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Norbäck Ivarsson, L., Andrén, T., Moros, M., Andersen, T. J., Lönn, M. & Andrén, E. (2019). Baltic Sea Coastal Eutrophication in a Thousand Year Perspective. Frontiers in Environmental Science, 7, Article ID 88.
Open this publication in new window or tab >>Baltic Sea Coastal Eutrophication in a Thousand Year Perspective
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2019 (English)In: Frontiers in Environmental Science, ISSN 2296-665X, Vol. 7, article id 88Article in journal (Refereed) Published
Abstract [en]

Sediment cores from three sites along the east-coast of Sweden, north-western Baltic Proper, have been studied with respect to lithologies, geochemistry and diatom assemblages to trace and date early human impact with emphasis on nutrient discharge. The three sites Bråviken, Himmerfjärden and Ådfjärden, have been impacted to various degree during the last millennia by multiple stressors like excessive nutrient discharge and hazardous substances, leading to coastal hypoxia, eutrophication and pollution. These stressors are mainly caused by drivers in the drainage area as increased human population, changed land use and point sources as industries and a sewage treatment plant. Even though their detailed history differs, the results show similar general patterns for all three sites. We find no evidence in our data from the coastal zone supporting the hypothesis that the extensive areal distribution of hypoxia in the open Baltic Sea during the Medieval Climate Anomaly was caused by human impact. Timing of the onset of man-made eutrophication, as identified from d15N and changes in diatom composition, differs between the three sites, reflecting the site specific geography and local environmental histories of these areas. The onset of eutrophication dates to 1800 CE in Bråviken and Himmerfjärden areas, and to 1900 CE in the less urban area of Ådfjärden. We conclude that the recorded environmental changes during the last centuries are unique in a thousand year perspective.

Place, publisher, year, edition, pages
Frontiers Media S.A., 2019
Keywords
diatom stratigraphy, stable nitrogen isotopes, hypoxia, Medieval Climate Anomaly, NW Baltic proper, nutrient discharge
National Category
Environmental Sciences
Research subject
Environmental Studies; Baltic and East European studies
Identifiers
urn:nbn:se:sh:diva-38479 (URN)10.3389/fenvs.2019.00088 (DOI)2-s2.0-85068480167 (Scopus ID)1562/3.1.1/2013 (Local ID)1562/3.1.1/2013 (Archive number)1562/3.1.1/2013 (OAI)
Funder
The Foundation for Baltic and East European Studies, 1562/3.1.1/2013Stockholm County Council
Available from: 2019-06-25 Created: 2019-06-25 Last updated: 2019-08-06Bibliographically approved
Stepanova, A., Obrochta, S., Quintana Krupinski, N. B., Hyttinen, O., Kotilainen, A. & Andrén, T. (2019). Late Weichselian to Holocene history of the Baltic Sea as reflected in ostracod assemblages. Boreas, 48(3), 761-778
Open this publication in new window or tab >>Late Weichselian to Holocene history of the Baltic Sea as reflected in ostracod assemblages
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2019 (English)In: Boreas, ISSN 0300-9483, E-ISSN 1502-3885, Vol. 48, no 3, p. 761-778Article in journal (Refereed) Published
Abstract [en]

The study presents the first description and analysis of ostracod records from three sites cored in different parts of the Baltic Sea during the IODP Expedition 347, Baltic Sea Paleoenvironment. Our data present the first high-resolution ostracod records from the Late Weichselian and Holocene sediments collected across the Baltic Sea Basin. Using published data on modern ostracod species ecology of the Baltic Sea, we were able to provide ostracod-based palaeoreconstructions of the history of the region. The stratigraphical framework for the sites is based on radiocarbon-based age models. The three studied sites reveal different ostracod assemblage successions that reflect environmental changes in the study area. Site M0060, located in the Kattegat area, contains the oldest ostracod assemblages that document a marine environment with very high sedimentation rates during the most recent deglaciation. Between ~13 000 and 7500 cal. a BP a modern-like near-shore environment developed. Site M0059 in the southwestern Baltic Sea, Little Belt area, contains assemblages reflecting the transition from a freshwater lake to the brackish Littorina Sea between ~7500 and 7300 cal. a BP. Site M0063 is the deepest location in the central Baltic, Landsort Deep, and yielded very limited ostracod data, but comparison with our organic carbon data allowed us to distinguish the Yoldia Sea, Ancylus Lake and Littorina Sea intervals. The ostracod record correlates well with the organic carbon record with alternation between periods of hypoxia and periods of low oxygen that still supported ostracods.

Place, publisher, year, edition, pages
John Wiley & Sons, 2019
National Category
Geology
Research subject
Baltic and East European studies
Identifiers
urn:nbn:se:sh:diva-37621 (URN)10.1111/bor.12375 (DOI)000484327000014 ()2-s2.0-85060756108 (Scopus ID)2207/3.1.1/2014 (Local ID)2207/3.1.1/2014 (Archive number)2207/3.1.1/2014 (OAI)
Funder
The Foundation for Baltic and East European Studies, 2207/3.1.1/2014
Available from: 2019-02-08 Created: 2019-02-08 Last updated: 2019-10-10Bibliographically approved
Mhatre, S. S., Kaufmann, S., Marshall, I. P., Obrochta, S., Andrén, T., Jørgensen, B. B. & Lomstein, B. A. (2019). Microbial biomass turnover times and clues to cellular protein repair in energy-limited deep Baltic Sea sediments. FEMS Microbiology Ecology, 95(6), Article ID fiz068.
Open this publication in new window or tab >>Microbial biomass turnover times and clues to cellular protein repair in energy-limited deep Baltic Sea sediments
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2019 (English)In: FEMS Microbiology Ecology, ISSN 0168-6496, E-ISSN 1574-6941, Vol. 95, no 6, article id fiz068Article in journal (Refereed) Published
Abstract [en]

The discovery of active microbial life deeply buried beneath the seafloor has opened important questions: how do microorganisms cope with extreme energy limitation, what is their metabolic activity, and how do they repair damages to essential biomolecules? We used a D:L-amino acid model to calculate microbial biomass turnover times. We used a metagenome and metatranscriptome analysis to investigate the distribution of the gene that encodes Protein-L-iso aspartate(D-aspartate) O-methyltransferase (PCMT), an enzyme which recognizes damaged L-isoapartyl and D-aspartyl residues in proteins and catalyzes their repair. Sediment was retrieved during the Integrated Ocean Drilling Program (IODP) Expedition 347 from Landsort Deep and the Little Belt in the Baltic Sea. The study covers the period from the Baltic Ice Lake ca. 13 000 years ago to the present. Our results provide new knowledge on microbial biomass turnover times and protein repair in relation to different regimes of organic matter input. For the first time, we show that the PCMT gene was widely distributed and expressed among phylogenetically diverse groups of microorganisms. Our findings suggest that microbial communities are capable of repairing D-amino acids within proteins using energy obtained from the degradation of a mixture of labile compounds in microbial necromass and more recalcitrant organic matter.

Place, publisher, year, edition, pages
Oxford University Press, 2019
Keywords
D:L-amino acid model, Glacial-Holocene transition, Protein-L-isoaspartate(D-aspartate) O-methyltransferase, biomass turnover times, marine deep biosphere, microbial necromass, organic matter diagenesis, protein repair
National Category
Environmental Sciences
Research subject
Baltic and East European studies
Identifiers
urn:nbn:se:sh:diva-38303 (URN)10.1093/femsec/fiz068 (DOI)000474762800012 ()31095297 (PubMedID)
Funder
EU, FP7, Seventh Framework Programme, 294200
Available from: 2019-06-11 Created: 2019-06-11 Last updated: 2019-08-19Bibliographically approved
van Wirdum, F., Andrén, E., Wienholz, D., Kotthoff, U., Moros, M., Fanget, A.-S. -., . . . Andrén, T. (2019). Middle to late holocene variations in salinity and primary productivity in the central Baltic Sea: A multiproxy study from the landsort deep. Frontiers in Marine Science, 6, Article ID 51.
Open this publication in new window or tab >>Middle to late holocene variations in salinity and primary productivity in the central Baltic Sea: A multiproxy study from the landsort deep
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2019 (English)In: Frontiers in Marine Science, E-ISSN 2296-7745, Vol. 6, article id 51Article in journal (Refereed) Published
Abstract [en]

Anthropogenic forcing has led to an increased extent of hypoxic bottom areas in the Baltic Sea during recent decades. The Baltic Sea ecosystem is naturally prone to the development of hypoxic conditions due to its geographical, hydrographical, geological, and climate features. Besides the current spreading of hypoxia, the Baltic Sea has experienced two extensive periods of hypoxic conditions during the Holocene, caused by changing climate conditions during the Holocene Thermal Maximum (HTM; 8–4.8 cal ka BP) and the Medieval Climate Anomaly (MCA; 1–0.7 cal ka BP). We studied the variations in surface and bottom water salinity and primary productivity and their relative importance for the development and termination of hypoxia by using microfossil and geochemical data from a sediment core retrieved from the Landsort Deep during IODP Expedition 347 (Site M0063). Our findings demonstrate that increased salinity was of major importance for the development of hypoxic conditions during the HTM. In contrast, we could not clearly relate the termination of this hypoxic period to salinity changes. The reconstructed high primary productivity associated with the hypoxic period during the MCA is not accompanied by considerable increases in salinity. Our proxies for salinity show a decreasing trend before, during and after the MCA. Therefore, we suggest that this period of hypoxia is primarily driven by increasing temperatures due to the warmer climate. These results highlight the importance of natural climate driven changes in salinity and primary productivity for the development of hypoxia during a warming climate.

Place, publisher, year, edition, pages
Frontiers Media S.A., 2019
Keywords
paleoceanography, hypoxia, geochemistry, diatoms, foraminifera, palynomorphs, IODP Expedition 347
National Category
Climate Research
Research subject
Baltic and East European studies; Environmental Studies
Identifiers
urn:nbn:se:sh:diva-37781 (URN)10.3389/fmars.2019.00051 (DOI)2-s2.0-85061721558 (Scopus ID)1562/3.1.1/2013 (Local ID)1562/3.1.1/2013 (Archive number)1562/3.1.1/2013 (OAI)
Funder
The Foundation for Baltic and East European Studies, 1562/3.1.1/2013The Foundation for Baltic and East European Studies, 2207/3.1.1/2014Swedish Research Council, 826- 2012-5114
Note

This research was supported by the Foundation for Baltic and East European Studies (Grants 1562/3.1.1/2013 and 2207/3.1.1/2014), the Swedish Research Council (Grant 826- 2012-5114), the Carlsberg Foundation (IVAR-347 project) and Geocenter Denmark (DAN-IODP-SEIS project), the Independent Research Fund Denmark (Grant 7014-00113B, G-Ice), and the German Research Foundation (DFG, projects Ko3944/6-1 and Ko3944/8–1).

Available from: 2019-03-01 Created: 2019-03-01 Last updated: 2019-06-25Bibliographically approved
Hyttinen, O., Kotilainen, A. T., Virtasalo, J. J., Kekäläinen, P., Snowball, I., Obrochta, S. & Andrén, T. (2017). Holocene stratigraphy of the Ångermanälven River estuary, Bothnian Sea. Geo-Marine Letters, 37(3), 273-288
Open this publication in new window or tab >>Holocene stratigraphy of the Ångermanälven River estuary, Bothnian Sea
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2017 (English)In: Geo-Marine Letters, ISSN 0276-0460, E-ISSN 1432-1157, Vol. 37, no 3, p. 273-288Article in journal (Refereed) Published
Abstract [en]

This study explores the Holocene depositional succession at the IODP Expedition 347 sites M0061 and M0062 in the vicinity of the Ångermanälven River estuary in the Bothnian Sea sector of the Baltic Sea in northern Scandinavia. Site M0061 is located in a coastal offshore setting (87.9 m water depth), whereas site M0062 is fully estuarine (69.3 m water depth). The dataset comprises acoustic profiles and sediment cores collected in 2007 and late 2013 respectively. Three acoustic units (AUs) were recognized. Lowermost AU1 is interpreted as a poorly to discontinuous stratified glaciofluvial deposit, AU2 as a stratified conformable drape of glaciolacustrine origin, and AU3 as a poorly stratified to stratified mud drift. A strong truncating reflector separates AU2 and AU3. Three lithological units (LUs) were defined in the sediment cores. LU1 consists of glaciofluvial sand and silt gradating into LU2, which consists of glaciolacustrine varves. A sharp contact interpreted as a major unconformity separates LU2 from the overlying LU3 (brackish-water mud). In the basal part of LU3, one debrite (site M0061) or two debrites (site M0062) were recognized. Information yielded from sediment physical properties (magnetic susceptibility, natural gamma ray, dry bulk density), geochemistry (total carbon, total organic carbon, total inorganic carbon and nitrogen), and grain size support the LU division. The depositional succession was formally subdivided into two alloformations: the Utansjö Alloformation and overlying Hemsön Alloformation; the Utansjö Alloformation was further subdivided into two lithostratigraphic formations: the Storfjärden and Åbordsön formations. The Storfjärden (sandy outwash) and Åbordsön (glaciolacustrine rhythmite) formations represent a glacial retreat systems tract, which started at ca. 10.6 kyr BP. Their deposition was mainly controlled by meltwater from the retreating ice margin, glacio-isostatic land uplift and the regressive (glacial) lake level. The Hemsön Alloformation (organic-rich brackish-water mud) represents a period of forced regression, starting possibly at ca. 9.5 kyr BP. At about 7 kyr BP, brackish water reached the study area as a result of the mid-Holocene marine flooding of the Baltic Sea Basin, but the rapid land uplift soon surpassed the associated (Littorina) transgression. Changed near-bottom current patterns, caused by the establishment of a permanent halocline, and the reduced sediment consistency caused by increased organic deposition resulted in a sharp and erosional base of the brackish-water mud. Estuarine processes and salinity stratification at site M0062 started to play a more important role. This study applies a combined allostratigraphic and lithostratigraphic approach over the conventional Baltic Sea stages. This approach makes it more straightforward to study this Baltic Sea deglaciation–postglacial sequence and compare it to other formerly glaciated shallow sea estuaries.

National Category
Earth and Related Environmental Sciences
Research subject
Environmental Studies; Politics, Economy and the Organization of Society
Identifiers
urn:nbn:se:sh:diva-31525 (URN)10.1007/s00367-016-0490-2 (DOI)000401411000006 ()2-s2.0-85027842380 (Scopus ID)
Available from: 2016-12-23 Created: 2016-12-23 Last updated: 2019-06-25Bibliographically approved
Jakobsson, M., Andrén, T., Gyllencreutz, R., Noormets, R. & Sturkell, E. (2017). In memoriam of Tom Flodén: obituary. GFF, 139(3), 241-242
Open this publication in new window or tab >>In memoriam of Tom Flodén: obituary
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2017 (English)In: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 139, no 3, p. 241-242Article in journal (Other academic) Published
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:sh:diva-33709 (URN)10.1080/11035897.2017.1305207 (DOI)000413398600008 ()
Available from: 2017-12-22 Created: 2017-12-22 Last updated: 2017-12-22Bibliographically approved
Kotthoff, U., Groeneveld, J., Ash, J., Fanget, A.-S., Krupinski, N., Peyron, O., . . . Bauersachs, T. (2017). Reconstructing Holocene temperature and salinity variations in the western Baltic Sea region: a multi-proxy comparison from the Little Belt (IODP Expedition 347, Site M0059). Biogeosciences, 14, 5607-5632
Open this publication in new window or tab >>Reconstructing Holocene temperature and salinity variations in the western Baltic Sea region: a multi-proxy comparison from the Little Belt (IODP Expedition 347, Site M0059)
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2017 (English)In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 14, p. 5607-5632Article in journal (Refereed) Published
Abstract [en]

Sediment records recovered from the Baltic Sea during Integrated Ocean Drilling Program Expedition 347 provide a unique opportunity to study paleoenvironmental and climate change in central and northern Europe. Such studies contribute to a better understanding of how environmental parameters change in continental shelf seas and enclosed basins. Here we present a multi-proxy-based reconstruction of paleotemperature (both marine and terrestrial), paleosalinity, and paleoecosystem changes from the Little Belt (Site M0059) over the past  ∼  8000 years and evaluate the applicability of inorganic- and organic-based proxies in this particular setting. All salinity proxies (diatoms, aquatic palynomorphs, ostracods, diol index) show that lacustrine conditions occurred in the Little Belt until  ∼  7400 cal yr BP. A connection to the Kattegat at this time can thus be excluded, but a direct connection to the Baltic Proper may have existed. The transition to the brackish–marine conditions of the Littorina Sea stage (more saline and warmer) occurred within  ∼  200 years when the connection to the Kattegat became established after  ∼  7400 cal yr BP. The different salinity proxies used here generally show similar trends in relative changes in salinity, but often do not allow quantitative estimates of salinity. The reconstruction of water temperatures is associated with particularly large uncertainties and variations in absolute values by up to 8 °C for bottom waters and up to 16 °C for surface waters. Concerning the reconstruction of temperature using foraminiferal Mg  /  Ca ratios, contamination by authigenic coatings in the deeper intervals may have led to an overestimation of temperatures. Differences in results based on the lipid paleothermometers (long chain diol index and TEXL86) can partly be explained by the application of modern-day proxy calibrations to intervals that experienced significant changes in depositional settings: in the case of our study, the change from freshwater to marine conditions. Our study shows that particular caution has to be taken when applying and interpreting proxies in coastal environments and marginal seas, where water mass conditions can experience more rapid and larger changes than in open ocean settings. Approaches using a multitude of independent proxies may thus allow a more robust paleoenvironmental assessment.

National Category
Geosciences, Multidisciplinary
Research subject
Environmental Studies
Identifiers
urn:nbn:se:sh:diva-33885 (URN)10.5194/bg-14-5607-2017 (DOI)000417849900001 ()2-s2.0-85038405810 (Scopus ID)2207/3.1.1/2014 (Local ID)2207/3.1.1/2014 (Archive number)2207/3.1.1/2014 (OAI)
Funder
The Foundation for Baltic and East European Studies, 1562/3.1.1/2013The Foundation for Baltic and East European Studies, 2207/3.1.1/2014
Available from: 2017-12-14 Created: 2017-12-14 Last updated: 2019-08-19Bibliographically approved
van Helmond, N. A. .., Quintana Krupinski, N. B., Lougheed, B. C., Obrochta, S. P., Andrén, T. & Slomp, C. P. (2017). Seasonal hypoxia was a natural feature of the coastal zone in the Little Belt, Denmark, during the past 8 ka. Marine Geology, 387, 45-57
Open this publication in new window or tab >>Seasonal hypoxia was a natural feature of the coastal zone in the Little Belt, Denmark, during the past 8 ka
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2017 (English)In: Marine Geology, ISSN 0025-3227, E-ISSN 1872-6151, Vol. 387, p. 45-57Article in journal (Refereed) Published
Abstract [en]

The extent of the hypoxic area in the Baltic Sea has rapidly expanded over the past century. Two previous phases of widespread hypoxia, coinciding with the Holocene Thermal Maximum (HTM; 8–4 ka before present; BP) and the Medieval Climate Anomaly (MCA; 2–0.8 ka BP), have been identified. Relatively little is known about bottom water redox conditions in the coastal zone of the Baltic Sea during the Holocene, however. Here we studied the geochemical composition of a sediment sequence from a currently seasonally hypoxic site in the Danish coastal zone, the Little Belt, retrieved during Integrated Ocean Drilling Program Expedition 347 (Site M0059). The base of the studied sediment sequence consists of clays low in organic carbon (Corg), molybdenum (Mo) and iron sulfides (Fe-sulfides), and rich in iron oxides (Fe-oxides), indicative of a well-oxygenated, oligotrophic (glacial) meltwater lake. An erosional unconformity separates the glacial lake sediments from sediments that are rich in Corg. The absence of Mo, in combination with high Corg/S values, indicates that these sediments were deposited in a highly productive, well-oxygenated freshwater lake. The transition to modern brackish/marine conditions was very rapid, and subsequent continuous sequestration of Mo in the sediment and high ratios of reactive iron (FeHR) over total Fe (FeTOT) suggest (seasonal) hypoxia occurred over the last ~ 8 ka. Maxima in sediment Corg, Mo and FeHR/FeTOT ratios during the HTM and MCA suggest that the hypoxia intensified. Our results demonstrate that the Little Belt is naturally susceptible to the development of seasonal hypoxia. While periods of climatic warming led to increased deoxygenation of bottom waters, high nutrient availability in combination with density stratification were likely the main drivers of hypoxia in this part of the coastal zone of the Baltic Sea during the Holocene.

National Category
Environmental Sciences
Research subject
Baltic and East European studies
Identifiers
urn:nbn:se:sh:diva-32309 (URN)10.1016/j.margeo.2017.03.008 (DOI)000403526400004 ()2-s2.0-85016412063 (Scopus ID)
Available from: 2017-03-24 Created: 2017-03-24 Last updated: 2017-07-07Bibliographically approved
Obrochta, S. P., Andrén, T., Fazekas, S. Z., Lougheed, B. C., Snowball, I., Yokoyama, Y., . . . Fehr, A. (2017). The undatables: Quantifying uncertainty in a highly expanded Late Glacial-Holocene sediment sequence recovered from the deepest Baltic Sea basin—IODP Site M0063. Geochemistry Geophysics Geosystems, 18(3), 858-871
Open this publication in new window or tab >>The undatables: Quantifying uncertainty in a highly expanded Late Glacial-Holocene sediment sequence recovered from the deepest Baltic Sea basin—IODP Site M0063
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2017 (English)In: Geochemistry Geophysics Geosystems, ISSN 1525-2027, E-ISSN 1525-2027, Vol. 18, no 3, p. 858-871Article in journal (Refereed) Published
Abstract [en]

Laminated, organic-rich silts and clays with high dissolved gas content characterize sediments at IODP Site M0063 in the Landsort Deep, which at 459 m is the deepest basin in the Baltic Sea. Cores recovered from Hole M0063A experienced significant expansion as gas was released during the recovery process, resulting in high sediment loss. Therefore, during operations at subsequent holes, penetration was reduced to 2 m per 3.3 m core, permitting expansion into 1.3 m of initially empty liner. Fully filled liners were recovered from Holes B through E, indicating that the length of recovered intervals exceeded the penetrated distance by a factor of >1.5. A typical down-core logarithmic trend in gamma density profiles, with anomalously low-density values within the upper ∼1 m of each core, suggests that expansion primarily occurred in this upper interval. Thus, we suggest that a simple linear correction is inappropriate. This interpretation is supported by anisotropy of magnetic susceptibility data that indicate vertical stretching in the upper ∼1.5 m of expanded cores. Based on the mean gamma density profiles of cores from Holes M0063C and D, we obtain an expansion function that is used to adjust the depth of each core to conform to its known penetration. The variance in these profiles allows for quantification of uncertainty in the adjusted depth scale. Using a number of bulk 14C dates, we explore how the presence of multiple carbon source pathways leads to poorly constrained radiocarbon reservoir age variability that significantly affects age and sedimentation rate calculations.

Keywords
Paleoclimatology and paleoceanography, Uncertainty quantification, Sedimentation, Statistical methods: Inferential, Magnetic and electrical methods, sediment expansion, radiocarbon, paleomagnetics, age modeling
National Category
Environmental Sciences
Research subject
Baltic and East European studies
Identifiers
urn:nbn:se:sh:diva-32368 (URN)10.1002/2016GC006697 (DOI)000399677600003 ()2-s2.0-85015164849 (Scopus ID)2207/3.1.1/2014 (Local ID)2207/3.1.1/2014 (Archive number)2207/3.1.1/2014 (OAI)
Funder
The Foundation for Baltic and East European Studies, 2207/3.1.1/2014Swedish Research Council, 2012-5114
Available from: 2017-04-10 Created: 2017-04-10 Last updated: 2019-06-25Bibliographically approved
Hardisty, D. S., Riedinger, N., Planavsky, N. J., Asael, D., Andrén, T., Jorgensen, B. B. & Lyons, T. W. (2016). A Holocene History Of Dynamic Water Column Redox Conditions In The Landsort Deep, Baltic Sea. American Journal of Science, 316(8), 713-745
Open this publication in new window or tab >>A Holocene History Of Dynamic Water Column Redox Conditions In The Landsort Deep, Baltic Sea
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2016 (English)In: American Journal of Science, ISSN 0002-9599, E-ISSN 1945-452X, Vol. 316, no 8, p. 713-745Article in journal (Refereed) Published
Abstract [en]

The modern Baltic Sea is the world's largest anthropogenically forced anoxic basin. Using integrated geochemical records collected during Integrated Ocean Drilling Program (IODP) Expedition 347 from the deepest and one of the most reducing sub-basins in the Baltic Sea, Landsort Deep, we explore the degree and frequency of natural anoxia through the Baltic Holocene. A marked decrease in carbon-to-sulfur ratios (C/S) from the cores indicate the transition from the Baltic Ice Lake to the current brackish sea, which occurred about 8.5 kyrs B.P. Following this, laminations throughout sediments recording brackish deposition suggest sustained anoxia or extreme low oxygen, while high molybdenum (Mo) concentrations of >100 ppm and iron (Fe) geochemistry suggest water column sulfide accumulation, or euxinia, that persisted beyond seasonal timescales during deposition of two distinct sapropel units. Sedimentary Mo isotope values range from +1.11 to -0.50 permil, which are distinctly fractionated from modern Baltic seawater (+2.26 to -2.67 parts per thousand) and thus indicate that each of the sapropels experienced only weak and/or oscillatory euxinia-in contrast to the more stable euxinic conditions of more restricted basins. A shift in delta Mo-98 starting above the lower sapropel to a distinctly more negative range suggests particularly weak and oscillatory euxinia, with an enhanced contribution of manganese (Mn) redox cycling to Mo deposition relative to the lower portion of the profile. This conclusion is supported by extreme sedimentary Mn enrichments of up to 15 weight percent. We interpret the combined data to indicate episodic but major Baltic inflow events of saline and oxygenated North Sea water into the anoxic Landsort Deep that limited the concentrations and residence time of water column sulfide and caused episodic oxide deposition. Considering the temporal overlap between the most reducing conditions and periods of redox instability, we hypothesize that major Baltic inflows, as is observed today, lead to short-term instability while simultaneously supporting longer-term Baltic anoxia by strengthening the halocline. Ultimately, our results indicate that periods more reducing than the modern Baltic Sea have occurred naturally over the Holocene, but the characteristic dynamic saline inputs have historically prevented the relatively more widespread and stable anoxia observed in other classic restricted basins and will likely continue to do so.

Keywords
IODP Expedition 347, Baltic Sea, Landsort Deep, paleoredox, molybdenum isotopes
National Category
Environmental Sciences
Research subject
Baltic and East European studies
Identifiers
urn:nbn:se:sh:diva-31074 (URN)10.2475/08.2016.01 (DOI)000384939300001 ()2-s2.0-84990239020 (Scopus ID)
Available from: 2016-11-03 Created: 2016-11-03 Last updated: 2019-08-19Bibliographically approved
Projects
IODP Expedition 347 Baltic Sea Paleoenvironment [2012-05114_VR]; Södertörn University; Publications
Stepanova, A., Obrochta, S., Quintana Krupinski, N. B., Hyttinen, O., Kotilainen, A. & Andrén, T. (2019). Late Weichselian to Holocene history of the Baltic Sea as reflected in ostracod assemblages. Boreas, 48(3), 761-778Mhatre, S. S., Kaufmann, S., Marshall, I. P., Obrochta, S., Andrén, T., Jørgensen, B. B. & Lomstein, B. A. (2019). Microbial biomass turnover times and clues to cellular protein repair in energy-limited deep Baltic Sea sediments. FEMS Microbiology Ecology, 95(6), Article ID fiz068. van Wirdum, F., Andrén, E., Wienholz, D., Kotthoff, U., Moros, M., Fanget, A.-S. -., . . . Andrén, T. (2019). Middle to late holocene variations in salinity and primary productivity in the central Baltic Sea: A multiproxy study from the landsort deep. Frontiers in Marine Science, 6, Article ID 51. Warnock, J., Bauersachs, T., Kotthoff, U., Brandt, H.-T. & Andrén, E. (2018). Holocene environmental history of the Ångermanälven Estuary, northern Baltic Sea. Boreas, 47(2), 593-608Hyttinen, O., Kotilainen, A. T., Virtasalo, J. J., Kekäläinen, P., Snowball, I., Obrochta, S. & Andrén, T. (2017). Holocene stratigraphy of the Ångermanälven River estuary, Bothnian Sea. Geo-Marine Letters, 37(3), 273-288Kotthoff, U., Groeneveld, J., Ash, J., Fanget, A.-S., Krupinski, N., Peyron, O., . . . Bauersachs, T. (2017). Reconstructing Holocene temperature and salinity variations in the western Baltic Sea region: a multi-proxy comparison from the Little Belt (IODP Expedition 347, Site M0059). Biogeosciences, 14, 5607-5632Obrochta, S. P., Andrén, T., Fazekas, S. Z., Lougheed, B. C., Snowball, I., Yokoyama, Y., . . . Fehr, A. (2017). The undatables: Quantifying uncertainty in a highly expanded Late Glacial-Holocene sediment sequence recovered from the deepest Baltic Sea basin—IODP Site M0063. Geochemistry Geophysics Geosystems, 18(3), 858-871Andrén, T., Jørgensen, B. B., Cotterill, C., Green, S. & Andrén, E. (2015). Baltic Sea Basin Paleoenvironment: Expedition 347 of the mission-specific drilling platform  from and to Kiel, Germany Sites M0059–M0067  12 September–1 November 2013. Integrated Ocean Drilling ProgramAndrén, T., Jørgensen, B. B., Cotterill, C. & Green, S. (2015). IODP expedition 347: Baltic Sea basin paleoenvironment and biosphere. Scientific Drilling, 20, 1-12Andrén, T., Andrén, E. & Zhang, R. (2014). Baltic Sea Basin Paleoenvironment: paleoenvironmental evolution of the Baltic Sea Basin through the last glacial cycle. Integrated Ocean Drilling Program
UPPBASER - Understanding Past and Present Baltic Sea Ecosystem Response - background for a sustainable future [34/2013_OSS]; Södertörn University; Publications
Norbäck Ivarsson, L., Andrén, T., Moros, M., Andersen, T. J., Lönn, M. & Andrén, E. (2019). Baltic Sea Coastal Eutrophication in a Thousand Year Perspective. Frontiers in Environmental Science, 7, Article ID 88. van Wirdum, F., Andrén, E., Wienholz, D., Kotthoff, U., Moros, M., Fanget, A.-S. -., . . . Andrén, T. (2019). Middle to late holocene variations in salinity and primary productivity in the central Baltic Sea: A multiproxy study from the landsort deep. Frontiers in Marine Science, 6, Article ID 51. Ning, W., Nielsen, A., Norbäck Ivarsson, L., Jilber, T., Åkesson, C., Slomp, C., . . . Filipsson, H. (2018). Anthropogenic and climatic impacts on a coastal environment in the Baltic Sea over the last 1000 years. Anthropocene, 21, 66-79Kotthoff, U., Groeneveld, J., Ash, J., Fanget, A.-S., Krupinski, N., Peyron, O., . . . Bauersachs, T. (2017). Reconstructing Holocene temperature and salinity variations in the western Baltic Sea region: a multi-proxy comparison from the Little Belt (IODP Expedition 347, Site M0059). Biogeosciences, 14, 5607-5632Andrén, E., Telford, R. J. & Jonsson, P. (2017). Reconstructing the history of eutrophication and quantifying total nitrogen reference conditions in Bothnian Sea coastal waters. Estuarine, Coastal and Shelf Science, 198, 320-328Andrén, E. & Andrén, T. (2014). Syrefria bottnar - orsakade av klimat, människa eller både och?. Havsutsikt (2), 12-14
Late Pleistocene and Holocene climate forcing on the Baltic Sea [75/2014_OSS]; Södertörn University; Publications
Stepanova, A., Obrochta, S., Quintana Krupinski, N. B., Hyttinen, O., Kotilainen, A. & Andrén, T. (2019). Late Weichselian to Holocene history of the Baltic Sea as reflected in ostracod assemblages. Boreas, 48(3), 761-778van Wirdum, F., Andrén, E., Wienholz, D., Kotthoff, U., Moros, M., Fanget, A.-S. -., . . . Andrén, T. (2019). Middle to late holocene variations in salinity and primary productivity in the central Baltic Sea: A multiproxy study from the landsort deep. Frontiers in Marine Science, 6, Article ID 51. Warnock, J., Bauersachs, T., Kotthoff, U., Brandt, H.-T. & Andrén, E. (2018). Holocene environmental history of the Ångermanälven Estuary, northern Baltic Sea. Boreas, 47(2), 593-608Kotthoff, U., Groeneveld, J., Ash, J., Fanget, A.-S., Krupinski, N., Peyron, O., . . . Bauersachs, T. (2017). Reconstructing Holocene temperature and salinity variations in the western Baltic Sea region: a multi-proxy comparison from the Little Belt (IODP Expedition 347, Site M0059). Biogeosciences, 14, 5607-5632Obrochta, S. P., Andrén, T., Fazekas, S. Z., Lougheed, B. C., Snowball, I., Yokoyama, Y., . . . Fehr, A. (2017). The undatables: Quantifying uncertainty in a highly expanded Late Glacial-Holocene sediment sequence recovered from the deepest Baltic Sea basin—IODP Site M0063. Geochemistry Geophysics Geosystems, 18(3), 858-871Hardisty, D. S., Riedinger, N., Planavsky, N. J., Asael, D., Andrén, T., Jorgensen, B. B. & Lyons, T. W. (2016). A Holocene History Of Dynamic Water Column Redox Conditions In The Landsort Deep, Baltic Sea. American Journal of Science, 316(8), 713-745
Seaside - A multidisciplinary study of maritime environmental history [55/2017_OSS]; Södertörn University
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-5615-6088

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