Ballast Water Report Sheds Light on Nonindigenous Species Introductions

A scientist collects wet residual sediment in a double bottom tank. See: Additional photos

On average, about 90 percent of saltwater ships entering the Great Lakes are considered NOBOBs, or ships loaded with cargo that carry no declarable ballast-on-board.

These ships do contain residual ballast and sediment, however, that can get mixed with Great Lakes water and eventually discharged—along with everything in it. According to a report released in May, this discharge of mixed ballast water can lead to the potential introduction of nonindigenous species (NIS) to the Great Lakes.

The 285-page report presents the results of a three-year, multifaceted study to systematically characterize the living organisms (biota) contained in residual ballast water and sediment and the associated risk of invasion. The study was led by Thomas Johengen, of the University of Michigan, Cooperative Institute for Limnology and Ecosystem Research, and David Reid of NOAA’s Great Lakes Environmental Research Laboratory.

The team surveyed 103 NOBOB vessels about their ballast management practices. They boarded 42 of those vessels to sample residual water and sediment in 82 ballast tanks.

The following are among the key findings:

About 40 percent of the 103 vessels surveyed for ballast management practices and history entered the Great Lakes with freshwater residual ballast. Such ships, according to the report, present the most serious threat of inoculation of new organisms into the Great Lakes ecosystem.

The presence of one or more microbial pathogens was detected in 26 of the 42 ships sampled. However, the research method determined only presence, not absolute concentrations, so the study cannot definitively assign a human health risk.

A diverse assemblage of phytoplankton and invertebrate biota was found in the residual ballast water and sediments sampled, including several nonindigenous species not reported for the Great Lakes.

The study concludes that the process of “ballast water exchange is an imperfect,
but generally beneficial management practice in the absence of more effective and consistent treatment options.”

The study was funded by the Great Lakes Protection Fund, NOAA, the U.S. EPA, and the U.S. Coast Guard.

To read the full report, see: www.glerl.noaa.gov/nobob
Contact: Thomas Johengen, (734) 764-2426

See: Additional

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