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  • Terry Gronwall

August 20 Update Lake Mixed (Click Here)

Updated: Aug 21


We found at noon on Thursday August 20, 2020 that the lake had completely mixed because of the relatively low air temperature of ~50 F last night. You can see that on our temperature and dissolved oxygen charts to the left. Today the surface water temperature was 24.9 c and the bottom temperature was 24.6 c. Temperature difference of only 0.3 c. The dissolved oxygen level at the surface was almost the same as at 9 m. This condition is called isothermal and confirms a complete lake mixing event.

1 meter (m) = 3.3 Feet and 1 Degree Centigrade ( C ) = 1.8 Fahrenheit (F)

Once the lake mixes, we are likely to have an Anabaena and Microcystis blooms. An Anabaena bloom looks like pea-soup and an Microcystis bloom looks like green paint on the lake surface. Be extra watchful for new blue-green algae blooms for the rest of the summer. Please report any suspicious blooms to us at

watershedtaskforce@gmail.com and the NYSDEC “Know it, Avoid it, Report it” at https://survey123.arcgis.com/share/66337b887ccd465ab7645c0a9c1bc5c0

We noticed today that there was an increase in algae in the water column and a drop in water clarity from last Monday in the South Lake Basin. However, the North Lake Basin appeared to have significantly higher water clarity.

We found an Anabaena and Gloeotrchia bloom that looked like pea soup near our dock this afternoon. See picture to left. We collected a sample and confirmed by looking at the sample with a microscope that it contained anabaena and gloeotrichia. You, your family, and pets should avoid contact with any visual bloom as the potential for blue-green algae toxins is always present.



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://nysdec.maps.arcgis.com/apps/webappviewer/index.html?id=ae91142c812a4ab997ba739ed9723e6e


August 17, 2020 Honeoye Lake Update (Click Here)


Surface Water Temperature: 78.4 F

Water Clarity: 5.5 Feet

Lake Level: 803.2 Feet above sea level

Lake Level Relative to Weir: -0.3 Feet

Observations: Monday (8/17/20), lake is in fair condition for mid-August. There was light to medium Gloeotrichia (blue-green algae) visible in the water column at about half of our 10 near shore HABs monitoring locations. The other half had medium to heavy Gloeotrichia in the water column. We did not see any surface algae scum in near shore areas. However, two of our Secchi Disk/HABs Monitor Volunteers reported near shore Gloeotrichia blooms this morning. Their pictures are below:


Gloeotrichia is a species of blue-green algae that gets its nutrients directly from the bottom sediments. https://www.honeoyelakewatershed.org/habs

Water clarity has decreased by ~2.0 feet to 5.5 feet since last week due to an increase in algae in the water column. This is lower than normal water clarity for mid-August (Water Clarity Ave. ~6.6 Feet). Surface water temperature declined about 1 F to 78.4 F.

The lake is now very “weakly” stratified and the water near the bottom below the thermocline has very low dissolved oxygen (anoxic). This means that the phosphorous/iron bond in the bottom sediments will weaken releasing phosphorus into the water near the bottom. The next time we get a North or South wind of ~15 MPH we may have a lake mixing event that will mix this phosphorus into the whole water column top to bottom providing fuel for a blue-green algae bloom.

Our lake Temperature and Dissolved Oxygen graphs on the left show how the lake has gone from being strongly startified to weakly stratified over the last month. On July 9th there was 7 degrees C difference between surface and bottom water temperature. On August 17th there was only 1.1 degrees C difference between surface and bottom temperature. The larger the temperature differential the higher the lake’s resistance to mixing. The lake is likely to mix soon.

1 meter (m) = 3.3 Feet and 1 Degree Centigrade ( C ) = 1.8 Fahrenheit (F)


Once the lake mixes, we are likely to have an Anabaena and Microcystis blooms. An Anabaena bloom looks like pea-soup and an Microcystis bloom looks like green paint on the lake surface. Be extra watchful for new blue-green algae blooms for the rest of the summer. Please report any suspicious blooms to us at watershedtaskforce@gmail.com and the NYSDEC “Know it, Avoid it, Report it” at https://survey123.arcgis.com/share/66337b887ccd465ab7645c0a9c1bc5c0

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://nysdec.maps.arcgis.com/apps/webappviewer/index.html?id=ae91142c812a4ab997ba739ed9723e6e

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Honeoye Lake Watershed Task Force Members:

Town of Richmond

Town of Canadice

Town of Bristol

Town of South Bristol

Town of Naples

Honeoye Valley Association