Allelopathy and Algae

[SHARPiE]

I have my hands on a copy of "Ecology of the Planted Aquarium" by Diana Walstad. It's a little outdated, but I believe the facts in this book are sighted and scientifically sound.
The Allelopathy section is an interesting read (I find chemistry and biology fascinating!)


Alage growth was tracked as a function of phenolics (humic substances or tannins) over a two year period, in 6 ponds. Seasonal floods meant that the phenolics concentration was between 4 to 26 mg/l. When phenolics were above 10 mg/l, algae and cyanobacteria growth was moderatley lessened.

Although phenolic allochemicals may help algae control, other compound types would be involoved in allelopathy.

• Skunk Weed produces two sulfur containing compounds, which were found to strongly inhibit algal growth.
• Fatty Acids found in water contacining spikerush inhibited blue-green algae.

Although most allelochemicals midly inhibit algae growth, some are more potent than others. Not all plants release algae inhibiting allelochemicals.


So from this info I draw this conclusion:

Plant's dont just "out-compete" the algae for nutrients, the release of the allochemical (which isn't condicive of plant growth) is what can strongly inhibit algae growth.
I agree that light can control algae, however if you blackout the tank, you not only inhibit the algae, but the flora you are trying to promote.
If you have a planted tank and are combating algae, check into which plants you can get that release algae inhibiting allelochemicals.


Has anyone else read into this topic?
Does anyone have a list of plants that release algae prohibiting allochemicals?

 

[aqua_chem]

Honestly, there are some gaping holes in the Allelopathy theory that need to be addressed.

One major one is activated carbon. Large molecules such as phenols should adsorb onto AC, effectively removing them permanently. But do we see huge algae blooms when AC is used? Not that I have ever heard of or observed. This leaves us with some questions about the veracity of these claims.

I don't think skunkweed is actually an aquatic plant. That being said, spikerush belongs to the family eleocharis, which includes dwarf hair grass. This was well documented and published by chemists (represent!) in the early 90s.


Here's a nifty read on the topic. The author takes a critical standpoint of Diana Walstad's book, which is a good alternate perspective. For what it's worth, Walstad only has a BS in microbiology, whereas this guy has a Ph.D and is an associate professor at the University of Coppenhagen and studies plant physiology.