top of page

Key Indicators of Lake Health - In the Water and Under the Ice

Updated: Jun 5, 2019

Dr. Danielle Wain, 7 Lakes Alliance, Emily Cunningham Colby College Student

7 Lakes Alliance’s Dr. Danielle Wain leads our collaboration with Colby College, working closely with Colby’s Dr. Whitney King to monitor all 7 lakes in the Belgrade Lakes Watershed. The following indicators are strongly linked together

and, when observed as a system, help us better understand lake health.

Stratification: Temperature gradients in the water column can form layers that prevent the transport of oxygen and nutrients from the deeper parts of the lake to the surface layer. Lake turnover - the mixing of these layers - is natural and supports healthy productivity. We monitor the timing of stratification and lake turnover to understand changing nutrient levels all year, including under the ice.

Phosphorus (water column): Phosphorus is a nutrient found in both lake sediments and the water column. At low levels, it supports healthy productivity in a lake, while at high levels can spark an algal bloom. Humans can contribute, including through erosion, to increased phosphorus levels and algal blooms, a process known as cultural eutrophication.

Oxygen: Oxygen tells us a few things about lake health, most importantly viability of a cold-water fish habitat and the likelihood of nutrients (like phosphorus) being released from sediment.

Sediment (iron, phosphorus, aluminum): To collect these samples, we “grab” sediment from the bottom of the lake. These tests are sent to Colby’s lab to be analyzed. They indicate the lake’s natural ability to bind excess nutrients and

the likelihood of further nutrient release during stratification.

Algae: Monitoring the balance of different algal species in a lake is key to understanding and anticipating changes in lake health. Some algae are harmless and support the bottom of the food chain (diatoms like Asterionella), and some are dangerous (Anabaena/Dolichospermum) because of the potential release of cyanotoxins.

Watershed Science – Current Issues and Updates This summer, 7 Lakes Alliance will be busy throughout the watershed! We’ll have assistance from and provide an excellent hands-on experience to 6 Colby interns. Three are made possible through a generous grant to 7 Lakes from Wells Fargo. On East Pond, where in 2018 the largest alum treatment to date in New England was conducted, we’ll perform intensive sampling to document post-alum treatment conditions to monitor the lake’s recovery. In 2018,

after the treatment, East Pond had excellent water quality. If this condition continues in 2019, 7 Lakes and its partners believe that the alum treatment will be effective for many years.

We’ll also keep a close eye on North Pond to help understand the drivers of last year’s algal bloom and if it might occur again this summer. We will continue in-lake monitoring of all the lakes and use this data along with the watershed surveys (such as those done by Great Pond and McGrath-Salmon in the past year) to determine the primary sources of phosphorus into the lakes to help inform action plans to prevent and remediate issues as indicated by the best

science. For news, watch the websites and Facebook for 7 Lakes and each watershed organization. Interns will also work on a variety of other projects, including detection of cyanotoxins from algae, modeling the lakes to look at the impacts of climate change, and the contribution of good water quality in lakes to the local economy.



bottom of page