LIMITATION OF PRIMARY PRODUCTION BY HETEROTROPHIC ASSIMILATION AND TRANSFORMATION OF INORGANIC NUTRIENTS

The planktonic environment is usually characterized by nonsteady state conditions with events of phytoplankton blooms and sedimentation. Ino rganic nutrients are stripped from the water column by sedimentation a nd end up in the sediments where they may be permanently deposited, or nitrogen may be liberated as nitrogen gas by denitrification. A major part of the denitrification activity is a coupled process of nitrific ation and denitrification which is dependent on a good supply of oxyge n to the sediment. Urea may constitute a major part of the total outfl ux of dissolved N compounds from the sediment.