Dissimilatory nitrate reduction processes in surface sediments of shrimp ponds during the culture period

Intensive aquaculture in estuaries and coasts has resulted in several ecological and environmental problems. Among various nitrogen transformation pathway, dissimilatory nitrate (NO3-) reduction is considered to be highly important in regulating reactive nitrogen. However, there are relatively few studies on the processes and contribution of NOx- reduction in sediment during the shrimp pond culture period. Three sediment NO3- reduction processes, denitrification (DNF), anaerobic ammonium oxidation (ANA), and dissimilatory NO3- reduction to ammonium (DNRA), were surveyed in eight shrimp ponds across three subtropical estuaries using 15N isotope tracing experiments. The rates of DNF, ANA and DNRA ranged from 2.87–18.11, 0.10–1.92, and 0.21–1.25 nmol N g -1 h -1, respectively. DNF was responsible for 64.2–91.6% of the total NO3- reduction. Regarding environmental factors, C and N substrates, as well as salinity, significantly affected NO3- reduction. In general, the N losses were approximately 32.43–131.64 g N m-2 yr-1 for DNF and 2.38–15.85 g N m-2 yr-1 for ANA in this study, indicating that coastal reclamation is a nonnegligible way to remove nitrogen. Our results provide a scientific foundation for understanding the mechanism of nitrogen cycling in the artificial aquatic environment of shrimp ponds

The impact of fintech development on the entrepreneurial behavior of farmers: evidence from the China Household Finance Survey

Abstract Fintech is disrupting the traditional financial models with the power of technology. Will it solve the problems faced by farmers in starting their own businesses and stimulate the vitality of rural entrepreneurship? In this paper, we focus on the impact of fintech development on the entrepreneurial behavior of farmers in China. First, we theoretically analyze the effects of fintech development on the entrepreneurial behavior of farmers and put forward the corresponding theoretical hypotheses. Second, using data from Baidu search index and the China Household Finance Survey (CHFS), we employ a Probit model to verify our theoretical hypotheses. Our findings suggest that (1) fintech development encourages farmer entrepreneurial behavior, (2) it achieves this by alleviating credit constraints, information constraints, and risk aversion effects, (3) in terms of the type of entrepreneurship, the development of fintech mainly promotes survival entrepreneurship among farmers, while the entrepreneurial effect of fintech is more significant among farmers with low education level, low income level and in the central and western regions. Overall, our study provides timely insights into boosting farmer entrepreneurship in emerging countries such as China by leveraging the potential of fintech

Shifts of ammonia-oxidation process along salinity gradient in an estuarine wetland

Ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) play an important role in nitrogen (N) cycling of the estuarine sediments. However, the shifts of potential ammonia oxidation rates (PARs) of AOA and AOB along different salinity gradients are not well understood. Here, salinity-treated (0, 5, 15, 25 and 35 ‰) incubation experiments of sediment from the Pearl River Estuary were performed to explore the influence of salinity on ammonia oxidation process, including the PARs and gene abundances of AOA and AOB. Significant shifts of PARs and amoA gene abundances of ammonia oxidation process along salinity gradient were observed during the incubation (0–60 d). After a long-term incubation, both PARtotal (4.61 ± 0.93 μg N g−1 d−1) and PARaob (3.05 ± 1.04 μg N g−1 d−1) reached their maximum values at 25 ‰ salinity, and PARaoa (1.96 ± 0.10 μg N g−1 d−1) reached its maximum values at 35 ‰ salinity, which showed that PARs had higher values under high salinity conditions. AOB amoA gene was more abundant than AOA under moderate and high salinity, and only a significant linear correlation was observed between PARaob and AOB abundances. In addition, the ammonia oxidation activities showed a wide range of salinity tolerance, which is worthy of further study on community structure and transcript richness. Our study illustrates that salinity plays a key role in regulating the ammonia oxidation process in estuarine sediments, and has guiding significance for N fixation and N loss associated with saltwater incursion

Identification and characterization of microRNAs from the tube foot in the sea urchin Strongylocentrotus intermedius

MicroRNAs (miRNAs) play critical roles in regulating many bio-processes of eukaryotes. The sea urchin Strongylocentrotus intermedius (an important fishery resource) is of great economic importance in Japan, North Korea, Russia, and China. In the current study, miRNAs of tube foot in S. intermedius were firstly identified and characterized. Data in this study can provide more genomic information for the further understanding of the complex regulation network in sea urchins and present a new way for monitoring the health status of cultured sea urchins

Distant hybrids of Heliocidaris crassispina (♀) and Strongylocentrotus intermedius (♂): identification and mtDNA heteroplasmy analysis

Abstract Background Distant hybridization between the sea urchin Heliocidaris crassispina (♀) and the sea urchin Strongylocentrotus intermedius (♂) was successfully performed under laboratory conditions. A new variety of hybrid sea urchin (HS hybrid) was obtained. However, the early-development success rates for the HS hybrids were significantly lower than those of purebred H. crassispina or S. intermedius offspring. In addition, it was difficult to distinguish the HS-hybrid adults from the pure H. crassispina adults, which might lead to confusion in subsequent breeding attempts. In this study, we attempted to develop a method to quickly and effectively identify HS hybrids, and to preliminarily investigate the molecular mechanisms underlying the poor early-development success rates in the HS hybrids. Results The hybrid sea urchins (HS hybrids) were identified both morphologically and molecularly. There were no significant differences in the test height to test diameter ratios between the HS hybrids and the parents. The number and arrangement of ambulacral pore pairs in the HS hybrids differed from those of the parental lines, which might serve as a useful morphological character for the identification of the HS hybrids. A primer pair that identified the HS hybrids was screened by comparing the mitochondrial genomes of the parental lines. Moreover, paternal leakage induced mitochondrial DNA heteroplasmy in the HS hybrids, which might explain the low rates of early development success in these hybrids. Conclusions The distant-hybrid sea urchins were accurately identified using comparative morphological and molecular genetic methods. The first evidence of mtDNA heteroplasmy after the distant hybridization of an echinoderm was also provided

Salinity effects on soil P cycling

[Methods] The field experiments were conducted in the growing (July) and non-growing seasons (January) in both the freshwater and brackish C. malaccensis wetlands. Three 1 × 1 m quadrats (5 m apart) were randomly established at each site, and three soil cores (0–20 cm) were randomly collected in each quadrat and pooled into one sample. All samples were then stored in a portable refrigerator and immediately transported to the laboratory. The samples were homogenized and then split into two subsamples: one subsample was air-dried for the determination of P fractions and physicochemical parameters, and the other subsample was frozen at −80°C for DNA extraction. Plant biomasses were also collected during each season. We used the Hedley scheme of sequential extraction to estimate the fractions and availabilities of soil P (Hedley et al., 1982), which can effectively distinguish between Pi and Po. Briefly, soil samples were successively extracted using an anion-exchange resin (resin-P), 0.5 M NaHCO3 (NaHCO3-Pi and NaHCO3-Po), 0.1 M NaOH (NaOH-Pi and NaOH-Po), 0.1 M NaOH with sonication (NaOHs-Pi and NaOHs-Po), and 1 M HCl (HCl-Pi). The residual soils were then digested with 4 mL of H2SO4 and 1 mL of HClO4 (residual-P). The concentration of P was measured using a spectrophotometer. The P was further classified as labile P (resin-P, NaHCO3-Pi, and NaHCO3-Po), moderately labile P (NaOH-Pi and NaOH-Po), and stable P (NaOHs-Pi, NaOHs-Po, HCl-P, and residual-P) based on its availability to plants and microbes (Rodrigues et al., 2016). The salinity of the water was measured in situ using a salinometer (Oakton Instruments, Springfield, USA). Soil electric conductivity (EC) and pH were determined using a 2265FS EC meter (Spectrum Technologies Inc., Aurora, USA) and a pH meter (IQ Scientific Instruments, Carlsbad, USA), respectively. Soil moisture was evaluated by determining the amount of water lost at 105°C. Soil organic C (SOC) was analyzed using the dichromate oxidation method. Soil concentrations of total C (TC) and N (TN) were measured using an elemental analyzer (Elementar, Frankfurt, Germany). Soil concentrations of ammonium-N (NH4+-N) and nitrate-N (NO3−-N) were determined using flow-injection analysis (Skalar Analytical SAN++, Lachat, Netherland) and extraction with 2 M KCl. The soil texture was determined using a Mastersizer 2000 particle-size analyzer (Malvern Panalytical Ltd., Melvin, UK). Plant biomasses were measured by drying samples to constant weight at 70°C. Soil microbial DNA was extracted using an OMEGA DNA Kit following the manufacturer’s instructions. The quality and quantity of the extracted DNA were determined using a NanoDrop ND-1000 spectrophotometer (Thermo Fisher Scientific, Waltham, USA) and agarose gel electrophoresis, respectively. The extracted microbial DNA was processed, and metagenomic shotgun sequencing libraries were constructed with insert sizes of 400 bp using an Illumina TruSeq Nano DNA LT Library Preparation Kit. Each library was sequenced on an Illumina HiSeq X-ten platform (Illumina, San Diego, USA) using the PE150 strategy at Personal Biotechnology Co., Ltd. (Shanghai, China). Please refer to the Supporting Information for more detailed descriptions (Appendix I). We obtained a total of 931 million qualified sequences from 12 metagenomes, ranging from 69 million to 88 million sequences per sample for downstream analyses (Table S1). [Usage Notes] The dataset can be opened using regular Office software.Accelerated sea-level rise is expected to cause the salinization of freshwater wetlands, but the responses to salinity of the availability of soil phosphorus (P) and of microbial genes involved in the cycling and transformation of P remain unexplored. Our results suggest that the P-cycling microbial community abundance and P availability respond positively to moderate increases in salinity by promoting the microbial solubilization and mineralization of soil P in brackish wetlands. Changes in microbial communities and microbially mediated P cycling may represent microbial strategies to adapt to moderate salinity levels, which in turn control soil function and nutrient balance.National Natural Science Foundation of China. Natural Science Foundation of Fujian Province. Fundación Ramón Areces Project. Spanish Government. Catalan Government.Peer reviewe

Reclamation of tidal flats to paddy soils reshuffles the soil microbiomes along a 53-year reclamation chronosequence: Evidence from assembly processes, co-occurrence patterns and multifunctionality

Coastal soil microbiomes play a key role in coastal ecosystem functioning and are intensely threatened by land reclamation. However, the impacts of coastal reclamation on soil microbial communities, particularly on their assembly processes, co-occurrence patterns, and the multiple soil functions they support, remain poorly understood. This impedes our capability to comprehensively evaluate the impacts of coastal reclamation on soil microbiomes and to restore coastal ecosystem functions degraded by reclamation. Here, we investigated the temporal dynamics of bacterial and fungal communities, community assembly processes, co-occurrence patterns, and ecosystem multifunctionality along a 53-year chronosequence of paddy soil following reclamation from tidal flats. Reclamation of tidal flats to paddy soils resulted in decreased β-diversity, increased homogeneous selection, and decreased network complexity and robustness of both bacterial and fungal communities, but caused contrasting α-diversity response patterns of them. Reclamation of tidal flats to paddy soils also decreased the multifunctionality of coastal ecosystems, which was largely associated with the fungal network complexity and α-diversity. Collectively, this work demonstrates that coastal reclamation strongly reshaped the soil microbiomes at the level of assembly mechanisms, interaction patterns, and functionality level, and highlights that soil fungal community complexity should be considered as a key factor in restoring coastal ecosystem functions deteriorated by land reclamation

Dual spectrometer system with spectral compounding for 1-μm optical coherence tomography in vivo

1 μm axial resolution spectral domain optical coherence tomography (OCT) is demonstrated for in vivo cellular resolution imaging. Output of two superluminescent diode sources is combined to provide near infrared illumination from 755 to 1105 nm. The spectral interference is detected using two spectrometers based on a Si camera and an InGaAs camera, respectively. Spectra from the two spectrometers are combined to achieve an axial resolution of 1.27 μm in air. Imaging was conducted on zebra fish larvae to visualize cellular details.NMRC (Natl Medical Research Council, S’pore)Accepted versio

One-micron resolution optical coherence tomography (OCT) in vivo for cellular level imaging

We developed a spectral domain OCT system combining two NIR, CW light sources of different spectral range. Its resolving power is validated by visualizing the cellular structures of zebra fish larvae in vivo. An NIR extended illumination from 755-1100 nm is achieved. The axial resolution is 1.27 μm in air, corresponding to 0.93μm in tissue (n=1.36), which is the highest axial resolution using NIR, CW laser sources up to date to the best of our knowledge. In vivo imaging is conducted to demonstrate the resolving power of proposed one-micron resolution OCT system. The top and bottom surfaces of individual disk-like red blood cell is reliably visualized, as well as flat, spindle shaped endothelial cells lining along the luminal surface of the blood vessel wall. This study provides a viable solution for cellular and subcellular level OCT imaging system which is also very competitive in cost.Published versio