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Is your local pond or lake thawing? State scientists want to know

A lake is frozen over during the winter.
Research suggests that "ice outs" on Vermont lakes and ponds, like Lake Champlain, are coming 1.5 days earlier every decade.

Some communities make spring-time contests out of the ice-out date, which is when a lake or pond loses all of its ice from shore to shore.

If you live near Joe’s Pond, or Lake Memphremagog, you can win a few thousand bucks if you come closest to guessing the right day.

But those Vermonters aren’t the only ones paying attention.

State scientists are asking residents around the state to report when their nearby ponds or lakes thaw. The dates mark when researchers can begin sampling water systems across Vermont — and they provide clues about the state’s changing climate.

To learn more about the research and why it’s important, VPR's Grace Benninghoff spoke with Mark Mitchell, a limnologist with Lake Champlain Sea Grant and the Vermont Department of Environmental Conservation. Their conversation below has been condensed and edited for clarity.

A man sits in a boat traveling across a lake.
Mark Mitchell
Limnologist Mark Mitchell collects samples at Lake Iroquois in northwest Vermont.

Grace Benninghoff: Why is it important to begin sampling shortly after the ice melts on a pond or lake?

Mark Mitchell: That kind of sampling gives us a clue to baseline conditions going into the summer. So when we're sampling at that time of the year, we're looking at nutrients, mainly phosphorus, to see how much is available for plants and algae to grow. And that gives us an idea what condition that lake is starting out that year.

Why is this important data to collect each each year? What do we need to learn about algae and about the conditions in the summer?

We're looking at tracking changes in algae levels, as well as plant growth. So we're trying to track trends over long periods of time to see if that's actually increasing. And if that's from human development, or climate change — or a combination of both.

How does aquatic plant growth like you're describing tie into what we know about a lake's or pond's health?

The plants are going to be taken up nutrients just like algae. So what we're seeing with warming temperatures is you can have increased plant growth. And that can start earlier in the year as well, with earlier lake ice outs.

That plant growth can be a nuisance. Also, if there's invasive plants — nonnative species — they can take advantage of that warming weather and, like I said earlier, get an advantage over the native species. And that can create an issue in the lake biologically, but also for recreation.

Recreation, do you mean we can have poisonous algae blooms? What does that mean?

We do have issues with certain invasive plants that can impede boating by getting caught up in the propeller. And also just sort of, you know, being a thick area to kind of navigate through. And same with swimming. A lake will look a little bit different as well, so aesthetics can also be affected.

And then as far as algae, yeah, for cyanobacteria, you can take advantage of some of the warmer temperatures, as well as nutrients from the bottom of the lake. And they can kind of take over and they can be toxic at times. But it's hard to predict exactly when that's going to happen. But we are seeing blooms in areas around the state seemingly occurring more frequently. But we're still needing to gather more data on that to consistently show differences from year to year.

Scientists are also tracking the ice-out dates themselves on lakes and ponds around the state. What are those dates telling us about Vermont's climate?

I've actually looked at about 15 lakes that we have 20 or more years of ice-out data on. And those 15 Lakes — all but one of them — are actually showing earlier ice-out trends. And when we look at all 15 lakes together, we can say that on average, it started getting earlier by about a day and a half each decade.

For the state as a whole, I mean, it's just an indication of getting ready for for changes in the climate. You know, it's definitely warming up here. The winters seem to be less cold. And things like ice fishing, for instance, are going to have a shorter season for that on the lake. But yeah, it all coincides with the warming temperatures. So kind of a changing environment, changing climate.

How can Vermonters help with the research your team is doing?

Thanks for asking that. So we do have a web form right now available on our website, the Department of Environmental Conservation Watershed Management Division website, and they can report the lake ice-out dates and a description of what exactly that means from year to year so we can track individual lakes.

And we also have a section for reporting lake ice-in dates as well, as those seem to be probably happening later in the fall now.

And we also have some other volunteer opportunities, including cyanobacteria monitoring. So having volunteers who, anytime they're at a lake, they can report visually what they see. The more information we have, the better. We can track these changes and see what's going on from lake to lake, as well as in the region.

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