European Mountain Lakes Research Articles

Comparing palaeolimnological and instrumental evidence of climate change for remote mountain lakes over the last 200 years

This paper compares the palaeolimnological evidence for climate change over the last 200 years with instrumental climate data for the same period at seven European remote mountain lakes. The sites are Ovre Neadalsvatn (Norway), Saanajarvi (Finland), Gossenkollesee (Austria), Hagelseewli (Switzerland), Jezero v Ledvici (Slovenia), Estany Redo (Spain, Pyrenees), and NiOne Terianske Pleso (Slovakia). We used multiple regression analysis to transfer homogenised lowland air temperature records to each of the sites, and these reconstructions were validated using data from on-site automatic weather stations. These data showed that mean annual temperature has varied over the last 200 years at each site by between 1 and 2 °C, typical of the high frequency variability found throughout the Holocene, and appropriate, therefore, to test the sensitivity of the various proxy methods used. Sediment cores from each site were radiometrically dated using 210 Pb, 137 Cs and 241 Am and analysed for loss-on-ignition, C, N, S, pigments, diatoms, chrysophytes, Cladocera and chironomids. Comparisons between the proxy data and the instrumental data were based on linear regression analysis with the proxy data treated as response variables and the instrumental data (after smoothing using LOESS regressions) as predictor variables. The results showed few clear or consistent patterns with generally low or very low r 2 values. Highest values were found when the data were compared after smoothing using a broad span, indicating that some of the proxy data were capturing climate variability but only at a relatively coarse time resolution. Probable reasons for the weak performance of the methods used include inaccurate dating, especially for earlier time periods, the influence of confounding forcing factors at This is the eleventh of 11 papers published in this special issue on the palaeolimnology of remote mountain lakes in Europe resulting from the MOLAR project funded by the European Union. The guest editor was Richard W. Battarbee.

Application of Static Critical Load Models for Acidity to High Mountain Lakes in Europe

Critical load models for acidityprovide a measure of the sensitivity of surfacewaters to acid deposition, and can be used todetermine critical load exceedance and potentiallong-term harmful effects. Three static models,the Steady-State Water Chemistry model, diatommodel and First-order Acidity Balance model, arehere applied to 11 high mountain lakes in Norway,Scotland, the Alps, the Pyrenees and the Tatras.Between five and seven of the lakes show criticalload exceedance, depending on the model used.Nitrogen as well as sulphur deposition isimportant in causing exceedance. Since soil andvegetation cover are generally sparse, geologyand lake retention time appear to be key factorsin the determination of critical load. Retentionof nitrogen is observed, but it is unclearwhether this occurs within the lake or theterrestrial part of the catchment.

Mercury and Organochlorine Contamination in Brown Trout (Salmo Trutta) and Arctic Charr (Salvelinus Alpinus) from High Mountain Lakes in Europe and the Svalbard Archipelago

High concentration of Hg, less volatile PCB congeners and p,p′-DDE in Arctic charr from an arctic lake was mainly causedby biomagnification in the food chain where cannibalism was thedriving force. We suggest that low sediment fluxes of Hg, low net production of methyl mercury, and short food chains excludingpiscivory explain the low levels of Hg in the invertebrate feeding fish population in five European high mountain lakes.Concentrations of less volatile PCB congeners in insectivorous fish populations from the European high mountain lakes were mainly influenced by fish age and atmospheric deposition, indicated by the sediment inventory. Atmospheric deposition influenced by local sources may explain the higher concentrationsof pesticides (p,p′-DDT, p,p′-DDE and γ-HCH) observedin fish from the Pyrenees compared to the other sites. Theconcentrations of Hg and organochlorines did not exceedthe guidelines for fish consumption, except for Hg levelsin the oldest fish from the arctic lake.

Lake Jezero v Ledvici ( NW Slovenia) - changes in sediment records over the last two centuries

Lake Jezero v Ledvici (NW Slovenia) is a 14 m deep mountain lake at an elevation of 1860 m, situated on limestone bedrock. It is an oligotrophic, alkaline and hard-water lake with a transparency of about 14 m and has suffered several times over recent centuries from strong earthquakes. In 1996 five sediment cores, between 35 and 45 cm long, were collected from the deepest part of the lake and analysed to reconstruct environmental changes over the last few centuries. The data indicate changes induced by pollution and climate change during the last two centuries similar to those in other European mountain and remote lakes. However, at this site earthquakes have also affected the lake and partly obscure the interpretation of the sediment record. From 1780 to 1890, sediment records show low abundance of diatoms and relatively high abundance of Cladocera. After 1890, the number of diatoms started to increase coinciding with a strong earthquake. From the beginning of the 20th century, concentrations of spheroidal carbonaceous particles (SCP), diatom valves and head capsules of chironomids gradually increased whilst in Cladocera the main difference observed was a change in the proportion of benthic taxa. After 1960, in parallel with a rise in air temperature, a further increase in accumulation rate of diatoms started, but there was a decrease in Cladocera.

The paleolimnological analysis of sediments from high mountain lake Nižné Terianske pleso in the High Tatras (Slovakia)

Sedimentological climate proxies and a 200-year long climate record, reconstructed using a data-set of European-wide meteorological data, have been compared at the high mountain lake Nižne Terianske pleso in the High Tatras, Slovakia. Diatoms, chrysophyte stomatocysts, chironomids, plant pigments and spheroidal carbonaceous particles (SCPs) were analysed as well as sediment lithostratigraphic parameters. Using a radiometric approach the sediment core was dated and a depth of 4.6 cm was found to correspond to 1852 AD. The sediment accumulation rate (0.0034 g·cm−2·yr−1) was one of the lowest identified in the European mountain lake project, MOLAR. Despite this slow accumulation rate a remarkably coherent lithological and stratigraphic record has been recovered. The sediments of this remote mountain site, largely free from the effects of direct human impact, have been found to display a wealth of variability over the last 200 years. The record of spheroidal carbonaceous particles, indicators of anthropogenic pollution deposition, begins around 4.5–5.0 cm in depth (1833–1857). Temporal patterns are typical of European lake sites with the concentration peaking in the late 1970's. The SCP/210Pb inventory ratio for the site is also in good agreement with the European latitudinal pattern. A strong influence of sample age on the chrysophyte assemblage composition in the upper-most 4–6 cm indicates that the main changes in the cysts have been related to long term environmental changes, probably pH. Analysis of chironomid remains revealed a stable profundal community. Chironomids as a whole showed no correlations to temperature fluctuations in the last 200 years. Relatively abundant remains of Diamesa sp. head capsules and other taxa closely associated with stream conditions in the older layers contrast with the absence of Diamesa sp. in the recent sediments. This change is considered to be evidence for the existence of a stronger, more stable inlet supplied from permanent granular snow fields in the lake basin. The most important changes in diatom assemblages were observed at 3cm. Many species of the genus Achnanthes spp. together with Navicula schmassmannii and Orthoseira roeseana made up the greatest part of the diatom community above 3 cm, being absent or rare lower in the record. A positive correlation between diatoms and mean summer temperature was found.

Hysteresis in Reversal of Central European Mountain Lakes from Atmospheric Acidification

Extremely high emissions of S and N compounds in Central Europe (both ∼280 mmol m-2 yr-1) declined by ∼70and ∼35%, respectively, during the last decade. Decreaseddeposition rates of SO4 -2, NO3 -, and NH4 + in the region paralleled emission declines. The reduction in atmospheric inputs of S and N to mountain ecosystemshas resulted in a pronounced reversal of acidification in the Tatra Mountains and Bohemian Forest lakes. Between the 1987–1990and 1997–1999 periods, concentrations of SO4 -2 and NO3 - decreased (average ± standard deviation) by 22±7 and 12±7 μmol L-1, respectively, in theTatra Mountains, and by 19±7 and 15±10 μmol L-1, respectively, in the Bohemian Forest. Their decrease was compensated in part (1) by a decrease in Ca2+ + Mg2+ (17±7 μmol L-1) and H+ (4±6 μmol L-1), and an increase in HCO3 -(10±10 μmol L-1) in the Tatra Mountains lakes, and (2) by a decrease in Al (7±4 μmol L-1), Ca2+ + Mg2+ (9±6 μmol L-1), and H+ (6±5 μmol L-1), in Bohemian Forest lakes. Despite the rapid decline in lake water concentrations of SO4 -2 and NO3 - in response to reduced S and N emissions, their present concentrations in some lakes are higher than predictionsbased on observed concentrations at comparable emission rates during development of acidification. This hysteresis in chemical reversal from acidification has delayed biological recovery of the lakes. The only unequivocal sign of biological recovery hasbeen observed in Cerne Lake (Bohemian Forest) where a cladoceran species Ceriodaphnia quadrangular has recentlyreached its pre-acidification abundance.

Deposition and Storage of Spheroidal Carbonaceous Fly-Ash Particles in European Mountain Lake Sediments and Catchment Soils

Spheroidal carbonaceous particles(SCPs) are produced only from high temperaturecombustion of fossil-fuels. In mountain lakesystems, they provide an unambiguous indicator ofatmospheric deposition. In order to comparedepositional fluxes of SCPs between mountainareas experiencing various pollutant regimes,intensive bulk deposition sampling was undertakenat five sites across Europe. Catchment soil coresand lake sediment cores were also taken at eachsite to compare SCP storage over the post-industrial period. Atmospheric, sediment and soilSCP data showed similar patterns. Highestcontamination was found in Scotland, Slovakia andSpain with the Austrian site intermediate and themid-Norwegian site least contaminated. A highproportion of accumulated SCPs were found to bestored in catchment soils at each site.Therefore, a significant increase in soilerosion, possibly as a result of future climatechange, could lead to the input of largequantities of catchment stored SCPs and, byimplication, other atmospherically depositedcontaminants to the lake ecosystem.

The historical record of PAH, PCB, trace metal and fly-ash particle deposition at a remote lake in north-west Scotland

Sediment cores taken from the deep basin of Loch Coire nan Arr in north-west Scotland were dated using 210Pb calibrated spheroidal carbonaceous particle (SCP) profiles and analysed for trace metals, polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs). These data show that the site is one of the least contaminated by atmospheric pollution in the UK. Peak concentrations of PAHs were found to be equivalent to background values at sites in the English Lake District. The date of concentration maxima for SCP, PCB and some metals were in agreement with previously published polychlorinated dibenzo-p-dioxin/polychlorinated dibenzofuran (PCDD/F) data suggesting long-range industrial sources. The date of individual PAH concentration maxima were earlier, but concomitant with each other, possibly suggesting the influence of a local source. Comparison with remote European mountain lakes shows Loch Coire nan Arr to be one of the least contaminated sites in Europe with respect to PCBs, but more contaminated with respect to PAHs.

Polycyclic aromatic hydrocarbons in remote mountain lake waters

Polycyclic aromatic hydrocarbons (PAH), including alkylated and sulfur derivatives, were identified and measured in the waters from three European remote mountain lakes during both ice-free and ice covered periods. The measured concentrations were in the same order in all three lakes (700–1100 pg/l). The PAH patterns in both dissolved and particulate water phases were dominated by the low molecular weight compounds (i.e. phenanthrene, fluoranthene and pyrene) in Lakes Redó (Pyrenees) and Gossenkölle (Alps). In contrast, the high molecular weight (HMW) compounds (i.e. chrysene+triphenylene, benzofluoranthenes, benzo[ e]pyrene) were very significant in lake Øvre Neådalsvatn (Caledonian). These HMW PAH correspond to mixtures originating from high temperature combustion processes which have been photodegraded during long range atmospheric transport and parallel the PAH mixtures encountered in the underlying lake sediments. In contrast, dissolved PAH exhibit temperature dependence with higher concentrations found at water temperatures below 6–7°C reflecting higher condensation from the atmospheric gas phase reservoir.

Selective trapping of organochlorine compounds in mountain lakes of temperate areas.

The study of fish concentrations and sediment inventories in 19 European high mountain lakes (40-67 degrees N) shows that a fraction of organochlorine compounds (OCs), the less volatile compounds (LVC; subcooled liquid vapor pressure < or = 10(-2.5) Pa), are trapped in the higher locations. This general trend is not significantly influenced by possible local sources. Compound distribution is related to average air temperatures. The phase-change pseudoenthalpies calculated from the sediment inventories closely match the summed theoretical volatilization and dissolution enthalpies. This fractionation effect is responsible for the accumulation of high concentrations of the LVC, the more persistent and toxic according to literature data, in organisms inhabiting sites far from the locations of synthesis or use.

Organochlorine pollutants in remote mountain lake waters.

Hexachlorocyclohexanes (HCHs; alpha- and gamma-isomers), endosulfans (alpha- and beta-isomers and the sulfate residue), hexachlorobenzene (HCB), dichlorodiphenyltrichloroethane (DDTs), and polychlorobiphenyls (PCBs) were measured in waters from three European remote mountain lakes situated in the Alps, Pyrenees, and Caledonian mountains. Sampling encompassed both ice-free and ice-covered periods at different water column depths. High HCH concentrations were found in all lakes, those in the Alps and Pyrenees (990-2,900 pg/L) being among the highest recorded in continental waters. Endosulfans and endosulfan sulfate (120-1,150 pg/L) were the second major group of organochlorine contaminants, showing a remarkable stability upon atmospheric long-range transport. The concentrations of HCB, DDTs, and PCB (4-8, 0.6-16, and 26-110 pg/L, respectively) were low in comparison with other continental waters. Hexachlorocyclohexanes, endosulfans, and HCB were essentially found in the dissolved phase. Phase partitioning of the more hydrophobic compounds exhibited a dependence on temperature and water-suspended particles. Comparison between different sampling seasons and water depths indicated a remarkable concentration uniformity within lake, but major interlake differences. Normalization to turnover rates showed higher interlake similarity. Preferential accumulation of the less volatile compounds in the Alp lake and significant increase of baseline contributions of organochlorine compounds and residues in the Caledonian lake are also evidenced from these turnover rates.

Persistent organic pollutants in snow from European high mountain areas

Snow cores were collected in the catchment area of five remote mountain lakes in Europe. They were analysed for polycyclic aromatic hydrocarbons (PAH), polychlorinated biphenyls (PCB), and organochlorine pesticides, namely DDTs, hexachlorobenzene (HCB) and hexachlorocyclohexanes (HCH). PAH are found in higher amounts in the Tatra and Caledonian mountains, PCB are higher in the Alps and HCH are highest in the Alps and Pyrenees. The qualitative PAH distributions are dominated by low molecular weight compounds, phenanthrene being the most abundant PAH in all but in one site. These compounds also occur predominantly in the gas phase in the atmosphere. Their high abundance in the snowpack witness the occurrence of effective transfer mechanisms from gas to snow flakes. In Starolesnianske (Tatra mountains), a higher contribution of high molecular weight compounds is found. This site exhibits the highest snow PAH and suspended particulate levels. Transformation of the concentration values of these compounds into annual deposition rates and correction for catchment/lake area indicates that in Scandinavia and the Alps a large proportion of PAH incorporation is mediated by snowfallout whereas in the Tatra mountains snow deposition only accounts for a small fraction of the compounds stored in the lake sediments. Among organochlorine compounds, only PCB and HCH have been found above method detection limit in most of the samples. The PCB congener distributions changes significantly between sites, although a predominance of the less chlorinated congeners have generally been observed.

Radiometric dating of sediment records in European mountain lakes

Sediment cores from seven European mountain lakes collected as part of a study of palaeolimnogical records of climate change (the MOLAR project) were dated radiometrically by 210Pb. In spite of the remote locations, only one site recorded more or less uniform sediment accumulation throughout the past 150 years. At three further sites the 210Pb record indicated uniform sedimentation up until ca 1950 but significant increases since then. Stratigraphic dates based on records of fallout 137Cs and 241Am showed that 210Pb supply rates to these core sites had nonetheless remained relatively constant and that the sediments could be dated by the CRS model. At the remaining sites there were indications of episodic changes in both sedimentation rates and 210Pb supply rates. Since the changes were not in proportion, neither of the simple dating models (CRS or CIC) was applicable. Using the 137Cs and 241Am stratigraphic dates as reference points it was however possible to construct a realistic chronology for these cores by applying the CRS model piecewise to each time-bounded section.

Reconstructing temperature variations at high elevation lake sites in Europe during the instrumental period

The longest instrumental climate records that exist anywhere in the world are those from lowland Europe. In contrast, instrumental climate records from European upland areas are generally short and scarce. The study of mountain climate is nevertheless important, since alpine areas represent some of the most pristine and unpolluted environments on Earth, and provide a variety of palaeoclimate proxy records (e.g. mountain lake sediments and alpine glaciers). Furthermore, air-temperature anomalies at mountain sites in the European Alps show an amplification of the climate signal with respect to nearby lowland stations (BENISTON et al. 1997), emphasizing the value of mountain areas for the study of climate change. Our aim here is to construct a statistical model to provide transfer functions from lowland to upland climates. This is made possible by the high correlation we find between lowland and upland temperature records (after removing seasonal effects). Our statistical model, which is based on stepwise multiple linear regression, provides the basis for the climate reconstruction at several remote mountain lakes in Europe now being studied as part of the MOLAR project. Climatic forcing is important for high altitude lakes (SOMMARUGA-WOGRATH et al. 1997). In particular, climate has an important effect on the duration of ice cover (e.g. RUOSTEENOJA 1986) and growing season (MELA 1996). Both ice cover and growing season condition the seasonal evolution of the lakes chemically (e.g. pH), physically (e.g. lake stratification and circulation) and ecologically (e.g. productivity). This paper describes the use of reconstructed surface air temperatures to derive long series (1781–1997) of estimates of ice-cover and growing season duration for five alpine lakes in Europe.

Investigations on pelagic food webs in mountain lakes - aims and methods

A methodical approach for the assessment of pelagic biomass and the main carbon fluxes in remote and hardly accessible mountain lakes was elaborated and tested. Number and biomass of bacteria (BAC), autotrophic picoplankton (APP), heterotrophic nanoflagellates (HNF), ciliates (CIL), phytoplankton (PHY), zooplankton smaller than 40 μm (ZOOS) and zooplankton larger than 40 μm (ZOOL) were investigated regularly during two ice-free periods in 13 European mountain lakes (1st level approach – fixed samples elaborated in specialized laboratories). Carbon fluxes measured in 9 lakes included: primary production, exudation by PHY and BAC uptake of exudates, BAC production, elimination of BAC. These processes were measured in the field by specialized teams (2nd level approach). The ranges of values found in mountain lakes were evaluated and possible methodical and interpretative errors discussed. BAC were a significant component of pelagic biomass. The intercomparison between different partners showed differences in bacterial counts lower than 10%, whereas the mean cell volumes measured fluctuated by more than 40%. APP was never found in a significant quantity, except in one lake. HNF and CIL, though regularly found, were usually scarce and only occasionally significant in terms of biomass. The main components of pelagic biomass were BAC, PHY and ZOOL+ZOOS, except for acidified lakes, where zooplankton was very low. In oligotrophic mountain lakes, the percentage of extracellular production in the total primary production was considerable. Bacterial abundance and production often reached values quite comparable with the situation found in lowland mesotrophic lakes during winter.

The spatial and temporal distributions of spheroidal carbonaceous fly-ash particles (SCP) in the sediment records of European mountain lakes

Sediment cores were taken from 31 mountain lakes in 11 countries across Europe. For each core a full spheroidal carbonaceous particle (SCP) profile was produced. SCP are derived from the high temperature combustion of fossil-fuels and provide an unambiguous record of the atmospheric deposition of anthropogenic pollutants. The data from the sediment cores were therefore able to show both temporal and spatial trends in pollutant deposition across the continent from Svalbard to southern Spain and from Ireland to the Tatra mountains. In general, the temporal trends throughout Europe were remarkably consistent and were seen to be in good agreement with known historical emissions, combustion figures and modelled historical pollutant patterns for source countries. Spatial patterns showed that highest concentrations and accumulation rates were in central Europe, with clear decreases northwards and southwards from the region. An east to west decrease was also apparent. SCP profiles can be converted to full post-Industrial inventories and normalised against a 210Pb inventory to create a ‘pollution index’ covering the whole of the SCP record. Such indices take into account sediment variability and some catchment influences and are therefore better for inter-site comparisons. These results were seen to show a clear latitudinal pattern, with a maximum at around 50°N and declining to the north and south. This agrees with European sulphur emissions data and are generally consistent with EMEP modelled distribution patterns. In many cases the SCP temporal profiles could only be explained by using emission and combustion statistics from more than one country emphasising the transboundary nature of particulate transport throughout Europe, in general, supporting EMEP modelled ‘blame matrices’.

Surface-sediment and epilithic diatom pH calibration sets for remote European mountain lakes (AL:PE Project) and their comparison with the Surface Waters Acidification Programme (SWAP) calibration set

A modern diatom-pH calibration data-set consisting of surface-sediment diatom assemblages from 118 lakes and 530 taxa is presented. The AL:PE data-set is from high-altitude or high-latitude lakes in the Alps, Norway, Svalbard, Kola Peninsula, UK, Slovenia, Slovakia, Poland, Portugal, and Spain (pH range = 4.5‐8.0; DOC range = 0.2‐3.2 mg l ‐1 ). In addition, 92 epilithon samples from 22 high-altitude or high-latitude lakes comprise an AL:PE epilithon diatom-pH data-set. Weighted averaging partial least squares regression is used to develop pH-inference models. The AL:PE data-set has a root-mean-square-error of prediction (RMSEP) of 0.33 and a maximum bias of 0.36 pH units and r 2 of 0.82, as assessed by leave-one-out cross-validation. The epilithon data-set has, after data-screening and the deletion of one very obvious outlier, a RMSEP of 0.23 and a maximum bias of 0.18 pH units and r 2 of 0.88. The 167 sample SWAP diatom-pH data-set from lowland or upland lakes in the UK, Norway, and Sweden has a RMSEP of 0.29 and a maximum bias of 0.23 pH units and r 2 of 0.86. The pH optima, as estimated by weighted averaging and Gaussian regression, are compared for the three datasets (AL:PE, SWAP, AL:PE epilithon). There is a good correspondence between the AL:PE and the AL:PE epilithon optima, but a consistent bias between the AL:PE and SWAP optima, with the SWAP optima being lower than the AL:PE estimates. The predictive performances of the AL:PE and SWAP calibration data-sets are compared using independent test samples and six core sequences, all from high-altitude lakes, one in south-east Siberia and five in eastern Scotland. The results show the importance of using the AL:PE data-set for inferring lake-water pH from diatom assemblages in high-altitude or high latitude lakes with low DOC concentrations. * Deceased

Carbonaceous particle record in lake sediments from the Arctic and other remote areas of the Northern Hemisphere

Lake sediments, including spheroidal carbonaceous particles produced by high temperature combustion of fossil fuels, contain a record of lake, catchment and atmospheric deposition history. The spatial and temporal distributions of these particles can indicate the extent to which a single lake or a region has been contaminated by airborne pollutants (e.g. sulfur, polycyclic aromatic hydrocarbons (PAHs)) derived from fossil fuels. The carbonaceous particle records of two Arctic lakes, Shuonija¨vr and Stepanovichja¨rvi, close to local pollution sources on the Kola Peninsula, Russia, are compared with the record of a remote lake on Svalbard and with mid-latitude remote mountain lakes in Europe and Asia. Although, Shuonija¨vr and Stepanovichja¨rvi show relatively high levels of contamination, as expected, the presence of carbonaceous particles at all of the remote sites studied suggests there is a hemispherical background of these particles. Other less remote mountain lakes in Europe have been found to contain significant concentrations of particles and these may represent regional deposition patterns. Carbonaceous particle analysis may provide an effective assessment of whether a lake site is receiving local, regional or background levels of deposition.

Southernmost high mountain lakes in Europe (Sierra Nevada) as reference sites for pollution and climate change monitoring

Southernmost high mountain lakes in Europe (Sierra Nevada) as reference sites for pollution and climate change monitoring