Sorry, you're wrong.By the way, your referring to "anaerobic" bacteria is not really correct - our good nitrate "eating" bacteria needs some oxygen in the water.
The absence of oxygen is indicated as anoxic; and anaerobic is used to indicate the absence of any electron acceptor (nitrate, sulfate or oxygen)
Denitrification takes place under special conditions in both terrestrial and marine ecosystems. In general, it occurs when oxygen (which is a more favourable electron acceptor) is depleted, and bacteria turn to nitrate in order to respire organic matter. Because our atmosphere is rich with oxygen, denitrification only takes place in some soils and groundwater, wetlands, poorly ventilated corners of the ocean, and in seafloor sediments.
The good nitrate eating bacteria does not live where oxygen is not depleted.