String algae. works for me

[Meyer Jordan]

This is what I have come across so far. I'm rooting some willow branches in my substrate pond right now and hope to update that thread soon. Apparently both birch and willow have salicin in their bark and roots,
http://www.wef.org/PublicInformation/page.aspx?id=775

edit, some additional resources
http://www.fairfaxcounty.gov/nvswcd/sciencefair/moscoso.htm

http://biosurvey.ou.edu/oas/02/papers/lFimple02.htm (this one doesn't seem to want to display the webpage properly in my browser, maybe someone else can test it out)

Your last link displayed OK in my browser and was the most detailed. It suggests that salicin as salicylic acid may also have the effect of blocking nutrient (Phosphorus) absorption in aquatic plants, which may be collateral damage that is not really wanted.

 

[MitchM]

Your last link displayed OK in my browser and was the most detailed. It suggests that salicin as salicylic acid may also have the effect of blocking nutrient (Phosphorus) absorption in aquatic plants, which may be collateral damage that is not really wanted.

I'm not clear yet as to whether that has more of an effect on algae that gets phosphorus from the water column, or rooted plants that obtain phosphorus from the substrate.

 

[Meyer Jordan]

I'm not clear yet as to whether that has more of an effect on algae that gets phosphorus from the water column, or rooted plants that obtain phosphorus from the substrate.

The authors of the paper were not clear either. First of all, the hypothesis was only tested on one specie of algae, Closterium, which is hardly definitive.

It also seems that the authors also were making a logical assumptive deduction that some level of nutrient blocking action would occur on aquatic plants. What the level of this blocking action would be is anyone's guess based on the limited data available.

 

[MitchM]

I found some anecdotal accounts on some freshwater forums, so I'll continue to look for some valid studies.
Thanks Meyer.