Ammonia (NH3) is a metabolite, but is very toxic to aquatic life. NH3 and ammonium (NH4) exist in equilibrium in an aqueous solution. The equilibrium constant K depends on temperature and pH. Nitrifying bacteria convert NH4' to nitrite (NO2). Nitrite can be further oxidized to nitrate (NO3). Finally denitrification bacteria convert NO3 to N2 completing the nitrogen cycle. Below are the reactions describing this part of the N cycle: NH3(a) H20NH (aq) k4 NO? (aq)3x0 (aq) NOj (aq) -N2(8) Ammonia (NH3) is a metabolite, but is very toxic to aquatic life. NH3 and ammonium (NH4) exist in equilibrium in an aqueous solution. The equilibrium constant K depends on temperature and pH. Nitrifying bacteria convert NH4' to nitrite (NO2). Nitrite can be further oxidized to nitrate (NO3). Finally denitrification bacteria convert NO3 to N2 completing the nitrogen cycle. Below are the reactions describing this part of the N cycle: NH3(a) H20NH (aq) k4 NO? (aq)3x0 (aq) NOj (aq) -N2(8)