Ultraviolet irradiation induced oxidative stress and response of antioxidant system in an intertidal macroalgae Corallina officinalis L.

The response of the antioxidant defense system of an intertidal macroalgae Corallina officinalis L.to different dosages of UV-B irradiation was investigated.Results showed that superoxide dimutase （SOD） and peroxidase （POX） increased and then maintained at a relatively stable level when subjected to UV-B irradiation.Catalase （CAT） activity under medium dosage of UV-B irradiation （Muv） and high dosage of UV-B irradiation （Huv） treatments were significantly decreased.Ascorbate peroxidase （APX） activity first remained unaltered and then increased in Huv treatment.In addition,the assay on isozymes was carried out using non-denaturing polyacrylamide gel electrophoresis （PAGE）.The activities of some SOD isoforms were altered by UV-B.Two new bands （POX V and POX VII） appeared upon exposure to all three UV-B dosages.CAT III activity was increased by low dosage of UV-B irradiation （Luv）,whereas CAT III and CAT IV disappeared when the alga was exposed to Muv and Huv.Two bands of APX （APX VI and APX VII） were increased and a new band （APX X） was observed under Huv exposure.H 2 O 2 and thiobarbituric acid reacting substance （TBARS） increased under Muv and Huv treatments.Overall,UV-B protection mechanisms are partly inducible and to a certain extent sufficient to prevent the accumulation of damage in C.officinalis.

Microbial Community Diversity and Vertical Distribution in a Columnar Sediment of Maluku Strait

The sediment samples were collected from Maluku Strait at a depth of 1250 m, which is influenced by Mindanao Current and Indonesian Throughflow. Based on 16S rRNA clone libraries, the community structure and vertical distribution of archaea and bacteria were studied in a columnar sediment of 2m in length. From the surface sediment, 16S sequences were derived from fourteen bacterial phyla (Gammaproteobacteria, Planctomycetes, Alphaproteobacteria, Deltproteobacteria were dominant), but were limited to two groups of archaea: Crenarchaeota (99%) and Euryarchaeota (1%). Besides, 90% of the archaea clones were ammonia oxidation-related which indicated that the ammonia-oxidizing archaea might make a significant contribution to the chemosynthesis in the surface sediment. Contrastively in the bottom sediment, six bacterial phylogenetic groups were obtained (Gammaproteobacteria and Firmicutes were absolutely dominant), however no archaea 16S rRNA was detected. The microbial diversity of surface sediment was much higher than the bottom and seven unique bacterial phyla were obtained from two sediment respectively. The geochemical elements analysis revealed that the content of C, TOC and S in the surface sediment was much higher than the bottom, but the content of P is contrary. The microbial communities might be in response to the geochemical substance transfer and deposit influenced by the ocean current and it deserves further study compared with the other sediment samples in this area.

Mapping the resting cysts of dinoflagellate Alexandrium catenella along the coast of Qinhuangdao,China

Dinoflagellate Alexandrium catenella is a cosmopolitan bloom-forming species with complex life cycle,the formation and germination of resting cysts are critical for its bloom dynamics.In the coastal waters of Qinhuangdao,A.catenella has been identified as the major causative agent for paralytic shellfish poisoning,but there is little knowledge concerning its resting cysts in this region.In this study,three surveys were carried out along the coast of Qinhuangdao from 2020 to 2021 to map the distribution of A.catenella resting cysts,using a quantitative PCR(qPCR)assay specific for A.catenella.The resting cysts were detected in surface sediments during all the three surveys,and their distribution patterns were similar.High abundance of resting cysts(maximum 1300 cysts/g sediment(wet weight))were found in a region(119.62°E-119.99°E,39.67°N-39.98°N)northeast to the coastal waters of Qinhuangdao,where surface sediments were mainly composed of clay and silt(percentage above 50%).Prior to the formation of the A.catenella bloom in March 2021,the abundance of A.catenella vegetative cells in seawater had extremely significant positive correlation with the abundance of resting cysts in surface sediments,reflecting the important role of resting cysts in the initiation of A.catenella blooms.As far as we know,this is the first report on the distribution of A.catenella cysts along the coast of Qinhuangdao.The results will of fer a sound basis for the future monitoring and mitigation of toxic A.catenella blooms and paralytic shellfish poisoning events in this region.

Investigation of the decline of Ulva prolifera in the Subei Shoal and Qingdao based on physiological changes

It has been a scientific consensus that Ulva prolifera green tide that break out annually between May and August in the recent decade off eastern coast of Yellow Sea.To investigate the ecological mechanism of the decline of U.prolifera green tide,we compared the physiological characteristics of U.prolifera samples collected in three stages of the green tide in Subei Shoal north Jiangsu,the initiation point,on May 10(early,the initiation),July 10(middle,the outbreak),and in Taipingjiao,Qingdao on August 10(late,the decline).Compared to the early samples,the middle,and late samples showed a lower chlorophyll content and photosynthetic e fficiency at a higher lipid peroxidation level.The middle and later samples had fewer chloroplasts in the cells of U.prolifera than those in the early samples.In addition,the cells of U.prolifera sampled in the late stage showed ruptured and deformed cell walls.Differences in physiological function were reflected in the growth rate.Both the middle and late U.prolifera samples presented negative growth rates.Correlation analysis results show that the rising temperature was mainly responsible for the local decline of U.prolifera green tide.The high light-intensity that could induce the photoinhibition was also an important factor for the decline.Therefore,U.prolifera population that remained in the Subei Shoal and those that northward drifted to Qingdao experienced the same decline processes:rising temperature and continuous high light conditions in the late phase of green tide reduced the photosynthetic capacity and destroyed the antioxidant system of the thallus,which lead to decrease of biomass.The only difference is that the temperature in the Subei Shoal rose earlier than that in Qingdao;thus,U.prolifera remaining in the Subei Shoal went disappeared first.

Comparison of environmental responding strategies between Ulva prolifera and Sargassum horneri:an in-situ study during the co-occurrence of green tides and golden tides in the Yellow Sea,China in 2017

Large-scale green tides in the Yellow Sea occurred for 13 consecutive years since 2007.The unusual co-occurrence of green tides and golden tides occurred in the Yellow Sea in 2017.The causative species are Ulva prolifera and/or Sargassum horneri.Previous studies on physiological response characteristics of U.prolifera and S.horneri are done in the laboratory mainly,and there is no in-situ comparative study in this regard.In this study,the in-situ physiological response characteristics of both species were measured.The results indicated that cyclic electron flow and antioxidant system play more important roles in protecting U.prolifera,while non-photochemical quenching is more important for adapting to the environment in S.horneri.U.prolifera has a stronger ability to utilize nutrients to rapidly increase its biomass under a suitable condition compared to S.horneri.

Green synthesis of functional metallic nanoparticles by dissimilatory metal-reducing bacteria“Shewanella”:A comprehensive review

The biosynthesis strategy of nanoparticles has attracted much attention due to the mild synthesis condi-tions,environmental-friendly properties,and low costs.Biosynthesized nanoparticles(bio-NPs)not only show excellent physicochemical properties,but also exhibit high stability,enlarged specific surface area,and excellent biocompatibility,which are crucial for industrial,agricultural,and medical fields.She-wanella,a kind of dissimilatory metal-reducing bacteria,is regarded as a typical biosynthesis-functional bacteria class with wide distribution and strong adaptability.Thus,in this paper,functional bio-NPs by Shewanella were reviewed to provide a comprehensive view of current research progress.The biosynthetic mechanisms of Shewanella are summarized as the Mtr pathway(predominant),extracellular polymeric substance-induced pathway,and enzyme/protein-induced pathway.During the biosynthesis process,bio-logical factors along with the physicochemical parameters highly influenced the properties of the resul-tant bio-NPs.Till now,bio-NPs have been applied in various fields including environmental remediation,antibacterial applications,and microbial fuel cells.However,some challenging issues of bio-NPs by She-wanella remain unsolved,such as optimizing suitable bacterial strains,intelligently controlling bio-NPs,clarifying biosynthesis mechanisms,and expanding bio-NPs applications.

Effects of two polybrominated diphenyl ethers(BDE-47,BDE-209) on the swimming behavior, population growth and reproduction of the rotifer Brachionus plicatilis

Polybrominated diphenyl ethers（PBDEs） are new kinds of persistent organic pollutants（POPs） and their potential threats to the equilibrium and sustainability of marine ecosystems have raised worldwide concerns. Here, two kinds of PBDEs, tetra-BDE（BDE-47）and deca-BDE（BDE-209） were applied, and their toxic effects on the swimming behavior,population growth and reproduction of Brachionus plicatilis were investigated. The results showed that：（1） The actual concentrations of BDE-47 and-209 in the seawater phase measured by GC–MS（Gas Chromatography-Mass Spectrometer） were much lower than their nominal concentrations.（2） In accordance with the 24-hr acute tests, BDE-209 did not show any obvious swimming inhibition to rotifers, but a good correlation did exist between the swimming inhibition rate and BDE-47 concentration suggesting that BDE-47 is more toxic than BDE-209.（3） Both BDE-47 and-209 had a significant influence on the population growth and reproduction parameters of B. plicatilis including the population growth rate, the ratio of ovigerous females/non-ovigerous females（OF/NOF）, the ratio of mictic females/amictic females（MF/AF）, resting egg production and the mictic rate, which indicate that these parameters in B. plicatilis population were suitable for monitoring and assessing PBDEs. Our results suggest that BDE-47 and-209 are not acute lethal toxicants and may pose a low risk to marine rotifers at environmental concentrations for short-term exposure. They also accumulate differently into rotifers. Further research data are needed to understand the mechanisms responsible for the effects caused by PBDEs and to assess their risks accurately.

Acute and chronic toxic effects of Pb^(2+)on polychaete Perinereis aibuhitensis:Morphological changes and responses of the antioxidant system

Perinereis aibuhitensis was used to assess adverse biological effects caused by acute and chronic Pb2＋exposure in artificial seawater under controlled laboratory conditions. In 96-hr acute toxicity experiments,the morphological changes showed a positive time/dose-dependent tendency,and the 96-hr LC50 value of Pb2＋was 686.41 mg/L. The responses of enzymatic and non-enzymatic antioxidants in tissues including catalase（CAT）,peroxidase（POD）,superoxide dismutase（SOD）,glutathione peroxidase（GSH-PX）,malondialdehyde（MDA） and the content of total soluble protein（TSP）,were investigated on days 1,4,7 and 10 after Pb2＋exposure under chronic toxicity testing. Results showed that the activation of the antioxidant system in P. aibuhitensis depended on the Pb2＋concentration and the duration of exposure time.Specifically,POD and SOD activities were induced on the first day of the exposure and decreased to the control level on day 10 after exposure. Therefore,these two indexes could be used to indicate oxidative stress associated with P. aibuhitensis exposure to Pb2＋.

Mechanism of Deca-BDE-induced apoptosis in Neuro-2a cells:Role of death-receptor pathway and reactive oxygen species-mediated mitochondrial pathway

Decabromodiphenyl ether（BDE-209） is a prevalent polybrominated diphenyl ether（PBDE）congener known to have neurotoxicity. Effects of BDE-209 on Neuro-2a cells were performed in the present study and the possible apoptotic pathway was discussed. Results indicated that BDE-209 induced Neuro-2a cell apoptosis, increased the protein expression of Fas and Fas-associated death domain-containing protein（FADD） and activated the caspase-8 and-3activities in a concentration-dependent manner, inferring the death-receptor pathway was involved in the apoptotic process. Meanwhile, BDE-209 exposure increased the Bax/Bcl-2 ratio and decreased the cellular mitochondrial membrane potential（MMP） which led to cytochrome C released to the cytoplasm. The intracellular caspase-9 was elevated simultaneously,which caused downstream caspase cascade and triggered cell apoptosis. Moreover, BDE-209 exposure increased cellular reactive oxygen species（ROS） level in a concentration-dependent manner and the addition of N-acetyl-L-cysteine（NAC）, known as ROS scavengers, obviously reduced the apoptotic rate and a positive relationship was observed between the degree of apoptosis blocking and the loss of MMP and ROS production. We thus concluded that BDE-209 induced Neuro-2a cell apoptosis via the combination of the death-receptor signaling pathway and the mitochondrial signaling pathway. The elevated ROS production was considered to magnify the intracellular apoptosis signal and played a crucial role in apoptosis of Neuro-2a cells induced by BDE-209.