Oxygen levels have dropped in hundreds of lakes in the United States and Europe over the last four decades, a new study found. Using data on nearly 400 temperate lakes throughout the world, researchers examined dissolved oxygen levels and temperatures of these aquatic ecosystems. They found that dissolved oxygen dropped 5.5% in surface waters and 18.6% in deep waters between 1980-2017. And one of the authors says this oxygen decline could lead to increased fish kills, algal blooms and methane emissions.
