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What about this green Algae?

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Not a major concern

We have had many inquiries, and almost as many theories, as to the source of the green algae blooms we have all noticed on the lake this last few weeks, particularly in the north cove area.

We have checked with Amy Smagula at DES and this is NOT an invasive or dangerous algae bloom.  It is filamentous green algae, perfectly normal in lakes here in our area.  We happen to have had an earlier and larger bloom this year than we normally experience.  Please do not chase the geese, or blame your neighbors for this.  Below is the response from Amanda McQuaid, from the Water Division, NH Dept of Environmental Services:


While the green algae bundles don’t look great, it is not a major concern. It will likely not persist and this doesn’t mean this is what you will experience every summer from now on. The good news is that it is not cyanobacteria. It is mostly a green filamentous algae called Mougeotia. This type typically prefers low-nutrient (oligotrophic) waters. It is free-floating and not attached to the bottom of the lake, though it can grow deeper in the lake and come up due to weather and natural lake processes. I believe it is in the cove due to currents and lake morphometry. Since you have been trying to remove it and it keeps coming back, that is another sign that the currents are moving it towards you.  It appears to be browning and dying off, likely not happy to be caught in a shallower cove…. Possible a reason why it is “disintegrating” as you try to remove it. If it is dying, it will sink or come to the shoreline where it can be raked and composted. I have reached out to a company that make limnological equipment to see if they have recommendations on a type of net that could possibly be used to help harvest it. In the future, if you start to see these return, it is best to try to remove before it gets this large and before it starts to die and break down.


The general feedback we must reiterate is that these events do happen. It cannot be linked to one single event. All lakes are moving towards eutrophication. There is not one single person to blame. It involves climate change, weather patterns, food webs, everyone in the watershed and complicated interactions between aquatic life. It is a slow process. Even though you haven’t seen this in 100 years, it cannot be blamed on the clear cutting alone, if at all. A quick fix is not possible for this. I would be concerned that if you tried to kill it with chemicals, you may get a bloom of something worse and that would be more likely to persist. Treatment would not result in an immediate clearing of the water either. If killed, it is possible that the nutrients released by the green algae could set-off other algae or cyanobacteria. Again these green algae like low nutrients and cyanobacteria prefer high nutrients.