The Segmented Zambezi Sedimentary System from Source to Sink: 1. Sand Petrology and Heavy Minerals

The Zambezi River rises at the center of southern Africa, flows across the low-relief Kalahari Plateau, meets Karoo basalt, plunges into Victoria Falls, follows along Karoo rifts, and pierces through Precambrian basement to eventually deliver its load onto the Mozambican passive margin. Reflecting its polyphase evolution, the river is subdivided into segments with different geological and geomorphological character, a subdivision finally fixed by man’s construction of large reservoirs and faithfully testified by sharp changes in sediment composition. Pure quartzose sand recycled from Kalahari desert dunes in the uppermost tract is next progressively enriched in basaltic rock fragments and clinopyroxene. Sediment load is renewed first downstream of Lake Kariba and next downstream of Lake Cahora Bassa, documenting a stepwise decrease in quartz and durable heavy minerals. Composition becomes quartzo-feldspathic in the lower tract, where most sediment is supplied by high-grade basements rejuvenated by the southward propagation of the East African rift. Feldspar abundance in Lower Zambezi sand has no equivalent among big rivers on Earth and far exceeds that in sediments of the northern delta, shelf, and slope, revealing that provenance signals from the upper reaches have ceased to be transmitted across the routing system after closure of the big dams. This high-resolution petrologic study of Zambezi sand allows us to critically reconsider several dogmas, such as the supposed increase of mineralogical “maturity” during long-distance fluvial transport, and forges a key to unlock the rich information stored in sedimentary archives, with the ultimate goal to accurately reconstruct the evolution of this mighty river flowing across changing African landscapes since the late Mesozoic

Subseafloor stratigraphic profiling and soil classification from piezocone tests: A case study in the Gulf of Lion (NW Mediterranean Sea)

We show the results provided by piezocone tests in determining the stratigraphic profile and the soil classification of two drilling sites in the outer shelf and the upper slope of the Gulf of Lion, PRGL2 and PRGL1, respectively. Correlations with grain-size data indicate that sleeve friction can be used for profiling fine-grained sediments (site PRGL1), whereas cone tip resistance is the most adequate for sequences made of alternations of coarse- and fine-grained intervals (site PRGL2). Normalized cone resistance and friction ratio proved to be also appropriate for soil stratigraphy as it depicts trends in the coarse fraction of the tested soil. Silts and clays present in similar proportions at site PRGL1 responded to piezocone testing as pure clays usually do. Consequently, classical soil classification methods resulted in erroneous interpretation of these sediments as clays, whereas classification of the heterogeneous deposits at PRGL2 was consistent with the grain size. When tied to a high-resolution seismic reflection profile, the stratigraphy interpreted from the piezocone profile matches with the main seismic sequences and discontinuities defined from seismic stratigraphy analysis. Graded bedding also matches with cone tip resistance and sleeve friction data

Neogene to Quaternary evolution of carbonate and mixed carbonate-siliciclastic systems along New Caledonia's eastern margin (SW Pacific)

Neogene and Quaternary shallow-water carbonate records surrounding New Caledonia main island, Grande Terre, provide a good example for understanding the stratigraphic architecture of tropical mixed carbonate-siliciclastic systems. Due to a southeastern tilt of the eastern margin, the eastern shelf of Grande Terre has been better preserved from erosion than the western part, favouring the development and preservation of shallow-water carbonates. Based on the integration of bathymetric and seismic data, along with paleoenvironmental and biostratigraphic constraints derived from dredged carbonate rocks, a comprehensive geomorphological and architectural characterization of the offshore eastern margin of Grande Terre has been made. During the Mio-Pliocene, a wide, up to 750 m-thick carbonate build-up developed and extended over at least 350 km from north to south. This Mio-Pliocene build-up, currently lying at 300 to 600 m water depths, is overlain by a Pleistocene-Holocene barrier reef-lagoon complex and associated slope deposits. The switch from aggrading Neogene carbonate banks to backstepping Quaternary platforms likely reflects an increase in accommodation due to a high subsidence rate or to relative sea-level rise, and/or results from a switch in carbonate producers associated with global environmental changes. The internal architecture of the Quaternary barrier reef-lagoon complex is highlighted, especially the development of lowstand siliciclastic prisms alternating with transgressive shallow-water carbonate sequences. This pattern agrees with the reciprocal sedimentation model typically invoked for mixed sedimentary systems. This stratigraphic pattern is well developed in front of the Cap Bayes inlet in the north of our study area, yet it is not observed southward along the eastern margin. This difference suggests that other factors than relative sea-level variations directed the architecture of the margin, such as low terrigenous inputs, lagoon paleo-drainage networks or sediment by-pass towards deep basins

Identification of Avramr1 from Phytophthora infestans using long read and cDNA pathogen-enrichment sequencing (PenSeq)

Potato late blight, caused by the oomycete pathogen Phytophthora infestans, significantly hampers potato production. Recently, a new Resistance to Phytophthora infestans (Rpi) gene, Rpi‐amr1, was cloned from a wild Solanum species, Solanum americanum. Identification of the corresponding recognized effector (Avirulence or Avr) genes from P. infestans is key to elucidating their naturally occurring sequence variation, which in turn informs the potential durability of the cognate late blight resistance. To identify the P. infestans effector recognized by Rpi‐amr1, we screened available RXLR effector libraries and used long read and cDNA pathogen‐enrichment sequencing (PenSeq) on four P. infestans isolates to explore the untested effectors. Using single‐molecule real‐time sequencing (SMRT) and cDNA PenSeq, we identified 47 highly expressed effectors from P. infestans, including PITG_07569, which triggers a highly specific cell death response when transiently coexpressed with Rpi‐amr1 in Nicotiana benthamiana, suggesting that PITG_07569 is Avramr1. Here we demonstrate that long read and cDNA PenSeq enables the identification of full‐length RXLR effector families and their expression profile. This study has revealed key insights into the evolution and polymorphism of a complex RXLR effector family that is associated with the recognition by Rpi‐amr1

Family members’ perspectives of child protection services, a metasynthesis of the literature

This review is part of a EC research project funded by RDAP-GBW-AG-2018-2 Domestic Violence/European Commission.This metasynthesis brings together what is known about family members’ perspectives of their relationship with social care practitioners as a starting point for developing a pan-European training resource for practitioners. Four databases were searched for qualitative literature with search terms relating to family members and social care practitioners. After the application of inclusion and exclusion criteria, 35 studies were critically appraised and were included in the metasynthesis. Three broad themes were identified through a thematic analysis of the studies’ findings: family members’ perspectives of the system; perceptions of how they were viewed by their worker; and view of their worker. The following aspects are discussed: whether partnership between family and worker is possible within a legal framework; the detrimental effects of cultural bias; and practical foundations for building trust. Recommendations are made for practical support, reflection on cultural practice and broader service provision.Publisher PDFPeer reviewe

The evolution of early diagenetic processes at the Mozambique margin during the last glacial-interglacial transition

The Mozambique continental margin experienced large variations in sedimentation rates, primarily due to re-routing of sediment deposition from the Zambezi River during the last glacial-Holocene transition. As changes in sediment accumulation and organic matter deposition impose a strong control on the formation of authigenic minerals in the sediment, the distribution of these minerals may reflect the regional paleoenvironmental and paleoclimatic evolution. Combining geochemical analyses of porewaters and sediments with a reactive transport modeling approach, we reconstruct the depositional history and its effect on pyrite formation and other biogeochemical transformations at a site on the Mozambique margin over the past 27 kyr. Fitting the model to match the observed geochemical patterns, most importantly authigenic pyrite, allowed for the reconstruction of past sulfate-methane transition zone depth, which migrated in response to changes in the sediment accumulation and organic matter deposition. Changes in sediment deposition quickly affected organoclastic sulfate reduction and associated pyrite formation, but the effect on anaerobic methane oxidation and subsequent pyrite formation occurred with a lag on the order of thousands of years. Model results reveal a transition from high diagenetic reaction rates representative of near-shore depositional environments during the late glacial maximum, to a setting typical of offshore sediments with low reaction rates at the present day. Notably, the remnants of methane and dissolved iron pools produced in the past still shape the diagenetic processes at and below the sulfate-methane transition zone today. Since deglacial shelf-flooding and corresponding changes in sediment deposition occurred along continental margins worldwide, our analysis highlights the important role of non-steady state diagenesis in continental margin sediments and its relevance for paleoceanographic interpretation of sediment cores experiencing strong variations in sediment input

A pan-European review of good practices in early intervention safeguarding practice with children, young people and families : evidence gathering to inform a multi-disciplinary training programme (the ERICA project) in preventing child abuse and neglect in seven European countries

Funded by the Rights, Equality and Citizenship Programme of the European Commission (European Commission 2019–2021).Child maltreatment has detrimental social and health effects for individuals, families and communities. The ERICA project is a pan-European training programme that equips non-specialist threshold practitioners with knowledge and skills to prevent and detect child maltreatment. This paper describes and presents the findings of a rapid review of good practice examples across seven participating countries including local services, programmes and risk assessment tools used in the detection and prevention of child maltreatment in the family. Learning was applied to the development of the generic training project. A template for mapping the good practice examples was collaboratively developed by the seven participating partner countries. A descriptive data analysis was undertaken organised by an a priori analysis framework. Examples were organised into three areas: programmes tackling child abuse and neglect, local practices in assessment and referral, risk assessment tools. Key findings were identified using a thematic approach. Seventy-two good practice examples were identified and categorised according to area, subcategory and number. A typology was developed as follows: legislative frameworks, child health promotion programmes, national guidance on child maltreatment, local practice guidance, risk assessment tools, local support services, early intervention programmes, telephone or internet-based support services, COVID-19 related good practices. Improved integration of guidance into practice and professional training in child development were highlighted as overarching needs. The impact of COVID-19 on safeguarding issues was apparent. The ERICA training programme formally responded to the learning identified in this international good practice review.Publisher PDFPeer reviewe

Pathogen enrichment sequencing (PenSeq) enables population genomic studies in oomycetes

The oomycete pathogens Phytophthora infestans and P. capsici cause significant crop losses world‐wide, threatening food security. In each case, pathogenicity factors, called RXLR effectors, contribute to virulence. Some RXLRs are perceived by resistance proteins to trigger host immunity, but our understanding of the demographic processes and adaptive evolution of pathogen virulence remains poor. Here, we describe PenSeq, a highly efficient enrichment sequencing approach for genes encoding pathogenicity determinants which, as shown for the infamous potato blight pathogen Phytophthora infestans, make up < 1% of the entire genome. PenSeq facilitates the characterization of allelic diversity in pathogen effectors, enabling evolutionary and population genomic analyses of Phytophthora species. Furthermore, PenSeq enables the massively parallel identification of presence/absence variations and sequence polymorphisms in key pathogen genes, which is a prerequisite for the efficient deployment of host resistance genes. PenSeq represents a cost‐effective alternative to whole‐genome sequencing and addresses crucial limitations of current plant pathogen population studies, which are often based on selectively neutral markers and consequently have limited utility in the analysis of adaptive evolution. The approach can be adapted to diverse microbes and pathogens

Novel SPG11 mutations in Asian kindreds and disruption of spatacsin function in the zebrafish

Autosomal recessive hereditary spastic paraplegia with thin corpus callosum (HSP-TCC) maps to the SPG11 locus in the majority of cases. Mutations in the KIAA1840 gene, encoding spatacsin, have been shown to underlie SPG11-linked HSP-TCC. The aim of this study was to perform candidate gene analysis in HSP-TCC subjects from Asian families and to characterize disruption of spatacsin function during zebrafish development. Homozygosity mapping and direct sequencing were used to assess the ACCPN, SPG11, and SPG21 loci in four inbred kindreds originating from the Indian subcontinent. Four novel homozygous SPG11 mutations (c.442+1G>A, c.2146C>T, c.3602_3603delAT, and c.4846C>T) were identified, predicting a loss of spatacsin function in each case. To investigate the role of spatacsin during development, we additionally ascertained the complete zebrafish spg11 ortholog by reverse transcriptase PCR and 5′ RACE. Analysis of transcript expression through whole-mount in situ hybridization demonstrated ubiquitous distribution, with highest levels detected in the brain. Morpholino antisense oligonucleotide injection was used to knock down spatacsin function in zebrafish embryos. Examination of spg11 morphant embryos revealed a range of developmental defects and CNS abnormalities, and analysis of axon pathway formation demonstrated an overall perturbation of neuronal differentiation. These data confirm loss of spatacsin as the cause of SPG11-linked HSP-TCC in Asian kindreds, expanding the mutation spectrum recognized in this disorder. This study represents the first investigation in zebrafish addressing the function of a causative gene in autosomal recessive HSP and identifies a critical role for spatacsin during early neural development in vivo