How oysters can indicate ecosystem health and resilience
Dr Paul Hick and Dr Marine Fuhrmann at Georges River Oyster Farm. Young Pacific oysters are used to monitor presence of Ostreid herpesvirus in the River. Mortality is recorded and oysters are sampled for testing in laboratory for presence of the virus.
In the face of emerging diseases, the Aquatic Animal Health Group at the Sydney School of Veterinary Science point of focus for the previous decade has been supporting oyster aquaculture. Pacific Oyster Mortality Syndrome (POMS) caused by Ostreid herpesvirus, has been particularly severe since 2008 in the northern hemisphere, and 2010 in Australia and New Zealand.
“Recurrent seasonal mortality of oysters caused by this new disease has reshaped the farming industry and left the most resilient farmers looking for answers. We have studied POMS in the field and laboratory to help decipher this complex multifactorial disease,” Dr Paul Hick explains.
A rich knowledge base was developed which has informed the multifaceted adaptations to farm management that are required to maintain health and productivity in a changing environment.
“Working at the Georges River, on the farm where POMS was first discovered in Australia, it is readily apparent that we live in a highly interconnected planet where people and vast quantities of commodities travel around the globe every day“ says Dr Marine Fuhrmann.
Most of these products are transported by oceanic vessels where opportunistic voyagers, biofouling organisms also journey across the ocean. The hulls of ocean tankers, pleasure cruisers, recreational and fishing boats provide an environment where complex ecosystems develop, including bivalves, ascidians, crustaceans and algae. These can become invasive species that damage ecosystems when distributed widely by shipping. More insidiously, biofouling may be a risk to aquaculture and marine life as a conduit for the dispersal of pathogens, such as the Ostreid herpesvirus. The Ministry for Primary Industries, New Zealand, commissioned a project to investigate that risk.
Dr Marine Fuhrmann is working on this project and recognised the value of the oyster health research tools to investigate if international shipping is a valid pathway for the international spread of Ostreid herpesvirus. Working with a well characterised disease model for laboratory infection she enlisted the help of farmers in the Georges River to generate authentic biofouling assemblages for laboratory and field exposure trials. A rigorous scientific approach was devised to provide evidence of this risk pathway for pathogen dispersal.
The aim was to provide the evidence needed to instigate changes in policy and procedures that will reduce the risk of national and international spread of aquatic pathogens.
Emeritus Professor Richard Whittington, who started the environmental immunology program at the University of Sydney's Camden campus in 2011, meticulously documented the pattern of oyster mortalities during successive POMS outbreaks, and then simulated them in a computer. He said “our conclusion is that this disease did not originate in Australia, and is not being spread around Australia by oyster farmers. It is not possible to stop the spread of the POMS by imposing additional biosecurity measures on farmers. The spread is environmental”.
Paul Hick