Do oxygenation reduce the growth of aquatic plants?

[paludarium]

Hi,

I know that some of the aquatic plants experts (in Germany) still believe that oxygenation or too much oxygen in water will reduce the growth of aquatic plants, maybe a study from Cooley et al in 1979 provides some evidences, http://www.clean-flo.com/files/aerat...l_hydrilla.pdf.

To my surprise, nitrogenation (aeration with pure nitrogen air) increased the growth of Hydrilla, while aeration with house air decreased the growth.

The authors also found that the effect of aeration upon Hydrilla growth appeared to be correlated with a decrease of iron. So, in the low CO2 environment, iron becomes one of the important factors to affect the growth of the aquatic plants?

Like to hear all comments on this issue.

Regards,
Erich

[Tom Barr]

Hi,

I know that some of the aquatic plants experts (in Germany) still believe that oxygenation or too much oxygen in water will reduce the growth of aquatic plants, maybe a study from Cooley et al in 1979 provides some evidences, http://www.clean-flo.com/files/aerat...l_hydrilla.pdf.

To my surprise, nitrogenation (aeration with pure nitrogen air) increased the growth of Hydrilla, while aeration with house air decreased the growth.

The authors also found that the effect of aeration upon Hydrilla growth appeared to be correlated with a decrease of iron. So, in the low CO2 environment, iron becomes one of the important factors to affect the growth of the aquatic plants?

Like to hear all comments on this issue.

Regards,
Erich

No one (researchers on aquatic weeds) in the USA uses aeration as management tool. There are some companies that claim it works, but that's marketing for you
This paper gets cited by those selling this baloney.

They say inorganic carbon decreased.........so less CO2.
If you have less CO2, then you will have more or less growth??

I'll let you answer that.

If you drive out most of the other gases leaving N2........reduction might play a role in that response, eg more Fe released, more PO4 etc.

Hydrilla is easily able to add O2 from photosynthesis and has little O2 demand overall.

Super saturation can cause photorespiration, when O2 gets about 150-200%, then you can have a decline in growth.
See Bowes for more on that.

I agree that too much is bad, eg, more than 150% etc, for extended periods, this is also bad for fish and live stock.
Aeration reduces growth since it drives out CO2/DIC, the Fe is another possible cause also.
In higher Redox values we have in our tanks.....we simply use chelated Fe.

You will also note than the Dissolved O2 levels where pretty similar.
So the O2 itself.......is not so much as factor. Aeration maybe.

But no one worth their salt uses aeration to control Hydrilla or aquatic weeds.

So too much O2(150-200%)... sure, it's bad, aeration is also bad, in that context, the German folks are correct.

[paludarium]

So too much O2(150-200%)... sure, it's bad, aeration is also bad, in that context, the German folks are correct.

Well, based on the observations that too much O2 is negatively correlated with the growth of the aquatic plants, so that siesta, reduced surface agitation or decreased water flow will improve the growth of the aquatic plants mainly was due to the reduced O2 level but not the increased CO2 level? For a long time I speculated that high CO2 level help overcome photorespiration caused by O2 super saturation. Maybe I was wrong.

Regards,
Erich

[Tom Barr]

Well, based on the observations that too much O2 is negatively correlated with the growth of the aquatic plants, so that siesta, reduced surface agitation or decreased water flow will improve the growth of the aquatic plants mainly was due to the reduced O2 level but not the increased CO2 level? For a long time I speculated that high CO2 level help overcome photorespiration caused by O2 super saturation. Maybe I was wrong.

Regards,
Erich

Siesta, reduced surface movement etc, will not do this, to get the level for serious PR in aquatic polanted systems, you need: A LOT oif light(eg, the sun), a weed choked cess pool, say a lake packed with Hydrilla(common in Florida), and then you start getting O2 levels in 150-200 % range, we rarely even get beyond 110-130%.

If you reduce water flow, then less CO2 will get to the plants and less nutrients etc, in a densely planted water column.
Denser than anything we might want, but a few neglected tanks might illustrate.

I think you are correct about CO2 helping to address PR with O2 super saturation above AMBIENT O2.
In that case, the more CO2, the less competition for O2 at RUBISCO's active site.

If you reduce one, say CO2 a great deal, then O2 is more likely to enter. If you increase CO2 and reduce O2, then the opposite.
If you increase the concentration of both of them, then the relative amounts should fairly equal if the concentrations are the same.

So if you add say 2x the O2, say go from 7ppm to 14ppm, then added say 7ppm then up to 14ppm........., we should see somewhat similar effects.........since the ratio of molecules coming into contact with RUBISCO are relatively the same, but at higher levels.
O2 is a rather toxic however and the radicals of O2 can cause issues. This occurs when photosynthesis is really driven very hard, too fast for the cells to respond or when something breaks down in the cellular machinery.

But for our case with CO2 enrichment, we are adding roughly 10-20X ambient levels of CO2 and then also only getting near 120% in a well run tank.
I'd say that's better than 3ppm or less and 100% O2 like in a non CO2 tank.
The ratio is much different there.

Here's Bowes' paper of CO2 and O2:
http://sesultan.web.wesleyan.edu/wes...nce_carbon.pdf

[Tom Barr]

Siesta, reduced surface movement etc, will not do this, to get the level for serious PR in aquatic polanted systems, you need: A LOT oif light(eg, the sun), a weed choked cess pool, say a lake packed with Hydrilla(common in Florida), and then you start getting O2 levels in 150-200 % range, we rarely even get beyond 110-130%.

If you reduce water flow, then less CO2 will get to the plants and less nutrients etc, in a densely planted water column.
Denser than anything we might want, but a few neglected tanks might illustrate.

I think you are correct about CO2 helping to address PR with O2 super saturation above AMBIENT O2.
In that case, the more CO2, the less competition for O2 at RUBISCO's active site.

If you reduce one, say CO2 a great deal, then O2 is more likely to enter. If you increase CO2 and reduce O2, then the opposite.
If you increase the concentration of both of them, then the relative amounts should fairly equal if the concentrations are the same.

So if you add say 2x the O2, say go from 7ppm to 14ppm, then added say 7ppm then up to 14ppm........., we should see somewhat similar effects.........since the ratio of molecules coming into contact with RUBISCO are relatively the same, but at higher levels.
O2 is a rather toxic however and the radicals of O2 can cause issues. This occurs when photosynthesis is really driven very hard, too fast for the cells to respond or when something breaks down in the cellular machinery.

But for our case with CO2 enrichment, we are adding roughly 10-20X ambient levels of CO2 and then also only getting near 120% in a well run tank.
I'd say that's better than 3ppm or less and 100% O2 like in a non CO2 tank.
The ratio is much different there.

Here's Bowes' paper of CO2 and O2:
http://sesultan.web.wesleyan.edu/wes...nce_carbon.pdf

You can clearly see that at lower O2 levels, it takes LESS CO2 to reach the Km half constants. So less CO2 is required.
If we have say more than 21% O2, say we have 25%........then instead of 200, we might now need 250 uM, so what?

We just add more CO2, but we are adding around 0.5 to 0.8 mM, or about 2-3x what those Km values are......... so this does not have much effect till the O2 gets way up there.
Still, it's not a big deal as far as a reducing in plant growth really............if we lose say 2-5%.....not a big deal as long as the O2 is from plant growth./that's some serious growth and algae are not likely an issue in such systems.