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[APD] RE: algae growing on leaky plants

>I have an article coauthored by one of the most respected limnologists
>in which the authors suggest not only that this is a mechanism for algae
>growth on leaves, but that it is an evolved-in defense mechanism.  The
>"intentionally" promote growth of algae on their leaves so that herbivores
>more likely to eat the algae and less likely to eat the leaves.

>I won't comment on whether that makes a lot of sense, but that is what
they said.

Algae are easier to digest and possess less cellulose=> both tastier and
more nutritious.
Herbivores will get far more nutrition from periphytion than plants.

Algae also grows much faster and is much more widely available food source
than aquatic macrophytes.
I read that article and it's a goodie. 

It has also been suggested that periphyton protects the plant from UV and
high light.
Bacteria embedded in the periphyton also provide a good protein resource
for tapole growth in frogs. 
There are other tiny critters, worms, insects crawling around in there
making it a good habitat for micro community.

The scale at which plants and periphyton exist are in two different niches.
Jensen 1989 goes into this concept in more detail.  
Folks like to compare them, but in many ways, they are like comparing mice
ecology to Elephant ecology.

The Evergaldes has a lot of periphyton research that has been done and a
lot more coming up and in progress.
Florida has granted IFAS about 2 million$ to do research on all things
I know some of the folks that will working on it and I am eager to see the
final report. 

One of my cohorts is working in Silver springs an doing some periphyton
work and I'm in a couple of other springs using a variety of substrates for
periphyton analysis/quantification. I also use live plants in my research
along with the common glass slides and then the plastic plant leaves which
have the same color, shape and flow characters that a live plant would
except for the cutin layer and the nutrient leakage.

Differences between the plastic vs the live plant can be traced to the
leakage/cutin layer in the living plant leaves.
It's a simple approach but no one's done it before that I am aware of.  
>> Is it possible that when something is in short supply, the other (now)
>> excess nutrients leak out, attracting algae as scavengers to absorb that
>> leakage?

>I talked to Claus Christensen about this at the AGA conference in Houston.
>agreed that plants will leak inorganic nutrients into the water.  I don't
>recall whether he also agreed that the leakage was accelerated by a
>limitation.  It makes sense that it would be.

I've read a number of research article suggesting plants do leak more
nutrients when stressed(salinity, light, nutrients, herbivores, plant
growing at high/max rates) , but the same can be said for algae. So these
muight balance out OR........attrach certain specialist species. 

>I'm not sure what significance this would have.  If those nutrients are
>to the plants then they are probably already present in the water at
>concentrations that are more than sufficient for algae growth. 

>Now extending that thought a little ...

>According to at least one authoritative source some -- perhaps most --
>are capable of autotrophic behavior.  They can use sugars and other fixed
>carbon sources from their environment as direct replacements for the sugars
>they would fix by their own photosynthesis.

Heterotrophic not autotrophic? They are already autotrophes(most).
It's have to be a fairly nutrient poor system such as the oceanic gyres I
would think rather than the rich nutrient planted tank.

I know can you grow Chlamydomonas with just acetate and no light etc.

Generally, it seems that the larger, filamentous species of algae that
generally plague us are less capable of this ability to use various
substrates beside the inorganic nutrients. 

>That made me wonder if plants might leak simple sugars with that leakage
>increasing under at least some conditions of nutrient limitation.  I asked
>around at the local university and a biology professor there told me that
>algae are known to lose quite a bit of fixed carbon when they are nutrient
>stressed, but he wasn't sure that plants did.  More recently I read that
>nutrient-stressed algae can lose as much as 50% of the carbon they fix. 
>are a major source of dissolved organics.

I've read the same thing in some literature on algae, when they are
actively driven at high rates of PS, they will leak out a lot(up tp 50%) as
I think what is important here is to be __species specific__ with the algae
we are talking about. 
There are roughly 25 species or so os "pesky" algae not including diatoms
which are in most aquarium samples.  
Not a lot.
Know thy enemy.
Most are greens and most are filimanetous. 

>If plants show the same or similar behavior then they could leak organics
>the water that some algae -- acting autotrophically -- might use.  If so
>we would have not only an explanation for why algae problems crop up when
>plants are nutrient-stressed, but also a part of the answer to why such a
>small number of algaes (out of the thousands out there) seem to reach
>levels in mature planted aquariums.

>This is all a rather complicated speculation that needs quite a bit of
>experimental work.  Just the same, the concept is to me an appealing
>explanation for some of the odd plant-algae relationships we see in

I can give you some feedback as I need to do some researching on this issue
coming uop soon anyway, it's one of the topics for a review paper myself
and a couple of other folks hope to publish. It'll be more based with
natural systems though.

Tom Barr

>Roger Miller

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