Showing papers by "Cooperative Research Centre published in 2012"

Eliciting Expert Knowledge in Conservation Science

Abstract: Expert knowledge is used widely in the science and practice of conservation because of the complexity of problems, relative lack of data, and the imminent nature of many conservation decisions. Expert knowledge is substantive information on a particular topic that is not widely known by others. An expert is someone who holds this knowledge and who is often deferred to in its interpretation. We refer to predictions by experts of what may happen in a particular context as expert judgments. In general, an expert-elicitation approach consists of five steps: deciding how information will be used, determining what to elicit, designing the elicitation process, performing the elicitation, and translating the elicited information into quantitative statements that can be used in a model or directly to make decisions. This last step is known as encoding. Some of the considerations in eliciting expert knowledge include determining how to work with multiple experts and how to combine multiple judgments, minimizing bias in the elicited information, and verifying the accuracy of expert information. We highlight structured elicitation techniques that, if adopted, will improve the accuracy and information content of expert judgment and ensure uncertainty is captured accurately. We suggest four aspects of an expert elicitation exercise be examined to determine its comprehensiveness and effectiveness: study design and context, elicitation design, elicitation method, and elicitation output. Just as the reliability of empirical data depends on the rigor with which it was acquired so too does that of expert knowledge.

CliMond: global high‐resolution historical and future scenario climate surfaces for bioclimatic modelling

Abstract: Summary 1. Gridded climatologies have become an indispensable component of bioclimatic modelling, with a range of applications spanning conservation and pest management. Such globally conformal data sets of historical and future scenario climate surfaces are required to model species potential ranges under current and future climate scenarios. 2. We developed a set of interpolated climate surfaces at 10¢ and 30¢ resolution for global land areas excluding Antarctica. Input data for the baseline climatology were gathered from the WorldClim and CRU CL1AE0 and CL2AE0 data sets. A set of future climate scenarios were generated at 10¢ resolution. For each of the historical and future scenario data sets, the full set of 35 Bioclim variables was generated. Climate variables (including relative humidity at 0900 and 1500 hours) were also gener

Regions of rapid sea ice change: An inter‐hemispheric seasonal comparison

Abstract: This bi-polar analysis resolves ice edge changes on space/time scales relevant for investigating seasonal iceocean feedbacks and focuses on spatio-temporal changes in the timing of annual sea ice retreat and advance over 1979/ 80 to 2010/11. Where Arctic sea ice decrease is fastest, the sea ice retreat is now nearly 2 months earlier and subsequent advance more than 1 month later (compared to 1979/80), resulting in a 3-month longer summer ice-free season. In the Antarctic Peninsula and Bellingshausen Sea region, sea ice retreat is more than 1 month earlier and advance 2 months later, resulting in a more than 3-month longer summer icefree season. In contrast, in the western Ross Sea (Antarctica) region, sea ice retreat and advance are more than 1 month later and earlier respectively, resulting in a more than 2 month shorter summer ice-free season. Regardless of trend magnitude or direction, and at latitudes mostly poleward of 70° (N/S), there is strong correspondence between anomalies in the timings of sea ice retreat and subsequent advance, but little correspondence between advance and subsequent retreat. These results support a strong ocean thermal feedback in autumn in response to changes in spring sea ice retreat. Further, model calculations suggest different net ocean heat changes in the Arctic versus Antarctic where autumn sea ice advance is 1 versus 2 months later. Ocean-atmosphere changes, particularly in boreal spring and austral autumn (i.e., during ~March-May), are discussed and compared, as well as possible inter-hemispheric climate connections.

Discriminative Separation of Gases by a “Molecular Trapdoor” Mechanism in Chabazite Zeolites

Abstract: Separation of molecules based on molecular size in zeolites with appropriate pore aperture dimensions has given rise to the definition of "molecular sieves" and has been the basis for a variety of separation applications. We show here that for a class of chabazite zeolites, what appears to be "molecular sieving" based on dimension is actually separation based on a difference in ability of a guest molecule to induce temporary and reversible cation deviation from the center of pore apertures, allowing for exclusive admission of certain molecules. This new mechanism of discrimination permits "size-inverse" separation: we illustrate the case of admission of a larger molecule (CO) in preference to a smaller molecule (N(2)). Through a combination of experimental and computational approaches, we have uncovered the underlying mechanism and show that it is similar to a "molecular trapdoor". Our materials show the highest selectivity of CO(2) over CH(4) reported to date with important application to natural gas purification.

Trends and seasonal cycles in the isotopic composition of nitrous oxide since 1940

Abstract: The atmospheric nitrous oxide concentration has increased by 20% since 1750. Analyses of Antarctic firn and archived air samples reveal seasonal cycles in the isotopic signature of nitrous oxide, which can help to disentangle the contribution of surface sources.

A global compilation of dissolved iron measurements: focus on distributions and processes in the Southern Ocean

Abstract: . Due to its importance as a limiting nutrient for phytoplankton growth in large regions of the world's oceans, ocean water column observations of concentration of the trace-metal iron (Fe) have increased markedly over recent decades. Here we compile >13 000 global measurements of dissolved Fe (dFe) and make this available to the community. We then conduct a synthesis study focussed on the Southern Ocean, where dFe plays a fundamental role in governing the carbon cycle, using four regions, six basins and five depth intervals as a framework. Our analysis highlights depth-dependent trends in the properties of dFe between different regions and basins. In general, surface dFe is highest in the Atlantic basin and the Antarctic region. While attributing drivers to these patterns is uncertain, inter-basin patterns in surface dFe might be linked to differing degrees of dFe inputs, while variability in biological consumption between regions covaries with the associated surface dFe differences. Opposite to the surface, dFe concentrations at depth are typically higher in the Indian basin and the Subantarctic region. The inter-region trends can be reconciled with similar ligand variability (although only from one cruise), and the inter-basin difference might be explained by differences in hydrothermal inputs suggested by modelling studies (Tagliabue et al., 2010) that await observational confirmation. We find that even in regions where many dFe measurements exist, the processes governing the seasonal evolution of dFe remain enigmatic, suggesting that, aside from broad Subantarctic – Antarctic trends, biological consumption might not be the major driver of dFe variability. This highlights the apparent importance of other processes such as exogenous inputs, physical transport/mixing or dFe recycling processes. Nevertheless, missing measurements during key seasonal transitions make it difficult to better quantify and understand surface water replenishment processes and the seasonal Fe cycle. Finally, we detail the degree of seasonal coverage by region, basin and depth. By synthesising prior measurements, we suggest a role for different processes and highlight key gaps in understanding, which we hope can help structure future research efforts in the Southern Ocean.

Design of a Bovine Low-Density SNP Array Optimized for Imputation

Abstract: The Illumina BovineLD BeadChip was designed to support imputation to higher density genotypes in dairy and beef breeds by including single-nucleotide polymorphisms (SNPs) that had a high minor allele frequency as well as uniform spacing across the genome except at the ends of the chromosome where densities were increased. The chip also includes SNPs on the Y chromosome and mitochondrial DNA loci that are useful for determining subspecies classification and certain paternal and maternal breed lineages. The total number of SNPs was 6,909. Accuracy of imputation to Illumina BovineSNP50 genotypes using the BovineLD chip was over 97% for most dairy and beef populations. The BovineLD imputations were about 3 percentage points more accurate than those from the Illumina GoldenGate Bovine3K BeadChip across multiple populations. The improvement was greatest when neither parent was genotyped. The minor allele frequencies were similar across taurine beef and dairy breeds as was the proportion of SNPs that were polymorphic. The new BovineLD chip should facilitate low-cost genomic selection in taurine beef and dairy cattle.

The influence of biochar and black carbon on reduction and bioavailability of chromate in soils.

Abstract: The widespread use of chromium (Cr) has a deleterious impact on the environment. A number of pathways, both biotic and abiotic in character, determine the fate and speciation of Cr in soils. Chromium exists in two predominant species in the environment: trivalent [(Cr(III)] and hexavalent [Cr(VI)]. Of these two forms, Cr(III) is nontoxic and is strongly bound to soil particles, whereas Cr(VI) is more toxic and soluble and readily leaches into groundwater. The toxicity of Cr(VI) can be mitigated by reducing it to Cr(III) species. The objective of this study was to examine the effect of organic carbon sources on the reduction, microbial respiration, and phytoavailability of Cr(VI) in soils. Organic carbon sources, such as black carbon (BC) and biochar, were tested for their potential in reducing Cr(VI) in acidic and alkaline contaminated soils. An alkaline soil was selected to monitor the phytotoxicity of Cr(VI) in sunflower plant. Our results showed that using BC resulted in greater reduction of Cr(VI) in soils compared with biochar. This is attributed to the differences in dissolved organic carbon and functional groups that provide electrons for the reduction of Cr(VI). When increasing levels of Cr were added to soils, both microbial respiration and plant growth decreased. The application of BC was more effective than biochar in increasing the microbial population and in mitigating the phytotoxicity of Cr(VI). The net benefit of BC emerged as an increase in plant biomass and a decrease in Cr concentration in plant tissue. Consequently, it was concluded that BC is a potential reducing amendment in mitigating Cr(VI) toxicity in soil and plants.

Localized subduction of anthropogenic carbon dioxide in the Southern Hemisphere oceans

Abstract: The Southern Ocean makes a substantial contribution to the oceanic carbon sink. Observationally based estimates of carbon subduction suggest that carbon sequestration depends on physical properties, such as mixed layer depth, ocean currents, wind and eddies, that are potentially sensitive to climate variability and change.

A simple technique for estimating an allowance for uncertain sea-level rise

Abstract: Projections of climate change are inherently uncertain, leading to considerable debate over suitable allowances for future changes such as sea-level rise (an ‘allowance’ is, in this context, the amount by which something, such as the height of coastal infrastructure, needs to be altered to cope with climate change). Words such as ‘plausible’ and ‘high-end’ abound, with little objective or statistically valid support. It is firstly shown that, in cases in which extreme events are modified by an uncertain change in the average (e.g. flooding caused by a rise in mean sea level), it is preferable to base future allowances on estimates of the expected frequency of exceedances rather than on the probability of at least one exceedance. A simple method of determining a future sea-level rise allowance is then derived, based on the projected rise in mean sea level and its uncertainty, and on the variability of present tides and storm surges (‘storm tides’). The method preserves the expected frequency of flooding events under a given projection of sea-level rise. It is assumed that the statistics of storm tides relative to mean sea level are unchanged. The method is demonstrated using the GESLA (Global Extreme Sea-Level Analysis) data set of roughly hourly sea levels, covering 198 sites over much of the globe. Two possible projections of sea-level rise are assumed for the 21st century: one based on the Third and Fourth Assessment Reports of the Intergovernmental Panel on Climate Change and a larger one based on research since the Fourth Assessment Report.

A phasing and imputation method for pedigreed populations that results in a single-stage genomic evaluation

Abstract: Efficient, robust, and accurate genotype imputation algorithms make large-scale application of genomic selection cost effective. An algorithm that imputes alleles or allele probabilities for all animals in the pedigree and for all genotyped single nucleotide polymorphisms (SNP) provides a framework to combine all pedigree, genomic, and phenotypic information into a single-stage genomic evaluation. An algorithm was developed for imputation of genotypes in pedigreed populations that allows imputation for completely ungenotyped animals and for low-density genotyped animals, accommodates a wide variety of pedigree structures for genotyped animals, imputes unmapped SNP, and works for large datasets. The method involves simple phasing rules, long-range phasing and haplotype library imputation and segregation analysis. Imputation accuracy was high and computational cost was feasible for datasets with pedigrees of up to 25 000 animals. The resulting single-stage genomic evaluation increased the accuracy of estimated genomic breeding values compared to a scenario in which phenotypes on relatives that were not genotyped were ignored. The developed imputation algorithm and software and the resulting single-stage genomic evaluation method provide powerful new ways to exploit imputation and to obtain more accurate genetic evaluations.

Natural iron fertilization of the Atlantic sector of the Southern Ocean by continental shelf sources of the Antarctic Peninsula

Abstract: In large parts of the Southern Ocean, primary production is limited due to shortage of iron (Fe). We measured vertical Fe profiles in the western Weddell Sea, Weddell-Scotia Confluence, and Antarctic Circumpolar Current (ACC), showing that Fe is derived from benthic Fe diffusion and sediment resuspension in areas characterized by high turbulence due to rugged bottom topography. Our data together with literature data reveal an exponential decrease of dissolved Fe (DFe) concentrations with increasing distance from the continental shelves of the Antarctic Peninsula and the western Weddell Sea. This decrease can be observed 3500 km eastward of the Antarctic Peninsula area, downstream the ACC. We estimated DFe summer fluxes into the upper mixed layer of the Atlantic sector of the Southern Ocean and found that horizontal advection dominates DFe supply, representing 54 ± 15% of the total flux, with significant vertical advection second most important at 29 ± 13%. Horizontal and vertical diffusion are weak with 1 ± 2% and 1 ± 1%, respectively. The atmospheric contribution is insignificant close to the Antarctic continent but increases to 15 ± 10% in the remotest waters (>1500 km offshore) of the ACC. Translating Southern Ocean carbon fixation by primary producers into biogenic Fe fixation shows a twofold excess of new DFe input close to the Antarctic continent and a one-third shortage in the open ocean. Fe recycling, with an estimated “fe” ratio of 0.59, is the likely pathway to balance new DFe supply and Fe fixation.

Tensile properties of carbon fibres and carbon fibre–polymer composites in fire

Abstract: The effect of fire on the tensile properties of carbon fibres is experimentally determined to provide new insights into the tensile performance of carbon fibre–polymer composite materials during fire. Structural tests on carbon–epoxy laminate reveal that thermally-activated weakening of the fibre reinforcement is the dominant softening process which leads to failure in the event of a fire. This process is experimentally investigated by determining the reduction to the tensile properties and identifying the softening mechanism of T700 carbon fibre following exposure to simulated fires of different temperatures (up to 700 °C) and atmospheres (air and inert). The fibre modulus decreases with increasing temperature (above ∼500 °C) in air, which is attributed to oxidation of the higher stiffness layer in the near-surface fibre region. The fibre modulus is not affected when heated in an inert (nitrogen) atmosphere due to the absence of surface oxidation, revealing that the stiffness loss of carbon fibre composites in fire is sensitive to the oxygen content. The tensile strength of carbon fibre is reduced by nearly 50% following exposure to temperatures over the range 400–700 °C in an air or inert atmosphere. Unlike the fibre modulus, the reduction in fibre strength is insensitive to the oxygen content of the atmosphere during fire. The reduction in strength is possibly attributable to very small (under ∼100 nm) flaws and removal of the sizing caused by high temperature exposure.

Components of the accuracy of genomic prediction in a multi-breed sheep population

Abstract: In genome-wide association studies, failure to remove variation due to population structure results in spurious associations. In contrast, for predictions of future phenotypes or estimated breeding values from dense SNP data, exploiting population structure arising from relatedness can actually increase the accuracy of prediction in some cases, for example, when the selection candidates are offspring of the reference population where the prediction equation was derived. In populations with large effective population size or with multiple breeds and strains, it has not been demonstrated whether and when accounting for or removing variation due to population structure will affect the accuracy of genomic prediction. Our aim in this study was to determine whether accounting for population structure would increase the accuracy of genomic predictions, both within and across breeds. First, we have attempted to decompose the accuracy of genomic prediction into contributions from population structure or linkage disequilibrium (LD) between markers and QTL using a diverse multi-breed sheep (Ovis aries) data set, genotyped for 48,640 SNP. We demonstrate that SNP from a single chromosome can achieve up to 86% of the accuracy for genomic predictions using all SNP. This result suggests that most of the prediction accuracy is due to population structure, because a single chromosome is expected to capture relationships but is unlikely to contain all QTL. We then explored principal component analysis (PCA) as an approach to disentangle the respective contributions of population structure and LD between SNP and QTL to the accuracy of genomic predictions. Results showed that fitting an increasing number of principle components (PC; as covariates) decreased within breed accuracy until a lower plateau was reached. We speculate that this plateau is a measure of the accuracy due to LD. In conclusion, a large proportion of the accuracy for genomic predictions in our data was due to variation associated with population structure. Surprisingly, accounting for this structure generally decreased the accuracy of across breed genomic predictions.

A Core Metabolic Enzyme Mediates Resistance to Phosphine Gas

Abstract: Phosphine is a small redox-active gas that is used to protect global grain reserves, which are threatened by the emergence of phosphine resistance in pest insects. We find that polymorphisms responsible for genetic resistance cluster around the redox-active catalytic disulfide or the dimerization interface of dihydrolipoamide dehydrogenase (DLD) in insects (Rhyzopertha dominica and Tribolium castaneum) and nematodes (Caenorhabditis elegans). DLD is a core metabolic enzyme representing a new class of resistance factor for a redox-active metabolic toxin. It participates in four key steps of core metabolism, and metabolite profiles indicate that phosphine exposure in mutant and wild-type animals affects these steps differently. Mutation of DLD in C. elegans increases arsenite sensitivity. This specific vulnerability may be exploited to control phosphine-resistant insects and safeguard food security.

Phosphine resistance in the rust red flour beetle, Tribolium castaneum (Coleoptera: Tenebrionidae): Inheritance, gene interactions and fitness costs

Abstract: The recent emergence of heritable high level resistance to phosphine in stored grain pests is a serious concern among major grain growing countries around the world. Here we describe the genetics of phosphine resistance in the rust red flour beetle Tribolium castaneum (Herbst), a pest of stored grain as well as a genetic model organism. We investigated three field collected strains of T. castaneum viz., susceptible (QTC4), weakly resistant (QTC1012) and strongly resistant (QTC931) to phosphine. The dose-mortality responses of their test- and inter-cross progeny revealed that most resistance was conferred by a single major resistance gene in the weakly (3.2×) resistant strain. This gene was also found in the strongly resistant (431×) strain, together with a second major resistance gene and additional minor factors. The second major gene by itself confers only 12–20× resistance, suggesting that a strong synergistic epistatic interaction between the genes is responsible for the high level of resistance (431×) observed in the strongly resistant strain. Phosphine resistance is not sex linked and is inherited as an incompletely recessive, autosomal trait. The analysis of the phenotypic fitness response of a population derived from a single pair inter-strain cross between the susceptible and strongly resistant strains indicated the changes in the level of response in the strong resistance phenotype; however this effect was not consistent and apparently masked by the genetic background of the weakly resistant strain. The results from this work will inform phosphine resistance management strategies and provide a basis for the identification of the resistance genes.

Modeling the basal melting and marine ice accretion of the Amery Ice Shelf

Abstract: The basal mass balance of the Amery Ice Shelf (AIS) in East Antarctica is investigated using a numerical ocean model. The main improvements of this model over previous studies are the inclusion of frazil formation and dynamics, tides and the use of the latest estimate of the sub-ice-shelf cavity geometry. The model produces a net basal melt rate of 45.6 Gt year�1 (0.74 m ice year�1) which is in good agreement with reviewed observations. The melting at the base of the ice shelf is primarily due to interaction with High Salinity Shelf Water created from the surface sea-ice formation in winter. The temperature difference between the coldest waters created in the open ocean and the in situ freezing point of ocean water in contact with the deepest part of the AIS drives a melt rate that can exceed 30 m of ice year�1. The inclusion of frazil dynamics is shown to be important for both melting and marine ice accretion (refreezing). Frazil initially forms in the supercooled water layer adjacent to the base of the ice shelf. The net accretion of marine ice is 5.3 Gt year�1, comprised of 3.7 Gt year�1 of frazil accretion and 1.6 Gt year�1 of direct basal refreezing.

East Antarctic Landfast Sea Ice Distribution and Variability, 2000–08

Abstract: This study presents the first continuous, high spatiotemporal resolution time series of landfast sea ice extent along the East Antarctic coast for the period March 2000–December 2008. The time series was derived from consecutive 20-day cloud-free Moderate Resolution Imaging Spectroradiometer (MODIS) composite images. Fast ice extent across the East Antarctic coast shows a statistically significant (1.43% ±0.30% yr−1) increase. Regionally, there is a strong increase in the Indian Ocean sector (20°–90°E, 4.07% ±0.42% yr−1), and a nonsignificant decrease in the western Pacific Ocean sector (90°–160°E, −0.40% ±0.37% yr−1). An apparent shift from a negative to a positive extent trend is observed in the Indian Ocean sector from 2004. This shift also coincides with a greater amount of interannual variability. No such shift in apparent trend is observed in the western Pacific Ocean sector, where fast ice extent is typically higher and variability lower than the Indian Ocean sector. The limit to the maximu...

The role of the small airways in the clinical expression of asthma in adults.

Abstract: Background The clinical relevance of increased ventilation heterogeneity, a marker of small-airways disease, in asthmatic patients is unclear. Ventilation heterogeneity is an independent determinant of airway hyperresponsiveness (AHR), improves with bronchodilators and inhaled corticosteroids (ICSs), and worsens during exacerbations, but its relationship to asthma control is unknown. Objective We sought to determine the association between ventilation heterogeneity and current asthma control before and after ICS treatment. Methods Adult subjects with asthma had lung function and asthma control (5-item Asthma Control Questionnaire [ACQ-5 score] ≥1.5 = poorly controlled, ACQ-5 score ≤0.75 = well controlled) measured at baseline. A subgroup with AHR had repeat measurements after 3 months of high-dose ICS treatment. The indices of ventilation heterogeneity in the regions of the lung where gas transport occurs predominantly through convection (ventilation heterogeneity in convection-dependent airways [Scond]) and through diffusion (ventilation heterogeneity in diffusion-dependent airways [Sacin]) were derived by using the multiple-breath nitrogen washout technique. Results At baseline (n = 105), subjects with poorly controlled asthma had worse FEV 1 , fraction of exhaled nitric oxide measured at 200 mL/s (Feno), Scond, and Sacin values. In the treatment group (n = 50) spirometric, Feno, residual volume (RV)/total lung capacity (TLC), AHR, and Scond values significantly improved. Asthma control also improved (mean ACQ-5 score, 1.3-0.7; P r s = 0.31, P = .03), Sacin ( r s = 0.32, P = .02), and Scond ( r s = 0.41, P = .003) values. The independent predictors of a change in asthma control were changes in Scond and Sacin values (model r 2 = 0.20, P = .005). Conclusions Current asthma control is associated with markers of small-airways disease. Improvements in ventilation heterogeneity with anti-inflammatory therapy are associated with improvements in symptoms. Sensitive measures of small-airway function might be useful in monitoring the response to therapy in asthmatic subjects.

An independently dated 2000-yr volcanic record from Law Dome, East Antarctica, including a new perspective on the dating of the 1450s CE eruption of Kuwae, Vanuatu

Abstract: Volcanic eruptions are an important cause of nat- ural climate variability. In order to improve the accuracy of climate models, precise dating and magnitude of the climatic effects of past volcanism are necessary. Here we present a 2000-yr record of Southern Hemisphere volcanism recorded in ice cores from the high accumulation Law Dome site, East Antarctica. The ice cores were analysed for a suite of chemistry signals and are independently dated via annual layer counting, with 11 ambiguous years at 23 BCE, which has presently the lowest error of all published long Antarc- tic ice cores. Independently dated records are important to avoid circular dating where volcanic signatures are assigned a date from some external information rather than using the date it is found in the ice core. Forty-five volcanic events have been identified using the sulphate chemistry of the Law Dome record. The low dating error and comparison with the NGRIP (North Greenland Ice Core Project) volcanic records (on the GICC05 timescale) suggest Law Dome is the most accurately dated Antarctic volcanic dataset, which will im- prove the dating of individual volcanic events and potentially allow better correlation between ice core records, leading to improvements in global volcanic forcing datasets. One of the most important volcanic events of the last two millennia is the large 1450s CE event, usually assigned to the eruption of Kuwae, Vanuatu. In this study, we review the evidence sur- rounding the presently accepted date for this event, and make the case that two separate eruptions have caused confusion in the assignment of this event. Volcanic sulphate deposition es- timates are important for modelling the climatic response to eruptions. The largest volcanic sulphate events in our record are dated at 1458 CE (Kuwae?, Vanuatu), 1257 and 422 CE (unidentified).

Human-induced global ocean warming on multidecadal timescales

Abstract: The possibility of anthropogenic ocean warming has led to a range of concerns, from impacts on fisheries and ocean acidification to rising sea level and changes in tropical cyclone frequency and intensity. This study substantially strengthens the attribution of the recently observed global ocean warming to human activity.

Osmolality and tear film dynamics

Abstract: The tear film is a nourishing, lubricating and protecting layer that bathes the ocular surface. It is continuously replenished through cycles of production and elimination via evaporation, absorption and drainage. These processes are often referred to as tear film dynamics. Osmolality is an objective clinical measurement that provides insight into the balance of these complex tear film dynamics. Balanced tear production and elimination is vital for tear film integrity, stability and normal osmolality. Imbalances cause alterations of the tear film structure and composition, ultimately leading to tear film instability and measurable tear film hyperosmolality. Elevated tear film osmolality is considered a core mechanism in dry eye, forming the basis of dry eye symptoms and leading to ocular surface damage. Despite its immense potential in the diagnosis of dry eye, tear film osmolality is not commonly assessed. This review will focus on the current knowledge of tear film dynamics and tear film osmolality.