| 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. |
- Aho, Kelly S., et al.
(författare)
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Distinct concentration-discharge dynamics in temperate streams and rivers : CO2 exhibits chemostasis while CH4 exhibits source limitation due to temperature control
- 2021
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Ingår i: Limnology and Oceanography. - : John Wiley & Sons. - 0024-3590 .- 1939-5590. ; 66:10, s. 3656-3668
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Tidskriftsartikel (refereegranskat)abstract
- Streams and rivers are significant sources of carbon dioxide (CO2) and methane (CH4) to the atmosphere. However, the magnitudes of these fluxes are uncertain, in part, because dissolved greenhouse gases (GHGs) can exhibit high spatiotemporal variability. Concentration-discharge (C-Q) relationships are commonly used to describe temporal variability stemming from hydrologic controls on solute production and transport. This study assesses how the partial pressures of two GHGs—pCO2 and pCH4—vary across hydrologic conditions over 4 yr in eight nested streams and rivers, at both annual and seasonal timescales. Overall, the range of pCO2 was constrained, ranging from undersaturated to nine times oversaturated, while pCH4 was highly variable, ranging from 3 to 500 times oversaturated. We show that pCO2 exhibited chemostatic behavior (i.e., no change with Q), in part, due to carbonate buffering and seasonally specific storm responses. In contrast, we show that pCH4 generally exhibited source limitation (i.e., a negative relationship with Q), which we attribute to temperature-mediated production. However, pCH4 exhibited chemostasis in a wetland-draining stream, likely due to hydrologic connection to the CH4-rich wetland. These findings have implications for CO2 and CH4 fluxes, which are controlled by concentrations and gas transfer velocities. At high Q, enhanced gas transfer velocity acts on a relatively constant CO2 stock but on a diminishing CH4 stock. In other words, CO2 fluxes increase with Q, while CH4 fluxes are modulated by the divergent Q dynamics of gas transfer velocity and concentration.
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| 5. |
- Albert, Séréna, et al.
(författare)
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Influence of settling organic matter quantity and quality on benthic nitrogen cycling
- 2021
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Ingår i: Limnology and Oceanography. - : Wiley. - 1939-5590 .- 0024-3590. ; 66:5, s. 1882-1895
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Tidskriftsartikel (refereegranskat)abstract
- Coastal sediments are major contributors to global carbon (C) mineralization and nutrient cycling and are tightly linked to processes in the pelagic environment. In this study, we aimed to investigate the regulating potential of quantity and quality of planktonic organic matter (OM) deposition on benthic metabolism, with a particular focus on nitrogen (N) cycling processes. We simulated inputs of spring (C : N 10.9) and summer (C : N 5.6) plankton communities in high and low quantities to sediment cores, and followed oxygen consumption, nutrient fluxes as well as nitrate reduction rates, that is, denitrification and dissimilatory nitrate reduction to ammonium for 10 d. Our results demonstrate the primary importance of OM quality in determining the fate of organic N once it settles to the sediment surface. Settling of N-rich summer plankton material resulted in a ∼ twofold lower denitrification efficiency (40–56%) compared to N-poor spring plankton (88–115%). This indicates that N-rich plankton deposition favors recycling of inorganic nutrients to the water column over N-loss via denitrification. OM quantity was positively related to mineralization activity, but this neither directly affected N fluxes nor denitrification activity, highlighting the complex interplay between the OM quantity and quality in regulating N cycling. In light of these new findings, we support the use of simple qualitative indicators such as C : N ratio of OM to investigate how future changes in benthic-pelagic coupling might influence N budgets at the sediment–water interface.
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| 6. |
- 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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| 7. |
- Alling, Vanja, et al.
(författare)
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Tracing terrestrial organic matter by delta S-34 and delta C-13 signatures in a subarctic estuary
- 2008
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Ingår i: Limnology and Oceanography. - 0024-3590 .- 1939-5590. ; 53:6, s. 2594-2602
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Tidskriftsartikel (refereegranskat)abstract
- A key issue to understanding the transformations of terrestrial organic carbon in the ocean is to disentangle the latter from marine-produced organic matter. We applied a multiple stable isotope approach using delta S-34 and delta C-13 isotope signatures from estuarine dissolved organic matter (DOM), enabling us to constrain the contribution of terrestrial-derived DOM in an estuarine gradient of the northern Baltic Sea. The stable isotope signatures for dissolved organic sulfur (delta S-34(DOS)) have twice the range between terrestrial and marine end members compared to the stable isotope signatures for dissolved organic carbon (delta C-13(DOC)); hence, the share of terrestrial DOM in the total estuarine DOM can be calculated more precisely. DOM samples from the water column were collected using ultrafiltration on board the German RV Maria S Merian during a winter cruise, in the Bothnian Bay, Bothnian Sea, and Baltic proper. We calculated the terrestrial fraction of the estuarine DOC (DOCter) from both delta C-13(DOC) and delta S-34(DOS) signatures and applying fixed C: S ratios for riverine and marine end members to convert S isotope signatures into DOC concentrations. The delta S-34(DOS) signature of the riverine end member was +7.02 parts per thousand, and the mean signatures from Bothnian Bay, Bothnian Sea, and Baltic proper were +10.27, +12.51, and +13.67 parts per thousand, respectively, showing an increasing marine signal southwards (d34SDOS marine end member = 18.1 parts per thousand). These signatures indicate that 87%, 75%, and 67%, respectively, of the water column DOC is of terrestrial origin (DOCter) in these basins. Comparing the fractions of DOCter in each basin-that are still based on few winter values only-with the annual river input of DOC, it appears that the turnover time for DOCter in the Gulf of Bothnia is much shorter than the hydraulic turnover time, suggesting that high-latitude estuaries might be efficient sinks for DOCter.
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| 8. |
- Alling, Vanja, 1978-, et al.
(författare)
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Tracing terrestrial organic matter by delta34S and delta13C signatures in a subarctic estuary
- 2008
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Ingår i: Limnology and Oceanography. - : Wiley. - 0024-3590 .- 1939-5590. ; 53:6, s. 2594-2602
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Tidskriftsartikel (refereegranskat)abstract
- A key issue to understanding the transformations of terrestrial organic carbon in the ocean is to disentangle the latter from marine-produced organic matter. We applied a multiple stable isotope approach using 34S and 13C isotope signatures from estuarine dissolved organic matter (DOM), enabling us to constrain the contribution of terrestrial-derived DOM in an estuarine gradient of the northern Baltic Sea. The stable isotope signatures for dissolved organic sulfur (34SDOS) have twice the range between terrestrial and marine end members compared to the stable isotope signatures for dissolved organic carbon (13CDOC); hence, the share of terrestrial DOM in the total estuarine DOM can be calculated more precisely. DOM samples from the water column were collected using ultrafiltration on board the German RV Maria S Merian during a winter cruise, in the Bothnian Bay, Bothnian Sea, and Baltic proper. We calculated the terrestrial fraction of the estuarine DOC (DOCter) from both 13CDOC and 34SDOS signatures and applying fixed C: S ratios for riverine and marine end members to convert S isotope signatures into DOC concentrations. The 34SDOS signature of the riverine end member was +7.02‰, and the mean signatures from Bothnian Bay, Bothnian Sea, and Baltic proper were +10.27, +12.51, and +13.67‰, respectively, showing an increasing marine signal southwards (34SDOS marine end member 5 18.1‰). These signatures indicate that 87‰, 75‰, and 67‰, respectively, of the water column DOC is of terrestrial origin (DOCter) in these basins. Comparing the fractions of DOCter in each basin—that are still based on few winter values only—with the annual river input of DOC, it appears that the turnover time for DOCter in the Gulf of Bothnia is much shorter than the hydraulic turnover time, suggesting that high-latitude estuaries might be efficient sinks for DOCter.
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| 9. |
- Andersson, Björn, 1985, et al.
(författare)
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Nitrogen fixation in shallow-water sediments: Spatial distribution and controlling factors
- 2014
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Ingår i: Limnology and Oceanography. - : Wiley. - 0024-3590 .- 1939-5590. ; 59:6, s. 1932-1944
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Tidskriftsartikel (refereegranskat)abstract
- Nitrogenase activity (NA) in shallow-water (< 1 m) sediments was investigated at 60 randomly selected sites along a 150 km stretch on the brackish-water Swedish west coast, without targeting any specific type of sediments, such as microbial mats. Benthic nitrogen (N) fixation and diazotrophs (nifH genes) were found at all sites, regardless of the presence of cyanobacterial or microbial mats. The majority of sites showed N fixation rates between 0.03 and 1 mmol N m−2 d−1. These rates were similar to those of benthic denitrification previously measured in the area. Maximum rates up to 3.4 mmol N m−2 d−1 were measured. A structural equation model was used to investigate direct and indirect effects of biogeochemical and physical factors on NA. Number of nifH genes had the largest direct positive influence on NA, whereas increasing wave exposure had an indirect negative effect on NA through its influence on the diazotrophic abundance. Increased salinity, previously been shown to suppress NA in coastal waters, was found to directly stimulate benthic N fixation, likely by generating favorable conditions for diazotrophic sulfate-reducing bacteria. Our field data confirmed previously observed negative effects of dissolved inorganic nitrogen on NA, which have so far mainly been experimentally studied. Both NA rates and the number of nifH genes correlated positively with pore-water dissolved inorganic phosphorus concentrations. These findings show that the potential for N fixation in illuminated sediments can be considerable, stretching beyond cyanobacterial mats, being controlled by complex interactions between biotic and abiotic factors.
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| 10. |
- Angeler, David, et al.
(författare)
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Effects of trophic status, water level, and temperature on shallow lake metabolism and metabolic balance: A standardized pan-European mesocosm experiment
- 2019
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Ingår i: Limnology and Oceanography. - : Wiley. - 0024-3590 .- 1939-5590. ; 64, s. 616-631
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Tidskriftsartikel (refereegranskat)abstract
- Important drivers of gross primary production (GPP) and ecosystem respiration (ER) in lakes are temperature, nutrients, and light availability, which are predicted to be affected by climate change. Little is known about how these three factors jointly influence shallow lakes metabolism and metabolic status as net heterotrophic or autotrophic. We conducted a pan-European standardized mesocosm experiment covering a temperature gradient from Sweden to Greece to test the differential temperature sensitivity of GPP and ER at two nutrient levels (mesotrophic or eutrophic) crossed with two water levels (1 m and 2 m) to simulate different light regimes. The findings from our experiment were compared with predictions made according the metabolic theory of ecology (MTE). GPP and ER were significantly higher in eutrophic mesocosms than in mesotrophic ones, and in shallow mesocosms compared to deep ones, while nutrient status and depth did not interact. The estimated temperature gains for ER of similar to 0.62 eV were comparable with those predicted by MTE. Temperature sensitivity for GPP was slightly higher than expected similar to 0.54 eV, but when corrected for daylight length, it was more consistent with predictions from MTE similar to 0.31 eV. The threshold temperature for the switch from autotrophy to heterotrophy was lower under mesotrophic (similar to 11 degrees C) than eutrophic conditions (similar to 20 degrees C). Therefore, despite a lack of significant temperature-treatment interactions in driving metabolism, the mesocosm's nutrient level proved to be crucial for how much warming a system can tolerate before it switches from net autotrophy to net heterotrophy.
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