Although the limits of life under individual extremes have been extensively studied, systematic experiments to quantify how combined extremes set the limits to life are lacking. We investigated the combined effects of extremes in temperature, salinity (NaCl) and pH on the growth limits of the marine bacterium Halomonas hydrothermalis, to test the hypothesis that limits to growth under combinations of the extremes establish a more restricted niche than the individual extremes. We show that the combination of supra-optimal temperature, pH and NaCl act synergistically in defining the limits of growth under multiple extremes. Although at optimal growth temperatures (30°C) maximum growth was achieved at pH 7, the maximum temperature limit of 43°C was achieved at pH 8. Under these conditions, the maximum NaCl concentration limit was 6.58% (wt/vol). Decreasing the temperature to 42 and 41/40°C increased the salinity limit to 7.01 % and 8.24 %, respectively. These data show that multiple extremes restrict the limits to growth of this organism to a greater extent than individual extremes and show how natural environments with extremes of temperature, pH and salinity could have restricted microbial diversity, or be uninhabitable, even when each individual extreme lies within the bounds of known microbial growth. These data imply that ‘maps’ of the limits to the biosphere based on laboratory-derived individual extremes may over-exaggerate growth limits in natural environments, which are rarely subject to single extremes, highlighting the need for multi-parameter analyses.

In heavy oil fields hosted in sandstone, steam flooding is a crucial technique for enhancing oil recovery. The swelling of clay minerals in these reservoirs, particularly those with high clay content, presents a significant challenge by causing permeability damage and hindering oil production. The objective of the present study was to investigate clay swelling phenomena in a sandstone oil reservoir where smectite-illite clays make up 40% of the reservoir rock. Through comprehensive static and dynamic tests, clay swelling behavior and its impact on permeability degradation were examined under varying temperature and salinity conditions typical of thermally enhanced oil recovery (EOR) processes. Results indicated that clay swelling is exacerbated under low salinity and high temperature, leading to severe permeability impairment. At high salinities (2000–4920 mg L–1), the swellability was relatively low, but it increased significantly as salinity decreased to a range of 0–2000 mg L–1. Static swelling tests revealed that the maximum clay expansion, with a 2.25-fold increase in volume, occurred in distilled water at 200°C. Additionally, the critical salt concentration (CSC) was found to increase with temperature, causing a more pronounced and earlier swelling effect. This increase in temperature coupled with a decrease in salinity impaired permeability significantly, with the most severe reduction, of 73.3%, observed at 150°C during distilled water flooding. Comparisons between static and dynamic tests showed consistent degrees of clay swelling across both methods. The findings of this study advance the understanding of clay swelling under thermal EOR conditions, particularly regarding the effects of salinity and temperature on permeability impairment in sandstone formations.

This study investigated the temporal and spatial variability of temperature, salinity, pH and suspended particulate matter (SPM) in surface water from Admiralty Bay, Antarctic Peninsula. The study aimed to understand how water parameters were affected during high meltwater runoff in the summer of 2019/2020, to verify the influence of rapid temperature changes from the spring and summer of 2022/2023 and to identify the sources of SPM. In January 2020, the water temperature and salinity in the region were influenced by rapid shifts in environmental conditions, while pH and SPM remained similar to previous years. The same pattern was observed in the summer of 2022/2023, with only water temperature and salinity varying towards the end of the summer. The SPM concentrations were mainly influenced by wind speed. Spatially, there was no sectorization between different inlets, with specific sites influenced by meltwater and higher SPM values. The study suggests that strong winds are the primary factor influencing SPM resuspension in Admiralty Bay, with atmospheric deposition and meltwater also contributing. This dynamic variability in the water column highlights the need to closely monitor the water’s physicochemical parameters and the influence of atmospheric conditions. This study contributes to our understanding of the SPM sources on the Antarctic coast.

Marine aerosols can enter the terrestrial environment via sea spray which is known to affect the stable isotope fingerprint of coastal samples (plants, animals/humans), including δ13C. However, the impact of sea spray on 14C dating of terrestrial organisms at coastal sites has not been investigated so far. Besides a direct effect, sea spray is accompanied by physiological effects, e.g., due to salinity. In an artificial sea spray experiment in the greenhouse, the effect of sea spray on 14C in plant tissue was investigated. Beach grass was sprayed with mineral salt solutions containing only traces of NaCl or with brackish water from the Schlei inlet or the Baltic Sea. These plants should give a 14C signal close to the modern atmospheric 14CO2 composition. However, three treatment groups showed variable radiocarbon concentrations. Plants sprayed with water from the Schlei inlet, Baltic Sea water, or with a mineral salt solution with very high HCO3– concentration are depleted in 14C content relative to contemporary atmospheric composition. While δ13C reflects physiological effects in the plants, caused either by salinity (NaCl) or HCO3– stress, resulting in decreased discrimination against 13C, the uptake of high amounts of 14C (ca. 53–67%) from DIC (dissolved inorganic carbon) partly masks the underlying physiological reactions, as is visible in the radiocarbon signature of the plant tissues. This preliminary study indicates that sea spray effects on plant tissue could potentially influence faunal tissue 14C composition at coastal sites. Further research is required to better understand the observed reservoir effect.

During a 2019 Chilean Antarctic Scientific Expedition (ECA 55) studying crustose coralline algae (CCA) diversity on the Antarctic Peninsula, bleaching of these algae was observed for the first time in this region. Here, we present initial findings on the physiological state of bleached and normally pigmented CCA (Clathromorphum sp.) assessed using chlorophyll-a fluorescence induction pulse amplitude modulation. The study site experienced high light exposure and salinity in the water column. Our analyses found that bleached CCA have relatively healthy photophysiology responses but lower photosynthetic efficiency, which could be associated with the low salinities recorded in the study area. However, seasonal monitoring and mesocosm experiments across the southern polar latitudes are urgently required to confirm this hypothesis.

Among the most widely distributed species globally, common reed [Phragmites australis (Cav.) Trin. ex Steud.] has generated extensive interest in invasive plant science and management because its introduced strains are highly invasive and often form monocultures that alter ecosystem properties. In desert wetlands in Las Vegas, NV, USA, where management goals included reducing hazardous P. australis fuels and increasing native plant diversity, we assessed variation in P. australis cover, the degree of native plant colonization, and soil seedbanks after P. australis management treatments (cutting, glyphosate–imazapyr herbicide) and wildfires across gradients in soil properties. Based on change in P. australis cover during six measurement events over 24 mo, 24 study sites formed three groups: (1) decreasing cover, where initially high P. australis cover (60% to 85%) decreased to <5% following multiple cutting or herbicide treatments; (2) sustaining low cover, where wildfire or clearing was associated with initially low P. australis cover which remained low (<30%) after multiple herbicide applications; and (3) sustaining high cover (45% to 100% initially and remaining at 30% to 100%), including sites unmanaged or treated/burned only once. High soil salinity correlated with low postmanagement P. australis cover. No native plants were detected in the sustaining high P. australis cover group, despite natives occurring in the seedbank. Where management reduced P. australis cover, minimal native plant colonization did occur. Secondary invasion by other non-native plants was nearly absent. Our results suggest that if P. australis can be initially cleared, multiple herbicide applications can persistently keep cover low, especially on drier, saline soils. Slow native plant colonization suggests that a phased approach may be useful to initially reduce P. australis cover, keep it low via repeated treatments, and actively revegetate sites with native species tailored to the moisture–salinity gradient across P. australis–invaded habitats.

Tropical ageratum (Ageratum conyzoides L.) is a problematic weed frequently observed in association with commercially important crops in Australian agroecosystems. Knowledge of the germination response of A. conyzoides is crucial for proactively managing this weed species, especially when herbicide resistance is involved. Herbicide screening and metsulfuron dose–response experiments were conducted on two separate populations of A. conyzoides (referred to as Sugarcane and Roadside) in an open environment to identify a metsulfuron-resistant population. Based on the survival percentage in the metsulfuron dose–response experiment, the Sugarcane population was found to be 54 times more resistant compared with the metsulfuron-susceptible population (Roadside). Subsequent laboratory experiments were performed to investigate the differential germination response of the two populations. No germination or emergence difference was observed between the Sugarcane and Roadside populations under various thermal regimes (15/5 to 35/25 C with a 12/12-h photoperiod), salinity levels (0 to 320 mM), osmotic potentials (0 to −1.6 MPa), and burial depths (1 to 4 cm). However, different environmental conditions significantly impacted the germination and emergence of A. conyzoides. Ageratum conyzoides germinated over a wide range of temperatures, with the highest germination rate (>90%) occurring at 30/20 C. With increasing levels of salinity, osmotic potential, and burial depth, the germination/emergence of A. conyzoides declined and was completely inhibited at 300 mM salinity, −0.8 MPa osmotic potential, and a 1-cm burial depth. The data generated from this study will be useful in developing a model-based approach to predict the occurrence of this weed species and thus aid in designing ecologically sustainable integrated weed management protocols.

The pH of Na-saturated, carbonate-containing and carbonate-free Leda clay, at salinities of 2 and 10 g/liter, was decreased from pH 8 to 4 by the addition of HCl. The Bingham yield stress, as determined with a coaxial viscometer, increased in all materials as the pH decreased. Above about pH 7 the 2-g/liter materials had a lower yield stress at any water content than the 10-g/liter materials, whereas, below about pH 6.8 the yield stress of the carbonate-containing soil at a salinity of 10 g/liter was lower. For the carbonate-free material, the change occurred at about pH 6.2. The influence of salinity on the remolded shear strength of these materials was pH-dependent. A yield stress increase with decreasing pH was likely due to a change in ion saturation. The carbonate-free material exhibited a maximum yield stress at about pH 5.5–6.2, depending on salinity. The isoelectric points for oxides and clay mineral edges most probably account for the existence of the maximum.

Changes in hydraulic conductivity (HC) and clay dispersion of smectite-sand mixtures as a function of exchangeable Na in Na-Ca and Na-Mg systems were measured. The charge density on the smectites had no effect on Na-Ca and Na-Mg equilibrium, and the affinity of the clays for Na was similar in both systems. A decrease in HC at 0.01 M concentration was found to be due to clay swelling. Mg was found to be less effective than Ca in preventing the breakdown of the packets by low concentrations of exchangeable Na, and Na-Mg-smectite swelled more than Na-Ca-smectites.

Na-Mg-clay particles dispersed more readily than Na-Ca-clay particles when the mixtures were leached with distilled water; however, if the electrolyte concentration in the clay-sand mixture was controlled by the leaching solutions, no difference between the Na-Mg- and Na-Ca-clays was noted. Thus, the effect of Mg on clay mixtures leached with distilled water was apparently due to the effect of Mg on the hydrolysis of the clays. Increase in charge density increased the stability of the R2+ clay packets, and higher concentrations of Na were needed to break the packets. Mg was less effective than Ca in stabilizing the packets, and lower concentrations of Na were needed to break the Mg-packets.

Changes in hydraulic conductivity of smectite-sand mixtures (using four reference smectites) as a function of the concentration (0.01, 0.003, 0.002, 0.001 M Cl- and distilled water) and potassium adsorption ratio (of 2, 4, and 6) of the percolating solution were measured. Swelling and dispersion of the clays were evaluated from the changes in hydraulic conductivity of the mixture and from the clay concentration in the effluent.

The effect of exchangeable potassium percentage (EPP) on the hydraulic conductivity of the smectites depended on the charge density of the clays. The effect of potassium at EPPs <20 on the hydraulic conductivity of smectites having high charge density was negligible. Conversely, the hydraulic conductivity of smectites having low charge density (smectites from Wyoming and Belle Fourche, South Dakota), changed markedly when leached with dilute solutions as the EPP of the clay increased. The dispersive effect of exchangeable potassium on low-charge smectites was similar to that of exchangeable sodium. The low hydration energy of the K+ cations, coupled with the strong electrostatic attraction forces between platelets of smectites with high charge density account for the “inefficiency” of K+ in dispersing these smectites.

Changes in hydraulic conductivity and clay dispersivity of clay-sand mixtures (four reference smectites and Fithian illite) as a function of concentration (0.01 M Cl− and distilled water) and sodium adsorption ratio (SAR ≤ 30) of the percolating solution were measured. In addition, the effect of sand percentage, sand particle size, and addition of AlCl3 and FeCl3 on the hydraulic conductivity of the mixtures were measured.

Clay dispersion and migration out of the 3% clay columns was substantial. The clay dispersed only in the distilled water system; dispersion increased with an increase in the percentage of exchangeable Na and was about the same for the Wyoming montmorillonite and Fithian illite. Conversely, the clay swelled in the 0.01 M Cl− solution. The swelling of the montmorillonites increased in the order: Upton, Wyoming = Belle Fourche, South Dakota > Polkville, Mississippi > Otay, California, and was higher than that of the Fithian illite. The swelling and dispersion of the clay accounted for the changes in hydraulic conductivity.

Mixtures treated with FeCl3 and AlCl3 were leached with NaCl-CaCl2 solutions until the pH of the effluent exceeded 6.5. The composition of the exchangeable phase was then determined by the SAR of the leach solutions. At pH > 6.5, the polycations hydrolyzed and were present as the hydroxy-polymer species. The hydraulic conductivity of the mixtures decreased as exchangeable Na increased, but the decrease was less than in untreated mixtures, AlCl3 was more effective in maintaining hydraulic conductivity than FeCl3. In montmorillonite clay with an ESP of 20, less than 5% of a complete Al-interlayer was enough to prevent a reduction in hydraulic conductivity. Packets in the day systems tested explain the high efficiency of the Fe and Al polycations.

Climate variability is expected to increase due to climate change, with projected increases in temperature and erratic rainfall patterns. These changes will alter the environmental cues sensed by seeds, and therefore will impact plant recruitment. This study investigated the effects of seed functional traits (germinability, germination time, synchrony and seed mass) on germination responses of several sub-tropical native Australian plant species under different environmental factors (water stress, salinity and pH). The effect of a hot water pre-treatment was also tested on Fabaceae seeds with known physical dormancy. Seed traits, environmental factors and seed pre-treatments had significant effects on final germination percentage and germination time. Seed mass and time to 50% germination (t50) were also positively correlated. In contrast, pH did not affect germination and there was no interaction between pH and any of the measured seed functional traits. Some species showed a high thermal tolerance to germination and germination was indifferent to light conditions for all species. Results showed that certain seed functional traits interact with environmental factors to influence germination percentage and time. These findings highlight the importance of considering seed functional traits when determining a species germination response under a changing climate. In addition, the findings provide important knowledge to better guide seed-based land restoration programmes.

The layer charge characteristics of expanding phyllosilicates in four salt-affected soils in Alberta, Canada were investigated using X-ray diffraction analysis of alkylammonium saturated samples. The layer charge was found to be lower and more heterogeneous than previously reported for non-saline Alberta soils, with the mean layer charge ranging between 0.261 to 0.339 tool (—)/O10(OH)2. Layer charge characteristics varied inconsistently with location, depth and particle size, likely the result of both different origins and weathering processes. Different degrees of K depletion from the micaceous component after equilibration with alkylammonium compounds may also account for some variability between samples. Extreme broadening and essential disappearance of smectite diffraction maxima was noted for some samples after intercalation with alkylammonium cations of all carbon chain lengths, indicating unusual alteration of the layer charge characteristics in some salt-affected soils.

Particle–particle interactions in natural clays can be evaluated by their rheological behavior, but the results are often affected by the physicochemical properties of the clays. The behaviors of two fundamentally different types of clays (low-activity and high-activity) differ with respect to salinity and a time factor (duration of shearing at a given shear rate): illite-rich Jonquiere clay (low-activity clay, Canada) and montmorillonite-rich Wyoming bentonite (high-activity clay, USA). The purpose of the present study was to investigate these different behaviors. Most natural clays exhibit shear-thinning and thixotropic behavior with respect to salinity and the volumetric concentration of the solids. Natural clays also exhibit time-dependent non-Newtonian behavior. In terms of index value and shear strength, lowactivity and high-activity clays are known to exhibit contrasting responses to salinity. The geotechnical and rheological characteristics as a function of salinity and the shearing time for the given materials are compared here. The clay minerals were compared to estimate the inherent shear strengths, such as remolded shear strength (which is similar to the yield strength). Low-activity clay exhibits thixotropic behavior in a time-dependent manner. High-activity clay is also thixotropic for a short period of shearing, although rare cases of rheopectic behavior have been measured for long periods of shearing at high shear rates. The change from thixotropic to rheopectic behavior by bentonite clay has little effect at low shearing speeds, but appears to have a significant effect at higher speeds.

Salinity is one of the major environmental stresses limiting growth and yield of rice. The objective of the present study was to analyze the impact of NaCl on yield-related parameters of Oryza glaberrima. Two contrasted cultivars of Oryza glaberrima previously tested for salt resistance at the vegetative stage [salt-resistant (TOG5307) and salt-sensitive (TOG5949)] were irrigated with a saline solution containing 30 mM NaCl (EC: 3 dS.m−1 NaCl). After 6 months of treatments, mineral nutrient and yield-related parameters were assessed. Proline was quantified in the panicle leaf at the start of the grain filling stage. NaCl treatment affected most yield-related parameters: panicle length, panicle leaf dry weight, number of branches per panicle, panicle leaf length, days to 50% heading, straw fresh weight per plant, grain yield per plant, number of spikelets per panicle, and number of filled grains per panicle. The weight of 1,000 grains decreased in the salt-sensitive cultivar only, suggesting that grain filling processes were compromised. The salt-resistant cultivar TOG5307 was less affected than the salt-sensitive TOG5949 and accumulated lower amounts of Na+ in the grains. For both cultivars, hulls contained higher concentration of Na+ and K+ than grains. TOG5307 also contained more proline in the panicle leaf than TOG5949, suggesting that TOG5307 can cope with the osmotic component of salt stress. The cultivar exhibiting the highest salt resistance at the vegetative stage also exhibited the highest resistance at the reproductive one.

Molluscs are a diverse phylum in coastal lagoons because the numerous taxa collectively display broad ranges of optima and tolerance with respect to ambient conditions. We report on the taxonomic composition, habitat preferences and feeding guilds of molluscs from Río Lagartos coastal lagoon, Mexico. Molluscs were collected in the rainy season (September/October 2017), during the winter (Nortes) season (February 2018) and at the end of the warm, dry season (May 2018). Samples were taken using a Ponar dredge, a cylindrical PVC core barrel, or a beach seine. We studied the abiotic characteristics (sediment grain-size distributions, submersed aquatic vegetation abundance and salinity) to explore assemblage differences across the broad salinity gradient that characterizes the system (~30–78 PSU). Molluscs were represented by 39 species, 34 genera, 23 families and two classes. Stenohaline species were more numerous overall than euryhaline species, but their occurrence in samples was low (<20% of the samples). Stenohaline taxa lived primarily in environments characterized by marine salinity, and few were found under hypersaline conditions. We collected a smaller number of species than did studies carried out in the lagoon >35 years ago. Species accumulation curves revealed that the full species richness was not captured in our study. Euhaline environments displayed greater mollusc species richness and had a larger proportion of amount (mass) of submersed aquatic vegetation. In the hypersaline environments, species richness may be favoured by the lower dominance of sands. Suspension feeders were the most diverse group in both the euhaline and hyperhaline environments.