Climate change warming area lakes

Photo of Katrina Koerting

The toxic blue-green algae blooms that plagued Connecticut lakes last summer, closing some beaches for weeks, could be a sign that climate change is already raising the temperature of the region’s waters.

Data for most Connecticut lakes is scattered, but summertime measurements at Candlewood Lake show a clear warming trend, with average surface temperatures increasing about 1.2 degrees Celsius, or near 2.2 degrees Fahrenheit, since the Candlewood Lake Authority began monitoring in 1985.

“We do see a very, very gradual increase in surface temperatures,” said Larry Marsicano, the authority’s executive director. “While it doesn’t seem significant to us, it’s significant to the environment.”

The rate of warming at Candlewood Lake is even faster than that reported in a recent global study funded by NASA and the National Science Foundation, which found that lakes worldwide are warming at an average rate of 0.34 degrees Celsius, or 0.61 degrees Fahrenheit, per decade. That rate is faster than that of the world’s oceans.

Scientists warn that lake warming will not only damage ecosystems — increasing algae blooms and killing off certain species of fish, for example — but could also create spinoff economic effects, eventually including devaluation of lakeside properties.

“All of these things can really affect how we use and enjoy the lake(s) for these goods and services,” said David Richardson, a biology professor at SUNY-New Paltz who is one of the lead scientists on a study of nearly 400 lakes in the northeastern U.S. and Canada, including Lake Lillinonah.

Connecticut environmental officials collect temperature data for dozens of lakes, but the measurements in most cases are for a year or two at most, and cannot be used to detect trends over time. Candlewood Lake, where the lake authority conducts its own tests, is an exception.

But scientists agree that lake warming is already detectable in the Northeast.

Richardson, whose study is being done for the Global Lake Ecological Observatory Network, said the health of lakes is an important indicator of the health of the surrounding ecosystems.

“They’re really our canary in the coal mine,” he said.

The effects of climate change on lakes in the Northeast are most noticeable in the summer and winter months.

During the winter, the warming trend means that ice forms later and melts earlier, reducing the insulating effect of the ice cover and leaving more time for the water to absorb heat, said Bob Kortmann, a scientist who has been studying Connecticut lakes since 1975.

During the summer, the natural stratification of warm and cold layers in the water intensifies as surface temperatures rise, creating ideal conditions for the growth of blue-green algae. These organisms produce a toxin that causes digestive problems and other ailments in humans, and is particularly dangerous to dogs.

“It’s hard to ignore when you see the amount of literature out there that connects the frequency of blue-green algae blooms with climate,” Marsicano said.

Last summer, algae blooms forced beach closures at many Connecticut lakes, including Candlewood, Lake Zoar and Squantz Pond.

As such closures become more frequent, the lakes would offer fewer opportunities for swimming, fishing and boating, which could affect the health of lake-dependent businesses like marinas and bait shops, and eventually lessen the value of lakeside property.

Although no study on the local economic effects of climate change has been done, Marsicano suspects home values could fall by 30 percent in lakeside communities.

But if long-term effects of warming waters on humans are hard to pin down, they’re easier to outline for organisms, such as fish.

Jennifer Klug, a Fairfield University biology professor who has been studying Lake Lillinonah since 2003, said changing water temperatures and the resulting change in oxygen levels could eventually be fatal to fish and the organisms they feed on.

Many species of fish can live only in a certain range of water temperatures and oxygen content.

“You may be in a situation where you’re decreasing the oxygen at the bottom and increasing the temperature stress on top, so the fish are squeezed and have no place to go,” Klug said.

One of her students has launched a study of the stresses water temperatures put on fish in Lillinonah, especially the northern pike. Klug said her own observations since 2003, however, have detected no major decline in pike populations.

Candlewood, which is considered a cold lake, has been a premier trout fishing destination for years. But Marsicano worries trout won’t survive if the water gets much warmer, and that the lake authority might have to begin stocking other fish species that do better in warm water.

Warming water also means a better environment for invasive species, especially those from southern climates. Hydrilla, a common invasive aquatic plant native to Asia, already has appeared in Squantz Pond and other Connecticut lakes.

“You can see shifts in the populations of the organisms living in the lakes,” Marsicano said.

Klug said it’s not too late to help reverse the effects of climate change. She and Richardson encourage people write to their representatives so the necessary legislation can be enacted.

“You don’t just have to sit there and watch it happen,” Klug said.

She also recommended people do things at the local level to improve the lakes’ health, such as restricting the amount of phosphorus that enters the water.

“Lakes in Connecticut are very valuable resources,” Klug said. “I think it’s something that people who live in Connecticut really appreciate.”

As surface waters warm, they mix less with the cooler waters below, in effect creating two layers in the lake. As a result his also prevents oxygen from getting to the deeper waters.

When the stratification occurs, the oxygen can’t get to the nutrients at the bottom of the lake and so the nutrients release phosphorus, which feed the blue-green algae. The blue green algae are unique because they can regulate their buoyancy, allowing them to stay at an intermediate depth where they can feed off the phosphorus below. Other organisms tend to drop out of the water column when the water warms and becomes less dense, Marsicano said.

Nutrient levels haven’t changed much since the 1980s when restrictions were created to limit the amount of phosphorus entering the water. However more blue-green algae blooms keep appearing.

“The problem is, the new factor — climate change — has kind of changed the game,” Marsicano said.