Mosquitoes of southern England and northern Wales: identification, ecology and host selection

As early as 1901, ecological and epidemiological studies were conducted to understand malaria transmission in the UK. Unfortunately, following the eradication of malaria after WWII, ecological studies on local mosquito species has been intermittent, leading to a significant gap in knowledge of the current habitat preference, distribution and vector capabilities of the 33 recorded species. This lack of current information makes the assessment of possible transmission of enzoonotic diseases such as Chikungunya and West Nile virus in UK difficult. Thus the overall purpose of this thesis was to facilitate the identification of potential vector species through the documentation and characterisation of the ecology of adult and larval stages, and the host selection of British mosquitoes, in southern England and northern Wales. A total of 13 out the 33 documented species are assessed in this study. Of which members of the Maculipennis and Pipiens Group comprised the bulk of the adult and immature collections respectively. The development of the ITS2 PCR-RFLP assay in this study allowed the identification of the three members of the Maculipennis Group, which revealed the widespread occurrence of the recently documented An. daciae in almost all localities sampled. While previously published assays discriminating the Pipiens Complex, did not yield congruent results questioning the prior identification methods and the validity of the taxonomic status of its members. In addition, host-specific primers designed herein to determine host selection in local mosquitoes revealed an indiscriminate host selection by An. atroparvus, An. daciae, An. messeae and Cx. pipiens thus indicating their potential role as vectors in the UK

Helium: Exploration Methodology for a Strategic Resource

Helium exploration is still in its infancy. Noble gas and stable isotopic analyses have proven to be effective tools in the past for determining the correlation between 4He and associated N2 and the role of groundwater in the transport and focusing of these gases alongside unrelated natural gases such as CH4 and CO2 into traps (Ballentine and Sherwood-Lollar, 2002). In this thesis these tracers are used to further understand aspects of the helium system such as source(s), gas migration pathways and trapping mechanisms and from this to ultimately present a framework for a helium exploration method. Geochemical studies were conducted on CH4-rich helium gas reservoirs in the Mid-Continent US and, for the first time, on N2-rich helium gas reservoirs in Utah, Montana and Saskatchewan, Canada. Both types of 4He-rich system showed consistent 4He-associated N2 endmembers with δ15N values between -3.00‰ and +2.45‰; a range associated with low grade metamorphic crustal sources indicating that the source of the economic 4He and associated N2 in shallow reservoirs is likely derived from variable isotopic mixing between the basement and overlying sediments. From these studies it was also ascertained that in all fields the mechanism for 4He and associated N2 degassing into reservoirs appears to be related in some degree to groundwater and to the saturation threshold of 4He-associated N2 thereby defining possible secondary migration pathways for the helium system. New noble gas data from thermal springs in the West and East branches of the Tanzanian section of the EARS show 4He concentrations of up to 10.5% indicating the active release or primary migration of high helium and high N2 gases in the region. This coupled with potential traps in the nearby Rukwa Basin could provide a high helium reservoir in the future. First estimates for the basin, derived from 4He analyses (< 4% 4He) combined with seismic and soil gas surveys for the basin translate to a P50 estimate of probable reserves of 98 Bcf which would be enough to supply the current global helium demand for ~14 years if current demand remains steady

Mosquitoes of southern England and northern Wales : identification, ecology and host selection

As early as 1901, ecological and epidemiological studies were conducted to understand malaria transmission in the UK. Unfortunately, following the eradication of malaria after WWII, ecological studies on local mosquito species has been intermittent, leading to a significant gap in knowledge of the current habitat preference, distribution and vector capabilities of the 33 recorded species. This lack of current information makes the assessment of possible transmission of enzoonotic diseases such as Chikungunya and West Nile virus in UK difficult. Thus the overall purpose of this thesis was to facilitate the identification of potential vector species through the documentation and characterisation of the ecology of adult and larval stages, and the host selection of British mosquitoes, in southern England and northern Wales. A total of 13 out the 33 documented species are assessed in this study. Of which members of the Maculipennis and Pipiens Group comprised the bulk of the adult and immature collections respectively. The development of the ITS2 PCR-RFLP assay in this study allowed the identification of the three members of the Maculipennis Group, which revealed the widespread occurrence of the recently documented An. daciae in almost all localities sampled. While previously published assays discriminating the Pipiens Complex, did not yield congruent results questioning the prior identification methods and the validity of the taxonomic status of its members. In addition, host-specific primers designed herein to determine host selection in local mosquitoes revealed an indiscriminate host selection by An. atroparvus, An. daciae, An. messeae and Cx. pipiens thus indicating their potential role as vectors in the UK.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Determining fluid migration and isolation times in multiphase crustal domains using noble gases

Geochemical characteristics in subsurface fluid systems provide a wealth of information about fluid sources, migration, and storage conditions. Determining the extent of fluid interaction (aquifer-hydrocarbon connectivity) is important for oil and gas production and waste storage applications, but is not tractable using traditional seismic methods. Furthermore, the residence time of fluids is critical in such systems and can vary from tens of thousands to billions of years. Our understanding of the transport length scales in multiphase systems, while equally important, is more limited. Noble gas data from the Rotliegend natural gas field, northern Germany, are used here to determine the length scale and isolation age of the combined water-gas system. We show that geologically bound volume estimates (i.e., gas to water volume ratios) match closed-system noble gas model predictions, suggesting that the Rotliegend system has remained isolated as a closed system since hydrocarbon formation. Radiogenic helium data show that fluid isolation occurred 63–129 m.y. after rock and/or groundwater deposition (ca. 300 Ma), which is consistent with known hydrocarbon generation from 250 to 140 Ma, thus corroborating long-term geologic isolation. It is critical that we have the ability to distinguish between fluid systems that, despite phase separation, have remained closed to fluid loss from those that have lost oil or gas phases. These findings are the first to demonstrate that such systems remain isolated and fully gas retentive on time scales >100 m.y. over >10 km length scales, and have broad implications for saline aquifer CO2 disposal site viability and hydrocarbon resource prediction, which both require an understanding of the length and time scales of crustal fluid transport pathways

Comparison of mosquito and fly derived DNA as a tool for sampling vertebrate biodiversity in suburban forests in Berlin, Germany

The use of invertebrate‐derived DNA (iDNA) is a promising non‐invasive tool to monitor wildlife. While most studies have been carried out in dense tropical and sub‐tropical forests and have focused on the use of a single category of invertebrates, this study compares the use of flies and mosquitoes‐derived DNA to assess vertebrate diversity in semi‐urban environments. We conducted our sampling in four different forest plots in Berlin, Germany. Pools of flies and non‐bloodfed mosquitoes were metabarcoded using 108‐bp vertebrate‐specific 12 S rRNA (12 S‐V5) and 94‐bp mammal‐specific 16 S rRNA (16Smam) mitochondrial markers, and individual bloodfed mosquitoes were sequenced using the 340‐bp vertebrate‐specific 12 S rRNA fragment (Mam‐12 S‐340). Most sequencing was only successful for mammal species. From the fly pools, we detected 10 mammal species using 16Smam, and six species using 12 S‐V5. From the non‐bloodfed mosquito pools, we only amplified putative contaminant DNA, indicating that mosquito females without visual signs of a blood meal carry no traces of vertebrate DNA. Finally, in the bloodfed mosquitoes, we identified four mammal species. We did not find significant differences in the proportion of mammal species detected regarding the total available number of species between sampling localities. Fly samples were easier to obtain and more abundant over the sampled localities compared to mosquito samples. We conclude that, while there are a few advantages in using mosquito blood meals, the use of flies in the detection of wildlife in a suburban environment is more effective in terms of collection of samples and detection of vertebrates, although this technique is limited to few mammal species in the urban environment

Numerical modelling of the rise of Taylor bubbles through a change in pipe diameter

The rise of Taylor bubbles through expansions in vertical pipes is modelled using Computational Fluid Dynamics. The predictions from the models are compared against existing experimental work and show good agreement, both quantitatively and qualitatively. Many workers, including the present work, find that, as the bubble passes through the expansion, it will either remain intact or split into one or more daughter bubbles. We find that the critical length of bubble, defined as the maximum length that will pass through intact, is proportional to the cosecant of the angle of the expansion. Further, we show that for an abrupt expansion, the critical bubble length became unaffected by the walls of the upper pipe as the diameter was increased

Potential vectors of equine arboviruses in the UK

There is growing concern about the increasing risk of disease outbreaks caused by arthropod-borne viruses (arboviruses) in both humans and animals. There are several mosquito-borne viral diseases that cause varying levels of morbidity and mortality in horses and that can have substantial welfare and economic ramifications. While none has been recorded in the UK, vector species for some of these viruses are present, suggesting that UK equines may be at risk. We undertook, therefore, the first study of mosquito species on equine premises in the UK. Mosquito Magnet traps and red-box traps were used to sample adults, and larvae were collected from water sources such as tyres, buckets, ditches and pools. Several species which are known to be capable of transmitting important equine infectious arboviruses were trapped. The most abundant, with a maximum catch of 173 in 72 hours was Ochlerotatus detritus, a competent vector of some flaviviruses; the highest densities were found near saltmarsh habitats. The most widespread species, recorded at >75% of sites, was Culiseta annulata. This study demonstrates that potential mosquito vectors of arboviruses, including those known to be capable of infecting horses, are present and may be abundant on equine premises in the UK