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Jenne Lake, Beaverton, native plant restoration #838144

Asked June 28, 2023, 5:45 PM EDT

Is the vegetation in the attached photos filamentous algae? is it a sign of poor water quality? This is growing in Jenne Lake in Beaverton, Oregon, which is a 1.98 acre man-made lake. Does this need to be controlled for water quality issues? We are applying for a small grant to TSWCD to revegetate the lakeshore with natives. That may help with runoff and erosion, But every summer this returns. Are there other approaches we should use? I'd prefer to avoid damaging toxins.

Washington County Oregon

Expert Response

Hi Wayne:

The photos your shared from Jenne Lake in Washington county resemble curly pondweed (Potamogeton crispus). The photos show wavy oblong "lasagne" shaped leaves, that alternate along a somewhat flatten stem. 


https://fortress.wa.gov/ecy/gisresources/lakes/AquaticPlantGuide/descriptions/potcri.html

Curly pondweed is an indicator of slow moving waters, accumulated sediments, nutrients and high sunlight.  Although a nusiance when in abundance, the plant traps nutrients and its dense growth creates shading that can prevent heavy algae growth.  However, high densities of curly pondweed can die off mid to late summer, creating oxygen poor water and odors.  Where possible it is best to physically remove the plants by raking before they decompose.

Shade, preventing further sediment accumulation, creating greater constant water movement with cirulators and raking/removal will help minimize both pondweed and algae growth.

Curly pondweed reproduces readily from fragments of the plant, its rhizomes (stems) and sometimes seeds  The plant  of Eurasian, African or Australian origin, was likely a plant that "tagged along" with carp fish  introduced from Europe to the USA in the late 19th century.  Since then the plant has spread through contaminated equipment, water craft, pond nursery plants contaminated curly pondweed fragments and although rare -birds.

Please feel free to contact me by phone if I can be of further assistance.

Sam

Samuel S. Chan

Statewide Watershed Health and Aquatic Invasive Species Specialist

Broader Impacts Research Team Leader, NSF Water Sustainability 2100

Sea Grant College Program; Extension Service, Oregon State University

1600 SW Western Blvd. Suite 350, Corvallis, OR, 97330 USA

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An Ask Extension Expert Replied June 29, 2023, 6:53 PM EDT

Thank you, Sam.

We are applying for a grant with the TSWCD to improve vegetation management around the lake. This information will be helpful.

 

A question occurs to me – Do you have expertise in Goose management. That is, knowing how to determine if the goose population on a small man-made lake is too large for maintaining  water quality? And what to do?

                Wayne

 

Wayne Rifer

245 NW Silverado Dr.

Beaverton, OR 97006

Mobile: +<personal data hidden>

<personal data hidden>

 

From: ask=<personal data hidden> <ask=<personal data hidden>> On Behalf Of Ask Extension
Sent: Thursday, June 29, 2023 3:53 PM
To: Wayne Rifer <<personal data hidden>>
Subject: Re: Jenne Lake, Beaverton, native plant restoration (#0108070)

 

The Question Asker Replied June 30, 2023, 2:37 PM EDT
Thanks for your call today!  In regards to native geese management, ODFW will have the expertise, including those situations where the geese become a nuisance.

https://www.dfw.state.or.us/resources/hunting/waterfowl/goose-permits/docs/Pacific%20Northwest%20Goose%20Management%20Aug2017.pdf
An Ask Extension Expert Replied July 06, 2023, 6:24 PM EDT

Samuel,

Thank you so much for your response and valuable information. Now I have a question. Or I write to ask advice.

 

Jenne Lake is really a mess now with extensive algae growth as well as curly pondweed. We have a landscape management firm that has poisoned the pondweed a few weeks ago and plans to do so again. So it will be dying off, I expect. They do not have budget to rake it out, so likely it will decay in the lake. I’m just wondering what kind of problems that may create for us. I don’t know where we could get the money to remove it.

 

When the rains arrive, that may flush the algae out and refresh the lake water. I’m concerned it may be stinky soon, since the drought seems to persist.

 

Do you have any ideas? Pretty vague question, but I was talking with the landscape managers today, and didn’t know whether I should tell them not to kill the pondweed. He said they generally just kill it and leave it.

 

Thank you for any advice you may have,

                wayne

 

 

 

Wayne Rifer

245 NW Silverado Dr.

Beaverton, OR 97006

Mobile: +<personal data hidden>

<personal data hidden>

 

From: ask=<personal data hidden> <ask=<personal data hidden>> On Behalf Of Ask Extension
Sent: Thursday, June 29, 2023 3:53 PM
To: Wayne Rifer <<personal data hidden>>
Subject: Re: Jenne Lake, Beaverton, native plant restoration (#0108070)

 

The Question Asker Replied August 23, 2023, 1:01 AM EDT
Hi Wayne.

Thanks for updating me. The heat wave and long dry spell is stressing aquatic systems and even our weather. Offshkre surface ocean temperatures have been about 7 to 9 degrees F above historic norms since late July. This has also partially contributed to the hot weather.

In the absence of fresh water flow and cooler temps, rhe decaying pondweed may lead to some odor issues and lower dissolved oxygen in the coming weeks. This may stress the fish and other aquatic organisms untill the rains and cooler temps return. The nutrients released from the decaying pondweed may encourage further algae growth.

One way to mitigate this is to install some temporary water circulators to move the water, aerate, to encourage and disperse concentrations of decomposing plants.
The circulators will also discourage the formation of large string algae mats.

Best regards.  Sam

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From: <personal data hidden> <<personal data hidden>>
Sent: Tuesday, August 22, 2023 9:48:04 PM
To: 'Ask Extension' <<personal data hidden>>; Chan, Samuel <<personal data hidden>>
Subject: RE: Jenne Lake, Beaverton, native plant restoration (#0108070)
 

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Samuel,

Thank you so much for your response and valuable information. Now I have a question. Or I write to ask advice.

 

Jenne Lake is really a mess now with extensive algae growth as well as curly pondweed. We have a landscape management firm that has poisoned the pondweed a few weeks ago and plans to do so again. So it will be dying off, I expect. They do not have budget to rake it out, so likely it will decay in the lake. I’m just wondering what kind of problems that may create for us. I don’t know where we could get the money to remove it.

 

When the rains arrive, that may flush the algae out and refresh the lake water. I’m concerned it may be stinky soon, since the drought seems to persist.

 

Do you have any ideas? Pretty vague question, but I was talking with the landscape managers today, and didn’t know whether I should tell them not to kill the pondweed. He said they generally just kill it and leave it.

 

Thank you for any advice you may have,

                wayne

 

 

 

Wayne Rifer

245 NW Silverado Dr.

Beaverton, OR 97006

Mobile: +<personal data hidden>

<personal data hidden>

 

From: ask=<personal data hidden> <ask=<personal data hidden>> On Behalf Of Ask Extension
Sent: Thursday, June 29, 2023 3:53 PM
To: Wayne Rifer <<personal data hidden>>
Subject: Re: Jenne Lake, Beaverton, native plant restoration (#0108070)

 

The Question Asker Replied August 23, 2023, 1:58 AM EDT

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