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• 1.
Stockholm University.
Changes in the composition of the diatom flora during the last century indicate increased eutrophication of the oder estuary, south-western Baltic Sea1999In: Estuarine, Coastal and Shelf Science, ISSN 0272-7714, E-ISSN 1096-0015, Vol. 48, p. 665-676Article in journal (Refereed)

Four short sediment cores from the Oder estuary, south-western Baltic Sea, were studied with respect to their siliceous microfossil and organic carbon content. The sediments were dated by Pb-210. The objective was to detect and date changes in the composition of the diatom flora and link these changes to increased human impact in the drainage area during recent centuries. Two of the cores showed an unperturbed sedimentary sequence representing a complete historical record. A change in the composition of the diatom assemblages attributable to anthropogenic factors was recorded. This was dated to about 1900 in the Oderhaff. The change consisted of an increase in species that thrive in eutrophic waters and those indicating increased salinity or the availability of inorganic nutrients.

• 2.
Södertörn University College, School of Chemistry, Biology, Geography and Environmental Science.
Naturliga halter – vad är det?: Historiska arkiv ger referensvärden.2005In: Miljötillståndet i egentliga Östersjön: Rapport 2005, Stockholm: Stockholms marina forskningscentrum , 2005, p. 50-62Chapter in book (Other (popular science, discussion, etc.))
• 3.
Södertörn University College, School of Life Sciences.
Reflektioner från BERINGIA 2005: en svensk polarforskningsexpedition till Kamtjatka2008In: Ymer, ISSN 0044-0477, p. 113-151Article in journal (Other academic)
• 4.
Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science.
Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science.
Syrefria bottnar - orsakade av klimat, människa eller både och?2014In: Havsutsikt, ISSN 1104-0513, no 2, p. 12-14Article in journal (Other (popular science, discussion, etc.))
• 5.
Stockholm University.
Stockholm University. Risø National Laboratory.
Holocene history of the Baltic Sea as a background for assessing records of human impact in the sediments of the Gotland Basin2000In: The Holocene, ISSN 0959-6836, E-ISSN 1477-0911, Vol. 10, p. 687-702Article in journal (Refereed)

Sediment cores from the Gotland Basin were studied for their siliceous microfossil assemblages and organic carbon content to compare recent environmental changes in the Baltic Sea with its natural long-term history. Age models were constructed using Pb-210, Cs-137 and corrected and calibrated C-14 dates. The transgression that marks the onset of the Ancylus Lake stage is recorded in the sediments as a small increase in organic carbon coinciding with a peak in diatom abundance and increased diatom diversity. A minor occurrence of brackish-freshwater diatoms is recorded in the Ancylus Lake c. 9950-9750 cal. yr BP (c. 8900-8800 C-14 yr BP), correlating with the onset of the Initial Litorina Sea in the Bornholm Basin. A high-productivity event is recorded in the end of the Post-Litorina Sea and corresponds to the Mediaeval warm event. An alteration in the diatom assemblage contemporaneous with a decrease in organic carbon, interpreted as representing a deterioration in the climate, correlates with the start of the ‘Little Ice Age’ about 850-700 cal. yr BP. A change dated to ad 1950-1960 is probably an effect of increased nutrient availability in the open Baltic Sea. This effect of eutrophication was probably caused by increased discharge of nutrients deriving from fertilizers, as the responding diatom species partly indicate a cold climate rather than a warm one, as would have been expected if this had been only a response to the warmer climate documented during the last 100 years or so.

• 6.
Stockholm University.
Stockholm University. Swedish University of Agriculture.
The Holocene history of the southwestern Baltic Sea as reflected in a sediment core from the Bornholm Basin2000In: Boreas, ISSN 0300-9483, E-ISSN 1502-3885, Vol. 29, p. 233-250Article in journal (Refereed)

A study of changes in siliceous microfossil assemblages and chemical analyses in a well-dated offshore sediment core from the Bornholm Basin, southwestern Baltic Sea, is carried out with the objective of increasing knowledge of the Holocene history of the area. The core covers about 11 300 calendar years from the brackish phase of the Yoldia Sea stage to the present. The first weak marine influence in the Ancylus Lake stage is recorded about 10 100 cal. yr BP (c. 8900 C-14 BP), indicating a complex transition to the Litorina Sea with different phases of brackish-water inflow. The lithology, organic carbon content and C/N and C/S ratios indicate no major changes in the sedimentary environment during the Litorina-Post-Litorina Sea stages. A high productivity event recorded in the Post-Litorina Sea stage around 950 cal. yr BP correlates with the Medieval warm event. A biostratigraphical change indicating a colder climate is recorded in the sediment at about 800 cal. yr BP, which might mark the beginning of the Little Ice Age.

• 7.
Södertörn University College, School of Life Sciences.
Defining Reference Conditions for Coastal Areas in the Baltic Sea2007Report (Other academic)

The overall aim of DEFINE is to provide a methodology to define reference conditions for nutrient concentrations in the coastal zone of the Baltic Sea. This will aid the national authorities that surround the Baltic basin in implementing the EU's Water Framework Directive (WFD) by providing decision-makers with a methodology to assess reference conditions and the degree of past and present departure from this state, such that appropriate policy and management measures can be taken at national and European levels. DEFINE adopts a palaeoecological approach grounded on diatom-based transfer functions, which can then be applied to define background total nitrogen (TN) concentrations in estuaries and coastal areas over the entire Baltic Sea. All transfer functions and necessary supporting documentation will be publicly available as a coherent management tool and accessible via the MOLTEN/DEFINE web page (http://craticula.ncl.ac.uk/Molten/jsp/).

• 8.
Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science.
Queen's University Belfast, UK. The Natural History Museum, London, UK. University of Western Ontario, London, Ontario, Canada. University of Cologne, Cologne, Germany. Kazan Federal University, Kazan, Russia / Uppsala University. Lund University, Lund, Sweden. University of Waterloo, Ontario, Canada. Kazan Federal University, Kazan, Russia / University College London, UK. Lund University, Lund, Sweden.
Holocene climate and environmental change in north-eastern Kamchatka (Russian Far East), inferred from a multi-proxy study of lake sediments2015In: Global and Planetary Change, ISSN 0921-8181, E-ISSN 1872-6364, Vol. 134, p. 41-54Article in journal (Refereed)

A sediment record from a small lake in the north-eastern part of the Kamchatka Peninsula has been investigated in a multi-proxy study to gain knowledge of Holocene climatic and environmental change. Pollen, diatoms, chironomids and selected geochemical parameters were analysed and the sediment record was dated with radiocarbon. The study shows Holocene changes in the terrestrial vegetation as well as responses of the lake ecosystem to catchment maturity and multiple stressors, such as climate change and volcanic eruptions. Climate change is the major driving force resulting in the recorded environmental changes in the lake, although recurrent tephra deposition events also contributed. The sediment record has an age at the base of about 10,000 cal yrs BP, and during the first 400 years the climate was cold and the lake exhibited extensive ice-cover during winter and relatively low primary production. Soils in the catchment were poor with shrub alder and birches dominatingthe vegetation surrounding the lake. At about 9600–8900 cal yrs BP the climate was cold and moist, and strong seasonal wind stress resulted in reduced ice-cover and increased primary production. After ca. 8900 cal yrs BP the forest density increased around the lake, runoff decreased in a generally drier climate resulting in decreasedprimary production in the lake until ca. 7000 cal yrs BP. This generally dry climate was interrupted by a brief climatic perturbation, possibly attributed to the 8.2 ka event, indicating increasingly windy conditions with thick snow cover, reduced ice-cover and slightly elevated primary production in the lake. The diatom record shows maximum thermal stratification at ca. 6300–5800 cal yrs BP and indicates together with the geochemical proxies a dry and slightly warmer climate resulting in a high productive lake. The most remarkably change in the catchment vegetation occurred at ca. 4200 cal yrs BP in the form of a conspicuous increase in Siberian dwarf pine (Pinus pumila), indicating a shift to a cooler climate with a thicker and more long-lasting snow cover. Thisvegetational change was accompanied by marked shifts in the diatom and chironomid stratigraphies, which are also indicative of colder climate and more extensive ice-cover.

• 9. Andrén, Elinor
Environmental changes of the last three centuries indicated by siliceous microfossil records from the southwestern Baltic Sea1999In: The Holocene, ISSN 0959-6836, E-ISSN 1477-0911, Vol. 9, p. 25-38Article in journal (Refereed)

Four short sediment cores from the southwestern Baltic Sea were analysed with respect to their content of siliceous microfossils. The aim was to detect and date changes in the composition of the diatom flora and to link these changes to variations in the anthropogenic load of nutrients during the last century. The study shows that the most significant change in the diatom assemblages occurred 130-140 years ago. The change is recorded in the sediments as a shift from periphytic diatom taxa to a predominance of planktonic taxa. This indicates that the photic layer has decreased in depth, probably due to eutrophication of the Baltic Sea, which consequently began to affect the area investigated approximately AD 1850. To support the results of a changing ratio of periphytic to planktonic diatoms, diatom accumulation rates were calculated In general, the diatom accumulation rate data show a decrease in the periphytic accumulation rates and an increase in the planktonic accumulation rates towards the sediment surface. Some indications of a colder climate are recorded in the sediments approximately 230 years ago. These results are in accordance with the record of maximum extent of sea ice in the same area and are suggested to represent a late stage in the ‘Little Ice Age’.

• 10.
Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science.
University of Bergen. Stockholm University.
Reconstructing the history of eutrophication and quantifying total nitrogen reference conditions in Bothnian Sea coastal waters2017In: Estuarine, Coastal and Shelf Science, ISSN 0272-7714, E-ISSN 1096-0015, Vol. 198, p. 320-328Article in journal (Refereed)

Reference total nitrogen (TN) concentrations for the Gårdsfjärden estuary in the central Bothnian Sea, which receives discharge from an industrial point-source, have been estimated from diatom assemblages using a transfer function. Sedimentological and diatom evidence imply a good ecological status before 1920 with an assemblage dominated by benthic taxa indicating excellent water transparency, high diatom species richness and less organic sedimentation resulting in homogeneous well oxygenated sediments. A change in the diatom assemblage starts between 1920 and 1935 when the species richness declines and the proportion of planktic taxa increases. Increased organic carbon sedimentation after 1920 led to hypoxic bottom waters, and the preservation of laminae in the sediments. The trend in the reconstructed TN-values agrees with the history of the discharge from the mill, reaching maximum impact during the high discharge between 1945 and 1990. The background condition for TN in Gårdsfjärden is 260-300 μg L-1, reconstructed until 1920.

• 11.
Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science.
Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science.
Did The Storegga tsunami affect the Baltic Sea?2001In: Baltica: an International Yearbook for Quaternary Geology and Palaeogeography, Coastal Morphology and Shore Processes, Marine Geology and Recent Tectonics of the Baltic Sea Area, ISSN 0067-3064, E-ISSN 1648-858X, Vol. 14, p. 115-123Article in journal (Refereed)
• 12.
Stockholm University.
Södertörn University, School of Life Sciences. Lund University. University of Minnesota.
New insights on the Yoldia Sea low stand in the Blekinge archipelago, southern Baltic Sea2007In: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 129, no 4, p. 277-285Article in journal (Refereed)

One sediment core from the Jarnavik bay in Blekinge archipelago has been investigated for its content of pollen and diatoms and its chemical properties. Two levels were also dated by radiocarbon. Based on the results the sediment sequence analysed has been divided into three environmental units largely corresponding to the lithology of the sequence. A lowermost unit consisting of weakly varved and homogeneous clay was deposited during the end of the brackish phase of the Yoldia Sea at a moderate water depth. On top of this unit a gyttja-clay unit was deposited. The onset of the deposition of this unit has been dated to c. 11 100 cal. yrs. BP. An increasing organic production and increased terrestrial influence is recorded in the chemical data and a very shallow water depth is indicated in the pollen and diatom flora. These results point to conditions in a bay probably isolated from the Yoldia Sea. A local tentative shore displacement curve have been constructed and it is proposed that this unit represents the low stand at c. -18 m during the Yoldia Sea stage in this part of the Baltic Sea basin. The uppermost unit consists of homogeneous clay with a low content of organic carbon. An increasing water depth is indicated by the composition of both pollen and diatoms. The diatom flora also displays an increase in freshwater species. This environmental change was probably the result of a transgression in the beginning of the Ancylus Lake stage.

• 13.
Södertörn University College, School of Life Sciences.
Södertörn University College, School of Life Sciences.
Östersjön förändras ständigt2005In: Upsala nya tidning, ISSN 1104-0173, no 8/6Article in journal (Other (popular science, discussion, etc.))
• 14.
Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science.
Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science.
Östersjön förändras ständigt2005In: Upsala Nya Tidning, ISSN 1104-0173, p. 3-Article in journal (Other (popular science, discussion, etc.))
• 15.
Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science.
Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science. Xiamen University, China.
Baltic Sea Basin Paleoenvironment: paleoenvironmental evolution of the Baltic Sea Basin through the last glacial cycle2014Report (Other academic)
• 16.
Södertörn University, School of Life Sciences, Environmental science. Södertörn University, School of Life Sciences, Geography.
Södertörn University, School of Life Sciences, Environmental science. Södertörn University, School of Life Sciences, Geography.
The development of the Baltic Sea basin during the last 130 000 years2011In: The Baltic Sea Basin / [ed] Jan Harff, Svante Björck, Peer Hoth, Springer Berlin/Heidelberg, 2011, p. 75-97Chapter in book (Other academic)
• 17.
Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science.
IODP expedition 347: Baltic Sea basin paleoenvironment and biosphere2015In: Scientific Drilling, ISSN 1816-8957, E-ISSN 1816-3459, Vol. 20, p. 1-12Article in journal (Refereed)

The Integrated Ocean Drilling Program (IODP) expedition 347 cored sediments from different settings of the Baltic Sea covering the last glacial–interglacial cycle. The main aim was to study the geological development of the Baltic Sea in relation to the extreme climate variability of the region with changing ice cover and major shifts in temperature, salinity, and biological communities. Using the Greatship Manisha as a European Consortium for Ocean Research Drilling (ECORD) mission-specific platform, we recovered 1.6 km of core from nine sites of which four were additionally cored for microbiology. The sites covered the gateway to the North Sea and Atlantic Ocean, several sub-basins in the southern Baltic Sea, a deep basin in the central Baltic Sea, and a river estuary in the north.

The waxing and waning of the Scandinavian ice sheet has profoundly affected the Baltic Sea sediments. During theWeichselian, progressing glaciers reshaped the submarine landscape and displaced sedimentary deposits from earlier Quaternary time. As the glaciers retreated they left a complex pattern of till, sand, and lacustrine clay, which in the basins has since been covered by a thick deposit of Holocene, organic-rich clay. Due to the stratified water column of the brackish Baltic Sea and the recurrent and widespread anoxia, the deeper basins harbor laminated sediments that provide a unique opportunity for high-resolution chronological studies.

The Baltic Sea is a eutrophic intra-continental sea that is strongly impacted by terrestrial runoff and nutrient fluxes. The Holocene deposits are recorded today to be up to 50m deep and geochemically affected by diagenetic alterations driven by organic matter degradation. Many of the cored sequences were highly supersaturated with respect to methane, which caused strong degassing upon core recovery. The depth distributions of conservative sea water ions still reflected the transition at the end of the last glaciation from fresh-water clays to Holocene brackish mud. High-resolution sampling and analyses of interstitial water chemistry revealed the intensive mineralization and zonation of the predominant biogeochemical processes. Quantification of microbial cells in the sediments yielded some of the highest cell densities yet recorded by scientific drilling.

• 18.
Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science.
Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science.
Baltic Sea Basin Paleoenvironment: Expedition 347 of the mission-specific drilling platform  from and to Kiel, Germany Sites M0059–M0067  12 September–1 November 20132015Report (Other academic)
• 19. Andrén, Thomas
Evidence of the final drainage of the Baltic Ice Lake and the brackish phase of the Yoldia Sea in glacial varves from the Baltic Sea2002In: Boreas, ISSN 0300-9483, E-ISSN 1502-3885, Vol. 31, p. 226-238Article in journal (Refereed)

A clay-varve chronology based on 14 cross-correlated varve graphs from the Baltic Sea and a mean varve thickness curve has been constructed. This chronology is correlated with the Swedish Time Scale and covers the time span 11 530 to 10 250 varve years BP. Two cores have been analysed for grain size, chemistry, content of diatoms and changes in colour by digital colour analysis. The final drainage of the Baltic Ice Lake is dated to c. 10800 varve years BP and registered in the cores analysed as a decrease in the content of clay. This event can be correlated with atmospheric D 14 C content and might have resulted in an increase in these values recorded between 11565 and 11545 years BP. The results of the correlation between the varve chronology from the Baltic Sea, the Greenland GRIP ice core and the atmospheric D 14 C record indicate that c. 760 years are missing in the Swedish Time Scale in the part younger than c. 10 250 varve years BP. A change in colour from a brownish to grey varved glacial clay recorded c. 10 770 varve years BP is found to be the result of oxygen deficiency due to an increase in the rate of sedimentation in the early Preboreal. The first brackish influence is recorded c. 10 540 varve years BP in the northwestern Baltic Sea and some 90 years later in the eastern Gotland Basin.

• 20. Clarke, A. L.
Södertörn University, School of Life Sciences.
Long-Term Trends in Eutrophication and Nutrients in the Coastal Zone2006In: Limnology and Oceanography, ISSN 0024-3590, E-ISSN 1939-5590, Vol. 51, no 1, p. 385-397Article in journal (Refereed)

We used high-resolution paleoecological records of environmental change to study the rate and magnitude of eutrophication over the last century in two contrasting coastal ecosystems. A multiproxy approach using geochemical and biological indicators and diatom-based transfer functions provides a long-term perspective on changes in nutrient concentrations and the corresponding biological and sedimentary responses. In Roskilde Fjord, Denmark, total nitrogen (TN) increased 85% during the last century, with the most rapid increase occurring after the 1950s, corresponding to the postwar increase in N fertilizer use. In Laajalahti Bay, an urban embayment near Helsinki, Finland, total dissolved nitrogen (TDN) increased with growing wastewater inputs and decreased with the remedial actions taken to reduce these discharges. These changes are small relative to the order of magnitude increases in nutrient loading that have occurred in northwestern Europe, where the dissolved inorganic nitrogen (DIN) load has increased more than threefold in certain areas.

• 21.
Lund University.
Queen's University, Belfast, UK. University of Western Ontario, London, Ontario, Canada. Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science. The Natural History Museum, Cromwell Road, London, UK . University College London, UK / Kazan Federal University, Kazan, Russia Kazan Federal University, Kazan, Russia . Kazan Federal University, Kazan, Russia / University of Cologne, Cologne, Germany . Lund University, Lund, Sweden . University of Waterloo, Waterloo, Ontario, Canada / University of Victoria, Victoria, British Columbia, Canada .
Late Holocene expansion of Siberian dwarf pine (Pinus pumila) in Kamchatka in response to increased snow cover as inferred from lacustrine oxygen-isotope records2015In: Global and Planetary Change, ISSN 0921-8181, E-ISSN 1872-6364, Vol. 134, no SI, p. 91-100Article in journal (Refereed)

Holocene records of cellulose-inferred lake-water δ18O were produced from two lake-sediment sequences obtained in central and northern Kamchatka, Russian Far East. The sediment records share similar fluctuations in δ18O during the interval of ca. 5000-800calyr BP that correspond (inversely) with changes in K+ content of the GISP2 ice-core record from Greenland, a proxy for the relative strength of the Siberian High, suggesting control by climate-related variability in δ18O of regional precipitation. The dramatic expansion of Siberian dwarf pine (Pinus pumila) in northern and central Kamchatka between ca. 5000 and 4000calyr BP, as inferred from pollen records from the same and neighbouring sites, appears to have occurred at a time of progressively declining δ18O of precipitation. This development is interpreted as reflecting a regional cooling trend accompanied by increasing winter snowfall related to gradual intensification of the Siberian High from ca. 5000 to ca. 3000calyr BP. A thicker and more long-lasting snow cover can be assumed to have favoured P. pumila by providing a competitive advantage over other boreal and subalpine tree and shrub species in the region during the later part of the Holocene. These results, which are the first of their kind from Kamchatka, provide novel insight into the Holocene vegetational and climatic development in easternmost Asia, as well as long-term atmospheric circulation dynamics in Beringia.

• 22.
School of Geography, Archaeology and Palaeoecology, Queen's University Belfast, BT7 1NN Northern Ireland, UK.
Quaternary Sciences, Department of Geology, Lund University, Sölvegatan 12, SE22362 Lund, Sweden. School of Geography, Archaeology and Palaeoecology, Queen's University Belfast, BT7 1NN Northern Ireland, UK. Institute of Geology and Mineralogy, University of Cologne, Zülpicher Str. 49a, D-50674 Cologne, Germany. Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science. Faculty of Soil Science, Moscow State University, Vorobievy Gory, 119899 Moscow, Russia. Quaternary Sciences, Department of Geology, Lund University, Sölvegatan 12, SE22362 Lund, Sweden.
Holocene environmental changes in southern Kamchatka, Far Eastern Russia, inferred from a pollen and testate amoebae peat succession record2015In: Global and Planetary Change, ISSN 0921-8181, E-ISSN 1872-6364, Vol. 134, no SI, p. 142-154Article in journal (Refereed)

High resolution palaeoenvironmental records in Far-Eastern Russia are rare, and the Kamchatka Peninsula is among the least studied areas of the region. This paper describes a record spanning the last ca. 11,000 yr, obtained from a bog in the southern part of Kamchatka. The radiocarbon dated core was analysed for pollen, testate amoebae, charcoal and loss-on-ignition (LOI).

The vegetation during the early Holocene was dominated by grasses (Poaceae), birch (Betula) and heath (Ericaceae p. p.). Around 10,300 cal yr BP there was a substantial change in the vegetation cover to shrub alder (Alnus viridis s.l.) stands with sedges and ferns (Polypodiophyta) as well as herbs such as meadow rue (Thalictrum) in the understory. In the surroundings of Utka peatlands started to form. The variations in the vegetation cover were most probably caused by climatic changes. At the beginning of sediment accumulation, before 10,300 cal yr BP, the composition of the vegetation points to cooler summers and/or decreased annual precipitation. Around 10,300 cal yr BP, changes in vegetation occurred due to rising temperatures and/or changed water regimes. Increased abundancies of dry indicating testate amoebae after 9100 cal yr BP point to intermediate to dry soil conditions. Between 8600 and 7700 cal yr BP tree alder (Alnus incana) was widely spread at the site which probably indicates optimal environmental conditions. The tephra layer at 381–384.5 cm (ca. 8500 cal yr BP) produces a strong impact on the testate amoebae assemblages. At 7700 cal yr BP there was a sudden drop of A.incana in the local vegetation. From this time on, A.incana and also A.viridis decrease continuously whereas Betula gradually increases. The upper part of the sequence (after 6300 cal yr BP) shows higher abundancies of meadowsweet (Filipendula) and sweet gale (Myrica) pollen. After 6300 cal yr BP, changes in testate amoebae demonstrate variable soil moisture conditions at the site. Between 3700 and 1800 cal yr BP, wet conditions dominate as dry indicating testate amoebae decrease. After 1800 cal yr BP soil conditions become more variable again but this time with dry dominating testate amoebae.

In contrast to surrounding regions, there is no evidence of trees such as spruce or larch growing in the surroundings of the site even though those trees are characteristic of many eastern Siberian sites. This difference might be because of the maritime influence of the Okhotsk Sea. Even dwarf pine (Pinus pumila), which is currently widely dispersed in northern Kamchatka, became part of the local vegetation only during the last 700 yr.

• 23.
University of Hamburg.
University of Bremen. UCLA. Aarhus University, Université de Perpignan. Lund University. University of Montpellier. Texas A&M University. Indiana University of Pennsylvania. Utrecht University. University of Michigan. Aarhus University. Geological Survey of Denmark and Greenland. Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science. Polish Geological Institute-National Research Institute Krakow. Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science. Lund University. Aarhus University. Utrecht University. Christian-Albrechts-Universität.
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)2017In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 14, p. 5607-5632Article in journal (Refereed)

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.

• 24.
Loughborough University, Loughborough, England.
Loughborough University, Loughborough, England. National Museum of Denmark, Lyngby, Denmark / Geological Survey of Denmark and Greenland (GEUS), Copenhagen, Denmark. Aarhus University, Aarhus, Denmark. Aarhus University, Aarhus, Denmark. Moesgård Museum, Højbjerg, Danmark. Geological Survey of Denmark and Greenland (GEUS), Copenhagen, Denmark. APEM Aquatic Scientists Ltd, Stockport, UK. Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science. Newcastle University, Newcaslte, England.
The shellfish enigma across the Mesolithic-Neolithic transition in southern Scandinavia2016In: Quaternary Science Reviews, ISSN 0277-3791, E-ISSN 1873-457X, Vol. 151, p. 315-320, article id http://dx.doi.org/10.1016/j.quascirev.2016.09.004Article in journal (Refereed)

The well-known and widespread replacement of oysters (abundant during the Mesolithic period) by cockles and mussels in many Danish Stone Age shell middens ca. 5900 cal yrs BP coincides with the transition to agriculture in southern Scandinavia. This human resource shift is commonly believed to reflect changing resource availability, driven by environmental and/or climatic change at the Mesolithic-Neolithic transition rather than cultural choice. While several hypotheses have been proposed to explain the “Mesolithic-Neolithic oyster decline”, an explanation based on a sudden freshening of the inner Danish waters has received most attention. Here, for the first time, we test and refute this long-standing hypothesis that declining salinity explains the marked reduction in oysters identified within numerous shell middens across coastal Denmark at the Mesolithic-Neolithic transition using quantitative and qualitative salinity inference from several, independent proxies (diatoms, molluscs and foraminifera) from multiple Danish fjord sites. Alternatively, we attribute the oyster decline to other environmental causes (particularly changing sedimentation), ultimately driven by external climatic forcing. Critical application of such high-quality environmental archives can reinvigorate archaeological debates and can aid in understanding and managing environmental change in increasingly impacted coastal regions.

• 25. Mertens, Kenneth
Södertörn University, School of Life Sciences, Environmental science. Södertörn University, School of Life Sciences, Geography.
Process length variation of the cyst of thedinoflagellate Protoceratium reticulatum in the NorthPacific and Baltic-Skagerrak region: calibration as anannual density proxy and first evidence ofpseudo-cryptic speciation2012In: Journal of Quaternary Science, ISSN 0267-8179, E-ISSN 1099-1417, Vol. 27, no 7, p. 734-744Article in journal (Refereed)

Process length variation of cysts of the dinoflagellate Protoceratium reticulatum (Claparede et Lachmann) Butschli in surface sediments from the North Pacific was investigated. The average process length showeda significant inverse relation to annual seawater density: $\sigma$t annual= -0.8674 x average process length +1029.3(R2=0.84), with a standard error of 0.78 kgm-3. A sediment trap study from Effingham Inlet in British Columbiarevealed the same relationship between average process length and local seawater density variations. In the Baltic–Skagerrak region, the average process length variation was related significantly to annual seawater density: $\sigma$t annual =3.5457 x average process length -993.28 (R2=0.86), with a standard error of 3.09 kgm3. These calibrations cannot be reconciled, which accentuates the regional character of the calibrations. This can be related to variations in molecular data (small subunit, long subunit and internal transcribed spacer sequences), whichshow the presence of several genotypes and the occurrence of pseudo-cryptic speciation within this species.

• 26.
Department of Geology, Lund University, Sweden.
Department of Geology, Lund University, Sweden; Department of Physical Geography and Ecosystems Science, Lund University, Sweden. Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science. Department of Earth Sciences, Faculty of Geosciences, Utrecht University, Utrecht, Netherlands; Department of Environmental Sciences, University of Helsinki, Helsinki, Finland. Department of Geology, Lund University, Sweden; Department of Biological Science, Florida Institute of Technology, Melbourne, USA. Department of Earth Sciences, Faculty of Geosciences, Utrecht University, Utrecht, Netherlands. Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science. The Archaeologists, Swedish National Historical Museums, Lund, Sweden. Department of Geology, Lund University, Lund, Sweden.
Anthropogenic and climatic impacts on a coastal environment in the Baltic Sea over the last 1000 years2018In: Anthropocene, E-ISSN 2213-3054, Vol. 21, p. 66-79Article in journal (Refereed)

Coastal environments have experienced large ecological changes as a result of human activities over the last 100−200 years. To understand the severity and potential consequences of such changes, paleoenvironmental records provide important contextual information. The Baltic Sea coastal zone is naturally a vulnerable system and subject to significant human-induced impacts. To put the recent environmental degradation in the Baltic coastal zone into a long-term perspective, and to assess the natural and anthropogenic drivers of environmental change, we present sedimentary records covering the last 1000 years obtained from a coastal inlet (Gåsfjärden) and a nearby lake (Lake Storsjön) in Sweden. We investigate the links between a pollen-based land cover reconstruction from Lake Storsjön and paleoenvironmental variables from Gåsfjärden itself, including diatom assemblages,organic carbon (C) and nitrogen (N) contents, stable C and N isotopic ratios, and biogenic silica contents. The Lake Storsjön record shows that regional land use was characterized by small-scale agricultural activity between 900 and 1400 CE, which slightly intensified between 1400 and 1800 CE. Substantial expansion of cropland was observed between 1800 and 1950 CE, before afforestation between 1950 and 2010 CE. From the Gåsfjärden record, prior to 1800 CE, relatively minor changes in the diatom and geochemical proxies were found. The onset of cultural eutrophication in Gåsfjärden can be traced to the 1800s and intensified land use is identified as the main driver. Anthropogenic activities in the 20th century have caused unprecedented ecosystem changes in the coastal inlet, as reflected in the diatom composition and geochemical proxies.

• 27.
Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science. Södertörn University, Centre for Baltic and East European Studies (CBEES), Baltic & East European Graduate School (BEEGS).
Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science. Leibniz Institute for Baltic Sea Research Warnemünde, Rostock, Germany. University of Copenhagen, Copenhagen, Denmark. Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Mathematics Teaching. University of Gävle. Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science.
Baltic Sea Coastal Eutrophication in a Thousand Year Perspective2019In: Frontiers in Environmental Science, ISSN 2296-665X, Vol. 7, article id 88Article in journal (Refereed)

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.

• 28.
Stockholm University.
Lund University. Stockholm University.
Early Holocene shore displacement and evidence of irregular isostatic uplift northwest of Lake Vanern, western Sweden1996In: Journal of Paleolimnology, ISSN 0921-2728, E-ISSN 1573-0417, Vol. 15, p. 47-63Article in journal (Refereed)

In the 1920’s the Swedish geologist Lennart von Post found evidence of irregular early Holocene isostatic uplift in the region northwest of Lake Vanern in western Sweden. von Post based his conclusions on levellings of ancient shore lines. These were indirectly dated by pollen stratigraphical investigations in basins situated at approximately the same altitudes as the shore lines. To test von Post’s hypothesis, we have adopted a different methodological approach. The sediments in twelve small lake basins, within five minor areas in this region, have been investigated with respect to when they became isolated from ancient Lake Vanern. Initially all the lake thresholds were levelled. Altitudes range between 165 and 96 m above sea level. By combining the results of mineral magnetic and diatom stratigraphical analyses it has been possible to determine the level in the sediment when the basin became isolated. The C-14 age of this isolation level has been inferred from AMS dates based on the NaOH-soluble fraction of bulk sediment, partly with very low organic content. Altogether, 36 radiocarbon datings have been carried out, ranging from 10080 to 8800 C-14 years BP. Pollen analyses, and subsequent correspondence analysis (CA) of all pollen spectra, were carried out around the isolation level in each basin as a complement to the AMS datings. If the region had been subject to irregular isostatic uplift, lakes at the same altitude in the five areas should have been isolated at different times. The AMS determined isolation ages, ‘corrected’ according to CA of the pollen stratigraphy and compensated for the relatively higher rebound of the northerly situated sites support von Post’s conclusion, from the beginning of this century, that the region northwest of Lake Va;nern has been subjected to irregular isostatic uplift.

• 29.
The Natural History Museum, Cromwell Road, London, UK.
Queen's University Belfast, Northern Ireland, UK. University College London, UK / Institute of Geology and Petroleum Technologies, Kazan, Russia. University College London, UK. Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science. Institute of Geology and Petroleum Technologies, Kazan, Russia / Universität zu Kӧln, Germany. Lund University. The Natural History Museum, London, UK.
The relative influences of climate and volcanic activity on Holocene lake development inferred from a mountain lake in central Kamchatka2015In: Global and Planetary Change, ISSN 0921-8181, E-ISSN 1872-6364, Vol. 134, no SI, p. 67-81Article in journal (Refereed)

A sediment sequence was taken from a closed, high altitude lake (informal name Olive-backed Lake) in the central mountain range of Kamchatka, in the Russian Far East. The sequence was dated by radiocarbon and tephrochronology and used for multi-proxy analyses (chironomids, pollen, diatoms). Although the evolution of Beringian climate through the Holocene is primarily driven by global forcing mechanisms, regional controls, such as volcanic activity or vegetation dynamics, lead to a spatial heterogeneous response. This study aims to reconstruct past changes in the aquatic and terrestrial ecosystems and to separate the climate-driven response from a response to regional or localised environmental change. Radiocarbon dates from plant macrophytes gave a basal date of 7800 cal yr BP. Coring terminated in a tephra layer, so sedimentation at the lake started prior to this date, possibly in the early Holocene following local glacier retreat. Initially the catchment vegetation was dominated by Betula and Alnus woodland with a mosaic of open, wet, aquatic and semi-aquatic habitats. Between 7800 and 6000 cal yr BP the diatom-inferred lake water was pH 4.4 -5.3 and chironomid and diatom assemblages in the lake were initially dominated by a small number of acidophilic/acid tolerant taxa. The frequency of Pinus pumila (Siberian dwarf pine) pollen increased from 5000 cal yr BP and threshold analysis indicates that P. pumila arrived in the catchment between 4200 and 3000 cal yr BP. Its range expansion was probably mediated by strengthening of the Aleutian Low pressure system and increased winter snowfall. The diatom-inferred pH reconstructions show that after an initial period of low pH, pH gradually increased from 5500 cal yr BP to pH 5.8 at 1500 cal yr BP. This trend of increasing pH through the Holocene is unusual in lake records, but the initially low pH may have resulted directly or indirectly from intense regional volcanic activity during the mid-Holocene. The chironomid-inferred July temperature reconstruction suggests cool periods between 3200 – 2800 cal yr BP and 1100 – 700 cal yr BP and a warmer period between 2800 and 1100 cal yr BP. Chironomid and diatom DCA scores decline from ca. 6000 cal yr BP, indicating compositional changes in these aquatic assemblages. In comparison declines in pollen PCA scores are delayed, starting ca. 5100 cal yr BP. The results suggest that while catchment vegetation was responding primarily to climate change, the biota within the lake and lake water chemistry were responding to localised environmental conditions.

• 30.
Stockholms universitet.
Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science.
Why is the Baltic Sea so special to live in?2017In: Biological Oceanography of the Baltic Sea / [ed] Snoeijs-Leijonmalm, Pauline; Schubert, Hendrik; Radziejewska, Teresa, Springer Netherlands, 2017, p. 23-84Chapter in book (Other academic)

"Why is the Baltic Sea so special to live in", is the main question the authors here give several arguments or answers for. Geographical position, geological development, hydrographical features, climate and physical drivers together create the Baltic Sea environment. The Baltic Sea water is brackish and characterized by pronounced salinity gradients, both in horizontal and vertical directions, because of the large volume of freshwater runoff from over 100 rivers, which mixes with the saline water from the Kattegat that enters the Baltic Sea via narrow shallow straits. Being a semi-enclosed continental sea with a large drainage area compared to its water volume , the Baltic Sea ecosystem is heavily impacted by the surrounding landmasses. The water residence time in the Baltic Sea is long (30–40 years), and therefore discharged nutrients and toxic compounds circulate within the sea for a long time, which contributes to its vulnerability to eutrophication and chemical contamination by hazardous substances. The Baltic Sea Area is geologically young and the Baltic Sea ecosystem is extremely young in an evolutionary perspective. Only few macroscopic species are fully adapted to its low-salinity environment. In an ecosystem-wide perspective, the large-scale Baltic Sea gradient is the principal ecological characteristic of the Baltic Sea.

• 31. Sohlenius, Gustav
Development of anoxia during the Holocene fresh-brackish water transition in the Baltic Sea2001In: Marine Geology, ISSN 0025-3227, E-ISSN 1872-6151, Vol. 177, p. 221-242Article in journal (Refereed)

One of the most pronounced environmental changes during the Holocene Baltic Sea history was the transition from the freshwater Ancylus Lake to the brackish water Litorina Sea. The establishment of brackish conditions during this transition (the A/L) was caused by an interplay of sea level rise and subsidence of sills in the Danish Straits. The northward progression of salt water influence caused the gradual and transgressive development of a halocline which obstructed vertical water circulation in the deep depositional basins. It caused changes in surface water properties (mirrored by diatom flora and productivity levels), in redox conditions of bottom waters, in organic carbon preservation of sediments, and in nutrient cycling. In seven cores from the Arkona, Bornholm and Gotland Basins, the A/L transition was WC dated and studied in high-resolution samples for minor and major element composition. The earliest marine inflows were small and can only be detected by sedimentary properties in the southern Baltic. Further north the salinity increase was gradual and retarded; only when the connection through the Danish Straits was well established the entire Baltic proper became brackish with a stratified water column. This development took altogether 2000 C-14 yr (c. 9000-7000 BP). Diatom analyses indicate a fast increase in salinity c. 7000 C-14 yr BP, which coincides with a transgressive phase in the straits, In the Gotland Basin, deposition of laminated sediments and periodically euxinic conditions were established first at the deepest bottoms, and rose to shallower water depth as the basin was gradually filled with dense brackish water. The laminated sequences have high organic carbon contents, which is attributed to better preservation under anoxic conditions. Litorina sediments from the Arkona and Bornholm Basins are bioturbated even though conditions became more reducing also in these sediments during the A/L transition. The development of reducing conditions during the A/L transition probably caused Pre-mobilization from the sediments and a decrease in the rates of denitrification. Both factors increased primary productivity. A comparison between isochronous sediments from different basins shows that certain elements (Mo, Cu, V and Cd) are enriched sediments deposited during predominantly anoxic conditions.

• 32.
University College London, UK / Kazan Federal University, Kazan, Russian Federation.
Queen's University Belfast, Northern Ireland, UK. The Natural History Museum, London, UK. University College London, UK. Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science. Kazan Federal University, Kazan, Russian Federation / University of Cologne, Köln, Germany. Lund University. Kamchatka Research Institute of Fisheries and Oceanography, Petropavlovsk-Kamchatski, Russian Federation. Kazan Federal University, Kazan, Russian Federation.
The Holocene environmental history of a small coastal lake on the north-eastern Kamchatka Peninsula2015In: Global and Planetary Change, ISSN 0921-8181, E-ISSN 1872-6364, Vol. 134, p. 55-66Article in journal (Refereed)

A radiocarbon and tephra-dated sediment core from Lifebuoy Lake, located on the north-east coast of Kamchatka Peninsula, was analysed for pollen, spores, diatoms, chironomids and tephra in order to uncover regional environmental history.

• 33.
Södertörn University, School of Natural Sciences, Technology and Environmental Studies.
Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science. University of Hamburg, Hamburg, Germany. University of Hamburg, Hamburg, Germany. Leibniz Institute for Baltic Sea Research Warnemünde, Rostock, Germany. University of Perpignan, Perpignan, France. Aarhus University, Aarhus, Denmark. Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science.
Middle to late holocene variations in salinity and primary productivity in the central Baltic Sea: A multiproxy study from the landsort deep2019In: Frontiers in Marine Science, E-ISSN 2296-7745, Vol. 6, article id 51Article in journal (Refereed)

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.

• 34.
Indiana University of Pennsylvania.
Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science. Newcastle University. Loughborough University. Loughborough University. Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science. University of Helsinki.
A high‐resolution diatom‐based Middle and Late Holocene environmental history of the Little Belt region, Baltic Sea2019In: Boreas, ISSN 0300-9483, E-ISSN 1502-3885Article in journal (Refereed)

The large‐scale shifts in the salinity of the Baltic Sea over the Holocene are well understood and have been comprehensively documented using sedimentary proxy records. More recent work has focused on understanding how past salinity fluctuations have affected other ecological parameters (e.g. primary productivity, nutrient content) of the Baltic basin, and salinity changes over key events and over short time scales are still not well understood. The International Ocean Drilling Program Expedition 347 cored the Baltic basin in order to collect basin‐wide environmental records through a glacial–interglacial cycle. Site M0059 is located in the Little Belt between the Baltic Sea and the Atlantic Ocean. A composite splice section from Site M0059 was analysed at a decadal resolution to study changes in salinity, nutrient conditions and other surface water column parameters based on changes in diatom assemblages and on quantitative diatom‐based salinity inferences. A mesotrophic slightly brackish assemblage is seen in the lowermost analysed depths, corresponding to 7800–7500 cal. a BP. An increase in salinity and nutrient content of the water column leads into a meso‐eutrophic brackish phase. The observed salinity increase is rapid, lasting from 7500 to 7150 cal. a BP. Subsequently, the Little Belt becomes oligotrophic and is dominated by tychopelagic diatoms from c. 7100 to c. 3900 cal. a BP. This interval contains some of the highest salinities observed followed by diatom assemblages similar to those of the Northern Atlantic Ocean, composed primarily of cosmopolitan open ocean marine diatoms. A return to tychopelagic productivity is seen from 3850 to 980 cal. a BP. Anthropogenic eutrophication is detected in the last 300 years of the record, which intensifies in the uppermost sediments. These results represent the first decadally resolved record in the region and provide new insight into the transition to a brackish basin and subsequent ecological development.

• 35.
University of Pennsylvania, Indiana, PA, USA.
Christian-Albrechts-University, Kiel, Germany. University of Hamburg, Hamburg, Germany. University of Hamburg, Hamburg, Germany. Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science.
Holocene environmental history of the Ångermanälven Estuary, northern Baltic Sea2018In: Boreas, ISSN 0300-9483, E-ISSN 1502-3885, Vol. 47, no 2, p. 593-608Article in journal (Refereed)

The Baltic Sea has experienced a complex geological history, with notable swings in salinity driven by changes to its connection with the Atlantic and glacio-isostatic rebound. Sediments obtained during International Ocean Drilling Program Expedition 347 allow the study of the effects of these changes on the ecology of the Baltic in high resolution through the Holocene in areas where continuous records had not always been available. Sites M0061 and M0062, drilled in the Ångermanälven Estuary (northern Baltic Sea), contain records of Holocene-aged sediments and microfossils. Here we present detailed records of palaeoecological and palaeoenvironmental changes to the Ångermanälven Estuary inferred from diatom, palynomorph and organic-geochemical data. Based on diatom assemblages, the record is divided into four zones that comprise the Ancylus Lake, Littorina Sea, Post-Littorina Sea and Recent Baltic Sea stages. The Ancylus Lake phase is initially characterized as oligotrophic, with the majority of primary productivity in the upper water column. This transition to a eutrophic state continues into the Initial Littorina Sea stage. The Initial Littorina Sea stage contains the most marine phase recorded here, as well as low surface water temperatures. These conditions end before the Littorina Sea stage, which is marked by a return to oligotrophic conditions and warmer waters of the Holocene Thermal Maximum. Glacio-isostatic rebound leads to a shallowing of the water column, allowing for increased benthic primary productivity and stratification of the water column. The Medieval Climate Anomaly is also identified within Post-Littorina Sea sediments. Modern Baltic sediments and evidence of human-induced eutrophication are seen. Human influence upon the Baltic Sea begins c. 1700 cal. a BP and becomes more intense c. 215 cal. a BP.

• 36.
Geological Survey of Denmark and Greenland, Chopenhagen, Denmark.
Loughborough University, Leicestershire, UK. Södertörn University, School of Natural Sciences, Technology and Environmental Studies, Environmental Science. University of Copenhagen, Copenhagen, Denmark. National Museum of Denmark, Kgs. Lyngby, Denmark . Bjerknes Centre for Climate Research, Bergen, Norway .
Palaeoenvironmental History of the Baltic Sea: One of the Largest Brackish-Water Ecosystems in the World2017In: Applications of Paleoenvironmental Techniques in Estuarine Studies / [ed] Weckström, Kaarina; Saunders, Krystyna M.; Gell, Peter A.; Skilbeck, C. Gregory, Springer Netherlands, 2017, p. 615-662Chapter in book (Other academic)

The past of the Baltic Sea has been intensively investigated using a wealth of techniques. By far the largest number of studies has focused on sea level and salinity changes, driven by global climate and isostatic crustal rebound after the Baltic Sea emerged underneath the Weichselian Ice Sheet ca. 15,000 cal. years BP. The post-glacial history of the Baltic has included both freshwater and brackish water stages depending on the connection of the Baltic Sea with the world’s oceans. As the Baltic is one of the most polluted sea areas in the world, many studies have also focused on both the long-term trends in nutrients and productivity and the relatively recent anthropogenic eutrophication. The long-term changes in the trophic state of the Baltic Sea have been found to be linked to changes in climate, which controls freshwater discharge from the catchment and weathering rates, as well as marine water inflow from the North Sea. The productivity of the Baltic Sea has followed major climate patterns: it was high during warm periods and lower during phases of deteriorating climate. Recent eutrophication of the Baltic Sea can mainly be explained by a marked increase in discharge of nutrients caused by a growing population and changes in the agricultural practice, although long-term climate variability also plays a part. Signs of recovery have recently been detected, however, the Baltic Sea is still far from its pre-industrial trophic state.

• 37.
Lund University.
Uppsala University. Lund University. Lund University. Lund University.
Holocene palaeoecology and shoreline displacement on the Biskopsmåla Peninsula, southeastern Sweden2003In: Boreas, ISSN 0300-9483, E-ISSN 1502-3885, Vol. 32, p. 578-589Article in journal (Refereed)

High-resolution palaeoecological proxies of pollen, macrofossils and diatoms from an isolation lake provide a long-term record of the Holocene landscape history and shoreline displacement on the Biskopsmala Peninsula in central Blekinge, SE Sweden. During the Preboreal/Boreal transition, the peninsula was sparsely vegetated by woodlands, along with lateglacial dwarf shrub/steppe communities. The lake basin was isolated from the shallow Yoldia Sea during this time. The regional climate improved from 10 700 cal. BP, evident as progressive expansion of Pinus -dominated mixed forest with deciduous trees. The lake basin was probably connected with the Ancylus Lake during the period 10 700-10 100 cal. BP. Subsequently the basin became isolated again, corresponding to the Early Littorina Sea phase. Replacement of freshwater diatoms by those with brackish-water affinity at 8100 cal. BP indicates the initial transgression of the Littorina Sea in this basin. But not until 7500 cal. BP were brackish conditions fully established. Peaks of brackish-marine diatoms and dinoflagellates during 7500-7000 cal. BP indicate increased saltwater inflow to the Baltic Sea in response to global meltwater pulse 3. However, interactive changes in seagrass and stonewort macrofossil concentrations suggest that three minor transgressions during 5900-5300, 5000-4700 and 4400-4000 cal. BP occurred locally, associated with centennial-scale variations in regional wind pattern or coastal storminess. By 3000 cal. BP, the lake basin was finally isolated from the Baltic, and thereafter the landscape on the peninsula became gradually more influenced by human activities.

• 38.
Lund University.
Lund University. Uppsala University. Lund University.
Mid-Holocene Baltic Sea transgression along the coast of Blekinge, SE Sweden ancient lagoons correlated with beach ridges2004In: GFF, ISSN 1103-5897, E-ISSN 2000-0863, Vol. 126, p. 257-272Article in journal (Refereed)

The mid-Holocene Littorina transgression in southern Scandinavia is well documented. Multiple-stratigraphic sequences in ancient Littorina lagoons in the coastal area of Blekinge, SE Sweden reveal a maximum relative sea level of 7-8 m above present sea level between 8000-6000 cal. BP. Evidence for at least two transgression waves is found within this period. In this study these are documented in one modern lake and correlated with an ancient beach-lagoon stratigraphy. Furthermore, two younger transgressions are documented at one site, altogether establishing a firm transgression chronology for the time span 8000-4000 cal. BP (sea level 5-8 m a.s.l.) as a basis for understanding the dynamics of Baltic sea-level changes. Neolithic cultural layers are correlated to regression periods, indicating more favorable conditions for beach settlement between stormy transgression periods.

• 39. Zillén, Lovisa
Södertörn University, School of Life Sciences. Södertörn University, School of Life Sciences.
Past occurrences of hypoxia in the Baltic Sea and the role of climate variability, environmental change and human impact2008In: Earth-Science Reviews, ISSN 0012-8252, E-ISSN 1872-6828, Vol. 91, p. 77-92Article in journal (Refereed)

The hypoxic zone in the Baltic Sea has increased in area about four times since 1960 and widespread oxygen deficiency has severely reduced macro benthic communities below the halocline in the Baltic Proper and the Gulf of Finland, which in turn has affected food chain dynamics, fish habitats and fisheries in the entire Baltic Sea. The cause of increased hypoxia is believed to be enhanced eutrophication through increased anthropogenic input of nutrients, such as nitrogen and phosphorus. However, the spatial variability of hypoxia on long time-scales is poorly known: and so are the driving mechanisms. We review the occurrence of hypoxia in modern time (last c. 50ï¿œyears), modern historical time (AD 1950-1800) and during the more distant past (the last c. 10ï¿œ000ï¿œyears) and explore the role of climate variability, environmental change and human impact. We present a compilation of proxy records of hypoxia (laminated sediments) based on long sediment cores from the Baltic Sea. The cumulated results show that the deeper depressions of the Baltic Sea have experienced intermittent hypoxia during most of the Holocene and that regular laminations started to form c. 8500-7800ï¿œcal. yr BP ago, in association with the formation of a permanent halocline at the transition between the Early Littorina Sea and the Littorina Sea s. str. Laminated sediments were deposited during three main periods (i.e. between c. 8000-4000, 2000-800ï¿œcal. yr BP and subsequent to AD 1800) which overlap the Holocene Thermal Maximum (c. 9000-5000ï¿œcal. yr BP), the Medieval Warm Period (c. AD 750-1200) and the modern historical period (AD 1800 to present) and coincide with intervals of high surface salinity (at least during the Littorina s. str.) and high total organic carbon content. This study implies that there may be a correlation between climate variability in the past and the state of the marine environment, where milder and dryer periods with less freshwater run-off correspond to increased salinities and higher accumulation of organic carbon resulting in amplified hypoxia and enlarged distribution of laminated sediments. We suggest that hydrology changes in the drainage area on long time-scales have, as well as the inflow of saltier North Sea waters, controlled the deep oxic conditions in the Baltic Sea and that such changes have followed the general Holocene climate development in Northwest Europe. Increased hypoxia during the Medieval Warm Period also correlates with large-scale changes in land use that occurred in much of the Baltic Sea watershed during the early-medieval expansion. We suggest that hypoxia during this period in the Baltic Sea was not only caused by climate, but increased human impact was most likely an additional trigger. Large areas of the Baltic Sea have experienced intermittent hypoxic from at least AD 1900 with laminated sediments present in the Gotland Basin in the Baltic Proper since then and up to present time. This period coincides with the industrial revolution in Northwestern Europe which started around AD 1850, when population grew, cutting of drainage ditches intensified, and agricultural and forest industry expanded extensively.

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