| 1. |
- Kjær, Kurt H., et al.
(författare)
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A 2-million-year-old ecosystem in Greenland uncovered by environmental DNA
- 2022
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Ingår i: Nature. - : Springer Nature. - 0028-0836 .- 1476-4687. ; 612:7939, s. 283-291
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Tidskriftsartikel (refereegranskat)abstract
- Late Pliocene and Early Pleistocene epochs 3.6 to 0.8 million years ago1 had climates resembling those forecasted under future warming2. Palaeoclimatic records show strong polar amplification with mean annual temperatures of 11–19 °C above contemporary values3,4. The biological communities inhabiting the Arctic during this time remain poorly known because fossils are rare5. Here we report an ancient environmental DNA6 (eDNA) record describing the rich plant and animal assemblages of the Kap København Formation in North Greenland, dated to around two million years ago. The record shows an open boreal forest ecosystem with mixed vegetation of poplar, birch and thuja trees, as well as a variety of Arctic and boreal shrubs and herbs, many of which had not previously been detected at the site from macrofossil and pollen records. The DNA record confirms the presence of hare and mitochondrial DNA from animals including mastodons, reindeer, rodents and geese, all ancestral to their present-day and late Pleistocene relatives. The presence of marine species including horseshoe crab and green algae support a warmer climate than today. The reconstructed ecosystem has no modern analogue. The survival of such ancient eDNA probably relates to its binding to mineral surfaces. Our findings open new areas of genetic research, demonstrating that it is possible to track the ecology and evolution of biological communities from two million years ago using ancient eDNA.
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| 2. |
- Alsos, Inger Greve, et al.
(författare)
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Ancient sedimentary DNA shows rapid post-glacial colonisation of Iceland followed by relatively stable vegetation until the Norse settlement (Landnam) AD 870
- 2021
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Ingår i: Quaternary Science Reviews. - : Elsevier. - 0277-3791 .- 1873-457X. ; 259
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Tidskriftsartikel (refereegranskat)abstract
- Understanding patterns of colonisation is important for explaining both the distribution of single species and anticipating how ecosystems may respond to global warming. Insular flora may be especially vulnerable because oceans represent severe dispersal barriers. Here we analyse two lake sediment cores from Iceland for ancient sedimentary DNA to infer patterns of colonisation and Holocene vegetation development. Our cores from lakes Torfdalsvatn and Nykurvatn span the last c. 12,000 cal yr BP and c. 8600 cal yr BP, respectively. With near-centennial resolution, we identified a total of 191 plant taxa, with 152 taxa identified in the sedimentary record of Torfdalsvatn and 172 plant taxa in the sedimentary record of Nykurvatn. The terrestrial vegetation at Torfdalsvatn was initially dominated by bryophytes, arctic herbs such as Saxifraga spp. and grasses. Around 10,100 cal yr BP, a massive immigration of new taxa was observed, and shrubs and dwarf shrubs became common whereas aquatic macrophytes became dominant. At Nykurvatn, the dominant taxa were all present in the earliest samples; shrubs and dwarf shrubs were more abundant at this site than at Torfdalsvatn. There was an overall steep increase both in the local accumulated richness and regional species pool until 8000 cal yr BP, by which time 3/4 of all taxa identified had arrived. The period 4500-1000 cal yr BP witnessed the appearance of a a small number of bryophytes, graminoids and forbs that were not recorded in earlier samples. The last millennium, after human settlement of the island (Landnam), is characterised by a sudden disappearance of Juniperus communis, but also reappearance of some high arctic forbs and dwarf shrubs. Notable immigration during the Holocene coincides with periods of increased incidence of sea ice, and we hypothesise that this may have acted as a dispersal vector. Thus, although ongoing climate change might provide a suitable habitat in Iceland for a large range of species only found in the neighbouring regions today, the reduction of sea ice may in fact limit the natural colonisation of new plant species.
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| 3. |
- Capo, Eric, et al.
(författare)
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Lake sedimentary dna research on past terrestrial and aquatic biodiversity: Overview and recommendations
- 2021
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Ingår i: Quaternary. - : MDPI. - 2571-550X. ; 4:1
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Forskningsöversikt (refereegranskat)abstract
- The use of lake sedimentary DNA to track the long-term changes in both terrestrial and aquatic biota is a rapidly advancing field in paleoecological research. Although largely applied nowadays, knowledge gaps remain in this field and there is therefore still research to be conducted to ensure the reliability of the sedimentary DNA signal. Building on the most recent literature and seven original case studies, we synthesize the state-of-the-art analytical procedures for effective sampling, extraction, amplification, quantification and/or generation of DNA inventories from sedimentary ancient DNA (sedaDNA) via high-throughput sequencing technologies. We provide recommendations based on current knowledge and best practises.
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| 4. |
- Davies, Neil S., et al.
(författare)
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Wood jams or beaver dams? : pliocene life, sediment and landscape interactions in the Canadian High Arctic
- 2022
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Ingår i: Palaios. - : Society for Sedimentary Geology. - 0883-1351 .- 1938-5323. ; 37:6, s. 330-347
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Tidskriftsartikel (refereegranskat)abstract
- During the mid-Pliocene (Zanclean, ca. ∼ 3.9 Ma), parts of the Canadian High Arctic experienced mean annual temperatures that were 14–22°C warmer than today and supported diverse boreal-type forests. The landscapes of this vegetated polar region left behind a fragmented sedimentary record that crops out across several islands in the Canadian Arctic Archipelago as the Beaufort Formation and correlative strata. Paleoecological information from these strata provides a high-fidelity window onto Pliocene environments, and prominent fossil sites yield unparalleled insights into Cenozoic mammal evolution. Significantly, many of the strata reveal evidence for life-sediment interactions in a warm-climate Arctic, most notably in the form of extensive woody debris and phytoclast deposits. This paper presents original field data that refines the sedimentological context of plant debris accumulations from the anactualistic High Arctic forests, most notably at the ‘Fyles Leaf Beds' and ‘Beaver Pond' fossil-bearing sites in the ‘high terrace deposits' of central Ellesmere Island. The former is a remarkably well-preserved, leaf-rich deposit that is part of a complex of facies associations representing lacustrine, fluvio-deltaic and mire deposition above a paleotopographic unconformity. The latter yields tooth-marked woody debris within a peat layer that also contains a rich assemblage of vertebrate and plant fossils including abundant remains from the extinct beaver-group Dipoides. Here we present sedimentological data that provide circumstantial evidence that the woody debris deposit at Beaver Pond could record dam-building in the genus, by comparing the facies motif with new data from known Holocene beaver dam facies in England. Across the Pliocene of the High Arctic region, woody debris accumulations are shown to represent an array of biosedimentary deposits and landforms including mires, driftcretions, woody bedforms, and possible beaver dams, which help to contextualize mammal fossil sites, provide facies models for high-latitude forests, and reveal interactions between life and sedimentation in a vanished world that may be an analogue to that of the near-future.
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| 5. |
- Heintzman, Peter D., et al.
(författare)
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The sedimentary ancient DNA workflow
- 2023
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Ingår i: Tracking environmental change using lake sediments. - : Springer Nature. - 9783031437984 - 9783031438011 - 9783031437991 ; , s. 53-84
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Bokkapitel (refereegranskat)abstract
- Sedimentary ancient DNA (sedaDNA) is continuing to revolutionise our understanding of past biological and geological processes by retrieving and analysing the ancient DNA preserved in lake, cave, open terrestrial, midden, permafrozen, and marine environments (Crump 2021). The study of sedaDNA began in the late 1990s (Coolen and Overmann 1998) with the first reports of extinct animal sedaDNA in 2003 (Hofreiter et al. 2003; Willerslev et al. 2003). Since then, it has been shown that sedaDNA can be recovered at high resolution from recent (101–102 year-old) (e.g., Capo et al. 2017) through to deep-time (105–106 year-old) sediments from a vast diversity of environments (Crump et al. 2021; Zavala et al. 2021; Armbrecht et al. 2022; Kjær et al. 2022). Unlike traditional palaeoenvironmental and palaeoecological proxies, sedaDNA is unique in that it is derived from any type of organism that was present in the local area and that may contain population-level information. This latter characteristic means that, unlike any other comparable proxy, sedaDNA can be used for evolutionary analyses (Gelabert et al. 2021; Lammers et al. 2021; Pedersen et al. 2021; Vernot et al. 2021).
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| 6. |
- Johnson, Fiona, et al.
(författare)
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Natural hazards in Australia: floods
- 2016
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Ingår i: Climatic Change. - : Springer Nature. - 0165-0009 .- 1573-1480. ; 139:1, s. 21-35
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Tidskriftsartikel (refereegranskat)abstract
- Floods are caused by a number of interacting factors, making it remarkably difficult to explain changes in flood hazard. This paper reviews the current understanding of historical trends and variability in flood hazard across Australia. Links between flood and rainfall trends cannot be made due to the influence of climate processes over a number of spatial and temporal scales as well as landscape changes that affect the catchment response. There are also still considerable uncertainties in future rainfall projections, particularly for sub-daily extreme rainfall events. This is in addition to the inherent uncertainty in hydrological modelling such as antecedent conditions and feedback mechanisms. Research questions are posed based on the current state of knowledge. These include a need for high-resolution climate modelling studies and efforts in compiling and analysing databases of sub-daily rainfall and flood records. Finally there is a need to develop modelling frameworks that can deal with the interaction between climate processes at different spatio-temporal scales, so that historical flood trends can be better explained and future flood behaviour understood.
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| 7. |
- Kiem, Anthony S., et al.
(författare)
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Natural hazards in Australia: droughts
- 2016
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Ingår i: Climatic Change. - : Springer Nature. - 0165-0009 .- 1573-1480. ; 139:1, s. 37-54
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Tidskriftsartikel (refereegranskat)abstract
- Droughts are a recurrent and natural part of the Australian hydroclimate, with evidence of drought dating back thousands of years. However, our ability to monitor, attribute, forecast and manage drought is exposed as insufficient whenever a drought occurs. This paper summarises what is known about drought hazard, as opposed to the impacts of drought, in Australia and finds that, unlike other hydroclimatic hazards, we currently have very limited ability to tell when a drought will begin or end. Understanding, defining, monitoring, forecasting and managing drought is also complex due to the variety of temporal and spatial scales at which drought occurs and the diverse direct and indirect causes and consequences of drought. We argue that to improve understanding and management of drought, three key research challenges should be targeted: (1) defining and monitoring drought characteristics (i.e. frequency, start, duration, magnitude, and spatial extent) to remove confusion between drought causes, impacts and risks and better distinguish between drought, aridity, and water scarcity due to over-extractions; (2) documenting historical (instrumental and pre-instrumental) variation in drought to better understand baseline drought characteristics, enable more rigorous identification and attribution of drought events or trends, inform/evaluate hydrological and climate modelling activities and give insights into possible future drought scenarios; (3) improving the prediction and projection of drought characteristics with seasonal to multidecadal lead times and including more realistic modelling of the multiple factors that cause (or contribute to) drought so that the impacts of natural variability and anthropogenic climate change are accounted for and the reliability of long-term drought projections increases.
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| 8. |
- Kjær, Kurt H., et al.
(författare)
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Glacier response to the Little Ice Age during the Neoglacial cooling in Greenland
- 2022
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Ingår i: Earth-Science Reviews. - : Elsevier. - 0012-8252 .- 1872-6828. ; 227
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Tidskriftsartikel (refereegranskat)abstract
- In the Northern Hemisphere, an insolation driven Early to Middle Holocene Thermal Maximum was followed by a Neoglacial cooling that culminated during the Little Ice Age (LIA). Here, we review the glacier response to this Neoglacial cooling in Greenland. Changes in the ice margins of outlet glaciers from the Greenland Ice Sheet as well as local glaciers and ice caps are synthesized Greenland-wide. In addition, we compare temperature reconstructions from ice cores, elevation changes of the ice sheet across Greenland and oceanographic reconstructions from marine sediment cores over the past 5,000 years. The data are derived from a comprehensive review of the literature supplemented with unpublished reports. Our review provides a synthesis of the sensitivity of the Greenland ice margins and their variability, which is critical to understanding how Neoglacial glacier activity was interrupted by the current anthropogenic warming. We have reconstructed three distinct periods of glacier expansion from our compilation: two older Neoglacial advances at 2,500 – 1,700 yrs. BP (Before Present = 1950 CE, Common Era) and 1,250 – 950 yrs. BP; followed by a general advance during the younger Neoglacial between 700-50 yrs. BP, which represents the LIA. There is still insufficient data to outline the detailed spatio-temporal relationships between these periods of glacier expansion. Many glaciers advanced early in the Neoglacial and persisted in close proximity to their present-day position until the end of the LIA. Thus, the LIA response to Northern Hemisphere cooling must be seen within the wider context of the entire Neoglacial period of the past 5,000 years. Ice expansion appears to be closely linked to changes in ice sheet elevation, accumulation, and temperature as well as surface-water cooling in the surrounding oceans. At least for the two youngest Neoglacial advances, volcanic forcing triggering a sea-ice /ocean feedback, could explain their initiation. There are probably several LIA glacier fluctuations since the first culmination close to 1250 CE (Common Era) and available data suggests ice culminations in the 1400s, early to mid-1700s and early to mid-1800s CE. The last LIA maxima lasted until the present deglaciation commenced around 50 yrs. BP (1900 CE). The constraints provided here on the timing and magnitude of LIA glacier fluctuations delivers a more realistic background validation for modelling future ice sheet stability.
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| 9. |
- Olajos, Fredrik, et al.
(författare)
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Fish colonization patterns in central Sweden from dropletdigital PCR and shotgun sequencing of sedimentary DNA
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The natural establishment of Scandinavian fish populations took place following the lastdeglaciation 9,000 to 12,000 years ago when the retreating ice exposed new habitats. Accessibilityof lakes from the Proto-Baltic sea and the southern freshwater habitats was influenced by theirelevation relative to the post-glacial coastline, with some lakes being unreachable due to migrationbarriers. Long standing hypotheses regarding colonization routes have been formulated based onmodern distribution patterns, knowledge of historic climate variations, and species’ tolerances toenvironmental conditions. These hypotheses have not been tested with other forms of evidencebecause long-term data on past fish histories are limited. In this study, the colonization history ofseveral fish species was investigated using historical data combined with analyses of sedimentaryDNA from Lake Hotagen in central Sweden which is located above the post-glacial coastline.DNA was analyzed with droplet digital PCR (ddPCR) and metagenomic shotgun sequencingapproaches. The ddPCR array used specific primers of seven species known to have beenhistorically present at the lake, and successfully detected 5/7 species in the top 80 cm (~3000 years)of the sediment core where DNA was best preserved. Metagenomics however detected 6/8expected genera in all sediment samples dating back 7000 years. Based on our findings, we inferthat 1) (dd)PCR based methods had too low sensitivity to allow consistent detection of fish inancient samples and 2) metagenomics, while sufficiently sensitive, require expanded databases toincrease granularity across species, especially those who are currently underrepresented. 3) Mostfish species likely colonized lake Hotagen soon after the last deglaciation despite the presence ofmigration barriers.
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| 10. |
- Rouillard, Alexandra, et al.
(författare)
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A model for inferring dissolved organic carbon (DOC) in lakewater from visible-near-infrared spectroscopy (VNIRS) measures in lake sediment
- 2011
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Ingår i: Journal of Paleolimnology. - : Springer. - 0921-2728 .- 1573-0417. ; 46:2, s. 187-202
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Tidskriftsartikel (refereegranskat)abstract
- We developed an inference model to infer dissolved organic carbon (DOC) in lakewater from lake sediments using visible-near-infrared spectroscopy (VNIRS). The inference model used surface sediment samples collected from 160 Arctic Canada lakes, covering broad latitudinal (60–83°N), longitudinal (71–138°W) and environmental gradients, with a DOC range of 0.6–39.6 mg L−1. The model was applied to Holocene lake sediment cores from Sweden and Canada and our inferences are compared to results from previous multiproxy paleolimnological investigations at these two sites. The inferred Swedish and Canadian DOC profiles are compared, respectively, to inferences from a Swedish-based VNIRS-total organic carbon (TOC) model and a Canadian-based diatom-inferred (Di-DOC) model from the same sediment records. The 5-component Partial Least Squares (PLS) model yields a cross-validated (CV) R2CV = 0.61 and a root mean squared error of prediction (RMSEP CV ) = 4.4 mg L−1 (11% of DOC gradient). The trends inferred for the two lakes were remarkably similar to the VNIRS-TOC and the Di-DOC inferred profiles and consistent with the other paleolimnological proxies, although absolute values differed. Differences in the calibration set gradients and lack of analogous VNIRS signatures in the modern datasets may explain this discrepancy. Our results corroborate previous geographically independent studies on the potential of using VNIRS to reconstruct past trends in lakewater DOC concentrations rapidly.
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