Re:Uptake of nutrients by aquatic plants

>Date: Thu, 21 Sep 95 10:31:33 CST
>Subject: RE: Aquatic Plants Digest V1 #24
>I am replying to  the comment about rooted plants outcompeting algae
>for nutrients.  Scientifically, there is no good basis for this statement
>if you mean nutrients in the water.  Research has shown that rooted
>plants take most of their required nitrogen and phosphorus from the
>sediment, not the water.  Algae are much more efficient at taking up
>nutrients from the water than rooted plants.  However, the dense plants
>will keep the sediment nutrients from leaching into the water, which
>then in turn promotes algal growth.
>John D. Madsen, PhD

I agree that it does not appear that most rooted aquatics can out-compete
green water algae for nutrients to the point where the algae disappears.
My experience has been that green water algae avidly take up nutrients and,
for nitrogen, at least, I get no detectible amounts in most green water
with my Hatch kit.   However, I have seen such rapid responses in rooted
aquatics when I add even tiny amounts of nutrients to the water, that I
have to conclude that they have good mechanisms for getting nutrients out
of water.  There does seem to be quite a bit of evidence that submerged
aquatics have a transpiration stream, and, therefore, they may pull
considerable volumes of water into their roots.  I suspect that this
transpiration stream plays an important role in nutrient uptake.

Does the research you mention show that aquatic plants take most of their
nitrogen and phosphorus from the sediment even when there is also a supply
of these nutrients in the water?

Paul Krombholz                  Tougaloo College, Tougaloo, MS  39174