Introduction Recent global assessments of the impact of climate change have highlighted the current and future risks of increasing vector-borne disease incidence. The UK government has responded to climate change risks through various legislation and planning frameworks. Some of the main concerns include the need to mitigate storm surges, prevent inland and coastal flooding, provide sustainable urban drainage and expand defragmented wetlands to enhance biodiversity value. Wetlands provide a wealth of benefits for biodiversity, flood -risk management and human mental health. However they can harbour mosquito species of nuisance and/or disease vector concern. With the increasing trend in mosquito-borne disease in Europe this warrants further investigation. Aim This PhD aims to investigate the impact of the creation, expansion and management of three types of wetland (i.e. coastal, urban and arable reversion) on mosquitoes in England. Methods A range of sampling strategies were employed to investigate the impact of the creation, expansion and management of coastal, urban and arable reversion wetlands on mosquitoes. Aquatic dipping was used to survey immature mosquitoes, and mosquito magnet traps were used to survey adult mosquitoes. In a coastal environment, mosquito surveys were conducted during two visits by larval sampling at the eight largest coastal realignment sites on the Humber and in Essex. An urban wetland in Wiltshire was also studied over two years post construction, investigating the colonisation of mosquitoes at a range of urban wetland and sewage treatment habitats. Adult and pre-imaginal mosquito densities were also compared across a range of wetland types in the Cambridgeshire Fens to assess the relative roles of different seral stages of ecological succession. Studies were also conducted at Woodwalton Fen in Cambridgeshire to investigate the the impact of wetland management and expansion by arable reversion. This involved fortnightly larval sampling of a range of aquatic habitats and fortnightly (4 nights per week) adult trapping in six different wetland communities. Results The apparent absence of anopheline mosquitoes exploiting aquatic habitats at all of the coastal sites suggests that the risk of malaria associated with managed realignment sites is currently negligible. However, three of the eight sites supported populations of two nuisance and potential arboviral vector species, Aedes detritus and Aedes caspius. The aquatic habitats that supported mosquitoes resulted from specific design aspects of the new sea wall such as (a) an additional bank of ballast to mitigate wave action providing a linear habitat supporting significant numbers of mosquitoes, (b) constructed saline borrow ditches, excavated during construction, that receive brackish waters at spring high tides, with tidal waters collecting on vegetated banks in culverts with minimal tidal flushing and (c) isolated pools created through silt accretion or expansion of flooded zones to neighbouring pasture. In urban wetlands, Culex pipiensltorrentium dominated in temporary (pre-imaginal densities 33x higher than permanent wetlands) and vegetated (pre-imaginal densities 41 times higher than unvegetated) wetland habitats. The drying and re-wetting of habitats was significantly associated with Culex presence/abundance. In the sewage treatment reedbed, the stilling basin (i.e. sewage capture structure) accounted for >80% of all pre-imaginal mosquitoes collected during the study , with mean densities 80 times higher than all other wetland types. The presence of raw sewage and subsequent algal blooms is significant for high Culex densities.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:686169 |
| Date | January 2015 |
| Creators | Medlock, Jolyon Matthew |
| Publisher | University of Bristol |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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