scholarly journals Isotope fractionation between dissolved and suspended particulate Fe in the oxic and anoxic water column of the Baltic Sea

2013 ◽  
Vol 10 (1) ◽  
pp. 233-245 ◽  
Author(s):  
M. Staubwasser ◽  
R. Schoenberg ◽  
F. von Blanckenburg ◽  
S. Krüger ◽  
C. Pohl
Keyword(s):  
Baltic Sea ◽  
Water Column ◽  
Isotope Composition ◽  
Open Water ◽  
Deep Basin ◽  
Strong Concentration ◽  
Suspended Particulate ◽  
Oxidative Precipitation ◽  
The Difference ◽  
The Baltic

Abstract. Fe isotope ratios and concentrations of dissolved Fe (Fedis, < 0.45 μm) and of suspended particulate Fe (FeSPM) were analyzed from a depth profile through the anoxic Eastern Gotland Basin water column, Baltic Sea. Results show a sharp gradient in δ56Fedis across the ferruginous layer with δ56Fedis = −0.4‰ in the euxinic deep basin and δ56Fedis = &amp;plus;0.3‰ in the oxic upper water column. The isotopic gradient overlaps with a strong concentration gradient of Fedis, a concentration maximum in FeSPM and lower δ56FeSPM values than δ56Fedis. These features indicate preferential loss of light Fe isotopes from solution to suspended iron-oxyhydroxides (FeIOH) during typical oxidative precipitation across the redox interface. The sign of the overall fractionation, Δ56FeIOH-Fe(II)(aq) < 0‰, is in contrast to similar, mostly non-marine redox environments, where Δ56FeIOH-Fe(II)(aq) > 0‰. The difference appears to be the result of isotope exchange dominated by reaction kinetics in the marine water column, rather than equilibrium fractionation generally inferred for oxidative Fe precipitation elsewhere. High residual δ56Fedis immediately above the oxic–ferruginous interface and throughout the oxic water column suggests that any potential dissolved Fe export from marine reducing waters into the oxic open water column is enriched in the heavy isotopes. In the deep, mildly euxinic water column above the level of Fe sulfide saturation, a decreasing δ56FeSPM trend with depth and a generally low δ56Fedis are comparable to trends generally observed in marine anoxic sediment profiles where microbial reductive Fe dissolution occurs. The isotope composition of the redox-cycled Fe inventory in anoxic marine basins mainly reflects the balance between external fluxes, driving the composition towards crustal δ56Fe values, and intensity of internal recycling, driving δ56Fe towards negative values.

scholarly journals Isotope fractionation between dissolved and suspended particulate Fe in the oxic and anoxic water column of the Baltic Sea

2012 ◽  
Vol 9 (4) ◽  
pp. 4793-4817
Author(s):  
M. Staubwasser ◽  
R. Schoenberg ◽  
F. von Blanckenburg ◽  
S. Krüger ◽  
C. Pohl
Keyword(s):  
Baltic Sea ◽  
Water Column ◽  
Open Water ◽  
Deep Basin ◽  
Strong Concentration ◽  
Suspended Particulate ◽  
Concentration Maximum ◽  
Oxidative Precipitation ◽  
The Difference ◽  
The Baltic

Abstract. Fe isotope ratios and concentrations of dissolved Fe (Fedis, < 0.45 μm) and of suspended particulate Fe (FeSPM) from a depth profile in the Eastern Gotland Basin, Baltic Sea, show a sharp gradient in δ56Fedis across the suboxic interface with δ56Fedis = −0.4 ‰ in the euxinic deep basin and δ56Fedis = +0.3 ‰ in the oxic upper water column. The isotopic gradient overlaps with a strong concentration gradient of Fedis, a concentration maximum in FeSPM and lower δ56FeSPM values than δ56Fedis. These features indicate preferential loss of light Fe isotopes into suspended iron-oxyhydroxides (FeIOH) during typical oxidative precipitation across the redox interface in the marine environment. The sign of the fractionation, Δ56FeFe_IOH–Fe(II)(aq) < 0 ‰, is in contrast to similar, mostly non-marine redox environments, where Δ56FeFe_IOH–Fe(II)(aq) > 0 ‰. The difference appears to be the result of isotope exchange dominated by reaction kinetics in the marine water column, rather than equilibrium fractionation generally inferred for oxidative Fe precipitation elsewhere. High residual δ56Fedis immediately above the suboxic interface and throughout the oxic water column suggest that any potential Fe export from reducing waters or sediments into the open water column is enriched in the heavy isotopes. Within the suboxic to euxinic deep basin the decreasing δ56FeSPM trend with depth and a generally low δ56Fedis are comparable to trends in marine anoxic sediment profiles indicative of microbial reductive Fe dissolution. This confirms supply of dissolved Fe to the euxinic water column mainly from reductive dissolution of settling particles.

The stable tungsten isotope composition of sapropels and manganese-rich sediments from the Baltic Sea

2022 ◽  
Vol 578 ◽  
pp. 117303
Author(s):  
Florian Kurzweil ◽  
Olaf Dellwig ◽  
Martin Wille ◽  
Ronny Schoenberg ◽  
Helge W. Arz ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Isotope Composition ◽  
The Baltic Sea ◽  
The Baltic

scholarly journals Bacteriohopanepolyols record stratification, nitrogen fixation and other biogeochemical perturbations in Holocene sediments of the central Baltic Sea

2013 ◽  
Vol 10 (4) ◽  
pp. 2725-2735 ◽  
Author(s):  
M. Blumenberg ◽  
C. Berndmeyer ◽  
M. Moros ◽  
M. Muschalla ◽  
O. Schmale ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Water Column ◽  
Stable Stratification ◽  
The Baltic Sea ◽  
Allochthonous Input ◽  
The North ◽  
Water Column Stratification ◽  
Gotland Deep ◽  
History Of ◽  
The Baltic

Abstract. The Baltic Sea, one of the world's largest brackish-marine basins, established after deglaciation of Scandinavia about 17 000 to 15 000 yr ago. In the changeable history of the Baltic Sea, the initial freshwater system was connected to the North Sea about 8000 yr ago and the modern brackish-marine setting (Littorina Sea) was established. Today, a relatively stable stratification has developed in the water column of the deep basins due to salinity differences. Stratification is only occasionally interrupted by mixing events, and it controls nutrient availability and growth of specifically adapted microorganisms and algae. We studied bacteriohopanepolyols (BHPs), lipids of specific bacterial groups, in a sediment core from the central Baltic Sea (Gotland Deep) and found considerable differences between the distinct stages of the Baltic Sea's history. Some individual BHP structures indicate contributions from as yet unknown redoxcline-specific bacteria (bacteriohopanetetrol isomer), methanotrophic bacteria (35-aminobacteriohopanetetrol), cyanobacteria (bacteriohopanetetrol cyclitol ether isomer) and from soil bacteria (adenosylhopane) through allochthonous input after the Littorina transgression, whereas the origin of other BHPs in the core has still to be identified. Notably high BHP abundances were observed in the deposits of the brackish-marine Littorina phase, particularly in laminated sediment layers. Because these sediments record periods of stable water column stratification, bacteria specifically adapted to these conditions may account for the high portions of BHPs. An additional and/or accompanying source may be nitrogen-fixing (cyano)bacteria, which is indicated by a positive correlation of BHP abundances with Corg and δ15N.

scholarly journals On contribution of horizontal and intra-layer convection to the formation of the Baltic Sea cold intermediate layer

2008 ◽  
Vol 5 (4) ◽  
pp. 581-623
Author(s):  
I. P. Chubarenko ◽  
N. Y. Demchenko
Keyword(s):  
Baltic Sea ◽  
Intermediate Layer ◽  
Heat Content ◽  
Field Measurements ◽  
Open Water ◽  
Early Spring ◽  
Cold Intermediate Layer ◽  
The Baltic Sea ◽  
The Baltic ◽  
Fast Increase

Abstract. Seasonal cascades down the coastal slopes and intra-layer convection are considered as the two mechanisms contributing to the Baltic Sea cold intermediate layer (CIL) formation. On the base of TS-diagrams, mean-annual and real-time temperature profiles, the CIL features are re-analyzed. The presence within the CIL of water with temperature below that of maximum density (Tmd) and that at the local surface allows tracing its formation. Field measurements are presented, showing specific features of denser water formation in marine environment. It is argued that such cascades formed during early spring heating (March–April) – before reaching the Tmd – are the source of the coldest waters of the CIL. Fast increase of the open water heat content during further spring heating indicates that horizontal exchange rather than direct solar heating is responsible for that. When the surface is covered with water, heated above the Tmd, the conditions within the CIL become favorable for intralayer convection due to the presence of waters of Tmd in intermediate layer, which can explain the observed increase of its salinity and deepening with time.

scholarly journals Hypoxia and nitrogen processing in the Baltic Sea water column

2012 ◽  
Vol 57 (1) ◽  
pp. 325-337 ◽  
Author(s):  
Susanna Hietanen ◽  
Helena Jäntti ◽  
Christo Buizert ◽  
Klaus Jürgens ◽  
Matthias Labrenz ◽  
...  
Keyword(s):  
Baltic Sea ◽  
Water Column ◽  
Sea Water ◽  
The Baltic Sea ◽  
The Baltic

scholarly journals Fractionation of iron species and iron isotopes in the Baltic Sea euphotic zone

2010 ◽  
Vol 7 (8) ◽  
pp. 2489-2508 ◽  
Author(s):  
J. Gelting ◽  
E. Breitbarth ◽  
B. Stolpe ◽  
M. Hassellöv ◽  
J. Ingri
Keyword(s):  
Baltic Sea ◽  
Isotope Composition ◽  
Salinity Gradient ◽  
Euphotic Zone ◽  
Early Spring ◽  
Strong Positive Correlation ◽  
The Baltic Sea ◽  
Gotland Deep ◽  
The Baltic ◽  
Bothnian Sea

Abstract. To indentify sources and transport mechanisms of iron in a coastal marine environment, we conducted measurements of the physiochemical speciation of Fe in the euphotic zone at three different locations in the Baltic Sea. In addition to sampling across a salinity gradient, we conducted this study over the spring and summer season. Moving from the riverine input characterized low salinity Bothnian Sea, via the Landsort Deep near Stockholm, towards the Gotland Deep in the Baltic Proper, total Fe concentrations averaged 114, 44, and 15 nM, respectively. At all three locations, a decrease in total Fe of 80–90% from early spring to summer was observed. Particulate Fe (PFe) was the dominating phase at all stations and accounted for 75–85% of the total Fe pool on average. The Fe isotope composition (δ 56Fe) of the PFe showed constant positive values in the Bothnian Sea surface waters (+0.08 to +0.20‰). Enrichment of heavy Fe in the Bothnian Sea PFe is possibly associated to input of aggregated land derived Fe-oxyhydroxides and oxidation of dissolved Fe(II). At the Landsort Deep the isotopic fractionation of PFe changed between −0.08‰ to +0.28‰ over the sampling period. The negative values in early spring indicate transport of PFe from the oxic-anoxic boundary at ∼80 m depth. The average colloidal iron fraction (CFe) showed decreasing concentrations along the salinity gradient; Bothnian Sea 15 nM; Landsort Deep 1 nM, and Gotland Deep 0.5 nM. Field Flow Fractionation data indicate that the main colloidal carrier phase for Fe in the Baltic Sea is a carbon-rich fulvic acid associated compound, likely of riverine origin. A strong positive correlation between PFe and chl-a indicates that cycling of suspended Fe is at least partially controlled by primary production. However, this relationship may not be dominated by active uptake of Fe into phytoplankton, but instead may reflect scavenging and removal of PFe during phytoplankton sedimentation.

Tracking the spatiotemporal variability of the oxic–anoxic interface in the Baltic Sea with broadband acoustics

2020 ◽  
Author(s):  
Elizabeth Weidner ◽  
Christian Stranne ◽  
Jonas Hentati Sundberg ◽  
Thomas C Weber ◽  
Larry Mayer ◽  
...  
Keyword(s):  
Dissolved Oxygen ◽  
Baltic Sea ◽  
Water Column ◽  
Acoustic Scattering ◽  
Spatiotemporal Variability ◽  
Coastal Zones ◽  
Anoxic Zone ◽  
The Baltic Sea ◽  
Impedance Contrast ◽  
The Baltic

Abstract Anoxic zones, regions of the water column completely devoid of dissolved oxygen, occur in open oceans and coastal zones worldwide. The Baltic Sea is characterized by strong salinity-driven stratification, maintained by occasional water inflows from the Danish Straights and freshwater input from rivers. Between inflow events, the stratification interface between surface and deep waters hinders mixing and ventilation of deep water; consequently, the bottom waters of large regions of the Baltic are anoxic. The onset of the anoxic zone is closely coincident with the depth of the halocline and, as a result, the interface between oxic and anoxic waters corresponds to a strong impedance contrast. Here, we track acoustic scattering from the impedance contrast utilizing a broadband split-beam echosounder in the Western Gotland Basin and link it to a dissolved oxygen level of 2 ml/l using ground truth stations. The broadband acoustic dataset provides the means to remotely observe the spatiotemporal variations in the oxic–anoxic interface, map out the extent of the anoxic zone with high resolution, and identify several mechanisms influencing the vertical distribution of oxygen in the water column. The method described here can be used to study other systems with applications in ongoing oceanographic monitoring programs.

scholarly journals Survival of reared and wild Atlantic salmon smolts: size matters more in bad years

2004 ◽  
Vol 61 (5) ◽  
pp. 782-787 ◽  
Author(s):  
I. Saloniemi ◽  
E. Jokikokko ◽  
I. Kallio-Nyberg ◽  
E. Jutila ◽  
P. Pasanen
Keyword(s):  
Survival Rate ◽  
Atlantic Salmon ◽  
Baltic Sea ◽  
Linear Models ◽  
River Mouth ◽  
High Survival ◽  
Lower Survival Rate ◽  
Explanatory Variables ◽  
The Difference ◽  
The Baltic

Abstract We compared the marine survival of Carlin-tagged wild and hatchery-reared Atlantic salmon smolts of the Simojoki river, northern Baltic Sea. All the reared and released smolts were the offspring of native spawners returning to the river. Reared smolts were adipose-fin-clipped and released from the hatchery several weeks before tagging. The wild and reared smolts were simultaneously caught and tagged at a smolt trap located at the Simojoki river mouth. The study was conducted in two years, 1991 and 1993, when post-smolt survival in the Baltic Sea was different. Tags were returned by fishermen and return rates were used to estimate the survival of the smolt groups. We applied generalized linear models with survival as response variable and the year, origin, and smolt size as explanatory variables. On average, wild smolts had a 4.5 times higher survival rate than reared fish of the same smolt size. The difference in observed tag recovery rates as such was only about twofold or less, as the larger size of the reared smolts compared with the wild ones compensated for their lower survival rate. The better survival of wild than reared smolts was more pronounced in the low-survival year (1993 smolt year class) than in the high-survival year (1991 smolt year class).

scholarly journals <I>nirS</I>-containing denitrifier communities in the water column and sediment of the Baltic Sea

2007 ◽  
Vol 4 (3) ◽  
pp. 255-268 ◽  
Author(s):  
S. Falk ◽  
M. Hannig ◽  
C. Gliesche ◽  
R. Wardenga ◽  
M. Köster ◽  
...  
Keyword(s):  
Phylogenetic Analysis ◽  
Baltic Sea ◽  
Water Column ◽  
Community Composition ◽  
Environmental Gradients ◽  
Marker Gene ◽  
The Baltic Sea ◽  
Marine Habitats ◽  
The Baltic ◽  
Denitrifier Communities

Abstract. The aim of this study was to compare structural differences in the nirS-type denitrifying microbial communities along the environmental gradients observed in the water column and coastal sediments of the Baltic Sea. To link community structure and environmental gradients, denitrifier communities were analyzed by terminal restriction fragment length polymorphism (T-RFLP) based on nirS as a functional marker gene for denitrification. nirS-type denitrifier community composition was further evaluated by phylogenetic analysis of nirS sequences from clone libraries. T-RFLP analysis indicated some overlap but also major differences between communities from the water column and the sediment. Shifts in community composition along the biogeochemical gradients were observed only in the water column while denitrifier communities were rather uniform within the upper 30 mm of the sediment. Specific terminal restriction fragments (T-RFs) indicative of the sulfidic zone suggest the presence of nitrate-reducing and sulfide-oxidizing microorganisms that were previously shown to be important at the suboxic-sulfidic interface in the water column of the Baltic Sea. Phylogenetic analysis of nirS genes from the Baltic Sea and of sequences from marine habitats all over the world indicated distinct denitrifier communities that grouped mostly according to their habitats. We suggest that these subgroups of denitrifiers had developed after selection through several factors, i.e. their habitats (water column or sediment), impact by prevalent environmental conditions and isolation by large geographic distances between habitats.

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