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  • Terry Gronwall

Monday July 12th 2021 Honeoye Lake Water Quality

Surface Water Temperature: 75.4 F

Water Clarity: 10.2 Feet

Lake Level: 803.3 Feet above sea level

Lake Level Relative to Weir: -0.2 Feet

Observations: Monday (7/12/21), The water clarity has decreased by ~1.3 feet over the last week to 10.2 feet and the surface water temperature has decreased 0.5 degrees Fahrenheit to 75.4 Fahrenheit. There was Gloeotrichia, an early season blue-green algae species, visible in the water column in most areas of the lake this morning. The Gloeotrichia varied from light to medium depending on location. We also found sparse amounts of anabaena a blue-green algae species which usually arrives in July. We did not see any Gloeotrichia or Anabaena surface scum. For more information on Gloeotrichia and Anabaena see the articles at HARMFUL ALGAL BLOOMS | Honeoye Lake (

The DEC recommends that you, your family, and pets avoid contact with water that contains blue-green algae bloom like Gloeotrichia. Everyone should be very careful to watch for blue-green algae blooms for the next few weeks.

Last week we made aquatic vegetation maps for use by the Honeoye Lake Weed Harvesting crew to give them information to be able to focus their efforts on areas of the lake where aquatic vegetation is growing to the lake surface (red areas on the maps) impeding recreational us of the lake. See our early July 2021 maps below:

We found that the aquatic vegetation growth was several weeks behind last years (2020) growth, but similar to what we found in late June in 2019. See 2021, 2020, & 2019, late June macrophyte maps at AQUATIC VEGETATION MANAGEMENT | Honeoye Lake (

Today, July 12th, the lake remains stratified releasing legacy phosphorus from the bottom sediments all over again. When a lake stratifies and forms a thermocline the decaying organic matter, dead algae and weed fragments, on the lake bottom consumes dissolved oxygen in the water below the thermocline. When the dissolved oxygen has been completely consumed the phosphorus iron bond in the bottom sediments becomes weak releasing legacy phosphorus into the water near the bottom sediments.

Always use your own visual assessment before making contact with the lake water at this time of year as the blue-green algae situation can change daily if not hourly. Please regularly check the DEC HABs alert map for more detailed updates on Honeoye Lake HABs alerts:

Click on the blue outlined box that says "Log in / Sign up" in the upper right hand corner of this page to sign-up to be notified when we update our weekly Honeoye Lake water quality blog.


- Click on this link for "2021 Honeoye Lake Aeration Engineering Planning Project"

- The NYSDEC has recently released a new report “Feasibility Assessment of Harmful Algal Bloom Management Options for Honeoye Lake and Conesus Lake” as a follow-up to their 2018 Honeoye and Conesus Lake HABs Action Plans. Click on the link SCIENTIFIC RESEARCH | Honeoye Lake ( to see report:

This report evaluates various techniques for mitigating Harmful Algae Blooms in Honeoye Lake by preventing the release of legacy phosphorus from the lake bottom sediments.

- Click on this link for HLWTF Winter newsletter: e6fc30_ef8d01223f42408ba11b3a7a5f83bebe.pdf

- Click on this link for "2020 Water Quality: What, Why, What's Next"

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