Characterization of the subsurface architecture and identification of potential groundwater paths in a clay-rich floodplain using multi-electrode resistivity imaging

The interaction between surface water and groundwater in clay-rich fluvial environments can be complex and is generally poorly understood. Airborne electromagnetic surveys are often used for characterizing regional groundwater systems, but they are constrained by the resolution of the method. A resistivity imaging survey has been carried out in the Macquarie Marshes (New South Wales, Australia) in combination with water chemical sampling. The results have enabled the identification of buried palaeochannels and the location of potential recharge points. The data have been compared with previously published airborne electromagnetic data in the same area. Deeper less conductive features suggest that there is a potential connection between the Great Artesian Basin and groundwater contained within the shallow sand aquifer. Even though the chemistry of the groundwater samples does not indicate interaction with the Great Artesian Basin, the observed discontinuity in the saprolite implies potential for this to happen in other locations

Implementing continuity of midwife carer – just a friendly face? A realist evaluation

BackgroundGood quality midwifery care saves the lives of women and babies. Continuity of midwife carer (CMC), a key component of good quality midwifery care, results in better clinical outcomes, higher care satisfaction and enhanced caregiver experience. However, CMC uptake has tended to be small scale or transient. We used realist evaluation in one Scottish health board to explore implementation of CMC as part of the Scottish Government 2017 maternity plan.MethodsParticipatory research, quality improvement and iterative data collection methods were used to collect data from a range of sources including facilitated team meetings, local and national meetings, quality improvement and service evaluation surveys, audits, interviews and published literature. Data analysis developed context-mechanism-outcome configurations to explore and inform three initial programme theories, which were refined into an overarching theory of what works for whom and in what context.ResultsTrusting relationships across all organisational levels are the context in which CMC works. However, building these relationships during implementation requires good leadership and effective change management to drive whole system change and foster trust across all practice and organisational boundaries. Trusting relationships between midwives and women were valued and triggered a commitment to provide high quality care; CMC team relationships supported improvements in ways of working and sustained practice, and relationships between midwives and providers in different care models either sustained or constrained implementation. Continuity enabled midwives to work to full skillset and across women’s care journey, which in turn changed their perspective of how they provided care and of women’s care needs. In addition to building positive relationships, visible and supportive leadership encourages engagement by ensuring midwives feel safe, valued and informed.ConclusionLeadership that builds trusting relationships across all practice and organisational boundaries develops the context for successful implementation of CMC. These relationships then become the context that enables CMC to grow and flourish. Trusting relationships, working to full skill set and across women’s care journey trigger changes in midwifery practice. Implementing and sustaining CMC within NHS organisational settings requires significant reconfiguration of services at all levels, which requires effective leadership and cannot rely solely on ground-up change

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Using stable isotopes to identify soil moisture sources of key species in drought-stressed riparian woodlands

Remnant riparian woodlands on the Upper Condamine floodplain of the northern Murray-Darling Basin are characterised by the dominant canopy species Eucalyptus camaldulensis (river red gum), a facultative phreatophyte which preferentially accesses shallow groundwater sources during drought conditions. Phyla canescens (lippia), a perennial clonal herb, is also dominant in these ecosystems. Lippia is an invasive alien species, readily dispersed by flooding, with potential to spread throughout much of the Murray-Darling system with significant economic and environmental impact. Recent research indicates that trees may facilitate the persistence of lippia, enabling it to survive and reproduce under drought conditions, and that lippia may in turn contribute to dieback severity in canopy eucalypts in these woodlands. Greater understanding of the intensity and direction of interactions between these two species will contribute to the management of both lippia and tree condition in this landscape. This research uses natural abundance stable isotopes to investigate the relative importance of water sources utilised by E. camaldulensis and P. canescens under low ambient soil moisture conditions. This approach will elucidate potentially important interactions between E. camaldulensis and P. canescens. It will also contribute to better understanding of the role of shallow groundwater resources in ecosystems subject to seasonal and long-term drought, and/or potentially at risk due to floodplain development and increasing climate variability

A small sensor for detecting animal burrows and monitoring burrow water conductivity

An electrical conductivity probe for measuring ground conductivity is described. The probe measures bulk ground conductivity in situ and can assist in locating animal burrows on a centimeter scale and in monitoring conductivity of burrow waters over long period of times. It is shown how burrow caves are located by their conductivity contrast relative to the soil. The conductivity of the water in a burrow cave 70thinspcm under the swamp surface has been recorded over 15 days. The conductivity dropped during/after periods of significant rainfall, and rapidly increased during tidal inundation of the swamp. At times with neither freshwater nor saltwater input through the openings of the burrow on the surface, the conductivity slowly increased presumably due to diffusion of salt through the burrow walls. The diffusion constant was estimated to be 2 × 10–9 m2/s, being comparable to previously determined diffusion constants for diffusion of salt within the substrate

Inputs of anthropogenic nitrogen influence isotopic composition and trophic structure in SE Australian estuaries

Urban development in coastal settings has increased the input of nitrogen into estuaries globally, in many cases changing the composition of estuarine ecosystems. By focussing on three adjacent estuaries with a gradient of anthropogenic N loadings, we used stable isotopes of N and C to test for changes due to increased anthropogenic N input on the structure of some key trophic linkages in estuaries. We found a consistent enrichment in δ¹⁵N corresponding to increased anthropogenic N at the three ecosystem levels studied: fine benthic organic matter, grazing invertebrate, and planktivorous fish. The degree of enrichment in δ¹⁵N between fine benthic organic matter and the grapsid crab Parasesarma erythrodactyla was identical across the three sites. The glassfish Ambassis jacksoniensis showed lower levels of enrichment compared to basal food sources at the higher N-loaded sites, suggesting a possible effect of anthropogenic N in decreasing food-chain length in these estuaries.7 page(s

Methods for monitoring tidal flushing in large animal burrows\ud in tropical mangrove swamps

The typically anaerobic nature of mangrove sediments provides significant challenges to the mangrove trees and biota inhabiting them. The burrowing activities and flow of water through the numerous and complex animal burrows perforating the sediments of mangroves have a major influence on the biogeochemistry of the sediments and are important to the enhancement of nutrient and oxygen\ud exchange. Two new methods are presented for monitoring the tidal flushing of Sesarma messa and Alpheus cf macklay burrows in a Rhizophora stylosa mangrove forest – by measuring oxygen content of burrow water and by determining the change in fluorescence of a dye tracer through tidal inundation. A case study using the first of these showed oxygen consumption rates at the burrow wall deep within the\ud burrow were found to be between 210 and 460 mmol O2m2 h1. The influx of oxygen during a flood tide was found to be significant and indicated that approximately 40% of the burrow water is flushed during a single tidal event. However, the high consumption rate of oxygen within the burrow resulted in the oxygen concentration remaining at or below one-third of the oxygen content of the flooding tidal water. A test application of the second method, using rhodamine dye as a tracer, indicated that the exchange of\ud water between the burrow and the flooding tide was found to be in the order of 30% of the burrow volume. These new techniques provide a means to further study the nutrient exchange within these burrow systems and verify the initial findings that several tidal inundations are necessary to completely flush the burrows

Geoelectrical characterization of hydrological processes in a buried braided river system

The Macquarie Marshes (NSW, Australia) cover approximately 200 square km of the Macquarie River flood-plains. The marshes are one of the largest remaining inland semi-permanent wetlands in southeastern Australia. Diversity of fauna and flora has decreased in the wetlands while the flood-drought cycles controlling these ecosystems have been affected by recent human activity. An Electrical Resistivity Tomography survey has been carried out to provide insight into the surface water/ groundwater interactions occurring at the north-western part of the marshes and to identify potential recharge areas of the aquifer systems. In the resistivity sections three main units can be identified: 1. A top unit of low-resistivity (1 to 6 ohm.m) with about 5 meter thick on average. 2. A middle unit of higher electrical resistivity (6 to 20 ohm.m) that continues to a depth of approximately 20 metres and is discontinuous laterally. 3. A bottom unit below a depth of 20 to 25 metres with resistivity decreasing to values similar to those of the top unit. The resistivity results has allowed to identify clay dominated and sand dominated materials. The groundwater is recharged from surface water following sandy windows in the clay created by modern channels on the surface of the marshes.22nd European Meeting of Environmental and Engineering Geophysics, Near Surface Geoscience 201

Identifying flood recharge and inter-aquifer connectivity using multiple isotopes in subtropical Australia

An understanding of hydrological processes is vital for the sustainable management of groundwater resources, especially in areas where an aquifer interacts with surface water systems or where aquifer interconnectivity occurs. This is particularly important in areas that are subjected to frequent drought/flood cycles, such as the Cressbrook Creek catchment in Southeast Queensland, Australia. In order to understand the hydrological response to flooding and to identify inter-aquifer connectivity, multiple isotopes (δ²H, δ¹⁸O, ⁸⁷Sr/⁸⁶Sr, ³H and ¹⁴C) were used in this study in conjunction with a comprehensive hydrochemical assessment, based on data collected 6 months after severe flooding in 2011. The relatively depleted stable isotope signatures of the flood-generating rainfall (δ²H: −30.2 to −27.8‰, δ¹⁸O: −5.34 to −5.13‰ VSMOW) were evident in surface water samples (δ²H: −25.2 to −23.2‰, δ¹⁸O: −3.9 to −3.6‰ VSMOW), indicating that these extreme events were a major source of recharge to the dam in the catchment headwaters. Furthermore, stable isotopes confirmed that the flood generated significant recharge to the alluvium in the lower part of the catchment, particularly in areas where interactions between surface waters and groundwater were identified and where diffuse aquifer recharge is normally limited by a thick (approximately 10 m) and relatively impermeable unsaturated zone. However, in the upper parts of the catchment where recharge generally occurs more rapidly due to the dominance of coarse-grained sediments in the unsaturated zone, the stable isotope signature of groundwater resembles the longer-term average rainfall values (δ²H: −12.6, δ¹⁸O: −3.4‰ VSMOW), highlighting that recharge was sourced from smaller rainfall events that occurred subsequent to the flooding. Interactions between the bedrock aquifers and the alluvium were identified at several sites in the lower part of the catchment based on ⁸⁷Sr/⁸⁶Sr ratios; this was also supported by the hydrochemical assessment, which included the modelling of evaporation trends and saturation indices. The integrated approach used in this study facilitated the identification of hydrological processes over different spatial and temporal scales, and the method can be applied to other complex geological settings with variable climatic conditions

Effect of acidification on elemental and isotopic compositions of sediment organic matter and macroinvertebrate muscle tissues in food web research

Stable isotope techniques in food web studies often focus on organic carbon in food sources which are subsequently assimilated in the tissue of consumer organisms through diet. The presence of non-dietary carbonates in bulk samples can affect their δ¹³C values, altering how their results are interpreted. Acidification of samples is a common practice to eliminate any inorganic carbon present prior to analysis. We examined the effects of pre-analysis acidification on two size fractions of sediment organic matter (SOM) from marine and freshwater wetlands and pure muscle tissue of a common freshwater invertebrate (Cherax destructor). The elemental content and isotopic ratios of carbon and nitrogen were compared between paired samples of acidified and control treatments. Our results showed that acidification does not affect the elemental or isotopic values of freshwater SOM. In the marine environment acidification depleted the δ¹³C and δ¹⁵N values of the fine fraction of saltmarsh and δ¹⁵N values of mangrove fine SOM. Whilst acidification did not change the elemental content of invertebrate muscle tissue, the δ¹³C and δ¹⁵N values were affected. We recommend to researchers considering using acidification techniques on material prepared for stable isotope analysis that a formal assessment of the effect of acidification on their particular sample type should be undertaken. Further detailed investigation to understand the impact of acidification on elemental and isotopic values of organic matter and muscular tissues is required.5 page(s