Carbon isotope discrimination in leaves of the common paperbark tree, Melaleuca quinquenervia, as a tool for quantifying past tropical and subtropical rainfall

Quantitative reconstructions of terrestrial climate are highly sought after but rare, particularly in Australia. Carbon isotope discrimination in plant leaves (Δleaf) is an established indicator of past hydroclimate because the fractionation of carbon isotopes during photosynthesis is strongly influenced by water stress. Leaves of the evergreen tree Melaleuca quinquenervia have been recovered from the sediments of some perched lakes on North Stradbroke and Fraser Islands, south-east Queensland, eastern Australia. Here, we examine the potential for using M. quinquenervia ∆leaf as a tracer of past rainfall by analysing carbon isotope ratios (δ13C) of modern leaves. We firstly assess Δleaf variation at the leaf and stand scale and find no systematic pattern within leaves or between leaves due to their position on the tree. We then examine the relationships between climate and Δleaf for an 11 year timeseries of leaves collected in a litter tray. M. quinquenervia retains its leaves for 1-4 years; thus cumulative average climate data are used. There is a significant relationship between annual mean ∆leaf and mean annual rainfall of the hydrological year for 1-4 years (i.e. 365-1460 days) prior to leaf fall (r2=0.64, p=0.003, n=11). This relationship is marginally improved by accounting for the effect of pCO2 on discrimination (r2=0.67, p=0.002, n=11). The correlation between rainfall and Δleaf, and the natural distribution of Melaleuca quinquenervia around wetlands of eastern Australia, Papua New Guinea and New Caledonia offers significant potential to infer past rainfall on a wide range of spatial and temporal scales

Development of a southern hemisphere subtropical wetland (Welsby Lagoon, south-east Queensland, Australia) through the last glacial cycle

Continuous records of terrestrial environmental and climatic variability that extend beyond the Last Glacial Maximum (LGM) in Australia are rare. Furthermore, where long records do exist, interpretations of climate and ecological change can be hampered by marked changes in sedimentary environment which, in turn, affect the taphonomy of palaeoecological remains. As a consequence, in order to determine how wetland systems responded to climatic and environmental changes, we first need to understand how their depositional environment changed through time. Here we document the development of freshwater Welsby Lagoon, south-east Queensland, from a 12.7 m sediment sequence with a basal age of ca. 130,000 years. We present a variety of proxies reflecting change within the wetland. Carbon and nitrogen concentrations and carbon and nitrogen isotope ratios are used to infer the source of organic matter. However, the nitrogen limited nature of the catchment soils and presence of the colonial algae Botryococcus meant that organic material with C:N ≥ 20 is likely to be derived from autochthonous sources rather than terrestrial sources. A combination of photosynthetic pigments, plant macrofossils, aquatic pollen and sedimentary lignin was used to identify the sources of organic matter and the changing nature of this wetland. Since its formation, Welsby Lagoon has undergone a progressive change from an open-water, algae and cyanobacteria dominated, freshwater lacustrine system, to an aquatic macrophyte-dominated palustrine swamp after ca. 40 ka. It did not revert to lacustrine conditions during the Holocene, despite what is widely viewed as an increase in the regional moisture balance, most likely due to continual infilling of the wetland with sediment. With so few records of terrestrial change throughout MIS3 and MIS4, adequately understanding the development of sites like Welsby Lagoon is imperative to advancing our knowledge of this important environmental and cultural period in Australia's history, which encompasses events such as the extinction of megafauna and human colonisation of the continent

A comparison of stomatal traits between contemporary and fossil leaves of Melaleuca quinquenervia: Do they reflect climate variation?

© 2019 Stomatal traits have been shown to vary in predictable ways in response to environmental change in many plant species. As a consequence, stomatal traits in fossil leaves are sometimes used as proxies for past CO2 and climate. Here we investigate the influence of temperature, rainfall and CO2 on stomatal traits in plant cuticle fine details of Melaleuca quinquenervia. We use both modern and fossil leaves deposited over the last c. 7500 years to evaluate the effect of CO2, and modern leaves for climate variables. We found a significant negative relationship between stomatal size and density across both modern and fossil leaves of M. quinquenervia. However, we were unable to find any relationship between stomatal traits and CO2 across a range from 260 to 380 ppm. We were unable to find any robust relationships between stomatal traits and either evaporation or temperature using the modern dataset. Apogeotropic roots account for the lack of stomatal anatomy response to evaporation in sites that experiences inundation. We conclude that stomatal size is a highly plastic trait in this species and changes do not necessarily reflect functional changes in the leaves

Too Hot to Handle: A Survey of Attitudes towards Fever of 462 Pediatric Intensive Care Unit staff

The role played by fever in the outcome of critical illness in children is unclear. This survey of medical and nursing staff in 35 paediatric intensive care units and transport teams in the United Kingdom and Ireland established attitudes towards the management of children with fever. Four hundred sixty-two medical and nursing staff responded to a web-based survey request. Respondents answered eight questions regarding thresholds for temperature control in usual clinical practice, indications for paracetamol use, and readiness to participate in a clinical trial of permissive temperature control. The median reported threshold for treating fever in clinical practice was 38 °C (IQR 38–38.5 °C). Paracetamol was reported to be used as an analgesic and antipyretic but also for non-specific comfort indications. There was a widespread support for a clinical trial of a permissive versus a conservative approach to fever in paediatric intensive care units. Within a trial, 58% of the respondents considered a temperature of 39 °C acceptable without treatment. Conclusions: Staff on paediatric intensive care units in the United Kingdom and Ireland tends to treat temperatures within the febrile range. There was a willingness to conduct a randomized controlled trial of treatment of fever

Genomic investigations of unexplained acute hepatitis in children

Since its first identification in Scotland, over 1,000 cases of unexplained paediatric hepatitis in children have been reported worldwide, including 278 cases in the UK1. Here we report an investigation of 38 cases, 66 age-matched immunocompetent controls and 21 immunocompromised comparator participants, using a combination of genomic, transcriptomic, proteomic and immunohistochemical methods. We detected high levels of adeno-associated virus 2 (AAV2) DNA in the liver, blood, plasma or stool from 27 of 28 cases. We found low levels of adenovirus (HAdV) and human herpesvirus 6B (HHV-6B) in 23 of 31 and 16 of 23, respectively, of the cases tested. By contrast, AAV2 was infrequently detected and at low titre in the blood or the liver from control children with HAdV, even when profoundly immunosuppressed. AAV2, HAdV and HHV-6 phylogeny excluded the emergence of novel strains in cases. Histological analyses of explanted livers showed enrichment for T cells and B lineage cells. Proteomic comparison of liver tissue from cases and healthy controls identified increased expression of HLA class 2, immunoglobulin variable regions and complement proteins. HAdV and AAV2 proteins were not detected in the livers. Instead, we identified AAV2 DNA complexes reflecting both HAdV-mediated and HHV-6B-mediated replication. We hypothesize that high levels of abnormal AAV2 replication products aided by HAdV and, in severe cases, HHV-6B may have triggered immune-mediated hepatic disease in genetically and immunologically predisposed children

A late glacial to present diatom record from lake Euramoo, wet tropics of Queensland, Australia

A new diatom record from Lake Euramoo on the Atherton Tableland, north Queensland, Australia is used to assess regional climate change and variability and their links to forcing at a local to global scale. The major factor driving diatom composition in the approximately fifteen thousand-year record appears to be regional moisture availability. Patterns of diatom preservation and other indicators, particularly sediment organic content, suggest that permanent deep water formed at the site from ca. 15,000 cal. yr BP. However, between 13,800 and 11,500 cal. yr BP, there was a notable phase of lower lake levels and effective precipitation. The timing and duration of this phase does not correspond to large-scale climate phenomena such as the Antarctic Cold Reversal or the Younger Dryas and supports emerging evidence for a variable climate regime in the south-west Pacific during the late glacial transition. The Early to Mid Holocene record is one of remarkable stability with 5000 years of sustained dominance by the planktonic diatom Aulacoseira ambigua. Conversely, the Mid to Late Holocene record is marked by distinct diatom variability superimposed on a series of sustained shifts in composition. Accentuated Late Holocene climate variability may aid in explaining intensified land use in indigenous populations and also suggests that Europeans may have arrived in the landscape at the time it was most vulnerable to perturbation

Influence of River Murray water on River Torrens' water quality

"Transfers of River Murray water to the River Torrens commenced in 1955. This box focuses on the water quality impacts of this transfer on River Torrens storages.