Viral invasions would make for a good plot in the next Spielberg blockbuster, but according to Michigan State University water researchers, it’s not a Hollywood fantasy. In fact, millions of tiny, dangerous microbes have been attacking native species in the Great Lakes for decades.
These pathogens are hitching rides in ballast water – the water in the hulls of large ships that help stabilize them when on the move – which is then released into new environments when the ships dock at their destinations, according to Joan Rose, Homer Nowlin Endowed Chair in Water Research at MSU.
Published in the journal Environmental Science and Technology, the study produced the most-detailed list of viruses in ballast water to date, and aims to provide engineers, environmental scientists and policy makers with vital information on how ships spread viruses. In addition, it will help support evaluation of ballast water quality to protect public health from invasive viral pathogens.
“Little attention has been paid to viruses traveling in ballast water until now,” Rose said. “But new methods have emerged that allow us to look at the entire viral community in ballast water, and we are learning much about the potential dangers these aquatic passengers pose to humans, animals, plants, bacteria and fungi.”
As ships prepare for a voyage, they slurp up water from the departure port. Current regulations require that these ships exchange this water 200 nautical miles from shore prior to docking at a destination. Here, the water may be dumped out. This act brings in new viral pathogens to local harbors.
“Viruses influence microbial communities because they require a host to replicate,” she said. “When you consider the ecological, economic and public health problems associated with taking up and discharging ballast water, we’re talking about potentially a large impact if waterborne viruses and diseases are spread over these long distances.”
Viruses are the smallest and likely the most abundant entities on earth. They exist through a wide range of relationships with hosts and can potentially infect every branch of the tree of life. The viral communities – called viromes – that the scientists investigated represented a wide, diverse and complex set of virus families that affect a range of freshwater fish, frogs and shrimp.
Rose and her team used a cutting-edge science called metagenomics to take a census of even the smallest microbes in each water sample. Metagenomics hones in on the genetic material, the DNA or RNA in a sample, allowing the team to classify large numbers of many different types of viruses. The team uncovered genetic material for many different fish viruses, including one strain that infects more than 40 different species of fish worldwide.
“Now that we have the technology to detect a wide range of viruses, we can determine the potential risks of transporting a virome in ballast water,” Rose said.
Fellow MSU scientists conducting the study with Rose included Yiseul Kim and Tiong Gim Aw. The study was supported by the National Science Foundation and Partnerships for International Research and Education.