Salinity Fluctuations Research Articles

Effect of oceanic turbulence on the propagation behavior of a radially polarized Laguerre-Gaussian Schell-model vortex beam.

Optical wireless communications applications are restricted by oceanic media-induced beam quality degradation. However, modulating the coherence and polarization structures of the laser beams can effectively diminish the negative influence of oceanic turbulence on the beams. The average intensity of a radially polarized Laguerre-Gaussian Schell-model vortex (RPLGSMV) beam propagating through oceanic turbulence is explored by employing the extended Huygens-Fresnel principle. We found that the average intensity of an RPLGSMV beam is greatly affected by oceanic turbulence with a large rate of dissipation of the mean-square temperature and a large relative strength of the temperature and salinity fluctuations as well as the small rate of dissipation of the turbulent kinetic energy per unit mass of fluid and small Kolmogorov microscale. It was also found that a RPLGSMV beam with a larger radial index, topological charge, initial coherent length, and beam waist has a stronger anti-turbulence ability. Our numerical findings may be of great significance for the detection and imaging of oceanic optical telecommunications links.

Effects of Salinity Stress on Histological Changes, Glucose Metabolism Index and Transcriptomic Profile in Freshwater Shrimp, Macrobrachium nipponense.

Salinity is an important factor in the aquatic environment and affects the ion homeostasis and physiological activities of crustaceans. Macrobrachium nipponense is a shrimp that mainly lives in fresh and low-salt waters and plays a huge economic role in China's shrimp market. Currently, there are only a few studies on the effects of salinity on M. nipponense. Therefore, it is of particular importance to study the molecular responses of M. nipponense to salinity fluctuations. In this study, M. nipponense was set at salinities of 0, 8, 14 and 22‱ for 6 weeks. The gills from the control (0‱) and isotonic groups (14‱) were used for RNA extraction and transcriptome analysis. In total, 593 differentially expressed genes (DEGs) were identified, of which 282 were up-regulated and 311 were down-regulated. The most abundant gill transcripts responding to different salinity levels based on GO classification were organelle membrane (cellular component), creatine transmembrane transporter activity (molecular function) and creatine transmembrane transport (biological function). KEGG analysis showed that the most enriched and significantly affected pathways included AMPK signaling, lysosome and cytochrome P450. In addition, 15 DEGs were selected for qRT-PCR verification, which were mainly related to ion homeostasis, glucose metabolism and lipid metabolism. The results showed that the expression patterns of these genes were similar to the high-throughput data. Compared with the control group, high salinity caused obvious injury to gill tissue, mainly manifested as contraction and relaxation of gill filament, cavity vacuolation and severe epithelial disintegration. Glucose-metabolism-related enzyme activities (e.g., pyruvate kinase, hexokinase, 6-phosphate fructose kinase) and related-gene expression (e.g., hexokinase, pyruvate kinase, 6-phosphate fructose kinase) in the gills were significantly higher at a salinity of 14‱. This study showed that salinity stress activated ion transport channels and promoted an up-regulated level of glucose metabolism. High salinity levels caused damage to the gill tissue of M. nipponense. Overall, these results improved our understanding of the salt tolerance mechanism of M. nipponense.

Biological responses of stellate sturgeon fingerlings (Acipenser stellatus) immersed in HSP inducer to salinity changes

Changes in salinity is a stressful and energy-consuming process in fish which give rise to mortalities, especially in fish fingerlings that are more sensitive during the early stages of their life. In the present study, the effects of three salinities, 3‰ (downstream of river), 8‰ (estuarine), and 13‰ (the maximum salinity in the Caspian Sea), on HSP70 gene expression, cortisol level, immune response (lysozyme, complement C3, IgM), and antioxidant enzyme activities (SOD, CAT, T-AOC) of the stellate sturgeon fingerlings in the presence of HSP inducer compound (TEX-OE®) were evaluated. Our results showed that levels of plasma cortisol and heat shock protein (HSP70) in Acipenser stellatus fingerlings increased due to salinity changes. In the presence of the HSP inducer, HSP70 expression in both gill and liver was significantly increased, whereas cortisol level was notably decreased. Exposure to salinity changes resulted in an increase in antioxidant defense activities (SOD, CAT, and T-AOC) and immune response (lysozyme, IgM, and C3) in the presence of an HSP inducer. In conclusion, an HSP-inducing compounds can have a positive effect in strengthening the immunity and antioxidant system of sturgeon fingerlings by increasing the expression of the HSP70 gene against salinity fluctuations and generally increase the body's physiological tolerance.

Combined effects of salinity and intermittent hypoxia on mitochondrial capacity and reactive oxygen species efflux in the Pacific oyster, Crassostrea gigas.

Coastal environments commonly experience fluctuations in salinity and hypoxia-reoxygenation (H/R) stress that can negatively affect mitochondrial functions of marine organisms. Although intertidal bivalves are adapted to these conditions, the mechanisms that sustain mitochondrial integrity and function are not well understood. We determined the rates of respiration and reactive oxygen species (ROS) efflux in the mitochondria of oysters, Crassostrea gigas, acclimated to high (33 psu) or low (15 psu) salinity, and exposed to either normoxic conditions (control; 21% O2) or short-term hypoxia (24 h at <0.01% O2) and subsequent reoxygenation (1.5 h at 21% O2). Further, we exposed isolated mitochondria to anoxia in vitro to assess their ability to recover from acute (∼10 min) oxygen deficiency (<0.01% O2). Our results showed that mitochondria of oysters acclimated to high or low salinity did not show severe damage and dysfunction during H/R stress, consistent with the hypoxia tolerance of C. gigas. However, acclimation to low salinity led to improved mitochondrial performance and plasticity, indicating that 15psu might be closer to the metabolic optimum of C. gigas than 33psu. Thus, acclimation to low salinity increased mitochondrial oxidative phosphorylation rate and coupling efficiency and stimulated mitochondrial respiration after acute H/R stress. However, elevated ROS efflux in the mitochondria of low-salinity-acclimated oysters after acute H/R stress indicates a possible trade-off of higher respiration. The high plasticity and stress tolerance of C. gigas mitochondria may contribute to the success of this invasive species and facilitate its further expansion into brackish regions such as the Baltic Sea.

Effect of soil and water salinity on dry season boro rice production in the south-central coastal area of Bangladesh

Salinity varies with location and time of the year. It can significantly impact crop production. The level of negative impacts depends on the salt concentration and time of its occurrence, which, however, has not been studied for many crops, especially for rice grown in the coastal area of Bangladesh. Our study explored the impact of spatio-temporal fluctuations in soil and water salinity on boro rice production in the south-central coast of Bangladesh. Here, we simulated the soil salinity from November 2020 to May 2021 for fourteen locations classes using the SWAP-WOFOST model. The model was calibrated and validated with measured secondary data. Next, the yield of two salt-tolerant boro rice varieties (BRRI dhan47 and BRRI dhan67) was simulated using the customized soil, weather, and crop data. We also simulated the yield by adopting agronomic management practices (i.e., changing planting time and using fresh irrigation water). Our results showed that salinity levels varied with different soil textural classes, soil depth, location, and time of the year, and that had a significant influence on boro rice production, giving spatial variability. Specifically, boro rice had a higher yield in coarse texture soil than in fine texture soil. Simulated yields in areas proximate to the sea ranged from 668 to 1239 kg ha−1, yields that are significantly lower than those simulated in moderate (2098–4843 kg ha−1) and low salinity zones (4213–4843 kg ha−1). Moreover, the simulation of yield with sowing/planting rice earlier by fifteen days provided a higher yield than the current planting practice since it could avoid salinity at later stages of growth. For a similar reason, growing rice inside the polder provided a higher yield than outside the polder. The insights gained from our study carry significant implications for contemporary crop-level adaptation strategies and policy-making in coastal districts.

A statistical analysis of tropical salinity and its relationship to SST, highlighting two contrasting areas

Tropical air-sea interactions, near-surface salinity (Ss), and sea surface temperature (SST) fluctuations are studied via ocean reanalysis products in the period 1980–2020. The statistical work considers how the net heat and water balance affects mixed layer depth (MLD) and coupling between the upper ocean and atmosphere. Field correlations of Ss – SST exhibit significant negative values in tropical latitudes 10S-15 N, between the semi-permanent marine anticyclones and the equatorial trough. Highlighting contrasts in two areas: the tropical east Atlantic and subtropical southwest Indian Ocean, annual cycles, inter-annual fluctuations of 6 – 8 yr, and long-term downward trends of Ss emerge. The SW Indian Ocean exhibits large swings of net heat and water balance as the monsoon reverses, and steady running-correlations of Ss and SST. The E Atlantic has a subdued annual cycle, and running-correlations are weak and unsteady. In both areas the Ss lags SST by a month. A fresh minus salty composite analysis reveals that the two contrasting areas respond to opposing phases of the Southern Oscillation: E Atlantic (La Nina) and SW Indian (El Nino). Projected long-term trends for increased tropical marine rainfall could be neutralized by declining runoff from continental monsoons. Statistical outcomes infer that a 0.1 ppt reduction of near-surface salinity leads to a 5 m reduction of MLD and a 0.4 C increase of tropical SST, contributing to deeper atmospheric convection. Limitations of the study derive from inferences based on infrequent salinity measurements.

An Overview of Climate Change Impacts on Agriculture and Their Mitigation Strategies

In recent years, the adverse effect of climate change on soil properties in the agricultural sector has become a dreadful reality worldwide. Climate change-induced abiotic stresses such as salinity, drought and temperature fluctuations are devastating crops’ physiological responses, productivity and overall yield, which is ultimately posing a serious threat to global food security and agroecosystems. The applications of chemical fertilizers and pesticides contribute towards further deterioration and rapid changes in climate. Therefore, more careful, eco-friendly and sustainable strategies are required to mitigate the impact of climate-induced damage on the agricultural sector. This paper reviews the recently reported damaging impacts of abiotic stresses on various crops, along with two emerging mitigation strategies, biochar and biostimulants, in light of recent studies focusing on combating the worsening impact of the deteriorated environment and climate change on crops’ physiological responses, yields, soil properties and environment. Here, we highlighted the impact of climate change on agriculture and soil properties along with recently emerging mitigation strategies applying biochar and biostimulants, with an aim to protecting the soil, agriculture and environment.

Whole Transcriptome Analysis Reveals the Global Molecular Responses of mRNAs, lncRNAs, miRNAs, circRNAs, and Their ceRNA Networks to Salinity Stress in Hong Kong Oysters, Crassostrea hongkongensis.

The Hong Kong oyster, Crassostrea hongkongensis, is an estuarine bivalve with remarkable commercial value in South China, and the increase of salinity in estuaries during the dry season has posed a major threat to the oyster farming. To explore the global transcriptional response to salinity stress, a whole-transcriptome analysis was performed with the gills of oysters in 6‰, 18‰, and 30‰ filtered seawater. Overall, 2243, 194, 371, and 167 differentially expressed mRNAs (DEmRNAs), differentially expressed long non-coding RNAs (DElncRNAs), differentially expressed circular RNAs (DEcircRNAs), and differentially expressed microRNAs (DEmiRNAs) were identified, respectively. Based on GO enrichment and KEGG pathway analysis, these important DEmRNAs, DElncRNAs, DEcircRNAs, and DEmiRNAs were predicted to be mainly involved in amino acids metabolism, microtubule movement, and immune defense. This demonstrated the complexity of dynamic transcriptomic profiles of C. hongkongensis in response to salinity fluctuation. The regulatory relationships of DEmiRNAs-DEmRNAs, DElncRNAs-DEmiRNAs, and DEcircRNAs-DEmiRNAs were also predicted, and finally, a circRNA-associated competing endogenous RNA (ceRNA) network was constructed, consisting of six DEcircRNAs, eight DEmiRNAs, and five DEmRNAs. The key roles of taurine and hypotaurine metabolism and phenylalanine metabolism were highlighted in this ceRNA network, which was consistent with the major contribution of free amino acids to intracellular osmolality and cell volume regulation. Collectively, this study provides comprehensive data, contributing to the exploration of coding and non-coding RNAs in C. hongkongensis salinity response. The results would benefit the understanding of the response mechanism of bivalves against salinity fluctuation, and provide clues for genetic improvement of C. hongkongensis with hyper-salinity tolerance.

Spatial coherence length and wave structure function for plane waves transmitted in anisotropic turbulent oceans.

The spatial coherence length and wave phase structure function are two important factors in describing turbulence's effect on light propagation in seawater. This paper derives the wave phase structure function and spatial coherence length of plane waves in moderate to strong turbulent channels by deriving a "modification seawater turbulence power spectrum" and an oceanic-modified Rytov approximation. The evolutions in wave structure function, coherence length with the temperature dissipation rate, energy dissipation rate, anisotropy turbulence factor, signal wavelength, and propagation distance are analyzed by numerical calculation. In the moderate and strong turbulence regions, the phase structure function and spatial coherence length increase and decrease with increasing transmission distance and turbulence strength, respectively, and there is a saturation tendency for both. The fluctuation of seawater salinity has a greater effect on the phase structure function and coherence length than the temperature fluctuation. In addition, the wave structure function decreases with increasing signal wavelength and degree of turbulent anisotropy, but the trend of spatial coherence length is reversed.

Beam intensity and spectral coherence of Hermite-cosine-Gaussian rectangular multi-Gaussian correlated Schell-model beam in oceanic turbulence

The beam spreading and evolution behavior of a partially coherent, Hermite-cosine-Gaussian (HcosG) rectangular multi-Gaussian correlated Schell-model beam propagating in oceanic turbulence is studied. Analytical expressions for the cross-spectral density function, as well as the root mean square (rms) beam width and the spectral degree of coherence, are derived based on the extended Huygens-Fresnel principle. The HcosG rectangular multi-Gaussian correlated Schell-model beam exhibits a multi-lobe pattern at short propagation distances. The dependencies of the number, size, shape, and centroid of the lobes on displacement parameters, source size, order of field distribution, and displacement are investigated. As the propagation distance increases, the spectral coherence decreases, and the differences between the spectral coherence curves gradually diminish. Additionally, for HcosG rectangular multi-Gaussian correlated Schell-model beams, better propagation performance was found in oceanic turbulence with larger mean square temperature dissipation rate, smaller turbulent kinetic energy dissipation rate per unit mass of fluid, and larger relative strength of temperature and salinity fluctuation.

Life in a Gilbert-type delta system: Ichnoassociations of the Ventimiglia palaeovalley and their sequence stratigraphic significance (Pliocene, NW Italy)

Gilbert-type deltas are inherently associated with stressful conditions for the benthic infauna, i.e. highly shifting substrates, coarse-grained sediments, traction sedimentation, supercritical flows, and salinity fluctuations. Nevertheless, trace fossils are locally abundant in the Gilbert-type delta system of Ventimiglia (NW Italy), representing the Pliocene infill of an incised valley that developed during the Messinian sea-level fall. The seismic-scale outcrops of the Ventimiglia delta system allow to link ichnological features (ichnotaxa, bioturbation intensity) to the major depositional environments of the deltaic system. Accordingly, rhizoliths characterize the delta plain, whereas delta top deposits are virtually unbioturbated. The delta slope is characterized by Planolites, Thalassinoides, Scolicia-like burrows, and Ophiomorpha. Proximal prodelta deposits show a characteristic Skolithos-Chondrites ichnoassociation, whereas Chondrites and sharp-walled burrows (Thalassinoides?) dominate the distal prodelta. Reworked beach deposits occasionally present bioerosional ichnotaxa (Entobia, Gastrochaenolites, and Maeandropolydora), which suggest the presence of a nearby rocky coast. Overall, bioturbation intensity increases with increasing distance from the delta-top setting, whereas ichnodiversity has its maximum in delta-toe and prodelta units. Moreover, a clear sequence-stratigraphic signature is observed for the Ventimiglia ichnoassociations. The ichnological evolution of the Ventimiglia delta system, with bioturbation intensity increasing in forced-regressive systems tracts of successive sequences, is here hypothesized as a signature of overfilled incised valleys. The Skolithos-Chondrites ichnoassociation is especially common in the highstand systems tract, possibly reflecting higher amounts of suspended matter during the sedimentation of the highstand systems tract itself. The basal surface of forced regression usually preserves passively filled burrows with a sharp unlined margin, which fits well with a sediment-starved seafloor.

Effect of hypersalinic stress on hemocyte morphology and hemolymph cellular composition of the ark clam (Anadarakagoshimensis).

Bivalve mollusks as typical osmoconformers are unable to maintain a constant level of internal osmolarity in conditions of salinity stress. Adaptation to fluctuations of environmental salinity is achieved through cellular osmoregulatory responses, which are accompanied with a substantial shift in functional state of cells. In the present work we investigated the effect of hypersalinity stress on hemolymph cellular composition and morphology of the ark clam (Anadara kagoshimensis) hemocytes. Ark clams were subjected to a gradual increase of environmental salinity from 18‰ to 35‰ and 45‰ and maintained at those conditions for two days. Exposure to hypersalinity 35‰ induced changes in erythrocyte morphology and led to a decrease of their diameter. At salinity 45‰ a substantial increase of hemocyte average diameter was observed, whereas the shape of cells did not change (18‰). Hyperosmotic stress was not associated with changes in hemocyte viability as well as changes in hemolymph cellular composition. The results of the present work demonstrate high tolerance of A. kagoshimensis to short-time exposure to hypersalinic conditions.

Hyposalinity reduces coordination and adhesion of sea urchin tube feet.

Climate change will increase the frequency and intensity of low-salinity (hyposalinity) events in coastal marine habitats. Sea urchins are dominant herbivores in these habitats and are generally intolerant of salinity fluctuations. Their adhesive tube feet are essential for survival, effecting secure attachment and locomotion in high wave energy habitats, yet little is known about how hyposalinity impacts their function. We exposed green sea urchins (Strongylocentrotus droebachiensis) to salinities ranging from ambient (32‰) to severe (14‰) and assessed tube feet coordination (righting response, locomotion) and adhesion [disc tenacity (force per unit area)]. Righting response, locomotion and disc tenacity decreased in response to hyposalinity. Severe reductions in coordinated tube foot activities occurred at higher salinities than those that affected adhesion. The results of this study suggest moderate hyposalinities (24-28‰) have little effect on S. droebachiensis dislodgement risk and survival post-dislodgment, while severe hyposalinity (below 24‰) likely reduces movement and prevents recovery from dislodgment.

Temporal Evolution of Phytoplankton Metacommunity in a Disused Mediterranean Saltwork

Saltworks are interesting sites for aquatic ecology, where marine phytoplankton plays a fundamental role in regulating ecosystem processes and sustaining large-scale biodiversity. This paper presents successional, structural, and dynamical traits of a phytoplankton metacommunity in a disused saltwork, where the industrial hydraulic management has been changed, leading to a different overlapping of natural and anthropic induced scales. We have considered the total phytoplankton biomass, size classes, and chemotaxonomical composition in monitoring the metacommunity dynamics in a series of single ponds spanning from marine to hypersaline ones between July 2008 and October 2009. Results indicate a large accumulation of biomass during summer to early autumn in hypersaline ponds, with the prevalence of small-size cells (&lt;20 μm) in the entire system. Despite severe salinity fluctuations as a consequence of rainy events and evaporating processes, chlorophytes represented the dominant group of hypersaline ponds, while diatoms were more abundant where the influence of seawater inflow was higher. Despite the absence of ordinary maintenance, the phytoplankton metacommunity dynamic and patterns observed suggest that the existing saline gradient ensures qualitative and quantitative aspects of the primary production usually found in active saltworks. This makes the Saline di Tarquinia an important site not only for the preservation of Mediterranean biodiversity and hypersaline biotopes but also for ecological studies dealing with the trait-based responses of the phytoplankton community to large environmental fluctuations.

Short-time salinity fluctuations are strong activators of oxidative stress in Mediterranean mussel (Mytilus galloprovincialis)

Salinity stress is an emerging key factor affecting aquatic animals in coastal waters. In bivalves, physiological responses to anisosmotic conditions are frequently associated with excessive reactive oxygen species (ROS) formation, lipid peroxidation processes and alterations of the antioxidant enzyme activity in tissues. In this study, we investigated whether short-time exposure to high (20-40 ‰) or low (6-14 ‰) salinity induces oxidative stress in hemocytes and gills of Mediterranean mussel (Mytilus galloprovincialis). Our findings showed that both hypoosmotic and hyperosmotic stress enhanced formation of ROS in hemocytes, which was accompanied by an increase in DNA damage. Experimental acclimation to low salinity (6‰, 10 ‰) led to a decrease of the activity of superoxide dismutase but did not affect catalase activity in gills. Exposure to high salinity (24 ‰) inhibited activities of both antioxidant enzymes, whereas at 30 ‰ activity of both enzymes recovered up to controls. We found that exposure to high salinity was associated with lower risks of oxidative stress in mussels, and changes in redox balance are observed in hemocytes and gills even if the range of salinity changes is in range of species adaptive potential. Taken together, this study suggests that short-time salinity fluctuations promote oxidative stress in bivalves.

Spatio-temporal variation of water salinity in mangroves revealed by continuous monitoring and its relationship to floristic diversity

Salinity is among the most critical factors limiting the growth and species distribution of coastal plants. Water salinity in estuarine ecosystems varies temporally and spatially, but the variation patterns across different time scales and salinity fluctuation have rarely been quantified. The effects of salinity on floristic diversity in mangroves are not fully understood due to the temporal and spatial heterogeneity of salinity. In this study, we monitored water salinity at an interval of 10-min over one year in three mangrove catchment areas representing the outer part, middle part, and inner part respectively of Dongzhai Bay, Hainan, China. The number of mangrove community types and dominant mangrove species of the three catchment areas were also investigated. We found that the diurnal variation and dry-season intra-month variation in water salinity were driven by tidal cycles. The seasonal variation in water salinity was mainly driven by rainfall with higher salinity occurring in the dry season and lower salinity occurring in the wet season. Spatially, water salinity was highest at the outer part, intermediate at the middle part, and lowest at the inner part of the bay. The intra-month and annual fluctuations of water salinity were highest at the middle part and lowest at the outer part of the bay. The number of mangrove community types and dominant species were lowest at the outer part, intermediate at the middle part, and highest at the inner part of the bay. These results suggest that the temporal variation of water salinity in mangroves is driven by different factors at different time scales and therefore it is necessary to measure water salinity at different time scales to get a complete picture of the saline environment that mangroves experience. Spatially, lower salinity levels benefit mangrove species richness within a bay landscape, however, further research is needed to distinguish the effects of salinity fluctuation and salinity level in affecting mangrove species richness.

Multidecadal climate variability dominated past trends in the water balance of the Baltic Sea watershed

The Baltic Sea watershed includes the territories of 14 countries in Northern, Central, and Eastern Europe. Long-term observations have shown that the climate in this area is characterised by a pronounced multidecadal variability, with a period of about 30 years, but its origin is thus far unknown. We propose that the observed ~30-year fluctuations in Baltic Sea salinity are caused by the Atlantic Multidecadal Variability and the North Atlantic Oscillation, which together modulate precipitation over the watershed and hence the river discharge into the Baltic Sea. The return of a large portion of the outflowing brackish Baltic Sea water with the inflowing salt water, due to mixing at the entrance area results in a positive feedback mechanism that amplifies the multidecadal variations in salinity. The strength of this self-amplification is considerable since atmospheric forcing has nearly the same periodicity as the response time of the freshwater content to external freshwater inputs.

Nephrocalcinosis in juvenile farmed Atlantic Salmon (Salmo salar) may be linked to osmoregulatory stress.

Nephrocalcinosis is a widespread challenge in intensive production of salmon smolt. There is however no consensus on its aetiology, which makes it problematic to implement proper measures to limit its development. We performed a survey of nephrocalcinosis prevalence and environmental factors in 11 different hatcheries in Mid-Norway as well as a 6-month monitoring in one of the hatcheries. A multivariate analysis indicated that the most influencing factor for the prevalence of nephrocalcinosis was the supplementation of sea water during smolt production. In the 6-month monitoring, the hatchery introduced salinity in the production water prior to the change in day length. Mismatch in those environmental signals may increase the risk for developing nephrocalcinosis. Salinity fluctuations prior to smoltification can cause osmotic stress and result in unbalanced levels of ions in fish blood. This was clearly illustrated in our study, as the fish experienced chronic hypercalcaemia and hypermagnesaemia. Both magnesium and calcium are excreted over the kidneys and it is possible that their prolonged, elevated levels in plasma resulted in an oversaturation of the urine when finally excreted. This again could have led to the aggregation of calcium deposits within the kidney. This study indicates a relationship between osmotic stress induced by salinity changes in juvenile Atlantic salmon and the development of nephrocalcinosis. Other factors that may affect the severity of nephrocalcinosis are currently subjects for discussion.

Application of multi-omics combined with bioinformatics techniques to assess salinity stress response and tolerance mechanisms of Pacific oyster (Crassostrea gigas) during depuration.

Depuration is a vital stage to ensure the safety of oyster consumption, and salinity had a great impact on the environmental adaptability of oysters, but the underlying molecular mechanism was poorly understood during depuration stage. Here, Crassostrea gigas was depurated for 72h at different salinity (26, 29, 32, 35, 38g/L, corresponding to ±20%, ±10% salinity fluctuation away from oyster's production area) and then analyzed by using transcriptome, proteome, and metabolome combined with bioinformatics techniques. The transcriptome showed that the salinity stress led to 3185 differentially expressed genes and mainly enriched in amino acid metabolism, carbohydrate metabolism, lipid metabolism, etc. A total of 464 differentially expressed proteins were screened by the proteome, and the number of up-regulated expression proteins was less than the down-regulated, indicating that the salinity stress would affect the regulation of metabolism and immunity in oysters. 248 metabolites significantly changed in response to depuration salinity stress in oysters, including phosphate organic acids and their derivatives, lipids, etc. The results of integrated omics analysis indicated that the depuration salinity stress induced abnormal metabolism of the citrate cycle (TCA cycle), lipid metabolism, glycolysis, nucleotide metabolism, ribosome, ATP-binding cassette (ABC) transport pathway, etc. By contrast with Pro-depuration, more radical responses were observed in the S38 group. Based on the results, we suggested that the 10% salinity fluctuation was suitable for oyster depuration and the combination of multi-omics analysis could provide a new perspective for the analysis of the mechanism changes.

Southern Flounder Life History Diversity and Contributions to Fisheries from Differing Estuarine Salinity Zones

AbstractOtolith chemistry is a useful natural tracer for discerning habitat‐use of estuarine fishes. For Southern Flounder Paralichthys lethostigma, recent otolith chemistry studies have revealed a diversity of residency patterns across salinity gradients. However, the contribution of recruits with specific residency patterns to fisheries is poorly understood. The objectives of this study were to (1) use otolith chemistry from fishery‐independent and fishery‐dependent collections in Mobile Bay, Alabama, to classify lifetime residency patterns (i.e., freshwater, transient, estuarine) in Southern Flounder collected across a large estuarine salinity gradient (0–30 psu); (2) to test if Southern Flounder exhibited resident or migratory behavior by determining if lifetime residency patterns in fishery‐independent samples matched expected salinity patterns in the region of collection after accounting for annual variation in river discharge; and (3) to examine which residency patterns contributed to the commercial and recreational Southern Flounder fisheries in nearby coastal waters. Age‐0 residency patterns in fishery‐independent samples were strongly correlated with region of collection and annual river discharge, suggesting that the majority of Southern Flounder had resided in the same region in which they spent their age‐0 growth phase. Southern Flounder with a combination of freshwater and estuarine salinity signals and classified as “transient” did not appear to have conducted large‐scale movements across salinity gradients, but instead resided in regions of the estuary experiencing seasonal fluctuations in salinity. The majority (57%) of commercially and recreationally harvested Southern Flounder were transients, while a minority (39%) were estuarine residents and lifetime freshwater residents (4%) were rarely harvested. Results from this study suggest that Southern Flounder settle in and remain in the certain habitats during the estuarine residency phase. Given the lack of movement across habitats, future efforts to understand how habitat‐specific conditions (e.g., abiotic, biotic, fishing exploitation) affect vital rates seems warranted for a species currently experiencing population declines.