Rising temperatures threaten ecosystems, drinking water, fish
OXFORD, Ohio —Climate change is rapidly warming the surface waters of lakes around the world, threatening freshwater supplies and ecosystems, according to a new study spanning six continents.
More than 60 scientists including Craig Williamson from Miami University’s Department of Biology and Center for Aquatic and Watershed Sciences took part in the research, published in the journal Geophysical Research Letters and announced yesterday in a press conference at the fall meeting of the American Geophysical Union.
The study, which includes Lake Lacawac and Lake Giles in the Poconos of northeastern Pennsylvania where Miami faculty and students work at the Lacawac Field Station, found lakes are warming an average of 0.34 degrees Celsius, or 0.61 degrees Fahrenheit, each decade. That’s greater than the warming rate of either the oceans or the atmosphere, and it can have profound effects, the scientists say.
At the current rate, algal blooms, which can ultimately rob water of oxygen, are projected to increase 20 percent in lakes over the next century. Algal blooms, which are a serious problem in many Ohio reservoirs, and that are toxic to fish and animals, would increase by five percent. And these rates imply that emissions of methane, a greenhouse gas 25 times more powerful than carbon dioxide, will increase four percent over the next decade.
“Lakes are important because society depends on surface water for the vast majority of human uses,” said co-author Stephanie Hampton, director of Washington State University’s Center for Environmental Research, Education and Outreach. “Not just for drinking water, but manufacturing, for energy production, for irrigationof our crops. Protein from freshwater fish is especially important in the developing world.”
Temperature is one of the most fundamental and critical physical properties of water. It controls a host of other properties that include intricate living processes that have evolved within strict boundaries. When the temperature swings quickly and widely from the norm, life forms in a lake can change dramatically and even disappear.
“‘These results suggest that large changes in our lakes are not only unavoidable, but are probably already happening,” said lead author Catherine O'Reilly, associate professor of geology at Illinois State University. Earlier research by O’Reilly has seen declining productivity in lakes with rising temperatures.
Funded in part by NASA and the National Science Foundation, the study is the largest of its kind and the first to use a combination of long-term hand measurements and temperature measurements made from satellites, offsetting the shortcomings of each method.
A total of 235 lakes were monitored for at least 25 years. While that’s a fraction of the world’s lakes, they contain more than half the world’s freshwater supply.
Study co-author Simon Hook, science division manager at the NASA Jet Propulsion Laboratory, said satellite measurements provide a broad view of lake temperatures over the entire globe. But they only measure surface temperature, while hand measurements can detect changes in temperature throughout a lake.
Williamson and colleague Rachel Pilla, a graduate and now Research Associate at Miami University, are working on an extension of this project that will examine changes in the deeper water as well as surface temperatures in a suite of over 100 lakes from around the world. Satellite measurements go back only 30 years while some lake measurements that Williamson and Pilla have collected from colleagues around the world go back more than a century.
The researchers said various climate factors are associated with the warming trend. In northern climates lakes are losing their ice cover earlier, and many areas of the world have less cloud cover, exposing their waters more to the sun’s warming rays.
Many lake surface temperatures, including those of the Great Lakes,are rising faster than the average air temperatures. Some of the greatest warming is seen at northern latitudes, where rates can average0.72 degrees Celsius, or 1.3 degrees Fahrenheit, per decade.Warm-water, tropical lakes may be seeing less dramatic temperature increases, but increased warming of these lakes can still have large negative impacts on fish. That can be particularly important in the African Great Lakes, home to one-fourth of the planet’s freshwater supply and an important source of fish for food.
Research published by Andrew Tucker and Kevin Rose, two previous Miami University PhD students working with Miami University professors Jim Oris and Craig Williamson, has shown that warming surface water temperatures in Lake Tahoe, combined with decreases in the transparency of these waters to ultraviolet radiation, may enable invasion of alien warm-water fish in clear, cold-water lakes.
In general, the researchers write, “The pervasive and rapid warming observed here signals the urgent need to incorporate climate impacts into vulnerability assessments and adaptation efforts for lakes.”
Contact: Susan Meikle, Miami University, 513-529-4619, firstname.lastname@example.org
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