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In recent years, mangrove restoration has gained significant attention due to its carbon storage capacity, role as a pollution sink, and ecological and economic benefits. Moreover, the United Nations Sustainable Development Goals' strategies include mangrove restoration. This review investigates the status of mangrove restoration research and the influence of restoration on trace metal accumulation, speciation, and associated risks in mangrove sediments. Our analysis reveals that research on mangrove restoration is increasing globally, with a notable surge in publications after 2017. However, fewer than 25 articles published between 2007 and 2024 address trace metals in restored mangroves, indicating limited focus from researchers on this topic. Research shows that mangrove restoration can quickly alter sediment properties, such as texture, salinity, and pH. As a result, restored sediments tend to accumulate higher organic carbon content than barren areas. Most studies also suggest that trace metal accumulation is higher in restored sites than in non-restored areas. However, metal speciation varies considerably between sites due to local environmental factors. Furthermore, many studies suggest that restoration may increase the risks posed by trace metals to aquatic biota. The challenges of mangrove restoration research include short study timeframes, low success rates, poorly defined targets, small-scale efforts, conflicts with local communities over resources and benefits, insufficient government funding, and a lack of historical data on community health and pollution status. [ABSTRACT FROM AUTHOR]

The Dongsha area, a key region in the northern South China Sea (SCS), features both diffusive deep and seepage shallow gas hydrate reservoirs. Utilizing sediment samples from gas hydrate reservoirs and adjacent layers at sites W08 and W16 in the Dongsha area, this study aims to uncover the sediment property differences between deep and shallow gas hydrate reservoirs and their impact on gas hydrate accumulation through grain size, X-ray diffraction, and specific surface area (SSA) analyses. The findings classify the study intervals into four distinct layers: shallow non-gas hydrate layer (shallow-NGHL), shallow gas hydrate reservoir (shallow-GHR), deep non-gas hydrate layer (deep-NGHL), and deep gas hydrate reservoir (deep-GHR). In the clayey silt sediment reservoirs, grain size has a minor influence on gas hydrate reservoirs. Both shallow and deep NGHLs, characterized by high smectite content and SSA, possess a complex structure that impedes gas and fluid migration and offers limited potential reservoir space. Consequently, both shallow and deep NGHLs function as sealing beds. The deep GHR, having low smectite content and SSA, exhibits a strong capacity for gas and fluid migration and greater potential reservoir space. As a result, sediment properties significantly influence the deep GHR. Seepage primarily controls the shallow GHR. [ABSTRACT FROM AUTHOR]

In recent years, mangrove restoration has gained significant attention due to its carbon storage capacity, role as a pollution sink, and ecological and economic benefits. Moreover, the United Nations Sustainable Development Goals’ strategies include mangrove restoration. This review investigates the status of mangrove restoration research and the influence of restoration on trace metal accumulation, speciation, and associated risks in mangrove sediments. Our analysis reveals that research on mangrove restoration is increasing globally, with a notable surge in publications after 2017. However, fewer than 25 articles published between 2007 and 2024 address trace metals in restored mangroves, indicating limited focus from researchers on this topic. Research shows that mangrove restoration can quickly alter sediment properties, such as texture, salinity, and pH. As a result, restored sediments tend to accumulate higher organic carbon content than barren areas. Most studies also suggest that trace metal accumulation is higher in restored sites than in non-restored areas. However, metal speciation varies considerably between sites due to local environmental factors. Furthermore, many studies suggest that restoration may increase the risks posed by trace metals to aquatic biota. The challenges of mangrove restoration research include short study timeframes, low success rates, poorly defined targets, small-scale efforts, conflicts with local communities over resources and benefits, insufficient government funding, and a lack of historical data on community health and pollution status.

Intertidal creek ecosystems in saltmarsh wetlands provide crucial ecological services, with burrows facilitating material exchange between these environments. Investigating burrow distribution in tidal creeks is essential, yet the underlying mechanisms remain poorly understood. Our study conducted field observations during two seasons, dividing the typical creek section into microhabitats: flat (F), gentle edge (GE), gentle slope (GS), steep slope (SS), and steep edge (SE). Comprehensive analysis of sediment samples encompassed assessments of water content, organic matter, particle size, and salinity. Burrow parameters were extracted using a deep learning method applied to sample images. Benthic biodiversity and community compositions were characterized through eDNA analysis. Our findings revealed significant variations in burrow distribution, sediment properties, and community compositions, both between and within creek sections. Temporal heterogeneity emerged as a substantial influencer of burrow characteristics, while the propensity of benthic communities to respond to topography and sediment properties constituted a chief determinant of burrow distribution. Utilizing a structural equation model based on field data, we illuminated four response pathways governing burrow distribution. Abiotic factors, especially under temporal heterogeneity, had a paramount impact, highlighting the need to explore relative biotic and abiotic influences, considering seasonal regulation. These findings establish a foundational understanding of burrow distribution and its driving mechanisms in creek ecosystems. They offer valuable insights for future field observations and research directions in this field.

Arsenic is a ubiquitous chemical element, occurring naturally worldwide. Yet due to its global cycle, its concentrations in the marine environment are manifold higher than the terrestrial background and may pose harm to biota. This is especially relevant for the Baltic Sea, which is very susceptible to any kind of pollution. Arsenic transported to the sea is adsorbed on iron oxides or precipitating as flocculating particulates and finally bounded in sediments. Therefore, despite the contemporary emission cuts, the existing pollution remains or constantly circulates in marine habitats. The purpose of the research was to recognize the spatial distribution of arsenic in the surface sediments of the southern parts of the Baltic Sea. The number of 483 samples allowed us to prepare reliable interpolation of arsenic contents in surface sediments. Although arsenic concentrations in the Baltic Sea can be considered low, in particular areas the levels are significantly higher. The observed arsenic concentrations distribution pattern could be mostly explained by natural transportation and accumulation bottom-type distribution.

An understanding of the behavior of cohesive sediment is required to solve various engineering problems such as scour around bridge elements, mitigation of soil erosion, pavement design, river bed degradation, stable channel design. Pavement foundation designers principally use the California bearing ratio (CBR) to describe the subgrade and subbase materials and their strength. Several laboratory experiments were done to study the variation in the CBR of cohesive mixtures comprised of clay–gravel mixtures. Nine different clay–gravel mixtures were used in which the clay content varies from 10% to 50% by weight. The variation of the CBR with clay percentage, moisture content, and undrained shear strength parameters was studied. The CBR value reduces with the increase in the moisture content and clay fraction in the mixtures and increases with an increase in the dry density of the mixture under unsoaked conditions. The CBR also increases with the increase of the angle of internal friction of clay–gravel mixtures. A functional relation has been identified to estimate the CBR of clay–gravel mixtures. Using multiple linear regression analysis (MLRA), a relation is proposed to estimate the CBR of clay–gravel mixtures under unsoaked conditions. A statistical analysis was done to judge the behavior of the pertinent variables on the CBR. The proposed relation predicts the CBR of clay–gravel mixtures very well. Artificial neural network (ANN) analysis using R programming was also done to determine the effects of the pertinent variables on the CBR. ANN methodology was applied to predict the contribution of each variable. Three different methods: Garson algorithm, Olden algorithm, and Lek's profile model are used to assess the influence of variable parameters. The Olden algorithm and Lek's profile both show positive association of cohesion with CBR in an unsoaked condition. The role of moisture content was found to be marginally negative in the Olden algorithm and Lek's profile results. It is found that both the ANN and MLRA models are accurate in predicting the CBR of clay–gravel mixtures. It was further found that the MLRA and ANN models are reliable and rapid tools for correct assessment of the CBR of cohesive soil mixtures using the basic soil properties. [ABSTRACT FROM AUTHOR]

The Dongsha area, a key region in the northern South China Sea (SCS), features both diffusive deep and seepage shallow gas hydrate reservoirs. Utilizing sediment samples from gas hydrate reservoirs and adjacent layers at sites W08 and W16 in the Dongsha area, this study aims to uncover the sediment property differences between deep and shallow gas hydrate reservoirs and their impact on gas hydrate accumulation through grain size, X-ray diffraction, and specific surface area (SSA) analyses. The findings classify the study intervals into four distinct layers: shallow non-gas hydrate layer (shallow-NGHL), shallow gas hydrate reservoir (shallow-GHR), deep non-gas hydrate layer (deep-NGHL), and deep gas hydrate reservoir (deep-GHR). In the clayey silt sediment reservoirs, grain size has a minor influence on gas hydrate reservoirs. Both shallow and deep NGHLs, characterized by high smectite content and SSA, possess a complex structure that impedes gas and fluid migration and offers limited potential reservoir space. Consequently, both shallow and deep NGHLs function as sealing beds. The deep GHR, having low smectite content and SSA, exhibits a strong capacity for gas and fluid migration and greater potential reservoir space. As a result, sediment properties significantly influence the deep GHR. Seepage primarily controls the shallow GHR.

Degradation of aquatic ecosystems from nutrient pollution is a global issue, and quantifying nutrient removal in coastal ecosystems is a topic of interest for coastal managers worldwide. Analysing relationships between natural nitrogen removal processes, such as denitrification, and environmental variables from an ecological (rather than biogeochemical) perspective may help to identify and predict biogeochemically important habitat patches (hot spots). However, in situ measurements of denitrification that are coupled with ecosystem variables are rare. In this study, we analysed a dataset encompassing 18 estuaries, broad environmental gradients, and two methods of measuring denitrification (denitrification enzyme activity (DEA) and in situ N2 flux quantification) to better understand natural estuarine nitrogen removal processes and to rationalise methods. Generally poor relationships between denitrification measures and environmental variables suggest strong context dependency, with different activation or limiting reactants affecting denitrification rates differentially in space and time. This research illustrates how biogeochemically important habitat patches may develop and demonstrates that single-method studies have the potential to miss hot spots or hot moments of nitrogen removal. A two-method approach that integrates both long-term (DEA) and short-term (in situ N2 flux) conditions is more likely to lead to the identification of biogeochemically important habitat patches. A better understanding of natural nitrogen removal processes in estuaries will clarify assimilative capacity questions and feed into eutrophication mitigation management efforts in these highly valued freshwater–coastal interface areas. [ABSTRACT FROM AUTHOR]

Intraspecific trait variability (ITV) can be considerably high and reveal plant local adaptation. The aim of this study is to investigate ITV of leaf traits (including petioles) in a rooted floating-leaved macrophyte (Nuphar lutea) at the local scale. We expected to see changes in resource-use strategies in relation to water and sediment properties. 96 leaves were sampled in a hyper-eutrophic shallow lake in central Italy, together with environmental parameters. Results highlight the influence of water depth and sediments in modulating environmental conditions and thus leaf traits. Leaf area and fresh and dry weight increased with water depth, a relation that catches the construction costs of petioles. The negative relation found between specific petiole area and conductivity suggests a stress imposed by high nutrient availability which triggers unfavorable conditions for N. lutea. We demonstrated the relevance of petiole traits for a rooted macrophyte. Petiole aerenchyma or photosynthetic extra surfaces fundamentally contribute to fit the environment, opening new questions for the functional investigation of macrophytes. Excluding petioles in the assessment of leaf traits reduces the possibility to understand the ecological/adaptive processes of nympheids. New data are urgently needed to increase the number of data and species to be analyzed. [ABSTRACT FROM AUTHOR]

Clonal integration benefits clonal plants by buffering environmental stress and increasing resource extraction efficiency. However, the number of connected ramet generations that benefit from clonal integration in a clonal system has received relatively little attention. A pot experiment was conducted to evaluate the extent of physiological integration within the clonal system of Vallisneria natans consisting of a mother ramet and three sequentially connected offspring ramets. Mother ramets were grown in full sunlight, and offspring ramets were heavily shaded with limited light availability. Stolons between mother ramets and offspring ramets were severed or connected, but connection among the three offspring ramets remained. The photosynthetic ability of unshaded mother ramets of V. natans was significantly enhanced, but their biomass accumulation was greatly reduced when connected to shaded offspring ramets. Clonal integration significantly increased biomass accumulation, C and N availabilities, extracellular enzyme activities and microbial biomass of the first ramet generation (adjacent ramet), but not later ramet generations. Our results indicate that support from the mother ramet of V. natans may be limited to the adjacent offspring ramet in a clonal system under severe light stress, implying an effect of ramet generation. Our results contribute to a better understanding of the hierarchy and segmentation of clonal plants. These findings suggest that the extent of clonal integration plays a vital role in ecological interactions of the ramet population. [ABSTRACT FROM AUTHOR]

Pond ecosystem not only provides essential agricultural irrigation and washing water, but also stores rainwater in rainy seasons. However, the pollution status of pond system around Poyang Lake was seldom studied. Here, we investigated the water and sediment chemical characteristics, phytoplankton and benthic macroinvertebrates, as well as habitat conditions of 23 rural ponds around Poyang Lake. Results showed that water quality of 91.3% rural ponds was inferior V (National Surface Water Environmental Quality Standard of China) with the main pollutants of total nitrogen (TN) and total phosphorus (TP). In rural ponds, fifty-nine species of phytoplankton and nineteen benthic macroinvertebrates were identified, Cyanophyta and Chlorophyta were the dominant phytoplankton groups, and oligochaetes and aquatic insects were the most dominant taxa among all benthic macroinvertebrates. And an integrated evaluation system based on chemical, biological and physical index was set up to assess the pollution status of rural ponds. According to the composite integrity index, 2 rural ponds (8.70%) were classified as Very poor, 9 rural ponds (39.13%) were classified as Poor, 9 rural ponds (39.13%) were classified as Fair, and 3 rural ponds (13.04%) were classified as Good. And the composite integrity index in 4 counties followed the sequence of Xingzi County (0.598, Fair) > Jinxian County (0.425, Fair) > Xinjian County (0.379, Poor) > Nanchang County (0.335, Poor). Therefore, measures should be taken for improving the water quality, habitat conditions and biotic community of rural ponds, especially for the severely polluted rural ponds in Xinjian and Nanchang County. [ABSTRACT FROM AUTHOR]

Diazinon is an organophosphorus pesticide widely used in agriculture and household pest control, and its use also poses several environmental and health hazards. In this study, we investigated the spatial and temporal distribution of diazinon in Baiyangdian, evaluated its potential ecological risk and toxicity to aquatic organisms based on RQ (Risk quotient) and TU (Toxic unit) analysis, and assessed the potential effects of diazinon accumulation on probiotics and pathogens based on statistical analysis of high-throughput sequencing data. The results showed that diazinon in Baiyangdian posed a low to moderate chronic risk to sediment-dwelling organisms and a low toxicity effect on aquatic invertebrates, which was mainly concentrated in October and human-intensive areas. Meanwhile, increases in sediment electrical conductivity (EC), amorphous iron oxides content and phenol oxidase activity favored diazinon accumulation in sediments, whereas the opposite was the case for sediment organic carbon, β-1,4-glucosidase, phosphatase, catalase and pH, suggesting that environmental indicators play a key role in the behavior and distribution of diazinon. In addition, diazinon in heavily contaminated areas seem to inhibit the rare probiotics (Bifidobacterium adolescentis and Serratia sp.), while promoted dominant pathogens (e.g., Burkholderia cenocepacia), which can lead to increased disease risk to humans and ecosystems, disruption of ecological balance and potential health problems. However, probiotic Streptomyces xiamenensis resist to diazinon would be a potential degrader for diazinon remove. In conclusion, this study unveiled the effects of diazinon pollution on wetland ecosystems, emphasizing ecological impacts and potential health concerns. In addition, the discovery of diazinon resistant probiotics provided new insights into wetland ecological restoration. [Display omitted] • Low to medium potential risk of diazinon (DIZ) in Baiyangdian sediments. • Absolute abundance of probiotic and pathogen was highest in DIZ contaminated areas. • DIZ may inhibit relative abundance of probiotics B.adolescentis and Serratia sp. • Probiotic S.xiamenensis resistant to DIZ maybe a potential degrader of DIZ. • DIZ may promote growth of dominant pathogens B.cenocepacia and others. [ABSTRACT FROM AUTHOR]

Coastal erosion and accretion may be defined to be natural processes for which predicting the coastal magnitude is essential for a better coastal monitoring. The purpose of this study is to investigate the shoreline sediment properties and prediction of coastal erosion in an eroded region in Batu Pahat. Pantai Punggur was chosen as one of the research locations because of the condition of the beaches, which were designated as eroded regions as it is experiencing erosion. Sampling points were separated into four zones to better understand sediment transport: Zones A, B, C, and D. The sediment parameters of the studied samples were determined and described as a result of this research. Moisture content, specific gravity, grain size distribution, pH value, shear strength, and organic content were the studied parameters. Further studies, such as settling velocity and erosion and accretion prediction, were calculated based on those properties. From the analysis, Zones A, B, and D were projected to erode, whereas Zone C was predicted to accrete. The results of this study are useful in terms of comprehending morphological traits, which will aid in the knowledge of sediment transport. Furthermore, these findings are significant for information in the management of coastal concerns. [ABSTRACT FROM AUTHOR]

[Display omitted] • The distribution of benthic macroinvertebrates is largely affected by temperature. • The sediment permeability varies significantly with the increasing biomass of benthic macroinvertebrates. • The mixed bioturbation mode of various benthic macroinvertebrates was better than the bioturbation mode of single-type benthic macroinvertebrates in improving sediment permeability. Water quality, aquatic habitat, and groundwater recharge, which have a critical impact on the river ecosystem health, are associated with the vertical hydraulic conductivity of streambed (K v). Macroinvertebrates bioturbation can generate heterogeneity in the benthic and hyporheic zones to influence K v by particle reworking and burrow construction, which are directly and indirectly related to the physicochemical conditions of sediments. However, understanding how these factors and processes influence K v and its role is deficient. Here the spatial distribution of benthic macroinvertebrates and its effects on K v in the Weihe River were investigated. Macroinvertebrate bioturbation had a significant effect on K v when the biomass was greater than 1 mg/m2, and yet when the biomass exceeded 102 mg/m2, bioturbation had a significant inhibitory effect on K v as the result of clogging due to the fine sediment particles and secrete mucus produced by benthic Macroinvertebrates. Macroinvertebrate distribution and biomass are often influenced by temperature which could also decrease the fluid viscosity, thus improving K v. Moreover, the mixed bioturbation mode with the predominated Tubificidae was better than the bioturbation mode of single-type benthic macroinvertebrates in improving sediment permeability. These findings have important implications for revealing the disturbance mechanism of benthic macroinvertebrates on K v and provide a reliable theoretical basis for the protection and planning of river ecosystems. [ABSTRACT FROM AUTHOR]

Vertical distribution of macrobenthos in sediments remains poorly studied; data from higher latitudes are especially scarce. At the same time, it is believed to contain important information about communities that should not be neglected. Hence, our main objectives are to study the peculiarities of macrobenthos vertical patterns in the Arctic and to find out features specific to this region. For this, 24 stations were sampled in 2019 aboard the R/V "Akademik Tryoshnikov" while drifting in the North Barents Sea and along a transect south-west of the Franz Joseph Land. Sediments were obtained using a box corer; afterwards, subsamples were taken by a tube corer and cut into vertical sub-cores. Three to four strata (depending on biotope) characterized by similar species composition and abundance were distinguished. No direct relation between the increase in species richness and the complication of vertical structure was found. Avoiding competition through dwelling in different layers at one station was observed in some groups of closely related species. Factors playing important roles in determining infaunal properties depended on the layer. The thin upper layer played a more important role in terms of species number and abundance as compared to lower latitudes. However, the most abundant and widespread polychaete species Spiochaetopterus typicus penetrated down to 30 cm. It formed vertical distribution patterns in deeper sediment layers at most stations, including facilitating penetration into deep layers for other species. The exception was stations dominated by large maldanid polychaetes. Such a vertical pattern, with a particularly large share of species richness and abundance concentrated in the several upper cm combined with the very deep penetration of a few species, is likely typical of the Eurasian Arctic shelf. • Three to four vertical layers (strata) differing in the infauna structure. • Different factors play significant role for invertebrates in each layer. • Close species avoid co-occurring in one sub-core, but may exchange relative position. • Increase in species diversity does not bring to complication of vertical structure. • Higher importance of the upper layer compared to lower latitudes. [ABSTRACT FROM AUTHOR]

Plant invasions and microplastics (MPs) have significantly altered the structure and function of aquatic habitats worldwide, resulting in severe damage to aquatic ecosystem health. However, the effects of MPs on plant invasion and the underlying mechanisms remain largely unknown. In this study, we conducted mesocosm experiments over a 90-day period to assess the effects of polystyrene microplastics on the invasion of exotic submerged macrophytes, sediment physicochemical properties, and sediment bacterial communities. Our results showed that PS-MPs significantly promoted the performance of functional traits and the invasive ability of exotic submerged macrophytes, while native plants remained unaffected. Moreover, PS-MPs addition significantly decreased sediment pH while increasing sediment carbon and nitrogen content. Additionally, MPs increased the diversity of sediment bacterial community but inhibited its structural stability, thereby impacting sediment bacterial multifunctionality to varying degrees. Importantly, we identified sediment properties, bacterial composition, and bacterial multifunctionality as key mediators that greatly enhance the invasion of exotic submerged macrophytes. These findings provide compelling evidence that the increase in MPs may exacerbate the invasion risk of exotic submerged macrophytes through multiple pathways. Overall, this study enhances our understanding of the ecological impacts of MPs on aquatic plant invasion and the health of aquatic ecosystems. [Display omitted] • PS-MPs enhanced exotic submerged macrophytes functional traits and promoted plant invasion. • PS-MPs significantly reduced soil pH, but increased soil carbon and nitrogen nutrient content. • PS-MPs significantly altered the bacterial diversity, composition and multifunctionality. • PS-MPs enhanced plant invasion by mediating sediment properties and microbial community. [ABSTRACT FROM AUTHOR]

Abstract Background Marine soft sediments are some of the most widespread habitats in the ocean, playing a vital role in global carbon cycling, but are amongst the least studied with regard to species composition and ecosystem functioning. This is particularly true of the Polar Regions, which are currently undergoing rapid climate change, the impacts of which are poorly understood. Compared to other latitudes, Polar sediment habitats also experience additional environmental drivers of strong seasonality and intense disturbance from iceberg scouring, which are major structural forces for hard substratum communities. This study compared sediment assemblages from two coves, near Rothera Point, Antarctic Peninsula, 67°S in order to understand the principal drivers of community structure, for the first time, evaluating composition across all size classes from mega- to micro-fauna. Results Morpho-taxonomy identified 77 macrofaunal species with densities of 464–16,084 individuals m−2. eDNA metabarcoding of microfauna, in summer only, identified a higher diversity, 189 metazoan amplicon sequence variants (ASVs) using the 18S ribosomal RNA and 249 metazoan ASVs using the mitochondrial COI gene. Both techniques recorded a greater taxonomic diversity in South Cove than Hangar Cove, with differences in communities between the coves, although the main taxonomic drivers varied between techniques. Morphotaxonomy identified the main differences between coves as the mollusc, Altenaeum charcoti, the cnidarian Edwardsia sp. and the polychaetes from the family cirratulidae. Metabarcoding identified greater numbers of species of nematodes, crustaceans and Platyhelminthes in South Cove, but more bivalve species in Hangar Cove. There were no detectable differences in community composition, measured through morphotaxonomy, between seasons, years or due to iceberg disturbance. Conclusions This study found that unlike hard substratum communities the diversity of Antarctic soft sediment communities is correlated with the same factors as other latitudes. Diversity was significantly correlated with grain size and organic content, not iceberg scour. The increase in glacial sediment input as glaciers melt, may therefore be more important than increased iceberg disturbance.

Sediment fingerprinting techniques are increasingly utilized across the globe to identify and quantify sources of sediment in catchments to assist adequate management and rehabilitation strategies. The technique generally includes classifying source groups, sampling sediment sources and sink zones, analysing tracers and applying statistical analyses to discriminate and quantify the contribution from sources. Although sediment fingerprinting has been used in southern African catchments, a contextual review of studies for the region does not exist. An overview is given of the basic methodological steps, including the tracers utilized in southern Africa, the history and main findings of the studies and recommendations for further research. There are many regions in southern Africa where this technique can still be implemented, especially erosion hotspots of Lesotho and Swaziland. Similar to regions elsewhere, the technique has not been standardized due to variability of erosion processes and causal factors in different environments. Several studies state that soil is the dominant erosion factor in South Africa, especially in catchments that consist of duplex and dispersive soils that are highly erodible. It is recommended that a tracer or set of tracers be found for these problem soils. Sediment fingerprinting has the potential to discriminate soils as potential sediment sources. [ABSTRACT FROM AUTHOR]

Sediment resuspension may play a major role in sediment-water exchange of nutrients, matter and energy in coastal areas where waves and currents dominate sediment transport. Biogeochemical sediment properties regulate sediment erodibility, but there is only limited knowledge of how temporal variability in environmental variables is reflected in the resuspension potential, especially for subtidal habitats. Further, the significance of resuspension on nutrient fluxes in coastal environments has remained unclear as contradicting results have been reported. Here we quantified the temporal variation in resuspension potential metrics (erosion threshold (τc; N m−2) and erosion constant (me; g N−1 s−1)) and associated nutrient fluxes from three sites in the Hanko archipelago (Finland) using a core-based erosion device (EROMES). The sites were sampled bi-monthly from April to December. We also quantified the temporal variation in biogeochemical sediment properties at each site. The τc exhibited the clearest temporal pattern in muddy sediment, where the coefficient of variation (= 67) was two to three times higher than the mixed (= 29) and sandy (= 16) sediments. Dry bulk density was the best predictor for sediment erodibility at all sites explaining 26–46% of the temporal variation in τc despite its limited variability at sandier sites. In addition, temporal variations in the macrofaunal community were important predictors of muddy sediment erodibility and therefore community dynamics need to be considered in sediment transport studies. All sites were potential nutrient sources, yet the overall role of sediment resuspension on nutrient release from the sediments was small. [ABSTRACT FROM AUTHOR]

Well-constrained marine sediment characteristics (sediment thickness and shear wave velocity) are important not only for the study of climate over geologic times scales but also for correcting and accounting for its presence in seismic data used to investigate deeper structures. We use data from the PI-LAB (Passive Imaging of the Lithosphere Asthenosphere Boundary) experiment, which consisted of 39 broadband ocean bottom seismometers deployed at the Equatorial Mid-Atlantic Ridge near the Chain fracture zone covering 0–80 Myr old seafloor. We compute admittance between the pressure to the vertical displacement at the seafloor at frequencies between 0.1 and 0.2 Hz for microseism-generated Rayleigh waves for 18 stations where data quality is good to determine the sediment thickness and shear wave velocity. We find a general trend of increasing sediment thickness with the seafloor ages, as expected with sediment thicknesses that range from 10–450 m and, shear wave velocities that range from 0.05–0.34 km/s. We find sediment thickness varies almost uniformly across both sides of the ridge, and it indicates that both sides experienced a similar sedimentation process. Our results are in good agreement with the global sediment model that is based on drilling cores and active source experiments, but thinner by up to 50 m at several stations on seafloor older than 25 My. Overlap of the 95% confidence regions between admittance and Ps estimates for thickness and shear velocity is found at 15 stations where we have both Ps and admittance estimates. It suggests that both methods yield accurate estimates for sediment thickness. In addition, our admittance result extends the lateral resolution of sediment characteristics to stations that were not previously resolved by Ps. [ABSTRACT FROM AUTHOR]

Abstract The emerging pollutants antibiotic resistance genes (ARGs) are prevalent in aquatic environments such as estuary. Coastal mangrove ecosystems always serve as natural wetlands for receiving sewage which always carry ARGs. Currently, the research considering ARG distribution in mangrove ecosystems gains more interest. In this work, we investigated the diversity of ARGs in an urban estuary containing mangrove and nonmangrove areas of the South China Sea. A total of 163 ARGs that classified into 22 resistance types and six resistance mechanisms were found. ARG abundance of the samples in the estuary is between 0.144 and 0.203. This is within the general range of Chinese estuaries. The difference analysis showed that abundances of total ARGs, six most abundant ARGs (mtrA, rpoB, rpoC, rpsL, ef‐Tu, and parY), the most abundant resistance types (elfamycin, multidrug, and peptide), and the most abundant resistance mechanism (target alteration) were significantly lower in mangrove sediment than that in nonmangrove sediment (p

Methylmercury (MeHg) presents high toxicity to humans and can be accumulated to organisms via the food chains. In aquatic environments, MeHg is mainly formed by microorganism using the bioavailable inorganic mercury in sediment. In this study, a total of 120 surface sediments from 20 sites in the Kaohsiung Harbor were collected quarterly in the period from July 2016 to October 2017 and analyzed for total mercury (THg), bioavailable inorganic mercury (BIHg), MeHg, and several geochemical parameters. The concentrations of THg, BIHg, and MeHg in sediment were 455–5108, 7.0–1021, and 0.84–24.1 μg/kg dw, respectively. Results indicated that the percentage of MeHg to THg (MeHg ratio) in most sediment (85%) is <1.2%. Correlation analysis showed that MeHg in sediment was mainly controlled by BIHg (r = 0.759, p < 0.01), while the concentration of BIHg in sediment was mainly related to TOC (r = 0. 480, p < 0.01) and THg (r = 0.435, p < 0.01). The relationship between total bioavailable inorganic mercury (containing BIHg and the bioavailable inorganic mercury used in the synthesis of MeHg) and MeHg concentration in the sediments that collected from the estuary, harbor channel, and the entrance was established by a Michaelis-Menten model to predict the maximum value of MeHg. The efficiency of Hg methylation in the sediments of Kaohsiung Harbor is significantly affected by the total bioavailable inorganic mercury and the related environmental factors. In addition, changes in environmental conditions caused by local seasonality should also be an important factor to consider when assessing the efficiency of Hg methylation. Unlabelled Image • MeHg in sediment was mainly controlled by the concentration of BIHg. • BIHg in sediment mainly related to the particle size, TOC, and THg. • Estuary sediment had high MeHg and THg together with high TOC and reducing status. [ABSTRACT FROM AUTHOR]

Abstract Many rivers are facing human-induced system regime shifts that have great environmental, ecological and social implications, necessitating an increasing need to quantify the human influence on sediment properties and their impacts on the source-to-sink system of marginal seas. The Huanghe and Changjiang Rivers have experienced a dramatic reduction in sediment flux in recent decades, typifying the human influence on sediment properties of global large rivers. Sediment samples from the two rivers were analyzed to obtain grain size, magnetic and geochemical data. The results show a large difference in sediment properties between pre- and post-dam periods. We applied a discrepancy factor to re-examine the magnetic and geochemical tracers that were previously used in the two rivers. The discrepancy factors of most magnetic and geochemical tracers in the mud-sized sediments of the two rivers increased by an average of about 109% after dam construction. This suggests that human-induced changes in sediment properties have greatly improved the discriminatory ability between the sediments from the two rivers. The results also raise the uncertainty of using previous tracers to distinguish between sediments from the two rivers after damming. Furthermore, significant changes in sediment properties that happened in a relatively short time may provide future geological time markers for sedimentary records with a temporal resolution of 100–101 years. For marine environments, an approach for identifying sediment sources based on multiple independent optimum tracers is also proposed, with composite magnetic (SIRM vs. HIRM) and geochemical (Na 2 O vs. Zn) tracers being considered. The results of this work can advance our knowledge of how human activities alter river systems, and identify a sustainable development model under system regime shifts for areas of high-intensity human activity. Graphical abstract Unlabelled Image Highlights • Large differences in sediment properties exist between pre- and post-dam periods. • An approach of using multiple independent optimum tracers is proposed. • Human activities increased the differences between the sediments from the two rivers. • Amplified endmember differences may provide a future geological time marker. [ABSTRACT FROM AUTHOR]

[Display omitted] • A multidisciplinary analysis, combining deep learning and eDNA methods was employed. • Considering spatial and shape distinctions in this burrow analysis. • Higher burrow distribution in parallel creek section was highlighted. • The abiotic-driven pattern of burrow holds significant seasonal differences. Intertidal creek ecosystems in saltmarsh wetlands provide crucial ecological services, with burrows facilitating material exchange between these environments. Investigating burrow distribution in tidal creeks is essential, yet the underlying mechanisms remain poorly understood. Our study conducted field observations during two seasons, dividing the typical creek section into microhabitats: flat (F), gentle edge (GE), gentle slope (GS), steep slope (SS), and steep edge (SE). Comprehensive analysis of sediment samples encompassed assessments of water content, organic matter, particle size, and salinity. Burrow parameters were extracted using a deep learning method applied to sample images. Benthic biodiversity and community compositions were characterized through eDNA analysis. Our findings revealed significant variations in burrow distribution, sediment properties, and community compositions, both between and within creek sections. Temporal heterogeneity emerged as a substantial influencer of burrow characteristics, while the propensity of benthic communities to respond to topography and sediment properties constituted a chief determinant of burrow distribution. Utilizing a structural equation model based on field data, we illuminated four response pathways governing burrow distribution. Abiotic factors, especially under temporal heterogeneity, had a paramount impact, highlighting the need to explore relative biotic and abiotic influences, considering seasonal regulation. These findings establish a foundational understanding of burrow distribution and its driving mechanisms in creek ecosystems. They offer valuable insights for future field observations and research directions in this field. [ABSTRACT FROM AUTHOR]

It is meaningful to investigate the impact of alien invasive plants on wetland sediment. Field experiments were conducted to study the impact of the alien invasive plant, Amaranthus retroflexus, on wetland sediment properties under two growth stages. The results showed that growth of A. retroflexus tended to increase moisture content, porosity, and could significantly decrease total nitrogen (TN) and nitrate (N-NO3ˉ) concentrations in sediment and ammonium (N-NH4+) concentration in interstitial water (p < 0.05). However, no obvious impact was observed on total phosphorus (TP) nor on N-NH4+ concentrations in sediment. There was a difference in impact of A. retroflexus on sediment properties under two growth stages. The plants with a longer growth stage significantly decreased loss on ignition in sediment and P-PO43ˉ concentration in interstitial water. There were also significant differences in N-NH4+ concentration in both sediment and interstitial water over the vertical profile of the plant. In the plant treatment with a longer growth stage, P-PO43ˉ concentration also showed significant differences over the vertical profile. Therefore, the growth of A. retroflexus can improve sediment physical and chemical properties, reducing N-NH4+ and P-PO43ˉ release from sediment to overlying water to some extent, thereby decreasing sediment nutrient loading.

Marine macrophytes help protect coastal habitats by modifying the energy of their environment, attenuating wave action, and stabilizing the sediment. The aim of this research was to examine the effect of the above ground parts of different seagrass and seaweed species on the deposition, retention, physical (dry bulk density and grain size), and chemical properties (organic carbon content and organic carbon density) of sediment. Six seagrass and seaweed communities with different above ground morphologies were studied between the dry (April 2015) and wet seasons (August 2015). The results suggested that the highest canopy complexity index was in the green alga, Halimeda macroloba Decaisne patches, which had the highest canopy score. High canopy complexity patches were likely to retain more sediment and store more organic carbon than lower canopy complexity patches and bare sand, respectively. The sediment retention and percent of organic carbon content were also affected by seasons. The wave action in the wet season affected the sediment through higher sediment deposition and movement, which caused increased sediment instability and led to changes in sediment properties. In addition, shoot density in the dry season was lower than that in the wet season, most likely due to damage from long exposure during low tide. Our results indicate that the canopy complexity of marine macrophytes and seasons influenced both sediment retention and properties of the sediment. This study examined the effect of canopy complexity of seaweed and seagrass species on deposition, retention, physical and chemical properties of sediment. We examined the canopy complexity index using leaf morphology, dimension of shoot and number of canopy level together with mean leaf length and plant coverage. The results suggested that greater canopy complexity was likely to retain more sediment and store more organic carbon. [ABSTRACT FROM AUTHOR]

Abstract Understanding the integrated effect of external factors (e.g., human activities) and internal factors (e.g., hydrodynamics, sediment properties) on metal(loid) distributions is necessary for relevant decision-makers to develop river basin management strategies. In attempts to understand the possible causes of the distribution of nine target metal(loid)s in riverbed sediments across Xijiang River basin in China, we grouped and portrayed the multiple metal(loid) distributions by calculating metal(loid)'s normalised-and-weighted average concentrations, and then canonical correlation analysis combined with a series of statistical operations, collectively called optimized CCA analysis, was applied to quantify the strength of relationship between multiple metal(loid) distribution and integrated effect of internal-external factors. Results showed that the target metal(loid)s can be divided into three groups according to their distribution patterns: Group A (including Zn, As, Cd, Sb and Pb), Group B (including Cr, Ni and Cu) and Group C (including Tl). Among them, metal(loid)s in Group A was significantly enriched in comparison with the reference values of Chinese sediments, and the wide-ranging accumulation of Cd and Sb in the whole study area needs paying great attention to. For those metals in natural states (e.g., metals in Group B), the affinity of sediment (e.g., Fe and Mn oxides) is responsible for their distributions. By contrast, when metal(loid)s (e.g., metal(loid)s in Group A and Group C) had obvious anthropogenic sources, the interferences of anthropogenic inputs (e.g., non-ferrous metal enterprises' waste-discharging activities) and the specific sedimentary characteristics (e.g. karst topography and low-energy hydrodynamic depositional conditions) in study area can weaken the correlation between the binding affinity of sediment and the contents of metal(loid)s. The optimized CCA analysis can be an alternative and advantageous statistical operation for determining the main types of causes of multiple metal(loid) distribution in the case of observations with relatively low case-per-variable ratios. Graphical abstract Unlabelled Image Highlights • Metal(loid) distributions in sediments are controlled by external-internal factors. • A procedure was developed based on optimized canonical correlation analysis. • This procedure was applied to study sediment metal(loid)s in Xijiang River basin. • Relationship between metal distributions and related factors could be quantified. • The contributions of related factors can reflect the extent of human interference. [ABSTRACT FROM AUTHOR]

Abstract Concentrations of arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), mercury (Hg), lead (Pb), and zinc (Zn), grain sizes, and concentrations of organic carbon (Corg) were measured in 323 river sediment samples from the Pearl River Delta (PRD). Results showed that the heavy metal concentrations in the sediments ranged from 1.6–93 mg/kg for As, 0.04–9.3 mg/kg for Cd, 2–315 mg/kg for Cr, 1.1–352 mg/kg for Cu, 0.01–0.67 mg/kg for Hg, 11–221 mg/kg for Pb, and 11–1234 mg/kg for Zn. The highest values of As, Cr, Cu, Hg, Pb, and Zn appeared in the Beijiang River, whereas Cd was high in the Xijiang River. The overall sediment quality in the area with respect to metal concentrations generally met the primary standard criteria of China (Marine Sediment Quality), except for Cd and Cu. The spatial distributions of the heavy metals were influenced by both grain sizes and Corg concentrations. The Igeo geo-accumulation index indicated that there was no significant Cr, Cu, Hg, or Zn pollution, slight to moderate pollution by As and Pb, and moderate Cd pollution in the study area. Spatial distributions of an eco-toxicological index based on probable effect levels indicated that there was a 21% probability that the combination of the seven metals was exerting a toxic stress in the PRD river sediments. Highlights • Heavy metal pollution was assessed in river sediments of the Pearl River Delta • Beijiang River had the highest values of As, Cr, Cu, Hg, Pb, and Zn • Slight to moderate pollution by As and Pb, and moderate Cd pollution appeared in the region. • A 21% probability of being toxic in the river sediments of PRD [ABSTRACT FROM AUTHOR]

For the first time, free-living ciliates were studied in sediments from a variety of habitats in the Kara Sea (the Arctic Ocean). Ciliates were found in a wide range of environmental conditions (from the intertidal zone up to depths of 554 m, from salinities ranging from 0 to 34 psu, and from coarse sands and gravel to muddy sediments), with total abundances varying from 1 to 127 ind/cm 3 . Altogether, 114 species were identified, most of which were widely distributed and were previously reported from other Arctic regions. An unsaturated species accumulation curve and the presence of many rare species indicated that the Kara Sea is potentially as rich in ciliates as other regions. Fine- and medium-grained sands exhibited the richest and most abundant ciliate fauna, with many interstitial forms occurring up to depths of 200 m; whereas both the coarse sands of the exposed intertidal beaches and the sublittoral muds were poorly inhabited by non-specific euryoecious species. The granulometric composition of sediments was suggested to be the main driver controlling the diversity and composition of ciliate communities, while the other factors, such as salinity, water productivity and depth, were of secondary importance. [ABSTRACT FROM AUTHOR]

The Harris mud crab Rhithropanopeus harrisii recently expanded into much of the Baltic Sea. This invasion is expected to have significant effects on the structure and functioning of benthic ecosystems due to the lack of native crabs. Habitat type potentially modulates the effects as crabs are expected to behave differently in different habitats. In this study we experimentally evaluated the effect of R. harrisii on the species composition and dominance structure of shallow water meiobenthos within common habitat types of the north-eastern Baltic Sea. Among the studied environmental variables R. harrisii had by far the strongest effects on meiobenthos. The effects of R. harrisii varied among different habitats with the crab mostly modifying taxonomic composition and species abundances of meiobenthic communities on unvegetated soft bottom sediments. Our experiment also showed that boulders provided shelter for R. harrisii and thereby reduced their burrowing activity and effects on the adjacent soft bottom meiobenthos. [ABSTRACT FROM AUTHOR]

Rare earth elements (REEs) disperse from indigenous rocks to the environment, thus making sediments one of the major sinks and sources of metal pollution. The emerging use of REEs and the subsequent opening of new mining areas may contribute to their release into surrounding ecosystems. For this reason, this study was performed in a natural area with geological material abundant in ferrocarbonatites and light REE. The aim of this work was to assess the natural REE availability and (eco)toxicity in freshwater sediments. Sediments showed high REE concentrations in samples with fine grain size fractions, and low in organic-rich sediments. The enrichment in LREE was mostly from rocks and the obtained enrichment factors (EF) confirmed that the sediments are not anthropogenically polluted. To assess REE availability and ecotoxicity, four toxicity tests were performed. REEs measured as the dissolved concentration in the test media were very low compared to the potentially available total REE in sediments and showed positive or negative correlations with fine or coarse grain sizes, respectively, and positive correlations with the content in Mg, Fe and Al. In tests performed in media supplemented with salts, the availability of REEs decreased considerably. Only some toxic effects could be linked to the REE contents in the ostracodtox and luminotox tests. However, measurement of toxicity could be influenced by the sediment properties and lead to a potential overestimation of ecotoxicity if only REE are regarded. Our study reveals that the physicochemical properties of sediments are a key factor controlling both REE availability and toxicity, whereas the determination of REE effects from toxicity tests using liquid media with salt addition will decrease REE availability and could mask toxic effects. Our findings provide new knowledge about REE behaviour in sediments and are a starting point for understanding potential REE pollution around prospective mining areas. [ABSTRACT FROM AUTHOR]

Marine sediments cover two-thirds of the earth, and porosity (or void ratio) is a major controlling parameter in virtually every model of seafloor properties, including strength, sound speed, hydrology, thermal conductivity, and electrical resistivity. Our new model of void ratio ( e ) is based on the proportional void ratio, [ e p = ( e − e r ) / ( e 0 − e r ) ], where e 0 is the depositional maximum at the sea floor, and e r is the minimum residual void ratio at depth. We assume the values of e 0 and e r are inherent characteristics of the sediment type. Our model further defines the compression index C c to be the square root of the proportional void ratio ( C c ( e ) = ( e p ) 1 / 2 ). This new formulation establishes a direct relation between void ratio and effective stress: e = ( e 0 − e r ) − 1 [ log 10 ⁡ ( σ 0 / σ ) + 2 ( e 0 − e r ) ] 2 / 4 + e r and exhibits several advantages over previous models that we demonstrate with compression test data from the Gulf of Mexico and Nankai Trough. [ABSTRACT FROM AUTHOR]

The distribution of diatoms in surface sediments in the Minjiang Estuary, southeast China, was investigated in 2009. Total 56 species and other species belonging to 25 genera were identified, among them 11 species were dominant over 5%. Dominant species included Actinocyclus ehrenbergii, Coscinodiscus curvatulus, C. divisus, C. jonesianus, C. radiatus, C. rothii, C. subtilis, Cyclotella stylorum, Epithemia hyndmanii, Hydrosera whampoensis, and Trachyneis aspera. Diatom abundance varied spatially, with the absolute abundance of diatoms ranging from 13 valves/g to 11×10 valves/g, and averaging 2.5×10 valves/g. A canonical correspondence analysis (CCA) was used to explain the relationships between diatom distribution and sediment properties in the Minjiang Estuary. CCA revealed that the major elements (FeO, NaO, CaO, MgO, TiO, SiO, AlO, and KO) were closely related to diatom abundance. Four diatom assemblages were distinguished, representing different sediment properties, which may assist late Quaternary palaeoceanographic reconstructions of the Minjiang Estuary. [ABSTRACT FROM AUTHOR]

Of the blue carbon sinks, mangroves have one of the highest organic matter (OM) storage capacities in their soil due to low mineralization processes resulting from waterlogging. However, mangroves are disappearing worldwide because of demographic increases. In addition to the loss of CO 2 fixation, mangrove clearing can strongly affect soil characteristics and C storage. The objectives of the present study were to quantify the evolution of soil quality, carbon stocks and carbon fluxes after mangrove clearing. Sediment cores to assess physico-chemical properties were collected and in situ CO 2 fluxes were measured at the soil-air interface in a mangrove of Northern Vietnam. We compared a Kandelia candel mangrove forest with a nearby zone that had been cleared two years before the study. Significant decrease of clay content and an increase in bulk density for the upper 35 cm in the cleared zone were observed. Soil organic carbon (OC) content in the upper 35 cm decreased by > 65% two years after clearing. The quantity and the quality of the carbon changed, with lower carbon to nitrogen ratios, indicating a more decomposed OM, a higher content of dissolved organic carbon, and a higher content of inorganic carbon (three times higher). This highlights the efficiency of mineralization processes following clearing. Due to the rapid decrease in the soil carbon content, CO 2 fluxes at sediment interface were > 50% lower in the cleared zone. Taking into account carbonate precipitation after OC mineralization, the mangrove soil lost ~ 10 MgOC ha − 1 yr − 1 mostly as CO 2 to the atmosphere and possibly as dissolved forms towards adjacent ecosystems. The impacts on the carbon cycle of mangrove clearing as shown by the switch from a C sink to a C source highlight the importance of maintaining these ecosystems, particularly in a context of climate change. [ABSTRACT FROM AUTHOR]

As part of research into the re-establishment of the native species Scirpus mariqueter in the salt marshes of the Yangtze Estuary, the roles of revegetation mode (planting density), site characteristics (sediment texture and hydrological regime) and community age (recently restored and mature marshes) in the storage of soil organic carbon (SOC) and nitrogen (SN) were examined. In recently restored marsh characterized by muddy sediments with moderate sediment accretion, vegetation growth and SOC and SN storage increased along with the increase in planting densities and the SOC storage was 1.14–1.52 times greater than that in non-vegetated plots after two years of revegetation. The SOC storage under a high planting density equated to approximately 75% of the carbon stock in the mature marsh. However, the increase in SOC storage was much less in those sites characterized by silty sediments than that in sites with muddy sediment, even when a high planting density was applied. This is attributed to a lower rate of sediment deposition and inhibition of below-ground root growth, which was found to be strongly correlated with carbon and nitrogen stocks in the soil. Additionally, the main rooting system of S. mariqueter and SOC and SN storage were concentrated in the top ∼20 cm in the recently restored marshes. These results demonstrate that successful vegetation restoration plays a key role in determining SOC and SN storage within a salt marsh. The restoration of native S. mariqueter for SOC and SN stocks is most effective when conducted in muddy sediments with good sedimentation rates and using a high planting density. In contrast, costs will be higher and recovery time longer in silty (or sandy) sediments, due to their poorer conditions for plant growth and significantly lower rates of carbon and nitrogen accumulation. [ABSTRACT FROM AUTHOR]

The electric conductivity and magnetic susceptibility of sediments are fundamental parameters in environmental geophysics. Both can be derived from marine electromagnetic profiling, a novel, fast and non-invasive seafloor mapping technique. Here we present statistical evidence that electric conductivity and magnetic susceptibility can help to determine physical grain-size characteristics (size, sorting and mud content) of marine surficial sediments. Electromagnetic data acquired with the bottom-towed electromagnetic profiler MARUM NERIDIS III were analysed and compared with grain size data from 33 samples across the NW Iberian continental shelf. A negative correlation between mean grain size and conductivity ( R =−0.79) as well as mean grain size and susceptibility ( R =−0.78) was found. Simple and multiple linear regression analyses were carried out to predict mean grain size, mud content and the standard deviation of the grain-size distribution from conductivity and susceptibility. The comparison of both methods showed that multiple linear regression models predict the grain-size distribution characteristics better than the simple models. This exemplary study demonstrates that electromagnetic benthic profiling is capable to estimate mean grain size, sorting and mud content of marine surficial sediments at a very high significance level. Transfer functions can be calibrated using grains-size data from a few reference samples and extrapolated along shelf-wide survey lines. This study suggests that electromagnetic benthic profiling should play a larger role for coastal zone management, seafloor contamination and sediment provenance studies in worldwide continental shelf systems. [ABSTRACT FROM AUTHOR]

Ecosystem engineers contribute to ecosystem functioning by regulating key environmental attributes, such as habitat availability and sediment biogeochemistry. While autogenic engineers can increase habitat complexity passively and provide physical protection to other species, allogenic engineers can regulate sediment oxygenation and biogeochemistry through bioturbation and/or bioirrigation. Their effects rely on the physical attributes of the engineer and/or its biogenic constructs, such as abundance and/or size. The present study focused on tube aggregations of a sessile, tube-building polychaete that engineers marine sediments, Lanice conchilega . Its tube aggregations modulate water flow by dissipating energy, influencing sedimentary processes and increasing particle retention. These effects can be influenced by temporal fluctuations in population demographic processes. Presently, we investigated the relationship between population processes and ecosystem engineering through an in-situ survey (1.5 years) of L. conchilega aggregations at the sandy beach of Boulogne-sur-Mer (France). We (1) evaluated temporal patterns in population structure, and (2) investigated how these are related to the ecosystem engineering of L. conchilega on marine sediments. During our survey, we assessed tube density, demographic structure, and sediment properties (surficial chl- a , EPS, TOM, median and mode grain size, sorting, and mud and water content) on a monthly basis for 12 intertidal aggregations. We found that the population was mainly composed by short-lived (6–10 months), small-medium individuals. Mass mortality severely reduced population density during winter. However the population persisted, likely due to recruits from other populations, which are associated to short- and long-term population dynamics. Two periods of recruitment were identified: spring/summer and autumn. Population density was highest during the spring recruitment and significantly affected several environmental properties ( i.e. EPS, TOM, mode grain size, mud and water content), suggesting that demographic processes may be responsible for periods of pronounced ecosystem engineering with densities of approx. 30 000 ind·m −2 . [ABSTRACT FROM AUTHOR]

Metal enrichment in lake sediments originating from multiple sources can threaten both the aquatic ecosystem and human health. Therefore, assessment of the eco-environmental risks and potential sources of metals in the sediments is essential for effective lake management. Here, we analyzed the sediment metal contents of Kaptai Lake, the largest lake in Bangladesh for the first time with this study. The results indicated that only Cr and Ni contents among the metals studied exceeded the probable effect concentrations (PEC) at 25.42 % and 55.93 % of the sampling stations, respectively. All metals at most sampling stations showed low contamination and low ecological risk based on the individual indices (geoaccumulation index, contamination factor, ecological risk factor, enrichment factor and modified hazard quotient). There was no significant risk from the combined metals in the sediments of the lake according to the synergistic indices (toxic risk index, Nemerow risk index, ecological risk index, Nemerow pollution index and pollution load index). Organic matter and silt were significant sediment parameters that favored the accumulation of Cr, Fe, Cu, Pb and Mn. In the absolute principle component scores-multiple linear regression model (APCS-MLR), five potential sources of metals were identified in the sediments: Zn, Mn, Co and Cd mainly from natural sources and to a lesser extent from agricultural and aquacultural activities, Ni, Cr and Fe from parent materials, Pb and Cu mainly from natural sources and to a lesser extent from vehicle emissions, Hg and U from lithogenic sources, and As from natural sources. This study will improve our knowledge of the sedimentary metal contents of Kaptai Lake and provide helpful information for developing effective lake management and pollution control strategies. [Display omitted] • Sediment metal contents of Kaptai Lake were determined for the first time. • Eco-environment risk indices and SQGs were used to assess metal pollution. • Effects of sediment properties on accumulation of metals were investigated. • APCS-MLR model was conducted for source apportionment of metals. [ABSTRACT FROM AUTHOR]

A quantidade e a distribuição de tamanho dos sedimentos transportados pela enxurrada são influenciadas pelo manejo, cobertura e cultivo do solo e pela chuva, entre outros fatores, constituindo-se em aspecto importante no planejamento conservacionista do solo. O objetivo deste trabalho foi quantificar os sedimentos transportados pela enxurrada e relacioná-los com a velocidade de enxurrada, durante o cultivo da soja, em um experimento de chuva simulada sobre um Nitossolo Háplico alumínico típico, nos sistemas de manejo do solo conduzido desde 1998: semeadura direta em solo nunca preparado e com resíduos queimados (SQ); e uma aração e duas gradagens (AG). Nesses tratamentos, cultivaram-se aveia, soja, ervilhaca, milho, aveia, feijão, nabo forrageiro, soja, ervilhaca, milho e soja, nesta sequência, durante cinco anos e meio. Estudou-se um tratamento adicional, em que o solo foi mantido sem cultivo, porém preparado com uma aração e duas gradagens na mesma época de semeadura das culturas nos demais tratamentos (SC). No último cultivo da soja, cinco testes de chuva simulada foram aplicados sobre os tratamentos, com intensidade variando de 63 a 67 mm h-1 e duração de uma hora, 24 h após ter sido aplicada uma chuva (molhamento) com intensidade de 65 mm h-1 e duração suficiente para iniciar a enxurrada. Os sedimentos foram quantificados em amostras de enxurrada coletadas 10 min antes do término de cada chuva simulada. O tamanho de sedimentos foi influenciado pelo sistema de manejo do solo e pela quantidade de chuva: na condição sem cultivo do solo, houve maior quantidade de sedimentos de maior diâmetro do que na condição em que o solo foi cultivado; na condição de solo cultivado, a quantidade de sedimentos de menor diâmetro foi maior do que no solo sem cultivo; e houve tendência de aumentar a quantidade de sedimentos na enxurrada com o aumento do número de chuva simulada, nas diversas condições de manejo do solo e de tamanhos de sedimento. O modelo exponencial ajustou-se aos dados de quantidade e tamanho dos sedimentos e aos de velocidade da enxurrada e cobertura do solo; a quantidade de sedimentos diminuiu com a redução de tamanho destes, e a velocidade da enxurrada diminuiu com o aumento da cobertura do solo. O modelo potencial ajustou-se aos dados de D50 e velocidade da enxurrada, tendo o D50 aumentado com o aumento da velocidade.Quantity and size distribution of sediments transported by runoff are influenced by soil management, cover and crop systems, and by rainfall, among other factors, representing an important aspect in soil conservation planning. The objective of this study was to quantify runoff sediments and relate them with runoff velocity, during soybean growth, in a simulated rainfall experiment initiated in 1998 on a typical Hapludox, under the following soil management systems: conventional tillage with one plowing plus two diskings (CT) and no-tillage on a never tilled soil with burned residues (NT). In these treatments, the rotation crop systems consisted of oat, soybean, vetch, corn, oats, bean, fodder radish, soybean, vetch, corn, and soybean. An additional treatment with bare soil with one plowing plus two diskings (BS) was also studied. Five simulated rainfall tests were applied to the treatments in the last soybean crop cycle, with an intensity of 63-67 mm h-1 for one hour, 24 h after a pre-wetting rainfall, with an intensity of 65 mm h-1 and long enough to initiate runoff. The sediments were quantified in runoff samples collected 10 minutes before the end of each simulated rainfall test, and were related with the runoff velocity. The sediment size in the runoff was influenced by soil management systems and the rainfall quantity. In the treatment without soil cover (BS), the quantity of coarse sediments was higher than in the treatments with cultivated soil, whereas in CT and NT treatments the quantity of fine-sized sediments was higher than in the BS treatment. More sediments tended to be transported in the runoff with the application of more rainfall events. The sediment quantity transported by runoff was related with the sediment size, fitting to a positive exponential model, while runoff velocity decreased exponentially with increased soil cover. The D50 index was related with other variables, fitting to the potential model and increasing with runoff velocity.

Grain size and concentrations of heavy metals (arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), mercury (Hg), lead (Pb), and zinc (Zn)) of 148 surface sediments and activities of Pb and heavy metal concetrantions of one sediment core from the Pearl River Estuary were analyzed. The surface sediments were dominated by silt and sandy silt. Sediment type controlled the spatial distribution patterns of the heavy metals. The heavy metal concentrations in the sediments ranged from 3.34 to 37.11 mg/kg for As, 0.06 to 2.06 mg/kg for Cd, 12 to 130 mg/kg for Cr, 5.8 to 170.6 mg/kg for Cu, 0.01 to 0.25 mg/kg for Hg, 23 to 78 mg/kg for Pb, and 32 to 259 mg/kg for Zn. Both contents of clay and organic carbons were significantly positively correlated with heavy metals. The baseline values of elements in the study area were 12.97 mg/kg for As, 0.14 mg/kg for Cd, 68 mg/kg for Cr, 28.9 mg/kg for Cu, 0.08 mg/kg for Hg, 33 mg/kg for Pb, and 92 mg/kg for Zn. The metal enrichment factor (EF) and geoaccumulation index (Igeo) were calculated to assess anthropogenic contamination. Results showed slight to moderate Cd contamination in the region. Principle component analysis indicated that Cd could be attributed to anthropogenic sources; As and Hg were predominantly affected by human activities; and Pb, Cr, Cu, and Zn were associated with both natural and anthropogenic sources. [ABSTRACT FROM AUTHOR]

It is meaningful to investigate the impact of alien invasive plants on wetland sediment. Field experiments were conducted to study the impact of the alien invasive plant,Amaranthus retroflexus,on wetland sediment properties under two growth stages. The results showed that growth ofA. retroflexustended to increase moisture content, porosity, and could significantly decrease total nitrogen (TN) and nitrate (N-NO3ˉ) concentrations in sediment and ammonium (N-NH4+) concentration in interstitial water (p< 0.05). However, no obvious impact was observed on total phosphorus (TP) nor on N-NH4+concentrations in sediment. There was a difference in impact ofA. retroflexuson sediment properties under two growth stages. The plants with a longer growth stage significantly decreased loss on ignition in sediment and P-PO43ˉ concentration in interstitial water. There were also significant differences in N-NH4+concentration in both sediment and interstitial water over the vertical profile of the plant. In the plant treatment with a longer growth stage, P-PO43ˉ concentration also showed significant differences over the vertical profile. Therefore, the growth ofA. retroflexuscan improve sediment physical and chemical properties, reducing N-NH4+and P-PO43ˉ release from sediment to overlying water to some extent, thereby decreasing sediment nutrient loading. [ABSTRACT FROM PUBLISHER]

Hurricane Sandy was an extraordinarily large storm that affected most of the eastern coast of the USA in October 2012. To assess this storm's impact, the benthic invertebrate community structure and sediment properties were compared in samples collected 3.5 months prior to (July 2012) and 8 months after (July 2013) the hurricane at 97 locations in Barnegat Bay, New Jersey, USA. Barnegat Bay is a shallow back-barrier estuary just north of where Sandy made landfall. For all locations taken together, sediment total nitrogen concentration was lower afterwards, while total organic carbon and total phosphorus concentrations were similar. Sediment median particle size was the same before and after, but the sediment was better sorted after the storm. There were no differences in total abundance of invertebrates, species richness, species diversity, or the abundance of polychaetes, bivalves, or gastropods. Malacostracan crustaceans were more abundant after Sandy (average 82 (0.04 m)) than they were before (average 64), due almost entirely to increased abundance of ampeliscid amphipods, which showed a shift toward smaller sizes in 2013. Annelids in the order Clitellata were on average less abundant after the hurricane (17) than before (53). The apparent minimal effect of Sandy on the benthic community in Barnegat Bay was probably because the passage of the hurricane had no detectable effects on salinity or dissolved oxygen concentrations throughout the bay. [ABSTRACT FROM AUTHOR]

Fine-grained sediment is perhaps the most widespread and pervasive contaminant in aquatic systems reflecting its role in influencing the quality of the water (e.g., turbidity, vector of chemicals and other pollutants) and its detrimental effect on infrastructure (e.g., dams, turbines) and aquatic habitats (e.g., salmonid spawning grounds) through sedimentation. Determining the sources of fine-grained sediment thus represents an important requirement for watershed and coastal management, as well as for understanding the evolution of landscapes and ocean basins. Sediment source fingerprinting utilizes the diagnostic physical, chemical and biological properties (i.e., tracers) of source materials to enable samples of collected sediment to be apportioned to these sources. This review examines the development of the technique within the earth and ocean sciences, focusing mainly on agricultural landscapes. However, the development of new tracers, such as compound-specific stable isotopes, has allowed the technique to be applied in a growing number of environmental settings including forested (including wildfire-impacted forests), urban and estuarine/coastal settings. This review also describes other applications of the fingerprinting approach such as geoarchaeological (e.g., archaeological site formation), forensic (e.g., identifying the sources of soil/sediment particles in criminal investigations) and human health (e.g., identifying the sources of airborne particulate matter, PM 2.5 ) applications. Identifying commonalities in methods and approaches between environments and disciplines should foster collaboration and the exchange of ideas. Furthermore, refinement of the sediment source fingerprinting technique requires that several methodological issues be addressed. These methodological issues range from the initial sampling design to the interpretation of the final apportionment results. This review also identifies and assesses these methodological concerns. [ABSTRACT FROM AUTHOR]