Alexandra Rouillard

UiT The Arctic University of Norway · Department of Geosciences

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...

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...

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...

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 glac...

During the last glacial–interglacial cycle, Arctic biotas experienced substantial climatic changes, yet the nature, extent and rate of their responses are not fully understood1–8. Here we report a large-scale environmental DNA metagenomic study of ancient plant and mammal communities, analysing 535 permafrost and lake sediment samples from across t...

Since the seminal paper in 1998 (Coolen and Overmann), sedimentary ancient DNA (sedaDNA) has become a powerful tool in paleoecology to reconstruct past changes in terrestrial and aquatic biodiversity. Still, sedaDNA is an emerging tool and there is a need for calibrations and validations to ensure the reliability of sedaDNA as a proxy to reconstruc...

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 i...

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...

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 i...

Arctic hotspots, local areas of high biodiversity, are potential key sites for conservation of Arctic biodiversity. However, there is a need for improved understanding of their long-term resilience. The Arctic hotspot of Ringhorndalen has the highest registered diversity of vascular plants in the Svalbard archipelago, including several remarkable a...

Evaporative flux from soils in arid and semi-arid climates can be very high and may substantially reduce soil moisture retained between infrequent rainfall events. Direct measurement of the evaporative losses from soils is technically challenging; however, environmental tracers such as stable hydrogen and oxygen isotope composition can be used to c...

Evaporative flux from soils in arid and semi-arid climates can be very high and may substantially reduce soil moisture retained between infrequent rainfall events. Direct measurement of the evaporative losses from soils is technically challenging. However, environmental tracers such as water stable hydrogen and oxygen isotope composition can be use...

Sediment cores from Kløverbladvatna, a threshold lake in Wahlenbergfjorden, Nordaustlandet, Svalbard were used to reconstruct Holocene glacier fluctuations. Meltwater from Etonbreen spills over a threshold to the lake, only when the glacier is significantly larger than at present. Lithological logging, loss-on-ignition, ITRAX scanning and radiocarb...

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...

Very small groundwater outflows have the potential to significantly impact the hydrochemistry and salt accumulation processes of notionally terminal basins in arid environments. However, this limited groundwater outflow can be very difficult to quantify using classical water budget calculations due to large uncertainties in estimates of evaporation...

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 drough...

Detection of source diagnostic molecular fossils (biomarkers) within sediments can provide valuable insights into the vegetation and climates of past environments. However, hot and arid regions offer particularly challenging interpretive frameworks for reconstructions because baseline data are scarce, organic matter is generally very low and in the...

Long-term hydrologic records provide crucial reference baselines of natural variability that can be used to evaluate potential changes in hydrologic regimes and their impacts. However, there is a dearth of studies of the hydrologic regimes for tropical drylands where intraseasonal and interannual variability in magnitude and frequency of precipitat...

Long-term hydrologic records provide crucial reference baselines of natural variability that can be used to evaluate potential changes in hydrologic regimes and their impacts. However, there is a dearth of studies of the hydrologic regimes for tropical drylands where intraseasonal and interannual variability in magnitude and frequency of precipitat...

The arid, sub-­‐tropical Pilbara region of northwest Australia is characterized by episodic flooding events brought by summer cyclones. However, records of cyclones occurrence and intensity are limited to recent decades. My objectives are to answer the following questions: Are pulse-­‐like events recorded in sediment in the Pilbara? • Can paleolimn...

Fossil diatom assemblages, and spectrally-inferred dissolved organic carbon (DOC) and sedimentary chlorophyll-a (SedChla) were analysed on lake sediment cores from two poorly buffered lakes on Pim Island (High Arctic Canada) to assess their responses to Holocene climate changes and to document lake ontogeny. Following deglaciation, diatom assemblag...

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 ran...