Pollution threats are growing deep in Maine lakes

Setting anchor at the deepest point of Androscoggin Lake, Buddy Cummings looked off the side of the boat. He started to choke up, witnessing what’s happened to the place he’s spent summers for most of his 69 years.

“It looks like pea soup. It looks really bad. You know, it’s not supposed to look like that,” Cummings said.

It’s early August and the 4,000-acre lake, about 20 miles west of Augusta, is on the verge of a full-blown algal bloom. This is the fourth year in a row the lake’s clear water has transformed into a green sludgy mess.

Cyanobacteria, also known as blue-green algae, tiny organisms that caused the bloom, thrive in warm water. At the beginning of August the top layer of Androscoggin Lake was 84 degrees Fahrenheit.

Conservationist Whitney Baker, from the 30 Mile River Watershed Association, was on the lake to conduct a battery of water quality tests. The nonprofit environmental association took a special interest in the lake after it started having wide-scale algal blooms in 2021.

Residents this summer said the lake feels like bath water — it’s not even refreshing to jump in to, Baker said.

“We’ve noticed locally in our watershed over the last roughly decade really since 2016, an increase in surface water temperatures with record breaking surface water temperatures just in the last two, three years,” she added.

Algae also need the nutrient phosphorus to grow out of control. Phosphorus often gets released into lakes from soil runoff, fertilizer, broken septic systems and other outside sources.

But as climate change keeps lake water warm for longer periods, phosphorus pollution can be unleashed from sediment deep below the surface.

As temperatures go up, lake water naturally divides into layers, state lake biologist Linda Bacon said.

The warmer top layer mixes with oxygen from the atmosphere. But the colder bottom layer doesn’t get any oxygen refills.

“Basically the amount of oxygen in those bottom waters has got to last the lake and the fish and all of the other critters that are there through the entire summer, until the lake cools down and it mixes again,” Bacon said.

These days, the bottom layer oxygen gets used up before it can be replenished. So the area becomes anoxic, or oxygen starved, which not only threatens cold water fish, but can also detach phosphorus from the lake bed.

“If that phosphorus begins to be released from the sediment and gets back up into the water column, where the light is penetrating and it’s warm, that is fueling algal growth, and you can end up with a lot more algae,” Bacon added.

This phenomenon used to be rare. Now it’s happening every summer in lakes across Maine.

Deeper lakes, such as Sebago, have more oxygen reserves in their lower layer, so they’ll probably resist this type of phosphorus release, according to Bacon.

Shallower lakes, however, anywhere between 25 feet and 75 feet deep, are more at risk, she added. If the land around lakes and ponds was historically farmed, there’s a better chance that legacy pollution can make its way into the upper layer and prompt a bloom. The same goes for areas of southern Maine, where there has been a lot of development in and around the watershed and more phosphorus deposits through stormwater and soil runoff.

“People don’t understand that even if their house is a quarter mile away from a lake, what’s going on in their yard, what’s running off their road systems in a watershed is going to end up downhill in that lake,” Bacon said.

Only 123 Maine lakes have at least one documented algal bloom and just 30 experience frequent blooms, according to the Maine Department of Environmental Protection. But that could change as pressures mount.

“We want to protect the lakes that do not experience those blooms, and try to restore the lakes that have those blooms,” Bacon said.

Back on Androscoggin Lake, Baker lowered a device that measures temperature and dissolved oxygen in the water column over the side of the boat meter by meter.

At 7 meters, roughly 23 feet down, the oxygen virtually disappears. Lake Androscoggin is 38 feet at its deepest point.

“The volume of water below seven meters is anoxic,” Baker said.

“So then all of the surface area of the sediment that’s exposed to those anoxic waters is potentially releasing phosphorus into the lake right now,” she added.

The bloom is the earliest ever recorded on Androscoggin Lake. In the past, water quality dipped in September and October. By then, most of the summer residents, tourists and summer camp kids were already gone.

Now, the bloom is happening when everyone wants to be in the water and enjoying camp, Baker said.

Some blooms can become toxic, but even if they do not, the Department of Environmental Protection cautions to avoid the water if it smells bad, has scum on the surface or is so green that it is hard to see than five feet down.

Repeated studies have demonstrated that poor water quality can hurt lakefront property values and tourism spending.

Longtime resident Buddy Cummings said that he’s already seeing the losses mount.

“My neighbors have a camp that they used to rent throughout the summer, to regular renters that have been coming for years,” Cummings said.

“And now they don’t feel that it’s fair to try and rent it in late August, because of the algal blooms that we’ve been having. And now this year with the bloom starting at the beginning of August, you know, who knows?”

This article appears through a media partnership with Maine Public .