Why Should I Care About Water Trends?

  • As native species composition and distribution change within the Kezar Lake watershed, our surface waters will become more susceptible to aquatic invasive plants, including milfoil.
  • Changing species composition will cause a shift in the ecological balance of water and nutrient cycles that could degrade water quality over time.
  • More frequent and intense rain events will cause more erosion and adsorbed nutrients to wash off the landscape to nearby surface waters, fueling algal blooms.
  • Earlier snowmelt will cause changes in seasonal duration and timing of spring, which greatly impacts life cycles, including the growth and survival rates of loons and other bird species.
  • Earlier spring turnover in the lake and ponds may also fuel algal blooms and cause more prominent late summer low dissolved oxygen levels, impacting fish and other aquatic species.

How Can I Help?

Water Quality Trends

Water quality data has been collected in the Kezar Lake watershed since 1970. These data provide a wealth of long-term information from which we can judge the health of the lake, ponds, and streams in the watershed. Because water quality can fluctuate significantly from year-to-year depending on local conditions and activities within the watershed, analyzing data over a longer time period can reveal subtle, yet steady directional changes in water quality. It is important to identify waterbodies at risk for degrading water quality as a result of climate change or development, so we can take action to combat the effects.

Key for Data Symbols – Current Conditions & Trends


Summary of Current Conditions & Trends

Click a water body or data-point on the chart below for more details

Lakes and Ponds

Water Body
Water Clarity
Total Phosphorus
Anoxic Extent

Brooks and Streams

Water Body
Total Phosphorus
Dissolved Oxygen

Sediment Core Sampling Results

One of the most effective ways to understand the long-term effects of climate change on lake ecosystems is to compare past conditions with current ones. Since sediments that accumulate at the bottom of a lake are the result of the biological, geological, and climatological changes within each lake’s watershed, they provide a sequential record of past conditions in lake productivity, stratification, oxygenation, and material inflows from streams and watershed runoff. The sediment core study of Kezar Lake aimed to better link water quality with climate and land use and to determine which stressors have put Kezar Lake water quality at greatest risk for future impairment.


  • Natural processes affecting water quality within the Kezar Lake watershed were relatively stable until the Europeans arrived in the 1800’s.
  • The Europeans logged forests, plowed fields, raised farm animals, trapped beavers, and built roads, resulting in significant changes to the landscape.
  • The Industrial Age added other stressors and pollutants, such as acid rain, heavy metals from the burning of fossil fuels, chemicals from fertilizers and other uses, and high-powered boats that create wakes and disturb bottom sediments.
  • The synergistic effect of human activities and rising temperatures due to climate change is having a measurable impact on our environment.

Major Study Findings

  • Between A.D. 2000-2015, the sediment accumulation rate and organic content of both the deep spot of Kezar Lake and the area near Great Brook increased dramatically, likely the result of intensified watershed runoff and erosion due to climate change effects of more frequent and more violent storms. This recent intensification of larger-scale flood and erosion events caused a notable increase in particle-size and decrease in aluminum concentrations in lake bottom sediments at both sites.
  • Preliminary diatom results indicate that a marked change in algal composition accompanied the increase in sediment accumulation rates after 2008. This supports the idea that the lake is not currently as stable as it was just a decade ago.
  • The particle-size record at the deep spot of Kezar Lake suggests that no large-scale events have occurred in the Kezar Lake watershed since the large hurricanes in the 1600’s, despite forest clearances in the 1800’s and fires in the 1930’s. The Great Brook core record showed the influence of many smaller-scale events that are most likely associated with minor flood events.
  • The deep spot of Kezar Lake showed a steady rise in lead and zinc from the burning of coal and gasoline since the 1800’s, then a sharp decline in the 1970’s after the ban of leaded gas. The Great Brook core record did not show as sharp a decline in lead and zinc as at the deep spot, which may indicate a continued source of heavy metal contamination from dredged or disturbed lake sediments with legacy contamination.

Future Core Studies

  • We expect to complete the diatom analysis and integrate those results with the existing data sets. Diatom (microscopic algae) assemblages provide information on how aquatic plant species changed over time. Depending on the aquatic species that changed, it is possible to estimate historic air and water temperature, as well as historic water qualityconditions, like pH, alkalinity, clarity, and nutrient availability.
  • We also plan to obtain a lead-210 (210Pb) dating of one of the Great Brook cores to more accurately correlate the data sets from the Kezar Lake deep spot and the Great Brook cores. Radiocarbon dating of a subsample (around A.D. 1600) of the Kezar deep spot core would also be helpful in validating the timeline for the rate of sediment accumulation.

Want More Information?

Refer to the 2016 Climate Change Observatory Annual Report for a more in-depth discussion of results.
Current Report PDF

Aquatic Plant Trends

Warming water temperatures, longer growing seasons, and changing precipitation patterns will cause shifts in the extent and abundance of native aquatic plant species.

Many aquatic plant species that thrive under cooler conditions will die out, giving opportunity for southern plant species to take root. This will cause a gradual change in aquatic plant species composition and distribution within the lake and ponds.

Different aquatic plant species have varying levels of nutrient and water needs, a change in which will alter cycling dynamics within the lake and ponds.

An immediate threat to Kezar Lake is the invasion ofnon-native plants that can outcompete native plants. This threat is being addressed by the Lovell Invasive Plant Prevention Committee (LIPPC). A list of aquatic plants native to waterbodies within the Kezar Lake watershed is being compiled using data collected by the Lake and Watershed Management Association from 2011-2015,as well as published survey reports funded by the LIPPC. Cushman Pond has already been invaded byvariable-leaf milfoil and efforts to eradicate this invasive have taken place over the last 20 years.

Fish Trends

Fish are a keystone species for the Kezar Lake fishing community, who have relied onabundant populations of coldwater fish for their recreational enjoyment. These coldwater fish species are extremely sensitive to changes in water temperature andchemistry. Coldwater fish will seek cold, deep areas of lakes, ponds, and streams toavoid warm surface waters in late summer. This can be problematic in productive lakes that have depleted oxygen in bottom waters, leaving little habitat for these fish species to survive.

pH is particularly critical to fish species and other aquatic life as it affects their metabolic functioning and reproductive capacity. This is a concern for Kezar Lake and its ponds given the naturally-low buffering capacity of the soil and water in the watershed. Low-pH rain (5.0) temporarily decreases the pH of surface waters, placing significant stress on aquatic organisms residing in those waters.

If climate change enhances the frequency and duration of precipitation events, then sensitive fish populations may face high disturbance, low pH environments that may be fatal. Because of this, fish can be a good indicator of climate change and should be monitored.

As an invasive species in Maine, the northern pike is a voracious predator of other fish, frogs, crayfish, small animals, and birds. It was originally introduced into the Belgrade Lakes and resembles the native chain pickerel. There are no effective control mechanisms for this sport fish other than catch and kill. A compilation of invasive species of concern in Maine is provided in Appendix B, which provides a description and image of these invaders and lists sources for more information on each species’ identification and mitigation.

Aquatic Bird Trends

Warmer air temperatures, variable precipitation patterns, and changes in vegetation will very likely reduce the abundance and diversity of aquatic bird species, including the iconic common loon. Earlier snowmelt means changes in seasonal duration and timing, which greatly impacts life cycles, including growth and survival rates of loons and other bird species. Monitoring these populations will help assess the effects of climate change on native species in the watershed.

In 2018, supported by a grant from the Stephen & Tabitha King (STK) Foundation, Loon Conservation Associates (LCA) headed a collaborative study with KLWA to conduct comprehensive common loon monitoring surveys in the Kezar Lake watershed. More than fifteen volunteers helped conduct over 500 independent surveys of seven waterbodies between 5/15/2018-8/30/2018. Out of fifteen documented territorial pairs, seven of thirteen pairs successfully nested and produced ten chicks. Eight adult loons were captured and banded on Kezar Lake and ponds using traditional night-lighting techniques. Five chicks survived to fledge (defined as more than six weeks of age). Overall productivity in the Kezar Lake watershed in 2018 was 0.33 fledged young per territorial pair. Three pairs used rafts to nest and successfully hatched one or two chicks. The rate of success was 100% for raft nesting loons compared to 33% for natural nests. These results indicate that the productivity of loons in the Kezar Lake watershed are below the 0.48 threshold needed to sustain a healthy loon population. Poor reproductive success is likely attributed to one or more causes, including predation, human disturbance, water level fluctuation, as well as contaminants such as lead (Pb) and mercury (Hg) and wintering hazards such as commercial fishing nets and oil spills.

Overall, the adult loon population at Kezar Lake has been constant with some annual changes in the last 35 years (Fig. 1). The chick population shows a statistically-significant but slight decline (based on Mann Kendall Trend Test) over the observation period.

Fig. 1.Annual loon counts for adult and chick populations observed at Kezar Lake.

The ponds have a much sparser data set:

  • Based on 15 non-consecutive years of observations, Horseshoe Pond hosts an annual chick population varying from zero to three, and Farrington Pond hosts a few adult loons with only two chicks seen in 2016. One nesting pair was documented on Horseshoe Pond in 2018 with one successful chick fledging. One territorial pair with no nest was documented on Farrington Pond in 2018.
  • Based on 19 non-consecutive years of observations, Heald Pond hosts an annual adult population varying from zero to three. The first and only chick was documented in 2015. One nesting pair was documented on Heald Pond in 2018, but the chicks did not survive to fledge.
  • Based on 30 years of non-consecutive observations, Cushman Pond hosts an annual adult population varying from zero to three. The first and only two chicks were documented in 2011. One nesting pair was documented on Cushman Pond in 2018, but the nest failed.
  • Based on 11 non-consecutive years of observations, Trout Pond hosts an annual adult population varying from zero to two. The first and only two chicks were documented in 2017. One nesting pair was documented on Trout Pond in 2018, but the nest failed.
  • Surveys were completed on Bradley Pond in 2018 but no loons were found.

Estimation of loon population in southern Maine conducted by the Maine Audubon show an increase in loon population despite climate change impacts. The study suggests that as long as lakes are clear, the food supply is abundant, and any adverse human impacts are avoided, the loon population will remain stable and/or increase.

Zooplankton Trends

Zooplankton play an important role in a lake’s ecosystem and are useful indicators of food web stability. As microscopic animals that consume phytoplankton, zooplankton serve as a valuable food source for fish. KLWA supported a study of zooplankton in Kezar Lake from 2004-2007, the results of which were published in a 2008 article titled, “Cladoceran and copepod zooplankton abundance and body size in Kezar Lake, Maine (MIDAS 0097)” by Nichole M. Cousins and Katherine E. Webster from the School of Biology and Ecology at the University of Maine, Orono. The results of the study show that the zooplankton population in Kezar Lake was consistent during the sampling period and can be used as a baseline for future studies. The CCO supports future zooplankton studies to assess long-term trends in zooplankton population as a result of climate change or other environmental stressors.

Mollusk & Crustacean Trends

KLWA supported a brief study of crayfish in Kezar Lake in August-September 2008. The study was conducted by Dr. Karen Wilson at the University of Southern Maine. The study found three native species and caught a total of 29 crayfish, which were mostly found around rocky islands. The spatial and temporal sample size were too small to gain any significant conclusions on population size, species composition, or size trends. No evidence of invasive crayfish was found. Anecdotal evidence suggests that the crayfish population has declined in Kezar Lake. The CCO supports a new, more comprehensive, crayfish study in the future.

Invasive aquatic mollusks and crustaceans on Maine’s watch list include some that have already invaded Maine’s waters like the Chinese mystery snail, as well as others that are poised to invade in the future, such as the spiny water flea, zebra and quagga mussels, Asian clam, rusty crayfish, and the Chinese mitten crab. A compilation of invasive species of concern in Maine is provided in Appendix B, which provides a description and image of these invaders and lists sources for more information on each species’ identification and mitigation.

Aquatic Pathogen Trends

Warmer water temperatures, along with increased population growth, will increase the risk of aquatic pathogens, including bacteria, protozoa, and parasites. While it is difficult to control the spread of these pathogens due to climate change, we can make sure proper waste disposal techniques are used for all existing and future development in the watershed and along the shoreline of Kezar Lake and its ponds.


The Kezar Lake watershed will experience a switch from northern to more southern species as native, cool-weather-loving species are forced further north. This will also foster the spread of more southern species of potentially-harmful pathogens.

Alkalinity in surface waters with a low-carbonate geology will continue to decline due to reduced snowpack and loss of soil CO2. Common loon populations are expected to decrease by 50% in the northeast.

Local Water Trends Summary

Generally, most water quality parameters measured at the lake and ponds are stable or improving and in excellent condition, with some notable exceptions.

  • Dissolved oxygen is regularly anoxic (< 2 ppm) at Bradley, Horseshoe, and Trout Ponds, impacting >10% of lake bottom area. The upper basin of Kezar Lake may also show a degrading trend of slightly increasing anoxia at lake bottom, but is of little concern for now.
  • Surface water temperature shows a degrading trend of increasing temperature at the upper and lower basins of Kezar Lake. This is very likely the result of rising air temperatures, but could also be from changes in precipitation patterns – both of which are the result of climate change.
  • pH shows a degrading trend of increasing acidity at Bradley, Heald, and Horseshoe Ponds; this is despite regional improvements in acidic conditions in surface waters following the Clean Air Act in the 1970’s. pH is low (acidic) in all waterbodies.
  • Alkalinity shows a degrading trend of decreasing buffering capacity (to protect against major swings in pH) at the upper and lower basins of Kezar Lake and Heald, Horseshoe, and Cushman Ponds. All sites have extremely low alkalinity (< 5 ppm), which is a natural condition for the region; thus, condition assessment is based primarily on the presence of degrading trends.

Climate change threatens aquatic species composition and distribution throughout the Kezar Lake watershed, which makes the landscape more susceptible to southern invaders, including aquatic invasive plants, new tree-shrub species, and aquatic pathogens.

Coldwater fish and northern birds will be forced to migrate or die-out as temperatures warm and seasonal spring timing is altered. These changes will equate to a much different landscape for our children and children’s children to enjoy.

References for Water Trends

Fernandez, I.J., C.V. Schmitt, S.D. Birkel, E. Stancioff, A.J. Pershing, J.T. Kelley, J.A. Runge, G.L. Jacobson, and P.A. Mayewski. “Maine’s Climate Future: 2015 Update.” Orono, ME: University of Maine (2015): 24 pp. www.climatechange.umaine.edu/research/publications/climate-future

Horton, R., G. Yohe, W. Easterling, R. Kates, M. Ruth, E. Sussman, A. Whelchel, D. Wolfe, and F. Lipschultz, 2014: Ch. 16: Northeast. Climate Change Impacts in the United States: The Third National Climate Assessment, J. M. Melillo, Terese (T.C.) Richmond, and G. W. Yohe, Eds., U.S. Global Change Research Program, 16-1-nn. http://nca2014.globalchange.gov/report/regions/northeast

IPCC [Core Writing Team, R.K. Pachauri and L.A. Meyer (eds.)]. “Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change.” IPCC, Geneva, Switzerland: (2014): 151. http://www.ipcc.ch/pdf/assessment-report/ar5/syr/SYR_AR5_FINAL_full.pdf

Meyer, Judy L., et al. “Impacts of climate change on aquatic ecosystem functioning and health.” Journal of the American Water Resources association 35.6 (1999): 1373-1386.

Stewart, Iris T., Daniel R. Cayan, and Michael D. Dettinger. “Changes toward earlier streamflow timing across western North America.” Journal of climate 18.8 (2005): 1136-1155.


Alkalinity: A measure of the buffering capacity of a lake, or the capacity of water to neutralize acids. It is a measure of naturally-available bicarbonate, carbonate, and hydroxide ions in the water, which is largely determined by the geology of soils and rocks surrounding the lake. Alkalinity is important to aquatic life because it buffers against changes in pH that could have dire effects on animals and plants.

Chlorophyll-a (Chl-a): A measurement of the green pigment found in all plants, including microscopic plants such as algae. It is used as an estimate of algal biomass; higher Chl-a equates to greater amount of algae in the lake.

Color: The influence of suspended and dissolved particles in the water as measured by Platinum Cobalt Units (PCU). A variety of sources contribute to the types and amount of suspended material in lake water, including weathered geologic material, vegetation cover, and land use activity. Colored lakes (>25 PCU) can have reduced transparency readings and increased TP values. When lakes are highly colored, the best indicator of algal growth is chlorophyll-a.

Dissolved Oxygen: The concentration of oxygen that is dissolved in the water. DO is critical to the healthy metabolism of many creatures that reside in the water. DO levels in lake water are influenced by a number of factors, including water temperature, concentration of algae and other plants in the water, and amount of nutrients and organic matter that flow into the waterbody from the watershed. Too little oxygen severely reduces the diversity and abundance of aquatic communities. DO concentrations may change dramatically with lake depth. Oxygen is produced in the top portion of a lake (where sunlight drives photosynthesis), and oxygen consumption is greatest near the bottom of a lake (where organic matter accumulates and decomposes).

E. coli: A type of bacteria that lives in the intestines of warm-blooded animals, including humans. The non-pathogenic form of E.coli is monitored in freshwater systems as an indicator of fecal contamination from wildlife, pets, or humans (e.g., malfunctioning septic systems). The State of Maine sets water quality criteria for bacteria in surface waters to protect designated uses, including primary contact recreation (e.g., swimming) and aquatic life. Levels of E.coli that exceed these criteria indicate the likely presence of harmful pathogens also found in fecal matter. Exposure to or consumption of these pathogens may cause gastrointestinal, respiratory, eye, ear, nose, throat, and skin infections.

Flow: The measure of discharge (area of stream cross-sectional profile multiplied by the average velocity of water moving through that profile). The amount of water flowing through a particular point in a stream is a result of the size of the drainage area (e.g., larger drainage areas feed larger streams), the type of land cover and soils within the drainage area (e.g., forests and loamy soils are able to absorb more water than developed areas and sandy soils), and the local climate (e.g., amount of rain falling within the drainage). Climate change is predicted to increase the frequency and intensity of precipitation, causing greater and more frequent fluxes in discharge; thus, stream flow is a critical indicator of climate change impacts to ecological systems.

pH: The standard measure of the acidity or alkalinity of a solution on a scale of 0-14. Most aquatic species require a pH between 6.5 and 8. As the pH of a lake declines, particularly below 6, the reproductive capacity of fish populations can be greatly impacted as the availability of nutrients and metals changes. pH is influenced by bedrock, acid rain or snow deposition, wastewater discharge, and natural carbon dioxide fluctuations.

Secchi Disk Transparency (SDT): The vertical measure of the transparency of water (ability of light to penetrate water) obtained by lowering a black and white disk into the water until it is no longer visible. Transparency is an indirect measure of algal productivity and is measured in meters (m).

Temperature: The measure of the degree of heat in water. Temperature affects the density of water (e.g., cooler water sinks), the solubility of gases (e.g., cooler water holds more dissolved oxygen), the rate of chemical reactions, and the activity of aquatic organisms (e.g., metabolic growth rates peak at different temperatures for different species; some species such as trout and salmon prefer cooler, more oxygen-rich waters; others such as bass prefer warmer waters). Humans can alter temperature by removing shade-providing trees near surface waters, constructing dams or other impoundments that restrict free flowing waters, and causing soil erosion (e.g., turbid water absorbs more heat from the sun). Climate change is predicted to increase surface water temperatures at a much faster rate than the observed increase in air temperature; thus, water temperature serves as a critical indicator of climate change impacts to ecological systems.

Total Phosphorus (TP): The total concentration of phosphorus found in the water, including organic and inorganic forms. TP is one of the major nutrients needed for plant growth. It is generally present in small amounts and limits plant growth in freshwater ecosystems. As phosphorus increases, the amount of algae generally increases. Humans can add phosphorous to a lake through stormwater runoff, lawn or garden fertilizers, and leaky or poorly maintained septic tanks.

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