Principal Investigators: Tom Johengen (CILER) and David F. Reid (GLERL)

We proposed to test the effectiveness (concentration-time-mortality) of high concentration salt solutions (sodium chloride brines) as a back-up to saltwater flushing of ballast tanks. Brine solutions are potentially available at many, if not most ports and could be delivered to ships in tank trucks and pumped directly into ballast tanks (Jenkins, pers. comm.). Brines have long been used for preservation of food and few organisms (halophiles) are adapted to highly saline environments. Those that are likely would not survive in the freshwater environment of the Great Lakes.

A ship entering the Great Lakes with residual ballast water of salinity less than the desired 30 ppt could add relatively small amounts of sodium chloride brine at the first port of call. Residual water is generally on a few centimeters deep and thus the typical volume of brine needed to flood a ballast tank with enough brine to raise the effective salinity to >30 ppt is also relatively small. However, NOBOB ships generally offload cargo at their initial ports of call in the Great Lakes and then must ballast with local Great Lakes water. This can make the window of opportunity for exposure as short as a few hours. We propose to explore the use of brines not simply to adjust the salinity of the residual water to the requisite 30 ppt, but instead to determine the minimum dosage of higher salt solutions that can effectively kill even salinity-tolerant organisms in a short (few hours) time span. This would support implementation of a back-up policy to open-ocean saltwater flushing that could be applied to ships not able to safely apply that best management practice at sea.

In order for informed recommendations to be made about the best strategy for brine exposures, we will require experimental data on the salinity tolerance of planktonic and benthic organisms of the type found within the ballast tanks of ships traveling among the ports of the Great Lakes, the North Sea, and the Baltic Sea.

The specific objectives proposed in this project are:

• To determine the minimum exposure time and sodium chloride concentration required to kill representative freshwater benthic invertebrates and zooplankton species using organisms commonly found in the Great Lakes.


• To determine the minimum exposure time and sodium chloride concentration required to kill the salinity-tolerant species previously identified by the Marine Invasions Laboratory (SERC) from the low salinity ports of the Chesapeake Bay, San Francisco Bay, and the Baltic Sea.