Director of Security
Grays' Aquatic Services
Lake Mohawk Property Owners Association
"Anyone who can solve the problems of water will be worthy of two Nobel prizes
one for peace and one for science"
John F. Kennedy - 1962
September 11, 2018
Lake Mohawk Fallfest
Saturday, September 15th, 2018
Fallfest -------> Lake Turnover (more below)
Lake Mohawk is now in Fall Turnover
Cold rain and cooler days and nights have started the process of fall turnover in Lake Mohawk.
Surface lake water now can start mixing with deeper water due to the temperature/density
differences in the lake becoming similar (figure 1 below). In summer, warm less dense water floats on top
of cooler more dense water at deeper depths.
One of the results of fall turnover in a lake is that deeper water that contained little or no oxygen during the
summer now starts mixing with surface water. This results in an overall depression of
Note how the temperature differences are very similar all the way through the 27ft. depth level.
Another result of fall turnover is the upwelling of nutrients such as phosphorus that have
been released from the sediments throughout the summer. This upwelling of phosphorus can
result in temporary late season blue-green algae blooms. These blooms are normally short lived as
cooler days and nights are not conducive to cyanobacteria growth.
Fall turnover provides a natural "cleansing" effect to the lake and prepares it for winter by re-oxygenating deeper water
thereby providing the wintering fisheries adequate oxygen during ice cover. It also
precipitates much of the phosphorus as the water becomes re-oxygenated The dissolved iron in the water
combines with phosphorus to form ferric phosphate which makes it biologically unavailable for plant
and algae growth.
(Old but possibly interesting information)
Blue-Green Algae (Cyanobacteria) Season !!!
NOTE: We are now on the downside of this period as of 9/11/2018
(Normal and Natural in most all northern lakes as illustrated in Fig. 19 below)
Based on recent questions and comments on Nextdoor about Lake Conditions
I believe it may be helpful and timely to discuss the following:
1) What are Blue-Green Algae (cyanobacteria)?
2) What can we do about them?
3) How are they controlled?
4) Considerations and Consequences of Copper Algaecide Control
Q1) What are Blue-Green algae a.k.a. "Cyanobacteria"?
A1) For the purpose of this discussion as it pertains to Lake Mohawk property owners, cyanobacteria are a
normal group of free floating microscopic organisms that were once considered to be algae but are now
classified as photosynthetic bacteria. Cyanobacteria are very primitive organisms and were a very early part of Earth's development. Google "Cyanobacteria" and you will find a voluminous amount of other information on these ubiquitous organisms.
Q2) What can we do about cyanobacteria?
A2) Cyanobacteria like normal bacteria are ubiquitous in nature. Just like bacteria that affects our personal health, there are both "good" and "bad" bacteria. "Good" bacteria such as those found in probiotic products such as yogurt are beneficial for a healthy digestive system. "Good" cyanobacteria are essential in oxygen production and as a food base for zooplankton which ultimately is beneficial for a healthy fisheries.
"Some" species of cyanobacteria can be "bad" in terms of how they may affect our health due to a variety of toxins that they can release into the water. For that reason, your lake manager Scott Noble routinely monitors the water quality for "potential" toxin issues. To date, NO water sample from Lake Mohawk has ever returned with toxin levels that exceed safe water contact recommendations.
So, what can we do about cyanobacteria?........ considering complete eradication is logistically not possible nor ecologically desirable, the only things we can do about cyanobacteria are 1) Monitor, 2) Naturally suppress their populations through selective aquatic plant management, phosphorus controls, and "selective" algaecide applications.
Q3) How are cyanobacteria best controlled?
A3) The most effective and preferred method of controlling cyanobacteria is through controlling the
primary nutrient phosphorus. Using phosphorus free fertilizers and detergents are certainly helpful however there is a vast reservoir of phosphorus reserves that have built up in Lake Mohawk sediments over it's now 55 year history. Sediment removal through dredging removes a significant amount of sedimentary phosphorus but can be expensive and is often times not feasible for entire lake removal. Phosphorus inactivation through alum and other products such as Phoslock (TM SeaPro) are also effective but often times not logistically practical or economically feasible. A natural approach to in lake phosphorus control is through selective plant management as aquatic plants are effective at removing phosphorus through plant competition. The dilemma with this approach at Lake Mohawk is that extensive aquatic plant communities are not well tolerated by all types of lake use. Balance and understanding on the part of the lake community is vital in maintaining a lake that can be used by a wide variety of individuals and at the same time remain ecologically healthy.
(see graphic below illustrating this concept and ramifications)
Topic 4) "Considerations and Consequences of Copper Algaecide Control"
Controlling algae blooms through the use of algaecides such as copper sulfate should not be taken lightly.
1)First of all, copper sulfate does not control all species of cyanobacteria and can lead to promoting
COPPER RESISTANT cyanobacteria that may actually produce toxins that are harmful to human and animal
2) Copper sulfate is a relatively short acting algaecide and is only effective for ashort period of time (a matter of hours before it precipitates to the lake sediments).
3) Copper sulfate applied in mid-summer can kill a predominant source of oxygen producing cyanobacteria!! Take a look at the August 8th, 2018 oxygen/temperature data and look at the oxygen concentrations through the 12 ft. depth strata... ONLY the upper 9 ft. of lake volume had sufficient oxygen to adequately support fish life. Most of that upper 9ft. of oxygen was being produced directly from the photosynthesis of the cyanobacteria. Imagine if you will applying a lethal dose of copper to the upper 9ft of water. Not only would you be losing a significant source of your oxygen producers......the bacterial degradation of the dead algae would consume even more oxygen!!!! possibly leading to a fish kill.
NOTE: Timing and Dosing is EXTREMELY critical at safely controlling cyanobacteria at this time of the year.
4) Copper sulfate inevitably kills many beneficial aquatic organisms such as zooplankton and other "good" algae and cyanobacteria. Proper application methods and dosing of copper sulfate can HELP reduce undesirable environmental impacts but cannot totally eliminate them.
5) Fifth and maybe most important, copper sulfate is NOT BIODEGRADABLE! What this means is that copper builds up in the lake sediments over time with each and every application!. "Copper Bottom" lakes do exist and have resulted in years of over application with copper algaecides. The consequences are many which include the inability of the lake to support aquatic plant life which often leads to severe and perpetual cyanobacteria blooms. The impact on property values can be significant.
Click for PDF Document of Lake Mohawk Temperature / Oxygen Profile
(Historical Data on Right)
Donna VanSickle - Another Lunker meets it's match ;)
July 24th, 2018
5 lbs. and 20 inches in length!!!
July 4th, 2018
Donna VanSickle - Catching "Two at a Time"
Note: For those of you that do not know Donna.....
Donna is the most avid fisherwoman at Lake Mohawk!
She fishes for a wide variety of fish including perch, bluegill, crappie
small and largemouth bass....and even at times a "perch-a-gill" ;-)
Lake Management Strategy and Mission Statement
By working with "Mother Nature", you can enhance the recreational value of freshwater aquatic ecosystems such as Lake Mohawk. Selective and judicial use of aquatic herbicides which promotes natural competition from native low growing aquatic plants is part of an integrated approach to improving property values, sport fisheries, as well as recreational usage from skiers, pleasure boaters, etc.. Studying and controlling the sources of phosphorus will also naturally reduce or eliminate the threat of toxic blue-green (cyanobacteria) algae blooms. The Lake Management Committee , consisting of dedicated members of the L.M.P.O.A. from a variety of backgrounds is vital to the success of any lake management program. Your support for this group of people is truly appreciated.
My mission at Lake Mohawk is to serve, share knowledge, and answer all questions about the aquatic ecosystem that is the focal point of this beautiful lake community. It is my desire to further enhance the existing fisheries while minimizing any negative impacts this may have on recreational boating, etc.. Above all, I am here to serve the greater good of the Lake Mohawk Property Owners Association and will at anytime be available to answer questions or to respond to concerns or observations regarding lake conditions. E-mail: JeffGray@GraysAquatic.com or Cell: 330.412.4139
(Click for PDF Viewing/Download)
Note: Rapid Temperature Increases / Dissolved Oxygen Declining / Transparency Increasing
Many things are going on in the lake at this time as weather patterns are controlling the overall
biological dynamics within the lake. Water temperatures are increasing, a thermocline is developing,
dissolved oxygen values are declining, water clarity is increasing and last but not least is that the
winter/spring aquatic plant commonly known as Curlyleaf pondweed is increasing!!
Considering that there are many inter-related associations between all these events (aquatic ecology), I
thought I would point out some of the more interesting ones.
1) There was an 11 degree average increase in water temperatures from 5/1 - 5/9 from the surface through
9 feet of depth. There was a 25 degree increase from 5/1 - 5/30.
This relatively rapid increase in water temperature affects most all biological activity within the lake
including the fisheries.
Rapid changes in water temperature can cause thermal stress....especially on spawning fish.
"Why have I seen a partial die off of crappie in the past several weeks?"
Please Visit the Following Links :
Biology/Ecology of Crappie Link
"Why a partial crappie die off may actually be beneficial to the overall ecology of the fisheries & MORE"
2) Rising water temperatures increase the activity of many aquatic organisms in the lake including bacteria in
the lake sediments and water column. Aerobic bacteria consume oxygen as they decompose organic matter.
Also consuming oxygen in the water column are microscopic organisms call zooplankton.
From a chemistry viewpoint, warm water holds less dissolved oxygen than cold water.
(think about a cold soda pop vs. a warm soda pop as a comparison)
The dissolved carbon dioxide (CO2) in a cold soda is much greater than a warm soda.
As an experiment... take two cans of soda and place one in the sun and the other in the refrigerator.
Open both cans over a sink or outside and see which one releases the most CO2 ;-)
3) Why is the water clarity increasing? (10' 2" to 14' 10") Answer - Because the Curlyeaf pondweed (CLP) is increasing.
CLP like all aquatic plants utilize the phosphorus in the water for growth of leaves and stems. The CLP
plants are basically "cleansing" the water of nutrients which otherwise would be free to be used
by microscopic phytoplankton/microscopic algae. The more phytoplankton you have in the water column,
the less clear the water is. Ironically, the less phytoplankton (microscopic plants) you have in
the water column.....the less natural oxygen production you have which is another reason
that dissolved oxygen values are decreasing.
"A potentially nuisance invasive aquatic plant that provides benefits for Lake Mohawk"
a.k.a. "Potamogetan crispus" (scientific name)
As you can see in the illustration below, CLP has a very different growth cycle than most all northern native aquatic plants.
CLP is most visible in spring especially in May when the plant reaches the water surface in depths up to 10 ft.
Seeds (Turions) are produced in May which then fall to the bottom of the lake where the CLP
once again starts to grow in late fall. It grows under the ice until early summer where it
naturally senesces (dies off) and repeats it's life cycle.
Curlyleaf pondweed in Lake Mohawk
1) CLP provides early structure, food, and habitat for the fisheries.
The below screenshots of the sonar images below were taken on May 1, 2018.
The left side of the screen shows the location of the screenshot (black triangle)
while the right side shows the depth and structure of the lake, including fish if any.
As you can see by comparing screenshot 1 and screenshot 2,
Screenshot 2 which shows an area of the lake WITH CLP has many
more fish associated with the plants compared to screenshot 1 that has no CLP.
NOTE: Both screenshots were taken at similar depths (10 ft.) for comparison purposes.
Because Lake Mohawk was man made, it does not have significant areas of
"structure" which would otherwise provide enhanced areas of food and shelter for fish.
Spring growth of CLP provides excellent natural temporary structure for the fisheries during critical spawning periods
which would otherwise be devoid of beneficial fish habitat.
2) CLP helps crowd out other less desirable exotic plants such as
Using natural plant competition to control other less desirable exotic plants is an excellent
ecological and economical approach to nuisance aquatic plant and algae control.
Eurasian watermilfoil is a much less desirable nuisance aquatic plant due to the fact
that it reaches the water surface during prime recreational periods of the lake season (June, July, August)
3) Curlyleaf pondweed naturally senesces (dies off) in June.
The beauty of CLP is that it matures and naturally dies off in June. Regardless of chemical treatment,
CLP will be very scarce by the 2nd or 3rd week in June.
4) CLP Control Strategy
Given all we know about CLP at Lake Mohawk and the wide variety of lake users within the L.M.P.O.A.,
the most sensible approach to managing CLP is selective custom control throughout May into June.
Controlling surface levels of CLP in high use jet ski, boating, and skiing areas is a priority as is
controlling CLP at lakefront properties that utilize their lakefront for early swimming.
Knowing the benefits of CLP on the Lake Mohawk fisheries, areas that are not high
use are left uncontrolled or minimally controlled knowing that CLP
will naturally die off regardless of control measures.
Common sense, understanding, and some compromise on the part of all lake users goes
a long way in peacefully sharing the natural resources that Lake Mohawk has to offer
so that everyone can enjoy
"Believe It or Not Photos"
(Received May 6th, 2018)
also known as "biting off more than you can chew"
Lake Mohawk Walleye
March 5, 2018
7 lbs - 25 inches
The Relationship between Aquatic Plants & Water Clarity
I believe it is important to have a basic
understanding of the important role of submersed aquatic plants as it relates to water clarity.
While many of us may know about the importance of aquatic plants to fish populations, it is
lesser known about how aquatic plants help maintain water clarity and purity.
Besides providing food and habitat for fish, aquatic plants stabilize lake sediments that are
high in phosphorus. Phosphorus that is mixed up from wind, wave, and other recreational
watercraft traffic "feed" undesirable algal blooms that reduce water clarity. In addition,
aquatic plants utilize and compete for available phosphorus making it less available to
the tiny planktonic algae. There is also some evidence that aquatic plants
secrete inhibitory chemicals that reduce algal blooms.
Our lake management goal at Lake Mohawk is to balance the needs and wants of a
variety of recreational users and property owners throughout the season without jeopardizing
the long term health of the lake. Using aquatic plants as much as possible to
reduce the intensity of algal blooms, reduces the need for ecologically undesirable algaecides.
Throughout the 2017 lake season, nuisance levels of aquatic plants will be selectively
controlled in specific areas where it most interferes with recreational use of the lake.
Lake Mohawk Depth Map
(Click to Enlarge in PDF Format)
Visitors to this page
Grays' Aquatic Services
Jeff Gray M.S
Applied Aquatic Biologist
Includes Historical Data
(Click on WU Graphic Below)