Sunday September 14, 2025 Honeoye Lake Water Quality

Terry Gronwall
Sep 14
3 min read

The blue-green algae blooms on Honeoye Lake that resulted from a complete lake mixing event 3 weeks ago are starting to slowly dissipate and should continue dissipating over the next several weeks.

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Surface Water Temperature: ~69.3 F

Water Clarity: ~5.3 Feet

Lake Level: 802.6 Feet above sea level

Observations: Sunday (9/14/25), Water clarity was ~5.3 feet about 1.3 feet more

than last week. The water clarity increase was due to a small decrease in algae in the water column. The surface water temperature was ~69.3 F about 1.1 F warmer than last week.

It was sunny with a calm wind today. A beautiful day to be out on Honeoye Lake!

We found heavy concentrations of blue-green algae in the water column often with light surface streaking lake wide. See open water picture on the left: Therefore, we expect that there will 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 17 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).

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

Anabaena (Dolchospermum) (looks like a spring or chain of beads), Limnoraphis (looks like a rod), and Microsystis (looks like a group of small round cells) are the current dominant blue-green algae species. We did not find any Aphanizomenon (looks like a leaf) in our algae sample today. 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 4.54 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 three weeks ago 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 recently. See temperature and DO graphs to the left.

You can see the complete lake mixing event on the above Temperature and Dissolved Oxygen graphs where the 0-9 m lines have converged to the same level three weeks ago. Also, you can see that the lake has started to stratify again by the drop in dissolved oxygen from 7-9 m 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:

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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