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Abstract Soil salinization impacts millions of hectares of land around the world and threatens many soil ecosystem services. Impacts of soil salinization are long lasting and impact agriculture productivity, reduce plant diversity and cause increase soil erosion due a reduction or loss in surface vegetation. Generally, remediation of saline soil relies on soil washing methods and phytoremediation to translocate salts below the rooting depth of plants. However, standard methods can often be unsuccessful as leached salts are able to return to the rooting zone through subsequent capillary rise in the soil. Surface application of iron (III) ferrocyanide has been used to remediate salt contaminated soil as the ferrocyanide complex induces salts to efflorescence at the soil surface as water evaporates rather than crystallising within the soil matrix. However, surface application of iron (III) ferrocyanide tends to be less successful in clay textured soil and does not work well when subsequent reapplications of water are made for further salt removal. In this study we investigate a biomimetic approach to desalinate soil by mimicking the capillary transport mechanisms employed by vascular plants. Our approach uses evapotranspiration to translocate saline soil water above the soil surface where it is effloresced with ferrocyanides. After 30 days of treatment, the biomimetic approach used 2.1 pore volume equivalents of water and was able to reduce the concentration of salts from 8% (g·NaCl/g·soil) to 0.8% (g·NaCl/g·soil), resulting in a reduction of soil EC from 120 mS/cm to 14 mS/cm. Our findings indicate that the method, with further refinement and expansion to field based trials, could be an effective tool to desalinate soil and reduce global soil salinization. Graphical abstract Unlabelled Image Highlights • Biomimicry of evaporative hydrostatic pressure and capillarity in vascular plants facilitated remediation of saline soil. • A 10 fold reduction in soil EC (120 mS/cm to 14 mS/cm) was achieved in 30 days. • Our approach may be a viable alternative to traditional methods for the remediation of saline soil. [ABSTRACT FROM AUTHOR]

Abstract Groundwater pollution in Israel mainly occurs in the populated urban areas. Yet, in the 90's a major salinization was identified in a deep well in the northeastern part of the Negev desert, and a trend of increasing salinity was recognized in an adjacent spring. Since then the salinity of the spring is on the rise reaching a rate of 21 mgCl/L per month. New geochemical data allows the identification of the source, composition and volume of the contaminant, as well as its dispersion in the aquifer. The source of the contamination is attributed to highly saline (~40,000 mgCl/L), acidic and trace elements-rich industrial wastewater that leaked from evaporation ponds and also drained through karstic sinkhole to the subsurface over a period of decades. The contamination is reflected by a sharp increase in the concentrations of most major elements and by a moderate increase in a few trace elements. The total waste water volume that leaked is assessed to be 75 MCM. The study reveals that most of the contaminated water is still far upstream of the natural outlet. Due to the specific geological configuration the highly contaminated groundwater is channeled into a narrow corridor of an elongated syncline. Unlike other similar contamination cases around the world, pumping along this syncline can reduce the flow of the contaminated water further downstream towards a region where it disperses. The study provides the decision makers with tools that can reduce the environmental hazard and enable development of water production in this arid region. The current research emphasizes the importance of a combined geological, hydrological and geochemical study of a contaminated aquifer to fully understand the flow regime and contamination process. Such studies are a crucial step before an optimal mitigation action can be undertaken to rehabilitate a contaminated aquifer. Graphical abstract Unlabelled Image Highlights • Salinization of a local carbonate aquifer is traced to leakage of waste water. • The waste water is highly saline, acidic and enriched in trace elements. • In the aquifer the acidity is buffered and the trace elements are adsorbed. • The flow of the polluted water is directed into a narrow corridor along a syncline. • Pumping in the syncline can reduce the dispersion of the contamination. [ABSTRACT FROM AUTHOR]

Abstract Coastal groundwater quality significantly affects the regional sustainable development, due to the water resource shortage in coastal zone. Current studies on coastal groundwater have mainly focused on saline water intrusion and over-extraction. Information on the heavy metal pollution of coastal groundwater with salinization trend is limited. This study investigated heavy metals in groundwater from a typical coastal region with intensive anthropogenic activities and saline water intrusion. The southwestern coastal plains of the study area showed significant groundwater salinization trend. Heavy metals in the coastal groundwater mainly originated from anthropogenic activities and groundwater salinization according to principal component analysis. Relative high concentrations of As, Co, Cr, Cu, Fe, Mn, and Ni occurred in the southwestern coast of the study area with high TDS level, indicating that the concentrations of these heavy metals in shallow aquifer of the study area might be influenced by the groundwater salinization. Average concentrations of heavy metals in groundwater of the study area ranged from 0.03 (Cd) to 686.92 (Fe) μg/L. Fe was the dominant heavy metal in groundwater with the maximal concentration of 2333.76 μg/L and exceeding-standard rate reaching 98.23%. Approximately 13.27% of sampling sites showed moderate or higher heavy metal pollution of groundwater based on heavy metal pollution index. Heavy metals in groundwater exerted low ecological risks. Elements Fe, Ni, and As were the main contributors for ecological risks. Cancer risks of heavy metals for both adults and children were high at all sampling sites. Non-cancer risks for adults and children were unacceptable at 4.42% and 17.70% of sampling sites, respectively. The salinization of the coastal groundwater could also lead to the increase in the ecological and health risks of heavy metals in coastal groundwater. These findings provide initial and important information on heavy metals pollution in coastal aquifer with saline water intrusion. Graphical abstract Unlabelled Image Highlights • Southwestern coastal plains of study area showed significant groundwater salinization. • About 13.27% of sampling sites showed moderate or more serious heavy metal pollution. • Heavy metals in groundwater exerted low ecological risks. • Heavy metals in groundwater exerted high cancer risks for adults and children. • Salinization of coastal groundwater caused the increase in pollution and risks. [ABSTRACT FROM AUTHOR]

Abstract The present study compiles new and literature data in a GIS platform aiming to (a) evaluate the extent and magnitude of Cr contamination in a Mediterranean region (Assopos-Thiva and Central Evia (Euboea) Basins, Greece); (b) combine spatial distribution of Cr in soil and groundwater with land use maps; (c) determine geochemical constraints on contamination by Cr; and (d) provide information that will be useful for better management of land use in a Mediterranean type ecosystem in order to prevent further degradation of natural resources. The spatial diversity of Cr distribution in soils and groundwater throughout the C. Evia and Assopos-Thiva Basins is considered. It is attributed to both natural Cr sources (Cr-bearing peridotites, affecting primarily soil) and human (industrial) activities (the dominant source of groundwater contamination). A combination of the spatial distribution of metals in soil and land use maps was used to define the specific areas of agricultural land use with elevated heavy metal contents. Furthermore, the combination of the spatial distribution of Cr in groundwater and land use maps allows for definition of specific areas of industrial land use with elevated Cr concentrations (Inofita, south Assopos-Thiva Basin). Despite the good correlation (r = 0.75) between Cr(VI) and the strong oxidant NO 3 − in C. Evia, the lower standard potential (E0) values for NO 3 − compared to those for Cr 2 O 7 2− (the latter is a stronger oxidant than the former) suggest that NO 3 − is not an oxidant of Cr. This detailed assessment and presentation of the available analytical data for soil and groundwater in Assopos-Thiva and C. Evia Basins on a land use map provides information for land management decision makers. Graphical abstract Unlabelled Image Highlights • Spatial distribution of Cr and other elements in an area of Greece investigated • Maps of land use and element contents in soil and groundwater were developed. • GIS and multivariate statistics were applied to assess the origin of Cr contamination. • Maps help distinguish Cr of geogenic and anthropogenic origin and salinization. • These provide information for sustainable land management. [ABSTRACT FROM AUTHOR]

Road salt mitigates winter highway icing but accumulates in watershed soils and receiving waters, affecting soil chemistry and physical, biological, and ecological processes. Despite efforts to reduce salt loading in watersheds, accumulated cations and Cl − continue to impact tributaries and lakes, and the recovery process is not well understood. Lake George, New York (USA) is typical of many temperate lakes at risk for elevated Cl − concentrations from winter deicing; the lake salt concentration increased by ~3.4% year −1 since 1980. Here, we evaluated the ionic composition in Finkle Brook, a major watershed draining to Lake George, studied intermittently since 1970 and typical of other salt-impacted Lake George tributaries. Salt loading in the Lake George basin since the 1940s displaced cations from exchange sites in basin soils; these desorbed cations follow a simple ion-exchange model, with lower sodium and higher calcium, magnesium and potassium fluxes in runoff. Reduced salt application in the Finkle Brook watershed during the low-snow winter of 2015–2016 led to a 30–40% decline of Cl − and base cations in the tributary, implying a Cl − soil half-life of 1–2 years. We developed a conceptual model that describes cation behavior in runoff from a watershed that received road salt loading over a long period of time, and then recovery following reduced salt loading. Next, we developed a dynamic model estimating time to steady-state for Cl − in Lake George with road salt loading starting in 1940, calibrating the model with tributary runoff and lake chemistry data from 1970 and 1980, respectively, and forecasting Cl − concentrations in Lake George based on various scenarios of salt loading and soil retention of Cl − . Our Lake George models are readily adaptable to other temperate lakes with drainage basins where road salt is applied during freezing conditions and paved roads cover a portion of the watershed. [ABSTRACT FROM AUTHOR]

Field-collected measures of dissolved salts and occurrences of aquatic invertebrates have been used to develop protective levels. However, sufficiently large field data sets of exposures and biota are often not available. Therefore, a model was developed to predict the exposure extirpating 5% of benthic invertebrate genera using only measures of specific conductivity (SC) as the independent variable. The model is based on 3 assumptions: (1) a genus will rarely occur where the background exceeds its upper physiological limit; (2) the lowest possible tolerance limit of a genus in a region is defined by the natural background; and (3) as a result, there will be a regular association between natural background SC and the SC at which salt-intolerant genera are present. Three steps were used to develop the model. First, background SC was characterized as the 25th centile of sampled sites for each of 24 areas in the United States with streams dominated by bicarbonate and sulfate ions. Second, the extirpation concentration (XC 95 ), an estimate of the upper tolerance limit with respect to SC, was calculated for genera in 24 data sets. Next, the lower 5th centile of each set of XC 95 values (XCD 05 ) was identified for the most salt-intolerant members in each data set. Finally, the relationship between the 24 background SC and the 24 XCD 05 values was empirically modeled to develop a background-to-criterion model. The least squares regression of XCD 05 values on log background SC ( log Y  = 0.658 logX  + 1.071) yields a strong linear relationship ( r  = 0.93). The regression model makes it possible to use SC background to predict the SC likely to extirpate the most salt-intolerant genera in an area. The results also suggest that species distribute along natural background gradients of SC and that this relationship can be used to develop criteria for ionic concentration. [ABSTRACT FROM AUTHOR]

Soil salinization is a major threat to agricultural lands. Among salt-affected lands, coastal areas could be considered as highly complex systems, where salinization degradation due to anthropogenic pressure and climate-induced changes could significantly alter system functioning. For such complex systems, conceptual models can be used as evaluation tools in a preliminary step to identify the main evolutionary processes responsible for soil and water salinization. This study aimed to propose a conceptual model for water fluxes in a coastal area affected by salinity, which can help to identify the relationships between agricultural landscape evolution and actual salinity. First, we conducted field investigations from 2012 to 2016, mainly based on both soil (EC 1/5 ) and water (EC w ) electrical conductivity survey. This allowed us to characterize spatial structures for EC 1/5 and EC w and to identify the river as a preponderant factor in land salinization. Subsequently, we proposed and used a conceptual model for water fluxes and conducted a time analysis (1962–2012) for three of its main constitutive elements, namely climate, river, and land systems. When integrated within the conceptual model framework, it appeared that the evolution of all constitutive elements since 1962 was responsible for the disruption of system equilibrium, favoring overall salt accumulation in the soil root zone. [ABSTRACT FROM AUTHOR]

Sea level rise, as a consequence of climate changes, is already causing seawater intrusion in some freshwater coastal ecosystems worldwide. The increase in salinity at these freshwater coastal ecosystems may occur gradually (through groundwater) or abruptly (through extreme weather events). Moreover, many of them are also being altered and threatened by anthropogenic activities. Accordingly, the present study aimed at assessing the multigenerational lethal and sublethal effects caused by increased salinity in six clonal lineages of the freshwater cladoceran Daphnia longispina differing in their sensitivity to lethal levels of copper. Three specific objectives were delineated: i) to compare the lethal and sublethal toxicity of sodium chloride (NaCl) and natural seawater (SW); ii) to evaluate possible multigenerational effects after exposure to low levels of salinity, and iii) to evaluate if an association exists between tolerance to lethal and sublethal levels of salinity and tolerance to metals. Overall, NaCl was found to elicit sublethal effects at lower or similar concentrations than SW, suggesting its use as a protective surrogate of SW in early phases of ecological risk assessment schemes. Multigenerational exposure to conductivities of 0.73 ± 0.015 mS cm − 1 led to dissimilar responses by the six clonal lineages. Significant associations were found neither between lethal and sublethal endpoints nor between salinity and metals, possibly indicating the absence of common mechanisms responsible to confer metal tolerance and salt stress. However, some clonal lineages presented an inverse sensitivity to lethal levels of NaCl and of copper. These results suggest that natural populations of D. longispina , by exhibiting clonal lineages with differential tolerance to increased salinity, may cope with long-term exposure to small increases of this stressor. However, over time those populations may face the occurrence of genetic erosion due to the loss of the most sensitive genotypes before or after a multigenerational exposure. [ABSTRACT FROM AUTHOR]

Soil salinity is recognized worldwide as a major threat to agriculture, particularly in arid regions. Producers and decision-makers thus require updated and accurate maps of salinity in agronomical and environmentally relevant regions. The goals of this study were to test various regression models for estimating soil salt content based on hyperspectral data, HJ-CCD images, and Landsat OLI data using; develop optimal band Difference Index (DI), Ratio Index (RI), and Normalization Index (NDI) algorithms for monitoring soil salt content using image and spectral data; and to compare the performances of the proposed models using a Bootstrap-BP neural network model (Bootstrap-BPNN) from different data sources. The results showed that previously published optimal remote sensing parameters can be applied to estimate the soil salt content in the Ebinur Lake Wetland National Nature Reserve (ELWNNR). Optimal band combination indices based on DI, RI, and NDI were developed for different data sources. Then, the Bootstrap-BP neural network model was built using 1000 groups of Bootstrap samples of remote sensing indices (DI, RI and NDI) and soil salt content. When verifying the accuracy of hyperspectral data, the model yields an R 2 value of 0.95, a root mean square error (RMSE) of 4.38 g/kg, and a residual predictive deviation (RPD) of 3.36. The optimal model for remote sensing images was the first derivative model of Landsat OLI, which yielded R 2 value of 0.91, RMSE of 4.82 g/kg, and RPD of 3.32; these data indicated that this model has a high predictive ability. When comparing the salinization monitoring accuracy of satellite images to that of ground hyperspectral data, the accuracy of the first derivative of the Landsat OLI model was close to that of the hyperspectral parameter model. Soil salt content was inverted using the first derivative of the Landsat OLI model in the study area. [ABSTRACT FROM AUTHOR]

Stream ecosystems are impacted by multiple stressors worldwide. Recent studies have shown that the effects of multiple stressors are often complex and difficult to predict based on the effects of single stressors. More research is needed to understand stressor impacts on stream communities and to design appropriate counteractions. We carried out an outdoor mesocosm experiment to assess single and interactive multiple-stressor effects on stream macroinvertebrates in a setup with controlled application of three globally important stressors, namely, reduced stream flow velocity, deposition of fine sediment and increased chloride concentration in a full-factorial design. Each mesocosm comprised three compartments (channel substratum, leaf litter bag and drift net) that were individually analyzed and also compared. We identified 102,501 specimens in total (mainly to family level), 36.5% of which were found in the substratum, 60.6% in litter bags and 2.9% in the drift. Added fine sediment and reduced flow velocity had strong negative single-stressor effects on the abundances of EPT taxa, i.e. Ephemeroptera (mayflies), Plecoptera (stoneflies) and Trichoptera (caddisflies), and a positive effect on chironomid abundances in the substratum. Increased salt concentration reduced abundances of Ephemeroptera. Chironomids migrated from litter bag to channel substratum when water velocity was reduced and Leptophlebiidae in the opposite direction when sediment was added. All three stressors caused higher drift propensities, especially added fine sediment. Both additive and complex multiple-stressor effects were common. A complex three-way interaction affected EPT richness in the substratum, demonstrating the need to evaluate higher-order interactions for more than two stressors. Our results add further evidence that multiple-stressor interactions, notably increased salinity with other stressors, affect a variety of invertebrate taxa across different habitats of stream communities. The results have direct implications for water management as they highlight the need to re-evaluate defined salinity thresholds in the context of multiple-stressor interactions. [ABSTRACT FROM AUTHOR]

The quality of groundwater used for human consumption and irrigation in the Hetao Basin of Inner Mongolia, China is affected by elevated salinity as well as high arsenic (As) concentrations. However, the origin of high salinity and its potential impact on As mobility in the Basin remain unclear. This study explores both issues using stable isotopic compositions and Cl/Br ratios of groundwater as well as the major ions of both groundwater and leachable salts in aquifer sediments. Limited variations in δ 18 O and δ 2 H (− 11.13 to − 8.10, − 82.23 to − 65.67) with the wide range of Total Dissolved Solid (TDS, 351–6734 mg/L) suggest less contribution of direct evaporation to major salinity in groundwater. Deuterium excess shows that non-direct evaporation (capillary evaporation, transpiration) and mineral/evaporite dissolution contribute to > 60% salinity in groundwater with TDS > 1000 mg/L. Non-direct evaporation, like capillary evaporation and transpiration, is proposed as important processes contributing to groundwater salinity based on Cl/Br ratio and halite dissolution line. The chemical weathering of Ca, Mg minerals and evaporites (Na 2 SO 4 and CaSO 4 ) input salts into groundwater as well. This is evidenced by the fact that lacustrine environment and the arid climate prevails in Pleistocene period. Dissolution of sulfate salts not only promotes groundwater salinity but affects As mobilization. Due to the dissolution of sulfate salts and non-direct evaporation, groundwater SO 4 2 − prevails and its reduction may enhance As enrichment. The higher As concentrations (300–553 μg/L) are found at the stronger SO 4 2 − reduction stage, indicating that reduction of Fe oxide minerals possibly results from HS − produced by SO 4 2 − reduction. This would have a profound impact on As mobilization since sulfate is abundant in groundwater and sediments. The evolution of groundwater As and salinity in the future should be further studied in order to ensure sustainable utilization of water resource in this water scarce area. [ABSTRACT FROM AUTHOR]

Salinization is of major global concern due to its effect on stream biota, and ecosystem functions and services. In small streams, litter decomposition is a key ecosystem-level process driven by decomposers, mainly fungi (aquatic hyphomycetes), which link litter and invertebrates. Here we assessed the effects of an environmentally relevant range of salt additions (0, 2, 4, 8, 16 g L − 1 NaCl) on (1) fungal growth and species-specific reproductive output and (2) fungal mediated-decomposition of Quercus robur leaves. Growth rates of eight out of nine species of aquatic hyphomycetes were negatively affected by salinity at concentrations ≥ 4 g L − 1 . EC50s were species-specific and ≥ 7.80 g L − 1 . Distinct thresholds were observed for reproduction: only five species sporulated at 2 g L − 1 , and a single one ( Flagellospora curta ) sporulated at 4 and 8 g L − 1 NaCl. Based on these results, we evaluated if tolerant fungal assemblages, with increasingly fewer species (9, 5, 1), were able to maintain similar functional functions and processes at the different salt levels. No significant differences were found in oak mass loss or sporulation rates at 0 or 2 g L − 1 NaCl; a clear inhibition of both parameters was observed at the highest concentrations (i.e., 4 and 8 g L − 1 NaCl). Different dominance patterns in multi-species fungal assemblages may determine bottom-up impacts on the stream food webs through effects on detritivore feeding preferences. Specific growth rate, characterized by RNA concentration, was higher in the single species, at the highest salt-concentration, and lower in the 9-species assemblage. Respiration was almost 2-times higher in mixed assemblages without added salt. Under salt-contamination, trade-offs between growth and sporulation seem to guarantee high levels of fungal growth and decomposition, particularly in multi-species assemblages. In the presence of salt contamination, aquatic hyphomycetes, even at reduced diversity, remain important drivers of leaf decomposition and ensure organic matter recycling. [ABSTRACT FROM AUTHOR]

The La Paz aquifer system (Baja California Sur, Mexico) is under severe anthropogenic pressure because of high groundwater abstraction for urban supply (city of La Paz, around 222,000 inhabitants) and irrigated agriculture (1900 ha). In consequence, seawater has infiltrated the aquifer, forcing the abandonment of wells with increased salinity. The objective of this study was to assess seawater intrusion, understand the hydrogeochemical processes involved and estimate the contribution of seawater in the wells tested. The aquifer comprises mainly the alluvial filling and marine sediments of a tectonic graben oriented north-south, in contact with the Gulf of California. Groundwater samples were collected in 47 locations and analyzed for major constituents. A subset of 23 samples was analyzed for strontium and boron concentrations and isotopic signatures ( 87 Sr/ 86 Sr and δ 11 B). Results were interpreted using standard hydrochemical plots along with ad hoc plots including isotopic data. Seawater intrusion was confirmed by several hydrogeochemical indicators, such as the high salinity in areas of intense pumping or the Na + -Ca 2 + exchange occurring in sediments that were previously in chemical equilibrium with fresh water. However, seawater contribution was not sufficient to explain the observed concentrations and isotopic signatures of Sr and B. According to the isotopic data, desorption processes triggered by a modification in chemical equilibrium and an increase in ionic strength by seawater intrusion significantly increased Sr and probably B concentrations in groundwater. From a calculation of seawater contribution to the wells, it was estimated that one-third of the sampled abstraction wells were significantly affected by seawater intrusion, reaching concentrations that would limit their use for human supply or even irrigated agriculture. In addition, significant agricultural pollution (nitrates) was detected. Planned management of the aquifer and corrective measures are needed in order to invert the salinization process before it severely affects water resources in the long term. [ABSTRACT FROM AUTHOR]

Chronic and pulse increments of salinity can cause different consequences on the aquatic communities, and its effects are related to factors such as the magnitude, frequency and ionic composition, as well as on the baseline salt concentrations in the water. The aim of this study was to explore the responses of the biofilms from a nutrient-rich stream to both pulse and chronic additions of salt, along with their recovery after the stressor had been removed. For this purpose, a microcosm study was conducted exposing biofilms to water enriched with sodium chloride in two treatments (press and pulse), and comparing the changes in the biofilm with control microcosms without salt additions. The experiment lasted 72 h, and the variables measured included bacterial density, chlorophyll- a concentration, community composition, total carbohydrate content, oxygen consumption and the percentage of nuclear alterations in diatoms. Both treatments resulted in a decrease in the bacterial density of the biofilm and in oxygen consumption; the chronic treatment in particular also caused an increased percentage of nuclear abnormalities in the diatom assemblage. The biofilm recovered to control levels after the treatments had been discontinued for 72 h. We concluded that the biofilms can be altered significantly under both chronic and pulse additions of salt even after a short-term exposure, and that the community can recover if the stressor is withdrawn. [ABSTRACT FROM AUTHOR]

Climate change and sea level rise (SLR) are global impacts threatening the sustainability of coastal territories and valuable ecosystems such as deltas. The Ebro Delta is representative of the vulnerability of coastal areas to SLR. Rice cultivation is the main economic activity in the region. Rice fields occupy most of the delta ( ca. 65%) and are vulnerable to accelerated SLR and consequent increase in soil salinity, the most important physical factor affecting rice production. We developed a model to predict the impacts of SLR on soil salinity and rice production under different scenarios predicted by the Fifth Assessment Report of the Intergovernmental Panel on Climate Change by coupling data from Geographic Information Systems with Generalized Linear Models. Soil salinity data were measured in agricultural parcels and rice production from surveys among farmers. The correlation between observed and soil salinity predicted values was high and significant (Pearson's r = 0.72, P < 0.0001), thus supporting the predictive ability of the model. Soil salinity was directly related to distances to the river, to the delta inner border, and to the river old mouth, while clay presence, winter river flow and surface elevation were inversely related to it. Surface elevation was the most important variable in explaining soil salinity. Rice production was negatively influenced by soil salinity, thus the models predict a decrease from higher elevation zones close to the river to the shoreline. The model predicts a maximum reduction in normalized rice production index from 61.2% in 2010 to 33.8% by 2100 in the worst considered scenario (SLR = 1.8 m), with a decrease of profit up to 300 € per hectare. The model can be applied to other deltaic areas worldwide, and help rice farmers and stakeholders to identify the most vulnerable areas to SLR impacts. [ABSTRACT FROM AUTHOR]

Implying large residence times and complex water origins deep coastal aquifers are of particular interest as they are remarkable markers of climate, water use and land use changes. Over the last decades, the Metropolitan Region of Recife (Brazil) went through extensive environmental changes increasing the pressure on water resources and giving rise to numerous environmental consequences on the coastal groundwater systems. We analysed the groundwater of the deep aquifers Cabo and Beberibe that are increasingly exploited. The processes potentially affecting groundwater residence times and flow paths have been studied using a multi-tracer approach (CFCs, SF6, noble gases, 14C, 2H and 18O). The main findings of these investigations show that: (1) Groundwaters of the Cabo and Beberibe aquifers have long residence times and were recharged about 20,000 years ago. (2) Within these old groundwaters we can find palaeo-climate evidences from the last glacial period at the tropics with lower temperatures and dryer conditions than the present climate. (3) Recently, the natural slow dynamic of these groundwater systems was significantly affected by mixing processes with contaminated modern groundwater coming from the shallow unconfined Boa Viagem aquifer. (4) The large exploitation of these aquifers leads to a modification of the flow directions and causes the intrusion through palaeo-channels of saline water probably coming from the Capibaribe River and from the last transgression episodes. These observations indicate that the current exploitation of the Cabo and Beberibe aquifers is unsustainable regarding the long renewal times of these groundwater systems as well as their ongoing contamination and salinisation. The groundwater cycle being much slower than the human development rhythm, it is essential to integrate the magnitude and rapidity of anthropogenic impacts on this extremely slow cycle to the water management concepts. [ABSTRACT FROM AUTHOR]

The hydrochemistry of minor elements and traces such as bromide, lithium, strontium, uranium and selenium, together with the chemical analysis of major ions, has been used in the study of salinization process. This process occurs in a semi-confined aquifer that corresponds to a Pliocene–Pleistocene fluvial environment. The semi-confined aquifer is located in the littoral of the cities of Ensenada and Berisso, in the region of the middle Río de la Plata estuary, Argentina. Groundwater salinization was detected in the semi-confined aquifer in the coastal plain area, with salt contents that increase from the loess plain towards the river. The content of major ions that predominate in sea water (Cl − , Na + and Mg 2 + ), as well as the Cl − /Br − and U vs. Cl − ratios, demonstrates that such salinization is related to sea water, which shows no correspondence with estuary water. In the salinized area, Li, Sr and Se enrichments occur, and are used as tracers of the average time that a substance remains in solution in sea water in the aquifer. The study of such minor ions together with the geological evolution of the area made it possible to recognize that the salt water in the semi-confined aquifer corresponds to a palaeo-intrusion of sea water associated with the Pleistocene–Holocene ingressions caused by the climate changes occurring during the Quaternary. [ABSTRACT FROM AUTHOR]

Human activities have greatly increased the salt concentration of the world's rivers, and this might be amplified by water scarcity in the future. While the lethal effects of salinity have been documented for a wide variety of stream invertebrates, the sub-lethal effects (i.e. changes in biological condition without mortality) are not deeply understood yet. One important sub-lethal effect that has yet to be investigated is changes in predation efficiency, which could trigger cascade effects associated to the abundance of herbivorous invertebrates that control algae biomass. In this study we combined the use of biomarkers with community-level data in a stream mesocosm to evaluate the potential cascade effect of increased salinity on the trophic food web. Both predation and salt treatments had an effect on the aquatic invertebrate abundance, richness and community composition. The presence of predators had a clear cascade effect, it reduced herbivorous invertebrate abundance and richness leading to higher chlorophyll a concentrations. The salt treatment significantly reduced taxa richness, but only in the gravel bed. The predators were significantly stressed by salt addition, as shown by the different analyzed biomarkers. Concordantly, in the presence of predators, Tanytarsini registered higher abundances and chlorophyll a showed a lower concentration when salt was added. However, none of these changes was significant. Therefore, although salt addition significantly stressed Dina lineata , our results suggest that a longer exposure time is needed to fully capture cascading effects (e.g. a decrease in chlorophyll a due to a relaxation of predation on herbivorous invertebrates). We suggest that the potential cascade effects of salinization need to be evaluated when addressing the impacts of water scarcity (as caused by climate change and increasing water demand) on river ecosystems, since flow reductions will lead to higher salt concentrations. [ABSTRACT FROM AUTHOR]

Groundwater contributions and sources of salinity to Oso Bay in south Texas were investigated using multivariate statistical analysis of geochemical data and multitemporal electrical resistivity tomography surveys. Both analysis of geochemical data and subsurface imaging techniques identified two commonalities for the investigated system: 1) hypersaline water occurs near the groundwater/surface water interface during wet conditions creating reverse hydraulic gradients due to density effects. The development and downward movement of these fluids as continuous plumes deflect fresher groundwater discharge downward and laterally away from the surface; and 2) more pronounced upwelling of fresher groundwater occurs during drought periods when density inversions are more defined and are expected to overcome dispersion and diffusion processes and create sufficiently large-enough unstable gradients that induce density-difference convection. Salinity mass-balance models derived from time-difference resistivity tomograph and in-situ salinity data reaffirm these findings indicating that groundwater upwelling is more prominent during dry to wet conditions in 2013 (~ 545.5 m 3 /d) and is less pronounced during wet to dry conditions in 2012 (~ 262.7 m 3 /d) for the 224 m 2 area surveyed. Findings show that the highly saline nature of water in this area and changes in salinity regimes can be attributed to a combination of factors, namely: surface outflows, evapoconcentration, recirculation of hypersaline groundwaters, and potential trapped oil field brines. Increased drought conditions will likely exacerbate the rate at which salinity levels are increasing in bays and estuaries in semi-arid regions where both hypersaline groundwater discharge and high evaporation rates occur simultaneously. [ABSTRACT FROM AUTHOR]

This study determined long-term changes in fish assemblages, river discharge, salinity, and local precipitation, and examined hydrological drivers of biotic homogenization in a dryland river ecosystem, the Trans-Pecos region of the Rio Grande/Rio Bravo del Norte (USA/Mexico). Historical (1977–1989) and current (2010–2011) fish assemblages were analyzed by rarefaction analysis (species richness), nonmetric multidimensional scaling (composition/variability), multiresponse permutation procedures (composition), and paired t -test (variability). Trends in hydrological conditions (1970s–2010s) were examined by Kendall tau and quantile regression, and associations between streamflow and specific conductance (salinity) by generalized linear models. Since the 1970s, species richness and variability of fish assemblages decreased in the Rio Grande below the confluence with the Rio Conchos (Mexico), a major tributary, but not above it. There was increased representation of lower-flow/higher-salinity tolerant species, thus making fish communities below the confluence taxonomically and functionally more homogeneous to those above it. Unlike findings elsewhere, this biotic homogenization was due primarily to changes in the relative abundances of native species. While Rio Conchos discharge was > 2-fold higher than Rio Grande discharge above their confluence, Rio Conchos discharge decreased during the study period causing Rio Grande discharge below the confluence to also decrease. Rio Conchos salinity is lower than Rio Grande salinity above their confluence and, as Rio Conchos discharge decreased, it caused Rio Grande salinity below the confluence to increase (reduced dilution). Trends in discharge did not correspond to trends in precipitation except at extreme-high (90th quantile) levels. In conclusion, decreasing discharge from the Rio Conchos has led to decreasing flow and increasing salinity in the Rio Grande below the confluence. This spatially uneven desertification and salinization of the Rio Grande has in turn led to a region-wide homogenization of hydrological conditions and of taxonomic and functional attributes of fish assemblages. [ABSTRACT FROM AUTHOR]

Abstract: Salinization of rivers resulting from industrial discharge or road-deicing can adversely affect macroinvertebrates. Trait-based approaches are a promising tool in ecological monitoring and may perform better than taxonomy-based approaches. However only little is known how and which biological traits are affected by salinization. We investigated the effects of anthropogenic salinization on macroinvertebrate communities and biological traits in the Werra River, Germany and compared the taxonomic and trait response. We found a change in macroinvertebrate community and trait composition. Communities at saline sites were characterized by the three exotic species Gammarus tigrinus, Apocorophium lacustre and Potamopyrgus antipodarum. The frequencies of trait modalities long life cycle duration, respiration by gill, ovoviviparity, shredder and multivoltinism were statistically significantly increased at saline sites. The trait-based ordination resulted in a higher explained variance than the taxonomy-based ordination, indicating a better performance of the trait-based approach, resulting in a better discrimination between saline and non-saline sites. Our results are in general agreement with other studies from Europe, indicating a trait convergence for saline streams, being dominated by the traits ovoviviparity and multivoltinism. Three further traits (respiration by gill, life cycle duration and shredders) responded strongly to salinization, but this may primarily be attributed to the dominance of a single invasive species, G. tigrinus, at the saline sites in the Werra River. [Copyright &y& Elsevier]

Abstract: Salinization poses a threat to many inland aquatic ecosystems, especially in areas where natural processes are compounded by anthropogenic salinization. Though physiological survival can be a challenge for stenohaline freshwater fishes facing increasing salinity, it is important to note that essential and complex activities such as reproduction may be affected well below physiological tolerance limits. Here, we exposed fathead minnows (Pimephales promelas) to four levels of salinity in order to assess any impacts on several egg production and behavioral endpoints. We found significant reductions in total eggs produced, percent fertilization, number of spawning days, clutch size, total time males spent in the nest, and duration of nest care events. Our data demonstrate that salinization can have negative effects on critical reproductive endpoints. [Copyright &y& Elsevier]

Abstract: Land salinization and desalinization are complex processes affected by both biophysical and human-induced driving factors. Conventional approaches of land salinization assessment and simulation are either too time consuming or focus only on biophysical factors. The cellular automaton (CA)-Markov model, when coupled with spatial pattern analysis, is well suited for regional assessments and simulations of salt-affected landscapes since both biophysical and socioeconomic data can be efficiently incorporated into a geographic information system framework. Our hypothesis set forth that the CA-Markov model can serve as an alternative tool for regional assessment and simulation of land salinization or desalinization. Our results suggest that the CA-Markov model, when incorporating biophysical and human-induced factors, performs better than the model which did not account for these factors when simulating the salt-affected landscape of the Yinchuan Plain (China) in 2009. In general, the CA-Markov model is best suited for short-term simulations and the performance of the CA-Markov model is largely determined by the availability of high-quality, high-resolution socioeconomic data. The coupling of the CA-Markov model with spatial pattern analysis provides an improved understanding of spatial and temporal variations of salt-affected landscape changes and an option to test different soil management scenarios for salinity management. [Copyright &y& Elsevier]

Abstract: Salinization of freshwater ecosystems is a global problem affecting many regions worldwide and can co-occur with pesticides in agricultural regions. Given that both stressors are potent to affect macroinvertebrate communities, their effects could interact. We investigated the effects of salinity and pesticides at 24 sites in an agricultural region of southern Victoria, South-East Australia. We used distance-based redundancy analysis to determine the influence of pesticides, salinity and other environmental variables on the composition of macroinvertebrate communities. Salinity and pesticide toxicity had a statistically significant effect on communities as had the substrate composition and the percentage of pool and riffle sections in the sampled stream reaches. We did not find evidence for interactive effects between salinity and pesticides, i.e. the effect of one of these variables did not depend on the level of the other. Nevertheless, our results show that salinization and exposure to pesticides can be major factors for the structure of macroinvertebrate communities in agricultural regions. Pesticide toxicity acted on a lower taxonomic level compared to salinity, potentially indicating evolutionary adaptation to salinity stress. [Copyright &y& Elsevier]

Abstract: Ecological risk assessments mostly consider measures of community composition (structure) across large spatial scales. These assessments, using species sensitivity distributions (SSDs) or the relative species retention (RSR), may not be protective of ecosystem functions and services at smaller spatial scales. Here we examine how changes in biological traits, as proxy for ecosystem functions/services, at a fine spatial scale relate to larger scale assessment of structure. We use functional traits of stream insect species in south-east Australia in two habitats (riffle and edge/pool). We find that the protection of community structure in terms of 95% of species over multiple sites against adverse effects of salinity (as electrical conductivity) and turbidity will mostly, but not always, protect traits at smaller scales. Considering different combinations of trait modalities, contaminants and habitat, a mean of 17.5% (range 0%–36.8) of cases would result in under-protection of trait modalities despite protecting species composition (in terms of Jaccard''s Index). This under-protection of trait modalities is only because of the different spatial scales that community structure and the traits were considered. We recommend that where the protection of biological traits, ecosystem functions or ecosystem services from stressors is a management goal, protective targets should not be solely set using measures of community structure such as SSDs or RSR. To protect both structural and functional attributes separate risk assessments should be done. [Copyright &y& Elsevier]