Zooplankton community size-structure change and mesh size selection under the thermal stress caused by a power plant in a semi-enclosed bay

Zooplankton samples were collected using 505, 160 and 77 μm mesh nets around a power plant during four seasons in 2011. We measured total length of zooplankton and divided zooplankton into seven size classes in order to explore how zooplankton community size-structure might be altered by thermal discharge from power plant. The total length of zooplankton varied from 93.7 to 40 074.7 μm. The spatial distribution of mesozooplankton(200-2 000 μm) populations were rarely affected by thermal discharge, while macro-(2 000-10 000 μm)and megalo-zooplankton(>10 000 μm) had an obvious tendency to migrate away from the outfall of power plant.Thus, zooplankton community tended to become smaller and biodiversity reduced close to power plant.Moreover, we compared the zooplankton communities in three different mesh size nets. Species richness,abundance, evenness index and Shannon-Wiener diversity index of the 505 μm mesh size were significantly lower than those recorded from the 160 and 77 μm mesh size. Average zooplankton abundance was highest in the 77 μm mesh net((27 690.0±1 633.7) ind./m^3), followed by 160 μm mesh net((9 531.1±1 079.5) ind./m^3), and lowest in 505 μm mesh net((494.4±104.7) ind./m^3). The ANOSIM and SIMPER tests confirmed that these differences were mainly due to small zooplankton and early developmental stages of zooplankton. It is the first time to use the 77 μm mesh net to sample zooplankton in such an environment. The 77 μm mesh net had the overwhelming abundance of the copepod genus Oithona, as an order of magnitude greater than recorded for 160 μm mesh net and 100% loss through the 505 μm mesh net. These results indicate that the use of a small or even multiple sampling net is necessary to accurately quantify entire zooplankton community around coastal power plant.

Development of a simplified and inexpensive RNA depletion method for plasmid DNA purification using size selection magnetic beads(SSMBs)

Plasmid DNA(pDNA)isolation from bacterial cells is one of the most common and critical steps in molecular cloning and biomedical research.Almost all pDNA purification in-volves disruption of bacteria,removal of membrane lipids,proteins and genomic DNA,purifi-cation of pDNA from bulk lysate,and concentration of pDNA for downstream applications.While many liquid-phase and solid-phase pDNA purification methods are used,the final pDNA preparations are usually contaminated with varied degrees of host RNA,which cannot be completely digested by RNase A.To develop a simple,cost-effective,and yet effective method for RNA depletion,we investigated whether commercially available size selection magnetic beads(SSMBs),such as Mag-Bind®TotalPure NGS Kit(or Mag-Bind),can completely deplete bacterial RNA in pDNA preparations.In this proof-of-principle study,we demonstrated that,compared with RNase A digestion and two commercial plasmid affinity purification kits,the SSMB method was highly efficient in depleting contaminating RNA from pDNA minipreps.Gene transfection and bacterial colony formation assays revealed that pDNA purified from SSMB method had superior quality and integrity to pDNA samples cleaned up by RNase A digestion and/or commercial plasmid purification kits.We further demonstrated that the SSMB method completely depleted contaminating RNA in large-scale pDNA samples.Furthermore,the Mag-bind-based SSMB method costs only 5-10%of most commercial plasmid purification kits on a per sample basis.Thus,the reported SSMB method can be a valuable and inexpensive tool for the removal of bacterial RNA for routine pDNA preparations.

Freeze–thaw effects on erosion process in loess slope under simulated rainfall

Seasonal freeze–thaw processes have led to severe soil erosion in the middle and high latitudes.The area affected by freeze–thaw erosion in China exceeds 13%of the national territory.So understanding the effect of freeze–thaw on erosion process is of great significance for soil and water conservation as well as for ecological engineering.In this study,we designed simulated rainfall experiments to investigate soil erosion processes under two soil conditions,unfrozen slope(UFS)and frozen slope(FS),and three rainfall intensities of 0.6,0.9 and 1.2 mm/min.The results showed that the initial runoff time of FS occurred much earlier than that of the UFS.Under the same rainfall intensity,the runoff of FS is 1.17–1.26 times that of UFS;and the sediment yield of FS is 6.48–10.49 times that of UFS.With increasing rainfall time,rills were produced on the slope.After the appearance of the rills,the sediment yield on the FS accounts for 74%–86%of the total sediment yield.Rill erosion was the main reason for the increase in soil erosion rate on FS,and the reduction in water percolation resulting from frozen layers was one of the important factors leading to the advancement of rills on slope.A linear relationship existed between the cumulative runoff and the sediment yield of UFS and FS(R2>0.97,P<0.01).The average mean weight diameter(MWD)on the slope erosion particles was as follows:UFS0.9(73.84μm)>FS0.6(72.30μm)>UFS1.2(72.23μm)>substrate(71.23μm)>FS1.2(71.06μm)>FS0.9(70.72μm).During the early stage of the rainfall,the MWD of the FS was relatively large.However,during the middle to late rainfall,the particle composition gradually approached that of the soil substrate.Under different rainfall intensities,the mean soil erodibility(MK)of the FS was 7.22 times that of the UFS.The ratio of the mean regression coefficient C2(MC2)between FS and UFS was roughly correspondent with MK.Therefore,the parameter C2 can be used to evaluate soil erodibility after the appearance of the rills.This article explored the influence mechanism of freeze–thaw effects on loess soil erosion and provided a theoretical basis for further studies on soil erosion in the loess hilly regions.

Geographical classification of Nanfeng mandarin by near infrared spectroscopy coupled with chemometrics methods

Near infrared spectroscopy(NIRS),coupled with principal component analysis and wavelength selection techniques,has been sed to develop a robust and reliable reduced-spectrum classifi-cation model for determining the geographical origins of Nanfeng mandarins.The application of the changeable size moving window principal component analysis(CSMWPCA)provided a notably improved lassification model,with correct classification rates of 92.00%,100.00%,90.00%,100.00%,100.00%,100.00%and 100.00%for Fujian,Guangxi,Hunan,Baishe,Baofeng,Qiawan,Sanxi samples,respectively,as well as,a total dassification rate of 97.52%in the wavelength range from 1007 to 1296 nm.To test and apply the proposed method,the procedure was applied to the analysis of 59 samples in an independent test set.Good identification results(correct rate of 96.61%)were also received.The improvement achieved by the application of CSMWPCA method was particularly remarkable when taking the low complexities of the final model(290 variables)into account.The results of the study showed the great potential of NIRS as a fast,nondestructive and environmentally acceptable method for the rapid and reliable determination for geographical classifcation of Nanfeng mandarins.

Square mesh codend improves size selectivity and catch pattern for Trichiurus lepturus in bottom trawl used along Northwest coast of India

The size selectivity and catch pattern of Trichiurus lepturus in 40 mm diamond and square mesh codends were investigated in this study.A 34 m high opening trawl was used,which is a common design used by fishermen operating along the northwest coast of India,and the cover codend method was employed to determine codend selectivity.Along with the changes in the length at 50%retention rate for Trichiurus lepturus with the usage of the square and diamond mesh codends,indicators to understand the exploitation pattern of this species in the fishery were assessed based on the total number of individuals and on total weight of the catch.The mean selection length increased and discard fraction is reduced when 40 mm square mesh codends are used in place of diamond meshes,however,it is observed that individuals at commercial length are also lost.The results demonstrate that mandatory use of legal mesh sizes alone will be insufficient to aid in the sustainable harvest of this species,given its estimated length at first sexual maturity of 61.2 cm.This is the first study to compare the size selection of this species in 40 mm diamond and square mesh codends along Northwest coast of India.Results of the study will help as a baseline for gear-based regulations in the region.

Effect of escape vents on retention and size selectivity of crab pots for swimming crab Portunus trituberculatus in the East China Sea

An increase in the crab pot fishery in the East China Sea has caused great pressure on swimming crab Portunus trituberculatus resources.Thus,it is essential to implement suitable measures to release sublegal-sized crabs to increase the number of recruits for legal-sized crabs.One of the measures considered is the installation of escape vents on crab pots.We tested crab pots with one and two escape vents and compared the catchability and size selectivity of these pots with control pots without an escape vent.Pots with one escape vent located on single side of the pot,top or bottom(SS),and another on both sides at top and bottom edges(BS)were tested in sea trial experiments following typical commercial fishing practice.The results show that both SS pots and BS pots caught significantly smaller number of sublegal-sized crabs(<116 mm carapace width,CW),but the difference in catch between the two types of crab pots is not significant.The 50%selective CWs(CW_(50))and the selective ranges(SRs)of both BS pots are slightly larger than those of SS pots.However,95%confidence intervals of CW_(50)s and SRs are overlapped,indicating that the discrepancy between them is small.Then,in a mixed effect model,the effect of locations of escape vents,taken as the fixed effect,on selectivity parameters and indexes was analyzed by hypothesis testing.The results show that null hypothesis of no effect of location of vents on size selectivity cannot be rejected,indicating that there is no significant difference in size selectivity between the two types of pots for P.trituberculatus.

One-step synthesis of Cu(Ⅱ) metal–organic gel as recyclable material for rapid, efficient and size selective cationic dyes adsorption

Efficient removal of non-biodegradable and hazardous dyes from wastewater remains a hot research topic.Herein,a rationally designed a Cu(Ⅱ)-based metal–organic gel(Cu-MOG)with a nanoporous 3 D network structure prepared via a simple one-step mixing method was successfully employed for the removal of cationic dyes.The Cu-MOG exhibited high efficiency,with an adsorption capacity of up to 650.32 mg/g,and rapid adsorption efficiency,with the ability to adsorb 80%of Neutral Red within 1 min.The high adsorption efficiency was attributed to its large specific surface area,which enabled it to massively bind cationic dyes through electrostatic interaction,and a nanoporous structure that promoted intra-pore diffusion.Remarkably,the Cu-MOG displayed size-selective adsorption,based on adsorption studies concerning dyes of different sizes as calculated by density functional theory.Additionally,the adsorption performance of the Cu-MOG still maintained removal efficiency of 100%after three regeneration cycles.These results suggested that the Cu-MOG could be expected to be a promising and competitive candidate to conveniently process wastewater.

Comparing the size selectivity of a novel T90 mesh codend to two conventional codends in the northern shrimp(Pandalus borealis)trawl fishery

The size selectivity and usability of three codends were quantified and compared for the first time in the inshore Northern shrimp(Pandalus borealis)trawl fishery of Iceland using the covered codend method:a conventional diamond-mesh codend(T0),conventional square-mesh codend(T45),and a 90◦turned mesh codend(T90)constructed of four panels and with shortened lastridge ropes.Fishers,wanting to increase the average-individual size of captured shrimp,had requested the T90 codend to be compared with conventional codends for consideration in the fishery.Results showed that,on average,the T45 and T90 codends had better size selectivity than the T0 codend in terms of releasing individuals smaller than 13 mm carapace length(Minimum References Size;MRS).The T90 codend retained significantly less Northern shrimps between 9 and 19 mm than the T0 codend and between 15 and 19 mm than the T45 codend.No significant difference of size selectivity between T45 and T0 codends was observed.All three codends presented high retention ratios of Northern shrimps above MRS(>63%)for the population encountered.However,the T0 codend was not effective at sorting out small Northern shrimps;at least 86%of Northern shrimps smaller than 13 mm were retained in the T0 codend if encountered.Catches from T45 and T90 codends had a lower proportion of shrimp below MRS.Since discarding of undersized Northern shrimps is prohibited in Iceland and fishers wanted to catch on average larger shrimp,using the novel T90 codend would enable fishers to use their quotas more efficiently.

Effectiveness of escape vent shape in crab pots for releasing swimming crab Portunus trituberculatus in the East China sea

To stop the decline of swimming crab(Portunus trituberculatus)stocks in the East China Sea,escape vents on crab pots are urgently required to improve pot selectivity and enable release of sublegal-sized crabs.This study presents field comparative fishing experiments,which examined the effectiveness of different shapes and sizes of escape vents in crab pots for the release of swimming crabs.Two sizes each of rectangular,elliptic,and circular escape vents were tested.The results of comparative fishing experiments indicated that experimental pots with escape vents,regardless of their configuration,caught significantly fewer sublegal-sized crabs(<49 mm carapace length,or<116 mm carapace width)than unmodified control pots.Although legal-sized swimming crabs were also less caught,analysis of size selectivity showed that rectangular vents produced steeper selectivity curves than elliptic and circular escape vents.This indicates that rectangular vents may be more suitable and controllable when escape vents will become a requirement and their use will be enforced in fisheries.Underwater observations were conducted using GoPro cameras and LED lights during the first 2.5 h of the deployments(which usually lasted between 5 and 12 h).Video recordings of experimental pots equipped with rectangular or elliptic escape vents showed that swimming crabs trapped in the pots could detect the vents,and readily approached and passed through these.However,no significant difference was detected in the response behavior of swimming crabs between rectangular and elliptic vent pots when quantitative indicators,derived from video recordings,were compared.The effect of different vent shapes on the escape behavior of swimming crab gradually manifested as an increased soak time and by the onset of the escape of larger crabs.Future underwater observations should thus last the entire duration of pot soaking to study how crabs escape from the pots.

Smaller bar spacings in a Nordmøre grid reduces the bycatch of redfish(Sebastes spp.)in the offshore Northern shrimp(Pandalus borealis)fishery of eastern Canada

The offshore Northern shrimp(Pandalus borealis)bottom trawl fishery in eastern Canada currently uses 22 and 28 mm bar spacing Nordmøre grids to limit bycatch from using small mesh codends.However,a recent rebound of juvenile redfish(Sebastes spp.),that can pass through the grids,has greatly increased bycatch.To address this concern,this study investigated the effectiveness of 17 and 15 mm bar spacing Nordmøre grids in a twin-trawl(paired)configuration against the traditional 22 mm bar spacing grid.Size selectivity analyses showed that the 17 and 15 mm grids resulted in no significant reduction in shrimp catch across all length classes.The 17 mm grid significantly reduced redfish bycatch for all length classes and the 15 mm grid significantly reduced redfish bycatch for individuals larger than 95 mm total length.Less redfish entered the codend with the experimental grids,however,the overlap in width between redfish and Northern shrimp limits the overall sorting efficiency of the grids,leaving some redfish still vulnerable to capture.

Pore scale numerical investigation of counter-current spontaneous imbibition in multi-scaled pore networks

The multi-scaled pore networks of shale or tight reservoirs are considerably different from the conventional sandstone reservoirs.After hydraulic fracturing treatment,the spontaneous imbibition process plays an important role in the productivity of the horizontal wells.Applying the color-gradient model of Lattice Boltzmann Method(LBM)accelerated with parallel computing,we studied the countercurrent spontaneous imbibition process in two kinds of pore structures with different interlacing distributions of large and small pores.The effect of geometry configuration of pore arrays with different pore-scale and the capillary number Ca on the mechanism of counter-current spontaneous imbibition as well as the corresponding oil recovery factor are studied.We found that the wetting phase tends to invade the small pore array under small Ca in both types of geometry configurations of different pore arrays of four pore arrays zones.The wetting phase also tends to invade the pore array near the inlet for injecting the wetting phase no matter if it is a large pore array or small pore array except for the situation when the Ca is large to a certain value.In this situation,the small pore arrays show resistance to the wetting phase,so the wetting phase doesn't invade the small pore near the inlet,but invades the large pore preferentially.Both the geometry configurations of different pore arrays and Ca have a significant effect on the oil recovery factor.This work will help to solve the doubt about the selectivity of the multi-scaled pores of the wetting phase and the role of pores with different sizes in imbibition and oil draining in countercurrent spontaneous imbibition processes.