Bacteria Able to Perform the NH4+ + NO2− → N2

Multiple Choice

Bacteria able to perform the NH4+ + NO2− → N2 + 2H2O reaction have been discovered in laboratory bioreactors and wastewater treatment systems. Researchers predicted that these bacteria should exist in oceans. They measured the concentration of NH4+, NO2−, NO3−, and O2 in the Black Sea as a function of water depth (M. Kuypers et al. 2003 Anaerobic ammonium oxidation by anammox bacteria in the Black Sea. Nature 422:608-11) to determine where in the sea the bacteria might live. By analyzing data presented in the accompanying figure, at what depth would you expect to find the bacteria? (Note: In the figure, different scales are used to show concentrations of NH4+, NO2−, NO3−, and O2.)

A) in the top 5 meters
B) in the top 50 meters
C) at a depth of 75 meters
D) at a depth of 92 meters
E) below 100 meters