Seasonal Changes In Water Temperature Research Articles

Seasonal constraint of dynamic water temperature on riverine dissolved inorganic nitrogen transport in land surface modeling

Riverine dissolved inorganic nitrogen (DIN) transport plays an important role in the link between terrestrial and marine ecosystems, while the seasonal changes of water temperature exert a strong control on DIN dynamics. However, the response of the flow of DIN to dynamic water temperature in large rivers is not well known at the global scale. In this study, based on a recently developed land surface model coupled with riverine water temperature and DIN transport schemes, two numerical simulations, with and without dynamic water temperature, were implemented to investigate the seasonal constraint of dynamic water temperature on the change in riverine DIN flow. Results show that the water temperature could be a key controlling factor for the spatial distribution of global DIN flows. After integrating dynamic water temperature estimation into land surface modeling, the annual amplitudes of DIN flow were 5%–25% smaller than before between 30°N and 30°S, while approximately 10% larger in other latitudinal zones. Less denitrification was out of the scope of 40°N–20°S in summer. In eastern China, the dynamic water temperature made the DIN flow reduce by 1%–3% in summer, while it made it increase by 1%–5% in winter. A seasonal constraint of dynamic water temperature, making the amplitude of monthly fluctuation reduce by about 60%, was found in global large rivers. This study shows the importance of dynamic water temperature in the seasonal modeling of riverine DIN flow, and provides a scientific reference for land surface model development and water environment management.摘要水体温度变化对河流可溶性无机氮(DIN)输送有着强烈控制作用. 然而, 在全球尺度上河流DIN输送量对水温度变化的响应尚不清楚. 因此, 本文基于陆面过程模式, 耦合河流水温估算和DIN传输方案, 设定有, 无动态水温情景, 对比研究陆面模拟中水温变化对河流DIN通量变化的影响. 结果表明: 在考虑水温动态变化后, 在30°N和30°S之间, DIN通量年振幅减小5%–25%. 在中国东部地区, 水温动态变化使河流DIN通量在夏季减少1%–3%, 在冬季增加1%–5%, 对DIN通量具有明显的季节性约束作用, 表明动态水温的表达在河流DIN输送模拟中的重要性.

Complete genome sequence of a winter season Vibrio facilitates discovery of a novel subclade of cold-adapted species in the albus clade.

In temperate marine climate zones, seasonal changes in water temperature contribute to distinct populations of warm- and cold-water vibrios. We report here the complete genome sequence (BUSCO score=94.8) of the novel strain Vibrio sp. VB16 isolated in late winter from the intertidal zone near Virginia Beach, Virginia, USA with the ability to form colonies at 4 °C. The 5.2 Mbp genome is composed of a large (3.6 Mbp) and small (1.6 Mbp) chromosome. Based on paired average nucleotide identity (ANI), average amino acid identity (AAI) and digital DNA-DNA hybridization (dDDH), V. sp. VB16 is the same species as V. sp. UBA2437 from a North Sea tidal flat and is closely related to V. sp. DW001 from Antarctic sea ice. Our phylogenomic and bioinformatic analyses placed VB16, UBA2437 and DW001 into a cold-tolerant subclade within the albus clade, along with two non-cold-tolerant subclades. Orthovenn analysis indicated that VB16 and its other albus clade members shared 1544 gene orthologue clusters, including clusters for biosynthesis of polar flagella and tight adhesion pili that predict multiple lifestyles, either free-living or as an opportunistic pathogen within a marine eukaryotic host. The cold-tolerant subclade shared 552 orthologue proteins, including genes known to promote survival in cold or freezing temperatures, such as the eicosapentaenoic acid biosynthetic gene cluster, syp exopolysaccharide gene cluster and novel giant proteins with ice-binding domains. This subclade represents a group of psychrotolerant or 'moderate psychrophile' winter season Vibrio species. The discovery of this subclade opens the door for experimental work on the physiological features, virulence potential and ecological importance of this subclade.

Water temperature and organic carbon control spatio‐temporal dynamics of particle‐attached and free‐living bacterial communities in a hypereutrophic urban river network

Abstract Bacteria are an important component of the aquatic ecosystem playing a key role in the transformation and mineralisation of allochthonous organic matter, nutrients and pollutants. However, there is no clear understanding of spatio‐temporal patterns of particle‐attached versus free‐living bacterial abundances, diversities and communities, which limits our in‐depth understanding of hypereutrophic urban river ecosystems and the mechanisms regulating nutrient cycling and biogeochemical transformations. In order to investigate spatio‐temporal patterns and associated factors for aquatic particle‐attached versus free‐living bacterial communities, we conducted a 2‐year study of four contrasting habitats in a hypereutrophic urban river network of eastern China. Bacterial abundance and community structure in relation to various environmental variables were assessed by epifluorescence microscopy and high‐throughput sequencing techniques. Results revealed that particle‐attached bacterial abundance depended mainly on suspended particle concentrations, whereas free‐living bacterial abundance was correlated with nutrient availability and water temperature. Organic carbon was related to a decrease of free‐living and particle‐attached bacterial richness, and particulate matter input increased free‐living bacterial diversity. Seasonal changes of water temperature were linked to the temporal dynamics of bacterial community composition, and the differences in total organic carbon concentrations contributed to spatial differences in bacterial community composition. There were significant differences in bacterial community composition between particle‐attached and free‐living assemblages in low‐turbidity/low‐nutrient rivers found in land areas comprising mainly natural vegetation. These differences were especially prominent for the relative abundances of Cyanobacteria and Actinobacteria, which were higher in the particle‐attached and free‐living fractions, respectively. However, no significant differences were found in turbid/nutrient‐rich rivers. Total organic carbon was the most significant factor shaping the composition similarity between particle‐attached and free‐living bacterial communities. Our findings indicate that spatio‐temporal variations in water temperature, suspended particle and resource availability, especially for organic carbon, appreciably contribute to changes in the abundance, diversity and composition of aquatic particle‐attached versus free‐living bacterial communities in the hypereutrophic urban river network. Considering that biodiversity is important for supporting ecosystem functioning, this study informs spatio‐temporal patterns of particle‐attached and free‐living bacterial abundance, diversity and composition of communities, and their underlying control mechanisms, thereby providing fundamental knowledge of microbial ecological functions for remediation and sustainable management of hypereutrophic urban river ecosystems.

Microeukaryotic predators shape the wastewater microbiome

The physicochemical parameters that shape the prokaryotic community composition in wastewater have been extensively studied. In contrast, it is poorly understood whether and how biotic interactions affect the prokaryotic community composition in wastewater. We used metatranscriptomics data from a bioreactor sampled weekly over 14 months to investigate the wastewater microbiome, including often neglected microeukaryotes. Our analysis revealed that while prokaryotes are unaffected by seasonal changes in water temperature, they are impacted by a seasonal, temperature-induced change in the microeukaryotic community. Our findings suggest that selective predation pressure exerted by microeukaryotes is a significant factor shaping the prokaryotic community in wastewater. This study underscores the importance of investigating the entire wastewater microbiome to develop a comprehensive understanding of wastewater treatment.

Variation of Gene Expression in the Endemic Dinaric Karst Cave-Dwelling Bivalve Mollusk Congeria kusceri during the Summer Season

The cave systems of the Neretva River basin in the Dinaric Karst are home to Congeria kusceri, one of the very few known examples of stygobiotic bivalve mollusks, which displays several unique life history traits and adaptations that allowed its adaptation to the subterranean environment. This endemic species is undergoing rapid decline, most likely linked with habitat degradation, which might seriously threaten its survival in the next few decades. Unfortunately, the urgent need for effective conservation efforts is hampered by the lack of effective regulations aimed at preserving remnant populations as well as by our limited knowledge of the biology of this species. Although the precise factors underlying the disappearance of C. kusceri from its type locations are not entirely clear, the alteration of seasonal changes in water temperatures and alkalinity is most likely involved, as these are the main drivers of shell growth, spawning, and the onset and progression of the new gametogenic cycle. While these aspects have so far only been studied using morphological and physiological observations, future conservation efforts would certainly benefit from an integrated multidisciplinary approach. Here, using RNA-sequencing, we provide an overview of the modulation of gene expression recorded in five key tissues (the mantle, gonads, gills, adductor muscle, and digestive gland) between early June and late September. We highlight the presence of markedly tissue-specific responses, with the most dramatic changes affecting the gonads, mantle, and gills. We further identified a drastic switch in the use of energy budgets between the two periods, with evidence of ongoing shell growth and high metabolic activity in the mantle and gills at the early time point, followed by a massive redirection of all available energy to the gonads for the generation of new gamete primordia in early autumn.

Holoplankton and meroplankton communities in surf zone waters of a temperate SW Atlantic sandy beach: Seasonal patterns

AbstractSandy beaches and their associated surf zones are the most common type of open shoreline, with significant ecological and socio‐economic importance. In this study, we explored the seasonal fluctuations of the surf zone holo‐ and meroplankton communities to understand the underlying environmental variables driving the temporal dynamics of each community. We also defined a surf‐zooplankton community on a temperate sandy beach (Monte Hermoso, Argentina) and related the organisms to those reported in a nearby estuary for a better understanding of the connection between adjacent coastal ecosystems. Holoplankton was very abundant (13.52–11070.4 ind m−3) and showed a strong seasonality, mainly related to the specific pattern of the two most abundant species: Acartia tonsa (>autumn) and Paracalanus parvus (>winter). This community was affected by seasonal changes in water temperature and salinity and variations in the velocity of currents, which showed that hydrodynamic forces were more significant on a short‐term time scale than seasonal ones. Meroplankton abundances (1.3–48.05 ind m−3) were significantly lower than those recorded for the holoplankton and were mainly dominated by Medusae and larvae of Bivalvia and Decapoda. This fraction also showed a clear seasonal pattern (>abundances in summer), primarily related to the seasonal changes in temperature. The abundances of the main surf‐zooplanktonic taxa were high and constant, emphasizing the importance of these waters as habitats for well‐established communities rather than being used as a transient area. Consequently, we proposed a “specific” surf‐zooplankton community for a temperate sandy beach, considering resident and non‐resident taxa. Finally, the comparison of the surf and estuarine communities indicated a faunal relationship between seascapes, highlighting the ecological role of coastal waters in planktonic life.

Effects of dimensionality on the performance of hydrodynamic models for stratified lakes and reservoirs

Abstract. Numerical models are an important tool for simulating temperature, hydrodynamics, and water quality in lakes and reservoirs. Existing models differ in dimensionality by considering spatial variations of simulated parameters (e.g., flow velocity and water temperature) in one (1D), two (2D) or three (3D) spatial dimensions. The different approaches are based on different levels of simplification in the description of hydrodynamic processes and result in different demands on computational power. The aim of this study is to compare three models with different dimensionalities and to analyze differences between model results in relation to model simplifications. We analyze simulations of thermal stratification, flow velocity and substance transport by density currents in a medium-sized drinking-water reservoir in the subtropical zone, using three widely used open-source models: GLM (1D), CE-QUAL-W2 (2D) and Delft3D (3D). The models were operated with identical initial and boundary conditions over a 1-year period. Their performance was assessed by comparing model results with measurements of temperature, flow velocity and turbulence. Our results show that all models were capable of simulating the seasonal changes in water temperature and stratification. Flow velocities, only available for the 2D and 3D approaches, were more challenging to reproduce, but 3D simulations showed closer agreement with observations. With increasing dimensionality, the quality of the simulations also increased in terms of error, correlation and variance. None of the models provided good agreement with observations in terms of mixed layer depth, which also affects the spreading of inflowing water as density currents and the results of water quality models that build on outputs of the hydrodynamic models.

Cool runnings: behavioural plasticity and the realised thermal niche of basking sharks

Long-distance migrations by marine vertebrates are often triggered by pronounced environmental cues. For the endangered basking shark (Cetorhinus maximus), seasonal changes in water temperature are frequently proposed as a cue for aggregation within (and dispersal from) coastal hotspots. The inference is that such movements reflect year-round occupancy within a given thermal ‘envelope’. However, the marked variance in timing, direction and depth of dispersal movements hint at a more nuanced explanation for basking sharks. Here, using data from pop-off archival transmitters deployed on individuals in Irish waters, we explored whether autumnal decreases in water temperature triggered departure from coastal habitats and how depth and location shaped the sharks’ realised thermal environment over time. Temperature was not an apparent driver of dispersal from coastal seas, and variance in daily temperature ranges reflected occupancy of different habitats; coastal mixed/stratified and offshore subtropical/tropical waters. Furthermore, individuals that moved offshore and into more southern latitudes off Africa, exhibited a distinct daily cycle of deep dives (00:00–12:00, 200 m–700 m; 12:00–00:00, 0–300 m), experiencing a more extreme range of temperatures (6.8–27.4 °C), including cooler minimum temperatures, than those remaining in European coastal habitat (9.2–17.6 °C). Collectively, these findings challenge the supposition that temperature serves as a universal driver of seasonal dispersal from coastal seas and prompts further studies of deep-water forays in offshore areas.

Dissolved oxygen stratification in a small lake depending on water temperature and density and wind impact

The dissolved oxygen (DO) is one of the most important parameters in lakes ecosystem. Variability of DO in lakes is associated with the absorption of oxygen due to the decomposition of organic matter and chemical reactions and the release of oxygen as a result of photosynthesis. The DO concentration also depends on seasonal changes in water temperature and mixing regime. The aim of this work is to assess the influence of seasonal thermal and density stratification on the DO stratification in a small mesotrophic lake and to develop a regression DO model, with water temperature and density and characteristics of wind regime as independent variables. Long-term measurements of water temperature and DO in small Karelian Lake Vendyurskoe in 2007-2020 were used. At the stage of spring-summer heating, three periods are considered when the water column was in the state of homothermy (May 15-June 15), weak stratification (July 15-August 15), and strong stratification (July 15-August 15). The wind load (number of days with wind speed more than 3 m/s for each period) was analysed based on the weather station Petrozavodsk data. As a result of multiple regression analysis, taking into account the wind load, dependences of DO stratification on water temperature stratification (R2 = 0.51) and water density stratification (R2 = 0.61) are found. Obtained regression DO models can be used for solving various environmental tasks.

A Multi-Year Assessment of Phytoplankton Fluorescence in a Large Temperate River Reveals the Importance of Scale-Dependent Temporal Patterns Associated With Temperature and Other Physicochemical Variables

An integrated temporal study of a long-term ecological research and monitoring database of the St. Lawrence River was carried out. A long and mostly uninterrupted high temporal resolution record of fluorometric data from 2014 to 2018 was used to examine phytoplankton fluorometric variables at several scales and to identify temporal patterns and their main environmental drivers. Sets of temporal eigenvectors were used as modulating variables in a multiscale codependence analysis to relate the fluorometric variables and various environmental variables at different temporal scales. Fluorometric patterns of phytoplankton biomass in the St. Lawrence River are characterized by large, yearly-scale patterns driven by seasonal changes in water temperature, and to a lesser extent water discharge, over which finer-scale temporal patterns related to colored dissolved organic matter and weather variables can be discerned at shorter time scales. The results suggest that such an approach to characterize phytoplankton biomass in large rivers may be useful for processing large data sets from remote sensing efforts for detecting subtle large-scale changes in water quality due to land use practices and climate change.

Tropical tufa and karst streams support unique and threatened assemblages of aquatic Diptera, Empididae in Thailand

AbstractAquatic Empididae (Diptera) in the subfamilies Hemerodromiinae and Clinocerinae were used as a model to provide the first appraisal of diversity, endemism, environmental preferences and anthropic threats to Diptera communities of calcareous streams and tufa ecosystems of tropical karst habitats of Thailand. Hemerodromia Mg. (Hemerodromiinae) was abundant and speciose with 17 spp., of which six were associated with tufa, two with calcareous streams, three occurred on both tufa and streams and six were eurytopic species also found away from karst. Clinocerinae were only represented by one rare species of Clinocera Mg. Local and regional‐scale endemism was apparent at species level in Hemerodromia. Assemblage similarity in tufa habitats decayed with distance but cluster analysis provided only weak support for community‐level endemism at any geographic scale. Ordination indicated that benthic substrate and canopy cover were the most important environmental variables for many species. The six obligate tufa species of Hemerodromia were absolutely associated with rapid shallow flows of water over tufa surfaces at waterfalls. Species richness and abundance varied through the monsoon cycle but there was little evidence of simple correlations with seasonal changes in water temperature, conductivity and pH. The hypothesis that cold‐adapted aquatic Empididae might have been marooned in cold emergent groundwaters at lower elevations was not supported. It is concluded that tropical tufa ecosystems in Thailand support distinctive, rich and often endemic populations of stenotopic species of considerable biological and conservation interest. Deteriorative changes linked to tourism, water abstraction and agricultural activity could threaten these unique communities.

Seasonal changes in kinetic parameters of trypsin in gastric and agastric fish

The objective of the present study was to assess if trypsin, a key enzyme involved in protein digestion, presents some kind of functional adaptations to seasonal changes in water temperature in freshwater fish. In order to test this hypothesis, individuals of two fish species Carassius gibelio (agastric) and Perca fluviatilis (gastric) were sampled in the basin of Chany Lake (Siberia, Russia) at two different seasons (spring and summer). Apparent kinetic parameters (Km and Vmax) were determined for both species and seasons at the actual pH values in fish guts, and at actual temperatures. Results showed a significant effect of both the species and sampling season on the apparent kinetic parameters of trypsin. In the case of Prussian carp, Km and Vmax were lower for each assayed temperature (for 5 and 15°C the differences were significant) for fish sampled in summer when compared to those sampled in spring. In contrast, values of Km in perch tended to be lower in spring at 5 and 25°C but these differences were not significant, while Vmax showed a significant decrease in summer samples. This suggests a sort of functional adaptation of the same trypsin enzymes to seasonal changes, oriented to maximize protein digestion under variable conditions.

Consistent Behavioral Syndrome Across Seasons in an Invasive Freshwater Fish

Understanding the linkage between behavioral types and dispersal tendency has become a pressing issue in light of global change and biological invasions. Here, we explore whether dispersing individuals exhibit behavioral types that differ from those remaining in the source population. We investigated a feral population of guppies (Poecilia reticulata) that undergoes a yearly range shift cycle. Guppies are among the most widespread invasive species in the world, but in temperate regions these tropical fish can only survive in winter-warm freshwaters. Established in a thermally-altered stream in Germany, guppies are confined to a warm-water influx in winter, but can spread to peripheral parts as these become thermally accessible. We sampled fish from the source population and a winter-abandoned site in March, June and August. Fish were tested for boldness, sociability and activity involving open-field tests including interactions with a robotic social partner. Guppies differed consistently among each other in all three traits within each sample. Average trait expression in the source population differed across seasons, however, we could not detect differences between source and downstream population. Instead, all populations exhibited a remarkably stable behavioral syndrome between boldness and activity despite strong seasonal changes in water temperature and associated environmental factors. We conclude that random drift (opposed to personality-biased dispersal) is a more likely dispersal mode for guppies, at least in the investigated stream. In the face of fluctuating environments, guppies seem to be extremely effective in keeping behavioral expressions constant, which could help explain their successful invasion and adaptation to new and disturbed habitats.

Исследование сезонного изменения температуры воды озёрной части Горьковского водохранилища в 2018 г. по данным in situ измерений и спутниковым изображениям высокого разрешения

Исследование сезонного изменения температуры воды озёрной части Горьковского водохранилища в 2018 г. по данным in situ измерений и спутниковым изображениям высокого разрешения

Seasonal variation in the invertebrate community and diet of a top fish predator in a thermally stable spring

Many life-history events in aquatic invertebrates are triggered by seasonal changes in water temperature, but other ecological factors may be important as well. To rule out the confounding effects of changing water temperature, we studied the seasonal dynamics of an aquatic invertebrate community and their effect on a top fish predator in a thermally stable freshwater spring in South Iceland. We sampled benthic invertebrates five times over a year and conducted a mark-recapture study on the top predator in the system, small benthic Arctic charr, Salvelinus alpinus (L.). We assessed variation in diet composition and feeding preferences by calculating the electivity and individual specialisation of each fish at each sampling time. There was a clear separation of winter and summer communities for the benthic invertebrates. The variation in prey availability was also reflected in the fish diet, with higher feeding selectivity in summer than in winter for the highly abundant Chironomidae larvae. In contrast, individual specialisation as a measure of intrapopulation niche variation was higher in winter when prey availability was lower. We furthermore found that groundwater amphipods might play an important role in the winter diet of spring-dwelling Arctic charr. In conclusion, seasonal variation in the invertebrate community is an important factor to consider and has the potential to alter the phenotype (e.g. growth rates) and behaviour (e.g. feeding preferences) of higher trophic levels.

Spatial analysis on the occurrence of inshore and offshore bottlenose dolphins (Tursiops truncatus) in Osa Peninsula waters and Golfo Dulce, Costa Rica

The aim of this assessment is to advance our understanding in the spatial ecology of the resident inshore and offshore population of bottlenosedolphins in Golfo Dulce (GD) and Osa Peninsula Waters (OPW). Our approach used niche-based models (Phillips et al., 2006, Thorne et al., 2012,Friedlaender et al., 2011), which provided details of how dolphins use coastal and oceanic habitats, describing the factors that influence theirdistribution in the study area and identifying the critical habitats to be considered for management and conservation. Our analyses indicate severalimportant aspects of the distribution of these two ecotypes of bottlenose dolphins. As expected in the study area, these two ecological races occurin close proximity, but differ in the structural factors of the habitat they occupy. The inshore population uses areas close to the mouths of the riversas critical foraging habitats, being influenced by tidal cycles and seasonal changes in water temperature and salinity. The offshore population inoceanic habitats must rely on prey species found in rare but profitable patches, therefore pelagic dolphins in the open ocean would often need totravel long distances searching for these patches. Distribution models illustrating the difference in habitat use presented in this assessment are keyto effective management of the marine mammals’ diversity in Costa Rica.

Monthly variation of growth, biochemical composition, fatty and amino acids patterns of gilthead sea bream (Sparus aurata) in offshore cage systems under brackish water conditions in the Black Sea

The aim of this study was to investigate seasonal variations of growth performance and biochemical composition, fatty and amino acids profiles of cage-cultured gilthead sea bream (Sparus aurata) in the Black Sea. The research was carried out on a yearly basis in the offshore cage systems of a commercial fish farm located on the coast of Samsun province, Turkey. Fish with an initial average weight of 2.44 ± 0.03 g reached a harvest weight of 474.60 ± 8.64 g with a survival rate of 94.26 ± 0.60% in 14 months. The average specific growth rate and feed conversion rate were 0.92 ± 0.30% and 1.45 ± 0.05 respectively. Seasonal variation of total essential and total non-essential amino acids and EAA/NEAA ratios ranged between 7.80 ± 0.00–11.22 ± 0.02 g/100 g, 8.19 ± 0.00–9.94 ± 0.01 g/100 g and 1.01 ± 0.00–1.18 ± 0.01 respectively (p < 0.05). The average of total ɷ-3, ɷ-6 and ɷ-9 values were 11.63 ± 0.68%, 24.29 ± 0.84% and 28.78 ± 0.17% respectively. It was determined that gilthead sea bream showed a remarkable growth performance over the 14 months period under offshore marine conditions in the Black Sea. Growth performance, biochemical composition, fatty and amino acids profiles in fish were influenced by seasonal changes of water temperature and nutritional value of the used diets. Findings of the present study provide remarkable information in terms of the year-round growth performance and meat quality of cage-cultured gilthead seabream based on a long-term evaluation throughout the full-cycle of 14-month production period of a commercial cage farm operating in offshore conditions in the Black Sea area.

Reservoir water stratification and mixing affects microbial community structure and functional community composition in a stratified drinking reservoir

To investigate how the aquatic bacterial community of a stratified reservoir drives the evolution of water parameters, the microbial community structure and network characteristics of bacteria in a stratified reservoir were investigated using Illumina MiSeq sequencing technology. A total of 42 phyla and 689 distinct genera were identified, which showed significant seasonal variation. Additionally, stratified variations in the bacterial community strongly reflected the vertical gradient and seasonal changes in water temperature, dissolved oxygen, and nutrition concentration. Furthermore, principal coordinate analysis indicated that most microorganisms were likely influenced by changes in water stratification conditions, exhibiting significant differences during the stratification period and mixing period based on Adonis, MRPP, and Anosim. Compared to the stratification period, 123 enhanced operational taxonomic units (OTUs; 29%) and 226 depleted OTUs (52%) were identified during the mixing period. Linear discriminant analysis effect size results showed that 15 major genera were enriched in the mixing period and 10 major genera were enriched in the stratification period. Importantly, network analysis revealed that the keystone species belonged to hgcI_clade, CL500-29, Acidibacter, Paucimonas, Flavobacterium, Prochlorothrix, Xanthomonadales, Chloroflexia, Burkholderiales, OPB56, KI89A_clade, Synechococcus, Caulobacter or were unclassified. Redundancy analysis showed that temperature, dissolved oxygen, pH, chlorophyll-α, total phosphorus, nitrate, and ammonia were important factors influencing the water bacterial community and function composition, which were consistent with the results of the Mantel test analysis. Furthermore, random forest analysis showed that temperature, dissolved oxygen, ammonia, and total dissolved phosphorous were the most important variables predicting water bacterial community and function community α- and β-diversity (P < 0.05). Overall, these results provide insight into the interactions between the microbial community and water quality evolution mechanism in Zhoucun reservoir.

Assessment of Seasonal Changes in Water Chemistry of the Ridracoli Water Reservoir (Italy): Implications for Water Management

The Ridracoli artificial basin is the main water reservoir of the Emilia-Romagna region (Northeast Italy). The reservoir was made by construction of a dam on the Bidente River in 1982. It is used as the main drinking water supply of the region and for hydropower production. The physical and chemical parameterseters (temperature, pH, electrical conductivity, and dissolved oxygen) of shallow water are continuously monitored whereas vertical depth profiles of water chemical data (major anions and cations, as well as heavy metals) are available on a bimonthly base. The dataset used in this research is related to the years 2015 and 2016. Data show that the reservoir is affected by an alternation of water stratification and mixing processes due to seasonal change in water temperature, density, and the reservoir water level. In late summer and winter months, the water column is stratified with anoxic conditions at the bottom. During the spring, on the other hand, when storage is at its maximum, water recirculation and mixing occur. The reservoir is characterized by a dynamic system in which precipitation, dissolution, and adsorption processes at the bottom affect water quality along the reservoir depth column. The temperature stratification and anoxic conditions at the reservoir bottom influence the concentration and mobility of some heavy metals (i.e., Fe and Mn) and, consequently, the quality of water that reaches the treatment and purification plant. This study is relevant for water resource management of the reservoir. Assessing the seasonal changes in water quality along the reservoir water column depth is fundamental to plan water treatment operations and optimize their costs. The reservoir assessment allows one to identify countermeasures to avoid or overcome the high concentrations of heavy metals and the stratification problem (i.e., artificial mixing of the water column, new water intakes at different depths operating at different times of the year, blowers, etc.).

A Preliminary Metagenome Analysis Based on a Combination of Protein Domains.

Metagenomic data have mainly been addressed by showing the composition of organisms based on a small part of a well-examined genomic sequence, such as ribosomal RNA genes and mitochondrial DNAs. On the contrary, whole metagenomic data obtained by the shotgun sequence method have not often been fully analyzed through a homology search because the genomic data in databases for living organisms on earth are insufficient. In order to complement the results obtained through homology-search-based methods with shotgun metagenomes data, we focused on the composition of protein domains deduced from the sequences of genomes and metagenomes, and we utilized them in characterizing genomes and metagenomes, respectively. First, we compared the relationships based on similarities in the protein domain composition with the relationships based on sequence similarities. We searched for protein domains of 325 bacterial species produced using the Pfam database. Next, the correlation coefficients of protein domain compositions between every pair of bacteria were examined. Every pairwise genetic distance was also calculated from 16S rRNA or DNA gyrase subunit B. We compared the results of these methods and found a moderate correlation between them. Essentially, the same results were obtained when we used partial random 100 bp DNA sequences of the bacterial genomes, which simulated raw sequence data obtained from short-read next-generation sequences. Then, we applied the method for analyzing the actual environmental data obtained by shotgun sequencing. We found that the transition of the microbial phase occurred because the seasonal change in water temperature was shown by the method. These results showed the usability of the method in characterizing metagenomic data based on protein domain compositions.