Salinity Range Research Articles

Semi-batch and batch low-salt-rejection reverse osmosis for brine concentration

Brine management strategies require efficient methods of desalinating high-salinity streams (> 7 wt%). Low-salt-rejection reverse osmosis (LSRRO) provides salt leakage to reduce the trans-membrane osmotic pressure, and has higher water recovery than reverse osmosis (RO). However, LSRRO has high energy consumption (e.g., >5kWh/m3 for seawater feed). In this work, we develop novel transient multistage processes (i.e., semi-batch and batch) that employ LSRRO membranes to desalinate high-saline streams. Herein, we use a simplified lumped model to capture the system performance under ideal and non-ideal conditions and optimize salt rejection per pass for the multistage system. The results show that the batch LSRRO system performs dewatering with fewer stages and more efficiently than the steady-state LSRRO. In particular, the multistage batch system significantly outperforms the steady-state LSRRO by reducing energy consumption between 38 % to 73 %. The ZLD application for 4-stage batch systems requires energy consumption between 1.07 and 6.96kWh/m3 for the feed salinity range between 0.1 and 1 mol/L. Conversely, semi-batch LSRRO is less efficient than steady-state and batch LSRRO. It is constrained by the loss due to the mixing of streams which results in more stages, tighter range for membrane selectivity, and higher energy consumption than batch LSRRO.

Latitudinal diversity of planktonic copepods in the Eastern Pacific: overcoming sampling biases and predicting patterns

Gradients of latitudinal diversity are one of the biogeographic features calling the most attention in ecology and macroecology. However, in pelagic communities of the marine environment, geographic trends and patterns are poorly known. We evaluated the latitudinal variation in species richness of marine planktonic copepods in the Eastern Pacific using spatial statistical models and approaches that mitigate and account for biases in occurrence data. A Boosted Regression Tree (BRT) and regression-Kriging based models allowed us to estimate and predict alpha diversity in poorly sampled regions, whereas beta diversity patterns were assessed using generalized dissimilarity analysis (GDM). Species richness showed a bimodal pattern, with a maximum of 291 species in the Northern Hemisphere and Tropical Eastern Pacific Ocean. Particulate Organic Carbon, salinity (max), spatial autocovariate, range of salinity and temperature, and Mixed Layer Depth, explained 85.2% of the latitudinal variability of copepods. Beta diversity was structured into four macrozones associated with the main water masses of the North and South Pacific.Our analytical approaches can overcome the limitations of data gaps, predicting greater diversity in subtropical and coastal areas, while providing insights into key drivers modulating spatial diversity patterns.

Relationship between hydro-environmental variables and Coilia nasus catch in a highly turbid macrotidal estuary in Japan

The effect of estuarine hydro-environmental parameters and tidal phases on the fish catch in the macrotidal Chikugo River estuary was investigated. This study focuses on the catch data of Etsu (Coilia nasus) fish, obtained during their spawning season from 2009 to 2020, employing traditional fishing techniques at a site situated 14.6–16 km upstream from the river mouth. It analyses various hydro-environmental parameters and identifies optimal ranges of environmental parameters. The optimal range of salinity (0.04–0.2) and suspended sediment concentration (SSC, 16–118 mg/L) indicated a higher fish catch at the saltwater-freshwater interface and upstream of the estuarine turbidity maximum (ETM) zone. By developing a generalized additive model (GAM) to analyze the relationship between CPUE and environmental parameters, the study assesses the relative importance of each variable in explaining CPUE variance. GAM exhibited a reasonable predictive capability (R2 = 0.509) and indicated the relative importance of each variable (SSC-24.69%, salinity-21.81%, temperature-24.41%, discharge-9.16%, and MTR-19.91%) in explaining the CPUE variance. Additionally, it aims to verify the maturity status and spawning migration patterns of C. nasus fish through standard-length distribution analysis during the spawning season. The standard-length distribution and comparison with previous literature confirmed that fishes caught by the fisherman belong to the category of matured fishes aged 2–3 years. The results indicated that the high CPUE of matured C. nasus at the upstream of ETM and freshwater-saltwater interface was related to the spawning migration and not to their feeding behaviour at the ETM. This research contributes to fisheries management strategies and conservation efforts in the Chikugo River estuary by providing valuable guidance for habitat restoration, informing fishing regulations, and understanding the behaviour of C. nasus.

Autochthonous bioaugmentation strategies for the successful bioremediation of high-salt petrochemical wastewater using a biosurfactant-producing Enterobacter cloacae Z11

Petrochemical wastewater contains a high concentration of refractory aliphatic and aromatic hydrocarbons. Bioremediation of these hazardous materials using autochthonous bioaugmentation (ABA) strategy is attracting increasing interest. Herein, an indigenous biosurfactant-producing bacteria Z11 was isolated and identified as Enterobacter sp. The reintroduction of Z11 into petrochemical wastewater led to a substantial reduction (P < 0.01) in TPHs, decreasing from 8099 to 1723 mg/L, as well as a significant decrease in COD, decreasing from 8064.2 to 1689.2 mg/L. At a critical micelle concentration of 200 mg/L, the biosurfactant synthesized by Z11 exhibited an extraordinary decrease in surface tension from 67.5 to 29 mN/m. The biosurfactant demonstrated favorable surface activity over a wide pH, temperature, and salinity range. Based on a series of chemical analyses, the biosurfactant was classified as phospholipid. The autochthonous bioaugmentation technique developed by Z11 indicated a significant increase (P < 0.05) in the degradation of n-alkanes of varying chain lengths and polycyclic aromatic hydrocarbons. The analysis of the microbial composition demonstrated that the addition of Z11 caused a rise in bacterial populations capable of hydrocarbon decomposition, such as Pseudomonas sp. and Stenotrophomonas sp. The activities of two enzymes involved in degradation, alkane hydroxylase and alcohol dehydrogenase, increased dramatically and showed a significant (P < 0.05) correlation with Enterobacter sp. Z11. The proposed mechanism could be elucidated that functional genes regulate the secretion of biodegradation enzymes and biosurfactants to promote the deep degradation of petroleum hydrocarbons. This study provides technical support for the reintroduction of autochthonous microorganisms capable of producing biosurfactants in implementing in situ ABA strategies.

Synthesis and emulsion stability of salt resistant viscosity reducer for heavy oil reservoirs with varying salinities

To address the inadequate salt resistance of viscosity reducers and their limited applicability to reservoirs with single salinity, we synthesized salt-resistant viscosity reducers PANxAn in this study. These compounds were derived from fatty alcohol polyoxyethylene ether acrylate, N-alkyl acrylamide, acrylamide, and 2-acrylamido-2-methylpropanesulfonic acid. The structures were identified using nuclear magnetic hydrogen spectroscopy. We investigated the effects of the hydrophilic group ethoxy-chain length (n = 14, 16, 18, 20 and 22) and hydrophobic group alkyl-chain length (x = 12, 14, 16, and 18) on the salt resistance, interfacial activity, wettability, interfacial viscoelasticity and emulsification viscosity reduction performance of the viscosity reducers. Futher, the structures of the viscosity reducers which can adapt to different salinities were determined. Based on the emulsification viscosity reduction effect, PAN14A16, PAN12A16, PAN12A18, PAN12A20/PAN16A16 and PAN12A22/PAN18A16 adapted to salinities range of 2 × 104-6 × 104, 4 × 104-8 × 104, 6 × 104-10 × 104, 8 × 104-12 × 104 and 10 × 104-14 × 104 mg/L, respectively. At the optimal salinity, PANxAn reduced the oil–water interfacial tension from 28.3 to 5.0 mN/m, dynamic contact angle from 130.0° to 61.0°, and heavy oil viscosity from 454.6 to 60.0 mPa·s with a viscosity reduction rate of 86.80 %. The synthesis of salt-resistant PANxAn provides theoretical guidance and application value for enhancing the recovery efficiency of viscosity-reducer flooding in high-salinity heavy oil reservoirs.

Biosurfactant production by a crude oil‐utilizing bacterium towards petroleum hydrocarbon biodegradation applications

AbstractBiosurfactants produced by microorganisms are green amphiphilic biomolecules. They have numerous advantages compared to chemical surfactants including a lower toxicity, better environmental compatibility and effective and stable properties under extreme conditions such as a wide range of temperature, pH and salinity. A highly bio‐surfactant‐producing strain of Bacillus, VTVK15 was selected among the Bacillus isolates from marine environment and oil contaminated sites in Ba Ria‐Vung Tau. Sequence analysis of 16S rDNA showed that the VTVK15 strain was 99% similar with 16s rDNA sequence of Bacillus megaterium. The suitable conditions for the bio‐surfactant production by the strain VTVK15 were 37 °C, pH 7; 2% w/v and 0.4% w/v for temperature, initial solution pH, concentration of carbon substrate (crude oil), and concentration of nitrogen substrate ((NH4)2SO4), respectively. The emulsification index (E24) increased from 51.8% to 67.7% with suitable conditions. The petroleum hydrocarbon degradation (TPH) efficiency by the strain Bacillus megaterium VTVK15 in crude oil estimated using TPH analysis was 72% after 14 days. These results revealed that the strain VTVK15 exhibited a tremendous potential for bioremediation of petroleum hydrocarbon contaminants.

Heavy halogen impact on Raman water bands at high pressure: Implications for salinity estimations in fluid inclusions

We present a new experimental dataset on the impact of the heavy halogens chlorine, bromine and iodine on the Raman water bands concerning pressure and their concentration at room temperature. These experiments were conducted at ambient temperature, with variations in halogen concentration and pressure ranging from 0 to 1.4 GPa.The strength of the Raman water band shift change increases with the ionic size from chlorine, over bromine, to iodine. Our experiments further demonstrate that increased pressure diminishes the impact of the halogen shift change to a varying extent for each of the three halogens. This finding can have significant implications for the salinity calculation of fluid inclusions in minerals such as quartz or olivine. Particularly in the low salinity range, the concentration can be markedly underestimated if the pressure effect is neglected. For experiments in diamond anvil cells involving halogens dissolved in water, the change in Raman water band shifts can serve either as a new tool to monitor pressure, or to monitor the salinity.

Effects of Temperature and Salinity on the LMS (Lysosomal Membrane Stability) Biomarker in Clams Donax trunculus and Chamelea gallina

Population of clams Donax trunculus and Chamelea gallina have been declining significantly in recent decades, and environmental pollution and accelerated global warming have been proposed as contributing factors to this decline, in addition to overfishing. Lysosomal membrane stability (LMS) is a sensitive indicator of health status of the organisms. In this study, we investigate the LMS in these species after exposure for 21 days to nine combined conditions of water temperature (12, 20, and 27.5 °C) and salinity ranges (27–28, 32–33, and 37–38). LMS was assessed in living hemocytes by using the neutral red retention assay. Mortality and the condition index of the organisms were evaluated as supporting parameters. The results indicated interspecies differences in the LMS under similar environmental conditions. Overall, LMS was found to be more sensitive to temperature than to salinity changes. Although both species can tolerate changes in either salinity or temperature seawater conditions, the tolerance range is narrower for D. trunculus, showing a significant cytotoxicity (NRRT &lt; 50 min) at temperatures above 27.5 °C and salinities above 32, and 100% mortality at 27.5 °C and a low salinity range (27–28). This study is the first to assess the combined effect of temperature and salinity on the LMS in C. gallina and D. trunculus, and provide necessary information before using LMS as contaminant-related biomarker in field studies with these species.

Strong associations between dissolved organic matter and microbial communities in the sediments of Qinghai-Tibetan Plateau lakes depend on salinity

In aquatic ecosystems, dissolved organic matter (DOM) plays a vital role in microbial communities and the biogeochemical cycling of elements. However, little is known about the associations between DOM and microbial communities in lake sediments. This study investigated the composition of water-extractable organic matter and microbial communities in surface sediments of lakes with different salinities on the Qinghai-Tibet Plateau. Ultrahigh-resolution mass spectrometry and high-throughput microbial sequencing techniques were employed to assess the associations between molecular diversity and microbial diversity and the effects of salinity in 19 lakes spanning a salinity range from 0.22 ‰ to 341.87 ‰. Our results show that increasing salinity of lake water led to higher molecular diversity of DOM in surface sediments. High-salinity lakes exhibited distinct DOM characteristics, such as lower aromaticity, smaller molecular weight, and higher oxidation degree, compared to freshwater lakes. The complexity of the microbial network composition of sediments first increased and then decreased with the increase of salinity. Moreover, as salinity increases, the dominant species transitioned from Gammaproteobacteria to Bacteroidia, and this transition was accompanied by a decrease in microbial diversity and an increase in molecular diversity. Microbial factors accounted for 34.68 % of the variation in the molecular composition of DOM. Overall, this study emphasizes the significant effects of salinity on both molecular and microbial diversity in lake sediments. Furthermore, our findings underscore the importance of microbes in controlling the range of organic compounds present in lakes and deepen our knowledge of the biogeochemical cycling of DOM.

INTERFACIAL TENSION AND CONTACT ANGLE TESTS OF RHAMNOLIPIDS AND SOPHOROLIPIDS IN SANDSTONE FOR ENHANCED OIL RECOVERY

In the context of the development of enhanced oil recovery technology, biotechnology can be used to develop new methods that are more environmentally friendly and sustainable, one of which is the use of biosurfactants. Rhamnolipids and sophorolipids are non-toxic biosurfactants, biodegradable, and environmentally favorable substances. This study compares the results of laboratory studies on fluid-to-fluid interactions, including the interfacial tension and rock wetness tests at various concentrations and salinities, which represent high salinity, medium salinity, and low salinity. The mechanism of these two biosurfactants is based on reducing the interfacial tension (IFT) between the fluids and changing the wettability of the rock to a more water-wet state. In the interfacial tension test, the reduction in the interfacial tension of rhamnolipids reached 10-2 mN/m, while that of sophorolipids only reached 10-1 mN/m. Then, the sandstone wettability test showed that the two biosurfactants were classified as water-wet (&lt;75°). This happens because of its chemical structure, which has two parts: the hydrophobic part and the hydrophilic part. Within the salinity range of 8,000-32,000 ppm, the rhamnolipids work better in the higher salinity to reduce interfacial tension, and the salinity has a subtle effect on the contact angle. On the other hand, sophorolipids were not affected by salinity for both interfacial tension and contact angle. These two biosurfactants have the potential to increase oil recovery in sandstone so that they can contribute to environmentally friendly biotechnology.

The Effect of Salt Concentration on Dielectric Permittivity and Interfacial Polarization in Carbonate Rocks with Complex Pore Structure

Summary Broadband dielectric dispersion measurements are attractive options for the assessment of water-filled porosity. Dielectric permittivity is influenced by salinity as well as other rock/fluid properties. However, the effect of salinity on Maxwell-Wagner polarization (i.e., interfacial polarization) and dielectric permittivity in rock samples with complex pore structures requires further investigation. The objectives of this work are (a) to perform frequency-domain dielectric permittivity numerical simulations on 3D pore-scale rock samples at different salt concentration levels, (b) to quantify the effect of salinity on dielectric permittivity and interfacial polarization in the frequency range between 20 MHz and 5 GHz, and (c) to quantify the critical frequency (i.e., the frequency at which the relative permittivity becomes frequency-independent). We first perform pore-scale frequency domain dielectric permittivity simulations in fully water-saturated carbonate samples with complex pore structures to obtain the complex dielectric permittivity in the frequency range of 0.01–5 GHz and at different salinity levels. Next, we numerically create partially water/hydrocarbon-saturated water-wet samples and perform simulations at different salinity and water saturation levels to investigate the combined effect of salinity and water saturation on dielectric permittivity. Finally, we investigate how reliable conventional mixing models, such as the complex refractive index model (CRIM) and Hanai-Bruggeman (HB), are in the assessment of water saturation at different salinity levels. We used 3D pore-scale rock samples with complex pore structures from Austin Chalk, Estaillades Limestone, and Happy Spraberry formations. The increase in salinity from 2 to 50 parts per thousand (PPT) resulted in the relative permittivity to increase by 18% at 20 MHz. Similarly, an increase in salinity from 2 PPT to 50 PPT resulted in electrical conductivity to increase by 15 times at 20 MHz. However, at 5 GHz, the difference between the relative permittivity of the samples at different salinities was negligible. We demonstrated that the critical frequency was above 1 GHz. Thus, if complex dielectric permittivity at 1 GHz is being used, an accurate salinity assumption is required in the interpretation of conventional dielectric mixture models in carbonate formations. Finally, we observed 52% and 42% average relative errors in water saturation quantification when applying CRIM and HB models at all the frequencies of interest, respectively. The results also indicated that conventional models should not be used in the presence of uncertainty in salinity at lower frequencies. The results of this work quantified the frequency at which the water-filled pore volume rather than the Maxwell-Wagner polarization controls the relative permittivity of rock samples saturated with a wide range of brine salinity. Moreover, the results demonstrated that the relative permittivity of the rock samples with complex pore structures may still be significantly affected by the interfacial polarization even at 1 GHz. Moreover, the results suggested that the conventional mixture methods cannot reliably take into account the salt concentration of formation water, and this can lead to significant errors in reserves assessment.

Maribacter halichondriae sp. nov., isolated from the marine sponge Halichondria panicea, displays features of a sponge-associated life style

A new member of the family Flavobacteriaceae (termed Hal144T) was isolated from the marine breadcrumb sponge Halichondria panicea. Sponge material was collected in 2018 at Schilksee which is located in the Kiel Fjord (Baltic Sea, Germany). Phylogenetic analysis of the full-length Hal144T 16S rRNA gene sequence revealed similarities from 94.3 to 96.6% to the nearest type strains of the genus Maribacter. The phylogenetic tree of the 16S rRNA gene sequences depicted a cluster of strain Hal144T with its closest relatives Maribacter aestuarii GY20T (96.6%) and Maribacter thermophilus HT7-2T (96.3%). Genome phylogeny showed that Maribacter halichondriae Hal144T branched from a cluster consisting of Maribacter arenosus, Maribacter luteus, and Maribacter polysiphoniae. Genome comparisons of strain Maribacter halichondriae Hal144T with Maribacter sp. type strains exhibited average nucleotide identities in the range of 75–76% and digital DNA-DNA hybridisation values in the range of 13.1–13.4%. Compared to the next related type strains, strain Hal144T revealed unique genomic features such as phosphoenolpyruvate-dependent phosphotransferase system pathway, serine-glyoxylate cycle, lipid A 3-O-deacylase, 3-hexulose-6-phosphate synthase, enrichment of pseudogenes and of genes involved in cell wall and envelope biogenesis, indicating an adaptation to the host. Strain Hal144T was determined to be Gram-negative, mesophilic, strictly aerobic, flexirubin positive, resistant to aminoglycoside antibiotics, and able to utilize N-acetyl-β-D-glucosamine. Optimal growth occurred at 25–30 °C, within a salinity range of 2–6% sea salt, and a pH range between 5 and 8. The major fatty acids identified were C17:0 3-OH, iso-C15:0, and iso-C15:1 G. The DNA G + C content of strain Hal144T was 41.4 mol%. Based on the polyphasic approach, strain Hal144T represents a novel species of the genus Maribacter, and we propose the name Maribacter halichondriae sp. nov. The type strain is Hal144T (= DSM 114563T = LMG 32744T).

Biodegradation of aryl-organophosphate flame retardants by Rhodococcus pyridinivorans YC-MTN: Performance, pathway and potential in environmental remediation

A strain capable of efficiently degrading aryl-organophosphate flame retardants (aryl-OPFRs) was isolated and identified as Rhodococcus pyridinivorans YC-MTN. The strain demonstrated high degradation efficiency within a wide range of pH (7.0–10.0), temperature (25–45 °C), and salinity (0–2%). Strain YC-MTN effectively utilized aryl-OPFRs as the sole carbon source, facilitating their rapid degradation. The estimated half-lives for four aryl-OPFRs, namely triphenyl phosphate (TPhP), tricresyl phosphate (TCrP), 2-ethylhexyl diphenyl phosphate (EHDPP), and resorcinol bis (diphenyl phosphate) (RBDPP), were found to be 8.73, 10.82, 30.28, and 16.14 h, respectively. Additionally, half of the aryl-OPFRs underwent mineralization after 7 d of incubation. In particular, hydrolysis played a dominant role in the metabolism of TPhP, EHDPP, and RBDPP by strain YC-MTN, while P–O bond cleavage generally occurred in the presence of phenol as the leaving group. In addition to hydrolysis, methylation participated in the biotransformation of TCrP. Strain YC-MTN exhibited significant degradability towards TPhP at various concentrations ranging from 1 to 1000 mg L−1. The remediation of TPhP was simulated in both freshwater and seawater, and within a span of 5 d, strain YC-MTN completely degraded the exogenous TPhP. Strain YC-MTN holds potential as a viable microbial agent in the bioremediation of aryl-OPFRs contamination.

Coupled Stable Isotope Tracing and Sulfamic Acid Reduction (SIT-SAR) Method to Determine the Ammonia and Nitrite Oxidation Rates in Water and Sediments.

Herein, a method was developed to measure the ammonia oxidation rate (Ra) and the nitrite oxidation rate (Rn) of water and sediment samples using a coupled stable isotope tracing and sulfamic acid reduction (SIT-SAR) method. 15NH4+ was used as a tracer to determine the ammonia oxidation rates (Ra) by calculating the concentrations of produced 15NO2- and 15NO3- during incubation, while 15NO2- was used as a tracer to determine the nitrite oxidation rates (Rn) by calculating the increase of 15NO3- during incubation. 15NO2- was chemically reduced to 29N2 with 15 mmol·L-1 sulfamic acid (SA). 15NO3- was first reduced to 15NO2- with a zinc-cadmium reducing agent, and then 15NO2- was subsequently reduced to 29N2 with SA. The produced 29N2 was measured by a membrane inlet mass spectrometer (MIMS). Under optimized experimental conditions, this method provides a sensitive (detection limit: 0.5 μmol·L-1) and precise (relative standard deviation: 4.80% for 15NO2-, 3.82% for 15NO3-) approach to quantify the concentrations of 15NO2- (0.5-150 μmol·L-1) and 15NO3- (0.5-120 μmol·L-1) in water and sediment samples over a wide range of salinities (0-30‰) with excellent calibration curves (R2 ≥ 0.999). This method was a successful application to estuarine water and sediments along the salinity gradient. Overall, the SIT-SAR method provided a rapid, accurate, and cost-effective means to determine Ra and Rn simultaneously.

Machine Learning-Based Interfacial Tension Equations for (H2 + CO2)-Water/Brine Systems over a Wide Range of Temperature and Pressure.

Large-scale underground hydrogen storage (UHS) plays a vital role in energy transition. H2-brine interfacial tension (IFT) is a crucial parameter in structural trapping in underground geological locations and gas-water two-phase flow in subsurface porous media. On the other hand, cushion gas, such as CO2, is often co-injected with H2 to retain reservoir pressure. Therefore, it is imperative to accurately predict the (H2 + CO2)-water/brine IFT under UHS conditions. While there have been a number of experimental measurements on H2-water/brine and (H2 + CO2)-water/brine IFT, an accurate and efficient (H2 + CO2)-water/brine IFT model under UHS conditions is still lacking. In this work, we use molecular dynamics (MD) simulations to generate an extensive (H2 + CO2)-water/brine IFT databank (840 data points) over a wide range of temperature (from 298 to 373 K), pressure (from 50 to 400 bar), gas composition, and brine salinity (up to 3.15 mol/kg) for typical UHS conditions, which is used to develop an accurate and efficient machine learning (ML)-based IFT equation. Our ML-based IFT equation is validated by comparing to available experimental data and other IFT equations for various systems (H2-brine/water, CO2-brine/water, and (H2 + CO2)-brine/water), rendering generally good performance (with R2 = 0.902 against 601 experimental data points). The developed ML-based IFT equation can be readily applied and implemented in reservoir simulations and other UHS applications.

Autekologi sebagai Tahapan Awal Rehabilitasi Ekosistem Mangrove Cuku Nyinyi, Desa Sidodadi, Kecamatan Teluk Pandan, Pesawaran

The presence of mangroves tends to decrease every year, one of the reasons being degradation due to land cultivation. Mangrove rehabilitation activities are crucial to maintain the mangrove ecosystem sustainability. Cuku Nyinyi Mangrove located in Sidodadi Village, Teluk Pandan District, Pesawaran Regency. This ecosystem plays a vital role for both resident and migratory wildlife, living among the roots of mangrove trees. This research represents the initial phase of mangrove rehabilitation activities, focusing on autecology, which includes the analysis of reproductive patterns, normal hydrological patterns, and the biophysical condition of the mangrove ecosystem. The study utilizes primary and secondary data collection from three different mangrove zones. The sampling technique involves the transect line spot method. The reproductive pattern of mangroves in all three zones of Cuku Nyinyi Mangrove is dominated by the Rhizophora sp., with propagules as the type of seeds. The normal hydrological pattern for the tidal zone type is consistently inundated with a tree height ranging from 1.6 meters to 7 meters. The biophysical condition of the mangrove ecosystem in the three zones shows a salinity range from 25 to 33 ppt, temperature ranging from 25 °C to 29 °C, and pH levels from 7.2 to 7.8.

Effect of salinity on the toxicokinetics, oxidative stress, and metallothionein gene expression in Meretrix meretrix exposed to cadmium

To understand the effect of salinity on the toxicokinetics, oxidative stress, and detoxification of cadmium-exposed Meretrix meretrix, M. meretrix were acclimatized to different salinities (8, 14, 20, 26, and 32 ppt) for 14 d, exposed to 10 μg/L Cd for 7 d, followed by a 28-day depuration period. The internal Cd concentration was determined, and the activities of antioxidant enzymes (superoxide dismutase (SOD), catalase (CAT), and glutathione-S-transferase (GST)), and the malondialdehyde (MDA) content were measured. The mRNA expression levels of antioxidant enzyme (Cu/Zn SOD, CAT) and detoxification-related genes metallothionein (MT) were analyzed. The mean concentrations of Cd in M. meretrix tissues were in the order gill > digestive gland > mantle > axe foot. The Cd uptake rate in the four tissues decreased with increasing salinity (range: 14–26 ppt). The Cd elimination half-lives were the highest at 8 ppt and 14 ppt salinity. Cadmium activated the four oxidative stress-related related enzymes in the gills. At the end of accumulation period, Cd exposure at 20 ppt salinity significantly increased the expression of Cu/Zn SOD. CAT expression was significantly inhibited at 20 ppt salinity, but was induced at 32 ppt. MT mRNA expression was only induced under Cd at 20 ppt salinity. At the end of depuration period, Cu/Zn SOD expression was inhibited at salinities of 8, 14, and 26 ppt. The results indicated that SOD, CAT, GST, MDA, Cu/Zn SOD, CAT, and MT were sensitive to cadmium in a water environment, and can be used as indicators of marine heavy metal pollution.

Ostracoda and Foraminifera as bioindicators of (aquatic) pollution in the protected area of uMlalazi estuary, South Africa

To mitigate ecological and health risks, implementing a comprehensive multidisciplinary monitoring strategy is imperative. This approach aims to effectively identify and record potential declines in water quality and ecological conditions. Utilizing cost-effective and efficient monitoring tools is crucial, especially for developing nations. Despite the previously reported uMlalazi River's pristine status within a protected natural reserve at South Africa's eastern coast, our findings challenge the assumption of its cleanliness, emphasizing the need for ongoing proactive monitoring. Here we reassess the pollution levels and ecological status of aquatic life of the river, and use this to enhance the indicator value of microfauna in South Africa. We analysed 25 surface sediment samples from the uMlalazi estuary, covering a salinity range from oligohaline to euhaline, with a focus on marginal marine Ostracoda and Foraminifera as potential indicators. All samples contained Ostracoda and Foraminifera, with the exception of two. Among the identified ostracod species, there were 17 species belonging to 14 genera. Typical taxa are the brackish water species Perissocytheridea estuaria, Sulcostocythere knysnaenis, and Australoloxoconcha favornamentata. We identified 19 Foraminifera species from 16 genera, with dominant taxa such as Ammonia sp., Quinqueloculina sp., and Miliolinella sp. Three distinct assemblages were observed: A) Ammonia sp. and Quinqueloculina sp., with very low diversity and abundances in general, located along the river course at stations exceeding Pollution Load Index (PLI), which indicates deterioration of sites quality; B) Ammonia sp., Quinqueloculina sp., and Sulcostocythere knysnaenis associated with higher salinity and lower PLI; C) Ammonia sp., Quinqueloculina agglutinans, and Cribroelphidium articulatum located in mudflats with minimal PLI. Our findings align with the commonly observed diversity trend, which indicates reduced species diversity corresponding to elevated pollution levels. Notably, the examined samples revealed a range of Foraminiferal Abnormality Index (FAI) up to 23%, exhibiting anomalies such as multiple tests, changes in coiling, and abnormal chamber shapes. Geochemical analysis indicates that the catchment is subjected to substantial anthropogenic pressure, as evidenced by elevated concentrations of heavy metals, sulphur, and microplastic. Sugarcane farming, urban sewage, titanium mining, and fish farming are the primary sources of pollution in the catchment area. Ongoing investigations in South African estuaries are expanding our dataset and will contribute to a better understanding of the species-specific responses of Ostracoda and Foraminifera to anthropogenic pressure.

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.

State of Surface and Vertical Salinity in Puttalam Lagoon during North-East Monsoon

Puttalam Lagoon which covers 226 km2 located in Sri Lanka‘s Northwest coast, plays an important role in aquaculture and lagoon capture fisheries. Kala oya and Mee oya are the major freshwater sources which empties into the Lagoon by eastern bank. Salinity variability is an important environmental variable in lagoon system that has an impact on aquaculture and aquatic resources. During the Northeast monsoon (NEM) in 2021, the spatial and vertical fluctuation of salinity in the lagoon was studied using SBE 19plus V2 CTD profiler. Field measurements show that the vertical salinity stratification in the lagoon was substantial during the study period. The lagoon has a significant spatial variability of salinity, ranging from 15 psu to 26 psu and Kala Oya river mouth has a salinity of 22 psu which impacted by freshwater and sea water circulation. The Salinity stratification in eastern section of the lagoon where the Kala Oya and Mee Oya streamflow reach is observed with surface salinity of 15 psu. During the NEM season, the average discharge of Kala Oya and Mee Oya to the lagoon was 10.8 m3/s and 9.4 m3/s, respectively, with a mean monthly precipitation of 48.89 mm. Fresh water from the Kala and Mee oya rivers flows into the lagoon during the season, while low evaporation and significant rainfall led the salinity to decline during the wet season, influencing the structure and function of lagoon ecosystems. The study reveals that a significant area of the lagoon is covered by the 20-30 psu salinity range, which is more appropriate for brackish water fisheries, particularly for shrimp and prawns during NEM. &#x0D; Keywords: Salinity, CTD profiling, Northeast Monsoon, Freshwater