In both studied prisms, the ammonia constituted a major fraction of the total nitrogen (85% ± 11% of TN in MP and 91% ± 7% of TN in PP). In addition to ammonia, nitrate and nitrite, other inorganic forms of nitrogen, were also observed in the MP and PP but in negligible amounts (not exceeding 1% and 0.1%, respectively) (Fig. 3).