Salinity Range Research Articles

Adsorption and mineralization of metalaxyl-m and chlorpyrifos in irrigated Mediterranean soil under the effects of salinity.

To evaluate the effects of salinity on the fate of pesticides in a Mediterranean irrigated system, experiments were carried out under laboratory conditions to determine the adsorption, desorption, and mineralization of chlorpyrifos (CPF) and metalaxyl-M (MET) in a soil sample from an irrigated field in northern Tunisia. Adsorption/desorption isotherms and mineralization kinetics data were obtained over a realistic range of salinities via batch equilibrium and incubation techniques. On the basis of the experimental results, MET has a lower sorption capacity than CPF does, and the adsorption data for both compounds were better fitted by the Freundlich equation, with Kf values of 0.477, 0.486, 0.426, 0.444 and 0.474 L kg-1 for MET and 38.994, 39.084, 40.644, 44.055 and 45.185 L kg-1 for CPF at salinities of 0, 1, 2, 5 and 10 g L-1, respectively. According to the mineralization experiments, increasing salinity increased the half-lives of both pesticides. For MET, the DT50 values in unsterilized soil were 206.68, 220.74, 222.16, and 238.73 days, and those in sterilized soil were 2772.58, 4077.33, 6301.33, and 8664.33 days at salinities of 0, 1, 2, 5, and 10 g L⁻1, respectively. For CPF, the DT50 values were 115.52, 138.62, 157.53, and 177.73 days in unsterilized soil and 346.57, 533.19, 693.14, and 990.21 days in sterilized soil. In terms of leaching behavior, the calculated groundwater ubiquity score (GUS) values for the MET and CPF indicate that the MET is classified as a leacher and that the CPF is classified as a nonleacher.

Effects of Temperature and Salinity on the Growth, Reproduction, and Carotenoid Accumulation in Artemia sinica and Transcriptome Analysis

Brine shrimp (Artemia), rich in carotenoids, are widely used in intensive aquaculture to supplement nutrients and enhance the coloration of farmed organisms. This study investigates the growth, reproduction, and carotenoid accumulation in Artemia sinica under varying salinity and temperature conditions. The results showed that temperature and salinity displayed significant interactions with survival, body length, and carotenoid accumulation in the body. The optimal survival and growth conditions of A. sinica (Bohai Sea Gulf) were a temperature range of 25–30 °C and a salinity range of 30–50‰. High temperatures accelerated growth and sexual maturity at the expense of survival rates, while temperatures below 20 °C prevented ovigerous development. Extreme salinity levels negatively affected survival and growth, though high salinity promoted sexual maturity. Carotenoids in A. sinica mainly accumulate as echinenone and canthaxanthin form. Carotenoid accumulation decreased with increased temperature and salinity, and the temperature effect decreased with rising salinity. A. sinica cultivated at a salinity of 10‰ and a temperature of 25 °C exhibits the highest carotenoid content. Transcriptomic analysis revealed that high temperatures primarily affected genes related to stress response and metabolism, while high-salinity regulated genes associated with ion balance and signaling pathways. These findings provide a theoretical basis for enhancing Artemia sinica aquaculture and optimizing cultivation conditions, offering novel insights into nutritional and environmental impacts on brine shrimp biology.

Boron to salinity ratios in the Fram Strait entering the Central Arctic: The role of sea ice formation and future predictions

The Arctic Ocean's sea ice loss dynamically impacts carbon uptake potential, as assessed through measured carbonate parameters, such as total alkalinity. In the open ocean, boron (B) is the third largest contributor to alkalinity via borate and is usually accounted for through the conservative boron to salinity ratio (B/S), and not directly measured. Here, we present findings on non-conservative boron dynamics, that results in significant B/S deviations, observed in ice melt zone waters, snow, slush, brine, and annual sea ice (n = 169) in the Fram Strait entering the Central Arctic. These samples were collected during the onset of the melt season on the 2023 ARTofMELT expedition, covering a wide practical salinity range (2–59). Barring snow, the average B/S ratio across the study was 0.1321 ± 0.0032 mg kg−1 ‰−1, similar to the mean B/S ratio measured amongst several polar water masses near Iceland, as well as the accepted B/S for other ocean regions. Results indicate minor deviations from accepted B/S ratios (indicating conservative behavior) across the sample practical salinity range and reflect an uncertainty in the borate contribution to total alkalinity of less than 2.9 μmol kg−1 at in-situ temperatures. B fractionation appears to occur during sea ice formation, causing greater B in the sea ice reservoir whereas brine, slush, lead, and under-ice water reservoirs are depleted in B. As such, under-ice and lead, brine, and slush samples all had measured B/S ratios (0.1305 ± 0.0011, 0.1305 ± 0.0018, and 0.1304 ± 0.0017 mg kg−1 ‰−1, respectively) lower than the established ratio whereas the average sea ice B/S ratio (0.1331 ± 0.0035 mg kg−1 ‰−1) was closest to accepted values (0.1336 ± 0.0005 mg kg−1 ‰−1). Arctic open ocean samples also had a lower B/S ratio (0.1304 ± 0.0014 mg kg−1 ‰−1). Our findings, together with a previous Arctic B ice study, suggest that B (probably in the form of B(OH)4−) is incorporated into authigenic CaCO3 minerals, replacing CO32− within the mineral lattice during sea ice formation. This process consequentially lowers the B/S ratio in the open Arctic Ocean, compared to the established global ocean ratio. Nevertheless, the incorporation of B into the sea ice reservoir does not fully account for the deficit of B in the Arctic Ocean samples, suggesting further accounting of B Arctic pathways is necessary. In future climate scenarios involving increased sea ice melt, the transition from multiyear to annual sea ice, permafrost thaw, and increased riverine discharge, the behavior of B in the Arctic Ocean is expected to become more dynamic.

The Divergent Responses of Salinity Generalists to Hyposaline Stress Provide Insights Into the Colonisation of Freshwaters by Diatoms.

Environmental transitions, such as the salinity divide separating marine and fresh waters, shape biodiversity over both shallow and deep timescales, opening up new niches and creating opportunities for accelerated speciation and adaptive radiation. Understanding the genetics of environmental adaptation is central to understanding how organisms colonise and subsequently diversify in new habitats. We used time-resolved transcriptomics to contrast the hyposalinity stress responses of two diatoms. Skeletonema marinoi has deep marine ancestry but has recently invaded brackish waters. Cyclotella cryptica has deep freshwater ancestry and can withstand a much broader salinity range. Skeletonema marinoi is less adept at mitigating even mild salinity stress compared to Cyclotella cryptica, which has distinct mechanisms for rapid mitigation of hyposaline stress and long-term growth in low salinity. We show that the cellular mechanisms underlying low salinity tolerance, which has allowed diversification across freshwater habitats worldwide, includes elements that are both conserved and variable across the diatom lineage. The balance between ancestral and lineage-specific environmental responses in phytoplankton have shaped marine-freshwater transitions on evolutionary timescales and, on contemporary timescales, will affect which lineages survive and adapt to changing ocean conditions.

Rheological investigation of heavy oil-in-water pickering emulsions for potential applications of fracturing fluids

Pickering emulsions as a kind of emulsified fracturing fluids can enhance the efficacy of shale fracturing. Investigation of the rheological properties of Pickering emulsions yields valuable insights for their in-situ fracturing applications. In this work, nano-clay particles and heavy crude oil were employed to form oil-in-water (O/W) Pickering emulsions. The impact of salinity, pH, and temperature on the rheological properties, including viscosity property and viscoelastic property, of Pickering emulsions were tested and analyzed. The results showed that the viscosity of heavy O/W Pickering emulsions were significantly affected by the change of salinity and pH values, with higher salinity or lower pH resulting in increased viscosity. Under ultra-high salinities (>5 wt% NaCl), the coalescence stability of Pickering emulsion strengthens and creaming stability declines. The massive formation of clay clusters leads to a reduction in the number of nano-clay particles used to generate the network, causing instability in the emulsion creaming. The heavy O/W Pickering emulsions exhibited high stability and high viscosity characteristics, which were mainly caused by the change of surface charge of nano-clay particles and the corresponding change of particle adsorption on droplet surface and particle-particle interactions. At a salinity of 2.5% NaCl and a pH of 4.6, the emulsion system remained stable at a temperature up to 120 °C, holding a viscosity reaching 74.1 mPa s at a shear rate of 6.81 s−1. Besides, heavy O/W Pickering emulsions were viscoelastic fluids, with both noticeable viscous property and elastic property at the same time. Elastic modulus (G′) and viscous modulus (G″) of the emulsion increased with increasing salinity and decreasing pH, enhancing great deformation capacity. Remarkably, the Pickering emulsions could maintain its viscoelastic behavior at varying temperature conditions. For the first time, rheological study of Pickering emulsions formed by nano-clay nanoparticles as a single emulsifier to heavy oil. Our study underscores the emulsifying ability of nano-clay particles to heavy crude oils, under a wide range of salinity and pH, yielding Pickering emulsions with exceptional stability and rheological properties. This novel emulsion system, possessing high resistance to temperature and salinity, holds promise for a high-performance fracturing fluid design.

Hypersalinity tolerance of mummichogs (Fundulus heteroclitus): A branchial transcriptomic analysis

Along the east coast of North America, mummichogs (Fundulus heteroclitus) are subjected to a broad range of salinities in their nearshore habitats. However, there is a paucity of information regarding the molecular and cellular processes that mummichogs (and other highly osmotolerant fishes) engage to survive environmental salinities greater than seawater (SW). To reveal branchial processes underlying their extraordinarily broad salinity tolerance, we performed an RNA-Seq analysis to identify differentially expressed genes (DEGs) in mummichogs residing in 3, 35, and 105 ppt conditions. We identified a series of DEGs previously associated with both freshwater (FW)- and SW-type ionocytes; however, the heightened expression of anoctamin 1a, a Ca2+-activated Cl− channel, in 35 and 105 ppt indicates that an undescribed Cl−-secretion pathway may operate within the SW-type ionocytes of mummichogs. Concerning FW-adaptive branchial processes, we identified claudin 5a as a gene whose product may limit the diffusive loss of ions between cellular tight junctions. Further, in response to hypersaline conditions, we identified DEGs linked with myo-inositol synthesis and kinase signaling. This study provides new molecular targets for future physiological investigations that promise to reveal the mechanistic bases for how mummichogs and other euryhaline species tolerate hypersaline conditions.

Potential of a novel marine microalgae Dunaliella sp. MASCC-0014 as feed supplements for sustainable aquaculture

Microalgae, as live feed organisms in aquatic ecosystems, play a crucial role in enhancing water quality by providing oxygen and nutrients. The accumulation of heavy metals in microalgae, however, can pose significant threats to environmental sustainability and human health. In this study, we focused on the marine microalgae Dunaliella sp. MASCC-0014, which exhibited resilience to a wide range of salinities from 0.5 to 4.5 M NaCl, with optimal growth at 0.5 M NaCl. Phylogenetic analysis revealed that MASCC-0014 is closely related to Dunaliella salina CCAP 19/25. Biosorption assay indicated that MASCC-0014 had limited capacity to absorb cadmium, cobalt, and nickel from the liquid medium, while Dunaliella salina CCAP 19/18, Dunaliella tertiolecta FACHB-821 and Dunaliella bardawil FACHB-847 showed varied degrees of cadmium biosorption. When exposed to cadmium stress, MASCC-0014 exhibited suppressed growth and increased activities of catalase (CAT) and peroxidase (POD), suggesting cadmium still triggered cellular responses in MASCC-0014. Furthermore, MASCC-0014 displayed reduced chlorophyll content per cell but increased biomass in warmer conditions, indicating its preference of tropical water over temperate water. This unique microalga strain, which is rich in protein but with limited heavy metal biosorption capabilities, shows promise as a sustainable feed source in aquaculture. The findings in this study offer valuable insights into mitigating the risks of heavy metal enrichment in the food chain through algae-based feeds.

Using desiccation-resistant eggs to explore the ecology of giant ostracods (subfamily Mytilocypridinae) in Australian salt lakes

AbstractGiant ostracods in the subfamily Mytilocypridinae are an important component of the biota of Australian salt lakes, which are predominantly temporary, and often located in remote arid areas. Mytilocypridines produce desiccation-resistant eggs to persist in these habitats during unfavourable conditions. In this study, we used mytilocypridine eggs collected from sediments in salt lakes in Western Australia to analyse aspects of the ecology of these ostracods. We conducted two rehydration trials, where sediment was collected from dry lakes or the dry margins of lakes, rehydrated in a laboratory setting, and selected mytilocypridine species hatched and raised in cultures. The first trial found that the eggs of mytilocypridine species were unevenly distributed in a dry lake and could be hatched even after 27 months of dry storage with no discernible loss of viability. The second trial assessed the capacity of selected mytilocypridines to hatch and develop into adults under different salinity treatments. One species, Australocypris insularis, hatched and developed across a very wide salinity range (0–100 g/L). Egg/sediment samples provide a means for testing species’ tolerance to physical and chemical variables throughout their entire life cycle, as well as for surveying the mytilocypridines in remote lakes that rarely hold water.

Hydroxy salt induced CoAl-LDH nanosheet composite membrane for pervaporation desalination

Pervaporation is a promising desalination technology. Developing high-performance and stable pervaporation membranes with high continuity structure remains a significant challenge. This study reports the development of a novel layered double hydroxide (LDH) nanosheet composite membrane fabricated using a hydroxyl salt induction method. This approach facilitated the in-situ nucleation and growth of the CoAl-LDH nanosheets on polyvinylidene fluoride (PVDF) substrate, reducing precursor concentration and enhancing preparation efficiency. The resulting cross-compatible architecture closely integrated the dense LDH nanosheet separation layer with the flexible PVDF support. The microstructure and morphology of the hydroxyl salt layer and its transformed CoAl-LDH composite membrane were comprehensively investigated. The optimized membrane was applied for pervaporation desalination (3 wt% NaCl, 50 °C), achieving a high flux of 38.4 kg·m−2·h−1 and exceptional NaCl rejection of 99.9 %. It also demonstrated excellent tolerance to a wide salinity range, maintaining 99.6–99.9 % rejection even at 20 wt% NaCl, while the flux remained stable at 26.7 kg·m−2·h−1. Long-term testing confirmed the consistent separation performance and operational stability, underscoring the great potential of this advanced membrane material for practical pervaporation desalination applications.

Stage‐by‐stage exploration of normal embryonic development in the Arabian killifish, Aphanius dispar

AbstractBackgroundArabian killifish, Aphanius dispar, lives in marine coastal areas of the Middle East, as well as in streams that experience a wide range of salinities and temperatures. It has been used as a mosquito control agent and for studying the toxicities of environmental pollutants. A. dispar's eggshell (chorion) and embryos are highly transparent and are suitable for high resolution microscopic observations, offering excellent visibility of live tissues.ResultsIn this study, the staging of normal embryonic development of A. dispar was described and investigated at different temperatures. Embryonic development was then examined under different thermal environments from 26 to 34°C. Our data suggest that temperature has a significant effect on embryonic development, with accelerated development at higher temperatures.ConclusionA. dispar exhibits broad thermal tolerance and extended independent feeding capabilities, making it a promising model organism for toxicology and pathogenesis studies conducted over an extended period of time (12 days post‐fertilization).

Salinity tolerance of the invasive blue crab Callinectes sapidus: From global to local, a new tool for implementing management strategy

The latest report from the Intergovernmental Platform on Biodiversity and Ecosystem Services (IPBES) raises concerns about the global proliferation of non-native species (NIS) driven by increasing temperatures. In 2023, the invasive blue crab Callinectes sapidus experienced a significant range expansion in the French Mediterranean lagoons, now present in over 20 lagoons and numerous estuaries with different invasion gradients. It has been established that this species is eurytherm (tolerates a wide range of temperatures; 0–40 °C), rendering temperature a non-limiting factor for its proliferation. On the other hand, salinity is a critical factor to consider, as C. sapidus requires brackish water for copulation and saline water for egg maturation. In this study, we present the salinity tolerance of C. sapidus using the metabolic performance to define the tolerance of the species to a large range of salinities (13 levels from 0 to 65 psu). Results showed that C. sapidus tolerates a large range of salinities with a minimum critical threshold (CTmin) at 0 psu, an optimum at 18.5 psu, and a CTmax at 62.4 psu. Using the performance curve equation, we applied the curve to real salinity data measured each month in 2023 in 20 lagoons invaded. Using this approach, we were able to map, on a fine spatial scale, the distribution of suitable habitats for C. sapidus in the year 2023. Additionally, we have developed a tool to prioritize the lagoons based on their suitability, thereby providing a decision-making framework for management measures in each lagoon. It emerged that 50 % of lagoons were priority areas, 10 % were intermediate and 40 % required monitoring. On the basis of this approach, we can respond to European regulations to help decision-makers implement action plans and/or early detection programs for invasive species management.

The effects of dissolved organic carbon and model compounds (DOC analogues) on diffusive water flux, oxygen consumption, nitrogenous waste excretion rates and gill transepithelial potential in Pacific sanddab (Citharichthys sordidus) at two salinities.

Many flatfish species are partially euryhaline, such as the Pacific sanddab which spawn and feed in highly dynamic estuaries ranging from seawater to near freshwater. With the rapid increase in saltwater invasion of freshwater habitats, it is very likely that in these estuaries, flatfish will be exposed to increasing levels of dissolved organic carbon (DOC) of freshwater origin at a range of salinities. As salinity fluctuations often coincide with changes in DOC concentration, two natural freshwater DOCs [Luther Marsh (LM, allochthonous) and Lake Ontario (LO, autochthonous) were investigated at salinities of 30 and 7.5 ppt. Optical characterization of the two natural DOC sources indicate salinity-dependent differences in their physicochemistry. LO and LM DOCs, as well as three model compounds [tannic acid (TA), sodium dodecyl sulfate (SDS) and bovine serum albumin (BSA)] representing key chemical moieties of DOC, were used to evaluate physiological effects on sanddabs. In the absence of added DOC, an acute decrease in salinity resulted in an increase in diffusive water flux (a proxy for transcellular water permeability), ammonia excretion and a change in TEP from positive (inside) to negative (inside). The effects of DOC (10mg C L-1) were salinity and source-dependent, with generally more pronounced effects at 30 than 7.5 ppt, and greater potency of LM relative to LO. Both LM DOC and SDS increased diffusive water flux at 30 ppt but only SDS had an effect at 7.5 ppt. TA decreased ammonia excretion at 7.5 ppt. LO DOC decreased urea-N excretion at both salinities whereas the stimulatory effect of BSA occurred only at 30 ppt. Likewise, the effects of LM DOC and BSA to reduce TEP were present at 30 ppt but not 7.5 ppt. None of the treatments affected oxygen consumption rates. Our results demonstrate that DOCs and salinity interact to alter key physiological processes in marine flatfish, reflecting changes in both gill function and the physicochemistry of DOCs between 30 and 7.5 ppt.

Fluid flow in the Katanga Supergroup: From Lufilian brittle tectonic stages to the post-Lufilian period (Democratic Republic of Congo)

The metasedimentary rock succession of the Neoproterozoic-Cambrian Katanga Supergroup in the Central Africa Copperbelt shows evidence of several complex tectonic events. The deformation of this supergroup started from the tectonic inversion at about 570 Ma and lasted up to today, but reached paroxysm at ∼550 Ma. This long period was characterized by folding and faulting throughout multiple compressive and extensional events, which controlled the regional fluid flow on the one hand, and played an important role during formation of the stratiform to stratabound Cu-Co (Ni, U) deposits and the polymetallic Cu-Zn-Pb (Ag, Ge, Mo, Cd) vein type deposits on the other hand. Based on the structural analysis and paleostress reconstruction, coupled with fluid inclusion characterization from mineralized structures in rocks from the Nguba, Kundelungu and Biano Groups, this study demonstrates that the composition of hydrothermal fluids changed during brittle tectonic deformation during the Lufilian orogeny and subsequent uplift and post-Lufilian faulting.During early brittle tectonic deformation along strike slip faults with sinistral and dextral movement related to a NE-SW transpression, the Cu-mineralizing fluid was hypersaline (27.9–31.1 eq. wt% NaCl) with moderate temperatures (Th = 128–216 °C). The subsequent Cu or Cu (Zn, Pb) mineralization formed within an E-W extensional stress regime, related to the late Lufilian orogenic collapse. The fluid inclusions present in the gangue minerals associated with this latter mineralization show a large range in Th (50–264 °C) and salinity (26.7–36.0 eq. wt% NaCl). The decrease in temperature is interpreted to be due to migration of the fluids at shallower depth in the subsurface after uplift and erosion of the orogen. The increased salinity of the fluid is related to the dissolution of evaporites, mainly NaCl. A second H2O-NaCl-CaCl2 fluid with a homogenization temperature below 55 °C has also been found associated with this brittle stage and mineralization phase, but only in rocks belonging to the Kundelungu Group. A third mineralization phase, also characterized by Cu or Cu (Zn, Pb), formed during the post-Lufilian period within a NW-SE transpressional inversion regime. The fluid inclusion in the gangue minerals of this mineralization phase have a smaller range in homogenization temperature (Th = 37–172 °C) and the largest range in salinity (0.71–30 eq. wt% NaCl), compared to the earlier fluid inclusions generations. This large range in salinity may be explained by the mixing of a high salinity fluid, already present during the earlier tectonic stages in the sedimentary basin, with meteoric water. During the more recent rift-related extension, a fluid with again a large and higher range in homogenization temperatures (Th = 47–257 °C) and with a typical low salinity (<10 eq. wt% NaCl) has been recognized in minerals filling NNE-SSW to NE-SW oriented faults and fractures. The upward migration of a relatively low-salinity fluid from deeper parts in the subsurface explains the variation in the temperatures observed with this tectonic event.

New Records of the Egg Development Phase of Varuna litterata in the Lower Serayu River, Central Java

One of the Brachyura crabs found in the lower reaches of the Serayu River is Varuna litterata, also known as the "herring bow crab". This crab usually inhabits shallow tidal areas and hides under rocks, logs, or dead leaves. It is a highly adapted crab found in a wide range of salinities. V. litterata is also a fishery product consumed in Thailand, the Philippines, and Indonesia. This research was conducted in the Lower Serayu River, Central Java, which consists of three observation stations, namely: 1) the first station is located above the dam with fresh water, 2) the second station is below the dam with fresh water properties and 3) the third station is downstream (estuary) of the Serayu River with brackish water. This research was conducted for four months, from October 2023 to January 2024. This study aimed to determine the level of egg development in V. litterata. The results showed that V. litterata experienced four stages in egg development and then hatched into zoea. At the initial development stage, V. litterata eggs will be purple; in the second stage, the eggs will turn reddish; in the third development stage, the eggs will turn orange to brownish; and in the fourth stage, the eggs will develop and become black. V. litterata that will spawn will migrate to brackish waters to hatch their eggs. V. litterata produces 20,708 - 85,886 eggs with an average egg diameter of 0.440 - 0.466 mm.

Modeling interfacial tension of methane-brine systems at high pressure high temperature conditions

In the present study, two white-box correlative models, namely gene expression programming (GEP) and group method of data handling (GMDH), were implemented to predict the interfacial tension (IFT) of brine-methane system. To achieve this, 790 data points were collected from literature, with pressure, temperature, and salinity as inputs and IFT as the output. The range of salinity, pressure, and temperature is from 0 to 107000 ppm, 0.01–260 MPa, and 278.1–477.59 K, respectively. The results show that the GMDH model with an R2 of 0.9321 and an average absolute percent relative error (AAPRE) of 3.68% outperforms the GEP, which has an AAPRE of 5.08% and an R2 of 0.8943. Based on our investigation, GMDH and GEP models follow the expected trend of IFT with the variation of pressure. It has been found that the GMDH model exhibits better performance compared to the previously developed correlations in the literature. Furthermore, the sensitivity analysis indicated that temperature has the greatest effect on IFT. By using the leverage approach, we proved that the GMDH model is statistically valid.

Using species population structure to assist in management and decision-making in the fight against invasive species: The case of the Atlantic blue crab Callinectes sapidus

The blue crab Callinectes sapidus Rathbun, 1896 is an invasive species in the Mediterranean, with a remarkable ability to adapt to various habitats, and thereby having significant impacts on biodiversity and artisanal fishing activities. Currently, fishing is a measure being considered to control blue crab populations in invaded sites. However, it is necessary to understand the temporal structure of blue crab populations (e.g., growth, reproduction, sexual maturity) to determine specific periods when control measures need to be implemented. Considering the species' ability to adapt to various habitats, it is crucial to evaluate how temperature and salinity influence population structure. In this study, we present fishers-dependent monitoring on the temporal population structure of blue crabs in two lagoons in Corsica (France) over 12 months. Through this approach, we provide new information that can assist in decision-making for the implementation of control measures. Even though these two lagoons are geographically close, blue crab populations showed differences, particularly in terms of sexual maturity. Specimens from Biguglia mature later (males: 16.16 cm; females: 16.79 cm) than those in the Palo Lagoon (males: 14.38 cm; females: 13.86 cm). Seasonal size distribution also showed differences between the lagoons and within the same lagoon between males and females. Temperature and salinity had a significant effect on the monthly relationship between carapace width and wet weight (referred to here as growth rate) for males and females and between the lagoons. In the Biguglia Lagoon, the higher the temperature, the greater the growth rate over a wide salinity window (16–30 psu); for females, the environmental window was restricted (temperature: 20–30°C; salinities > 16 psu). The dynamics differed in the Palo Lagoon, with a more restricted high growth rate window for males, and females showed a much wider window, with high growth rates over the entire temperature and salinity range. By employing blue crab’s populations monitoring along with environmental parameters, we were able to determine how the environment influenced the blue crab’s population structure, thus identifying periods conducive to species control. The most effective strategy would undoubtedly be to eliminate females before their period of sexual maturity and copulation ensue. In our case, this would involve intensive control in summer for Biguglia and in spring for Palo. These recommendations have been translated into operations to be implemented as part of the "Territorial Plan for Combating the Blue Crab (Callinectes sapidus) in Corsica (2024–2027)".

Biosurfactants as stabilizers of niclosamide nanocrystals: Enhancing stability, solubility, and cytotoxicity profiling

Biosurfactants are surface-active compounds of biological origin, stable over a wide range of temperature, pH, and salinity. In this work, the ability of the biosurfactants rhamnolipid (RAM), sophorolipid (SOFO) and surfactin (SURF) to stabilize a nanocrystal suspension of niclosamide (NCL) in water, and to enhance the drug solubility were evaluated. The performances were compared with those of the synthetic surfactants tween 80 (TW) and soluplus (SOLU). Overall, RAM, SOFO, and SURF proved to be as effective as TW and SOFO in terms of NCL nanocrystal suspension stabilization. Formulations containing 3 % (w/w) surfactant exhibited the best stability at 4 °C and 25 °C. The three biosurfactants also led to an improvement of aqueous NCL solubility, even when a slurry of the micronized drug was used without nanocrystal formulation. The best performance was observed for the SURF 3 % (w/w) nanocrystal formulation (1157.48 μg/mL), which released more than twice the amount of NCL compared to the best synthetic surfactant formulation (TW 3 % (w/w), 542.57 μg/mL), and 622 times more than the pure solid drug (1.86 μg/mL). Cell viability was not compromised by the surfactants alone, indicating that the formulation cytotoxic effect is related to the enhanced solubilization of NCL. Consistently, the NCL/SURF formulation was the most effective, achieving a maximum cytotoxicity effect of 80 % at a concentration of 1000 nM, while the other formulations reached a maximum effect of 71 % at concentrations starting from 1500 nM. Nevertheless, when the balance between formulation stability, drug release enhancement, and cytotoxicity is considered the three biosurfactants studied in this work showed significant potential advantages relative to synthetic analogues that can be explored in pharmaceutical development.

Molecular identification of rhamnolipids produced by Pseudomonas oryzihabitans during biodegradation of crude oil.

The ability to produce biosurfactants plays a meaningful role in the bioavailability of crude oil hydrocarbons and the bioremediation efficiency of crude oil-degrading bacteria. This study aimed to characterize the produced biosurfactants by Pseudomonas oryzihabitans during the biodegradation of crude oil hydrocarbons. The biosurfactants were isolated and then characterized by Fourier transform infrared (FTIR), liquid chromatography-mass-spectrometry (LC-MS), and nuclear magnetic resonance spectroscopy (NMR) analyses. The FTIR results revealed the existence of hydroxyl, carboxyl, and methoxyl groups in the isolated biosurfactants. Also, the LC-MS analysis demonstrated a main di-rhamnolipid (l-rhamnopyranosyll-rhamnopyranosyl-3-hydroxydecanoyl-3-hydroxydecanoate, Rha-Rha-C10-C10) along with a mono-rhamnolipid (l-rhamnopyranosyl-b-hydroxydecanoylb-hydroxydecanoate, Rha-C10-C10). In agreement with these findings, the NMR analysis confirmed the aromatic, carboxylic, methyl, sulfate moieties, and hexose sugar in the biosurfactants. The emulsion capacity of the biosurfactants decreased the surface tension of the aqueous system from 73.4 mN m-1 to around 33 mN m-1 at 200 mg L-1 as the critical micelle concentration. The emulsification capacity of the biosurfactants in the formation of a stable microemulsion for the diesel-water system at a wide range of pH (2-12), temperature (0-80°C), and salinity (2-20 g L-1 of NaCl) showed their potential use in oil recovery and bioremediation through the use of microbial enhancement. This work showed the ability of Pseudomonas oryzihabitans NC392 cells to produce rhamnolipid molecules during the biodegradation process of crude oil hydrocarbons. These biosurfactants have potential in bioremediation studies as eco-friendly and biodegradable products, and their stability makes them optimal for areas with extreme conditions.

A CO2-Modified Surfactant for Chemical Flooding

Summary Carbon dioxide (CO2) modification of a nonionic surfactant alkyl polyglycoside (C-APG) was conducted based on a commercial APG product under mild synthesis conditions, including a low temperature (50°C) and a low pressure (2.5 bar). Using this method, CO2 was incorporated into APG molecules through the formation of carbonyl structures. The effectiveness and performance of C-APG as a novel surfactant for enhanced oil recovery (EOR) application in carbonate reservoirs were investigated and compared with its precursor—the unmodified APG. The key factors in the chemical structure of C-APG were characterized by Fourier transform infrared spectroscopy (FTIR) to confirm successful CO2 modification. The properties, including compatibility, surface tension, wettability alteration, interfacial tension (IFT), phase behavior, and static and dynamic adsorption of both APG and C-APG, were evaluated by various techniques and methods. Crude oil displacement efficiency of the surfactants was investigated via spontaneous imbibition, visualized micromodel, and coreflooding tests, respectively. Both surfactants were compatible with a high-salinity water (HSW), they exhibited a similar critical micelle concentration (CMC) of 8.5 mg/L and 13.5 mg/L for APG and C-APG, respectively, and had the same contact angle of around 135°. Interestingly, C-APG was found more effective in reducing IFT between oil and water phases. The IFT of oil in the C-APG solution was 0.058 ±0.001 mN/m, one order of magnitude lower than the value of 0.47 ±0.02 mN/m obtained from the solution of original APG, suggesting a better performance of C-APG in chemical flooding for oil displacement. A Winsor Type I microemulsion was formed by APG within the salinity range, while a transition of Type I to Type II microemulsion was observed for C-APG. The static adsorption of APG and C-APG at 2 g/L in carbonate were 0.93 mg/g rock and 1.08 mg/g rock, and the adsorption decreased to 0.11 mg/g rock and 0.13 mg/g rock under dynamic conditions for APG and C-APG, respectively. The spontaneous imbibition test demonstrated a higher oil imbibition recovery of 18.0% from C-APG solution compared to the result of 10.2% obtained from APG solution. A micromodel test showed that more crude oil was displaced by injection of APG or C-APG solution after waterflooding, while C-APG injection exhibited a stronger emulsification. The oil displacement by coreflood test showed that C-APG injection led to a lower differential pressure and a higher cumulative oil production (48%) compared to APG chemical flooding with a cumulative oil production of 41%. The produced fluids containing displaced crude oil from C-APG flooding, and subsequent waterflooding demonstrated very strong emulsification compared to the fluids produced after APG injection. This study demonstrates the significant potential of C-APG in two aspects—CO2 reduction and chemical EOR for the upstream petroleum industry.

Carbon Stabilization in the Arid-Saline Soil Environment of Southern Morocco

Researchers examined the influence of irrigated grass and alfalfa established in arid locations with a range of soil salinity to determine their influence on C mineralization and accumulation. Overall, blue panicum grass-alfalfa mixtures could trigger C mineralization and support C stabilization suggesting a balance between microbial energy needs and nutrient cycling in these saline soils.