Acadia National Park is known for its beautiful lakes — and they can tell scientists a lot about the health of the environment. New research shows regulations to reduce man-made atmospheric sulfur have made a difference for lakes in Acadia National Park, although climate change could slow that recovery.
Research from the 1990s showed that man-made air pollution in the 20th century acidified lakes in eastern North America from the 1940s. Lake acidification leads to a decrease in dissolved organic carbon in lakes, affecting lake ecology and making the water appear clearer.
Since amendments to the Clean Air Act were enacted at the federal level in 1990, the Northeastern United States has received significantly less atmospheric acid deposition, with the goal of restoring ecosystems like lakes that were affected by pollution. However, climate change may also affect lake water clarity, as rising temperatures drive the production and release of dissolved organic carbon, while climate change-induced precipitation shifts may also bring in more organic matter.
Researchers from the University of Maine and the National Park Service wanted to see how these changing acidification dynamics are affecting ecosystems in different types of lakes in Maine. in a (n items Published in the Journal of Paleolimnology, scientists reconstructed historical pigment records of algae and diatoms — a specific type of algae with a silica shell that is normally adversely affected by acidification — from two lakes in Acadia National Park, Jordan Pond and Seal Cove Pond.
Despite the geographical proximity, the two lakes are very different. Jordan Pond is considered a “clear water” or oligotrophic lake, meaning its water is relatively low in plant nutrients with abundant oxygen in its depths. Seal Cove Pond is a “brown water” or mesotrophic lake with a moderate amount of nutrients.
“Recovery from acidification depends in part on water clarity, which is being affected by climate change. Across North America and northern and central Europe, there is an ongoing trend of lakes “browning”. Several studies have described ecological changes in clear and brown water lakes in response to a reduction in acid deposition and browning, and our paleolimnological study provides long-term context for interpreting these changes,” says Rachel Fowler, coordinator of the biology lab that acted as the Principal Investigator of the project for her Ph.D. at the University of Maine Institute for Climate Change.
The researchers took sediment cores from the deepest parts of both ponds and analyzed the concentrations of different types of algae and how they changed over time. The results showed that the algae in the lakes responded differently to acidification over time. Despite their differences, both ecosystems are recovering as environmental regulations have reduced the amount of atmospheric sulfur in the region and many species of algae are returning to where acidification once drove them out.
“An exciting finding is that this study illustrates the effectiveness of the Clean Air Act changes. We can see signs of recovery from acid deposition from the algal residues conserved in the sediments of Jordan Pond and Seal Cove Pond,” says Fowler.
However, the results also suggest that clear-water lakes like Jordan Pond are more sensitive to global warming than brown-water lakes like Seal Cove Pond. Algal ecosystem recovery has been slower for Jordan Pond and may continue to be hampered by the effects of climate change.
“Lake color and clarity are important regulators of lake ecology. They can change the physical and chemical structure of lakes and also contribute to the type and amount of algae living in lakes. With the trend towards browning of lakes due to climate change and other environmental factors, it’s important that we understand the ecological implications for the lakes we value for drinking water, recreation and year-round natural beauty,” says Fowler.
Fowler led the research with Jasmine Saros, associate director of the Climate Change Institute and professor in the School of Biology and Ecology; Kate Warner, Ph.D. in ecology and environmental sciences; and Bill Gawley, biologist at Acadia National Park. The research was funded in part by a Second Century Stewardship Award from the Schoodic Institute at Acadia National Park.
Contact: Sam Schipani, [email protected]