Pond Boss Forums INTRO Questions & Observations Are the Nutrients in a Pond "Well Mixed"?

Tired of fighting filamentous algae (FA), so I had an idea about controlling some of the nutrients utilized by the FA.

Do the nutrients primarily follow the flow of water in a pond, or does diffusion also control the local concentration of nutrients?

I have a good spot with clay very close to the surface to create a shallow marsh or bog adjacent to a 0.75-acre main fishing pond. I could easily strip the topsoil and get down to the clay at 2 feet and make a bay that was an additional 0.25 acres. After compacting, I could push back about 6" of topsoil to make the area very efficient for growing rooted aquatic plants, or could even deliberately start rice or millet. I would just let that area go and be a heavily vegetated oxygen source.

Question for the experts:

Would that area of abundant plants do an effective job of "stealing" the pond nutrients away from the FA?

I don't have any electricity in this area. However, it is in open ground that is typically subject to pretty good Kansas winds. I know from experience that the winds in our area are quite effective at stirring up open water. Unfortunately, I do NOT think the wind would stir up the water very much in the shallow bay with an emergent plant stalk protruding every 2 inches of exposed pond surface.

Hence my question about diffusion. If that plant-filled bay became "nutrient limited" as the plants proliferated, would it draw nutrients from the open-water area of the pond, or would that process be functionally insignificant?

P.S. The pond would be a BG/RES/LMB pond. I have tons of gambusia in the creek, so I would think the weed-filled bay would produce a million gams for the BG and small bass to eat. I would also put some heavy landscape fabric in the middle of the bay to see if I can keep some water open for the ducks, rather than controlling the plants in a "duck hunting pond" by raising and lowering the water levels.

Any advice and comments would be appreciated!

FishinRod, I am very interested in the replies you'll get from this wonderful question. If the macrophytes do deplete the nutrients in the bay, I suppose you could create a temporary current to move enriched water into and through the vegetation with a stationary boat and outboard, or a duck hunter's Ice Eater or other pump.

That's a great question and I've been dealing with it as well with some pretty good success this summer. I wrote thread about it:

https://forums.pondboss.com/ubbthreads.php?ubb=showflat&Main=44176&Number=576011#Post576011

My questions would be, how is your pond fed? How much water flows through your pond, is there a source of nutrients from farming or a swamp? Is your pond surrounded by vegetation or is it a manicured lawn all around it?

Also check out this article:

https://www.mdpi.com/2504-3129/5/4/53

Im not sure where you are located but do your weeds die off in the winter? If so that adds nutrients as well.

I guess in a nutshell you need something to use up the excess nutrients either before they hit your pond or once they hit your pond. Once in your pond theyll be used up by vegetation or potentially vegetation around your pond ie. trees and shore weeds/plants. There might be some denitrification and ammonia removal with the right type of aeration like cascade or water fountain potentially, check out the many studies online to see how waste water treatment plants deal with removing excess nutrients from effluent ponds.

Im pretty sure adding an area of weeds as a biofilter will be a good thing.

Cheers.

Pond would be topped off by creek water as needed. Planning to install a bottom drain to pull down and exchange some water as required.

Our creek is in a major sand bed. After the initial pulse of a big rain passes, the creek water elevation is absolutely determined by the regional aquifer level. When the farmers fertilize in the watershed, I am pretty sure the first decent rain brings some of the excess fertilizers into the aquifer, and then shortly thereafter into the creek water. I do not pull any water during the application period for fall fertilizer.

This pond is surrounded by multi-species tallgrass prairie. The height variance across the field traps almost everything blown by the wind.

We do get the first hard frost around the end of October. The winter is then cold enough to ice over small ponds. Some of our plants die off and re-grow from new shoots the next year. Some of our plants go dormant and then re-grow in the same vascular system the next year.

If I left the "bay" as a hard clay bottom, I could probably bush hog it and then chain harrow the material out of the pond basin. That wouldn't work with 6" of top soil put back into the pond. That would be too soft to mow unless I let it bake in the summer.

The other option would be pull the water down a little in the early spring and just burn the dried out vegetation. I have experience performing patch burns on our prairie grass since it is a fire adapted system that grows better after a burn.

Contemplating a prescribed burn brings in another interesting option. How many nutrients remain in the ash? What happens when the ash goes into the main body of the pond after the water level goes back up? Would the escaping volatile gases during a burn remove some of the nutrients out of the pond basin eutrophic cycle?

My ground is generally flat. However, to the east is some very rolling terrain called the Flint Hills. The ranchers there do completely property burns every spring, frequently several thousand acres at a time. The draws between the hills contain lots of watershed ponds of varying sizes. The subsequent rains have to wash a lot of ash into the ponds. I rarely see those ponds as weed-choked marshes, so I assume the ash is not overly detrimental?

[Just throwing out more data if this becomes a longer discussion thread.]

Hmm, interesting idea about burning, but wood ash is alkaline and still contains phosphorus....its hard to make that stuff go away but maybe less so than decaying plant matter.

I do notice that areas of my lake that are just clay dont have much weed growth, and seems to have shorter weeds - but I expect that might change as more materials decay and gather.

People have mentioned phosphorous binders and algaecides but i prefer to keep things more chemical free if i can.

When I had a bloom in the drought we just had I blasted water in from my upper swamp and it cleared the bloom right out and really cleaned up the water.

Could a wind vane aerator be used with creative plumbing to pull water from the main basin and discharge it in the bog filter? It is an efficient way to move water, just cannot do much gain in elevation.

liquid, I agree with that plan as an improvement after I get electricity on location. Circulating "bog filters" are very efficient at moving pond nutrients to the desirable plants.

I just wanted to start a thread to see if any of our experts thought a "passive" system might be worthwhile, or if it would only make a trivial difference.