Calcium isotope fractionation by intracellular amorphous calcium carbonate (ACC) forming cyanobacteria

The formation of intracellular amorphous calcium carbonate (ACC) by various cyanobacteria is a widespread biomineralization process, yet its mechanism and importance in past and modern environments remain to be fully comprehended. This study explores whether calcium (Ca) isotope fractionation, linked to ACC-forming cyanobacteria, can serve as a reliable tracer for detecting these microorganisms in modern and ancient settings. Accordingly, we measured stable Ca isotope fractionation during Ca uptake by the intracellular ACC-forming cyanobacterium Cyanothece sp. PCC 7425. Our results show that Cyanothece sp. PCC 7425 cells are enriched in lighter Ca isotopes relative to the solution. This finding is consistent with the kinetic isotope effects observed in the Ca isotope fractionation during biogenic carbonate formation by marine calcifying organisms. The Ca isotope composition of Cyanothece sp. PCC 7425 was accurately modeled using a Rayleigh fractionation model, resulting in a Ca isotope fractionation factor (Δ44Ca) equal to -0.72 ± 0.05‰. Numerical modeling suggests that Ca uptake by these cyanobacteria is primarily unidirectional, with minimal back reaction observed over the duration of the experiment. Finally, we compared our Δ44Ca values with those of other biotic and abiotic carbonates, revealing similarities with organisms that form biogenic calcite. These similarities raise questions about the effectiveness of using the Ca isotope fractionation factor as a univocal tracer of ACC-forming cyanobacteria in the environment. We propose that the use of Δ44Ca in combination with other proposed tracers of ACC-forming cyanobacteria such as Ba and Sr isotope fractionation factors and/or elevated Ba/Ca and Sr/Ca ratios may provide a more reliable approach.

Speed of thermal adaptation of terrestrial vegetation alters Earth's long-term climate

Earth's long-term climate is driven by the cycling of carbon between geologic reservoirs and the atmosphere-ocean system. Our understanding of carbon-climate regulation remains incomplete, with large discrepancies remaining between biogeochemical model predictions and the geologic record. Here, we evaluate the importance of the continuous biological climate adaptation of vegetation as a regulation mechanism in the geologic carbon cycle since the establishment of forest ecosystems. Using a model, we show that the vegetation's speed of adaptation to temperature changes through eco-evolutionary processes can strongly influence global rates of organic carbon burial and silicate weathering. Considering a limited thermal adaptation capacity of the vegetation results in a closer balance of reconstructed carbon fluxes into and out of the atmosphere-ocean system, which is a prerequisite to maintain habitable conditions on Earth's surface on a multimillion-year timescale. We conclude that the long-term carbon-climate system is more sensitive to biological dynamics than previously expected, which may help to explain large shifts in Phanerozoic climate.

Reproductive isolation in a three-way contact zone

Contact zones between divergent forms within a species provide insight into the role of gene flow in adaptation and speciation. Previous work has focused on contact zones involving only two divergent forms, but in nature, many more than two populations may overlap simultaneously and experience gene flow. Patterns of introgression in wild populations are, therefore, likely much more complicated than is often assumed. We begin to address this gap in current knowledge by investigating patterns of divergence and introgression across a complex natural contact zone. We use phenotypic and genomic data to confirm the existence of a three-way contact zone among divergent freshwater resident, saltwater resident and saltwater migratory three-spined stickleback (Gasterosteus aculeatus) on the island of North Uist, Scottish Western Isles. We find evidence for hybridization, mostly between saltwater resident and saltwater migratory forms. Despite hybridization, genomic analyses reveal pairwise islands of divergence between all forms that are maintained across the contact zone. Genomic cline analyses also provide evidence for selection and/or hybrid incompatibilities in divergent regions. Divergent genomic regions occur across multiple chromosomes and involve many known adaptive loci and several chromosomal inversions. We also identify distinct immune gene expression profiles between forms, but no evidence for transgressive expression in hybrids. Our results suggest that reproductive isolation is maintained in this three-way contact zone, despite some hybridization, and that reduced recombination in chromosomal inversions may play an important role in maintaining this isolation.

Genetic basis and expression of ventral colour in polymorphic common lizards

Colour is an important visual cue that can correlate with sex, behaviour, life history or ecological strategies, and has evolved divergently and convergently across animal lineages. Its genetic basis in non-model organisms is rarely known, but such information is vital for determining the drivers and mechanisms of colour evolution. Leveraging genetic admixture in a rare contact zone between oviparous and viviparous common lizards (Zootoca vivipara), we show that females (N = 558) of the two otherwise morphologically indistinguishable reproductive modes differ in their ventral colouration (from pale to vibrant yellow) and intensity of melanic patterning. We find no association between female colouration and reproductive investment, and no evidence for selection on colour. Using a combination of genetic mapping and transcriptomic evidence, we identified two candidate genes associated with ventral colour differentiation, DGAT2 and PMEL. These are genes known to be involved in carotenoid metabolism and melanin synthesis respectively. Ventral melanic spots were associated with two genomic regions, including a SNP close to protein tyrosine phosphatase (PTP) genes. Using genome re-sequencing data, our results show that fixed coding mutations in the candidate genes cannot account for differences in colouration. Taken together, our findings show that the evolution of ventral colouration and its associations across common lizard lineages is variable. A potential genetic mechanism explaining the flexibility of ventral colouration may be that colouration in common lizards, but also across squamates, is predominantly driven by regulatory genetic variation.

HIPTox-Hazard Identification Platform to Assess the Health Impacts from Indoor and Outdoor Air Pollutant Exposures, through Mechanistic Toxicology: A Single-Centre Double-Blind Human Exposure Trial Protocol

Over the past decade, our understanding of the impact of air pollution on short- and long-term population health has advanced considerably, focusing on adverse effects on cardiovascular and respiratory systems. There is, however, increasing evidence that air pollution exposures affect cognitive function, particularly in susceptible groups. Our study seeks to assess and hazard rank the cognitive effects of prevalent indoor and outdoor pollutants through a single-centre investigation on the cognitive functioning of healthy human volunteers aged 50 and above with a familial predisposition to dementia. Participants will all undertake five sequential controlled exposures. The sources of the air pollution exposures are wood smoke, diesel exhaust, cleaning products, and cooking emissions, with clean air serving as the control. Pre- and post-exposure spirometry, nasal lavage, blood sampling, and cognitive assessments will be performed. Repeated testing pre and post exposure to controlled levels of pollutants will allow for the identification of acute changes in functioning as well as the detection of peripheral markers of neuroinflammation and neuronal toxicity. This comprehensive approach enables the identification of the most hazardous components in indoor and outdoor air pollutants and further understanding of the pathways contributing to neurodegenerative diseases. The results of this project have the potential to facilitate greater refinement in policy, emphasizing health-relevant pollutants and providing details to aid mitigation against pollutant-associated health risks.

Diurnal fuel moisture content variations of live and dead Calluna vegetation in a temperate peatland

The increasing frequency and severity of UK wildfires, attributed in part to the effects of climate change, highlights the critical role of fuel moisture content (FMC) of live and dead vegetation in shaping wildfire behaviour. However, current models used to assess wildfire danger do not perform well in shrub-type fuels such as Calluna vulgaris, requiring in part an improved understanding of fuel moisture dynamics on diurnal and seasonal scales. To this end, 554 samples of upper live Calluna canopy, live Calluna stems, upper dead Calluna canopy, dead Calluna stems, moss, litter and organic layer (top 5 cm of organic material above mineral soil) were sampled hourly between 10:00 and 18:00 on seven days from March-August. Using a novel statistical method for investigating diurnal patterns, we found distinctive diurnal and seasonal trends in FMC for all fuel layers. Notably, significant diurnal patterns were evident in dead Calluna across nearly all sampled months, while diurnal trends in live Calluna canopy were pronounced in March, June, and August, coinciding with the peak occurrence of UK wildfires. In addition, the moisture content of moss and litter was found to fluctuate above and below their relative ignition thresholds throughout the day on some sampling days. These findings underscore the impact of diurnal FMC variations on wildfire danger during early spring and late summer in Calluna dominated peatlands and the need to consider such fluctuations in management and fire suppression strategies.

The role of male scent in female attraction in the bank vole, Myodes glareolus

Chemical signals are frequently utilised by male mammals for intersexual communication and females are often attracted to male scent. However, the mechanism underlying female attraction has only been identified in a small number of mammalian species. Mammalian scents contain airborne volatiles, that are detected by receivers at a distance from the scent source, as well as non-volatile molecules, such as proteins, that require physical contact for detection. Lipocalin proteins, produced within the scent secretions of many terrestrial mammals, are thought to be particularly important in chemical signalling. Here, we explore if the male-specific protein, glareosin, expressed by adult male bank voles, Myodes glareolus, stimulates female attraction to male scent. We show that female bank voles are more attracted to male compared to female scent, supporting the results of previous studies. Increased investigation and attraction to male scent occurred to both airborne volatiles and non-volatile proteins when they were presented separately. However, we found no evidence that attraction to male scent was driven by glareosin. Our results differ from those previously described in house mice, where a single protein induces female attraction to male scent, suggesting the mechanism underlying female attraction to male scent differs between species.

Shape-Selective Supramolecular Capsules for Actinide Precipitation and Separation

Improving actinide separations is key to reducing barriers to medical and industrial actinide isotope production and to addressing the challenges associated with the reprocessing of spent nuclear fuel. Here, we report the first example of a supramolecular anion recognition process that can achieve this goal. We have designed a preorganized triamidoarene receptor that induces quantitative precipitation of the early actinides Th(IV), Np(IV), and Pu(IV) from industrially relevant conditions through the formation of self-assembled hydrogen-bonded capsules. Selectivity over the later An(III) elements is shown through modulation of the nitric acid concentration, and no precipitation of actinyl or transition-metal ions occurs. The Np, Pu, and Am precipitates were characterized structurally by single-crystal X-ray diffraction and reveal shape specificity of the internal hydrogen-bonding array for the encapsulated hexanitratometalates. This work complements ion-exchange resins for 5f-element separations and illustrates the significant potential of supramolecular separation methods that target anionic actinide species.

Farmer preference for macadamia varieties and constraints to production in Malawi

Macadamia nuts constitute a vital component of both nutrition and livelihoods for smallholder producers in Malawi. We conducted a comprehensive mixed-methods study, combining qualitative and quantitative analyses, to explore varietal preferences and production challenges among these farmers. Leveraging cross-sectional data from 144 members of the Highlands Macadamia Cooperative Union Limited, our study underscores several significant findings. Our findings reveal that the majority of smallholder macadamia farmers (62%) are aged over 50, with farming as their primary occupation. Varied preferences are driven by yield-related traits, including high yield potential (38%), nut quality (29%), and extended flowering patterns (15%). Among the macadamia varieties, the top five choices, grown by over half of the farmers, include HAES 660 (18%), 800 (10%), 791 (9%), 816 (8%), and 246 (7%). Additionally, our study identifies five primary constraints faced by smallholder macadamia farmers: insect pests (81%), diseases (34%), limited market access (33%), wind damage (25%), and inadequate agricultural advisory services (17%). Based on these findings, we propose two policy recommendations to enhance smallholder macadamia production and productivity in Malawi and other regions. Specifically, we advocate for informed breeding programs that align with farmer preferences to promote greater adoption of macadamia varieties. Additionally, we emphasize the crucial role of the Malawian government in the macadamia value chain, suggesting active participation in providing extension services and marketing support, akin to its support for other cash crops.

Potential of APSIS-InSAR for measuring surface oscillations of tropical peatlands

Tropical peatland across Southeast Asia is drained extensively for production of pulpwood, palm oil and other food crops. Associated increases in peat decomposition have led to widespread subsidence, deterioration of peat condition and CO2 emissions. However, quantification of subsidence and peat condition from these processes is challenging due to the scale and inaccessibility of dense tropical peat swamp forests. The development of satellite interferometric synthetic aperture radar (InSAR) has the potential to solve this problem. The Advanced Pixel System using Intermittent Baseline Subset (APSIS, formerly ISBAS) modelling technique provides improved coverage across almost all land surfaces irrespective of ground cover, enabling derivation of a time series of tropical peatland surface oscillations across whole catchments. This study aimed to establish the extent to which APSIS-InSAR can monitor seasonal patterns of tropical peat surface oscillations at North Selangor Peat Swamp Forest, Peninsular Malaysia. Results showed that C-band SAR could penetrate the forest canopy over tropical peat swamp forests intermittently and was applicable to a range of land covers. Therefore the APSIS technique has the potential for monitoring peat surface oscillations under tropical forest canopy using regularly acquired C-band Sentinel-1 InSAR data, enabling continuous monitoring of tropical peatland surface motion at a spatial resolution of 20 m.

Novel functional insights into the microbiome inhabiting marine plastic debris: critical considerations to counteract the challenges of thin biofilms using multi-omics and comparative metaproteomics

BACKGROUND

Microbial functioning on marine plastic surfaces has been poorly documented, especially within cold climates where temperature likely impacts microbial activity and the presence of hydrocarbonoclastic microorganisms. To date, only two studies have used metaproteomics to unravel microbial genotype-phenotype linkages in the marine 'plastisphere', and these have revealed the dominance of photosynthetic microorganisms within warm climates. Advancing the functional representation of the marine plastisphere is vital for the development of specific databases cataloging the functional diversity of the associated microorganisms and their peptide and protein sequences, to fuel biotechnological discoveries. Here, we provide a comprehensive assessment for plastisphere metaproteomics, using multi-omics and data mining on thin plastic biofilms to provide unique insights into plastisphere metabolism. Our robust experimental design assessed DNA/protein co-extraction and cell lysis strategies, proteomics workflows, and diverse protein search databases, to resolve the active plastisphere taxa and their expressed functions from an understudied cold environment.

RESULTS

For the first time, we demonstrate the predominance and activity of hydrocarbonoclastic genera (Psychrobacter, Flavobacterium, Pseudomonas) within a primarily heterotrophic plastisphere. Correspondingly, oxidative phosphorylation, the citrate cycle, and carbohydrate metabolism were the dominant pathways expressed. Quorum sensing and toxin-associated proteins of Streptomyces were indicative of inter-community interactions. Stress response proteins expressed by Psychrobacter, Planococcus, and Pseudoalteromonas and proteins mediating xenobiotics degradation in Psychrobacter and Pseudoalteromonas suggested phenotypic adaptations to the toxic chemical microenvironment of the plastisphere. Interestingly, a targeted search strategy identified plastic biodegradation enzymes, including polyamidase, hydrolase, and depolymerase, expressed by rare taxa. The expression of virulence factors and mechanisms of antimicrobial resistance suggested pathogenic genera were active, despite representing a minor component of the plastisphere community.

CONCLUSION

Our study addresses a critical gap in understanding the functioning of the marine plastisphere, contributing new insights into the function and ecology of an emerging and important microbial niche. Our comprehensive multi-omics and comparative metaproteomics experimental design enhances biological interpretations to provide new perspectives on microorganisms of potential biotechnological significance beyond biodegradation and to improve the assessment of the risks associated with microorganisms colonizing marine plastic pollution. Video Abstract.

Individuals departing non-breeding areas early achieve earlier breeding and higher breeding success

Conditions experienced by an individual during migration have the potential to shape migratory tactic and in turn fitness. For large birds, environmental conditions encountered during migration have been linked with survival and subsequent reproductive output, but this is less known for smaller birds, hindering our understanding of mechanisms driving population change. By combining breeding and tracking data from 62 pied flycatchers (Ficedula hypoleuca) representing two breeding populations collected over 2016-2020, we determine how variation in migration phenology and tactic among individuals affects subsequent breeding. Departure date from West African non-breeding areas to European breeding grounds was highly variable among individuals and had a strong influence on migration tactic. Early departing individuals had longer spring migrations which included longer staging duration yet arrived at breeding sites and initiated breeding earlier than later departing individuals. Individuals with longer duration spring migrations and early arrival at breeding sites had larger clutches, and for males higher fledging success. We suggest that for pied flycatchers, individual carry-over effects may act through departure phenology from West Africa, and the associated spring migration duration, to influence reproduction. While our results confirm that departure date from non-breeding areas can be associated with breeding success in migratory passerines, we identify spring staging duration as a key component of this process.

Land cover changes across Greenland dominated by a doubling of vegetation in three decades

Land cover responses to climate change must be quantified for understanding Arctic climate, managing Arctic water resources, maintaining the health and livelihoods of Arctic societies and for sustainable economic development. This need is especially pressing in Greenland, where climate changes are amongst the most pronounced of anywhere in the Arctic. Ice loss from the Greenland Ice Sheet and from glaciers and ice caps has increased since the 1980s and consequently the proglacial parts of Greenland have expanded rapidly. Here we determine proglacial land cover changes at 30 m spatial resolution across Greenland during the last three decades. Besides the vastly decreased ice cover (- 28,707 km2 ± 9767 km2), we find a doubling in total areal coverage of vegetation (111% ± 13%), a quadrupling in wetlands coverage (380% ± 29%), increased meltwater (15% ± 15%), decreased bare bedrock (- 16% ± 4%) and increased coverage of fine unconsolidated sediment (4% ± 13%). We identify that land cover change is strongly associated with the difference in the number of positive degree days, especially above 6 °C between the 1980s and the present day. Contrastingly, absolute temperature increase has a negligible association with land cover change. We explain that these land cover changes represent local rapid and intense geomorphological activity that has profound consequences for land surface albedo, greenhouse gas emissions, landscape stability and sediment delivery, and biogeochemical processes.

Droplet Microfluidic-Based In Situ Analyzer for Monitoring Free Nitrate in Soil

Monitoring nutrients in the soil can provide valuable information for understanding their spatiotemporal variability and informing precise soil management. Here, we describe an autonomous in situ analyzer for the real-time monitoring of nitrate in soil. The analyzer can sample soil nitrate using either microdialysis or ultrafiltration probes placed within the soil and quantify soil nitrate using droplet microfluidics and colorimetric measurement. Compared with traditional manual sampling and lab analysis, the analyzer features low reagent consumption (96 μL per measurement), low maintenance requirement (monthly), and high measurement frequency (2 or 4 measurements per day), providing nondrifting lab-quality data with errors of less than 10% using a microdialysis probe and 2-3% for ultrafiltration. The analyzer was deployed at both the campus garden and forest for different periods of time, being able to capture changes in free nitrate levels in response to manual perturbation by the addition of nitrate standard solutions and natural perturbation by rainfall events.

Comparing the Fate and Transport of MS2 Bacteriophage and Sodium Fluorescein in a Karstic Chalk Aquifer

Groundwater flow and contaminant migration tracing is a vital method of identifying and characterising pollutant source-pathway-receptor linkages in karst aquifers. Bacteriophages are an attractive alternative tracer to non-reactive fluorescent dye tracers, as high titres (>1012 pfu mL-1) can be safely released into the aquifer, offering improved tracer detectability. However, the interpretation of bacteriophage tracer breakthrough curves is complicated as their fate and transport are impacted by aquifer physicochemical conditions. A comparative tracer migration experiment was conducted in a peri-urban catchment in southeast England to characterise the behaviour of MS2 bacteriophage relative to sodium fluorescein dye in a karstic chalk aquifer. Tracers were released into a stream sink and detected at two abstraction boreholes located 3 km and 10 km away. At both sites, the loss of MS2 phage greatly exceeded that of the solute tracer. In contrast, the qualitative shape of the dye and phage breakthrough curves were visually very similar, suggesting that the bacteriophage arriving at each site was governed by comparable transport parameters to the non-reactive dye tracer. The colloid filtration theory was applied to explain the apparent contradiction of comparable tracer breakthrough patterns despite massive phage losses in the subsurface. One-dimensional transport models were also fitted to each breakthrough curve to facilitate a quantitative comparison of the transport parameter values. The model results suggest that the bacteriophage migrates through the conduit system slightly faster than the fluorescent dye, but that the former is significantly less dispersed. These results suggest that whilst the bacteriophage tracer cannot be used to predict receptor concentrations from transport via karstic flow paths, it can provide estimates for groundwater flow and solute contaminant transit times. This study also provides insight into the attenuation and transport of pathogenic viruses in karstic chalk aquifers.

Chemical Science Research, Elementary School Children and Their Teachers Are More Closely Related than You May Imagine: The "I Bet You Did Not Know" Project

Topics associated with the chemical sciences form a significant part of the curriculum in science at the primary school level in the U.K. In this methodology paper, we demonstrate how a wide range of research articles associated with the chemical sciences can be disseminated to an elementary school audience and how children can carry out investigations associated with cutting-edge research in the classroom. We discuss how the Primary Science Teaching Trust's (PSTT's) "I bet you did not know" (IBYDK) articles and their accompanying Teacher Guides benefit children, primary (elementary) school teachers, and other stakeholders including the researchers themselves. We define three types of research articles; ones describing how children can reproduce the research themselves without much adaptation, others where children can mirror the research using similar methods, and some where an analogy can be used to explain the research. We provide exemplars of each type and some preliminary feedback on articles written.

Effect of Polymer Host on Aggregation-Induced Enhanced Emission of Fluorescent Optical Brighteners

Fluorophores displaying concentration-dependent luminescence are becoming increasingly valuable in stress-sensing, tagging, and dyeing applications, including the quantification of recycled content in plastic packaging. In this work, we investigate the effects of the polymer matrix, dye structure, and crystallinity on aggregation-induced enhanced emission (AIEE). We demonstrate that the aggregation threshold required for successful quantification can be adjusted through modulation of guest-host (dye-polymer) interactions and monitored using an array of fluorescence characterization. Modification of guest-host interactions is realized through choice of host, change of guest, and tuning of the crystallinity of the host system. Increasing the number of guest-host interactions and solubility between guest and host, loosely predicted through the calculation of the solubility parameter, increases the aggregation threshold relative to other low-polarity and low-interacting systems. We demonstrate that issues, such as loading level and cost, associated with high aggregation thresholds, can be circumvented by increasing system crystallinity, improving spectral intensities, and subsequent quantification. These insights explore the fundamental understanding of supramolecular interactions that govern dye-polymer systems.

Near-source passive sampling for monitoring viral outbreaks within a university residential setting

Wastewater-based epidemiology (WBE) has proven to be a powerful tool for the population-level monitoring of pathogens, particularly severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). For assessment, several wastewater sampling regimes and methods of viral concentration have been investigated, mainly targeting SARS-CoV-2. However, the use of passive samplers in near-source environments for a range of viruses in wastewater is still under-investigated. To address this, near-source passive samples were taken at four locations targeting student hall of residence. These were chosen as an exemplar due to their high population density and perceived risk of disease transmission. Viruses investigated were SARS-CoV-2 and its variants of concern (VOCs), influenza viruses, and enteroviruses. Sampling was conducted either in the morning, where passive samplers were in place overnight (17 h) and during the day, with exposure of 7 h. We demonstrated the usefulness of near-source passive sampling for the detection of VOCs using quantitative polymerase chain reaction (qPCR) and next-generation sequencing (NGS). Furthermore, several outbreaks of influenza A and sporadic outbreaks of enteroviruses (some associated with enterovirus D68 and coxsackieviruses) were identified among the resident student population, providing evidence of the usefulness of near-source, in-sewer sampling for monitoring the health of high population density communities.

Mapping urban mobility using vehicle telematics to understand driving behaviour

Telematics data, primarily collected from on-board vehicle devices (OBDs), has been utilised in this study to generate a thorough understanding of driving behaviour. The urban case study area is the large metropolitan region of the West Midlands, UK, but the approach is generalizable and translatable to other global urban regions. The new approach of GeoSpatial and Temporal Mapping of Urban Mobility (GeoSTMUM) is used to convert telematics data into driving metrics, including the relative time the vehicle fleet spends idling, cruising, accelerating, and decelerating. The telematics data is also used to parameterize driving volatility and aggressiveness, which are key factors within road safety, which is a global issue. Two approaches to defining aggressive driving are applied and assessed, they are vehicle jerk (the second derivative of vehicle speed), and the profile of speed versus acceleration/deceleration. The telematics-based approach has a very high spatial resolution (15-150 m) and temporal resolution (2 h), which can be used to develop more accurate driving cycles. The approach allows for the determination of road segments with the highest potential for aggressive driving and highlights where additional safety measures could beneficially be adopted. Results highlight the strong correlation between vehicle road occupancy and aggressive driving.

HPAIV outbreak triggers short-term colony connectivity in a seabird metapopulation

Disease outbreaks can drastically disturb the environment of surviving animals, but the behavioural, ecological, and epidemiological consequences of disease-driven disturbance are poorly understood. Here, we show that an outbreak of High Pathogenicity Avian Influenza Virus (HPAIV) coincided with unprecedented short-term behavioural changes in Northern gannets (Morus bassanus). Breeding gannets show characteristically strong fidelity to their nest sites and foraging areas (2015-2019; n = 120), but during the 2022 HPAIV outbreak, GPS-tagged gannets instigated long-distance movements beyond well-documented previous ranges and the first ever recorded visits of GPS-tagged adults to other gannet breeding colonies. Our findings suggest that the HPAIV outbreak triggered changes in space use patterns of exposed individuals that amplified the epidemiological connectivity among colonies and may generate super-spreader events that accelerate disease transmission across the metapopulation. Such self-propagating transmission from and towards high density animal aggregations may explain the unexpectedly rapid pan-European spread of HPAIV in the gannet.

Evaluating the use of lake sedimentary DNA in palaeolimnology: A comparison with long-term microscopy-based monitoring of the phytoplankton community

Palaeolimnological records provide valuable information about how phytoplankton respond to long-term drivers of environmental change. Traditional palaeolimnological tools such as microfossils and pigments are restricted to taxa that leave sub-fossil remains, and a method that can be applied to the wider community is required. Sedimentary DNA (sedDNA), extracted from lake sediment cores, shows promise in palaeolimnology, but validation against data from long-term monitoring of lake water is necessary to enable its development as a reliable record of past phytoplankton communities. To address this need, 18S rRNA gene amplicon sequencing was carried out on lake sediments from a core collected from Esthwaite Water (English Lake District) spanning ~105 years. This sedDNA record was compared with concurrent long-term microscopy-based monitoring of phytoplankton in the surface water. Broadly comparable trends were observed between the datasets, with respect to the diversity and relative abundance and occurrence of chlorophytes, dinoflagellates, ochrophytes and bacillariophytes. Up to 20% of genera were successfully captured using both methods, and sedDNA revealed a previously undetected community of phytoplankton. These results suggest that sedDNA can be used as an effective record of past phytoplankton communities, at least over timescales of <100 years. However, a substantial proportion of genera identified by microscopy were not detected using sedDNA, highlighting the current limitations of the technique that require further development such as reference database coverage. The taphonomic processes which may affect its reliability, such as the extent and rate of deposition and DNA degradation, also require further research.

GIA imaging of 3-D mantle viscosity based on palaeo sea level observations - Part I: Sensitivity kernels for an Earth with laterally varying viscosity

A key initial step in geophysical imaging is to devise an effective means of mapping the sensitivity of an observation to the model parameters, that is to compute its Fréchet derivatives or sensitivity kernel. In the absence of any simplifying assumptions and when faced with a large number of free parameters, the adjoint method can be an effective and efficient approach to calculating Fréchet derivatives and requires just two numerical simulations. In the Glacial Isostatic Adjustment problem, these consist of a forward simulation driven by changes in ice mass and an adjoint simulation driven by fictitious loads that are applied at the observation sites. The theoretical basis for this approach has seen considerable development over the last decade. Here, we present the final elements needed to image 3-D mantle viscosity using a dataset of palaeo sea-level observations. Developments include the calculation of viscosity Fréchet derivatives (i.e. sensitivity kernels) for relative sea-level observations, a modification to the numerical implementation of the forward and adjoint problem that permits application to 3-D viscosity structure, and a recalibration of initial sea level that ensures the forward simulation honours present-day topography. In the process of addressing these items, we build intuition concerning how absolute sea-level and relative sea-level observations sense Earth's viscosity structure and the physical processes involved. We discuss examples for potential observations located in the near field (Andenes, Norway), far field (Seychelles), and edge of the forebulge of the Laurentide ice sheet (Barbados). Examination of these kernels: (1) reveals why 1-D estimates of mantle viscosity from far-field relative sea-level observations can be biased; (2) hints at why an appropriate differential relative sea-level observation can provide a better constraint on local mantle viscosity and (3) demonstrates that sea-level observations have non-negligible 3-D sensitivity to deep mantle viscosity structure, which is counter to the intuition gained from 1-D radial viscosity Fréchet derivatives. Finally, we explore the influence of lateral variations in viscosity on relative sea-level observations in the Amundsen Sea Embayment and at Barbados. These predictions are based on a new global 3-D viscosity inference derived from the shear-wave speeds of GLAD-M25 and an inverse calibration scheme that ensures compatibility with certain fundamental geophysical observations. Use of the 3-D viscosity inference leads to: (1) generally greater complexity within the kernel; (2) an increase in sensitivity and presence of shorter length-scale features within lower viscosity regions; (3) a zeroing out of the sensitivity kernel within high-viscosity regions where elastic deformation dominates and (4) shifting of sensitivity at a given depth towards distal regions of weaker viscosity. The tools and intuition built here provide the necessary framework to explore inversions for 3-D mantle viscosity based on palaeo sea-level data.

Changing streetlighting schemes and the ecological availability of darkness

Artificial light at night (ALAN), from streetlights and other sources, has a wide variety of impacts on the natural environment. A significant challenge remains, however, to predict at intermediate spatial extents (e.g. across a city) the ALAN that organisms experience under different lighting regimes. Here we use Monte Carlo radiative Transfer to model the three-dimensional lighting environment at, and just above, ground level, on the spatial scales at which animals and humans experience it. We show how this technique can be used to model a suite of both real and hypothetical lighting environments, mimicking the transition of public infrastructure between different lighting technologies. We then demonstrate how the behaviour of animals experiencing these simulated lighting environments can be emulated to probe the availability of darkness, and dark corridors, within them. Our simulations show that no single lighting technology provides an unmitigated alleviation of negative impacts within urban environments, and that holistic treatments of entire lighting environments should be employed when understanding how animals use and traverse them.

Shifts in internal stem damage along a tropical precipitation gradient and implications for forest biomass estimation

Woody biomass is a large carbon store in terrestrial ecosystems. In calculating biomass, tree stems are assumed to be solid structures. However, decomposer agents such as microbes and insects target stem heartwood, causing internal wood decay which is poorly quantified. We investigated internal stem damage across five sites in tropical Australia along a precipitation gradient. We estimated the amount of internal aboveground biomass damaged in living trees and measured four potential stem damage predictors: wood density, stem diameter, annual precipitation, and termite pressure (measured as termite damage in downed deadwood). Stem damage increased with increasing diameter, wood density, and termite pressure and decreased with increasing precipitation. High wood density stems sustained less damage in wet sites and more damage in dry sites, likely a result of shifting decomposer communities and their differing responses to changes in tree species and wood traits across sites. Incorporating stem damage reduced aboveground biomass estimates by > 30% in Australian savannas, compared to only 3% in rainforests. Accurate estimates of carbon storage across woody plant communities are critical for understanding the global carbon budget. Future biomass estimates should consider stem damage in concert with the effects of changes in decomposer communities and abiotic conditions.