Thursday, Sep 20, 2007
Emergency restrictions went into effect this week prohibiting ballast water discharges and exchanges in the waters of Isle Royale National Park by freighters and recreational boaters. Superintendent Phyllis Green said the move is aimed at preventing the spread of viral hemorrhagic septicemia (VHS) to fish communities surrounding the park.
âIâm trying to stop the inter-lake transfer of an invasive that hurt the lower lake system,â Green said.
Isle Royale National Parkâs waters extend four and a half miles from the islandâs shore in all directions. They overlap two shipping routes from the Soo Locks to Thunder Bay, Ontario.
VHS makes fish bleed internally, often leading to fatal organ failures.
âItâs a huge threat in all of the Great Lakes,â said NPS fisheries biologist Jay Glase. âItâs already spread pretty widely in the Great Lakes since we first discovered it in 2005.â
VHS was documented in three places in Lakes Erie and Ontario in 2005. Since then, the number of documented cases has grown to 26 throughout the Great Lakes, including three in northwestern Lake Michigan and one near the Straits of Mackinac.
Glase said it is not yet known how many fish species are threatened by the disease, but Lake Whitefish mortality from VHS has been reported and âLake Trout has been shown to be susceptible.â
Rainbow trout and turbot are especially vulnerable to VHS, according to the Michigan Department of Natural Resources.
While no outbreaks have yet been documented in Lake Superior, Green is concerned about the spread of the disease by means of the Soo Locks.
Scientists are especially concerned about its potential impact in the cold waters of Lake Superior. The virus prefers cold temperatures, becoming less active in water 59 degrees Fahrenheit or warmer.
âIn the lower lakes, itâs not too bad because they do heat up, but this lake does not heat up,â said Michigan Technological University professor of civil and environmental engineering David Hand.
Hand devised a system by which boats could treat their ballast water to kill the virus by chlorinating the water at a concentration of 3 mg of chlorine per liter of water. The chlorine kills any VHS that may be in the water in about two and a half hours, after which time ascorbic acid (vitamin C) is added. The ascorbic acid reacts with the chlorine and turns it into salt.
At a press conference Monday morning, Hand and Ed Hickey, chief engineer for the National Park Serviceâs Ranger III, demonstrated the method, pouring household bleach into Ranger IIIâs ballast tanks through ballast vents. Green said it is important that the parkâs own boat abide by the new restrictions.
Hand said the method could be employed on a large scale with dockside tanks to treat freighters at the Soo Locks. He said the discharge of salt resulting from the process would not have a significant impact on the lake.
He said if such a policy had been implemented years ago, it could have stopped the spread of zebra mussels to the Great Lakes region.
But Hand cautioned the dockside method would only be a temporary solution.
âItâs not the answer,â he said. âItâs a temporary process for disinfecting ballast water for ships entering Lake Superior at the Soo.â
But, he said, it could stem the tide of invasives until a more permanent solution, such as on-board treatment systems, can be implemented.
The shipping industry has opposed on-ship treatment requirements, possibly on the grounds of the cost of purchasing and installing the equipment.
A state law passed in 2005 took effect at the beginning of this year banning ocean-going vessels that dock at Michigan ports from discharging ballast water without first treating it.
But no law exists regulating ballast water exchanges for boats starting their voyages within the Great Lakes system. The restrictions at Isle Royale, though they only apply within the parkâs waters, are the first to affect all ballast-carrying vessels.