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Urea and algae

Most algae that possess urease as do the higher plants. But some algae that
don't have urease get around this problem by using two speparate enyzmes to
yield the NH4 and 2 CO2's.

Some other interesting note with __*certain*__ algae.
Urea is taken up at the same rate at lower concentration than free
NH4(roughly 1.7X as much or higher) and around 7x more for NO3 than NH4.
So if any Urea is present, even trace amounts, the algae will remove it
faster than NH4 or 12X as fast as NO3.
"Guanine" also showed rapid uptake rates at low concentration interestingly,
faster than Urea. 

Ammonium is the most common excretory product of critters. But this NH4 is
often at very low levels so if the algae wish to use it, they must have very
effective means to take it in before some other plant/weed/algae gets it.
The enzymes are very sensitive to trace amounts. So any "small pulses" that
enter the system will be utilized quickly.

I have stated a number of time to this effect.
Laboratory studies also confirm this.

Algae growing under NO3 or NH4 cultures grow at the same exponential rates.
But algae will take in _only NH4_ when _both_ are supplied till the NH4 runs
out then it goes back to taking in NO3. It's a "lazy" algae thing again.
There's likely some sort of feedback mechanism that allows the algae to take
in the easy NH4 and conserve sugars when it can.

NH4 uptake suppresses NO3 uptake. In some algae this happens only in CO2
rich or cells from CO2 rich environments.

It should be noted that in some plants ammonium is not inhibitory at all.

I think it'd be interesting to complex some NH4 in something like Flourite
rather than a water column based fertilizers for NH4 beside the fish
themselves. But it would have to only be able to removed via the roots.

CO2 and NO3 relationships:
Virtually all N products need a carbon skeleton to convert the inorganic N
into organic N. Good CO2, good NO3/NH4 utilization.

Tom Barr