Salinity Variations Research Articles

A systematic evaluation on the relationship between hypo-osmoregulation and hyper-osmoregulation in decapods of different habitats.

Decapods occupy all aquatic, and terrestrial and semi-terrestrial environments. According to their osmoregulatory capacity, they can be osmoconformers or osmoregulators (hypo or hyperegulators). The goal of this study is to gather data available in the literature for aquatic decapods and verify if the rare hyporegulatory capacity of decapods is associated with hyper-regulatory capacity. The metric used to quantify osmoregulation was the osmotic capacity (OC), the gradient between external and internal (hemolymph) osmolalities. We employ phylogenetic comparative methods using 83 species of decapods to test the correlation between hyper OC and hypo OC, beyond the ancestral state for osmolality habitat, which was used to reconstruct the colonization route. Our analysis showed a phylogenetic signal for habitat osmolality, hyper OC and hypo OC, suggesting that hyper-hyporegulators decapods occupy similar habitats and show similar hyper and hyporegulatory capacities. Our findings reveal that all hyper-hyporegulators decapods (mainly shrimps and crabs) originated in estuarine waters. Hyper OC and hypo OC are correlated in decapods, suggesting correlated evolution. The analysis showed that species which inhabit environments with intense salinity variation such as estuaries, supratidal and mangrove habitats, all undergo selective pressure to acquire efficient hyper-hyporegulatory mechanisms, aided by low permeabilities. Therefore, hyporegulation can be observed in any colonization route that passes through environments with extreme variations in salinity, such as estuaries or brackish water.

Multifarious Plant Growth-Promoting Rhizobacterium Enterobacter sp. CM94-Mediated Systemic Tolerance and Growth Promotion of Chickpea (Cicer arietinum L.) under Salinity Stress.

Chickpea is one of the most important leguminous crops and its productivity is significantly affected by salinity stress. The use of ecofriendly, salt-tolerant, plant growth-promoting rhizobacteria (PGPR) as a bioinoculant can be very effective in mitigating salinity stress in crop plants. In the present study, we explored, characterized, and evaluated a potential PGPR isolate for improving chickpea growth under salt stress. A potential PGPR was isolated from rhizospheric soils of chickpea plants grown in the salt-affected area of eastern Uttar Pradesh, India. The isolate was screened for salt tolerance and characterized for its metabolic potential and different plant growth-promoting attributes. Further, the potential of the isolate to promote chickpea growth under different salt concentrations was determined by a greenhouse experiment. A rhizobacteria isolate, CM94, which could tolerate a NaCl concentration of up to 8% was selected for this study. Based on the BIOLOG carbon source utilization, isolate CM94 was metabolically versatile and able to produce multiple plant growth-promoting attributes, such as indole acetic acid, 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase, siderophore, hydrogen cyanide (HCN), and ammonia as well as solubilized phosphate. A polyphasic approach involving the analysis of fatty acid methyl ester (FAME) and 16S rRNA gene sequencing confirmed the identity of the isolate as Enterobacter sp. The results of greenhouse experiments revealed that isolate CM94 inoculation significantly enhanced the shoot length, root length, and fresh and dry weight of chickpea plants, under variable salinity stress. In addition, inoculation improved the chlorophyll, proline, sugar, and protein content in the tissues of the plant, while lowering lipid peroxidation. Furthermore, isolate CM94 reduced oxidative stress by enhancing the enzymatic activities of superoxide dismutase, catalase, and peroxidase compared to in the respective uninoculated plants. Overall, the results suggested that using Enterobacter sp. CM94 could significantly mitigate salinity stress and enhance chickpea growth under saline conditions. Such studies will be helpful in identifying efficient microorganisms to alleviate salinity stress, which in turn will help, to devise ecofriendly microbial technologies.

Impact of freshwater diversions on vegetation in coastal wetlands based on remote sensing derived vegetation index

There exist contrasting results on the impact of large-scale freshwater and sediment diversions on land gain/loss. To improve understanding on the efficacy of diversion projects in restoring coastal wetlands, we aim to evaluate the long-term impacts of diversion-altered salinity and water level on vegetation productivity in coastal wetlands. Two freshwater diversion projects Caernarvon and Davis Pond in Louisiana, U.S. and associated reference sites were selected for inclusion in this study. We implemented multi-level Bayesian models to evaluate 1) how vegetation productivity approximated by Landsat-derived Normalized Difference Vegetation Index (NDVI) in peak biomass season changed over time (pre- and post-construction and operation of the freshwater diversions), and 2) how peak-season NDVI responded to mean and variability of water level and salinity among a suite of factors that could affect vegetation productivity. Analysis showed difference in temporal trends of NDVI between the reference and diversion site for the Caernarvon project with a significant increase at the diversion site although NDVI negatively responded to diversion at the beginning. Diversion did not seem to negatively affect NDVI for the Davis Pond project and NDVI only marginally increased at the diversion site. For both projects, NDVI negatively responded to water level, while salinity negatively affected NDVI or showed quadratic relation with NDVI. At the Caernarvon diversion project, the negative impact of water level on NDVI was greater at the diversion site than at the reference site. At the Davis Pond project, it was the salinity that showed different impact between the diversion and reference site. The temporal increase of NDVI at the Caernarvon diversion site can be explained by the lower salinity driven by diversion. The quadratic relation between salinity and NDVI at the Davis Pond diversion project led to only marginal increase at the diversion site. This study provided uncertainty estimates in temporal trend of NDVI and the impact of two key abiotic drivers on NDVI. The improved understanding on vegetation productivity will help predict landscape change in response to freshwater diversions.

Assessment and Mapping of Soil Salinity Using the EM38 and EM38MK2 Sensors: A Focus on the Modeling Approaches

Soil salinization and its detrimental agricultural, environmental, and socioeconomic impact over extended regions represent a major global concern that needs to be addressed. The sustainability of agricultural lands and the development of proper mitigation strategies require effective monitoring and mapping of the saline areas of the world. Therefore, robust modeling techniques and efficient sensors that assess and monitor the spatial and temporal variations in soil salinity within an area, promptly and accurately, are essential. The aim of this paper is to provide a comprehensive and up-to-date review of the modeling approaches for the assessment and mapping of saline soils using data collected by the EM38 and EM38MK2 (MK2) sensors at different scales. By examining the current and latest approaches and highlighting the most noteworthy considerations related to their accuracy and reliability, the intention of this review is to elucidate and underline the role of the EM38 and the MK2 type in the recent needs of detecting and interpreting soil salinity. Another aim is to assist researchers and users in selecting the optimal approach for future surveys and making well-informed decisions for the implementation of precise management practices. The study’s findings revealed that the integration of the EM38 and MK2 sensors with remote sensing data and advanced methods like machine learning and inversion is a promising approach to the accurate prediction and mapping of the spatiotemporal variations in soil salinity. Therefore, future research focused on validating and expanding such sophisticated modeling applications to regional and global scales should be increased.

Deterministic assessment of the ecological vulnerability of coastal freshwater canals: A perspective on social awareness and conservation

Abstract. Khan NS, Islam MS, Bari JBA, Uddin M, Mashkova I, Kostryukova A, Trofimenko V. 2023. Deterministic assessment of the ecological vulnerability of coastal freshwater canals: A perspective on social awareness and conservation. Biodiversitas 24: 5179-5188. Inland freshwater canals are formed by geomorphological evolutions or artificially for communal welfare. The freshwater canal ecology differs mainly from rivers, estuaries, and the ocean for salinity variables, nutrient concentrations, morphological structure, and unique flora and fauna distribution. These canals and their aquatic organisms are very sensitive to surface runoff and direct sewage pollution. Thus, these freshwater canals become threats to society in case of contamination. The current study focused on the water quality, microalgae, and zooplankton communities in two renowned canals: Basurhat (BH) canal and Dotterhat (DH) canal in coastal Noakhali, Bangladesh. The study attempted to demonstrate these canals' aquatic and ecological status by evaluating plankton distribution and some important water quality parameters. Furthermore, a classic Palmer's algal organic pollution Index and wetland zooplankton Index were applied to determine the water quality according to species assemblages of freshwater algae and zooplankton, respectively. The present study identified 27 phytoplankton genera from Bashurhat Canal and 21 from Datterhat Canal. At the same time, 16 genera of zooplankton were observed with 2,269.09±52.12 ind/L and 4,588.54±40.79 ind/L from Bashurhat Canal and Datterhat Canal, respectively. The water quality differed from Bashurhat Canal and Datterhat Canal, where the highest temperature was found at Bashurhat Canal at 23.55±0.15°C and the lowest was 22.6±0.1°C. Moreover, the highest and lowest temperature was found from Datterhat Canal as 29.8±0.9°C and 29.67±0.78°C respectively. The highest transparency (cm), Dissolve Oxygen (mg/L), alkalinity (mg/L), free carbon dioxide (mg/L), ammonia (mg/L) and TSS (mg/L) were found as 29±1.0, 1.25±0.25, 58.76±0.26, 59.25±0.66, 8.25±0.25, 2.25±0.05 and the lowest were found 20.5± 0.5, 0.75±0.25, 27.73±0.49, 11.28±0.69, 8.15±0.15, 2.2±0.1 in Bashurhat Canal. Additionally, the highest transparency (cm), Dissolve oxygen (mg/L), alkalinity (mg/L), free carbon dioxide (mg/L), ammonia (mg/L), and TSS (mg/L) were found as 15.75±0.25, 1.85±0.50, 53.96±0.5, 55.09±0.8, 8.1±0.1, 4.0±0.1 and the lowest were identified 14.5± 0.5, 1.25±0.25, 23.1±0.4, 49.23±0.38, 7.65±0.50, 2.54±0.75 in Datterhat Canal. The study results indicate the deterioration of water quality in urbanized canals and that aquatic ecosystems face many long-term anthropogenic pressures. The current canal state requires measures to restore them. In addition, there is a need for strict control over the discharge of waste and pollutants from residential areas, fish markets, and hospitals.

Impacts of stronger winds and less sea ice on Canadian Beaufort Sea shelf ecosystems since the late 1990s

Continuous and multi-decadal records of faunal abundance and diversity helping to identify the impacts of ongoing global warming on aquatic ecosystems are rare in the coastal Arctic. Here, we used a 50-year-long microfaunal record from a sediment core collected in the Herschel Basin (YC18-HB-GC01; 18 m water depth) to document some aspects of the environmental responses of the southern Canadian coastal Beaufort Sea to climate change. The microfaunal indicators include benthic foraminiferal assemblages, ostracods and tintinnids. The carbonate shells of two foraminiferal species were also analyzed for their stable isotope signatures (δ13C and δ18O). We compiled environmental parameters from 1970 to 2019 for the coastal region, including sea ice data (break-up date, freeze-up date, open season length and mean summer concentration), the wind regime (mean speed, direction of strong winds and the number of storms), hydrological data (freshet date, freshet discharge and mean summer discharge of the Firth and the Mackenzie rivers), and air temperature. Large-scale atmospheric patterns were also taken into consideration. Time-constrained hierarchal clustering analysis of foraminiferal assemblages and environmental parameters revealed a near-synchronous shift around the late 1990s. The microfaunal shift corresponds to an increased abundance of taxa tolerant to variable salinity, turbulent bottom water conditions, and turbid waters towards the present. The same time interval is marked by stronger easterly winds, more frequent storms, reduced sea-ice cover, and a pervasive anticyclonic circulation in the Arctic Ocean (positive Arctic Ocean Oscillation; AOO+). Deeper vertical mixing in the water column in response to intensified winds was fostered by increased open surface waters in summer leading to turbulence, increased particle loading and less saline bottom waters at the study site. Stronger easterly winds probably also resulted in enhanced resuspension events and coastal erosion in addition to a westward spreading of the Mackenzie River plume, altogether contributing to high particulate-matter transport. Increase food availability since ∼2000 was probably linked to enhanced degradation of terrestrial organic carbon, which also implies higher oxygen consumption. The sensitivity of microfaunal communities to environmental variations allowed capturing consequences of climate change on a marine Arctic shelf ecosystem over the last 50 years.

Seasonal dynamics of water circulation and exchange flows in a shallow lagoon-inlet-coastal ocean system

A wave–current coupled, unstructured-grid, three-dimensional hydrodynamic model was applied to investigate the seasonal dynamics of the Maryland Coastal Bays system. The model's performance was validated successfully against hydrodynamic observations from the spring to fall of 2014, and the driving forces of water circulation and exchange flows were discussed. Results indicate that seasonal dynamics are primarily controlled by tides, modulated by winds, waves, and density variations, and regulated by the inlet orientation and geometry. Seasonal circulation in the surface layer is stronger than that near the bottom. The strong coastal circulation, net outflows via inlets, and the clockwise movements in the southern Isle of Wight Bay are primarily controlled by tides. The directional alignment between winds and the bay's principal axis and inlet orientation are key to the seasonal circulation and exchange flows in Sinepuxent Bay and via inlets. Wave-induced effects are comparable to tides in particular regions (e.g., reaching 30 cm/s in Isle of Wight Bay), and much larger than those caused by density variations overall. Additional numerical experiments indicate that spatial variations in salinity are mainly responsible for the density-induced circulation (e.g., 6 cm/s at the mouth of Newport River in Newport Bay). Further analysis indicates that the net exchange flows vary from the surface to bottom layers (e.g., different magnitudes or transporting directions) both in the lagoon and via the paired inlets. This work is beneficial to coastal communities and numerical modelers in understanding the dynamics of shallow lagoon-inlet-coastal ocean systems at a seasonal timescale.

Salinity is an important factor in carbon emissions from an inland lake in arid region

Saline lakes, serving as the ultimate destination for most hydrological systems, accumulate substantial amounts of nutrients and organic matter from basins, and act as vast carbon reservoirs. These lakes exhibit exceptionally active biogeochemical cycling processes of carbon dioxide (CO2) and methane (CH4), and constitute integral components of the global carbon cycle. However, understanding of greenhouse gas emissions from saline lakes remains unclear mostly due to scarce data. In this study, we obtained CO2 and CH4 diffusive fluxes and biogeochemical parameters during ice-free period of 2021 at Bosten Lake, which is a representative inland saline lake located in China's arid region. Results revealed that Bosten Lake was a significant source of atmospheric gas carbon emissions, with average diffusion emissions of 12.645 ± 3.475 mmol m−2 d−1 for CO2 and 0.279 ± 0.069 mmol m−2 d−1 for CH4. Temporally, field measurements found a positive correlation between conductivity (Spc, a proxy of salinity) and CO2 emissions (R2 = 0.50, p < 0.01). Furthermore, the CH4 diffusive fluxes increased with the trophic state index (TSI, R2 = 0.31, p < 0.01). Spatially, exogenous inputs led to the spatial heterogeneity of carbon emissions. Our results highlighted that temporal variations in salinity constitute a crucial factor influencing CO2 emissions, and the saline lake has greater global warming potential compared to freshwater. The study provides an in-depth analysis of greenhouse gas emissions and driving factors in saline lakes of arid regions, and supports a further understanding of the carbon cycle in different types of lakes.

Nanoemulsions stabilized by nonionic surfactants to promote spontaneous imbibition in ultra-low permeability reservoirs: performance evaluation and mechanism study

Nano-emulsions stabilized by nonionic surfactants have the characteristics of ultra-low interfacial tension (IFT) and altered wettability in ultra-low permeability reservoirs. Thus, in this work, a new nanoemulsion is proposed to enhance spontaneous imbibition recovery in ultra-low permeability reservoirs. The nanoemulsion is prepared using n-dodecane, Tween-20, and coconut oil acid diethanolamine n-amyl alcohol. The effects of temperature and salinity on particle size, IFT, and wettability alteration performance of the nanoemulsions were systematically studied. Experimental results show that the particle size of nanoemulsions increases with salinity, and the highest level is up to 100 nm, while an increase in temperature is beneficial to the formation of smaller nanoemulsions. The IFT of the nanoemulsion system can be reduced to an ultra-low level (10–3 mN/m) when the salinity is lower than 50,000 mg/L. As for the wettability alteration property of a nanoemulsion system, an increase in temperature can improve its performance, but variations in salinity seldom have any effects. At 56 °C and 30,000 mg/L salinity, the spontaneous imbibition recovery of 1.00 wt% nanoemulsion can reach 53.8% under the synergistic effect of three mechanisms: extremely small droplet size, excellent wettability alteration performance, and ultra-low IFT. These three mechanisms work together to significantly improve the displacement efficiency of ultra-low-permeability reservoirs.

Soil Quality Improvement with Increasing Reclamation Years in the Yellow River Delta

The saline soils in the Yellow River Delta are primarily affected by seawater intrusion resulting from the intersection of land and sea, which exhibit variations in salinity. The quality of these soils is also influenced by anthropogenic reclamation, including fertilization and irrigation. This study quantitatively evaluated the distinct soil properties and soil quality characteristics of the Yellow River Delta during different reclamation years (i.e., 0a, 1a, 5a, 10a, and 20a) using principal component analysis (PCA) and the Soil Quality Index (SQI). The findings indicated that the soil salt content (SSC) significantly decreased (p &lt; 0.05) from 6.60 g/kg in the initial reclamation year (0a) to 1.63 g/kg in the 10th year (10a) and then slightly increased to 2.85 g/kg in the 20th year (20a). Consequently, the soil salinity level shifted from saline soil to slight salinity and then increased to medium salinity. Ammonium nitrogen (NH4+-N) notably increased by 8.31 mg/kg during the first five years of reclamation (0a to 5a) and gradually decreased by 2.56 mg/kg in the 20th year (20a). On the other hand, nitrate nitrogen (NO3−-N) experienced a significant decrease of 2–5 times after reclamation but continued to increase by 8.96 mg/kg with subsequent reclamation years. The available nitrogen (AN), available phosphorus (AP), and soil organic carbon (SOC) exhibited a significant increase of 24.87 mg/kg, 10.11 mg/kg, and 6.76 g/kg, respectively, with increasing reclamation years. However, available potassium (AK) gradually decreased after reclamation and then increased in the 20th year (20a). The values of SQI for different reclamation years were 0.307 for 0a, 0.339 for 1a, 0.320 for 5a, 0.318 for 10a, and 0.327 for 20a, indicating an increasing trend with increasing reclamation years. It was discovered that long-term reclamation significantly reduced soil salinity and improved soil quality, leading to the sustainable development of reclaimed saline soils in the Yellow River Delta.

Habitat structure shapes temperate reef assemblages across regional environmental gradients

Intertidal artificial habitats are proliferating, but are generally simpler in structure and host lower biodiversity than natural rocky reefs. Eco-engineering aims to enhance the biodiversity of coastal infrastructure, often through physical structural modifications that mimic topographic properties of natural shores. Relationships between biotic assemblages and structural properties of natural and artificial reefs have been extensively studied at sampling scales of up to 1 m2. But evidence that quantified local structural variation has an appreciable influence on biotic assemblages, at a shore-wide scale across regional environmental gradients, is lacking. Here we addressed this knowledge gap with an observational study at 32 natural and artificial intertidal reef sites in Wales, UK. We used multivariate community analysis and permutation tests to examine associations between local physical structure, regional environmental variables and sessile biotic assemblages. A potential influence of local habitat structure on assemblage composition was evident across regional-scale environmental gradients. Compared to natural sites, artificial reefs had lower taxonomic richness, distinct and more variable assemblage composition, and different physical structure. After removing the effect of habitat (natural or artificial), canonical correspondence analysis showed that environmental variables (wave exposure, sea surface temperature and salinity variation), along with two metrics of physical structure (standard deviation in log-transformed detrended roughness and skewness of surface verticality, both at 0.5 m scale), explained 40 % of the variation in assemblage composition among sites. The two structural metrics independently explained 14.5 % of the variation. Associations identified between individual taxa and environmental variables indicated that sites with a higher proportion of horizontal surfaces hosted more canopy macroalgae, which in turn support other algae and invertebrates. Our findings provide evidence to inform scaling-up of structural eco-engineering interventions from experimental contexts to enhance the biodiversity of coastal infrastructure across regional extents.

Portable Conductometric Sensing Probe for Real-Time Monitoring Ammonia Profile in Coastal Waters.

An ability to real-time and continuously monitor ammonium/ammonia profiles of coastal waters over a prolonged period in a simple and maintenance-free fashion would enable economic conducting large-scale assessments, providing the needed scientific insights to better control and mitigate the impact of eutrophication on coastal ecosystems. However, this is a challenging task due to the lack of capable sensors. Here, we demonstrate the use of a membrane-based conductometric ammonia sensing probe (CASP) for real-time monitoring of ammonia levels in coastal waters. A boric acid/glycerol receiving phase is investigated and innovatively utilized to overcome the high salinity of coastal water-induced analytical errors. A calibration-free approach is used to eliminate the need for ongoing calibration, while the issues concerning practical applications, such as salinity variation, ammonia intake capability, and biofouling, are systematically investigated. The field deployment at an estuary confluence water site over a half-moon cycle period confirms that CASP is capable of continuously monitoring the ammonia profile of coastal waters in real-time with high resolution and accuracy to unveil the dynamic ammonia concentration changes over a prolonged period.

Do Salinity Variations Along the East Greenland Shelf Show Imprints of Increasing Meltwater Runoff?

AbstractAccelerated melting of the Greenland Ice Sheet is considered a tipping element in the freshwater balance of the subpolar North Atlantic (SPNA). The East Greenland Current (EGC) and Coastal Current (EGCC) are the major conduits for transporting Arctic‐sourced and Greenland glacial freshwater. Understanding freshwater changes in the EGC system and drivers thereof is crucial for connecting tipping elements in the SPNA. Using the eddy‐rich model VIKING20X (1/20°) and Copernicus GLORYS12 (1/12°), we find that from 1993 to 2019 freshwater remains close to the shelf with interannual extremes in freshwater content (FWC) attributable to the imprint of Greenland melt only in years 2010 and 2012. Runoff increased significantly from 1995 to 2005 and Arctic freshwater export after 2005. Overall, regional wind patterns, sea ice melt and increasingly glacial ice and snow meltwater runoff along with the Arctic‐sourced Polar Water set interannual FWC variations in the EGC system. We emphasize that these freshwater sources have different seasonal timing. South of 65°N sea ice melts year round and retreats to north of 65°N, where melt in summer prevails. Greenland runoff peaks in June–August with only some locations of year round discharge. Alongshore winds intensify in fall and winter where reduced onshore Ekman transport allows for freshwater to spread laterally in the EGC. We show that sea ice melt, runoff and wind can cause interannual variations of comparable magnitude. All of which makes attributing ocean freshening events to Greenland meltwater inflow at current magnitudes a major challenge.

Urticating macromedusae and stinging bathers on the South Atlantic coast: Oceanographic and climatological conditions of Olindias sambaquiensis (Müller, 1861) outbreaks

Incidents of bathers being stung by jellyfish on the coast of southern Brazil have been monitored from 2012 to 2022 to identify the species involved and to search for patterns of behavior in different summer seasons. For 10 years of monitoring, data on occurrence, density and the crossing with the abiotic variables of temperature and salinity of the water and wind direction were obtained. During the investigated period, seven species of macro jellyfish were recorded out, four of them were urticating species, in wich Olindias sambaquiensis was the most frequent and abundant. Based on physical-chemical data on the seawater in this area, the cohorts, and consequently the success in the recruitment and the density of the O. sambaquiensis, may be related with years of low salinity of these Coastal Water. This hydrozoan was also the only species that showed a correlation between average annual density values and incidents of bathers being stung in subsequent summers. Likewise, on a monthly time scale, incidents of stings were correlated with winds from the south quadrant that could promote the transport of organisms to the beach region. A predictive model of the occurrence of jellyfish stinging events is presented and applied for the summer of 2023.

Toward assimilation of acoustic travel times into an ocean state estimate

Direct ocean observing systems are a scarce set of data that build the backbone for understanding the current state of the ocean. These systems are limited in areas of high variability in temperature and salinity. Pioneering work of Wunsch (1977) proposed efforts to extract detailed hydrographic information using sound propagation through the ocean, providing the scaffolding to improve our understanding of the ocean's interior. The integrated nature of such measurements makes acoustic thermometry a powerful application for monitoring regional to basin-averaged hydrographic changes in the ocean, a measurement that is difficult to achieve by individual “point” measurements (moorings, ship-borne CTD casts, or autonomous floats) alone. This work models acoustic travel times corresponding to eigenrays between a fixed source and receiver from an evolving ocean state. Inclusive computation of acoustic travel times within a dynamically evolving modeled ocean state provide a novel approach to model data comparison within a general ocean circulation model. An adjoint assimilation framework combines observations with numerical models to estimate and update oceanic state variables Forget et al. (2015). This process provides the necessary operators for model data comparison of ocean acoustic observable quantities within a consistent state estimation framework allowing for data assimilation from acoustic tomography measurements.

Compositional Streamline-Based Modeling of Polymer Flooding Including Rheology, Retention, and Salinity Variation.

The chemical enhanced oil recovery (CEOR) technology that is most used worldwide is polymer flooding due to its proven commercial success at field scale, maturity, and versatility to combine with other technologies. So, there has been an increasing interest in expanding its applicability to more unfavorable mobility ratio conditions and adverse environments (such as high-temperature, high-salinity carbonate reservoirs, pH-sensitive polymers, and formations with active clays). Therefore, a requirement for successful field application is to find the design parameters of the process that balance material requirements and oil recovery benefits in a cost-effective manner, which is usually done through reservoir modeling. Polymer flooding predictive tools normally require detailed information and are based on time-consuming field reservoir simulations. Thus, for effective project management, a quick and sound tool is needed to screen for polymer flooding applications without giving up key physical-chemical phenomena that govern the oil recovery. In this research, we developed a two-dimensional polymer flooding model based on the streamlines approach. This is an alternative to having a multidimensional practical tool thoroughly representing the physical and chemical behavior of polymer flooding by considering key phenomena such as rheology behavior (shear thinning and shear thickening), salinity variations, permeability reduction, and polymer adsorption. Previously published streamline multidimensional models for polymer flooding lack the integrated modeling of the above-mentioned key phenomena. Additionally, the models to represent rheology and retention phenomena in the proposed tool consider a more complete description than the present streamline-based simulators. For the construction of streamlines, we considered a black oil formulation to estimate the pressure and saturation 2D distribution by applying the implicit in pressure and explicit in saturation method, coupled with an explicit formulation for the 2D composition computation. For saturation-composition along the streamlines, the 1D practical tool incorporated represents the polymer flooding key phenomena. The numerical algorithm used by the streamline-based tool is supported by laboratory experiments for waterflooding in homogenous porous media, analytical results for waterflooding in heterogeneous media, polymer flooding field scale simulation cases, and a CMG-STARS model built as a reference for waterflooding in both media (homogenous and heterogeneous) and for polymer flooding. The practical tool developed contributes to simplifying the upscaling from laboratory observations to field applications with better fitted numerical simulation models and to determining favorable scenarios; thus, it could assist in understanding how key parameters affect oil recovery without performing time-consuming CEOR simulations.

Fluid-fluid interfacial properties during low salinity waterflooding

Understanding the fluid–fluid interfacial interactions is critical to enhancing oil recovery, underground CO2 storage, and soil remediation. Fluid-fluid interfacial interactions were identified as key parameters to govern fluid–fluid interfacial properties. In this investigation, we aim to evaluate the properties of the oil-brine interface in function of fluid compositions during low salinity waterflooding (LSW). Specifically, the main target is to unravel the oil-brine structure, including orientation of the carboxylic group (–COOH), interfacial structure, and species distribution. We utilized molecular dynamics (MD) simulation to evaluate the species distribution and surface structure at the molecular scale. The MD results showed that the carboxylic group accumulated near the oil-brine interface. The orientation of C=O in the carboxylic group is closer to 90° in the brines with all salinity ranges, which is perpendicular to the oil-brine interface. The accumulation and orientation of the carboxylic group is, however, not sensitive to salinity variations. Furthermore, the oil-brine interfacial area turns to be wider with lowering salinity. Radial distribution function (RDF, g(r)) confirmed that lowering salinity decreases g(r) between –COOH and water and thus looses the affinity of oil to water. This investigation provides insights into the fluid–fluid interfacial properties of LSW at the molecular level.

Gaping behaviour of Blue mussels (Mytilus edulis) in relation to freshwater runoff risks

Shellfish grown for food are vulnerable to environmental contamination, potentially rendering them unsafe for human consumption. Non-invasive gape (valve openness) sensing allows in-situ monitoring of bivalve shellfish behaviours, such as feeding, that can result in exposure to contaminated waters. Sensors were attached to Blue mussels and deployed for 10 days on natural mussel beds in Dundrum Bay, Northern Ireland. Data showed a tidally synchronous behaviour pattern of high openness at high water and vice versa. It is likely that this is, at least in part, due to extreme salinity variation (1.8–33.6) resulting from near total water exchange with each tide in the bay. This behaviour is likely to infer a degree of protection from contaminants during periods of low water, a time at which runoff-derived pollutants are most concentrated.

Mechanism and impact of zonally contrasting seasonal variations in sea-surface salinity in the North Pacific and North Atlantic oceans

We investigated the characteristics of seasonal variations in sea surface salinity (SSS) in the subtropical North Pacific and North Atlantic oceans by analyzing observational datasets. As noted in previous studies, the seasonal variation in SSS markedly differs between the western and eastern parts of the basins. These contrasting seasonal variations in SSS have nonnegligible impacts on surface density for each basin and translate into changes in temperature at the outcropping isopycnals of about 1.0 °C. Further analysis of the mixed-layer salinity budget reveals that the zonally contrasting seasonality is attributed to a combination of seasonal variations in the freshwater flux and mixed layer (ML) depth. In the western basins, the wintertime increase in evaporation and reduction in precipitation, as well as the vertical entrainment of salty water below the ML contribute to salinification, whereas the seasonal freshening in summer is mostly attributed to increase in precipitation, reduction in evaporation, and strengthening of geostrophic currents. In contrast, evaporation exceeds precipitation throughout a year in the eastern basins, and seasonal variations in freshwater flux cannot fully explain the seasonal cycle of SSS in the region. Rather, the wintertime freshening there is aided by the deepening of the ML, which acts to mitigate salinification by the evaporation and sustain vertical entrainment of fresher water below the ML. Summertime salinification there can be understood as a mirror image of the wintertime condition, but seasonal strengthening of Ekman currents and associated salinity advection also play a role. (241 words)

Reconstruction of the Late Miocene to Pliocene continental succession of Samos Island: Palaeoenvironmental implications for the Eastern Aegean domain

AbstractOn the Island of Samos (East Aegean region, Greece), two sedimentary basins are filled by thick continental series dated to the Late Miocene to Early Pliocene. A multidisciplinary study has been performed including (1) the definition of 21 sedimentary facies, (2) a review of the biological components and (3) carbon, oxygen and strontium stable isotope analyses. The succession is characterised by various depositional settings and hydrochemical compositions. Five main stages of basin evolution have been identified: (1) The Late Serravallian is marked by the development of alluvial fans and fan delta; (2) during the Lower Tortonian, isolated shallow lakes with variable salinity, from fresh to brackish, developed under warm and relatively humid conditions; (3) the Middle to Upper Tortonian is marked by the development of a large and deep lake with saline and alkaline waters, under colder and drier conditions; (4) the Latest Tortonian to Messinian period is represented by an ephemeral alluvial system, developed under a dry climate; (5) during the Zanclean, a palustrine and paludal wetland system, dominated by tufa carbonates, developed under moderately humid conditions. This succession is of particular interest for the reconstruction of the palaeoenvironmental evolution of the transition zone between the Mediterranean domain, and the Paratethys and circum‐Paratethys areas. The geochemical data and the presence of flora (diatoms) and fauna (gastropods) of marine affinity suggest transient ingressions of marine‐related water or groundwater inflows as early as the Lower Tortonian. The Samos succession records the complex interaction between the regional geodynamics and climate. The extensional regime of the Eastern Aegean zone generates subsidence, interrupted in the mid‐Tortonian (9 Ma) by a brief compressive event and a major exposure of the basins. Furthermore, the Late Miocene progressive aridification, followed by a change to a more humid climate (Pliocene) is also a major driver of the sedimentation.