Regarding strong sunlight and suspended algae...

[MitchM]

Problems with suspended algae during hot sunny weather?

How many of us knew that a contributor to algae blooms during periods of strong sunlight can be caused by the bond between DOC's (dissolved organic carbon) and iron to break, thereby making iron available to algae for a nutrient? I did not previously know that.

This is from the book 'Ecology of the Planted Aquarium" by Diana Walstad.

Plants can get their iron from the substrate, but algae depend on free iron (Fe2 + and Fe3 +) in the water. Although iron in the water is indeed bound up, often to dissolved organic carbon, it is made transiently available by a common process called the ‘photoreduction of iron’. The reaction for the photoreduction of DOC-bound iron is: DOC-Fe3 + + light ⇒ Fe2 + + oxidized DOC This light-requiring reaction, which also applies to manganese and copper, is greatly accelerated by DOC [31,32,33]. The photoreduction of DOC-bound iron is invariably accompanied by the decomposition of DOC (see page 59). 4 The Fe2 + released may be taken up by algae or quickly oxidized to Fe3 +, which can also be taken up by algae or bind to fresh DOC, whereby the process repeats itself.


I recommend anyone interested in plants and their contribution to water quality to download the ebook. It was about $10 CDN from Amazon.

(no, I'm not a vendor.)

 

[Priscilla]

Awesome. What does it mean? LOL! Seriously though, what does it mean? Bit on the technical side for me.

 

[Mmathis]

I'm with Priscilla..... Is it saying that the sunlight causes the bond to break, releasing the iron, which is then used by the algae?

I thing some of my plants are lacking in iron, but afraid to add it -- afraid to spark the algae!

 

[Tula]

Too many nutrients in the water....DOC ?

 

[MitchM]

Unless you have a pond with a stream running through it, our ponds are basically a nutrient trap and it's up to us to remove excess nutrients, right?

We're always reading threads from pond owners each spring where they suddenly have green water.

There are so many chemical reactions constantly taking place while the water adjusts to changing temperature, decaying organic matter, food additions, fish producing waste, ...ect, that it's not reasonable to pinpoint one thing to do that keeps excess algae at bay.
I found it pretty interesting that sunlight can make iron available as food for algae.
Iron has been shown to stay in solution (before it oxidizes) for 13 hours at a PH of 6.3, but will stay in solution for only about 3 minutes at a PH of 8. If your pond water has a lower PH, your plants have a better chance of using iron for their growth.


I've learned that floating plants like water lettuce and water hyacinth are most effecient at consuming ammonia, submerged plants prefer to get their nitrogen from ammonium at lower PH levels, emergent plants (bog plants) have the best of both worlds - their roots are submerged in pond substrate while their leaves can use atmospheric CO2 which is more abundant than CO2 in your pond water.

TM, LisaK found that a foliar application of iron fertilizer helped her plants, that makes sense, doesn't it?
The tip roots of pond plants can access oxidized iron, but it takes longer.

Anyways, cool stuff, imo.

.

 

[MitchM]

Too many nutrients in the water....DOC ?

DOC's are always present. "Too many" is subjective. DOC's can be beneficial - they adsorb heavy metals.

 

[Mmathis]

@MitchM I just posted this in another thread that I started, but will post here as well: Advice, please, on a product to use as a foliar spray for iron...... Brands would be nice, and advice on applying it.