Session 10: Maine Lakes: Climate Change Impacts and Adaptations

Afternoon Session

* 2 credits are available for this session through APA AICP
* Three presentations in this session have been approved for training contact hours (TCH) through the State of Maine Board of Licensure of Water System Operators. Please see below for details.

Co-Chairs:
Amanda Gavin, FB Environmental
Margaret Mills, FB Environmental
Rachel Hovel, University of Maine, Farmington
Ben Peierls, Lakes Environmental Association

Lakes are often considered sentinel ecosystems, in that they respond rapidly to regional environmental change. As the lowest point in the catchment, lakes integrate inputs from the surrounding watershed, so changes in lake biological and physical properties act as “canaries in the coal mine” and reflect changes occurring in the climate, atmosphere, and surrounding terrestrial ecosystems. Ongoing research has demonstrated that Maine lakes are experiencing climate change through changes in water temperature and clarity, duration of ice cover, invasive plant populations, algal blooms, zooplankton composition, and more. This session invites talks that creatively address how Maine lakes are responding to climate change, what makes lake ecosystems less resilient to climate change, and what adaptations, both natural and anthropogenic, can mitigate impacts of climate change.

Session Schedule

Reception

  • 3:30PM-4:30pm – Main Auditorium
    Poster and exhibit viewing. Light refreshments.

* Speakers are indicated in bold font.

1:30PM-1:55PM
Is Maine’s Climate Changing? What the Lakes Are Telling Us

Approved for 0.5 TCH

Lloyd C. Irland
The Irland Group, Wayne, ME

Instrumental records of Maine air temperatures are rare before the turn of the 20th century. Snowfall, streamflow, precipitation, and other climate variables become available for much of the state only by mid or late 20th century. Even then, geographic coverage is spotty. For this reason, many scientists studying climate change have employed lake ice regimes, summarized by ice-in and out-out dates, as proxies for changing climate and growing seasons. This talk analyzes ice-out data for a population of 24 Maine lakes with statistical time series analysis. I show averages of the four lakes with the longest and most complete series (180 yrs to 2019), and a second, wider set of 11 lakes with the most complete data from 1928 (91 yrs). Geographic patterns for the full dataset are explored. These analyses show several patterns: 1)  patterns over time are not uniform across the state; 2) Ice out dates can move away from longterm trend for considerable periods; and 3) Limited data show that total ice fee days per year can change by twice as much as do ice free days. These results are striking given that temperature changes over this period have not been large.

2:00PM-2:25PM
Lake Ice-Out Changes in Maine During the Last Two Centuries

Approved for 0.5 TCH

Glenn Hodgkins
USGS New England Water Science Center, Augusta, ME

Maine has an incredible wealth of historical lake ice-out data collected by citizen scientists during the last two centuries. This data is useful for analyzing changes over time and putting recent changes into perspective. Lake ice-out dates are much earlier in recent decades than in the 1800s, but trends have been non-linear and have multi-decadal components. Ice-out dates at representative lakes in Maine have been shown to be highly correlated with March-April air temperatures. Hypolimnion dissolved oxygen (DO) levels are an important factor in lake eutrophication and coldwater fish survival. Based on historical data available at three lakes in Maine, 32 to 46 % of the interannual variability of late summer hypolimnion DO levels was related to ice-out dates; earlier ice-outs were associated with lower DO levels.

2:30PM-2:55PM
Differences in the Effects of Storms on Dissolved Organic Carbon (DOC) in Boreal Lakes During an Early Summer Storm and an Autumn Storm

Kate A. Warner, Jasmine E. Saros, Rachel A. Fowler
Climate Change Institute and School of Biology and Ecology, University of Maine, Orono, ME, 04469

Extreme precipitation events pose threats to Maine’s lakes. These events have been linked to increased concentrations of dissolved organic carbon (DOC), however the effects of seasonal differences on DOC and subsequent lake storm response remain unclear. Precipitation events have increased by 70% since the 1950’s, and in the northeastern U.S. specifically, precipitation has increased by more than 15% in the autumn and by about 3% in the spring since 1901. We evaluated DOC concentration and a set of DOC quality metrics during an early summer storm and an autumn storm on a suite of six lakes in Acadia National Park. Our results revealed differences in the response of DOC quality metrics to the two storms. In the early summer storm, the response of DOC quality metrics suggests that photobleaching was the primary process contributing to change in deep lakes with long residence times. In the autumn storm, the response of DOC quality metrics suggests that more allochthonous inputs and bacterial processing were the primary processes contributing to observed changes in lakes with large watershed area to lake area ratios. Our research provides evidence of seasonal differences in the effects of storms on boreal lakes, which are ultimately mediated by a combination of lake and watershed characteristics and, importantly, seasonal changes in climate including solar radiation and antecedent weather conditions. Continued changes in these climate variables and precipitation could alter important lake water quality metrics, therefore identifying these changes is important for future lake management.

3:00PM-3:25PM
Lake Phenology and Climate Change: Zooplankton as Indicators of Shifting Seasons in Remote Maine Lakes

Approved for 0.5 TCH

Stephanie Dykema1 (Student), Sarah Nelson2, Ivan Fernandez3, Rachel Hovel4, Jasmine Saros5
1. Ecology and Environmental Sciences, University of Maine, Orono
2. Appalachian Mountain Club
3. School of Forest Resources, University of Maine, Orono
4. Department of Biology, University of Maine, Farmington
5. School of Biology and Ecology, University of Maine, Orono

Climate change is influencing the timing of seasonally reoccurring events in ecosystems across the globe. Shifts have already been detected in northeastern lakes including earlier ice breakup and longer periods of thermal stratification. For many organisms, phenology is driven by temperature cues but for others, shifts in day length, availability of nutrients, or other seasonal cues are more important drivers. Even among those that depend on temperature cues, individual species respond at different rates depending on their life history traits and such asynchronies can result in a reorganization of ecological communities. Zooplankton, primary consumers in lentic food webs, react quickly to change due to their relatively short life cycles. Variability among different species’ responses to geochemical or physical shifts has resulted in measurable shifts in lake community structure. This research aims to understand how zooplankton communities, in lakes across the extremes of elevations and climate zones in Maine, respond to lake phenology. Zooplankton, chlorophyll-a, and water chemistry was measured under ice in winter, repeatedly over the course of spring warming, and during summer stratification and fall mixing in eight remote lakes. A chain of thermistors measured temperature in the epilimnion and hypolimnion throughout the year. We are comparing zooplankton phenology and community structure among seasons and among lakes to understand how variation in physical lake phenology influences the phenology of different plankton species. Interpreting the drivers of phenological shifts among lake ecosystem members will be imperative for understanding and predicting the complex effects of climate change on freshwater systems.