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[Display omitted] • China's large river sediment loadings and runoff have not universally synchronously changed in the past 20 years. • There were 9/13 of large river systems showed downward trends of annual sediment loadings. • Lower reaches of the Yellow River had the maximum annual average sediment loadings. • Runoff volume accounted for over 30% of sediment loading variations among all river systems. • Afforestation plays a crucial role in reducing sediment in arid regions. Understanding the relationship between sediment loading and its environmental implications in river systems is crucial for water resource management and environmental protection. This study explored the spatiotemporal characteristics of sediment loading and their environmental relationships in seven large rivers in China, aiming to quantify the contributions of various factors to changes in sediment transport. Monitoring data spanning twenty-one years (2002 to 2022) on sediments, hydrology, and the environment collected by sixty-five stations were analysed. The multivariate statistical techniques employed included Spearman's correlation analysis, principal component analysis, and multivariate regression modeling. The results show that sediment transport in various river systems exhibited spatial heterogeneity, the maximum annual average sediment loadings (1.59 × 108 t/yr) occur in the lower reaches of the Yellow River, the middle reaches have the highest sediment concentration (41.54 kg/m3), followed by the downstream of the Yellow River (5.85 kg/m3). Sediment loading and runoff changes in the basins did not adhere universally to synchronous patterns. Eleven of the thirteen basins of these river systems showed upward trends in annual runoff volume, whereas nine basins showed downward trends in annual sediment loading. Runoff volume accounted for over 30 % explanatory of sediment loading variations in all seven large river systems, with the Yangtze, Huaihe, Qiantang, and Songhua rivers surpassing 60 % of the explanatory power. The Normalized Difference Vegetation Index of all watersheds showed an increasing trend, whereas the index of nine of the thirteen watersheds was correlated negatively with sediment transport. The influence of human activities on basin sediment transport was higher than that of natural resilience, whereas afforestation significantly reduced sediment in arid regions. This study provides insight into the temporal and spatial characteristics of sediment loadings and the driving effects of environmental factors, which has great significance for watershed environmental management. [ABSTRACT FROM AUTHOR]

The extent to which soil bioengineering preserves the ecological functions of riverbank vegetation beyond erosion control remains largely unexplored. This study compared the functional response of plant communities on soil-bioengineered riverbanks with those on natural and hard-engineered (ripraps) riverbanks across 124 sites in Quebec, Canada. We hypothesized that the Community Weighted Means (CWM) of 10 functional traits and three ecological attributes relevant in a riparian context and based on 356 plant taxa would be similar between bioengineered and natural sites, while functional diversity measured as richness (FRic) and dispersion (FDis) would be higher in bioengineered sites due to the diverse conditions (substrate, microhabitats). Contrary to expectations, we found trait-specific results. Compared to ripraps, natural sites were dominated by plants that were taller and had lighter seeds, as well as higher dispersion in specific leaf area, height, and seed mass, higher FRic, more dispersion of propagules by water and less by animals, and more plants with vegetative reproduction, shade tolerance, wetland-affinity, native, and fewer ruderal species. Bioengineered sites had intermediate mean trait values and dispersion, and only small differences among the three techniques applied (pure, keyed, and mixed) regarding the proportion of living and mineral material. Consistent with a previous study that used the same set of sites, we found higher plant cover, species richness, and diversity in natural sites compared to ripraps, with bioengineered sites falling in between the two. Bioengineering can partially reproduce natural riparian plant communities both taxonomically and functionally. Practitioners should consider functional diversity in their designs. • Bioengineering may partially restore functionality of riverbank plant communities. • Functional response of riparian vegetation to soil stabilization is trait-specific. • Riverbank stabilization should consider trait diversity as well as species identity. [ABSTRACT FROM AUTHOR]

This study investigated the concentrations of 39 polybrominated diphenyl ether (PBDE) congeners in sediments from three rivers in the western Niger Delta of Nigeria that have been affected by pollution from urbanization and industrial activities. The Σ39 PBDE concentrations in sediments from these rivers ranged from 0.29 to 95.5, 5.15 to 121, and 0.73 to 66.1 ng g−1 for the Afiesere (AR), Edor (ER), and Okpare Rivers (OR), respectively. The homologue distribution patterns indicated the prominence of tetra- and penta-BDE congeners in sediments from these rivers. The ecological risk assessment results showed that the penta-BDEs were the primary source of risk to sediment-dwelling organisms in these rivers. However, the human health risk assessment indicated negligible risks for exposure of both adults and children to PBDEs in these sediments. The source apportionment suggests that the PBDE contamination in these river sediments was derived from long-distance migration, debromination of highly brominated congeners, and commercial penta-BDEs. These results reflect the use of penta-BDE formulations in this region rather than octa- and deca-BDE formulations. • Sediments from these rivers are contaminated with PBDEs. • Industrial and urban activities are potent contributors of PBDEs to the sediment. • Tetra and penta-BDEs were the dominant species in sediments from these Rivers. • Penta-BDEs in these sediments are of potential risk to the ecosystem. • PBDE profiles in these sediments reflect the use of penta-BDE formulation. [ABSTRACT FROM AUTHOR]

Highlights • A new quantitative longitudinal functional connectivity index (LFCI) was proposed for delta plains. • The slightly increasing trend in the average LFCI in the Taihu Plain became more significant after 1978. • The average LFCIs in June, July, and August of the flood season were less than those in other months. • Spatial-temporal changes in the average LFCI exhibited larger differences at the subregional and station scales. • The average LFCI had significant correlations with precipitation, river density, and water surface ratio. Abstract The longitudinal functional connectivity of river systems refers to the process-based connections between upstream and downstream areas and is fundamental to understanding the dynamic and nonlinear hydrological behaviour of river basins. However, the quantification of such connectivity remains a challenge due to the absence of a consensus on the appropriate data and methods, especially in delta plains. In this study, based on the difference between water level fluctuations at adjacent stations, a new and quantitative longitudinal functional connectivity index (LFCI) was developed for delta plains. Focusing on the Taihu Plain, we then analysed the spatial-temporal changes in the LFCI during 1960–2012 and investigated the correlations between the LFCI and climate change and human activities. We found that the decadal, annual and seasonal changes in the average LFCI all presented slightly increasing trends in the recent 50 period, but the annual average LFCI increased significantly after 1978; the average LFCIs in June, July, and August of the flood season were less than those in other months in the Taihu Plain. We also found that the spatial-temporal changes in the average LFCI exhibited larger differences at the subregional and station scales; those in the Wu-Cheng-Xi-Yu subregion were least, and the average LFCIs at stations near the borders of adjacent subregions were less than those at other stations. Moreover, we found that the average LFCI had significant correlations with precipitation, river density and water surface ratio. Our results were consistent with common sense facts, which demonstrated that the indicator developed in this study can quite effectively quantify the longitudinal functional connectivity of river systems in delta plains. [ABSTRACT FROM AUTHOR]

This study developed the potential regulation capacity ( PRC ) and actual regulation capacity ( ARC ) to characterize the flood regulation function of river systems in the delta plains. Spatial autocorrelation and the grey relational analysis were then employed to investigate the spatial-temporal change of the flood regulation function in the urbanization process, of which the results revealed its spatial coupling and quantitative relation with the urbanization process and river systems changes in the Taihu Plain. The results indicated that: (1) the PRC exhibited a 20.3%-decrease during the 1960s to the 2010s, though its change exhibited significant structural and hierarchical differences. The global distributions of the PRC s all presented insignificant clustered characteristics, and the local distribution of smaller PRC regions with a high flood risk was stable; (2) the ARC exhibited a 33.2%-reduction in the recent 50 years, and its decrement also exhibited an accelerating trend. The global ARC distribution changed from significant clusters to insignificant aggregations, and the local distribution range of the smaller ARC regions with a high flood risk gradually increased; (3) the spatial coupling degree between the change in the PRC and the urbanization process was greater than that between the change in the ARC and the urbanization process, and the effect of urbanization on the change in the PRC was also larger than the change in the ARC ; (4) the spatial coupling degree between the changes in the ARC and the river systems was greater than that between the changes in the PRC and the river systems, though the impacts of the river systems changes on the change in the PRC were larger than that on the change in the ARC . Therefore, the developed indicators based on limited and available information can serve as references for planning effective flood control strategies in the delta plains. [ABSTRACT FROM AUTHOR]

Corals on the reef corridor of the southwestern Gulf of Mexico have evolved on a terrigenous shallow continental shelf under the influence of several natural river systems. As a result, water turbidity on these reefs can be high, with visibility as low as <1 m, depending on reef location and season. Using a presence-absence species database from field surveys, literature search, and satellite data on sea surface temperature, turbidity and chlorophyll-a, the coral species composition and environmental variables were analyzed for the three main reef systems of the reef corridor of the southwestern Gulf of Mexico. Completeness of the data set was assessed using species accumulation curves and non-parametric estimators of species richness. Differences in coral assemblages’ composition between the reef systems were investigated using univariate (ANOVA) and multivariate (nMDS, ANOSIM, SIMPER) analyses and the relationship between the assemblages and environmental data was assessed using a forward selection process in canonical correspondence analysis (CCA) to eliminate non-significant environmental variables. The northern and central Veracruz reef systems share a similar number of coral species (p=0.78 mult. comp.) and both showed higher species richness than the southern system (p<0.001 mult. comp.). In terms of the assemblages’ structure, significant differences were found (ANOSIM R=0.3, p=0.001) with larger average dissimilitude between north-south (75.4% SIMPER) and central-south (74.2%) than north-central (27%) comparisons. Only environmental variables related to water turbidity and productivity were significant on the final CCA configuration, which showed a gradient of increasing turbidity from north to south. Reef geomorphology and the effect of turbidity help explain differences in coral assemblages’ composition. More studies are necessary to establish if turbidity could function as a refuge for future environmental stress. Each Veracruz reef system is at the same time unique and shares a pool of coral species. To protect these ecosystems it is necessary to effectively manage water quality and consider coral diversity on the reef corridor of the southwestern Gulf of Mexico. [ABSTRACT FROM AUTHOR]

Microplastics (MPs), <5 mm in size, are a concerning pollutant in bodies of water because they can be ingested by biological organisms, posing risks to humans and the environment. This study assessed the extent of MPs contamination in various fish species (Oreochromis niloticus , Arius manillensis , and Pterygoplichthys spp.) in selected sites along two major river systems in the Philippines – Pasig and Marikina Rivers. An optimized Raman microspectroscopy technique was used for imaging and identification of MPs using a mean laser spot size of about 1 μm, which is advantageous in the identification of fibers which have small diameters (<50 μm). It also allowed the simultaneous identification of MPs and their pigment additives, which in turn enabled the tracing of possible sources of these MPs. This is important because the fate and accumulation of MPs in rivers systems, as well as its toxicity is dependent on various factors including polymer type and surface chemistry. Majority of the MPs identified from all the fish species were composed of polypropylene and polyethylene in the form of fragments, which reflects both the widespread use of these polymers for packaging and their environmental fate as riverine plastic debris. Moreover, the detection of MPs in the fish species may affect the food chain and eventually pose health risks for humans. The study could provide guidance on waste and environmental water management in the surrounding region. • Raman microspectroscopy of microplastics in fish shows mostly PE and PP. • Microplastics are mostly <1.6 mm with irregularly shaped fragments. • Janitor fish from Marikina River had the most number of ingested microplastics. [ABSTRACT FROM AUTHOR]

Understanding the spatial–temporal distribution characteristic and evolution tendency of river systems is important in integrated river basin management. In this paper, six indicators were adopted to describe the physical characteristic of river systems. The spatial–temporal evolution of the distribution pattern of river systems in the plain river network region of the Taihu Basin (PRNRTB) during the 1960s–2000s was analyzed using exploratory spatial data analysis (ESDA) and the gravity centre model. The impacts of urbanization were then investigated. Results indicated that the global distribution patterns of box dimension and river density were all statistically significant spatially clustered, and river sinuosity was partially spatially clustered, while water surface ratio, main river area length ratio and river development coefficient were not spatially clustered. Moreover, the water surface ratio was the most stable parameter, box dimension was also relatively stable parameter, but the others were unstable. Meanwhile, the mutual transformations of hot and cold spots of river systems especially water surface ratio, river development coefficient, and river sinuosity were frequent. The hot spot regions were mainly located in the northeast region. In addition, most gravity centres migrated gradually from southeast to northwest with low distance, except those of river development coefficient and river density. These aforementioned differences were caused by the rapid urbanization. Based on the integrated river basin management suggestions for PRNRTB, the river density, box dimension and river sinuosity should be maintained and restored across the whole watershed, and the river conservation and restoration should focus on countermeasures against the reduction of river development coefficient, and main attention should be paid on the river systems conserving and restoring in Haiyan and Haining in southeast PRNRTB. [ABSTRACT FROM AUTHOR]

Engineered nanoparticle (ENP) fate models developed to date — aimed at predicting ENP concentration in the aqueous environment — have limited applicability because they employ constant environmental conditions along the modeled system or a highly specific environmental representation; both approaches do not show the effects of spatial and/or temporal variability. To address this conceptual gap, we developed a novel modeling strategy that: 1) incorporates spatial variability in environmental conditions in an existing ENP fate model; and 2) analyzes the effect of a wide range of randomly sampled environmental conditions (representing variations in water chemistry). This approach was employed to investigate the transport of nano-TiO 2 in the Lower Rhône River (France) under numerous sets of environmental conditions. The predicted spatial concentration profiles of nano-TiO 2 were then grouped according to their similarity by using cluster analysis. The analysis resulted in a small number of clusters representing groups of spatial concentration profiles. All clusters show nano-TiO 2 accumulation in the sediment layer, supporting results from previous studies. Analysis of the characteristic features of each cluster demonstrated a strong association between the water conditions in regions close to the ENP emission source and the cluster membership of the corresponding spatial concentration profiles. In particular, water compositions favoring heteroaggregation between the ENPs and suspended particulate matter resulted in clusters of low variability. These conditions are, therefore, reliable predictors of the eventual fate of the modeled ENPs. The conclusions from this study are also valid for ENP fate in other large river systems. Our results, therefore, shift the focus of future modeling and experimental research of ENP environmental fate to the water characteristic in regions near the expected ENP emission sources. Under conditions favoring heteroaggregation in these regions, the fate of the ENPs can be readily predicted. [ABSTRACT FROM AUTHOR]

Highlights: [•] We measured 29N2 and 30N2 using membrane inlet mass spectrometry. [•] Potential anammox rates varied spatially and temporally in the studied rivers. [•] Water temperature and in sediments were the main controls of anammox activity. [•] Candidatus Kuenenia was the dominated anammox species in the river sediments. [ABSTRACT FROM AUTHOR]

Abstract: The uncertainties involved in remote sensing inversion of CDOM (Colored Dissolved Organic Matter) were analyzed in estuarine and coastal regions of three North American rivers: Mississippi, Hudson, and Neponset. Water optical and biogeochemical properties, including CDOM absorption and above-surface spectra, were collected in very high resolution. CDOM’s concentrations (ag (440), absorption coefficient at 440nm) were inverted from EO-1 Hyperion images, using a quasi-analytical algorithm for CDOM (QAA-CDOM). Uncertainties are classified to five levels, in which the underwater measurement uncertainty (level 1), image preprocessing uncertainty (level 4) and inverse model uncertainty (level 5) were evaluated. Results indicate that at level 1, in situ CDOM measurement is significant with 0.1 in the unit of QSU and 0.01 in the unit of ag (440) (m−1). At level 4, surface wave is a potential uncertainty source for high-resolution images in estuarine and coastal regions. The remote sensing reflectance of wavy water is about 10 times of the truth. At level 5, the overall uncertainty of QAA-CDOM inversion is 0.006m−1, with accuracy R 2 =0.77, k =1.1 and RMSE log =0.33m−1. The correlations between uncertainties and other water properties indicate that the large uncertainty in some rivers, such as the Neponset and Atchafalaya, might be caused by high-concentration chlorophyll or sediments. The relationships among the three level uncertainties show that the level 1 uncertainty generally does not propagate into level 4 and 5, but the large uncertainty at level 4 usually introduce large uncertainty at level 5. [Copyright &y& Elsevier]

Abstract: The Mesoproterozoic Belt-Purcell Supergroup (BPS) preserves a thickness of 17km of dominantly siliciclastic rocks deposited between 1470 and 1400Ma. The total range of Chemical Index of Alteration (CIA) values, corrected for diagenetic K-addition, are 62–88 for argillites and 55–80 for sandstones, with averages of 72±6 and 68±7, respectively. More intense CIA values, in conjunction with low absolute contents of Sr, Ca and Na, and high Rb/Sr ratios (average 4), reflect an intensely weathered provenance in a hot-wet climate with hot-arid intervals resulting in evaporitic sediments. Covariations of CIA-Eu/Eu* and Sr-Eu/Eu* are consistent with a large catchment area including extensive provenance terranes of weathered recycled sedimentary rocks for the most extreme CIA and Eu/Eu* values, with smaller less intensely weathered juvenile terranes represented by lower CIA values. Accordingly, variations of CIA within the BPS stratigraphic sequence may record some combination of shifting catchment terranes and weathering intensity. Stratigraphic trends in CIA within the Appekunny and Grinnell Formations of 80±6 to 66±4 to 79±5 record the variation in this combination with time. Siliciclastic rocks record a first order trend of CIA values from CIA ∼80–100 in the Mesoarchean, through ∼80–90 in the Neoarchean, and ∼70–85 in the Proterozoic, to ∼72 for global Phanerozoic shales. These values reflect progressive drawdown of greenhouse gases that promote silicate weathering by their sequestration into carbonates and black shales, as preserved in the geologic record. Second order secular peaks in CIA values correlate in time with mantle plumes that emit greenhouse gases, which enhance silicate weathering. Some of the more intense CIA values in the BPS may also stem from release of volcanic gases during magmatism that accompanied rifting of Laurentia during breakup of the Supercontinent Columbia at ∼1.4Ga. Overall, CIA values are within the range of modern humid-temperate and humid-tropical climatic catchment areas drained by large river systems such as the Orinoco, Nile and Amazon rivers. Proterozoic rivers have been viewed as mostly braided systems due to the lack of influence of rooted vegetation, which resulted in fast channel lateral migration, high run-off rates, and low bank stability. Many large-scale Proterozoic siliciclastic basins have been preserved, formed by river systems up to pan-continental scale. However, their significance as archives of continental weathering intensity remains under-explored. This study suggests that BPS CIA values reflect more aggressive chemical weathering, since Proterozoic rivers had less sediment residence times due to a lack of vegetation cover, and therefore faster transport time than their modern counterparts. To achieve high CIA values in shorter periods of time without vegetation cover, more intense chemical weathering conditions must have been present. [Copyright &y& Elsevier]

Summary: This study presents gene-expression programming (GEP), which is an extension of genetic programming (GP), as an alternative approach to predict the transverse mixing coefficient in open channel flows. Laboratory data were collected in the present study and also from the literature for the transverse mixing coefficient covering wide range of flow conditions. These data were used for the development and testing of the proposed method. A functional relation for the estimation of transverse mixing coefficient has been developed using GEP. The proposed GEP approach produced satisfactory results compared to the existing predictors for the transverse mixing coefficient. [Copyright &y& Elsevier]

Abstract: Fast-paced watershed change, driven by anthropogenic development, is threatening the sustainability of freshwater resources across the globe. Developments within watersheds interact in a manner that is additive and synergistic over space and time. Such cumulative environmental effects are defined as the results of actions that are individually minor but collectively significant when added to other past, present, and reasonably foreseeable future actions. Cumulative effects assessment (CEA) then is broadly defined as the process of evaluating the potential impacts of such collective actions on the environment and is a requirement in many countries, including in Canada at the federal level under the Canadian Environmental Assessment Act. However, current approaches to CEA for river systems are proving to be ineffective, which is largely attributed to the disconnect between CEA science and practice. We highlight this gap herein by discussing contradictions in the CEA literature, challenges in quantifying cumulative interactions, including overcoming spatiotemporal scale issues, multiple hydrologic and ecological pathways, and lack of predictive analysis. Our analysis shows there is a need for improved CEA for river systems, and in responding to this need we propose a conceptual framework for better integrating science and practice for improved CEA for river systems using one of the most adversely affected rivers basins in Canada, the Athabasca River, as our model. We conclude by addressing the challenges inherent to CEA with the intent of providing scientists with ways to help improve CEA of river systems. [Copyright &y& Elsevier]

Abstract: Over the last decade several computational models, and several types of model, have been developed to simulate the response of river systems to environmental change over time scales of decades to millennia: hydrological models, flood inundation models, channel morphology models, channel network models, models of river meandering and river braiding, alluvial stratigraphy models, and landscape evolution models. Each type of model simulates different aspects of a river''s response to changes in environmental inputs such as climate and land-use — and to changes in these inputs. And each type of model has its abilities, advantages and limitations. We provide an overview of the different types of model that have been developed, and we evaluate their suitability for testing hypotheses about past environmental conditions, as well as for investigating the response of alluvial river systems to future environmental change. Additionally, we discuss the general issues and problems of computational modelling (e.g. scale and resolution, data availability, process representation, process parameterization, model calibration, non-linearity, and uncertainty), and the extent to which these hamper the usefulness of the models as a tool in environmental landscape studies. Finally, we identify trends in computational modelling research to outline possible future directions of the discipline. [Copyright &y& Elsevier]

Abstract: Over the past 15 years, artificial neural networks (ANNs) have been used increasingly for prediction and forecasting in water resources and environmental engineering. However, despite this high level of research activity, methods for developing ANN models are not yet well established. In this paper, the steps in the development of ANN models are outlined and taxonomies of approaches are introduced for each of these steps. In order to obtain a snapshot of current practice, ANN development methods are assessed based on these taxonomies for 210 journal papers that were published from 1999 to 2007 and focus on the prediction of water resource variables in river systems. The results obtained indicate that the vast majority of studies focus on flow prediction, with very few applications to water quality. Methods used for determining model inputs, appropriate data subsets and the best model structure are generally obtained in an ad-hoc fashion and require further attention. Although multilayer perceptrons are still the most popular model architecture, other model architectures are also used extensively. In relation to model calibration, gradient based methods are used almost exclusively. In conclusion, despite a significant amount of research activity on the use of ANNs for prediction and forecasting of water resources variables in river systems, little of this is focused on methodological issues. Consequently, there is still a need for the development of robust ANN model development approaches. [Copyright &y& Elsevier]

Abstract: There is a long history of human–riverine interactions throughout the period of agriculture that in some regions of the world started several thousand years ago. These interactions have altered rivers to human dominated systems with often negative impacts on fluvial environments. To achieve a good ecological and chemical status of rivers, as intended in the European Water Framework Directive (WFD), a better understanding of the natural status of rivers and an improved quantification of human–riverine interactions is necessary. Over the last decade the PAGES-LUCIFS (Land Use and Climate Impact on Fluvial Systems) program has been investigating both contemporary and long-term (centuries to millennia) river responses to global change with the principal aims of: 1) quantifying land use and climate change impacts of river-borne fluxes of water, sediment, C, N and P; 2) identification of key controls on these fluxes at the catchment scale; and 3) identification of the feedback on both human society and biogeochemical cycles of long-term changes in the fluxes of these materials. Here, we review recent progress on identifying fluvial system baselines and quantifying the response of long-term sediment budgets, biogeochemical fluxes and flood magnitude and frequency to Holocene global change. Based on this review, we outline the future LUCIFS research agenda within the scope of the PAGES-PHAROS (Past Human-Climate-Ecological Interactions) research program. Key research strategies should be focused on: 1) synthesising the data available from existing case studies; 2) targeting research in data-poor regions; 3) integrating sediment, C, N and P fluxes; 4) quantifying the relative roles of allogenic and autogenic forcing on fluvial regimes, extreme events and sediment fluxes; 5) improving long-term river basin modelling; and 6) integration of LUCIFS with other research communities within PHAROS, namely HITE (land cover) and LIMPACS (water quality and biodiversity). [Copyright &y& Elsevier]

Abstract: We describe the statistical properties of two large river systems: the Danube and the Mississippi. The properties of the two rivers are compared qualitatively to the general properties of a critical steady-state system. Specifically, we test the recent suggestion by Bramwell et al. (Europhys. Lett. 57 (2002) 310) that a universal probability density function (PDF) exists for the fluctuations in river level, namely the Bramwell–Holdsworth–Pinton (BHP) PDF. The statistical properties investigated in this paper are: the PDF of the river flow and river level; moment scaling with basin area; moment to moment scaling or relative scaling; and power spectral properties of the data. We find that the moments of the flow scale approximately with basin area and that the seasonally adjusted flows exhibit relative moment scaling. Compared to the Mississippi, the Danube shows large deviations from spatial scaling and the power spectra show considerable dependence on system size. This might be due to water use and regulations as well as inhomogeneities in the basin area. We also find that the PDF of level data in some, but not all, cases can be qualitatively approximated by the BHP PDF. [Copyright &y& Elsevier]

The behavior and impact of trace metals discharged into rivers depend on their solid/liquid fractionation and the fate of these two phases according to hydro-sedimentary processes. The solid/liquid fractionation depends on many environmental factors which imply uncertainties of several orders of magnitude in the evaluation of the partition coefficients, whether by geochemical modelling, in situ measurements or sorption-desorption experiments. In this context, this paper presents a model of solid/liquid fractionation of trace metals with suspended sediments in rivers which integrates the hydro-sedimentary conditions and the properties of the watershed. Its comparison with the 137Cs concentrations measured in the Rhône River (France) thanks to monitoring shows that the solid/liquid fractionation of 137Cs with suspended sediments in rivers depends on chemical processes but also and above all on variations in water flow rate, size and load of suspended sediments and the balance between anthropogenic discharges and the average trace metal content of soils in the watershed. • K d modelling according to hydro-sedimentary conditions. • Particle size effect on K d. • Geochemical background effect on K d. • Colloidal pumping effect on K d. [ABSTRACT FROM AUTHOR]

• Genetic structure was assessed using seven polymorphic SSR markers. • High genetic diversity and the absence of a spatial genetic structuring were detected. • Ecoregion differences might not be responsible for the diversity within Ottelia ulvifolia. • Floodplains and river systems connectivity were likely to contribute to the high gene flow among populations. As vital components of freshwater ecosystems, river systems directly boost the dispersal and gene flow of aquatic species. However, various river systems might also increase the potential for isolation of these species and their genetic differentiation. In Africa, the roles of river systems in shaping the genetic diversity and structures of aquatic species are still poorly studied. In order to assess the influence of river systems in freshwater ecoregions on the genetic variation of Ottelia ulvifolia , we genotyped 307 individuals of 18 populations from Bangweulu-Mweru, Middle Zambezi-Luangwa, and Upper Zambezi Floodplain ecoregions in Zambia using ten microsatellite markers. Our results revealed an overall high genetic diversity (H E = 0.475) and high gene flow (Nm > 1) among the three ecoregions. Notably, a relatively higher diversity (H E = 0.485; I = 0.836) was detected in Bangweulu-Mweru compared to those other ecoregions, which could be contributed by frequent river capture events in the area. STRUCTURE, TESS, PCoA, and NJ analyses identified two distinct clusters that were further divided into five sub-clusters, three in bisexual populations and two in the unisexual populations, respectively. The lower genetic differentiation among 18 populations (Fst = 0.258) in the present study could be attributed to the frequent hybridization among populations via insect pollination and water-mediated seed dispersal. A significant positive correlation between Jost's D/(1-Jost's D) and geographic distance among populations (r = 0.142, P = 0.050) indicated deviation for mutation-drift equilibrium. The current findings, however, do not support the hypothesis that variations within ecoregions drive the genetic variation and population structure of O. ulvifolia in Zambia. Lastly, habitat specialization and floral characteristics are examples of behavioral factors that may promote a genetic difference in O. ulvifolia. Our study provides general knowledge of the genetic variation of O. ulvifolia in tropical Africa and indicates a possible regional alteration of various macrophyte dispersal mechanisms at a vast geographic scale, therefore encouraging the need for further research on the genus. [ABSTRACT FROM AUTHOR]

Abstract: In field monitoring, sex ratio as an endpoint of possible endocrine effects at population level can only be recorded as the deviation from the natural sex ratio. Unfortunately, data on natural sex ratios of many species cannot be used to control for such effects. This also applies to bream (Abramis brama L.), an important fish species in passive biomonitoring. Here we show that in natural bream populations the sex ratio decreases with increasing age. Age class specific correction coefficients were derived to eliminate age-dependency of the sex ratio. [Copyright &y& Elsevier]