March 1, 2008
Since the St. Lawrence Seaway opened to ocean-going vessels in 1959, 65 per cent of aquatic invaders have hitched a ride in the ballast water and tanks of these ships.
The U.S. St. Lawrence Seaway Corporation recently introduced their intent to develop new regulations that would require all no-ballast-on-board ocean-vessels (NOBOBs) entering the St. Lawrence River to first flush their ballast tanks with salty ocean water to kill invaders lurking in the tank.
The effort is an attempt to improve measures to prevent invasive species introduced by ocean-vessels, and to better harmonize management of the Seaway with Canadian regulations, which require saltwater flushing of NOBOBs. The new rule would take effect when the Seaway opens for traffic in March.
Most of the ocean-vessels entering the Great Lakes each year are NOBOBs, heavy with cargo and not needing ballast for stabilization. They have been historically exempted from U.S. and Canadian ballast water exchange regulations which targeted vessels whose ballast tanks are full upon entry. But, the near empty tanks of NOBOBs are known to harbor invasive species.
The proposed rule is a helpful interim measure that Great Lakes United has long advocated for, and we have publicly applauded the Seaway’s action, but this is not the solution to the invasive species crisis.
According to research from the National Oceanic Atmospheric Administration, salt water flushing will reduce the risk but not eliminate the problems associated with NOBOB invaders.
NOBOBs with high salinity have fewer live organisms in both water and sediment residuals. This means the introduction of a smaller number of organisms, which reduces the risk of a new species establishing a population. But flushing does not completely clean tanks or remove all species. And, the salt water does not kill all species, for some have wide tolerances to salinity. In addition, salt-water flushing is unlikely to be effective against resting eggs and spores of small organisms.
For example, many invertebrates, like Gammarus tigrinus, a small shrimp-like creature that was first reported in 2001, have a high salinity tolerance. The fishhook water flea is known to produce resting eggs which are able to survive harsh conditions such as high salinity.
Salt-water flushing probably would not have prevented the zebra mussel, whose ability to seal itself from the outside environment allows it to survive extended exposure to salt water. Salt-water flushing might have delayed arrival of the zebra mussel, but probably would not have prevented it from establishing populations in the Great Lakes and spreading across the country as far away as California.
In addition, ballast tanks must be regularly and thoroughly cleaned to remove all sediment, and sufficient quantities of ocean water must be used when flushing. Given harsh weather conditions which can make ballast exchange on the open seas unsafe (and thus exempted) and differences in application by shipmasters, it would be challenging to ensure that every vessel executes the ballast management technique thoroughly and consistently.
An effective solution to the threat of invasive species from both ballasted and NOBOB vessels is on-board treatment. In this manner, the actual water being discharged from the boat is treated consistently to meet a stringent discharge standard to ensure that non-native organisms, pathogens or viruses are removed or killed.
Federal legislation is moving in the U.S. House and Senate that would require such treatment by a near-term deadline. Canada’s Shipping Act adopted an international ballast discharge standard but unfortunately failed to set a national date for implementation.
While the Seaway Corporation has taken an important step forward in protecting the Great Lakes from aquatic invaders, we cannot pause in our efforts to secure strong federal legislation implemented on both sides of the border. |
