Optimizing electron backscatter diffraction of carbonate biominerals—resin type and carbon coating

Electron backscatter diffraction (EBSD) is becoming a widely used technique to determine crystallographic orientation in biogenic carbonates. Despite this use, there is little information available on preparation for the analysis of biogenic carbonates. EBSD data are compared for biogenic aragonite and calcite in the common blue mussel, <i>Mytilus edulis</i>, using different types of resin and thicknesses of carbon coating. Results indicate that carbonate biomineral samples provide better EBSD results if they are embedded in resin, particularly epoxy resin. A uniform layer of carbon of 2.5 nm thickness provides sufficient conductivity for EBSD analyses of such insulators to avoid charging without masking the diffracted signal. Diffraction intensity decreases with carbon coating thickness of 5 nm or more. This study demonstrates the importance of optimizing sample preparation for EBSD analyses of insulators such as carbonate biominerals

The response of Physical Science post-graduates to training courses and the connection to their PhD studies

Training in both employability and discipline-specific skills has been provided and expanded over a number of years for post-graduate research students, (PGRs) in the Faculty of Physical Sciences administered by the Physical Sciences Graduate School (PSGS) at the University of Glasgow. This project explored the training provided in 2005/06 with a view to further developing a programme that students and faculty alike consider appropriate, timely and developmental for the needs of research students. The training provided by the PSGS had grown over a number of years in response to suggestions from academic staff in the Faculty of Physical Sciences. Data were collected from Postgraduate Research students (PGRs) from all the stages of the 3 year PhD process to enable a complete map of views to emerge. In particular, the way PGR students perceive the training they undergo in relation to their core PhD research and career progression was examined. The students in our study also identified clearly where they perceived they were developing such transferable skills, and training sessions are not seen as the sole or even major source; the research group itself would appear to play a major role. The authors believe the finding could inform the provision of PGR training in other UK institution

Tuning of Calcite Crystallographic Orientation to Support Brachiopod Lophophore

Organisms exert exquisite control on mineral formation by tuning structural and material properties to meet functional requirements. Brachiopods are sessile marine organisms that filter feed via a large lophophore which is supported by a delicate calcite loop that grows from the inner surface of the shell. How does the loop support the weight of the large lophophore? Electron backscatter diffraction (EBSD) and nanoindentation analyses of the loop as it emerges from the shell of Laqueus rubellus reveal that calcite fiber crystallography generates asymmetry in the material properties of the structure. In the core of the emergent loop, the fibers are short and kernel‐like. Either side of the core, the long fibers have a different crystallographic orientation and resultant material properties. fibers on the anterior, load‐bearing side, are harder (H = 3.76 ± 0.24 GPa) and less stiff (E = 76.87 ± 4.87 GPa) than the posterior (H = 3.48 ± 0.31 GPa, E = 81.79 ± 5.33 GPa). As a consequence of the asymmetry in the material properties, the loop anterior may be more flexible under load. The brachiopod strategy of tuning crystallographic orientation to confer spatially determined material properties is attractive for additive manufacturing of synthetic materials that have complex heterogeneous material property requirements

Ocean acidification impacts mussel control on biomineralisation

Ocean acidification is altering the oceanic carbonate saturation state and threatening the survival of marine calcifying organisms. Production of their calcium carbonate exoskeletons is dependent not only on the environmental seawater carbonate chemistry but also the ability to produce biominerals through proteins. We present shell growth and structural responses by the economically important marine calcifier Mytilus edulis to ocean acidification scenarios (380, 550, 750, 1000≈ atm pCO 2). After six months of incubation at 750≈ atm pCO 2, reduced carbonic anhydrase protein activity and shell growth occurs in M. edulis. Beyond that, at 1000≈ atm pCO 2, biomineralisation continued but with compensated metabolism of proteins and increased calcite growth. Mussel growth occurs at a cost to the structural integrity of the shell due to structural disorientation of calcite crystals. This loss of structural integrity could impact mussel shell strength and reduce protection from predators and changing environments

Red coralline algae assessed as marine pH proxies using 11B MAS NMR

Reconstructing pH from biogenic carbonates using boron isotopic compositions relies on the assumption that only borate, and no boric acid, is present. Red coralline algae are frequently used in palaeoenvironmental reconstruction due to their widespread distribution and regular banding frequency. Prior to undertaking pH reconstructions using red coralline algae we tested the boron composition of the red coralline alga Lithothamnion glaciale using high field NMR. In bulk analysed samples, thirty percent of boron was present as boric acid. We suggest that prior to reconstructing pH using coralline algae 1) species-specific boron compositions and 2) within-skeleton special distributions of boron are determined for multiple species. This will enable site selective boron analyses to be conducted validating coralline algae as palaeo-pH proxies based on boron isotopic compositions

Crystallographic Interdigitation in Oyster Shell Folia Enhances Material Strength

Shells of oyster species belonging to the genus Crassostrea have similar shell microstructural features comprising well-ordered calcite folia. However, the mechanical strengths of folia differ dramatically between closely related species. For example, the calcareous shells of the Hong Kong oyster Crassostrea hongkongensis are stronger than those of its closest relative, the Portuguese oyster, Crassostrea angulata. Specifically, after removal of organic content, the folia of C. hongkongensis are 200% tougher and able to withstand a 100% higher crushing force than that of C. angulata. Detailed analyses of shell structural and mechanical features support the hypothesis that crystallographic interdigitations confer elevated mechanical strength in C. hongkongensis oyster shells compared to C. angulata shells. Consequently, the folia of C. hongkongensis are structurally equipped to withstand a higher external load compared to C. angulata. The observed relationships between oyster shell structure, crystallography, and mechanical properties provided an insightful context in which to consider the likely fate of these two species in future climate change scenarios. Furthermore, the interdisciplinary approach developed in this study through integrating electron backscatter diffraction (EBSD) data into finite element analysis (FEA) could be applied to other biomineral systems to investigate the relationship between crystallography and mechanical behavior

Biomineral Proteins from Mytilus edulis Mantle Tissue Transcriptome

The common blue mussel, Mytilus edulis, has a bimineralic shell composed of approximately equal proportions of the two major polymorphs of calcium carbonate: calcite and aragonite. The exquisite biological control of polymorph production is the focus of research interest in terms of understanding the details of biomineralisation and the proteins involved in the process of complex shell formation. Recent advances in ease and availability of pyrosequencing and assembly have resulted in a sharp increase in transcriptome data for invertebrate biominerals. We have applied Roche 454 pyrosequencing technology to profile the transcriptome for the mantle tissue of the bivalve M. edulis. A comparison was made between the results of several assembly programs: Roche Newbler assembler versions 2.3, 2.5.2 and 2.6 and MIRA 3.2.1 and 3.4.0. The Newbler and MIRA assemblies were subsequently merged using the CAP3 assembler to give a higher consensus in alignments and a more accurate estimate of the true size of the M. edulis transcriptome. Comparison sequence searches show that the mantle transcripts for M. edulis encode putative proteins exhibiting sequence similarities with previously characterised shell proteins of other species of Mytilus, the Bivalvia Pinctada and haliotid gastropods. Importantly, this enhanced transcriptome has detected several transcripts that encode proteins with sequence similarity with previously described shell biomineral proteins including Shematrins and lysine-rich matrix proteins (KRMPs) not previously found in Mytilus. © 2013 The Author(s)

Biomineral shell formation under ocean acidification: A shift from order to chaos

Biomineral production in marine organisms employs transient phases of amorphous calcium carbonate (ACC) in the construction of crystalline shells. Increasing seawater pCO2 leads to ocean acidification (OA) with a reduction in oceanic carbonate concentration which could have a negative impact on shell formation and therefore survival. We demonstrate significant changes in the hydrated and dehydrated forms of ACC in the aragonite and calcite layers of Mytilus edulis shells cultured under acidification conditions (1000 μatm pCO2) compared to present day conditions (380 μatm pCO2). In OA conditions, Mytilus edulis has more ACC at crystalisation sites. Here, we use the high-spatial resolution of synchrotron X-ray Photo Emission Electron Microscopy (XPEEM) combined with X-ray Absorption Spectroscopy (XAS) to investigate the influence of OA on the ACC formation in the shells of adult Mytilus edulis. Electron Backscatter Diffraction (EBSD) confirms that OA reduces crystallographic control of shell formation. The results demonstrate that OA induces more ACC formation and less crystallographic control in mussels suggesting that ACC is used as a repair mechanism to combat shell damage under OA. However, the resultant reduced crystallographic control in mussels raises concerns for shell protective function under predation and changing environments. © 2016, Nature Publishing Group. All rights reserved

The Stirling Protocol - Putting the environment at the heart of prosperity and social inclusion

While the global coronavirus crisis impacts society and the economy in a myriad of ways, it provides, what is likely to be, a once in a lifetime opportunity for us to rethink our response to climate change. According to the 2020 Global Risk Register, extreme weather and climate action failure are the two most likely and impactful risks to the global economy, which now more than ever needs to be avoided. Addressing the major challenges that we face from climate change can often appear to conflict with economic priorities. Add to this the fact that environmental mitigation steps can inadvertently exclude sections of the population and the enormity and complexity of climate change responses can result in paralysis. In contrast, the Stirling Protocol provides the framework for rapid, effective action and comprises three pillars: Environment, Economy & Inclusion. By addressing and balancing these three pillars, the simple protocol can be adopted throughout organisations putting the environment at the heart of sustainable prosperity and inclusion and provide a benchmark for positive action

Putting the environment at the heart of prosperity & social inclusion: The Stirling Protocol

Scotland’s Programme for Government 2019-20, Protecting Scotland’s Future, sets out an ambitious target to achieve net-zero greenhouse gas emissions by 2045. Meeting this objective will require policymakers, businesses and other organisations to reconsider how they operate, and make the transition to alternative, sustainable ways of working. All too often, it can seem as if there is a conflict between the need to address climate change and demands for economic growth. Where solutions are put in place, they can often exclude certain sections of the population, or can be impractical or burdensome for smaller organisations to adopt. This complexity often leads to paralysis, leaving headline pledges to decarbonise unfulfilled. This briefing paper overviews the Stirling Protocol, a simple framework which enables organisations to balance the demands of economic growth, environmental sustainability, and social inclusion. As Scotland emerges from the economic shock of the global coronavirus pandemic, the Protocol will be relevant to all those with an interest in placing sustainable, inclusive prosperity at the heart of Scotland’s economic recovery.Scotland-specific policy Briefing based on: Cusack et al. The Stirling Protocol – Putting the environment at the heart of prosperity and social inclusion, Science of The Total Environment, Volume 737, 1 October 2020, doi: https://doi.org/10.1016/j.scitotenv.2020.14007