Saline Sites Research Articles

Inorganic geochemistry of saline substrates associated with coastal turf, Otago Peninsula, New Zealand

ABSTRACT Halophytic plant communities have developed on exposed coastal landforms to form low-stature turf in several locations around New Zealand. We quantify the inorganic geochemistry, mineralogy and simulated ephemeral surface water composition of saline soil-free bare ground at a well-preserved site at Maori Head on Otago Peninsula, where halophytes have colonised from adjacent coastal turf. The community at this site is dominated by Leptinella dioica, Samolus repens, Disphyma australe and Selliera radicans. Maori Head substrates are dominated by clay-altered basalt colluvium and show a general trend from high electrical conductivity (EC > 10 mS/cm) and weakly acid pH (< 6) on bare ground to low EC (< 1 mS cm−1) and higher pH (> 7) in turf and adjacent pasture soils. High salinities on dry substrates and in simulated ephemeral surface waters result from surface evaporation of airborne sea spray and contain halite (NaCl) with some gypsum (CaSO4.2H2O). Chemical interactions with the substrate are minor. The high surface salinities were maintained despite a major winter rain event with strong onshore winds. However, surface salinity is frequently leached by rain and shallow groundwater, whereas inland saline sites (pH 8–11) have substantial salt accumulations driven by lower rainfall, high evaporation and chemical interaction with Otago Schist-derived substrates.

Salicylic acid and thiourea mitigate salinity and drought stress in wheat (Triticum aestivum)

Water and salinity stresses are the major environmental concerns limiting crop production, particularly in arid and semi-arid ecologies. Focused research is required to develop mitigating strategies to manage such stresses. Application of plant-bioregulators (PBRs) may be an effective option to manage water and salinity stresses. Therefore, a field experiment was conducted during 2016–17 and 2017–18 at semi-arid saline site of NW (north-western) India to assess the effectiveness of salicylic acid and thiourea in easing out the adverse effect of variable water deficit and irrigation water salinity regimes. Increasing water deficit and its salinity significantly (P&lt;0.001) reduced all the studied growth parameters, viz. plant height, crop stand, no. of tillers, leaf area index and relative growth rate; and yield attributes like no. of effective tillers, spike length, grains/spike, grain weight/spike, 1000-grain weight, specific weight. Application of either salicylic acid or thiourea significantly improved growth parameters in comparison to control and thiourea proved more effective. Thiourea application improved grain yield by 3.96 and 17.36%, biological yield by 4.21 and 14.82%, effective no. of tillers by 3.77 and 11.91%, weight/spike by 2.83 and 15.17%, 1000-grain weight by 3.72 and 12.66% and specific weight by 2.04 and 8.84% compared to salicylic acid and control, respectively. This might be due to better nutrient uptake, water relations, enhanced CO2 fixation and effective partitioning of assimilates. Thus, thiourea and salicylic acid application in wheat found better as compared to control under saline water stress.

Species composition of shoreline wolf spider communities vary with salinity, but their diets vary with wrack inflow.

Wolf spiders are typically the most common group of arthropod predators on both lake and marine shorelines because of the high prey availability in these habitats. However, shores are also harsh environments due to flooding and, in proximity to marine waters, to toxic salinity levels. Here, we describe the spider community, prey availabilities, and spider diets between shoreline sites with different salinities, albeit with comparatively small differences (5‰ vs. 7‰). Despite the small environmental differences, spider communities between lower and higher saline sites showed an almost complete species turnover. At the same time, differences in prey availability or spider gut contents did not match changes in spider species composition but rather changed with habitat characteristics within a region, where spiders collected at sites with thick wrack beds had a different diet than sites with little wrack. These data suggest that shifts in spider communities are due to habitat characteristics other than prey availabilities, and the most likely candidate restricting species in high salinity would be saline sensitivity. At the same time, species absence from low-saline habitats remains unresolved.

Adaptation of Some Quinoa Genotypes (Chenopodium quinoa Willd.), Grown in a Saharan Climate in Algeria.

Agriculture in southern Algeria faces several challenges that hinder its development, including drought, high temperatures and the excessive salinity of soil and groundwater. The introduction of crops resistant to these factors is one of the solutions chosen to address these abiotic constraints. This research aimed to evaluate the behavior of quinoa (Chenopodium Quinoa Willd.) grown in the Ouargla region of southeastern Algeria. Five varieties of quinoa (Santa maria, Giza1, Amarilla Sacaca, Blanca de Junin and Kancolla) were tested at two sites that differed in terms of soil salinity (9.95 mS/cm and 0.85 mS/cm) during 2019 and 2020. A complete random block experimental design with four repetitions was used for the agronomic tests. Our results clearly show that higher grain yields were obtained at the high salinity site (site 1) compared to the low salinity site (site 2). However, plant height, grain yield per plant and harvest index differed between varieties and sites. In contrast, stem diameter was not greatly affected by salinity. The varieties that seem to be best adapted to the growing conditions of the Ouargla region are, in descending order: Santa Maria, Giza1, Amarilla Sacaca and Blanca de Junin. When testing quinoa in new environments, it is critical to adapt the cropping cycle of varieties to avoid very high temperatures. The choice to switch to winter cultivation instead of spring cultivation can be an essential criterion for success. The biogeographical approach conducted in this research opens up new perspectives for the adaptation and cultivation of quinoa outside its region of origin to satisfy the food security of the people of North Africa.

Anatomical and physiological systematics of Capparis decidua (Forsskal.) Edgew from different habitats of Cholistan Desert, Pakistan

Capparis decidua a medicinal shrub belonging to the family Capparaceae, grows abundantly in wild regions of Asia, Africa, and Saudi Arabia. Due to its medicinal and nutritional value, a study on anatomical and physiological adaptations under various desert habitats was conducted. Results revealed that plants in saline areas showed significant anatomical and physiological modifications particularly in stem and roots show better survival under the harsh saline conditions of the desert. It was noted that the root epidermis thickness was not affected in a slightly saline environment as it showed no significant increasing or decreasing trend in the cross-section of the plant population from non-saline to slightly saline (p > 0.05) while it increased significantly in plants growing at highly saline (p < 0.05). Whereas endodermis cell area differs significantly between plants growing at all selected study sites it increased continuously with a rise in the salinity level of the soil (p < 0.05). Meanwhile, water storage capacity and reduction of water loss in the stem area, epidermis, and sclerenchyma were also recorded. In a highly saline environment, results intimate the deduction of photosynthetic pigments, an increase in total soluble proteins, total free amino acids, total soluble sugars, and proline, and a rise in stem and root tissue Na+, K+, Ca2+, and Cl− contents and meanwhile, accumulation of secondary metabolites (Phenolics and flavonoids). These anatomical and physiological adaptations in natural populations appear to be very important for their better survival in a harsh saline desert environment. It was concluded that C. decidua was found in all different edaphic habitats of the Cholistan Desert, due to its adaptive features, which were very obvious in this plant and highly saline site.

Changes of organic matter composition in surface sediments from the Pearl River estuary to the coastal South China Sea revealed by rapid molecular screening using FTICR-MS

The Pearl River drains the second largest watershed in China, funnelling large amounts of freshwater and organic matter into the northern part of the South China Sea through an estuary characterized by pronounced biogeochemical gradients. In this study we used a newly developed single injection Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) method to analyze organic extracts of surface sediments transitioning from freshwater to marine settings in the Pearl River estuary and coastal South China Sea. Results show a complex mixture of molecular markers, with distinct fingerprints characterizing the freshwater and saline sites. Notable examples include steroidal and thiophenic species at the freshwater site, indicative of possible anthropogenic organic matter inputs from the continent; on the other hand, samples from the coastal site are uniquely characterized by putative tetrapyrrole species, indicative of phaeopigments sourced from marine phytoplankton. This study demonstrates the potential application of single injection FTICR-MS in rapidly probing the dynamic changes of organic matter sources and fates occurring in estuaries influenced by anthropogenic activities.

Effects of soil salinity on nutritional compositions of fresh Jak (Nypa fruticans) sap

The nutritional compositions of fresh Jak (Nypa fruticans) sap grown in mangrove environments with varying soil salinities were examined between sap from non saline (ECe < 2 dS/m), moderately saline (ECe = 4–8 dS/m), and saline soil (ECe = 8–16 dS/m). In saline sites, sap significantly (p < 0.05) increased in total soluble solids and sugar concentration. The total amino acid in the saline site was higher than in the other sites. The fresh Jak sap was rich in functional nutrients such as sugars (sucrose, glucose, fructose, starchyose, galactose, arabinose, maltose), organic acids (niacin, succinic, tartaric, malic, citric, lactic, acetic acids), minerals (P, K, Na, Ca, Mg, Al, Mn, Fe, Cu, Zn, Ni, B), essential amino acids (arginine, lysine, valine, histidine, threonine), seven non-essential amino acids (i.e. glutamic acid) and vitamins (B1, B3, B6, B12, E). Furthermore, potassium was significantly increased in salinity soil, and the decrease in potassium was associated with the increase in sodium. Fresh Jak sap from all salinity soils was shown to be an excellent source of several nutritional elements in this investigation. However, it appeared that Jak sap from the non saline site would be the best choice for use in the development of healthy food products.

Solent oyster enhancement reef concrete colonisation trials

The Interreg funded project RECIF (2012-2015) developed waste shell concrete formulations specifically for artificial reefs. Its successor MARINEFF continues these evaluating further formulations to maximise both physical performance and endurance with biological attractiveness. Four formulations were produced by ESITC Caen for trials based on combinations of two cement types (CEM II and CEM IV) with either coarse aggregate or crushed oyster shells replacing 20% of the aggregate. The most extensive colonisation trials were carried out with 5x5x2cm blocks by both UK and French partners. These test blocks also had smooth and rough faces. This paper describes the results of Southampton biological colonisation trials. Four blocks, one of each formulation along with an oyster shell cut to the same area were secured in a framework and pairs of these were suspended vertically at 6 fully saline sites around the Solent region (Calshot, Beaulieu River, Hamble River, Itchen River, Portsmouth and Langstone Harbours) from May to August 2019. On recovery these were analysed for Total Biomass, Algae (PAM & %cover), Anemones (n), Ascidians (%cover), Barnacles (n & % cover), Bryozoans (%cover), Hydroids (%cover), Mytilus edulis (n), Pomatoceros sp. (n), Sponges (%), Spirorbis sp (n). There were considerable differences in colonisation between the sites which are described in detail, but overall in terms of overall biomass the formulation using CEM V and 20% oyster shell performed as well as the oyster shell. Given that it is accepted that oysters are attracted to natural shell substrate, this concrete was promising for the choice mix of the final oyster reef modules deployed at Calshot, September 2020.

Isolation and Characterization a Novel Catabolic Gene Cluster Involved in Chlorobenzene Degradation in Haloalkaliphilic Alcanivorax sp. HA03

Simple SummaryThis study has demonstrated for the first time the metabolic pathway of chlorobenzene (CB) in haloalkaliphilic bacteria Alcanivorax sp. HA03 isolated from soda lakes in Wadi E1Natrun-Egypt. The complete chlorobenzene dioxygenase gene cluster (α and β subunits, ferredoxin and ferredoxin reductase) was detected by PCR amplification and confirmed by DNA sequencing and expression. This gene cluster has the capability to ring-hydroxylating CB transformed into 3-chlorocatechol during the first steps of biodegradation; with further chloride release and subsequent paths, HA03 showed capability for CB mineralization.Chlorobenzene (CB) poses a serious risk to human health and the environment, and because of its low degradation rate by microorganisms, it persists in the environment. Some bacterial strains can use CB as growth substrates and their degradative pathways have evolved; very little is known about these pathways and the enzymes for CB degradation in high pH and salinity environments. Alcanivorax sp. HA03 was isolated from the extremely saline and alkaline site. HA03 has the capability to degrade benzene, toluene and chlorobenzene (CB). CB catabolic genes were isolated from HA03, which have a complete gene cluster comprising α and β subunits, ferredoxin and ferredoxin reductase (CBA1A2A3A4), as well as one gene-encoding enzyme for chlorocatechol 1,2-dioxygenase (CC12DOs). Based on the deduced amino acid sequence homology, the gene cluster was thought to be responsible for the upper and lower catabolic pathways of CB degradation. The CBA1A2A3A4 genes probably encoding a chlorobenzene dioxygenase was confirmed by expression during the growth on CB by RT-PCR. Heterologous expression revealed that CBA1A2A3A4 exhibited activity for CB transformation into 3-chlorocatechol, while CC12DOs catalyze 3-chlorocatechol, transforming it into 2-chloromucounate. SDS-PAGE analysis indicated that the sizes of CbA1 and (CC12DOs) gene products were 51.8, 27.5 kDa, respectively. Thus, Alcanivorax sp. HA03 constitutes the first bacterial strain described in the metabolic pathway of CB degradation under high pH and salinity conditions. This finding may have obvious potential for the bioremediation of CB in both highly saline and alkaline contaminated sites.

Contribution of structural and functional adaptations of hyper-accumulator Suaeda vera Forssk. ex J.F. Gmel. for adaptability across salinity gradients in hot desert.

The role of ionic excretions and hyper-accumulation of salts through alterations of structural and functional traits in five populations of Suaeda vera Forssk. ex J.F. Gmel., a halophytic salt-indicator species of saline environments, was explored. Differently adapted populations of S. vera exhibited specific structural and functional responses for the survival in hyper-saline conditions. Better growth in population from moderately saline habitat (25-30 dS m-1) was linked to high shoot and root K+ and increased ion selectivity (K+/Na+ and Ca2+/Na+). Increased excretion of Na+ and Cl- with increasing salinity level was a critical mechanism in maintaining ionic balance. Drastic differences were observed for anatomical characteristics in populations inhabiting differentially salt-affected lands. The plants from highly saline sites were characterized by narrow metaxylem vessels, low proportion of cortical parenchyma, and reduced phloem area leading to stunted growth. Contrariwise, root area significantly increased due to high proportion of sclerified xylem tissue, which was associated with easier conduction of solutes and protection of roots from collapsing. Root sclerification particularly at the highest salinity regime was a key factor in the survival of this species in salt-affected compact soils. Leaf anatomical characteristics showed reduction with increasing salinity, but the leaf thickness responded otherwise. This contributed to increased leaf succulence because of high proportion of storage parenchyma in populations colonizing hyper-saline habitats. It was concluded that moderate salinity conditions were more suitable for the growth of S. vera, though some populations of this species were able to tolerate much higher salinity levels.

The seasonal response of in situ denitrification and DNRA rates to increasing nitrate availability

Climate change may dramatically increase nitrate (NO3−) production and transport from watersheds to the coastal area due to short-term heavy precipitation events. However, the response of the coastal filter to such pulse NO3− delivery is poorly studied. We measured NO3− reduction rates via denitrification and DNRA in intact sediments collected from the Goro Lagoon (Po River Delta, Italy). We contrasted 2 seasons (spring and summer) and 2 sites (with lower and higher than average lagoon salinity). We performed 15NO3− additions along a concentration series (50–2000 μM) far exceeding the annual NO3− variations (20–150 μM) to quantify nitrate reduction saturation thresholds. In both seasons and sites denitrification largely outcompeted DNRA and increased along the NO3− gradient, following Michaelis-Menten kinetics. At the site characterized by low salinity, maximum potential denitrification rates decreased from spring to summer, following the decrease in the abundance of burrowing macrofauna. DNRA followed the same seasonal trend but was not affected by NO3− addition. At the site characterized by high salinity, denitrification rates slightly increased and DNRA decreased from spring to summer, despite the establishment of chemically reduced conditions and the increase in pore water free sulfides concentration. The Goro Lagoon sediments displayed elevated buffering capacity against NO3− pulse additions. Such buffer capacity was mainly supported by denitrification through spring bioturbation, decreased summer pathlength of NO3− to the anoxic zone, and unknown mechanisms preventing sulfide toxicity and the dominance of DNRA at the high salinity site.

ADAPTIVE COMPONENTS OF Cyperus exaltatus UNDER HARSH SALINE ENVIRONMENT

Among the environmental problems, salinity is one of the major threats to agriculture around the globe which affects more than 6% of the available land on earth. However halophytes are blessed with the ability to cope with high salinity by various mechanisms. The present study was aimed to explore adaptive components of Cyperus exaltatus which is now growing widely at a number of saline areas across the Pakistan. Extensive trips were made across the country to collect the populations of Cyperus exaltatus from all sorts of environments with varying levels of salinity. The morphological study of ecotypes showed that many growth parameters were affected negatively under higher salinity. However, root length, shoot length, plant height, shoot fresh and dry weight showed a high association with hyper saline sites. Moreover the physiological parameters such as proline content, total soluble proteins and total soluble sugars were accumulated in higher concentrations among populations at hyper saline sites while in lower concentrations at moderately saline and less saline sits which may have supported the production of higher biomass under salinity. The results show that the plants like Cyperus exaltatus can be grown under various types of environmental stresses especially under salinity. Thus the barren saline lands can be used to produce fodder as well as the growth of plants may also help to reduce the levels of salinity in such areas.

The Biochemical Composition and Antioxidant Properties of Fucus vesiculosus from the Arctic Region.

Fucus vesiculosus is one of the most prominent brown algae in the shallow waters of the seas of the Arctic region (Barents (BS), White (WS), Norwegian (NS), and Irminger (IS)). The aim of this study was to determine the biochemical composition of F. vesiculosus from the Arctic at different reproductive phases, and to evaluate the antioxidant properties of F. vesiculosus extracts. The amounts of monosaccharides, phlorotannins, flavonoids, and ash and the mineral composition significantly varied in the algae. A strong correlation was established between monosaccharide, phlorotannin, and flavonoid accumulation and water salinity (Pearson’s correlation coefficients r = −0.58, 0.83, and 0.44, respectively; p < 0.05). We noted a negative correlation between the antioxidant activity and the amount of the structural monosaccharides of fucoidan (r = −0.64). A positive correlation of phlorotannins and flavonoids with antioxidant power was confirmed for all samples. The ash accumulation was relatively lower in the sterile phase for the algae from the BS and WS. The correlation between the Metal Pollution Index (MPI) and the reproductive phases was medium with high fluctuation. Meanwhile, the MPI strongly correlated with the salinity and sampling site. The gradient of the MPI values across the sea was in the following ranking order: BS < WS < NS < IS. Taken together, and based on our data on the elemental contents of F. vesiculosus, we believe that this alga does not accumulate toxic doses of elements. Therefore, the Arctic F. vesiculosus could be safely used in food and drug development as a source of active biochemical compounds and as a source of dietary elements to cover the daily nutritional requirements of humans.

Improvements in Soil Physical, Chemical and Biological Properties at Natural Saline and Non-Saline Sites Under Different Management Practices.

Soil salinity is known to be a significant threat to food security for the increasing population, which is further aggravated under the climate change scenario. Indo-Gangetic plain (IGP) is one of the most productive in the world and is most affected by salinity. To understand the modifications in soil characteristics under different management practices followed to reclaim salinity affected land, the present study was conducted at variously reclaimed saline areas of three districts of Uttar Pradesh situated in IGP. Soil from six sites (electrical conductivity (EC) ranging from 0.89 to 10.28 mS) following different management practices, RJT (Rajatalab, rice-wheat +organic), BBN (Beerbhanpur, rice-wheat +inorganic), MZM (Mirzamurad, rice-mustard +organic), BRP (Baraipur, rice-wheat +organic), DHR (Dharahara, rice-fallow +organic) and SLM (Salempur, rice-wheat +inorganic) were assessed for physical, chemical and biological properties during the vegetative stage and after harvest of crops. Soil quality index (SQI) based on representative parameters obtained by principal component analysis and yield of crops were also calculated at saline and non-saline sites. The SLM site showed highest salinity followed by BRP, DHR, MZM, while BBN and RJT were non-saline. Total organic carbon, total nitrogen, microbial activity, and microbial biomass were low at saline compared to non-saline sites but were higher under organic matter amendment compared to inorganic. Activities of soil enzymes were negatively influenced while β-glucosidase and alkaline phosphatase activities were enhanced under higher salinity. Organic amendments were more efficient in improving the soil properties along with SQI at saline soil resulting into a better yield in all crop combinations compared to inorganic amendments.

Dryland field validation of genotypic variation in salt tolerance of chickpea (Cicer arietinum L.) determined under controlled conditions

Chickpea ( Cicer arietinum L.) is a moderately salt-susceptible grain legume species. Genotypic differences in salt tolerance/susceptibility have been identified in chickpea genotypes grown in adequately-watered soil in pots with different salt concentrations, but few studies have been conducted in saline fields. This three-year study compared the growth and yield of chickpea genotypes to determine whether genotypic differences in salt tolerance/susceptibility identified in glasshouse pot experiments applied when grown in a dryland saline field. The emergence, phenology, growth, leaf ion concentration, yield and yield components of 10–20 chickpea genotypes were compared under controlled saline and water conditions in the glasshouse, and saline and non-saline conditions in the field in a semiarid environment. In the field, soil salinity and yields varied from year to year in the non-saline and saline treatments. Genotypic differences in salt tolerance and sensitivity were observed in the controlled salt and water conditions in the glasshouse. The salt tolerant and salt sensitive check genotypes, GENESIS 836 and RUPALI, respectively, grown in all three comparison years were similarly tolerant and sensitive in the glasshouse and dryland field in all three comparison years. However, other genotypes selected for salt tolerance under controlled conditions were not observed to be tolerant in the dryland field. While salinity slowed the rate of emergence and increased the time to flowering, the variation in saline yields among genotypes was associated with aboveground biomass, filled pod number and seed number at maturity in both the glasshouse and field, but not the number of emerged plants that survived to maturity or the delay in flowering. Salinity significantly increased the leaf Na + , K + and Cl - concentrations in the glasshouse and field (except in the glasshouse in 2010). Na + increased in young and old leaves by 28–84%, but the concentrations of Na + or K + in the leaves across genotypes was not correlated with yield in saline soil. Salinity increased leaf Cl – concentrations by 80–290%; the increase in young leaves had a significant association with reduced yield among genotypes only in the glasshouse in one year. We conclude that selection under controlled soil salinity and water content in pots can identify some genotypes that are salt tolerant, but for dryland saline environments verification of their tolerance in comparable environments is essential. • Chickpeas for dryland saline sites require phenotyping in appropriate environments. • Genotypic variation in water-limited yield confounds salt tolerance in the field. • Salt tolerant chickpeas do not universally exhibit cross-tolerance for water-limited yield. • Dryland salt tolerance is associated with increased biomass and reproductive success.

Halophytic flora and vegetation in southern Moravia and northern Lower Austria

Halophytic habitats are distinctive components of the landscape in southern Moravia, Czech Republic, and the Pulkau valley in northern Lower Austria. We provide a historical overview of their flora and vegetation since the early 19th century and describe the current state assessed in the field at all remaining sites in 2020. We summarized the historical and current distribution of 17 species with the strongest affinity for saline habitats in the study area: Bupleurum tenuissimum, Cirsium brachycephalum, Crypsis aculeata, C. schoenoides, Galatella cana, Glaux maritima, Juncus gerardii, Plantago maritima, Salicornia perennans, Samolus valerandi, Scorzonera parviflora, Spergularia marina, S. media, Suaeda prostrata, Taraxacum bessarabicum, Triglochin maritima and Tripolium pannonicum. Of these, Galatella cana, Salicornia perennans, Suaeda prostrata and Triglochin maritima are regionally extinct. We also characterized the bryoflora typical of saline habitats. We classified historical and newly recorded releves and identified 14 halophytic associations belonging to the alliances Chenopodion rubri, Meliloto dentati-Bolboschoenion maritimi, Cypero-Spergularion salinae, Salicornion prostratae, Puccinellion limosae, Juncion gerardii and Festucion pseudovinae. The vegetation of the alliance Salicornion prostratae had disappeared in the study area by the 1970s. The alliance Festucion pseudovinae, with the association Centaureo pannonicae-Festucetum pseudovinae, was recognized as a new vegetation type for the Czech Republic. Using soil pH and electrical conductivity measurements, we evaluated the relationships of individual species and vegetation types to soil salinity. This synthetic study shows that the once well-developed halophytic flora and vegetation in the study area steadily declined from the early 19th century to the 1980s, initially mainly due to drainage and after the mid-20th century due to the combination of drainage and cessation of grazing. The introduction of conservation management in the 1990s and ecological restoration contributed to stabilizing plant diversity at the last saline sites. The future of halophytic flora and vegetation depends on the continuation of conservation management.

Experiments to parametrise a growth and nutrient storage model for Agarophyton spp.

Management of eutrophication in estuaries requires modelling tools to gauge the consequences of nutrient loading from land. We conducted laboratory experiments to quantify the growth response of the opportunistic red algae Agarophyton spp. to seawater nutrient (nitrogen and phosphorus) concentrations, salinity, temperature and light. We derived parameters for a Droop kinetics-type model and calculated critical (corresponding to 67% of maximum growth rates) and minimum values of these environmental factors required for growth. We compared our results with long-term time series of water quality data across a large, highly eutrophic estuary in southern New Zealand. Nitrogen availability and salinity were the environmental factors most likely to restrict summertime growth of Agarophyton spp., but nutrient limitation appeared unlikely at all but the most seaward, high salinity sites. When combined with models of estuarine mixing, this work may aid prediction of growth responses of Agarophyton spp. to nutrient loading at an estuary scale.

SWAT-SF: A flexible SWAT-based model for watershed-scale water and soil salinity modeling

Natural and anthropogenic complex processes release salts into the environment. These change the balances of natural systems in the watersheds. Models can assist study of salinity processes throughout watersheds. This study proposes a flexible water and soil salinity module for the Soil and Water Assessment Tool (SWAT) that can profitably incorporate expert scientific judgments into a deterministic salinity framework to adapt predicted salinity processes to actual salinity processes watershed-scale. The proposed flexible salinity model (SWAT-SF) was developed using new equations for salinity assessment and then successfully applied to the Dehram River Basin located south of Iran that endangers natural and anthropogenic salinity problems. The SWAT-SF model uses a general framework that can be utilized with/without the direct guidance of experts for the determination of salinity processes, the extent of the salinity, identification and investigation of the saline site, assessment and management of the salinity, and evaluation of salinity economics throughout the world.

Salinity Monitoring at Saline Sites with Visible–Near-Infrared Spectral Data

To address the global phenomenon of the salinisation of large land areas, a quantitative inversion model of the salinity of saline soils and soil visible–near-infrared (NIR) spectral data was developed by considering saline soils in Zhenlai County, Jilin Province, China as the research object. The original spectral data were first subjected to Savitzky–Golay (SG) smoothing, multiplicative scattering correction (MSC) pre-processing, and a combined transformation technique. The pre-processed spectral data were then analysed to construct the difference index (DI), ratio index (RI), and normalised difference index (NDI), and the Spearman rank correlation coefficient (r) between these three spectral indices and the salt content in the samples was calculated, while a combined spectral index (r &gt; 0.8) was eventually selected as a sensitive spectral index. Finally, a quantitative inversion model for the salinity of saline soils was developed, and the model’s accuracy was evaluated based on partial least squares regression (PLSR), the random forest (RF) algorithm, and the radial basis function (RBF) neural network algorithm. The results indicated that the inversion of soil salt content using the selected combination of spectral indices based on the RBF neural network algorithm was the most effective, with the prediction model yielding an R2 value of 0.950, a root mean square error (RMSE) of 1.014, and a relative percentage deviation (RPD) of 4.479, which suggested a good prediction effect.

Assessment of physiological, biochemical and yield responses of wheat plants under natural saline and non-saline field conditions.

Soil salinity is a major threat to crop productivity all over the world including the Indo-Gangetic plain (IGP) region of India. Therefore, a field study was conducted for two consecutive years in wheat growing areas in IGP affected by salinity. Plants grown at a saline site (Salempur, SLM) and a non-saline site (Rajatalab, RJT), were analysed for selected biochemical, physiological and yield traits. Results showed that photosynthetic rate was not significantly affected, but transpiration rate and stomatal conductance declined at saline compared to non-saline site. Photosynthetic pigments increased during vegetative growth period, but decreased during reproductive stage at SLM site, while anthocyanin showed an opposite trend. Membrane damage, solute leakage, H2O2 and ·O2 - productions were intensified at saline site, SLM. Accumulation of osmolytes and antioxidants occurred in plants at saline compared to non-saline sites. K/Na and Ca/Na ratios in plants at SLM were reduced significantly compared to non-saline site, RJT. Biomass and yield also declined at SLM compared to RJT. Principle component and path analyses on the measured parameters clearly showed that defense strategies adopted by plants helped to maintain the photosynthetic rate but biomass and yield of wheat got compromised under high salinity.