Maximum Salinity Research Articles

Semi-continuous cultivation of microalgae to treat coal mine effluent in pilot scale: Nutrient removal, biodesalination and fatty acid composition analysis

Coal excavation is associated with discharge of an enormous amount of mine water rich in salt and trace metal ions, which require efficient treatment before use. Considering the potentiality of microalgae for high salt tolerance, salt removal and metallic pollutant removal from aqueous system, present study focuses semi-continuous cultivation of candidate microalgae Chlorella pyrenoidosa (NCIM 2738) in bubble column reactor (BCR) and open raceway pond (ORP) for nutrient supplemented coal mine effluent (NSCME) treatment. In between different hydraulic retention times (HRTs), HRT 6 d provide maximum average biomass productivity of 950 mg L−1 d−1 in BCR and 728.4 mg L−1 d−1 in ORP. HRT 9 d facilitates a maximum lipid content of 1.8 g L ̶ 1 in BCR and 1.4 g L ̶ 1 in ORP. Further, HRT 9 d had the maximum COD removal efficiency (96.5 % in BCR and 94.2 % in ORP) and maximum salinity removal efficiency (93 % in BCR and 92 % in ORP). Fatty acid methyl esters (FAME) characterization highlighted potential biodiesel applicability with cetane number (CN) of 53.94. Energy dispersive X-ray spectroscopy (EDS) revealed an excess amount of salt and metal ions deposition on the surface of harvested microalgae samples. Outdoor large-scale C. pyrenoidosa cultivation can be integrated with coal mine closure plans to meet sustainable development goals (SDGs) 6, 7 and 13.

Observation of a moderate major Baltic Sea inflow in December 2023

Just before Christmas 2023, the low-pressure system storm “Zoltan” struck Germany, resulting in widespread damage and two consecutive large storm surges on the North Sea coast in the night from Thursday 21 December 2023 to Friday 22 December 2023. Storm Zoltan brought heavy rainfall, accompanied by thunderstorms and winds ranging between 90 and 115 kmh-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathrm {km\\,h^{-1}}$$\\end{document}, with gusts reaching up to 140 kmh-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathrm {km\\,h^{-1}}$$\\end{document} along the coast which caused severe damage, particularly in northern Germany. Characteristics of the inflowing water at the Fehmarn Belt buoy (FEB), Darss Sill station (DAR) and the Arkona Basin buoy (ARK), including salinity, temperature, dissolved oxygen and ocean currents properties, were analysed to understand the impact of storm Zoltan in the western Baltic Sea. In addition to the damage along its path, following the onset of strong westerly winds associated with storm Zoltan, a large volume of water, containing saline (17–22 psu), cold (5–6 °C), and oxygen-rich 7–8 (mll-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\,\\mathrm { ml\\,l^{-1}}$$\\end{document}) water from the Kattegat and the North Sea reached into the western Baltic Sea. The sea level at Landsort Norra increased by +57 cm over a period of 14 days, from 15 December to 29 December 2023. This resulted in a total volume change of 198 km3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathrm {km^3}$$\\end{document} in the entire Baltic Sea, with 169 km3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathrm {km^3}$$\\end{document} and 29 km3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathrm {km^3}$$\\end{document} provided via the Belt Sea and the Sound Sea, respectively. Observations at the DAR indicated a significant inflow between 19 December 2023 and 1 January 2024 with salinity above 13 psu, temperature below 5.5 °C and dissolved oxygen of about 7.5–8 mll-1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathrm { ml\\,l^{-1}}$$\\end{document}. While the maximum salinity of the bottom layer at the DAR was about 17 psu, the ARK exhibited significantly higher salinities, reaching up to 22 psu at the bottom layer. During the main inflow period, 75 km3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathrm {km^3}$$\\end{document} of highly saline water entered the western Baltic Sea. This corresponds to an average salt transport of 1.75 Gt into the western Baltic Sea (1.39 Gt from the Belt Sea and 0.36 Gt from the Sound Sea), representing more than 20% of the total annual salt import into the Baltic Sea), which places the event in the moderate range of major Baltic inflows. This event brought an amount of about 0.8 106\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathrm {10^6}$$\\end{document} t oxygen into the Baltic Sea. This was the strongest inflow into the Baltic Sea since 2016.

Note on volume and distribution of fresh water in the Amazon River plume under low discharge conditions

In this research communication, we report the results of a field survey conducted in a part of the plume of the Amazon River between 0° and 5°N and offshore of the 28 m isobaths in November of 2022, during the low river discharge season. By comparing the observed vertical salinity profiles ‘disturbed’ by continental discharges within the plume with the virtually ‘undisturbed’ ones outside the plume, we estimated the total content of fresh water in the area covered by the measurements as 203 ± 22 km3, which equals to less than 3% of the average annual Amazon River discharge. Furthermore, we argue that the river-borne continental water was not confined to the upper mixed layer and show that about 37%, or 76 km3, of its volume was entrained into the plume-underlying layer between the mixed layer and the salinity maximum. This point is additionally supported by analysis of chromophoric dissolved organic matter (CDOM) fluorescence in water samples, demonstrating significant concentrations of terrigenous CDOM to depths up to 140 m. We also observed that there was a significant direct correlation between the volume of freshwater accumulated in the affected layer and background stratification (expressed as buoyancy frequency) in the unaffected layer below it.

Formation and Variability of Barrier Layer in the South Pacific

AbstractThe oceanic barrier layer (BL), dominated by salinity stratification, plays an important role in regulating heat exchange between the mixed layer and the interior ocean. However, the salinity contribution is ignored or underestimated when analyses relying only on temperature threshold methods. Here we introduce the Turner Angle method to quantify the salinity contribution and to obtain relatively accurate BL thickness (BLT), and further to investigate the spatial‐temporal distribution, thickness variation and formation mechanism of the BL in the South Pacific using the updated Argo data during 2005–2021. With the successful usage of this method, we eliminate 41% of the invalid BLs and therefore improve the assessment of the BLs in the South Pacific. Formation of the thick BLs in the South Pacific is attributed to the faster deepening rate of the isothermal layer than the mixed layer. The deepening rate of the isothermal layer is facilitated by subsurface subantarctic mode water while that of the mixed layer is constrained by the subsurface salinity maximum in the South Pacific. On the interannual scale, the BLT in the South Pacific manifests a quasi‐biennial variability, which is closely connected with the variability in the isothermal layer depth and is primarily caused by the anomalous winds driven by the Southern Annular Mode (SAM). The SAM‐related anomalous winds regulate the isothermal layer and further the BL by exerting influences air‐sea heat fluxes and the Ekman layer advection.

Morpho-physiological Alteration of Mangifera indica L. in Response to Sea Water Induced Salt Stress

Salinity is one of the biggest challenges in the southern part of Bangladesh, which is affecting the coastal ecosystem adversely. A pot experiment was conducted to find out the morpho-physiological changes in mango (Mangifera indica L.) seedlings in response to sea water induced salt stress at the Agroforestry and Environment research field of Bangabandhu Sheikh Mujibur Rahman Agricultural University (BSMRAU). The experiment was laid out in a Randomized Complete Block Design (RCBD) with five replications, where four treatments, viz 4, 8, 12 dS m-1 salinity level (prepared from sea water), and the tap water (control) were imposed. The results indicated that plant height of mango shortened with the higher level of salinity and the declining magnitude was 28.44% over control at maximum salinity level. Number of leaves per plant of mango were reduced by 27.51% at 12 dS m-1 salinity level compared to that tap water, and the size of mango leaf was also reduced for salinity. Both shoot and root biomass of mango seedlings were significantly reduced due to salinity. The Salt tolerance index in mango was 56.76 only at 12 dS m-1. In case of physiological parameters, the lowest relative water content (RWC) was found in 12 dS m-1, while water saturation deficit (WSD) and water uptake capacity (WUC) were found to be the lowest in control for this plant. Water saturation deficit and water uptake capacity were increased with the increment of salinity level. Total chlorophyll and carotenoid content of mango were decreased by 66.27% and 61.07%, respectively, at the highest salinity level. Proline content of mango increased by 73.07% at 12 dS m-1 salt level in comparison to that of seawater devoid control plants. Considering the overall results, it can be concluded that, although mango seedlings were significantly affected by high salinity (12 dS m-1), but can survive up to moderate salinity (8 dS m-1) at sapling stage.

Salt intrusion dynamics in a well-mixed sub-estuary connected to a partially to well-mixed main estuary

Abstract. Salt intrusion in estuaries has been exacerbated by climate change and human activities. Previous studies have primarily focused on salt intrusion in the mainstem of estuaries, whereas those in sub-estuaries (those that branch off their main estuaries) have received less attention. During an extended La Niña event from 2021 to 2022, a sub-estuary (the East River estuary) alongside the Pearl River estuary, China, experienced severe salt intrusions, posing a threat to the freshwater supply in the surrounding area. Observations revealed that maximum salinities in the main estuary typically preceded spring tides, exhibiting significant asymmetry in salinity rise and fall over a fortnightly timescale. In contrast, in the upstream region of the sub-estuary, the variation in salinity was in phase with that of the tidal range, and the rise and fall of the salinity were more symmetrical. Inspired by these observations, we employed idealized numerical models and analytical solutions to investigate the underlying physics behind these behaviors. It was discovered that under normal dry conditions (with a river discharge of 1500 m3 s−1 at the head of the main estuary), the river–tide interaction and change in horizontal dispersion accounted for the in-phase relationship between the salinity and tidal range in the upstream region of the sub-estuary. Under extremely dry conditions (i.e., a river discharge of 500 m3 s−1 at the head of the main estuary), salinity variations were in phase with those of the tidal range in the middle as well as the upstream region of the sub-estuary. The variation in salinity in the main estuary along with those in salt dispersion and freshwater influx inside the sub-estuary collectively influenced salinity variation in the well-mixed sub-estuary. These findings have important implications for water resource management and salt intrusion prevention in the catchment area.

Growth Performance of Rice Genotypes at the Seedling Stage under Different Salinity Stresses

Background: Worldwide coastal rice growing areas are severely affected by salinity which has become a major constraint to rice production. Salinity is a serious soil problem in rice-growing countries, severely limiting global rice production. Methods: In this study, the seedlings of 21 rice genotypes were tested against seven different levels of salinity concentrations (0.3, 2, 4, 6, 8, 10 and 12 dSm-1) under a hydroponic system in a glasshouse condition at Field 10, Faculty of Agriculture, Universiti Putra Malaysia (UPM). Data on seedling growth and salinity injury of the tested rice genotypes were recorded. Result: The results showed that Pokkali, FL478 and Binadhan-10 were tolerant at 12 dSm-1; BRRI dhan73, BRRI dhan61, Binadhan-8, BRRI dhan67 and BRRI dhan47 were tolerant at 10 dSm-1; Putra-1 were moderately tolerant at 8 dSm-1 and MR263, MR284, MR211 and MRQ74 were tolerant at 4 dSm-1 and rest of the genotypes were salt susceptible. The lower amount of Na: K and Na: Ca were measured from rice genotypes, Pokkali and FL478 at maximum salinity levels. The promising rice genotypes that were tolerant at 12 dSm-1 would be taken into consideration for a hybridization program to develop a new salt-tolerant rice variety.

Diatom-based reconstruction of Lake Turgoyak (Southern Urals) ecosystem changes in the Holocene

Lake Turgoyak development through more than 12 thousand years was studied based on diatom analysis of the lake sediment core. Altogether 142 diatom taxa were identified. Four diatom zones corresponding to main stages of the lake ecosystem development were distinguished with application of stratigraphically constrained cluster analysis. It was found that in the period from 12.1 to 11.0 cal ka BP Lake Turgoyak had maximum salinity and a high degree of overgrowth with hydrophytes. Desalination and an increase in the lake depth occurred between 11.0 and 7.7 cal ka BP. Substantial fluctuations of the lake parameters about 8.0-7.0 cal ka BP were followed by period of lower flow rate and accumulation of sediments with a high content of organic matter. Approximately 2.7 ka cal BP the lake depth increased and salinity decreased. It was concluded that the chronological boundaries of the main stages of the lake ecosystem development coincide with the climatic events previously determined for the Holocene and Late Glacial of the Urals.

Transformation of South Pacific Water Masses in the Halmahera Sea

The Halmahera Sea is part of the eastern entry route of the Indonesian throughflow (ITF) passages. The characteristics and transformation of the South Pacific water masses are presented based on the HYCOM model (Hybrid Coordinate Ocean Model) and direct observations of CTD (Conductivity, Temperature, Depth) acquired during the East Indonesian Expedition in October 2017 using RV Baruna Jaya VIII. This study is aimed at characterizing the typical water masses observed in the Halmahera Sea and tracking the transformation of the South Pacific water masses in the region. The results show that there was an indication of strong vertical mixing of maximum salinity of the South Pacific thermocline water masses, i.e., South Pacific Subtropical Water (SPSW), from ~35.2 PSU at isopycnal 24 – 25 kg m-3 becomes ~34.8 PSU in the Southern Halmahera Strait (around 200 km from the entry passage, the Northern Halmahera Strait), and rapidly decreases from the Southern Halmahera Strait and Obi Strait to become 34.6 PSU in the Maluku Sea. These preliminary findings suggest a strong mixing in the southern Halmahera Strait and Obi Strait.

Assessment of heavy metal contamination in seawater in Agadir coastline, Morocco

The coastal region of Agadir, Morocco, is subject to various human activities and industrial development, raising concerns about potential heavy metal pollution in the surrounding seawater. This study aimed to assess the levels of heavy metals pollution in seawater along the coast of Agadir by conducting sampling at six sites: Aglou Beach (S1), Wassay Beach (S2), Douira Desalination Plant (S3), Agadir Beach (S4), Anza Beach (S5), and Cap Ghir (S6). In addition to the heavy metal analysis, various physicochemical parameters such as temperature (T°C), pH, conductivity, salinity, chlorides, sulfates, nitrate, and nitrite were measured further to understand the overall water quality in these areas. The concentration of selected metals was in the range 10 – 70 μg/l, 24 – 440 μg/l, 20 – 85 μg/l, 40 – 1500 μg/l and 400 – 980 μg/l for Cd, Hg, Pb, Zn, and Fe, respectively. The maximal concentration of these heavy metals was recorded from sampling site 5, and minimum in location 6. The pH ranges from 8.18–8.35 in stations 6 and 1, respectively. Electrical conductivity values of surface seawater ranged from 44,254 to 50,210 μS/cm at stations 6 and 5. The minimum and maximum salinity concentrations were 30.29 and 34.37 g/L in sites 4 and 3, respectively. Our results revealed that the physicochemical parameters and concentrations of heavy metals were nearly identical across all zones apart from Anza and Douira. This is probably related to anthropogenic activities (industrial, wastewater, desalination plants, etc.…) in these two areas.

Seasonal Water Mass Transformation in the Eastern Indian Ocean from In Situ Observations

The Eastern Indian Ocean (EIO) is one of the eastern boundary areas, which control currents circulation and atmospheric dynamics. This research mainly aimed to identify and analyze the water mass transformation in the EIO. The investigated physical properties of the ocean are the temperature, salinity, seasonal temperature–salinity, and water column stability. An extensive amount of in situ data measurements from 1950 to 2018 was downloaded from the global datasets inventory. The visualization and analysis of the data were defined in monthly spatial and vertical profiles. The result showed the mixed layer is shallower during the northwest monsoon relative to the southwest monsoon. The surface water in the EIO is documented to be warmer due to the interaction with the atmosphere. Furthermore, low-salinity surface water around the Java Seas area is caused by a mixing with fresh water from the eastern Indonesia rivers. The data also confirmed that, at latitude 16° S, the maximum salinity occurred at a depth between 150 and 350 m. There are ten types of water masses found in the EIO, which originate from several regions, including the Indonesia Seas, Pacific Ocean, Indian Ocean, and Antarctic. During the northwest and southeast monsoons, a stable layer is found at a depth of 40 to 150 m and 80 to 150 m, respectively. For further research, it is recommended to focus on the coastal region, particularly the Timor Sea and Northwestern Australia, to investigate the dynamics between the Indonesian Throughflow, Holloway Currents, and Leeuwin Currents. Additionally, deep water observations below 800 m are crucial for a comprehensive understanding of the oceanographic variability in the deep layers of the EIO.

Monitoring of individual indicators of safety and quality of water and fish of Khadzhibey estuary

Water significantly influences the quality and safety of fish because it is the environment for the life and cultivation of fish. A study of hydrochemical and microbiological indicators of the water of Khadzhibey estuary was conducted; the content of heavy metals in it was determined. In the Khadzhibey estuary, from 2022 to 2023, the water acidity indicator was stable, did not exceed the established hygienic standards for fish farms, and was within the range of 7.6 ± 0.4–8.4 ± 0.3 mg/L, which completely meets the requirements for fish farming. The maximum salinity in the estuary is observed in summer and is 15 % higher compared to winter and spring indicators. The water type of the estuary is mixed with moderate mineralization. It was established that the zinc content in water samples from the estuary exceeds the maximum permissible concentration by 2.6 %. The content of Cadmium, Lead, Copper, and Mercury is constant and does not exceed the maximum allowable concentration for fish farms. An increase in zinc content in water is a stress factor and affects the quality of fish meat. The research results showed that the content of mesophilic aerobic and facultative anaerobic organisms does not exceed the maximum permissible level in muscle tissue cultures of common carp and round bull caught by commercial fishing from the Khadzhibey estuary. Escherichia coli bacteria, Staphylococcus aureus, Listeria monocytogenes, and pathogenic microorganisms were not detected in the samples of the fish subject to the study. According to the microbiological indicators of water and fish, common carp and Round goby caught by industrial fishing in the Khadzhibey estuary are safe and allowed for further consumption by humans and animals.

An Intrathermocline Eddy Observed in the Southeastern Tropical Indian Ocean

AbstractAn intrathermocline eddy (ITE) was observed over the southeastern tropical Indian Ocean (SETIO) from early February to early May 2020. The ITE was generated near the southwest of Java, and was long lived with a long propagation distance. It had pronounced surface anticyclonic anomalies during westward propagation. Observations from an anchored buoy and several Argo profiles suggested a typical lens‐like vertical structure within the thermocline during the passage of the ITE. The ITE carried a saline water mass with maximum salinity at core depths of 100–150 m. The saline water mass originated from the equatorial Indian Ocean and was transported to the southwest of Java in early January. The formation of the ITE was characterized by a rapid increase of positive sea level anomaly in the southwest of Java, which was closely associated with the local positive wind stress curl in late January and early February.

Connecting subtropical salinity maxima to tropical salinity minima: Synchronization between ocean dynamics and the water cycle

Recent satellite observations reveal that the annual cycles of tropical sea surface salinity (SSS) minimum (Smin) and subtropical SSS maximum (Smax) are phased locked, with the former leading the latter by six months. The evidence suggests an interconnected nature between the salinity extrema, motivating an investigation into the underlying mechanisms. It is found that the poleward Ekman transport, driven by trade winds, stands as a pivotal conduit linking the influence of tropical freshwater to high salinities in the subtropical oceans. Two key aspects are central to the operation of this advective oceanic pathway. One is the annual formation of the near-equatorial Smin zones by Ekman convergence of the freshwater sourced from the double Intertropical Convergence Zones. The other is the advection time taken by Ekman transport traveling at an average speed of approximately 7 cm s−1. This speed allows the near-equatorial salinity anomalies to be carried to the subtropical Smax fringes in six months, aligning closely with the observed semi-annual phase shift between Smin and Smax. During El Niño - Southern Oscillation (ENSO) warm and cold episodes in recent decade, poleward propagation of near-equatorial low salinity anomalies was particularly prominent, leading to substantial surface freshening in the subtropical Pacific. Interestingly, the latitudinal spread of the ENSO-triggered SSS anomalies is confined within the domain of the poleward Ekman transport. This confinement reaffirms the inherent connection between the tropical Smin and subtropical Smax regions, shedding light on the intricate interplay between oceanic processes, the water cycle, and SSS distributions.

Investigation of theoretical maximum water yield and efficiency-optimized temperature for cyclopentane hydrate-based desalination

Hydrate-based desalination (HBD) shows promise as a freshwater production technology for saline water. Liquid-phase hydrate formers, with their ability to facilitate hydrate formation at atmospheric pressure, have gained attention for their high energy efficiency in HBD. This study explored cyclopentane (CP) HBD by experimentally measuring the thermodynamic properties of CP hydrate in saline solutions and developing a theoretical framework to estimate the water yield of CP HBD under various operating conditions. The measured dissociation enthalpy of CP hydrate was found to be 12 % and 22 % lower compared to those of propane and R134a hydrates, respectively. The equilibrium dissociation temperatures of CP hydrate at different NaCl concentrations under atmospheric pressure were experimentally measured and then predicted using the Hu–Lee–Sum correlation. The theoretically achievable maximum salinity and water yield for CP HBD were calculated in the temperature range of 268–280 K and the initial salinity range of 0–8 wt.%. Additionally, the concept of HBD heat efficiency, representing the maximum amount of pure water producible per unit of heat, was introduced to identify an optimal operating condition for the HBD process. Efficiency-maximized temperatures, where the HBD heat efficiency reached its peaks, were determined for various initial salinities in the process, for example, 273.4 K for NaCl 3.5 wt.% solution. This novel approach provides invaluable guidance for determining the most energy-efficient operating conditions in the HBD process and establishes a solid foundation for further advancements in this field.

Simultaneous measurement of temperature and salinity of seawater based on the semi-encapsulated tapered no-core fiber

An optical fiber sensor for simultaneously measuring temperature and salinity of seawater based on polydimethylsiloxane (PDMS) and tapered no-core fiber (TNCF) is proposed. The sensing probe consists of a section of TNCF half coated with PDMS spliced between two sections of single mode fiber (SMF). PDMS is used as not only the temperature sensitive material due to its high thermal-optic coefficient but also the encapsulant. The sensing probe is immersed in the seawater with different temperature and salinity. Because the dip wavelengths in the transmission spectra have different sensitivities to the temperature and salinity of seawater, simultaneous measurement of temperature and salinity can be achieved using the transfer matrix method. The temperature and salinity responses of the sensing probe based on the SMF - TNCF - SMF (STNS) structure with TNCF half coated with PDMS are experimentally measured. The maximum temperature sensitivity is about −2.21 nm/°C with the range from 25 °C to 31 °C and the maximum salinity sensitivity is 1.43 nm/% in the salinity range of 0–9 %. In the experiment of simultaneous measurement of temperature and salinity, the average temperature and salinity relative errors are 1.54 % and 2.1 %, respectively. The proposed sensor has the advantages of simple fabrication, low cost, robust and compact structure and good stability.

Biological responses of stellate sturgeon fingerlings (Acipenser stellatus) immersed in HSP inducer to salinity changes

Changes in salinity is a stressful and energy-consuming process in fish which give rise to mortalities, especially in fish fingerlings that are more sensitive during the early stages of their life. In the present study, the effects of three salinities, 3‰ (downstream of river), 8‰ (estuarine), and 13‰ (the maximum salinity in the Caspian Sea), on HSP70 gene expression, cortisol level, immune response (lysozyme, complement C3, IgM), and antioxidant enzyme activities (SOD, CAT, T-AOC) of the stellate sturgeon fingerlings in the presence of HSP inducer compound (TEX-OE®) were evaluated. Our results showed that levels of plasma cortisol and heat shock protein (HSP70) in Acipenser stellatus fingerlings increased due to salinity changes. In the presence of the HSP inducer, HSP70 expression in both gill and liver was significantly increased, whereas cortisol level was notably decreased. Exposure to salinity changes resulted in an increase in antioxidant defense activities (SOD, CAT, and T-AOC) and immune response (lysozyme, IgM, and C3) in the presence of an HSP inducer. In conclusion, an HSP-inducing compounds can have a positive effect in strengthening the immunity and antioxidant system of sturgeon fingerlings by increasing the expression of the HSP70 gene against salinity fluctuations and generally increase the body's physiological tolerance.

Estuarine Mixing Patterns and Siltation Impact: A Case Study of Air Rami River Estuary

Investigating the Air Rami River Estuary in Mukomuko Regency, this study examines the influence of siltation on mixing characteristics within the estuarine environment. The research aims to discern and characterize mixing patterns in the estuary, employing direct field measurements conducted during both tide and low tide conditions in March 2023. Descriptive and quantitative analyses reveal notable salinity variations, with tidal conditions exhibiting a peak salinity of 10 ppt at a depth of 2 meters, and low tide conditions showing a maximum salinity of 5 ppt at 1.5 meters depth. Temperature variations are also observed, with tide conditions reaching 31.5°C and low tide conditions at 27.2°C. Calculation of the estuary number indicates a perfectly mixed stratified estuary mixing type, characterized by an estuary number magnitude of 0.53. These findings offer insights into estuarine mixing dynamics and their implications for coastal ecosystems.
 Highlight:
 
 Siltation Impact: Investigates the influence of siltation on mixing patterns in the Air Rami River Estuary, Mukomuko Regency.
 Salinity and Temperature Variations: Describes notable variations in salinity and temperature during tide and low tide conditions, providing insights into estuarine dynamics.
 Estuary Number Analysis: Utilizes the estuary number to classify estuarine mixing type, revealing a perfectly mixed stratified estuary with implications for coastal ecosystems.
 
 Keyword: Estuarine Mixing, Siltation Influence, Salinity Variations, Temperature Dynamics, Coastal Ecosystems

Exogenous application of sodium hydrosulfide and salicylic acid mitigate salinity stress in maize by regulating ionic balance, biochemical attributes, photosynthetic pigments and some key antioxidants

Hydrogen sulfide (H2S) and salicylic acid (SA) have been recently explored as important priming agents for plant growth and development. The effects of NaHS alone and in combination with SA to alleviate salt stress effects on maize plants are not determined yet. Here, we executed an approach to examine the effects of NaHS (H2S donor) and SA treatments to overcome the salt stress in maize plants. In vitro screening exhibited that SA (0.1 mM) and NaHS (0.5 mM) as the most effective concentrations to increase biomass and germination of maize plant under salt stress. Furthermore, data revealed that alone and combined treatments of H2S and SA during salt stress showed improved morphological, biochemical, and physiological attributes compared to non-treated plants. However, combined treated plants exhibited maximum salinity resistance than individual treatments. The combined treatment showed increased chlorophyll a (165%), chlorophyll b (138%) and carotenoid (54.4%) and increased activities of antioxidants enzymes like catalase (CAT), superoxide dismutase (SOD), peroxidase (POD), and polyphenol oxidase (PPO) by 441%, 416.7%, 501.4% and 510%, respectively while reduced Na+accumulation and enhanced K+accumulation. Combined treatment protects the plants by lowering proline and MDA content by 300% and 108% respectively. Our in-silico outcomes of the NaHS-SA pathway verify experimental results regarding modulation of salt stress response mechanisms depicts ideal picture of above-mentioned parameters during stress hence suggesting NaHS-SA mediated biofertilizers could strengthen genomic stability and maintenance capability under stress.

Zapiola Gyre, Velocities and Mixing, New Argo Insights

AbstractThe Zapiola Gyre is a large, full‐depth, bottom‐intensified, anticyclonic recirculation in the Argentine Basin. It rotates around the Zapiola Drift, a sedimentary rise standing a few hundred meters above the abyssal plain, tall enough to create closed contours of planetary potential vorticity. Hence the gyre has been posited to be an eddy‐driven free mode that is damped primarily by the bottom Ekman layer. It describes approximately a zonally elongated ellipse with a zonal semi‐major axis of ∼440 km and a meridional semi‐minor axis of ∼125 km. Its volume transport is estimated here at ∼110 (±25) × 106 m3 s−1. It has peak depth‐averaged meridional velocities of ∼0.06 and ∼0.08 m s−1, and peak depth‐averaged zonal velocities of ∼0.11 and ∼0.12 m s−1. Peak surface velocities are ∼57% of peak bottom velocities, consistent with the dynamics of a bottom‐intensified Taylor column in a stratified flow. Deep and Core Argo float trajectories follow the gyre, with a couple of Core Argo floats with 1000‐dbar parking depths executing more than three anticyclonic rotations around it, and Core Argo floats that approach within ∼75 km of the gyre center executing on average ∼1.7 circumnavigations. Deep Argo temperature‐salinity profiles combined with historical shipboard CTD profile data afford maps newly illuminating the advective swirling of water‐mass signatures around the gyre at the density of the North Atlantic Deep Water salinity maximum. Their patterns are consistent with a Peclet number of ∼30 estimated here using previously published lateral eddy diffusivities in the region.