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[APD] RE: algae/plant competition and uptake rates

Tom -

Thanks for your comments. 

>I'm suggesting, as I have for some time, that algae "know" when something
>else is growing and if the system is stable.

And I guess that this is where I find the thought of allelopathy so
attractive. I think we can all agree that algae are not well organized
enough to set up the bureaucracies necessary to do assays or surveys, or
even have a good look around. So how do they "know" when there's good plant
growth? What other explanation could there be than something in the water?

In effect, you're saying that the plant growth inhibits algae growing in
the same body of water. You can't explain how it happens, but you're sure
that it's NOT the plants secreting some chemicals that inhibit the algae,
because that would be allelopathy.

So I guess I'm at the point where I understand except for that last point.
Short of plant telepathy, how would the algae "know" the plants were
growing well unless there was some chemical secretion?

If the answer is that no one understands how this inhibition works, I can
accept that. But then it seems like a long stretch to say it can't be
allelopathy. Even the activated carbon argument doesn't necessarily hold
water if the mechanisms are poorly understood. After all, activated carbon
is pretty much saturated after only a short time in a high-DOC environment.
Maybe it takes that long for algae to rid themselves of allelopathic

An interesting experiment would be to change the carbon daily for a couple
of weeks to keep DOC low for an extended period of time, and see what the
algae do. If they still fail to thrive, that would be much better proof
that it's not allelopathy at work.

- Jim

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