Figure 26.1 -Bacteria Able to Perform the NH₄⁺ + NO₂^- -N₂

Figure 26.1
-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. Analyzing data presented in Figure 26.1 above, 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 metres
B) below 100 metres
C) in the top 50 metres
D) at a depth of 92 metres
E) at a depth of 75 metres