Ms Amber Brooks1
1NIWA
Biography:
Amber started working with eDNA as a summer student for Plant and Food Research during postgraduate studies then was a part of the Manaaki Whenua Biocontrol & Molecular Biology team for 2 years before starting at NIWA, where she has been for 2.5 years as part of NIWA's Molecular Biology team. Amber has used eDNA methods for analysis of soils, plants, sediments, water and gut contents for various purposes including biosecurity, monitoring, and community composition assessments.
Abstract:
Infections by the parasite Bonamia ostreae cause over 90% mortality in flat oysters Ostrea chilensis. B. ostreae was first detected in New Zealand in the Marlborough Sounds in 2015 and then in Big Glory Bay, Rakiura Stewart Island in 2017. Since then, targeted surveillance of oyster infections using ddPCR indicates an increasing prevalence and range expansion within Big Glory Bay, threatening to spread into the nearby Foveaux Strait wild fishery.
The mechanisms by which the parasite is transmitted and persists outside the oyster host are crucial elements for developing effective management strategies. However, the lifecycle of B. ostreae outside its oyster host is unknown, although anecdotal evidence suggests direct transmission occurs through an environmental medium, indicating a role for eDNA-based surveillance
The existing ddPCR assay targets B. ostreae in oyster tissues but can be adapted for testing environmental samples, removing the requirement for destructive oyster sampling and creating a rapid surveillance tool. We present the results of test validation for eDNA samples, which had comparable analytical specificity and sensitivity to the original oyster tissue assay. We also discuss findings from initial efforts to identify the medium of transmission, as well as potential intermediate hosts for B. ostreae. Plans for future testing of eDNA from seawater, sediments and other potential parasite reservoirs will increase understanding of lifecycle and transmission pathways of B. ostreae. Furthermore, the ability to use environmental samples would extend the scope of the Bonamia surveillance programme and help guide pest management programs and measures to manage translocation risks.