7 Lakes Alliance and the North Pond Association have increased the frequency of their water clarity measurements so they can advise the public about the safety of swimming in North Pond in the wake of a lake-wide algae bloom.
The most recent measurement yielded a water clarity of 4 feet. 7 Lakes Alliance recommends avoiding prolonged contact with green water, and avoiding surface scums entirely. Should the clarity decrease to 3 feet, 7 Lakes will urge people to avoid going into the water, consistent with Maine Department of Environmental Protection guidelines. Generally, swimmers should not go into the water if they cannot see their feet.
Toxin tests conducted Friday, July 22, found no microcystin present at shoreline sites on Northshore Drive, Fairview Grange and Pine Tree Camp. Microcystin is the toxin most likely to be observed in Maine lakes.
North Pond last suffered a July algal bloom in 2020. That episode lasted a month before the algae eventually consumed the available phosphorus, the nutrient upon which algae feeds. The thickness of the algae in 2020 also blocked out the sunlight needed for continuous growth.
Algal blooms in 2019 and last year were shorter in duration because they occurred in August, when Maine’s temperatures begin to cool. Warmer temperatures spur algal growth.
Dr. Danielle Wain, Lake Sciences Director for the 7 Lakes Alliance, said the duration of a bloom often depends on weather conditions. Rain on Monday, July 25, coupled with high temperatures that top out in the mid-80s this week may help dissipate the bloom, particularly if high winds are also present.
Dr. Wain said development along North Pond’s shores are contributing to algal blooms, noting the proximity of many camps, homes and gravel roads to the water. Erosion carries phosphorus into streams and lakes.
Other contributing factors could include the nature of North Pond’s sediment and the lake’s depth, Wain said. Shallower lakes have greater oxygenation down to the bottom sediment; without aeration, sediment emits phosphorus, she said. Conversely, deeper lakes are typically stratified by temperature, which keeps algal blooms at bay until the fall when temperatures are colder and conditions are not as hospitable to algae.
That Little North Pond, which is connected to North Pond, has not suffered an algae bloom may be attributed to the minimal water exchange between the two bodies, the absence of development around Little North Pond, and differences in sediment and depth, Wain said.
7 Lakes Alliance and the North Pond Association are crafting a watershed-based management plan that will identify sources of phosphorus and offer research-based recommendations to mitigate erosion and phosphorus loading in North Pond. Similar studies have recently been completed on Great Pond and Long Pond, and were conducted on East Pond before its alum treatment in 2018 to combat algal blooms.
7 Lakes’ science team, led by Dr. Wain and Dr. Whitney King of Colby College, test water quality in all seven lakes year-round, including boring through ice in the winter. Along with tracking water quality trends, that data, combined with watershed-based management plans, helps determine the best actions for preserving and restoring water quality in each lake.
Dr. Wain noted an approach that works on one lake may not be suitable for another because of sediment makeup, depth, tributary characteristics, development, chlorophyll, oxygen and phosphorus levels in the water, and other factors.
7 Lakes works year-round to protect the lakes by testing water, minimizing erosion, preventing the spread of invasive plants and conserving land, which serves as a buffer against erosion. That work is critical to avoiding future blooms on North Pond and the six other lakes.
“Algal blooms and the threat of blooms are an ongoing concern throughout the Belgrade Lakes watershed,” 7 Lakes President and CEO Laura Rose Day said. “That is why we and our partners must remain vigilant on efforts to minimize erosion, conserve land and educate people on how they can be part of the solutions.”
pages. For more information on blooms and toxins, along with other recommendations for camp owners, visit the Maine Department of Environmental Protection website.
UPDATE at 12:43 p.m. July 26: Today's water quality measurements showed no appreciable improvement. Measurements will be taken again tomorrow.