Centre for the Observation and Modelling of Earthquakes, Volcanoes and Tectonics
NERC Open Research ArchiveNot a member yet
55023 research outputs found
Sort by
Modelling the impact of large-scale hydroclimate change on prehistoric Polynesian island life
Get PDFThe South Pacific was one of the last regions on earth to be colonised by humans and offers a unique opportunity to study early climate-human interactions in environments previously untouched by people. Palaeoclimate evidence suggests the South Pacific has experienced shifts between dry and wet periods throughout the past three thousand years, the broad period of colonisation, with extremes in both modes being prevalent. Drought has significant repercussions for small Pacific islands, affecting water and food resources, with potential consequences on the viability of life on these islands leading to internal stress, conflict, collapse or migration. Previously, socio-ecological models have been developed to test mechanisms of change within prehistoric societies worldwide that can lead to migration or societal change, but thus far the connections between past climatic change and prehistoric island life within the tropical South Pacific have not been fully explored. This study utilises palaeoclimatic data alongside a new system dynamics socio-ecological model to explore the relationship between climate, agricultural carrying capacity and population dynamics on the Polynesian island of Mangaia (Cook Islands) in the tropical South Pacific. Model results suggest that as the population density of the island increases, the impact of drought events on population dynamics increases. We also show that the severity of the drought rather than the return frequency drove the largest changes in carrying capacity and population dynamics. Changes in long-term rainfall leading to persistent dry conditions impacted the timing and rate of population growth due to its role as a limiting factor for agricultural productivity. We compare our modelled results with the known history of population stress and societal change from Mangaia and found these corresponded with drought periods and low food availability. We demonstrate the potential for droughts to have impacted on the early colonisation and societal change on Eastern Polynesian islands
Spatial segregation and bycatch risk as potential drivers of population trends of wandering albatrosses at South Georgia
No full textSpatial segregation in at-sea distribution is frequently observed in seabirds and can have important implications for conservation and management. Globally, many albatross and petrel populations are declining due to bycatch in fisheries. In South Georgia, the decrease in wandering albatrosses (Diomedea exulans) differs among breeding sites, which could reflect segregation in foraging areas, leading to differing degrees of overlap with particular fishing fleets and hence unequal bycatch risk. We investigated whether spatial segregation could explain the different rates of population decline of wandering albatrosses at South Georgia. We tracked wandering albatrosses from 2 breeding sites at South Georgia, Prion Island, and Bird Island, located 50 km apart. We investigated potential causes of spatial segregation with species distribution models and by comparing wind conditions among sites. Overlap with fisheries was quantified for each population. Although overall distributions were from the Antarctic to the subtropics, virtually all wandering albatrosses from Bird Island foraged only to the west of the island group, whereas those from Prion Island foraged to the east and west. Preferred habitat characteristics were similar at both colonies, and waters to the east and west provided foraging habitat. Wind conditions when birds departed were also similar at the 2 sites. Because neither habitat specialization nor wind conditions appeared to be factors in the observed spatial segregation among colonies, this segregation likely reflected a combination of past experience, information exchange, and cultural evolution. Breeding birds from both sites overlapped most with Chinese squid jiggers, Argentinian trawlers, and South Korean set (demersal) longliners, but the spatial segregation led to a higher overlap with demersal longline, demersal trawl, and pelagic longline fisheries by wandering albatrosses at Bird Island, which could have resulted in the faster population decline. Ours is one of the first studies to demonstrate how spatial segregation may affect population dynamics, which has important implications for the conservation of this globally threatened species
Millijoule-level ultra-large core ytterbium-doped pulsed fiber amplifier operating at 980 nm
No full textWe report a record-high 5.5-mJ amplified pulse energy at 980 nm, achieving 0.55 kW peak power using a 1-meter long ultra-large-mode-area ( 290 μ m core) ytterbium fiber in a co-directional, amplifier configuration. Pumped at 915 nm and seeded by a modulated 980-nm laser diode. We provide a detailed fiber spectroscopy analysis, optimizing key parameters—such as seed and pump repetition rates to mitigate thermal load and other detrimental effects (e.g., re-absorption), enabling high-energy output. The amplifier’s performance highlights its applications for high-brightness ultraviolet and visible light generation, and as an efficient pump for erbium-doped fiber systems, advancing their performances in fluorescence imaging, marine engineering and biophotonics. To the best of our knowledge, the achieved output energy of 5.5 mJ is the highest reported to date in an ytterbium-doped-fiber amplifier at 980-nm, while offering simpler fabrication, configuration and enhanced compatibility compared to other fiber systems at similar wavelengths
Optimising grass-legume mixtures based on growth strategies for high N-yield and low N loss in fertilised grasslands
Get PDF•Aims: Managed grasslands are important agro-ecosystems, consisting of grass monocultures with high nitrogen (N) fertiliser inputs. This management results in low N use efficiency and high N losses to the environment. Growing mixtures of plant species with diverse N acquisition strategies can reduce N losses and maintain high grassland productivity, yet determining the best mixture remains a challenge. The aim of this study was to investigate how grass-legume mixtures with contrasting growth strategies affect plant productivity, N use efficiency, N uptake, and soil mineral N, and how these effects depend on the N-fertilisation level.
•Methods: Two complementing field experiments were established: the first determined how monocultures and mixtures (two and four grass-legume mixtures) with contrasting growth strategies (fast- vs . slow-growing) affect productivity and N-cycling. The second determined the effect of fertilisation level on productivity and N-cycling in monocultures and two-species mixtures.
•Results: We found that productivity and N uptake of the four-species mixture was as high as the most productive monoculture and two-species mixtures. This was associated with an increase in legume N fixation and high N use efficiency of the plant community. Fast-growing grass and legume combination increased productivity and reduced soil mineral N, thus reducing the risk of N loss at both N-fertilisation levels, while combining a fast-growing grass with a slow-growing legume promoted high legume N fixation under low N-fertilisation.
•Conclusions: This study shows that productivity and N-cycling decreases via complementarity effects when growing mixtures of fast- and slow-growing grasses and a fast-growing legume at moderate level of N-fertilisation
Major-Minor-Trace Element Analyses and Oceanographic Modeling Confirms Circumpolar Transport of the 1962 Protector Shoal Pumice Raft
Get PDFPumice rafts derived from submarine eruptions can remain afloat for months or even years, traveling thousands of kilometers on ocean currents. These natural phenomena disperse marine organisms and provide important evidence for submarine volcanism yet are not fully understood. Here, we describe pumice clasts from Falkland Islands shorelines and use major-minor-trace element analyses to trace their provenance to the 1962 volcanic eruption on Protector Shoal, a large seamount in the South Sandwich Islands, Scotia Sea. Compositional variability between rafted and dredged pumice from Protector Shoal suggests eruptions have varied from explosive to non- or mildly explosive (the latter from lava domes and during neptunian events) and the seamount is volcanically diverse. Oceanographic modeling simulations and historical observations show that clasts from the 1962 eruption reached the Falkland Islands via the Antarctic Circumpolar Current, a journey of ∼20,000 km that took approximately three years. Although oceanographic variability strongly affects modeled transport pathways, in all simulations particles consistently reach the Falkland Islands from Protector Shoal seamount, suggesting a persistent long-distance connection. The results highlight the potential for pumice rafting to disperse non-native, potentially invasive, marine organisms throughout the Southern Ocean as climate warms
Eukaryotic diversity associated with the phycosphere of the seaweed Ulvaria obscura (Kützing) Gayral (Chlorophyta, Ulvophyceae) in the Svalbard Archipelago, Arctic region assessed using DNA metabarcoding
Get PDFMicroorganisms often occur in association with macroalgae, with the term “phycosphere” referring to the seaweed surface where they may be present. Phycosphere represents a poorly explored niche of marine diversity, especially in the polar regions. DNA metabarcoding provides a new and accessible method for the detection of DNA from different organisms, especially applicable for poorly known groups where taxonomic expertise is limited or unavailable. In this study we used DNA metabarcoding to provide an initial survey of eukaryotic communities associated with marine macroalgae obtained from the shores of Svalbard. Samples of Ulvaria obscura were sequenced and the DNA reads found were assigned to 75 taxa of six Kingdoms and 17 phyla: Chromista (Ciliophora, Haptophyta, Ochrophyta, Oomycota and Chrysophyta), Fungi (Ascomycota, Basidiomycota, Chytridiomycota, Mortierellomycota and Rozellomycota), Holozoa (Ichthyosporia), Metazoa (Cnidaria), Protozoa (Cercozoa, Discosea and Heterolobosea) and Viridiplantae (Bryophyta and Chlorophyta). The most abundant group was Viridiplantae, followed by Fungi. Our environmental DNA study confirmed that the phycosphere of U. obscura shelters a rich and complex microbiome, suggesting that Arctic macroalgae provide a hotspot of currently undescribed polar biodiversity. Additionally, our results were obtained during the first official Brazilian Arctic expedition, representing a historic step for the Brazilian Antarctic Program (PROANTAR)
Wildfires impact the thermal stability and molecular composition but not the age of dissolved organic carbon exported by Northern streams
Get PDFUnderstanding how wildfires impact the biogeochemistry of dissolved organic matter (DOM) in peatland catchments is important for predicting how they may respond to climate change. However, the net effects of wildfires on the composition of DOM are not yet well understood. We investigated how fire changes the age, thermal stability, and molecular composition of stream DOM in blanket peatlands in the Flow Country and the Isle of Lewis, North of Scotland. Radiocarbon measurements showed that stream DOC was predominantly modern in both bulk and ramped thermal fractions with no apparent change observed due to wildfires. Ramped thermal oxidation revealed higher thermal stability of stream DOM in wildfire impacted areas, as demonstrated by higher activation energies, a proxy for organic C bond strength. This was prominent between 350 and 470°C and was also associated with an increase in the content of thermally stable C and a reduction in bond diversity. Using ultra high-resolution mass spectrometry, we found an increase in the molecular diversity of DOM and in the relative abundance of highly unsaturated and phenolic class. There was also a higher relative abundance of highly oxygenated N- and S-containing formula, potentially from partially combusted plant and soil material, which could explain the shift in activation energy. Together, our results demonstrate ways that wildfires can impact the reactivity and composition of DOM, with implications for its stability and residence time along the terrestrial-aquatic continuum
Deep-sea ecosystems of the North Atlantic Ocean: discovery, status, function and future challenges
Get PDFThe North Atlantic is an ocean basin with a diversity of deep-sea ecosystems. Here we provide a summary of the topography and oceanography of the North Atlantic including the Gulf of Mexico and Caribbean Sea, provide a brief overview of the history of scientific research therein, and review the current status of knowledge of each of 18 pelagic and benthic deep-sea ecosystems, with a particular focus on knowledge gaps. We analyse biodiversity data records across the North Atlantic and highlight spatial data gaps that could provide important foci for future expeditions. We note particular data gaps in EEZs of nations within and bordering the Caribbean Sea. Our data provide a baseline against which progress can be tracked into the future. We review human impacts caused by fishing, shipping, mineral extraction, introduction of substances, and climate change, and provide an overview of international, regional and national measures to protect ecosystems. We recommend that scientific research in the deep sea should focus on increasing knowledge of the distribution and the connectivity of key species and habitats, and increasing our understanding of the processes leading to the delivery of ecosystem services. These three pillars - distribution, connectivity, ecosystem function - will provide the knowledge required to implement conservation and management measures to ensure that any deep-sea development in the future is sustainable. Infrastructure and capacity are unevenly distributed and implementation of strategies that will lead to more equitable deep-sea science is required to ensure that essential science can be delivered
Scratching beyond the surface: examining macroecological patterns in avian eggshell texture
No full textThe surface texture of bird eggshells differs remarkably between species and is thought to play a substantial role in providing physical and microbial protection for the developing embryo. We used high-resolution optical profilometry to establish the key evolutionary drivers of surface textural diversity in eggshells from 453 bird species across 98 families. Within a phylogenetically informed framework, we aimed to determine which life-history traits and nesting environments probably determine eggshell surface texture. We measured surface roughness ( S a , nm), surface skewness ( S sk ) and surface kurtosis ( S ku ), which describe different aspects of the properties of eggshell surface texture. S a represents the average height variations on the surface, providing a measure of smoothness or roughness. In contrast, S sk reveals the distribution of surface features, where positive values signify a predominance of peaks, while negative values indicate a greater presence of valleys. Lastly, S ku assesses the geometry of these features, with values exceeding 3 suggesting the presence of sharp peaks or deep troughs, and values below 3 indicating a flatter, more uniform surface. Overall, eggshell surfaces were smoother among species that lay immaculate eggs, meaning those without any pattern, in contrast to maculate eggs. Eggshells from semi-enclosed nests had smoother surfaces than those laid in exposed (cup, bowl, platform, no nest) nests. We found that 90.1% of the species had eggshell surfaces mainly composed of valleys rather than peaks, based on their S sk . By exploring the properties and performance of porous surfaces in nature, we may inspire future biomimicry designs that take advantage of these discoveries
Genomic analyses reveal trans-generational haul out site fidelity in leopard seals
No full textAs top predators, leopard seals (Hydrurga leptonyx) have a key role in Southern Ocean ecosystems. For example, this species has driven the local collapse of Antarctic fur seals (Arctocephalus gazella) at Cape Shirreff, in the northern Antarctic Peninsula. However, little is known about leopard seal haul out site fidelity and social behavior. Here, we employ “genomic tagging” and relatedness analyses from a genome-wide single nucleotide polymorphism (SNP) dataset obtained from 88 leopard seal tissue samples to investigate patterns of seasonal haul out site fidelity and social structure at Cape Shirreff, a leopard seal hotspot during austral summers. Although many seals were observed only once, some females had remarkably high site fidelity returning to the same location across timeframes of up to eight years. Most leopard seals were unrelated, but we identified a trio of closely related females, including a mother-daughter pair, indicating that seasonal site fidelity can span generations. Interestingly, the mother leopard seal identified through our relatedness analyses is a foraging specialist that targets Antarctic fur seal pups; her diet changed very little over the past decade. Our findings suggest high individual variability in leopard seal behavior regarding site fidelity and social structure. Such flexibility may play a key role in this species’ responses to environmental change
Data sources:
Access Repository Dashboard
Do you manage NERC Open Research Archive? Access insider analytics, issue reports and manage access to outputs from your repository in the CORE Repository Dashboard!