Monday August 25, 2025 Honeoye Lake Water Quality

Terry Gronwall
3 days ago
4 min read

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Surface Water Temperature: ~74.5 F

Water Clarity: ~7.9 Feet

Lake Level: 802.8 Feet above sea level

Observations: Monday (8/25/25), Water clarity was ~7.9 feet about 2.9 feet more

than last week. The increase in water clarity was probably due to the wind blowing the algae away from our deepwater sampling location. The surface water temperature was ~74.5 F about 3.9 F less than last week due to the colder weather we have been having. It was partly cloudy with a light wind today. A beautiful day to be out on Honeoye Lake!

Today the visible blue-green algae was denser in the Northern Lake Basin than the Southern Lake Basin due to wind patterns over the last few days. Over the last week there has been a significant increase in isolated near shore blue-green algae blooms occurring around the lake. See picture on the left. Therefore, we expect that there could still be surface blue-green algae blooms at isolated near shore locations around the lake given the amount of blue-green algae in the water column. There were 12 blue-green algae blooms on Honeoye Lake reported to the DEC HABs alert map, dark blue circles, 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).

https://experience.arcgis.com/experience/e5dec19912454731a308bbb7af605fb3/

Anabaena (Dolchospermum) (looks like a spring or chain of beads), Aphanizomenon (looks like a leaf), Limnoraphis (looks like a rod), and Microsystis (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, Aphanizomenon, and Limnoraphis blooms lake wide. These are all blue-green (cyanobacteria) algae species. We expect to see blue-green algae blooms continue over the next few weeks particularly when we have 80-90 F days with calm winds. 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 ~8.0 m (~26.4 feet) was 0.44 mg/L and at ~9 m (~30 feet) was 0.23 mg/L today. This means that phosphorus is currently being released from the deep bottom sediments into the deepest part of the lake water. When we have a complete lake mixing event the deep lake water, with excessive amounts of phosphorus, will be mixed into the whole water column potentially fueling a blue-green algae bloom. Lake was stratified (i.e. had a thermocline) at ~8 m (~26.4 feet) deep. See temperature and DO graphs to the left.

The lake has experienced a partial mixing event down to ~7 m (~23.1 feet). This has mixed a lot of deep phosphorus rich water with the whole water column. You can see this mixing on the above Temperature and Dissolved Oxygen graphs where the 0-7 m lines have converged to the same level. This is why we had an increase in blue-green algae blooms over the last week. However, the deepest part of the lake between 8-9 m (26.4-30.0 feet) is still stratified and has not mixed yet. We are likely to keep experiencing blue-green algae blooms for the next serval weeks.

The water temperature differential between the surface and 9 m (30 feet) has decreased to only 1.5 C today. In July this temperature differential was ~9 C. As this water temperature differential decreases the lake’s resistance to mixing decreases. This trend should continue as we get cooler weather in a few weeks. Therefore, we expect that the lake should have a complete mixing event later in August or early September.

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:

https://experience.arcgis.com/experience/e5dec19912454731a308bbb7af605fb3/

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2025 Honeoye Lake Fishery Update

Pete Austerman

Aquatic Biologist

NYSDEC Region 8 Fisheries

Click on the link below:

https://www.honeoyelakewatershed.org/_files/ugd/e6fc30_385359c02d77474fa8d32fa5ec6b9970.pdf

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