| 1. |
- 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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| 2. |
- Alling, Vanja, 1978-, et al.
(författare)
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Tracing terrestrial organic matter by delta34S and delta13C signatures in a subarctic estuary
- 2008
-
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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| 3. |
- Humborg, Christoph, et al.
(författare)
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Nutrient variations in boreal and subarctic Swedish rivers : Landscape control of land–sea fluxes
- 2004
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Ingår i: Limnology and Oceanography. - 0024-3590 .- 1939-5590. ; 49:5, s. 1871-1883
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Tidskriftsartikel (refereegranskat)abstract
- We examined the hypothesis that the extent of vegetation cover governs the fluxes of nutrients from boreal and subarctic river catchments to the sea. Fluxes of total organic carbon (TOC) and dissolved inorganic nitrogen, phosphorus, and dissolved silicate (DIN, DIP, and DSi, respectively) are described from 19 river catchments and subcatchments (ranging in size from 34 to 40,000 km2) in northern Sweden with a detailed analysis of the rivers Lulea¨lven and Kalixa¨lven. Fluxes of TOC, DIP, and DSi increase by an order of magnitude with increasing proportion of forest and wetland area, whereas DIN did not follow this pattern but remained constantly low. Principal component analysis on landscape variables showed the importance of almost all land cover and soil type variables associated with vegetation, periglacial environment, soil and bedrock with slow weathering rates, boundary of upper tree line, and percentage of lake area. A cluster analysis of the principal components showed that the river systems could be separated into mountainous headwaters and forest and wetland catchments. This clustering was also valid in relation to river chemistry (TOC, DIP, and DSi) and was confirmed with a redundancy analysis, including river chemistry and principal components as environmental variables. The first axis explains 89% of the variance in river chemistry and almost 100% of the variance in the relation between river chemistry and landscape variables. These results suggest that vegetation change during interglacial periods is likely to have had a major effect on inputs of TOC, DIP, and DSi into the past ocean.
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| 4. |
- Rahm, Lars, 1948-
(författare)
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Oxygen consumption in the Baltic proper
- 1987
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Ingår i: Limnology and Oceanography. - 0024-3590 .- 1939-5590. ; 32:4, s. 973-978
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Tidskriftsartikel (refereegranskat)abstract
- Total oxygen consumption rate, averaged over 1957-1982, and its variations with salinity in the deep water of the Baltic proper are calculated by a system of diagnostic advection-diffusion equations in a "natural" coordinate frame of reference. Although the data set used is not ideal for a more thorough investigation of the sensitivity of the model, an oxygen budget is formulated. A gross consumption rate of 3 x 10-9 mol m-3 s-1 is obtained. Further, a total consumption of about 0.14 x 10-6 mol m-2 s-1 is found, which is equivalent to an annual carbon input of 10 g C m-2 yr-1.
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| 5. |
- Rahm, Lars, 1948-
(författare)
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The thermally forced circulation in a small, ice-covered lake
- 1985
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Ingår i: Limnology and Oceanography. - 0024-3590 .- 1939-5590. ; 30:5, s. 1122-1128
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Tidskriftsartikel (refereegranskat)abstract
- A simple, one-dimensional model of the stratification in a small, ice-covered lake is developed. It is shown that the heat flux from the sediments gives rise to a stable stratification and an organized circulation pattern. Data from a field study are compared with the predictions of the model. The good agreement found suggests that the buoyancy layer at the nonhorizontal boundaries is essential in modeling the thermal circulation in this type of lake.
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| 6. |
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