Acadia National Park is famed for its magnificent lakes, which can reveal a lot about the state of the environment to scientists. According to new research, rules aimed at reducing human-caused sulfur in the atmosphere have helped lakes in Acadia National Park recover, however climate change may hinder this process.
Human-induced atmospheric pollution in the twentieth century triggered the acidity of lakes across eastern North America beginning in the 1940s, according to research from the 1990s. Acidification of lakes reduces the amount of dissolved organic carbon in the water, affecting lake ecology and making the water appear clearer.
The northeastern United States has experienced much less atmospheric acid depositions since the Clean Air Act Amendments were legally passed in 1990, with the purpose of rehabilitating ecosystems such as lakes that were damaged by pollution.
Climate change, on the other hand, can have an impact on lake water clarity because rising temperatures accelerate the creation and release of dissolved organic carbon, while climate change-related precipitation variations can also bring in additional organic matter.
Researchers from the University of Maine and the National Park Service wanted to explore how different types of lakes in Maine were affected by shifting acidity dynamics.
Scientists reconstructed historical pigment records of algae and diatoms, a form of algae with a silica shell that is normally negatively damaged by acidification, from two lakes in Acadia National Park, Jordan Pond, and Seal Cove Pond, in an article published in the Journal of Paleolimnology.
An exciting takeaway is that this study illustrates the effectiveness of the Clean Air Act Amendments. We can see signs of recovery from acid deposition using the remains of algae preserved in the sediments of Jordan Pond and Seal Cove Pond.
Rachel Fowler
Despite their proximity in terms of geography, the two lakes are vastly different. Jordan Pond is classified as a “clear-water” or oligotrophic lake, which means its waters are low in plant nutrients and have plenty of oxygen at depth. Seal Cove Pond is a moderately nutrient-rich “brown-water” or mesotrophic lake.
“Recovery from acidification is partially dependent on water clarity, which is impacted by climate change. Across North America and northern and central Europe, there is an ongoing trend toward ‘brownification’ of lakes. Several studies have described ecological changes in clear- vs. brown-water lakes in response to reductions in acid deposition and browning, and our paleolimnological study provides long-term context for interpreting those changes,” says Rachel Fowler, biology lab coordinator who served as the principal investigator of the project for her Ph.D. in the University of Maine Climate Change Institute.
The researchers investigated the quantities of different forms of algae and how they changed over time in sediment cores taken from the deepest regions of both ponds. The findings revealed that the algae in the lakes responded to acidification in varied ways throughout time.
Despite their differences, both ecosystems are recovering since environmental laws reduced the quantity of sulfur in the atmosphere in the area, with several varieties of algae returning to areas where acidity had previously forced them out.
“An exciting takeaway is that this study illustrates the effectiveness of the Clean Air Act Amendments. We can see signs of recovery from acid deposition using the remains of algae preserved in the sediments of Jordan Pond and Seal Cove Pond,” says Fowler.
The findings also indicated that clear-water lakes, such as Jordan Pond, are more vulnerable to climate change than brown-water lakes, such as Seal Cove Pond. Jordan Pond’s algal ecosystem recovery has been delayed, and the consequences of climate change may continue to stymie it.
“Lake color and clarity are major regulators of lake ecology. They can alter the physical and chemical structure of lakes, and contribute to the types and amount of algae living in lakes, too. With the trend toward brownification of lakes due to climate change and other environmental factors, it’s essential that we understand the ecological consequences for the lakes we value for drinking water, recreation, and year-round natural beauty,” says Fowler.
Fowler conducted 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.
Schoodic Institute in Acadia National Park provided some funding for the study through a Second Century Stewardship award.
