Sample Coverage Research Articles

Age estimation of archeological populations using secondary dentin analysis

The innermost dental tissue, termed secondary dentin (SD), has been established as a valuable parameter for aging, as its thickness is highly correlated with age and can be viewed in a non-invasive manner using micro-computerized tomography (μCT). Dental remnants show a high preservation rate in an archeological context and may be used as age indicators, thus possibly supplementing traditional skeletal-based demographics. As the SD age assessment method was based on unworn teeth, in the current study, we adjusted the approach to allow age estimation of highly worn teeth and later to explore prehistoric samples. In order to do so, 90 lower premolars from known age and gender individuals with various degrees of occlusal attrition were included. The teeth originated from the Hamann-Todd Osteologic Collection (Cleveland, OH, USA) and from the Tel Aviv University collection (Israel). Combining SD measurements and occlusal Attrition slightly improved the standard error of age estimate from ±7.7 years based on SD and ±9.5 years based on Attrition to a range of ±6.5 years.The SD-age method was used to evaluate the age of individuals from three Natufian and Neolithic sites using dental remains (Hayonim Cave, Ein Mallaha 14,900–11,750 cal BP, and Kfar Hahoresh ∼12,175–8250 cal BP). Population coverage increased substantially with the addition of forty-eight premolars to previous skeletal age assessments to create new life tables. The addition of dental age assessments, representing unaccounted individuals, shifted the age distributions and increased the expected lifespan between 4.7 and 1.8 years. Using the SD-age analysis, isolated, fragmented teeth can be included in the paleodemographic study, thus broadening the coverage of samples and providing better insight into archaic populations' structure.

Macrofauna-sized foraminifera in epibenthic sledge samples from five areas in the eastern Clarion-Clipperton Zone (equatorial Pacific)

Benthic foraminifera cannot be sampled adequately using a single device. Smaller taxa are best collected using multicorers, the larger with box corers, but towed devices (dredges, trawls and epibenthic sledges) also retain many larger species. Here, we describe macrofaunal (>300 µm) foraminiferal assemblages obtained using an epibenthic sledge (EBS) in the Clarion-Clipperton Zone (eastern equatorial Pacific), a region hosting seafloor deposits of polymetallic nodules. Twelve EBS samples were collected in four areas licenced for exploration by the International Seabed Authority (ISA) to German, IOM, Belgium and French contractors, and to APEI-3, one of the protected Areas of Special Scientific Interest designated by the ISA. We recognised 280 morphospecies among 1954 specimens, with between 74 (IOM) and 121 (Belgium) in particular areas. Most (92.7%) were single-chambered monothalamids, of which 75 species (26.8%) belonged to the Komokioidea (‘komoki’), 47 (16.8%) to branched and unbranched tubes, 33 (11.8%) to chain-like and 32 (11.4%) to various ‘komoki-like’ forms. Fragments of megafaunal xenophyophores represented 21 species (7.50%), including Spiculammina delicata, previously reported only from the Russian area. Rarefaction curves and sample coverage completeness curves suggest that only a fraction of the macrofaunal foraminiferal diversity had been sampled. The occurrence of 71.8% of species in 1-2 of the 12 samples and 84.9% in 1-3 of the samples was a likely result of substantial undersampling. Dissimilarity in species composition between areas was very high: 64.2% (German vs IOM area) to 86.9% (German area vs APEI-3). Similarity within a single area was quite low: 29.1% (German) to 45.1% (IOM). In multidimensional scaling (MDS) plots, the APEI-3 area was clearly distinct in terms of faunal composition from all other areas, the French area somewhat separated from the German, IOM and Belgium areas, with the German and IOM samples being the most similar. These patterns may reflect the geographical separation of the French and APEI-3 areas and their location in deeper, more oligotrophic waters. Our study demonstrates that EBS samples from the eastern CCZ are a rich source of novel foraminiferal taxa, particularly light, easily resuspended komoki, providing a valuable perspective on foraminiferal biodiversity.

The Urgency of Agrarian Reform Policy: A Study of the Impact of Land Access on Farmer Household Welfare

Abstract: Inequality of land ownership is caused by unequal access to land. This study examined the impact of land access on total farmer's household expenditure. The Agrarian reform policy assumed open and expand access to land for groups of landless or near landless farmer households. Through state-led and market-led approaches, this research provided a categorization of access to land in two ways, which are access opening and access expansion variables with each sample coverage. Using the two periods difference-in-difference (DID) method, this study analyzed the impact of opening and expanding access to the total expenditure of farmer households using IFLS 2007 and 2014 data. The results showed that there is a significant difference in the total expenditures of farmer households due to the opening and expansion of access referring to the land distribution scheme (state-led approach), and there is no significant difference through the market-led approach. Therefore, agrarian reform policies need to be carried out by emphasizing the role of the state in implementing land redistribution to landless and small farmers. Keywords: Agrarian reform, state-led approach, market-led approach, impact of land access, total farmer household expenditure

Linking host plants to damage types in the fossil record of insect herbivory

AbstractStudies of insect herbivory on fossilized leaves tend to focus on a few, relatively simple metrics that are agnostic to the distribution of insect damage types among host plants. More complex metrics that link particular damage types to particular host plants have the potential to address additional ecological questions, but such metrics can be biased by sampling incompleteness due to the difficulty of distinguishing the true absence of a particular interaction from the failure to detect it—a challenge that has been raised in the ecological literature. We evaluate a range of methods for characterizing the relationships between damage types and host plants by performing resampling and subsampling exercises on a variety of datasets. We found that the components of beta diversity provide a more valid, reliable, and interpretable method for comparing component communities than do bipartite network metrics and that the rarefaction of interactions represent a valid, reliable, and interpretable method for comparing compound communities. Both beta diversity and rarefaction of interactions avoid the potential pitfalls of multiple comparisons. Finally, we found that the host specificity of individual damage types is challenging to assess. Whereas bipartite network metrics are sufficiently biased by sampling incompleteness to be inappropriate for fossil herbivory data, alternatives exist that are perfectly suitable for fossil datasets with sufficient sample coverage.

Spatial and Temporal Sampling Properties of a Large GNSS-R Satellite Constellation

Using large constellations of smallsats, mission designers can improve sampling density and coverage. We develop performance metrics that characterize key sampling properties for applications in numerical weather prediction and optimize orbit design parameters of the constellation with respect to those metrics. Orbits are defined by a set of Keplerian elements, and the relationship between those elements and the spatial and temporal coverage metrics are examined in order to maximize global and zonal (latitude-dependent) coverage. Additional optimization is performed by dividing a constellation into multiple orbit planes. An iterative method can be applied to this design process to compare the performance of current and previous designs. The main objective of this work is the design of optimized configurations of satellites in low Earth orbiting constellations to maximize the spatial and temporal sampling and coverage provided by its sensors. The key innovations developed are a new cost function which measures the temporal sampling properties of a satellite constellation, and the use of it together with existing cost functions for spatial sampling to design satellite constellations that optimize performance with respect to both performance metrics.

Rare osteohistological evidence of skeletal maturity in the early diverging traversodontid Scalenodon angustifrons, with comments on histological sampling coverage in Cynodontia

ABSTRACT To date, 25 species of non-mammalian cynodonts have been histologically sampled, but few record a definitive and well-developed external fundamental system (EFS) indicative of skeletal maturity. Here, I report an EFS in the femoral histology of Scalenodon angustifrons and discuss the factors that could explain why skeletally mature tissue is rarely documented in cynodont osteohistology. My sample includes two equivalently sized individuals that document marked histological variation, as only one shows evidence of slowing growth rate and an EFS. Variation in the bone histology between femora of the same size suggests that attainment of skeletal maturity does not follow a discrete developmental pattern for S. angustifrons, a pattern that is also seen in the bone histology of other traversodontids and some non-gomphodontian cynodonts. From these results, a flexible growth strategy is inferred for S. angustifrons. To contextualize the validity of this pattern among other cynodont species, I summarize the sampling coverage of cynodonts that have been thin-sectioned and report limited coverage across size classes/ inferred development stages. This is often a result of sampling one isolated element that is not standardized to one skeletal element, which contributes to a poorly constrained comparative sample (in terms of size coverage, spatial and temporal resolution, and taxonomic coverage). Despite this, many cynodont species show shifts towards slow growth, but very few instances of unequivocal evidence of skeletal maturity. This result underscores the need for standardized iterative histological sampling to assess longevity, life history, and developmental patterns of non-mammalian cynodonts more accurately.

ЭКСПЕРИМЕНТАЛЬНОЕ ИССЛЕДОВАНИЕ ХАРАКТЕРА И ПОСЛЕДСТВИЙ ВЗАИМОДЕЙСТВИЯ СОЛЯНЫХ ПОРОД С ГИДРОЗАКЛАДОЧНЫМИ РАССОЛАМИ ПРИ ПОДЗЕМНОЙ РАЗРАБОТКЕ МЕСТОРОЖДЕНИЙ КАЛИЙНЫХ СОЛЕЙ

Introduction. The research methodology included selection and comparative tests of strength characteristics of the initial core of sylvinite and carnallite in air-dry condition and, respectively, core samples after their contact with model hydrofilling brines. During the tests on the press under uniaxial compression load it was noted that most of the samples are very heterogeneous, characterized by layering and the presence of various inclusions, varying even within the same well. The specimens differ in the character of deformation at compression failure. It seems that the character of contact of targets with hydrofilling brines is different than in the soil of mine workings, through which drainage brines will flow, where the processes of frizzling have been revealed, indicating the influence on the development of fracturing of sylvinite protective pack in the soil and on the side walls of targets. The obvious risk of drainage brines penetrating into the cracks and the nature of their movement through the soil of the workings require full coverage of the sylvinite samples with brine from all sides. Research results. It is established that as a result of contact of samples of sylvinite rocks with saturated brine there is a decrease in strength characteristics by 1.2-1.7 times. It is determined that as a result of contact with model brines the deformation diagram of samples under load has changed. Monolithic sample of carnallite after incubation for 58 days in concentrated salt brine there was a complete loss of strength and the sample crumbled in a measuring cup. On the basis of the performed researches it is concluded that at hydrofilling of the excavated space with saturated hydrofilling brines there will be a decrease in strength of the contour part of the massif of chambers, pillars and in the soil of drainage excavations. Conclusion. In the laboratory experiment the fact of decrease in uniaxial compression strength of salt rock samples was established: already on the 36th day of ageing in brine the strength of samples decreased by 24-25%, deformation modulus - by 22-28%. On 56 days the compressive strength of the specimen decreased on average by 2 times in comparison with the initial ones in air-dry condition. It is also proved that at carrying out of hydrofilling works with application of saturated brines there is a decrease in strength of rocks of the contour part of the massif of chambers and drainage excavations. For the chamber being laid these processes are not so critical, but the influence of hydrofill brines on the strength and deformation modulus reduction for the underlying rocks at the base of drainage excavations, through which the excess brine will flow. Reduced strength and deformation characteristics may result in an increased risk of accidents at the underground mine. Resume. The influence of brines of the potash mineral processing plant on selected sylvinite cores has been assessed. Regularities of change of strength characteristics of sylvinite samples on uniaxial compression in «dry» state and after prolonged soaking in saturated brine of the processing plant were established.

Characterizing Microearthquakes Induced by Hydraulic Fracturing With Hybrid Borehole DAS and Three-Component Geophone Data

Fluids injected during hydraulic fracturing (fracking) in unconventional shale oil and gas reservoirs, geothermal system enhancement, wastewater disposal, and carbon capture and storage can induce microearthquakes. The spatiotemporal distribution of induced earthquakes is often used to trace the growth of fractures in target layers and guides production. We analyze microseismicity behavior induced by fracking in the Montney Formation, one of the largest unconventional oil and gas reservoirs in North America. An optical fiber deployed in a horizontal well provides extensive spatial sampling and data coverage for microseismic imaging. We design median and F-k filters to predict instrumental and random noise and further suppress them by adaptive noise subtraction. An elliptical vertical transverse isotropic (VTI) velocity model is derived from the Backus-averaged well-log sonic data and is modified to match the microseismic wavefronts by a grid search. We image 41 previously cataloged microearthquakes recorded by DAS using Geometric-mean Reverse Time Migration. We find that the fiber geometry’s lack of 2D/3D variations increases the non-uniqueness of the image point location, and the P-wave particle motions derived from 3C geophones data can effectively eliminate the location ambiguity. The spatiotemporal distribution of our updated locations agrees with the fracking schedule. Predicted P- and S-wave traveltimes from the updated locations also match with the observed waveforms. Analyzing data sensitivity to source locations confirms the potential limitations imposed on source imaging by the geometry of borehole observations and shows that relocation accuracy is directionally dependent. We also investigate the feasibility of estimating source focal mechanisms using realistic DAS and geophone observations. Our study provides guidance for characterizing microearthquake sources and optimizing observation geometry for unconventional reservoirs.

False negative of defects estimation in crowdsourced testing

AbstractEstimating the population of defects is a key reference for completion evaluation in crowdsourced testing. Current studies commonly use the biological capture–recapture model (CRC model) to estimate the population of defects in crowdsourced tests with good results. However, the lack of consideration of false negatives for defects in existing studies leads to imprecise estimation of completion in crowdsourced testing, which in turn influences decision support during crowdsourced testing. This study analyzes the basic assumptions of the CRC model in biology and maps them to the field of crowdsourced testing, improves the Lincoln–Peterson estimator and sample coverage estimator utilizing false negative assumptions, and compares them with original estimators in 29 real crowdsourced testing projects. The experimental results show that our improved estimators can effectively reduce the estimation relative error of the population of defects caused by false negatives.

Feasibility of diffuser-incorporated near-infrared trans-reflectance measurement for quantitative detection of microplastics captured in perfluorocarbon

A diffuser-incorporated near-infrared (NIR) trans-reflectance measurement is demonstrated for quantitative detection of polyethylene (PE) particles captured in perfluorohexane (PFH, C6F14). PFH effectively captures PE particles through its hydrophobicity and absorbs little NIR radiation, recommending it for use in background-free NIR detection of captured PE particles. A reflective metal disk was used to push the captured PE particles in PFH toward the bottom of the vial that contained the sample, and the trans-reflectance measurement was performed by illuminating NIR radiation from the bottom of the vial at 45o. Reproducibility is limited by the variation in the positions of small PE-particle aggregates at the water/PFH interface and the difficulty in ensuring full NIR sampling (coverage) of large aggregates. An effective way to secure improved reproducibility under these circumstances is illumination of broader and more uniform NIR radiation for measurement. For this purpose, a polytetrafluoroethylene (PTFE) disk was uniquely incorporated as a diffuser for the trans-reflectance measurement. Compared to the measurement with no diffuser, the diffuser-incorporated scheme produced more distinct PE peaks of low-quantity samples (0.1 and 0.2 mg) and enhanced the reproducibility in measurements of all the samples (0.1–4.0 mg of PE). As a result, the correlation between peak intensity and particle quantity was excellent (R2: 0.997), and a limit of detection of 0.07 mg was achieved.

Elevated pan traps optimise the sampling of bees, including when the availability of floral resources is high

Abstract To sample bee communities, a combination of methods is necessary, the most common being hand netting (HN) and pan traps (PT). However, there has been little exploration into how vertical distribution of PT can improve their sampling efficiency, also taking the temporal variation of floral resources into account. Here, we analysed the properties of bee communities sampled with PT at different heights (1.6 and 4.0 m) compared with PTs close to the ground, HN and large blue bucket trap (BB). In addition, we tested the effect of variation in the availability of floral resources on the performance of each method. Bees were collected in fragments of the Brazilian Caatinga. We captured 60 bee species with PTs, HN and BB, with significant increases in the sample coverage with elevated bowls (BB = 56.7%, HN = 60.0%, PT0.3 m = 23.3%, PT1.6 m = 36.7%, PT4.0 m = 50.0%). Elevating the bowls increased the sampling of bees with larger body size. Considering the three heights, PTs registered similar richness compared to HN and BB, but differed in the composition of species and ecological traits. When floral resource availability was greater, the abundance and richness of bees caught in PTs decreased, however, the elevated PT increased their ecological uniqueness (degree of uniqueness of the samples in terms of community composition). Thus, elevating PTs enables the capture of bees that forage at a specific height when floral resources increase. Our results highlight the importance of the vertical distribution of PT for sampling bees, since it improves their performance and its complementarity with other methods.

Bird migrant assemblages in urban and rural areas of central Argentina: a regional-scale comparison


 
 
 Migrant birds are negatively impacted by urbanization. However, most of the studies about urbanization effects on migrant birds were conducted in the Northern Hemisphere, and studies performed in South America are scarce. This study compares the migrant bird assemblages of urban parks and rural areas of cen- tral Argentina. Summer migrant birds were surveyed by standardized point counts in urban parks of six cities. In contrast, rural migrant assemblages were assessed through species lists of the citizen science project eBird in six paired sites. Sample coverage was similar between urban parks and rural areas (0.89 and 0.92, respectively). Migrant species richness was higher in rural than in urban parks. Migrant species composition changed between habitats, and species turnover was the dominant aspect of species dissimilarity. Urban parks had more occurrences of the Glittering-bellied Emerald (Chlorostilbon lucidus) and the Tropical Kingbird (Tyrannus melancholicus), whereas rural sites had more occurrences of the Vermillion Flycatcher (Pyrocephalus rubinus) and the Double-collared Seedeater (Sporophila caerulescens). Grasslands present in rural areas may favor the presence of the Vermillion Flycatcher and the Double-collared Seedeater. Therefore, cities are related to significant changes in the migrant bird communities.
 
 

The Ground-Dwelling Ant Fauna from a Cerrado Reserve in Southeastern Brazil: Vegetation Heterogeneity as a Promoter of Ant Diversity.

Ants represent one of the most diverse and ecologically important group of insects in tropical ecosystems, including in highly threatened ones such as the Brazilian Cerrado. Yet, a detailed understanding of the species diversity and composition of local Cerrado ant assemblages is lacking in many cases. Here we present the results of a comprehensive ant inventory performed within a region of the Cerrado (in São Paulo state) where most of the original vegetation has already been lost and where few conservation units exist. We performed consecutive surveys of the ant fauna that forage on the ground in replicated plots established in open savanna (campo sujo), dense savanna (cerrado sensu stricto), and forest (cerradão). Our surveys, with an estimated sample coverage of 99.4%, revealed a total of 219 species of ants from 60 genera, of which 36.1% were found in all the three vegetation types and 29.7% in just one. Rarefied species richness did not differ between vegetation types, but species composition differed markedly, especially between the two savannas in one hand and the forest in the other. Several species (60.1% of the 128 species analyzed) were significant "indicator" species due to their strong association with a given vegetation type. Overall, our findings reinforce the idea that habitat heterogeneity enhances ant diversity and that the mosaic of vegetation types that characterizes the Cerrado biome is one of the main factors explaining the elevated number of species that can be found at relatively small scales.

Deposition characteristics of CoCrFeMnNi high-entropy alloys thin film via simulation

HEAs are composed of five or more principal elements, each of which contributes 5–35 atomic percent. Here, we investigate the CoCrFeMnNi high-entropy alloys (HEAs) thin film deposited on Ni substrate via molecular dynamics simulation. The incident atoms deposit with different incident velocity levels and compositions on different surface crystalline orientations. The surface morphology, layer coverage, structure state, lattice distortion, stress, potential, and entropy distributions of the HEAs sample are analyzed. The results reveal that the higher incident velocity results in a higher stress level and a broader high-potential zone. From 50 m/s to 200 m/s, the crystalline structure ratio improves when the incident velocity increases due to a greater penetration rate. However, improving the incident velocity from 200 m/s to 400 m/s results in a decrease in crystalline structure ratio as the excess kinetic energy causes structural damage. Because of the increase in planar density, the layer coverage value decreases gradually from orientation (001) to (110) and finally (111). From the thin film surface, potential and entropy are distributed in a gradient pattern. The potential value increases from the interface to the HEAs thin film's outer surface. While the local entropy level decreases rapidly from the top to the bottom layer. The incident atoms create a high-stress and lattice distortion in the substrate matrix. Moreover, increasing Fe content from 20 % to 60 % declines the HEAs potential rate, the FCC structure ratio, and the penetration rate between the incident and substrate atoms.

Quick and Accurate Estimates of Mutation Effects on Transition-State Stabilization of Enzymes from Molecular Simulations with Restrained Transition States.

Data science and machine learning are revolutionizing enzyme engineering; however, high-throughput simulations for screening large libraries of enzyme variants remain a challenge. Here, we present a novel but highly simple approach to comparing enzyme variants with fully atomistic classical molecular dynamics (MD) simulations on a tractable timescale. Our method greatly simplifies the problem by restricting sampling only to the reaction transition state, and we show that the resulting measurements of transition-state stability are well correlated with experimental activity measurements across two highly distinct enzymes, even for mutations with effects too small to resolve with free energy methods. This method will enable atomistic simulations to achieve sampling coverage for enzyme variant prescreening and machine learning model training on a scale that was previously not possible.

Comparing fishery-independent and fishery-dependent data for analysis of the distributions of Oregon shelf groundfishes

We investigate whether fishery-dependent time series can be used to fill in spatial and temporal data gaps where scientific, fishery-independent data are not available. Limitations in sampling coverage combined with a historical focus on continental slope-dwelling groundfish resulted in a gap in understanding Oregon’s nearshore groundfish fishery. Although fisheries-independent surveys have been conducted across most of the fishery’s depth range, the data are limited by years and seasons surveyed, as well as the absence of data for areas shallower than 55 m water depth. Fishery-dependent data are available for those shallow waters and for a broader temporal range. However, these data are self-reported and the coverage was determined by where fishers choose to fish. To investigate the potential for future combined uses for these data sources, we analyzed spatial and temporal changes in catch rates, as well as gaps in fishery (logbook) and scientific (NOAA survey) data, for six flatfishes. We found that more heavily targeted species that live in deeper water, like Dover sole and petrale sole, had more spatial scientific sampling coverage compared to less frequently targeted species that live in shallow water, such as starry flounder and sand sole. Overlap between datasets was variable in space and time but consistently higher near large ports. We identified the winter season, and the pre-2003 time-period as having the highest potential to benefit from complementary use of fishery-dependent data. Prior to 2003, the survey design was variable and there was greater spatial and temporal coverage of logbook data compared to post-2003. Integration of these data sets may be useful for future research given their differences in spatial and temporal range. This work provides a new perspective on the value of using fishery-dependent data to understand the spatial distribution of species in habitats that are under sampled in scientific surveys.

Monitoring recovery of tree diversity during tropical forest restoration: lessons from long-term trajectories of natural regeneration.

Given the importance of species diversity as a tool for assessing recovery during forest regeneration and active restoration, robust approaches for assessing changes in tree species diversity over time are urgently needed. We assessed changes in tree species diversity during natural regeneration over 12-20 years in eight 1-ha monitoring plots in NE Costa Rica, six second-growth forests and two old-growth reference forests. We used diversity profiles to show successional trajectories in measures of observed, asymptotic and standardized tree diversity and evenness as well as sample completeness. We randomly subsampled 1-ha plot data to evaluate how well smaller spatial subsamples would have captured temporal trajectories. Annual surveys in eight 1-ha plots were missing substantial numbers of rare or infrequent species. Older second-growth sites showed consistent declines in tree diversity, whereas younger sites showed fluctuating patterns or increases. Subsample areas of 0.5 ha or greater were sufficient to infer the diversity of abundant species, but smaller subsamples failed to capture temporal trajectories of species richness and yielded positively biased estimates of evenness. In tropical forest regions with high levels of diversity, species diversity from small sample plots should be assessed using methods that incorporate abundance information and that standardize for sample coverage. This article is part of the theme issue 'Understanding forest landscape restoration: reinforcing scientific foundations for the UN Decade on Ecosystem Restoration'.

Evaluating tools for capture-recapture model selection to estimate the size of hidden populations: it works in practice, but does it work in theory?

Capture-recapture methods estimate the size of hidden populations by leveraging the proportion of overlap of the population on independent lists. Log-linear modeling relaxes the assumption of list independence, but best model selection criteria remain uncertain. Incorrect model selection can deliver incorrect and even implausible size estimates. We used simulations to model when capture-recapture methods deliver biased or unbiased estimates and compare model selection criteria. Simulations included five scenarios for list dependence among three incomplete lists of population of interest. We compared metrics of log-linear model selection, accuracy, and precision. We also compared log-linear model performance to the decomposable graph approach (a Bayesian model average), the sparse multiple systems estimation (SparseMSE) approach that accounts for zero or low cell counts, and the Sample Coverage approach. Log-linear models selected by Akaike's information criterion (AIC) calculated accurate population size estimates in all scenarios except for those with sparse or zero cell counts. In these scenarios, the decomposable graph and the Sample Coverage models produced more accurate size estimates. Conventional capture-recapture model selection fails with sparse cell counts. This naïve approach to model selection should be replaced with the implementation of multiple different models in order triangulate the truth in real-world applications.

Structural Diversity of Bacterial Communities and Its Relation to Environmental Factors in the Surface Sediments from Main Stream of Qingshui River

This paper aims to preliminarily understand the structure and diversity of the bacterial community in the sediments of the Qingshui River, and analyze the differences of dominant bacteria in different river reaches, and identify the influence degree of environmental factors. In this study, surface sediments of the main stream of the Qingshui River were selected to analyze both bacterial community composition and a diversity index using the high-throughput sequencing analysis of bacterial 16S rDNA, further exploring their relationships with environmental factors. Results showed that 16,855 OTUs in the surface sediments belonged to 66 phyla, 164 classes, 274 orders, 317 families, and 501 genera of bacteria, while carbon/nitrogen-fixing bacteria were dominant at the class and genus level. There was a significant (p < 0.05) spatial difference between bacterial species composition and the diversity index in surface sediments. Proteobacteria was the most abundant phylum in the sediments of the main stream of the Qingshui River, with an average abundance of 48.15%, followed by Bacteroidetes (21.74%) and Firmicutes (5.71%). The abundance of Alphaproteobacteria in Proteobacteria was the highest (15.38%) and followed by Flavobacteriia in Bacteroidetes (11.57%). The most dominant bacteria genera were different at different areas. The most dominant genera were Phyllobacterium in Kaicheng, Qiying, Liwang, Tongxin and Changshantou, with relative abundances of 4.27%, 4.67%, 5.88%, 4.15% and 6.22%, respectively. Flavobacterium was the most dominant genus in both Dongjiao and Sanying, with a relative abundance of 5.03% and 5.84%, respectively. Rhodobacter was the most dominant genus in Hexi, with a relative abundance of 8.29%. Gillisia was the most dominant genus in Quanyanshan, with a relative abundance of 5.51%. Pearson correlation analysis further indicated that NH4+, pH, and Cr were the main factors affecting the bacterial community structure and diversity in surface sediments. Therefore, our findings suggest that both nutrient elements (i.e., N) and toxic heavy metalloids affect the abundance and diversity of bacteria in surface sediments from the main stream of the Qingshui River. Areas of the river sampled in this study provide the biggest microbial sampling coverage to date. The results provide a preliminary understanding of bacterial communities in sediments of different reaches of the Qingshui River, and provide a reference for further research on the application of functional bacteria in pollution control of the Qingshui River.

Sediment depth and accretion shape belowground mangrove carbon stocks across a range of climatic and geologic settings

AbstractEstimating the long‐term sedimentary carbon sinks of mangroves and other blue carbon ecosystems has rapidly become a focus of coastal research and conservation attention. Sampling coverage, however, remains low, with sediment cores sparsely distributed across a subset of mangrove environmental settings globally. Furthermore, the ecological and geological drivers of variation in these stocks remain incompletely understood. We assessed the limits of mangrove sedimentary carbon storage by sampling sediments in diverse mangrove environments across four geographic areas: the volcanic Galapagos, the arid Baja Peninsula, and the geologically and climatically distinct Caribbean and Pacific coasts of Panama. At 80 sites across these areas, we quantified the organic carbon density, sampled with depth, of entire sediment columns. Depth‐integrated carbon stocks are highly variable, from <17 to >1700 MgCorg ha−1. The positive relationship between sediment carbon density and annual rainfall demonstrated in global studies was not observed across these areas, though some carbon density differences were evident. Variation in sediment depth, ranging from 7 to 427 cm across sites, largely explained variation in carbon stock across the areas studied. These results underscore the importance of using measurements of sediment depth to estimate carbon stock. Long‐term geomorphological processes, such as the build‐up of sediment deposits shaped by coastal dynamics, play a major role in shaping mangrove carbon stocks. Investigating and accounting for these processes will enable more accurate estimation of this variable and valuable carbon pool.