Ammonia is a potentially highly toxic naturally-occurring constituent of sediment pore waters, derived from the microbial breakdown of organic nitrogen in microplankton and microphytobenthos,and is consumed in the microbial nitrification and denitrification
processes that involve reduction of nitrate and nitrite to nitrogen gas. In anoxic, high organic environments, the nitrogen transformation reactions stop at the conversion of organic nitrogen to ammonia. Since ammonia is highly soluble, it is recycled via the
pore water to the water column.