Microbial community structure analyses and cultivable denitrifier isolation of Myriophyllum aquaticum constructed wetland under low C/N ratio

With the rapid expansion of livestock production,the amount of livestock wastewater accumulated rapidly.Lack of biodegradable organic matter makes denitrification of livestock wastewater after anaerobic digestion more difficult.In this study,Myriophyllum aquaticum constructed wetlands(CWs)with efficient nitrogen removal performance were established under different carbon/nitrogen(C/N)ratios.Analysis of community composition reveals the change of M.aquaticum CWs in microbial community structure with C/N ratios.The proportion of Proteobacteria which is one of the dominant phyla among denitrifier communities increased significantly under low C/N ratio conditions.Besides,to obtain cultivable denitrifier that could be added into CWs in situ,33 strains belonging to phylum Proteobacteria were isolated from efficient M.aquaticum CWs,while the best-performing denitrification strain M3-1 was identified as Bacillus velezensis JT3-1(GenBank No.CP032506.1).Redundancy analysis and quadratic models showed that C/N ratio had significant effects on disposal of nitrate(NO_(3)^(−)-N)and the strains isolated could perform well in denitrification when C/N ratio is relatively low.In addition,they have relatively wide ranges of carbon sources,temperature and a high NO_(3)^(−)removal rate of 9.12 mg/(L·hr)at elevated concentrations of 800 mg/L nitrate.Thus,strains isolated from M.aquaticum CWs with low C/N ratio have a practical application value in the treatment of nitrate-containing wastewater.These denitrifying bacteria could be added to CWs to enhance nitrogen removal efficiency of CWs for livestock wastewater with low C/N ratio in the future.

Effects of lighting mode on the growth performance,cortisol level and oxidative stress of juvenile Chinese three-keeled pond turtle(Chinemys Reevesii)

To improve the light environment and welfare of the turtle cultured indoors,the effects of lighting mode on growth performance,cortisol level,and oxidative stress of juvenile Chinese three-keeled pond turtle,Chinemys reevesii,were investigated in this study.The experimental turtles with an initial weight of 5.61±0.09 g were reared in tanks under four different lighting modes:three groups with light(lighting the basking area and water area,LBW;lighting the water area only,LW;lighting the basking area only,LB)and control group(no light,NL).The experiment was conducted for more than six months,with each group having three replicates.After 203 d of the experiment,the turtle in the LW group exhibited higher weight gain rate(WGR)and a specific growth rate(SGR,%/d)compared to other treatments.Also,results showed that the final body weight of the turtle exposed to LW was higher than that exposed to other treatments.On the physiological level,serum cortisol level in turtles exposed to LW was significantly lower than that in other treatments.Regarding oxidative stress,the level of catalase(CAT)in turtles exposed to LW and LB was significantly lower than that exposed to LBW and NL.The malonaldehyde(MDA)activity in turtles exposed to LW was significantly lower than other treatments.Based on the growth performance and health status,it is suggested that lighting the water area only is the optimal lighting mode for the juvenile threekeeled pond turtle cultured indoors.

A quantitative study of the scale and distribution of tight gas reservoirs in the Sulige gas field, Ordos Basin, northwest China

Gas and water distribution is discontinuous in tight gas reservoirs,and a quantitative understanding of the factors controlling the scale and distribution of effective reservoirs is important for natural gas exploration.We used geological and geophysical explanation results,dynamic and static well test data,interference well test and static pressure test to calculate the distribution and characteristics of tight gas reservoirs in the H_(8) Member of the Shihezi Formation,Sulige gas field,Ordos Basin,northwest China.Our evaluation system examines the scale,physical properties,gas-bearing properties,and other reservoir features,and results in classification of effective reservoirs into types Ⅰ,Ⅱ,and Ⅲ that differ greatly in size,porosity,permeability,and saturation.The average thickness,length,and width of type Ⅰ effective reservoirs are 2.89,808,and 598 m,respectively,and the porosity is>10.0%,permeability is>1010^(–3)µm^(2),and average gas saturation is>60%.Compared with conventional gas reservoirs,tight gas effective reservoirs are small-scale and have low gas saturation.Our results show that the scale of the sedimentary system controls the size of the dominant microfacies in which tight gas effective reservoirs form.The presence of different types of interbeds hinders the connectivity of effective sand body reservoirs.The gas source conditions and pore characteristics of the reservoirs control sand body gas filling and reservoir formation.The physical properties and structural nature of the reservoirs control gas–water separation and the gas contents of effective reservoirs.The results are beneficial for the understanding of gas reservoir distribution in the whole Ordos Basin and other similar basins worldwide.

Effects of flow velocity on water quality and ammonia excretion in recirculating aquaculture system culturing juvenile largemouth bass(Micropterus salmoides)

Flow velocity plays an important role in recirculating aquaculture systems(RAS)and the growing practice of culturing juvenile largemouth bass(Micropterus salmoides).In this study,the effects of flow velocity on the water quality as well as the ammonia excretion were discussed from the perspective of actual production,and a polynomial model of ammonia nitrogen excretion was established,using the juvenile largemouth bass.Results showed that the range of ammonia nitrogen and nitrite nitrogen decreased with flow velocity increasing,while the number and volume share of large particles increased.According to the polynomial model,compared with the medium flow velocity(11 cm/s,2.45 body length(bl)/s),the ammonia excretion of juvenile largemouth bass at high(18 cm/s,4.00 bl/s),and low(4 cm/s,0.90 bl/s)flow velocity changed faster with time,and the excretion rate peaked at the 6th hour after feeding,earlier than that under medium flow velocity.Therefore,it is suggested to increase the flow velocity at the 5th hour after feeding and then decreased it at the 10th hour,to ensure better water quality in RAS culturing juvenile largemouth bass.