Larger Size Fractions Research Articles

Пространственная и временная изменчивость нанофитопланктона в фьордах Западного Шпицбергена в летний период.

The paper presents the results of studies of nanophytoplankton in the fjords of Western Spitsbergen in the summer of 2001, 2002, 2003 and 2017. It is shown that the water area of each fjord is characterized by a fragmentation of the community of planktonic nanoalgae with depth and from the apex to the mouth region, as well as a deepening of the core of maximum abundance at the exit from the fjord, regardless of the density structure of the water column. For fjords of different latitudinal locations, a decline in integral indicators, a lowering of the community core from the surface horizon, and the replacement of large size fractions by cells smaller than 5 μm in the northern direction as the water temperature increases were recorded. In terms of interannual variability, the total abundance and structural organization of nanophytoplankton were determined by the degree of temperature stratification. In the summer of 2017 an increase in the absolute values of abundance and biomass by 1–2 orders of magnitude compared to zero years was revealed, while maintaining the main features of the structural organization of the community.

Carbon Cycling in Marine Particles Based on Inorganic and Organic Stable Isotopes

The marine carbon cycle has a central role in biogeochemical cycling and a close interaction with the climate system. Here, we use the stable carbon isotope (δ13C) of particulate inorganic carbon (PIC) and particulate organic carbon (POC) in marine particles to diagnose carbonate dissolution and organic matter respiration processes in the ocean water column. We show PIC dissolution both in the euphotic zone, potentially driven by POC remineralization, and a preferential dissolution of coccoliths compared to foraminifera below the saturation horizon in the water column. Within the oxygen deficient zone (ODZ), POC remineralization and consequent respiration-driven PIC dissolution are both significantly diminished. We also demonstrate that POC remineralization preferentially removes a 13C-enriched component compared to isotopically-light bulk POC in both the large size fraction (LSF, > 51μ m) and small size fraction (SSF, 0.5 – 51μ m) of the pump particles, but exhibits a greater impact on the large particles because of its smaller inventory. Simultaneously, addition of a 13C-enriched heterotrophic or chemoautotrophic component to the SSF further increases the isotopic offset between SSF and LSF POC. Overall, this study uses δ13C to provide novel evidence for different biogeochemical processes in marine particles, and demonstrates carbonate dissolution in the ocean water column, both driven by bulk seawater chemistry and organic matter respiration within particles. The absence of O2 in the ODZ likely protects carbonate from dissolving by severely limiting organic matter respiration, thus reducing shallow PIC dissolution within the ODZs.

Differential association of key bacterial groups with diatoms and Phaeocystis spp. during spring blooms in the Southern Ocean.

Interactions between phytoplankton and heterotrophic bacteria significantly influence the cycling of organic carbon in the ocean, with many of these interactions occurring at the micrometer scale. We explored potential associations between specific phytoplankton and bacteria in two size fractions, 0.8-3 µm and larger than 3 µm, at three naturally iron-fertilized stations and one high nutrient low chlorophyll station in the Southern Ocean. The composition of phytoplankton and bacterial communities was determined by sequencing the rbcL gene and 16S rRNA gene from DNA and RNA extracts, which represent presence and potential activity, respectively. Diatoms, particularly Thalassiosira, contributed significantly to the DNA sequences in the larger size fractions, while haptophytes were dominant in the smaller size fraction. Correlation analysis between the most abundant phytoplankton and bacterial operational taxonomic units revealed strong correlations between Phaeocystis and picoeukaryotes with SAR11, SAR116, Magnetospira, and Planktomarina. In contrast, most Thalassiosira operational taxonomic units showed the highest correlations with Polaribacter, Sulfitobacteria, Erythrobacter, and Sphingobium, while Fragilariopsis, Haslea, and Thalassionema were correlated with OM60, Fluviicola, and Ulvibacter. Our in-situ observations suggest distinct associations between phytoplankton and bacterial taxa, which could play crucial roles in nutrient cycling in the Southern Ocean.

A novel method to fabricate curved piezoelectric composites with high piezoelectric phase volume fraction

Underwater acoustic transducer based on high piezoelectric phase volume fraction, large thickness, large area and curved piezoelectric composites (PC) possess wider beam width, higher source level and better directivity. However, the curved PC with large size is difficult to fabricate. The preparation of curved PC with large size and high piezoelectric phase volume fraction is even more tricky. The reported methods have risks of depolarization, deformation and poor periodicity and are not suitable for preparing PC with high piezoelectric phase volume fraction and large thickness. In this work, we proposed a novel fabrication method of the shaped-mold-assisted dice and fill technology. The 1–3 PC with high piezoelectric ceramic volume fraction of 80 %, thickness of 4.3 mm and area of 340 mm × 77 mm and the 2-2 PC with high piezoelectric ceramic volume fraction of 89.5 %, thickness of 5 mm and area of 262 mm × 20 mm were fabricated. The piezoelectric coefficient d33 and relative constant stress permittivity ε33T/ε0 of 1–3 and 2-2 PCs were comparable to piezoelectric phase itself. In addition, both 1–3 and 2-2 PCs exhibited a favorable performance consistency. This method solved the problem of limited cutting depth of thin blade, realizing PC with the structure of high piezoelectric phase volume fraction (＞ 70 %) and large thickness (＞ 3 mm) and eliminates the risk of depolarization, deformation and poor periodicity. This work enabled the potential for achieving large area, high piezoelectric phase volume and special-shaped PCs, which offers new ideas for designing innovative acoustic transducers and facilitates the progress of acoustic sensing technology.

Globorotalia truncatulinoides as indicator of Subtropical Convergence and thermocline change during the late Quaternary in the Southeast Atlantic

Planktic foraminifera in biogenic sediments are widely applied as palaeoceanographic tools and the abundances of Globorotalia truncatulinoides have been used over the past few decades as indicators of upper water column changes over geologic time. The two morphological coiling directions of this species (sinistral and dextral) can provide valuable insight into how the upper water masses of the South Atlantic vary in response to climate change. This study aims to document and analyse the abundances of the planktic foraminiferal species G. truncatulinoides and its two morphological coiling directions in two cores from the continental slope of western South Africa at >3500 m water depth to assess the response of upper water masses to Quaternary climate change. The relative abundances of total G. truncatulinoides in the >125 μm size fraction, abundances of the dextral and sinistral forms in the >212 μm fraction and the division into further size fractions (212 μm, 250 μm, 300 μm, 355 μm, >400 μm) were analysed and considered to determine whether these abundances can be related to oceanographic regime shifts in the eastern South Atlantic during the late Pleistocene from MIS 6 to MIS 1. It was found that the Subtropical Convergence was located at a more southern location during MIS 5 and MIS 1, which allows for warmer subtropical species to increase in abundance with increasing Agulhas leakage around the southwestern margin. The thermocline is interpreted to have deepened during glacial terminations and interglacial periods when productivity was relatively lower and temperatures increased. The size fraction of the sinistral form in the >355 μm is dominant in MIS 5, MIS 3 and MIS1, indicating implications for the use of this species at certain size ranges. This study therefore indicates that G. truncatulinoides is a useful tracer of past Quaternary oceanographic changes along the western margin of South Africa, particularly when the coiling directions at the larger size fraction is taken into account.

Weakly agglomerated NANO/MICRO-particles of Gd2O3:Tb3+: Structure, luminescence and thermometry

Gadolinium oxide nanostructures have been actively studied as multimodal materials for both technical applications and biomedical research. Doping of this oxide structure with a given concentration of chosen rare earth ions allows one to obtain predefined optical properties. Weakly agglomerated nanoscale and submicron Gd2O3:Tb3+ particles were synthesized by a modified Pechini method in a single chemical process. The nanoscale fraction was transferred into aqueous solution without the addition of surfactant. Zeta potential of this solution was found to be about −17 (±1) mV. The crystal structure of cubic gadolinium oxide is confirmed for the large and small size fraction. The optimal concentration of terbium ions, at which the highest luminescence is observed, was 1.2 at.%. The concentration quenching mechanism for Tb3+-doped Gd2O3 samples was determined as a dipole–quadrupole energy migration with subsequent quenching on impurities. The luminescence properties of sub-micron and nanoparticles, including lifetimes, were found to be almost identical. The effect of temperature on both steady-state and kinetic luminescent properties was studied. Gd2O3:Tb3+ phosphors were found to be promising as lifetime-based luminescent thermometers.

Diatom bloom trigger notable variations in microzooplanktonic ciliate composition, body-size spectrum and biotic-abiotic interaction in the Arctic Ocean

How microzooplanktonic ciliate adaptative strategies differ across diatom bloom and non-diatom bloom areas in the Arctic Ocean remains poorly documented. To address this gap, two different situations were categorized in the Arctic Ocean at summer 2023: diatom bloom stations (DBS) (genus Thalassiosira, chain-like) and non-diatom bloom stations (nDBS). Total abundance of ciliate at 3 m and 25 m in DBS was 2.8 and 1.8 folds higher than in nDBS, respectively. Aloricate ciliates were singled out in both DBS and nDBS, whilst their average abundance and biomass of large size-fraction (>50 μm) in former were 4.5–5.6 folds higher than in latter. Regarding tintinnids, high abundance of Ptychocylis acuta (Bering Strait species) mainly occurred at DBS, coupled with distribution of co-occurring Pacific-origin species Salpingella sp.1, collectively suggested a strong intrusion of Pacific Inflow during summer 2023. Additionally, presence of high abundance of Acanthostomella norvegica and genus Parafavella in nDBS might indicate the trajectory of the Transpolar Drift. Alternatively, tintinnids can serve as credible bioindicators for either monitoring currents or evaluating microzooplankton Borealization. Average abundance of total ciliate within 15–135 μm body-size spectrum in DBS was higher than nDBS. Moreover, spearman's rank correlation between biotic and abiotic analysis revealed that temperature and dissolved oxygen at DBS determined tintinnid species richness and ciliate total abundance, respectively. The results clearly demonstrate that remarkable divergences in large size-fraction of ciliate abundance between DBS and nDBS validate their irreplaceable role in controlling phytoplankton outbreak and associated biological processes in polar seas.

Strong and efficient summertime carbon export driven by aggregation processes in a subarctic coastal ecosystem

AbstractSinking marine particles, one pathway of the biological carbon pump, transports carbon to the deep ocean from the surface, thereby modulating atmospheric carbon dioxide and supplying benthic food. Few in situ measurements exist of sinking particles in the Northern Gulf of Alaska; therefore, regional carbon flux prediction is poorly constrained. In this study, we (1) characterize the strength and efficiency of the biological carbon pump and (2) identify drivers of carbon flux in the Northern Gulf of Alaska. We deployed up to five inline drifting sediment traps in the upper 150 m to simultaneously collect bulk carbon and intact sinking particles in polyacrylamide gels and measured net primary productivity from deck‐board incubations during the summer of 2019. We found high carbon flux magnitude, low attenuation with depth, and high export efficiency. We quantitatively attributed carbon flux between 10 particle types, including various fecal pellet categories, dense detritus, and aggregates using polyacrylamide gels. The contribution of aggregates to total carbon flux (41–93%) and total carbon flux variability (95%) suggest that aggregation processes, not zooplankton repackaging, played a dominant role in carbon export. Furthermore, export efficiency correlated significantly with the proportion of chlorophyll a in the large size fraction (> 20 μm), total aggregate carbon flux, and contribution of aggregates to total carbon flux. These results suggest that this stratified, small‐cell‐dominated ecosystem can have sufficient aggregation to allow for a strong and efficient biological carbon pump. This is the first integrative description of the biological carbon pump in this region.

Inhibiting effects of humic acid on iron flocculation hindered As removal by electro-flocculation on air cathode iron anode

Activated carbon air cathode combined with iron anode oxidation-flocculation synergistic Arsenic (As) removal was a new groundwater purification technology with low energy consumption and high efficiency for groundwater with high As concentration. The presence of organic matter such as humic acid (HA) had ambiguous effects on formation of organic colloids in the system. The effects of the particle size distribution characteristics of these colloids on the formation characteristics of flocs and the efficiency of As purification was not clear. In this work, we used five different pore size alumina filter membranes to separate mixed phase solutions and studied the corresponding changes in iron and arsenic concentrations in the presence and absence of humic acid conditions. In the presence of HA, the arsenic concentration of < 0.05 µm particle size components was 1.01, 1.28, 3.07, 7.69, 2.85 and 1.24 times of that in the absence of HA. At the same time, the arsenic content in 0.05–0.1 µm and 0.1–0.45 µm particle size components was also higher than that in the system without HA, which revealed that the presence of HA hindered the flocculation behavior of As distribution to higher particle sizes in the early stage of the reaction. The presence of HA affected the flocculation rate of iron flocs from small to large particle size fractions and it had limited effect on the behavior of large-size flocs in adsorption of As. These results provide a theoretical basis for targeted, rapid, and low consumption synergistic removal of arsenic and organic compounds in high arsenic groundwater.

Preserved particulate organic carbon is likely derived from the subsurface sulfidic photic zone of the Proterozoic Ocean: evidence from a modern, oxygen-deficient lake.

Biological processes in the Proterozoic Ocean are often inferred from modern oxygen-deficient environments (MODEs) or from stable isotopes in preserved sediment. To date, few MODE studies have simultaneously quantified carbon fixation genes and attendant stable isotopic signatures. Consequently, how carbon isotope patterns reflect these pathways has not been thoroughly vetted. Addressing this, we profiled planktonic productivity and quantified carbon fixation pathway genes and associated organic carbon isotope values (δ13 CPOC ) of size-fractionated (0.2-2.7 and >2.7 μm) particulate matter from meromictic Fayetteville Green Lake, NY, USA. The high-O2 Calvin-Benson-Bassham (CBB) gene (cbbL) was most abundant in the <2.7 μm size fraction in shallow oxic and deep hypoxic waters, corresponding with cyanobacterial and eukaryote algal populations. The low-O2 CBB gene (cbbM) was most abundant near the lower oxycline boundary in the larger size fraction, coincident with purple sulfur bacteria populations. The reverse citric acid cycle gene (aclB) was equally abundant in both size fractions in the deepest photic zone, coinciding with green sulfur bacteria populations. Methane coenzyme reductase A (mcrA), of anaerobic methane cyclers, was most abundant at the lower oxycline boundary in both size fractions, coinciding with Methanoregula populations. δ13 CPOC values overlapped with the high-O2 CBB fixation range except for two negative excursions near the lower oxycline boundary, likely reflecting assimilation of isotopically-depleted groundwater-derived carbon by autotrophs and sulfate-reducers. Throughout aphotic waters, δ13 CPOC values of the large size fraction became 13 C-enriched, likely reflecting abundant purple sulfur bacterial aggregates. Eukaryote algae- or cyanobacteria-like isotopic signatures corresponded with increases in cbbL, cbbM, and aclB, and enrichment of exopolymer-rich prokaryotic photoautotrophs aggregates. Results suggest that δ13 CPOC values of preserved sediments from areas of the Proterozoic Ocean with sulfidic photic zones may reflect a mixture of alternate carbon-fixing populations exported from the deep photic zone, challenging the paradigm that sedimentary stable carbon isotope values predominantly reflect oxygenic photosynthesis from surface waters.

Coccolith-calcite Sr/Ca as a proxy for transient export production related to Saharan dust deposition in the tropical North Atlantic

Atmospheric dust deposition can modulate the earth’s climate and atmospheric CO2 through fertilising the ocean (nutrient source) and by accelerating the biological carbon pump through fuelling the ballasting process. To distinguish the biogeochemical effects of Saharan dust with respect to fertilization and ballasting, and to gain a broader perspective on the coccolith calcite Sr/Ca in relation to the drivers of coccolith export production, we determined the coccolith-Sr/Ca from a one-year (2012–2013) time-series sediment trap record in the western tropical North Atlantic (M4—49°N/12°W). High Sr/Ca were linked to enhanced export production in the upper part of the photic zone, most notably under windier, dry, and dustier conditions during spring. Attenuated Sr/Ca in the autumn probably reflect a combination of lower Sr-incorporation by dominant but small-size placolith-bearing species and the presence of “aged” coccoliths rapidly scavenged during a highly productive and usually fast export event, likely added by (wet) dust ballasting. Higher Sr/Ca observed in the large coccolith size fractions support the existing notion that larger-sized coccolithophores incorporate more Sr during calcification under the same environmental conditions. The presence of the abnormally Sr-rich species Scyphosphaera apsteinii is also shown in the separated large fraction of our Sr/Ca seasonal data.

Unusual sources of fossil micrometeorites deduced from relict chromite in the small size fraction in ~467 Ma old limestone

ABSTRACTExtraterrestrial chrome spinel and chromite extracted from the sedimentary rock record are relicts from coarse micrometeorites and rarely meteorites. They are studied to reconstruct the paleoflux of meteorites to the Earth and the collisional history of the asteroid belt. Minor element concentrations of Ti and V, and oxygen isotopic compositions of these relict minerals were used to classify the meteorite type they stem from, and thus to determine the relative meteorite group abundances through time. While coarse sediment‐dispersed extraterrestrial chrome‐spinel (SEC) grains from ordinary chondrites dominate through the studied time windows in the Phanerozoic, there are exceptions: We have shown that ~467 Ma ago, 1 Ma before the breakup of the L chondrite parent body (LCPB), more than half of the largest (&gt;63 μm diameter) grains were achondritic and originated from differentiated asteroids in contrast to ordinary chondrites which dominated the meteorite flux throughout most of the past 500 Ma. Here, we present a new data set of oxygen isotopic compositions and elemental compositions of 136 grains of a smaller size fraction (32–63 μm) in ~467 Ma old pre‐LCPB limestone from the Lynna River section in western Russia, that was previously studied by elemental analysis. Our study constitutes the most comprehensive oxygen isotopic data set of sediment‐dispersed extraterrestrial chrome spinel to date. We also introduce a Raman spectroscopy‐based method to identify SEC grains and distinguish them from terrestrial chrome spinel with ~97% reliability. We calibrated the Raman method with the established approach using titanium and vanadium concentrations and oxygen isotopic compositions. We find that ordinary chondrites are approximately three times more abundant in the 32–63 μm fraction than achondrites. While abundances of achondrites compared to ordinary chondrites are lower in the 32–63 μm size fraction than in the &gt;63 μm one, achondrites are approximately three times more abundant in the 32–62 μm fraction than they are in the present flux. We find that the sources of SEC grains vary for different grain sizes, mainly as a result of parent body thermal metamorphism. We conclude that the meteorite flux composition ~467 Ma ago ~1 Ma before the breakup of the LCPB was fundamentally different from today and from other time windows studied in the Phanerozoic, but that in contrast to the large size fraction ordinary chondrites dominated the flux in the small size fraction. The high abundance of ordinary chondrites in the studied samples is consistent with the findings based on coarse extraterrestrial chrome‐spinel from other time windows.

MarrowCellDLD: a microfluidic method for label-free retrieval of fragile bone marrow-derived cells

Functional bone marrow studies have focused primarily on hematopoietic progenitors, leaving limited knowledge about other fragile populations, such as bone marrow adipocytes (BMAds) and megakaryocytes. The isolation of these cells is challenging due to rupture susceptibility and large size. We introduce here a label-free cytometry microsystem, MarrowCellDLD, based on deterministic lateral displacement. MarrowCellDLD enables the isolation of large, fragile BM-derived cells based on intrinsic size properties while preserving their viability and functionality. Bone marrow adipocytes, obtained from mouse and human stromal line differentiation, as well as megakaryocytes, from primary human CD34+ hematopoietic stem and progenitor cells, were used for validation. Precise micrometer-range separation cutoffs were adapted for each cell type. Cells were sorted directly in culture media, without pre-labeling steps, and with real-time imaging for quality control. At least 106 cells were retrieved intact per sorting round. Our method outperformed two FACS instruments in purity and yield, particularly for large cell size fractions. MarrowCellDLD represents a non-destructive sorting tool for large, fragile BM-derived cells, facilitating the separation of pure populations of BMAds and megakaryocytes to further investigate their physiological and pathological roles.

Typology of planktonic food webs and associated emerging properties as indicators of the ecological status of a permanently disturbed Gulf of Gabès

This study highlights the importance of coupling the typology of planktonic food webs and their emerging properties to better describe the ecological status of an ecosystem under permanent disturbance mainly caused by phosphate industry. Linear inverse models were built to describe four stations under various levels of nutrient pressure, using the Markov Chain Monte Carlo method to estimate known and unknown carbon flows, later used to calculate food web typology ratios. Ecological network analysis (ENA) was used to describe the structural and functional properties of each food web. Based on the food web typology ratios, three planktonic trophic pathways (PTP) with different functional indices were distinguished according to nutrient stress. The microbial food web dominated in the least nutrient-rich environment. It mainly relied on phytoplankton production (picophytoplankton <2 μm) that was mainly transferred by the high microbivory of protozooplankton. In contrast, the herbivorous food web developed in the most nutrient-rich environment, where biogenic carbon was mainly produced by large phytoplankton (microphytoplankton >10 μm) and channeled to higher trophic levels by herbivorous protozooplankton and metazooplankton. In the other two stations – moderately nutrient-rich systems – the PTP acted as a multivorous food web. Phytoplankton (small and large size fractions) and non-living components (detritus and dissolved organic carbon) played a significant role in carbon production, and competed with protozooplankton and metazooplankton for its transport. ENA indices revealed that the herbivorous food web, with the highest total system throughput and lowest relative Ascendency and cycling, was the most active but the least organized and stable system. In contrast, the microbial food web, with the lowest total system flux and highest Ascendency, was least active but more organized than the herbivorous food web. The multivorous food web displayed the most recycling and most organized system, with high values of the detritivory-to-herbivory ratio, cycling and Ascendency. In addition to ENA indices, which are considered effective tools for studying the structural and functional properties of food webs, marine ecosystem management efforts heavily focus on using the “marine food web” as a descriptor of the system's ecological status. However, we suggest that the combination of food web typology and ecological indices could be used as an effective tool for the management and assessment of ecosystem health wherever possible, as well as for the study of anthropogenic pressures.

Eukaryotic genomes from a global metagenomic data set illuminate trophic modes and biogeography of ocean plankton.

Single-celled eukaryotes play ecologically significant roles in the marine environment, yet fundamental questions about their biodiversity, ecological function, and interactions remain. Environmental sequencing enables researchers to document naturally occurring protistan communities, without culturing bias, yet metagenomic and metatranscriptomic sequencing approaches cannot separate individual species from communities. To more completely capture the genomic content of mixed protistan populations, we can create bins of sequences that represent the same organism (metagenome-assembled genomes [MAGs]). We developed the EukHeist pipeline, which automates the binning of population-level eukaryotic and prokaryotic genomes from metagenomic reads. We show exciting insight into what protistan communities are present and their trophic roles in the ocean. Scalable computational tools, like EukHeist, may accelerate the identification of meaningful genetic signatures from large data sets and complement researchers' efforts to leverage MAG databases for addressing ecological questions, resolving evolutionary relationships, and discovering potentially novel biodiversity.

Concentration of mercury and other metals in an Arctic planktonic food web under a climate warming scenario

Arctic marine ecosystems act as a global sink of mercury (Hg) and other metals, and high concentrations of these have been measured in higher trophic-level organisms. Nevertheless, the concentrations of metals at the basis of the marine food web in the Arctic is less known despite the likelihood of biomagnification from dietary sources. We investigated the concentrations of mercury (Hg) and other metals in different size fractions of plankton in West Greenland. All size fractions contained detectable levels of Hg (ranging from 4.8 to 241.3 ng g dw−1) at all stations, although with high geographic variability, likely reflecting the sources of mercury (e.g., meltwater). In many cases, the concentrations in the larger-size fractions were lower than in the smaller-size fractions, suggesting depuration through the metabolic activity of mesozooplankton. Concentrations of Cd, Pb, V, Ni, and Cr were higher than previously reported elsewhere in the Arctic.

The effect of particle size on the sublimation behavior of butylhydroxytoluene as antioxidant in tablets during storage and coating

The effect of particle size on the sublimation behavior of butylhydroxytoluene (BHT) was investigated when BHT was included as antioxidant in tablets. Sublimation of pure BHT was found to be independent of its particle size, with pore formation on the surface of all tablets after storage at room temperature and above. Moreover, a higher residual BHT content after storage was detected in tablets containing a larger size fraction. X-ray µCT scans revealed the formation of peripherally larger pores at higher BHT particle sizes, implying a slower sublimation rate in the tablet core. A stability study indicated an increase in the extent of BHT sublimation at higher temperature and longer exposure time for all size fractions. The influence of BHT particle size was more pronounced when the tablets were stored at higher temperature, but the effect receded with longer exposure time. Similar trends were seen in film-coated tablets. Due to the short exposure time to elevated temperatures, a gradient in pore size was also observed at smaller particle sizes, with peripheral pores being larger in uncoated tablets. Superficial pores disappeared when a film coating was deposited onto the tablets. After storage of the film-coated tablets, less BHT had sublimated compared to the uncoated tablet. The coating layer did not prevent sublimation, but the process was slowed down.

Wood xerogel for fabrication of high-performance transparent wood

Optically transparent wood has been fabricated by structure-retaining delignification of wood and subsequent infiltration of thermo- or photocurable polymer resins but still limited by the intrinsic low mesopore volume of the delignified wood. Here we report a facile approach to fabricate strong transparent wood composites using the wood xerogel which allows solvent-free infiltration of resin monomers into the wood cell wall under ambient conditions. The wood xerogel with high specific surface area (260 m2 g–1) and high mesopore volume (0.37 cm3 g–1) is prepared by evaporative drying of delignified wood comprising fibrillated cell walls at ambient pressure. The mesoporous wood xerogel is compressible in the transverse direction and provides precise control of the microstructure, wood volume fraction, and mechanical properties for the transparent wood composites without compromising the optical transmittance. Transparent wood composites of large size and high wood volume fraction (50%) are successfully prepared, demonstrating potential scalability of the method.

Innovative reference materials for method validation in microplastic analysis including interlaboratory comparison exercises

Reference materials (RMs) are vital tools in the validation of methods used to detect environmental pollutants. Microplastics, a relatively new environmental pollutant, require a variety of complex approaches to address their presence in environmental samples. Both interlaboratory comparison (ILC) studies and RMs are essential to support the validation of methods used in microplastic analysis. Presented here are results of quality assurance and quality control (QA/QC) performed on two types of candidate microplastic RMs: dissolvable gelatin capsules and soda tablets. These RMs have been used to support numerous international ILC studies in recent years (2019–2022). Dissolvable capsules containing polyethylene terephthalate (PET), polyvinyl chloride (PVC), polyethylene (PE), and polystyrene (PS), in different size fractions from 50 to 1000 µm, were produced for one ILC study, obtaining relative standard deviation (RSD) from 0 to 24%. The larger size fraction allowed for manual addition of particles to the capsules, yielding 0% error and 100% recovery during QA/QC. Dissolvable capsules were replaced by soda tablets in subsequent ILC studies and recovery test exercises because they were found to be a more reliable carrier for microplastic RMs. Batches of soda tablets were produced containing different single and multiple polymer mixtures, i.e., PE, PET, PS, PVC, polypropylene (PP), and polycarbonate (PC), with RSD ranging from 8 to 21%. Lastly, soda tablets consisting of a mixture of PE, PVC, and PS (125–355 µm) were produced and used for recovery testing during pretreatment of environmental samples. These had an RSD of 9%. Results showed that soda tablets and capsules containing microplastics >50 µm could be produced with sufficient precision for internal recovery tests and external ILC studies. Further work is required to optimize this method for smaller microplastics (< 50 µm) because variation was found to be too large during QA/QC. Nevertheless, this approach represents a valuable solution addressing many of the challenges associated with validating microplastic analytical methods.

Diel variations in planktonic ciliate community structure in the northern South China Sea and tropical Western Pacific

Though diel variations are geographically widespread phenomena among phytoplankton and zooplankton, knowledge is limited regarding diel variations in planktonic ciliate (microzooplankton) community structure. In this study, we analyzed diel variations in community structure of planktonic ciliates in the northern South China Sea (nSCS) and tropical Western Pacific (tWP). Hydrological characteristics during day and night were slightly different over both the nSCS and tWP, while ciliate average abundance at night was clearly higher than in the day in the upper 200 m. In both the nSCS and tWP, abundance proportions of large size-fraction (> 30 μm) aloricate ciliates at night were higher than in the day. While for tintinnids, abundance proportion of large lorica oral diameter at night were lower than in the day. The relationship between environmental factors and ciliate abundance pointed out that depth and temperature were main factors influencing aloricate ciliate and tintinnid in both day and night. For some dominant tintinnid species, chlorophyll a was another important factor influencing their diel vertical distribution. Our results provide fundamental data for better understanding the mechanisms of planktonic ciliate community diel variation in the tropical Western Pacific Ocean.