Optical properties of dissolved organic matter relate to different dept-specific patterns of archaeal and bacterial community structure in the North Atlantic Ocean

ArticleProkaryotic abundance, activity and community composition were studied in the euphotic, intermediate and deep waters off the Galician coast (NW Iberian margin) in relation to the optical characterization of dissolved organic matter (DOM). Microbial (archaeal and bacterial) community structure was vertically stratified. Among the Archaea, Euryarchaeota, especially Thermoplasmata, was dominant in the intermediate waters and decreased with depth, whereas marine Thaumarchaeota, especially Marine Group I, was the most abundant archaeal phylum in the deeper layers. The bacterial community was dominated by Proteobacteria through the whole water column. However, Cyanobacteria and Bacteroidetes ocurrence was considerable in the upper layer and SAR202 was dominant in deep waters. Microbial composition and abundande were not shaped by the quantity of dissolved organic carbon, but instead they revealed a strong connection with the DOM quality. Archaeal communities were mainly related to the fluorescence of DOM (which indicates respiration of labile DOM and generation of refractory subproducts), while bacterial communities were mainly linked to the aromaticity/age of the DOM produced along the water column. Taken together, our results indicate that the microbial community composition is associated with the DOM composition of the water masses, suggesting that distinct microbial taxa have the potential to use and/or produce specific DOM compounds.Versión del edito

Vertical stratificaction of bacterial communities driven by multiple environmental factors in the dark waters off the Galician coast (NW Spain)

scientific articleThe processesmediatedbymicrobialplanktoniccommunitiesoccuralongtheentirewatercolumn,yet the microbialactivityandcompositionhavebeenstudiedmainlyinsurfacewaters.Thisresearchex- amined theverticalvariationinbacterialabundance,activityandcommunitycompositionandstructure from surfacedownto5000mdepthfollowingalongitudinaltransectofftheGaliciancoast(NWIberian margin, from43°N, 9°W to43°N, 15°W). Communityactivityandcompositionchangedwithdepth.The leucine incorporationratesdecreasedfromtheeuphoticlayertothebathypelagicwatersbythreeorders of magnitude,whereasprokaryoticabundancedecreasedonlybyoneorderofmagnitude.Therelative abundance ofSAR11and Alteromonas, determined bycatalyzedreporteddeposition fluorescenceinsitu hybridization(CARD-FISH),decreasedwithdepth.Meanwhile,thecontributionofSAR202andSAR324 wassignificantly higherinthedeeperlayers(i.e.NEADW,NorthEastAtlanticDeepWaterandLDW, LowerDeepWater)thanintheeuphoticzone.Bacterialcommunitystructure,assessedbyAutomated Ribosomal IntergenicSpacerAnalysis(ARISA),wasdepth-specific. Adistancebasedlinearmodel (DistLM) revealedthatthevariabilityfoundinbacterialcommunitystructurewasmainlyexplainedby temperaturenitrate,phosphate,dissolvedorganicmatter(DOM) fluorescence, prokaryoticabundance, leucine incorporationandtoalesserextentsalinity,oxygen,CDOMabsorbanceanddissolvedorganic carbon concentration.Ourresultsdisplayedabacterialcommunitystructureshapednotonlybydepth- relatedphysicochemicalfeaturesbutalsobyDOMquality,indicatingthatdifferentprokaryotictaxahave the potentialtometabolizeparticularDOMsources.Postprint2,421

Facile conversion of commercial coarse-type LiCoO2 to nanocomposite-separated nanolayer architectures as a way for electrode performance enhancement

Coarse-type LiCoO2 is the state-of-the-art cathode material in small-scale lithium-ion batteries (LIBs); however, poor rate performance and cycling stability limit its large-scale applications. Here we report the modification of coarse-type LiCoO2 (LCO) with nanosized lithium lanthanum titanate (Li3xLa2/3–xTiO3, LLTO) through a facile sol–gel process, the electrochemical performance of commercial LiCoO2 is improved effectively, in particular at high rates. The crystalline structure of pristine LiCoO2 is not affected by the introduction of the LLTO phase, while nanosized LLTO particles are likely incorporated into the space of the LiCoO2 layers to form a LCO-LLTO nanocomposite, which separate the LCO layers with the increase of layer spacing to ∼100 nm. The LLTO incorporation through the facile post-treatment effectively reduces the charge-transfer resistance and increases the electrode reactions; consequently, the LLTO-incorporated LCO electrode shows higher capacity than LiCoO2 at a higher rate and prolonging cycling stability in both potential ranges of 2.7–4.2 V and 2.7–4.5 V, making it also suitable for high-rate operation. This novel concept is general, which may also be applicable to other electrode materials. It thus introduces a new way for the development of high rate-performance electrodes for LIBs for large scale applications such as electric vehicles and electrochemical energy storage for smart grids