This is the set up used to test the effect of hypoxia. On the right, you can see a clear vertical tower containing sea-water. Nitrogen is bubbled through this tower to eliminate some of the oxygen (the level is checked with an oxygen meter, the black cable coming out of the tower). The water is then pumped out and into a flask in which some worms are placed. The normoxia control group is in the container where air is bubbled. Image courtesy of Gulf of Mexico 2002, NOAA/OER.
