The Nitrogen Cycle and Importance of Oxygen
Nitrogen
is a vital element of protein and is absorbed by green plants in the form of
nitrate. Together
with ammonia, ammonium and nitrite, it is found naturally in rivers, lakes
and streams in very small quantities In
a pond environment, nitrogen compounds (nutrients) can be created quickly by
faeces, urine and other excreta, plant remains and decaying food.
When
concentrated these nutrients can have a harmful effect on a ponds
inhabitants
Organic
nitrogenous substances decay in stages in the presence of oxygen, a process
called ‘oxidative breakdown’. It produces various nitrogen compounds
(nutrients) as follows…
Toxic
ammonia and non-toxic ammonium are produced in the first stage of the
nitrogen cycle.
The pH value
determines which of the two will predominate. Ammonia occurs at a pH of 7.0
and over.
The second
stage of the nitrogen cycle is nitrite which is the result of the bacterial
oxidation,
or combustion, of ammonia/ammonium.
Nitrite is
also toxic to aquatic life, but not as toxic as ammonia.
In
the third and final stage nitrite is converted to nitrate. Nitrate is
harmful only in very high concentrations.
The key
element and most important factor to get all of the above to work is the
availability of free oxygen.
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