Duckweed in the news

[Tanked]

While searching for something else on the web I found a story about Sharon Lake in Hamilton County Ohio.  Late this summer the sluice gates on the dam will be opened to drain the lake for dredging.  The fish must fend for themselves.  Some will be flushed into the nearby creek the others will die in the muck, or be eaten by predators.  The dredged material will be used to create nutrient rich “wetlands” that will add additional water filtration and attract new wildlife. The 35 acre lake will be “restored” by 2025. 

This is part of a larger restoration plan that will hopefully make future draining of the lake for dredging unnecessary.

What I find interesting is the WHY?  Apparently 35 years of runoff has created a deep layer of nutrient rich sediment.  The sediment has caused DUCKWEED to “grow rampant.” 

According to the Great Parks of Hamilton County: 

• “Duckweed robs the water of oxygen and sunlight, both important to fish and plants.
• “Duckweed impedes boats and other recreational activities.”

 

What I find interesting is the WHY?  Apparently 35 years of runoff has created a deep layer of nutrient rich sediment.  The sediment has caused DUCKWEED to “grow rampant.” 

The Duckweed onslaught ebbs and flows over the years, but a July ’21 Google Earth photo indicates that it can be a real problem.  On the other hand, it could have been a picture of a major algae bloom! 

According to their website the lake is limited to fishing and the biggest registered recreational watercraft that you can pick up and carry.  My kayak has never been impeded by Duckweed. I can’t say the same for a massive water lily explosion on a lake closer to home.  I might have to set a day aside to see for myself how bad it really is.

[Odd Duck]

Duckweed appears to have choked out my Wolffia.  Wolffia.  Once more - Wolffia, the tiniest, most insidious, most easily spreadable plant I’ve ever come across, got choked out by duckweed.

Any floating plant that grows densely enough to inhibit surface gas exchange can be problematic for the fish below and block enough light to be problematic for the plants below.  I once had a tank crash that I’m fairly certain happened because the red root floaters got too dense and covered the entire surface of the tank to over an inch thick.  I now limit my floaters to no more than 75% of the tank surface or less now, unless there’s very good water circulation and even with that, I usually try to keep it less.  Yes, they produce oxygen but most is sent into the air, not the water.

[nabokovfan87]

Someone needs to design a boat with a comb attachment to get rid of duckweed.

Feed it to compost.... Win win.

I first saw this off mark's shrimp tanks video. Here's an example.

 

Edited June 2, 2023 by nabokovfan87

[Andy's Fish Den]

I saw a show several years ago on TV, maybe something like Dirty Jobs , they were showing a lake someplace down south that water hyacinth and duckweed had grown so thick that boats could not navigate. There was a boat with a conveyer sort of thing on the front that would pull the hyacinth and some duckweed up out of the water and into a pile that then got off loaded into a dump truck to be taken someplace to be composted. I remember them saying that they were working on something new to be able to strain the duckweed because a lot of it fell through and went back into the waterway so there was some areas that was chock full of duckweed and it was growing very thick, and becoming difficult for boats to get through. 

[Tanked]

I find it hard to believe that duckweed is responsible for the required dredging.  I am also curious as to where these "wetlands" will be located, and wonder if they will drain back into the lake?  Once again, I guess a road trip is in order to  see for myself. 

The lily pads in one inlet of a different lake are 12" wide.  Having roots and stems anchored in the lake bottom, they actually can impede boat traffic.  They completely cover the surface, and are so numerous that it's a struggle to get a kayak in there.  On the upside, the District has removed lilies at the innermost point to provide a waterfowl sanctuary.  On the downside, The lilies have expanded their range and are invading the rest of the lake.

On 6/2/2023 at 4:35 AM, Pepere said:

All that goes through my mind, is “good luck with that plan”…

I have a hard time believing that dredging the nutrient rich sediment will be a game changer.  
 

I fully realize I might be wrong and this may be a proven solution, but I have fund Duckweed such a pernicious problem plant, I wouldn't be all that hopeful.

I'm sure that the plan will seriously reduce the DW population in the lake, but I think it will also introduce DW and sediment  to the creek on the other side of the dam. I doubt that DW and sediment remediation is the  only reason to totally drain the lake.

[Tanked]

On 6/2/2023 at 10:20 AM, Pepere said:

I marvel at the audacity of humankind to contemplate draining a lake to dredge it and remediate it….

 

Can anyone contemplate doing this without mechanized equipment?   How many acres is this lake?

I know a man with a lake big enough to ride his jet skies on.  Over the last 20 years runoff has reduced it to a small farm pond.

Unfortunately, without our help, lakes will eventually silt up and disappear.  It is my understanding that Sharon creek was dammed in 1936 creating a 30 acre lake.  Somewhere in the past it was drained and dredged, enlarging it to 35 acres.  If you want to keep a lake, dredging will be needed.  I have a problem getting my head around DW being listed as the cause and impeding boats.  I can't begin to imagine any part of this project without mechanized equipment.

[sumplkrum]

Completely silly ... if they miss one piece, they'll have to dredge it again. 😂

And if they're going to move that material to make 'wetlands', they'll essentially just be making a swamp full of duckweed.

[Torrey]

On 6/2/2023 at 8:57 AM, Tanked said:

you want to keep a lake, dredging will be needed. 

Or, reestablish the plants and animals that help keep wild rivers clean and healthy.

Our (lack of) hubris keeps creating problems:

Bugs are pests!!! ==> Chemical assault, or introduction of invasive species as population control, or some other quick fix that causes long term problems

Dam river for lakes, electricity, and control flooding down stream so we can build more houses==> water not being returned to aquifers, beavers not being allowed to do their jobs of shaping rivers, wetlands and lakes....

An overgrowth of duckweed in nature indicates imbalance.

Duckweed will grow up to 4" deep in an aquarium, before the bottom layer starts breaking down and returning nutrients to the soil.

The mat in one of my tanks is thick enough to support riparian plants, but proper water movement keeps the duckweed, dwarf water lettuce, and dwarf hyacinth to a 10" × 4" × 4" chunk. (Some hyacinth roots are 18" long, but fish and shrimp easily navigate through the roots)

I'm watching nature try to heal herself in my tank, and watching (and learning) that everything has a purpose... even if I don't understand it yet.

So what's in the lake causing the duckweed to feel like it needs to choke out what's underneath, and attempt a restart?

Duckweed is FABULOUS at phytoremediation.

What is it cleaning up?

Is it a good idea to disturb it, whatever "it" is?

The water ways that are being rewilded under the supervision of various First Nations in Canada, as well as Indigenous supervision in the Pacific Northwest, the coastal areas of Maine & NY, and I believe the wild rice in Montana and the Dakotas are performing better than the Army Corps of Engineers remediation projects.

 

Maybe find out who is overseeing this project @Tanked and you'll have a better idea at the likelihood of success based on the most recently published papers.