do not support a major role of the phytoplankton community or aquatic bac- teria on TEP concentrations and dynamics. This suggests a strong external control of TEP concentrations in boreal freshwaters, which can in turn affect particle dynamics and sedimentation in the recipient aquatic ecosystem.
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| 6. |
- Balmonte, John Paul, et al.
(författare)
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A sea change in microbial enzymes : Heterogeneous latitudinal and depth-related gradients in bulk water and particle-associated enzymatic activities from 30 degrees S to 59 degrees N in the Pacific Ocean
- 2021
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Ingår i: Limnology and Oceanography. - : John Wiley & Sons. - 0024-3590 .- 1939-5590. ; 66:9, s. 3489-3507
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Tidskriftsartikel (refereegranskat)abstract
- Heterotrophic microbes initiate the degradation of high molecular weight organic matter using extracellular enzymes. Our understanding of differences in microbial enzymatic capabilities, especially among particle-associated taxa and in the deep ocean, is limited by a paucity of hydrolytic enzyme activity measurements. Here, we measured the activities of a broad range of hydrolytic enzymes (glucosidases, peptidases, polysaccharide hydrolases) in epipelagic to bathypelagic bulk water (nonsize-fractionated), and on particles (>= 3 mu m) along a 9800 km latitudinal transect from 30 degrees S in the South Pacific to 59 degrees N in the Bering Sea. Individual enzyme activities showed heterogeneous latitudinal and depth-related patterns, with varying biotic and abiotic correlates. With increasing latitude and decreasing temperature, lower laminarinase activities sharply contrasted with higher leucine aminopeptidase (leu-AMP) and chondroitin sulfate hydrolase activities in bulk water. Endopeptidases (chymotrypsins, trypsins) exhibited patchy spatial patterns, and their activities can exceed rates of the widely measured exopeptidase, leu-AMP. Compared to bulk water, particle-associated enzymatic profiles featured a greater relative importance of endopeptidases, as well as a broader spectrum of polysaccharide hydrolases in some locations, and latitudinal and depth-related trends that are likely consequences of varying particle fluxes. As water depth increased, enzymatic spectra on particles and in bulk water became narrower, and diverged more from one another. These distinct latitudinal and depth-related gradients of enzymatic activities underscore the biogeochemical consequences of emerging global patterns of microbial community structure and function, from surface to deep waters, and among particle-associated taxa.
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| 7. |
- Balmonte, John Paul, et al.
(författare)
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Sharp contrasts between freshwater and marine microbial enzymatic capabilities, community composition, and DOM pools in a NE Greenland fjord
- 2020
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Ingår i: Limnology and Oceanography. - : WILEY. - 0024-3590 .- 1939-5590. ; 65:1, s. 77-95
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Tidskriftsartikel (refereegranskat)abstract
- Increasing glacial discharge can lower salinity and alter organic matter (OM) supply in fjords, but assessing the biogeochemical effects of enhanced freshwater fluxes requires understanding of microbial interactions with OM across salinity gradients. Here, we examined microbial enzymatic capabilities-in bulk waters (nonsize-fractionated) and on particles (>= 1.6 mu m)-to hydrolyze common OM constituents (peptides, glucose, polysaccharides) along a freshwater-marine continuum within Tyrolerfjord-Young Sound. Bulk peptidase activities were up to 15-fold higher in the fjord than in glacial rivers, whereas bulk glucosidase activities in rivers were twofold greater, despite fourfold lower cell counts. Particle-associated glucosidase activities showed similar trends by salinity, but particle-associated peptidase activities were up to fivefold higher-or, for several peptidases, only detectable-in the fjord. Bulk polysaccharide hydrolase activities also exhibited freshwater-marine contrasts: xylan hydrolysis rates were fivefold higher in rivers, while chondroitin hydrolysis rates were 30-fold greater in the fjord. Contrasting enzymatic patterns paralleled variations in bacterial community structure, with most robust compositional shifts in river-to-fjord transitions, signifying a taxonomic and genetic basis for functional differences in freshwater and marine waters. However, distinct dissolved organic matter (DOM) pools across the salinity gradient, as well as a positive relationship between several enzymatic activities and DOM compounds, indicate that DOM supply exerts a more proximate control on microbial activities. Thus, differing microbial enzymatic capabilities, community structure, and DOM composition-interwoven with salinity and water mass origins-suggest that increased meltwater may alter OM retention and processing in fjords, changing the pool of OM supplied to coastal Arctic microbial communities.
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| 8. |
- Bastviken, David, et al.
(författare)
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Degradation of dissolved organic matter in oxic and anoxic lake water
- 2004
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Ingår i: Limnology and Oceanography. - : John Wiley & Sons. - 0024-3590 .- 1939-5590. ; 49:1, s. 109–116-
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Tidskriftsartikel (refereegranskat)abstract
- Decades of conflicting results have fueled a debate about how O-2 affects organic matter (OM) degradation and carbon cycling. In a laboratory study, using both OM taken directly from a humic lake and chemically isolated fulvic acid, we monitored the mineralization of dissolved OM in freshwater under purely oxic and anoxic conditions, under oxic then anoxic conditions, and under anoxic then oxic conditions, for 426 d. Between 5% and 24% of the initial OM was mineralized, with most extensive mineralization occurring under purely oxic and anoxic-oxic conditions. A sequential change in the O-2 regime did not result in greater overall degradation, but initially anoxic conditions favored subsequent oxic mineralization. A substantially greater fraction of the OM was degraded than in previous shorter studies, with as much as 50% of the total OM degradation occurring after 147 d into the experiment. Three fractions of the degradable OM were identified: OM degraded only under oxic conditions (68-78%), OM degraded more rapidly under anoxic conditions than under oxic conditions (16-18%), and OM degraded at equal rates under both oxic and anoxic conditions (6-14%). The degradation patterns of natural dissolved OM from a humic lake and chemically isolated fulvic acid were very similar, which indicates a similar level of bioavailability. The difference between anoxic and oxic degradation was greater in our long-term studies than in previous short-term experiments, which indicates that the oxic and anoxic degradation potentials vary with increasing overall OM recalcitrance and that similar oxic and anoxic degradation rates can be expected in short-term experiments in which <30% of the long-term degradable OM is allowed to decompose.
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| 9. |
- Beier, Sara, et al.
(författare)
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Uncoupling of chitinase activity and uptake of hydrolyses products in freshwater bacterioplankton
- 2011
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Ingår i: Limnology and Oceanography. - : Wiley. - 0024-3590 .- 1939-5590. ; 56:4, s. 1179-1188
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Tidskriftsartikel (refereegranskat)abstract
- We investigated to what extent chitinolytic bacteria subsidize bacterial populations that do not produce chitinolytic enzymes but still use the products of chitin hydrolysis. Applying single-cell techniques to untreated and chitin-enriched lake water, we show that the number of planktonic cells taking up chitin hydrolysis products by far exceeds the number of cells expressing chitinases. Flavobacteria, Actinobacteria, and specifically members of the abundant and ubiquitous freshwater Ac1 cluster of the Actinobacteria, increased in abundance and were enriched in response to the chitin amendment. Flavobacteria were frequently observed in dense clusters on chitin particles, suggesting that they are actively involved in the hydrolysis and solubilization of chitin. In contrast, Actinobacteria were exclusively planktonic. We propose that planktonic Actinobacteria contain commensals specialized in the uptake of small hydrolysis products without expressing or possibly even possessing the machinery for chitin hydrolysis. More research is needed to assess the importance of such "cheater'' substrate acquisition strategies in the turnover and degradation of polymeric organic matter in aquatic ecosystems.
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| 10. |
- Bertilsson, Stefan, et al.
(författare)
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Non-cyanobacterial diazotrophs dominate nitrogen-fixing communities in permafrost thaw ponds
- 2020
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Ingår i: Limnology and Oceanography. - : Wiley. - 0024-3590 .- 1939-5590. ; 65, s. S180-S193
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Tidskriftsartikel (refereegranskat)abstract
- There is a growing concern about the implications of accelerated thawing of permafrost for regional biogeochemical cycling of carbon and other bioreactive elements. One such element of concern is nitrogen, and in this study, we investigated the diversity and biogeography of potential diazotrophs within a series of thaw ponds representing different ontogenetic stages in pond development. Using metagenomic sequence data from subarctic thaw ponds, we identified an array of nitrogenase genes across the ponds. The iron-only nitrogenase gene (anfH) was positively correlated with sulfate, while there was no correlation with methane despite previous findings that organisms carrying anfH can simultaneously participate in nitrogen fixation and methanogenesis. Sulfate is known to inhibit microbial uptake of molybdate, an element essential for the activity of the nifH (molybdenum-iron) nitrogenase and this may explain the high potential for nitrogen fixation utilizing anfH in sulfate-rich ponds. NifH was particularly abundant in the hypolimnion of the deeper and older ponds, with Deltaproteobacteria and Chlorobi as the putative dominant diazotrophs. In the epilimnetic waters, nifH composition was more variable, with various Gammaproteobacteria as abundant representatives, while cyanobacterial diazotrophs were scarce. Interestingly, nifH gene abundance was significantly positively correlated with in situ methane concentration. Based on genome-resolved metagenomics, we hypothesize that diazotrophs and methanogens engage in syntrophic interactions in anoxic waters, possibly via propionate oxidation or (in Geobacter) by interspecies electron transfer. Our results also suggest that nitrogen fixers may supply bioreactive nitrogen compounds to the thaw pond communities, thereby enhancing growth and activity of methanogens.
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