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  • Terry Gronwall

September 11th, 2020 Lake Update (Click Here)

Updated: Sep 11

We noticed today, Friday September 11th, 2020 that the lake had a little less algae in the water column and water clarity had increase by one (1) foot to 5 feet from last Monday 9/7 at our open water monitoring site. We did not see any algae surface scum today. This decrease in algae was due to today’s colder (58 F) weather and overcast sky. However, there is still a lot of of algae in the water column, so if we get another weather pattern of 80+ F temperature, calm wind, and sunny skies, we could have a flare up of a blue-green algae bloom again. All near shore locations we checked today looked like the picture below:


Today the lake was still isothermal. Isothermal means the water column has uniform water temperature from top to bottom. The water temperature was about the same as last Monday. The dissolved oxygen level is starting to drop in deeper water depths due to the decomposition of dead algae. The dissolved oxygen level near the bottom is still 2.5 ug/L. This means that currently no additional legacy phosphorus is being released from the bottom sediments. However, if dissolve oxygen level near the bottom drops below 1 ug/L another round of phosphorus may be released from the bottom sediments.


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

Because the Thursday August 20th mixing (turn over) event mixed nutrients released by the bottom sediments when the dissolved oxygen level was below 1 ug/L into the water column, we are likely to continue to have an Anabaena and Microcystis blooms until the lake water gets substantially below 75 F (24 c). An Anabaena bloom looks like pea-soup and an Microcystis bloom looks like green paint on the lake surface. Anabaena and Microcystis blooms have the potential to produce toxins that could affect people and their pets. Therefore, 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


September 7, 2020 Honeoye Lake Update (Click Here)


Surface Water Temperature: 72.0 F

Water Clarity: 4.0 Feet

Lake Level: 803.4 Feet above sea level

Lake Level Relative to Weir: -0.1 Feet

Observations: Monday (9/7/20), lake is still experiencing a lake wide blue-green algae bloom due to the nutrients that were mixed in the water column on Thursday 8/20 when the lake had its traditional late August lake mixing (turn over) event. There was medium to heavy Anabaena and Microcystis (blue-green algae) visible in the water column at most of our near shore and open water HABs monitoring locations. We did not see any algae surface scum because today was completely overcast and windy. Yesterday, Sunday 9/6, when there was bright sun and calmer water, we had what appeared to be isolated near shore Microcystis blooms with surface scum reported to us from both the NE and SE corners of the lake. See pictures below:


Anabaena and Microcystis are a species of blue-green algae that we see starting usually after a lake mixing (turn over) event. Anabaena and Microcystis has the potential to produce toxins that can be harmful to people and pets. We strongly urge you to follow the DEC guidelines of “Know it, Avoid it, Report it” For more info go to: https://www.honeoyelakewatershed.org/habs

Water clarity was 4.0 feet the about the same as last week. This is lower than normal water clarity for late August (Water Clarity Ave. ~6.6 Feet) due to a moderate to heavy amount of algae in the water column. Surface water temperature declined about 3.0 F to 72.0 F. Lake level dropped 0.1 feet to 803.4 feet above sea level.

Today, Monday September 7, 2020, the lake was still isothermal due to the cooler fall air temperatures we have been having over the last week. Isothermal means the water column has uniform water temperature from top to bottom. The dissolved oxygen level was also relatively high and well mixed from top to bottom in the water column. This means that currently no additional legacy phosphorus is being released from the bottom sediments given the relatively high dissolved oxygen level near the bottom.

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


Now that the lake has mixed (turned over), we are likely to have Anabaena and Microcystis blooms until our cooler fall weather significantly lowers the water temperature. An Anabaena bloom looks like pea-soup and a 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 at https://survey123.arcgis.com/share/66337b887ccd465ab7645c0a9c1bc5c0

Blue-green algae's optimum water temperature for growth is 75 F (24 c) and warmer. Once the water temperature starts falling below 75 F (24 c) the algae's growth rate starts to slow. Then the bloom slowly dissipates as the water temperature declines in the fall. You should watch our weekly water temperature trend for the lake getting colder and water clarity increases to signal that this blue-green algae bloom is starting to dissipate. We will keep you posted on these indicators.

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