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Re:DO and algae

> On Thu, 2 Aug 2001, Tom Barr wrote:
> 
>> You can get 500% saturation values with
>> algae in natural waters.(40-50ppm of O2) or 200-300% in ponds even during a
>> eutrophic bloom.
> 
> Tom,
> 
> This observation seems to conflict with the idea that high DO suppresses
> algae.  If algae were suppressed by high DO how would they ever be able to
> push oxygen levels in a eutrophic system to 2-5 times saturation?

No, it does not conflict. A species in log growth suppresses OTHER species,
it could be other algae, bacteria or plants causing the suppression, not the
algae that causing the high DO. At some point in TIME, low DO's existed and
allowed one species(or several) to sense a good ripe time to bloom. No other
competitor was there then( or at least producing much DO).

 The algae once in bloom will drive the DO sky high fast. As long as it's in
the log growth phase it will not relent till all the nutrients are gone due
to the massive amount of algae present. All this primary production sends
the DO's off then scales. It doesn't stay like this for too long.

 Most high DO algae blooms like this in nature are followed by the opposite,
extremely depleted DO's. They go full blast till they fry out and die off
fast. All this dead algae gets decomposed by bacteria and repackaged into a
new wave of nutrients. That causes severe DO depletion. Also a very bad time
to grow. But right after is a great time to start. So the timing of when to
grow so you can produce a decent amount of spores for the next generation is
extremely important. If you(say your a red algae) start in the middle of a a
green algae bloom, what are your chances that nutrients will be available
any time soon for you? And then you have to get enough spores off to have
enough to compete well the next cycle when the nutrients become available
again. "Early germinators" get the advantage here. Or perhaps real fast
growers that can exploit the nutrients faster than the early germinators
etc.

 Hopefully if you add a ton of plants from the start they will become the
"Early germinators". Is it truly competition in the nutrient sense? Or is
competition in the temporal sense? High DO's means someone else is going
full blast, "All of us Odegogoniums think we'll sit this round out." We'll
wait till the environment looks better to get a good foot hold." If they did
not do this algae would waste more spores/energy/gametes and have greater
losses in fecundity. Evolution has worked over the algae longer than the
plants so it would make sense that they all sorts of methods to sense and
time things to grow. It would be to their advantage to wait till the DO
drops so that they would have a much better survival rate. This same sort of
thing happens with plant seeds. You would be better off to germinate in the
spring before all the other plants cover you up and before winter comes and
dries/freezes you out etc. Algae live in a different place but much of
strategy is similar.

Our tanks remove all the environmental changes allowing the cycles to
maintain the high DO's from the plants and the algae thinks it's another
algae (or perhaps a plant) making all the DO so they wait and do not grow
unless the DO drops.
If the DO stays high all the time, algae stays in a resting spore phase.

We go in and mess with our tanks too much and this DO drops from bacterial
die off(massive uprooting, removals of big sword plants etc), big plant mass
removals, poor CO2, deficiency errors, not enough light, etc. Anything that
lowers DO causes algae to wake up and bloom.

Why would you want to start to try to grow if someone else was growing like
mad? It would be a bad idea to even start. So you'd sit and wait(gamete or
spore etc) till the DO goes down and try to get the first jump next cycle
around.

So if the plants are in the primary grower in a body of water,
The algae can sense that something(plants, another species of algae or
bacteria) is already there. Not exactly a good time to try and grow or get a
foot hold. After a bloom you get a die off and this causes a reverse of high
DO from decomposition(and then some more from higher food web animals dying
from the low DO). Then a new wave of algae or another species comes in a
uses the repackaged nutrients now that the DO levels are about the right
range.  

> 
> The algae in our tanks probably isn't the same algae that can thrive with
> 300% oxygen saturation in a pond.  Perhaps the algae that are common in
> our aquariums are suppressed by high oxygen levels, while algae in general
> are not.

This could be true as well.
I have to test this though.
Regards, 
Tom Barr