Distribution of Nonconservative Concentrations
By nonconservative concentrations are meant primarily concentrations whose distributions are influenced by biological processes besides
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those of mixing and transport by currents. For example, the oxygen content is changed by the production of oxygen by plants in the euphotic zone and by the consumption of oxygen by respiratory processes, the phosphate content and that of other plant nutrients are removed from the water when they are utilized by plants and are returned to solution when organic tissues decompose, or the number of organisms of a given species increases or decreases depending upon the relation of the rate of multiplication to the rate at which organisms die off or are consumed.
The local time change of concentration due to biological processes will be called R. Adding this quantity at the right-hand side of equation (V, 5) one can state
In words, local time change of concentration equals effects of diffusion minus advection plus biological processes.
This equation can be simplified in the same manner as equations (V, 5)
and (V, 6)
, Sverdrup and Fleming, 1941