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  • Terry Gronwall

Monday September 27 2021 Honeoye Lake Water Quality

Surface Water Temperature: 67.8 F

Water Clarity: 5.26 Feet

Lake Level: 803.6 Feet above sea level

Lake Level Relative to Weir: +0.1 Feet

Observations: Monday (9/27/21), The water clarity has decreased ~0.25 foot to 5.25 feet and the surface water temperature has decreased ~3.6 F to 67.8 F over the last week. There was Anabaena, Microcystis, Aphanizomenonand, and Lyngbya visible in the water column. The lake mixing event over Labor Day Weekend brought nutrients released from the bottom sediments to the surface which are still fueling a blue-green algae bloom. Open water had visible blue-green algae (small green dots) in the water column, but no surface scum. A number of isolated near North shore locations had dense blue-green algae in the water column because there was a strong SW wind this morning. See picture picture above.

We took the images below of today’s Anabaena (looks like a coiled spring), Microcystis (looks like a blob of cells), Aphanizomenon (looks like a thin long leaf), and Lyngbya (looks like a long straight filament) algae samples using a high-powered microscope. You can Google Anabaena, Microcystis, Aphanizomenon, Lyngbya to learn more about them. For more information on Anabaena and Microcystis 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 Anabaena Microcystis, and Aphanizomenon. Everyone should be very careful to watch for blue-green algae blooms for the next few weeks.

The lake mixed again over Labor Day Weekend (9/4 & 9/5). The lake was still will mixed today (9/27). You can see the lake mixing event on our temperature and dissolved oxygen charts to the left. The temperature and dissolved oxygen at every depth becomes uniform and the lines on the graph converge. When the lake mixed on 9/4-9/5 it mixed some bottom water with phosphorus and ammonia released from the bottom sediments into the whole water column. This has fueled the blue-green algae bloom that we have been having for the last three weeks. This blue-green algae bloom will likely continue until we get much colder fall weather. Surface water temperature 67.8 F. Bottom water temperature 67.8 F.

When a lake stratifies and forms a thermocline the decaying organic matter, dead algae and weed fragments, on the lake bottom consumes dissolved oxygen (DO) in the water below the thermocline. When the DO 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:

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- Click on this link to see the new HLWTF Honeoye Lake Watershed Storm Water Took Kit if you are planning any storm water projects on your property:

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

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

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

- Click on this link to register for the HVA Spotted lantern Fly talk on Wednesday October 6th: <>

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