Institute of Hydrobiology, Chinese Academy Of Sciences
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Effect evaluation of microplastics on activated sludge nitrification and denitrification
No full textA large amount of microplastics have entered conventional wastewater treatment plants, and their effects on activated sludge nitrification and denitrification are rarely reported. This study investigated the effects of microplastics on activated sludge nitrification and denitrification using five typical microplastics, namely, polyvinyl chloride (PVC), polypropylene, polyethylene, polystyrene, and polyester (PES) with concentrations of 0, 1000, 5000, and 10,000 particles/L. Results indicated that microplastics had negative effects on ammonia oxidation rate and low effect on nitrite oxidation rate during nitrification. The total inorganic nitrogen did not have much difference during 3 h nitrification under all the tested conditions. The addition of microplastics showed positive effects on denitrification, especially for PVC and PES at microplastic concentration of 5000 particles/L. Nitrification and denitrification did not evidently stop under all the tested conditions, indicating that the selected microplastic types and concentrations were not toxic to nitrification and denitrification within 3 h. The high abundance of PVC microplastics remarkably increased the nitrous oxide (N2O) emission during denitrification. The N2O emission in the test with 10,000 particle/L of PVC was 4.6times higher than the blank control. This study indicated that microplastics with <10,000 particle/L concentration in wastewater had low effects on nitrification and denitrification, whereas they had high effects on the N2O emission during denitrification. (C) 2019 Elsevier B.V. All rights reserved
Effect evaluation of microplastics on activated sludge nitrification and denitrification
No full textA large amount of microplastics have entered conventional wastewater treatment plants, and their effects on activated sludge nitrification and denitrification are rarely reported. This study investigated the effects of microplastics on activated sludge nitrification and denitrification using five typical microplastics, namely, polyvinyl chloride (PVC), polypropylene, polyethylene, polystyrene, and polyester (PES) with concentrations of 0, 1000, 5000, and 10,000 particles/L. Results indicated that microplastics had negative effects on ammonia oxidation rate and low effect on nitrite oxidation rate during nitrification. The total inorganic nitrogen did not have much difference during 3 h nitrification under all the tested conditions. The addition of microplastics showed positive effects on denitrification, especially for PVC and PES at microplastic concentration of 5000 particles/L. Nitrification and denitrification did not evidently stop under all the tested conditions, indicating that the selected microplastic types and concentrations were not toxic to nitrification and denitrification within 3 h. The high abundance of PVC microplastics remarkably increased the nitrous oxide (N2O) emission during denitrification. The N2O emission in the test with 10,000 particle/L of PVC was 4.6times higher than the blank control. This study indicated that microplastics with <10,000 particle/L concentration in wastewater had low effects on nitrification and denitrification, whereas they had high effects on the N2O emission during denitrification. (C) 2019 Elsevier B.V. All rights reserved.</p
Enhancement of DNA damage repair potential in germ cells of Caenorhabditis elegans by a volatile signal from their irradiated partners
No full textRadiation-induced bystander effects have been demonstrated within organisms. Recently, it is found that the organisms can also signal irradiation cues to their co-cultured partners in a waterborne manner. In contrast, there is a limited understanding of radiation-induced airborne signaling between individuals, especially on the aspect of DNA damage responses (DDR). Here, we establish a co-culture experimental system using Caenorhabdis elegans in a top-bottom layout, where communication between "top" and "bottom" worms is airborne. The radiation response of top worms is evaluated using radio-adaptive response (RAR) of embryonic lethality (F1), which reflects an enhancement in repair potential of germ cells to subsequent DNA damage. It is shown that gamma-irradiation of bottom worms alleviates the embryonic lethality of top worms caused by 25 Gy of subsequent gamma-irradiation, i.e. RAR, indicating that a volatile signal might play an essential role in radiation-induced inter-worm communication. The RAR is absent in the top worms impaired in DNA damage checkpoint, nucleotide excision repair, and olfactory sensory neurons, respectively. The induction of RAR is restricted to the mitotic zone of the female germline of hermaphrodites. These results indicate that the top worms sense the volatile signal through cephalic sensory neurons, and the neural stimulation distantly modulates the DDR in germ mitotic cells, leading to the enhancement of DNA damage repair potential. The volatile signal is produced specifically by the L3-stage bottom worms and functionally distinct from the known sex pheromone. Its production and/or release are regulated by water-soluble ascaroside pheromones in a population-dependent manner
Challenges to saving China's freshwater biodiversity: Fishery exploitation and landscape pressures
No full textChina has over 1320 freshwater fish species, 877 of which are endemic. In recent decades, over-exploitation and landscape pressures have threatened them and led to a severe aquatic biodiversity crisis. In response, large-scale fishing bans have been promulgated to protect freshwater biodiversity in major Chinese rivers since the early 1980s. Here, we present the historical background and current challenges to the fishing bans. Implementing large-scale fishing bans may help improve China's current freshwater biological resources and biodiversity to some extent. But implementing fishing bans alone is not sufficient to solve the crisis because of shortcomings of the current bans and expanding human pressures in most river basins. Thus, we recommend regulating other anthropogenic pressures, expanding duration and extent of current fishing regulations, establishing a comprehensive monitoring program, and initiating basin-scale ecological rehabilitation. These programs are also needed in other developing countries facing similar biodiversity crises and human pressures
Dynamic nano-Ag colloids cytotoxicity to and accumulation by Escherichia coli: Effects of Fe3+, ionic strength and humic acid
No full textReleased Ag ions or/and Ag particles are believed to contribute to the cytotoxicity of Ag nanomaterials, and thus, the cytotoxicity and mechanism of Ag nanomaterials should be dynamic in water due to unfixed Ag particle:Agthorn ratios. Our recent research found that the cytotoxicity of PVP-Ag nanoparticles is attributable to Ag particles alone in 3 hr bioassays, and shifts to both Ag particles and released Ag+ in 48 hr bioassays. Herein, as a continued study, the cytotoxicity and accumulation of 50 and 100 nm Ag colloids in Escherichia coli were determined dynamically. The cytotoxicity and mechanisms of nanoAg colloids are dynamic throughout exposure and are derived from both Ag ions and particles. Ag accumulation by E. coli is derived mainly from extracellular Ag particles during the initial 12 hr of exposure, and thereafter mainly from intracellular Ag ions. Fe3thorn accelerates the oxidative dissolution of nano-Ag colloids, which results in decreasing amounts of Ag particles and particle-related toxicity. Nathorn stabilizes nano- Ag colloids, thereby decreasing the bioavailability of Ag particles and particle-related toxicity. Humic acid (HA) binds Agthorn to form Agthorn -HA, decreasing ion-related toxicity and binding to the E. coli surface, decreasing particle-related toxicity. HA in complex conditions showed a stronger relative contribution to toxicity and accumulation than Nathorn or Fe3thorn. The results highlighted the cytotoxicity and mechanism of nano- Ag colloids are dynamic and affected by environmental factors, and therefore exposure duration and water chemistry should be seriously considered in environmental and health risk assessments. (c) 2019 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V
Picoeukaryotic Diversity and Distribution in the Reservoir Ecological System
No full textThe Three Gorges Reservoir of China is a remarkable water conservancy project. It is thus significant to study the dynamics of the reservoir ecological system and plankton distribution. In this study, we used Sanger-based sequencing of the clone libraries of the 185 rRNA gene to analyze the picoeukaryotic diversity (size class 0.7-5 mu m) from two sampling sites along the Three Gorges Reservoir during the four seasons in 2013. The community investigated by our approach was dominated by three main phyla, Cryptophyta (30.88% of clones), Chlorophyta (9.6%), and Bacillariophyta (8.7%). In spring, the parasitic population of chytrids in the reservoir is high and may limit the abundance of diatoms. Moreover, the spatial pattern prevails over temporal variability in picoeukaryotic community structure of the Three Gorges Reservoir. Further analyses show that the spatial differences in community structure are mainly caused by the variability of non-dominant phyla. This leads to the hypothesis that the injection of tributaries will have a certain effect on the plankton community structure of the main stream of the Three Gorges Reservoir.</p
Ultrahigh-cell-density heterotrophic cultivation of the unicellular green microalga Scenedesmus acuminatus and application of the cells to photoautotrophic culture enhance biomass and lipid production
No full textAlthough production of biodiesels from microalgae is proved to be technically feasible, a commercially viable system has yet to emerge. High-cell-density fermentation of microalgae can be coupled with photoautotrophic cultivation to produce oils. In this study, by optimizing culturing conditions and employing a sophisticated substrate feed control strategy, ultrahigh-cell-density of 286 and 283.5 g/L was achieved for the unicellular alga Scenedesmus acuminatus grown in 7.5-L bench-scale and 1,000-L pilot-scale fermenters, respectively. The outdoor scale-up experiments indicated that heterotrophically grown S. acuminatus cells are more productive in terms of both biomass and lipid accumulation when they are inoculated in photobioreactors for lipid production as compared to the cells originally grown under photoautotrophic conditions. Technoeconomic analysis based on the pilot-scale data indicated that the cost of heterotrophic cultivation of microalgae for biomass production is comparable with that of the open-pond system and much lower than that of tubular PBR, if the biomass yield was higher than 200 g/L. This study demonstrated the economic viability of heterotrophic cultivation on large-scale microalgal inocula production, but ultrahigh-productivity fermentation is a prerequisite. Moreover, the advantages of the combined heterotrophic and photoautotrophic cultivation of microalgae for biofuels production were also verified in the pilot-scale
Disodium 2-oxoglutarate promotes carbon flux into astaxanthin and fatty acid biosynthesis pathways in Haematococcus
No full textImproving carbon availability in astaxanthin production is pivotal in Haematococcus industry. In this study, disodium 2-oxoglutarate (2-OG-2Na) was observed to be a potential carbon regulator to increase the astaxanthin content. To illustrate its efficacy in astaxanthin production, key genes and enzyme were analyzed. Upon 2-OG-2Na treatment, genes ipi, bkt and crtR-b were up regulated, concomitantly, carotenoids and astaxanthin content increased by 15.4% and 14.0% at 120 h, respectively; additionally, Acetyl-CoA carboxylase was activated, consistent with 1.27-fold increase in fatty acids content. PUFAs increased earlier as fatty acids assembly gene fad was up-regulated to 20.56. It was also found that cell division was not compromised. Altogether, it was suggested that increased carbon skeletons were re-directed into the astaxanthin and fatty acids biosynthesis pathway. Furthermore, 2-OG-2Na was applied in ten Haematococcus strains. Of these strains, astaxanthin contents were accelerated with average net increase of 10.48%, exhibiting a scalable paradigm for commercial production
Construction of a high-density genetic map and mapping of growth related QTLs in the grass carp (Ctenopharyngodon idellus)
No full textAbstractBackgroundGrass carp (Ctenopharyngodon idellus) are important species in Asian aquaculture. A draft genome for grass carp has already been published in 2015. However, there is still a requirement for a suitable genetic linkage map to arrange scaffolds on chromosomal frameworks. QTL analysis is a powerful tool to detect key locations for quantitative traits, especially in aquaculture. There no growth related QTLs of grass carp have been published yet. Even the growth trait is one of the focuses in grass carp culture.ResultsIn this study, a pair of distantly related parent grass carps and their 100 six-month-old full-sib offspring were used to construct a high-density genetic map with 6429 single nucleotide polymorphisms (SNPs) by 2b-RAD technology. The total length of the consensus map is 5553.43?cM with the average marker interval of 1.92?cM. The map has a good collinearity with both the grass carp draft genome and the zebrafish genome, and it assembled 89.91% of the draft genome to a chromosomal level. Additionally, according to the growth-related traits of progenies, 30 quantitative trait loci (QTLs), including 7 for body weight, 9 for body length, 5 for body height and 9 for total length, were identified in 16 locations on 5 linkage groups. The phenotypic variance explained for these QTLs varies from 13.4 to 21.6%. Finally, 17 genes located in these regions were considered to be growth-related because they either had functional mutations predicted from the resequencing data of the parents.ConclusionA high density genetic linkage map of grass carp was built and it assembled the draft genome to a chromosomal level. Thirty growth related QTLs were detected. After the cross analysis of Parents resequencing data, 17 candidate genes were obtained for further researches.</p
Comparative allometric growth of rare minnow (Gobiocypris rarus) in two culture environments
No full textAllometry, a growth pattern in which different parts of an organism grow at defined rates, is a common feature of fish and can be influenced by environmental factors. The rare minnow Gobiocypris rarus Ye et Fu, 1983 undergoes allometric growth, and this study investigated its allometry patterns and assessed whether the culture environment affects them by comparing growth patterns in conventional (CV) and specific pathogen-free (SPF) stocks using 14 morphological characters. A U-shaped pattern of allometric growth was found in both groups, characterized by higher growth rates of the head and caudal regions than the trunk region. Although the overall allometric growth pattern was similar between these two inbred groups of rare minnows, allometric coefficients for morphometric characters before inflection were higher for SPF fish than CV fish. Growth rates of total length and body mass were also higher for SPF than CV individuals. These results indicate that the environment does play a vital role in rare minnow growth and development, and that a clean culture environment and a U-shaped pattern of allometric growth are highly beneficial for its early growth