Sediment–Water Surface Area Along Rivers: Water Column Versus Benthic

Aquatic ecosystems have two distinct zones: the water column and benthic zone. Although the benthic zone has received considerable attention, recent studies have found the water column capable of accounting for a majority of whole ecosystem processes in rivers. The relative role of these zones inevitably varies across a size continuum of rivers, from headwaters to large transcontinental systems. A fundamental question in aquatic science is where along this size continuum do ecosystem processes potentially shift from occurring largely in the benthic zone to largely in the water column? Sediment structures the physical template of the benthic and water column zones of rivers and the contact area between water and sediment mediates ecological, geochemical, and physical processes. High concentrations of suspended sediments are hypothesized to cause a shift from benthic to water column dominance in rivers. We developed an analytical model for the contact area between surface water and all sediment particles in benthic and water column volumes. The model was implemented with empirical data along the main stem of major US rivers. The ratio of water column to benthic sediment contact area scaled as a power function of watershed area. There was more sediment–water contact area in the water column than the benthic zone in rivers equal to or greater than 5th to 9th order depending on the river basin. This suggests material processing could be occurring largely in the water column in rivers greater than 5th order. However, dams and variation in discharge caused rivers to oscillate between water column and benthic dominance over time and space.     

Differential Scanning Calorimetry of Unfreezable Water in Water–Protein–Polyol Systems

The amount of unfreezable water in lysozyme and bovine serum albumin in aqueous solutions of xylitol, sorbitol, glucose and sucrose was estimated by a differential scanning calorimeter according to new analytical methods. The antemelting point of aqueous polyol solutions seemed to shift to a higher temperature upon addition of protein, but the incipient melting point was not affected by the coexisting protein. The amount of unfreezable water in both proteins, as well as the heat of fusion of ice, decreased with increasing polyol concentration, regardless of the kind of polyols added. On the basis of these results, the solvation structure of the protein in these three-component systems and the mechanism of the polyol-induced stabilization of protein were discussed assuming protein–polyol interactions.     

Rutland Water — from conception to operation

Rutland Water was planned in the 1960s to meet the water needs of the expanding East Midland region of England. Chosen from 64 possible sites, it was approved in 1970 and construction started in 1971. The dam was closed and the reservoir started to fill from its natural catchment in 1975; pumping started from the rivers Welland and Nene in 1976 and the reservoir was full by March 1979.Details of the stages in its development are given together with an indication of the ways in which the recreational uses of the reservoir have been integrated with its water supply function.     

Water? What's so special about it?

What is so special about water? Why does it have the properties it has, and how might these reasons be relevant to its apparent biological importance? By exploring the structure and dynamics of water, from the isolated molecule and its interactions, through its many crystalline phases and to its so-called anomalous liquid phase, some of its apparently unusual behaviour is rationalized. The way in which it interacts with some relatively simple interfaces is also discussed. As a result of this exploration, a checklist of possible molecular-level reasons for its biological importance is devised.     

Water Striders： The Biomechanics of Water Locomotion and Functional Morphology of the Hydrophobic Surface （Insecta： Hemiptera-Heteroptera）

Water striders are insects living on the water surface, over which they can move very quickly and rarely get wetted. We measured the force of free walking in water striders, using a hair attached to their backs and a 3D strain gauge. The error was calculated by comparing force and data derived from geometry and was estimated as 13%. Females on average were stronger （1.32 mN） than males （0.87 mN）, however, the ratio of force to weight was not significantly different. Compared with other lighter species, Aquarius paludum seems stronger, but the ratio of force to weight is actually lower. A. paludum applies about 0.3 mN.cm^-1 to 0.4 mN.cm 1 with its mid-legs, thus avoiding penetrating the surface tension layer while propelling itself rapidly over the water surface. We also investigated the external morphology with SEM. The body is covered by effectively two layers of macro-and micro-hairs, which renders them hydrophobic. The setae are long （40 μm-60μm） and stiff, being responsible for waterproofing, and the microtrichia are much smaller （〈10μm）, slender, and flexible, holding a bubble over the body when submerged.     

Weather and Prey Predict Mammals’ Visitation to Water

Throughout many arid lands of Africa, Australia and the United States, wildlife agencies provide water year-round for increasing game populations and enhancing biodiversity, despite concerns that water provisioning may favor species more dependent on water, increase predation, and reduce biodiversity. In part, understanding the effects of water provisioning requires identifying why and when animals visit water. Employing this information, by matching water provisioning with use by target species, could assist wildlife management objectives while mitigating unintended consequences of year-round watering regimes. Therefore, we examined if weather variables (maximum temperature, relative humidity [RH], vapor pressure deficit [VPD], long and short-term precipitation) and predator-prey relationships (i.e., prey presence) predicted water visitation by 9 mammals. We modeled visitation as recorded by trail cameras at Sevilleta National Wildlife Refuge, New Mexico, USA (June 2009 to September 2014) using generalized linear modeling. For 3 native ungulates, elk (Cervus Canadensis), mule deer (Odocoileus hemionus), and pronghorn (Antilocapra americana), less long-term precipitation and higher maximum temperatures increased visitation, including RH for mule deer. Less long-term precipitation and higher VPD increased oryx (Oryx gazella) and desert cottontail rabbits (Sylvilagus audubonii) visitation. Long-term precipitation, with RH or VPD, predicted visitation for black-tailed jackrabbits (Lepus californicus). Standardized model coefficients demonstrated that the amount of long-term precipitation influenced herbivore visitation most. Weather (especially maximum temperature) and prey (cottontails and jackrabbits) predicted bobcat (Lynx rufus) visitation. Mule deer visitation had the largest influence on coyote (Canis latrans) visitation. Puma (Puma concolor) visitation was solely predicted by prey visitation (elk, mule deer, oryx). Most ungulate visitation peaked during May and June. Coyote, elk and puma visitation was relatively consistent throughout the year. Within the diel-period, activity patterns for predators corresponded with prey. Year-round water management may favor species with consistent use throughout the year, and facilitate predation. Providing water only during periods of high use by target species may moderate unwanted biological costs.     

Drinking Water Fluoride and Blood Pressure? An Environmental Study

The relationship between intakes of fluoride (F) from drinking water and blood pressure has not yet been reported. We examined the relationship of F in ground water resources (GWRs) of Iran with the blood pressure of Iranian population in an ecologic study. The mean F data of the GWRs (as a surrogate for F levels in drinking water) were derived from a previously conducted study. The hypertension prevalence and the mean of systolic and diastolic blood pressures (SBP & DBP) of Iranian population by different provinces and genders were also derived from the provincial report of non-communicable disease risk factor surveillance of Iran. Statistically significant positive correlations were found between the mean concentrations of F in the GWRs and the hypertension prevalence of males (r?=?0.48, p?=?0.007), females (r?=?0.36, p?=?0.048), and overall (r?=?0.495, p?=?0.005). Also, statistically significant positive correlations between the mean concentrations of F in the GWRs and the mean SBP of males (r?=?0.431, p?=?0.018), and a borderline correlation with females (r?=?0.352, p?=?0.057) were found. In conclusion, we found the increase of hypertension prevalence and the SBP mean with the increase of F level in the GWRs of Iranian population.     

The Effects of Water Stress on Photosystem Ⅱ in Wheat

The fluorescence yield at room temperature, the capacity of excitation energy distribution between photosystem Ⅰ and Ⅱ by Mg2+, variable fluorescence yield, variable fluorescence quenching rate and fluorescence complementary area were decreased under water stress. These indicated that photosystem Il was impaired. The inhibited variable fluorescence yield could be partly recovered by the addition of artificial electron donor DPC. Therefore, water stress inhibited not only the oxidizing site of photosystem Ⅱ but also impaired partly the reaction center of photosystem Ⅱ.     

Water Biology and Security(ISSN 2772-7351)

Volume 1 Issue 1,2022中国科学院水生生物研究所创办的开放获取英文期刊Water Biology and Security(ISSN 2772-7351)第一期于2022年2月在Elsevier平台和KeAi平台同步发行。本期共计10篇文章,包括1篇开刊词、4篇综述文章和5篇研究性论文,作者分布在中国、美国、加拿大、英国、巴西等国家地区,领域涉及水生生物免疫学研究、基因组学研究、生物技术及遗传育种、水域生态学研究等各领域。     

Water Biology and Security(ISSN 2772-7351)

Volume 1 Issue 1,2022中国科学院水生生物研究所创办的开放获取英文期刊Water Biology and Security(ISSN 2772-7351)第一期于2022年2月在Elsevier平台和KeAi平台同步发行。本期共计10篇文章,包括1篇开刊词、4篇综述文章和5篇研究性论文,作者分布在中国、美国、加拿大、英国、巴西等国家地区,领域涉及水生生物免疫学研究、基因组学研究、生物技术及遗传育种、水域生态学研究等各领域。     

Towards Physarum Robots： Computing and Manipulating on Water Surface

Plasmodium of Physarum polycephalum is an ideal biological substrate for implementing concurrent and parallel com-putation, including combinatorial geometry and optimization on graphs. The scoping experiments on Physarum computing in conditions of minimal friction, on the water surface were performed. The laboratory and computer experimental results show that plasmodium of Physarum is capable of computing a basic spanning tree and manipulating of light-weight objects. We speculate that our results pave the pathways towards the design and implementation of amorphous biological robots.     

Water transporters: how so fast yet so selective?

A high-resolution X-ray structure of an aquaporin has revealed water molecules bound within the transmembrane pore and provided new clues to the mechanisms of rapid water transport and high selectivity in this important class of membrane proteins.     

Water deficit and growth. Co-ordinating processes without an orchestrator?

Water deficit affects plant growth via reduced carbon accumulation, cell number and tissue expansion. We review the ways in which these processes are co-ordinated. Tissue expansion and its sensitivity to water deficit may be the most crucial process, involving tight co-ordination between the mechanisms which govern cell wall mechanical properties and plant hydraulics. The analyses of sensitivities, time constants and genetic correlations suggest that tissue expansion is loosely co-ordinated with cell division and carbon accumulation which may have limited direct effects on growth under water deficit. We therefore argue for essentially uncoupled mechanisms with feedbacks between them, rather than for a co-ordinated re-programming of all processes. Consequences on plant modelling and plant breeding in dry environment are discussed.     

Geckos Race Across the Water’s Surface Using Multiple Mechanisms

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Much Improved Water Use Efficiency of Rice under Non-Flooded Mulching Cultivation

Water shortage is increasingly limiting the luxury use of water in rice cultivation. In this study, non-flooded mulching cultivation of rice only consumed a fraction of the water that was needed for traditional flooded cultivation and largely maintained the grain yield. We also investigated the growth and development of rice plants and examined grain yield formation when rice was subjected to non-flooded mulching cultivation. One indica hybrid rice combination was grown in a field experiment and three cultivation methods, traditional flooding （TF）, non-flooded straw mulching cultivation （SM） and non-flooded plastic mulching cultivation （PM）, were conducted during the whole season. Grain yield showed that there was no significant difference between SM and TF rice, but the grain yield of SM cultivation was significantly higher than that of PM. The tiller numbers were inhibited in the early stage under non-flooded mulching cultivation, but the situation was reversed at the later period. Both SM and PM rice reduced dry matter accumulation of shoot, but increased root dry weight, enhanced the remobilization of assimilates from stems to grains and increased the harvest index. During the middle and later grain filling period, mulched plants showed a faster decrease in chlorophyll concentrations, photosynthetic rates of flag leaves and root activity than TF rice, indicating that non-flooded mulching cultivation enhanced plant senescence. In comparison, SM treatment produced higher grain yield and, more dry matter accumulation and panicle numbers than the PM treatment. The overall results suggest that high yield of non-flooded mulching cultivation of rice can be achieved with much improved irrigaUonal water use efficiency.     

Does Water Deficit Stress Promote Ethylene Synthesis by Intact Plants?

The effect of plant water deficit on ethylene production by intact plants was tested in three species, beans (Phaseolus vulgaris L.), cotton (Gossypium hirsutum L.) and miniature rose (Rosa hybrida L., cv Bluesette). Compressed air was passed through glass, plant-containing cuvettes, ethylene collected on chilled columns, and subsequently assayed by gas chromatography. The usual result was that low water potential did not promote ethylene production. When plants were subjected to cessation of irrigation, ethylene production decreased on a per plant or dry weight basis of calculation. No significant promotion of ethylene production above control levels was detected when water deficit-treated bean or cotton plants were rewatered. The one exception to this was for cotton subjected to a range of water deficits, plants subjected to deficits of −1.4 to −1.6 MPa exhibited a transient increase of ethylene production of 40 to 50% above control levels at 24 or 48 hours. Ethylene was collected from intact leaves while plants developed a water deficit stress of −2.9 megapascals after rewatering, and no significant promotion of ethylene production was detected. The shoots of fruited, flowering cotton plants produced less ethylene when subjected to cessation of irrigation. In contrast, the ability of bench drying of detached leaves to increase ethylene production several-fold was verified for both beans and cotton. The data indicate that detached leaves react differently to rapid drying than intact plants react to drying of the soil with regard to ethylene production. This result suggests the need for additional attention to ethylene as a complicating factor in experiments employing excised plant parts and the need to verify the relevance of shock stresses in model systems.     

Introducing Titratable Water to All-Atom Molecular Dynamics at Constant?pH

Recent development of titratable coions has paved the way for realizing all-atom molecular dynamics at constant pH. To further improve physical realism, here we describe a technique in which proton titration of the solute is directly coupled to the interconversion between water and hydroxide or hydronium. We test the new method in replica-exchange continuous constant pH molecular dynamics simulations of three proteins, HP36, BBL, and HEWL. The calculated pK_a values based on 10-ns sampling per replica have the average absolute and root-mean-square errors of 0.7 and 0.9 pH units, respectively. Introducing titratable water in molecular dynamics offers a means to model proton exchange between solute and solvent, thus opening a door to gaining new insights into the intricate details of biological phenomena involving proton translocation.Solution pH is an important factor in biology. Although neutral pH in extracellular medium accounts for balanced electrostatics and proper folding of protein structures, pH gradients across cell membranes induce large conformational changes that are necessary for biological functions, such as ATP synthesis and efflux of small molecules out of the cell. To gain detailed insights into pH-dependent conformational phenomena, several constant pH molecular dynamics (pHMD) methods, based on either discrete or continuous titration coordinates, have been developed in the last decade (1–4). In the continuous pHMD (CpHMD) framework (2,4), a set of titration coordinates {λ_i} are simultaneously propagated along with the conformational degrees of freedom. Although the original CpHMD method based on the generalized Born (GB) implicit-solvent models (2,4) offers quantitative prediction of pK_a values and pH dependence of folding and conformational dynamics of proteins (5), its accuracy and applicability to highly charged systems and those with dominantly hydrophobic regions are limited due to the approximate nature of the underlying implicit-solvent models.Motivated by the above-mentioned need, three groups have made efforts to develop a CpHMD method using exclusively the explicit-solvent models (6–8). In our development, the titration of acidic and basic sites is coupled with that of coions to level the total charge of the system (8). To further improve physical realism, here we replace the coions by titratable water molecules, which not only absorb the excess charge but also enable direct modeling of solute-solvent proton exchange in classical molecular dynamics simulations.To illustrate the utility of the new methodology, we applied it to the titration simulations of three proteins that were previously used to benchmark the GB-based CpHMD. Although this work does not explore specific interactions between titratable waters and proteins, the methodology can be further tested or improved to provide a rigorous way for modeling proton transfer in molecular dynamics, which is a computationally efficient alternative to the empirical valence-bond theory-based methodologies (9,10).We define titration of water as:

• 1.Loss of a proton to give a negatively charged hydroxide,

H₂O ? OH^? + H⁺, (1)or

• 2.Gain of a proton to give a positively charged hydronium,

H₂O + H⁺ ? H₃O⁺.(2)We now couple the titration of hydroxide (Eq. 1) with that of an acidic site of the solute in the CpHMD simulation,HA+OH−⇌KaA−+H2O.(3)The use of hydronium is avoided here to prevent a potential artifact due to prolonged attraction with A⁻. Analogously, we couple the titration of hydronium (Eq. 2) with that of a basic site,BH++H2O⇌KbH3O++B.(4)Thus, effectively, a proton is transferred between the solute and solvent. However, we should note that in CpHMD simulations, titratable protons are represented by covalently attached dummies (2,4). Through varying the atomic charges and van der Waals interactions, they are seen by other atoms in the protonated state but not in the unprotonated state (see Table S1 in the Supporting Material). Furthermore, the solution proton concentration is implicitly modeled through a free energy term (2,4).In CpHMD, the reference potential of mean force (PMF) for titration is that of the model compound (blocked single amino acid in water) along λ (2,4). In the presence of cotitrating water molecules, it is necessary to add the PMF for the conversion of water to hydroxide or hydronium. One-nanosecond NPT simulations at ambient pressure and temperature were performed to calculate the average force, 〈dU/d,θ〉 at given θ-values, which are related to λ by λ = sin² θ (see Fig. S1 in the Supporting Material). Thermodynamic integration was then applied to calculate the PMF. We found that the average force can be accurately fit when assuming the PMF is quadratic in λ (Fig. 1). The same applies to the PMFs for titration of models Asp, Glu, and His. After testing on the titration of model compounds (see Table S2), we performed 10-ns all-atom CpHMD simulations with the pH replica-exchange protocol for three proteins: HP36, BBL and HEWL (see the Supporting Material for details). Most of the calculated pK_a values were converged in 10 ns per replica (see Fig. S3). Results are summarized in Fig. S4. Based on the 10-ns data, the root-mean-square (RMS) and average absolute errors are 0.9 and 0.7 pH units, respectively, while the largest absolute error is 2.5 (Glu³⁵ of HEWL). Linear regression of the calculation versus experiment gives R² of 0.8 and slope of 1.2.Open in a separate windowFigure 1Average force and potential of mean force for converting a water molecule to hydroxide (A) and hydronium. (B) (Data points) Average forces. (Dashed curves) Best fits using a linear function, 2A(λ − B). (Solid curves) Corresponding potential of mean force.

Table 1

Calculated and experimental pK_a values of three proteins

Do Protozoa Control the Elimination of Vibrio choleraein Brackish Water?

Elimination of inoculated Vibrio cholerae (≥10⁷ cells ml⁻¹) within a brackish water bacteria assemblage (Mecoacán Lagoon, State of Tabasco, Mexico) was studied in laboratory microcosms with filtration‐fractionated water. Feeding of a ciliate, Cyclidium glaucoma was evaluated using fluorescently labelled V. cholerae o1. Even though V. cholerae was not exploited as the major food source, ciliates were able to eliminate it efficiently. An addition of chitin directly supported the growth of bacteria, although not so much of V. cholerae, and indirectly the growth of the protistan assemblage. Generally, the changes in a bacterial assemblage structure were the most important in V. cholerae elimination.