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[APD] RE: Why algae don't grow and plants do under non limiting conditions

>I hope I'm correct in interpreting this to mean: If the healthy,
well-nourished plants consume all the ammonium ion, NH4+, that is produced,
then there is nothing to >signal the algae spores to grow. The old algae
dies off, the new spores don't grow, and you are left with a tank with no
*visible* algae.
>I'm sure Tom (or others) will correct me if I've misinterpreted his
>John T. Fitch

You are correct.

NH4 needs 8 less electrons to be incorporated into Glutamine than NO3.
This means it takes less energy. That does not mean a lot to a large plant
with plenty of storage space and enzymes already in place to the same
degree it does to small single celled algal spore.

I'm not sure how far into biochem and genetic inducement folks want to go,
but chemicals such as NO3 and NH4 will elicit different responses to the
genes responsible for Nitrogen metabolism depending on their concentration
ranges. Plants switch and induce NO3 uptake enzymes and have both low and
high affinity enzymes. 

A high NO3ppm level allows the plant to adapt to this higher level.
Adding high NO3 also allows Cyanobacteria to induce the cells to go
dormant, BGA tends to bloom when the nutrients are very low. 

Once the concentration reaches a certain critical level, the gene is
induced and off the algae spore goes for better or worse.

At critically low NH4+ levels, that tells the algae "someone else" (another
alga) is growing already and it's a bad time to try and make a run at a
You can see this effect with other algae.
Some algae seem to reduce or remove other species of algae even at non
limiting levels. Green water and other's seem particularly good at this. 
It also may simply mean that there's very low nutrients but we artificially
add NO3 and having all the plants keeps the NH4 at 0.

Consider a newly set up tank/a tank with only a few plants.......
The bacteria help stabilize the new tank...........but how does this
prevent algae?
We know it's not excess nutrients..............
So what about NH4?
What do bacteria do? That might help with NH4 => NO3

If you add the bacteria or a cycled filter, or also add a lot of
plants(over stuff the tank), you also get the same result as an established

All just luck?
Probably not.

This nutrient is fairly universal, the model fits well with algae=algae
interactions as well as plant algae dynamics, explains how the algae spores
"know" if someone else is there, adding high O2 does not show this, so we
can rule that out. Low O2 or high O2 does not help or harm algae. We know
excess nutrients such as K, PO4, NO3, Fe don't cause algae.   
Adding NH4 does very clearly.
Adding other observations dealing with tank set up and bacteria, the model
is fairly clear.
Tom Barr

Plant fest is filling up, it will be fun, don't be let at home!

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