Sediment supply dampens the erosive effects of sea-level rise on reef islands

AbstractLarge uncertainty surrounds the future physical stability of low-lying coral reef islands due to a limited understanding of the geomorphic response of islands to changing environmental conditions. Physical and numerical modelling efforts have improved understanding of the modes and styles of island change in response to increasing wave and water level conditions. However, the impact of sediment supply on island morphodynamics has not been addressed and remains poorly understood. Here we present evidence from the first physical modelling experiments to explore the effect of storm-derived sediment supply on the geomorphic response of islands to changes in sea level and energetic wave conditions. Results demonstrate that a sediment supply has a substantial influence on island adjustments in response to sea-level rise, promoting the increase of the elevation of the island while dampening island migration and subaerial volume reduction. The implications of sediment supply are significant as it improves the potential of islands to offset the impacts of future flood events, increasing the future physical persistence of reef islands. Results emphasize the urgent need to incorporate the physical response of islands to both physical and ecological processes in future flood risk models.</jats:p

Modelling reef hydrodynamics and sediment mobility under sea level rise in atoll reef island systems

This is the author accepted manuscript. The final version is available on open access from Elsevier via the DOI in this record. Low-lying coral reef islands will be significantly impacted by future sea level rise (SLR). It is generally expected that SLR will destabilise reef islands because increasing reef submergence allows larger waves, and therefore greater energy transmission, across reef flats. However, the impact of SLR on altering both reef flat sediment transport and sediment delivery to island shorelines is poorly understood. Here, we use the currents of removal approach (coupling two-dimensional wave modelling with settling velocity data from 186 benthic sediment samples) to model shifts in both reef hydrodynamics and benthic sediment transport under scenarios of mean reef submergence (MRS = +0 m, +0.5 m, +1 m) at two atoll rim reef sites in the Maldives. Under contemporary conditions (MRS = +0 m), we found that benthic sediment transport is likely occurring, consistent with active reef-to-island sediment connectivity. Under conditions of increased MRS, shifts in wave velocities, and in turn sediment potential mobility, were both non-linear and non-uniform. Significant between-site differences were found in the magnitude of projected shifts in sediment mobility under scenarios of increased MRS, which implies that morphological responses to increases in MRS are likely to be diverse, even over local scales. Under increased MRS, the largest increases in sediment mobility were projected on the inner reef flat, whereas lagoonal zones remained as sinks for sediment deposition. We thus hypothesize that while reef islands will persist as sedimentary landforms under projected rates of MRS, lagoonward reef island migration is likely to occur. Findings have implications for predicting the future adaptive capacity of atoll nations. The challenge is to incorporate such potential increases in island mobility and intra-regional diversity in reef system geomorphic responses to sea level rise into national-scale vulnerability assessments.NER

The impact of local networks on subsistence resilience and biodiversity in a low-lying Moluccan reef system between 1600 and the present

Using field data for the 1980s and historical material, I show how the central places of networks crucial for regional and long-distance trade in the Moluccas between 1600 and the present were often environmentally vulnerable volcanic islands and low-lying reefs. After reviewing existing data on hazards, and evaluating the evidence for erosion and degradation, I suggest how resilience has been historically achieved through social and material exchanges between islands, accommodating the consequences of specific perturbations. Re-interpretation of published data shows how inter-island trade has re-organised patterns of biological interaction spatially and over the long-term, helping us assesses whether in the face of climate change effects such areas are zones of robustness or of potential fragility

Reply to J.J. Muñoz-Perez et al. Comments on “Confirmation of beach accretion by grain-size trend analysis: Camposoto beach, Cádiz, SWSpain” by E. Poizot et al. (2013) Geo-Marine Letters 33(4)

In a novel finding for a beach environment, Poizot et al. (2013) identified an FB+ trend (sediments becoming finer, better sorted and more positively skewed upshore) on a well-developed swash bar on the upper foreshore of the Camposoto beach of Cádiz in SW Spain. In their Discussion of that paper, Muñoz-Perez et al. (2014) provide some supporting arguments and also report grain-size, beach profile and other data from nearby beaches which differ from those of Poizot and colleagues for Camposoto beach, pointing out that a trend observed on one beach may not apply to a neighbouring beach. However, even though the absolute values differ, the overall trends actually do show the same general behaviour. In our Reply to their comments, we also address some difficulties in comparing granulometric datasets generated by different analytical techniques

Recruitment and Activation of Pancreatic Stellate Cells from the Bone Marrow in Pancreatic Cancer: A Model of Tumor-Host Interaction

BACKGROUND AND AIMS: Chronic pancreatitis and pancreatic cancer are characterised by extensive stellate cell mediated fibrosis, and current therapeutic development includes targeting pancreatic cancer stroma and tumor-host interactions. Recent evidence has suggested that circulating bone marrow derived stem cells (BMDC) contribute to solid organs. We aimed to define the role of circulating haematopoietic cells in the normal and diseased pancreas. METHODS: Whole bone marrow was harvested from male β-actin-EGFP donor mice and transplanted into irradiated female recipient C57/BL6 mice. Chronic pancreatitis was induced with repeat injections of caerulein, while carcinogenesis was induced with an intrapancreatic injection of dimethylbenzanthracene (DMBA). Phenotype of engrafted donor-derived cells within the pancreas was assessed by immunohistochemistry, immunofluorescence and in situ hybridisation. RESULTS: GFP positive cells were visible in the exocrine pancreatic epithelia from 3 months post transplantation. These exhibited acinar morphology and were positive for amylase and peanut agglutinin. Mice administered caerulein developed chronic pancreatitis while DMBA mice exhibited precursor lesions and pancreatic cancer. No acinar cells were identified to be donor-derived upon cessation of cerulein treatment, however rare occurrences of bone marrow-derived acinar cells were observed during pancreatic regeneration. Increased recruitment of BMDC was observed within the desmoplastic stroma, contributing to the activated pancreatic stellate cell (PaSC) population in both diseases. Expression of stellate cell markers CELSR3, PBX1 and GFAP was observed in BMD cancer-associated PaSCs, however cancer-associated, but not pancreatitis-associated BMD PaSCs, expressed the cancer PaSC specific marker CELSR3. CONCLUSIONS: This study demonstrates that BMDC can incorporate into the pancreas and adopt the differentiated state of the exocrine compartment. BMDC that contribute to the activated PaSC population in chronic pancreatitis and pancreatic cancer have different phenotypes, and may play important roles in these diseases. Further, bone marrow transplantation may provide a useful model for the study of tumor-host interactions in cancer and pancreatitis

Loss of coral reef growth capacity to track future increases in sea level

Water-depths above coral reefs is predicted to increase due to global sea-level rise (SLR). As ecological degradation inhibits the vertical accretion of coral reefs, it is likely that coastal wave exposure will increase but there currently exists a lack of data in projections concerning local rates of reef growth and local SLR. In this study we have aggregated ecological data of more than 200 tropical western Atlantic and Indian Ocean reefs and calculated their vertical growth which we have then compared with recent and projected rates of SLR across different Representative Concentration Pathway (RCP) scenarios. While many reefs currently show vertical growth that would be sufficient to keep-up with recent historic SLR, future projections under scenario RCP4.5 reveal that without substantial ecological recovery many reefs will not have the capacity to track SLR. Under RCP8.5, we predict that mean water depth will increase by over half a metre by 2100 across the majority of reefs. We found that coral cover strongly predicted whether a reef could track SLR, but that the majority of reefs had coral cover significantly lower than that required to prevent reef submergence. To limit reef submergence, and thus the impacts of waves and storms on adjacent coasts, climate mitigation and local impacts that reduce coral cover (e.g., local pollution and physical damage through development land reclamation) will be necessary

Pan-cancer analysis of whole genomes

Cancer is driven by genetic change, and the advent of massively parallel sequencing has enabled systematic documentation of this variation at the whole-genome scale(1-3). Here we report the integrative analysis of 2,658 whole-cancer genomes and their matching normal tissues across 38 tumour types from the Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium of the International Cancer Genome Consortium (ICGC) and The Cancer Genome Atlas (TCGA). We describe the generation of the PCAWG resource, facilitated by international data sharing using compute clouds. On average, cancer genomes contained 4-5 driver mutations when combining coding and non-coding genomic elements; however, in around 5% of cases no drivers were identified, suggesting that cancer driver discovery is not yet complete. Chromothripsis, in which many clustered structural variants arise in a single catastrophic event, is frequently an early event in tumour evolution; in acral melanoma, for example, these events precede most somatic point mutations and affect several cancer-associated genes simultaneously. Cancers with abnormal telomere maintenance often originate from tissues with low replicative activity and show several mechanisms of preventing telomere attrition to critical levels. Common and rare germline variants affect patterns of somatic mutation, including point mutations, structural variants and somatic retrotransposition. A collection of papers from the PCAWG Consortium describes non-coding mutations that drive cancer beyond those in the TERT promoter(4); identifies new signatures of mutational processes that cause base substitutions, small insertions and deletions and structural variation(5,6); analyses timings and patterns of tumour evolution(7); describes the diverse transcriptional consequences of somatic mutation on splicing, expression levels, fusion genes and promoter activity(8,9); and evaluates a range of more-specialized features of cancer genomes(8,10-18).Peer reviewe

Physical modelling of the response of reef islands to sea-level rise

Abstract Sea-level rise and increased storminess are expected to destabilize low-lying reef islands formed on coral reef platforms, and increased flooding is expected to render them uninhabitable within the coming decades. Such projections are founded on the assumption that islands are geologically static landforms that will simply drown as sea-level rises. Here, we present evidence from physical model experiments of a reef island that demonstrates islands have the capability to morphodynamically respond to rising sea level through island accretion. Challenging outputs from existing models based on the assumption that islands are geomorphologically inert, results demonstrate that islands not only move laterally on reef platforms, but overwash processes provide a mechanism to build and maintain the freeboard of islands above sea level. Implications of island building are profound, as it will offset existing scenarios of dramatic increases in island flooding. Future predictive models must include the morphodynamic behavior of islands to better resolve flood impacts and future island vulnerability.</jats:p