We conducted  a total of 4 experiments in which we deployed 'hatching chambers' in the bottom of ships' ballast tanks to experimentally assess hatching in NOBOB vessels.  These chambers were lined with Nitex mesh, allowing water to circulate into the chambers when the tank is filled on the Great Lakes.  We placed 500g of sediment obtained from another vessel (that we  already characterized as to resting stage abundance and viability) into the chambers, and sealed the chamber.  We  flooded the ballast tank with Great Lakes water.  If sediments contain viable resting stages of invertebrates, algae or microbes, then these species may begin to hatch.  Because the windows are lined with relatively fine Nitex  mesh (40-54 um), the hatched animals cannot escape or enter.  At a later port (upstream), we re-visited the vessel after it has discharged the ballast water in our experimntal tank.  We recovered our chambers and determined in the lab what hatched out.  Our studies revealed that hatching does occur in situ, but at rates much lower than that in the lab.  Most of the species hatched were rotifer species that already are present in the Great Lakes.  Our studies indicate that the risk posed by NOBOB ship sediment is  quite low.  A greater risk may be associated with living invertebrate species present in residual fresh water in ballast tanks.  This work appeared in Diversity and Distributions (2005).