Invasive Species and Water Resources: Developing the Evidence Base for Effective Mitigation to Prevent the Spread of Invasive Alien Species in Raw Water Transfer Networks

Invasive alien species (IAS) are a driver of biodiversity decline and incur considerable economic costs. This thesis investigated biosecurity to prevent IAS spread within water company assets, focusing on two key pathways; accidental contamination of vectors, and Raw Water Transfers (RWT). Study organisms were IAS taxa of concern to the water industry. Chapter Two explored whether pH alterations could provide a biosecurity option for RWT. The results indicate that pH alteration is unlikely to provide an effective RWT biosecurity measure. Chapter Three focussed on dreissnenid veligers, a high-risk dispersal stage. Immersion for 60 minutes in the recommended concentrations of chlorine, Virkon Aquatic and Virkon S demonstrated their suitability as part of personal biosecurity. The effectiveness of altered water pH was also explored. However, extreme pH conditions and long exposure times were required to cause mortality, making this approach unsuitable for RWT biosecurity. Chapter Four investigated the attachment of D. polymorpha to materials commonly used in RWT pipelines. The results suggest that material selection could reduce biofouling in RWT pipeline design. Field-based trials of RWT biosecurity are constrained by costs, biosecurity risks and impact on water resources. Chapter Five presents a laboratory-scaled RWT designed to test mechanical biosecurity options under controlled conditions. The modular design allows integration of different mechanical biosecurity options and flow regimes supporting the development of effective RWT biosecurity interventions. Chapter Six evaluated an inline hydrocyclone as mechanical biosecurity for RWT. Hydrocyclones may therefore offer an effective biosecurity option where dreissenid spp. are present.