We investigate the potential of hyperspectral imaging spectrometry for the analysis of fresh sediment cores. A sediment-core-scanning system equipped with a camera working in the visual to near-infrared range (400 to 1000 nm) is described and a general methodology for processing and calibrating spectral data from sediments is proposed. We present an application from organic sediments of Lake Jaczno, a freshwater lake with biochemical varves in northern Poland. The sedimentary pigment bacteriopheophytin $a$ (BPhe $a$) is diagnostic for anoxia in lakes and, therefore, an important ecological indicator. Calibration of the spectral data (BPhe $a$ absorption $∼800$ to 900 nm) to absolute BPhe $a$ concentrations, as measured by high-performance-liquid-chromatography, reveals that sedimentary BPhe $a$ concentrations can be estimated from spectral data with a model uncertainty of $∼10%$. Based on this calibration model, we use the hyperspectral data from the sediment core to produce high-resolution intensity maps and time series of relative BPhe $a$ concentrations ($∼10$ to 20 data points per year, pixel resolution $70×70μm2$). We conclude that hyperspectral imaging is a very cost- and time-efficient method for the analysis of lake sediments and provides insight into the spatiotemporal structures of biogeochemical species at a degree of detail that is not possible with wet chemical analyses.

Plastics are a recent particulate material in Earth’s history. Because of plastics persistence and wide-range presence, it has a great potential of being a global age marker and correlation tool between sedimentary profiles. In this research, we query whether microplastics can be considered among the array of proxies to delimit the Anthropocene Epoch (starting from the year 1950 and above). We present a study of microplastics deposition history inferred from sediment profiles of lakes in northeastern Europe. The sediments were dated with independent proxies from the present back to the first half of the 18th century. Regardless of the sediment layer age, microplastic particles were found throughout the cores in all sites. Depending on particles’ aspect ratio, less elongated particles were found deeper, while more elongated particles and fibers have reduced mobility. We conclude that interpretation of microplastics distribution in the studied sediment profiles is ambiguous and does not strictly indicate the beginning of the Anthropocene Epoch.

Pollen, charcoal and geochemical investigations were carried out on annually laminated sediments of Lake Żabińskie (54°07′54.5″N; 21°59′01.1″E) and the results were combined with historical and climate data to better understand the mechanism behind plant cover transformations. A millennium-long record of environmental history at 6-years time resolution permitted an assessment of vegetation responses to past human impact and climate fluctuations. Our results show that the history of the region with repeated periods of warfare, epidemics, famine and crop failures is well reflected by environmental proxies. Before the Teutonic Order crusade (ad 1230–1283), agricultural activities of the Prussian tribes were conducted at a distance from the studied lake and caused slight disturbances of local forests. A stronger human impact was registered after ca ad 1460. We confirm that co-domination of pine forests with spruce and oak-hornbeam forests on drier habitats as well as the presence of birch and alder woods on wet surfaces near the lake lasted until ad 1610. We identified a transition period of 20 years between ad 1590 and 1610, when forest cover was significantly reduced and the area was partly transformed into open land used for farming activities. The comparison of our data with other pollen datasets from the region confirms significant spatio-temporal differences in the initiation of large-scale woodland clearings in the Great Masurian Lake District. A strong increase in local cultivation was noted after ad 1750 and became even stronger in the period ad 1810–1940. The last 60 years experienced a succession from arable fields and open grasslands to more tree-covered habitats overgrown by birch and alder.

Glacial landscapes of the Land of Great Masurian Lakes and Suwałki Lakelands in northeast Poland are characterized by very high abundance of lakes. These two areas were surveyed for lakes containing laminated sediments. Using bathymetry as a criterion, 60 small, deep lakes, representing preferred conditions for formation and preservation of lacustrine non-glacial varves, were selected for gravity coring. We found laminated sediments in 24 of the lakes, 15 in the Land of Great Masurian Lakes and 9 in the Suwałki Lakeland. Seven of these 24 sediment records were laminated in the topmost part only. Analysis of lake morphometric variables showed that the relation between surface area and maximum water depth can be used to identify lakes with laminated sediments. Most of the newly discovered lakes with laminated deposits have surface areas ≤0.3 km² and maximum depths of 15–35 m. Multivariate statistical analysis (Linear Discriminant Analysis) of the lake dataset identified the morphological features of lake basins and their catchments that largely control preservation of laminated sediments. Microscopic and geochemical analyses revealed a biogenic (carbonaceous) type of lamination typical for lakes in northeast Poland. Such lakes are characterized by a spring-summer lamina that is rich in calcium carbonate and an autumn-winter lamina composed of organic and minerogenic detritus. This pattern may be modified by multiple periods of calcite deposition during a single year or substantial contribution of clastic material. Laminations and high sedimentation rates offer the possibility of high-resolution investigation of past climate and environmental changes through application of myriad biological, isotopic and geochemical proxies.