Nitrous oxide is also produced from burning fossil fuels, due to the trace nitrogen contaminants in those materials. And N 2 O is involved in catalytic breakdown of ozone in the stratosphere. But bacterial processes may also contribute to the increase above natural levels, because the nitrogen that bacteria utilize is often originally supplied as fertilizer. In fact, our excessive application of fertilizers on land is in effect fertilizing the coastal ocean. Bacteria also are primary agents in the natural environment that actually can do something about pollution via natural or enhanced bioremediation.
Bacteria can metabolize just about anything, including crude oil and even long-lived pesticides.
It was big news in the environmental community when fertilizer-augmented bioremediation was shown to increase crude oil degradation rates on the beaches of Alaska after the Exxon Valdez tanker spill. Adding nitrogen and phosphorus in oil soluble formulations seemed to help the resident bacteria degrade the spilled oil. Not long after that paper was published, an agent from California Fish and Game visited me and asked if he should be prepared to undertake a fertilizer addition remediation strategy, should there be an oil spill in San Francisco Bay. My research group investigated that suggestion by doing some experiments to measure the rate of degradation of hydrocarbons in the bay in the presence and absence of various fertilizer additions. The main thing we found out was that bacteria in San Francisco Bay were not nitrogen or phosphorus limited, so fertilization would not help speed up oil degradation.