# pond hypothesis



## garryc (Jan 21, 2006)

Through out the plant kingdom many plants have natural defenses to the creatures that consume them. Tobacco has nicotine and coffee has caffeine. Other plants put out hormones and enzymes that block germination of competing plants. 

We know that algae and phytoplankton respire at night dropping the available O2 levels, often dramatically. Different rotifers feed on plankton, yet require O2. I wonder then, is that respire dark phase a natural defense to the rotifers? I imagine the densest part of a bloom might drop O2 levels to below 2 ppm, at which time everything dies.

If you aerate continuously with an efficient diffuser you would be at least evening out the O2 levels in the water body. That would seem to break the plankton and algae defense and allow the zooplankton and rotifers to flourish. That would allow step two of the food chain to work efficiently both eliminating excessive algae and phytoplankton growth and increasing the carrying capacity of the entire water body.


Am I off base with that?


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## PapawSmith (Feb 13, 2007)

I hope someone else has the keys to your car. You've had way too much to drink already today.


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## garryc (Jan 21, 2006)

PapawSmith said:


> I hope someone else has the keys to your car. You've had way too much to drink already today.


Never touch the stuff. 

I know that if you increase the base of any food chain you increase the carrying capacity of the system. There is no, or very little, direct transition from plankton to higher levels without the zooplankton and rotifers. So by simple progression increasing the level of those microscopic creatures we can increase the size and number of the top of the food chain. Rotifers are actually being raised to feed fish fry.

Preventing plankton algae from effectively respiring, reducing the available O2 and reducing the level of rotifers, we then allow the zooplankton and rotifers to multiply in direct proportion to the available plankton. This enhances the food chain and turns plankton into food the fish can eat. If it takes 10 pounds of prey to make one pound of predator then that ration goes all the way up the food chain. So 10 pounds of rotifers would make 1 pound of minnows and 1/10th pound of bass. Simple math


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## [email protected] (Dec 22, 2006)

I'm not exactly following but it sounds a lot like a movie I recently saw where the plants were making chemicals that were causing people to kill themselves.

The way I understand it is that the bubbles themselves aren't adding much oxygen but lifting volumes of water to the surface to expose the upper molecular level to air continuously, allowing more gas exchange (among otherthings but I'll try to stay on point).

I'm really not sure about all of this, we really need a bioligist to answer but I'll give it a shot. In a body of water that is not being circulated, the planktonic algae will form a layer near the suface. This layer becomes dense enough to block out light below preventing oxygen from being produced below. Once the sun goes down the upper dense layer of plantonic algae begins taking up oxygen and since little or no oxygen was being produced below (or possibly that organic material breakdown is using it up), there is a chance that oxygen could be depleted enough to cause problems. 

I've noticed at certain times the water will go from a greenish tint to more of a brownish tint. I believe this is due to the zooplankton over-consuming the planktonic algae and the color of the zooplankton becomes dominant over the green algae. A similar predator/prey ratio balance that happens much quicker than with fish, say on a daily or weekly basis. Oftentimes in ponds that normally support fish life, oxygen depletion enough to cause a fish kill occurs from an unusual event where either the plantonic algae and or other plants die really fast and the decay uses up oxygen while no oxygen is being produced or the fertility is increased and the plantonic algae outgrows what the zooplankton can eat, then when night comes it takes up too much oxygen. 

When you begin aerating, you may notice that the water is a bit clearer. I believe that probably more or less the same amount of planktonic algae is present but it's being mixed top to bottom giving the appearance that it's clearer rather than being concentrated in the upper level. Since the water is constantly being mixed and exposed to the atmosphere and gases are being exchanged, and light is also penetrating deeper due to the dilution effect, the chance of a fish kill is far less likely. 

In some fish farming operations, fertilizer is added to the point that the planktonic algae bloom is so dense that visability is reduced to 3". This high plankton density also grows more zooplankton for little fish and so on. They get away with this because it is done in shallow, usually 4-5' deep ponds with high oxygen transfer surface agitators that can exchange enough oxygen to make up the difference at night. These surface aerators are more effective at shallow depths at transfering oxygen directly through agitation and circulation but also use considerably more power. Deeper ponds can be aerated better, cheaper with bottom diffuser type but will not support as many pounds per gallon of water as the commercial shallow systems.


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## garryc (Jan 21, 2006)

> I believe this is due to the zooplankton over-consuming the planktonic algae and the color of the zooplankton becomes dominant over the green algae.


No, the phytoplankton is a single cell plant. I does not have enough energy stored in it to survive very long without sun light or nutrition. That turning brown is it dieing.


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## [email protected] (Dec 22, 2006)

It's possible but less likely than brown algae or zooplankton given the circumstances in which it occurs. Not really as far out there as the phytoplankton defending itself against the grazers with chemicals. Only 1 way to find out for sure would be to take a sample and look at it under magnification.


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## garryc (Jan 21, 2006)

> Not really as far out there as the phytoplankton defending itself against the grazers with chemicals.


I didn't say that. I said it depletes the oxygen level which would have the effect of reducing the zooplankton and rotifer level. Now that may be happenstance, but it also may be an evolutionary trait. That zoo plankton and rotifers are dramatically presence have a direct relation to both available food and oxygen is a known fact. If they have food and abundant oxygen they can not fail to flourish.


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## [email protected] (Dec 22, 2006)

So it ABSORBS a chemical to defend against the grazers? My mistake. 

I do think your off base with this idea. It's a necessary part of the life of the plant. All plants do this and I'm pretty sure my lawn isn't trying to kill me. The way I understand it, the microalgae has to produce more oxygen than it takes up and only in unusual circumstances would it take up more than it's making, otherwise we probably wouldn't be standing here since the net result is the source of a large portion of the oxygen on our planet. In effect, if it is taking up more oxygen than it's making...wouldn't it be killing itself as well?

How do you plan to test this hypothesis?


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## garryc (Jan 21, 2006)

> I do think your off base with this idea.



Maybe so. Oxygen is an element by the way, just to be technical


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## [email protected] (Dec 22, 2006)

garryc said:


> Maybe so. Oxygen is an element by the way, just to be technical


Just as much as it is a chemical....since we're being technical.


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## garryc (Jan 21, 2006)

[email protected] said:


> Just as much as it is a chemical....since we're being technical.



I'm just being a smart alec Pond


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