Seasonal Variation of Environmental Variables and Phytoplankton Community Structure and Their Relationship in Liaodong Bay of Bohai Sea,China

In this paper, systematic studies on the changes in concentrations of the environmental factors and the net-phytoplankton community, and the relationship between them in the Liaodong Bay, Bohai Sea during 2013 are presented. The PCA results showed that higher levels of nutrients and dissolved heavy metals in the river-estuary-bay system were closely related to the river runoff. Since the influences of industrial and anthropogenic activities, the Liaodong Bay coastal areas are facing a huge environmental challenge of nutrients and heavy metal pollution. Net-phytoplankton community structure showed obvious seasonal succession, among which the dominant and(or) key species were the main factors affecting community structure change and stability. Under certain environmental conditions, the dominant species and(or) key species dominated the phytoplankton community structure succession. The Bio-ENV results suggested that the seawater temperature, nutrient, Cu, Pb, Zn, and Cd in Liaodong Bay are important environmental variables that affect the phytoplankton community structure. Anthropogenic activities have significantly contributed to the changes in concentrations of environmental factors and the net-phytoplankton community structure and stability, and the relationship between them.

Origin and formation of the Ryukyu Current revealed by HYCOM reanalysis

The origin of the Ryukyu Current(RC)and the formation of its subsurface velocity core were investigated using a 23-year(1993–2015)global Hybrid Coordinate Ocean Model(HYCOM)dataset.The volume transport of the RC comes from the Kuroshio eastward branch(KEB)east of Taiwan and part of the North Pacific Subtropical Gyre(p-NPSG).From the surface to 2000m depth,the KEB(p-NPSG)transport contributes 41.5%(58.5%)to the mean total RC transport.The KEB originally forms the subsurface velocity core of the RC east of Taiwan due to blockage of the subsurface Kuroshio by the Ilan Ridge(sill depth:700 m).Above 700m,the Kuroshio can enter the East China Sea(ECS)over the Ilan Ridge,meanwhile,the blocked Kuroshio below 700m turns to the right and flows along the Ryukyu Islands.With the RC flowing northeastward,the p-NPSG contribution strengthens the subsurface maximum structure of the RC owing to the blockage of the Ryukyu Ridge.In the surface layer,the p-NPSG cannot form a stable northeastward current due to frequent disturbance by mesoscale eddies and water exchange through the gaps(with net volume transport into ECS)between the Ryukyu Islands.

Effects of florfenicol exposure on growth,development and antioxidant capacity of flounder Paralichthys olivaceus larvae at different developmental stages

Antibiotics are widespread in various environmental media,and may pose a potential threat to aquatic ecosystems and non-target aquatic organisms.Florfenicol(FLO)is one of the most commonly used antibiotics in aquaculture,and extensively used to substitute chloramphenicol with its strong sterilization and low adverse ef fect.In this study,flounder Paralichthys olivaceus,an important economic fish species in seawater was used as an experimental subject.Five exposure concentrations of FLO(including environmentrelated concentrations)were set at 0,0.01,0.1,1,and 10 mg/L.Ef fects of FLO exposure for 168 h on growth and development,motor behavior,antioxidant enzyme activity,malondialdehyde(MDA)content,and thyroid hormone level of P.olivaceus larvae were studied in pre-larvae(1 dpf)and post-larvae(20 dpf).The results show that the short-term FLO exposure could promote the larvae growth to some degrees,but inhibit them as the exposure time prolonged.For pre-larvae,FLO at 0.01 mg/L could stimulate the motor nerve system and increase the swimming ability,but inhibited it at 1 mg/L.With the increasing dosage of FLO,the superoxide dismutase(SOD)and MDA contents were elevated,reaching the maximum in the 1 mg/L FLO group.The pre-larvae were more sensitive than the post-larvae to FLO in the environment,and the growth and immune resistance could be damaged with long exposure.Post-larvae were more tolerant to external pollutants,FLO at 1 mg/L could promote the motor behavior and reduce SOD and MDA contents.Therefore,FLO can be used as an antibiotic at a proper concentration but as a drug to prevent disease in a long-term way.

Surveillance of enteric pathogens in imported seafood and environmental surfaces in five seafood markets before the outbreak of COVID-19

To monitor the presence of enteric pathogens in imported seafood,a total of 140 seafood samples imported from eight overseas countries were collected from Beijing,Dalian,Shanghai,Guangzhou,and Wuhan seafood markets from June to November 2019.Additionally,116 viral,environmental swab samples were also collected from the Wuhan and Guangzhou seafood markets.Five typical enteric bacterial pathogens(Aeromonas spp.,Shigella spp.,Salmonella spp.,Vibrio spp.,and Listeria monocytogenes)and four viruses(Rotavirus,Norovirus,Astrovirus,and Sapovirus)were detected positive.Results showed that eight Vibrio parahaemolyticus isolates appeared in seafood imported to Dalian,Wuhan,Shanghai,Guangzhou,and Beijing.In contrast,Vibrio fluvialis and Aeromonas were isolated in another two samples.Norovirus was detected in one oyster sample imported from France and environmental surface in Guangzhou.The remaining pathogens were negative in all the samples being tested.With 120 V.parahaemolyticus isolates from the above countries,the genomic analysis revealed that sequence type ST1152 isolates imported from Canada were clustered with two V.parahaemolyticus isolates from Canada.This study presented the first microbiological analysis of the Wuhan seafood market before the outbreak of COVID-19,which demonstrated that supervision should be strengthened to prevent enteric pathogens via imported seafood.

First-Principles Calculations for Stable β-Ti–Mo Alloys Using Cluster-Plus-Glue-Atom Model

Construction of suitable structural models in order to account for chemical short-range orders is the reason behind the difficult multi-scale computational simulation methods for solid solutions.Herein,using Ti-Mo alloys as representative,we used our cluster-plus-glue-atom model to address the chemical short-range orders for body-center cubic lattice.In accordance with the atomic interaction mode,an Mo solute atom would prefer 14 Ti solvent atoms as its nearest neighbors,forming a rhombic-dodecahedral cluster,and some next outer-shell Mo and Ti atoms would serve as the glue atoms,which is formulated as [Mo-Ti14](Mo,Ti)x.The number of glue atoms x corresponds to different spatial distribution of the clusters.One of the formula having good stability is [Mo-Ti14]Mo,i.e.,with one Mo as the glue atom.To verify its stability,mechanical properties and electronic density of state are obtained using the first-principles calculations and the Young’s modulus agrees with the experimental values.Also the formulated structural unit [Mo-Ti14]Mo is indeed verified by the cluster expansion method.This work then confirms the existence of simple structural unit covering the nearest neighbors and a few next outershell atoms for the Ti-Mo alloy of high structural stability.