Effect of dredging and capping with clean soil on the mitigation of algae-induced black blooms in Lake Taihu, China: A simulation study.

Sediment is an important source of matter that causes blackening and odor formation in a water body. The restoration of polluted sediment can suppress algae-induced black blooms to a certain degree. In this study, we compared the control effects of sediment dredging and capping with clean soil on algae-induced black blooms in Lake Taihu using indoor simulation experiments. In addition, we explored the driving effect of temperature on algae-induced black blooms using the method of gradual warming (18, 23, and 28 °C) during the experiment. No blackening of the water body was observed in the simulation stages I (18 °C) and II (23 °C), and the blackening and odor formation occurred within 3 d when the temperature increased to 28 °C in stage III, implying that high temperature was an important driving factor for algae-induced black blooms. Dredging and capping inhibited the blackening and odor formation to some extent, and the colorimetric values in the water columns were lower in the treatment groups than in the control group. At the end of the experiment, the colorimetric values of dredging and capping treatments were 56.5% and 96.7% of the colorimetric value of the control group, respectively. The control effect of dredging on the blackening elements, i.e., Fe2+ and S2- and the main odor forming compounds, i.e., dimethyl disulfide (DMDS) and dimethyl trisulfide (DMTS) was observed in stage II (11-20 d) and stage III (21-27 d), respectively, and the inhibition ability of dredging to suppress algal-induced black blooms was superior than that of capping with clean soil.

Identification, expression and pro-inflammatory effect of interleukin-17 N in common carp (Cyprinus carpio L.).

Two interleukin (IL)-17 N genes (CcIL-17Na and b) present on different linkage groups were identified in the common carp (Cyprinus carpio) genome and confirmed by polymerase chain reaction (PCR) and real time (RT)-PCR in this experiment. Synteny analysis revealed that IL-17 N is transcribed by the complement sequence of TOP3B's intron 2. It is flanked by SDF2L and PPM1F in all fish studied to date, except fugu (Takifugu rubripes). The open reading frames of the two CcIL-17Ns are 411 base pairs long and encode 136 amino acids. The amino acid identity/similarity between CcIL-17Na and b is 91.2%/97.1%. The CcIL-17Ns share identity (46.8-90.4%) with their orthologs from other teleosts. Identities/similarities to other members of the IL-17 family in common carp were low at 21.4-30.2%/31.4-51.4%. In the phylogenetic tree, IL-17Ns from spotted gar (Lepisosteus oculatus, the ancestor of teleosts) and coelacanth (Latimeria chalumnae, the ancestor of tetrapods) were grouped within the same branch with a high bootstrap value of 97%, which indicates that IL-17 N is an ancient and conserved gene. Quantitative RT-PCR results showed that CcIL-17Ns were most highly expressed in the brain of healthy individuals. The expression in brain was significantly induced at 6 h post Aeromonas hydrophila infection; at 1 day post infection, expression in liver, muscle, skin, spleen, and head kidney was up-regulated. In addition, the upregulated expression of proinflammatory cytokines IL-1ß, IFN-γ, IL-6, chemokine CCL20, NF - κ B and TRAF6 in kidney tissue by ccIL-17 N recombinant protein also indicate that IL-17 N can promote inflammation through NF-κB pathway and induce the expression of chemokines and inflammatory factors.

Molecular insights into information processing and developmental and immune regulation of Eriocheir sinensis megalopa under hyposaline stress.

Eriocheir sinensis is an important euryhaline catadromous crustacean of the Yangtze River and an important commercial species for breeding in China. However, wild E. sinensis have suffered serious damage attributed to overfishing, climate change, etc. The Ministry of Agriculture of China issued a notice banning the commercial fishing of wild E. sinensis. E. sinensis megalopa migrates upriver into fresh water for growth and fattening, which creates optimal conditions to experimentally explore its hyposaline osmoregulation mechanism. We performed comparative transcriptome analyses of E. sinensis megalopae under hyposaline stress. The results suggest that KEGG pathways and genes related to genetic information processing, developmental regulation, immune and anti-stress responses were differentially expressed. The present study reveals the most significantly enriched pathways and functional gene groups, and explores the hyposaline osmoregulation mode of E. sinensis megalopae. This study lays a theoretical foundation for further studies on the osmoregulation and developmental mechanisms of E. sinensis.

Molecular insights into the sex-differential regulation of signal transduction in the cerebral ganglion and metabolism in the hepatopancreas of Eriocheir sinensis during reproduction.

The Chinese mitten crab (Eriocheir sinensis), an economically valuable crustacean that is popular for its flavor, exhibits catadromous spawning migration. Overfishing and environmental pollution have inflicted serious damage on wild E. sinensis populations, and the Chinese government has banned the commercial fishing of this species in the Yangtze River. Studies have examined the sexual dimorphism in the body size and morphology of crabs, but there are few reports on the molecular regulatory mechanisms that occur during the reproduction of E. sinensis. In this study, we performed the first comparative transcriptome analyses of the cerebral ganglion and hepatopancreas of E. sinensis during reproduction. The results indicate that E. sinensis has significant sexual dimorphism in signal transduction, metabolism, substance transportation, and cellular protection. This study aims to provide information that can be used as a basis for further research on the molecular mechanisms that underlie sexual dimorphism in E. sinensis during reproduction. Furthermore, the results can be used to support the development of the E. sinensis breeding industry and the restoration of wild E. sinensis.

Identification, expression and enzyme activity of the group III sPLA2 s in Cyprinus carpio L.

Five group III secreted phospholipase (pla2g3s) homologous genes located on different linkage groups were identified from common carp (Cyprinus carpio), which we named Ccpla2g3a1, Ccpla2g3a2, Ccpla2g3b, Ccpla2g3c1 and Ccpla2g3c2. The five genes encode 530, 525, 461, 752 and 753 amino acids, respectively. Sequence analysis showed that the Ccpla2g3as contain seven exons and the others contain four exons. Synteny analysis of fish pla2g3s indicated that pla2g3a and pla2g3b were from the same ancestor gene, and Ccpla2g3a1, Ccpla2g3a2, Ccpla2g3c1 and Ccpla2g3c2 were from the specific genome duplication of common carp. Due to the significant variation of the pla2g3bs from common carp and zebrafish (Danio rerio), they formed a separate group in the phylogenetic tree. The tissue distributions of Ccpla2g3s coincided with their expression profiles during the embryo stages. The expression levels of Ccpla2g3as and Ccpla2g3cs were low at the embryo stages, and they were abundant in the liver and brain, respectively, whereas the expression of Ccpla2g3b was high at 0.5 h after fertilization and in the ovary. We obtained three soluble recombinant proteins of the bee venom-like PLA2 (BVLP) from Ccpla2g3 and evaluated their PLA2 enzyme properties. The optimum pHs of MBP-a1-BVLP, MBP-b-BVLP and MBP-c1-BVLP were 7.5, 7.0 and 8.0, respectively, and specific activities were 7.68 ± 0.66, 4.155 ± 0.158 and 1.93 ± 0.05 U µmol-1 , respectively. The Kd for Ca2+ of MBP-b-BVLP was the lowest (2.6 µM), whereas the values for both MBP-a1-BVLP and MBP-c1-BVLP were about 15 µM. The Km values of three proteins ranged from 31.9 to 41.91 µM.

Cloning, expression analysis, and antibacterial propertiesof three serum amyloid A in common carp (Cyprinus carpio).

Three serum amyloid A (SAA) genes were identified from the common carp (Cyprinus carpio) by PCR and RT-PCR. Considering both direction and sequence similarity with mammal's orthologs, they were named CcSAA3a, CcSAA3b and CcSAA1. CcSAA3b and CcSAA1 are adjacent on contig LHQP01017858, suggesting that the prototype of or the simplest SAA multigene family have occurred in common carp. A phylogenetic analysis of the SAAs indicated that the fish SAAs were closer to those of invertebrates and Ornithorhynchus anatinus, a primitive mammal, than to mammalian SAAs. Quantitative real-time RT-PCR results displayed different expression profiles of three CcSAAs. The CcSAA3a was detected in all tested tissues, and was most abundant in the muscle; CcSAA3b was predominately expressed in the intestine and liver, and CcSAA1 in the skin. The expression level of CcSAA3a was higher than that of CcSAA3b and CcSAA1 in most tissues. Stimulation with Aeromonas hydrophila dramatically induced the expression of the three CcSAAs in all examined tissues, especially in the liver. Like Epinephelus coioides SAA, all of three rCcSAA fusion proteins could bind to both Gram-negative bacteria (A. hydrophila and E. coli) and Gram-positive bacterium (S. aureus), playing a role in the identification of bacteria. However, only rCcSAA3a showed significantly anti-A. hydrophila and anti-E. coli in vitro antibacterial activity assays. These results suggested that the three CcSAAs were in functional differentiation and play significant roles in the innate immunity of common carp.

Carbon Emission from Cascade Reservoirs: Spatial Heterogeneity and Mechanisms.

Carbon emission from reservoirs is considered to tarnish the green credentials of hydropower and has been extensively studied in single reservoirs. However, it remains unclear how carbon emission differs in cascade reservoirs and the mechanism behind the differences. In this study, carbon dioxide (CO2) and methane (CH4) emissions from cascade hydropower reservoirs were measured in the Lancang River, the Chinese section of the Mekong River. Our results demonstrate that carbon emissions from the river were increased by dam construction but exhibited spatial heterogeneity among cascade reservoirs. The first, most upstream, reservoir acted as the hotspot of CH4 and CO2 emissions, which were 13.1 and 1.7 times higher than those in downstream reservoirs, respectively. Similarly, the CH4/CO2 ratio of 0.023 in the first reservoir was higher than the others and made a greater contribution to the global warming effects of the cascade reservoirs. The sediment organic carbon in downstream reservoirs was negatively correlated with reservoir age (r2 = 0.993) and decreased at a rate of 0.389 mg g-1 yr-1, suggesting a potential decrease of carbon emission in the future. This study adds to our understanding of carbon emissions from cascade reservoirs and helps to screen effective strategies for future mitigation of the global warming effects from cascade hydropower systems.

Cloning and characterization of two duplicated interleukin-17A/F2 genes in common carp (Cyprinus carpio L.): Transcripts expression and bioactivity of recombinant IL-17A/F2.

Interleukin-17 (IL-17) plays an important role in inflammation and host defense in mammals. In this study, we identified two duplicated IL-17A/F2 genes in the common carp (Cyprinus carpio) (ccIL-17A/F2a and ccIL-17A/F2b), putative encoded proteins contain 140 amino acids (aa) with conserved IL-17 family motifs. Expression analysis revealed high constitutive expression of ccIL-17A/F2s in mucosal tissues, including gill, skin and intestine, their expression could be induced by Aeromonas hydrophila, suggesting a potential role in mucosal immunity. Recombinant ccIL-17A/F2a protein (rccIL-17A/F2a) produced in Escherichia coli could induce the expression of proinflammatory cytokines (IL-1ß) and the antimicrobial peptides S100A1, S100A10a and S100A10b in the primary kidney in a dose- and time-dependent manner. Above findings suggest that ccIL-17A/F2 plays an important role in both proinflammatory and innate immunity. Two duplicated ccIL-17A/F2s showed different expression level with ccIL-17A/F2a higher than b, comparison of two 5' regulatory regions indicated the length from anticipated promoter to transcriptional start site (TSS) and putative transcription factor binding site (TFBS) were different. Promoter activity of ccIL-17A/F2a was 2.5 times of ccIL-17A/F2b which consistent with expression results of two genes. These suggest mutations in 5'regulatory region contributed to the differentiation of duplicated genes. To our knowledge, this is the first report to analyze 5'regulatory region of piscine IL-17 family genes.

Transcriptome analysis reveals that insulin is an immunomodulatory hormone in common carp.

Common carp (Cyprinus carpio) is a widespread freshwater fish and economically important species in China and other East Asian countries. Recent studies suggest that insulin can alter the expression of immune genes and, thus, can be regarded as an immunomodulatory hormone. To understand the mechanism of the immune response to insulin, we performed a comparative RNA-seq transcriptome analysis using livers from common carp injected with insulin (5 µg/g bodyweight) or saline as a control. After filtering the low-quality reads and removing the adaptors, the clean raw reads were assembled into 60,421 unigenes with mean length of 746.81 bp. Furthermore, 37,107 unigenes were annotated based on homology after blast search in public databases. Differentially expressed genes were identified using the fragments per kb per million fragments method and EdgeR software. In total, 782 differentially expressed genes were found. Thereinto, 444 and 338 genes were upregulated and downregulated, respectively, in the insulin-injected group. A Gene Ontology analysis indicated that these genes were concentrated in glucose metabolism, hormone secretion, andimmune system processes. Moreover, 153 enriched KEGG pathways were associated with the differentially expressed genes, including the Toll-like receptor (TLR) and nuclear factor kappa beta (NF-κB) signaling pathways. Signal transducer and activator of transcription 1 (10.56-fold), TLR3 (0.089-fold), activator protein-1 (0.007-fold), tumor necrosis factor-α (0.139-fold), and macrophage inflammatory protein-1ß (0.038-fold) expression were significantly changed after the insulin injection. This study characterized the profile of genes expression response to insulin in common carp liver for the first time and provided new insight into understanding the molecular mechanism of insulin as an immunomodulatory hormone.

Development and evaluation of the first high-throughput SNP array for common carp (Cyprinus carpio).

BACKGROUND: A large number of single nucleotide polymorphisms (SNPs) have been identified in common carp (Cyprinus carpio) but, as yet, no high-throughput genotyping platform is available for this species. C. carpio is an important aquaculture species that accounts for nearly 14% of freshwater aquaculture production worldwide. We have developed an array for C. carpio with 250,000 SNPs and evaluated its performance using samples from various strains of C. carpio. RESULTS: The SNPs used on the array were selected from two resources: the transcribed sequences from RNA-seq data of four strains of C. carpio, and the genome re-sequencing data of five strains of C. carpio. The 250,000 SNPs on the resulting array are distributed evenly across the reference C.carpio genome with an average spacing of 6.6 kb. To evaluate the SNP array, 1,072 C. carpio samples were collected and tested. Of the 250,000 SNPs on the array, 185,150 (74.06%) were found to be polymorphic sites. Genotyping accuracy was checked using genotyping data from a group of full-siblings and their parents, and over 99.8% of the qualified SNPs were found to be reliable. Analysis of the linkage disequilibrium on all samples and on three domestic C.carpio strains revealed that the latter had the longer haplotype blocks. We also evaluated our SNP array on 80 samples from eight species related to C. carpio, with from 53,526 to 71,984 polymorphic SNPs. An identity by state analysis divided all the samples into three clusters; most of the C. carpio strains formed the largest cluster. CONCLUSIONS: The Carp SNP array described here is the first high-throughput genotyping platform for C. carpio. Our evaluation of this array indicates that it will be valuable for farmed carp and for genetic and population biology studies in C. carpio and related species.

Characterization and expression analysis of two distinct neuropeptide Ya paralogues in Jian carp (Cyprinus carpio var. Jian).

Two distinct neuropeptide Ya paralogues (jlNPYa1 and jlNPYa2) were cloned and characterized in Jian carp (Cyprinus carpio var. Jian), with a highly conserved organization encoded by four exons and three introns. The cDNAs for jlNPYa1 and jlNPYa2 were 693 and 730 bp in size, respectively. jlNPYa1 and jlNPYa2 both encoded a 96-amino acid protein, which shared 97.9 % identity. Phylogenetic tree showed that it has two NPYa genes, called jlNPYa1 and jlNPYa2, that presumably resulted from the tetraploidization event in the carp lineage. Analysis of expression profiles of jlNPYa1 and jlNPYa2 showed that the two NPY genes had a broad tissue distribution but expressed primarily in the forebrain, hypothalamus, testis and liver. The expression pattern was different in juvenile and adult (female and male) Jian carp. In juvenile, the highest expression level of jlNPYa1 and jlNPYa2 was detected in the testis. In adult, it was detected in the forebrain. In female hypothalamus, the expression level of jlNPYa1 was significantly higher than that of jlNPYa2. However, the opposite was true in male hypothalamus. The differing distribution patterns of the two NPY genes suggested that jlNPYa1 and jlNPYa2 might play different roles in Jian carp.

[Sequences analysis of jlFABP2 and the correlation between polymorphisms and body weight gain in Cyprinus carpio var. jian].

Two replicate intestine fatty acid binding protein genes (jlFABP2a and jlFABP2b) were cloned from Cyprinus carpio var. jian using PCR. Both ORFs were 399 bp in length sharing 92.2% similarity with each other, and 88.0% and 90.5% with their counterpart in zebrafish, respectively. The gene structure of jlFABP2s was same as other FABPs, which contained four exons and three introns. Sequences and lengths of introns between 2a and 2b. were obviously different Phylogenetic tree displayed that two jlFABP2s corresponded to one zebrafish FABP2 which matches the fact that the chromosome number of common carp was twice of zebrafish. Real time-PCR showed that jlFABP2 genes mainly expressed in intestine and the expression level was very significantly higher than other tissues such as brain, liver, muscle, kidney, and gonad (P<0.01). The expression level of jlFABP2a was significantly (male, P<0.05) or very significantly (females, P<0.01) higher than 2b in intestine; and 2b was expressed slightly higher than 2a in other tissues. It seemed that 2a expressed specifically in intestine, while 2b expressed ubiquitously. Twelve and four SNP loci were found at jlFABP2a and 2b introns through comparison sequences from 8 individuals, respectively. Genotypes of I1-A15G, I1-A99G, I2-C487T, and I3-A27T on jlFABP2a were detected using PCR-RFLP in selection population of C. carpio var. jian. The SNP genotypes and individual weight gain correlation indicated that four SNPs were significantly (P<0.05 or P<0.01) associated with adult weight gain. Diplotype analysis displayed that individuals with genotype AGGGCCXX or AGGGXXAT grew faster than other individuals by 15%. The individuals with these two genotypes only occupied 9% in total selection populations, indicating the presence of large selection space. The 4 SNPs detected in this experiment can be used in C. carpio var. Jian growth selection breeding plan.

Controlling internal nitrogen and phosphorus loading using Ca-poor soil capping in shallow eutrophic lakes: Long-term effects and mechanisms.

Clean soil is a potential capping material for controlling internal nutrient loading and helping the recovery of macrophytes in eutrophic lakes, but the long-term effects and underlying mechanisms of clean soil capping under in-situ conditions remain poorly understood. In this study, a three-year field capping enclosure experiment combining intact sediment core incubation, in-situ porewater sampling, isotherm adsorption experiments and analysis of sediment nitrogen (N) and phosphorus (P) fractions was conducted to assess the long-term performance of clean soil capping on internal loading in Lake Taihu. Our results indicate that clean soil has excellent P adsorption and retention capacity as an ecologically safe capping material and can effectively mitigate NH4+-N and SRP (soluble reactive P) fluxes at the sediment-water interface (SWI) and porewater SRP concentration for one year after capping. The mean NH4+-N and SRP fluxes of capping sediment were 34.86 mg m-2 h-1 and -1.58 mg m-2 h-1, compared 82.99 mg m-2 h-1 and 6.29 mg m-2 h-1 for control sediment. Clean soil controls internal NH4+-N release through cation (mainly Al3+) exchange mechanisms, while for SRP, clean soil can not only react with SRP due to its high Al and Fe content, but also stimulate the migration of active Ca2+ to the capping layer, thus precipitating as Ca-bound P (Ca-P). Clean soil capping also contributed to the restoration of macrophytes during the growing season. However, the effect of controlling internal nutrient loading only lasted for one year under in-situ conditions, after which the sediment properties returned to pre-capping conditions. Our results highlight that clean Ca-poor soil is a promising capping material and further research is needed to extend the longevity of this geoengineering technology.

[Establishment of a Patient-Derived T-Cell Acute Lymphoblastic Leukemia Xenograft Model in Novel Immunodeficient NCG Mice].

OBJECTIVE: The leukemia cells from patients with T-cell acute lymphoblastic leukemia (T-ALL) were inoculated into NCG mice to establish a stable human T-ALL leukemia animal model. METHODS: Leukemia cells from bone marrow of newly diagnosed T-ALL patients were isolated, and the leukemia cells were inoculated into NCG mice via tail vein. The proportion of hCD45 positive cells in peripheral blood of the mice was detected regularly by flow cytometry, and the infiltration of leukemia cells in bone marrow, liver, spleen and other organs of the mice was detected by pathology and immunohistochemistry. After the first generation mice model was successfully established, the spleen cells from the first generation mice were inoculated into the second generation mice, and after the second generation mice model was successfully established, the spleen cells from the second generation mice were further inoculated into the third generation mice, and the growth of leukemia cells in peripheral blood of the mice in each group was monitored by regular flow cytometry to evaluate the stability of this T-ALL leukemia animal model. RESULTS: On the 10th day after inoculation, hCD45+ leukemia cells could be successfully detected in the peripheral blood of the first generation mice, and the proportion of these cells was gradually increased. On average, the mice appeared listless 6 or 7 weeks after inoculation, and a large number of T lymphocyte leukemia cells were found in the peripheral blood and bone marrow smear of the mice. The spleen of the mice was obviously enlarged, and immunohistochemical examination showed that hCD3+ leukemia cells infiltrated into bone marrow, liver and spleen extensively. The second and third generation mice could stably develop leukemia, and the average survival time was 4-5 weeks. CONCLUSION: Inoculating leukemia cells from bone marrow of patients with T-ALL into NCG mice via tail vein can successfully construct a patient-derived tumor xenografts (PDTX) model.

Identification of housekeeping genes suitable for gene expression analysis in Jian carp (Cyprinus carpio var. jian).

Jian carp (Cyprinus carpio var. jian) is an important economic fish species cultured in China. In this report, we performed a systematic analysis to identify an appropriate housekeeping (HK) gene for the study of gene expression in Jian carp. For this purpose, partial DNA sequences of four potential candidate genes (elongation factor 1 alpha (EF-1α), glyceraldehyde-3-phosphate (GAPDH), beta-actin (ACTB), and 18S ribosomal RNA (18S rRNA) were isolated, and their expression levels were studied using RNA extracted from nine tissues (forebrain, hypothalamus, liver, fore-intestine, hind-intestine, ovary, muscle, heart, kidney) in juvenile and adult Jian carp. Gene expression levels were quantified by quantitative real time RT-PCR (qRT-PCR), and expression stability was evaluated by comparing the coefficients of variation (CV) of the Ct values. The results showed that EF-1α was the most suitable HK gene in all tissues of juvenile and adult Jian carp. However, at distinct juvenile and adult developmental stages, there was not a single optimal gene for normalization of expression levels in all tissues. EF-1α was the most stable gene only in forebrain, hypothalamus, liver, heart, and kidney. These results provide data that can be expected to aid gene expression analysis in Jian carp research, but underline the importance of identifying the optimal HK gene for each new experimental paradigm.

[Microsatellite markers for parentage identification in Jian Carp (Cyprinus carpio var. Jian)].

Using 16 microsatellite loci we estimated the parentage of 647 progeny in 10 Jian Carp full-sib families. Cervus 3.0 analysis showed that mean PIC value of 16 microsatellites, mean number of allele, and mean expected heterozygosity were 0.7025, 6.63, and 0.7405, respectively. The combined probability of exclusion was 0.99922456 when both parents were unknown and the combined probability of exclusion was 0.99999557 when only one of the parental genotype was known, with the confidence level of 95%. Further simulations based on allele frequencies suggested that to achieve the requirements of paternity test usually took 8 to 12 microsatellite loci when both parents were unknown and 5 to 8 microsatellite loci when one parent was known. Out of 647 progenies, 94.6% were assigned to their parental pairs without the information of both parents in parentage analysis, which were lower than the theoretical assignment rates predicted by the Cervus simulations. This could be explained by the relationship between the candidate parents or existence of null and by typing errors. The identification of 9 families was useful for linkage analysis of Jian Carp and QTL location, also for marker assisted selection for economical traits.

Pathways of soil N2O uptake, consumption, and its driving factors: a review.

Nitrous oxide (N2O) is an important greenhouse gas that plays a significant role in atmospheric photochemical reactions and contributes to stratospheric ozone depletion. Soils are the main sources of N2O emissions. In recent years, it has been demonstrated that soil is not only a source but also a sink of N2O uptake and consumption. N2O emissions at the soil surface are the result of gross N2O production, uptake, and consumption, which are co-occurring processes. Soil N2O uptake and consumption are complex biological processes, and their mechanisms are still worth an in-depth systematic study. This paper aimed to systematically address the current research progress on soil N2O uptake and consumption. Based on a bibliometric perspective, this study has highlighted the pathways of soil N2O uptake and consumption and their driving factors and measurement techniques. This systematic review of N2O uptake and consumption will help to further understand N transformations and soil N2O emissions.

Understanding the Heavy Metal Pollution Pattern in Sediments of a Typical Small- and Medium-Sized Reservoir in China.

Heavy metal pollution in sediments is a common environmental issue in small- and medium-sized reservoirs not only in China but also worldwide; however, few interpretations of the pollution pattern exist. Based on the analyses of accumulation characteristics, ecological risks, and source apportionments of eight heavy metals (As, Cd, Cr, Cu, Hg, Pb, Ni, and Zn) in sediments, we derived a paradigm to describe the pollution pattern of heavy metals in sediments of a typical small- and medium-sized Tongjiqiao Reservoir. The results showed high levels of Cd, Hg, and As pollutants in the surface and upper sediment layers of the pre-dam area. Additionally, As, Cd, Hg, and Pb pollutants peaked in the middle layers of the inflow area, indicating a high ecological risk in these areas. The positive matrix factorization results implied that industrial, agricultural, and transportation activities were the main sources of heavy metals. The heavy metal pollution pattern exhibited three distinct stages: low contamination, rapid pollution, and pollution control. This pattern explains the heavy metal pollution process in the sediments and will provide scientific guidance for realizing the green and sustainable operation and development of the reservoir.

Soil moisture determines nitrous oxide emission and uptake.

Soils are major sources and sinks of nitrous oxide (N2O). The main pathway of N2O emission is performed through soil denitrification; however, the uptake phenomenon in denitrification is overlooked, leading to an underestimation of N2O production. Soil moisture strongly influences denitrification rates, but exact quantifications coupled with nosZ, nirK, and nirS gene analysis remain inadequately unaccounted for. In this study, a 15N-N2O pool dilution (15N2OPD) method was used to measure N2O production rates under different soil moisture levels. Therefore, 20%, 40%, 60%, 80% and 100% soil water holding capacity (WHC) were used. The results revealed that N2O uptake rates increased proportionally with soil moisture content and peaked at 80% WHC with 4.17 ± 2.74 µg N kg-1 soil h-1. The N2O production and net emission rates similarly peaked at 80% WHC, reading at 32.50 ± 4.86 and 27.63 ± 3.09 µg N kg-1 soil h-1 during the incubation period (18 days). Soil moisture content increased the gene copy number of the nosZ, NH4+ content, and denitrification potential in soil. N2O uptake at WHC 80-100% was significantly greater than that at WHC 20-60%. It was attributed to a decrease in O2 and the high NO3- concentration inhibition (> 50 mg N kg-1 of soil NO3--N content). Principal components analysis (PCA) indicated that the number of nosZ genes was the major driver of N2O uptake, especially nosZ clade II. Thus, the results of this study deepen our understanding of the mechanisms underpinning N2O sources and sinks in soils and provide a useful gene-based indicator to estimate N2O uptake.

Alterations of amino acid metabolism and intestinal microbiota in Chinese mitten crab (Eriocheir sinensis) fed on formulated diet and iced trash fish.

Formulated diet (FD) and iced trash fish (ITF) are common diets during E. sinensis farming. However, whether FD can completely replace ITF during long-term E. sinensis farming is still unclear. Thus this study was conducted to compare the differences in amino acid metabolism and intestinal microbiota of the E. sinensis fed on different diets. The crabs were randomly divided into three groups fed on FD, ITF and mixed diet (MD, FD: ITF = 1:1), respectively. The results showed that there were no significant differences in amino acid composition among FD, MD and ITF groups. The activities of AST and ALT, and the mRNA levels of amino acid metabolism-related genes were significantly up-regulated in FD or/and MD groups compared with ITF group. The diversity of intestinal bacterial community was similar between the FD and ITF groups, but the relative abundance of dominant taxa showed marked differences between the two groups. At the phylum level, the relative abundance of Firmicutes was significantly higher, but the relative abundance of Proteobacteria was significantly lower in the FD group than that in ITF group. Meanwhile, at genus level, the relative abundance of Candidatus_Hepatoplasma in FD was higher than that in ITF group. Data related to functional prediction demonstrated that the significantly differenced pathways between the two groups were observed in metabolism (Pyrimidine metabolism, Glycolysis/Gluconeogenesis and Citrate cycle) and environmental information processing (transporters). The overall results indicated that replacement of ITF by FD did not affect amino acid composition, but altered amino acid metabolism and the relative abundance of intestinal microbiota. Our data provided a valuable reference for FD application replacing ITF during long-term E. sinensis farming.