141 research outputs found
Macrofauna community of the cold seep area at Site F, South China Sea
A cold seep is one of the typical deep-sea chemical energy ecosystems and a hotspot for studying unique life processes and biogeochemical cycles in the deep sea. Macrofauna, which is one of the most important components of the cold seep ecosystem, has not been thoroughly studied. We examined the macrofauna community at Site F using images collected in 2016 by an imaging and laser profiling system and biological samples collected in 2020 and 2021 by TV grab and a remotely operated vehicle. In total, 41 species were found. The overall number of macrofauna identified at Site F (20,000 m2) reached 252,943 individuals, and the biomass reached 726.15Â kg by dry weight. As the dominant species, Gigantidas platifrons and Shinkaia crosnieri reached their highest densities of 629 and 396 individuals/m2, respectively. The comparisons between different stations revealed that the diversity and density, even the biomass of dominant species, were much higher in the south than in the north at Site F in 2020. Correlation analysis showed that methane had a positive effect on macrofauna density. Compared with S. crosnieri, G. platifrons seems to be more adapted to the harsh cold seep environment. Methane consumption rates of the dominant species show that macrofauna are important in influencing seafloor methane fluxes. Our findings provide valuable insights into the ecology, community structure, and biota-environment interaction in the cold seep at Site F
Transmission electron microscopy analysis of some transition metal compounds for energy storage and conversion
This work was preliminarily supported by the National Key Research Program of China (2016YFA0202604), the Natural Science Foundation of China (21476271), NSFC-RGC (21461162003) and Natural Science Foundation (2014KTSCX004 and 2014A030308012) of Guangdong Province, China.Recently, transition metal compounds (TMCs) have been employed as high-performance electrode materials for lithium ion batteries (LIBs) and supercapacitors (SCs) owing to their high specific capacities, high electrical conductivity, and high chemical and thermal stability. While the characterization of electrochemical properties of TMC anodes is well developed, new challenges arise in understanding the structure-property relationships. Transmission electron microscopy (TEM) is a powerful tool for studying microstructural characteristics. With TEM and related techniques, fundamental understanding of how the microstructures affect the properties of the TMC nanostructured anodes can be improved. In this article, the application of TEM in characterization of some typical TMC anode materials optimized through structural engineering, elemental doping, surface modification, defect-control engineering, morphological control, etc. is reviewed. Emphasis is given on analyzing the microstructures, including surface structures, various defects, local chemical compositions and valence states of transition metals, aimed at illustrating a structure-property relationship. The contribution and future development of the TEM techniques to elucidation of the electrochemical properties of the TMC anodes are highlighted.PostprintPeer reviewe
Toxicological effects of cadmium on deep-sea mussel Gigantidas platifrons revealed by a combined proteomic and metabolomic approach
IntroductionMarine metal contamination caused by deep-sea mining activities has elicited great concern from both social and scientific communities. Among the various metals deep-sea organisms might encounter, cadmium (Cd) is a widely detected metal that in very small amounts is nonetheless capable of severe toxicity. Yet due to both remoteness and technical challenges, insights into the effects of metal exposure resulting from mining activities upon deep-sea organisms are limited.MethodsHere, we investigated Cd’s toxicological effects on deep-sea mussels of Gigantidas platifrons exposed to 100 or 1000 g/L of Cd for 7 days; an integrated approach was used that incorporated proteomics and metabolomics along with traditional approaches (metal concentrations, metal subcellular distribution, and anti-oxidative and immune-related biochemical indexes).Results and DiscussionResults showed that Cd exposure caused significant Cd’s accumulation in mussel gills and redistribution of Cd among subcellular compartments, with cellular debris being the primary binding site. Although anti-oxidative enzymes activities (superoxide dismutase and catalase) were not significantly altered in mussel gills of both exposed groups, the markedly increased level of glutathione S-transferase detected via proteomic technique clearly evinced that deep-sea mussels suffered from oxidative stress under Cd exposure. Besides, altered activities of acid phosphatase and alkaline phosphatase assayed by traditional methods along with the predominant presence of largely altered immune-related proteins detected by proteomic data strongly revealed an immune response of deep-sea mussels elicited by Cd. In addition, results of proteomics combined with those of non-targeted metabolomics demonstrated that Cd could exert toxicity by disrupting cytoskeleton structure, ion homeostasis, and primary metabolisms of energy, lipid, and nucleotide in deep-sea mussels. As demonstrated in this study, proteomics and metabolomics can be used in tandem to provide valuable insights into the molecular mechanisms of deep-sea organisms’ response to Cd exposure and for helping to discover potential biomarkers for application during deep-sea mining assessments
Variation in epibiotic bacteria on two squat lobster species of Munidopsidae
The relationships between epibiotic bacteria on deep-sea hosts and host lifestyle factors are of particular interest in the field of deep-sea chemoautotrophic environmental adaptations. The squat lobsters Shinkaia crosnieri and Munidopsis verrilli are both dominant species in cold-seep ecosystems, and they have different distributions and feeding behaviors. These species may have evolved to have distinct epibiotic microbiota. Here, we compared the epibiotic bacterial communities on the M. verrilli carapace (MVcarapace), S. crosnieri carapace (SCcarapace), and S. crosnieri ventral plumose setae (SCsetae). The epibiotic bacteria on SCsetae were dense and diverse and had a multi-layer configuration, while those on MVcarapace and SCcarapace were sparse and had a monolayer configuration. Chemoautotrophic bacteria had the highest relative abundance in all epibiotic bacterial communities. The relative abundance of amplicon sequence variant 3 (ASV3; unknown species in order Thiotrichales), which is associated with sulfide oxidation, was significantly higher in SCsetae than MVcarapace and SCcarapace. Thiotrichales species seemed to be specifically enriched on SCsetae, potentially due to the synthetic substrate supply, adhesion preference, and host behaviors. We hypothesize that the S. crosnieri episymbionts use chemical fluxes near cold seeps more efficiently, thereby supporting the host’s nutrient strategies, resulting in a different distribution of the two species of squat lobster
DNA barcoding of Antarctic marine zooplankton for species identification and recognition
Polar zooplankton are particularly sensitive to climate change, and have been used as rapid-responders to indicate climate-induced changes in the fragile Antarctic ecosystem. DNA barcoding provides an alternative approach for rapid zooplankton species identification. Ninety-four specimens belonging to 32 Antarctic zooplankton species were barcoded to construct a comprehensive reference library. An 830 to 1 050 base-pair region of the mitochondrial cytochrome c oxidase subunit I (mtCOI) gene was obtained as DNA barcodes. The intraspecific variation of the gene ranged from 0 to 2.6% (p-distance), with an average of 0.67% (SD=0.67%). The distance between species within the same genera ranged from 0.1% (Calanus) to 29.3%, with an average of 15.3% (SD=8.4%). The morphological and genetic similarities between Calanus propinquus and C. simillimus raise new questions about the taxonomic status of C. simillimus. With the exception of the two Calanus species, the intraspecific genetic divergence was much smaller than the interspecific divergence among congeneric species, confirming the existence of a barcode gap for Antarctic zooplankton. In addition, species other than Calanus sp. formed a monophyletic group. Therefore, we have confirmed DNA barcoding as an accurate and efficient approach for zooplankton identification in the Antarctic area (except for Hydromedusa, Tunicata, and other gelatinous zooplankton). Indicator vector analysis further confirmed this conclusion. The new primer sets issued here may facilitate the study of Antarctic marine zooplankton species composition by environmental metagenetic analysis
Temporal and Spatial Variations in spatial variations in symbiont communities of catch bowl coral Isopora palifera (Scleractinia: Acroporidae) on reefs in Kenting National Park, Taiwan
Acclimatization through Symbiodinium shuffling is one of potential mechanisms in reef-building corals to survive environmental stress. In our previous study, the catch bowl coral Isopora palifera in Tantzei Bay (TZB), Nanwan, Kenting National Park (KNP), southern Taiwan was demonstrated to shuffle thermal-tolerant Symbiodinium D1a and thermal-sensitive Symbiodinium C3 in response to seasonal variations in sea surface temperatures (SSTs) in 2000 and 2001. In this study, we reexamined the temporal dynamics of the Symbiodinium community of I. palifera in TZB in 2006-2009. In addition, spatial variations in Symbiodinium communities in I. palifera were also examined at 6 other sites of Nanwan, KNP in 2009, including a site located at a nuclear power plant outlet (NPP-OL) in southern Taiwan with a yearly mean SST 0.6-1.5 degrees C higher compared to the other sites. Phylotyping and DNA sequence analyses of Symbiodinium ribosomal 28S and ITS2 markers showed that I. palifera colonies at TZB continued to show seasonal shuffling, but shifted to thermal-sensitive type C3 dominant in 2006-2009. This differed from the symbiont community originally dominated by the thermal-tolerant Symbiodinium D1a in 2000 and 2001 after the 1998 mass-bleaching event. Significant differences in spatial variations of the symbiont community in Nanwan were detected with I. palifera colonies at the NPP-OL dominated by Symbiodinium D1a. Our study results suggest that I. palifera can acclimatize to SST anomalies by shuffling to thermal-tolerant Symbiodinium D1a and can revert to thermal-sensitive C3 when the stress disappears, but will maintain the thermally tolerant Symbiodinium D1a as the dominant symbiont if the heat stress continues
Probing resistive switching in HfO2/Al2O3 bilayer oxides using in-situ transmission electron microscopy
In this work, we investigate the resistive switching in hafnium dioxide (HfO2) and aluminum oxide (Al2O3) bilayered stacks using in-situ transmission electron microscopy and X-ray energy dispersive spectroscopy. Conductance of the HfO2/Al2O3 stack changes gradually upon electrical stressing which is related to the formation of extended nanoscale physical defects at the HfO2/Al2O3 interface and the migration and re-crystallization of Al into the oxide bulk. The results suggest two competing physical mechanisms including the redistribution of oxygen ions and the migration of Al species from the Al electrode during the switching process. While the HfO2/Al2O3 bilayered stack appears to be a good candidate for RRAM technology, the low diffusion barrier of the active Al electrode causes severe Al migration in the bi-layered oxides leading to the device to fail in resetting, and thereby, largely limiting the overall switching performance and material reliability
Identification and Transformation Difficulty in Problem Solving: Electrophysiological Evidence from Chunk Decomposition
A wealth of studies have investigated how to overcome experience-based constraints in creative problem solving. One such experience-based constraint is the tendency for people to view tightly organized visual stimuli as single, unified percepts, even when decomposition of those stimuli into component parts (termed chunk decomposition) would facilitate problem solving. The current study investigates the neural underpinnings of chunk decomposition in creative problem solving by analyzing event-related potentials. In two experiments, participants decomposed Chinese characters into the character’s component elements and then used the base elements to form a new valid character. The action could require decomposing a “tight” chunk, meaning that the component elements intersected spatially, or a “loose” chunk, in which the component elements did not overlap in space. Behaviorally, individuals made more errors and responded slower to trials involving tight chunks relative to loose chunks. Analysis of the ERPs revealed that relative to loose chunks, the electrophysiological response to tight chunks contained an increased N2, an increased N400, and a decreased late positive complex. Taken together, these results suggest that chunk tightness is a principle determinant of the difficulty of chunk decomposition, and that chunk tightness provokes neural conflict and semantic violations, factors known to influence the N2 and N400 ERP components
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