The 11 largest lakes on the planet contain more than 50 percent of the freshwater surface that millions of people and many other living things need to survive. A new study highlights how these lakes absorb carbon dioxide from the atmosphere and how their ability to do so has changed over the past two decades. The study uses a combination of satellite observation and fieldwork to establish the root cause of the lake’s carbon dioxide, where carbon dioxide is absorbed from the atmosphere.
The Phytoplankton is tiny algae that synthesize photosynthesis or generate energy from sunlight. Part of photosynthesis is carbon fixation, where inorganic carbon dioxide is converted into organic compounds. The amount of phytoplankton and the rate of photosynthesis they give the rate of carbon fix in body water like a lake. Estimating the initial production of phytoplankton can indicate how much carbon dioxide these algae will draw from the air.
The study, published in the Water Journal, was the first to use the same method for 11 of the world’s largest lakes, including the five Laurentian Great Lakes bordering the United States and Canada; Great Bear and Great Slave Lakes in Canada; Three African Great Lakes, Tanganyika, Victoria and Malawi; And Lake Baikal in Russia.
Co-author Gary Fahnenstiel from Michigan Tech Research Institute said in a statement, “The basis of the food chain in this lake is algal productivity. These lakes are ocean-shaped, and phytoplankton – teaming up with small algae. ” “We measured the rate of carbon fixation, which means that the rate at which algae photosynthesis in these lakes is increasing or decreasing, means that the entire reservoir is changing, encircling all food chains from zooplankton to fish.”
Using NASA data from 2003 to 2018, researchers used the color of the lake from satellite images to estimate the productivity of the algae. Although the team found that the productivity of most lakes did not change much over the years, for the three lakes, the change was dramatic. The team was amazed at how quickly these changes happened. Both Great Bear and Great Slave Lakes in northern Canada saw large increases in productivity. On the other hand, Lake Tanganyika in southeastern Africa has seen a significant decline.
Fahnenstiel said, “The three largest lakes in the world have shown major changes related to climate change, with a 20-25% change in overall biological productivity in the last 16 years.” Researchers say that changes in these three lakes are associated with rising water temperatures, solar radiation, and declining wind speeds.
Lead author Michael Sayers added, “Temperature and solar radiation cause climate change.” Factors affecting algae productivity include their abundance in the lake, how much sunlight comes into the lake, how deep that light can penetrate, water temperature, and wind speed. All of these factors are influenced by climate change. Understanding how these giant waters are changing is the key to their future and the future of those who depend on them.
