Evaporative Water Loss Research Articles

Melatonin loaded lipid enriched chitosan microspheres – Hybrid dressing for moderate exuding wounds

The aim of this study was to develop nanostructured lipid carrier (NLC)-loaded chitosan-based microspheres as innovative dry powder wound dressing, with melatonin incorporated in both, NLC and chitosan matrix of the proposed hybrid system. Melatonin-loaded NLCs were prepared by a hot homogenization technique, while NLC-loaded microspheres were produced by a spray-drying method. To optimize the critical formulation and process parameters for both NLC and hybrid system, a definitive screening design was employed. NLC particle size, hybrid system production yield, particle size, moisture content, and zeta potential were investigated as responses. The optimized hybrid system was characterized by prolonged melatonin release, good flowability and appropriate extent of fluid uptake. In contact with simulated wound fluid, the hybrid system swelled, turning into a hydrogel layer. The presence of lipid nanoparticles attenuated the evaporative water loss showing the potential to provide optimal hydration for moderate exuding wounds. The hybrid system was proven to be biocompatible with skin keratinocytes and fibroblasts and moreover, showed antimicrobial activity against Staphylococcus aureus and S. aureus MRSA strain.

Sensitivity of a Continuum‐Scale Porous Media Heat and Mass Transfer Model to the Spatial‐Discretization Length‐Scale of Applied Atmospheric Forcing Data

AbstractFundamental process understanding and description of heat, mass, and momentum exchanges across the land‐atmosphere interface in model boundary forcing parameterizations is critical to the simulation of near‐surface soil moisture dynamics (e.g., bare‐soil evaporation). This study explores the sensitivity of a continuum‐scale porous media heat and mass transfer model to the spatial‐discretization length‐scales (i.e., spatial‐resolution) of near‐surface atmospheric data; the goal is to determine how much data are needed to force the model and adequately capture evaporative water losses and subsurface state variable distributions. The requisite atmospheric forcing data were taken from the high‐resolution, precision bare‐soil evaporation experiments of Trautz et al. (2018, https://doi.org/10.1029/2018WR023102). Simulation results demonstrated that shallow subsurface mass and heat transfer dynamics can be adequately captured with forcing data averaged over large length‐scales, or a minimal number of measurements, provided that soil conditions are properly described. The soil moisture spatial distributions were found to be insensitive to horizontal variations in the forcing data. The model failed to capture small‐scale trends observed experimentally; this did not impact the accuracy of total evaporative water loss estimates however. These results indicate that in future physical experimental efforts conducted at 1–10‐m length‐scales, there is no need to focus on the generation of high‐spatial resolution atmospheric measurements—time and effort would be better spent in characterizing soil conditions and properties. Even though a theoretical foundation was not provided to directly extrapolate this work to the field scale, these findings have practical value in designing field data collection strategies.

Evaluating Operational Hydrodynamic Models for Real‐time Simulation of Evaporation From Large Lakes

AbstractMethods for simulating evaporative water loss from Earth's large lakes have lagged behind advances in hydrodynamic modeling. Here we explore use of oceanographic models to simulate lake evaporation from a long‐term water balance perspective. More specifically, we compare long‐term monthly simulations of latent heat flux from two configurations of a current operational hydrodynamic forecasting system (based on the Finite Volume Community Ocean Model, or FVCOM) for the Laurentian Great Lakes. We then compare these simulations to comparable simulations from a legacy conventional lake thermodynamics model, and from a recently developed statistical water balance model. We find that one of the FVCOM configurations that is currently used in operations for short‐term hydrodynamic forecast guidance is also suitable for real‐time simulation of evaporation from very large lakes. The operational versions of FVCOM should therefore be considered a readily available tool for supporting regional water supply management and, pending further research, extended water supply forecasting.

Scaling of total evaporative water loss and evaporative heat loss in birds at different ambient temperatures and seasons

Scaling of total evaporative water loss and evaporative heat loss in birds at different ambient temperatures and seasons

Scaling of total evaporative water loss and evaporative heat loss in birds at different ambient temperatures and seasons

Scaling of total evaporative water loss and evaporative heat loss in birds at different ambient temperatures and seasons

Vegetation and location of water inflow affect evaporation in a subtropical wetland as indicated by the deuterium excess method

AbstractEvaporation represents a principal form of water loss from water bodies, but quantifying evaporation with transpiring vegetation is challenging, owing to the difficulties in disentangling evaporation from transpiration. As the two processes have different effects on water isotope signatures (i.e., oxygen and hydrogen stable isotope ratios expressed by δ18O and δ2H), we used both the δ18O and δ2H values of water samples to calculate their deuterium excess (d) values, which are proportionate to fraction of evaporation loss (Ef) of water being sampled. Comparing with a single isotope method, the d method holds the advantage that it does not require knowledge of the initial isotope ratios of source water. Limitations of the d method, for example, effects of prior‐evaporation of water before entering water bodies, can be checked and corrected. The sampling locations throughout our study site differed in vegetation coverage, water depth, and distance to water inflow (or discharge gate of water inflow), which are three important factors in water management. This sampling design offered us a unique opportunity to quantify the influences of the above three factors on Ef. We found the following: (1) There was a spatiotemporal pattern in δ18O distribution. (2) The Ef was negatively related to the vegetation coverage, positively related to distance to the water source inflow but nonsignificantly related to water depth. Therefore, vegetation and distance to the water inflow are two important considerations for the control of evaporative water loss, and evaporation calculated by the d method can lead to more informed water management.

Interactions between humidity and evaporative heat dissipation in a passerine bird.

Environmental humidity is thought to be a major determinant of evaporative cooling capacity at high air temperatures (Ta), but the technical challenges of experimentally manipulating humidity in respirometry chambers have resulted in far less being known about the effects of humidity compared to those of Ta. We tested the prediction that at Ta approaching and exceeding normothermic body temperature (Tb), high humidity would result in higher Tb, lower evaporative water loss (EWL) and/or higher resting metabolic rate (RMR) in a passerine bird, the white-browed sparrow-weaver (Plocepasser mahali). We used open-system flow-through respirometry to measure EWL, RMR and Tb in sparrow-weavers experiencing Ta = 36-44°C and chamber humidities of 6, 13, 19 or 25g m- 3. Increasing humidity was associated with significantly higher Tb. The strongest effect of humidity, however, involved significant increases in RMR; at Ta = 40°C, RMR at a humidity of 25g m- 3 was ~ 40% higher compared to a humidity of 6g m- 3. Moreover, the interaction between Ta and humidity exerted a significant effect on the ratio of evaporative heat loss (EHL) to metabolic heat production (MHP), evident as an increasing effect of humidity with increasing Ta. Our results, when compared with those of the limited number of previous studies that involved similar ranges of Ta and humidity, reveal that the relative effects of humidity on EWL and RMR vary among avian taxa, and support the notion that the overall effect of high humidity is a reduction in maximum EHL/MHP.

Crassulacean Acid Metabolism Abiotic Stress-Responsive Transcription Factors: a Potential Genetic Engineering Approach for Improving Crop Tolerance to Abiotic Stress.

This perspective paper explores the utilization of abiotic stress-responsive transcription factors (TFs) from crassulacean acid metabolism (CAM) plants to improve abiotic stress tolerance in crop plants. CAM is a specialized type of photosynthetic adaptation that enhances water-use efficiency (WUE) by shifting CO2 uptake to all or part of the nighttime when evaporative water losses are minimal. Recent studies have shown that TF-based genetic engineering could be a useful approach for improving plant abiotic stress tolerance because of the role of TFs as master regulators of clusters of stress-responsive genes. Here, we explore the use of abiotic stress-responsive TFs from CAM plants to improve abiotic stress tolerance and WUE in crops by controlling the expression of gene cohorts that mediate drought-responsive adaptations. Recent research has revealed several TF families including AP2/ERF, MYB, WRKY, NAC, NF-Y, and bZIP that might regulate water-deficit stress responses and CAM in the inducible CAM plant Mesembryanthemum crystallinum under water-deficit stress-induced CAM and in the obligate CAM plant Kalanchoe fedtschenkoi. Overexpression of genes from these families in Arabidopsis thaliana can improve abiotic stress tolerance in A. thaliana in some instances. Therefore, we propose that TF-based genetic engineering with a small number of CAM abiotic stress-responsive TFs will be a promising strategy for improving abiotic stress tolerance and WUE in crop plants in a projected hotter and drier landscape in the 21st-century and beyond.

A mechanistic model to scale up biophysical processes into geographical size gradients in ectotherms

AbstractAimUnderstanding the mechanisms behind broad‐scale gradients in animal body size remains challenging. In contrast to endotherms, the extent to which biophysical properties of ectotherms scale up into interspecific size gradients at macroecological scales remains elusive. Our aim here is to investigate what latitudinal body size gradients are expected to emerge from first biophysical principles regarding heat and water balances in terrestrial vertebrate ectotherms.LocationNearctic and Western Palaearctic.Time periodTheoretical model under current climatic conditions.Major taxa studiedTerrestrial vertebrate ectotherms.MethodsWe developed a biophysical model to derive heat balances and rates of water loss of lizard‐like reptiles and anuran‐like amphibians from microclimatic variables. We projected geographically model predictions for different size classes to explore how body temperature (Tb) and cutaneous evaporative water loss (EWL) are influenced by body size at macroscales.ResultsLarge‐bodied ectotherms (over 100 g) attain a slightly higher Tb and conserve it for longer than small animals (5 g), owing to the lower convective heat dissipation and their greater thermal inertia. While large animals are more at risk of overheating in warm regions, all organisms, irrespective of body size, are constrained by low temperatures experienced at boreal latitudes. Furthermore, because of the nonlinear decrease in EWL with increasing size, larger size allows reduction of water loss of small wet‐skinned ectotherms in more evaporative environments.Main conclusionsSize differences in heat balance offer a mechanistic explanation for the pattern of increasing body size northwards, as well as for the associated decrease in species richness. Water conservation is also identified as a potential mechanism for larger body sizes in dryer areas in wet‐skinned ectotherms such as amphibians. Moreover, our model reveals nonlinear relationships involving size and optimum states of thermal and hydric functions, accounting for complexities that are unnoticeable by traditional, correlative investigations.

Gill remodelling during terrestrial acclimation in the amphibious fish Polypterus senegalus.

Fishes are effectively weightless in water due to the buoyant support of the environment, but amphibious fishes must cope with increased effective weight when on land. Delicate structures such as gills are especially vulnerable to collapse and loss of surface area out of water. We tested the 'structural support' hypothesis that amphibious Polypterus senegalus solve this problem using phenotypically plastic changes that provide mechanical support and increase stiffness at the level of the gill lamellae, the filaments, and the whole arches. After 7 d in terrestrial conditions, enlargement of an inter-lamellar cell mass filled the water channels between gill lamellae, possibly to provide structural support and/or reduce evaporative water loss. Similar gill remodelling has been described in several other actinopterygian fishes, suggesting this may be an ancestral trait. There was no change in the mechanical properties or collagen composition of filaments or arches after 7 days out of water, but 8 months of terrestrial acclimation caused a reduction in gill arch length and mineralized bone volume. Thus, rather than increasing the size and stiffness of the gill skeleton, P. senegalus may instead reduce investment in supportive gill tissue while on land. These results are strikingly similar to the evolutionary trend of gill loss that occurred during the tetrapod invasion of land, raising the possibility that genetic assimilation of gill plasticity was an underlying mechanism.

Global patterns of terrestriality in amphibian reproduction

AbstractAimAmphibians exhibit two basic reproductive modes, terrestrial and aquatic, each with different ecophysiological constraints related to evaporative water loss. We hypothesize that these fundamental niche differences will generate strong geographical patterns at the global scale in response to spatial heterogeneity in temperature and water availability.LocationGlobal.Time periodPresent.Major taxa studiedAmphibians.MethodsWe used global distribution maps of 5,434 amphibian species, classified into terrestrial or aquatic breeders, to estimate the occurrence and proportion of terrestrial breeding species per 1° cell. We used multiple regression models to test the relative importance of seven abiotic variables: annual precipitation, annual mean temperature, annual mean relative air humidity, annual mean actual evapotranspiration, availability of lotic and lentic environments and slope. We used residuals autocovariate (RAC) generalized multiple regression models to control for spatial autocorrelation and a spatial vector based on amphibian phylogeny to account for phylogenetic dependencies among cells. Model generality was evaluated by contrasting results between 11 widely recognized world zoogeographical realms.ResultsGlobally, the occurrence of terrestrial breeding species was better explained by temperature followed by total annual rainfall, relative air humidity and terrain slope. In contrast, the proportion of terrestrial breeders was better explained by terrain slope, followed by total rainfall, temperature and relative air humidity. Actual evapotranspiration and the extension of large lotic and lentic water bodies played a minor role. However, the relative importance and even the sign of the regression coefficients varied among realms, revealing different evolutionary pressures.Main conclusionsNiche differences among terrestrial and aquatic breeding amphibian species are reflected in their distinct geographical distribution across the globe. Adequate conditions for terrestrial reproduction to evolve and thrive are reached in distinct ways in different realms. Temperature constraints and slope suggest that reproductive modes will be impacted differently by climate change.

The functional significance of facultative hyperthermia varies with body size and phylogeny in birds

Abstract Facultative hyperthermia, the elevation of body temperature above normothermic levels, during heat exposure, importantly affects the water economy and heat balance of terrestrial endotherms. We currently lack a mechanistic understanding of the benefits hyperthermia provides for avian taxa. Facultative hyperthermia has been proposed to minimize rates of water loss via three distinct mechanisms: M1) by maintaining body temperature (Tb) above environmental temperatures (Te), heat can be lost non‐evaporatively, saving water; M2) by minimizing the thermal gradient when Te > Tb, environmental heat gain and evaporative water loss rates are reduced; and M3) by storing heat via increases in Tb which reduces evaporative heat loss demands and conserves water. Although individuals may benefit from all three mechanisms during heat exposure, the relative importance of each mechanism has not been quantified among species that differ in their body size, heat tolerance and mechanisms of evaporative heat dissipation. We measured resting metabolism, evaporative water loss and real‐time Tb from 33 species of birds representing nine orders ranging in mass from 8 to 300 g and estimated the water savings associated with each proposed mechanism. We show that facultative hyperthermia varies in its benefits among species. Small songbirds with comparatively low evaporative cooling capacities benefit most from (M1), and hyperthermia maintains a thermal gradient that allows non‐evaporative heat losses. Other species benefited most from (M2) minimizing evaporative losses via a reduced thermal gradient for heat gain at high Te. We found that (M3), heat storage, only improved the water economy of the sandgrouse, providing little benefit to other species. We propose that differences in the frequency and magnitude of hyperthermia will drive taxon‐specific differences in temperature sensitivity of tissues and enzymes and that the evolution of thermoregulatory mechanisms of evaporative heat dissipation may contribute to differences in basal metabolic rate among avian orders. Understanding the mechanistic basis of heat tolerance is essential to advance our understanding of the ecology of birds living in hot environments that are warming rapidly, where extreme heat events are already re‐structuring avian communities. A plain language summary is available for this article.

Estimation of Evaporative Loss of Surface Water Using Stable Isotopes in a Lowland Rice Field, Suphanburi, Thailand

Water scarcity resulting from erratic rainfall pattern is a major problem over the world. As diminishing water resources for agriculture and increasing demand for rice yield, understanding on hydrological cycle is crucial on water management. The loss of water due to evaporation from rivers and canals constitutes a substantial part of useable water. The estimated evaporation loss can be obtained by using the isotope compositions of precipitation and an established local evaporation line. It is recognized a very useful tool in providing a quick and cost effective insight into the water balance of surface water pool. In this study of 2015-2017 in Suphanburi province, the isotopic signatures of precipitation and surface water canal resulted in a local meteoric water line of δ2H = 7.63 δ18O – 1.05 (n = 168, r2= 0.94) and local evaporation line for surface water creek of δ2H = 5.95 δ18O – 14.42 (n = 155, r2= 0.90), respectively. The estimated evaporation loss using theHydrocalculatorsoftware indicated that the estimated fractional water loss by evaporation in the surface water canal of Sri Prachan district, Suphanburi was ~12%.

Combined effects of grazing and climate warming drive shrub dominance on the Tibetan Plateau

Encroachment of shrubs into the unique pastoral grassland ecosystems of the Tibetan Plateau has significant impact on ecosystem services, especially forage production. We developed a process-based ecohydrological model to identify the relative importance of the main drivers of shrub encroachment for the alpine meadows within the Qinghai province. Specifically, we explored the effects of summer livestock grazing (intensity and type of livestock) together with the effects of climate warming, including interactions between herbaceous and woody vegetation and feedback loops between soil, water and vegetation. Under current climatic conditions and a traditional herd composition, an increasing grazing intensity above a threshold value of 0.32±0.10 large stock units (LSU) ha−1 day−1 changes the vegetation composition from herbaceous towards a woody and bare soil dominated system. Very high grazing intensity (above 0.8 LSU ha−1 day−1) leads to a complete loss of any vegetation. Under warmer conditions, the vegetation showed a higher resilience against livestock farming. This resilience is enhanced when the herd has a higher browser:grazer ratio. A cooler climate has a shrub encroaching effect, whereas warmer conditions increase the cover of the herbaceous vegetation. This effect was primarily due to season length and an accompanied competitive loss of slower growing shrubs, rather than evaporative water loss leading to less soil water in deeper soil layers for deeper rooting shrubs. If climate warming is driving current shrub encroachment, we conclude it is only indirectly so. It would be manifest by an advancing shrubline and could be regarded as a climatic escape of specific shrub species such as Potentilla fruticosa. Under the recent high intensity of grazing, only herding by more browsing animals can potentially prevent both shrub encroachment and the complete loss of herbaceous vegetation.

Service crop management to maximize crop water supply and improve agroecosystem resilience: A review

Service crops (commonly known as cover crops) are plants grown in agroecosystems for the ecosystem services they provide rather than a harvestable product. One such service they provide is that of increased crop water supply. By reducing evaporative water loss and increasing soil water storage, storage capacity, and the successive crop9s ability to access stored water, service crops may be used to increase agroecosystem resiliency to seasonal water deficits and so improve crop yields. In many instances, however, these benefits are not realized. This is more likely a consequence of suboptimal management, or management tailored to provide other services, rather than the ultimate capacity of service crops to contribute to agroecosystem resilience. After reviewing the literature, we propose that service crop polycultures—in contrast with monocultures—have the greatest potential to provide this service, and that, if properly managed, a grass/legume/taproot service crop mixture could maximize multifunctionality while also offsetting the challenges associated with the component species when grown in monoculture.

Swimming Pool Evaporative Water Loss and Water Use in the Balearic Islands (Spain)

The Balearic Islands are a major Mediterranean tourist destination that features one of the greatest swimming pool densities within Europe. In this paper, standard meteorological data were combined with a diachronic swimming pool inventory to estimate water evaporation from swimming pools over the Balearic archipelago. Evaporation was estimated using an empirical equation designed for open-water surfaces. Results revealed a 32% increase in swimming pools’ water use by 2015. Evaporation from swimming pools added 9.6 L of water to touristic consumption per guest night and person, and represented 4.9% of the total urban water consumption. In 2015, almost 5 hm3 (5 billion L) were lost from pools across the Balearic Islands. In several densely urbanized areas, evaporative water loss from pools exceeded four million litres per square kilometre and year. The water needed to refill the total of 62,599 swimming pools and to counteract evaporative water loss is equivalent to 1.2 pools per year. Swimming pools have rapidly proliferated across the islands. We have expounded on this development in view of much-needed responsible water management across the islands.

Dehydration as a stressor in toads (Rhinella ornata).

Availability of a humid environment is essential for amphibians to carry out their activities and most species are characterized by low resistance to evaporative water loss. Moreover, dehydration severely compromises amphibian locomotor and foraging performance, representing a relevant selective factor modulating the evolution of its integrative phenotype. In this way, we hypothesized that dehydration is a stressor for toads, inducing a stress response comparable to that elicited by another commonly used stress protocol: restraint challenge. We evaluated changes in plasma levels of corticosterone (CORT), hematocrit (Hct), and neutrophil:lymphocyte (N:L) ratio in adult males of Rhinella ornata, experimentally submitted to different levels of hydration (100%, 90%, and 80% of standard body mass) and to restraint challenge. Our results showed that dehydrating toads by 10% increase CORT to levels equivalent to that obtained by restraint. Moreover, toads dehydrated by 20% show a more pronounced increase in CORT, along with increased Hct and N:L ratio. In this way, we corroborated the hypothesis that dehydration triggers a pronounced stress response in R. ornata.

Substantial reduction in thermo-suitable microhabitat for a rainforest marsupial under climate change.

Increases in mean temperatures caused by anthropogenic climate change increase the frequency and severity of temperature extremes. Although extreme temperature events are likely to become increasingly important drivers of species' response to climate change, the impacts are poorly understood owing mainly to a lack of understanding of species' physiological responses to extreme temperatures. The physiological response of Pseudochirops archeri (green ringtail possum) to temperature extremes has been well studied, demonstrating that heterothermy is used to reduce evaporative water loss at temperatures greater than 30°C. Dehydration is likely to limit survival when animals are exposed to a critical thermal regime of ≥30°C, for ≥5 h, for ≥4 consecutive days. In this study, we use this physiological information to assess P. archeri's vulnerability to climate change. We identify areas of current thermo-suitable habitat (validated using sightings), then estimate future thermo-suitable habitat for P. archeri, under four emission scenarios. Our projections indicate that up to 86% of thermo-suitable habitat could be lost by 2085, a serious conservation concern for the species. We demonstrate the potential applicability of our approach for generating spatio-temporally explicit predictions of the vulnerability of species to extreme temperature events, providing a focus for efficient and targeted conservation and habitat restoration management.

Thermal physiology of a range-restricted desert lark.

Much recent work on avian physiological adaptation to desert environments has focused on larks (Passeriformes: Alaudidae). We tested the prediction that the threatened red lark (Calendulauda burra), a species restricted to very arid parts of South Africa and which is not known to drink, exhibits highly efficient evaporative cooling and makes pronounced use of facultative hyperthermia when exposed to high air temperatures (Ta). We also predicted that C. burra possesses similarly low basal metabolic rate (BMR) and total evaporative water loss (EWL) at moderate Ta as reported for species from the deserts of the Middle East. Rest-phase thermoregulation in C. burra was characterized by an unusually low lower critical limit of thermoneutrality at Ta = ~ 21°C and a BMR of 0.317 ± 0.047W, the lowest BMR relative to allometrically-expected values yet reported in any lark. During the diurnal active phase, red larks were able to tolerate Ta up to 50°C, with the onset of panting occurring at Ta = 38°C. Maximum EWL was 1.475 ± 0.107g h- 1 at Ta = 50°C, equivalent to 620% of minimum EWL at thermoneutrality. The maximum ratio of evaporative heat dissipation to metabolic heat production was 1.58, a value towards the lower end of the range reported for passerines. Our data support the prediction that C. burra shows metabolic traits similar to those of other larks inhabiting extremely arid climates, but not the notion that evaporative cooling at high Ta in this species is more efficient than in most passerines.

Influence of wind direction on the surface roughness of vineyards

Remote sensing-based models are the most viable means of collecting the high-resolution spatially distributed estimates of evaporative water loss needed to manage irrigation and ensure the effective use of limited water resources. However, due to the unique canopy structure and configuration of vineyards, these models may not be able to adequately describe the physical processes driving evapotranspiration from vineyards. Using data collected from 2014 to 2016 as a part of the Grape Remote sensing Atmospheric Profile and Evapotranspiration Experiment (GRAPEX), the twofold objective of this study was to (1) identify the relationship between the roughness parameters, zero-plane displacement height (do) and roughness length for momentum (zo), and local environmental conditions, specifically wind direction and vegetation density and (2) determine the effect of using these relationships on the ability of the remote sensing-based Two-Source Energy Balance (TSEB) model to estimate the sensible (H) and latent (λE) heat fluxes. Although little variation in do was identified during the growing season, a well-defined sigmoidal relationship was observed between zo and wind direction. When the output from a version of the TSEB model incorporating these relationships (TSEBVIN) was compared to output from the standard model (TSEBSTD), there were large changes to the roughness parameters, particularly zo, but only modest changes in the turbulent fluxes. When the output from TSEBVIN was compared to that of a version using a parameterization scheme representing open canopies (TSEBOPN), the mean absolute difference between the estimates of do and zo were 0.44 m and 0.25 m, respectively. While these values represent differences in excess of 45%, the turbulent fluxes differed by just 13 W m−2 or 10%, on average. The results suggest that the TSEB model is largely insensitive to changes in the roughness parameters for the range in roughness values evaluated in this study. This also suggests that the requirement for highly accurate roughness values has limited utility in the application of the TSEB model in vineyard systems. Since there is no significant advantage to using the more complex TSEBOPN and TSEBVIN models, it is recommended that the standard model be used.