1 LIAN Bin, XIAO Leilei, and SUN Qibiao 2017. Ecological effects of the microbial weathering of silicate minerals. Acta Geologica Sinica (English Edition), 91(supp. 1): 150-152.

An eight-frame gated microchannel plate (MCP) camera and a gating electrical pulse are described in this article. The gating electrical pulse is obtained by first generating a high voltage fast step pulse using avalanche transistors in Marx bank configuration, and then shaping it using avalanche diodes. The high voltage fast step pulse is about 200 ps in fall time and 4 kV in amplitude. The gating pulse wave form with width of 160 ps and amplitude of 2.5 kV is achieved. Each frame photocathode coated with gold on the MCP is part of a 12 Omega transmission line with open circuit end driven by the gating electrical pulse. The camera is tested by illuminating its photocathode with ultraviolet laser pulses, 266 nm in wavelength, which shows exposure time as short as 120 ps.

Free-living (FL) and particle-associated (PA) bacterioplankton communities play critical roles in biogeochemical cycles in the ocean. However, their community composition, assembly process and functions in the continental shelf and slope regions are poorly understood. Based on 16S rRNA gene amplicon sequencing, we investigated bacterial communities’ driving factors, assembly processes and functional potentials at a subtropical marginal sea. The bacterioplankton community showed specific distribution patterns with respect to lifestyle (free living vs. particle associated), habitat (slope vs. shelf) and depth (surface vs. DCM and Bottom). Salinity and water temperature were the key factors modulating turnover in the FL community, whereas nitrite, silicate and phosphate were the key factors for the PA community. Model analyses revealed that stochastic processes outweighed deterministic processes and had stronger influences on PA than FL. Homogeneous selection (Hos) was more responsible for the assembly and turnover of FL, while drift and dispersal limitation contributed more to the assembly of PA. Importantly, the primary contributor to Hos in PA was Gammaproteobacteria:Others, whereas that in FL was Cyanobacteria:Bin6. Finally, the PICRUSt2 analysis indicated that the potential metabolisms of carbohydrates, cofactors, amino acids, terpenoids, polyketides, lipids and antibiotic resistance were markedly enriched in PA than FL.

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Flux and efficiency of carbon export in the ocean has been widely studied using sediment traps, but due to limitations of traditional methods, differential contribution of different organisms is poorly understood. Here, we used DNA metabarcoding to document taxonomic composition for sediment traps deployed at a continental shelf (C6) and a continental slope (C9) site in the South China Sea. The results indicated that metazoans (mainly copepods) and dinoflagellates were the most dominant contributors overall, while dinoflagellates, diatoms, and haptophytes dominated the photosynthetic assemblage. For prokaryotes, Gammaproteobacteria dominated all samples. Furthermore, comparing the trap flora to overlying plankton revealed that metazoans and Polycystinea from Eukaryota and Gammaproteobacteria and Bacteroidetes from Prokaryota were enriched in the trap at both stations whereas haptophytes and Dinophyceae were consistently attenuated during sinking. In addition, Oceanospirillaceae and Rhodobacteraceae exhibited negative correlations with dinoflagellates, and based on overlying plankton metatranscriptomes, were most transcriptionally active lineages for metabolizing labile and semi‐labile organic carbon, potentially contributing to the Martin's decay of sinking particulate organic carbon. Using DNA and RNA sequencing technologies, this study provides novel insights into the lineage‐specific contribution and dynamic impacts of microbes to carbon export in a subtropical marginal sea.