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What to do if you think you've spotted an exotic weed or plant in the water!  First you can look at some identifying pictures here. Then if you think you have one and want confirmation you can send in a picture or sample to Energy and Environmental Affairs for confirmation.


One of the most important water quality programs for Lake Monomonac is New Hampshire's Volunteer Lake Assessment Program (VLAP) The program is headed by Lourdis Gray and other volunteers on the lake. This has been very educational and is a vital program to monitor and protect the quality of our lake water.  After reviewing the Latest Annual Report and observing a larger than usual growth in development over the past few years, I am nervous about the delicate balance between a quality and an undesirable lake condition.  However, I am confident that if we all work together as a community that we can improve the quality of Lake Monomonac’s water, which is linked to many other lake issues, including toxic algae blooms, extensive weed growth, recreational value and you guessed it PROPERTY VALUE.


Here is a list of 10 things all of us can practice to improve the quality of the lake water. 



Our lake has approximately 30 Acres of Variable Milfoil in identified areas in both Massachusetts and New Hampshire. In June 2016 our lake had approximately 70 acres of Variable Milfoil in identified areas in both Massachusetts and New Hampshire.  This map indicates areas that have been identified as growth areas as well as areas that were treated in June 2016.


In spite of our on going efforts, we are not winning the battle and are now exploring ways to  better identify, manage, and treat these areas in hopes of eradicating it.


What is Variable Milfoil and What does it look like?

  • Variable Milfoil is an aquatic rooted, submerged non-native plant with a “raccoon-tail” or pipe cleaner appearance.

  • Variable Milfoil can form dense mats at the water surface and can grow in the photic zone, in up to 10 feet of water.

  • The delicate green underwater leaves are feather-like and average ½ to 2 inches across. Leaves are arranged around the stem in whorls of 4-6. The leaves have 6-12 segments.

  • During late summer a 4-6 inch emergent bract develops, protruding above the water surface. The small bright green leaves on the bract are oval and are both serrated and non-serrated. (The lower female section of the bract has serrated leaves, and the upper male portion has smooth margins).

  • The stems are thick, robust and usually red.

  • Variable milfoil can live out of the water for hours and then rejuvenate once it is introduced to water again.

  • Small fragments of variable milfoil carried by water currents and waves created by boat traffic float in the water and form roots, allowing the plant to take hold in shallow waters and colonize another area of the lake.

  • One small fragment of variable milfoil can potentially multiply into 250 million new plants within a year’s time. It can grow one inch per day to reach 18 feet in length, creating a mat-like canopy near the water’s surface.

  • At this time, Monomonac Lake has approximately 30 acres that have been colonized by variable milfoil. 


MANAGEMENT METHODS currently include mechanical removal, drawdowns, and herbicides. No known biological controls exist.


  • Although harvesting can greatly reduce the Variable Milfoil biomass in a water body, harvesting also causes fragmentation, and fragments are capable of producing new plants. Some fragments may drift down stream or attach to boats and wildlife and create new infestations elsewhere.

  • Drawdowns can be an effective mode of Variable Milfoil control if the drawdown is extensive enough to prevent re-growth from seeds. Drawdowns may impact fish, aquatic organisms, reptiles, amphibians and downstream conditions. • Several herbicides have been use to control Variable Milfoil, including Diquat and 2,4-D.

  • Benthic barriers may be used in small areas including swimming beaches, boating lanes and around docks. The barriers restrict light and upward growth but can have a negative impact on benthic organisms, and need to be properly anchored and maintained. 

Cyanobacteria or blue-green algae?


What is often called blue-green algae is actually not algae at all and is instead bacteria.   More specifically, they are a class of bacteria known as cyanobacteria of which there are over 6000 types.  Cyanobacteria are some of the oldest known organisms on the planet, dating back over 3.5 billion years.  They are native to freshwater bodies as well as salt water and soils.  Some types of cyanobacteria produce toxins while others are used for food such as the spirulina type.  Here, we will focus on those types that produce toxins and what you should know about them.


Cyanobacteria are always present in freshwater ponds and lakes but typically only exists in small, dilute quantities.  They become problematic to humans and their pets when they form larger colonies that are plainly visible to the naked eye which are referred to as Harmful Algal Blooms (HAB).  This term continues to be used by many agencies to refer to cyanobacteria blooms along with other harmful, true algal blooms such as red tide.  These blooms are triggered when both the temperature and nutrients reach optimal levels.  Typically, blooms occur in warmer weather and following rain events.  The rain brings nutrients from runoff that feed into the rivers and brooks that in turn feed the lake.  Fertilizers and leaky septic systems also contribute to the nutrient levels.


A bloom may be seen as a film, blobs, filaments, or just a discoloration of the water.  One person described it as looking like bright green Silly String.  While typically associated with warmer weather in the summer, cyanobacteria based HABs have been extending into the fall and have even been detected under ice.  They are also more likely to form in stagnant waters.  Unfortunately, these HABs are increasing in both frequency and severity.  Because not all cyanobacteria produce toxins, not all blooms are harmful.  University of New Hampshire has coined the phrase the “Dirty Dozen” which represents the 12 most common types of cyanobacteria that occur in New England along with their associated toxins, images, and associated odors, see link below.  However, HABs should not be confused with common green algae which may look like underwater moss, thick stringy mats, or floating slimy scum, and tends to be more “sticky”.  That is, when a green algal bloom is poked with a stick, it is likely to cling to the stick.


genera: Cyanobacteria of New England (


The toxins produced by these cyanobacteria are generally either hepatotoxins (affecting the liver) or neurotoxins (affecting the nervous system).  Unfortunately for people, the early symptoms of exposure to cyanobacteria toxins can appear like very common issues caused by numerous other health issues and can include irritation of the skin, eyes, nose, throat, and lungs, stomach pain, headache, vomiting, and diarrhea.  These can also lead to more serious damage to the liver or nervous system. Pets, particularly dogs who are often attracted to the water, are more prone to serious illness as it is believed that they often drink the water and retain the toxins in the fur which they may later lick.


What to do if you suspect a cyanobacteria HAB?  Stay out of the water anywhere near the observed bloom and keep pets out of the water as well.  If exposed to the water, wash with soap and water.  If your pet has been exposed, contact your vet.  If possible, try to take lots of photos of the bloom(s).  Note the date, time, weather conditions, and where the bloom(s) were observed.  Blooms can be reported to the Winchendon Board of Health, or if NH you can contact the cyanobacteria hotline at (603) 848-8094 or email them at The EPA also has also sponsored a citizen science app called bloomWatch which allows anyone to download the app onto their smartphone which can be used to photograph and log HABs.  See below for the link to the app.


bloomWatch | Cyanobacteria Monitoring Collaborative – Cyanobacteria Monitoring Collaborative (


What can you do to help prevent HABs?  Have your septic system inspected to make sure it’s not leaking or draining improperly to the lake.  Reconsider fertilizing lawns and gardens where the runoff flows right into the lake.  Try using phosphate free soaps and detergents since two of the most important nutrients for algal blooms are phosphorus and nitrogen.  Consider planting native shrubs and trees along the shoreline to prevent runoff.


Additional information can be found using the links below.  I’d also like to thank Karen Seaver and the Harris Center for their permission to reproduce some of the content of their webinar: Seaver, K. (2021). Cyanobacteria: What you need to know. The Harris Center for Conservation Education. Presentation retrieved from;


Learn about Cyanobacteria and Cyanotoxins | US EPA

Facts about Cyanobacterial Harmful Algal Blooms for Poison Center Professionals | Harmful Algal Blooms | CDC

Top Ten List:


  1. Communicate and Educate – Talk to your family, neighbors, and guests.  Tell them how important all of these things are.

  2. Don’t use phosphorus fertilizers - use organic fertilizers or none at all.  Because our lake is so acidic it is actually good to use lime.

  3. Update failing or failed septic systems - Several new technologies exist that are ideal for small lots close to the water.  See for more information on a new type of system.

  4. Use indoor bathrooms – schedule water activities before meals so people are less likely to have to use the lake as a restroom, especially small children.  Do not bathe yourself or you pets in the lake water with soap and shampoo.

  5. Feeding the Ducks – they do not need it, and their waste is bad for the water.

  6. Landscaping – Plan native plantings on or near the shore to prevent run off into the lake. See NativePlantList.pdf for a guide to plans selection.

  7. Choose biodegradable dish and laundry detergents that do not contain phosphates.

  8. In the winter use de-icers that do not contain salt.

  9. Do as much as possible to eliminate fuel leaks from aging motors and fueling equipment.  Do not store any fuel, cleaning supplies, batteries, etc... near the water.

  10. Choose non toxic building supplies for Docks and Rafts.  Pressure Treated Lumber, Railroad Ties, Telephone Poles etc are bad and against the law to put into the water.  Use cedar, aluminum, plastic and other approved composite materials.

All of these items are common sense when you think about it, yet you will see all of them happening on a daily basis on the lake. As development continues and more people discover our lake it will become increasingly important for people to follow these simple rules.


You can do your part by continuing to communicate and educate.  The volunteers that participate in the VLAP will continue to monitor the lake quality and keep you informed of changes and trends in our water quality.  If you would like to take it a step further and participate in the water sampling process please contact Lorraine Gauthier. We could really use somebody with a pontoon boat to drive to sampling locations.  Testing is done 3 times in the summer, usually Monday morning.  There is also a request from the state of NH for volunteers to monitor weed growth. If you are interested in volunteering for this program visit  This is highly recommended if you have new or more than usual weed growth near your property and you want to find out what it is.



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