July 10, 2007
The authors of a three-year study
"saltwater flushing," the practice of rinsing a ship's ballast
tanks with deep-ocean water before it
enters the St. Lawrence Seaway, be added to a set of requirements
Code of Best Practices for Ballast Water Management. In 2002, the St.
Seaway corporations in the
The study, released July 10, focuses on
so-called NOBOB (no
ballast on board) ships, those that carry no pumpable water in their
tanks. More than 90 percent of the cargo ships entering the Great Lakes
Various approaches for sanitizing ballast water – using chemicals, heat, ozone or ultraviolet radiation, for example – are being explored but have not yet been adopted. In the interim, saltwater flushing provides an inexpensive alternative that would likely kill most of the lingering freshwater organisms in NOBOB ballast tanks, said U-M nutrient chemist Thomas Johengen, one of the study's co-leaders.
"We think that saltwater exposure is an
to protect freshwater systems. If we could apply it in every NOBOB, we
that we can close a loophole," said Johengen, an assistant research
scientist at U-M's
Johengen and project co-leader David
Reid of the Ann
Arbor-based Great Lakes Environmental Research Laboratory (GLERL)
scientists from the
The report, "Identifying, Verifying and Establishing Options for Best Management Practices for NOBOB Vessels," was funded by the Great Lakes Protection Fund, with additional support provided by the U.S. Coast Guard and NOAA. Known informally as NOBOB-B, the study is a follow-up to another report (NOBOB-A) the same research team released two years ago.
NOBOB ships are loaded to capacity with
cargo and carry no
declarable ballast water on board. But once they unload their cargo,
on tons of
At least 185 nonnative aquatic species
have been identified
The invaders include the notorious
zebra mussel, a small but
aggressive Eurasian fish called the river ruffe, and two types of goby.
hemorrhagic septicemia, which caused a huge
The latest NOBOB study included more
salinity-tolerance experiments designed to mimic saltwater flushing of
tanks and its effects on various invertebrates – including larval
stages of the
zebra and quagga mussels. The tests were conducted in Lake Erie, Lake
The experiments showed that many organisms originating in low-salinity ports can be quickly eradicated from ballast water through exposure to full-strength seawater.
"One of the key findings here has been to confirm that saltwater can be quite effective at reducing the risk of invasions from ballast water," Reid said. "It's not 100 percent effective against all types of organisms, but it's far better than what's been going on, which has been basically no regulation at all for NOBOBs."
The study also evaluated the effectiveness of the current Code of Best Practices for Ballast Water Management.
The code requires vessels entering the
The team concluded that the real-world constraints of cargo loading and unloading often make it impractical for crews to carry out the environmental precautions. In addition, the precautionary measures "require information on local water quality conditions that is not generally available to the shipping industry," the researchers determined.
In 2005, the U.S. Coast Guard issued a
encouraging mid-ocean ballast tank flushing. Last year,
"This report is actually providing, finally, the basis of support for why the Canadians did what they did," Reid said. "We've been keeping the regulatory agencies apprised of our results all along, and they (Canadian officials) actually jumped on it before we were completely finished."
Nearly 2,000 oceangoing vessels
conducted Great Lakes trade
Read the final NOBOB-B report: http://www.glerl.noaa.gov/res/Task_rpts/2004/aisreid04-1.html
By fax: (734) 764-7084
-- Jim Erickson News Service University of Michigan 412 Maynard Ann Arbor, MI 48109-1399 Direct: 734-647-1842 Main: 734-764-7260 Fax: 734-764-7084 Office web: http://www.umich.edu/news