AbstractInvasive alien species (IAS) negatively impact freshwater ecosystems worldwide. As suppression and eradication techniques for established invader populations are often complex, costly and resource-intensive, the prevention of further invader spread is considered a key aspect of proactive management strategies. Despite this, the application of many proposed spread-prevention practices are frequently inhibited due to low practicality, high expense, undesirable non-target effects and a lack of known efficacy. Similarly, as suppression techniques are not always successful, or necessarily suitable for all field scenarios, there is a clear and urgent need to develop readily-available control methods, which maximise efficacy of treatment towards target species, but minimises broad-scale environmental damage. Accordingly, the development of simple but expeditious spread-prevention, control and eradication protocols remain a management priority.
Here, the efficacy of various disinfectant solutions and thermal shock treatments to rapidly kill propagule stages of selected invasive species is assessed. The examined species included eight invasive macrophyte, Quagga (Dreissena bugensis) and Zebra (Dreissena polymorpha) mussels, Asian clam (Corbicula fluminea), killer shrimp (Dikerogammarus villosus), and bloody red shrimp (Hemimysis anomala). Each species was independently exposed to aquatic disinfectants or steam spray treatments (≥100 °C). Dikerogammarus villosus, and H. anomala were also exposed to disinfectant mist sprays. Overall, it appeared that the examined aquatic disinfectants will not completely prevent the spread of the assessed invasive macrophyte or bivalve species. However, disinfectant solutions efficaciously killed 100% of D. villosus, and H. anomala, even following mist spray treatments. Steam spray was also highly effective, causing 100% mortality of all examined macrophyte, bivalve and crustacean species, even following short exposure times of ≤ 30 seconds.
Further, this thesis demonstrated that cold thermal shock treatments, following an application of dry ice pellets (-78 °C), can be used to kill C. fluminea. Similarly, hot thermal shock treatments delivered through steam spray and open-flame burns (~1000 °C) also effectively killed adult D. polymorpha and substrate dwelling C. fluminea. This efficacy was especially evident when thermal treatments were applied following initial disruption of the substrate, or as combined cold and hot thermal shock applications. In general, although multiple applications may be needed for complete extermination to be achieved, thermal shock treatments appear to be an effective, rapid response mechanism to control and possibly eradicate low-water exposed bivalve populations.
Although aquatic disinfectants will likely have a beneficial role within decontamination protocols, the innovative and simple technique of direct steam exposure can be used to improve biosecurity practices to inhibit the spread of invasive macrophytes, bivalves, and crustacean species. In particular, in-field decontamination stations could be established to facilitate the provision of biosecurity protocols at waterway exit and entry points. Although promising, further development of thermal shock treatments for suppression of IAS is required, especially to account for differences in the physical structure of habitats, and time of year.
Overall, this thesis has developed a suite of tools for improved invader spread-prevention and control. Although further research will be required to ascertain the reliability of the proposed tools under in situ conditions, this work represents a realistic starting-point for researchers to be built upon with more in-depth field assessments tailored to the unique requirements and challenges of different field sites.
|Date of Award
|Environmental Protection Agency
|Jaimie Thomas Allan Dick (Supervisor) & Neil Reid (Supervisor)