By Kevin Bunch, IJC
Ships moving within the Great Lakes could be carrying viral passengers inside ballast tanks from one port to another.
These viruses are seemingly entering the Great Lakes from a variety of potential pathways: they may be spread by waterfowl, infected fish migrating from the Atlantic coast, bait transport or aquaculture. They also could be hitchhiking along in ballast water tanks that ships use to maintain balance, according to a 2015 study published in the American Chemical Society journal. What’s more, a followup study published since then suggests some viruses can make it to marine ports around the globe.
State and provincial governments around the Great Lakes have issued an advisory for an invasive virus called viral hemorrhagic septicemia (VHS) in fish in the Great Lakes, first detected in Lake Ontario in 2005. The disease has led to major fish die-offs in all Great Lakes, Lake St. Clair and the St. Lawrence River. Although researchers aren’t sure how VHS entered the Great Lakes, it has proven to be a challenge to fisheries management.
Ballast water is used to fill these ballast tanks when a ship has less cargo to keep a ship stable. As more cargo is loaded onto the ship, ballast water is discharged to balance out the weight. Aquatic and marine life can get sucked up in that ballast water and discharged in completely different parts of the world, which accounts for the bulk of the invasive species in the Great Lakes. Canada and the United States have taken steps to prevent new invasive species from getting a lift from ballast water, by instituting one of the most stringent ballast water management regimes in the world, halting new aquatic invasive species from entering the basin from ballast water since 2006. This largely constitutes exchanging freshwater for seawater.
The 2015 study sampled ballast water from ships in a variety of locations on the lakes, including harbors like Toledo on Lake Erie, Essexville on Lake Huron, Burns Harbor on Lake Superior, and Hamilton on Lake Ontario. The ships were heading to Duluth on Lake Superior, one of the busiest harbors on the Great Lakes, and the ballast water was compared against the waters there as well, according to researcher Dr. Yiseul Kim, a recent graduate from the Michigan State University Department of Microbiology and Molecular Genetics studying under Dr. Joan Rose (a member of the IJC’s Health Professionals Advisory Board).
The ballast waters contained virus communities, Kim said, corresponding to the harbors from where the ships had picked up their ballast water. By comparing the virus’ genetic sequences against those in a database for Duluth’s harbor, she was able to determine whether they were local to the area or unwanted passengers. These viral communities targeted life in a variety of scientific kingdoms, including algae, plants, invertebrates (like insects), and vertebrates (like fish). More than half of these sampled viral communities target bacteria, the study said.
“Viruses influence microbial communities because they require a host to replicate,” according to Rose. “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.”
The study didn’t investigate viruses coming into the Great Lakes from other parts of the world, but Kim said a study she worked on that was published in 2016 looked at virus communities in ballast water traveling around the world to marine ports. She had similar findings in that study, with seemingly nonnative viruses riding along to different parts of the globe. Limiting the spread of these viruses by shipping would require ballast water treatment technology that Kim said is still in the research phase, as well as more information about virus types and their impact. Ballast water treatment systems are going to be required for ships entering the Great Lakes in the coming years, however, as regulations include new discharge limits for microbes for human health concerns.
A virus not native to a particular region does not necessarily mean it’s invasive. An invasive species is a nonnative species that is having a detrimental impact on its new environment and disrupts the ecosystem.
“I found that ballast water contains viruses,” Kim said. “It can potentially bring viruses (to new areas) but to confirm if they are invasive species I need to investigate the impact of the viruses on the new water system.”
Kevin Bunch is a writer-communications specialist at the IJC’s US Section office in Washington, D.C.