Decrease In Salinity Research Articles

Evaluation of the Effects of Water and Salinity Stress on the Growth and Biochemistry of Alfalfa (Medicago sativa L.) at the Branching Stage

The response of alfalfa to water and salinity stress differs during the whole growth period, and water stress has the most severe effects on the yield of alfalfa at the branching stage. However, the presence of soil salt can also enhance its drought resistance and alleviate the impact of water stress on yield. Thus, information on the responses of aboveground biomass, water-use efficiency and osmolytes to water and salinity stress at the branching stages of alfalfa development is urgently required. A pot experiment that combined three irrigation levels of 55–70% (W1), 70–85% (W2) and 85–100% (W3) of field capacity (FC) and four salinity levels was conducted in Dengkou County, Inner Mongolia, China, in 2018 and 2019. The percentage of mixed salt (NaCl:Na2SO4 = 1:1 [w/w]) added for the salinity treatments was 0, 2, 4 and 6% of the soil dry weight and was designated as S0–S3, respectively. The water consumption, biomass, osmolytes, such as proline and Na+, and the activities of antioxidant enzymes, such as superoxide dismutase (SOD) and peroxidase (POD), of alfalfa were measured during its early flowering stage. In general, the plant height, aboveground biomass, root biomass and water consumption of alfalfa increased with the decrease in soil salinity and increase in the amount of irrigation applied. When the salt >3 g kg−1, alfalfa could improve its stress resistance by increasing the contents of proline and Na+ and the activity of POD and decreasing the activity of SOD, but the aboveground biomass and water consumption decreased. However, alfalfa has a certain cross adaptation ability under water and salt stress at the branching stage, particularly when salt is less than 3 g kg−1. Compared with single water stress, adding an appropriate amount of salt (≤3 g kg−1) increased the contents of proline and Na+ and the activities of SOD and POD, which led to water consumption and aboveground biomass of alfalfa increases of 11.93% and 17.51%, respectively. In conclusion, the alfalfa was tolerant to moderate (3 g kg−1) salt stress. The alfalfa with higher proline, SOD and POD activity and Na+ was better able to yield well under salt stress. Meanwhile, combined with moderate irrigation (70–85% FC), the productivity of alfalfa was improved better. The results can provide a theoretical basis for the utilization of alfalfa in salinized land.

Spatiotemporal Patterns and Key Driving Factors of Soil Salinity in Dry and Wet Years in an Arid Agricultural Area with Shallow Groundwater Table

Soil salinization is a major eco-environmental problem in irrigated agro-ecosystems. Understanding regional soil salinity spatial patterns and seasonal dynamics and their driving factors under changing environments is beneficial to managing soil salinity to maintain agricultural production in arid agricultural areas. To better investigate this topic, soil salinity was measured, ranging from topsoil to the depth of 1.8 m in an irrigation district with 68 sampling sites before and after the crop growing seasons of the dry year of 2017 and wet year of 2018. Soil texture, groundwater table depth, groundwater salinity, and crop type were monitored. The results indicated that an increase in soil salinity in the root zone (0–0.6 m) was accompanied by a decrease in soil salinity in the deep soil (0.6–1.8 m) through the crop growing season due to water movement from the deep layer to shallow layer, whereas the opposite trend was observed during the fallow seasons. During the dry year, the area with soil desalted was measured to be 19.89%, 14.42%, and 2.78% lower at depths of 0–0.6 m, 0.6–1.2 m, and 1.2–1.8 m than that during the wet year. The groundwater table depth in the crop growing season had the least impact on the change in root zone soil salinity (p > 0.05). Interactions between crop types and groundwater table depth had a significant effect on the change of soil salinity in the root zone during the growing season of the dry year, but were insignificant during the wet year. Crop types, groundwater table depth, and climate conditions determined the contribution of shallow groundwater to crop water consumption and, to a greater extent, soil salinity. Regression tree analysis showed that groundwater salinity and soil texture had a greater influence on soil salinity than groundwater table depth and land elevation. The effect of groundwater on soil salinity is strongly related to soil texture, and the salinity of fine-textured soil was 36–54% greater than that of coarse-textured soil due to large capillary action. Therefore, we suggest strengthening groundwater management in areas with fine-textured soil to relieve soil salinization, particularly during dry years.

Genesis of the Dongpuzi Gold Deposit in the Liaodong Peninsula, NE China: Constraints from Geology, Fluid Inclusion, and C–H–O–S–Pb Isotopes

The Dongpuzi deposit is an epithermal gold deposit located in the southern margin of the Shaozihe volcanic fault basin in the Liaodong Peninsula. On the basis of fluid inclusion and C–H–O–S–Pb isotope data, a metallogenic model is established for the Dongpuzi deposit. The mineralization at the Dongpuzi deposit has experienced quartz–pyrite (I), quartz–sulfide (II), and quartz–calcite (III) stages. The quartz from ore stage II has liquid-dominated aqueous inclusions, which have homogenization temperatures ranging from 113 to 162 °C and salinities varying from 3.2 to 9.6 wt% NaCl equiv. The quartz from the quartz–calcite stage has decreasing homogenization temperatures (106~143 °C) and salinities (2.7~6.9 wt% NaCl equiv.). The fluid inclusion data indicate that the gold ores were precipitated from low-temperature and low-salinity solutions, with an obvious decrease in temperature and salinity from ore stages II to III. The calculated δ18Owater values for the quartz of ore stage II range from −14.71‰ to −13.31‰, and the corresponding δDwater values range from −103.3‰ to −96.1‰, indicating that the ore-forming fluids could be of a meteoric origin. The calcite from ore stage III has δ13CV-PDB values of −4.5‰ to −4.2‰ and δ18OV-SMOW values of +7.0‰ to +7.4‰, indicating a mantle source for the carbon. The pyrite yielded δ34S values of +4.1‰ to +6.6‰ and Pb isotopes consistent with those of the host trachyte porphyry and volcanic rocks of the Xiaoling Formation, which suggests that the S and Pb in gold ores were dominantly derived from the host trachyte porphyry and volcanic rocks of the Xiaoling Formation, with some combination of Paleoproterozoic metamorphic rocks of the Gaixian Formation. These results, together with the ore geology, indicate that the Dongpuzi deposit is a typical low-sulfidation epithermal gold deposit with important ore-forming materials input from the host trachyte porphyry, volcanic rocks of the Xiaoling Formation, and Paleoproterozoic metamorphic rocks of the Gaixian Formation. The Dongpuzi deposit was formed under an extensional setting related to the Early Cretaceous lithospheric extension and thinning of the eastern North China Craton.

Ocean Surface Salinity Response to Atmospheric River Precipitation in the California Current System

Abstract Atmospheric rivers (ARs) result in precipitation over land and ocean. Rainfall on the ocean can generate a buoyant layer of freshwater that impacts exchanges between the surface and the mixed layer. These “fresh lenses” are important for weather and climate because they may impact the ocean stratification at all time scales. Here we use in situ ocean data, collocated with AR events, and a one-dimensional configuration of a general circulation model, to investigate the impact of AR precipitation on surface ocean salinity in the California Current System (CCS) on seasonal and event-based time scales. We find that at coastal and onshore locations the CCS freshens through the rainy season due to AR events, and years with higher AR activity are associated with a stronger freshening signal. On shorter time scales, model simulations suggest that events characteristic of CCS ARs can produce salinity changes that are detectable by ocean instruments (≥0.01 psu). Here, the surface salinity change depends linearly on rain rate and inversely on wind speed. Higher wind speeds (U > 8 m s−1) induce mixing, distributing freshwater inputs to depths greater than 20 m. Lower wind speeds (U ≤ 8 m s−1) allow freshwater lenses to remain at the surface. Results suggest that local precipitation is important in setting the freshwater seasonal cycle of the CCS and that the formation of freshwater lenses should be considered for identifying impacts of atmospheric variability on the upper ocean in the CCS on weather event time scales. Significance Statement Atmospheric rivers produce large amounts of rainfall. The purpose of this study is to understand how this rain impacts the surface ocean in the California Current System on seasonal and event time scales. Our results show that a greater precipitation over the rainy season leads to a larger decrease in salinity over time. On shorter time scales, these atmospheric river precipitation events commonly produce a surface salinity response that is detectable by ocean instruments. This salinity response depends on the amount of rainfall and the wind speed. In general, higher wind speeds will cause the freshwater input from rain to mix deeper, while lower wind speeds will have reduced mixing, allowing a layer of freshwater to persist at the surface.

Interplay of Seasonality, Major and Trace Elements: Impacts on the Polychaete Diopatra neapolitana.

Simple SummaryCoastal systems often serve as sinks for toxic elements, and seasonality has been responsible for many changes in the physical and chemical parameters of waters and sediments, leading to geochemical alterations in aquatic systems and the alteration of element uptake rates in organisms. Diopatra neapolitana worms were collected from five sites of the Ria de Aveiro lagoon in the autumn, winter, spring, and summer of 2018/2019 and were tested to check for differences in the biochemical responses (cell damage, antioxidant enzymes, biotransformation enzymes, and energy-related parameters) among seasons and sites. In general, the results demonstrated that enzyme activities were higher in spring and summer due to high temperatures and element bioaccumulation. Energy-related parameters presented with higher levels in spring and autumn, which was mainly due to element bioaccumulation. Oxidative damage was higher during winter and was related to salinity and decreases in temperature. This study demonstrated that abiotic factors influence the geochemistry of elements and that both significantly affect organism performance in low-contamination systems, such as the Ria de Aveiro lagoon. This knowledge is important to understand how ecological and economically relevant species such as D. neapolitana respond to environmental changes.Polychaetes are known to be good bioindicators of marine pollution, such as inorganic contamination. Major and trace elements are commonly present in sediment and may be accumulated by polychaetes such as the tubiculous Diopatra neapolitana. In this study, D. neapolitana individuals were collected in the autumn, winter, spring, and summer of 2018/2019 from the Ria de Aveiro lagoon (western Portugal) to understand how seasonality influences element accumulation. The impact of the interaction of seasonality and elements on oxidative status, energy metabolism, and oxidative damage was also assessed. The obtained results showed that the activity of the antioxidant enzymes catalase, glutathione S-transferases, and non-protein thiol levels were higher in summer and that superoxide dismutase, lipid peroxidation, and electron transport system activity increased in winter. The lowest glycogen levels were observed during spring, and protein carbonylation was the highest during autumn. These results could mainly be related to high temperatures and the bioaccumulation of Al, As, Mn, and Zn. Energy-related parameters increased during spring and autumn, mainly due to the bioaccumulation of the same elements during spring and summer. Lipid damage was higher during winter, which was mainly due to salinity and temperature decreases. Overall, this study demonstrates that seasonality plays a role in element accumulation by polychaetes and that both impact the oxidative status of D. neapolitana.

Copepod oxygen consumption along a salinity gradient

ABSTRACT Climate change-induced salinity decrease is currently occurring in many estuarine coastal zones, due to increased outflow of freshwater. This freshening can be a problem for brackish-water animals, already living on the edge of their salinity tolerance. We measured oxygen consumption of common copepod Eurytemora affinis along a natural salinity gradient in the western Gulf of Finland. The salinity varied between 3 in the inner bay and 7 in the offshore area along the gradient, pH varied between 7.05 and 7.86. Our results show that respiration increased with decreasing salinity, as expected for a genus more commonly found in estuarine/saline waters, even if it has colonised brackish waters. Our results suggest that future decreasing salinity could enhance respiration rate, and so energy requirements, of large-bodied zooplankton in estuarine areas such as the Baltic Sea and could lead to lower food quality availability for coastal planktivorous fish, such as herring and sprat.

Provision of Desalinated Irrigation Water by the Desalination of Groundwater Abstracted from a Saline Aquifer

Globally, about 54 million ha of cropland are irrigated with saline water. Globally, the soils associated with about 1 billion ha are affected by salinization. A small decrease in irrigation water salinity (and soil salinity) can result in a disproportionally large increase in crop yield. This study uses a zero-valent iron desalination reactor to effect surface processing of ground water, obtained from an aquifer, to partially desalinate the water. The product water can be used for irrigation, or it can be reinjected into a saline aquifer, to dilute the aquifer water salinity (as part of an aquifer water quality management program), or it can be injected as low-salinity water into an aquifer to provide a recharge barrier to protect against seawater intrusion. The saline water used in this study is processed in a batch flow, bubble column, static bed, diffusion reactor train (0.24 m3), with a processing capacity of 1.7–1.9 m3 d−1 and a processing duration of 3 h. The reactor contained 0.4 kg Fe0. A total of 70 batches of saline water (average 6.9 g NaCl L−1; range: 2.66 to 30.5 g NaCl L−1) were processed sequentially using a single Fe0 charge, without loss of activity. The average desalination was 24.5%. The reactor used a catalytic pressure swing adsorption–desorption process. The trial results were analysed with respect to Na+ ion removal, Cl− ion removal, and the impact of adding trains. The reactor train was then repurposed, using n-Fe0 and emulsified m-Fe0, to establish the impact of reducing particle size on the amount of desalination, and the amount of n-Fe0 required to achieve a specific desalination level.

Compositional and Metabolic Responses of Autotrophic Microbial Community to Salinity in Lacustrine Environments.

ABSTRACTThe compositional and physiological responses of autotrophic microbiotas to salinity in lakes remain unclear. In this study, the community composition and carbon fixation pathways of autotrophic microorganisms in lacustrine sediments with a salinity gradient (82.6 g/L to 0.54 g/L) were investigated by using metagenomic analysis. A total of 117 metagenome-assembled genomes (MAGs) with carbon fixation potentially belonging to 20 phyla were obtained. The abundance of these potential autotrophs increased significantly with decreasing salinity, and the variation of sediment autotrophic microbial communities was mainly affected by salinity, pH, and total organic carbon. Notably, along the decreasing salinity gradient, the dominant lineage shifted from Desulfobacterota to Proteobacteria. Meanwhile, the dominant carbon fixation pathway shifted from the Wood-Lungdahl pathway to the less-energy-efficient Calvin-Benson-Bassham cycle, with glycolysis shifting from the Embden-Meyerhof-Parnas pathway to the less-exergonic Entner-Doudoroff pathway. These results suggest that the physiological efficiency of autotrophic microorganisms decreased when the environmental salinity became lower. Metabolic inference of these MAGs revealed that carbon fixation may be coupled to the oxidation of reduced sulfur compounds and ferrous iron, dissimilatory nitrate reduction at low salinity, and dissimilatory sulfate reduction in hypersaline sediments. These results extend our understanding of metabolic versatility and niche diversity of autotrophic microorganisms in saline environments and shed light on the response of autotrophic microbiomes to salinity. These findings are of great significance for understanding the impact of desalination caused by climate warming on the carbon cycle of saline lake ecosystems.IMPORTANCE The Qinghai-Tibetan lakes are experiencing water increase and salinity decrease due to climate warming. However, little is known about how the salinity decrease will affect the composition of autotrophic microbial populations and their carbon fixation pathways. In this study, we used genome-resolved metagenomics to interpret the dynamic changes in the autotrophic microbial community and metabolic pathways along a salinity gradient. The results showed that desalination drove the shift of the dominant microbial lineage from Desulfobacterota to Proteobacteria, enriched autotrophs with lower physiological efficiency pathways, and enhanced coupling between the carbon cycle and other element cycles. These results can predict the future response of microbial communities to lake desalination and improve our understanding of the effect of climate warming on the carbon cycle in saline aquatic ecosystems.

Formation damage of sandstone geothermal reservoirs: During decreased salinity water injection

Water reinjection was widely implemented in the geothermal development for not only disposing tailwater but also maintaining reservoir pressure. Accompanying this was the formation damage, especially in the injection of decreased salinity water which was synthesized by adding surface water and condensed water into produced water for inhibiting the process equipment corrosion, treating the cooling tower condensate, and etc. Fine migration is the prevailing mechanism; however, it is insufficient in some scenarios. Multiple experiments were conducted to investigate the characteristics and mechanisms of formation damage of sandstone geothermal reservoirs during the decreased salinity water injection. First, coreflooding (CF), nuclear magnetic resonance (NMR), and contact angle (CA) experiments were conducted to analyze the characteristics of the formation damage. Subsequently, scanning electron microscopy (SEM), X-ray diffraction (XRD), inductively coupled plasma optical emission spectrometry (ICP-OES), and nanoindentation experiments were implemented to study the corresponding mechanisms. Finally, the damage mode of sandstone geothermal reservoirs in decreased salinity water injection was proposed. The CF, NMR, and CA experimental results indicated that the decreased salinity water injection resulted in severe formation damage, as manifested by the reduction of permeability, shrinkage of the pore-throat, and enhancement of the water-wettability of core samples. That is, formation damage not only indicates that the fluid is more difficult to be injected but also that it is more difficult for the injected fluid to flow. As the salinity decreases, these trends gradually enhance. The SEM results illustrated that fine migration is noticeable in decreased salinity water injection, meanwhile mineral dissolution which causes secondary pores and microfracture is also apparent. Both reactions are enhanced as the salinity decreases. The same conclusion was validated by the XRD and ICP-OES results, as manifested by the decrease in the concentrations of clay, K-feldspar, and plagioclase, and the increase in quartz, as well as the emergence of Si4+, Mg2+, Ca2+, and K+ in the effluents produced during the decreased salinity water injection. The nanoindentation results explicated that mineral dissolution weakened the mechanical strength of the minerals, which might effectively facilitate compaction. The elastic modulus and hardness of the quartz, K-feldspar, and plagioclase decreased from 107.5&93.7&72.3GPa and 13.7&10.1&7.4GPa of the original sandstone to 108.1&86.0&69.5GPa and 13.6&10.3&6.4GPa of the deionized water flushed one, respectively. In conclusion, formation damage was synergistically dominated by the external cause of compaction and the internal causes of fine migration and mineral dissolution. These factors compressed the pore-throat, decreased the connectivity of the porous media, enhanced the water-wettability of the sandstone surface, and consequently impeded water flow.

The Role of Soil Salinization in Shaping the Spatio-Temporal Patterns of Soil Organic Carbon Stock

Soil salinization is closely related to land degradation, and it is supposed to exert a significant negative effect on soil organic carbon (SOC) stock dynamics. This effect and its mechanism have been examined at site and transect scales in previous studies while over a large spatial extent, the salinity-induced changes in SOC stock over space and time have been less quantified, especially by machine learning and remote sensing techniques. The main focus of this study is to answer the following question: to what extent can soil salinity exert an additional effect on SOC stock over time at a larger spatial scale? Thus, we employed the extreme gradient boosting models (XGBoost) combined with field site-level measurements from 433 sites and 41 static and time-varying environmental covariates to construct methods capable of quantifying the salinity-induced SOC changes in a typical inland river basin of China between the 1990s and 2020s. Results showed that the XGBoost models performed well in predicting the soil electrical conductivity (EC) and SOC stock at 0–20 cm, with the R2 value reaching 0.85 and 0.81, respectively. SOC stock was found to vary significantly with increasing soil salinity following an exponential decay function (R2 = 0.27), and salinity sensitivity analysis showed that soils in oasis were expected to experience the largest carbon loss (−137.78 g m−2), which was about 4.84, 14.37, and 25.95 times higher than that in the saline, bare, and sandy land, respectively, if the soil salinity increased by 100%. In addition, the decrease in the soil salinity (−0.32 dS m−1) from the 1990s to the 2020s was estimated to enhance the SOC stock by 0.015 kg m−2, which contributed an additional 10% increase to the total SOC stock enhancement. Overall, the proposed methods can be applied for quantification of the direction and size of the salinity effect on SOC stock changes in other salt-affected regions. Our results also suggest that the role of soil salinization should not be neglected in SOC changes projection, and soil salinization control measures should be further taken into practice to enhance soil carbon sequestration in arid inland river basins.

Adsorption mechanism of trace heavy metals on microplastics and simulating their effect on microalgae in river

Microplastics (MPs) and heavy-metal contamination in freshwater is an increasing concern. Fe, Mn, Pb, Zn, Cr, and Cd are common heavy metals that can easily flow into rivers causing water pollution. Microplastics act as carriers for heavy metals and increase the transport of contaminants in freshwater systems. We investigated the adsorption mechanisms of three kinds of MPs having similar particle sizes, namely polypropylene (PP), polystyrene (PS), and polyvinyl chloride (PVC), with respect to trace heavy metals of Pb, Cu, Cr, and Cd under different temperature and salinity conditions. The reaction kinetics of the adsorption of different trace heavy metals on different MPs were consistent with both the quasi primary and quasi secondary kinetic models, indicating the complexity of heavy metal adsorption by MPs. The adsorption rate of heavy metal on MPs was mainly controlled by intra-particle diffusion, and the isotherm model indicated that the adsorption of Pb, Cu, Cr, and Cd by MPs occurred in the form of monolayer physical adsorption. Additionally, an increase in temperature and decrease in salinity were favourable to improve the affinity of MPs toward heavy metals (through adsorption). Zeta potential measurements and Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) analyses indicated that electrostatic force interaction was the main mechanism of the adsorption process; oxygen-containing functional groups, π-π interaction, and halogen bonds played important roles in the process of adsorption. Furthermore, the growth inhibition and oxidative stress of microalgae Chlorella vulgaris (GY-D27) due to PP, PS, and PVC were analysed; notably, MPs or Pb inhibited the growth of Chlorella vulgaris. However, the reduced toxicity to Chlorella vulgaris, with respect to a mixture of Pb and MPs, was confirmed using superoxide dismutase and catalase enzyme activities. Our results can be applied for the risk assessment of heavy metals and MPs in aquatic environments.

Macroinvertebrates as bio-indicators of water quality in Omubira Stream, in Kakamega County, Kenya

Human-induced environmental stress can impair freshwater ecosystems by destroying them or altering them in negativeways. Laws and ordinances that stress Kenya's water resources' correct management and utilization were prompted by worries about the management of freshwater bodies. Therefore, understanding of the health status of aquatic environments, particularly their biodiversity, is crucial in order to comprehend the status of water quality and limit the rate of pollution in our streams and rivers. Several well-known biological markers of water quality can be used for this. Bio-indicators are species or groups of species that can quickly reveal the abiotic or biotic condition of an environment, show how environmental change has affected a habitat or ecosystem. In many industrialized nations, including those in Europe and North America, macroinvertebrates are widely utilized as bio-indicators and are part of their national and technical standards for water quality monitoring. Their use is still relatively restricted in developing nations like Kenya. Furthermore, the use of aquatic macroinvertebrates as bio-indicators of water quality to assess the condition of aquatic ecosystems is not stressed by Kenyan environmental laws and regulatory bodies. This can be because the nation doesn't have a well-known and established biomonitoring system. However, only a small number of studies have begun utilizing macroinvertebrate species as bio-indicators at this time. A greater comprehension of the macroinvertebrate variety of the Omubira River could help in the stream management due to continued municipal and agricultural activities along this river. As a result, this study examined the use of macroinvertebrates as bio-indicators of river water quality and determined how they reacted to water quality in the various region of the stream.Macroinvertebrates and selected physicochemical variables were sampled monthly in four sites for a period of four months. On each sampling sites at every sampling episode physicochemical variables including temperature, conductivity, salinity, turbidity, pH, dissolved oxygen and percentage saturation oxygen were measured using a Hydrolab Quanta Multi-Probe Meter. A Surber sampler of an area 1200 cm2 and corer sampler were used with catching area of 20.83 cm2 to capture macroinvertebrates. There was a general decrease of Temprature, turbidity, salinity, conductivity and pH from the town area to the forested area. However, dissolved oxygen increased from the town area to forested area. A general variation of macroinvertebrates species from manucipal area to forested area in the river was observed. The highest abundance of Belostomatidae (16.87), Chironomidae (16.77), Naididae (14.07) and Gomphidae (18.67) were found in the manucipal reach of the river. The highest abundance of Elmidae (20.49) and Notonectidae (19.87) were found in the agricultural reach while the highest abundance of Gerridae (10.53), Hydropsychidae (28.65) and Perlidae (33.92) were found at the forested reach. From the diverse makeup of the macroinvertebrates, Omubira stream's water quality can be described as moderately clean. This could be harmful to aquatic life and communities living along, which depends on highly clean water to exist. This study therefore recommends continuious monitoring and proper management of pollution sources into the stream by the pertinent authorities as well as embracing bio-indictors.

Cabbeling due to mixing of the Bering Strait and the Chukchi Sea waters on seasonal and climatic scale

Cabbeling due to mixing of the surface waters from the Bering Strait and the Chukchi Sea is evaluated quantitatively and variations of its impact on seasonal and climatic scale are analyzed. The cabbeling effect increases additionally the mixed water density in 0.059 kg/m3 in summer and in 0.001 kg/m3 in winter. Seasonal variation of the cabelling repeats the seasonal variation of temperature difference between the interacted water masses (ΔT ~ 5,0 оC in summer, ΔT ~ 0,5 оC in winter). This process provides additional energy for sinking of warm and salt mixed water in summer, when it penetrates far into the Arctic. In winter, the temperature difference between the mixing waters is about zero, so the cabbeling almost disappears. Both temperature and salinity have climatic trends in the Chukchi Sea that causes the climate-scale variation of the cabbeling: its impact increases in 0.002 kg/m3 per decade in summer because of climatic heating (~0,13 оC/decade) and salinity decrease (~0.04 psu/decade).

Different Responses of Chlorophyll a to the Passage of the Tropical Storm Wipha (2019) in the Coastal Waters of the Northern Beibu Gulf

Tropical storms (TS) are important drivers of short-term changes and affects the coastal and marine environment. Based on in situ observational data from four locations in the coastal area of the northern Beibu Gulf and satellite data, we analyzed the changes in temperature, salinity, and turbidity during the transit of TS “Wipha” in 2019 and assessed the environmental factors controlling chlorophyll a concenteation (Chl-a) increases in the coastal area. Our results showed that in the coastal area, the growth of phytoplankton after the TS was mainly controlled by the nutrient and light availability. The increased input of freshwater by TS, including direct inputs from rainfall and increased river discharge, reduced the salinity. The decrease in salinity may indicate an increased input of nutrient-rich freshwater at all four stations (nutrients input: S1>S2>S3>S4). Nutrient concentration at S1, S2, and S3 implied by salinity was high, but that at S4 was limited. The shorter recovery time of turbidity after TS indicated the faster improvement of light conditions in this area [recovery time: S4 (2 days)< S1 (3 days)< S3 (5 days)< S2 (10 days)]. The high turbidity associated with poor light penetration was an important factor limiting phytoplankton growth at station 2, with a slow recovery of the turbidity to pre-TS levels. The rapid recovery of the turbidity to the pre-TS levels at S1, S3, and S4 suggested good light conditions soon after the TS, and probably led to a significant increase in Chl-a after the TS ([Chl-a]: S1>S3>S4). The less of an increase of Chl-a at S4 was not only related to nutrient restriction but also related to weak mixing of the water column, while the least significant decrease in the SST at S4 implied that the enhancing mixing after TS was limited.

Subsurface Water Property Structures Along 80°E Under the Positive Indian Ocean Dipole Mode in December 2019

High-accuracy ship-based observations were conducted at 80°E in the Indian Ocean. Salinity below the mixed layer in 2019 was observed to be lower than that in 1995. This decrease in salinity was mainly attributed to anomalous advection associated with one of the strongest positive Indian Ocean dipole (pIOD) events in 2019 through analysis of the gridded time series of the salinity distributions based on the Argo float array. Increases and decreases in nitrate and dissolved inorganic carbon (DIC) and dissolved oxygen (DO), respectively, were also detected on the isopycnal surfaces where decreases in salinity were observed, suggesting that the anomalous upwelling and westward advection associated with the pIOD in the eastern part of the equatorial region resulted in low-salinity, low-oxygen, and nutrient-rich waters in the central off-equatorial region of the Indian Ocean. However, downward isopycnal heaving, which was also associated with the pIOD, was too strong to have increased nitrate below the mixed layers, and thus might have suppressed biological activity. The heaving also affected the DIC and DO distributions, and the effect of interannual changes such as those associated with the Indian Ocean dipole is essential to estimating changes in anthropogenic carbon storage. This research represents a case study, based on only two occupations; therefore, an assessment utilizing more intensive observations and more realistic numerical simulations is necessary in the future.

Survival, osmoregulatory and hemocyte changes in Litopenaeus vannamei postlarvae acclimated to different intervals of salinity reduction

The goal of this study was to assess osmotic stress in Litopenaeus vannamei postlarvae (PL12) in three different progressive osmotic stress levels ranging from sea water (35‰) to low salinity (5‰). The survival of PL12 reduced as medium salinity decreased. PL12 acclimated to a gradual acclimation of 5‰ showed significantly higher survival (with a survival percentage (SP) of 90%) than those acclimated to a gradual acclimation of 10‰ (SP = 80%) and 15‰ (SP = 58%). At the end of the acclimation period (at 5‰), PL12 acclimated to a gradual acclimation of 15‰ (Trial 3) exhibited significantly greater hemolymph osmolality (696 mOsm/kg H2O) than those gradually acclimated to a gradual acclimation of 10‰ (546 mOsm/kg H2O, Trial 2) and 5‰ (450 mOsm/kg H2O, Trial 1). The levels of Na+, K+ and Cl- in the hemolymph of PL12 decreased with decreasing salinity in all three trials. Na+-K+-ATPase levels of PL12 increase as salinity decreases. Total hemocyte count levels decreased when the salinity decreased from 35‰ to 5‰. The longer acclimation time may account for the greater survival rate, as it likely ensures ion balance between the shrimp hemolymph and the surrounding environment thus minimizing osmoregulatory stress.

Effects of mesoscale eddies on intraseasonal variability of intermediate water east of Taiwan

The intraseasonal variability of the intermediate water (IW) and its characteristics east of Taiwan are studied utilizing 17 months of long-term, continuous and synchronous measurements of temperature, salinity and current from mooring sites deployed at 122° E/23° N from January 2016 to May 2017. Direct measurements revealed water masses east of Taiwan alternately show complete South China Sea Intermediate Water or North Pacific Intermediate Water (NPIW) characteristics, mostly in a mixed state, with NPIW dominating 70% of the time. For the first time, it is demonstrated that the variation of IW with periods of ~ 80 days is mainly related to mesoscale eddies. Anticyclonic (cyclonic) eddies corresponding to an increase (decrease) in temperature and salinity in the intermediate layer. Further mechanism analysis indicates the vertical motion of the water mass inside the eddies is one of the reasons for the thermohaline change in the intermedaiter layer. In addition, the anticyclonic eddies may increase the salinity concentration gradient across the Luzon Strait, and the enhanced advection is favorable to the outflow of water masses in the South China Sea. When the cyclonic eddies acts on the eastern part of Taiwan, the influence of the northward advection is weakened and the southward flow on its left side is more favorable to the transport of NPIW.

Salinity tolerance mechanisms of an Arctic Pelagophyte using comparative transcriptomic and gene expression analysis

Little is known at the transcriptional level about microbial eukaryotic adaptations to short-term salinity change. Arctic microalgae are exposed to low salinity due to sea-ice melt and higher salinity with brine channel formation during freeze-up. Here, we investigate the transcriptional response of an ice-associated microalgae over salinities from 45 to 8. Our results show a bracketed response of differential gene expression when the cultures were exposed to progressively decreasing salinity. Key genes associated with salinity changes were involved in specific metabolic pathways, transcription factors and regulators, protein kinases, carbohydrate active enzymes, and inorganic ion transporters. The pelagophyte seemed to use a strategy involving overexpression of Na+-H+ antiporters and Na+ -Pi symporters as salinity decreases, but the K+ channel complex at higher salinities. Specific adaptation to cold saline arctic conditions was seen with differential expression of several antifreeze proteins, an ice-binding protein and an acyl-esterase involved in cold adaptation.

Multiproxy constraints on Central Paratethys Sea and Lake Pannon paleoclimate and paleoenvironment transitions during the Middle-Late Miocene (Danube Basin, Slovakia)

The Danube Basin represents a northwestern depocenter of the Middle Miocene Central Paratethys Sea, which was succeed by the Late Miocene Lake Pannon. Although this is an extensively examined area, the application of multidisciplinary studies has proven capable of drawing attention to novel information concerning the depositional environment. Thus, this study aims to reveal climatic and paleoenvironmental changes by using both archive and fresh data drawn from biomarkers, palynology, sedimentology, and geochemistry. The article also addresses the quality, quantity, and thermal maturity of organic matter in relation to hydrocarbon potential. In general, the beginning of Serravallian stage relates to a regression forced by the development of the Antarctic icesheet followed by a pronounced transgression. The results presented here show that the Central Paratethys Sea reacted to the late Badenian (Serravallian) flooding, by an event which triggered a dysoxic, but not euxinic, bottom waters. The climate remained warm and humid, with paratropical to subtropical forests on the continent. Several new depocenters developed during the Sarmatian and divided the depositional environments into a shelf-brake slope in the central part of the Danube Basin, and into deltaic and swamp environments on the basin margins. The climate changed to temperate, leading to the disappearance of subtropical taxa. A shallow lake and swamp environment developed at the beginning of the Pannonian (Tortonian), forcing a salinity decrease connected to the increase in humidity. The degree of hydrocarbon richness of the mudstones is generally fair to good, and the kerogen is of mixed marine-terrestrial origin (II and III). Nonetheless, sediments at the basin margin are clearly immature due to insufficient burial.

The impact of salinity, alkalinity and nanoparticle concentration on zeta-potential of sand minerals and their implication on sand production

The effect of brine salinity, cation type, pH, and produced sand on zeta potential (ZP) measurements with and without the presence of silica nanoparticles is investigated through pH measurement, static tests for sand and ZP measurements as well as Field Emission Scanning Electron Microscope (FESEM) analyses. Three important factors were investigated: composition of the injected brine, surface charge and pH. Their influence on stability of nanoparticles in the injected brine and amount of sand segregation was determined and the analysis of the new outcomes based on rock/brine ZP measurements was reported. The results show that the use of silica nanoparticles with high pH helps in preventing sand production and that pH has a main effect on the surface charge of the sand particle released, affecting the ZP of the solution. Nanoparticles can be active as a coating on sand grains and prevent sand segregation during water flooding. Divalent cations have been found to acquire a more substantial impact on neutralizing the negative charge of the sand particles than monovalent cations at the same concentration and pH conditions at 25 ℃. The value of ZP becomes of higher negative value with the decrease of brine salinity. The effectiveness of SiO2 nanoparticles is quite different for soft water and smart water. For soft water, the nanoparticles work more effective at pH higher than 8; and for smart water, the nanoparticles perform better at pH lower than 8. To reduce sand production with the use of silica nanoparticles, it is highly suggested to increase pH, as pH and sand production mechanisms were observed to be inversely related.