On a sunny day in August, environmental scientist Kellie Merrell scans the shoreline from a motorboat in the shallows on Lake Fairlee. There are lots of cottages. White pine trees tower over the water, reaching out from a few rocky points.
Merrell is here with a team of scientists from the state to do a yearly assessment of the lake’s health. This happens at a handful of Vermont’s 800-plus lakes every year.
“We’re kind of doing, like, a check-up on the lake — a two-day [check-up], sort of like going to your general practitioner," Merrell said. "And then we’re going to see if Lake Fairlee might need to go see a specialist or two when we’re done,” she added with a laugh.
The state can’t check on every lake each summer, so the ones with troubling trends rise to the top of the list. And this year, Lake Fairlee was a frontrunner.
Phosphorous has been increasing on this lake in the summer over the last 40 years, and in the spring since at least the 1990s. There’s also been a decline in the water clarity.
Phosphorous is a major source of clean water concerns in Vermont. When there’s too much in a lake, it can cause toxic algae blooms and hurt fish habitat.
So this trend is something Vermont's Lakes and Ponds Management and Protection Program has been keeping an eye on.
From another motor boat — this one in the middle of the lake — Ph.D. aquatic ecologist Leslie Mathews and watershed planner Danielle Owczarski are measuring things like water chemistry, temperature and nutrient levels.
This data is key to knowing how to make Lake Fairlee healthy again. Scientists call it restoration.
Kind of like when a person is sick, a doctor might run a lot of tests, but they also look at your medical records to get a sense for your history. And in the case of a lake, that history is millions of years old.
One way to get that history? Look at the layers of muck that have piled up on top of each other at the bottom of the lake over centuries.
To do this, scientists take a big plastic tube, about as thick as your thigh, with a rubber plug on top, and rocket it into the bottom of a lake. In this case, from the deck of the motorboat.
Back at the dock at Lake Fairlee’s public boat launch, Leslie and Danielle unload their core samples.
There are layers of different colored soil, stacked up like in a bottle of sand. At the very bottom is the oldest muck. It’s rich and it’s dark, and it’s older than any post and beam farmhouse in Vermont.
And, like a time capsule, it could tell us what Lake Fairlee was like before Vermont was a state.
Leslie and Kellie are part of the Northeast Diatom Collaborative, a team of scientists across New England who want to know: What did lakes look like before European colonists came here?
The answer lies in tiny, microscopic algae called diatoms. They’re invisible, but they’re all around us, on every surface that is at all wet.
Sylvia Lee is a Ph.D. environmental scientist with the EPA. She's spent her career studying these tiny plants.
“Diatoms are these single-celled algae with cell walls made of glass," she said. "And those cell walls have these intricate patterns that make them look like beautiful jewels of the sea.”
Diatoms produce as much as 50% of the world’s oxygen. When they die, their glass cell walls can last for a very long time. Some have been dated back to the Jurassic era.
Each diatom species is very finicky about how warm it likes the water to be, how acidic, and what sorts of nutrients it needs. So if you can identify the diatoms in sludge you pull from the bottom of a lake, you can tell what the water was like when that sludge was piling up.
“Diatoms are these single-celled algae with cell walls made of glass. And those cell walls have these intricate patterns that make them look like beautiful jewels of the sea.”Sylvia Lee, Ph.D. environmental scientist with the EPA
But with as many as 2 million species globally and new discoveries ongoing, scientists in Vermont and New England are in need of a local field guide.
“Researchers are still describing lots of new species," Lee said.
That’s also where she comes in. She’s helping to lead an effort right now to build one. And Leslie and Danielle’s core sample will help.
Lee says when they’re done, this will be the first time the EPA has gotten this clear a picture of what lakes in New England looked like before they were impacted by industry and development.
That's really important. Because climate change is affecting Vermont’s lakes too. And it could make threats like runoff — which is already the biggest source of pollution to Vermont’s waters — worse.
“It's important to understand how aquatic life in lakes has changed in the past and in the future, with climate change," Lee said. "So that way, we can set benchmarks for how much nutrient can go into lakes and still protect the aquatic life that depends on the lake ecosystem.”
That means the faster scientists can diagnose lakes like Fairlee that are changing — the better they can protect them.
As Dr. Leslie Matthews with the Vermont Department of Environmental Conservation points out, to restore a lake that has already seen its water quality decline dramatically costs a lot of money.
“It’s much less expensive and less difficult to stop the problem before it gets away from you, than it is to restore a lake that has become much more significantly deteriorated,” Matthews said.
Leslie and Kellie, and their colleagues at the EPA hope these teeny, tiny plants just might paint a picture of the past, that will make the future of lakes in the face of climate change more clear.
Have questions, comments or tips? Send us a message or get in touch with reporter Abagael Giles @AbagaelGiles.
