Centennial Records of Microplastics in Lake Cores in Huguangyan Maar Lake, China.

Microplastic records from lake cores can reconstruct the plastic pollution history. However, the associations between anthropogenic activities and microplastic accumulation are not well understood. Huguangyan Maar Lake (HML) is a deep-enclosed lake without inlets and outlets, where the sedimentary environment is ideal for preserving a stable and historical microplastic record. Microplastic (size: 10-500 µm) characteristics in the HML core were identified using the Laser Direct Infrared Imaging system. The earliest detectable microplastics appeared unit in 1955 (1.1 items g-1). The microplastic abundance ranged from n.d. to 615.2 items g-1 in 1955-2019 with an average of 134.9 items g-1. The abundance declined slightly during the 1970s and then increased rapidly after China's Reform and Opening Up in 1978. Sixteen polymer types were detectable, with polyethylene and polypropylene dominating, accounting for 23.5 and 23.3% of the total abundance, and the size at 10-100 µm accounted for 80%. Socioeconomic factors dominated the microplastic accumulation based on the random forest modeling, and the contributions of GDP per capita, plastic-related industry yield, and total crop yield were, respectively, 13.9, 35.1, and 9.3% between 1955-2019. The total crop yield contribution further increased by 1.7% after 1978. Coarse sediment particles increased with soil erosion exacerbated microplastics discharging into the sediment.

Vertical variation of antibiotic resistance genes and their interaction with environmental nutrients in sediments of Taihu lake.

Antibiotic resistance is a growing environmental issue. As a sink for antibiotic resistance genes (ARGs), lake surface sediments are well known for the spread of ARGs. However, the distribution pattern of ARGs and their relationship with environmental factors in vertical sediment layers are unclear. In this study, we investigated the resistome distribution in sediment cores from Taihu Lake using metagenomic analysis. The results showed that the abundance of total ARGs increased by 153% as the sediment depth rose from 0 to 50 cm, and the ARG Shannon index significantly increased. Among all the ARG types, efflux pump genes (e.g., mexT and mexW) were dominant, especially in 40-50 cm sediment. The variation in ARG with depth described above was related to the changes in bacterial adaptation to environmental gradients. Specifically, sulfate and nitrate concentrations decreased with depth, and random forest analysis showed that they were the main factors affecting the changes in ARG abundance. Environmental factors were also found to indirectly impact the distribution of ARGs by affecting the bacterial community. Potential sulfate-reducing gene/nitrate-reducing gene-ARG co-hosts were annotated through metagenomic assembly. The dominant co-hosts, Curvibacter, and Comamonas, which were enriched in deeper sediments, may have contributed to the enrichment of ARGs in deep sediments. Overall, our findings demonstrated that bacterial-mediated sulfate and nitrate reduction was closely related to sediment resistance, which provided new insights into the control of antibiotic resistance.

Sediment core records and impact factors of polycyclic aromatic hydrocarbons in Chinese lakes.

Lake sediment is a natural sink for polycyclic aromatic hydrocarbons (PAHs). PAH sedimentation characteristics and their impact factors of Chinese lakes have mainly been qualitative assessed. However, quantitative impacts of PAH sedimentation from different factors have not been well analyzed. To fill this gap, we screened PAH sedimentation records from the literature, for 51 lakes in China and other regions of the world, to identify historical concentration variation and the impact factors of PAHs in different regions, in lake sediment. The results show that PAH concentrations in the sediment core in the selected Chinese lakes (478 ± 812 ng/g dry weight (dw)) were significantly lower than those in North America (5518 ± 6572 ng/g dw) and Europe (3817 ± 4033 ng/g dw). From 1900 to 2015, most of the lakes in China showed an increasing trend of PAH sedimentation concentrations, with the lakes in Southeastern China showed a decreasing trend of PAH concentration in the period of 2001-2015, which was later than the peak times shown in Western countries (1941-1970). The 2-3-ring PAHs were the main components in the sediment core of Chinese lakes, but the proportion to the total PAHs decreased from 72% in 1900-1940 to 55% in 2001-2015. Generalized additive modeling (GAM) was adopted to simulate the associations between PAH sedimentation records and the impact factors. There are large regional variations of economic and industrial development in China. The impact factors of PAH accumulation in the lake sediments differ in different regions. However, population and the consumption of coal, pesticides, and fertilizer were identified to be the most important impact factors influencing PAH sedimentation. The Chinese government needs to strengthen control measures on pollutant discharge to reduce the anthropogenic impact of PAH sedimentation in lakes.

Rapid urbanization affects microplastic communities in lake sediments: A case study of Lake Aha in southwest China.

Effective management of pollutants in urban environments is crucial for achieving sustainable cities. Microplastics, as an emerging pollutant widely present in contemporary environments, have received widespread attention in recent years. However, limited studies have reported the impact of rapid urbanization on regional microplastics. In this study, the abundance and composition of microplastic communities in the sediments of Lake Aha were analyzed using a "microplastic community" and slicing the sediments at 5 cm intervals. Results showed that microplastic abundance of sediments in Lake Aha was relatively high (up to 1700 items/kg) and decreased with increasing depth, with the highest abundance found in the surface layer (0-5 cm, 1090 ± 474 items/kg). Hierarchical cluster analysis (HCA), principal component analysis (PCA), and analysis of similarities (ANOSIM) revealed that the different sediment layers could be classified into high and low urbanization level groups based on the composition of microplastic communities. Linear discriminant analysis effect size (LEfSe) indicated that agricultural input was the main source of microplastic pollution during low urbanization levels, characterized by low abundance, large particle size, and high fiber proportion, while urban activities dominated during high urbanization levels, with high abundance, small particle size, high proportion of Polyethylene terephthalate (PET), fragments, and granules, and colorful microplastics. This study clarifies the impact of urbanization on the abundance and composition of microplastics in lake sediments, which has implications for more effective management and control of microplastic pollution in regions undergoing rapid urbanization.

Levels and sources of hydrocarbons in the Patos Lagoon estuary and Cassino Beach mud bank (South Atlantic, Brazil): evidence of transference between environments.

This study assessed the concentrations and sources of natural and anthropogenic aliphatic (AHs) and polycyclic aromatic hydrocarbons (PAHs) in superficial sediments collected along the Patos Lagoon estuary and in sediment cores obtained from the Cassino Beach mud bank. Levels and distribution of n-alkanes indicate terrestrial sources, overlapping with a low amount of petrogenic hydrocarbons (heavy oils). Unresolved complex mixture (UCM) was observed in all samples. On the other hand, the distribution of PAHs in the sediments showed a predominance of pyrolytic over petrogenic sources. In general, hydrocarbons (HCs) contamination in the Patos Lagoon estuary and its adjacent coastal area can be considered low, except for sites near urban or industrial effluents, where moderate to high levels of contamination were found. Concentrations of hydrocarbons were homogeneous throughout the sediment cores, suggesting that mixing processes may have occurred along the layers or that HCs inputs to the mud banks were uniform during the studied deposition period. In addition, the levels and profile of HCs in the coastal sediments were similar to those observed in the estuary. Moreover, the frequent remobilization of sediments from the mud bank towards Cassino beach does not seem to pose any threats to the local biota or beach users since the levels of contamination were relatively low and below the threshold limits of sediment quality guidelines.

Radiocesium accumulation in Lake Kasumigaura by riverine input and migration following the Fukushima Dai-ichi nuclear power plant accident.

Vertical radiocesium concentration profiles and inventories in sediments were measured in Lake Kasumigaura following the 2011 Fukushima Dai-ichi Nuclear Power Plant accident. Further measurements of radiocesium concentrations in suspended solids (SS) have been conducted since September 2012 in the Koise and Sakura rivers inflowing into the lake. Cesium-137 (137Cs) accumulated intensively near the inflow outlets in the lake. At the lake center, the 137Cs inventory in sediments increased during 2011-2014; however, few changes were observed during 2014-2016. The 137Cs surface concentration and inventory decreased considerably in Tsuchiura-iri Bay until 3 years after the accident, indicating 137Cs migration. However, the rate of decrease subsequently slowed due to the 137Cs supply from the river. The 137Cs concentration in river SS declined during 2012-2015; however, it remained 1-2 orders of magnitude above its pre-accident level. The entrainment coefficient of particulate 137Cs in the inflows was initially higher in the Koise River but decreased exponentially more rapidly in the Koise River than in the Sakura River until 2015. Therefore, in the future, the difference in 137Cs concentrations will be smaller. The 137Cs concentration in the Koise River will continue to decrease; thus, the difference in the 137Cs inventory between the northern and southern parts of the lake will decrease. Total estimated amounts of 137Cs in the entire lake were 3.72 × 1012 Bq in December 2012 and 4.18 × 1012 Bq in August 2016. The accumulated amount of 137Cs in the entire lake based on sediment analysis was similar to the riverine input of particulate 137Cs based on riverine SS analysis from December 2012‒;August 2016, confirming the high trapping performance of the lake for particulate matter provided by the basin. Moreover, the amount of 137Cs accumulated in the lake in 2016 may have originated from comparable rates of atmospheric deposition and riverine input. These findings provide useful insights for future prediction and management of radiocesium contamination and the effects of riverine inputs in general shallow lakes.

Heavy metal background levels and pollution temporal trend assessment within the marine sediments facing a brownfield area (Gulf of Pozzuoli, Southern Italy).

In this study, site-specific natural background levels (NBLs) were determined for 18 elements (Al, As, Be, Cd, Co, Cu, Cr, Fe, Hg, K, Mn, Mo, Ni, Pb, Tl, U, V, and Zn) in two sediment cores collected offshore the Bagnoli-Coroglio brownfield site (Gulf of Pozzuoli, southern Italy) to accurately assess the degree of contamination and the historical trends in Heavy Metals (HMs) enrichment. This objective was pursued taking in account the high temporal and spatial variability of the geochemical properties of the area due to the local geothermal activity. Moreover, the temporal variation of Polycyclic Aromatic Hydrocarbons (PAHs) was investigated.226Ra was used as an extraordinary marker to confirm 210Pb dating. It especially allowed defining the geochronological framework of the sediment core closer the brownfield up to around 1500, providing compelling support to correlate the investigated elements' occurrences with natural geogenic dynamic. Sediment samples were accurately dated and analyzed for chemical and particle size composition. The contamination factor (Cf) and the pollution load index (PLI) showed very high enrichment of Cd, Cu, Hg, Pb, and Zn. The contamination profiles of HMs and PAHs follow the same pattern in both sediment cores, increasing from deep to upper layers. The highest contamination levels for HMs and PAHs were observed between 10 and 30 cm, corresponding to the periods of most intense industrial activity. Decreasing trends of pollutants were observed in the surface layers (0-10 cm), probably affected by a natural attenuation process due to the cessation of industrial activities.

Chronological deposition record of trace metals in sediment cores from Chaohu Lake, Anhui Province, China.

Lakes located in the mid-low reaches of the Yangtze River watershed have been subjected to various degrees of human perturbation that would have resulted in toxic metal concentrations and would pose potential risk to the natural habitats. Therefore, in the present study, two sediment cores from Chaohu Lake were collected to determine any such concentration, expressed as the enrichment characteristics of major and trace metals (Al, Fe, Mn, Cu, Pb, Zn, Cr, Cd, As, Hg, and Ni) in response to natural and anthropogenic changes. An approximate 180-year (1840-2021) deposition record of trace metals in sediment cores was obtained on the basis of 137Cs and 210Pb dating. Enrichment factors (EFs) and the geo-accumulation index (Igeo) were adopted to evaluate the enrichment state and pollution status of trace metals. The results showed that Cu and Zn were persistently more enriched in sediment, whereas Mn, Pb, Cd, and Hg has shown remarkable increasing trends in the west lake since the 1970s. Evaluation of the Igeo confirmed that sediment was moderately polluted with Cu and Zn within the whole lake and with Cd in the west lake area, whereas it was uncontaminated with Cr and slightly contaminated with other metals. Furthermore, source identification based on multivariate statistical analysis including correlation analysis, principal component analysis, and cluster analysis suggested similar pollution sources for the studied metals. Combined with the natural and anthropogenic changes within the watershed, enhanced soil erosion due to population expansion and agricultural intensification was a major contributor to sedimentary metals before the 1970s while industrial wastewater, urban runoff, and domestic sewage were predominant inputs of trace metals after the 1970s.

Sedimentary phosphorus fractions in typical lacustrine wetland of Changshou Lake flowing into the Three-Gorges Reservoir.

River damming is ubiquitous which would impact the nutrient cycles of the river systems. Here an early eutrophicated reservoir (Changshou Lake) of the Three Gorges Reservoir (TGR) was selected to investigate the phosphorus (P) biogeochemical migration. Nine sediment cores were collected in the littoral nature lacustrine wetland to help to determine the phosphorus distribution and fraction along the water level. Results revealed that the concentrations of phosphorus varied from 106 to 1178 mg/kg, with the highest concentration reported in the shallow water area. This was affected by the fluctuations of the water level and algae accumulation from the deep-water. In addition, it also indicated that the higher accumulation of phosphorus in the shallow water areas was predominated by HCl-P and BD-P fractions, which were potentially the main source of phosphorus in lacustrine wetlands. Hence, more attention should be paid to the autochthonous phosphorus control in the water level fluctuation area.

Algal Community Change in Mountain Lakes of the Alps Reveals Effects of Climate Warming and Shifting Treelines1.

The biological communities of mountain lakes are suspected to be highly sensitive to global warming and associated catchment changes. To identify the parameters determining algal community responses, subfossil pigments from 21 different mountain lakes in the Bavarian-Tyrolean Limestone Alps were investigated. Sediment cores were radio-isotopically dated, and their pigment preservation evaluated. General additive models (GAM) of pigment compositions were calculated with temperature as the explanatory variable and generalized linear models with several lake parameters explaining log-transformed GAM P-values. Lake depth and trophic state were identified as major control variables of the algal community and productivity changes. Shifts in a deep oligotrophic alpine lake (lg(P) = -1.04) were half as strong as in a shallow mesotrophic alpine lake (lg(P) = -1.86) with faster warming and higher productivity forcing the development of biomass. Phytoplankton and macrophyte pigments increased clearly with warming, at lower altitudes, and decreased at the treeline, so that periphytic pigments dominated alpine sediments. This pattern is probably the result of interactions of UV radiation and allochthonous inputs of DOM. Our findings suggest that (sub)alpine shallow lakes with higher nutrient levels are most vulnerable to climate change-driven changes whereas deep, nutrient-poor lakes appear more resilient.

Ecological risks associated to trace metals of contaminated sediments from a densely urbanized tropical eutrophic estuary.

The sediment contamination by trace metals in coastal aquatic ecosystems is a worldwide environmental problem, since metals can be toxic, persistent, and bioaccumulated. In case of natural events, such as storms, or anthropogenic activities, like dredging, the sediment resuspension to the water column occurs and can solubilize metals, probably increasing their bioavailability and consequently the risk to aquatic life. This study evaluated the bioavailability on reactive trace metals (Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn) in estuarine sediments from Iguaçu and Meriti Rivers, both in the drainage basin of Guanabara Bay (Rio de Janeiro, Brazil). Additionally, a discussion about the anthropogenic interference throughout time of six short sediments cores, calculating three different indexes (contamination factors, CF; potential ecological risk index for a single heavy metal, Eif for short; potential ecological risk, PERI) was performed. It was considered as reactive phase, the metal concentrations obtained using a weak acid extraction (in HCl 1 mol L-1 solution). Zn presented high concentrations after resuspension, being above effect range medium (ERM) (52.81 to 1337.4 mg kg-1). The CF indicated very high contamination degree for Cu (14.62 to 17.96) and Zn (27.80 to 35.85) for both rivers. The Eif for short presented higher risk to Cu and Zn for Iguaçu and Meriti rivers. PERI index classified Meriti River samples as severely contaminated (238.10 to 351.62).

Sedimentation rates by the 210Pb chronological method in Itanhaém river watershed, southeast Brazil.

The historical variation of sedimentation rate was investigated in five cores collected from the Itanhaém watershed main rivers, the second largest coastal watershed of the São Paulo state, Brazil, using the lead-210 radioisotope as a geochronometer. The main characteristics of the rivers' waters and sediments were determined in order to support the geochronological analysis results and associate sediments with possible source areas. In this context, the fluvial waters' general classification indicated the facies sulfated or chlorinated sodium in the winter and summer seasons, except for the Branco river waters in summer, which were classified as calcium or magnesium bicarbonate. A longitudinal salinity gradient was found in the downstream river courses, under greater marine influence, with the ions Cl-, Na+, SO42+, Mg2+, Ca2+, and K+ being most common in the waters. Silica is the predominant constituent in the sediment cores and is inversely related to the organic matter (OM) presence. Inverse correlations were also found between silica and other constituents. The watershed sedimentation rates were determined in the range of 0.31 up to 3.97 g/cm2/year and 0.30 up to 3.40 cm/year, highlighting the core extracted from Branco river, which showed the highest sedimentation rate. The profiles corresponding to Preto and Aguapeú rivers presented discontinuities in the sedimentation rates. The discontinuities were dated and would probably be related to the anthropic activities, which intensified in the municipality of Itanhaém around the middle of the twentieth century.

Content of nutrients, trace elements, and ecotoxicity of sediment cores from Roznów reservoir (Southern Poland).

The aims of the study were to investigate the concentration of trace elements, nutrients, and ecotoxicity in bottom sediment cores collected from the silted part of the Roznów reservoir (Southern Poland). Significant differences in the content of nutrients, trace elements, and ecotoxicity between five sediment cores were found. However, in the vertical distribution, there was no high variability of the above parameters, which means that the intensely suspended matter transported by the Dunajec river is and, at various times, has been homogeneous. Significant correlations between nutrients and trace elements (r = 0.33-0.91, at p ≤ 0.05) point to the same sources of the above-mentioned substances and similar levels of contamination in the sediment cores. However, the PCA results showed that cadmium and phosphorus in the sediment cores had different behaviors than other elements and can be associated mainly with anthropogenic sources. According to the degree of contamination factor, sediment cores fall under the category of considerable contamination of metals. Geochemical factors indicated that nickel, chromium, and cadmium (only sediment core C1) were found to be the cause of significant pollution in the sediment cores. Toxicity assessment found that most of the bottom sediment samples were classified as non-toxic or slightly toxic, only 10% of the sediment samples were toxic for Vibrio fischeri, and 6% of the samples were toxic for Sinapis alba. The two test organisms showed a different sensitivity, and higher toxic responses were recorded for V. fischeri than for S. alba. Cadmium and phosphorus were associated with toxicity for S. alba (r = 0.29-0.58, at p ≤ 0.05), whereas TOC, N, and S, and Ca for stimulation of growth this plants. Trace elements (r = 0.32-0.51, at p ≤ 0.05) and nutrients (S, K, Mg, Na, r = 0.44-0.58, at p ≤ 0.05) were positively correlated with inhibition of luminescence of V. fischeri. The studies of concentration and relation between trace elements, nutrients, and ecotoxicity are important in the ecological risk assessment and describing the quality of sediments with multiple sources contamination.

Urban effects in the sediment of an Intermittently Closed and Open Lagoon (ICOLL) in southeastern Brazil-a high-resolution study.

ICOLLs are extremely sensitive to human activities when it comes to sediment metal and nutrient enrichment. To better understand anthropogenic influences associated with Carapebus ICOLL basin historical land use based in Serra, Great Vitória, ES, Brazil, two sediment cores were studied for trace and major elements, organic matter, C/N ratios, total sulfur, and phosphorus. Two stratigraphic units could be found in the sediment cores, one that is related to urbanization, more specifically sewage discharges, and an older one of lithogenic origin with maritime influence. A transition period was also identified from terrestrial influence (upper plants), probably due to deforestation. The more recent stratigraphic unit is characterized by higher organic and metal contents, while the former one is sandy, enriched in detrital metals and calcite. We derived that the Carapebus ICOLL hydrological regime of recent years was changed by the land-use changes in the watershed, specifically due to a larger sediment loading and subsequent closure of the berm. An originally mesotrophic system, Carapebus Lagoon shows the first signs of eutrophication.

Assessing potential release tendency of As, Mo and W in the tributary sediments of the Three Gorges Reservoir, China.

As the largest man-made reservoir in China, the Three Gorges Reservoir (TGR) has significant influence on national drinking water safety. The geochemical behavior of trace elements at the sediment-water interface (SWI) is still unknown. The mobilization characteristics of trace elements (As, Mo and W)-determined by diffusive gradients in thin films (DGT)-were studied to quantitatively calculate the release trends in the SWI in three typical tributaries and the mainstream of the TGR in the summer. The results showed that concentrations of DGT-labile As, Mo and W in the overlying water and sediment cores showed significant variations in the ranges of 0.05-50.90, 0.30-1.63 and 0.01-0.42µgL-1, respectively. The apparent net diffusive fluxes were significantly positive in most sampling sites (77.8% for As, 88.8% for Mo and 66.6% for W), suggesting that the sediment was the source of these three elements. It was noteworthy that the maximum net diffusive fluxes of As and W were found in the upstream of Meixi tributary, which may be attributed to anthropogenic activities. In addition, As, Mo and W may be incorporated in Fe and Mn oxyhydroxides and these three elements simultaneously remobilized with Fe and Mn.

Vertical profile, contamination assessment of mercury and arsenic in sediment cores from typical intertidal zones of China.

The vertical profiles, contamination levels, and potential ecological risks of mercury and arsenic were studied from the sediment cores of seven typical intertidal zones, including the Liaohe River Estuary, the Jianhe River Estuary, the Dagu River Estuary, Yancheng Shoal, the Dongtan Yangtze River Estuary, Hangzhou Bay, and the Pearl River Estuary. Marine sediment quality standards, the threshold effect level (TEL), and the probable effect level (PEL) were used as guidelines to evaluate sediment quality. In addition, the geo-accumulation index (Igeo) and potential ecological risk index ([Formula: see text]) were used to assess contamination and potential ecological risks from mercury and arsenic. The results showed that the Pearl River Estuary was moderately polluted by mercury and represented a high potential ecological risk, while other areas were uncontaminated or mildly contaminated with low or moderate potential ecological risks. The Pearl River Estuary was mildly polluted by arsenic and represented a mild potential ecological risk, while other areas were unpolluted and also posed a mild potential ecological risk.

Deposition behavior, risk assessment and source identification of heavy metals in reservoir sediments of Northeast China.

Sediment cores from five reservoirs, located in the Liaoning and Jilin Provinces in Northeast China, were collected to investigate the accumulation and potential toxicity of heavy metals (Fe, Mn, Cu, Cd, Pb, Zn, and Cr) during a sampling campaign in February, 2015. The results showed that all the detected metals accumulated significantly, especially Cd, compared to their respective background values. Among these reservoirs, Biliuhe Reservoir had markedly increasing trends for organic matter and all the metals, among which Mn was elevated by 280% to 3411mg/kg in a core of only 18cm in depth. Xinlicheng Reservoir was characterized by heavy siltation and varying metal distribution due to its regular geometric features and pulsed flood events. The Enrichment factor (EF) and geo-accumulation index (Igeo) indicated Cd was strongly enriched by anthropogenic inputs, with the values of EF and Igeo greater than 8 and 3, respectively. The toxicity assessment calculated using consensus-based sediment quality guidelines (SQGs) implied the whole cores of Tanghe and Dahuofang and the upper cores of Biliuhe, Xinlicheng and Fengman exhibited toxicity to sediment-dwelling organisms. Cr contributed more to Qm-PEC than the other heavy metals, because only Cr exceeded the probable effect concentration (PEC) despite its low enrichment. According to the results of correlation analysis (CA) and principal components analysis (PCA), mining industries and agricultural activities within the basin were the main anthropogenic pollution sources for these heavy metals.

Assessing remobilization characteristics of arsenic (As) in tributary sediment cores in the largest reservoir, China.

The environmental impact of the Three Gorges Reservoir (TGR) in China has raised widespread concern especially in relation to metal pollution. The diffusive gradient in thin films (DGT) technology was applied to investigate arsenic (As) remobilization in sediment cores collected from the main stream and a tributary in the TGR during July 2015. The results showed that the horizontal and vertical distributions of CDGT-As varied among the four sampling sites. For the same DGT probe, the horizontal distributions of CDGT-As (0-6mm, 6-12mm, 12-18mm) exhibited similarity in the overlying water and different tendencies in the sediment profiles; the vertical variations of CDGT-As showed different mobilization tendencies. Moreover, the mobility patterns of As in the sediment profile showed the diffusion potential of As from the deep sediment to the surface sediment and overlying water were in the order of MX-2< MX-1< CJ < MX-3. In addition, similar distribution characteristics and correlation analysis showed that the mechanisms of As mobility were associated with Fe and Mn. The results also showed that sulphide and As were simultaneous remobilization in the tributary sediment core in the TGR.

An assessment of butyltins and metals in sediment cores from the St. Thomas East End Reserves, USVI.

Tributyltin (TBT) concentrations near a marina complex in Benner Bay on St. Thomas, US Virgin Islands, were elevated relative to other areas in a larger study of the southeastern shore of the island. At the request of the USVI Coastal Zone Management Program, sediment cores and surface sediment samples were collected to better define the extent and history of TBT deposition in the vicinity of Benner Bay. The sediment cores were sectioned into 2-cm intervals and dated with 210Pb and 137Cs. The core sections and the surface samples were analyzed for butyltins and 16 elements. Deposition rates varied from 0.07-5.0 mm/year, and were highest in the marina complex. Core ages ranged from 54 to 200 years. The bottoms of the cores contained shell hash, but the top layers all consisted of much finer material. Surface concentrations of TBT exceeded 2000 ng Sn/g (dry weight) at two locations. At a depth of 8 cm TBT exceeded 8800 ng Sn/g in the marina complex sediment. Based on the ratio of tributyltin to total butyltins, it appears that the marina sediments are the source of contamination of the surrounding area. There is evidence that vessels from neighboring islands may also be a source of fresh TBT. Copper concentrations increase over time up to the present. Gradients of virtually all metals and metalloids extended away from the marina complex. NOAA sediment quality guidelines were exceeded for As, Pb, Cu, Zn, and Hg.

Insight into environmental adaptability of antibiotic resistome from surface water to deep sediments in anthropogenic lakes by metagenomics.

The escalating antibiotic resistance threatens the long-term global health. Lake sediment is a vital hotpot in transmitting antibiotic resistance genes (ARGs); however, their vertical distribution pattern and driving mechanisms in sediment cores remain unclear. This study first utilized metagenomics to reveal how resistome is distributed from surface water to 45 cm sediments in four representative lakes, central China. Significant vertical variations in ARG profiles were observed (R2 = 0.421, p < 0.001), with significant reductions in numbers, abundance, and Shannon index from the surface water to deep sediment (all p-values < 0.05). ARGs also has interconnections within the vertical profile of the lakes: twelve ARGs persistently exist all sites and depths, and shared ARGs (e.g., vanS and mexF) were assembled by diverse hosts at varying depths. The 0-18 cm sediment had the highest mobility and health risk of ARGs, followed by the 18-45 cm sediment and water. The drivers of ARGs transformed along the profile of lakes: microbial communities and mobile genetic elements (MGEs) dominated in water, whereas environmental variables gradually become the primary through regulating microbial communities and MGEs with increasing sediment depth. Interestingly, the stochastic process governed ARG assembly, while the stochasticity diminished under the mediation of Chloroflexi, Candidatus Bathyarcaeota and oxidation-reduction potential with increasing depth. Overall, we formulated a conceptual framework to elucidate the vertical environmental adaptability of resistome in anthropogenic lakes. This study shed on the resistance risks and their environmental adaptability from sediment cores, which could reinforce the governance of public health issues.