A new Illinois State University report says temperatures in the world's lakes are rising more than in the oceans or the atmosphere - which could worsen problems such as algae blooms and oxygen-deprived dead zones where fish can't survive.
The study combined satellite and ground measurements of 235 lakes over the past 25 years. It found their temperature has risen an average of 0.61 degrees Fahrenheit (0.34 degrees Celsius) per decade.
That may seem small, but scientists say it's significant for aquatic ecosystems.
Catherine O'Reilly of Illinois State University led the study. She says warming temperatures are among stresses damaging water quality in lakes that people rely on for drinking, crop irrigation and other vital uses.
The study predicts warming will increase algae blooms in lakes by 20 percent over the next century.