Environmental survival and mobilisation dynamics of E. coli and intestinal enterococci associated with common wildlife and wildfowl faecal sources

Abstract

Faecal pollution of water in rural catchments can lead to downstream impacts associated with water-borne pathogens. However, levels of faecal pollution are most commonly measured by faecal indicator organisms (FIOs) rather than any specific pathogen. While the evidence-base to support our understanding of FIO fate and transfer in the environment is growing, there remain gaps in our understanding of the relative contributions of wildlife versus livestock to microbial impairment of watercourses. The research in this thesis comprises a series of controlled laboratory experiments complemented with an online survey designed to solicit views on the opportunities and challenges of managing microbial pollution in agricultural catchments from different catchment stakeholders. FIO fate and transfer is investigated at three levels: sources of FIOs in the environment; their mobilisation into hydrological pathways; and their delivery to receiving waters and subsequent persistence in streambed sediments. A survival experiment quantifies FIO die-off in dairy cow versus red deer faecal sources exposed to repeated freeze-thaw cycles under controlled laboratory conditions. A laboratory-based approach then investigates whether FIOs are mobilised in different quantities from a typical agricultural, wildlife and wildfowl source, namely dairy, red deer and greylag goose faeces. A final laboratory experiment determines FIO persistence profiles after delivery of dairy, deer and goose faeces into streambed sediment. The online surveys revealed differences in perceptions of livestock versus wildlife contributions to microbial pollution issues at the landscape scale across different catchment stakeholder communities. Characterising how indicators of waterborne pathogens survive and transfer in the environment is of fundamental importance to inform and develop effective strategies for microbial pollution in catchment drainage waters and to reduce associated downstream impacts.