Vertical Scale Research Articles

Increasing the availability of oxygen promotes the metabolic activities and population growth of cable bacteria in freshwater sediments

Cable bacteria have been discovered in various marine and freshwater habitats, and their unique metabolism named electrogenic sulfide oxidation (e-SOx) is of great ecological significance to aquatic ecosystems. However, the environmental factors that determining the dynamics and abundance of cable bacteria in freshwater sediments are not well understood. In this study, we examined the activity and growth of cable bacteria in response to the change of oxygen availability in freshwater sediments. The metabolic activity of cable bacteria was quantified by microsensor profiling, while their abundance was determined by fluorescence in situ hybridization and 16S rRNA gene sequencing. The increase of oxygen availability greatly promoted the metabolic activity and proliferation of cable bacteria, as reflected by a higher rate of e-SOx and a larger population size. As affected by the change of sulfide availability and oxygen demand with the proliferation of cable bacteria, these promoting effects were more pronounced at later development stage. Moreover, the elevation of oxygen availability drove the downwards growth of cable bacteria and the increased inventories of dissolved sulfate in deeper sediment layers, which may expand the influences of cable bacteria on sediment biogeochemical cycling on the vertical scale. Our results contribute to further understanding of the correlations between oxygen availability and growth dynamics of cable bacteria in natural environments.

Spatial and temporal variations in salt marsh microorganisms of the Wadden Sea.

Salt marshes exist at the interface of the marine and the terrestrial system. Shore height differences and associated variations in inundation frequency result in altered abiotic conditions, plant communities, and resource input into the belowground system. These factors result in three unique zones, the upper salt marsh (USM), the lower salt marsh (LSM), and the pioneer zone (PZ). Marine detritus, such as micro‐ and macroalgae, is typically flushed into the PZ daily, with storm surges moving both salt marsh detritus and marine detritus into higher salt marsh zones. Microbial assemblages are essential for the decomposition of organic matter and have been shown to sensitively respond to changes in abiotic conditions such as oxygen supply and salinity. However, temporal and spatial dynamics of microbial communities of Wadden Sea salt marshes received little attention. We investigated the dynamics of soil microbial communities across horizontal (USM, LSM, and PZ), vertical (0–5 and 5–10‐cm sediment depth), and temporal (spring, summer, and autumn) scales in the Wadden Sea salt marsh of the European North Atlantic coast using phospholipid fatty acid (PLFA) analysis. Our results show strong spatial dynamics both among salt marsh zones and between sediment depths, but temporal dynamics to be only minor. Despite varying in space and time, PLFA markers indicated that bacteria generally were the dominant microbial group across salt marsh zones and seasons, however, their dominance was most pronounced in the USM, whereas fungal biomass peaked in the LSM and algal biomass in the PZ. Only algal markers and the stress marker monounsaturated to saturated fatty acid ratio responded to seasonality. Overall, therefore, the results indicate remarkable temporal stability of salt marsh microbial communities despite strong variability in abiotic factors.

Scaling Up: Molecular to Meteorological via Symmetry Breaking and Statistical Multifractality

The path from molecular to meteorological scales is traced and reviewed, beginning with the persistence of molecular velocity after collision induces symmetry breaking, from continuous translational to scale invariant, associated with the emergence of hydrodynamic behaviour in a Maxwellian (randomised) population undergoing an anisotropic flux. An empirically based formulation of entropy and Gibbs free energy is proposed and tested with observations of temperature, wind speed and ozone. These theoretical behaviours are then succeeded upscale by key results of statistical multifractal analysis of airborne observations on horizontal scales from 40 m to an Earth radius, and on vertical scales from the surface to 13 km. Radiative, photochemical and dynamical processes are then examined, with the intermittency of temperature implying significant consequences. Implications for vertical scaling of the horizontal wind are examined via the thermal wind and barometric equations. Experimental and observational tests are suggested for free running general circulation models, with the possibility of addressing the cold bias they still exhibit. The causal sequence underlying atmospheric turbulence is proposed.

Item Complexity: A Neglected Psychometric Feature of Test Items?

Despite its frequent consideration in test development, item complexity receives little attention in the psychometric modeling of item response data. In this address, I consider how variability in item complexity can be expected to emerge in the form of item characteristic curve (ICC) asymmetry, and how such effects may significantly influence applications of item response theory, especially those that assume interval-level properties of the latent proficiency metric and groups that vary substantially in mean proficiency. One application is the score gain deceleration phenomenon often observed in vertical scaling contexts, especially in subject areas like math or second language acquisition. It is demonstrated how the application of symmetric IRT models in the presence of complexity-induced positive ICC asymmetry can be a likely cause. A second application concerns the positive correlation between DIF and difficulty commonly seen in verbal proficiency (and other subject area) tests where problem-solving complexity is minimal and proficiency-related guessing effects are likely pronounced. Here we suggest negative ICC asymmetry as a probable cause and apply sensitivity analyses to demonstrate the ease with which such correlations disappear when allowing for negative ICC asymmetry. Unfortunately, the presence of systematic forms of ICC asymmetry is easily missed due to the considerable flexibility afforded by latent trait metrics in IRT. Speculation is provided regarding other applications for which attending to ICC asymmetry may prove useful.

Primary Productivity in the Mid-Atlantic Bight: Is the Shelf Break a Location of Enhanced Productivity?

Estimates of primary production represent the input of carbon into food webs, as well as the initial step in the biological pump. For the past 60 years, much of the productivity information has been obtained using measurements of 14C-bicarbonate removal during simulated in situ incubations. However, such measurements often do not reflect the complexity of the environment, and also suffer from uncertainties, biases and limitations. A vertically resolved bio-optical model has been used to estimate productivity based on profiles commonly assessed in oceanographic investigations, but comparisons with simultaneous measurements of 14C-uptake are limited. We conducted three cruises off the coast of New England that included sampling continental shelf waters, the shelf-break region, and deeper waters at scales of 7 km, all of which had productivity estimated by a vertically resolved productivity model as well as by traditional 14C-uptake measurements using simulated in situ techniques. We found that the vertically resolved bio-optical model gave results that appear to be more robust and resolved productivity at smaller vertical and horizontal scales, and seem less biased by some of the uncertainties in 14C-uptake measurements. Both estimates suggest that the New England waters are highly productive due to a variety of biological and physical processes occurring at different times of the year, but there was no consistent stimulation at the shelf break over the time scales of these estimates.

Challenging the Disk Instability Model. I. The Case of YZ LMi

Abstract Observations of YZ LMi show enhanced emission along the stream trajectory beyond impact at the disk rim during outbursts as well as when the quiescent disk is large. We investigated whether these features can be explained in terms of either gas stream overflow or penetration within the frameworks of the disk instability model (DIM) and the mass-transfer instability model (MTIM) of outbursting disks. Gas stream overflow is not possible because the vertical scale height of the stream is significantly lower than that of the outer disk and because there is no combination of parameters which enables stream overflow on a larger disk while preventing it on a smaller disk. Stream penetration requires the gas stream to be denser than the outer disk regions. This requirement cannot be met by a low-viscosity DIM disk because its density is significantly larger than that of the gas stream over the whole range of mass-transfer rates where the thermal-viscous instability occurs. On the other hand, the high-viscosity MTIM disk has much lower densities which decrease with increasing radius, easily allowing for gas stream penetration during outbursts (when mass-transfer rate and stream density increase) as well as in large quiescent disks. The observed features are not consistent with DIM, but can be plausibly explained by MTIM. These results suggest that the outbursts of YZ LMi are the response of a high-viscosity disk to bursts of enhanced mass-transfer rate. In this case, the outburst decline timescale of (2–3) days implies a viscosity parameter in the range α = 3–4.

Submesoscale Coherent Vortices Observed in the Northeastern South China Sea

AbstractAlthough submesoscale coherent vortices (SCVs) have been observed in different parts of the world's oceans, most of them were captured by accident by a limited number of hydrographic profiles. Here, using concurrent velocity and temperature/salinity measurements from a submesoscale‐resolving mooring array (2 km), two oppositely rotating SCVs are for the first time reported in detail in the northeastern South China Sea (NESCS). For the anticyclonic (cyclonic) SCV, its core lays at 210 m (180 m) with a mean Rossby number of −0.76 (0.65); its maximum swirl velocity, radius, vertical scale, and Burger number are estimated to be 0.43 m s−1, 31 ± 5 km, 235 m, and 1.5 (0.23 m s−1, 16 ± 3 km, 100 m, and 2.5), respectively. Corresponding to the SCVs' submesoscale nature, their momentum is governed by gradient‐wind rather than geostrophic balance. Consequently, kinetic energy of the anticyclonic (cyclonic) SCV would be on average underestimated (overestimated) by 47% (68%) if the traditional geostrophic relation was used to diagnose the velocity. Further analysis shows that thermohaline properties within the anticyclonic and cyclonic SCVs are close to the Kuroshio water and the local NESCS water, respectively. By combing water mass tracing and high‐resolution simulations, we suggested that the anticyclonic (cyclonic) SCV was generated in the southern Luzon Strait (southwest of Taiwan) through current‐topography interaction. We further proposed that the observed SCVs here should be a common phenomenon in the NESCS, which may provide a novel route for the tracer exchange between the NESCS and the western Pacific.

Fine-Scale Velocity Measurement on the Wirewalker Wave-Powered Profiler

Abstract The Wirewalker (WW) ocean-wave-powered vertical profiling system allows the collection of high-resolution oceanographic data due to its rapid profiling, hydrodynamically quiet operation, and long endurance. We have assessed the potential for measuring fine-scale ocean velocities from the Wirewalker platform using commercially available acoustic velocimeters. Although the vertical profiling speed is relatively steady, platform motion affects the velocity measurements and requires correction. We present an algorithm to correct our velocity estimates using platform motion calculated from the inertial sensors—accelerometer, gyroscope, and magnetometer—on a Nortek Signature1000 acoustic Doppler current profiler (ADCP). This correction, carried out ping by ping, was effective in removing the vehicle motion from the measured velocities. The motion-corrected velocities contain contributions from surface wave orbital velocities, especially near the surface, and the background currents. To proceed, we use an averaging approach that leverages both the vertical platform profiling of the system and the ∼15–20 m vertical profiling range resolution of the down-looking ADCP to separate the surface wave orbital velocities and the background flow. The former can provide information on the wave conditions. From the latter, we are able to estimate fine-scale velocity and shear with spectral wavenumber rolloff at vertical scales around 3 m, a vertical resolution several times finer than that possible from modern shipboard or fixed ADCPs with similar profiling range, and similar to recent glider measurements. When combined with a continuous time series of buoy drift calculated from the onboard GPS, a highly resolved total velocity field is obtained, with a unique combination of space and time resolution.

The drivers of avian-haemosporidian prevalence in tropical lowland forests of New Guinea in three dimensions.

Haemosporidians are among the most common parasites of birds and often negatively impact host fitness. A multitude of biotic and abiotic factors influence these associations, but the magnitude of these factors can differ by spatial scales (i.e., local, regional and global). Consequently, to better understand global and regional drivers of avian‐haemosporidian associations, it is key to investigate these associations at smaller (local) spatial scales. Thus, here, we explore the effect of abiotic variables (e.g., temperature, forest structure, and anthropogenic disturbances) on haemosporidian prevalence and host–parasite networks on a horizontal spatial scale, comparing four fragmented forests and five localities within a continuous forest in Papua New Guinea. Additionally, we investigate if prevalence and host–parasite networks differ between the canopy and the understory (vertical stratification) in one forest patch. We found that the majority of Haemosporidian infections were caused by the genus Haemoproteus and that avian‐haemosporidian networks were more specialized in continuous forests. At the community level, only forest greenness was negatively associated with Haemoproteus infections, while the effects of abiotic variables on parasite prevalence differed between bird species. Haemoproteus prevalence levels were significantly higher in the canopy, and an opposite trend was observed for Plasmodium. This implies that birds experience distinct parasite pressures depending on the stratum they inhabit, likely driven by vector community differences. These three‐dimensional spatial analyses of avian‐haemosporidians at horizontal and vertical scales suggest that the effect of abiotic variables on haemosporidian infections are species specific, so that factors influencing community‐level infections are primarily driven by host community composition.

Joint Occurrence of Heavy PM2.5 Pollution Episodes and Persistent Foggy Days in Central East China

Although many severe pollution events in Central and East China have been analyzed in recent years, the heavy PM2.5 pollution episode happened on persistent foggy days from January 13 to 18, 2018 was unique, characterized by explosive increase and sharp decrease in PM2.5 (particles with kinetic equivalent diameter less than or equal to 2.5 microns) concentration. Based on hourly data of ground level meteorological parameters, PM2.5 data and CALIPSO-based (the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation) aerosol data, combined with ECMWF (European Centre for Medium-Range Weather Forecasts) reanalysis data and radiosonde temperature profile, a comprehensive analysis was conducted to reveal the meteorological reasons for the evolution of the episode at horizontal and vertical scales. The PM2.5 concentration experienced four stages: a slow-increase phase, rapid-increase phase, rapid-decrease phase, and rebound phase. Results show that because Central and East China (CEC) were located at the back of a high-pressure system, humid southerly winds and near surface inversion (NSI) were responsible for the slow accumulation of pollutants. The rapid-increase phase was attributed to pollution transport at both ground level and in the lower troposphere because of weak cold air invasion. The significant subsidence at 500 hPa and 700 hPa intensified the NSI and led to dense fog. In that case, corresponding to the supersaturated atmosphere, the particles entered the fog droplets and were scavenged partly by deposition at night and were resuspended on the next day when the atmosphere was unsaturated. Our findings provide convincing evidence that surface PM2.5 rapid-decrease phase and the rebound phase were closely associated with dense fog process.

Length Scale Analyses of Background Error Covariances for EnKF and EnSRF Data Assimilation

Data assimilation (DA) combines incomplete background values obtained via chemical transport model predictions with observational information. Several 3-Dimensional variational (3DVAR) and sequential methods (e.g., ensemble Kalman filter (EnKF)) are used to define model errors and build a background error covariance (BEC) and are important factors affecting the prediction performance of DA. The BEC determines the spatial range, where observation concentration is reflected in the model when DA is applied to an air pollution transport model. However, studies investigating the characteristics of BEC using air quality models remain lacking. In this study, horizontal length scale (HLS) and vertical length scale (VLS) analyses of a BEC were applied to EnKF and ensemble square root filter (EnSRF), respectively, and two ensemble-based DA methods were performed; the characteristics were compared with those of a BEC applied to 3DVAR. The results of 6 h PM2.5 predictions performed for 42 days were evaluated for a control run without DA (CTR), 3DVAR, EnKF, and EnSRF. HLS and VLS respectively exhibited a high correlation with the ground wind speed and with the planetary boundary layer height for diurnal and daily variations; EnKF and EnSRF exhibited superior performances among all the methods. The root mean square errors were 11.9 μg m−3 and 11.7 μg m−3 for EnKF and EnSRF, respectively, while those for 3DVAR and CTR were 12.6 μg m−3 and 18.3 μg m−3, respectively. Thus, we proposed a simple method to find a Gaussian function that best described the error correlation of the BEC based on the physical distance.

A New Parameterization of Turbulent Mixing Enhanced Over Rough Seafloor Topography

AbstractExisting parameterizations of turbulent mixing enhanced over high‐wavenumber seafloor topography miss the fact that internal tidal waves emanating from the seafloor transform to internal lee waves as the tide‐topography interaction strengthens. This motivates us to replace the vertical decay scale of bottom‐enhanced turbulent mixing with the “vertical mean free path” of internal lee waves, namely, the average vertical distance over which internal lee waves propagate until they discharge their energy through interactions with the background internal waves. The resulting formula shows that the vertical extent of turbulent mixing becomes proportional to the abyssal barotropic tidal or steady flow amplitude squared and the inverse abyssal buoyancy frequency squared, but independent of the wavenumber of the seafloor, consistent with recent eikonal calculations and field observations. We propose a new parameterization of turbulent mixing enhanced over high‐wavenumber seafloor topography through incorporating the formulated vertical decay scale.

Energy Transfer From PSI‐Generated M1 Subharmonic Waves to High‐Frequency Internal Waves

AbstractInternal tides (ITs) represent one of the major energy sources available for small‐scale mixing in the ocean. Here, the energy pathway associated with ITs is examined based on measurements obtained at the East China Sea shelf slope. We reveal that after the occurrence of parametric subharmonic instability (PSI), energy can be further transferred from the PSI‐generated subharmonic waves to high‐frequency internal waves (HFIWs) through nonlinear interactions between them. This interprets the observed similar varying trends of magnitude between internal waves at near‐inertial and high‐frequency bands. Bispectrum and bicoherence estimates confirm that the M1 subharmonic wave interacts with a pair of HFIW which have larger vertical scales and a broad range of frequencies. The averaged net value of the energy transfer rate reaches 2 10−7 W kg−1, which has implications for a further significant role of this energy pathway on the spatial distribution of ocean mixing.

Comparative Microbial Nitrogen Functional Gene Abundances in the Topsoil vs. Subsoil of Three Grassland Habitats in Northern China.

The microbial groups of nitrogen fixers, ammonia oxidizers, and denitrifiers play vital roles in driving the nitrogen cycle in grassland ecosystems. However, the understanding of the abundance and distribution of these functional microorganisms as well as their driving factors were limited mainly to topsoil. In this study, the abundances of nitrogen functional genes (NFGs) involved in nitrogen fixation (nifH), ammonia oxidation (amoA), and denitrification (nirK, nirS, and nosZ) were investigated in both topsoil (0–10 cm, soil layer with concentrated root) and subsoil (30–40 cm, soil layer with spare root) of three grassland habitats in northern China. The abundance of NFGs decreased with soil depth except for the archaeal amoA gene and the distribution of nifH, archaeal amoA, nirK, and nirS gene was significantly impacted by grassland habitats. Moreover, the distribution of NFGs was more responsive to the vertical difference than horizontal spatial heterogeneity. Redundancy analysis revealed that the distribution pattern of overall NFGs was regulated by grassland habitats, and these regulations were more obvious in the subsoil than in the topsoil. Variance partitioning analysis further indicated that soil resource supply (e.g., organic matter) may control the vertical distribution of NFGs. Taken together, the findings in this study could fundamentally improve our understanding of the distribution of N cycling-associated microorganisms across a vertical scale, which would be useful for predicting the soil N availability and guiding the soil N management in grassland ecosystems.

Riemann-Liouville fractional derivatives of hidden variable recurrent fractal interpolation functions with function scaling factors and box dimension

In [M.G. Ri and C.H. Yun, Smoothness and fractional integral of hidden variable recurrent fractal interpolation function with function vertical scaling factors, Fractals 29(6) (2021) 2150136], the authors proved that the partial and mixed Riemann-Liouville fractional integrals of bivariable hidden variable recurrent fractal interpolation function(HVRFIF) with function scaling factors are HVRFIFs. As its continuation, in this paper, we show that Riemann-Liouville fractional derivatives of one variable and bivariable HVRFIFs are HVRFIFs under certain conditions. We also derive the relationship between the order of fractional calculus and the upper box dimension of its graph. To do it, firstly, we prove that Riemann-Liouville fractional derivative of one variable HVRFIF is HVRFIF. Secondly, we obtain estimation of the upper box dimension of the graph of one variable HVRFIF and derive the relationship between the upper box dimension and the order of fractional calculus. Finally, in the similar way to one variable, we show that the partial and mixed Riemann-Liouville fractional derivatives of bivarible HVRFIF are HVRFIFs.

Wet-based digital etching on GaN and AlGaN

Many advanced III-nitride devices, such as micro-LEDs, vertical FinFETs, and field emitters, require the fabrication of high aspect ratio vertical pillars or nanowires. Two-step etchings combining dry and wet etching steps have been used on vertical devices in the past, but they show poor control in vertical nanostructures with sub-50 nm diameter. In this work, we demonstrate a wet-chemical digital etching on GaN and AlGaN and apply it to both vertical nanostructure scaling and planar etching along the c-axis. In this digital etching process, a mixture of H2SO4 and H2O2 is applied to oxidize the III-nitrides surface, and the oxide layer is then removed by dilute HCl. This digital etching approach can finely sharpen vertical structures and does not require any vacuum or plasma systems, which will enable advanced device structures in the future.

Characteristic Analysis of nirS Denitrifying Bacterial Community in Lijiahe Reservoir During Stratification

To explore the composition of the nirS denitrifying bacterial community during stratification in spring(March to May) in a drinking water reservoir and its relationship with water quality, the water quality and relative abundance and structure of the denitrifying bacterial community were analyzed using in-situ monitoring coupled with Illumina high-throughput sequencing technology in the Lijiahe Reservoir. The results showed that:① through high-throughput sequencing, 4 phyla and 13 genera were identified. The dominant bacterial phylum was Proteobacteria, and its relative abundance was between 52.5% and 70.6%. The overall trend of the relative abundance of Proteobacteria decreased on the time scale (P<0.05), and its relative abundance in the surface and middle layers was higher than that of the bottom layer on the spatial scale (P<0.05). There was no difference in the proportion of Proteobacteria between the surface and middle layers (P>0.05), and the abundance of its bottom layer was relatively stable; eight genera of bacteria with denitrification function were identified, among which the dominant bacterial genera (relative abundance>1%) were Dechloromonas and Pseudomonas. The relative abundance of Dechloromonas showed a trend of first decreasing and then increasing on the time scale, whereas the relative abundance of Pseudomonas showed a trend of increasing first and then decreasing on the time scale. There were no differences on the spatial scale between these two genera (P>0.05); the changes in bacterial diversity and abundance were basically similar, with a trend of first increasing and then decreasing on the time scale. The highest diversity and abundance of the bacterial community gradually increased with increasing depth on the spatial scale. ② ρ(TN) of the reservoir during stratification was 2.35-2.91 mg·L-1, and the nitrogen pollution was more serious. In March and April, ρ(TN) on the vertical scale was basically similar and showed a decreasing trend. In May, the content of total nitrogen was higher than that in March and April, and the highest value of total nitrogen content occurred in the surface layer. ③ Redundancy analysis showed that water temperature, dissolved oxygen, nitrate, and ammonia nitrogen were the main driving factors, and ammonia nitrogen showed a significantly negative correlation with Dechlormonas. In summary, the study of nirS-type denitrification communities and related influencing factors will contribute to analyzing the characteristics of denitrifying bacterial community changes in a micro-polluted drinking water reservoir and provide a theoretical research basis for the biological remediation of nitrogen pollution in such reservoirs in the future.

A Statistical Investigation of Inertia Gravity Wave Activity Based on MST Radar Observations at Xianghe (116.9°E, 39.8°N), China

AbstractUsing three‐dimensional wind observations from a Mesosphere‐Stratosphere‐Troposphere radar at Xianghe for two years from September 2011 to August 2013, we study inertia gravity wave (IGW) activity in the two height segments of 3–10 and 15–25 km to reveal the characteristics of waves in the source region at midlatitude. Case investigation indicates that three‐dimensional wind fluctuations are usually dominated by a strong IGW. Statistics on 15,617 IGWs extracted show that most waves have typical horizontal scales of tens to thousands of kilometers, the vertical scale of a few kilometers, intrinsic frequencies in 1–4 times the inertial frequency, and amplitudes of 1–4 ms−1 in horizontal winds but less than 0.3 ms−1 in the vertical wind. In the lower region, occurrence possibilities of upward and downward propagating waves are almost the same throughout the year. Whereas in the upper region, IGWs display a predominant upward propagation with a maximum of 85.3% in February but a minimum of 63.6% in July, and a preferential propagation in the zonal direction relative to the meridional direction. Meanwhile, wave energy has a prominent seasonal cycle with the maximum in winter and the minimum in summer. Subtropical jet, as wave source and propagation condition, plays an important role in these different features between the two regions. The annual average of momentum flux indicates that the IGWs in the lower stratosphere can apply a persistent eastward drag on the background flow at higher altitudes through momentum transported by these waves.

Temporal and vertical variation of phytoplankton and zooplankton in two tropical reservoirs with different trophic states.

In tropical reservoirs, limnological factors are responsible for changes in plankton and vary at temporal and vertical scales. The aim of this study was to evaluate the effects of temporal and vertical variation of the water column on phytoplankton and zooplankton dynamics in two tropical reservoirs (mesotrophic and supereutrophic) in Northeastern Brazil. Monthly collections from three depths in the limnetic region of the reservoirs were performed to analyze the phytoplankton, zooplankton, and limnological variables. The temporal and vertical variation of the physical and chemical water variables, including their interactions, influenced the phytoplankton and zooplankton community. In the supereutrophic reservoir, decreased nitrogen and increased phosphorus and temperature contributed to the dominance of Microcystis panniformis Komárek, Komárková-Legnerová, Sant'Anna, M.T.P.Azevedo & P.A.C.Senna. Conversely, Planktothrix agardhii (Gomont) Anagnostidis & Komárek was dominant under high nitrogen concentrations and low temperatures. In the mesotrophic reservoir, the desmids were dominant and showed a positive relationship with nitrogen. Copepoda Calanoida was dominant and correlated to phytoplankton in both reservoirs. The results showed that nitrogen forms directly influenced phytoplankton, and the importance of nitrogen for management strategies of tropical reservoirs, as well as demonstrated the ability of Calanoida to adapt to different trophic conditions and phytoplankton compositions.

Predictive Hybrid Autoscaling for Containerized Applications

One of the main challenges in deploying container service is providing the scalability to satisfy the service performance and avoid resource wastage. To deal with this challenge, Kubernetes provides two kinds of scaling mode: vertical and horizontal. Several existing autoscaling methods make efforts to improve the default autoscalers in Kubernetes; however, most of these works only focus on one scaling mode at the same time, which results in some limitations. Only horizontal scaling may lead to low utilization of containers due to the fixed amount of resources for each instance, especially in the low-request period. In contrast, only vertical scaling may not ensure the quality of service (QoS) requirements in case of bursty workload due to reaching the upper limit. Besides, it is also necessary to provide burst identification for auto-scalers to guarantee service performance. This paper proposes a hybrid autoscaling method with burst awareness for containerized applications. This new approach considers a combination of both vertical and horizontal abilities to satisfy the QoS requirement while optimizing the utilization of containers. Our proposal uses a predictive method based on the machine learning technique to predict the future demand of the application and combines it with a burst identification module, which makes scaling decisions more effective. Experimental results show an enhancement in maintaining the response time below the QoS constraint whereas remaining high utilization of the deployment compared with existing baseline methods in single scaling mode.