The Influences of Climate Change on Lakes

Carol Gillis

The 2019 annual conference of the Lake Stewards of Maine was held in Turner on Saturday, July 27th, with 12 people from New Gloucester joining attendees from across the state.  Lake Stewards’ volunteers monitor the health of over 450 Maine lakes. Volunteers from New Gloucester monitor the health of Sabbathday Lake, tracking water clarity and conducting invasive plant surveys.  The data gathered helps to monitor the health of the lake as well as follow changes over time. The health of this and other lakes affects aquatic life and recreational value. The associated property valuation may impact tax revenue for the town.

Lake Stewards of Maine is a network of volunteers who monitor water quality and invasive species in lakes throughout Maine. Photo of volunteers and staff from their 2016 annual conference from

The theme of this year’s conference was “The Influence of Climate Change on Lakes: What’s Coming and What’s Already Happening.” Influences of climate change on lakes include decreased water clarity, loss of dissolved oxygen, increased algae growth and fish death.

“Maine Lake Ice Out Dates: 1807 to 2018” presented by Lloyd Irland, PhD, Forester and Economist with  The Irland Group, reviewed available data for several Maine lakes within each of Maine’s climate regions.  Although there can be noticeable variation from year to year there is a clear trend of change in ice out dates occurring earlier per decade since the late 19th century. At Lake Auburn, the ice cover days decreased 20 days between 1952 and 2017.  The increase in ice-free days affects fish habitat, migratory water fowl, water stratification (water layers that act as barriers to water mixing) and seasonal changes in plants and animals.

“The Influences of Climate Change on Lake Water Quality, Including Recent Case Histories” presented by
Linda Bacon, Limnologist and Unit Leader with Maine DEP Lakes Program, described significant, unanticipated changes in water quality experienced by a number of Maine lakes during the past 10-15 years. A warming climate appears to have been a common factor in the complex interaction of conditions and circumstances that contributed to these changes. Case studies of several Maine lakes that have been pushed “over the edge” in recent years were presented, as well as efforts underway to slow or reverse their decline. The presented data showed how the land and water are warming. 

The impact of these changes include a longer growing season, earlier warming of shallow waters, longer periods of water stratification, increased potential for oxygen loss in deeper water, and increased nutrient cycling from sediments.  These changes can alter lake biology with changes in species composition, earlier appearance of some species, disruption in timing of life cycle events such as spawning, out‐of‐sync interactions between species, decreasing oxygen in deep water, release of phosphorus from sediments and stress on cool water and cold water fish.

“Effects of a Changing Climate on Invasive Aquatic Species: Threats to Maine Lakes” presented by Roberta Hill, Aquatic Ecologist and Invasive Aquatic Species Program Director with Lake Stewards of Maine, covered some of the impacts of a warming climate in Maine.  As stated in her presentation, the Scientific Consensus is 97% – 99.999 % that the climate is warming in ways that are globally disruptive, that the phenomena is caused by humans, and that there is more CO2 in the atmosphere from burning of fossil fuels, and the natural greenhouse effect has been intensified by human activities. 

Maine’s average annual temperature has increased by 3 degrees and average precipitation has increased by 6” since 1895. Changes include wetter winters and springs, drier summers, patchy droughts, heavy rains, and a longer growing season.

Higher precipitation in winter and spring, when trees are not able to take up the water, results in run-off carrying small soil particles and phosphorous into the lakes.  Warmer water holds less dissolved oxygen and increases the proportion of toxins, such as lead and mercury, that are able to be absorbed by wildlife.  These changes impact native species in many ways, creating a disadvantage for cold weather wildlife such as moose, loons, puffins, bobcats and brook trout.

FMI and slides from these presentations and more, see h