Low Salinity Levels Research Articles

The Influence of Chemical Fertilizers on the Effectiveness of Biochar in Mitigating Cadmium Mobility in Soil

The focus of this study was to explore how various fertilizers influence the movement of cadmium in soil treated with biochar. The research utilized a strong acid sandy loam soil from Chanthaburi Province, naturally rich in organic matter with moderate cation exchange capacity and low nitrogen, potassium, phosphorus, sulfate, salinity and chloride levels. The soil was purposely contaminated with 50 mg kg-1 of cadmium and treated with biochar derived from water hyacinth through pyrolysis at 450°C for an hour. This biochar displayed moderate alkalinity, high organic matter, phosphorus, potassium, and cation exchange capacity, but low nitrogen content. Analytical techniques like Scanning Electron Microscopy and Fourier-Transform Infrared Spectroscopy were employed to study the surface characteristics of the biochar. The cadmium adding soil was blended with 10% biochar and various chemical fertilizers at a 0.04% ratio. Diethylenetriamine pentaacetate (DTPA) extraction was used to assess the bioavailability of cadmium to plants in the soil, while sequential extraction was conducted to identify the different forms of cadmium present in the soil. The study revealed distinct effects of different fertilizers on cadmium mobility. Fertilizers like 46-0-0 and 0-3-0 caused a transformation of cadmium from stable to less stable forms, increasing the bioavailability of cadmium to plants. Conversely, fertilizers such as 15-15-15, 0-0-50, 0-0-60, and 0-52-34 shifted cadmium from less stable to more stable forms, resulting in decreased cadmium extracted by DTPA. Other fertilizers showed no significant impact on cadmium mobility in the soil. A stepwise linear regression analysis highlighted that nitrogen content, potassium content, and electrical conductivity were influential factors affecting cadmium mobility.

Effects of Vermicompost and Salinity on Proctor Optimum Water Content, Maximum Dry Bulk Density and Consistency of a Sandy Clay Loam Soil

ABSTRACT Salinity and sodicity greatly influences ongoing physical processes in soils. Organic matter may rehabilitate physical and mechanical properties of soils. Vermicompost as an amendment influences moisture-related parameters including consistency (plastic – PL and liquid limit – LL) and compaction. This study was conducted on soils (sandy-clay-loam) treated with different salinity levels (0.58 (control – irrigation water quality, tap water), 4 and 8 dS m−1) to investigate the effects of different vermicompost doses (0% (control), 2.5% and 5% w/w) on soil consistency limits and compaction. The pot experiment was carried out in a total of 27 pots, i.e. 3 (vermicompost doses) x 3 (salinity levels) x 3 (number of replicates). For Proctor compaction properties, maximum dry bulk density (MDD) reduced and optimum water contents (OWC) increased with increasing vermicompost doses under different salinity levels (p < .01). Increasing vermicompost doses under the lowest salinity level (0.58 dS m−1) yielded increasing optimum water contents for control (LL = 35.93% and PL = 25.85%). Optimum water contents were determined as 42.19% (LL) and 29.93% (PL) for 2.5% vermicompost dose and as 47.33% (LL) and 36.01% (PL) for 5% vermicompost dose under the lowest salinity level. LL, PL, OWC and MDD were significantly affected by vermicompost x salinity interactions. The highest maximum dry bulk density (1.92 g cm3) and the lowest optimum water contents (13.50%) were obtained from 0% vermicompost under the 8 dS m−1 NaCl level. Mean weight diameter (MWD) values ranged from 0.690 mm for 0% VC treatment under high Na salt level (8 dS m−1 NaCl) to 0.821 mm for 5% VC treatment under lowest Na salt level (0.58 dS m−1 NaCl). The correlations between aggregate stability (particle size group 1–2 mm) and optimum water content were 0.647*, 0.587* and 0.598* as compared to correlations of −0.512*, −0.470*, and −0.617** between aggregate stability (particle size group 1–2 mm) and maximum dry bulk density for the 0, 4 and 8 dS m−1 NaCl levels, respectively. MWD was positively correlated with OWC (0.386*) and negatively correlated with MDD (−0.385*). The greatest (2.39%) and the lowest (0.32%) soil organic matter values were respectively observed in 5% VC under the lowest salinity level (0.58 dS m−1) and 0% VC with at high Na salt level (8 dS m−1 NaCl). It was concluded that vermicompost reduced compaction-induced damage in soils.

Mulching and drip irrigation to mitigate soil salinity on tomato (Lycoperscon esculentum L.) production in coastal area

Bangladesh’s coastal regions are rich in saline water resources. The majority of these resources are still not being used to their full potential. In the southern Bangladeshi region of Patuakhali, research was conducted to investigate the effects of mulching and drip irrigation on tomato yield, quality, and blossom-end rot (BER) at different soil salinity thresholds. There were four distinct treatments applied: T1= drip irrigation with polythene mulch, T2 = drip irrigation with straw mulch, T3 = drip irrigation without mulch, and T4 = standard procedure. While soil salinity was much greater in treatment T3 (1.19–8.42 dS/m) fallowed by T4 (1.23–8.63 dS/m), T1 treatments had the lowest level of salinity and the highest moisture retention during every development stage of the crops, ranging from 1.28–4.29 dS/m. Treatment T3 exhibited the highest soil salinity levels (ranging from 1.19 to 8.42 dS/m), followed by T4 with a range of 1.23 to 8.63 dS/m. In contrast, T1 treatments consistently maintained the lowest salinity levels (ranging from 1.28 to 4.29 dS/m) and the highest moisture retention throughout all stages of crop development. In terms of yield, drip irrigation with no mulch treatment (T3) provided the lowest output (13.37 t/ha), whereas polyethylene mulching treatment (T1) produced the maximum yield (46.04 t/ha). According to the study, conserving moisture in tomato fields and reducing soil salinity may both be achieved with drip irrigation combined with polythene mulch. The research suggests that employing drip irrigation in conjunction with polythene mulch could effectively preserve moisture in tomato fields and concurrently decrease soil salinity.

Community stability of free-living and particle-attached bacteria in a subtropical reservoir with salinity fluctuations over 3 years

Changes in salinity have a profound influence on ecological services and functions of inland freshwater ecosystems, as well as on the shaping of microbial communities. Bacterioplankton, generally classified into free-living (FL) and particle-attached (PA) forms, are main components of freshwater ecosystems and play key functional roles for biogeochemical cycling and ecological stability. However, there is limited knowledge about the responses of community stability of both FL and PA bacteria to salinity fluctuations. Here, we systematically explored changes in community stability of both forms of bacteria based on high-frequency sampling in a shallow urban reservoir (Xinglinwan Reservoir) in subtropical China for 3 years. Our results indicated that (1) salinity was the strongest environmental factor determining FL and PA bacterial community compositions – rising salinity increased the compositional stability of both bacterial communities but decreased their α-diversity. (2) The community stability of PA bacteria was significantly higher than that of FL at high salinity level with low salinity variance scenarios, while the opposite was found for FL bacteria, i.e., their stability was higher than PA bacteria at low salinity level with high variance scenarios. (3) Both bacterial traits (e.g., bacterial genome size and interaction strength of rare taxa) and precipitation-induced factors (e.g., changes in salinity and particle) likely contributed collectively to differences in community stability of FL and PA bacteria under different salinity scenarios. Our study provides additional scientific basis for ecological management, protection and restoration of urban reservoirs under changing climatic and environmental conditions.

Effect of low-salt on the survival of mussel Mytilus coruscus and its molecular responses to chronic prolonged low-salt stress

Mussel Mytilus coruscus is a coastal economic culture species. However, massive mortalities associated with low-salt environments caused by persistent rainfall and freshwater inflow threaten its development. Herein, we examined its survival under different low-salt conditions. The survival rate of umbo and eyed larvae significantly decreased with the decline in salinity or prolonged stress time. The umbo larvae were more tolerant to low-salt stress than the eyed larvae. When the salinity levels dropped suddenly, the adults could not survive below 16‰ salinity, and their survival rate decreased faster with the increase in salinity span or the decrease in final stress salinity. However, the adults could tolerate a lower salinity levels when it dropped slowly, and their low-salt tolerance limit was 10‰. Therefore, mussel M. coruscus could adapt to a lower salinity only when the salinity levels dropped gradually. We also explored the physiological and adaptive responses of the foot in response to chronic prolonged low-salt stress by transcriptome analysis. We found that most genes in the “calcium ion binding” term and the osmoregulation-related genes were significantly induced in the salt 12 and 14 groups, suggesting the strong positive response in calcium signal transduction and osmoregulation under prolonged low-salt stress. The HSP70 and IAP genes were upregulated, suggesting that mussel M. coruscus protects itself from low-salt environments by inhibiting apoptosis. The cytoskeleton and cell cycle were inhibited, and the byssus attachment-related genes, such as tyrosinase and foot-protein genes, were suppressed, suggesting a negative response of cell division and byssus thread attachment during prolonged low-salt stress. The enhancement of carbohydrate metabolism indicated its positive role in maintaining energy homeostasis during prolonged low-salt stress. Our findings contribute to the improvement of culture technology and the guidance of selective breeding program for mussel M. coruscus and enhance our understanding of low-salt adaptation mechanism.

Coupling and decoupling of soil carbon and nutrients cycles at different salinity levels in a mangrove wetland: Insights from CUE and enzymatic stoichiometry

Soil carbon (C), nitrogen (N), and phosphorus (P) cycling, in conjunction with microbial metabolism, varies significantly with salinity in coastal areas. However, microbial metabolism limitation on salinity levels has received limited attention. Based on soil microbial carbon use efficiency and enzymatic stoichiometry, microbial nutrient limitation characteristics of soil microbial communities in different salinity levels (4.45 mS·cm−1 - 17.25 mS·cm−1) in a subtropical mangrove wetland were investigated. Compared to low-salinity levels, the activity of soil C-acquiring enzyme activities, enzymatic C:N ratios and enzymatic C:P ratios decreased with medium salinity levels and high salinity levels. Soil microbial metabolism was primarily constrained by C and N at different salinity levels. Boosted regression tree analysis revealed that abiotic factors had the greatest influence on C and N limitation of microbial metabolism at different salinity levels. This study underscores the significance of salinity in microbial metabolic processes and enhances our understanding of how future salinity changes induced by rising sea levels will affect soil carbon and nutrient cycling in coastal wetlands.

Response of leaf photosynthesis, chlorophyll content and yield of hydroponic tomatoes to different water salinity levels.

Tomato (Solanum lycopersicum L.) is an important vegetable crop that grows easily under controlled conditions, such as in greenhouses and hydroponics. To overcome freshwater scarcity, researchers are searching for alternatives to groundwater sources such as desalinated water (saline water) for irrigation. High salinity in irrigation water alters physiological functions and crop development, thereby reducing the yield. Best management practices and the use of grafted tomato plants on salt-tolerant rootstocks can alleviate salinity stress. The present study was conducted to address the impact of salinity stress on leaf transpiration (Tr), stomatal conductance (gs), photosynthesis (Pn), leaf chlorophyll content, proline content, and yield of hydroponically cultivated tomato plants. Saline (NaCl) water was used for the preparation of nutrient solution with three salinity levels, electrical conductivity (EC, dS m-1) of 2.5 (control), 6.0, and 9.5. Three commercial tomato cultivars (Valouro-RZ, Ghandora-F1, and Feisty-Red) were used. Both self-rooted plants and plants grafted onto Maxifort rootstocks were transplanted onto a perlite substrate. The recorded data revealed that all studied cultivars were critically affected by higher salinity (≈ 9.5 dS m-1) compared to low (≈ 2.5 dS m-1) and medium (≈ 6.0 dS m-1) salinity levels. The Variations in Tr, Pn, gs, chlorophyll content of leaf, and yield between medium and high salinity trials were reported at 3%, 5%, 9%, 5%, and 7.1%, respectively, whereas no significant differences were observed between low and medium salinities. However, at medium salinity levels, grafted plants performed better in photosynthesis than non-grafted plants. This is due to the accumulation of leaf proline, which maintains osmotic regulation and photosynthetic activity by preventing cell damage at medium salinities. Hence, this study confirmed the use of saline water for growing tomatoes under hydroponic conditions up to an EC of 6.0 dS m-1 including the EC of nutrient fertilizers.

Impact of macronutrients and salinity stress on biomass and biochemical constituents in Monoraphidium braunii to enhance biodiesel production

Microalgal lipids are precursors to the production of biodiesel, as well as a source of valuable dietary components in the biotechnological industries. So, this study aimed to assess the effects of nutritional (nitrogen, and phosphorus) starvations and salinity stress (NaCl) on the biomass, lipid content, fatty acids profile, and predicted biodiesel properties of green microalga Monoraphidium braunii. The results showed that biomass, biomass productivity, and photosynthetic pigment contents (Chl. a, b, and carotenoids) of M. braunii were markedly decreased by nitrogen and phosphorus depletion and recorded the maximum values in cultures treated with full of N and P concentrations (control, 100%). These parameters were considerably increased at the low salinity level (up to 150 mM NaCl), while an increasing salinity level (up to 250 mM NaCl) reduces the biomass, its productivity, and pigment contents. Nutritional limitations and salt stress (NaCl) resulted in significantly enhanced accumulation of lipid and productivity of M. braunii, which represented more than twofold of the control. Furthermore, these conditions have enhanced the profile of fatty acid and biodiesel quality-related parameters. The current study exposed strategies to improve M. braunii lipid productivity for biodiesel production on a small scale in vitro in terms of fuel quality under low nutrients and salinity stress.

Multiple microbial guilds mediate soil methane cycling along a wetland salinity gradient.

Estuarine wetlands harbor considerable carbon stocks, but rising sea levels could affect their ability to sequester soil carbon as well as their potential to emit methane (CH4). While sulfate loading from seawater intrusion may reduce CH4 production due to the higher energy yield of microbial sulfate reduction, existing studies suggest other factors are likely at play. Our study of 11 wetland complexes spanning a natural salinity and productivity gradient across the San Francisco Bay and Delta found that while CH4 fluxes generally declined with salinity, they were highest in oligohaline wetlands (ca. 3-ppt salinity). Methanogens and methanogenesis genes were weakly correlated with CH4 fluxes but alone did not explain the highest rates observed. Taxonomic and functional gene data suggested that other microbial guilds that influence carbon and nitrogen cycling need to be accounted for to better predict CH4 fluxes at landscape scales. Higher methane production occurring near the freshwater boundary with slight salinization (and sulfate incursion) might result from increased sulfate-reducing fermenter and syntrophic populations, which can produce substrates used by methanogens. Moreover, higher salinities can solubilize ionically bound ammonium abundant in the lower salinity wetland soils examined here, which could inhibit methanotrophs and potentially contribute to greater CH4 fluxes observed in oligohaline sediments.IMPORTANCELow-level salinity intrusion could increase CH4 flux in tidal freshwater wetlands, while higher levels of salinization might instead decrease CH4 fluxes. High CH4 emissions in oligohaline sites are concerning because seawater intrusion will cause tidal freshwater wetlands to become oligohaline. Methanogenesis genes alone did not account for landscape patterns of CH4 fluxes, suggesting mechanisms altering methanogenesis, methanotrophy, nitrogen cycling, and ammonium release, and increasing decomposition and syntrophic bacterial populations could contribute to increases in net CH4 flux at oligohaline salinities. Improved understanding of these influences on net CH4 emissions could improve restoration efforts and accounting of carbon sequestration in estuarine wetlands. More pristine reference sites may have older and more abundant organic matter with higher carbon:nitrogen compared to wetlands impacted by agricultural activity and may present different interactions between salinity and CH4. This distinction might be critical for modeling efforts to scale up biogeochemical process interactions in estuarine wetlands.

Effect of Water Temperature and Salinity on the Jet Erosion Test (JET) Discharge Coefficient

Highlights The JET discharge coefficient Cd was negatively correlated to water temperature and positively correlated to salinity. The impact of water temperature was more significant than that of salinity, especially at lower temperatures. Increasing water temperatures reduced Cd by as much as 20% per 10°C increment. Low levels of salinity initially increased Cd , but its magnitude remained relatively constant for levels greater than 5 ppt. Abstract. The discharge coefficient (Cd) of the Jet Erosion Test (JET) directly affects the calculation of applied shear stresses (to) during testing and, therefore, of JET-derived erodibility parameters, namely, the soil’s critical shear stress (tc) and erodibility coefficient (kd). Typically, Cd is assumed to be constant for a given combination of JET device (e.g., original vs. mini) and setup (e.g., head tank vs. pressure gage), disregarding the effects of varying environmental conditions. The objective of this study was to quantify the impact of changing water temperature and salinity on the Cd of a mini-JET device fed by a pressure head tank. Laboratory experiments were conducted to determine the variability in Cd for ranges of water temperature between 10 and 30°C and salinity between 0 and 35 ppt. Results showed that Cd was sensitive to changes in both variables, with water temperature generating a more significant impact. Cd was negatively correlated to water temperature, decreasing by as much as 20% when temperature increased from 10 to 20°C, and positively correlated to salinity, increasing at low levels but remaining relatively constant for levels greater than 5 ppt. When extrapolated to erosion curves and JET-derived erodibility parameters, the variability in Cd significantly impacted the calculation of to and the magnitude of tc and kd, highlighting the degree of uncertainty that could be associated with these variables because of an uncalibrated Cd. Lastly, results from the laboratory experiments were used to develop a normalized predictive model and associated curves for application to other mini-JET devices with similar setups. Keywords: Discharge Coefficient, Erodibility, Jet Erosion Test, Salinity, Temperature.

Association between the salinity level with miscarriage and unintended pregnancy in Bangladesh: Impact of salinity level on miscarriage and unintended pregnancy in Bangladesh

Miscarriage is a significant public health concern worldwide, particularly in developing nations like Bangladesh. Moreover, people in coastal areas are more affected by miscarriage as compared to other areas. Increasing sea levels and salinity is the main reason for this discrepancy. This study aimed to investigate the association between different salinity levels (S1, S2, S3, S4, and S5) and miscarriage and unintended pregnancy. The outcome variables are pregnancy-related outcomes (miscarriage, unintended pregnancy), and the independent variables are different salinity levels. A frequency table and correlation analysis were done to find the descriptive scenarios of miscarriage, unintended pregnancy, and salinity levels. We found 621 miscarriage patients and 2271 unintended pregnant patients in our study. Furthermore, the Poisson regression model was used to observe the incidence of miscarriage and unintended pregnancy for different salinity levels. A higher amount of miscarriage and unintended pregnancy rate was found in Dhaka and Khulna, while these rates were lower in Barisal and Chittagong. However, the salinity levels were highest in Barisal and Khulna. Both miscarriage and unintended pregnancy are highly and negatively correlated with salinity levels. The Poisson regression model shows that the salinity levels s1-s5 are strongly associated with miscarriage. Lower and moderate levels of salinity are strongly associated with miscarriage than higher levels of salinity. Again, the average number of miscarriages decreases with the salinity levels. Likewise, unintended pregnancy was also negatively associated with salinity levels. However, it only reported a significant association with lower and moderate salinity levels, and higher salinity levels did not affect unintended pregnancy. Taking initiatives for raising awareness from government and non-government organizations, setting up deep tube water pumps extensively, and properly treating coastal areas women during pregnancy would be the ideal next step to reduce the miscarriage and unintended pregnancy rate in coastal zones in Bangladesh.

Effects of Low-Salinity Environments on Growth, Antioxidant Response, and Intestinal Microorganisms of the Largemouth Bass (Micropterus salmoides)

This research revealed that low-salinity environments have positive effects on largemouth bass (Micropterus salmoides), with the study finding that low-salinity levels can have beneficial impacts on this species. A 8-week experiment was conducted using four salinity gradients S0, S1, S2, S3 (0, 2, 4, 6 psu), and biochemical indicators and 16S rRNA sequencing were analyzed. Results showed relatively good growth performance at S0 and S1, and no significant antioxidant stress response at S3. Na+–K+–ATPase activity was significantly lower in the S2 group. The diversity showed no significant differences between the treatment groups. However, with increasing salinity, the proportion of potentially pathogenic bacteria in freshwater decreased significantly while that in the seawater increased. Indicator species analysis showed a significantly higher abundance of positive microbial species in the 4 psu group. In conclusion, although growth performance decreased at 4 psu, antioxidant damage was relatively small and disease risk was significantly reduced, indicating a positive effect on the largemouth bass.

Fine Root Production and Its Benefaction to carbon storage of the Sundarbans Mangrove Forest

The quantification of fine root production (FRP) and biomass (FRB) is of utmost importance in gaining insights into ecosystem dynamics. However, these aspects have received limited attention in mangrove forests, primarily due to the considerable time and labor required for accurate assessment. Therefore, our study aims to estimate FRP and FRB stocks in the Sundarbans mangrove forest in Bangladesh, specifically focusing on two distinct saline zones: oligohaline and mesohaline. To accomplish our objectives, we employed soil coring and long-term ingrowth core methods to collect soil samples from 20 study plots, each covering an area of 200 square meters. Additionally, we assessed the forest structure by measuring the tree height and diameter at breast height. Our findings revealed that the mean FRB and FRP across the study area were 12.65±1.12 Mgha-1 and 2.25±0.13 Mgha-1 y-1, respectively. Notably, the oligohaline zone, characterized by lower salinity levels, exhibited higher FRB stocks and FRP compared to the mesohaline zone. Furthermore, our analysis showed that FRP in the diameter class of 1-2 mm surpassed that of the 0.5-1 mm and ≤0.5 mm classes. In terms of biomass, the mean above-ground, below-ground, and total biomass carbon were determined to be 87.18 ± 18.3, 48.38 ± 8.0, and 135.57 ± 26.3 Mgha-1, respectively. Through species importance value (Iv) analysis, we identified Excoecaria agallocha as the dominant species in the oligohaline zone, while Sonneratia apetala exhibited the highest Iv value in the mesohaline area. Heritiera fomes emerged as the primary contributor to total biomass carbon, particularly in the oligohaline zone, whereas S. apetala contributed the most biomass carbon in the mesohaline zone. These findings emphasize the importance of protecting and conserving mangrove ecosystems as valuable contributors to global carbon dynamics due to its higher fine root production and its contribution to carbon stocks.

DNA metabarcoding reveals evidence of inter- and intra-guild predation by Scylla paramamosain in a marine ecosystem

IntroductionCrustacean predators exhibit diverse trophic interactions across various habitats in aquatic ecosystems. To assess their ecological roles, it is essential to understand their complete dietary spectrum. Recently, DNA-based techniques such as DNA metabarcoding and high-throughput sequencing have provided insights into trophic networks and their response to environmental drivers.MethodsIn this study, we used these methods to investigate the impact of salinity gradients on the trophic networks of mud crabs (Scylla paramamosain) in marine ecosystems.ResultsOur results revealed that mud crabs prey on a wide range of taxa, including crabs (other than the host species), fish, shrimps, and other prey factions. Salinity gradients had a significant influence on the specific prey items, such as high predation on Metapenaeus, and Trigonopterus species in high salinity sites. Notably, crabs exhibited a greater infestation of Portunion parasites in environments with high salinity levels, in contrast to environments with lower salinity levels. Ordination analysis showed that mud crabs adapt their diet according to environmental constraints.DiscussionFurthermore, the results indicate that mud crabs showed opportunistic predation behavior as they were observed preying on other Portunidae species sharing the same trophic guild. Overall, these findings demonstrate the dietary plasticity and associated parasite infestation of an important crustacean predator, and provide evidence that environmental changes may affect incidences of the associated parasites as well as the specific predator-prey interactions indirectly through fluctuations in marine ecosystems.

Transport Properties of NaCl in Aqueous Solution and Hydrogen Solubility in Brine.

Ion transport properties and hydrogen solubility in brine play pivotal roles in various engineering and scientific scopes including chemical, physical, geochemical, and geothermal domains. Molecular dynamics simulations were performed to obtain transport properties of NaCl in the binary H2O + NaCl system using different force fields. Brine density, ion diffusivity, molar conductivity, conductivity, and hydrogen solubilities were obtained as functions of temperature and salt concentration. We compared the performance of different force fields against the experimental correlation model and developed three mathematical models. The first was the modified brine density model based on the simulated brine density over a wide range of salinity levels, and the second and third analytical mathematical models were derived for the ion diffusivity and molar conductivity as a function of salinity and temperature. The results of this study illustrated that the modified brine density model not only produced the same results of the previous model for lower salinity levels but also applied well to predict the brine density for a higher salinity level. The derived mathematical models indicated that the ion diffusivity and molar conductivity decreased linearly with salinity, and the slope and y-intercept of the lines of diffusivity and molar conductivity versus temperature were third-order polynomials of temperature. The developed models provided the mechanism for the behavior of decreasing molar conductivity with increasing salinity and increasing conductivity with increasing salinity. The directions of the effect of salinity on the molar conductivity and conductivity were opposite. The molar conductivity increased with a decreasing salinity level. However, the conductivity increased with increasing salinity, as the contribution of the ion concentration or salinity level to conductivity dominated over that of the ion movement.

Salinity and Variety Effects on Yield, Yield Attributes and Soil of Tomato under Greenhouse Conditions of Central Fiji

Background: Tomato (Lycopersicon esculentum Mill) is a widely cultivated vegetable crop worldwide, including in Fiji. However, the suitability of tomato cultivation under greenhouse conditions in the central region of Fiji, which experiences salinity issues, remains unclear. Methods: A pot experiment was conducted at the Instructional Agricultural Farm Complex of the College of Agriculture, Fisheries and Forestry, Fiji National University, Fiji, to determine the effect of different levels of salinity on the growth and yield of tomato (Lycopersicon esculentum Mill) varieties. The experiment included two factors: three tomato varieties (V1= Melrose; V2= Alton; V3= Alafua Large) and four levels of NaCl salinity (T1= Control; T2= 2 dSm-1; T3= 4 dSm-1 and T4= 8 dSm-1) randomized thrice in a randomized complete block design. The effects of various varieties and salinity levels on tomato yield were studied in this experiment. Result: The results revealed that variety Alafua Large performed comparatively better in all cases. This recorded maximum fruit length (4.22 cm), fruit breadth (3.31 cm), individual fruit weight (45.60 g), number of fruits (7.83) and fruit yield (352.10 g) whereas Alton recorded the minimum of the above yield attributes. In the case of the combined effect of variety and salinity, Alafua Large showed better yield (432.17 g and 394.51 g) per plant than the other varieties when combined with the lower salinity level i.e., EC 2 dSm-1 and 4 dSm-1, respectively. The yield of tomato varieties declined with the increasing salinity level condition. The yield of Alafua Large was 194.54 g when applied with the highest level of salinity i.e., EC 8 dSm-1 and the yield of Alton was 64.69 g which was the lowest yield among the varieties with the highest level of salinity condition. Therefore, from the results, Alafua Large is comparatively more salt tolerant than the other varieties which were studied in this experiment.

Diversity and structure of bacterial communities in saline and non-saline rice fields in Cilacap Regency, Indonesia

Abstract Increased concerns for sustainable agriculture have led to increased use of beneficial rhizobacteria as biofertilizers. Soil bacteria play a significant role in the nutrient cycle of soil, but their presence can be affected by abiotic stress, such as salinity. This study aimed to compare the chemical characteristics of slightly saline and non-saline rice soil and examine the bacterial community structure in both rhizosphere and bulk soil. We utilized 16SrRNA gene sequencing and performed arithmetic means clustering, a type of hierarchical clustering, on the samples collected from the rice fields of Cimrutu and Rawaapu Village in Cilacap Regency, Indonesia. Although the nutrient content was similar in both soils, there was a noticeable difference in their electrical conductivity (EC) despite the two locations being less than 4 km apart. The EC value in the Cimrutu soil suggests that it is non-saline, while the Rawaapu soil exhibits a low salinity level. The study found that Proteobacteria was the most prevalent phylum in saline rhizospheric soil. In contrast, Firmicutes was the most abundant group in saline bulk soil and non-saline rhizospheric and bulk soil. Additionally, Halothiobacillus, Thioalkalispira-Slvurivermis, and Acidothermus genera dominated the saline rhizospheric soil, suggesting that halotolerant microbes play a significant role as plant growth-promoting rhizobacteria in saline soil. The study provides valuable insights into cultured or uncultured bacterial populations and structure in saline and non-saline soil to develop future strategies related to salinity by introducing beneficial microbes.

Effects of the salinity-temperature interaction on seed germination and early seedling development: a comparative study of crop and weed species

BackgroundWeeds represent a great constraint for agricultural production due to their remarkable adaptability and their ability to compete with crops. Climate change exacerbates the abiotic stresses that plants encounter. Therefore, studying plant responses to adverse conditions is extremely important. Here, the response to saline stress at different temperatures of three weed species (Chenopodium album, Echinochloa crus-galli and Portulaca oleracea) and three crops (maize, soybean and rice) was investigated.ResultsThe germination percentage of soybean notably decreased as salinity and low temperatures increased. In contrast, maize and rice consistently maintained a high germination percentage, particularly when subjected to low salinity levels. Regarding weed species, the germination percentage of C. album was not significantly affected by salinity, but it decreased in E. crus-galli and P. oleracea with increasing salinity. The mean germination time for all species increased with salinity, especially at lower temperatures. This effect was most pronounced for soybean and E. crus-galli. C. album exhibited significant reduction in stem growth with high salinity and high temperatures, while in E. crus-galli stem growth was less reduced under similar conditions.ConclusionThis study showed that successful germination under saline stress did not ensure successful early development and emphasizes the species-specific nature of the temperature-salinity interaction, perhaps influenced by intraspecific variability. Increasing salinity levels negatively impacted germination and seedling growth in most species, yet higher temperatures partially alleviated these effects.

ADAPTATION OF ANADARA KAGOSHIMENSIS (TOKUNAGA, 1906) TO HYPO- AND HYPEROSMOTIC ENVIRONMENTAL CONDITIONS: HEMOCYTE RESPONSE

Anadara kagoshimensis (Tokunaga, 1906) is an invasive species that has successfully colonized the waters of the Black Sea and the sea of Azov, despite the significantly lower salinity level of these waters in comparison with the native region. The morphological and morphometric characteristics of bivalve mollusk A. kagoshimensis erythrocytes were analyzed by light microscopy during adaptation to hypo- and hyperosmotic experimental conditions. The control group of mollusks was kept at 18‰ salinity. Experimental groups were acclimated to 8, 14, 35 and 45‰ salinity. A decrease of salinity was achieved by diluting seawater with distilled water at a rate of 1.5±0.5‰ per day. Sea salt was added to each aquarium to increase salinity. Salinity was increased at a rate of 2.5±0.5‰ per day. Exposure period was 2 days. It has been shown that the salinity range of 14-35‰ is natural for ark clam. No significant changes in cell morphology were observed under these conditions. At the same time, environmental salinity levels of 8 and 45‰ caused obvious stress: cellular anomalies appeared, and the linear characteristics of erythrocytes were changed. However, cell lysis did not occur, the values of the specific surface area and nuclear-cytoplasmic ratio did not change. The results of the present work indicate the ability of the arc clam to exist for some time in regions with extremely low and high salinity of the aquatic environment.

Effect of varieties and salinity on the growth and yield performance of tomato under greenhouse conditions in central Fiji

A pot experiment was conducted in 2022 at the Instructional Agricultural Farm Complex of the College of Agriculture, Fisheries and Forestry, Fiji National University, Fiji to determine the effect of different levels of salinity on the growth of tomato (Lycopersicon esculentum Mill) varieties. The experiment included two factors: three tomato varieties (V1 = Melrose; V2 = Alton; V3 = Alafua Large) and four salinity levels (T1 = Control with no application of saline water; T2 = 2 dSm-1; T3 = 4 dSm-1 and T4 = 8 dSm-1) arranged in a randomized complete block design with three replications. The effects of various varieties and salinity levels on tomato growth were studied in this experiment. Results revealed that variety significantly affected the growth of the tomato. Alafua Large recorded maximum plant height of 67.63 cm and 135.68 cm, number of leaves of 7.3 and 33.5 per plant, 0.64 cm, and 0.92 cm plant stem diameter, 3.67 primary branches per plant, 13.08 days flowering duration, 11.92 flower clusters per plant, 59.83 flowers per plant at 20 and 40 DAT respectively. The combined effect of variety and the salt concentration of Alafua Large also showed a better growth performance than other varieties. Alafua Large also showed better yield (432.17 g and 394.51 g) per plant compared to other varieties when combined with lower salinity levels i.e., EC 2 dSm-1 and 4 dSm-1, respectively (P less than 0.05). The yield per plant of Alafua Large yielded 194.54 g when applied at the highest level of salinity i.e., EC 8 dSm-1, and the yield of Alton was 64.69 g which was the lowest yield among the varieties with the highest level of salinity condition. Alafua Large performed better than all other varieties and recorded higher growth parameters and yield at higher salinity levels.