This story by Claire Potter was published Aug. 24 in the Valley News.
FAIRLEE — Temperatures climbed near 90 degrees Tuesday morning on Lake Morey. The wind was still, and the water was smooth as glass. Phosphorus levels in the lake have been climbing for years.
“We’re sitting on the perfect conditions for cyanobacteria,” said Kellie Merrell, an environmental scientist with the Vermont Department of Environmental Conservation.
Lakes Morey and Fairlee are sparking the concern of state scientists who want to act before levels of cyanobacteria, which creates blue-green blooms in the water and is toxic to humans and pets, reach a tipping point. One of the biggest reasons for the slimy, sometimes deadly blooms is increased phosphorus levels and nutrient-rich runoff as a byproduct of human development. But they’re pushing to get ahead of the problem.
“Something is changing now and that gives us hope that if we find the sources of phosphorus responsible for the increasing trends, we can turn those trends around or ‘flatten the curve’ before it gets to a new steady state at a high level of phosphorus like Lake Carmi (in Franklin, Vt.), which will require a lot of intervention to restore,” said Kellie Merrell, an environmental scientist with the Vermont Department of Environmental Conservation.
Spherical colonies of cyanobacteria glistened in the water Tuesday as scientists with the DEC and the University of Vermont launched into Lake Morey to collect samples of water and sediment. Nearer the shore, denser colonies clustered into long, yellow-green streaks.
They were likely a species called “gloeotrichia,” a variety of cyanobacteria especially well-adapted to Lake Morey, Merrell said. The microorganisms feed on nutrients, including the phosphorus released from the sediment at the bottom of the lake, and then move up in the water column to collect the sunlight they need for photosynthesis. A little wind would have disturbed their movement, but the calm breeze registered barely a ripple in the water.
Cyanobacteria, also known by the misnomer blue-green algae (their cellular structure is different from algae), are freshwater microorganisms that photosynthesize their own food. They produce toxins that poison dogs and irritate the skin, said Mark Mitchell, who coordinates over 100 volunteer lake monitors across the state. Small children should not swim in a lake with an active bloom.
Human activity fosters their proliferation. Runoff from agricultural land increases the nutrient loads that feed cyanobacteria, while deforestation and development along the lakeshore can deliver more nutrient-heavy runoff into the lake.
Merrell and her colleagues said climate change is exacerbating the problem and making the need to protect healthy lakes more urgent. Cyanobacteria thrives in warmer water, and a longer growing season means more nutrient-rich runoff. Warmer lakes also move less, which leaves the lower depths of the lake with depleted oxygen levels. When oxygen levels are low, the sediment along the lakebed releases phosphorus that has built up over centuries.
Lake Morey saw cyanobacteria blooms for decades and even had a major summer fish kill in 1985, according to a paper by Eric Smeltzer, a former DEC scientist. Picturesque lake homes line Morey’s banks, and the community became increasingly concerned about the quality of the water and looked for ways to restore it. In 1986, scientists aboard a high-speed transport barge administered an “alum treatment” with money from the federal Clean Lakes Program, which Merrell said has gone without congressional funding for about 25 years.
“Impervious surfaces” — a category that includes a wide range of manmade structures including riprap, driveways and paved boat launches — make up 15% of Morey’s lakeshore, and may be fueling cyanobacteria’s recent growth, Merrell said.
Leslie Matthews is also an environmental scientist with the DEC. She and Merrell work together to collect samples on Vermont’s inland lakes. She said that water moves faster along impervious surfaces, which means that it picks up more nutrient-laden sediment. An impervious lakeshore also cannot absorb sediment, so the sediment makes it right into the water.
Samples collected each summer show that phosphorus levels are climbing to worrisome levels, although the spring samples and water quality levels are still favorable.
A green haze glowing out of the water near a lake house on Morey’s shore showed where a relatively harmless variety of algae was thriving. Merrell said that it was a “smoking gun for nutrients.” Along the lakeshore, high levels of algae near developed sites suggest that localized runoff and a lack of shade may be fostering conditions for cyanobacteria, Merrell said.
“It is easier to protect and identify places starting to tip than to start an intervention too late,” Matthews said.
Merrell said Vermont’s lakes are relatively healthy, but that the state struggles to access federal funding to protect its watersheds because the EPA’s funding pathways favor restoring lakes that need intervention rather than preserving lakes before they get worse.
A few miles south, Lake Fairlee has seen steeper increases in phosphorus levels. Both spring and summer levels of phosphorus are rising, and its water clarity levels — a key indicator of the lake’s health — are declining.
“There are a lot of stressors in that watershed,” Merrell said. “It’s death by a thousand paper cuts.”
Runoff from the 108 acres of agricultural land within 100 feet of its tributaries may be fueling the watershed with the nutrients that feed cyanobacteria, as might runoff from roads without erosion control. Fourteen percent of its lakeshore is made up of impervious surfaces. The lake has never seen a bloom, but the sediment in a crater along its bed is releasing phosphorus it has stored over centuries.
The Vermont Lake Wise program, coordinated by Amy Picotte with the DEC, helps lakeshore owners be better stewards, which may mean stopping mowing so that natural vegetation can grow, or more proactive interventions such as installing waterbars or digging trenches to limit runoff. Her work with lakeshore owners around Lake Seymour in Morgan, Vt., “helped to turn the increasing phosphorus trends on that lake around and flatten their curve,” Merrell said.
With early intervention, lakes Morey and Fairlee may see the same success.
Claire Potter is a Report for America corps member. She can be reached at [email protected] or 603-727- 3242.
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