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Paleolimnology is a rapidly expanding field within the natural sciences. To date, many scientific papers have been published focusing on studies of remains from single sediment cores in specific lakes, or a few cores from the same water body. However, few previous publications have provided a comprehensive comparative analysis of taphocenosis (and maternal community) changes in different water bodies from a large geographical region during whole Holocene using multivariate statistical methods. We conducted a joined statistical analysis of data obtained as a result of the cladoceran analysis of the sediment samples from six cores taken along the North-South transect from the Kola Peninsula to the Karelian Region (North-West Russia). Our aim was to identify, based on quantitative statistical methods, general whole-Holocene patterns in cladoceran taphocenosis changes. All taphocenoses in all cores from six lakes can be classified into six clusters based on their species composition. Our unexpected conclusion is that different taphocoenoses are formed by the same set of species, but their proportions vary significantly. This suggests that the same species may play different functional roles in different maternal communities. During whole Holocene, we observed a single taphocenosis cluster in the Holocene core from Lake Antyukh-Lambina, and four taphocenosis clusters in the Lake Medvedevskoe, with an intermediate number of clusters in the lakes between them. Furthermore, it can be asserted that the potential for cluster changes in the core is greater for the more southern studied water bodies (0–3 clusters for northern lakes vs. 4 clusters for southern lakes). Based on our data, we hypothesize that the diversity of cladoceran associations during the Holocene was lower in Arctic/Subarctic lakes, possibly due to their formation by ubiquitous species. Our study suggests that at least some Arctic lake ecosystems have remained unchanged since deglaciation times. Further studies are necessary to determine if this is a general rule. [ABSTRACT FROM AUTHOR]

This study investigated the tolerance of resting eggs of Eurytemora pacifica to storage under low temperatures, which is of particular interest in light of the recent use of nauplii as living food in aquaculture, other than conditions experienced also in the wild during winter cold events in the Northern Hemisphere. Sediment samples collected in August 2020 were used to store the resting eggs at two different freezing temperatures (−5 and −20 °C) for five different durations (1, 3, 6, 9, and 12 months). The mean hatching success rates of the resting eggs after one month of storage were 85.3 ± 1.5% (−5 °C) and 85.0 ± 3.6% (−20 °C), with no significant difference between freezing temperatures. However, significant differences emerged over time, with the mean hatching success rate remaining at 85.0 ± 3.6% at −5 °C after three months, while it dropped sharply to 1.7 ± 2.1% at −20 °C. For the non-freezing conditions, the hatching success at 10 °C increased gradually over the one-month incubation period, ultimately reaching 71.0%. These findings demonstrate the remarkable cold tolerance of E. pacifica but also indicate a limit to this tolerance at longer durations. These results underscore the importance of considering the adoption of storage freezing for resting eggs to be used for aquaculture and also suggest the possibility of the species better surviving the extreme weather events in comparison with other species. [ABSTRACT FROM AUTHOR]

The first systematic sediment survey by the icebreaker Shirase (AGB-5003) was conducted during the 61st Japanese Antarctic Research Expedition (JARE-61). Sediment samples were obtained from a total of 28 sites in 3 areas of the Totten Glacier front–Dalton polynya, Lützow-Holm Bay and Cape Darnley polynya using a large-bore gravity corer and GSJ-type K-grab sampler. In this paper, details of the survey operation are described as a reference for the future experience. In addition, preliminary results of the obtained sediments are reported as a fundamental information for future analysis using these samples.

A modified gravity corer (MGC) for more efficient and high-quality sediment core sampling is considered. Such design elements as the core catcher, section muff joints, the weight, and loop have been modified; the crown and locking plate have been removed. As a result of comparative testing in the South Chukchi Basin of the Chukchi Sea, it is shown that the MGC sampled 30% longer cores than the standard gravity corer (SGC). Judging from the distribution of such a redox-sensitive element as iron in the cores, when the MGС is used, a surface oxidized film remains in sediments. Thus, the disturbance of properties and textures/structures of sediments under sampling is the lowest. [ABSTRACT FROM AUTHOR]

We present a multiproxy analysis of a sediment core from Freshwater Pond, Barbuda, one of just a few inland paleoenvironmental records from the Lesser Antilles. Our results shed light on the relative contributions of climate variability and Pre- and Post-Columbian human activities to vegetation and fire dynamics on Barbuda. The presence of macroscopic charcoal and pollen of ethnobotanically-useful and disturbance-indicator plant taxa in the sediment record suggests that Pre-Columbian subsistence activities occurred within a few kilometers of the pond between ~150 BCE and ~1250 CE. Our record extends anthropogenic fires back into the early Ceramic (500 BCE–1500 CE) and possibly late Archaic Ages (3000–500 BCE) adding evidence to the timing of arrival of the island's earliest inhabitants. The history of island-wide biomass burning inferred from microscopic charcoal fragments showed heightened fire activity between ~540 and ~1610 CE followed by a period of quiescence that reflected the transition from Pre- to Post-Columbian land-use practices associated with European colonization of the region. The British established a permanent settlement on Barbuda in the 1660s, but given Barbuda's unsuitability for large-scale agriculture, timber harvesting, small-scale farming, and livestock rearing, activities that left no detectable charcoal footprints likely dominated post-colonial land use. The lack of any clear correspondence between the reconstructed histories of fire and effective moisture at Freshwater Pond supports the idea that Late-Holocene fire activity on Barbuda was driven primarily by human activity. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons (PAHs) are produced by incomplete combustion of biomass and fossil fuel, yet PAHs have been rarely analyzed in coastal sediment cores as a tracer for human activities before industrialization. The aim of this study was to assess if the historical trend of PAHs can be related to past human activities. To this end, we have determined the concentrations of PAHs in a 9 m-long sediment core from Osaka Bay, which records history of the last 2400 years. The concentration of PAHs before the beginning of the 17th century CE, the beginning of the peaceful Edo period, was consistently low (<100 ng g−1) and mainly comprised of smoke-derived PAHs reflecting the natural background. A relative higher abundance of 4−6 ring PAHs from the early 17th century CE and a higher PAH concentration from the early 18th century CE until approximately 1800 CE agreed with a population increase, Cu smelting activities and increasing combustion of charcoal. The constant PAH concentration until the late 19th century CE overlapped with a decline in the population in the Osaka area. An increasing PAH concentration from the late 19th century CE marked the beginning of industrialization in the Modern age. The peak in PAH concentration in 1945 CE was likely caused by burning of wooden structures due to air raids on Osaka City. A second peak around 1980 CE indicated the introduction of cleaner energies. We conclude that PAHs in coastal sediment cores can be used to reconstruct past human activities. [ABSTRACT FROM AUTHOR]

A new hydrothermal field (Tianshi) was discovered on the rift valley wall through plume anomaly surveys and geological work conducted in 2012 and 2018 between 2°35′N and 2°43′N of the slow-spreading Carlsberg Ridge (CR). Here, the results of two expeditions conducted to detect and characterize the new hydrothermal field are reported. Mineralogical and geochemical data, as well as 14C ages of a sediment core collected near the field are presented to reveal the hydrothermal history. Results show that the Tianshi field is a basalt-hosted hydrothermal system. Geochemical data of the sediments collected near the field indicate a strong hydrothermal contribution, and hydrothermal Fe and Cu fluxes range from 30 to 155 mg/(cm2.ka) and 0.59 to 11.49 mg/(cm2.ka), respectively. Temporal variations in the fluxes of hydrothermal Fe indicate that there have been at least three amplified hydrothermal venting events (H1, H2, and H3) in the Tianshi field over the last 35.2 ka, in 28.6–35.2 ka BP, 22.0–27.6 ka BP, and 1.2–11.4 ka BP, respectively. Hydrothermal event H2 was driven by an increased magmatic production associated with sea level fall during the Last Glacial Maximum, while event H3 was promoted by tectonic activity associated with a rapid sea level rise. This study further verified the role of sea level change in modulating hydrothermal activity on mid-ocean ridges. [ABSTRACT FROM AUTHOR]

The complex aquatic system of dam reservoirs is known to trap emerging pollutants as microplastics (MPs) in sediments and water column. Considering the knowledge gaps in this type of environment, we investigated the amount and distribution of MPs in the surface water layer, as well as in the surface and deep sediments of the Siriu Reservoir in the Buzău River system, which is located in the southern area of the Eastern Carpathians, Romania. There was a discrepancy between MP abundancy in both water and sediment samples collected near the reservoir (5.3 MPs/m3, 315.5 MPs/kg) and at several kilometers downstream of the dam (1.4 MPs/m3, 132.5 MPs/kg). The chronological accumulation of MPs in the lacustrine sediments was determined by analyzing 5 cm intervals of a 50 cm length core extracted from the reservoir bed. By comparing the concentration of MPs identified in each interval with the solid debit volumes registered in the last decade, we found that flood events could be traced easily due to abundant MP accumulation. Morphologically, the particles were observed mainly as fibers and fragments. Fourier transform infrared spectroscopy (FT-iR) investigations identified most of the MPs as polypropylene (28%), polyethylene (26%), and polyethylene terephthalate (19%). [ABSTRACT FROM AUTHOR]

Marine microplastics have received considerable attention, and efforts are underway to develop standardised methods for sampling, sample treatment, and analysis, while the observation of freshwater ecosystems remains relatively overlooked. To address this understudied environment, we present a comprehensive case study on microplastics in an urban lake from Baltic region of Northern Europe covering the seasonal dynamics of microplastics in surface water, deposition rate throughout one year in sediment traps and distribution of microplastics in dated sediment archive to determine the most representative environmental compartment for microplastic pollution monitoring. The following well-established microplastic research methods have been used: Manta trawling for surface water, trapping for assessing microplastics sedimentation rate and coring for sediments. Attenuated total reflection and micro-Fourier transform infrared spectroscopy methods were used to investigate the synthetic nature of identified particles. The sediment core chronology was based on 210Pb and Bayesian Plum model revealing sediment layers to represent even the time before the beginning of plastic mass production (approximately 1950). The surface water microplastic concentrations were higher in summer (5.71 particles/m3) and gradually decreased towards winter (0.75 particles/m3); they were almost 25 times higher in more recent (2018) sediments than in the deeper layers referring to years prior to 1890. Surprisingly, microplastic particles were found in sediments before the year 1950. The microplastic deposition rate was 9.47 particles/cm2/year or 4.31 µg/cm2/year. The most abundant polymers were polyethylene, polystyrene and polypropylene, and the prominent particle shapes were fibres in surface water and fragments in sediments. Our results provide a baseline for evaluating future contamination level changes in highly urbanized area. We recommend the combination of surface water filtering with net and sediment trapping methods for monitoring microplastics in lakes since this method requires little time and financial resources for sampling and processing and produces information on temporal microplastic occurrence and deposition.

Methane (CH4) emissions from reservoir to the atmosphere depend on the balance of microbial CH4 production and oxidation, and temperature is an important factor to both processes by influencing directly the activity of microorganism. Six sediment cores of 30 cm were collected from the Meiziya Reservoir, China, a small water conservancy project with the maximum water depth of 9.7 m. The main input of reservoir was terrigenous organic matter, and the δ13C of organic matter in sediments ranged from − 27.5 to − 23.3‰. Using a self-made device for monitoring CH4 production rate, we measured the CH4 production and oxidation rates in sediment cores simultaneously at the range of 6–27 °C with an interval of 3 °C. The CH4 net production rates and oxidation rates in sediment cores varied in the range of (4.2–2489.0) × 10−3 µmol/L·h−1 and (16.0–1287.5) × 10−3 µmol/L·h−1, respectively. Increasing temperature enhanced the CH4 production and oxidation rates, and the former increased over temperature with an exponential trend. In the Meiziya Reservoir, a large proportion of CH4 (69.7–70.6%) that originated from sediments was depleted before escaping to the surface sediments. During the mineralization of organic matter in sediments, the release of CH4 accounted for 1.1–66.8% of gaseous carbon (calculated by the mass of C). [ABSTRACT FROM AUTHOR]

Evaluating the ecological risks of metals and identifying their sources is useful for preventing and controlling heavy metal pollution in water bodies. Four sediment cores (S1~-S4) were collected from the Changhu Reservoir of South China to determine lead (Pb) concentrations and geochemical fractions, as well as the isotopic compositions of core S1. The results show that Pb concentrations increased from the upstream site (S1:173.2 mg kg-1) to the downstream site (S4:313.5 mg kg-1), resulting in a moderate to significant enrichment in the sediments. Sediment Pb in the geochemical fractions followed a decreasing order of residual (F4:54.7%) > reducible (F2: 23.1%) > oxidizable (F3: 16.6%) > acid-soluble fraction (F1: 5.8%). The geoaccumulation index (Igeo) and risk assessment code (RAC) showed that sediments were moderately polluted by Pb in S1 and S2 core, while sediments were moderately to heavily polluted in S3 and S4 core. The ecological risk of Pb in all sediment samples is generally at a low risk level, except for the sediments at a depth of 30-40 cm in the S4 core. Significant correlation between Pb concentration and 206Pb/207Pb ratios suggested possible binary mixing of Pb. In the present study, mining activities, which was the major anthropogenic Pb source base on its isotopic composition, contributed significantly (means: 45.3-77.5%) to sediment Pb. The anthropogenic Pb in sediments is most likely to come from Sphalerite and Galena. [ABSTRACT FROM AUTHOR]

The historical sedimentary and evolutionary characteristics of persistent organic pollutants and endocrine disruptors in typical regions of the Three Gorges Reservoir are scarcely studied. Herein, the 96-year data on contaminated sediment history were reconstructed using Caesium 137 isotope dating. Polychlorinated biphenyl concentrations in the involved sediment cores ranged from non-detected (ND) to 11.39 ng/g. The concentrations of polycyclic aromatic hydrocarbons ranged from ND to 2075.20 ng/g and peaked in the 1970s owing to natural, agricultural and human activities. Further, phthalate esters (PAEs) and heavy metals (HMs) were detected at concentrations ranging from ND to 589.2 ng/g and 12.10–93.67 μg/g, respectively, with highest values recorded in the 1980s owing to rapid industrialisation and insufficient management during China's early reform and development stages. PAE and HM concentrations have increased in recent years, suggesting the need to focus on industrial and agricultural activities that have caused this impact. Although current pollutant concentrations in sediments do not pose a risk to the aquatic ecosystem, they should be continuously monitored.

This study presents morphological descriptions and ecological information for 58 terrestrial pollen taxa and seven water-related pollen taxa from the Brazilian Cerrado, obtained from two sediment cores, Lake Feia (LFB1) and Getulio Swamp (VGE-17), encompassing the last 5000 and 15,000 cal yr BP, respectively. The relationships between the ecological and morphological traits (pollination syndrome, vegetation stratum and grain size) within each of the two depositional environments were investigated. In the LFB1 core, the pollen assemblages were dominated by arboreal pollen from closed physiognomies and lower storey trees (<10 m in height), while a combination of closed and open physiognomies was observed in the pollen assemblages from the VGE-17 core. The vast majority of the pollen taxa exhibited the entomophilous pollination syndrome, and a higher influx of entomophilous pollen was observed in both cores. Anemophilous and anemophilous/entomophilous syndromes were less well represented. Small and medium pollen grain classes were the most abundant, while the large pollen grain class was rare. The influx of small pollen grains was slightly more abundant in the lake record, while in the swamp record medium pollen grains were more abundant. Our results show that swamps and lakes differ in their representation of local versus regional pollen and in their sensitivity and responses to water-level changes. Landscape physiognomy also influences pollen dispersion: a closed physiognomy increases the local pollen signal, while a more open physiognomy results in better representation of local and regional signals. [ABSTRACT FROM AUTHOR]

Perfluoroalkyl substances (PFAS) are an emerging class of contaminants that have been produced since the 1950s. The first report on PFAS to raise global concerns was published in 2001. Since then, many countries have implemented policies to control PFAS. In this study, PFAS in the water, sediment, and biota in coastal areas were surveyed to review their use since their earliest production by using chronological methods combined with previous policy restrictions imposed on PFAS. In the meantime, reports of existing PFAS were evaluated to assess the ecological and health risks of seafood consumption by coastal populations. Following the restrictions on PFAS, the concentrations of PFAS have been decreasing steadily. With regard to the current occurrences of PFAS in water and sediment, there is almost no ecological risk. However, different gender and age groups are still at risk of exposure to perfluorooctane sulfonate and require constant monitoring. It is expected that the negative impacts of PFAS on the environment and human health will continue to decrease with the implementation of the emerging pollution control policy by the Chinese government in 2023.

This study investigated the tolerance of resting eggs of Eurytemora pacifica to storage under low temperatures, which is of particular interest in light of the recent use of nauplii as living food in aquaculture, other than conditions experienced also in the wild during winter cold events in the Northern Hemisphere. Sediment samples collected in August 2020 were used to store the resting eggs at two different freezing temperatures (−5 and −20 °C) for five different durations (1, 3, 6, 9, and 12 months). The mean hatching success rates of the resting eggs after one month of storage were 85.3 ± 1.5% (−5 °C) and 85.0 ± 3.6% (−20 °C), with no significant difference between freezing temperatures. However, significant differences emerged over time, with the mean hatching success rate remaining at 85.0 ± 3.6% at −5 °C after three months, while it dropped sharply to 1.7 ± 2.1% at −20 °C. For the non-freezing conditions, the hatching success at 10 °C increased gradually over the one-month incubation period, ultimately reaching 71.0%. These findings demonstrate the remarkable cold tolerance of E. pacifica but also indicate a limit to this tolerance at longer durations. These results underscore the importance of considering the adoption of storage freezing for resting eggs to be used for aquaculture and also suggest the possibility of the species better surviving the extreme weather events in comparison with other species.

Identifying the baseline status and the timing of ecosystem disturbances are essential for restoration programs. The historical bioaccumulation of heavy metals was assessed from an 80-cm-long core from the Manzala Lagoon (Nile Delta). The heavy metal concentrations increased slightly upward and peaked around 1964, after the completion of Aswan High Dam. The metal concentrations of shells are 2-3 times less than those of bulk sediment. The topmost sediments are enriched in Cd, Cu, and Pb above USEPA. Sediment type and sediment grain size have a minor effect on the heavy metal concentration in mollusk shells, suggesting a priority over bulk sediments. Although correlated, the shells of the grazer gastropod Melanoides tuberculata have the highest concentration of all metals relative to the suspension-feeder bivalves Cerastoderma glaucum and Saccostrea cuculata. This was attributed to the influences of the eco-physiological traits, which exert a similar influence on the bioaccumulation process of all metals., Competing Interests: Declaration of competing interest We declare no conflict of interest., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Despite declining anthropogenic emissions of polycyclic aromatic hydrocarbons (PAHs) due to global control strategies, forest fire emissions have been increasing, significantly affecting PAH dynamics in global sinks. This study investigated the spatiotemporal variations of sedimentary PAHs in three Tibetan lakes-Yiong Tso, Yamdrok Yumtso, and Urru Tso-to determine the influence of forest fires on PAH levels and historical trends. Yiong Tso Lake, located in a fire-affected watershed, exhibited the highest PAH concentrations (average of 43.4 ± 25.7 ng/g) with significant fluctuations since the 1920s, peaking in the 1960s (46.3 ng/g) and 1980s (91.3 ng/g), corresponding to periods of intense forest fires. This pattern aligned with source contribution estimates using the modified Cohen's d (mcd), indicating the dominance of forest fires as a PAH source until the 1990s. PAH concentrations decreased with increasing distance from the southeastern Tibetan Forest, as observed in Yamdrok Yumtso (average of 36.1 ± 19.9 ng/g) and Urru Tso (average of 16.4 ± 6.9 ng/g). Temporal variations in PAH concentrations and mcd values from these lakes also reflected a response to forest fires during the 1960s, suggesting a widespread influence of forest-fire-derived PAHs across the plateau. The impact of forest fires on sedimentary PAHs was expected to persist for decades, with an estimated half-life of approximately 11-12 years. These findings highlight significant emissions of PAHs from forest fires in the Tibetan Plateau, potentially transforming regional PAH dynamics and influencing global cycling., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

High concentrations of microplastics (MPs) have been documented in the deep-sea surface sediments of the Arctic Ocean. However, studies investigating their high-resolution vertical distribution in sediments from the European waters to the Arctic remain limited. This study examines MPs in five sediment cores from the Norwegian Coastal Current (NCC), encompassing the water-sediment interface and sediment layers up to 19 cm depth. Advanced analytical methods for MP identification down to 11 μm in size were combined with radiometric dating and lithology observations. MPs were present across all sediment cores, including layers predating the introduction of plastics, with concentrations exhibiting significant variation (54-12,491 MP kg -1 ). The smallest size class (11 μm) predominated in most sediment layers (34-100%). A total of 18 different polymer types were identified across all sediment layers, with polymer diversity and depth correlations varying widely between stations. Our findings suggest that differences in seafloor topography and the impact of anthropogenic activities (e.g., fishing) lead to varying environmental conditions at the sampling sites, influencing the vertical distribution of MPs. This challenges the reliability of using environmental parameters to predict MP accumulation zones and questions the use of MPs in sediment cores as indicators of the Anthropocene.

The historical sedimentary and evolutionary characteristics of persistent organic pollutants and endocrine disruptors in typical regions of the Three Gorges Reservoir are scarcely studied. Herein, the 96-year data on contaminated sediment history were reconstructed using Caesium 137 isotope dating. Polychlorinated biphenyl concentrations in the involved sediment cores ranged from non-detected (ND) to 11.39 ng/g. The concentrations of polycyclic aromatic hydrocarbons ranged from ND to 2075.20 ng/g and peaked in the 1970s owing to natural, agricultural and human activities. Further, phthalate esters (PAEs) and heavy metals (HMs) were detected at concentrations ranging from ND to 589.2 ng/g and 12.10-93.67 μg/g, respectively, with highest values recorded in the 1980s owing to rapid industrialisation and insufficient management during China's early reform and development stages. PAE and HM concentrations have increased in recent years, suggesting the need to focus on industrial and agricultural activities that have caused this impact. Although current pollutant concentrations in sediments do not pose a risk to the aquatic ecosystem, they should be continuously monitored., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors.)

Seagrass beds can trap large amounts of marine debris leading to areas of accumulation, known as 'sinks', of anthropogenic particles. While the presence of vegetation can enhance accumulation, less is known about how the trapping effect changes from vegetated to less vegetated patches. To test this, vegetation and sediment were sampled along a vegetation percent cover gradient from the centre of seagrass beds to nearby less vegetated patches. To determine whether trapped particles can lead to increased accumulation in associated fauna, gastropods were also collected from the transects laid across this gradient. Extracted anthropogenic particles were counted and characterised. Particles were detected in all sample types and reached quantifiable limits in at least 50% of sediment and gastropod samples. There was no significant difference in the distribution of particles found in seagrass beds compared to less vegetated patches, suggesting other factors contribute to the trapping efficiency of biogenic habitats besides simply the presence or absence of vegetation. • Seagrass beds are considered to be a 'sink' for anthropogenic particles. • Sediment, vegetation, and fauna were sampled along a gradient of seagrass cover. • LOD/LOQ blank correction protocol for detected or quantifiable anthropogenic particles. • No difference in particle abundance between vegetated and less vegetated patches. • Results provide evidence that seagrass bed trapping efficiency is variable. [ABSTRACT FROM AUTHOR]

The quantification of microplastic (MP) pollution in rivers is often constrained by a lack of historical data on a multi-decadal scale, which hinders the evaluation of public policies. In this study, MP contents and trends were analyzed in dated sediment cores sampled upstream and downstream of a large metropolis, in environmental deposits that exhibited consistent sedimentation patterns from the 1980s to 2021. After a thorough sedimentological analysis, MPs were quantified in samples by micro Fourier Transform InfraRed spectroscopy (μFTIR imaging) and a density separation and organic matter digestion procedure. Microplastics recorded in the upstream core are relatively ubiquitous all along the dated sequence. The results also confirmed a sever increase of microplastics levels in the downstream core, by one order of magnitude, and an increase of polymer types. Polypropylene, polyethylene, and polystyrene represent ubiquitous contamination and were predominant at the two stations, whereas polyvinyl chloride and polytetrafluoroethylene were suspected to be abundant at the downstream station, but were not detected at the upstream station. Their presence could be linked to local contamination from specific industrial sources that manufactured and utilized these polymers. Surprisingly, in the downstream station sediment has recorded a relative improvement in polymers associated with industrial sources since the 2000s and, to a lesser extent, for ubiquitous ones since the 2010s. This trend of mitigation diverges from that of global assessments, that assume uncontrolled MP pollution, and suggest that European Union wastewater policy and regulation on industrial discharges have positively influenced water quality, and certainly also on MPs. However, the accumulation of microplastics remains high in recent deposits and raises the emerging concern of the long-term management of these reservoirs. [Display omitted] • Microplastic trends were retraced over four decades using river sediment cores. • Downstream of the metropolis, microplastic levels were notably higher. • Polymer-type compositions reflected urban and industrial sources. • Recent trends diverged from plastic demand, suggesting source control. [ABSTRACT FROM AUTHOR]

• Dolichospermum akinetes isolated from a 10cm sediment core represent a 45-year history. • Samples with 10 akinete cells produced near complete genomes using single-cell genome amplification. • Lake Stechlin akinete genomes were very similar over the 45 year history. • SNP analysis revealed two populations that changed dominance with environmental conditions. Dolichospermum is a cyanobacterial genus commonly associated with toxic blooms in lakes and brackish water bodies worldwide, and is a long-term resident of Lake Stechlin, northeastern Germany. In recent decades, shifts in the phosphorus loading and phytoplankton species composition have seen increased biomass of Dolichospermum during summer blooms from 1998, peaking around 2005, and declining after 2020. Cyanobacteria are known to rapidly adapt to new environments, facilitated by genome adaptation. To investigate the changes in genomic features that may have occurred in Lake Stechlin Dolichospermum during this time of increased phosphorus loading and higher biomass, whole genome sequence analysis was performed on samples of ten akinetes isolated from ten, 1 cm segments of a sediment core, representing a ∼45-year period from 1970 to 2017. Comparison of these genomes with genomes of extant isolates revealed a clade of Dolichospermum that clustered with the ADA-6 genus complex, with remarkable genome stability, without gene gain or loss events in response to recent environmental changes. The genome characteristics indicate that this species is suited to a deep-chlorophyll maximum, including additional light-harvesting and phosphorus scavenging genes. Population SNP analysis revealed two sub-populations that shifted in dominance as the lake transitioned between oligotrophic and eutrophic conditions. Overall, the results show little change within the population, despite diversity between extant populations from different geographic locations and the in-lake changes in phosphorus concentrations. [ABSTRACT FROM AUTHOR]

[Display omitted] • Two sources of toxic metals were quantitatively identified. • Ecological risks from various sources were quantitatively analyzed. • Cd from human sources was the priority control factor in the cascade reservoirs. Determining the priority control factor is crucial for managing sediment toxic metals (TMs) pollution. Therefore, the vertical profiles of TMs in core sediments from the Nuozhadu (NZD) and Jinghong (JH) cascade reservoirs in the Lancang River were studied to assess the source-oriented ecological risks. The geo-accumulation index (I geo), enrichment factor (EF), potential ecological risk factor (Er), and potential ecological risk index (RI) were employed. Then, combined with principal component analysis (PCA) and the positive matrix factorization (PMF) model, the effects of TMs and contamination sources on ecological risks were revealed. Results showed that the concentrations of As, Cd, Hg, Pb, and Zn in the NZD Reservoir were significantly lower than those in the JH Reservoir, which might be related to the coarser grain size of the NZD Reservoir sediments. While both reservoirs demonstrated elevated contamination levels of Cd and As among all the TMs, the NZD Reservoir also exhibited high levels of Cr, whereas the JH Reservoir showed relatively high levels of Hg. Natural and anthropogenic sources of TMs were quantitatively identified in cascade reservoirs. Cd and Hg exhibited higher ecological risk levels than other TMs in both reservoirs. The JH Reservoir was exposed to significantly higher ecological risks from TMs compared to the NZD Reservoir, and 40.0 % of the sediments in the JH Reservoir were exposed to considerable risk (300 < RI < 600). Results of source-oriented ecological risks showed that Cd from anthropogenic sources was identified as the priority control factor in the NZD and JH cascade reservoirs. Our findings give scientific backing for the prevention and control of TM contamination and the planning of sustainable development of water resources in the Lancang-Mekong River. [ABSTRACT FROM AUTHOR]

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 organisms 1 , 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 studies 1 , 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 approaches 9 , 10 , 11 and highlights the untapped potential for retrospective "evolve and resequence" natural experiments using sedaDNA., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

In the decades since plastic has become widely used, deep-sea areas, specifically cold seeps, have developed into plastic sinks. Cold seeps contain clean energy natural gas hydrates and act as a barrier reducing methane migration to the upper water column. However, the impacts of microplastics (MPs) on the carbon content in the cold seep remain unclear. In this study, we explored spatial changes in the MPs ' carbon content (MPC) selecting the Haima cold seep (HCS) as the study area. The main conclusions are as follows: (1) For active seepage areas, the mass abundance of the MPs increases with the methane seepage strength in all water columns and sediment of strong seepage areas. It decreases with the seepage strength in the sediment cores in other areas. (2)The MPC is positively correlated with the depth of the water column in the non-seepage area, while it is negatively correlated in the sediment core. (3) The surface roughness of the MPs was greater in the middle of the water column and the sediment core at ROV1. In the high-pressure and oligotrophic cold seep, the amount and method of microbial utilization of carbon from the MPs deserve greater attention. [Display omitted] • The polymer distributions differ between methane seepage and non-seepage areas. • The sediment is the dominant sink. • The MPC in the sediment is significantly higher than that in the seawater. • The MPC is significantly correlated with microplastic abundance. • The MPs at the strong methane seepage are rougher than the non-seepage area. [ABSTRACT FROM AUTHOR]