Abiotic Mechanisms Research Articles

Are Large Sulfur Isotope Variations Biosignatures in an Ancient, Impact-Induced Hydrothermal Mars Analog?

Discrepancies have emerged concerning the application of sulfur stable isotope ratios as a biosignature in impact crater paleolakes. The first in situ δ34S data from Mars at Gale crater display a ∼75‰ range that has been attributed to an abiotic mechanism. Yet biogeochemical studies of ancient environments on Earth generally interpret δ34S fractionations >21‰ as indicative of a biological origin, and studies of δ34S at analog impact crater lakes on Earth have followed the same approach. We performed analyses (including δ34S, total organic carbon wt%, and scanning electron microscope imaging) on multiple lithologies from the Nördlinger Ries impact crater, focusing on hydrothermally altered impact breccias and associated sedimentary lake-fill sequences to determine whether the δ34S properties define a biosignature. The differences in δ34S between the host lithologies may have resulted from thermochemical sulfate reduction, microbial sulfate reduction, hydrothermal equilibrium fractionation, or any combination thereof. Despite abundant samples and instrumental precision currently exclusive to Earth-bound analyses, assertions of biogenicity from δ34S variations >21‰ at the Miocene Ries impact crater are tenuous. This discourages the use of δ34S as a biosignature in similar environments without independent checks that include the full geologic, biogeochemical, and textural context, as well as a comprehensive acknowledgment of alternative hypotheses.

Biotic and abiotic factors shaping bat activity in Maryland soybean fields

AbstractBats are important pest control agents in agriculture. Yet, the underlying fine‐scale biotic and abiotic mechanisms that drive their foraging behaviors and responses to insect outbreaks are unclear. Herbivore‐induced plant volatiles (HIPVs) can attract both invertebrate and vertebrate natural enemies that use the chemical plant cues to locate insect prey. The ability of HIPVs to attract multiple species raises the question of whether they may also be a biotic factor influencing insectivorous bat activity. Additionally, abiotic factors, such as weather conditions, can affect bat activity in agricultural settings, but little is known about how bats respond to shifting environmental conditions on short timescales in this landscape context. Using a model crop system, soybean (Glycine max), our study asked three questions: (1) Which bat species are active in eastern Maryland soybean fields? (2) Is insectivorous bat activity affected by naturally occurring soybean HIPVs and/or synthetic soybean HIPVs (indole or farnesene)? (3) How is insectivorous bat activity affected by hourly weather conditions in this landscape? In soybean fields in eastern Maryland, we created paired treatment plots: HIPV plots (damaged plants or synthetic HIPV dispensers) and control plots (undamaged plants or empty dispensers). We measured bat activity using ultrasonic recorders, summarizing hourly and nightly activity, and detected 10 total species. The most abundant species were big brown/silver‐haired bats (Eptesicus fuscus/Lasionycteris noctivagans). Bat activity did not significantly differ between control and HIPV plots in any of the three experiments. Thus, our results do not support our expectation that bats in eastern Maryland use soybean HIPVs to locate insect prey. However, bat activity did increase with increasing average hourly temperature and wind speed. This initial study of bats and HIPVs, as well as the fine‐scale examination of weather conditions on bat activity, may serve as a guide for future research on bat–plant interactions that can support the development of new strategies for sustainable pest management.

Catching up with the trees: empirical advancements to improve herbaceous representation in models.

This article is a Commentary on Curasi et al. (2023), 239: 562–575.

Modeling biological denitrification in the presence of metal ions and elevated chloride content: Insights into abiotic and biotic mechanisms regulating metal bioprecipitation

Biological denitrification is a critical process in which microorganisms convert nitrate to nitrogen gas. Metal ions, such as those found in industrial wastewater, can be toxic to microorganisms and impede denitrification. It is critical to identify the mechanisms that allow microorganisms to tolerate metal ions and understand how these mechanisms can be utilized to improve denitrification efficiency by modeling the process. This study presents a mathematical model of biological denitrification in the presence of metal ions. The model includes key biotic and abiotic mechanisms and is based on pilot scale results. The model predicts the bioprecipitation of metal ions due to pH shift and alkalinity production during the metabolic activity of microorganisms. The model parameters are estimated to fit the experimental results and the mechanisms regulating metal detoxification via biological metal precipitation are presented. The model provides a valuable tool for understanding the behavior of denitrification systems in the presence of metal ions and can be used to optimize these systems for more efficient and effective treatment of industrial wastewater.

Dithionite promoted microbial dechlorination of hexachlorobenzene while goethite further accelerated abiotic degradation by sulfidation in paddy soil

It is of great scientific and practical importance to explore the mechanisms of accelerated degradation of Hexachlorobenzene (HCB) in soil. Both iron oxide and dithionite may promote the reductive dechlorination of HCB, but their effects on the microbial community and the biotic and abiotic mechanisms behind it remain unclear. This study investigated the effects of goethite, dithionite, and their interaction on microbial community composition and structure, and their potential contribution to HCB dechlorination in a paddy soil to reveal the underlying mechanism. The results showed that goethite addition alone did not significantly affect HCB dechlorination because the studied soil lacked iron-reducing bacteria. In contrast, dithionite addition significantly decreased the HCB contents by 44.0–54.9%, while the coexistence of dithionite and goethite further decreased the HCB content by 57.9–69.3%. Random Forest analysis suggested that indicator taxa (Paenibacillus, Acidothermus, Haliagium, G12-WMSP1, and Frankia), Pseudomonas, richness and Shannon’s index of microbial community, and immobilized Fe content were dominant driving factors for HCB dechlorination. The dithionite addition, either with or without goethite, accelerated HCB anaerobic dechlorination by increasing microbial diversity and richness as well as the relative abundance of the above specific bacterial genera. When goethite and dithionite coexist, sulfidation of goethite with dithionite could remarkably increase FeS formation and then further promote HCB dechlorination rates. Overall, our results suggested that the combined application of goethite and dithionite could be a practicable strategy for the remediation of HCB contaminated soil.

Carbon Sequestration and Stabilisation Mechanisms in the Agricultural Soils: A Review

Rapidly increasing levels of atmospheric CO2 and other greenhouse gases (GHGs) initiate unprecedented changes in climate systems, leading to severe ecological and economic disruptions. Climate change mitigation is possible through a reduction in net GHG emission by the process of carbon sequestration. Storage of carbon in a stable solid form through direct and indirect fixation in soil leading to carbon sequestration can result in an annual growth rate of 0.4% in the soil carbon stock and significantly reduce CO2 concentration in the atmosphere. The long term sequestration of carbon, viz, carbon stabilization is possible through both abiotic and biotic factors. This research paper aims to establish a literature review about the role of different agricultural management strategies for carbon sequestration and their stabilization mechanisms. Agricultural practices such as tillage, fallow elimination, erosion control and methane mitigation reduce carbon loss while crop management, nutrient management, land use systems, agro forestry and nano technology enhances carbon inputs. These agricultural management practices can facilitate carbon stabilization by acting through both biotic and abiotic mechanisms.

Biotic and abiotic drivers of ecosystem multifunctionality: Evidence from the semi-arid grasslands of northern China

Ecosystem functioning plays a crucial role in maintaining human welfare. Terrestrial ecosystems provide multiple ecosystem services simultaneously, such as carbon sequestration, nutrient cycling, water purification, and biodiversity conservation, known as ecosystem multifunctionality (EMF). However, the mechanisms by which biotic and abiotic factors, and their interactions regulate EMF in grasslands are unclear. We conducted a transect survey to illustrate the single and combined effects of biotic factors (including plant species diversity, trait-based functional diversity, community-weighted mean (CWM) of traits, and soil microbial diversity) and abiotic factors (including climate and soil) on EMF. Eight functions were investigated, including aboveground living biomass and litter biomass, soil bacterial biomass, fungal biomass, arbuscular mycorrhizal fungi biomass, and soil organic carbon storage, total carbon storage and total nitrogen storage. We detected a significant interactive effect between plant species diversity and soil microbial diversity on the EMF; Structural equation model showed that soil microbial diversity indirectly affected EMF by regulating plant species diversity. These findings highlight the importance of the interaction effect of above- and below-ground diversity on EMF. Both plant species diversity and functional diversity had similar explanatory power for the variation in EMF, implying that niche differentiation and multifunctional complementarity among plant species and traits are essential in regulating the EMF. Furthermore, the effects of abiotic factors on EMF were stronger than those of biotic factors via direct and indirect pathways affecting above- and below-ground biodiversity. As a dominant regulator, the soil sand content was negatively correlated with EMF. These findings indicate the vital role of abiotic mechanisms in affecting EMF, and deepen our understanding of the single and combined effects of biotic and abiotic factors on EMF. We conclude that soil texture and plant diversity, representing crucial abiotic and biotic factors, respectively, are important determinants of the EMF of grasslands.

Microbial community succession in soil is mainly driven by carbon and nitrogen contents rather than phosphorus and sulphur contents

Organic manure is widely applied in agricultural systems to improve soil nutrient cycling and other physicochemical properties. However, the biotic and abiotic mechanisms that drive C, N, P, and S cycling following manure application are not completely understood. In this study, soil samples were collected from long-term experimental plots that had been amended with farmyard manure or mineral fertilisers since 1964. Isotope labelling with 15N, 33P, and 35S; metagenomics; and high-throughput sequencing were used to reveal the relationships between C, N, P, and S dynamics and microbial community composition and functions depending on fertilisation. A clear niche differentiation was observed between bacteria and fungi under mineral and manure regimes. A network analysis showed that long-term manure application reduced the complexity and stability of soil microbial network. Furthermore, a variation partitioning analysis based on redundancy analysis indicated that microbial community variation was mainly driven by soil Cand N contents. Dissolved organic C was the most important factor regulating microbial community structure. Soil C and N contents explained 43.5% of bacterial and 37.9% of fungal community variations. In contrast, soil P and S contents explained 29.9% of bacterial and 20.3% of fungal community variations. Long-term manure application increased the abundance of most functional genes related to C, N, P, and S cycling. This led to increased C and N cycling rates under manure application, which provided sufficient substrates for microbial growth. Partial least squares path modelling indicated that soil physicochemical properties, especially dissolved organic carbon, directly influenced C and S cycling, whereas the N and P cycles were indirectly affected by the changes in microbial community composition. These results provide a new perspective on both direct and indirect effects of organic manure and inorganic fertilisers on the soil nutrient cycling processes mediated by soil microbial community.

Evolutionary history and patterns of divergence in three tropical east Asian squirrels across the Isthmus of Kra

AbstractAimUnderstanding the biotic and abiotic mechanisms underlying the generation and maintenance of biogeographic transitions represent long‐standing topics in evolutionary biology. The Isthmus of Kra (IOK) divides Sundaland and Indochina and constitutes a poorly characterized terrestrial biogeographic transition. Here we looked at population genetic structure of three species that are distributed across the IOK to gain insights into the drivers that have shaped this transition and regional diversification patterns.LocationTropical east Asia: Sundaland and Indochina.TaxaCallosciurus caniceps, Tamiops mcclellandii, and Dremomys rufigenis‐ornatus species complex (Mammalia: Rodentia: Sciuridae).MethodsWe generated complete mitogenomes and sequences of 11 nuclear intron fragments from 61 and 67 museum specimen samples, respectively. We assessed population structure by constructing Maximum Likelihood mitogenome phylogenies (IQTREE2), and nuclear marker haplowebs and conspecificity matrices (HaplowebMaker and CoMa). We estimated divergence dates through Bayesian phylogenetic inference (BEAST2) and put these results in the context of climatic and geological history.ResultsHigh levels of mitochondrial and nuclear divergence were identified across the IOK in all three squirrels. Lineage turnover was consistent with the two major mammal species distribution transitions near the Kangar‐Pattani Line and at the juncture between the Thai‐Malay peninsula and the mainland. Divergence of mitochondrial lineages across Kra was estimated in the late Pliocene/ early Pleistocene for all three taxa. Older Miocene/Pliocene divergences were estimated within Indochina in D. rufigenis‐ornatus and T. mcclellandii, which were paraphyletic.Main ConclusionsSundaic and Indochinese populations have possibly diverged in allopatric habitat refugia in or around mountains during periods of increased aridity and evergreen forest contraction. Ecological differences and/or topography might have influenced genetic differentiation during periods of rainforest expansion. Alternative hypotheses remain to be tested with more informative nuclear markers and additional geographic sampling.

Production of Molecular Iodine via a Redox Reaction between Iodate and Organic Compounds in Ice.

The abiotic mechanism of molecular iodine (I2) production from iodate (IO3-) remains largely unknown. Here, we demonstrate the production of I2 in the presence of IO3- and organic compounds in ice. When the solution containing IO3- (100 μM) and furfuryl alcohol (100 μM) at pH 3.0 was frozen at -20 °C, 13.1 μM of I2 was produced with complete degradation of furfuryl alcohol after 20 min. However, there was little change in the IO3- and furfuryl alcohol concentrations in water at 25 °C. The production of I2 in ice is due to the freeze concentration effect, which induces the accumulation of IO3-, furfuryl alcohol, and protons in the ice grain boundaries. This behavior facilitated the production of I2 via a redox reaction between IO3- and organic compounds. The production of I2 increased with increasing furfuryl alcohol concentration and decreasing pH. However, freezing temperature had a minor effect on the maximum production of I2. The production of I2 is highly dependent on the type of organic compounds. It was higher for organic compounds with higher electron-donating properties. This study suggests a new mechanism for I2 production, which is helpful for predicting precisely the atmospheric I2 budget in cold regions.

Understanding the abiotic mechanisms for the removal of Cr(VI) through interactions with the components of an Oxisol and peat as part of a nature-based solution

Understanding the abiotic mechanisms for the removal of Cr(VI) through interactions with the components of an Oxisol and peat as part of a nature-based solution

Soil Microbes from Saline–Alkali Farmland Can Form Carbonate Precipitates

The formation of soil inorganic carbon in saline–alkali lands is of great significance for enhancing soil carbon sequestration. As for the formation mechanisms, in addition to the discovered abiotic mechanisms, the microbial mechanisms remain unclear. To address this, soil microbes were isolated from the saline–alkali farmland of the Yellow River Delta in north China. Then, their capacity for carbonate precipitation formation was determined. Ten microbial strains were obtained from the soil. Of these, seven strains (four bacterial strains and three fungal strains), belonging to Rhodococcus sp., Pseudomonas sp., Bacillus sp., Streptomyces sp., Aspergillus sp., Cladosporium sp., and Trichoderma sp., formed carbonate precipitates in the range of 89.77~383.37 mg. Moreover, the formation of carbonate precipitates was related to specific metabolisms by which microbes can raise the pH (from 7.20 to >8.00), suggesting that soil microbes that can enhance pH values by specific metabolisms containing the function of carbonate formation. Although an in situ experiment is needed to confirm such capacity, these results showed that soil bacteria and fungi existing in the saline–alkali farmland soil can form carbonate precipitates. The present study provided a microbial perspective for the mechanism of soil inorganic carbon formation, further implying a microbial potential of soil carbon sequestration in saline–alkali farmlands.

Cleaning up black carbon using plant strategies

Black carbon aerosol is able to absorb solar radiation and the earth's surface, which results in warming of the air. In addition, aerosols that are directly absorbed through inhalation can have a negative impact on human health. Meanwhile, the ability of air to reduce the level of pollution is the deconcentrating of pollutants through abiotic mechanisms in the form of distribution, dilution, precipitation and washing when it rains. To strengthen the abiotic approach, this study aims to develop a biotic strategy by preparing plants capable of deconcentrating black carbon. The research method is based on a literature review, which specifically addresses the issue of black carbon. Literature is collected from the Mendeley platform and enriched through resource searches in open access journals. The results obtained are cleaning priorities for the closest source of aerosol generation, plant placement in priority areas, selection of plant species, intensification of vegetation quality and management of land cover extensification. The contribution of biotic strategies and phytoremediation pathways enhances the aerosol cleaning process. Plant maintenance and regeneration determine the sustainability of aerosol phytoremediation.

Mechanisms shaping the gypsum stromatolite-like structures in the Salar de Llamara (Atacama Desert, Chile)

The explanation of the origin of microbialites and specifically stromatolitic structures is a problem of high relevance for decoding past sedimentary environments and deciphering the biogenicity of the oldest plausible remnants of life. We have investigated the morphogenesis of gypsum stromatolite-like structures currently growing in shallow ponds (puquíos) in the Salar de Llamara (Atacama Desert, Northern Chile). The crystal size, aspect ratio, and orientation distributions of gypsum crystals within the structures have been quantified and show indications for episodic nucleation and competitive growth of millimetric to centimetric selenite crystals into a radial, branched, and loosely cemented aggregate. The morphogenetical process is explained by the existence of a stable vertical salinity gradient in the ponds. Due to the non-linear dependency of gypsum solubility as a function of sodium chloride concentration, the salinity gradient produces undersaturated solutions, which dissolve gypsum crystals. This dissolution happens at a certain depth, narrowing the lower part of the structures, and producing their stromatolite-like morphology. We have tested this novel mechanism experimentally, simulating the effective dissolution of gypsum crystals in stratified ponds, thus providing a purely abiotic mechanism for these stromatolite-like structures.

Emission mitigation of CH4 and N2O during semi-permeable membrane covered hyperthermophilic aerobic composting of livestock manure

Membrane-covered composting and hyperthermophilic composting technologies have been proven to be effective and have been widely applied as organic waste recycling strategies. However, attempts to combine the two technologies have not been reported. Thus, this study constructed a novel semi-permeable membrane covered hyperthermophilic composting (smHTC) and investigated its potential in CH4 and N2O mitigation. Results showed that smHTC reduced the average emission flux of CH4 and N2O in the thermophilic phase of composting by 79% and 45%, compared to conventional thermophilic composting (cTC). The abiotic mechanism of CH4 and N2O emission mitigation could be attributed to the double barrier of semi-permeable membrane and sub-membrane water layer, which made it difficult for CH4 and N2O to escape, resulting in less CH4 and N2O being released into environment. As for the biotic mechanism, smHTC could suppress the abundance of mcrA gene and methanogens participated in methanogenic process through the high-temperature, which also contribute to the reduction of CH4 emissions. smHTC also could reduce the abundance of denitrification-related functional genes and related microbial taxa, this also facilitated the N2O mitigation. Overall, this work demonstrated the advantages of smHTC in greenhouse gas mitigation and could be a promising recycling strategy for organic waste.

Mechanistically-grounded pathways connect remotely sensed canopy structure to soil respiration

Variation in the soil-to-atmosphere C flux, or soil respiration (Rs), is influenced by a suite of biotic and abiotic factors, including soil temperature, soil moisture, and root biomass. However, whether light detection and ranging (lidar)-derived canopy structure is tied to soil respiration through its simultaneous influence over these drivers is not known. We assessed relationships between measures of above- and belowground vegetation density and complexity, and evaluated whether Rs is linked to remotely sensed canopy structure through pathways mediated by established biotic and abiotic mechanisms. Our results revealed that, at the stand-scale, canopy rugosity–a measure of complexity–and vegetation area index were coupled to soil respiration through their effects on light interception, soil microclimate, and fine root mass density, but this connection was stronger for complexity. Canopy and root complexity were not spatially coupled at the stand-scale, with canopy but not root complexity increasing through stand development. Our findings suggest that remotely sensed canopy complexity could be used to infer spatial variation in Rs, and that this relationship is grounded in known mechanistic pathways. The broad spatial inference of soil respiration via remotely sensed canopy complexity requires multi-site observations of canopy structure and Rs, which is possible given burgeoning open data from ecological networks and satellite remote sensing platforms.

Effect of Particle Character and Calcite Dissolution on the Hydraulic Conductivity and Longevity of Biosand Filters Treating Winery and Other Acidic Effluents

Acidic effluent such as winery wastewater is challenging to remediate. Biological sand reactors can simultaneously remove organics and neutralize winery wastewater via biotic and abiotic mechanisms. The systems have been shown to be suitable for treating the intermittent flow of wastewater at small wineries. It has been shown that dissolution of calcite is the most important abiotic mechanism for increasing the pH of the influent. In this study, sand column experiments were used to determine the effects of (i) sand particle size distribution on calcite dissolution kinetics, and (ii) the effects of calcite particle dissolution on the hydraulic conductivity. The results were then used to calculate the theoretical temporal abiotic neutralization capacity of biological sand reactors with differently sized sand fractions, including unfractionated (raw) sand. The results were compared with those determined from a pilot system treating winery wastewater over a period of 3 years. Sand fractions with larger particles contained lower amounts of calcite (using Ca as a proxy), but exhibited higher hydraulic conductivities (3.0 ± 0.05 %Ca and 2.57 to 2.75 mm·s−1, respectively) than those containing smaller particles and/or raw sand (4.8 ± 0.04 to 6.8 ± 0.03 %Ca and 0.19 to 1.25 mm·s−1, respectively). The theoretical abiotic neutralization capacity of biological sand reactors was compared with a pilot system with the same flow rates, and a temporal abiotic neutralization capacity of 37 years was calculated for biological sand reactors, which compared favorably with the theoretical results obtained for wastewater with pH values between 2 (8.2 years) and 3 (82 years). It was concluded that biological sand filters with around 10% calcite will be able to abiotically neutralize winery wastewater and other wastewaters with similar acidities for the projected life span of the system. Future work should focus on determining the effect of sand grain size on the bioremediation capacity, as well as the use of biological sand reactors for treating other acidic organic wastewaters such as fruit processing, food production and distillery wastewater.

What Wilhelm Ostwald meant by "Autokatalyse" and its significance to origins-of-life research: Facilitating the search for chemical pathways underlying abiogenesis by reviving Ostwald's thought that reactants may also be autocatalysts: Facilitating the search for chemical pathways underlying abiogenesis by reviving Ostwald's thought that reactants may also be autocatalysts.

A closer look at Wilhelm Ostwald's articles that originally proposed the concept of autocatalysis reveals that he accepted reactants, not just products, as potential autocatalysts. Therefore, that a process is catalyzed by some of its products, which is the common definition of autocatalysis, is only a proper subset of what Ostwald meant by "Autokatalyse." As a result, it is necessary to reconsider the definition of autocatalysis, which is especially important for origins-of-life research because autocatalysis provides an abiotic mechanism that yields reproduction-like dynamics. Here, we translate and briefly review the two key publications on autocatalysis by Ostwald to revive his understanding of autocatalysis, and we introduce the concepts of recessive and expansive autocatalysis. Then we discuss the twofold significance of such a revival: first, facilitating the search for candidate processes underlying the origins of life, and second, updating our view of autocatalysis in complex reaction networks and metabolism.

Superabsorbent Polyacrylamide Effects on Hydrophysical Soil Properties and Plant Biomass in a Sandy Loam soil

ABSTRACT There is a complicated relationship between land degradation, water efficiency, and crop yield in arid and semiarid regions. In the Semiarid Pampa region, Argentina, land use changes that affected fragile lands (high content of fine sands plus silt and low organic carbon) have decreased soil quality, thus endangering agricultural activities. The use of polyacrylamide (PAM) is an option for increasing productivity and protecting soil resources. However, there is scarce information about superabsorbent PAM on water storage linked to aggregate stability mechanisms in this fragile land. Hydrophysical variables and plant biomass were evaluated in a greenhouse pot experiment. Three factors were analyzed: 1) PAM rates (doses): D0 = 0%, D1 = 0.04%, and D2 = 0.08%; 2) vegetation presence (Festuca arundinacea ssp.): vegetation (+) and vegetation (–) and; 3) water regime: field capacity (FC) and half field capacity (FC/2). After 5 months, the incorporation of superabsorbent PAM had a strong effect on most hydrophysical variables. Storage variables (available water content and easily available water content) were improved mainly by increasing water retention at lower suctions (i.e. large pores). Dose increments regardless of the water regime led to higher plant biomass (P < .05). PAM incorporation enhanced abiotic mechanisms (swelling–shrinkage, cracks formation) and biotic mechanisms (root activity – direct, increment water retention – indirect) acting synergically to increase aggregate stability and water storage. Aggregate stability tests (fast wetting test – FW, slow wetting test – SW, and stirring aggregates after ethanol submersion – Stir) proved to be useful in discriminating stabilization mechanisms of soils, highlighting the effect of PAM incorporation on soil cohesion (Stir). Finally, superabsorbent PAM may contribute to maintain crop yields, leading to soil quality amelioration.

Transcriptome analysis reveals fluid shear stress (FSS) and atherosclerosis pathway as a candidate molecular mechanism of short-term low salinity stress tolerance in abalone

BackgroundTranscriptome sequencing is an effective tool to reveal the essential genes and pathways underlying countless biotic and abiotic stress adaptation mechanisms. Although severely challenged by diverse environmental conditions, the Pacific abalone Haliotis discus hannai remains a high-value aquaculture mollusk and a Chinese predominantly cultured abalone species. Salinity is one of such environmental factors whose fluctuation could significantly affect the abalone’s cellular and molecular immune responses and result in high mortality and reduced growth rate during prolonged exposure. Meanwhile, hybrids have shown superiority in tolerating diverse environmental stresses over their purebred counterparts and have gained admiration in the Chinese abalone aquaculture industry.The objective of this study was to investigate the molecular and cellular mechanisms of low salinity adaptation in abalone. Therefore, this study used transcriptome analysis of the gill tissues and flow cytometric analysis of hemolymph of H. discus hannai (DD) and interspecific hybrid H. discus hannai ♀ x H. fulgens ♂ (DF) during low salinity exposure. Also, the survival and growth rate of the species under various salinities were assessed.ResultsThe transcriptome data revealed that the differentially expressed genes (DEGs) were significantly enriched on the fluid shear stress and atherosclerosis (FSS) pathway. Meanwhile, the expression profiles of some essential genes involved in this pathway suggest that abalone significantly up-regulated calmodulin-4 (CaM-4) and heat-shock protein90 (HSP90), and significantly down-regulated tumor necrosis factor (TNF), bone morphogenetic protein-4 (BMP-4), and nuclear factor kappa B (NF-kB).Also, the hybrid DF showed significantly higher and sustained expression of CaM and HSP90, significantly higher phagocytosis, significantly lower hemocyte mortality, and significantly higher survival at low salinity, suggesting a more active molecular and hemocyte-mediated immune response and a more efficient capacity to tolerate low salinity than DD.ConclusionsOur study argues that the abalone CaM gene might be necessary to maintain ion equilibrium while HSP90 can offset the adverse changes caused by low salinity, thereby preventing damage to gill epithelial cells (ECs).The data reveal a potential molecular mechanism by which abalone responds to low salinity and confirms that hybridization could be a method for breeding more stress-resilient aquatic species.