Aquifers and their biota (stygobites) are some of the least well known ecosystems. Previous research indicates geology is an important control of stygobites and the primary thesis aim was therefore to examine how geology shapes the distributions of stygobites across different spatial scales, considering high lithological detail. The food web functionality of groundwater ecosystems is also rarely explored and the secondary thesis aim was therefore to examine the trophic effects of stygobites in experimental groundwater microcosms. The new habitat typology shows that 11 higher resolution geo-habitats are characterised by significantly different hydrochemistry and a heterogeneous distribution of high-quality habitat patches. Furthermore, the habitat scoring system developed based on the variability of influential abiotic parameters shows that overall geo-habitat quality varies considerably, with karstic geo-habitats (e.g. Chalk) having a higher quality than most porous and fractured geo-habitats. Major parts of England and Wales are covered by poor quality habitats, probably limiting dispersal. Testing the new typology on species distributions shows that biodiverse and / or abundant communities occur in all geo-habitats. Karstic aquifers generally form the best habitats with the highest stygobite species diversity and frequency of occurrence. However, some fractured aquifers (e.g. Igneous Rock) are also significant habitats for stygobites, while more geological detail needs to be considered to explain stygobite communities in other fractured aquifers (e.g. Mudstones & Siltstones). However, many species are not distributed throughout entire connected aquifers, and in individual sites copepod biomass is not explained by geology, showing that other environmental controls (glacial history, site characteristics) may supersede geological controls. The grazing experiments show that stygobites significantly increase protozoan abundance and morphotype diversity, and alter microbial community structure, indicating they may modulate the ecosystem services provided by these groups. Overall, this thesis enhances our knowledge of the factors governing the distribution and functionality of groundwater ecosystems.
|Date of Award||30 May 2017|
|Sponsors||National Environment Research Council|
|Supervisor||Anne Robertson (Supervisor), Louise Maurice (Supervisor), J Bloomfield (Supervisor) & Julia Reiss (Supervisor)|