Deakin University postgraduate researcher Ben Roennfeldt uncovered the virus which affects copepod zooplankton in south-west estuaries. Zooplankton are a critical part of estuarine ecosystems and the virus has potential to have a huge impact on the food chain. 

Dr Roennfeldt started his PhD on the ecology of fish larvae in the Hopkins River estuary, but after discovering the virus his research took a new direction.

“I had done a couple of years’ groundwork on my original topic but I redefined the PhD because of the importance of what I was observing,” he said. 

He said the research detected viral infection in copepods that had turned iridescent blue. 

Infections were also observed in many zooplankton population from other aquatic environments, including ocean and freshwater ecosystems. 

Copepods are tiny crustaceans that can be in high abundance in the water column. Many species are less than three millimetres long. 

They are an important and nutritious food item for fish larvae, small fishes such as anchovies and pilchards and other small crustaceans. 

Some whale species seek out copepod swarms for food. 

“Therefore, if there is a problem at the bottom of the food chain, it spreads through the whole system,” Dr Roennfeldt said. He consulted with CSIRO scientists who validated the virus was causing the disease and worked collaboratively to uncover its genetic identity. 

It was found to belong to a family of viruses that cause insects to change colour, but was the first of its type described in copepods. 

He said he believed climate change and stress in the ecosystem increased the occurrence of high infection levels throughout the zooplankton population and hopes his findings will influence the management of the estuary. 

“It is early days so we’re not sure of a solution, but I hope this data will contribute to further developing techniques for detecting and monitoring zooplankton viruses and in forecast-management of affected fisheries,” he said.