Size Spectrum Research Articles

Role of environmental filtering and functional traits for species coexistence in a harsh tropical montane ecosystem

AbstractEnvironmental filtering and niche differentiation are often invoked to explain species coexistence at local scales. The ironstone campo rupestre of Brazil provides a biodiverse natural experiment in which edaphic gradients represent filters to test the hypothesis that plant community functional composition, despite converging on extreme stress tolerance, exhibits a co-structure with environmental parameters. At the Serra do Rola-Moça State Park, soil physico-chemical parameters were characterized alongside community-weighted mean plant functional traits and Grime’s competitor, stress-tolerator and ruderal strategies for species at each sampling site. In general, species exhibited a high degree of stress tolerance (between 72.6% and 100%), while ruderalism was 0% for all species. Soil nutrients related to plant metabolism (e.g. P, Ca, Mg) were associated with the stress-tolerant strategy and with traits involved in the leaf economics and size spectra. Despite a major edaphic filter selecting stress tolerance, fine-scale microhabitat variability represented by soil parameters related to fertility (i.e. P, Ca, Mg) and water retention capacity (i.e. clay content) was associated with subtle variation in ecological strategies and functional traits of species in the ironstone campo rupestre.

A model to estimate the effect of variables causing erosion in wind turbine blades

AbstractThe quantification of the severity of erosion in wind turbine blades is challenging due to the many aspects involved, including meteorology, aerodynamics, materials science, and wind turbine dynamics. A complete model relies on several building blocks, which cover the characterization of precipitation and aerosols, the trajectories of droplets and particles, the operational settings of the wind turbine, and finally the structural response of the leading edge to the large number of impacts across a spectrum of particle sizes and impacts speeds. This paper presents a multidisciplinary model, defining magnitudes representative of erosion severity and formulating their dependencies. The method uses the formula for the erosion incubation time as defined by Springer. The model incorporates the effect of wind velocity and density, particle size, and erosion intensity, and it allows four erosion mechanisms to be considered: rainfall, snowfall, sea spray, and fog. Comparison of the predicted erosion incubation time versus blade inspections shows good qualitative agreement. The equations from the model suggest that the characterization of atmospheric conditions at the site is essential for an accurate estimation of the severity of erosion. Equally important are the material properties, and the impingement process at the leading edge.

Laterite as a Potential Seepage Barrier From a Karst-Depression Tailings Impoundment

AbstractIn the absence of the necessary valley topography, karst depressions are sometimes used to construct conventional impoundments in order to contain tailings. Leakage is a primary concern for such impoundments. The purpose of the current study was to determine the characteristics and barrier performance of laterite mantling karst depressions, using, as an example, the Wujiwatang (WJWT) tailings impoundment, located in the Gejiu mining area, southwestern China. The geotechnical-hydrogeological properties, geochemistry, mineral compositions, and particle shapes of the laterite were investigated by geotechnical techniques, chemical analysis, X-ray diffraction (XRD), and scanning electron microscopy (SEM). The results showed that the laterite contained poorly sorted particles that covered a wide spectrum of grain sizes (<5 mm to <50 nm), and was unexpectedly categorized as silty clay or silt with a high liquid limit. The continuous gradation and small D90 value helped the laterite achieve saturated hydraulic conductivities in the range of <10–6 cm/s required for impoundment liners. The laterite beneath the tailings impoundment was finer-grained and had a lower permeability than that of the laterite on the depression walls within the same depression. Geochemically and mineralogically, the laterite was classified as true laterite and its major mineralogical constituents were gibbsite and goethite with chlorite occurring in trace amounts. The laterite was dominated by subspherolitic–spherolitic cohesionless grains (concretions) made up of Al, Fe, Ti, and Mn oxides and hydroxides. The laterite did not have plasticity indices in the clay range. Fortunately, slopewash prior to tailings containment selectively transported the finer oxide concretions to the depression floor, creating a natural low-permeability barrier for the WJWT tailings impoundment. This is undoubtedly important for the planning and design of future karst depression-type tailings impoundments around the world.

Lineal energy calibration of a mini-TEPC via the proton-edge technique

PurposeThe possibility to calibrate microdosimetric spectra using the proton- and electron-edge was proposed many years ago. It consists of two steps: first identifying the edge and a marker point on it and then ascribing the correct lineal energy value to the position of the edge in the event size spectrum. The purpose of this work is to study rigorously the marker identification for the proton-edge in the mini-TEPC spectra measured in neutron and in clinical proton fields, and the correspondent lineal energy value to assign to it. Materials and methodsMicrodosimetric measurements were performed with a cylindrical miniaturized tissue-equivalent proportional-counter (mini-TEPC) in neutron and gamma rays radiation fields at the CN accelerator of the Legnaro National Laboratories of the Italian National Institute for Nuclear Physics (LNL-INFN) and in the clinical 62 MeV proton beam of the Southern National Laboratories of INFN (LNS-INFN). The fitting of the proton-edge region of the microdosimetric spectra with a Fermi-like function was studied in both neutron and proton fields to identify the most precise marker point. The lineal energy value to ascribe to it was determined starting from the maximum energy deposit in protons obtained in FLUKA simulations. ResultsBoth in neutron radiation field and in clinical proton beams the flex and the intercept of the tangent through the inflection point are determined with similar precision. The flex was chosen as the most suitable marker of the proton-edge in sealed detectors because it is known to be less sensitive to pressure variations. The lineal energy value to ascribe to the flex position for 0.75 μm of propane depends on the irradiation geometry: 194 keV/μm for isotropic radiation fields and 165 keV/μm for mono-directional radiation fields orthogonal to the axis of the cylinder. The calibration values for the proton-edge have been converted in water by means of the mean stopping power ratio of water and propane for protons obtaining 171 keV/μm for isotropic radiation fields and 145 keV/μm for mono-directional radiation fields.

Bubble characteristics and turbulent dissipation rate in horizontal bubbly pipe flow

The energy dissipation rate is a crucial parameter for system control and turbulence modeling but is difficult to quantify in gas–liquid two-phase flows. Little relevant information is available, especially in horizontal pipe flows. Based on the consideration that the bubble characteristics in a stable bubbly flow are a reflection of flow turbulence, the bubble shape and bubble size spectrum are investigated in a 10-m-long horizontal rectangular pipe by means of high-speed imaging and graphic processing techniques. The bubble size spectra indicate a critical length scale, deemed to be the Hinze scale, and the spectral shape is related to turbulent fragmentation and, thus, enables calculation of the turbulence dissipation rate. After careful validation of the approach for estimating the turbulence dissipation rate, an empirical prediction equation is proposed based on the present tested flow conditions, reflecting the effects of both the pipe flow velocity and the gas flow rate. Such information is useful for the modeling of turbulent two-phase flows.

In Situ Assembly of Gold Nanoparticles in the Presence of Poly-DADMAC Resulting in Hierarchical and Highly Fractal Nanostructures

The presence of the polycationic macromolecule poly(diallyldimethylammonium chloride) (poly-DADMAC) has a strong effect on the shape and size of colloidal gold nanoparticles formed by the reduction of tetrachloroauric acid with ascorbic acid in aqueous solution. It slows down nanoparticle growth and supports the formation of nonspherical, partially highly fractal and hierarchical nanoparticle shapes. Four structural levels have been recognized from the near-spherical gold nanoparticles in the lower nanometer range over compact aggregates in the midnanometer range and flower and star-like particles in the submicron range up to larger filamentous aggregates. High-contrast scanning electron microscope (SEM) images show that single gold nanoparticles and clusters of them are connected by bundles of macromolecules in large aggregates. The investigation showed that a large spectrum of different nanoparticle shapes and sizes can be accessed by tuning the poly-DADMAC concentrations and their ratio to other reactants. The nanoassemblies with a very high specific surface area might be of interest for SERS and heterogeneous catalysis.

Droplet spectral dispersion by lateral mixing process in continental deep cumulus clouds

In situ flight observations and theoretical analysis are used to investigate the dispersion properties of droplet size distribution (DSD) in continental deep cumulus clouds under the influence of lateral entrainment and mixing processes. The study attempts to relate the spectral width (σr) and relative dispersion (ν) of DSD with liquid water content (LWC), droplet number concentration (Nd) and mean radius (rm), which decrease from their adiabatic values due to dry air mixing.The diffusional-evaporation theory suggests that DSD spectra may broaden during the mixing as smaller droplets evaporate faster than the larger droplets under a constant saturation ratio (S < 1). However, in observations, three regimes of adiabatic fraction (AF = LWC/LWCa; subscript ‘a’ denotes adiabatic value) have been identified with different characteristics of spectral dispersion by lateral entrainment and subsequent mixing processes. Broadening of size spectra, i.e., increasing σr is seen in the highly diluted cloud edge regime (AF < 0.25) where droplet evaporation is significant. A narrowing of the size spectra is observed in the moderately diluted regime (0.65 >AF > 0.25). Whereas, in the less diluted regime (AF > 0.65), a slight spectral broadening towards the smaller size tail is noted, possibly due to reactivation of condensation nuclei. Relative dispersion (ν=σr/rm) is almost invariant (≅0.22) in the less diluted and moderately diluted regimes but increased (≅ 0.35) rapidly with decreased Nd (and LWC) in the highly diluted regime that forms the outer shell of cumulus clouds.

Spatio-Temporal Variations in Community Size Structure of Arctic Protist Plankton in the Fram Strait

The Arctic Ocean is subject to severe environmental changes, including the massive decline in sea ice due to continuous warming in many regions. Along with these changes, the Arctic Ocean's ecosystem is affected on various scales. The pelagic microbial food web of the Arctic is of particular interest, because it determines mass transfer to higher trophic levels. In this regard, variations in the size structure of the microbial community reflect changes in size-dependent bottom-up and top-down processes. Here we present analyses of microscopic data that resolve details on composition and cell size of unicellular plankton, based on samples collected between 2016 and 2018 in the Fram Strait. Using the Kernel Density Estimation method, we derived continuous size spectra (from 1 μm to ≈ 200 μm Equivalent Spherical Diameter, ESD) of cell abundance and biovolume. Specific size intervals (3–4, 8–10, 25–40, and 70–100 μm ESD) indicate size-selective predation as well as omnivory. In-between size ranges include loopholes with elevated cell abundance. By considering remote sensing data we could discriminate between polar Arctic- and Atlantic water within the Fram Strait and could relate our size spectra to the seasonal change in chlorophyll-a concentration. Our size spectra disclose the decline in total biovolume from summer to autumn. In October the phytoplankton biovolume size-spectra reveal a clear relative shift toward larger cell sizes (&amp;gt; 30 μm). Our analysis highlights details in size spectra that may help refining allometric relationships and predator-prey dependencies for size-based plankton ecosystem model applications.

Effects of surrounding pressure on cone–jet formation in electrospray process

A numerical approach has been employed to investigate the role of surrounding gas pressure in the electrospray cone–jet status as the most desired and practical mode in various applications. The simulations carried out based on heptane as the working liquid and air as the surrounding gas, over an extent of absolute pressures lying in 10 kPa to 1000 kPa for the liquid flow rate 6.2 mLh−1 and the electric potential 4 kV. The simulating cases fall in the range of dimensionless numbers 82.2 < $${\text{Re}}_{j}$$ < 112.3, 17.3 < $${\text{We}}_{j}$$ < 44.0, 0.2 < $${\text{Ca}}_{j}$$ < 0.4 and $${\chi }_{j}$$ < 4 × 10–4, confirming the formation of a stable cone–jet pattern in compliance with the convective instability limits. Despite the preservation of cone–jet geometry, the results clarify that the surrounding pressure could obviously contribute a dual effect through the length and surface undulations of the jet owing to change in the drag force. The jet tip disintegration into droplets remarkably demonstrates a transition from a prolate to an oblate mode at the upper bound pressures. The surrounding medium also influences flow pattern within the cone zone by means of contracting and relocating vortices further downstream as the pressure rises up. The droplet mean size shows 7.9% variation all over the pressure extent, however, the droplet number size appears to earn more weight as the size spectrum broadens while the surrounding pressure increases.

The infancy of core-collapse supernova remnants

ABSTRACT We present 3D hydrodynamic simulations of neutrino-driven supernovae (SNe) with the Prometheus-HotB code, evolving the asymmetrically expanding ejecta from shock breakout until they reach the homologous expansion phase after roughly one year. Our calculations continue the simulations for two red supergiant and two blue supergiant progenitors by Wongwathanarat et al., who investigated the growth of explosion asymmetries produced by hydrodynamic instabilities during the first second of the explosion and their later fragmentation by Rayleigh–Taylor instabilities. We focus on the late time acceleration and inflation of the ejecta caused by the heating due to the radioactive decay of 56Ni to 56Fe and by a new outward-moving shock, which forms when the reverse shock from the He/H-shell interface compresses the central part of the ejecta. The mean velocities of the iron-rich ejecta increase between 100 and 350 km s−1 (∼8–30 per cent), and the fastest 1 per cent of the iron accelerates by up to ∼1000 km s−1 (∼20–25 per cent). This ‘Ni-bubble effect’, known from 1D models, accelerates the bulk of the nickel in our 3D models and causes an inflation of the initially overdense Ni-rich clumps, which leads to underdense, extended fingers, enveloped by overdense skins of compressed surrounding matter. We also provide volume and surface filling factors as well as a spherical harmonics analysis to characterize the spectrum of Ni-clump sizes quantitatively. Three of our four models give volume filling factors larger than 0.3, consistent with what is suggested for SN 1987A by observations.

Interaction between strong sound waves and cloud droplets: Cloud chamber experiment

Acoustic agglomeration refers to the group effect of micro-particle groups in a strong sound field, which promotes relative motion among the particles, leading to the rapid agglomeration of the particle groups. The existing theoretical and experimental research on acoustic agglomeration is focused on solid particles such as soot particles and aerosols, and the acoustic agglomeration of micron-scale cloud droplets has not been intensively investigated. In this study, a cloud with an average particle size of ~10 μm is generated in a cloud chamber at room temperature, and a series of acoustic agglomeration experiments of cloud droplets under the action of sound waves with a frequency and sound pressure level (SPL) of 35–100 Hz and 112–122 dB, respectively, are conducted to examine the impact law of the sound waves with different frequencies and SPLs on the cloud droplet size spectrum. At a constant sound frequency, the agglomeration effect of the cloud droplets is more pronounced under the action of sound waves with a higher SPL. Under a constant SPL, the agglomeration effect is the most notable when the sound frequency ranges from 50 to 65 Hz. The threshold SPL for the effective agglomeration ranges from 114 to 121 dB when the sound frequency is 35–100 Hz, and the threshold SPL gradually increases with the sound frequency. The findings can clarify the effect of the sound waves in promoting cloud condensation and provide guidance to develop atmospheric intervention technologies based on strong sound waves.

Estimation of film antitranspirant spray coverage on rapeseed (Brassica napus L.) leaves using titanium dioxide

Film antitranspirant (AT) forms a physical layer to block stomata on the leaf surface and thus improve plant water status under drought. There is little understanding of how leaf coverage relates to the physiological mechanism, so a reliable method of evaluating AT spray deposition is needed. Titanium dioxide (TiO2) is widely applied to heighten the whiteness, brightness and opacity of materials, which can be potentially used as an inert marker to visualize AT deposited on leaves. This study aimed to evaluate the effect of TiO2 on the spray characteristics and coverage of film AT (a.i. di-1-p-menthene) on water-sensitive papers (WSP) and its subsequent use to explore the dose-response relationship between this AT and leaf coverage. Spray characteristics when applied through standard 110° flat fan nozzles were assessed using a droplet analyzer and coverage was measured using image analysis of deposition on water sensitive paper (WSP) and oilseed rape leaves. There was no significant difference observed with TiO2 added to film AT and water in droplet size spectra. Spray coverage averaged 46.8% and 57.3% respectively when WSP were positioned at 70 cm and 50 cm below nozzles. Adding TiO2 to AT solutions with different dose rates had no significant effects on WSP spray coverage at either nozzle height. Leaf coverage was positively correlated with the dose rates of AT at the distance of 50 cm from nozzles to the canopy. Overall, results suggest that TiO2 did not affect droplet size spectra or deposition on WSP of the AT when applied through a flat fan nozzle. Therefore, TiO2 can be effective as a tool to estimate the leaf coverage of film AT on rapeseed for use in future physiological studies.

Luminescence method to characterize the synthesis of ZnCdS quantum dots in real time

Studying the methods for the synthesis of nanoparticles are known, but to obtain nanoparticles with specified properties that allow them to be used as a biosensor is something totally different. Many problems arise associated with the implementation of the technique for creating reproducible and time-stable nanostructures. For investigation the effectiveness of the synthesis method on the state of nanoparticles and their optical characteristics, we synthesized ZnCdS, nanoparticles by various methods, and also studied their size, structure, absorption and luminescence spectra. The results show that the aggregation of Cd in the ZnS lattice causes distortions that eventually produce structural changes. The synthesis of Zn 1-x Cd x S, nanoparticles at x < 0.25, does not allow obtaining nanoparticles with a maximum wavelength of the luminescence band of more than 800 nm. While at x > 0.25, the intensity of the luminescence bands decreases sharply. This shift is due to a distortion of the luminescent energy states and surface defects.

Identification of full-length circular nucleic acids using long-read sequencing technologies.

Unlike the traditional perception in genomic DNA or linear RNA, circular nucleic acids are a class of functional biomolecules with a circular configuration and are often observed in nature. These circular molecules encompass the full spectrum of size and play an important role in organisms, making circular nucleic acids research worthy. Due to the low abundance of most types of circular nucleic acids and the disadvantages of short-read sequencing platforms, accurate and full-length circular nucleic acid sequencing and identification is difficult. In this review, we have provided insights into full-length circular nucleic acid detection methods using long-read sequencing technologies, with a focus on the experimental and bioinformatics strategies to obtain accurate sequences.

Droplet Size Spectrum, Activation Pressure, and Flow Rate Discharged from PWM Flat-Fan Nozzles

HighlightsDroplet sizes, activation pressures acting on nozzle orifices, and flow rates were investigated.Droplet sizes varied with duty cycles, nozzle orifice sizes, and PWM solenoid valve manufacturers.Activation pressures decreased as duty cycles decreased and increased as nozzle orifice sizes decreased.Flow rates increased with increases in both duty cycles and nozzle orifice sizes.Abstract. Pulse width modulated (PWM) spray systems can produce variable spray rates for precision applications of pesticide and fertilizer; however, there are also concerns over their spray performance stability. Droplet size distributions, activation pressures acting on nozzle orifices, and flow rates discharged from nozzles were investigated for test combinations of ten PWM duty cycles (10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and 100%), six flat-fan nozzles with different orifice sizes (XR8001, XR8002, XR8003, XR8004, XR8005, and XR8006), and two PWM solenoid valves from two different manufacturers. Test results showed that the droplet size distribution, activation pressure, and flow rate varied with the duty cycle, nozzle orifice size, and PWM solenoid valve source. For XR8001 and XR8002 nozzles, droplet sizes did not vary significantly with all duty cycles from 10% to 100%. To obtain relatively consistent droplet size distributions, XR8003 and XR8004 nozzles required PWM duty cycles of at least 20%, while XR8005 and XR8006 nozzles required duty cycles of 30% or greater. The activation pressure directly on nozzle orifices increased as the duty cycle increased but decreased as the nozzle orifice size increased. In addition, the same nozzles coupled with PWM solenoid valves from two different manufacturers discharged different flow rates for the same duty cycle in the range of 10% to 90%. Therefore, careful selection of PWM solenoid valves for different orifice nozzles operated at different duty cycles was necessary to achieve consistent variable-rate spray performances. Keywords: Droplet diameter, Variable rate, PWM solenoid valve, Pesticide, Fertilizer, Precision farming.

Nanopore Formation and Structural Changes in Black Shale During the Initial Weathering Stage: A Longmaxi Formation Profile in Northwestern Hunan, China.

Understanding the controls on composition changes and porosity evolution in the critical zone of shale remains a major challenge. The aim of the present study is to develop a model of the changes in mineral compositions, chemical compositions and nanopore formation in shale during the initial weathering stage. To understand these processes, we selected a Silurian shale profile rich in pyrite and organic matter located in South China. Based on X-ray diffraction (XRD) and bulk elemental data, the variations in mineralogical and chemical compositions with depth were studied. To characterize the full pore size spectrum and to gain insight into the nature of secondary pores and their relationship with weathering, nuclear magnetic resonance (NMR) measurements and petrographic observations were combined with scanning electron microscopy (SEM) imaging. The results show that Al and K are enriched slightly, while Ca and Na are depleted in the upper part of the weathering profile. Si, Mn and Ti are relatively stable from the bottom to the top of the profile. Quartz, feldspar, mica, illite and chlorite are the main minerals in the parent rock, and they are relatively stable along the profile. The rock density gradually decreases from 2.6 g/cm³ to 2.1 g/cm³ from the bottom to the top, and the color of the shales changes from black to grayish yellow, but no secondary minerals are detected. The chemical weathering of black shale is dominated by the oxidation of pyrite and organic matter, giving rise to color variation and nanopore formation. The increase in interparticle pores at the nanometer-micron scale is initiated by the dissolution of easily weathered components such as organic matter and pyrite. The removal of clay minerals and tiny particles by groundwater seepage may be the main cause of porosity enhancement during the initial weathering stage. This study suggests that nanoporosity may play an important role in the process of fluid-rock interaction within black shale during the initial weathering stage.

3D pore microstructures and computer simulation: Effective permeabilities and capillary pressure during drainage in Opalinus Clay

The 3D reconstruction of the pore space in Opalinus Clay is faced with the difficulty that high-resolution imaging methods reach their limits at the nanometer-sized pores in this material. Until now it has not been possible to image the whole pore space with pore sizes that span two orders of magnitude. Therefore, it has not been possible to predict the transport properties of this material with the help computer simulations that require 3D pore structures as input. Following the concept of self-similarity, a digital pore microstructure was constructed from a real but incomplete pore microstructure. The constructed pore structure has the same pore size spectrum as measured in the laboratory. Computer simulations were used to predict capillary pressure curves during drainage, which also agree with laboratory data. It is predicted, that two-phase transport properties such as the evolution of effective permeability as well as capillary pressures during drainage depend both on transport directions, which should be considered for Opalinus Clay when assessing its suitability as host rock for nuclear waste. This directional dependence is controlled on the pore scale by a geometric anisotropy in the pore space.

ECO-FLORISTIC STUDY OF WEED FLORA OF MAIZE CROP IN DISTRICT SWABI,KHYBER PAKHTUNKHWA, PAKISTAN

The present study explains floristic composition and ecological attributes characteristics of weeds of maize crop in district Swabi during September-October, 2018. A total of 28 weeds species distributed in 27 genera and 15 families were reported from the selected maize fields of the study area. Out of 15 families, 12 were dicots having (17 genera and 18 species) and 3 were monocots having (10 genera and 10 species). Poaceae was dominant family contributed 8 species. Amaranthaceae (5 spp.) followed by Aizoaceae and Convolvulaceae (2 spp.) each. The rest of 11 families were represented by single species each. Annuals contributed 19 (67.8%) species while perennials shared 9 (32.2%) species. Life-form spectra indicated that therophytes were dominant and abundant life form with 17 (60.7%) species. Leaf size spectra revealed that microphylls were major leaf size class with 12 (42.8 %) species. There were 25 (89.3%) species with simple leaves, 2 (7.1 %) species with compound leaves while 1 (3.6 %) species was represented by dissected leaves.

Биогеохимические характеристики мелководных струйных метановых газовыделений в прибрежных районах Крыма в сравнении с глубоководными сипами Чёрного моря

Струйные метановые газовыделения (сипы) — широко распространённый феномен в Мировом океане, в том числе в бассейне Чёрного моря. Актуальность исследований метановых сипов обусловлена их важной ролью в качестве источника метана как парникового и средообразующего газа для водной толщи и атмосферы. В работе представлен сравнительный анализ данных собственных биогеохимических исследований мелководных сипов Крымского полуострова, охватывающих последние десять лет, и материалов, посвящённых глубоководным газовыделениям Чёрного моря. В этот период были проведены поисковые гидроакустические исследования, выявлен компонентный состав пузырькового газа, измерен изотопный состав углерода метана, а также молекулярно-биологическими методами определена структура микробного сообщества бактериальных матов, покрывающих площадки газовыделений, и выполнена оценка газовых потоков от отдельных сипов. В течение многолетнего мониторинга обнаружено и описано 14 отдельных газовыделяющих площадок в прибрежных районах Крыма, которые располагались от мыса Тарханкут на западе полуострова до бухты Двуякорная на юго-востоке. Превалирующая часть прибрежных сипов Крыма имела биогенную природу и сезонный характер газовыделений. К глубинному газу термокаталитического генезиса отнесены сипы в бухте Ласпи. Наблюдался значительный разброс величин изотопного состава углерода метана δ13C-CH4 пузырькового газа прибрежных мелководных районов (−94…−34 ‰), что указывает на разные условия его генерации и созревания в донных отложениях. Так же, как и глубоководным сипам, прибрежным струйным газовыделениям сопутствовали бактериальные маты разной структуры с различными доминирующими видами. Показано, что для формирования устойчивой бактериальной биомассы, основу которой составляли, как правило, сульфид- и сероокисляющие бактерии, необходим флюидный поток восстановленных растворённых газов, тогда как точечная разгрузка пузырькового газа не обеспечивает достаточных градиентов концентрации и может механически разрушать структуру образующегося сообщества. Различными методами сделаны оценки размерных спектров пузырьков и потоков от отдельных струй. Диапазон значений газового потока варьировал от 1,8 л·сут−1 (бухта Мартынова) до 40 л·сут−1 (бухта Ласпи). Проанализированы средообразующие эффекты, связанные с выделением пузырькового газа в прибрежных районах: влияние сипов на кислородный режим в донных осадках и в толще воды́ над точками газовыделений; вертикальное перемешивание вод за счёт газлифтового эффекта; флюидная разгрузка на площадках струйных газовыделений.

High-Resolution Sampling of a Broad Marine Life Size Spectrum Reveals Differing Size- and Composition-Based Associations With Physical Oceanographic Structure

Observing multiple size classes of organisms, along with oceanographic properties and water mass origins, can improve our understanding of the drivers of aggregations, yet acquiring these measurements remains a fundamental challenge in biological oceanography. By deploying multiple biological sampling systems, from conventional bottle and net sampling to in situ imaging and acoustics, we describe the spatial patterns of different size classes of marine organisms (several microns to ∼10 cm) in relation to local and regional (m to km) physical oceanographic conditions on the Delaware continental shelf. The imaging and acoustic systems deployed included (in ascending order of target organism size) an imaging flow cytometer (CytoSense), a digital holographic imaging system (HOLOCAM), an In Situ Ichthyoplankton Imaging System (ISIIS, 2 cameras with different pixel resolutions), and multi-frequency acoustics (SIMRAD, 18 and 38 kHz). Spatial patterns generated by the different systems showed size-dependent aggregations and differing connections to horizontal and vertical salinity and temperature gradients that would not have been detected with traditional station-based sampling (∼9-km resolution). A direct comparison of the two ISIIS cameras showed composition and spatial patchiness changes that depended on the organism size, morphology, and camera pixel resolution. Large zooplankton near the surface, primarily composed of appendicularians and gelatinous organisms, tended to be more abundant offshore near the shelf break. This region was also associated with high phytoplankton biomass and higher overall organism abundances in the ISIIS, acoustics, and targeted net sampling. In contrast, the inshore region was dominated by hard-bodied zooplankton and had relatively low acoustic backscatter. The nets showed a community dominated by copepods, but they also showed high relative abundances of soft-bodied organisms in the offshore region where these organisms were quantified by the ISIIS. The HOLOCAM detected dense patches of ciliates that were too small to be captured in the nets or ISIIS imagery. This near-simultaneous deployment of different systems enables the description of the spatial patterns of different organism size classes, their spatial relation to potential prey and predators, and their association with specific oceanographic conditions. These datasets can also be used to evaluate the efficacy of sampling techniques, ultimately aiding in the design of efficient, hypothesis-driven sampling programs that incorporate these complementary technologies.