Monday September 22, 2025 Honeoye Lake Water Quality
- Terry Gronwall
- Sep 23
- 3 min read
There has been very little change in the blue-green algae bloom over the last week. However, we still expect the bloom to slowly dissipate over the next several weeks.
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Monday September 22, 2025 Honeoye Lake Water Quality
Surface Water Temperature: ~68.4 F
Water Clarity: ~4.6 Feet
Lake Level: 802.4 Feet above sea level
Observations: Monday (9/22/25), Water clarity was ~4.6 feet about 0.7 feet less than last week. Today had an overcast sky which reduced the measured water clarity. The surface water temperature was ~68.4 F about 0.9 F Colder than last week. A beautiful day to be out on Honeoye Lake as fall color is starting to appear!
There has been very little change in the amount of blue-green algae in the water column over the last week. On cloudy windy days like Monday 9/22 the blue-green algae moves lower in the water column and is not very visible (See top picture on left). However, on a calm sunny day like Tuesday 9/23 the blue-green algae rises to the surface and forms
a visible surface scum (See bottom picture on the left at the same location as the top picture). Therefore, we expect that there will continue to be surface blue-green algae blooms at isolated near shore and open water locations around the lake given the amount of blue-green algae in the water column for the next few weeks particularly when we have 80-90 F days with calm winds. There were 9 blue-green algae blooms on Honeoye Lake reported to the NYS DEC HABs alert map, dark blue circle, over the last two weeks. The light blue circles are blue-green algae blooms reported to the DEC more than two weeks ago. See NYS DEC HABs alert map below: Since Honeoye Lake has ~10 miles of shoreline your most accurate source of blue-green algae blooms is the crowd source bloom data found on the DEC HABs alert map (NYHABS).
The Finger Lake Region has been experiencing heavy HABs over the last few weeks. September is often the peak month for HABs. See today’s DEC Finger Lakes HABs alert map below:
Anabaena (Dolchospermum) (looks like a spring or chain of beads), Limnoraphis (looks like a rod), and Microcystis (looks like a group of small round cells) are the current dominant blue-green algae species. See picture on the left. You should be watchful for Microcystis, Anabaena, and Limnoraphis blooms lake wide. These are all blue-green (cyanobacteria) algae species. More information on blue-green algae can be found at: https://www.honeoyelakewatershed.org/habs
Several research studies have found that most of the phosphorus that fuels Honeoye Lake’s blue-green algae blooms is released from the lake bottom sediments when the lake’s dissolved oxygen level goes below 0.5 mg/L in the deeper parts of the lake breaking the phosphors/iron bond in the bottom sediments releasing phosphorus into the water column. The dissolved oxygen (DO) level near the lake bottom at ~9 m (~30 feet) was 7.84 mg/L today. This means that phosphorus is not currently being released from the deep bottom sediments into the deepest part of the lake water. We had a complete lake mixing event in late August that mixed the deep lake water, with excessive amounts of phosphorus, with the whole water column fueling the blue-green algae bloom the lake has been experiencing in September. See temperature and DO graphs to the left.
You can see the complete lake mixing event in late August on the above Temperature and Dissolved Oxygen graphs where the 0-9 m lines have converged to the same level. Also, you can see that the lake started to stratify again last week but completely mixed again in the last few days and is isothermal (water temperature uniform at all water depths) again today.
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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2025 Honeoye Lake Fishery Update
Pete Austerman
Aquatic Biologist
NYSDEC Region 8 Fisheries
Click on the link below:
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Click on the link below to see the Honeoye Lake Watershed Task Force 2025 Winter Newsletter:
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All operators of motorized vessels, regardless of age, will need a boating safety certificate by January 1, 2025.
Click on the link below for more information on how to get a NYS Safe Boating certificate:
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Click on the link below to see the Honeoye Lake Watershed Stormwater Toolkit:
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