Holocene El Niño–Southern Oscillation variability reflected in subtropical Australian precipitation

The La Niña and El Niño phases of the El Niño-Southern Oscillation (ENSO) have major impacts on regional rainfall patterns around the globe, with substantial environmental, societal and economic implications. Long-term perspectives on ENSO behaviour, under changing background conditions, are essential to anticipating how ENSO phases may respond under future climate scenarios. Here, we derive a 7700-year, quantitative precipitation record using carbon isotope ratios from a single species of leaf preserved in lake sediments from subtropical eastern Australia. We find a generally wet (more La Niña-like) mid-Holocene that shifted towards drier and more variable climates after 3200 cal. yr BP, primarily driven by increasing frequency and strength of the El Niño phase. Climate model simulations implicate a progressive orbitally-driven weakening of the Pacific Walker Circulation as contributing to this change. At centennial scales, high rainfall characterised the Little Ice Age (~1450–1850 CE) in subtropical eastern Australia, contrasting with oceanic proxies that suggest El Niño-like conditions prevail during this period. Our data provide a new western Pacific perspective on Holocene ENSO variability and highlight the need to address ENSO reconstruction with a geographically diverse network of sites to characterise how both ENSO, and its impacts, vary in a changing climate

First Observation of Coherent π0\pi^0 Production in Neutrino Nucleus Interactions with Eν<E_{\nu}< 2 GeV

The MiniBooNE experiment at Fermilab has amassed the largest sample to date of $\pi^0$s produced in neutral current (NC) neutrino-nucleus interactions at low energy. This paper reports a measurement of the momentum distribution of $\pi^0$s produced in mineral oil (CH$_2$) and the first observation of coherent $\pi^0$ production below 2 GeV. In the forward direction, the yield of events observed above the expectation for resonant production is attributed primarily to coherent production off carbon, but may also include a small contribution from diffractive production on hydrogen. Integrated over the MiniBooNE neutrino flux, the sum of the NC coherent and diffractive modes is found to be (19.5 $\pm$1.1 (stat) $\pm$2.5 (sys))% of all exclusive NC $\pi^0$ production at MiniBooNE. These measurements are of immediate utility because they quantify an important background to MiniBooNE's search for $\nu_{\mu} \to \nu_e$ oscillations.Comment: Submitted to Phys. Lett.

Test of Lorentz and CPT violation with Short Baseline Neutrino Oscillation Excesses

The sidereal time dependence of MiniBooNE electron neutrino and anti-electron neutrino appearance data are analyzed to search for evidence of Lorentz and CPT violation. An unbinned Kolmogorov-Smirnov test shows both the electron neutrino and anti-electron neutrino appearance data are compatible with the null sidereal variation hypothesis to more than 5%. Using an unbinned likelihood fit with a Lorentz-violating oscillation model derived from the Standard Model Extension (SME) to describe any excess events over background, we find that the electron neutrino appearance data prefer a sidereal time-independent solution, and the anti-electron neutrino appearance data slightly prefer a sidereal time-dependent solution. Limits of order 10E-20 GeV are placed on combinations of SME coefficients. These limits give the best limits on certain SME coefficients for muon neutrino to electron neutrino and anti-muon neutrino to anti-electron neutrino oscillations. The fit values and limits of combinations of SME coefficients are provided.Comment: 14 pages, 3 figures, and 2 tables, submitted to Physics Letters

Diving into the vertical dimension of elasmobranch movement ecology

Knowledge of the three-dimensional movement patterns of elasmobranchs is vital to understand their ecological roles and exposure to anthropogenic pressures. To date, comparative studies among species at global scales have mostly focused on horizontal movements. Our study addresses the knowledge gap of vertical movements by compiling the first global synthesis of vertical habitat use by elasmobranchs from data obtained by deployment of 989 biotelemetry tags on 38 elasmobranch species. Elasmobranchs displayed high intra- and interspecific variability in vertical movement patterns. Substantial vertical overlap was observed for many epipelagic elasmobranchs, indicating an increased likelihood to display spatial overlap, biologically interact, and share similar risk to anthropogenic threats that vary on a vertical gradient. We highlight the critical next steps toward incorporating vertical movement into global management and monitoring strategies for elasmobranchs, emphasizing the need to address geographic and taxonomic biases in deployments and to concurrently consider both horizontal and vertical movements

Polyphasic identification of cyanobacterial isolates from Australia

Reliable identification of cyanobacterial isolates has significant socio-economic implications as many bloom-forming species affect the aesthetics and safety of drinking water, through the production of taste and odour compounds or toxic metabolites. The limitations of morphological identification have promoted the application of molecular tools, and encouraged the adoption of combined (polyphasic) approaches that include both microscopy- and DNA-based analyses. In this context, the rapid expansion of available sequence data is expected to allow increasingly reliable identification of cyanobacteria, and ultimately resolve current discrepancies between the two approaches.In the present study morphological and molecular characterisations of cyanobacterial isolates (n=39), collected from various freshwater sites in Australia, were compared. Sequences were obtained for the small ribosomal subunit RNA gene (16S rDNA) (n=36), the DNA-dependent RNA polymerase gene (rpoC1) (n=22), and the phycocyanin operon, with its intergenic spacer region (cpcBA-IGS) (n=19). Phylogenetic analyses identified three cyanobacterial orders: the Chroococcales (n=8), Oscillatoriales (n=6), and Nostocales (n=25). Interestingly, multiple novel genotypes were identified, with 22% of the strains (17/77) having <95% similarity to available sequences in GenBank.Morphological and molecular data were in agreement at the species level for only 26% of the isolates obtained (10/39), while agreement at the genus level was obtained for 31% (12/39). Confident identification of the remaining 44% of the strains (17/39) beyond the order level was not possible. The present study demonstrates that, despite the taxonomic revisions, and advances in molecular-, and bioinformatics-tools, the lack of reliable morphological features, culture-induced pleomorphism, and proportion of misidentified or poorly described sequences in GenBank, still represent significant factors, impeding the confident identification of cyanobacteria species

Variation in leaf wax n-alkane characteristics with climate in the broad-leaved paperbark (Melaleuca quinquenervia)

In higher plants, leaf waxes provide a barrier to non-stomatal water loss, and their composition varies both between and within species. Characteristics of n-alkanes, a suite of ubiquitous compounds in these waxes, are thought to be influenced by the availability of water and the temperature in a plant’s growing environment. Longer n-alkane distributions with less variability in chain length are hypothesised to confer greater resistance to non-stomatal water loss and thus are expected in higher abundance in desiccating environments. Relationships between the distribution of n-alkanes and both precipitation and temperature have previously been observed. Despite this, it is unclear whether n-alkane chain length distributions vary plastically in response to climate, or whether they are fixed within populations in different climate settings. To better understand this, we examine the relationship between n-alkane characteristics of Melaleuca quinquenervia and both spatial and temporal climate variation. Across eastern Australia, we find that n-alkane homolog concentrations and distributions in leaves of M. quinquenervia do not vary with climate where samples are proximate, even when climate shows significant variability. However, the concentration and distribution of n-alkane homologs do differ considerably between geographically separated populations in very different climate regimes. These results suggest n-alkane characteristics are not a plastic response to climate variability, and instead are likely fixed and could be driven by genetic differences between populations. This has important implications for the use of n-alkane characteristics as palaeoenvironmental proxies.Jake W. Andrae, Francesca A. McInerney, John Tibby, Andrew C.G. Henderson, P. Anthony Hall, Jonathan C. Marshall, Glenn B. McGregor, Cameron Barr, Margaret Greenwa