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This study aims to reconstruct the changes in storminess during the past 7600 years in the northeastern Baltic Sea region. For storminess reconstructions, aeolian sand influx (ASI) in coastal peat bog deposits was applied as an indicator of the past storminess. We analyzed cores from four peat bogs in the western and northern coastal areas of Estonia: the cores from Hiiumaa N, Hiiumaa SW, Saaremaa and Juminda study sites covered the past 3700, 3750, 2400, and 8400 years, respectively. The sediment chronologies were established using 36 14C dates. Image-analysis method (ImageJ) was used to count and measure the grain size of all sand particles at every centimeter to gain high-resolution ASI records. Although minor site-to-site variations exist, all four ASI records were in general consistent, suggesting that stormier periods occurred around 7300, 6600, 5900, 4600, 3600, 2900, 2400, 2100, and 1600 cal yr BP and over the last 1200 years. The results and comparisons with other storminess and climate studies indicate a shift in climatic conditions around 2500 cal yr BP when stormy periods became more frequent. The ASI values were also high during the last millennium, suggesting either higher storminess or more suitable transport mechanisms for sand into the coastal bogs: the niveo-aeolian transport mode could have been favored in winters, especially during the Little Ice Age, and human impact on landscapes has probably increased over the past centuries. [ABSTRACT FROM AUTHOR]

In France, in the last few years, a lot of ponds have been removed during operations of river restoration, remobilizing the sediments that had been deposited behind the dam over the years. Pond sediments are complicated mixtures predominantly consisting of rocks and soils particles from the watershed, atmospheric dust brought by winds, algae and organic remains or particles that were produced by processes in the water column, such as amorphous silica or calcite. Sediments “can be dressed” with chemical elements of various kinds, including pollutants that settle on the bottom of the ponds. It is therefore important to understand what types of substances can be found in pond and to understand the effect of operations of river restoration on water quality. We applied the X-ray fluorescence spectrometry (XRF), where sample is irradiated with X-rays from a radioactive source, which excites the elements in the sample and generates secondary fluorescent X-rays. Elements emit energy of unique wavelengths, which allows their qualitative and quantitative determination. Commonly, elements from atomic number 11 (Na) to 92 (U) can be detected. Using this methodology, analyses were made on sediments samples from a pond located in the centre of France: results show that the pond is relatively free of pollutants. Starting from this reference, we will think which substances can be remobilized after operations of rivers restoration. [ABSTRACT FROM AUTHOR]

Palaeolimnological techniques were utilized to determine the extent of the effect of anthropogenic pollutants or other environmental stressors on three lake ecosystems over the last 200 years. The ecology of the study sites has experienced significant changes due to various activities such as (1) extensive catchment drainage and using poisoning as a fish management measure, (2) seepage of urban waste water due to establishment and growth of a town and (3) artificial inflow of oil-shale mining waters. Sediment geochemical composition, fossil pigments and Cladocera remains from the sediment cores were analysed to demonstrate that sufficient information can be derived from sediments to permit a historical reconstruction. The integrated use of archival maps, historical records and lake monitoring data confirmed links to anthropogenic pollutants, primarily on the catchment level. The examples show how the sediment indicators provide unique insights into the causes and temporal dynamics of lake ecosystem changes relevant for environmental management decisions. This study demonstrates that palaeolimnology has great potential to assist in eutrophication assessment and management efforts in waterbodies. [ABSTRACT FROM AUTHOR]

Studies of four sediment cores from the littoral zone of a small Lake Verevi with a well-established history of lake hydrochemistry and hydrobiology were conducted. Observational data describe essential changes in the composition of macrophytes and the trophic state of the lake during the last century. Lithological composition (organic, siliciclastic, and carbonaceous matter) in the four sediment profiles taken within a distance of 20 m showed good lithostratigraphical correspondence but differences (up to two times) in the mass accumulation rates of various compounds. Most of the organic matter (75-85%) in the sediment originates from phytoplankton as demonstrated by low organic carbon/nitrogen ratios. Accumulation of organic matter is not directly related to changes in lake trophicity and primary production but rather seems to be dependent on the accumulation of siliciclastic matter, which engages the organic matter in the settling processes. This is supported by the extremely high correlations between the mass accumulation rates of siliciclastic and organic matter (R² > 0.8). Although the greatest changes in the lake environment took place after 1970 due to severe human impact on the lake, most of the changes in the sediment records started earlier. Precipitation of CaCO3 began already in the 1930s due to natural eutrophication processes and reached its highest values in the 1970s, which can be related to the anthropogenic impact. Also the share of carbon from algae, indicating a rise in the trophic status, started to increase in the 1930s. Macrofossil records reveal that also major changes in the vegetation may have started earlier than historically recorded. The rise in the trophic status of the lake had no direct effect on the accumulation of organic matter. [ABSTRACT FROM AUTHOR]

Surveys and mapping of macrophyte vegetation and its remains in the surface sediments of two Estonian lakes demonstrate that about 50% of the submerged and floating-leaved plants growing in the lake are represented as macrofossils in the sediment. Only one third of the helophyte taxa were found in the sediment, and they had a very limited distribution close to their growing place. Part of the macrofossils, such as fragments of Nymphaea alba seeds, were distributed over the entire lake bed and were not connected with the actual growing place. The bottom topography of the lake affects the distribution of macrofossils. [ABSTRACT FROM AUTHOR]

Shifts in storm regime have significant impacts on natural, social and cultural systems in coastal regions. Aeolian sand influx (ASI) to peat bogs has been applied for reconstruction of the past storminess in northern Europe and elsewhere. However, verification of the method has been limited. This study first evaluates the ASI records from four sites along the Estonian coast against instrumentally-measured meteorological and historical records of storm activities in the region over the last two centuries. Although minor variations exist among the sites, our high-resolution ASI records mostly depict the characteristic patterns of measured storm occurrences expressed by significant positive cross-correlation values.We then reconstructed the past storminess over the last 8000 years using ASI records from the same four sites. The chronologies of the peat cores were established with 36 AMS 14C dates in total; the number and grain size of all mineral particles >65 µm were counted and measured from each sample (5 ml in volume) using a digital microscope camera and an image analysis system. The ASI record was compared with the patterns of coastal sand ridge formations, an independent information of the past storminess; the ridge sequence was dated by 50 OSL ages and their internal structure was imaged with ground-penetrating radar (GPR). Fossil pollen from the studied peat cores was also analyzed for vegetation reconstructions in relation to storminess.The ASI records among four sites are consistent, in general. The frequency and/or magnitude of storminess appear high around 7500, 6400, 6000, 3500, 3000, 2000, and 1500 cal yr BP. The ASI values during the last 1200 years are higher than those in the previous millennia, indicating the stormiest period over the last 8000 years in the region. The sand ridge sequences reveal two clear events in ridge-formation around 3500 and 800 cal yr BP; the latter event created high (up to 10 m) dunes in two study areas. Overall, the sand ridges formed during the periods of decreased ASI are lower. Pollen-based reconstructions of the regional vegetation suggest a weak positive correlation between pine abundance and storminess.We can conclude that the storminess has increased since 3500 cal yr BP and especially during the last 1200 years in the northeastern Baltic Sea region, in general. The shift in storminess around 3500 years ago is also supported by the previous palaeoclimatic studies suggesting changes towards cooler, more humid and stormier conditions. [ABSTRACT FROM AUTHOR]