Search

Marginal sea ecosystems, such as the Baltic Sea, are severely affected by anthropogenic pressures, such as climate warming, pollution, and eutrophication, which increased in the course of the past century. Biodiversity monitoring data and assessment of environmental status in such systems have typically been carried out only for the past few decades, if at all, and knowledge on pre-impact stability and good ecological status is limited. An extension of monitoring time series can potentially be achieved through analyses of paleoecological records, e.g. for phytoplankton, which form the base of the food web and are highly susceptible to environmental changes. Within the phytoplankton community, dinoflagellates and diatoms play a significant role as primary producers, and their relative dominance in the spring bloom, calculated as Dia/Dino index, is used as an indicator for the environmental status of the Baltic Sea. To extend time series on the dominance patterns and include non-fossilized dinoflagellates, we here establish a simple droplet digital PCR (ddPCR) reaction on ancient DNA from sediment cores that decodes phytoplankton dynamics. We focus on two common spring bloom species, the diatom Skeletonema marinoi and the dinoflagellate Apocalathium malmogiense, for which we evaluate a DNA based dominance index. It performs very well in comparison to DNA metabarcoding and modern monitoring and can elucidate past species dominance across the past century and across millennia in different basins of the Baltic. For the past century, we see a dominance shift already starting before the mid-20th century in two of the Baltic Sea basins, thus substantially predating current monitoring programs. Shifts are only partly coeval among the cores and the index shows different degrees of stability. This pattern is confirmed across millennia, where a long-term stable relationship between the diatom and the dinoflagellate is observed in the Eastern Gotland Basin, while data from the G

Directly observing the chronology and tempo of adaptation in response to ecological change is rarely possible in natural ecosystems. Sedimentary ancient DNA (sedaDNA) has been shown to be a tractable source of genome-scale data of long-dead organisms1,2,3 and to thereby potentially provide an understanding of the evolutionary histories of past populations.4,5 To date, time series of ecosystem biodiversity have been reconstructed from sedaDNA, typically using DNA metabarcoding or shotgun sequence data generated from less than 1 g of sediment.6,7 Here, we maximize sequence coverage by extracting DNA from ∼50× more sediment per sample than the majority of previous studies1,2,3 to achieve genotype resolution. From a time series of Late Pleistocene sediments spanning from a marine to freshwater ecosystem, we compare adaptive genotypes reconstructed from the environmental genomes of three-spined stickleback at key time points of this transition. We find a staggered temporal dynamic in which freshwater alleles at known loci of large effect in marine-freshwater divergence of three-spined stickleback (e.g., EDA)8 were already established during the brackish phase of the formation of the isolation basin. However, marine alleles were still detected across the majority of marine-freshwater divergence-associated loci, even after the complete isolation of the lake from marine ingression. Our retrospective approach to studying adaptation from environmental genomes of three-spined sticklebacks at the end of the last glacial period complements contemporary experimental approaches9,10,11 and highlights the untapped potential for retrospective “evolve and resequence” natural experiments using sedaDNA.

Directly observing the chronology and tempo of adaptation in response to ecological change is rarely possible in natural ecosystems. Sedimentary ancient DNA (sedaDNA) has been shown to be a tractable source of genome-scale data of long-dead organisms1,2,3 and to thereby potentially provide an understanding of the evolutionary histories of past populations.4,5 To date, time series of ecosystem biodiversity have been reconstructed from sedaDNA, typically using DNA metabarcoding or shotgun sequence data generated from less than 1 g of sediment.6,7 Here, we maximize sequence coverage by extracting DNA from ∼50× more sediment per sample than the majority of previous studies1,2,3 to achieve genotype resolution. From a time series of Late Pleistocene sediments spanning from a marine to freshwater ecosystem, we compare adaptive genotypes reconstructed from the environmental genomes of three-spined stickleback at key time points of this transition. We find a staggered temporal dynamic in which freshwater alleles at known loci of large effect in marine-freshwater divergence of three-spined stickleback (e.g., EDA)8 were already established during the brackish phase of the formation of the isolation basin. However, marine alleles were still detected across the majority of marine-freshwater divergence-associated loci, even after the complete isolation of the lake from marine ingression. Our retrospective approach to studying adaptation from environmental genomes of three-spined sticklebacks at the end of the last glacial period complements contemporary experimental approaches9,10,11 and highlights the untapped potential for retrospective “evolve and resequence” natural experiments using sedaDNA.

High-altitude Pyrenean lakes are ecosystems far from local pollution sources, and thus they are particularly sensitive to the atmospheric deposition of metals and metalloids. This study aims to quantify the effect of human activity in 18 lakes located in both side of the France–Spain frontier. Sediment cores were collected in summer 2013, sampled at a 1cm resolution and the concentration of 24 elements was measured by ICP-MS. Statistic and chemometric analysis of the results highlights the influence of the geographical position and lithogenic features of each lake basin on trapping pollutants. More than the 80% of the lakes showed values of enrichment factor (EF) above 2 for at least one of the elements investigated in at least one core interval, which corroborates the existence of historical anthropogenic inputs of elements in the studied area. The results demonstrate the natural origin of As and Ti in Pyrenees, together with the significant anthropogenic inputs of Cd, Pb, Sb and Sn from ancient times. The data set points mining activities as the main historical source of pollution and illustrate the large impact of the industrial revolution. The regional variability could reflect also differential long-range transport, followed by dry or wet deposition.

High-altitude Pyrenean lakes are ecosystems far from local pollution sources, and thus they are particularly sensitive to the atmospheric deposition of metals and metalloids. This study aims to quantify the effect of human activity in 18 lakes located in both side of the France–Spain frontier. Sediment cores were collected in summer 2013, sampled at a 1cm resolution and the concentration of 24 elements was measured by ICP-MS. Statistic and chemometric analysis of the results highlights the influence of the geographical position and lithogenic features of each lake basin on trapping pollutants. More than the 80% of the lakes showed values of enrichment factor (EF) above 2 for at least one of the elements investigated in at least one core interval, which corroborates the existence of historical anthropogenic inputs of elements in the studied area. The results demonstrate the natural origin of As and Ti in Pyrenees, together with the significant anthropogenic inputs of Cd, Pb, Sb and Sn from ancient times. The data set points mining activities as the main historical source of pollution and illustrate the large impact of the industrial revolution. The regional variability could reflect also differential long-range transport, followed by dry or wet deposition.

High-altitude Pyrenean lakes are ecosystems far from local pollution sources, and thus they are particularly sensitive to the atmospheric deposition of metals and metalloids. This study aims to quantify the effect of human activity in 18 lakes located in both side of the France–Spain frontier. Sediment cores were collected in summer 2013, sampled at a 1cm resolution and the concentration of 24 elements was measured by ICP-MS. Statistic and chemometric analysis of the results highlights the influence of the geographical position and lithogenic features of each lake basin on trapping pollutants. More than the 80% of the lakes showed values of enrichment factor (EF) above 2 for at least one of the elements investigated in at least one core interval, which corroborates the existence of historical anthropogenic inputs of elements in the studied area. The results demonstrate the natural origin of As and Ti in Pyrenees, together with the significant anthropogenic inputs of Cd, Pb, Sb and Sn from ancient times. The data set points mining activities as the main historical source of pollution and illustrate the large impact of the industrial revolution. The regional variability could reflect also differential long-range transport, followed by dry or wet deposition.

The suitability of lake sediment cores to reconstruct past inputs, regional pollution, and usage patterns of pesticides has been shown previously. Until now, no such data exist for lakes in eastern Germany. Therefore, 10 sediment cores (length 1 m) of 10 lakes in eastern Germany, the territory of the former German Democratic Republic (GDR), were collected and cut into 5–10-mm layers. In each layer, concentrations of trace elements (TEs) As, Cd, Cr, Cu, Ni, Pb, S, and Zn, as well as of organochlorine pesticides (OCPs), i.e., dichlorodiphenyltrichloroethane (DDT) and hexachlorocyclohexane (HCH), were analyzed. A miniaturized solid–liquid extraction technique in conjunction with headspace solid-phase microextraction (HS-SPME) and gas chromatography–mass spectrometry (GC–MS) was used for the latter. The progression of TE concentrations over time is uniform. It follows a trans-regional pattern and is indicative of activity and policy making in West Germany before 1990 instead of those in the GDR. Of OCPs, only transformation products of DDT were found. Congener ratios indicate a mainly aerial input. In the lakes’ profiles, several regional features and responses to national policies and measures are visible. Dichlorodiphenyldichloroethane (DDD) concentrations reflect the history of DDT use in the GDR. Lake sediments proved to be suitable to archive short- and long-range impacts of anthropogenic activity. Our data can be used to complement and validate other forms of environmental pollution long-term monitoring and to check for the efficiency of pollution countermeasures in the past.

Reconstructing sediment accumulation rates reveals historical environmental shifts. We analyzed 15 element concentrations and accumulation rates in two Red Sea sediment cores over 500 years. Post-1870s, the South Red Sea experienced a significant drop in element accumulation rates, with a noticeable decline in nutrients like magnesium (−8.52%), organic carbon (−14.9%), nitrogen (−14.0%), phosphorus (−16.4%), sulfur (−17.2%), and calcium (−17.8%). This suggests a potential reduction in nutrient inflow from the Indian Ocean, possibly due to warming-induced ocean stratification. Conversely, the North Red Sea saw an increase in all element accumulation rates after the 1870s, highlighting a rise in trace elements such as iron (4.56%), cadmium (8.69%), vanadium (12.6%), zinc (13.8%), copper (14.4%), chromium (17.6%), and nickel (19.5%), indicative of increased anthropogenic coastal activities. We introduce the term “Cai-Agusti Marine Crisis Conflux” to encapsulate the escalating thermal stress, nutrient depletion, and elemental pollution in the Red Sea, underscoring potential risks to its ecosystems and global implications.

The suitability of lake sediment cores to reconstruct past inputs, regional pollution, and usage patterns of pesticides has been shown previously. Until now, no such data exist for lakes in eastern Germany. Therefore, 10 sediment cores (length 1 m) of 10 lakes in eastern Germany, the territory of the former German Democratic Republic (GDR), were collected and cut into 5–10-mm layers. In each layer, concentrations of trace elements (TEs) As, Cd, Cr, Cu, Ni, Pb, S, and Zn, as well as of organochlorine pesticides (OCPs), i.e., dichlorodiphenyltrichloroethane (DDT) and hexachlorocyclohexane (HCH), were analyzed. A miniaturized solid–liquid extraction technique in conjunction with headspace solid-phase microextraction (HS-SPME) and gas chromatography–mass spectrometry (GC–MS) was used for the latter. The progression of TE concentrations over time is uniform. It follows a trans-regional pattern and is indicative of activity and policy making in West Germany before 1990 instead of those in the GDR. Of OCPs, only transformation products of DDT were found. Congener ratios indicate a mainly aerial input. In the lakes’ profiles, several regional features and responses to national policies and measures are visible. Dichlorodiphenyldichloroethane (DDD) concentrations reflect the history of DDT use in the GDR. Lake sediments proved to be suitable to archive short- and long-range impacts of anthropogenic activity. Our data can be used to complement and validate other forms of environmental pollution long-term monitoring and to check for the efficiency of pollution countermeasures in the past.

Introduction Bryophyte diaspore banks are a critical aspect of the life strategy of some species yet remain neglected and poorly understood. This study investigated the longevity in natural habitat of the diaspore bank of Physcomitrium eurystomum Sendtn., a moss species that is threatened with extinction in Europe. Methods Undisturbed soil cores of 40 cm depth were collected from Langmere, Norfolk, UK, and were split into investigated sediment layers of 1 cm depth. Dating of sediment layers was done by an analysis of radionuclides, and diaspore germination trials of each layer were carried out in a growth chamber. DNA barcoding was used to help identify plants that germinated. Key results and conclusions Viable diaspores of Physcomitrium eurystomum frequently occurred in sediment layers that were at least 100 years old and continued to occur in much lower layers that were probably several hundred years old. The long-term survival of bryophytes underground can have important implications for conservation decisions.

Since 1945, a large amount of heterogeneous data has been acquired to survey river sediment quality, especially concerning regulatory metals such as Cd, Cr, Cu, Hg, Ni, Pb, and Zn. Large-scale syntheses are critical to assess the effectiveness of public regulations and the resiliency of the river systems. Accordingly, this data synthesis proposes a first attempt to decipher spatio-temporal trends of metal contamination along seven major continental rivers in Western Europe (France, Belgium, Germany, and the Netherlands). A large dataset (>12,000 samples) from various sediment matrices (bed and flood deposits – BFD, suspended particulate matter – SPM, dated sediment cores – DSC) was set up based on monitoring and scientific research from the 1950s to the 2010s. This work investigates the impact of analytical protocols (matrix sampling, fractionation, extraction), location and time factors (related to geology and anthropogenic activities) on metal concentration trends. Statistical analyses highlight crossed-interactions in space and time, as well as between sediment matrices (metal concentrations in SPM ≃ DSC > BFD) and extraction procedures (also related to river lithology). Major spatio-temporal trends are found along several rivers such as (i) an increase of metal concentrations downstream of the main urban industrial areas (e.g. Paris-Rouen corridor on the Seine River, Bonn-Duisburg corridor on the Rhine River), (ii) a long-term influence of former mining areas located in crystalline zones, releasing heavily contaminated sediments for decades (Upper Loire River, Middle Meuse section), (iii) a decrease of metal concentrations since the 1970s (except for Cr and Ni, rather low and stable over time). The improvement of sediment quality in the most recent years in Europe reflects a decisive role of environment policies, such as more efficient wastewater treatments, local applications of the Water Framework Directive and urban industrial changes in the river va

Carbon accumulation in coastal wetlands is normally assessed by extracting a sediment core and estimating its carbon content and bulk density. Because carbon content and bulk density are functionally related, the latter can be estimated gravimetrically from a section of the core or, alternatively, from the carbon content in the sample using the mixing model equation from soil science. Using sediment samples from La Paz Bay, Mexico, we analyzed the effect that the choice of corer and the method used to estimate bulk density could have on the final estimates of carbon storage in the sediments. We validated the results using a larger dataset of tropical mangroves, and then by Monte Carlo simulation. The choice of corer did not have sizable influence on the final estimates of carbon density. The main factor in selecting a corer is the operational difficulties that each corer may have in different types of sediments. Because of the multiplication of errors in a product of two variables subject to random sampling error, when using gravimetric estimates of bulk density, the dispersion of the data points in the estimation of total carbon density rises rapidly as the amount of carbon in the sediment increases. In contrast, the estimation of total carbon density using only the carbon fraction as a predictor is very precise, especially in sediments rich in organic matter. This method, however, depends critically on the accurate estimation of the two parameters of the mixing model: the bulk density of pure peat and the bulk density of pure mineral sediment. The estimation of carbon densities in peaty sediments can be very imprecise when using gravimetric bulk densities. Estimating carbon density in peaty sediments using only the estimate of organic fraction can be much more precise, provided the model parameters are estimated with accuracy. These results open the door for simplified and precise estimates of carbon dynamics in mangroves and coastal wetlands.

Sediment cores can inform about the temporal trend of pollutants in an environment. Different sediment layers, settled at different times represent the pollution in that moment. A sediment core in the inner part of the Ría de Vigo was collected and some layers analysed in order to determine the temporal trend of PAHs in the last decades. PAHs can have a natural (biogenic) and anthropogenic origin but generally the last one is the predominant. The main sources of PAHs to the environment are petroleum and coal combustions as well as fires or even the use of pitch or other petroleum products. In this study 35 individual PAHs were analysed (including parent and alkylated ones) as well as some groups of alkylated PAHs. A QA/QC is put in place to guarantee the quality of the analysis- The sum of 16 EPA PAHs was in the range of 200-1000 µg/kg d.w. with a clear increase in the values in the more recent layers pointing at the anthropogenic activity as one of the main drivers of the PAH concentrations in sediments. The values are in the range of other estuarine areas with values above the reference values (background) but generally below the ERL and so not expected to be causing adverse biological effects. The study of the isomeric ratios of PAHs show that the origin has not changed during the period studied and it is mainly petroleum combustion mixed with different types of combustion.

During the 20th century, many lakes in the Northern Hemisphere were affected by increasing human population and urbanization along their shorelines and catchment, resulting in aquatic eutrophication. Ecosystem monitoring commenced only after the changes became apparent, precluding any examination of timing and dynamics of initial community change in the past and comparison of pre- and postimpact communities. Peri-Alpine Lake Constance (Germany) underwent a mid-century period of eutrophication followed by re-oligotrophication since the 1980s and is now experiencing warm temperatures. We extended the period for which monitoring data of indicator organisms exist by analysing historical environmental DNA (eDNA) from a sediment core dating back some 110 years. Using three metabarcoding markers-for microbial eukaryotes, diatoms and cyanobacteria-we revealed two major breakpoints of community change, in the 1930s and the mid-1990s. In our core, the latest response was exhibited by diatoms, which are classically used as palaeo-bioindicators for the trophic state of lakes. Following re-oligotrophication, overall diversity values reverted to similar ones of the early 20th century, but multivariate analysis indicated that the present community is substantially dissimilar. Community changes of all three groups were strongly correlated to phosphorus concentration changes, whereas significant relationships to temperature were only observed when we did not account for temporal autocorrelation. Our results indicate that each microbial group analysed exhibited a unique response, highlighting the particular strength of multimarker analysis of eDNA, which is not limited to organisms with visible remains and can therefore discover yet unknown responses and abiotic-biotic relationships.

During the 20th century, many lakes in the Northern Hemisphere were affected by increasing human population and urbanization along their shorelines and catchment, resulting in aquatic eutrophication. Ecosystem monitoring commenced only after the changes became apparent, precluding any examination of timing and dynamics of initial community change in the past and comparison of pre- and postimpact communities. Peri-Alpine Lake Constance (Germany) underwent a mid-century period of eutrophication followed by re-oligotrophication since the 1980s and is now experiencing warm temperatures. We extended the period for which monitoring data of indicator organisms exist by analysing historical environmental DNA (eDNA) from a sediment core dating back some 110 years. Using three metabarcoding markers-for microbial eukaryotes, diatoms and cyanobacteria-we revealed two major breakpoints of community change, in the 1930s and the mid-1990s. In our core, the latest response was exhibited by diatoms, which are classically used as palaeo-bioindicators for the trophic state of lakes. Following re-oligotrophication, overall diversity values reverted to similar ones of the early 20th century, but multivariate analysis indicated that the present community is substantially dissimilar. Community changes of all three groups were strongly correlated to phosphorus concentration changes, whereas significant relationships to temperature were only observed when we did not account for temporal autocorrelation. Our results indicate that each microbial group analysed exhibited a unique response, highlighting the particular strength of multimarker analysis of eDNA, which is not limited to organisms with visible remains and can therefore discover yet unknown responses and abiotic-biotic relationships.

Since 1750, human emissions of greenhouse gases have created a temperature increase, affecting the whole world. Diatoms, single-celled microscopic algae that lives in waters all over the world, have different environmental preferences such as the water depth at which the thrive, salinity, nutrients, pH-values and more. Diatoms also responds quickly to changing circumstances, which makes the suitable as environmental indicators. The purpose of the study is to investigate how the abundance and composition of diatoms has changed during the last 200 years in lake Ensjön, located just south of Norrköping, and to relate those changes both to climate change and known events and environmental factors in the area. The survey is conducted by subsampling sediment cores from which each diatom sample was prepared in accordance with the scheme of Battarbee (1984). The diatoms in the samples were counted under a microscope and the results were analyzed and related to the Cyclotella-Aulacoseira-Fragilaria-theory (CAF) and documented historical events in the local environment. The result of the analysis shows that the composition and abundance of diatoms has changed during the last 200 years, and that this change is due to both climate change (temperature and precipitation increase) and the land-use history of Ensjön. The cahnges in composition of Aulacoseira spp. and Cyclotella spp., where Aulacoseira spp. is expected to decrease, and Cyclotella spp. is expected to increase with a rising temperature, match the CAF-theory for the most part. The change in composition also coincides with several documented environmental factors in the area, especially the change in use of fertilizers and herbicides in agriculture., Människans utsläpp av växthusgaser har sedan år 1750 skapat en temperaturökning som går allt snabbare, och påverkar hela världen. Kiselalger, encelliga mikroskopiska alger som lever i vatten över hela världen, har olika miljöpreferenser såsom bland annat på vilket vattendjup de trivs, optimal halt av salt, näringsvärden, pH-värden, samt reagerar snabbt på förändrade omständigheter, vilket gör dem lämpliga som miljöindikatorer. Syftet med studien är att studera förändringar i kiselalgernas sammansättning under de senaste 200 åren i den lilla sjön Ensjön belägen något söder om Norrköping och att relatera dessa förändringar till dokumenterade händelser och miljöfaktorer i sjöns avrinningsområde samt till de pågående klimatförändringarna. Undersökningen är utförd genom provtagning av sedimentkärnor från vilka prover preparerades enligt Battarbees (1984) flödesschema. Proverna av kiselalger räknades under mikroskop och sammansättningen analyserades utifrån teorin Cyclotella-Aulacoseira-Fragilaria (CAF) och kända historiska händelser i närmiljön. Analysresultatet visade att kiselalgssammansättningen har förändrats under de senaste 200 åren, och att denna förändring sannolikt kan kopplas både till klimatförändringar (en ökad temperatur) och Ensjöns markanvändningshistoria. Förändringen hos Aulacoseira spp. och Cyclotella spp. följer till stor del CAF-teorin om att det första släktet skulle minska och det andra skulle öka vid en temperaturökning. Vid flera tillfällen sammanfaller förändringar i kiselalgssammansättningen med kända miljöfaktorer i närmiljön, främst i samband med utvecklingen i användningen av mineralgödsel och växtskyddsmedel.

Purpose: Intact lake sediments reflect the development of terrestrial ecosystems. This development can be understood by decoding mineral and geochemical information of sedimentary archives. Therefore, we characterized a Holocene lake sediment core and revealed bulk to micro-scale variations via a combination of geochemical techniques and statistical methods. Methods: A 2.3 m sediment core was collected from Hotagen, a lake in west-central Sweden; a sediment sample was collected every 5 cm. A part of each sediment sample was kept untreated (named bulk) and another part was size-fractionated into < 4, 4–16, 16–64, and > 64 µm subsamples. Characterization was then made with respect to grain size distribution (GSD), physico-chemical parameters, geochemical properties, organic composition, and mineralogy. The sediments were investigated at bulk, micro-, and elemental scales using powder X-ray diffraction (XRD), diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), and scanning electron microscopy coupled to energy-dispersive X-ray spectroscopy (SEM–EDX). Results: The deepest sediment was identified as glacial till dating back to the Late Pleistocene. The bulk sediments showed a clear distinction between 0–195 cm (unit 1, U1) and 200–225 cm (unit 2, U2) depths. Quartz and feldspar minerals decreased and organic matter and clay minerals increased from the till towards the lower limit of U1. The development in the sedimentary properties marked the transformation of the terrestrial ecosystem from glacier-covered land to vegetated areas. This development was also well reflected by the appearance of X-ray amorphous materials and the formation of distinct organo-mineral aggregates; chlorite was the predominant clay mineral in these aggregates. The geochemical variation between U2 and U1 sediments was further established by resolving the DRIFT spectral components through multivariate curve resolution alternating least square (MCR-ALS). The U1 sediments settl

Purpose: Intact lake sediments reflect the development of terrestrial ecosystems. This development can be understood by decoding mineral and geochemical information of sedimentary archives. Therefore, we characterized a Holocene lake sediment core and revealed bulk to micro-scale variations via a combination of geochemical techniques and statistical methods. Methods: A 2.3 m sediment core was collected from Hotagen, a lake in west-central Sweden; a sediment sample was collected every 5 cm. A part of each sediment sample was kept untreated (named bulk) and another part was size-fractionated into < 4, 4–16, 16–64, and > 64 µm subsamples. Characterization was then made with respect to grain size distribution (GSD), physico-chemical parameters, geochemical properties, organic composition, and mineralogy. The sediments were investigated at bulk, micro-, and elemental scales using powder X-ray diffraction (XRD), diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), and scanning electron microscopy coupled to energy-dispersive X-ray spectroscopy (SEM–EDX). Results: The deepest sediment was identified as glacial till dating back to the Late Pleistocene. The bulk sediments showed a clear distinction between 0–195 cm (unit 1, U1) and 200–225 cm (unit 2, U2) depths. Quartz and feldspar minerals decreased and organic matter and clay minerals increased from the till towards the lower limit of U1. The development in the sedimentary properties marked the transformation of the terrestrial ecosystem from glacier-covered land to vegetated areas. This development was also well reflected by the appearance of X-ray amorphous materials and the formation of distinct organo-mineral aggregates; chlorite was the predominant clay mineral in these aggregates. The geochemical variation between U2 and U1 sediments was further established by resolving the DRIFT spectral components through multivariate curve resolution alternating least square (MCR-ALS). The U1 sediments settl

Purpose: Intact lake sediments reflect the development of terrestrial ecosystems. This development can be understood by decoding mineral and geochemical information of sedimentary archives. Therefore, we characterized a Holocene lake sediment core and revealed bulk to micro-scale variations via a combination of geochemical techniques and statistical methods. Methods: A 2.3 m sediment core was collected from Hotagen, a lake in west-central Sweden; a sediment sample was collected every 5 cm. A part of each sediment sample was kept untreated (named bulk) and another part was size-fractionated into < 4, 4–16, 16–64, and > 64 µm subsamples. Characterization was then made with respect to grain size distribution (GSD), physico-chemical parameters, geochemical properties, organic composition, and mineralogy. The sediments were investigated at bulk, micro-, and elemental scales using powder X-ray diffraction (XRD), diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), and scanning electron microscopy coupled to energy-dispersive X-ray spectroscopy (SEM–EDX). Results: The deepest sediment was identified as glacial till dating back to the Late Pleistocene. The bulk sediments showed a clear distinction between 0–195 cm (unit 1, U1) and 200–225 cm (unit 2, U2) depths. Quartz and feldspar minerals decreased and organic matter and clay minerals increased from the till towards the lower limit of U1. The development in the sedimentary properties marked the transformation of the terrestrial ecosystem from glacier-covered land to vegetated areas. This development was also well reflected by the appearance of X-ray amorphous materials and the formation of distinct organo-mineral aggregates; chlorite was the predominant clay mineral in these aggregates. The geochemical variation between U2 and U1 sediments was further established by resolving the DRIFT spectral components through multivariate curve resolution alternating least square (MCR-ALS). The U1 sediments settl

Paleoceanographic archives derived from 17 marine sediment cores reconstruct the response of the Southwest Pacific Ocean to the peak interglacial, Marine Isotope Stage (MIS) 5e (ca. 125 ka). Paleo-Sea Surface Temperature (SST) estimates were obtained from the Random Forest model - an ensemble decision tree tool - applied to core-top planktonic foraminiferal faunas calibrated to modern SSTs. The reconstructed geographic pattern of the SST anomaly (maximum SST between 120 and 132 ka minus mean modern SST) seems to indicate how MIS 5e conditions were generally warmer in the Southwest Pacific, especially in the western Tasman Sea where a strengthened East Australian Current (EAC) likely extended subtropical influence to ca. 45°S off Tasmania. In contrast, the eastern Tasman Sea may have had a modest cooling except around 45°S. The observed pattern resembles that developing under the present warming trend in the region. An increase in wind stress curl over the modern South Pacific is hypothesized to have spun-up the South Pacific Subtropical Gyre, with concurrent increase in subtropical flow in the western boundary currents that include the EAC. However, warmer temperatures along the Subtropical Front and Campbell Plateau to the south suggest that the relative influence of the boundary inflows to eastern New Zealand may have differed in MIS 5e, and these currents may have followed different paths compared to today. Key Points Oceanic conditions at 125 kyr seem to agree with recent observations/trendsEast Australian Current probably stronger and Tasman Front cooler during MIS 5eObserved oceanographic changes likely linked to increases in wind stress curl ©2013. American Geophysical Union. All Rights Reserved.

A device used for paleomagnetic sampling has been improved which allows sampling friable, poorly to moderate lithified sedimentary and volcanic materials. The new device attaches to a portable gasoline drill and employs two steel cutting disks with a 2 cm separation, which cuts two parallel slots in the material being sampled. A second set of cuts orthogonal to the first set produces a square pedestal over which a plastic sample box can be placed and oriented to extract a cubic sample; this procedure permits using the same orientation parameters as for conventionally drilled cylindrical samples. The method allows sampling at localities where conventional drilling fails in weak materials. To test the method, sedimentary sandstones of the Amaga' Formation (Eocene-Miocene) in the NW portion of the Central Colombian Andes were sampled. The anisotropy of magnetic susceptibility (AMS) was measured on samples using the new method and compared with results from conventionally drilled cores at the same sites. Results show better AMS within-site precision for box samples compared with the drilled cores. This device improves on previous battery-powered samplers used for sampling by the double-slot procedure. Also the new device can be used with the same gasoline-powered motor for standard core drilling. Copyright © 2013, SEPM (Society for Sedimentary Geology).

Relatively little is known about the long-term response of Caribbean mangroves to human and natural disturbances during the 'Little Ice Age' (LIA). We present new palynological information on the dynamics of the Bahia Honda mangrove from the eastern coast of San Andres Island in the southwestern Caribbean for the late Holocene. Major changes in the Bahia Honda pollen record show the combined effects of natural events (strong storms and sea-level rise), and human disturbances. These changes are supported by 14C dates, sedimentological and palynological information. A storm (most probably a hurricane) was recorded around AD 1600, caused sediment reworking and the subsequent loss of about 2000 years of the vegetation record. The devastation of tree vegetation by this event allowed the expansion of heliophytic vegetation (e.g. grasses and vines). Mangroves and coastal vegetation started to recover at AD 1700, reaching their maximum extent within a few decades, when microforaminifera shells became abundant at the coring site, thus suggesting a relative sea-level rise because of the geomorphic reconfiguration of the coastal plain after the storm. Furthermore, the pollen evidence indicates more humid regional climates during the late LIA (AD 1700-1850). Mangrove and coastal vegetation declined sharply as a consequence of the establishment of coconut plantations around AD 1850. The recovery of the mangroves after AD 1960 is a result of the combined effect of relative sea-level rise and drastic changes in the local economy from coconut plantations to commerce. © 2010 The Author(s).

During the 20th century, many lakes in the Northern Hemisphere were affected by increasing human population and urbanization along their shorelines and catchment, resulting in aquatic eutrophication. Ecosystem monitoring commenced only after the changes became apparent, precluding any examination of timing and dynamics of initial community change in the past and comparison of pre- and postimpact communities. Peri-Alpine Lake Constance (Germany) underwent a mid-century period of eutrophication followed by re-oligotrophication since the 1980s and is now experiencing warm temperatures. We extended the period for which monitoring data of indicator organisms exist by analysing historical environmental DNA (eDNA) from a sediment core dating back some 110 years. Using three metabarcoding markers-for microbial eukaryotes, diatoms and cyanobacteria-we revealed two major breakpoints of community change, in the 1930s and the mid-1990s. In our core, the latest response was exhibited by diatoms, which are classically used as palaeo-bioindicators for the trophic state of lakes. Following re-oligotrophication, overall diversity values reverted to similar ones of the early 20th century, but multivariate analysis indicated that the present community is substantially dissimilar. Community changes of all three groups were strongly correlated to phosphorus concentration changes, whereas significant relationships to temperature were only observed when we did not account for temporal autocorrelation. Our results indicate that each microbial group analysed exhibited a unique response, highlighting the particular strength of multimarker analysis of eDNA, which is not limited to organisms with visible remains and can therefore discover yet unknown responses and abiotic-biotic relationships.

Purpose: Intact lake sediments reflect the development of terrestrial ecosystems. This development can be understood by decoding mineral and geochemical information of sedimentary archives. Therefore, we characterized a Holocene lake sediment core and revealed bulk to micro-scale variations via a combination of geochemical techniques and statistical methods. Methods: A 2.3 m sediment core was collected from Hotagen, a lake in west-central Sweden; a sediment sample was collected every 5 cm. A part of each sediment sample was kept untreated (named bulk) and another part was size-fractionated into < 4, 4–16, 16–64, and > 64 µm subsamples. Characterization was then made with respect to grain size distribution (GSD), physico-chemical parameters, geochemical properties, organic composition, and mineralogy. The sediments were investigated at bulk, micro-, and elemental scales using powder X-ray diffraction (XRD), diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), and scanning electron microscopy coupled to energy-dispersive X-ray spectroscopy (SEM–EDX). Results: The deepest sediment was identified as glacial till dating back to the Late Pleistocene. The bulk sediments showed a clear distinction between 0–195 cm (unit 1, U1) and 200–225 cm (unit 2, U2) depths. Quartz and feldspar minerals decreased and organic matter and clay minerals increased from the till towards the lower limit of U1. The development in the sedimentary properties marked the transformation of the terrestrial ecosystem from glacier-covered land to vegetated areas. This development was also well reflected by the appearance of X-ray amorphous materials and the formation of distinct organo-mineral aggregates; chlorite was the predominant clay mineral in these aggregates. The geochemical variation between U2 and U1 sediments was further established by resolving the DRIFT spectral components through multivariate curve resolution alternating least square (MCR-ALS). The U1 sediments settl

Purpose: Intact lake sediments reflect the development of terrestrial ecosystems. This development can be understood by decoding mineral and geochemical information of sedimentary archives. Therefore, we characterized a Holocene lake sediment core and revealed bulk to micro-scale variations via a combination of geochemical techniques and statistical methods. Methods: A 2.3 m sediment core was collected from Hotagen, a lake in west-central Sweden; a sediment sample was collected every 5 cm. A part of each sediment sample was kept untreated (named bulk) and another part was size-fractionated into < 4, 4–16, 16–64, and > 64 µm subsamples. Characterization was then made with respect to grain size distribution (GSD), physico-chemical parameters, geochemical properties, organic composition, and mineralogy. The sediments were investigated at bulk, micro-, and elemental scales using powder X-ray diffraction (XRD), diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), and scanning electron microscopy coupled to energy-dispersive X-ray spectroscopy (SEM–EDX). Results: The deepest sediment was identified as glacial till dating back to the Late Pleistocene. The bulk sediments showed a clear distinction between 0–195 cm (unit 1, U1) and 200–225 cm (unit 2, U2) depths. Quartz and feldspar minerals decreased and organic matter and clay minerals increased from the till towards the lower limit of U1. The development in the sedimentary properties marked the transformation of the terrestrial ecosystem from glacier-covered land to vegetated areas. This development was also well reflected by the appearance of X-ray amorphous materials and the formation of distinct organo-mineral aggregates; chlorite was the predominant clay mineral in these aggregates. The geochemical variation between U2 and U1 sediments was further established by resolving the DRIFT spectral components through multivariate curve resolution alternating least square (MCR-ALS). The U1 sediments settl

This work reports the first high-resolution deposition records of anthropogenic uranium (236U and 233U) in a sediment core taken at the continental slope of the Philippine Sea off Mindanao Island in the equatorial northwest Pacific Ocean. Two notable peaks were observed in both profiles of 236U and 233U concentrations, with a narrower peak in 1951–1957 corresponding to close-in Pacific Proving Grounds (PPG) signal, and a broader peak in 1960s–1980s corresponding to the global fallout from nuclear weapons testing. 236U and 233U areal cumulative inventories in the studied sediment core are (2.79 ± 0.20) ∙ 1012 atom ∙ m−2 and (3.12 ± 0.41) ∙ 1010 atom ∙ m−2, respectively, about 20–30% of reported 233U and 236U inventories from the direct global fallout deposition. The overall 233U/236U atomic ratios obtained in this work vary within (0.3–3.5) ∙ 10−2, with an integrated 233U/236U atomic ratio of (1.12 ± 0.17) ∙ 10−2. The contribution from global fallout and close-in PPG fallout to 236U in the sediment core is estimated to be about 69% and 31%, respectively. We believe the main driving process for anthropogenic uranium deposition in the Philippine sediment is continuous scavenging of dissolved 236U from the surface seawater by sinking particles.

Since 1750, human emissions of greenhouse gases have created a temperature increase, affecting the whole world. Diatoms, single-celled microscopic algae that lives in waters all over the world, have different environmental preferences such as the water depth at which the thrive, salinity, nutrients, pH-values and more. Diatoms also responds quickly to changing circumstances, which makes the suitable as environmental indicators. The purpose of the study is to investigate how the abundance and composition of diatoms has changed during the last 200 years in lake Ensjön, located just south of Norrköping, and to relate those changes both to climate change and known events and environmental factors in the area. The survey is conducted by subsampling sediment cores from which each diatom sample was prepared in accordance with the scheme of Battarbee (1984). The diatoms in the samples were counted under a microscope and the results were analyzed and related to the Cyclotella-Aulacoseira-Fragilaria-theory (CAF) and documented historical events in the local environment. The result of the analysis shows that the composition and abundance of diatoms has changed during the last 200 years, and that this change is due to both climate change (temperature and precipitation increase) and the land-use history of Ensjön. The cahnges in composition of Aulacoseira spp. and Cyclotella spp., where Aulacoseira spp. is expected to decrease, and Cyclotella spp. is expected to increase with a rising temperature, match the CAF-theory for the most part. The change in composition also coincides with several documented environmental factors in the area, especially the change in use of fertilizers and herbicides in agriculture., Människans utsläpp av växthusgaser har sedan år 1750 skapat en temperaturökning som går allt snabbare, och påverkar hela världen. Kiselalger, encelliga mikroskopiska alger som lever i vatten över hela världen, har olika miljöpreferenser såsom bland annat på vilket vattendjup de trivs, optimal halt av salt, näringsvärden, pH-värden, samt reagerar snabbt på förändrade omständigheter, vilket gör dem lämpliga som miljöindikatorer. Syftet med studien är att studera förändringar i kiselalgernas sammansättning under de senaste 200 åren i den lilla sjön Ensjön belägen något söder om Norrköping och att relatera dessa förändringar till dokumenterade händelser och miljöfaktorer i sjöns avrinningsområde samt till de pågående klimatförändringarna. Undersökningen är utförd genom provtagning av sedimentkärnor från vilka prover preparerades enligt Battarbees (1984) flödesschema. Proverna av kiselalger räknades under mikroskop och sammansättningen analyserades utifrån teorin Cyclotella-Aulacoseira-Fragilaria (CAF) och kända historiska händelser i närmiljön. Analysresultatet visade att kiselalgssammansättningen har förändrats under de senaste 200 åren, och att denna förändring sannolikt kan kopplas både till klimatförändringar (en ökad temperatur) och Ensjöns markanvändningshistoria. Förändringen hos Aulacoseira spp. och Cyclotella spp. följer till stor del CAF-teorin om att det första släktet skulle minska och det andra skulle öka vid en temperaturökning. Vid flera tillfällen sammanfaller förändringar i kiselalgssammansättningen med kända miljöfaktorer i närmiljön, främst i samband med utvecklingen i användningen av mineralgödsel och växtskyddsmedel.

During the 20th century, many lakes in the Northern Hemisphere were affected by increasing human population and urbanization along their shorelines and catchment, resulting in aquatic eutrophication. Ecosystem monitoring commenced only after the changes became apparent, precluding any examination of timing and dynamics of initial community change in the past and comparison of pre- and postimpact communities. Peri-Alpine Lake Constance (Germany) underwent a mid-century period of eutrophication followed by re-oligotrophication since the 1980s and is now experiencing warm temperatures. We extended the period for which monitoring data of indicator organisms exist by analysing historical environmental DNA (eDNA) from a sediment core dating back some 110 years. Using three metabarcoding markers-for microbial eukaryotes, diatoms and cyanobacteria-we revealed two major breakpoints of community change, in the 1930s and the mid-1990s. In our core, the latest response was exhibited by diatoms, which are classically used as palaeo-bioindicators for the trophic state of lakes. Following re-oligotrophication, overall diversity values reverted to similar ones of the early 20th century, but multivariate analysis indicated that the present community is substantially dissimilar. Community changes of all three groups were strongly correlated to phosphorus concentration changes, whereas significant relationships to temperature were only observed when we did not account for temporal autocorrelation. Our results indicate that each microbial group analysed exhibited a unique response, highlighting the particular strength of multimarker analysis of eDNA, which is not limited to organisms with visible remains and can therefore discover yet unknown responses and abiotic-biotic relationships.

During the 20th century, many lakes in the Northern Hemisphere were affected by increasing human population and urbanization along their shorelines and catchment, resulting in aquatic eutrophication. Ecosystem monitoring commenced only after the changes became apparent, precluding any examination of timing and dynamics of initial community change in the past and comparison of pre- and postimpact communities. Peri-Alpine Lake Constance (Germany) underwent a mid-century period of eutrophication followed by re-oligotrophication since the 1980s and is now experiencing warm temperatures. We extended the period for which monitoring data of indicator organisms exist by analysing historical environmental DNA (eDNA) from a sediment core dating back some 110 years. Using three metabarcoding markers-for microbial eukaryotes, diatoms and cyanobacteria-we revealed two major breakpoints of community change, in the 1930s and the mid-1990s. In our core, the latest response was exhibited by diatoms, which are classically used as palaeo-bioindicators for the trophic state of lakes. Following re-oligotrophication, overall diversity values reverted to similar ones of the early 20th century, but multivariate analysis indicated that the present community is substantially dissimilar. Community changes of all three groups were strongly correlated to phosphorus concentration changes, whereas significant relationships to temperature were only observed when we did not account for temporal autocorrelation. Our results indicate that each microbial group analysed exhibited a unique response, highlighting the particular strength of multimarker analysis of eDNA, which is not limited to organisms with visible remains and can therefore discover yet unknown responses and abiotic-biotic relationships.

The sedimentary system of the Algiers Bay has been impacted in the last decades by the exponential increases in population, urbanism and industrial activities of the city of Algiers, and by episodic floods, mudflows, earthquakes and tsunamis. Activity concentrations of environmental gamma-emitters, namely 210Pb, 226Ra, 40K, 228Ra, 228Th and 137Cs, were measured in a sediment core sampled in 2015 at the central zone of this bay, at 73 m depth from the surface water. The 210Pb-based radiometric dating was challenging due to the incomplete recovery of the inventory, the absence of 137Cs peaks, and the failure of classical models. The analysis of clusters in the logarithmic plot of the excess 210Pb versus mass depth profile allowed for establishing a reliable chronology. Fluxes of excess 210Pb and sediment accumulation rates (SAR) have both varied over the last five decades. Recent SAR values are of 0.73 ± 0.21 g cm−2y−1. Major and trace elements were determined by X-Ray Fluorescence in some selected sediment slices. Moderate enrichments have been observed for Mn, Zn, Br, Rb, Sr, Y and Pb in the 0–1 cm sediment layer (when using Al as normalization element), being governed by Fe-rich carriers. The major impact is observed in the carbon content, which increased by two orders of magnitude (from their basal values) for three decades since early 70's. The dataset also allowed for a radioecological assessment in the area, performed using the ERICA software.

The sedimentary system of the Algiers Bay has been impacted in the last decades by the exponential increases in population, urbanism and industrial activities of the city of Algiers, and by episodic floods, mudflows, earthquakes and tsunamis. Activity concentrations of environmental gamma-emitters, namely 210Pb, 226Ra, 40K, 228Ra, 228Th and 137Cs, were measured in a sediment core sampled in 2015 at the central zone of this bay, at 73 m depth from the surface water. The 210Pb-based radiometric dating was challenging due to the incomplete recovery of the inventory, the absence of 137Cs peaks, and the failure of classical models. The analysis of clusters in the logarithmic plot of the excess 210Pb versus mass depth profile allowed for establishing a reliable chronology. Fluxes of excess 210Pb and sediment accumulation rates (SAR) have both varied over the last five decades. Recent SAR values are of 0.73 ± 0.21 g cm−2y−1. Major and trace elements were determined by X-Ray Fluorescence in some selected sediment slices. Moderate enrichments have been observed for Mn, Zn, Br, Rb, Sr, Y and Pb in the 0–1 cm sediment layer (when using Al as normalization element), being governed by Fe-rich carriers. The major impact is observed in the carbon content, which increased by two orders of magnitude (from their basal values) for three decades since early 70's. The dataset also allowed for a radioecological assessment in the area, performed using the ERICA software.

The sedimentary system of the Algiers Bay has been impacted in the last decades by the exponential increases in population, urbanism and industrial activities of the city of Algiers, and by episodic floods, mudflows, earthquakes and tsunamis. Activity concentrations of environmental gamma-emitters, namely 210Pb, 226Ra, 40K, 228Ra, 228Th and 137Cs, were measured in a sediment core sampled in 2015 at the central zone of this bay, at 73 m depth from the surface water. The 210Pb-based radiometric dating was challenging due to the incomplete recovery of the inventory, the absence of 137Cs peaks, and the failure of classical models. The analysis of clusters in the logarithmic plot of the excess 210Pb versus mass depth profile allowed for establishing a reliable chronology. Fluxes of excess 210Pb and sediment accumulation rates (SAR) have both varied over the last five decades. Recent SAR values are of 0.73 ± 0.21 g cm−2y−1. Major and trace elements were determined by X-Ray Fluorescence in some selected sediment slices. Moderate enrichments have been observed for Mn, Zn, Br, Rb, Sr, Y and Pb in the 0–1 cm sediment layer (when using Al as normalization element), being governed by Fe-rich carriers. The major impact is observed in the carbon content, which increased by two orders of magnitude (from their basal values) for three decades since early 70's. The dataset also allowed for a radioecological assessment in the area, performed using the ERICA software.

The sedimentary system of the Algiers Bay has been impacted in the last decades by the exponential increases in population, urbanism and industrial activities of the city of Algiers, and by episodic floods, mudflows, earthquakes and tsunamis. Activity concentrations of environmental gamma-emitters, namely 210Pb, 226Ra, 40K, 228Ra, 228Th and 137Cs, were measured in a sediment core sampled in 2015 at the central zone of this bay, at 73 m depth from the surface water. The 210Pb-based radiometric dating was challenging due to the incomplete recovery of the inventory, the absence of 137Cs peaks, and the failure of classical models. The analysis of clusters in the logarithmic plot of the excess 210Pb versus mass depth profile allowed for establishing a reliable chronology. Fluxes of excess 210Pb and sediment accumulation rates (SAR) have both varied over the last five decades. Recent SAR values are of 0.73 ± 0.21 g cm−2y−1. Major and trace elements were determined by X-Ray Fluorescence in some selected sediment slices. Moderate enrichments have been observed for Mn, Zn, Br, Rb, Sr, Y and Pb in the 0–1 cm sediment layer (when using Al as normalization element), being governed by Fe-rich carriers. The major impact is observed in the carbon content, which increased by two orders of magnitude (from their basal values) for three decades since early 70's. The dataset also allowed for a radioecological assessment in the area, performed using the ERICA software.

The sedimentary system of the Algiers Bay has been impacted in the last decades by the exponential increases in population, urbanism and industrial activities of the city of Algiers, and by episodic floods, mudflows, earthquakes and tsunamis. Activity concentrations of environmental gamma-emitters, namely 210Pb, 226Ra, 40K, 228Ra, 228Th and 137Cs, were measured in a sediment core sampled in 2015 at the central zone of this bay, at 73 m depth from the surface water. The 210Pb-based radiometric dating was challenging due to the incomplete recovery of the inventory, the absence of 137Cs peaks, and the failure of classical models. The analysis of clusters in the logarithmic plot of the excess 210Pb versus mass depth profile allowed for establishing a reliable chronology. Fluxes of excess 210Pb and sediment accumulation rates (SAR) have both varied over the last five decades. Recent SAR values are of 0.73 ± 0.21 g cm−2y−1. Major and trace elements were determined by X-Ray Fluorescence in some selected sediment slices. Moderate enrichments have been observed for Mn, Zn, Br, Rb, Sr, Y and Pb in the 0–1 cm sediment layer (when using Al as normalization element), being governed by Fe-rich carriers. The major impact is observed in the carbon content, which increased by two orders of magnitude (from their basal values) for three decades since early 70's. The dataset also allowed for a radioecological assessment in the area, performed using the ERICA software.

Late Quaternary volcanic basins are active landscapes from which detailed archives of past climate and seismic and volcanic activity can be obtained. A multidisciplinary study performed on a transect of sediment cores was used to reconstruct the depositional evolution of the highelevation Laguna del Maule (LdM) (36 S, 2180ma.s.l., Chilean Andes). The recovered 5m composite sediment sequence includes two thick turbidite units (LT1 and LT2) and numerous tephra layers (23 ash and 6 lapilli). We produced an age model based on nine new 14C AMS dates, existing 210Pb and 137Cs data, and the Quizapú ash horizon (1932 CE). According to this age model, the relatively drier Early Holocene was followed by a phase of increased productivity during the mid-Holocene and higher lake levels after 4.0 ka cal BP. Major hydroclimate transitions occurred at ca. 11, 8.0, 4.0 and 0.5 ka cal BP. Decreased summer insolation and winter precipitation due to a southward shift in the southern westerly winds and a strengthened Pacific Subtropical High could explain Early Holocene lower lake levels. Increased biological productivity during the mid- Holocene ( 8:0 to 6.0 ka cal BP) is coeval with a warm-dry phase described for much of southern South America. Periods of higher lake productivity are synchronous to a higher frequency of volcanic events. During the Late Holocene, the tephra layers show compositional changes suggesting a transition from silica-rich to silica-poor magmas at around 4.0 ka cal BP. This transition was synchronous with increased variability of sedimentary facies and geochemical proxies, indicating higher lake levels and increased moisture at LdM after 4.0 ka cal BP, most likely caused by the inception of current El Niño-Southern Oscillation and Pacific Decadal Oscillation (ENSO-PDO) dynamics in central Chile. © 2020 Copernicus GmbH. All rights reserved.

Humans have utilized the Mesoamerican Reef for millennia but the effects of prehistorical and historical fishing on this ecosystem remain understudied. To assess long-term trends in reef fish abundance in the central Belizean portion, we used three reef matrix cores from this region to construct a record of parrotfish (Labridae) tooth abundance relative to the total number of all fish tooth subfossils. Parrotfish positively affect reef accretion rates and play a pivotal role in maintaining reefs in a coral-dominated state. Our study examined a 1200-year record across three coral cays: Elbow and Lagoon Cays and Bakers Rendezvous. Despite initial increases of fish tooth abundance at all three cays, declines were observed well before modern reef degradation. At Elbow Cay, an initial decline, likely due to Pre-Columbian Maya fishing, appears to be halted near the time of Spanish arrival. A subsequent decline begins at Elbow and Lagoon Cays likely due to Spanish colonization. The religious practices of the Catholic Spanish and the arrival of English privateers and logwooders likely increased fishing pressure. Bakers Rendezvous shows rapid accretion and parrotfish tooth accumulation as well as high tooth abundances, even as the other two cays show declines. Its sharper, more recent decline is likely the result of either the use of new, more southern fishing territories for Catholic Maya converts, the 1832 founding of Stann Creek Town by the Catholic Garifuna, or an interaction of the two. Our data suggest that the origins of reef degradation began hundreds of years before modern declines.

The Iron Gate I Reservoir is the largest impoundment on the Danube River. It retains gt 50% of the incoming total suspended solids load and the associated organic contaminants. In the sediment core of the Iron Gate I Reservoir we report the presence and fate of four classes of emerging contaminants (pharmaceuticals, pesticides, steroids and perfluorinated compounds), predominantly not covered by the EU monitoring programs, but considered as future candidates. Based on contaminant's partitioning behavior in the water/sediment system and the suspected ecotoxicological potential asserted from the literature data, the risk of recorded concentrations for sediment-dwelling organisms was discussed. The high anticipated risk was associated with antibiotics sulfamethoxazole and erythromycin, and pesticides linuron and carbendazim (banned in the EU, but still approved for use in the investigated area) and malathion. This indicated the need for better control of release of these compounds into the river, and implied their inclusion in future regular monitoring. Higher concentrations of pharmaceuticals and most pesticides and sterols were recorded in the fragment of allochthonous coarser sediment, assumed to have entered the reservoir during a high discharge event. Only one perfluorinated compound was recorded in the upper part of the sediment core. The vertical concentration profiles of pesticides propazine and malathion indicated their uniform source, most likely atmospheric transport and deposition of particles deriving from agricultural land.

Humans have utilized the Mesoamerican Reef for millennia but the effects of prehistorical and historical fishing on this ecosystem remain understudied. To assess long-term trends in reef fish abundance in the central Belizean portion, we used three reef matrix cores from this region to construct a record of parrotfish (Labridae) tooth abundance relative to the total number of all fish tooth subfossils. Parrotfish positively affect reef accretion rates and play a pivotal role in maintaining reefs in a coral-dominated state. Our study examined a 1200-year record across three coral cays: Elbow and Lagoon Cays and Bakers Rendezvous. Despite initial increases of fish tooth abundance at all three cays, declines were observed well before modern reef degradation. At Elbow Cay, an initial decline, likely due to Pre-Columbian Maya fishing, appears to be halted near the time of Spanish arrival. A subsequent decline begins at Elbow and Lagoon Cays likely due to Spanish colonization. The religious practices of the Catholic Spanish and the arrival of English privateers and logwooders likely increased fishing pressure. Bakers Rendezvous shows rapid accretion and parrotfish tooth accumulation as well as high tooth abundances, even as the other two cays show declines. Its sharper, more recent decline is likely the result of either the use of new, more southern fishing territories for Catholic Maya converts, the 1832 founding of Stann Creek Town by the Catholic Garifuna, or an interaction of the two. Our data suggest that the origins of reef degradation began hundreds of years before modern declines.

The Iron Gate I Reservoir is the largest impoundment on the Danube River. It retains gt 50% of the incoming total suspended solids load and the associated organic contaminants. In the sediment core of the Iron Gate I Reservoir we report the presence and fate of four classes of emerging contaminants (pharmaceuticals, pesticides, steroids and perfluorinated compounds), predominantly not covered by the EU monitoring programs, but considered as future candidates. Based on contaminant's partitioning behavior in the water/sediment system and the suspected ecotoxicological potential asserted from the literature data, the risk of recorded concentrations for sediment-dwelling organisms was discussed. The high anticipated risk was associated with antibiotics sulfamethoxazole and erythromycin, and pesticides linuron and carbendazim (banned in the EU, but still approved for use in the investigated area) and malathion. This indicated the need for better control of release of these compounds into the river, and implied their inclusion in future regular monitoring. Higher concentrations of pharmaceuticals and most pesticides and sterols were recorded in the fragment of allochthonous coarser sediment, assumed to have entered the reservoir during a high discharge event. Only one perfluorinated compound was recorded in the upper part of the sediment core. The vertical concentration profiles of pesticides propazine and malathion indicated their uniform source, most likely atmospheric transport and deposition of particles deriving from agricultural land.

There are very few data available of 236U in marine sediment cores. In this study we present the results from the first oceanic depth profile of 236U in a sediment core sampled in the North Atlantic Ocean, at the PAP site (4500 m depth, Porcupine Abyssal Plain (PAP) site, 49°0′ N, 16°30′ W). Additionally, the sediment core was radiologically characterized through the measurement of anthropogenic 137Cs, 239Pu, 240Pu, 129I and 14C and natural 210Pb, 40K and 226Ra. The measured 236U concentrations decrease from about 90·106 at g−1 at the seafloor down to 0.5·106 at g−1 at 6 cm depth. They are several orders of magnitude lower than the reported values for soils from the Northern Hemisphere solely influenced by global fallout (i.e. from 2700·106 to 7500·106 at g−1). 236U/238U atom ratios measured are at least three orders of magnitude above the estimated level for the naturally occurring dissolved uranium. The obtained inventories are 1·1012 at m−2 for 236U, 80 Bq m−2 for 137Cs, 45 Bq m−2 for 239+240Pu and 2.6·1012 at m−2 for 129I. Atomic ratios for 236U/239Pu, 137Cs/236U and 129I/236U, obtained from the inventories are 0.036, 0.11 and 2.5 respectively. Concentration profiles show mobilization probably due to bioturbation from the abundant detritivore holothurian species living at the PAP site sea-floor. The range of 236U, 137Cs, 239+240Pu and 129I values, inventories and ratios of these anthropogenic radionuclides are more similar to the values due to fall-out than values from a contribution from the Nuclear Fuel Reprocessing Plants dispersed to the south-west of the North Atlantic Ocean. However, signs of an additional source are detected and might be associated to the nuclear wastes dumped on the Eastern North Atlantic Ocean.

There are very few data available of 236U in marine sediment cores. In this study we present the results from the first oceanic depth profile of 236U in a sediment core sampled in the North Atlantic Ocean, at the PAP site (4500 m depth, Porcupine Abyssal Plain (PAP) site, 49°0′ N, 16°30′ W). Additionally, the sediment core was radiologically characterized through the measurement of anthropogenic 137Cs, 239Pu, 240Pu, 129I and 14C and natural 210Pb, 40K and 226Ra. The measured 236U concentrations decrease from about 90·106 at g−1 at the seafloor down to 0.5·106 at g−1 at 6 cm depth. They are several orders of magnitude lower than the reported values for soils from the Northern Hemisphere solely influenced by global fallout (i.e. from 2700·106 to 7500·106 at g−1). 236U/238U atom ratios measured are at least three orders of magnitude above the estimated level for the naturally occurring dissolved uranium. The obtained inventories are 1·1012 at m−2 for 236U, 80 Bq m−2 for 137Cs, 45 Bq m−2 for 239+240Pu and 2.6·1012 at m−2 for 129I. Atomic ratios for 236U/239Pu, 137Cs/236U and 129I/236U, obtained from the inventories are 0.036, 0.11 and 2.5 respectively. Concentration profiles show mobilization probably due to bioturbation from the abundant detritivore holothurian species living at the PAP site sea-floor. The range of 236U, 137Cs, 239+240Pu and 129I values, inventories and ratios of these anthropogenic radionuclides are more similar to the values due to fall-out than values from a contribution from the Nuclear Fuel Reprocessing Plants dispersed to the south-west of the North Atlantic Ocean. However, signs of an additional source are detected and might be associated to the nuclear wastes dumped on the Eastern North Atlantic Ocean.

There are very few data available of 236U in marine sediment cores. In this study we present the results from the first oceanic depth profile of 236U in a sediment core sampled in the North Atlantic Ocean, at the PAP site (4500 m depth, Porcupine Abyssal Plain (PAP) site, 49°0′ N, 16°30′ W). Additionally, the sediment core was radiologically characterized through the measurement of anthropogenic 137Cs, 239Pu, 240Pu, 129I and 14C and natural 210Pb, 40K and 226Ra. The measured 236U concentrations decrease from about 90·106 at g−1 at the seafloor down to 0.5·106 at g−1 at 6 cm depth. They are several orders of magnitude lower than the reported values for soils from the Northern Hemisphere solely influenced by global fallout (i.e. from 2700·106 to 7500·106 at g−1). 236U/238U atom ratios measured are at least three orders of magnitude above the estimated level for the naturally occurring dissolved uranium. The obtained inventories are 1·1012 at m−2 for 236U, 80 Bq m−2 for 137Cs, 45 Bq m−2 for 239+240Pu and 2.6·1012 at m−2 for 129I. Atomic ratios for 236U/239Pu, 137Cs/236U and 129I/236U, obtained from the inventories are 0.036, 0.11 and 2.5 respectively. Concentration profiles show mobilization probably due to bioturbation from the abundant detritivore holothurian species living at the PAP site sea-floor. The range of 236U, 137Cs, 239+240Pu and 129I values, inventories and ratios of these anthropogenic radionuclides are more similar to the values due to fall-out than values from a contribution from the Nuclear Fuel Reprocessing Plants dispersed to the south-west of the North Atlantic Ocean. However, signs of an additional source are detected and might be associated to the nuclear wastes dumped on the Eastern North Atlantic Ocean.

Some heavy metals in farmland soil can be transported into the waterbody, affecting the water quality and sediment at the watershed outlet, which can be used to determine the historical loss pattern. Cd is a typical heavy metal leached from farmland that is related to phosphate fertilizers and carries serious environmental risk. The spatial-vertical pattern of Cd in soil and the vertical trend of Cd in the river sediment core were analyzed, which showed the migration and accumulation of Cd in the watershed. To prevent watershed Cd loss, biochar was employed, and leaching experiments were conducted to investigate the Cd loss from soil depending on the initial concentration. Four rainfall intensities, 1.25 mm/h, 2.50 mm/h, 5.00 mm/h, and 10.00 mm/h, were used to simulate typical rainfall scenarios for the study area. Biochar was prepared from corn straw after pretreatment with ammonium dihydrogen phosphate (ADP) and pyrolysis at 400 °C under anoxic conditions. To identify the effects of biochar amendment on Cd migration, the biochar was mixed with soil for 90 days at concentrations of 0%, 0.5%, 1.0%, 3.0%, and 5.0% soil by weight. The results showed that the Cd leaching load increased as the initial load and rainfall intensity increased and that eluviation caused surface Cd to diffuse to the deep soils. The biochar application caused more of the heavy metals to be immobilized in the amended soil rather than transported into the waterbody. The sorption efficiency of the biochar for Cd increased as the addition level increased to 3%, which showed better performance than the 5% addition level under some initial concentration and rainfall conditions. The research indicated that biochar is a potential material to prevent diffuse heavy metal pollution and that a lower addition makes the application more feasible., EcoChange

The detailed structure and composition of turbiditic channel-mouth lobes is still largely unknown because they commonly lie at abyssal water depths, are very thin and are therefore beyond the resolution of hull-mound acoustic tools. The morphology, structure and composition of the Congo turbiditic channel-mouth lobe complex (90×40 km; 2525 km2) were investigated with hull-mounted swath bathymetry, air gun seismics, 3.5 kHz sub-bottom profiler, sediment piston cores and also with high-resolution multibeam bathymetry and video acquired with a Remote Operating Vehicle (ROV). The lobe complex lies 760 km off the Congo River mouth in the Angola abyssal plain between 4740 and 5030 m deep. It is active and is fed by turbidity currents that deposit several centimetres of sediment per century. The lobe complex is subdivided into five lobes that have prograded. The lobes are dominantly muddy. Sand represents ca. 13% of the deposits and is restricted to the feeding channel and distributaries. The overall lobe body is composed of thin muddy to silty turbidites. The whole lobe complex is characterized by in situ mass wasting (slumps, debrites). The 1-m-resolution bathymetry shows pervasive slidings and block avalanches on the edges of the feeding channel and the channel mouth indicating that sliding occurs early and continuously in the lobe build-up. Mass wasting is interpreted as a consequence of very-high accumulation rates, over-steepening and erosion along the channels and is therefore an intrinsic process of lobe building. The bifurcation of feeding channels is probably triggered when the gradient in the distributaries at the top of a lobe becomes flat and when turbidity currents find their way on the higher gradient on the lobe side. It may also be triggered by mass wasting on the lobe side. When a new lobe develops, the abandoned lobes continue to collect significant turbiditic deposits from the feeding channel spillover, so that the whole lobe complex remains active. A c

The detailed structure and composition of turbiditic channel-mouth lobes is still largely unknown because they commonly lie at abyssal water depths, are very thin and are therefore beyond the resolution of hull-mound acoustic tools. The morphology, structure and composition of the Congo turbiditic channel-mouth lobe complex (90×40 km; 2525 km2) were investigated with hull-mounted swath bathymetry, air gun seismics, 3.5 kHz sub-bottom profiler, sediment piston cores and also with high-resolution multibeam bathymetry and video acquired with a Remote Operating Vehicle (ROV). The lobe complex lies 760 km off the Congo River mouth in the Angola abyssal plain between 4740 and 5030 m deep. It is active and is fed by turbidity currents that deposit several centimetres of sediment per century. The lobe complex is subdivided into five lobes that have prograded. The lobes are dominantly muddy. Sand represents ca. 13% of the deposits and is restricted to the feeding channel and distributaries. The overall lobe body is composed of thin muddy to silty turbidites. The whole lobe complex is characterized by in situ mass wasting (slumps, debrites). The 1-m-resolution bathymetry shows pervasive slidings and block avalanches on the edges of the feeding channel and the channel mouth indicating that sliding occurs early and continuously in the lobe build-up. Mass wasting is interpreted as a consequence of very-high accumulation rates, over-steepening and erosion along the channels and is therefore an intrinsic process of lobe building. The bifurcation of feeding channels is probably triggered when the gradient in the distributaries at the top of a lobe becomes flat and when turbidity currents find their way on the higher gradient on the lobe side. It may also be triggered by mass wasting on the lobe side. When a new lobe develops, the abandoned lobes continue to collect significant turbiditic deposits from the feeding channel spillover, so that the whole lobe complex remains active. A c

The detailed structure and composition of turbiditic channel-mouth lobes is still largely unknown because they commonly lie at abyssal water depths, are very thin and are therefore beyond the resolution of hull-mound acoustic tools. The morphology, structure and composition of the Congo turbiditic channel-mouth lobe complex (90×40 km; 2525 km2) were investigated with hull-mounted swath bathymetry, air gun seismics, 3.5 kHz sub-bottom profiler, sediment piston cores and also with high-resolution multibeam bathymetry and video acquired with a Remote Operating Vehicle (ROV). The lobe complex lies 760 km off the Congo River mouth in the Angola abyssal plain between 4740 and 5030 m deep. It is active and is fed by turbidity currents that deposit several centimetres of sediment per century. The lobe complex is subdivided into five lobes that have prograded. The lobes are dominantly muddy. Sand represents ca. 13% of the deposits and is restricted to the feeding channel and distributaries. The overall lobe body is composed of thin muddy to silty turbidites. The whole lobe complex is characterized by in situ mass wasting (slumps, debrites). The 1-m-resolution bathymetry shows pervasive slidings and block avalanches on the edges of the feeding channel and the channel mouth indicating that sliding occurs early and continuously in the lobe build-up. Mass wasting is interpreted as a consequence of very-high accumulation rates, over-steepening and erosion along the channels and is therefore an intrinsic process of lobe building. The bifurcation of feeding channels is probably triggered when the gradient in the distributaries at the top of a lobe becomes flat and when turbidity currents find their way on the higher gradient on the lobe side. It may also be triggered by mass wasting on the lobe side. When a new lobe develops, the abandoned lobes continue to collect significant turbiditic deposits from the feeding channel spillover, so that the whole lobe complex remains active. A c

When assigning site-specific restoration targets for deteriorating aquatic systems, it is necessary to have an understanding of the undisturbed or background state of the system. However, the sitespecific characteristics of aquatic systems prior to disturbance are mostly unknown, due to the lack of historical water and sediment quality data. This study aims to introduce a method for filling this gap in our understanding, using dated sediment cores from the beds of aquatic environments. We used Bolin Billabong, a floodplain lake of the Yarra River (South-East Australia), as a case study to demonstrate the application of this method. We identified the concentrations of aluminium, cadmium, chromium, copper, iron, lead, manganese, nickel, tin and zinc at 8 cm intervals through the sediment core. This showed that aluminium, chromium, copper, iron, lead, nickel, tin and zinc concentrations in Bolin Billabong sediments significantly increased after European settlement in the river catchment in the mid-19th century. The differences between current Australian sediment quality guidelines trigger values and the background metal concentrations in Bolin Billabong sediments underscore the value of using locally relevant background toxicant concentrations when setting water and sediment quality targets.

Anthropogenic activities are contributing to the changing hydrology of rivers, often resulting in their degradation. Understanding the drivers and nature of these changes is critical for the design and implementation of effective mitigation strategies for these systems. However, this can be hindered by gaps in historical measured flow data. This study therefore aims to use sediment cores to identify historical hydrological changes within a river catchment. Sediment cores from two floodplain lakes (billabongs) in the urbanised Yarra River catchment (Melbourne, South-East Australia) were collected and high resolution images, trends in magnetic susceptibility and trends in elemental composition through the sedimentary records were obtained. These were used to infer historical changes in river hydrology to determine both average trends in hydrology (i.e., coarse temporal resolution) as well as discrete flood layers in the sediment cores (i.e., fine temporal resolution). Through the 20th century, both billabongs became increasingly disconnected from the river, as demonstrated by the decreasing trends in magnetic susceptibility, particle size and inorganic matter in the cores. Additionally the number of discrete flood layers decreased up the cores. These reconstructed trends correlate with measured flow records of the river through the 20th century, which validates the methodology that has been used in this study. Not only does this study provide evidence on how natural catchments can be affected by land-use intensification and urbanisation, but it also introduces a general analytical framework that could be applied to other river systems to assist in the design of hydrological management strategies.

Diatoms are microscopic, photosynthetic, single-celled organisms that are useful in studies of water qualities (eg pH, nutrients, salinity). By analyzing changes in the species composition of diatoms back in time, gives an opportunity to interpret the marine environment affected by various factors (Andren et al, 1999). The aim of the study was to study changes in diatom abundance and composition in Hallsfjärden, a bay in the Baltic Sea located north of Himmerfjärden in Södertälje. The site was chosen because it is a bay that is assumed to have a large environmental impact due to external factors such as increased population growth, water treatment plants, industrial areas, dredging and a link to Lake Mälaren. The purpose of the study therefore to investigate whether there was an environmental impact in Hallsfjärden, in order to draw conclusions about what happened in the area and what has affected the water the last 100 years. The survey is conducted by sampling sediment cores, studied by biostratigraphy of fossil diatoms to reconstruct past environmental conditions. The results of the analysis showed that oxygen deficiency was a particular problem, which is related to the eutrophication that are threatening some diatoms and thereby changes the species composition of ecosystems in Hallsfjärden. A plausible interpretation of the analyze results is that Hallsfjärden was adversely affected by the Södertalje area's population growth and Himmerfjärdsverkets startup by high emissions of nutrients. It has on the other hand appeared a positive impact for Himmerfjärdsverkets gradually improved purification with clearer water conditions. Hallsfjärden have proved to be a particularly sensitive ecosystem in this study, with low salinity and strong thermocline, which means that it is more affected by eutrophication and pollution in its drainage area. This causes a problem of eutrophication in Hallsfjärden due to the bay showing the influence of the surrounding areas and its, Kiselalger är mikroskopiska, fotosyntetiserande, encelliga organismer som är användbara vid studier om vattenkvalitéer (till exempel pH, näringsämnen, salthalt). Genom att analysera förändringar i artsammansättningen av kiselalger bakåt i tiden kan tolkningar göras om hur havsmiljön påverkats av olika faktorer (Andrén m.fl., 1999). Målet med studien var att studera förändringar i kiselalgernas förekomst i Hallsfjärden, en havsvik i Östersjön belägen norr om Himmerfjärden i Södertälje. Platsen valdes för att det är en havsvik som antas ha stor miljöpåverkan på grund av yttre faktorer såsom en ökad befolkningstillväxt, reningsverk, industriområden, muddring och en kontakt med sjön Mälaren. Syftet med studien var därmed att undersöka om en miljöpåverkan fanns i fjärden, detta för att kunna dra slutsatser om vad som hänt samt vad som påverkat vattenområdet de senaste 100 åren. Undersökningen är utförd genom provtagning av sedimentkärnor som undersökts avseende biostratigrafin av fossila kiselalger för att rekonstruera tidigare miljöförhållanden. Analysresultatet visade att syrebrist var ett utmärkande problem, vilket i samband med eutrofiering hotar vissa kiselalgsarter och förändrar därmed artsammansättningen i ekosystemen i Hallsfjärden. En sannolik tolkning av analysresultatet är att Hallsfjärden påverkats negativt av Södertäljeområdets befolkningstillväxt och Himmerfjärdsverkets uppstart genom höga utsläpp av näringsämnen. Det har å andra sidan synts en positiv inverkan efter Himmerfjärdsverkets successivt förbättrade rening med klarare vattenförhållanden. Hallsfjärden har i studien visat sig vara ett särskilt känsligt ekosystem med låg salthalt och starka språngskikt, vilket gör att det påverkas mer av eutrofiering och föroreningarna i området. Detta medför en övergödningsproblematik i Hallsfjärden, då fjärden visar en påverkan av omkringliggande områden och dess utsläpp av föroreningar, vilka även sedan exporteras ut i Östersjön via Himmerfjärden med den sydg