| 1. |
- Bernd, Schneider, et al.
(författare)
-
Biogeochemical cycles : Biological Oceanography of the Baltic Sea
- 2017
-
Ingår i: Springer. - Dordrecht : Springer. - 9789400706675 ; , s. 87-122
-
Bokkapitel (refereegranskat)abstract
- 1. The internal cycles of carbon, nitrogen and phosphorus in the Baltic Sea are, like in other seas, mainly controlled by biological production and degradation of organic matter (OM). 2. Biological activity also modulates the acid/base balance (pH), which is mainly a function of alkalinity and the total CO2 concentration. 3. Particulate organic matter (POM) produced in the photic zone sinks into deeper water layers and is deposited on the sediment surface, where it is mineralised. Mineralisation is a form of microbial oxidation and thus leads to oxygen depletion. Due to its semi-enclosed position and its bottom topography, large-scale oxygen depletion of deep bottoms is common in the Baltic Sea. 4. Under anoxic conditions, the burial of phosphorus bound to ferric oxide is inhibited and the availability of phosphate for incorporation in new OM production increases. 5. In stagnant waters, the oxic/anoxic interface may migrate from the sediment into the water column, forming a pelagic redoxcline. Such a redoxcline occurs in large areas of the Baltic Sea. 6. At oxygen concentrations close to zero, nitrate acts as an oxidant and is reduced to elemental nitrogen (denitrification). After the exhaustion of both oxygen and nitrate, OM is oxidised by sulphate, which is reduced to toxic hydrogen sulphide. 7. The final step in the mineralisation process is the microbial formation of methane in deeper sediment layers, which reflects the internal oxidation/reduction of OM. 8. A significant fraction of the organic carbon, nitrogen and phosphorus escapes mineralisation and is permanently buried in the sediment. On a long-term basis, this loss, together with export to the North Sea and internal sinks, is mainly balanced by riverine inputs and atmospheric deposition to the Baltic Sea.
|
|
| 2. |
- Czymzik, Markus, et al.
(författare)
-
Delayed Western Gotland Basin (Baltic Sea) ventilation in response to the onset of a Mid-Holocene climate oscillation
- 2021
-
Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791. ; 273
-
Tidskriftsartikel (refereegranskat)abstract
- The marine-terrestrial Baltic ecosystem is sensitive to a range of environmental forcing and thresholds. Multi-archive investigations of its evolution require a precise synchronization of the considered archives. Here, we apply globally common cosmogenic radionuclide production rate variations to synchronize 10Be records from brackish Western Gotland Basin (Baltic Sea) and terrestrial lake Tiefer See (NE Germany) sediments to the atmospheric 14C time-scale and investigate phase-relationships in proxy responses in the southern Baltic realm associated with the onset of a centennial Mid-Holocene climate oscillation ∼5800 a BP. Based on paired molybdenum and titanium records, we identify a 98 ± 81-year delay in Western Gotland Basin ventilation, compared to the terrestrial response at the onset of the recorded Mid-Holocene climate oscillation. Most plausible mechanism for this delay is strengthened stratification in response to enhanced freshwater input during the first decades of the oscillation.
|
|
| 3. |
- Czymzik, Markus, et al.
(författare)
-
Lagged atmospheric circulation response in the Black Sea region to Greenland Interstadial 10
- 2020
-
Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 1091-6490. ; 117:46, s. 28649-28654
-
Tidskriftsartikel (refereegranskat)abstract
- Northern Hemispheric high-latitude climate variations during the last glacial are expected to propagate globally in a complex way. Investigating the evolution of these variations requires a precise synchronization of the considered environmental archives. Aligning the globally common production rate variations of the cosmogenic radionuclide 10Be in different archives provides a tool for such synchronizations. Here, we present a 10Be record at <40-y resolution along with subdecadal proxy records from one Black Sea sediment core around Greenland Interstadial 10 (GI-10) ∼41 ka BP and the Laschamp geomagnetic excursion. We synchronized our 10Be record to that from Greenland ice cores based on its globally common production rate variations. The synchronized environmental proxy records reveal a bipartite climate response in the Black Sea region at the onset of GI-10. First, in phase with Greenland warming, reduced sedimentary coastal ice rafted detritus contents indicate less severe winters. Second, and with a lag of 190 (± 44) y, an increase in the detrital K/Ti ratio and authigenic Ca precipitation point to enhanced regional precipitation and warmer lake surface temperatures. We explain the lagged climatic response by a shift in the dominant mode of atmospheric circulation, likely connected with a time-transgressive adjustment of the regional thermal ocean interior to interstadial conditions.
|
|
| 4. |
- Czymzik, Markus, et al.
(författare)
-
Synchronizing the Western Gotland Basin (Baltic Sea) and Lake Kälksjön (central Sweden) sediment records using common cosmogenic radionuclide production variations
- 2024
-
Ingår i: Holocene. - 0959-6836.
-
Tidskriftsartikel (refereegranskat)abstract
- Multi-archive studies of climate events and archive-specific response times require synchronous time scales. Aligning common variations in the cosmogenic radionuclide production rate via curve fitting methods provides a tool for the continuous synchronization of natural environmental archives down to decadal precision. Based on this approach, we synchronize 10Be records from Western Gotland Basin (WGB, Baltic Sea) and Lake Kälksjön (KKJ, central Sweden) sediments to the 14C production time series from the IntCal20 calibration curve during the Mid-Holocene period ~6400 to 5200 a BP. Before the synchronization, we assess and reduce non-production variability in the 10Be records by using 10Be/9Be ratios and removing common variability with the TOC record from KKJ sediments based on regression analysis. The synchronizations to the IntCal20 14C production time scale suggest decadal to multi-decadal refinements of the WGB and KKJ chronologies. These refinements reduce the previously centennial chronological uncertainties of both archives to about ± 20 (WGB) and ±40 (KKJ) years. Combining proxy time series from the synchronized archives enables us to interpret a period of ventilation in the deep central Baltic Sea basins from ~6250 to 6000 a BP as possibly caused by inter-annual cooling reducing vertical water temperature gradients allowing deep water formation during exceptionally cold winters.
|
|
| 5. |
- Janssen, Rene, et al.
(författare)
-
Machine Learning Predicts the Presence of 2,4,6-Trinitrotoluene in Sediments of a Baltic Sea Munitions Dumpsite Using Microbial Community Compositions
- 2021
-
Ingår i: Frontiers in Microbiology. - : Frontiers Media SA. - 1664-302X. ; 12
-
Tidskriftsartikel (refereegranskat)abstract
- Bacteria are ubiquitous and live in complex microbial communities. Due to differences in physiological properties and niche preferences among community members, microbial communities respond in specific ways to environmental drivers, potentially resulting in distinct microbial fingerprints for a given environmental state. As proof of the principle, our goal was to assess the opportunities and limitations of machine learning to detect microbial fingerprints indicating the presence of the munition compound 2,4,6-trinitrotoluene (TNT) in southwestern Baltic Sea sediments. Over 40 environmental variables including grain size distribution, elemental composition, and concentration of munition compounds (mostly at pmol.g(-1) levels) from 150 sediments collected at the near-to-shore munition dumpsite Kolberger Heide by the German city of Kiel were combined with 16S rRNA gene amplicon sequencing libraries. Prediction was achieved using Random Forests (RFs); the robustness of predictions was validated using Artificial Neural Networks (ANN). To facilitate machine learning with microbiome data we developed the R package phyloseq2ML. Using the most classification-relevant 25 bacterial genera exclusively, potentially representing a TNT-indicative fingerprint, TNT was predicted correctly with up to 81.5% balanced accuracy. False positive classifications indicated that this approach also has the potential to identify samples where the original TNT contamination was no longer detectable. The fact that TNT presence was not among the main drivers of the microbial community composition demonstrates the sensitivity of the approach. Moreover, environmental variables resulted in poorer prediction rates than using microbial fingerprints. Our results suggest that microbial communities can predict even minor influencing factors in complex environments, demonstrating the potential of this approach for the discovery of contamination events over an integrated period of time. Proven for a distinct environment future studies should assess the ability of this approach for environmental monitoring in general.
|
|
| 6. |
- Nantke, Carla K.M., et al.
(författare)
-
Human influence on the continental Si budget during the last 4300 years : δ30Sidiatom in varved lake sediments (Tiefer See, NE Germany)
- 2021
-
Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791. ; 258
-
Tidskriftsartikel (refereegranskat)abstract
- The continental silicon (Si) cycle, including terrestrial and freshwater ecosystems (lakes, rivers, estuaries), acts as a filter and modulates the amount of Si transported to the oceans. In order to link the variation in the terrestrial Si cycle to aquatic ecosystems, knowledge on changes in vegetation cover, soil disturbance and the impact of human activity are required. This study on varved lake sediments from Tiefer See near Klocksin (TSK) in northeastern Germany investigates Si isotope variations in diatom frustules (δ30Sidiatom) over the last ∼4300 years. δ30Sidiatom values vary between 0.37 and 1.63‰. The isotopic signal measured in centric (mostly planktonic) and pennate (mostly benthic) diatoms shows the same trend through most of the record. A decrease in δ30Sidiatom coinciding with early deforestation between 3900 and 750 a BP in the catchment area, points to an enhanced export of isotopically light dissolved silica (DSi) from adjacent soils to the lake. The burial flux of biogenic silica (BSi) observed in the lake sediments increases with cultivation due to enhanced nutrient supply (N, P and Si) from the watershed and nutrient redistribution caused by wind-driven increased water circulation. When the cultivation intensifies, we observe a shift to higher δ30Sidiatom values that we interpret to reflect a diminished Si soil pool and the preferential removal of the lighter 28Si by crop harvesting. Human activity influences the DSi supply from the catchment and appears to be the primary driver controlling the Si budget in TSK. Our data shows how land use triggers variations in continental Si cycling on centennial timescales and provides important information on the underlying processes.
|
|
| 7. |
- Schneider, Bernd, et al.
(författare)
-
Biogeochemical cycles
- 2017
-
Ingår i: Biological Oceanography of the Baltic Sea. - Dordrecht : Springer. - 9789400706682 - 9789400706675 ; , s. 87-122
-
Bokkapitel (refereegranskat)abstract
- 1. The internal cycles of carbon, nitrogen and phosphorus in the Baltic Sea are, like in other seas, mainly controlled by biological production and degradation of organic matter (OM).2. Biological activity also modulates the acid/base balance (pH), which is mainly a function of alkalinity and the total CO2 concentration.3. Particulate organic matter (POM) produced in the photic zone sinks into deeper water layers and is deposited on the sediment surface, where it is mineralised. Mineralisation is a form of microbial oxidation and thus leads to oxygen depletion. Due to its semi-enclosed position and its bottom topography, large-scale oxygen depletion of deep bottoms is common in the Baltic Sea.4. Under anoxic conditions, the burial of phosphorus bound to ferric oxide is inhibited and the availability of phosphate for incorporation in new OM production increases.5. In stagnant waters, the oxic/anoxic interface may migrate from the sediment into the water column, forming a pelagic redoxcline. Such a redoxcline occurs in large areas of the Baltic Sea.6. At oxygen concentrations close to zero, nitrate acts as an oxidant and is reduced to elemental nitrogen (denitrification). After the exhaustion of both oxygen and nitrate, OM is oxidised by sulphate, which is reduced to toxic hydrogen sulphide.7. The final step in the mineralisation process is the microbial formation of methane in deeper sediment layers, which reflects the internal oxidation/reduction of OM.8. A significant fraction of the organic carbon, nitrogen and phosphorus escapes mineralisation and is permanently buried in the sediment. On a long-term basis, this loss, together with export to the North Sea and internal sinks, is mainly balanced by riverine inputs and atmospheric deposition to the Baltic Sea.
|
|
