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Photo and article by Ramona du Houx

July 7, 2020

With record heat and drought-like conditions, Maine’s lakes are more likely to experience algal blooms according to Linda Bacon, Maine Department of Environmental Protection (DEP) lead lakes biologist.

Algae are a natural part of healthy freshwater ecosystems, but algae, like land plants love warmth and sun. With abundant sunshine, warm weather and plenty phosphorus from the spring’s runoff Maine lakes have perfect conditions for an algal bloom.

When a lake is blooming people often describe the lake water as green.

Maine DEP describes an algal bloom as a nuisance bloom when the clarity of the water is 2 meters (6.6 feet) or less. If the water clarity is less than 1 meter (3.3 feet), Maine considers it a Harmful Algal Bloom (HAB). It is important to know that not all lakes that bloom and not all lakes that are experiencing a HAB are producing toxins.

Cyanobacteria can produce toxins which if ingested can cause illness and even death in people, livestock or pets. Since there is no quick and easy test to tell if a blooming lake is safe, Bacon recommends that “when in doubt, stay out.”

If the lake looks green or cloudy or you can’t see the bottom through 4-5 feet of water (about chest height) because the water is too green, don’t go in.

The causes of algal blooms stem from human activity, which includes climate change.

“The phosphorus attached to soil particles is washed off our roads, driveways, and agricultural fields and enters our lakes during storm events. These phosphorus sources in combination with phosphorus that is being recycled from lake bottom sediments is over feeding algae in some of our lakes. If we want to keep our lakes healthy and avoid nuisance or HABs we must reduce the amount of phosphorus entering our lakes,” said Jeff Dennis, a DEP biologist who has studied the interaction between land use and water quality for nearly 50 years.

Keep yourself and your pets out of any water that looks discolored, smells bad, or has scum on the surface. Bacon adds that scums pushed by wind to the shoreline will have the highest levels of toxins. Scums often stink, which attracts dogs to investigate and drink. Don’t let them drink this water.

Maine has no reported human or pet cases of HAB poisonings but that doesn’t mean it can’t happen. Maine has seen an increasing number of lakes with more regular nuisance algal blooms. This is due to climate change and too much phosphorus being washed into our lakes during storm events.

“The phosphorus attached to soil particles is washed off our roads, driveways, and agricultural fields and enters our lakes during storm events. These phosphorus sources in combination with phosphorus that is being recycled from lake bottom sediments is over feeding algae in some of our lakes. If we want to keep our lakes healthy and avoid nuisance or HABs we must reduce the amount of phosphorus entering our lakes,” said Jeff Dennis, a DEP biologist who has studied the interaction between land use and water quality for nearly 50 years.

Dennis said that Maine doesn’t have to resign itself to blooming lakes, because we can prevent most from blooming by taking a few easy steps to work to reduce phosphorus inputs to the lake not only from lake shore properties, but from all areas that drain to the lake.

Those steps are:

  • Seed and mulch bare soil
  • Divert driveway runoff into stable vegetated areas,
  •  Properly maintaining gravel roads.

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