We have conducted surveys of residual sediments of NOBOB vessels on the Great Lakes to identify live invertebrates in water and sediment, and to determine the number and viability of invertebrate resting stages in residual sediments.  Hatching experiments were conducted both in the lab and in situ on operating vessels to determine viability of resting stages.

Below are several pictures of organims and their resting stage collected by Sarah Bailey in sediment samples from a vessel in December 2000.  These organisms were hatched out in the synthetic freshwater medium.  Of the >50 NOBOB ships sampled during the study, most contained either live invertebrates or some viable resting stages of invertebrates in their ballast tanks.  This work is published in Bailey et al. papers in Limnology and Oceanography, Canadian Journal of Fisheries and Aquatic Sciences, in Freshwater Biology and in Diversity and Distributions.

Overall, this study demonstrated that NOBOBs pose some risk, tohugh far lower than ballasted vessels with fresh water (which historically dumped into the Great Lakes).   After considering the likelihood of discharge, live animals in residuall water were more like to to be discharged and pose a risk than either live animals in sediment or viable eggs in sediment.
 
 

Chydoridae ephippia (resting stage)              chydorid zooplankton
 

  Daphnia ephippium                  Daphnia female hatched from ephippium in ship