Recent publications in Science and Engineering
Barramundi (Lates calcarifer) is a tropical finfish species rapidly growing in popularity for aquaculture production. However, sperm quality tests have yet to be adapted to enable selection of highly fertile male broodstock in this species. Accordingly, in this study advanced tools were optimized to evaluate barramundi sperm function to facilitate the future study of male fertility and address some of the reproductive constraints currently observed in captive-bred broodstock. Sperm morphology data were used to calibrate and validate automated sperm counting and motility detection by computer-assisted sperm analysis (CASA; AndroVision, Minitube). Several parameters were examined to determine the optimum settings for accurate CASA sperm counting and were compared to manual haemocytometer methods including: sample dilution (1:1000, r = 0.87), minimum number of fields (n = 4, CV = 7.5%), and the effect of motile vs. immotile spermatozoa on automated counting (no effect, r = 0.99, P < .001). Assays for cell viability and DNA damage were also validated for barramundi spermatozoa using 70 °C heat-treated controls and a 5-point intact:damaged dilution curve (r = 0.98, P < .001), and DNase-treated sperm controls, respectively. Data from these optimized assessments indicated high variation between individuals for each parameter assessed and the presence of high rates of DNA and membrane damage in sperm samples tested. Further research building upon this preliminary sperm quality data, is required to identify the cause of DNA and membrane damage in barramundi spermatozoa and understand any potential relationships with paternal performance in commercial spawns.
Zhou, Ming, Li, Tianling, Zu, Meng, Zhang, Shanqing, Liu, Yang, and Zhao, Huijun (2021) Membrane-based colorimetric flow-injection system for online free chlorine monitoring in drinking water. Sensors and Actuators B: Chemical, 327. 128905.
The majority of water utilities currently employ the in-lab tests of the grabbed samples to determine the free chlorine (FC) residual levels. Under certain circumstances, such approaches are inadequate to timely and accurately reflect the dynamically changed FC residual levels, leading to inappropriate dosages. This work reports a uniquely configured membrane-based colorimetric flow-injection system (MCFIS) capable of accurately and reliably online monitoring drinking water FC residual levels in a rapid (1−5 min per measurement) fashion. The embedded gas-permeable membrane makes MCFIS an interference-free FC monitoring system. The developed pre-calibration strategy avoids the need for on-going calibration. The accuracy of the conventional analytical principles is almost exclusively determined by the absolute analytical signal value of one measurement data point, and any errors from such a single-data point measurement will be directly transferred to the result, which induces uncertainties, hence, poor accuracy and reliability. Differing distinctively from such conventional analytical principles, MCFIS quantifies chlorine concentration based on N, N-diethyl-p-phenylenediamine – Cl2 colorimetric reaction-controlled membrane transport process that enables the determination of gaseous chlorine concentration according to multiple measurement data points to greatly enhance the accuracy and reliability. The inherent analytical features of this slope-based signal quantification principle, interference-free and on-going calibration-free empower MCFIS with an enormous superiority over other systems for online FC monitoring applications.
Chaturvedi, Iti, Cambria, Erik, Cavallari, Sandro, and Welsch, Roy E. (2020) Genetic programming for domain adaptation in product reviews. In: Proceedings of the IEEE Congress on Evolutionary Computation. From: CEC 2020: IEEE Congress on Evolutionary Computation, 19-24 July 2020, Glasgow, UK.
There is a large variety of products sold online and the websites are in several languages. Hence, it is desirable to train a model that can predict sentiments in different domains simultaneously. Previous authors have used deep learning to extract features from multiple domains. Here, each word is represented by a vector that is determined using co-occurrence data. Such a model requires that all sentences have the same length resulting in low accuracy. To overcome this challenge, we model the features in each sentence using a variable length tree called a Genetic Program. The polarity of clauses can be represented using mathematical operators such as '+' or '-' at internal nodes in the tree. The proposed model is evaluated on Amazon product reviews for different products and in different languages. We are able to outperform the accuracy of baseline multi-domain models in the range of 5-20%.
Wheatley, Greg (2020) On the design of racing car suspension. International Journal on Interactive Design and Manufacturing. (In Press)
Fuller, Zachary L., Mocellin, Veronique J. L., Morris, Luke A., Cantin, Neal, Shepherd, Jihanne, Sarre, Luke, Peng, Julie, Liao, Yi, Pickrell, Joseph, Andolfatto, Peter, Matz, Mikhail, Bay, Line K., and Przeworski, Molly (2020) Population genetics of the coral Acropora millepora: toward genomic prediction of bleaching. Science, 369 (6501). eaba4674.
INTRODUCTION Coral reefs worldwide are suffering losses at an alarming rate as a result of anthropogenic climate change. Increased seawater temperatures, even only slightly above long-term maxima, can induce bleaching—the breakdown of the symbiotic relationship between coral hosts and their intracellular photosynthetic dinoflagellates from the family Symbiodiniaceae. Because these symbionts provide the majority of energy required by the coral host, prolonged periods of bleaching can eventually lead to the death of the colony. In the face of rapidly increasing temperatures, new conservation strategies are urgently needed to prevent future mass losses of coral cover, and these benefit from an understanding of the genetic basis of bleaching. RATIONALE Bleaching responses vary within and among coral species; in the reef-building coral Acropora millepora, a commonly distributed species across the Indo-Pacific, these differences have been shown to be at least partly heritable. In principle, therefore, interindividual differences in bleaching should be predictable from genomic data. Here, we demonstrate the feasibility of using a genomics-based approach to predict individual bleaching responses and suggest ways in which this can inform new strategies for coral conservation. RESULTS We first generated a chromosome-scale genome assembly as well as whole-genome sequences for 237 samples collected at 12 reefs distributed across the central Great Barrier Reef during peak bleaching in 2017. We showed that we can reliably impute genotypes in low-coverage sequencing data with a modestly sized reference haplotype panel, demonstrating a cost-effective approach for future large-scale whole-genome sequencing efforts. Very little population structure was detected across the sampled reefs, which was likely the result of the broadcast spawning mode of reproduction in A. millepora. Against this genomic background, we detected unusually old variation at the heat-shock co-chaperone sacsin, which is consistent with long-term balancing selection acting on this gene. Our genomic sequencing approach simultaneously provides a quantitative measure of bleaching and identifies the composition of symbiont species present within individual coral hosts. Testing more than 6.8 million variants for associations with three different measures of bleaching response, no single site reached genome-wide significance, indicating that variation in bleaching response is not due to common loci of large effect. However, a model that incorporates genetic effects estimated from the genome-wide association data, genomic data on relative symbiont species composition, and environmental variables is predictive of individual bleaching phenotypes. CONCLUSION Understanding the genetics of heat and bleaching tolerance will be critical to predict coral adaptation and the future of coral reef ecosystems under climate change. This knowledge also supports both conventional management approaches and the development of new interventions. Our work provides insight into the genetic architecture of bleaching response and serves as a proof of principle for the use of genomic approaches in conservation efforts. We show that a model based on environmental factors, genomic data from the symbiont, and genome-wide association data in the coral host can help distinguish individuals most tolerant to bleaching from those that are most susceptible. These results thus build a foundation toward a genomic predictor of bleaching response in A. millepora and other coral species.
Mukul, Sharif A., Huq, Saleemul, Herbohn, John, Seddon, Nathalie, and Laurance, William F. (2020) Saving the Sundarbans from development. Science, 368 (6496). p. 1198.
[Extract:] To protect the Sundarbans, any development in the region should also comply with policies that conserve local ecosystems and livelihoods.
Van Oosterzee, Penny, and Laurance, Bill (2020) The next global pandemic could easily erupt in your backyard. The Conversation.
[Extract:] We know the virus that causes COVID-19 is linked to very similar viruses in bats, possibly passed to humans via an intermediate species such as pangolins. The chance of a similar pandemic breaking out in Australia might seem far-fetched. But in fact, we tick all the boxes.
Housley, David M., Pinyon, Jeremy L., Jonquieres, Georg von, Perera, Chamini J., Smout, Michael, Liddell, Michael J., Jennings, Ernest A., Wilson, David, and Housley, Gary D. (2020) Australian scorpion Hormurus waigiensis venom fractions show broad bioactivity through modulation of bio-impedance and cytosolic calcium. Biomolecules, 10 (4). 617.
Scorpion venoms are a rich source of bioactive molecules, but characterisation of toxin peptides affecting cytosolic Ca2+, central to cell signalling and cell death, is limited. We undertook a functional screening of the venom of the Australian scorpion Hormurus waigiensis to determine the breadth of Ca2+ mobilisation. A human embryonic kidney (HEK293) cell line stably expressing the genetically encoded Ca2+ reporter GCaMP5G and the rabbit type 1 ryanodine receptor (RyR1) was developed as a biosensor. Size-exclusion Fast Protein Liquid Chromatography separated the venom into 53 fractions, constituting 12 chromatographic peaks. Liquid chromatography mass spectroscopy identified 182 distinct molecules with 3 to 63 components per peak. The molecular weights varied from 258 Da—13.6 kDa, with 53% under 1 kDa. The majority of the venom chromatographic peaks (tested as six venom pools) were found to reversibly modulate cell monolayer bioimpedance, detected using the xCELLigence platform (ACEA Biosciences). Confocal Ca2+ imaging showed 9/14 peak samples, with molecules spanning the molecular size range, increased cytosolic Ca2+ mobilization. H. waigiensis venom Ca2+ activity was correlated with changes in bio-impedance, reflecting multi-modal toxin actions on cell physiology across the venom proteome.
Wei, Yujie, Lin, Dongdong, Xu, Zhanning, Gao, Xiaoman, Zeng, Chaoshu, and Ye, Haihui (2020) A possible role of crustacean cardioactive peptide in regulating immune response in hepatopancreas of mud crab. Frontiers in Immunology, 11. 711.
Crustacean cardioactive peptide (CCAP), a cyclic amidated non-apeptide, is widely found in arthropods. The functions of CCAP have been revealed to include regulation of heart rate, intestinal peristalsis, molting, and osmotic pressure. However, to date, there has not been any report on the possible involvement of CCAP in immunoregulation in crustaceans. In this study, a CCAP precursor (designated as Sp-CCAP) was identified in the commercially important mud crab Scylla paramamosain, which could be processed into four CCAP-associated peptides and one mature peptide (PFCNAFTGC-NH2). Bioinformatics analysis indicated that Sp-CCAP was highly conserved in crustaceans. RT-PCR results revealed that Sp-CCAP was expressed in nerve tissues and gonads, whereas the Sp-CCAP receptor gene (Sp-CCAPR) was expressed in 12 tissues of S. paramamosain, including hepatopancreas. In situ hybridization further showed that an Sp-CCAPR-positive signal is mainly localized in the F-cells of hepatopancreas. Moreover, the mRNA expression level of Sp-CCAPR in the hepatopancreas was significantly up-regulated after lipopolysaccharide (LPS) or polyriboinosinic polyribocytidylic acid [Poly (I:C)] challenge. Meanwhile, the mRNA expression level of Sp-CCAPR, nuclear transcription factor NF-kappa B homologs (Sp-Dorsal and Sp-Relish), member of mitogen-activated protein kinase (MAPK) signaling pathway (Sp-P38), pro-inflammatory cytokines factor (Sp-TNFSF and Sp-IL16), and antimicrobial peptide (Sp-Lysozyme, Sp-ALF, Sp-ALF4, and Sp-ALF5) in the hepatopancreas were all up-regulated after the administration of synthetic Sp-CCAP mature peptide both in vivo and in vitro. The addition of synthetic Sp-CCAP mature peptide in vitro also led to an increase in nitric oxide (NO) concentration and an improved bacterial clearance ability in the hepatopancreas culture medium. The present study suggested that Sp-CCAP signaling system might be involved in the immune responses of S. paramamosain by activating immune molecules on the hepatopancreas. Collectively, our findings shed new light on neuroendocrine-immune regulatory system in arthropods and could potentially provide a new strategy for disease prevention and control for mud crab aquaculture.
Alamgir, Mohammed, Campbell, Mason J., Sloan, Sean, Engert, Jayden, Word, Jettie, and Laurance, William F. (2020) Emerging challenges for sustainable development and forest conservation in Sarawak, Borneo. PLoS ONE, 15 (3). e0229614.
The forests of Borneo—the third largest island on the planet—sustain some of the highest biodiversity and carbon storage in the world. The forests also provide vital ecosystem services and livelihood support for millions of people in the region, including many indigenous communities. The Pan-Borneo Highway and several hydroelectric dams are planned or already under construction in Sarawak, a Malaysian state comprising part of the Borneo. This development seeks to enhance economic growth and regional connectivity, support community access to services, and promote industrial development. However, the implications of the development of highway and dams for forest integrity, biodiversity and ecosystem services remained largely unreported. We assessed these development projects using fine-scale biophysical and environmental data and found several environmental and socioeconomic risks associated with the projects. The highway and hydroelectric dam projects will impact 32 protected areas including numerous key habitats of threatened species such as the proboscis monkey (Nasalis larvatus), Sarawak surili (Presbytis chrysomelas), Bornean orangutans (Pongo pygmaeus) and tufted ground squirrel (Rheithrosciurus macrotis). Under its slated development trajectory, the local and trans-national forest connectivity between Malaysian Borneo and Indonesian Borneo would also be substantially diminished. Nearly ~161 km of the Pan-Borneo Highway in Sarawak will traverse forested landscapes and ~55 km will traverse carbon-rich peatlands. The 13 hydroelectric dam projects will collectively impact ~1.7 million ha of forest in Sarawak. The consequences of planned highway and hydroelectric dams construction will increase the carbon footprint of development in the region. Moreover, many new road segments and hydroelectric dams would be built on steep slopes in high-rainfall zones and forested areas, increasing both construction and ongoing maintenance costs. The projects would also alter livelihood activities of downstream communities, risking their long-term sustainability. Overall, our findings identify major economic, social and environmental risks for several planned road segments in Sarawak—such as those between Telok Melano and Kuching; Sibu and Bintulu; and in the Lambir, Limbang and Lawas regions—and dam projects—such as Tutoh, Limbang, Lawas, Baram, Linau, Ulu Air and Baleh dams. Such projects need to be reviewed to ensure they reflect Borneo’s unique environmental and forest ecosystem values, the aspirations of local communities and long-term sustainability of the projects rather than being assessed solely on their short term economic returns.
Bodhinayake, Geeth, Ginger, John, and Henderson, David (2020) Correlation of internal and external pressures and net pressure factors for cladding design. Journal of Wind and Structures, 30 (3). pp. 219-229.
Net pressures on roofs and walls of buildings are dependent on the internal and external pressure fluctuations. The variation of internal and external pressures are influenced by the size and location of the openings. The correlation of external and internal pressure influences the net pressures acting on cladding on different parts of the roof and walls. The peak internal and peak external pressures do not occur simultaneously, therefore, a reduction can be applied to the peak internal and external pressures to obtain a peak net pressure for cladding design. A 1:200 scale wind tunnel model study was conducted to determine the correlations of external and internal pressures and effective reduction to net pressures (i.e., net pressure factors, ????????) for roof and wall cladding. The results show that external and internal pressures on the windward roof and wall edges are well correlated. The largest ????????̌,????????????, highest correlation coefficient and the highest ???????? are obtained for different wind directions within 90o ≤ ???? ≤ 135o , where the large openings are on the windward wall. The study also gives net pressure factors ???????? for areas on the roof and wall cladding for nominally sealed buildings and the buildings with a large windward wall opening. These factors indicate that a 5% to 10% reduction to the action combination factor, ???????? specified in AS/NZS 1170.2(2011) is possible for some critical design scenarios.
Tuladhar, Rabin, Marshall, Amelia, and Sivakugan, Siva (2020) Use of recycled concrete aggregate for pavement construction. In: Pacheco-Torgal, Fernando, Ding, Yining, Colangelo, Francesco, and Tuladhar, Rabin, (eds.) Advances in Construction and Demolition Waste Recycling: Management, Processing and Environmental Assessment. Woodhead Publishing . Elsevier, Duxford, United Kingdom, pp. 181-197.
Construction and demolition (C&D) wastes comprise waste generated from construction, renovation, and demolition of buildings, roads, and other infrastructures, and excavation of land associated with construction activities (QDERM, 2011). C&D wastes include a wide range of different waste materials such as concrete, asphalt, bricks, tiles, timber, steel, and soil. In 2016/2017, 20.4 Mt of C&D wastes were produced in Australia, which accounts for more than 40% of Australia’s total annual waste (Pickin et al., 2018). Hydraulically bound materials are made by mixing aggregates and granular aggregates with cement as a binding material. On the other hand, unbound pavement materials consist of quarry materials, natural gravels, and recycled materials without the use of binding materials like cement. Unbound granular materials are the most commonly used material for base/subbase construction in Australia owing to their strength, ease in construction, and low cost. Traditionally, natural crushed rocks are used as granular unbound material for road base and subbase constructions. With the increasing scarcity of natural aggregates and the need to reduce the waste going into landfills, alternative sustainable materials such as recycled C&D wastes are increasingly being considered as a substitute for natural aggregates.
Clements, Kendall D., German, Donovan P., Piche, Jacinthe, Tribollet, Aline, and Choat, John Howard (2020) Integrating ecological roles and trophic diversification on coral reefs: multiple lines of evidence identify parrotfishes as microphages. Biological Journal of the Linnean Society. (In Press)
Coral reef ecosystems are remarkable for their high productivity in nutrient-poor waters. A high proportion of primary production is consumed by the dominant herbivore assemblage, teleost fishes, many of which are the product of recent and rapid diversification. Our review and synthesis of the trophodynamics of herbivorous reef fishes suggests that current models underestimate the level of resource partitioning, and thus trophic innovation, in this diverse assemblage. We examine several lines of evidence including feeding observations, trophic anatomy, and biochemical analyses of diet, tissue composition and digestive processes to show that the prevailing view (including explicit models) of parrotfishes as primary consumers of macroscopic algae is incompatible with available data. Instead, the data are consistent with the hypothesis that most parrotfishes are microphages that target cyanobacteria and other protein-rich autotrophic microorganisms that live on (epilithic) or within (endolithic) calcareous substrata, are epiphytic on algae or seagrasses, or endosymbiotic within sessile invertebrates. This novel view of parrotfish feeding biology provides a unified explanation for the apparently disparate range of feeding substrata used by parrotfishes, and integrates parrotfish nutrition with their ecological roles in reef bioerosion and sediment transport. Accelerated evolution in parrotfishes can now be explained as the result of (1) the ability to utilize a novel food resource for reef fishes, i.e. microscopic autotrophs; and (2) the partitioning of this resource by habitat and successional stage.
Nordborg, F. Mikaela, Jones, Ross J., Oelgemöller, Michael, and Negri, Andrew P. (2020) The effects of ultraviolet radiation and climate on oil toxicity to coral reef organisms – a review. Science of the Total Environment, 720. 137486.
Oil pollution remains a significant local threat to shallow tropical coral reef environments, but the environmental conditions typical of coral reefs are rarely considered in oil toxicity testing and risk assessments. Here we review the effects of three environmental co-factors on petroleum oil toxicity towards coral reef organisms, and show that the impacts of oil pollution on coral reef taxa can be exacerbated by environmental conditions commonly encountered in tropical reef environments. Shallow reefs are routinely exposed to high levels of ultraviolet radiation (UVR), which can substantially increase the toxicity of some oil components through phototoxicity. Exposure to UVR represents the most likely and harmful environmental co-factor reviewed here, leading to an average toxicity increase of 7.2-fold across all tests reviewed. The clear relevance of UVR co-exposure and its strong influence on tropical reef oil toxicity highlights the need to account for UVR as a standard practice in future oil toxicity studies. Indeed, quantifying the influence of UVR on toxic thresholds of oil to coral reef species is essential to develop credible oil spill risk models required for oil extraction developments, shipping management and spill responses in the tropics. The few studies available indicate that co-exposure to elevated temperature and low pH, both within the range of current daily and seasonal fluctuations and/or projected under continued climate change, can increase oil toxicity on average by 3.0- and 1.3-fold, respectively. While all three of the reviewed environmental co-factors have the potential to substantially increase the impacts of oil pollution in shallow reef environments, their simultaneous effects have not been investigated. Assessments of the combined effects of oil pollution, UVR, temperature and low pH will become increasingly important to identify realistic hazard thresholds suitable for future risk assessments over the coming century.
Hierro, José L., Eren, Özkan, Montesinos, Daniel, Andonian, Krikor, Kethsuriani, Liana, Özkan, Rabia, Diaconu, Alecu, Török, Katalin, Cavieres, Lohengrin, and French, Kristine (2020) Increments in weed seed size track global range expansion and contribute to colonization in a non-native region. Biological Invasions, 22 (3). pp. 969-982.
Assessing global variation in phenotypic traits and linking that variation to colonization and range expansion is notably rare in invasion biology. Here, we studied variation in seed size in Centaurea solstitialis, a weed with worldwide distribution. Additionally, we explored how seed size variation affects seedling survival of C. solstitialis under favorable precipitation conditions in Anatolia, an ancestral region, and unfavorable precipitation conditions in Argentina, a non-native region. To that end, we conducted seed collections following dispersal pathways of C. solstitialis in ancestral, expanded, and non-native ranges. Locally, collections followed elevation gradients. Also, we performed a greenhouse experiment with C. solstitialis populations varying in seed size and water additions simulating precipitation patterns in Anatolia and Argentina. Seeds from ancestral populations at low elevation were smaller than those from the rest of study populations. Also, seed size in populations at high elevation in the expanded range, the main source of non-native populations, was similar to that in all, but one non-native population, where seeds exhibited further increase. Increments in seed size thus track range expansion in C. solstitialis. Locally, seed size increased with elevation in all three ranges, suggesting convergent responses to that gradient. Seedlings from larger seeds displayed greater survival than those from smaller seeds only under Argentinean conditions. Consequently, populations with large seeds may have been instrumental for colonizing that non-native region. Our findings suggest that ancient and recent dispersal of large-seeded populations contribute to explain the reported global pattern of seed size divergence and worldwide distribution of C. solstitialis.
Bai, Haihua, Yin, Yanting, Addison, Jane, Hou, Yulu, Wang, Linhe, and Hou, Xiangyang (2020) Market opportunities do not explain the ability of herders to meet livelihood objectives over winter on the Mongolian Plateau. Journal of Arid Land, 12 (2). pp. 522-537.
Drylands under pastoral land use are considered one of the most vulnerable social-ecological systems to global climate change, but the abilities of different adaptive strategies to adapt to the impacts of different extreme weather events on herders’ livelihood have received little attention in the drylands. Herders on the Mongolian Plateau (MP; including Inner Mongolia Autonomous Region of China and Mongolia), have had a long history of adapting climatic variability and extreme weather events. However, it is unclear how changes such as increased levels of infrastructure and market integration affect the ability of herders to achieve the two key livelihood objectives: the minimisation of the death and abortion rates of livestock in the winter. Here, we used remotely sensed and household survey data to map, model and explore the climate exposure and sensitivity of herders in the settled area (Inner Mongolia of China) and nomadic area (Mongolia) in the winter of 2012–2013. We aimed to quantify the multi-scaled characteristics of both climate exposure and sensitivity through the lens of key adaptive strategies utilized by herders. Our results showed that the higher levels of infrastructure and market integration, and the lower levels of remoteness on the MP did not increase the herders' ability to achieve the two key livelihood objectives. Our results also suggested that exposure to the snow that is comparatively greater than the long-term average (cumulative exposure) may be more important in determining the social-ecological vulnerability than absolute exposure. We suggested that neither the risk management strategies available to these herders, nor the demographic variables, could compensate for the mode of production governing the pastoral systems. Our study could provide further evidence for the complex and scaled nature of climate exposure and sensitivity, and the results imply that any analysis of the relationship between exposure, sensitivity and vulnerability of pastoral households to climate change in the drylands will require a multi-scaled and interdisciplinary approach.
Munksgaard, Niels C., Zwart, Costijn, Haig, Jordahna, Cernusak, Lucas A., and Bird, Michael I. (2020) Coupled rainfall and water vapour stable isotope time series reveal tropical atmospheric processes on multiple timescales. Hydrological Processes, 34 (1). pp. 111-124.
High-frequency stable isotope data are useful for validating atmospheric moisture circulation models and provide improved understanding of the mechanisms controlling isotopic compositions in tropical rainfall. Here, we present a near-continuous 6-month record of O- and H-isotope compositions in both water vapour and daily rainfall from Northeast Australia measured by laser spectroscopy. The data set spans both wet and dry seasons to help address a significant data and knowledge gap in the southern hemisphere tropics. We interpret the isotopic records for water vapour and rainfall in the context of contemporaneous meteorological observations. Surface air moisture provided near-continuous tracking of the links between isotopic variations and meteorological events on local to regional spatial scales. Power spectrum analysis of the isotopic variation showed a range of significant periodicities, from hourly to monthly scales, and cross-wavelet analysis identified significant regions of common power for hourly averaged water vapour isotopic composition and relative humidity, wind direction, and solar radiation. Relative humidity had the greatest subdiurnal influence on isotopic composition. On longer timescales (weeks to months), isotope variability was strongly correlated with both wind direction and relative humidity. The high-frequency records showed diurnal isotopic variations in O- and H-isotope compositions due to local dew formation and, for deuterium excess, as a result of evapotranspiration. Several significant negative isotope anomalies on a daily scale were associated with the activity of regional mesoscale convective systems and the occurrence of two tropical cyclones. Calculated air parcel back trajectories identified the predominant moisture transport paths from the Southwest Pacific Ocean, whereas moisture transport from northerly directions occurred mainly during the wet season monsoonal airflow. Water vapour isotope compositions reflected the same meteorological events as recorded in rainfall isotopes but provided much more detailed and continuous information on atmospheric moisture cycling than the intermittent isotopic record provided by rainfall. Improved global coverage of stable isotope data for atmospheric water vapour is likely to improve simulations of future changes to climate drivers of the hydrological cycle.
Nawaz, M., and Wasson, R. (2020) Sediment transfer in an extremely low-gradient, low-relief and highly buffered system: Darwin Harbour catchment, northern Australia. Australian Journal of Earth Sciences, 67 (3). pp. 351-359.
Sediment yields from and sediment transfer within catchments of very low relief and gradient, which make up about 50% of Earth's surface, are poorly documented and their internal sediment dynamics are poorly known. Sediment sources, their proportionate contributions to valley floors and sediment yield, and storage are estimated using fallout radionuclides ²¹⁰Pb₍ₑₓ₎ and ¹³⁷Cs in the catchments that drain into Darwin Harbour, northern Australia, an example of this understudied catchment type that appears to be globally at the extreme end of this category of catchments. Unchannelled grassy valley floors (dambos, or seasonal wetlands) trap ~90% of the sediment delivered from hillslopes by sheet and rill erosion. Further down valley, small channels transport ~10% of the sediment that escapes from the dambos, and the remaining sediment comes from erosion of the channels. In this case, the fractional sediment storage is very high as a result of the existence of dambos, a landform that depends for its existence on low gradients.
Mahan, Brandon M., Wu, Fei, Dosseto, Anthony, Chung, Roger, Schaefer, Bruce, and Turner, Simon (2020) SpinChem™: rapid element purification from biological and geological matrices via centrifugation for MC-ICP-MS isotope analyses – a case study with Zn. Journal of Analytical Atomic Spectrometry, 35. pp. 863-872.
Emerging applications in isotope geochemistry using stable metal isotope systems, including those in archaeological, environmental and medical sciences, along with commercial/industrial applications such as environmental source tracing and ore exploration, require high sample throughput that conventional element purification techniques—i.e. gravity flow ion exchange chromatography (IEC)—cannot match. Here, a simple and robust method for element purification from biological and geological samples has been developed, SpinChem™, wherein element purification via IEC is greatly facilitated through centrifugation. In brief, this involves adapting chromatographic columns for encapsulation within large (50 mL) centrifuge tubes, and subsequent element purification at enhanced flow rates (1.2–1.5 mL min⁻¹) generated by centrifugal force. As proof of concept, Zn IEC purification from biological and geological materials has been detailed, demonstrating the utility of this method across the sample spectrum, and validating high yields (97 ± 4%), high separation efficiency and low contamination levels (blanks ≤1 ng). SpinChem™ IEC in the centrifuge proceeds at rates up to an order of magnitude faster than in gravity flow protocols, with 8–10 samples processed through IEC in under 2 hours (vs. 4–10 hours in gravity flow), while maintaining high subsequent MC-ICP-MS analytical precision, with average errors of 0.06‰ (2s) or better for δ⁶⁶Zn. Benchmarking this technique using an element very sensitive to endogenous and exogenous contamination (e.g. inefficient separation and external contaminants, respectively)—Zn— exemplifies the utility and high performance of this technique, and its ready adaptation to other isotope systems of interest, including Ca, Fe, Cu, Sr/Nd, Mo and Sn.
Noble, Tansyn N., Coman, Gregory J., Wade, Nicholas M., Thomson, Peter C., Raadsma, Herman W., Khatkar, Mehar S., Guppy, Jarrod L., and Jerry, Dean R. (2020) Genetic parameters for tolerance to gill-associated virus under challenge-test conditions in the black tiger shrimp (Penaeus monodon). Aquaculture, 516. 734428.
Diseases in shrimp aquaculture cause significant economic losses, particularly those caused by viruses. Genetic improvement of disease tolerance through selective breeding can be an important tool for managing the risk of disease in shrimp farming as long as the trait has a genetic basis (i.e. heritable) and is able to be accurately and reliably measured. This study presents the first estimates of genetic variation associated with tolerance to gill-associated virus (GAV) in Penaeus monodon using a unique controlled challenge test design. Shrimp families (n = 72) were communally spawned and reared prior to replicated communal challenge testing when they reached an average size of ~8 g. Pedigree determination was carried out using genotyping and shrimp were challenged by intramuscular injection with a weight standardised dose of GAV. Daily mortality data were collected over 15 days from 1717 individuals and GAV infection load was measured on the challenge test survivors (n = 963). Overall mortality after 15 days was 35.5% and ranged from 0 to 71% among families. Heritability estimates for mortality were 0.11 ± 0.03 using a binomial model and 0.14 (standard error not estimated) using Cox's proportional hazards model. The estimated heritability for GAV infection load was 0.21 ± 0.07. The genetic correlation between mortality and GAV infection load was not significantly different from zero, rg = 0.30 ± 0.23, suggesting that the two traits may be genetically independent, at least in the way they were measured in this study. Results from this study suggest a low but significant genetic basis for GAV tolerance in P. monodon and that selection may be a viable option to manage GAV-related disease. The study also demonstrated, for the first time in shrimp, communal-based spawning and rearing can be used for large-scale genetic analysis of disease tolerance, eliminating the need for single family rearing tanks and associated confounding environmental effects.
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