scholarly journals Anthropogenic Inputs of Terrestrial Organic Matter Influence Carbon Loading and Methanogenesis in Coastal Baltic Sea Sediments

2021 ◽  
Vol 9 ◽  
Author(s):  
Tom Jilbert ◽  
Greg Cowie ◽  
Luukas Lintumäki ◽  
Sami Jokinen ◽  
Eero Asmala ◽  
...  
Keyword(s):  
Organic Matter ◽  
Baltic Sea ◽  
20Th Century ◽  
Coastal Sediments ◽  
Optical Parameters ◽  
Terrestrial Organic Matter ◽  
Late 20Th Century ◽  
Anthropogenic Inputs ◽  
Diagenetic Processes ◽  
Carbon Loading

Coastal regions globally have experienced widespread anthropogenic eutrophication in recent decades. Loading of autochthonous carbon to coastal sediments enhances the demand for electron acceptors for microbial remineralization, often leading to rearrangement of the sediment diagenetic zonation and potentially enhancing fluxes of methane and hydrogen sulfide from the seafloor. However, the role of anthropogenic inputs of terrestrial organic matter (OMterr.) in modulating diagenesis in coastal sediments is often overlooked, despite being of potential importance in regions of land-use and industrial change. Here we present a dated 4-m sediment and porewater geochemistry record from a eutrophic coastal location in the northern Baltic Sea, to investigate sources of recent carbon loading and their impact on modern diagenetic processes. Based on an end-member mixing model of sediment N/C ratios, we observe that a significant fraction of the late-20th century carbon loading at this location was contributed by OMterr.. Furthermore, analysis of lignin in this material shows depleted ratios of syringyl/vanillyl (S/V) and cinnamyl/vanillyl (C/V) phenols, indicative of enhanced inputs of woody gymnosperm tissue likely from forest industries. The rapid loading of organic matter from combined terrestrial and autochthonous sources during the late 20th century has stimulated methanogenesis in the sediment column, and shoaled the sulfate-methane transition zone (SMTZ) to a depth of 5–20 cm. Optical parameters of colored dissolved organic matter confirm that OMterr. is actively degrading in the methanogenic layer, implying a role for this material in diagenetic processes. Porewater CH4, SO42− δ13C-DIC, and ∑S2− data suggest that the modern SMTZ is a broad zone in which organoclastic sulfate reduction, methanogenesis and anaerobic oxidation of methane (AOM) co-occur. However, fluxes of CH4 and SO42− show that rates of these processes are similar to other marine locations with a comparably shallow SMTZ. We suggest that the shallow depth of the modern SMTZ is the principal reason for high observed diffusive and ebullitive methane fluxes from sediments in this area. Our results highlight that anthropogenic activities lead to multiple pathways of carbon loading to coastal sediments, and that forest industry impacts on sedimentation in the northern Baltic Sea may be more widespread than previously acknowledged.

Aromatic hydrocarbons from the Middle Jurassic fossil wood of the Polish Jura

2013 ◽  
Vol 2 (1) ◽  
pp. 82-90
Author(s):  
Justyna Smolarek ◽  
Leszek Marynowski
Keyword(s):  
Organic Matter ◽  
Aromatic Hydrocarbons ◽  
Middle Jurassic ◽  
Vitrinite Reflectance ◽  
Fossil Wood ◽  
Terrestrial Organic Matter ◽  
Weathering Processes ◽  
Diagenetic Processes ◽  
Almost All ◽  
Parameter Values

ABSTRACT Aromatic hydrocarbons are present in the fossil wood samples in relatively small amounts. In almost all of the tested samples the dominating aromatic hydrocarbon is perylene and its methyl and dimethyl derivatives. The most important biomarkers present in the aromatic fraction are dehydroabietane, siomonellite and retene, compounds characteristic for conifers. The distribution of discussed compounds is highly variable due to such early diagenetic processes affecting the wood as oxidation and the activity of microorganisms. MPI1 parameter values (methylphenanthrene index) for the majority of the samples are in the range of 0.1 to 0.5, which results in the highly variable values of Rc (converted value of vitrinite reflectance) ranging from 0.45 to 0.70%. Such values suggest that MPI1 parameter is not useful as maturity parameter in case of Middle Jurassic ore-bearing clays, even if measured strictly on terrestrial organic matter (OM). As a result of weathering processes (oxidation) the distribution of aromatic hydrocarbons changes. In the oxidized samples the amount of aromatic hydrocarbons, both polycyclic as well as aromatic biomarkers decreases.

scholarly journals Large variations in iron input to an oligotrophic Baltic Sea estuary: impact on sedimentary phosphorus burial

2018 ◽  
Vol 15 (22) ◽  
pp. 6979-6996 ◽  
Author(s):  
Wytze K. Lenstra ◽  
Matthias Egger ◽  
Niels A. G. M. van Helmond ◽  
Emma Kritzberg ◽  
Daniel J. Conley ◽  
...  
Keyword(s):  
Organic Matter ◽  
Baltic Sea ◽  
Reactive Transport ◽  
Bottom Water ◽  
Transport Model ◽  
Coastal Sediments ◽  
Estuarine Sediments ◽  
Water Salinity ◽  
The Baltic Sea ◽  
The Baltic

Abstract. Estuarine sediments are key sites for removal of phosphorus (P) from rivers and the open sea. Vivianite, an Fe(II)-P mineral, can act as a major sink for P in Fe-rich coastal sediments. In this study, we investigate the burial of P in the Öre Estuary in the northern Baltic Sea. We find much higher rates of P burial at our five study sites (up to ∼0.145 molm-2yr-1) when compared to more southern coastal areas in the Baltic Sea with similar rates of sedimentation. Detailed study of the sediment P forms at our site with the highest rate of sedimentation reveals a major role for P associated with Fe and the presence of vivianite crystals below the sulfate methane transition zone. By applying a reactive transport model to sediment and porewater profiles for this site, we show that vivianite may account for up to ∼40 % of total P burial. With the model, we demonstrate that vivianite formation is promoted in sediments with a low bottom water salinity and high rates of sedimentation and Fe oxide input. While high rates of organic matter input are also required, there is an optimum rate above which vivianite formation declines. Distinct enrichments in sediment Fe and sulfur at depth in the sediment are attributed to short periods of enhanced input of riverine Fe and organic matter. These periods of enhanced input are linked to variations in rainfall on land and follow dry periods. Most of the P associated with the Fe in the sediment is likely imported from the adjacent eutrophic Baltic Proper. Our work demonstrates that variations in land-to-sea transfer of Fe may act as a key control on burial of P in coastal sediments. Ongoing climate change is expected to lead to a decrease in bottom water salinity and contribute to continued high inputs of Fe oxides from land, further promoting P burial as vivianite in the coastal zone of the northern Baltic Sea. This may enhance the role of this oligotrophic area as a sink for P imported from eutrophic parts of the Baltic Sea.

Unraveling seasonal carbon-limitation of benthic nitrate-reduction in the coastal Baltic Sea

2021 ◽  
Author(s):  
Dana Hellemann ◽  
Sanni-Leea Aalto ◽  
Eero Asmala ◽  
Tom Jilbert ◽  
Mikko Kiljunen ◽  
...  
Keyword(s):  
Organic Matter ◽  
Baltic Sea ◽  
Nitrate Reduction ◽  
Coastal Sediments ◽  
Carbon Limitation ◽  
Main Process ◽  
Coastal Eutrophication ◽  
Coastal System ◽  
Fresh Organic Matter ◽  
N Removal

<p>Excess bioavailable nitrogen (N) is the key driver of coastal eutrophication, thus knowledge on the fate of N in coastal systems is imperative for improving eutrophication mitigation measures. In the coastal Baltic Sea, benthic heterotrophic denitrification, the main process of bioavailable N-removal from a coastal system, has recently been suggested to be seasonally limited by labile organic carbon (OC) availability<sup>1</sup> - despite the system´s richness in labile organic matter from long-term eutrophication. This challenges our common understanding of the intrinsic link between C- and N-cycling, and highlights the need for a more advanced concept of OC availability. Hence, in this project, we (i) extensively characterized the biochemical composition of coastal OC beyond traditional descriptors of ‘lability’, applying techniques such as isotopic fingerprinting and Fourier transform ion cyclotron resonance mass spectrometry, and (ii) concurrently quantified benthic nitrate reduction rates both with and without addition of easily degradable OC (glucose), to ultimately confirm and understand proposed OC-limitation of denitrification in coastal sediments. All measurements were done in high temporal and spatial resolution at the southern coast of Finland, covering a three-month period from late winter to early summer that included the peak annual input of fresh organic matter to the benthic system by the phytoplankton spring bloom. First results will be presented and their implications for understanding seasonal N turnover and coastal eutrophication dynamics will be discussed.</p><p><sup>1</sup>Hellemann D, Tallberg P, Aalto SL, Bartoli M, Hietanen S (2020) Seasonal cycle of benthic denitrification and DNRA in the aphotic  coastal zone, northern Baltic Sea. Mar Ecol Prog Ser 637:15–28</p>

scholarly journals Seasonal contribution of terrestrial organic matter and biological oxygen demand to the Baltic Sea from three contrasting river catchments

2014 ◽  
Vol 11 (1) ◽  
pp. 1355-1382
Author(s):  
H. E. Reader ◽  
C. A. Stedmon ◽  
E. S. Kritzberg
Keyword(s):  
Organic Matter ◽  
Baltic Sea ◽  
Oxygen Demand ◽  
Biological Oxygen Demand ◽  
Low Flow ◽  
Terrestrial Organic Matter ◽  
The Baltic Sea ◽  
Forested Catchments ◽  
The Baltic ◽  
River Catchments

Abstract. To examine the potential influence of terrestrially derived DOM on the Baltic Sea, a year-long study of dissolved organic matter (DOM) was performed in three river catchments in Sweden. One catchment drains into the Bothnian Sea, while two southern catchments drain into the Baltic Proper. Dissolved organic carbon (DOC) concentrations were positively correlated with discharge from forested catchments over the year and while the overall concentrations of DOC were several times higher in the southern two catchments, annual loading of DOC was on the same order for all three catchments, due to differences in discharge. Biological oxygen demand (BOD) was used as a proxy for the lability of carbon in the system. The range of BOD values was similar for all three catchments, however, the ratio of BOD to DOC (an indication of the labile fraction) in Ume älv was four times higher than in the southern two catchments. Total annual BOD loading to the Baltic Sea was twice as high in the northern catchment. Lower winter temperatures and preservation of organic matter in the northern catchment combined with an intense spring flood help to explain the higher concentrations of labile carbon in the northern catchment. Lower lability of DOM as well as higher colour in the southern catchments suggest that wetlands (i.e. peat bogs) may be the dominant source of DOM in these catchments, particularly in periods of low flow. With climate change expected to increase precipitation events and temperatures across the region, the supply and quality of DOM delivered to the Baltic Sea can also be expected to change. Our results indicate that DOM supply will be more stable throughout the year, and potentially have a lower bioavailability.

scholarly journals Seasonal contribution of terrestrial organic matter and biological oxygen demand to the Baltic Sea from three contrasting river catchments

2014 ◽  
Vol 11 (12) ◽  
pp. 3409-3419 ◽  
Author(s):  
H. E. Reader ◽  
C. A. Stedmon ◽  
E. S. Kritzberg
Keyword(s):  
Organic Matter ◽  
Baltic Sea ◽  
Oxygen Demand ◽  
Biological Oxygen Demand ◽  
Low Flow ◽  
Terrestrial Organic Matter ◽  
The Baltic Sea ◽  
Forested Catchments ◽  
The Baltic ◽  
River Catchments

Abstract. To examine the potential influence of terrestrially derived DOM on the Baltic Sea, a year-long study of dissolved organic matter (DOM) was performed in three river catchments in Sweden. One catchment drains into the Bothnian Sea, while two southern catchments drain into the Baltic proper. Dissolved organic carbon (DOC) concentrations were positively correlated with discharge from forested catchments over the year. While the overall concentrations of DOC were several times higher in the southern two catchments, higher discharge in the northern catchment resulted in the annual loadings of DOC being on the same order of magnitude for all three catchments. Biological oxygen demand (BOD) was used as a proxy for the lability of carbon in the system. The range of BOD values was similar for all three catchments, however, the ratio of BOD to DOC (an indication of the labile fraction) in Ume river was four times higher than in the southern two catchments. Total annual BOD loading to the Baltic Sea was twice as high in the northern catchment than in the two southern catchments. Lower winter temperatures and preservation of organic matter in the northern catchment combined with an intense spring flood help to explain the higher concentrations of labile carbon in the northern catchment. Lower lability of DOM as well as higher colour in the southern catchments suggest that wetlands (i.e. peat bogs) may be the dominant source of DOM in these catchments, particularly in periods of low flow. With climate change expected to increase precipitation events and temperatures across the region, the supply and quality of DOM delivered to the Baltic Sea can also be expected to change. Our results indicate that DOM supply to the Baltic Sea from boreal rivers will be more stable throughout the year, and potentially have a lower bioavailability.

scholarly journals Variations in river input of iron impact sedimentary phosphorus burial in an oligotrophic Baltic Sea estuary

2018 ◽  
Author(s):  
Wytze K. Lenstra ◽  
Matthias Egger ◽  
Niels A. G. M. van Helmond ◽  
Emma Kritzberg ◽  
Daniel J. Conley ◽  
...  
Keyword(s):  
Organic Matter ◽  
Baltic Sea ◽  
Reactive Transport ◽  
Bottom Water ◽  
Coastal Sediments ◽  
Estuarine Sediments ◽  
Water Salinity ◽  
The Baltic Sea ◽  
The Baltic ◽  
Organic Matter Input

Abstract. Estuarine sediments are key sites for removal of phosphorus (P) from rivers and the open sea. Vivianite, an iron (Fe)(II)-P mineral, can act as a major sink for P in Fe-rich coastal sediments. In this study, we investigate the burial of P in the Öre Estuary in the northern Baltic Sea. We find much higher rates of P burial at our five study sites (up to ~ 0.145 mol m−2 yr−1) when compared to more southern coastal areas in the Baltic Sea with similar rates of sedimentation. Detailed study of the sediment P forms at our site with the highest rate of sedimentation reveals a major role for P associated with Fe and the presence of vivianite crystals below the sulfate methane transition zone. By applying a reactive transport model to sediment and porewater profiles for this site, we show that vivianite may account for up to 40 % of total P burial. With the model, we demonstrate that vivianite formation is promoted in sediments with a low bottom water salinity and high rates of sedimentation and Fe oxide input. While high rates of organic matter input are also required, there is an optimum rate above which vivianite formation declines. Distinct enrichments in sediment Fe and sulfur at depth in the sediment are attributed to short periods of enhanced riverine Fe and organic matter input linked to variations in rainfall on land. Most of the P associated with the Fe in the sediment is likely imported from the adjacent eutrophic Baltic Proper. Our work demonstrates that variations in land-to-sea transfer of Fe may act as a key control on burial of P in coastal sediments. Ongoing climate change is expected to lead to a decrease in bottom water salinity and contribute to continued high inputs of Fe oxides from land, further promoting P burial as vivianite in the coastal zone of the northern Baltic Sea. This may enhance the role of this oligotrophic area as a sink for P imported from eutrophic parts of the Baltic Sea.

“Band Wagon and Gravy Train”: uses and abuses along the Silk Road

Afghanistan ◽  
2019 ◽  
Vol 2 (2) ◽  
pp. 171-194
Author(s):  
Warwick Ball
Keyword(s):  
20Th Century ◽  
21St Century ◽  
Silk Road ◽  
Late 20Th Century ◽  
Ancient Trade ◽  
International Image ◽  
Academic Discussion ◽  
The Silk Road

The Silk Road as an image is a relatively new one for Afghanistan. It appeals to both the pre-Islamic and the perceived Islamic past, thus offering an Islamic balance to previous identities linked to Bamiyan or to the Kushans. It also appeals to a broader and more international image, one that has been taken up by many other countries. This paper traces the rise of the image of the Silk Road and its use as a metaphor for ancient trade to encompass all contacts throughout Eurasia, prehistoric, ancient and modern, but also how the image has been adopted and expanded into many other areas: politics, tourism and academia. It is argued here that the origin and popularity of the term lies in late 20th century (and increasingly 21st century) politics rather than any reality of ancient trade. Its consequent validity as a metaphor in academic discussion is questioned

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