Christian Bigler

Umeå University | UMU · Department of Ecology and Environmental Science

Accelerations of ecosystem transformation raise concerns, to the extent that high rates of ecological change may be regarded amongst the most important ongoing imbalances in the Earth system. Here, we used high-resolution pollen and diatom assemblages and associated ecological indicators (the sum of tree and shrub pollen and diatom-inferred total p...

Accelerations of ecosystem transformation raise concerns, to the extent that high rates of ecological change may be regarded amongst the most important ongoing imbalances in the Earth system. Here, we used high-resolution pollen and diatom assemblages and associated ecological indicators (the sum of tree and shrub pollen and diatom-inferred total p...

Bioavailable nitrogen (N) controls marine biological productivity and thus the capacity of the global ocean to sequester atmospheric CO 2 in the abyss through the production and remineralization of sinking algal organic matter. In lakes, high concentrations of bioavailable N cause eutrophication, increased algal growth, and in turn oxygen loss. Pas...

Sedimentary environmental DNA (sed-eDNA) coupled with metabarcoding is increasingly exploited for ecological studies, but application of the method to resolve fish dynamics in lakes still needs better validation. This study (1) evaluated the sed-eDNA yields from the commonly used DNeasy PowerSoil DNA Kit from mineral-rich and organic-rich sediments...

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...

On the annual and interannual scales, lake microbial communities are known to be heavily influenced by environmental conditions both in the lake and in its terrestrial surroundings. However , the influence of landscape setting and environmental change on shaping these communities over a longer (millennial) timescale is rarely studied. Here, we appl...

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...

The temporal trajectory of lake microbial communities is still rarely investigated over timescales that encompass the full history of an aquatic ecosystem and, therefore, its response to global or local long-term environmental changes. Thanks to the development of molecularbased procedures in paleoecology, it is today possible to assess changes in...

To assess the sensitivity of lakes to anthropogenically-driven environmental changes (e.g., nutrient supply, climate change), it is necessary to first isolate the effects of between-year variability in weather conditions. This variability can strongly impact a lake's biological community especially in boreal and arctic areas where snow phenology pl...

The history of mining and smelting and the associated pollution have been documented using lake sediments for decades, but the broader ecological implications are not well studied. We analyzed sediment profiles covering the past ~10,000 years from three lakes associated with an iron blast furnace in central Sweden, as an example of the many small-s...

Disentangling the process information contained in a diatom sediment signature is crucial for reliable future predictions based on paleolimnological records. In this study, we combine limnological and paleolimnological monitoring to address the fundamental question: Which environmental information is contained in a diatom sediment signal? We compar...

Sediment trap studies and high frequency monitoring are of great importance to develop a deeper understanding of how seasonal environmental processes are imprinted in sediment signal formation. We collected whole year diatom assemblages from 2002 to 2014 with a sequential sediment trap from a varved boreal lake (Nylandssjön, Sweden) together with e...

Climate change is a key driver of changes in lakes, especially in northern ecosystems. The structure, composition and metabolism of aquatic communities may be highly sensitive to climate-driven weather variability with possible negative effects on lake functioning and ecosystem services. Ice-covered lakes are particularly interesting because of the...

Unglaciated forelands and summits protruding from ice-sheets are commonly portrayed as areas where plants first establish at the end of glacial cycles. But is this prevailing view of ice-free refugia too simplistic? Here, we present findings suggesting that surface debris supported plant communities far beyond the rim of the Late Weichselian Ice-sh...

Paleogenetics provides a powerful framework to reconstruct the long-term temporal dynamics of various biological groups from aquatic sediments. However, validations are still required to ensure the authenticity of the molecular signal obtained from sedimentary DNA. Here, we investigated the effects of early diagenesis on the DNA signal from micro-e...

Aim We provide the first European‐scale geospatial training set relating the charcoal signal in surface lake sediments to fire parameters (number, intensity and area) recorded by satellite moderate resolution imaging spectroradiometer (MODIS) sensors. Our calibration is intended for quantitative reconstructions of key fire‐regime parameters by usin...

Albeit subfossil Cladocera remains are considered as a reliable proxy for tracking historical lake development, they have been scarcely studied in large subalpine lakes south of the Alps. In this study, subfossil Cladocera remains from Lake Garda in northern Italy were analyzed to track the lake’s environmental changes since the Middle Ages. One co...

Understanding the response of sensitive Arctic and subarctic landscapes to climate change is essential to determine the risks of ongoing and projected climate warming. However, these responses will not be uniform in terms of timing and magnitude across the landscape because of site-specific differences in ecosystem susceptibility to climate forcing...

Annually laminated (varved) lake sediments constitutes excellent environmental archives, and have the potential to play an important role for understanding past seasonal climate with their inherent annual time resolution and within-year seasonal patterns. We propose to use functional data analysis methods to extract the relevant information with re...

The study of lake sediments allows to place limnological investigations within a secular temporal perspective, providing a longer time-span compared to monitoring data. A multi-site and multi-proxy paleoecological approach was applied to Lake Garda, the largest Italian lake, in order to disentangle the effects of local anthropogenic forcings, such...

The late-Holocene shift from Picea glauca (white spruce) to Picea mariana (black spruce) forests marked the establishment of modern boreal forests in Alaska. To understand the patterns and drivers of this vegetational change and the associated late-Holocene environmental dynamics, we analyzed radiocarbon-dated sediments from Grizzly Lake for chiron...

Two short sediment cores collected at the deepest points of the two sub-basins of Lake Garda (Northern Italy) were radiometrically dated and analyzed for geochemistry, spheroidal carbonaceous particles, photosynthetic pigments and diatoms aimed at reconstructing the lake's ecological evolution over the last ~700 years, and at defining its reference...

Significance Monitoring programs have recorded increases in organic carbon concentrations in northern lakes, which have important implications for water quality and ecosystem functioning. Current hypotheses interpret this trend in light of recent environmental changes such as acidification and climate but do not include an examination of long-term...

The origin and degradation/preservation state of organic matter (OM) in lacustrine systems can be studied using its molecular composition. Pyrolysis gas chromatography-mass spectrometry (Py-GC-MS) allows rapid assessment of OM-rich samples and has proven a useful tool for peat, lacustrine and marine deposits, but is rarely applied specifically to l...

To assess the rates of compaction in recent, varved (annually laminated) lake sediments, we used a collection of 13 freeze cores sampled from 1979 to 2012 in Nylandssjön (northern Sweden). This unique series of stored freeze cores allowed us to measure how the thickness of individual varves changed when they were overlain by new varves. The compact...

The main aim of this contribution is to evaluate the vulnerability of Lake Garda, the largest Italian lake, respect to specific human stressors (e.g. nutrients, hydroelectrical exploitation) in a climate change scenario and through a palaeolimnological approach. Lake's sediments have been studied within the EuLakes project (Reg. Nr. 2CE243P3) and r...

Here we present δ18Odiatom data from two high-latitude lakes; one has short residence time and a water isotopic composition (δ18Olake) that fluctuate due to seasonal variations in precipitation and temperature, and the other has δ18Olake that is influenced by longer lake water residence times and evaporation. The δ18Odiatom records reveal common re...

Paleolimnological studies rely on sediment cores taken from the deepest point of a lake. The deposited sediment and its embedded biological record are expected to be chronological and to display the lakes ecological past. Therefore many studies use micropalaeontological approaches, since, e. g., unicellular organisms like diatoms are directly depen...

Implementation of the European Union Water Framework Directive and associated national guidelines has emphasized the value of using biota, such as epilithic diatoms in streams, as indicators of water quality. However, guidelines for evaluating diatom samples have been established without explicitly evaluating their statistical robustness. We used e...

Introduction Lake acidification became an environmental issue of international significance in the late 1960s and early 1970s when Scandinavian scientists claimed that “acid rain” was the principal reason why fish populations had declined dramatically in Swedish and Norwegian lakes (Odén, 1968; Jensen & Snekvik, 1972; Almer et al., 1974). Similar c...

Waters from high-altitude alpine lakes are mainly recharged by meteoric water. Because of seasonal variations in precipitation and temperature and relatively short hydraulic residence times, most high-altitude lakes have lake water isotopic compositions (δ18Olake) that fluctuate due to seasonality in water balance processes. Input from snowmelt, in...

Abrupt climatic shifts between cold stadials and warm interstadials, termed Dansgaard-Oeschger (DO) cycles, occurred frequently during the Last Glacial. Their imprint is registered in paleorecords worldwide, but little is known about the actual temperature change both annually and seasonally in different regions. A recent hypothesis based on modell...

In the 1960s and 1970s, acidification was identified as a major environmental problem in Scandinavia, Great Britain and North America. In Sweden, a liming program was launched in order to counteract the effects of acidification on surface waters. More than 30years after large-scale liming began, there is still debate about whether liming actually a...

Over the past two decades considerable effort has been devoted to quantitatively reconstructing temperatures from biological proxies preserved in lake sediments, via transfer functions. Such transfer functions typically consist of modern sediment samples, collected over a broad environmental gradient. Correlations between the biological communities...

Lake sediments from four small lakes on western Spitsbergen (Svalbard Archipelago, Norwegian High Arctic) preserve biostratigraphic and isotopic evidence for a complex suite of twentieth century environmental changes. At Lake Skardtjørna and Lake Tjørnskardet on Nordenskiöldkysten, there is a marked diatom floristic change coupled to increased diat...

Can a climate-triggered export of old contaminants from the soil alter the lead (Pb) contaminant burden of subarctic lakes? To address this question, we reconstructed the pollution history of three high latitude lakes situated in a region where a recent climatic shift has occurred. Dated sediment records were used as archives of past Pb inputs to t...

Establishment of plans for environmental planning and management requires that a number of natural and societal factors must be taken into consideration. Insights into the inherent dynamics of nature as well as the role that past human activities have played for establishing the current condition of the landscape and the natural environment in gene...

To assess the long-term (27 yr) effects of sediment aging on stable carbon and nitrogen isotope values (delta C-13 and delta N-15), we used a collection of eight freeze cores of annually laminated (varved) lake sediment collected from 1979 to 2007 in Nylandssjon (northern Sweden). Previous research has shown that 20-23% of carbon and 35% of nitroge...

Lake sediment archives have played an important role in understanding long-term climate fluctuations, especially in remote places such as alpine, subarctic or arctic regions. The ultimate goal of paleoclimatological reconstructions using lake sediments is to improve the understanding of past climate conditions at high temporal and spatial resolutio...

Inferred temperatures from chironomids preserved in the varved sediment of Lake Silvaplana in the Eastern Swiss Alps were compared with instrumental data obtained from a meteorological station in Sils-Maria, on the shore of Lake Silvaplana, for the time interval 1850–2001. At near-annual resolution, the general patterns of chironomid-inferred tempe...

A surface-sediment survey of pigments in 100 lakes in the Scandes Mountains, northern Sweden, was combined with a reconstruction of Holocene sedimentary pigments from Lake Seukokjaure to assess the major factors regulating phototrophic communities, and how these controls may have changed during the period from the deglaciation (~9700cal.years BP) t...

1. Lake phytoplankton community structure may be influenced by both internal factors (predation, competition, resource constraints) and external ones, such as dispersal of materials and cells between connected habitats. However, little is known about the importance of cell dispersal for phytoplankton community structure in lakes. 2. We investigated...

Surface water acidification was identified as a major environmental problem in the 1960s. Consequently, a liming program was launched in Sweden in the 1970s. The primary purpose of liming is to restore conditions that existed prior to acidification. To reach this goal, as well as achieve 'good status' (i.e. low levels of distortion resulting from h...

The goal of this study was a harmonization of diatom identification and counting among diatomists from the Scandinavian and Baltic countries to improve the comparison of diatom studies in this geographical area. An analysis of the results of 25 diatomists following the European standard EN 14407 during an intercalibration exercise showed that a hig...

Heinrichs, M. L., Peglar, S. M., Bigler, C. & Birks, H. J. B. 2005 (May): A multi-proxy palaeoecological study of Alanen Laanijärvi, a boreal-forest lake in Swedish Lapland. Boreas, Vol. 34, pp. 192–206. Oslo. ISSN 0300–9483. Chironomids, pollen and spores were used to reconstruct Holocene aquatic and terrestrial environments at Alanen Laanijärvi,...

Recent observations and model simulations have highlighted the sensitivity of the forest-tundra ecotone to climatic forcing. In contrast, paleoecological studies have not provided evidence of tree-line fluctuations in response to Holocene climatic changes in Alaska, suggesting that the forest-tundra boundary in certain areas may be relatively stabl...

Sedimentary diatom assemblages from three lakes in the southeastern Swiss Alps were analysed at high temporal resolution since AD 1800. Altered land-use patterns, increasing population and exploitation through tourism are clearly reflected in annually laminated sediments of Lej da San Murezzan (Lake St Moritz) and Lej da Silvaplauna (Lake Silvaplan...

A quantitative high-resolution autumn (September–November) temperature reconstruction for the southeastern Swiss Alps back to AD 1580 is presented here. We used the annually resolved biogenic silica (diatoms) flux derived from the accurately dated and annually sampled sediments of Lake Silvaplana (46°27′N, 9°48′E, 1800 m a.s.l.). The biogenic silic...

Despite many years of research about mercury pollution, data concerning high-latitude regions of Europe are limited, particularly studies of long-term temporal trends. It is not clear whether the mercury load at high latitudes follows the recent decreasing trends in European mercury emissions or whether the load is still high because of continuing...

There is an increasing demand for cost-effective methods for environmental monitoring, and here we assess the potential of near-infrared spectroscopy (NIRS) on epilithic material from streams (material covering submerged stones) as a new method for monitoring the impact of pollution from mining and mining-related industries. NIRS, a routine techniq...

We analysed a 42cm long sediment record from Lej da la Tscheppa, a high-altitude lake (2,616ma.s.l.) in the Upper Engadine valley (Switzerland) for subfossil diatoms, chironomids and pollen. The chronology of the top 21cm of the record was established using 210Pb analysis using a constant-rate-of-supply model, and validated with 137Cs measurements...

Since the 1970s liming has been practised on a large scale in Sweden to mitigate acidification and several thousand lakes and streams are limed repeatedly. The Swedish monitoring program ISELAW (Integrated Studies of the Effects of Liming Acidified Waters) studies the long-term effects of liming. This paper summarizes the paleolimnological part of...

Holocene environmental and climatic changes are reconstructed using analyses of biological proxies in lake sediments from Vuolep Njakajaure, a lake located near the altitudinal treeline in northern Sweden (68°20′ N, 18°47′ E). We analysed biological proxy indicators from both aquatic and terrestrial ecosystems, including diatoms, pollen and chirono...

A short sediment core from Lago Grande di Avigliana (Piedmont, Italy), the second most eutrophied lake in Italy, was analysed for pollen and diatoms to reconstruct land-use changes and to estimate baseline conditions for total phosphorus (TP) in the water column. Varve counts on sediment thin-sections and 210Pb, 226Ra, and 137Cs dating provided a r...

Surface sediments from 30 mountain lakes in south-eastern Switzerland (Engadine, Grisons) were analysed for subfossil diatom, chironomid, and cladoceran assemblages. Ordination techniques were used to identify relevant physical and chemical environmental parameters that best explain the distribution of these biota in the studied lakes. Diatom assem...

We analysed a 42 cm long sediment record from Lej da la Tscheppa, a high-altitude lake (2,616 m a.s.l.) in the Upper Engadine valley (Switzerland) for subfossil diatoms, chironomids and pollen. The chronology of the top 21 cm of the record was established using 210 Pb analysis using a constant-rate-of-supply model, and validated with 137 Cs measure...

A combination of empirical modeling and a diatom-based transfer function was developed to reconstruct air temperature and ice-cover duration through the study of lake sediments. By using a thermal degree-day modeling approach, ice-cover duration on European mountain and sub-Arctic lakes is found to be very sensitive to temperature change. For examp...

To reconstruct the vegetation history of the Upper Engadine, continuous sediment cores covering the past 11 800 years from Lej da Champfèr and Lej da San Murezzan (Upper Engadine Valley, c. 1800 m a.s.l., southeastern Switzerland) have been analysed for pollen and plant macrofossils. The chronologies of the cores are based on 16 and 22 radiocarbon...

A combination of empirical modeling and a diatom-based transfer function was developed to reconstruct air temperature and ice-cover duration through the study of lake sediments. By using a thermal degree-day modeling approach, ice-cover duration on European mountain and sub-Arctic lakes is found to be very sensitive to temperature change. For examp...

A quantitative temperature reconstruction using chironomids and diatoms has been attempted from a high elevation lake in northern Sweden (Lake 850). Since 7000 cal. years BP, both chironomids and diatoms recorded similar temperatures (in the range of present-day estimates) but the correspondence between chironomid and diatom-inferred temperatures w...

This study evaluates the ability of diatoms to estimate past changes in temperature by directly comparing diatom-based inferences of mean July air temperature (July T) with measured values of century-long meteorological records. The comparison includes sediment cores from three lakes in northern Sweden (Alanen Laanijärvi, 365 m above sea level (a.s...

We assess Holocene environmental change at alpine Lake Njulla(6822N, 1842E, 999 m a.s.l.) innorthernmost Sweden using sedimentary remains of chironomid head capsules anddiatoms. We apply regional calibration sets to quantitatively reconstruct meanJuly air temperature (using chironomids and diatoms) and lake-water pH(using diatoms). Both chironomids...

Quantitative reconstructions are made of Holocene changes in climatic and environmental conditions from analyses of pollen, chironomids and diatoms in identical stratigraphic levels of a sediment core from Vuoskkujávri (68°20'43 N, 19°06'00 E, 348 m a.s.l.) near Abisko in northern Sweden (Lapland). Transfer functions, based on regional calibration...

This study investigated the distribution of subfossil diatom assemblages in surficial sediments of 100 lakes along steep ecological and climatic gradients in northernmost Sweden (Abisko region, 67.07 N to 68.48 N latitude, 17.67 E to 23.52 E longitude) to develop and cross-validate transfer functions for paleoenvironmental reconstruction. Of 19 env...

Holocene climatic variability was studied in a 9500-year lake-sediment sequence from the Abisko region in Swedish Lapland, using the oxygen-isotope ratio in diatom biogenic silica (18 O si). Oxygen-and hydrogen-isotope ratios of waters from the Abisko area suggest that in this region the evaporative flux is small and the isotopic composition of mos...

ment core from Hagelseewli (2339 m asl, Swiss Alps) give information about the present-day seasonal cycle of diatom blooms, taphonomic processes in the lake basin and the lake’s history. Analyses of surficial sediments show that water depth and thus light and nutrient availability is the most important factor influencing the production and distribu...

The response of the physical and chemical limnology of Hagelseewli (2339 m a.s.l.) to local meteorological forcing was investigated from 1996 to 1998 using an automatic weather station, thermistor chains, water samples and sediment traps. On-site meteorological measurements revealed the paramount importance of local topographic shading for the limn...