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[APD] Seed theory and NH4 signaling, why doesn't algae grow when the plants are.

I think there are several reasons for low algae presence at moderate non
limiting nutrients with macrophytes. 

PR may cause some of algae basal cells to release on plant leaves(but my
own study with CO2/O2 levels were inconclusive, algae did well on all gas
conditions, high O2, high CO2/O2, high CO2 only and the control). Both
algae and plants respond well to high O2 and both prefer CO2 over HCO3.  
Water changes always seem to help. Removes many epiphytic algae and any
that are floating around(see Zimba and Hopson, roughly 80% of the epiphytes
were removed by swirling in water in a flask for 90sec). 
We scrub, prune old leaves that get infected. 
We add herbivores. 
Some suggest allelopathy, but all 300 species of plants elicit the same
response? What is the likelyhood that all 300 species have the same
chemical and effect? Extremely small. 

It has to be something more general and I see this occur in non CO2 planted
tanks as well and in nature.
I've suggested that algae know "when someone else is home." and don't
bloom. When the plant growth is sour, the NH4 uptake declines, bacteria
don't have enough time to respond, algae gets a free meal of NH4 even if a
slight increase, this means a lot more relatively to a small algae than a
larger plant.

This is the best idea thus far:

Algae spores may not have any signal like => NH4 presence telling them to
grow(plants remove all the NH4 when they are healthy!).
So very low/absent NH4 may tell algae that someone else is there. 

This idea would make sense in general terms and also explain why good
plants growth => poor algae growth even if there are nutrients available
for vegetative growth.
I;ve observed that many algae just stop growing when placed into a  tank
that has good plant growth and also with tanks that had poor plant growth,
got some algae, ansd then stopped growing after the plant health improved. 

Another two stage pathway:
High O2 levels may activate bacteria in the substrate that suppress algal
spores that are generally present in the substrate much like a seed
I did not test for this as I used no substrate in the original test with
high O2/CO2 etc.

The nutrient levels are great for plants, they out pace and out grow algae
when feed a stable diet, algae are better able to deal with dramatic
changes while it takes much more time for plants to get established. You
can see this in shallow lake ecology where macrophytes are removed or as
they fill in. It takes years for them to redominate again. It does not take
long for the algae to take over. 

Shallow lakes are very prone to wind resuspension of nutrients from the
sediments. This allows a bloom of algae since it suspends NH4(and other
Macrophytes reduce wave action and prevent resuspension and this leads to
gin clear water. There is some arguement with this theory but it seems
correct to me from what I've read about resuspension.

We do this when we replant and rework the tank, doing a water change right
takes care of this. 

This issue has not been explore much in the literature, mainly
phytoplankton vs macrophytes , the pickings are slim for
periphyton/epiphytes vs macrophytes in the context that is useful for
planted aquarist. 

These are a few ideas. 
Observations are fairly clear, why this occurs is not so clear. 
I have suggested a few ideas. 

It has to be something general. 
I think it has a lot to do with algae's signaling to bloom or stay put till
things get ripe again like with NH4. 

Everything I've done with NH4 tells me it's the problem in natural
ecosystems and in planted tanks, SW or FW. 
Many bothersome algae bloom readily with NH4 additions. 
But they don't if you add NO3+the other nutrients. 
You can try this by adding more and more fish to a thriving healthy tank. 
Once you pass by the rate of NH4 uptake by those plants, you provide a ripe
place for algae to grow. You can add everything else and not get a

Plants and algae occupy different ecological habitats also. A small amount
of NH4 means a lot to the algae vs the plant.

So that's the seed theory/notion idea that algae know when or when not to
grow based on NH4 and why healthy plant growth => poor algae when there are
enough nutrients for either group. 

This seems like the best expaination so far. Now I need to test this:-)
It's a combination of things but I think this is why the new algae does not
This also applied to lakes and non CO2 planted tanks.

Non CO2 planted tanks also have this same pattern, they have low inputs of
NH4 from fish food only and if there's enough plant biomass, there's
generally sufficent NH4 uptake. These tanks also have less light and slower
growth of both the plants but importantly also the Algae.
CO2 is preferred by algae as well, but a fair number of plants will use the
HCO3 and most all algae do or can. Some algae just need very little CO2 in
their environment to do well. 

So the algae grow slower in non CO2 planted tanks, they have plenty of
plants to remove the NH4, then growth rates are slow so the nutrients
demands can be met from fish waste and substrate uptake, cycling resulting
in extremely low algae presence.

Since you do not resuspend the tank weekly with water changes, the tank
does well/better without water changes. If you added CO2, that's fine since
the higher growth rates in those tanks removes all the NH4
resuspended/leeched out at a faster rate than the non CO2 planted tank.    

Then if you apply this to a CO2 enriched low light tank, then you get
extremely low algae presence as well.

This theory seems applicable to all planted tank methods also. Even some
lakes and streams.  

Tom Barr

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