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Environmental filtering and dispersal limitation are important processes within the metacommunity concept. Non‐random species turnover occurs in places where environmental filtering plays the key role in determining local community structure, whereas dispersal limitation causes nested patterns of species assemblages organized by non‐random colonization processes. However, factors that modify the relative importance of these processes remain unclear for many ecosystems. We tested whether salinity gradient affect the relative importance of environmental filtering and dispersal limitation for structuring epifaunal and infaunal communities in three lagoons in Hokkaido, Japan, that have different salinity gradients. Specifically, we compared patterns of species diversity and similarity of eelgrass‐associated invertebrate assemblages across space. Beta diversity (i.e., species turnover among different sites in each lagoon) was highest in Akkeshi, the lagoon with the salinity gradients. Variation partitioning of similarity components showed that spatial variation in the community assemblage pattern was mostly explained by environmental filtering in Akkeshi, but that it was explained more by species dispersal patterns and the difference in eelgrass biomass and shoot density in Notoro and Saroma, the lagoons without clear salinity gradient. Redundancy analysis showed that spatial variation in community structure was related to salinity and eelgrass biomass in Akkeshi, and to eelgrass aboveground biomass in Notoro and Saroma. Our findings highlight the effects of environmental heterogeneity on beta diversity and community structure and indicate that environmental gradients can be a key factor causing a shift in the relative importance of different metacommunity processes and the role of the foundation species in provisioning habitat. [ABSTRACT FROM AUTHOR]

Questions: What are the plant communities and vegetation pattern on shorelines of a hypersaline desiccating lake and which environmental factors influence the zonation pattern of these communities? How is the species richness along salt and moisture gradients? Which plant communities and rare species are threatened by the impact of lake shrinkage? Which advice can be offered for the management and restoration of the area? Study area: Lake Urmia, NW Iran, one of the world's largest saltwater lakes. Methods: We established 14 transects with 174 relevés in different parts of the lake and collected soil samples. TWINSPAN was used for vegetation classification and NMDS for ordination. Results: We distinguished 27 plant communities and described as new the associations Salicornio iranicae-Bolboschoenetum affinis, Tamaricetum octandrae, Salicornietum iranicae, Climacopteretum crassae, Suaedo altissimae-Climacopteretum crassae and the Atriplici leucocladae-Caroxyletum dendroidis. We present an overview of the syntaxa and illustrate typical zonation patterns of the lake's salt marsh vegetation under current conditions of desiccation. Conclusions: The vegetation pattern and vegetation dynamics of the area is seriously affected by the hydrological changes around Lake Urmia. Fragmentation of wetland plant communities due to water shortage, increasing disturbance and invasion of ruderal species affect the floristic composition of the lakeside. Increasing soil salinity and decreasing moisture lead to area loss or even disappearance of certain plant communities. Plant communities with C4 annuals or pioneer ruderal species are developing or spreading in sites with low soil salinity or on sandy soils. We strongly recommend vegetation monitoring using permanent plots to improve the predictability of succession trends. Groundwater exploitation, unsustainable use of water resources in the catchment area, any further disturbance in the lakeside area including grazing and artificial plantation activities need to be prohibited. [ABSTRACT FROM AUTHOR]

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Many clades that span the marine–freshwater boundary are disproportionately more diverse in the younger, shorter lived, and scarcer freshwater environments than they are in the marine realm. This disparity is thought to be related to differences in diversification rates between marine and freshwater lineages. However, marine and freshwaters are not ecologically homogeneous, so the study of diversification across the salinity divide should also account for other potentially interacting variables. In diatoms, freshwater and substrate‐associated (benthic) lineages are several‐fold more diverse than their marine and suspended (planktonic) counterparts. These imbalances provide an excellent system to understand whether these variables interact with diversification. Using multistate hidden‐state speciation and extinction models, we found that freshwater lineages diversify faster than marine lineages regardless of whether they inhabit the plankton or the benthos. Freshwater lineages also had higher turnover rates (speciation + extinction), suggesting that habitat transitions impact speciation and extinction rates jointly. The plankton–benthos contrast was also consistent with state‐dependent diversification, but with modest differences in diversification and turnover rates. Asymmetric and bidirectional transitions rejected hypotheses about the plankton and freshwaters as absorbing, inescapable habitats. Our results further suggest that the high turnover rate of freshwater diatoms is related to high turnover of freshwater systems themselves. [ABSTRACT FROM AUTHOR]

We have studied iron (Fe)-isotope signals in particles (> 0.22 µm) and the dissolved phase (< 0.22 µm) in two subarctic, boreal rivers, their estuaries and the adjacent sea in northern Sweden. Both rivers, the Råne and the Kalix, are enriched in Fe and organic carbon (up to 29 µmol/L and up to 730 µmol/L, respectively). Observed changes in the particulate and dissolved phase during spring flood in May suggest different sources of Fe to the rivers during different seasons. While particles show a positive Fe-isotope signal during winter, during spring flood, the values are negative. Increased discharge due to snowmelt in the boreal region is most times accompanied by flushing of the organic-rich sub-surface layers. These upper podzol soil layers have been shown to be a source for Fe-organic carbon aggregates with a negative Fe-isotope signal. During winter, the rivers are mostly fed by deep groundwater, where Fe occurs as Fe(oxy)hydroxides, with a positive Fe-isotope signal. Flocculation during initial estuarine mixing does not change the Fe-isotope compositions of the two phases. Data indicate that the two groups of Fe aggregates flocculate diversely in the estuaries due to differences in their surface structure. Within the open sea, the particulate phase showed heavier δ56Fe values than in the estuaries. Our data indicate the flocculation of the negative Fe-isotope signal in a low salinity environment, due to changes in the ionic strength and further the increase of pH. [ABSTRACT FROM AUTHOR]

Anthropogenic coastal activities and natural stressors aggravate degradation of small coastal patches of mangroves, which in turn destroy local resilience of mangrove forests in the Indian Sundarbans, the continuous mangrove habitat that spans between India and Bangladesh. We conducted an analytical survey across 19 shoreline mangrove fringes spanning the Sundarbans, including both healthy and disturbed forests, and evaluated ninety-five 60-cm composite sediment cores across a degradation and salinity gradient from ~ 4 to ~ 12 ppt. Increased salinity and anoxicity greatly inhibited nutrient cycling and release by microbial decomposers, subsequently resulting in nutrient-poor soil as a condition of degradation. Nutrient limitation, salinity rise, anoxicity increase, and sulfide build-up negatively controlled forest structure causing declines of forest coverage from ~ 98 to ~ 11%. In addition, the tide-dominated salinity gradient controlling species zonation was disrupted in disturbed forests with salinity-sensitive species gradually disappearing. An obvious change in species distribution is anticipated while salt-sensitive Heritiera fomes, Xylocarpus spp., and Phoenix paludosa failed to cope with increased salinity, evident by their absence from many forests. Excoecaria agallocha and Avicennia spp. acclimated well and expanded freely into degraded forests across the Sundarbans. Overall, our study strongly establishes salinity intrusion as primary mechanism for mangrove degradation. [ABSTRACT FROM AUTHOR]

Pressure retarded osmosis has been proposed for power generation from a salinity gradient resource. The process has been promoted as a promising technology for power generation from renewable resources, but most of the experimental work has been done on a laboratory size units. To date, pressure retarded osmosis optimization and operation is based on parametric studies performed on laboratory scale units, which leaves a gap in our understanding of the process behaviour in a full-scale modular system. A computer model has been developed to predict the process performance. Process modelling was performed on a full-scale membrane module and impact of key operating parameters such as hydraulic feed pressure and feed and draw solution rates were evaluated. Results showed that the optimum fraction of feed/draw solution in a mixture is less than what has been earlier proposed ratio of 50% and it is entirely dependent on the salinity gradient resource concentration. Furthermore, the optimized pressure retarded osmosis process requires a hydraulic pressure less than that in the normal (unoptimized) process. The results here demonstrate that the energy output from the optimized pressure regarded osmosis process is up to 54% higher than that in the normal (unoptimized) process. • A full-scale pressure retarded osmosis module was optimized using a computer model. • Optimum power generation was achieved at P < Δ π / 2. • Fraction of feed solution in mixture depends on concentration salinity gradient resource. • Optimized operating parameters were dependent on salinity gradient and modules in pressure vessel. • Optimization resulted in up to 54% increase in the performance of pressure retarded osmosis. [ABSTRACT FROM AUTHOR]

A hybrid energy utilization system, integrating dish solar SE and salinity gradient based energy storage system, was proposed to realize clean and stable power generation from solar energy. Power output of dish solar Stirling engine was utilized to pressurize the salt water into RO (reverse osmosis) for storing the energy in the form of concentration gradient, and stable power output was generated from the concentration gradient via PRO (pressure retarded osmosis). The system performance was systematically investigated under the ideal and non-ideal models, to evaluate the theoretical and realistic energy conversion ability. Results indicate that higher initial concentration presents better energy efficiency, for it has slower decreasing slope of transmembrane water flux in PRO. Optimal RO and PRO operating pressure exist for achieving the maximal energy efficiency. The ideal maximal overall energy conversion efficiency reaches 9.23% within the research scope. With the detrimental factors being considered, the maximal overall efficiency of 5.07% is achieved. • High initial concentration of salt solution is beneficial for better performance. • Improvement of optical and regenerative performance achieves better efficiency. • Concentration polarization reduces the driving force then limits energy efficiency. • Maximal ideal efficiency of 9.23% and non-ideal efficiency of 5.07% are predicted. [ABSTRACT FROM AUTHOR]

Reverse Electrodialysis (RED) extracts electrical energy from the salinity difference between two solutions using selective ion exchange membranes. In RED, conditions yielding a large net power density (NPD) are generally desired, due to the still large cost of the membranes. NPD depends on a large number of physical and geometric parameters. Some of these, for example the inlet concentrations of concentrate and diluate, can be regarded as "scenario" variables, imposed by external constraints (e.g., availability) or chosen by different criteria than NPD maximization. Others, namely the thicknesses H CONC , H DIL and the velocities U CONC , U DIL in the concentrate and diluate channels, can be regarded as free design parameters and can be chosen so as to maximize NPD. In the present study, a simplified model of a RED stack was coupled with an optimization algorithm in order to determine the conditions of maximum NPD in the space of the variables H CONC , H DIL , U CONC , U DIL for different sets of "scenario" variables. The study shows that an optimal choice of the free design parameters for any given scenario, as opposed to the adoption of standard fixed values for the same parameters, may provide significant improvements in NPD. • A simplified model of Reverse Electrodialysis is used to predict Net Power Density. • Quantities affecting NPD are classified into optimization and scenario variables. • The model is coupled with a gradient-ascent optimization algorithm. • Conditions of maximum NPD in the space of optimization variables are determined. • Optimum working conditions change significantly with the scenario variables. [ABSTRACT FROM AUTHOR]

The high number of freshwater species at low salinity and the correspondingly high number of marine species at high salinity enveloping a conspicuous richness minimum at intermediate salinities has shaped our basic understanding of biodiversity along a coastal salinity gradient for almost 80 years. Visualized as the Remane curve, this iconic concept was originally based on sedentary macroinvertebrates in the Baltic Sea. To what extent the concept can be generalized, particularly to free-drifting organisms, is currently debated. Here we use approximately 16,000 phytoplankton samples from two large coastal ecosystems—the Baltic Sea and Chesapeake Bay—to analyze the relationship between salinity and phytoplankton species richness. Alpha diversity showed a consistent variation along the salinity gradient, with a minimum at mesohaline salinities of around 7–9. Rarefied species pools at narrow salinity intervals also showed reduced diversity at intermediate salinities, surrounded by high richness toward both ends of the gradient. The cumulative likelihood of species presence validated the minimum at intermediate salinities. Community composition changed abruptly at the α diversity minimum in the Baltic Sea, while it changed gradually along the salinity gradient in Chesapeake Bay. We conclude that the Remane concept is in every respect valid for phytoplankton. [ABSTRACT FROM AUTHOR]

Evaporation measurements over lakes are limited by physical constraints, logistics and financial demands. Thermal satellite images and land-based meteorology can be combined to derive evaporation rates from large lakes. The Dead Sea is a large hypersaline lake that can be used to examine the utility of thermal satellite images along with land-based meteorology to assess evaporation rates. Sea surface tmperature was retrieved for a 12-month period using band 10 onboard Landsat 8. Monthly SST was combined with nearby land-based meteorology to estimate evaporation from the sea surface using a mass transfer method and two variations of the Penman procedure. The Mass transfer gave an annual evaporation rate of 1005 mm whereas the Penman and the Priestley-Taylor methods gave 1308 and 1140 mm, respectively. These values are commensurate with extensive field measurement and theoretically derived evaporation values. Analysis shows a tradeoff between wind speed increase over the smoother lake surface and the drop in the saturation water vapor pressure deficit across the lake-atmosphere boundary. Wind speed has profound effects on evaporation differences during the warm season but diminish appreciably in the cold season when the vapor pressure deficit is small. Thermal images were able to resolve the presence of large pockets of cool water over the Dead Sea resulting from freshwater input. Modifications to evaporation caused by freshwater input to a hypersaline lake are investigated from a thermodynamic perspective. The alteration to evaporation depends on the simultaneous departure of surface temperature and the activity of the brine. [ABSTRACT FROM AUTHOR]

Recent studies have shown that anguillid eel populations in habitats spanning the marine–freshwater ecotone can display extreme plasticity in the range of catadromy expressed by individual fish. The apparent use of marine and freshwater habitats by the European eel Anguilla anguilla was examined by analysing the strontium (Sr) and calcium (Ca) concentrations in otoliths of eels collected from a tidal Atlantic lake system in Ireland. Variations of the Sr:Ca ratio in the otoliths indicated that a variety of environmental salinities had been experienced in the habitats that were occupied during the growth phase of these individuals in the tidal Atlantic lake system. The otolith microchemistry of these eels indicated that most of the eels had entered each salinity environment (freshwater (FW); brackish water (BW); marine-dominated water (MW) and full seawater (SW)) from fresh water to full seawater just after recruitment and had stayed in each environment until maturation without movement to other salinity environments. Only 2 of 93 (2%) eels had shifted their habitat once in their lives. This result suggests that each individual might have an environmental habitat preference, although each individual could move along a short (<2 km) salinity gradient. [ABSTRACT FROM AUTHOR]

We numerically investigate renewable power generation using reverse electrodialysis (RED), by harnessing salinity gradient energy of two constant inflows of salt solutions of different concentrations via a charged nanochannel. We compute and elucidate coupled flow, ion flux, electrical potential, and resultant electric outputs in the nanofluidic RED battery. The results of power output density and ion transfer across the nanochannel strongly depend on nanochannel height, whereas open-circuit voltage, short circuit current, and nanochannel resistance on the length. Energy conversion efficiency, on the other hand, display a non-linear dependence on both dimensions. More importantly, the results of nanochannel resistance and power output density reveal a power-law dependence on the concentration difference, quantitatively shedding light on the optimal RED flow designs. For the first time, our simulations at different inflow velocities show that the output power and conversion efficiency remain nearly constant at low speed but increase by ≈ 2.3 times and 10 % , respectively, at high rate when advection effect becomes significant comparing to diffusion. These results quantitatively show profound effects of nanochannel dimensions, concentration difference, and inflow velocity on the renewable electrical energy outputs, offering optimal designs for maximizing reverse electrodialysis power. [ABSTRACT FROM AUTHOR]

Abstract The Mandovi Estuary, located along the tropical west coast of India, transforms from being a freshwater-dominated body during the monsoon season to a tide-dominated system during post-monsoon season, with a salinity gradient developing from the freshwater end to the estuarine mouth (∼0–33). The sulphate reduction (SR) rates were measured by the 35SO 4 2− radiotracer method in the estuarine sediments at three different sites. The porewater H 2 S concentrations were negligible at all the sites and SR rates did not exhibit any clear trend along the salinity gradient. Pyrite content (3.45–12.9 mg g−1) was the highest at the marine end and decreased towards the freshwater end. The SR rate (15.71 mmol m−2 d−1) and total Fe content (14–20%) were highest in sediments of mid-estuary with intermediate salinity and variable porosity. Organic carbon (OC) mineralization rate through SR also did not show any trend along the salinity gradient with intermediate salinity site having higher values (31.83 mmol C m2 d−1) compared to other sites (3.12–8.62 mmol C m2 d−1). SR was responsible for ∼8–50% of sedimentary OC mineralization implying that OC mineralization through Fe (III) and Mn (IV) reduction possibly played major role owing to their high concentrations in the estuarine sediments. [ABSTRACT FROM AUTHOR]

Algae (and their extracts) are increasingly important for pharmaceutical applications due to the diversity of useful compounds they contain. The genus Fucus contains one of the most studied species, Fucus vesiculosus. The species F. ceranoides differs from the others of the genus by presenting longitudinal air-vesicles and a capacity to survive at low salinities. It is an alga that inhabits the Mondego River estuary (Portugal), at the southern limit of its distribution, and can serve as a role model to understand the effect of a salt gradient on the production of bioactive compounds. We assessed the phenolic content and antioxidant activity of different F. ceranoides extracts (e.g. methanolic, aqueous and polysaccharide) prepared from samples harvested from two different zones to evaluate if the adaptation of F. ceranoides to different salinity levels influenced its chemical composition. The antioxidant activity of the extracts was determined using 1,2-diphenyl-picrylhydrazyl (DPPH) and 2.2-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radicals. These assays demonstrated that the methanolic extract of lyophilized F. ceranoides that grew at low salinities was the most bioactive, i.e. DPPH (IC50=50.39 µg/mL) and ABTS (TEAC=2.42). The total phenolic content (Folin-Ciocalteu method) and the methanolic extract of the lyophilized F. ceranoides collected from a low salinity habitat exhibited the highest phenolic content (PGE=49.48 µg/mg of lyophilized extract) amongst those sampled. Thin layer chromatography (TLC) and Fourier transform infrared spectroscopy (FTIR) were used for the identification of compounds in the extracts. This characterization allowed confirmation that the various extracts contained almost the same compounds but with notable quantitative differences. Based on these results, we conclude that there were differences in the quantity of the compounds due to the effect of salinity. The drying methods used were also found to have influenced the quality of the extracted compounds. [ABSTRACT FROM AUTHOR]

Abstract Few organisms can live in harsh transitional waters due to highly variable and rapid changeable physicochemical conditions. Fortunately, connecting the community structure of such fauna to specific environmental parameters can be used in tracing past and recent environmental changes. Herein, we analyzed the benthic communities in the Manzala lagoon (Nile–Delta), a region very impacted by the construction of the High–Dam at Aswan, along the inshore-offshore gradient. Approx. 3000 specimens belonging to 31 species sampled in 54 sampling sites were identified. The environmental and biological data were subjected to multivariate data analyses. Hierarchical clustering and non–metric multidimensional scaling identified three biotopes along a gradient of water salinity and sediment grain–size. The epifaunal/infaunal ratio was negatively correlated with salinity (R2 = – 0.72, p < 0.01). The low salinity–stations with a high content of silt and clay sediments were dominated by deposit-feeders, opportunistic gastropods. In contrast, the suspension–feeding bivalves dominated the more saline water and sand-sized sediments (R = 0.83, p < 0.001) near the Mediterranean outlets. The general low diversity and high dominance in the lagoon indicate high environmental stress and biodiversity loss as the background freshwater species have declined and only a few opportunistic taxa have flourished. In addition, a specific salinity-range was estimated at both species and community level. The results confirm that salinity and substrate type are major determinants for the structure of the molluscan community (feeding habit and life–mode) in marginal marine environments. Consequently, the feeding habit and life–mode of the mollusks, which have a continuous and very complete fossil record, can be used as a robust indicator for paleosalinity and paleo-hydrodynamics. Graphical abstract Image 1 Highlights • The biotic/abiotic interactions in the Nile-largest lagoon were quantitatively assessed. • Molluscan feeding habit and life-mode can predict salinity and sediment grain-size and vice versa. • Epifaunal/infaunal ratio was negatively correlated with salinity and sediment grain-size. • In contrast, suspension/deposit feeder ratio was positively correlated. • A specific salinity range was estimated for every species and faunal association. [ABSTRACT FROM AUTHOR]

Salinity is a significant factor for structuring microbial communities, but little is known for aquatic fungi, particularly in the pelagic zone of brackish ecosystems. In this study, we explored the diversity and composition of fungal communities following a progressive salinity decline (from 34 to 3 PSU) along three transects of ca. 2000 km in the Baltic Sea, the world's largest estuary. Based on 18S rRNA gene sequence analysis, we detected clear changes in fungal community composition along the salinity gradient and found significant differences in composition of fungal communities established above and below a critical value of 8 PSU. At salinities below this threshold, fungal communities resembled those from freshwater environments, with a greater abundance of Chytridiomycota, particularly of the orders Rhizophydiales, Lobulomycetales, and Gromochytriales. At salinities above 8 PSU, communities were more similar to those from marine environments and, depending on the season, were dominated by a strain of the LKM11 group (Cryptomycota) or by members of Ascomycota and Basidiomycota. Our results highlight salinity as an important environmental driver also for pelagic fungi, and thus should be taken into account to better understand fungal diversity and ecological function in the aquatic realm. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Inlet flow rates and loads are controlled in real-time for maximum power. • Increase in power is demonstrated relative to default conditions used in literature. • The controller is effective for variety of membranes systems and applications. • The controller provides real-time mitigation of non-ideal dynamics such as fouling. • Higher specific energy values can be achieved at the expense of power. Abstract A feedback control system is developed for coordinated control of feed rates, draw rates, and loading on an osmotic power system. Carefully balancing these parameters in order to reduce the overall effect of various non-ideal phenomena has been previously discussed in the literature, however this is the first-ever system developed for automated, real-time, simultaneous control of all three of these operating parameters. The ability of the system to achieve maximum net power output is demonstrated for various commercial membranes, in response to fouling, and for both stand-alone pressure retarded osmosis as well as for combined reverse osmosis and pressure retarded osmosis application. Results provide insight into best operating conditions which can be helpful for rule of thumb design, and also clearly show that best conditions are case specific, and that osmotic energy conversion systems ultimately require feedback control for efficient performance especially in response to dynamic phenomena such as membrane fouling. The tradeoff between net power and energy is also demonstrated, and a maximum energy controller is also described. [ABSTRACT FROM AUTHOR]

Understanding whether and how different habitat features affect patterns of life-history variation is an intriguing aim in evolutionary ecology. We tested how a suite of biotic and abiotic factors simultaneously affect life-history patterns in six populations of the livebearing fish Poecilia vivipara inhabiting coastal lagoons in southeastern Brazil, varying greatly in salinity and fish communities. We sampled potential competitors (cyprinodontiform fishes) and piscivores, and we measured nine limnological variables in the wet and dry seasons during 2 years. We found that size at maturity and offspring size were strongly and negatively influenced by the abundance of piscivores, and that reproductive allocation was strongly and positively influenced by variations in resource abundance and temperature among seasons. Effects of salinity on size at maturity, female reproductive investment and offspring size were indirect, via piscivore abundance, highlighting the potential for indirect effects that can be detected only by analysing multiple habitat features simultaneously. This suggests caution in interpreting associations between life histories and salinity in wild populations. Observed patterns generally matched theoretical predictions and prior empirical work, but some predictions were not met. Our results suggest that life histories result from a partly predictable complex combination of direct and indirect effects of habitat features, which can sometimes act antagonistically. [ABSTRACT FROM AUTHOR]

"Candidatus Methylomirabilis oxyfera" (M. oxyfera) bacteria has attracted much attention recently since it plays an important role in performing methane oxidation. Most studies on M. oxyfera-like bacteria have been carried out in freshwater ecosystems, however it remains unclear about its distribution along the salinity gradient of estuarine and coastal environments. In this study, we used molecular analyses to reveal the community, diversity and abundance of M. oxyfera-like bacteria in the Yangtze estuarine and coastal sediments. Clone library analyses confirmed the wide distributions of M. oxyfera-like bacterial 16S rRNA and pmoA genes in the study area. The M. oxyfera-like bacterial 16S rRNA gene sequences were grouped into eleven separate OTUs, which were assigned to groups A and B of M. oxyfera-like bacteria. Most sequences (89.4-97.6% of total sequences) of M. oxyfera-like bacterial 16S rRNA gene were affiliated with group B, while only few clone sequences (2.4-10.6% of total sequences) were affiliated with group A. The retrieved M. oxyfera-like bacterial pmoA gene sequences were grouped into five distinct clusters. Bray-Curtis dissimilarity of M. oxyfera-like bacterial 16S rRNA and pmoA genes differed greatly among the low, middle and high salinity sites. M. oxyfera-like bacterial 16S rRNA and pmoA abundances were mainly recovered from the oligohaline sites rather than from the saline sites. In addition, the large differences in 16S rRNA and pmoA gene sequences between estuarine and land freshwater environments suggested that salinity could be able to affect the community distribution of M. oxyfera-like bacteria. Also, sediment nitrate/ammonium played an important role in affecting the M. oxyfera-like bacteria. Overall, these results indicate that salinity has a great influence on M. oxyfera-like bacteria community in estuarine environments. [ABSTRACT FROM AUTHOR]

Highlights • An assessment of salinity gradient stability of an industrial solar pond was performed. • Two methodologies based on the stratification principle were adapted and used. • The boundaries of the salinity gradient appeared as the main source of instability. • The methodology based on coefficients of expansion is useful to control the solar pond. Abstract In this study, an assessment of salinity gradient stability of an industrial solar pond during two operation seasons (2014 and 2105) is presented. An industrial solar pond was constructed to supply a low-temperature heat (up to 60 °C) to achieve the temperature requirements of the flotation stage in a mineral processing plant (Solvay Minerales in Granada (Spain)). Along the first season, the salinity gradient was considered technically destroyed in April 2015 as the height to the upper convective zone increases from 0.3 m in July 2014 to 0.8 m. Two different methodologies based on the stratification principle were adapted and used in order to evaluate the salinity gradient stability. The boundaries of the salinity gradient appeared as the main source of instability. In the upper zone it is associated with the environmental parameters (e.g., rain and wind) that affect the upper convective zone and the upper layers of the non-convective zone that subsequently transmit the instability to the lower layers. In the bottom zone it is caused by operation parameters, such as the heat extraction or the addition of salt. Both methodologies provided similar predictive capability of stability results. However, the results provided by the stability analysis using the thermal and salinity expansion coefficients are a more useful tool in the control of the salinity gradient for solar pond technology. [ABSTRACT FROM AUTHOR]

Abstract To examine how the rates and pathways of anaerobic organic carbon mineralization (AOCM) of tidal freshwater wetlands change with low-level increases in salinity, we investigated the rates and controls of microbial iron and sulfate reduction, methane production, and total AOCM in tidal wetlands along a freshwater to oligohaline (0.1–3.3 ppt) gradient in the Min River Estuary in southeastern China. Porewater chloride was found to be strongly correlated with total organic carbon (TOC), carbon to nitrogen (C:N) ratios, and porewater geochemistry (sulfate, pH, ammonium, and dissolved methane levels). Furthermore, a higher plant biomass, larger iron oxides pool, and lower sulfide levels were observed in the oligohaline wetlands. The contribution of microbial sulfate reduction to AOCM increased from 16% to 67%. In contrast, the contribution of microbial iron reduction and methane production declined from 52% to 22% and 12% to 2%, respectively, along the increasing salinity gradient. No consistent changes were found in the total AOCM rates. The rates of methane production were primarily controlled by the C:N ratios and concentrations of porewater ammonium and amorphous iron oxides, while the microbial sulfate and iron reduction rates were mainly controlled by belowground biomass, water content, and concentrations of porewater chloride and sulfate. Our findings provide insight into the potential consequences of modest saltwater intrusion; these may not alter the rates of AOCM in the Min River Estuary, but could change the dominant AOCM pathway from microbial iron reduction to sulfate reduction and accelerate sulfidic effects in this historically freshwater wetland ecosystem. Graphical abstract Unlabelled Image Highlights • The rates of total anaerobic organic matter mineralization are tolerant to a low-level increase in salinity. • The anaerobic organic matter mineralization pathway is sensitive to minor salinity changes. • Salinity are responsible for the decline in microbial iron reduction, suppression of methane production, and enhancement of sulfate reduction. [ABSTRACT FROM AUTHOR]

Abstract Salinity gradient energy is a kind of the Gibbs free energy of mixing, and it is a clean, sustainable, and renewable energy source which is projected of the capacity to generate about 2.6 TW of electricity from all rivers flowing into the sea. However, the current technology to convert the salinity gradient energy to electricity suffers from low conversion efficiency, which results in a low output power density. In this work, we develop a new type of the graphene reverse electrodialysis (GRED) device which can efficiently convert the salinity gradient energy into electricity. The GRED device is fabricated based on a simple and straightforward ion irradiation perforation approach, and it is demonstrated to exhibit a record-high energy conversion efficiency of 39% and a record-high output power density of 27 W/m2 at room temperature, manifesting its high promise for the clean energy harvesting from the salinity gradient. Theoretical simulations based on molecular dynamics and continuum theory further show that the charge at the pore edge is of crucial importance for achieving high ion selectivity. In light of this finding, we show that the output power density of GRED can be further boosted to 126 W/m2 if it is operated at a slightly elevated temperature of 47 °C, for which the heating could be from industrial thermal waste in a practical sense. Graphical abstract A new-type graphene reverse electrodialysis (GRED) device is fabricated to convert the salinity gradient energy into electricity, and the GRED device shows a high output power density up to 126 W/m 2 and a high energy conversion efficiency of 39%. fx1 Highlights • A new graphene reverse electrodialysis (GRED) device is fabricated. • The GRED device can convert salinity gradient energy into electricity. • The energy conversion efficiency of GRED can be up to 39%. • The output power density can be 126 W/m2 if it is operated at 47 °C. • The ion selectivity of GRED is investigated by MD and PNP simulations. [ABSTRACT FROM AUTHOR]

Environmental variability within estuaries and lagoons creates environmental gradients. Spatial variations in environments associated with environmental gradients shape spatial variations in primary producer and invertebrate communities. However, whether larger spatial variations are linked to greater temporal variations in the communities remained unclear. To understand the linkage between spatial and temporal variations in the communities and the factors shaping these variations, we targeted various functional groups of primary producers and invertebrates (epifauna) in eelgrass (Zostera marina) ecosystems in lagoons with and without distinct salinity gradients. We tested the following hypotheses: 1) larger spatial variation in the primary producer biomasses and epifaunal community structures (abundance, biomass, and species richness) are associated with greater temporal variation in the structures, and 2) salinity would be a more pronounced factor than water temperature and biomasses of primary producers in shaping the community structures in the lagoon with a salinity gradient. Our results showed that temporal and spatial variations in the primary producer biomasses and community structures of epifauna were larger in the lagoon with a salinity gradient. Moreover, salinity, water temperature, and the biomasses of primary producers affected the spatio-temporal variations in the community structures of epifauna, regardless of the presence of the gradients. We present from these results the connection between spatial and temporal variations of the primary producer and epifaunal community structures and the effects of abiotic and biotic factors shaping the communities. [Display omitted] • Environmental variability, such as salinity, shapes invertebrate communities in estuaries and lagoons. • We tested if eelgrass communities are temporally and spatially variable in the presence of the distinct salinity gradient. • Temporal and spatial variations in the communities were larger in the lagoon with a distinct salinity gradient. • The effects of salinity and water temperature on the communities were stronger in the lagoon with a distinct salinity gradient. • The effects of primary producer biomasses on the communities were stronger in the lagoon with a distinct salinity gradient. [ABSTRACT FROM AUTHOR]

The present study investigates effects of three different types of freshet events (varying in intensity, duration, and period of discharge) on the early life stages of fish, macroinvertebrates inhabiting in the water column, and the environmental conditions within the hiperturbid estuary of the Guadalquivir River. Freshet events compressed the salinity gradient and increased turbidity; during the most intense freshet event, the oxygen concentration also decreased. These environmental changes had significant effects on the abundance and distribution of aquatic organisms, reducing the nursery area from 40 km upstream to 20 or 10 km, depending on the freshet. Recovery of physicochemical conditions was relatively rapid (within one or two weeks) for less intense freshets, while the most intense event showed only partial recovery even one month later. Biological responses varied among species and time periods. Pelagic species (e.g., anchovies) were flushed out of the estuary. The populations of these species can show a posterior reintroduction and a recovery to levels similar to before the freshet, or a nonrecovery, probably depending on larval supplied from the offshore stock. In contrast, benthic and estuarine species (e.g., gobies, mysids), were just displaced downstream during the freshets. In the most intense freshet event, which occurred before the high recruitment period of these species (early spring), their abundances increased significantly, exceeding the levels of normal years (without freshets). This suggests that, depending on the intensity and the period in which the freshet occur, they could act as attraction signals for certain species. In general, estuarine and benthic species, such as gobies and other macroinvertebrates, coped better with freshets than pelagic marine migrant species, such as anchovies. However, the estuary and its estuarine organisms showed high resilience to environmental fluctuations. • Freshets can compress salinity gradient, increase turbidity and decrease oxygen. • The shift in physicochemical conditions reduces the nursery area. • Individuals can be flushed out, predated or hide in refuge areas during freshets. • The benthic-estuarine species seem to better cope with freshets. • Some species showed an attraction effect due to the extent of estuarine cues. [ABSTRACT FROM AUTHOR]

Low-grade heat energy is enormous and widely distributed around the world, but it cannot be effectively converted to electricity owing to the small temperature difference and fluctuating heat source. As a promising technology that can convert low-grade heat energy into electricity while obtaining additional freshwater, thermo-osmotic energy conversion has attracted attentions of numerous researchers. However, traditional thermo-osmotic energy conversion technologies lack the utilization of the accompanying variation in salinity gradients throughout the process. In this study, a hybrid system was presented to achieve simultaneous freshwater production and electricity generation by combining thermo-osmosis system with a salinity gradient power recovery module. Continuous operation of the thermo-osmosis system will naturally produce a range of salinity differences, which will then be converted into electricity by the salinity gradient power recovery module. Our results show that this hybrid system can optimally increase the electricity output by ∼0.99 W m−2 over the conventional thermo-osmotic energy conversion system. Overall, our research demonstrates a promising device to harvest low-grade waste heat for co-generation of electricity and freshwater. This innovative approach has the potential to broaden the application possibilities of thermo-osmosis technology. • Salinity gradient recovery combined thermal-osmosis hybrid system was proposed. • A theoretical model was developed to predict electricity output of the system. • Comparing to traditional TOEC, increasing electricity output by ∼0.99 W m−2. • Co-generation of freshwater and electricity was achieved under real seawater. [ABSTRACT FROM AUTHOR]

In order to simultaneously produce hydrogen and reduce the salinity of concentrated wastewater (brine) from the desalination plant, a lab-scale reverse electrodialysis (RED) hydrogen production system driven by salinity gradient energy is designed and its performance is experimentally studied. The energy conversion of the RED system is found affected by the ionic compositions of the desalination concentrated brine (DCB). The effects of ionic types (multivalent cation, anion, and phosphorous salt) and ionic concentration (from 0.01 to 0.05 M) and pH of DCB (from 5 to 11) on the hydrogen production are investigated. The results show that the existence of multivalent ions in brine significantly degrade the capability of output voltage and hydrogen production of the RED system. Compared to the control group, the additions of 0.05 mol·L−1 NaBr and 0.05 mol·L−1 FeCl 3 into the simulated brines lead to the output voltage drops of 29 % and 60 %, respectively, when the current is maintained at 0.2A. Additionally, the experiment yields an MHP of 128 mL·h−1 at the current of 0.3A. Generally, the performances of the RED stack can be improved as increasing the pH of an acidic DCB, but declined as the increasing the pH of an alkaline DCB. • A RED system driven by the desalination concentrated brine was designed. • Effects of multivalent ion types and concentration on system performance is studied. • Presence of multivalent ions hinders the salinity gradient energy extraction. • The RED stack performance is elevated with enlarging the pH of an acidic feed solution • The H 2 production is dropped-down for increasing the pH of an alkaline feed solution. [ABSTRACT FROM AUTHOR]

Salinity gradient energy harvesting by reverse electrodialysis (RED) is a promising renewable source to decarbonize desalination. This work surveys the potential reduction in energy consumption and carbon emissions gained from RED integration in 20 medium-to-large-sized seawater reverse osmosis (SWRO) desalination plants spread worldwide. Using the validated RED system’s model from our research group, we quantified the grid mix share of the SWRO plant’s total energy demand and total emissions RED would abate (i) in its current state of development and (ii) if captured all salinity gradient exergy (SGE). Results indicate that more saline and warmer SWRO brines enhance RED’s net power density, yet source availability may restrain specific energy supply. If all SGE were harnessed, RED could supply ~40% of total desalination plants’ energy demand almost in all locations, yet energy conversion irreversibility and untapped SGE decline it to ~10%. RED integration in the most emission-intensive SWRO plants could relieve up to 1.95 kg CO2-eq m−3. Findings reveal that RED energy recovery from SWRO concentrate effluents could bring desalination sector sizeable energy and emissions savings provided future advancements bring RED technology closer to its thermodynamic limit.

Coastal wetlands contribute to the mitigation of climate change through the sequestration of "blue carbon". Microbial necromass, lignin, and glycoproteins (i.e., glomalin-related soil proteins (GRSP)), as important components of soil organic carbon (SOC), are sensitive to environmental change. However, their contributions to blue carbon formation and the underlying factors remain largely unresolved. To address this paucity of knowledge, we investigated their contributions to blue carbon formation along a salinity gradient in coastal marshes. Our results revealed decreasing contributions of microbial necromass and lignin to blue carbon as the salinity increased, while GRSP showed an opposite trend. Using random forest models, we showed that their contributions to SOC were dependent on microbial biomass and resource stoichiometry. In N-limited saline soils, contributions of microbial necromass to SOC decreased due to increased N-acquisition enzyme activity. Decreases in lignin contributions were linked to reduced mineral protection offered by short-range-ordered Fe (Fe SRO ). Partial least-squares path modeling (PLS-PM) further indicated that GRSP could increase microbial necromass and lignin formation by enhancing mineral protection. Our findings have implications for improving the accumulation of refractory and mineral-bound organic matter in coastal wetlands, considering the current scenario of heightened nutrient discharge and sea-level rise.

Phosphorus (P) conveyed by surface runoff plays an essential role in regulating nutrient balance and primary production in estuarine waters. In this study, basic physiochemical properties, total phosphorus (TP, including speciation), particulate iron (PFe), particulate manganese (PMn), and particulate aluminum (PAl) of the surface water in the Pearl River Estuary (PRE) in different seasons were determined to investigate the spatiotemporal distribution characteristics of P and to identify the crucial factor controlling P migration and transformation in the freshwater-saltwater interaction zone. TP concentrations (28.88-233.68 μg·L -1 ) decreased with increasing salinity gradient owing to deposition and dilution. The proportions of P speciation followed a decreasing order as dissolved inorganic phosphorus (DIP, 37.3%) &gt; particulate inorganic phosphorus (PIP, 22.7%) &gt; dissolved organic phosphorus (DOP, 21.0%) &gt; particulate organic phosphorus (POP, 19.0%). PIP was positively related to PFe, PMn, and PAl ( P &lt; 0.05), confirming their concurrent migration behaviors. In addition, the increase in salinity promoted the desorption of phosphate on the suspended particulate matters, which mainly took place near the freshwater-saltwater interface. A significant positive correlation ( P &lt; 0.001) between the solid-liquid phase partitioning coefficient ( K d ) of phosphate and salinity indicated that PIP was present mainly in more stable forms in the brackish water. Most importantly, a better relationship between K d and PMn ( P &lt; 0.01) supported our scientific hypothesis of the "load-unload" effect of Mn oxides on P:particulate-carrying phosphates transported from the freshwater zone tend to be desorbed and released into the brackish water.

This work presents the use of the schlieren imaging to quantify the salinity gradients in a microfluidic device. By partially blocking the back focal plane of the objective lens, the schlieren microscope produces an image with patterns that correspond to spatial derivative of refractive index in the specimen. Since salinity variation leads to change in refractive index, the fluid mixing of an aqueous salt solution of a known concentration and water in a T-microchannel is used to establish the relation between salinity gradients and grayscale readouts. This relation is then employed to map the salinity gradients in the target microfluidic device from the grayscale readouts of the corresponding micro-schlieren image. For saline solution with salinity close to that of the seawater, the grayscale readouts vary linearly with the salinity gradient, and the regression line is independent of the flow condition and the salinity of the injected solution. It is shown that the schlieren technique is well suited to quantify the salinity gradients in microfluidic devices, for it provides a spatially resolved, non-invasive, full-field measurement.

Abstract The main purpose of salinity gradient solar ponds (SGSPs) is to store the maximum possible solar thermal energy. A well-established salinity and temperature gradients are the main points to achieved optimum storage efficiency. In this work, a high-fidelity model is developed using computational fluid dynamics (CFD) to simulate the SGSP behavior under hot climate regions. The model is able to simulate the double convective effect by solving Navier-Stokes and energy equations, simultaneously. Brines with different salinities (i.e. 10%,15, and 25%) are used to investigate their role on the developed salinity/temperature gradients. Simulation results show the successful establishment of the three zones (i.e. upper convective, non-convective, and lower convective) with relatively stable salinity and temperature gradients. However, injecting the lower convective zone (or storage zone) with 10% saline brine results in preserving the highest storage temperature of around 79.2°C after flow time of six hours. [ABSTRACT FROM AUTHOR]

Abstract This paper presents the experimental analysis to find the optimum alkaline-surfactant-polymer (ASP) formula and the effects of salinity gradient suitable for oil reservoirs with low salinity formation water. It has been challenging to obtain high oil recovery when the reservoir salinity is lower than the injection salinity of ASP formulation. This paper carried out phase behavior tests for 28 experiments with 22 kinds of surfactant and subsequent coreflooding for the optimum formula with pre-designed salinity gradient profiling for pre-flush, ASP slug, and polymer drive. The optimum ASP formula from the phase behavior study, i.e., 0.5 wt% Linear alkylbenzene sulfonate (LAS), 2 wt% Diethylene glycol butyl ether (DGBE), and 1 wt% Na 2 CO 3 , results in the optimum salinity of 2.8 wt% NaCl with 10 cc/cc solubilization ratio, and the middle phase type III microemulsion occurs in the range of 2.5–3.4 wt% NaCl. The oil recovery implementing this formula and negative salinity gradient, i.e. Winsor type II-III-I for coreflooding experiments are about 75.8% which is better than the other salinity gradients such as Winsor type I-II-I and I-III-I. Excluding high saline pre-flush, the salinity gradient consisted of Winsor type I-II-I and Winsor type I-III-I are able to recover the desirable amount of oil. The results could be applicable on designing the optimal ASP flooding at low salinity formation considering the formulation of surfactants and co-solvents, and the effects of salinity gradients. Highlights • Phase behavior tests examine ideal ASP formula for low-saline-light-oil reservoir. • High optimum salinity formula is applicable to a low saline reservoir. • Winsor type II-III-I gradient shows the desirable ASP flooding performances. • Excluding high saline pre-flush; type I-II-I&I-III-I gradients are attractive design. [ABSTRACT FROM AUTHOR]

Abstract RED is a technology for harvesting energy using the salinity gradient between river (RW) and seawater (SW). Membrane fouling can decrease the net power density. Fouling inhibition might be indispensable. For implementing antifouling strategies more detailed insights upon fouling are required. In RED stacks investigations of single membranes are practically impossible. We introduce the RED Fouling Monitor, in which one side of a single ion-exchange membrane in contact to a foulant-containing feed stream can be studied under OCV and current conditions. Fouling is detectable in four configurations: (1) SW/AEM, (2) RW/AEM, (3) SW/CEM and (4) RW/CEM. Functionality is provided by a novel flow-through salt bridge enabling ionic connection and the incorporation of reference electrodes in close proximity to the membrane surface. The results indicate a stable, reproducible performance under un-fouled conditions. Upon SDBS exposure RW/AEM fouling showed a more pronounced fouling response than SW/AEM fouling. Fouling is partly attributable to the current density and the current field direction. An irreversible, internal fouling of the AEM is indicated when exposed to SDBS in SW. RW/AEM fouling shows to be reversible. With prospect to future systematic investigations this tool can be used to test various configurational, operational designs, different pre-treatment schemes and the fouling potential of feed streams at different seasons. This will result in valuable insights for new constructional sites for future RED plants. Graphical abstract fx1 Highlights • The RED Fouling Monitor enables a detailed fouling analysis. • Centerpiece is a novel flow-through salt bridge. • Applicable under OCV and current conditions. • The current field and its extent affects organic fouling. [ABSTRACT FROM AUTHOR]

Abstract Reverse electrodialysis (RED) has vast potential as a clean, nonpolluting, and sustainable renewable energy source; however, pilot-scale RED studies employing real waters remain rare. This study reports the largest RED (1000 cell pairs, 250 m2) with municipal wastewater effluent (1.3–5.7 mS/cm) and seawater (52.9–53.8 mS/cm) as feed solutions. The RED stack was operated at a velocity of 1.5 cm/s and the pilot plant produced 95.8 W of power (0.38 W/m2 total membrane or 0.76 W/m2 cell pair). During operation of the RED, the inlet design of the stack, comprising thin spacers, and the water dissociation reaction at the cathode were revealed as vulnerabilities of the stack. Specifically, pressure drops at the fluid inlet parts had the most detrimental effects on power output due to clogged spacers around the inlet parts. In addition, precipitates resulting in inorganic fouling were inevitable during the water dissociation reaction due to significant potential generated by the stack in the cathode chamber. Na+ and Cl− accounted for the majority of ions transferred from seawater to wastewater effluent through ion exchange membranes (IEMs). Moreover, some divalent cations in seawater, Mg2+ and Ca2+, were also transferred to the wastewater effluent. Some organics with relatively low molecular weights in the wastewater effluent passed through the IEMs, and their hydrophobic properties elevated the specific UV absorbance (SUVA) level in the seawater. Highlights • A 1000-cell-pair RED with wastewater effluent and seawater is presented. • RED operation achieved a power output of 96 W (0.76 W/m2 cell pair). • Dissolved organic carbon with low molecular weights passed through the IEMs. • Precipitates were observed on the shielding CEM and cathode in the cathode chamber. [ABSTRACT FROM AUTHOR]

Highlights • Heavy metal levels generally decreased with increasing salinities. • The unpolluted to moderate pollution levels were observed for all sampling sites. • Heavy metals originated from a similar source and As had two sources. • As and Cr exhibited higher contributions to the toxic units than other heavy metals. Abstract Salt ions can affect the toxicity, mobility and transfer of metals/metalloids in estuarine wetlands. Soil samples were collected to a depth of 30 cm along a salinity gradient at four sampling sites, including bare land (B), Tamarix Chinensis wetlands (T), Suaeda salsa wetlands (S) and Phragmites australis wetlands (P) in drained coastal wetlands in the Yellow River Estuary, China. Arsenic (As) and heavy metals (i.e., Cd, Cr, Cu, Pb and Zn) were measured to investigate their levels, depth distributions, sources and toxic risks. The results showed that As and heavy metals generally showed a decline with increasing salinities. Arsenic concentrations in all samples exceeded the threshold effects levels (TELs) value and were below the probable effects levels (PELs). The concentrations of Cd, Pb and Zn in all soil samples were below TEL values, while Cr and Cu concentrations were grouped to the range of TELs-PELs in several soil samples. According to the geoaccumulation index (I geo), Cd exhibited unpolluted to moderate pollution at Sites B, S and P, whereas no pollution for other heavy metals were observed in all soils. Generally, higher I geo values for Cd were observed at those sites with lower salinities. The average toxic unit (TU) values of As and heavy metals at Sites B and T followed the order Cr > As > Zn > Cu > Pb > Cd, and the followed order was As > Cr > Zn > Cu > Pb > Cd at Sites S and P. As and Cr showed higher contributions to the TUs than other metals. Correlation analysis showed that As and heavy metals were negatively correlated with electrical conductivity (EC), sand content, Cl−, Cl−/ S O 4 2 - ratio and Mg2+ (P < 0.05), while were positively correlated with soil moisture, clay and silt contents and soil organic carbon (SOC) (P < 0.05). The mutivariate analysis indicated that these heavy metals originated from the same source, while As also had another source. The findings of this work can contribute to pollution control and ecosystem health conservation of coastal wetlands. [ABSTRACT FROM AUTHOR]

Abstract For investigating the influence of coexisting ions (K+, Mg2+, Ca2+ and SO 4 2−), temperature and their synergistic effect on energy generation by reverse electrodialysis, two series of cells dividing with Yadeshi membranes are fed with different solutions at 10 °C, 25 °C and 40 °C. The presence of K+, Mg2+, Ca2+ and SO 4 2− results in lower open circuit voltage, higher internal resistance and lower maximum power density, and the influence order of ions coexisting with NaCl is Ca2+ > Mg2+ (>SO 4 2−) > K+. With the temperature risen, the open circuit voltage and the internal resistance show a trend of increase and decrease respectively, resulting in a bigger power density. Based on the synergistic effect of coexisting ions and temperature, the maximum power density of the pure NaCl system shows a greater increment (0.15 W m−2) than that of NaCl-CaCl 2 (0.10 W m−2) and NaCl-MgCl 2 (0.11 W m−2) systems when temperature increases from 10 °C to 40 °C. Furthermore, the transport quantities of ions in each system increased with temperature at different degrees, and the uphill of Ca2+ and Mg2+ was more obvious, which can reasonably explain the different effects of temperature on the maximum power density. Moreover, these results are further verified when simulated concentrated seawater is used for both the Yadeshi- and Fujifilm membranes, and the Fujifilm shows better energy generation performance mainly due to a lower internal resistance. Graphical abstract The coexisting ions (K+, Mg2+, Ca2+ and SO 4 2−) with NaCl and temperature variation have synergistic effects on energy generation performance of reverse electrodialysis stack. Image Highlights • The presence of K+, Mg2+, Ca2+ and SO 4 2− has a negative impact on power density. • The influence order of coexisting ions with NaCl is Ca2+ > Mg2+ (>SO 4 2−) > K+. • Rising temperature would enhance the power density of reverse electrodialysis. • Temperature affects less on power density in NaCl-CaCl 2 or NaCl-MgCl 2 than NaCl. [ABSTRACT FROM AUTHOR]

Biological conversion of CO 2 to value-added chemicals and biofuels has emerged as an attractive strategy to address the energy and environmental concerns caused by the over-reliance on fossil fuels. In this study, an innovative microbial reverse-electrodialysis electrolysis cell (MREC), which combines the strengths of reverse electrodialysis (RED) and microbial electrosynthesis technology platforms, was developed to achieve efficient CO 2 -to-value chemicals bioconversion by using the salinity gradient energy as driven energy sources. In the MREC, maximum acetate and ethanol concentrations of 477.5 ± 33.2 and 46.2 ± 8.2 mg L −1 were obtained at the cathode, catalyzed by Sporomusa ovata with production rates of 165.79 ± 11.52 and 25.11 ± 4.46 mmol m −2 d −1 , respectively. Electron balance analysis indicates that 94.4 ± 3.9% of the electrons derived from wastewater and salinity gradient were recovered in acetate and ethanol. This work for the first time proved the potential of innovative MREC configuration has the potential as an efficient technology platform for simultaneous CO 2 capture and electrosynthesis of valuable chemicals. [ABSTRACT FROM AUTHOR]

In tropical coastal and estuarine environments, such as the mangroves of the Amazon region, salinity is considered to be one of the principal factors limiting the farming of bivalve mollusks. In this context, the present study evaluated the effects of the location of the farm (proximity to the ocean) and seasonality on the growth of the mangrove oyster Crassostrea gasar , and identified the environmental factors that most influenced the growth performance of the oysters over the course of the year. The oysters analyzed in this study were raised over a one-year period on farms in three areas of mangrove on the Brazilian Amazon coast, located at different distances from the ocean. These farms rear oysters using a fixed-tray system. The study period was divided into four seasonal divisions - the rainy-dry transition period, the dry season, dry-rainy transition, and the rainy season. The salinity, pH, temperature, and dissolved oxygen concentration of the water were measured in situ using a multiparameter probe during specimen collection. A mean of 20 specimens were collected each month from each of the three study areas. Once collected, the oysters were weighed and measured. Salinity and precipitation were the environmental parameters that most varied over the course of the study period, with significant differences being found among study areas during this period. The best growth performance was recorded for the farms in areas 1 and 2, which were closest to the ocean, and were significantly different from area 3 (the furthest from the ocean), where the oysters were smallest in size. The evidence indicates that areas located closest to the coast, are the most appropriate for commercial-scale oyster farming, while areas furthest from the ocean and influenced primarily by fluvial discharge, is much less favorable for the production of oysters. Overall, the data showed that, when raised in its natural environment, C. gasar presents a better growth performance during the rainy-dry transition period and the dry season, especially on farms located close to the coast, where salinity is between 25 and 35, given that this condition favors the development of the oysters, and optimizes their growth performance in commercial scale farming operations. [ABSTRACT FROM AUTHOR]

The paper presents the results of research on the efficient use of concentrates obtained during the desalination of different types of geothermal water using membrane processes. The analysis is based on results for 18 concentrates which included macroelements and certain therapeutic ingredients, potentially toxic elements (heavy metals) and radioactive elements. The research demonstrated that concentrations of potentially toxic metals in most concentrates do not exceed the limits recognised as safe for human health, irrespective of the manner in which the human body comes into contact with them. These concentrates can be used: (1) for inhalation and rinsing the nose and mouth for the purpose of loosening and removing mucus and relieving inflammation; (2) for cosmetic purposes in the form of cleansing and moisturising liquids; (3) for bathing, both individual and in recreational or therapeutic pools. The second innovative approach is related to harvesting energy from the salinity gradient. The purpose is to purify geothermal water while also extracting the energy generated by mixing effluents with different salinity levels. The RO process results in the discharge of concentrated brine which can be considered a source of salinity gradient energy. In this respect, two methods are considered: reverse electrodialysis and capacitive mixing. [ABSTRACT FROM AUTHOR]

Abstract Saltworks are artificial ecosystems that are exploited for salt production. These extreme environments create particular habitats for a diversity of species. In "extreme" environments organisms must adapt to stressful environmental conditions. Saltworks are particularly influenced by biotic factors, such as biodiversity and its interspecific interactions, which are linked to abiotic factors. The large variation of abiotic factors in extreme ecosystems helps explain the causal relationships between them, as well as the structure of the communities that inhabit them. Species that live in these habitats develop adaption strategies in order to survive and reproduce. Despite the important role of saltwork communities, especially regarding the ecological aspects of the biota of high saline environments that remain poorly understood, few studies have been carried out in these ecosystems. In this context saltworks are a particularly interesting type of study given that they contain a large diversity of species and environments. Many ecosystems are found around Salinor, such as: mangroves, flooded areas and Caatinga vegetation fragments. Based on existing literature, we were able to identify 13 types of services, of which one pertained to support services, two pertained to regulation services, five pertained to provision services and four pertained to cultural services. Most of the studies we consulted were classified as support services (36.36%), whereas biodiversity maintenance was present in 100% of these studies. The second category corresponded to provision services (22.73%). With respect to regulation services, five studies examined water quality maintenance (62.50%), one study examined climate regulation (12.50%), and the other two examined pest and disease control (25%). The studies that focused on cultural services examined tourism (41.67%), cultural and historical values (25%) and scientific research (33.33%). With respect to the study carried out in Salinor, we were able to identify a considerable number of ecosystem services. From our analysis of the biodiversity found in this saltwork, we were able to identify a total of 42 ecosystem services generated by the different habitats (mangroves, flooded areas, Caatinga, evaporation and crystallizer ponds). Although it is considered to be an artificial ecosystem, Salinor and its surroundings preserve natural characteristics, therefore demonstrating great potential to supply of ecosystem services. These ecosystem services consist of four types of ecosystem functions, such as food supply, biodiversity maintenance, carbon sequestration, research and ecotourism. Highlights • It was possible to identify the main ecosystem services provided by artificial saltworks from several regions of the world. • The potential ecosystem services provided by a saltwork in Brazil were identified. • The salt production process determines ecological separations, contributing to habitat heterogeneity and species diversity. • Saltworks are an artificial ecosystem that supplies ecosystem services by conserving characteristics of natural environments. [ABSTRACT FROM AUTHOR]

Considering the highly complex flow structure of saltwater lakes during freshwater supplementation, a three-dimensional numerical model was developed to simulate suspended sediment transport in saltwater lakes. The model was validated using measurements of the salinity and sediment concentration during a pumping test at Yamdrok Lake. The simulation results were in quantitative agreement with the measured data. The observed and simulated results also indicated that the wind stress and vertical salinity gradient have a significant influence on salinity and sediment transport in a saltwater lake. The validated model was then used to predict and analyze the contributions of wind, the supplement flow rate and salinity stratification to the sediment transport process in Yamdrok Lake during continuous river water supplementation. The simulation results showed that after the sandy river water was continuously discharged into the saltwater lake, the lateral diffusion trends of the sediment exhibited three stages: linear growth in the inflow direction, logarithmic growth in the wind direction, and stabilization. Furthermore, wind was the dominant factor in driving the lake flow pattern and sediment transport. Specifically, wind can effectively reduce the area of the sediment diffusion zone by increasing the lateral sediment carrying and dilution capacities. The effect of inflow on the lake current is negligible, but the extent of the sediment turbidity zone mainly depends on the inflow. Reducing the inflow discharge can decrease the area of the sediment turbidity zone to proportions that far exceed the proportions of inflow discharge reductions. In addition, the high-salinity lake water can support the supplemented freshwater via buoyancy forces, which weaken vertical mixing and sediment settlement and increase lake currents and sediment diffusion near the surface. [ABSTRACT FROM AUTHOR]

Dissolved organic matter (DOM) is a major component of the organic matter pool, playing a key role in the global ocean functioning. However, studies on DOM in waters of many ocean regions, such as the Gulf of Cadiz (GoC), are poorly known. Advanced aquatic sensors enable autonomous for long-term deployments in situ collection of high frequency DOM data using fluorescent dissolved organic matter (FDOM) as a proxy. The present study evaluates the relevance of FDOM, the estuarine influence and the environmental factors that determine its spatial distribution in the GoC. Our results suggest that the GoC water mass, under the estuarine influence of three main rivers, is receiving large amounts of DOM transported mainly by Guadalquivir and Guadiana rivers and much less from Tinto-Odiel. Salinity is the main factor explaining the FDOM variability within the Guadalquivir and Guadiana rivers and in the inner shelf of the GoC. In the outer shelf of the GoC, plankton-produced DOM could explain the persistent spatial pattern of FDOM, playing an important role in the dynamics of FDOM from the North area of the GoC through the persistent low-salinity Eastern North Atlantic Central Water. The oceanographic dynamics and the spatial pattern of FDOM concentration in the continental shelf of the GoC suggest a net transport of FDOM through the GCC (Gulf of Cadiz Current) to the Mediterranean Sea. [ABSTRACT FROM AUTHOR]

Mixing of fresh (river) water and salty water (seawater or saline brine) in a controlled environment produces an electrical energy known as salinity gradient energy (SGE). Two main conversion technologies of SGE are membrane-based processes: pressure retarded osmosis (PRO) and reverse electrodialysis (RED). Exergy calculations for a representative river-lake system are investigated using available data in the literature between 2000 and 2008 as a case study. An exergy analysis of an SGE system of sea-river is applied to calculate the maximum potential power for electricity generation. Seawater is taken as reference environment (global dead state) for calculating the exergy of fresh water since the sea is the final reservoir. Aqueous sodium chloride solution model is used to calculate the thermodynamic properties of seawater. This model does not consider seawater as an ideal solution and provides accurate thermodynamics properties of sodium chloride solution. The chemical exergy analysis considers sodium chloride (NaCl) as main salt in the water of this highly saline Lake with concentration of more than 200 g/L. The potential power of this system is between 150 and 329MW depending on discharge of river and salinity gradient between the Lake and the River based on the exergy results. This result indicates a high potential for constructing power plant for SGE conversion. Semipermeable membranes with lifetime greater than 10 years and power density higher than 5 W/m2 would lead to faster development of this conversion technology. [ABSTRACT FROM AUTHOR]

River systems worldwide have been modified for human use and the downstream ecological consequences are often poorly understood. In the Colorado River estuary, where upstream water diversions have limited freshwater input during the last century, mollusc remains from the last several hundred years suggest widespread ecological change. The once abundant clam Mulinia modesta has undergone population declines of approximately 94% and populations of predators relying on this species as a food source have probably declined, switched to alternative prey species or both. We distinguish between the first two hypotheses using a null model of predation preference to test whether M. modesta was preyed upon selectively by the naticid snail, Neverita reclusiana, along the estuary's past salinity gradient. To evaluate the third hypothesis, we estimate available prey biomass today and in the past, assuming prey were a limiting resource. Data on the frequency of drill holes--identifiable traces of naticid predation on prey shells--showed several species, including M. modesta, were preferred prey. Neverita reclusiana was probably able to switch prey. Available prey biomass also declined, suggesting the N. reclusiana population probably also declined. These results indicate a substantial change to the structure of the benthic food web. Given the global scale of water management, such changes have probably also occurred in many of the world's estuaries. [ABSTRACT FROM AUTHOR]

Changes in zooplankton community structure and function were analyzed in 24 lakes covering a wide salinity gradient (from 0.5 to 115 g l−1) in a semiarid region in northwest China. We hypothesized that species richness (S), species diversity (H), functional diversity (FD), biomass, and size of zooplankton would decrease with increasing salinity. We found that S, H, and FD did decrease with increasing salinity, whereas zooplankton sizes, size range, and biomasses did not. In fact, the sizes of microcrustaceans were mainly regulated by the abundance of small fish. Besides the impoverishment of FD, the zooplankton functional groups also varied along the salinity gradient. A shift occurred from selective raptorial to more generalist microphagous rotifers, from selective to more generalist filter feeder cladocerans, and from dominance of microphagous herbivorous copepods to microphagous carnivores. Our study indicates that the ongoing salinization of lakes with climate warming will result in important changes in the zooplankton, affecting not only the structure but also the functioning of this community. A weakened top-down control by zooplankton on phytoplankton at moderate high salinities may be an indirect consequence, leading to a worsening of eutrophication symptoms. Loss of fish at high salinities may, however, counteract this effect. [ABSTRACT FROM AUTHOR]

Lakes from semiarid areas are generally temporary and saline, depending on the precipitation cycles. The negative effect of salinity on zooplankton richness when a lake dries up is well known, but much less is known about the outcome when a lake reduces its salinity because of rainfall events. Parque Luro Reserve is located in Argentina’s semiarid area, and it has a hypersaline shallow lake with extreme variations of depth and salinity. The objective of this research was to analyze the changes in zooplankton diversity when the lake’s salinity decreased. We also analyzed the hatching conditions of Artemia persimilis Piccinelli and Prosdocimi, 1968 and the grazing effect of this species on the algal community. We incubated lake sediments in microcosms with lake water for 45 days at salinities between 25 and 300 g L −1 . The only species that hatched at salinities less than or equal to 100 g L −1 was A. persimilis . Hatching at higher salt concentrations, as observed in the field, would only occur if occasional rainfall produced a vertical stratification of salinity. The density and biomass of Artemia (dominated by post-naupliar stages) peaked at 50 g L −1 . At salinities less than or equal to 100 g L −1 , phytoplankton was not abundant, while periphyton was very abundant. The inverse relationship between A. persimilis and phytoplankton biomasses allowed us to corroborate a strong grazing effect of Artemia . The absence of other zooplankton species could be due to egg bank deterioration caused by the persistence of long-term hypersaline conditions. If other species appeared, they would by necessity have come from external sources. [ABSTRACT FROM AUTHOR]