Effect of gradual increase of salt on performance and microbial community during granulation process.

Salinity was considered to have effects on the characteristics, performance microbial communities of aerobic granular sludge. This study investigated granulation process with gradual increase of salt under different gradients. Two identical sequencing batch reactors were operated, while the influent of Ra and Rb was subjected to stepwise increments of NaCl concentrations (0-4 g/L and 0-10 g/L). The presence of filamentous bacteria may contribute to granules formed under lower salinity conditions, potentially leading to granules fragmentation. Excellent removal efficiency achieved in both reactors although there was a small accumulation of nitrite in Rb at later stages. The removal efficiencies of chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP) in Ra were 95.31%, 93.70% and 88.66%, while the corresponding removal efficiencies in Rb were 94.19%, 89.79% and 80.74%. Salinity stimulated extracellular polymeric substances (EPS) secretion and enriched EPS producing bacteria to help maintain the integrity and stability of the aerobic granules. Heterotrophic nitrifying bacteria were responsible for NH4+-N and NO2--N oxidation of salinity systems and large number of denitrifying bacteria were detected, which ensure the high removal efficiency of TN in the systems.

Synergistic effect of silicon availability and salinity on metal adsorption in a common estuarine diatom.

Increasing nitrogen and phosphorus discharge and decreasing sediment input have made silicon (Si) a limiting element for diatoms in estuaries. Disturbances in nutrient structure and salinity fluctuation can greatly affect metal uptake by estuarine diatoms. However, the combined effects of Si and salinity on metal accumulation in these diatoms have not been evaluated. In this study, we aimed to investigate how salinity and Si availability combine to influence the adsorption of metals by a widely distributed diatom Phaeodactylum tricornutum. Our data indicate that replete Si and low salinity in seawater can enhance cadmium and copper adsorption onto the diatom surface. At the single-cell level, surface potential was a dominant factor determining metal adsorption, while surface roughness also contributed to the higher metal loading capacity at lower salinities. Using a combination of non-invasive micro-test technology, atomic force microscopy, X-ray photoelectron spectroscopy, and Fourier transform infrared spectroscopy, we demonstrate that the diversity and abundance of the functional groups embedded in diatom cell walls vary with salinity and Si supply. This results in a change in the cell surface potential and transient metal influx. Our study provides novel mechanisms to explain the highly variable metal adsorption capacity of a model estuarine diatom.

Cotransport of nanoplastics with nZnO in saturated porous media: From brackish water to seawater.

The ocean serves as a repository for various types of artificial nanoparticles. Nanoplastics (NPs) and nano zinc oxide (nZnO), which are frequently employed in personal care products and food packaging materials, are likely simultaneously released and eventually into the ocean with surface runoff. Therefore, their mutual influence and shared destiny in marine environment cannot be ignored. This study examined how nanomaterials interacted and transported through sea sand in various salinity conditions. Results showed that NPs remained dispersed in brine, while nZnO formed homoaggregates. In seawater of 35 practical salinity units (PSU), nZnO formed heteroaggregates with NPs, inhibiting NPs mobility and decreasing the recovered mass percentage (Meff) from 24.52% to 12.65%. In 3.5 PSU brackish water, nZnO did not significantly aggregate with NPs, and thus barely affected their mobility. However, NPs greatly enhanced nZnO transport with Meff increasing from 14.20% to 25.08%, attributed to the carrier effect of higher mobility NPs. Cotransport from brackish water to seawater was simulated in salinity change experiments and revealed a critical salinity threshold of 10.4 PSU, below which the mobility of NPs was not affected by coexisting nZnO and above which nZnO strongly inhibited NP transport. This study highlights the importance of considering the mutual influence and shared destiny of artificial nanoparticles in the marine environment and how their interaction and cotransport are dependent on changes in seawater salinity.

Unraveling the synergistic promotion mechanism of Fe0 coupling phragmites australis biomass for nitrogen removal in coastal wetland: From low to moderate salinities.

The simulated coastal constructed wetlands supplemented with Fe0 and phragmites australis (P.A) biomass (CW-M) were constructed to improve nitrogen removal under different salinities (0-15‰). Results showed that the denitrification performance of CW-M were improved significantly, with the higher NO3--N removal of 72-94% and lower N2O emission flux, when compared with mono-P.A biomass(CW-bio), mono-Fe0 system (CW-Fe) and control system. The nitrogen removal showed a trend of first increasing (0‰-7‰) and then decreasing (7‰-15‰) with the highest NO3--N removal of 94% and enhanced removal efficiency of 41% in CW-M. Fe0 and P.A biomass coupling could reduce the stress of salinity on denitrification. Batch experiments have demonstrated that Fe0 and P.A biomass could mutually stimulate more total organic carbon and total iron (TFe) release as electron donors for denitrification. Meanwhile, appropriate salinity could also promote the release of TFe. The typical heterotrophic denitrifying genera Bacillus and iron autotrophic denitrifying genera Thermomonas have the highest proportion in CW-M, with 21.83% and 0.10%, respectively. Fe0 and P.A biomass adding simultaneously promoted the carbon and iron metabolism, further enhancing the nitrogen metabolism process. The joint enhancement of autotrophic and heterotrophic denitrification contributes to NO3--N removal in CW-M for treating saline, low C/N wastewater in coastal wetlands.

Studies on immunological characteristics and transcriptomic analysis of Litopenaeus vannamei low salt-tolerance family.

Litopenaeus vannamei is a widely distributed euryhaline aquatic animal, affected by low salinity, which can impact its disease resistance and immunity. However, there is a limited understanding of the adaptation mechanisms of L. vannamei with different genetic backgrounds to low salinity. Therefore, the present study aimed to compare the immunity characteristics and transcriptomics of L. vannamei low salt-tolerant (FG I/J) and low salt-sensitive (control) families. Also, the disease resistance and immune parameters (including [THC], hemolymph cell viability, lysozyme activity [LZM], phenoloxidase content [PO], interleukin-6 [IL-6], and tumor necrosis factor-alpha [TNF-α]) of the FG I/J and control families of L. vannamei under low salinity (5‰) and ambient salinity (24‰) were examined. Additionally, hepatopancreas transcriptomics of the FG I/J and control families were analyzed at a salinity of 5‰. The results showed that the FG I/J family had higher disease resistance to Vibrio parahaemolyticus and stronger immunological capacity than the control family. Transcriptomic analysis showed significantly enriched energy metabolism and immune regulation pathways. Therefore, we speculated that energy metabolism provides sufficient energy for immunological modulation in the FG I/J family to deal with long-term low-salt stress and achieve high growth and survival rates.

TPT disrupts early embryonic development and glucose metabolism of marine medaka in different salinites.

Triphenyltin (TPT) is an organotin compound frequently detected in coastal estuaries, yet studies on TPT's effects in regions with significant salinity fluctuations, such as coastal estuaries, are currently limited. To investigate the toxic effects of TPT under different salinity conditions, this study focused on marine medaka (Oryzias melastigma) embryos. Through early morphological observations, RNA-seq analysis, biochemical marker assays, and qPCR detection, we explored the impact of TPT exposure on the early embryonic development of marine medaka under varying salinities. The study found that TPT exposure significantly increased embryo mortality at salinities of 0 ppt and 30 ppt. RNA-seq analysis revealed that TPT primarily affects glucose metabolism and glycogen synthesis processes in embryos. Under high salinity conditions, TPT may inhibit glucose metabolism by suppressing glycolysis and promoting gluconeogenesis. Furthermore, TPT exposure under different salinities led to the downregulation of genes associated with the insulin signaling pathway (ins, insra, irs2b, pik3ca, pdk1b, akt1, foxo1a), which may be linked to suppressed glucose metabolism and increased embryonic mortality. In summary, TPT exposure under different salinities affects the early development of marine medaka embryos and inhibits glucose metabolism. This study provides additional data to support research on organotin compounds in coastal estuaries.

Rice OsCIPK17-OsCBL2/3 module enhances shoot Na+ exclusion and plant salt tolerance in transgenic Arabidopsis.

Soil salinity is detrimental to plant growth and remains a major threat to crop productivity of the world. Plants employ various physiological and molecular mechanisms to maintain growth under salt stress. Identification of genes and genetic loci underlying plant salt tolerance holds the key to breeding salt tolerant crops. CIPK-CBL pathways regulate adaptive responses of plants (especially ion transport) to abiotic stresses via fine-tuned Ca2+ signal transduction. In this study, we showed that over-expression of OsCIPK17 in Arabidopsis enhanced primary root elongation under salt stress, which is in a Ca2+ dependent manner. Further investigation revealed that, under salt stress, OsCIPK17 transcript level was significantly induced and its protein moved from the cytosol to the tonoplast. Using both Y2H and BiFC, tonoplast-localised OsCBL2 and OsCBL3 were shown to interact with OsCIPK17. Interestingly, over-expressing salt-induced OsCBL2 or OsCBL3 in Arabidopsis led to enhanced primary root elongation under salt stress. In this process, OsCIPK17 was shown recruited to the tonoplast (similar to the effect of salt stress). Furthermore, transgenic Arabidopsis lines individually over-expressing OsCIPK17, OsCBL2 and OsCBL3 all demonstrated larger biomass and less Na + accumulation in the shoot under salt stress. All data combined suggest that OsCIPK17- OsCBL2/3 module is a major component of shoot Na+ exclusion and therefore plant salt tolerance, which is through enhanced Na + compartmentation into the vacuole in the root. OsCIPK17 and OsCBL2/3 are therefore potential genetic targets that can be used for delivering salt tolerant rice cultivars.

Unveiling osmoregulation and immunological adaptations in Eleutheronema tetradactylum gills through high-throughput single-cell transcriptome sequencing.

The fourfinger threadfin fish (Eleutheronema tetradactylum) is an economically significant species renowned for its ability to adapt to varying salinity environments, with gills serving as their primary organs for osmoregulation and immune defense. Previous studies focused on tissue and morphological levels, whereas ignored the cellular heterogeneity and the crucial gene information related to core cell subsets within E. tetradactylum gills. In this study, we utilized high-throughput single-cell RNA sequencing (scRNA-seq) to analyze the gills of E. tetradactylum, characterizing 16 distinct cell types and identifying unique gene markers and enriched functions associated within each cell type. Additionally, we subdivided ionocyte cells into four distinct subpopulations for the first time in E. tetradactylum gills. By employing weighted gene co-expression network analysis (WGCNA), we further investigated the cellular heterogeneity and specific response mechanisms to salinity fluctuant. Our findings revealed the intricate osmoregulation and immune functions of gill cells, highlighting their crucial roles in maintaining homeostasis and adapting to fluctuating salinity levels. This comprehensive cell-type atlas provides valuable insights into the species adaptive strategies, contributing to the conservation and management of this commercially significant fish as well as other euryhaline species.

Promoting salt tolerance, growth, and phytochemical responses in coriander (Coriandrum sativum L. cv. Balady) via eco-friendly Bacillus subtilis and cobalt.

In plant production, evaluation of salt stress protectants concerning their potential to improve growth and productivity under saline stress is critical. Bacillus subtilis (Bs) and cobalt (Co) have been proposed to optimize salt stress tolerance in coriander (Coriandrum sativum L. cv. Balady) plants by influencing some physiological activities. The main aim of this work is to investigate the response of (Bs) and (Co) as eco-safe salt stress protectants to resist the effect of salinity, on growth, seed, and essential oil yield, and the most important biochemical constituents of coriander produced under salt stress condition. Therefore, in a split-plot factorial experiment design in the RCBD (randomized complete block design), four levels of salinity of NaCl irrigation water (SA) were assigned to the main plots; (0.5, 1.5, 4, and 6 dS m-1); and six salt stress protectants (SP) were randomly assigned to the subplots: distilled water; 15 ppm (Co1); 30 ppm (Co2); (Bs); (Co1 + Bs); (Co2 + Bs). The study concluded that increasing SA significantly reduced coriander growth and yield by 42.6%, which could be attributed to ion toxicity, oxidative stress, or decreased vital element content. From the results, we recommend that applying Bs with Co (30 ppm) was critical for significantly improving overall growth parameters. This was determined by the significant reduction in the activity of reactive oxygen species scavenging enzymes: superoxide dismutase (SOD), catalase (CAT), and malondialdehyde (MDA) and non-enzyme: proline by 5, 11.3, 14.7, and 13.8% respectively, while increasing ascorbic acid by 8% and preserving vital nutrient levels and enhancing plant osmotic potential to buffer salt stress, seed yield per plant, and essential oil yield increased by 12.6 and 18.8% respectively. The quality of essential oil was indicated by highly significant quantities of vital biological phytochemicals such as linalool, camphor, and protein which increased by 10.3, 3.6, and 9.39% respectively. Additional research is suggested to determine the precise mechanism of action of Bs and Co's dual impact on medicinal and aromatic plant salt stress tolerance.

A novel stepwise salinity acclimation method to improve the survival of freshwater microalgae Haematococcus lacustris in seawater salinity.

Freshwater microalga Haematococcus lacustris rich in astaxanthin, as a supplemental live diet can directly supply natural astaxanthin to the aquaculture organisms, except marine aquaculture organisms, since H. lacustris cannot tolerate seawater salinity. The objective of the present study is to provide a salinity acclimation method that allows H. lacustris to survive and accumulate astaxanthin with the aim of developing a novel supplemental live diet for marine aquaculture organisms. H. lacustris cultured in freshwater was subjected to different stepwise salinity acclimation processes (two-, three-, and four-shift). As the controls, H. lacustris was exposed to five constant salinities conditions (0, 0.05, 0.075, 0.3, and 0.6 M NaCl, respectively). Among the controls, almost all cells in the 0.3 M and 0.6 M NaCl conditions died immediately. In contrast, H. lacustris in the stepwise salinity acclimation processes survived in 0.6 M NaCl (equivalent to seawater salinity of 35 psu), showing the highest living-cell proportion (50.0%) and astaxanthin yield (0.72 mg·L-1) in the four-shift. The present study first demonstrated that H. lacustris tolerated seawater salinity through a stepwise acclimation process, proving a new strategy to supply live microalgal diets rich in natural astaxanthin for marine aquaculture.

Massively Enhanced Charge Selectivity, Ion Transport, and Osmotic Energy Conversion by Antiswelling Nanoconfined Hydrogels.

Developing a nanofluidic membrane with simultaneously enhanced ion selectivity and permeability for high-performance osmotic energy conversion has largely been unexplored. Here, we tackle this issue by the confinement of highly space-charged hydrogels within an orderedly aligned nanochannel array membrane. The nanoconfinement effect endows the hydrogel-based membrane with excellent antiswelling property. Furthermore, experimental and simulation results demonstrate that such a nanoconfined hydrogel membrane exhibits massively enhanced cation selectivity and ion transport properties. Consequently, an amazingly high power density up to ∼52.1 W/m2 with an unprecedented energy conversion efficiency of 37.5% can be reached by mixing simulated salt-lake water (5 M NaCl) and river water (0.01 M NaCl). Both efficiency indexes surpass those of most of the state-of-the-art nanofluidic membranes. This work offers insights into the design of highly ion-selective membranes to achieve ultrafast ion transport and high-performance osmotic energy harvesting.

Effect of brine concentration on the quality of salted large yellow croaker during processing and refrigeration.

This study aimed to evaluate the effect of brine concentrations (4%, 8%, 12%, 16%) on the quality of salted large yellow croakers. During the wet salting processing, increased salinity inhibited myogenic fibers swelling and extracellular space expansion, and resulted in lower water content and higher salt content of salted large yellow croaker products. During refrigeration of salted large yellow croakers at 4 °C for 24 days, SDS-PAGE patterns showed that high salinity slowed down the degradation of proteins, which was further confirmed by changes in free amino acids (FAAs) and biogenic amine contents. The increases in K value, total volatile basic nitrogen (TVB-N) content, total viable counts (TVC) and the deterioration in sensory were delayed by increasing salinity. Notably, high salinity enhanced malondialdehyde (MDA) accumulation. The results suggested that high salinity inhibited tissue structure destruction, microbial growth, protein degradation and freshness reduction, but accelerated lipid oxidation of salted large yellow croakers. Supplementary Information: The online version contains supplementary material available at 10.1007/s10068-024-01573-5.

Co-infection is linked to infection prevalence and intensity in oysters amidst high environmental and spatial variation.

Co-infecting parasites modify infection outcomes in the wild. However, it is unclear how multiple environmental factors influence co-infection. The Chesapeake Bay metapopulation of the eastern oyster, Crassostrea virginica, provides an opportunity to test the importance of co-infection across heterogeneous environments because multiple parasites infect oysters across a broad salinity gradient. This study leverages Maryland and Virginia oyster monitoring for a large-scale survey of four co-infecting organisms, including two tissue parasites and two shell bio-eroding parasites. We diagnosed infection in 440 oysters across 16 paired harvested and unharvested reefs and tested the importance of co-infecting organisms for each parasite relative to environmental conditions, host traits, and marine spatial management. Microscopic visual methods were used to diagnose prevalence and intensity of tissue infections with Perkinsus marinus (the causative agent of dermo disease) and Haplosporidium nelsoni (the causative agent of MSX disease). Macroscopic visual methods were used to diagnose prevalence and intensity of shell infections with Cliona boring sponges and blister-inducing Polydora worms. For the three oyster parasites that were detected [H. nelsoni infections were absent in all oysters], salinity was the overall strongest predictor, corresponding to bay-wide patterns of parasite prevalence and/or intensity. Despite high environmental and spatial variation, co-infections corresponded to altered prevalence and/or intensity for all three oyster parasites. The correlational patterns suggest that P. marinus acts as a lynchpin in co-infection, as its intensity increased with Cliona sponge prevalence and P. marinus co-infection predicted higher Polydora blister intensity. Oyster shell height, reef habitat, and harvest status also predicted parasite prevalence and intensity, further reflecting the multivariate drivers of infections in this system. Unharvested reefs had greater vertical habitat structure and higher intensities of Cliona sponge infections, but no differences in the prevalence of any of the three parasites. Spatial patterns unexpectedly show that reef-level predictors of parasite patterns were more important than differences between tributaries. This correlational survey provides novel insights through the statistical relationships between the three oyster parasites, environmental conditions, host traits, and human resource management. New and more detailed scenarios are needed to expand disease ecological theory to encompass co-infection in anthropogenically impacted wildlife populations.

Response of aerobic granular sludge to salinity fluctuations in formation, stability and microbial community structures.

Aerobic granular sludge (AGS) exhibits excellent resistance to adverse environment due to its unique layered structure. However, the mechanism about how salinity fluctuations in municipal wastewater impact AGS formation and its physicochemical properties has not been thoroughly revealed. In this study, AGS was cultivated under additional 0 % salinity (R1), additional 1.5 % constant salinity (R2), and additional 0-1.5 % fluctuant salinity (R3), respectively. The results indicate that increased salinity can enhance extracellular polymeric substances (EPS) production and improve sludge settleability, thereby facilitating AGS formation. However, the AGS experienced frequent environmental conversion between dehydration and swell due to salinity fluctuations, resulting in higher content of loosely-bond EPS and low settleability, which delayed the maturation of AGS for over 14 days. Additional salinity significantly inhibited the nitrification process, but the formation of AGS promoted the recovery of ammonia oxidation activity and facilitated the construction of short-range nitrification denitrification processes, resulting in over 16.0 % higher total nitrogen removal efficiency than R1. The microbial community analysis revealed that Thauera played an important role in the granulation process under salinity stress, due to its salt tolerance and EPS secretion abilities. As expected, the formation of AGS enhanced the salt resistance of microorganisms, allowing for the enrichment of functional bacteria, such as Flavobacterium and Candidatus_Competibacter. Generally, microorganisms required extended adaptation periods to cope with salinity fluctuations. Nevertheless, the resulting AGS proved stable and efficient wastewater treatment performance.

Elucidating the Composition and Transformation of Dissolved Organic Matter at the Sediment-Water Interface Using High-Resolution Mass Spectrometry.

The exchange and transformation of dissolved organic matter (DOM) at the sediment-water interface are crucial factors in regulating watershed biogeochemistry, with the molecular composition of DOM serving as a pivotal determinant in elucidating this process. High-resolution mass spectrometry (HRMS) is an effective tool for resolving the composition of DOM. By analyzing the compositional characteristics of DOM at the sediment-water interface under three different salinities at the same latitude region in northern China, the findings indicate certain variations in component characteristics of DOM between low-salinity inland waters and high-salinity seawaters, with the former exhibiting greater molecular diversity and higher molecular weights, whereas the latter displayed a higher saturation and bioavailability. Notably, the presence of more CHOS substances in the low-salinity inland waters underscores the transformation of the DOM influenced by terrestrial inputs and anthropogenic activities. Conversely, the presence of more CHO and CHNO substances in high-salinity seawater underscores the microbial effects. The chemical transformation process from overlying water to pore water to sediments was characterized by methylation, hydrogenation, decarboxylation, and reduction, as determined by calculating the relations between the H/C and O/C ratios of different compound types. These findings indicate that HRMS can yield more refined results in revealing the process of DOM at the sediment-water interface under different environments, which provides a more reliable basis for a deeper understanding of the source-sink mechanism of sediment organic matter.

Evaluation of direct and transgenerational influences of salinity on germination and early seedling growth in an edible halophyte, Crithmum maritimum.

BACKGROUND AND AIMS: Crithmum maritimum is a wild, edible halophyte with large potential as a cash crop for salinized soils. However, the tolerance during seed germination appears to be highly site-specific and contradictory, whereas little is known on salinity tolerance during early seedling growth. This study was aimed at characterizing variation in the responses of germination and early seedling growth in diverse C. maritimum populations along the Iberian Southwest coast. Specifically, we sought to distinguish between direct salinity effects and those influenced by the salinity of maternal environments. METHODS: Physicochemical properties, including salinity of maternal environments, were assessed across diverse habitats. A total of 3480 seeds from 58 mother plants were utilized. Seeds were subjected to germination assays under various salinity treatments (0-500 mM NaCl), with subsequent monitoring of germination parameters. Non-germinated seeds were tested for recovery germination, and viability was assessed using the tetrazolium test. Of germinated seeds, 1160 seedlings were monitored for survival and early growth metrics. General Linear Models were employed to analyze the effects of salinity and maternal environmental influence on germination and early growth. KEY RESULTS: Despite reduced and delayed germination under salinity, seeds showed remarkable tolerance up to 150 mM, surpassing prior reports, with consistent viability up to 500 mM, indicating substantial salinity-induced dormancy. Seedling growth was more sensitive to continued treatment; no plants survived above 150 mM. The salinity experienced by maternal plants had only a marginal effect on germination but significantly contributed to reduce seedling biomass production, both above and below ground. CONCLUSIONS: This study highlights the significance of maternal salinity on early growth in C. maritimum, emphasizing the species' resilience to salt stress during germination and recovery. These insights are crucial for optimizing cultivation techniques and informing research on other halophytes in saline environments.

Zinc oxide nanoparticles application alleviates salinity stress by modulating plant growth, biochemical attributes and nutrient homeostasis in Phaseolus vulgaris L.

Salt stress poses a significant challenge to global agriculture, adversely affecting crop yield and food production. The current study investigates the potential of Zinc Oxide (ZnO) nanoparticles (NPs) in mitigating salt stress in common beans. Salt-stressed bean plants were treated with varying concentrations of NPs (25 mg/L, 50 mg/L, 100 mg/L, 200 mg/L) using three different application methods: foliar application, nano priming, and soil application. Results indicated a pronounced impact of salinity stress on bean plants, evidenced by a reduction in fresh weight (24%), relative water content (27%), plant height (33%), chlorophyll content (37%), increased proline (over 100%), sodium accumulation, and antioxidant enzyme activity. Application of ZnO NPs reduced salt stress by promoting physiological growth parameters. The NPs facilitated enhanced plant growth and reduced reactive oxygen species (ROS) generation by regulating plant nutrient homeostasis and chlorophyll fluorescence activity. All the tested application methods effectively mitigate salt stress, with nano-priming emerging as the most effective approach, yielding results comparable to control plants for the tested parameters. This study provides the first evidence that ZnO NPs can effectively mitigate salt stress in bean plants, highlighting their potential to address salinity-induced growth inhibition in crops.

Bi-layered spring-neap variability of water masses in estuaries and the impact of human activities.

Estuaries are one of the most important ecosystems in the world, which are economically developed and densely populated. However, the intricate hydrodynamic environment and frequent human activities within estuaries have left the spatiotemporal variability of water properties in these areas inadequately understood. Recently, based on in situ observations and numerical simulations, we found significant spring-neap variability of water mass properties in the Yangtze River Estuary, which exhibited a bi-layered vertical structure. In the Yangtze River Estuary, salinity could decrease (increase) over 4 psu during spring (neap) tides in the upper layer, and satellite observations confirmed that both sea surface chlorophyll-a concentration and particulate organic carbon concentration also showed significant spring-neap variabilities. Decreasing salinity in the upper layer induced a shoreward pressure gradient force in the lower layer, which caused shoreward advection of high salinity water from the deep ocean and resulted in salinity increasing up to 2 psu in the lower layer of the Yangtze River Estuary. Dynamical diagnoses proved that spring-neap variability of water mass properties were caused by the asymmetry of tidal currents via modulating the ratio of freshwater to seawater. Similar situations also occurred in the Mississippi River Estuary. Furthermore, constructions of dams and other hydraulic projects in the watershed could greatly alter the locations with significant spring-neap water masses variability through reducing the riverine sediment flux and thus, leading to the erosion of the tidal flats in estuaries. The above results highlight the important roles of tidal asymmetry and human activities in affecting spring-neap variabilities of water mass properties in estuaries.

Effects of different culture salinities on the growth and muscle quality of grass carp (Ctenopharyngodon idellus).

Grass carp (Ctenopharyngodon idellus) is an economically important farmed fish. This experiment was conducted to study the effects of different culture salinities on the growth and muscle quality of grass carp. We found that salinity of 0 - 5 had no significant effect on the growth of grass carp, but it significantly decreased at salinities above 5. Compared to salinity 0, the protein content of serum was significantly higher at salinities of 3 and 5. However, all serum biochemical compound measured, except glucose and total protein, decreased significantly at salinity 9. Muscle textural properties of grass carp were significantly higher at salinities of 3 and 5 than at 0, 7, and 9. Salinities of 0 - 3 had no significant effect on muscle nutrition of grass carp, but this parameter tended to decrease at salinities above 7. Salinities of 3 and 5 significantly favored muscle growth and expression of collagen-related genes, whereas the opposite was true for salinities of 7 and 9. These results indicated that grass carp grew normally at salinities of 3 and 5, with some improvement in muscle quality, whereas salinities of 7 and 9 had a negative effect on growth and quality. Therefore, appropriate salinity levels can help to improve the muscle quality of grass carp without affecting their growth.

Local cryptic diversity in salinity adaptation mechanisms in the wild outcrossing Brassica fruticulosa.

It is normally supposed that populations of the same species should evolve shared mechanisms of adaptation to common stressors due to evolutionary constraint. Here, we describe a system of within-species local adaptation to coastal habitats, Brassica fruticulosa, and detail surprising strategic variability in adaptive responses to high salinity. These different adaptive responses in neighboring populations are evidenced by transcriptomes, diverse physiological outputs, and distinct genomic selective landscapes. In response to high salinity Northern Catalonian populations restrict root-to-shoot Na+ transport, favoring K+ uptake. Contrastingly, Central Catalonian populations accumulate Na+ in leaves and compensate for the osmotic imbalance with compatible solutes such as proline. Despite contrasting responses, both metapopulations were salinity tolerant relative to all inland accessions. To characterize the genomic basis of these divergent adaptive strategies in an otherwise non-saline-tolerant species, we generate a long-read-based genome and population sequencing of 18 populations (nine inland, nine coastal) across the B. fruticulosa species range. Results of genomic and transcriptomic approaches support the physiological observations of distinct underlying mechanisms of adaptation to high salinity and reveal potential genetic targets of these two very recently evolved salinity adaptations. We therefore provide a model of within-species salinity adaptation and reveal cryptic variation in neighboring plant populations in the mechanisms of adaptation to an important natural stressor highly relevant to agriculture.