Carbon emissions to the atmosphere from streams and rivers are expected to increase as warmer water temperatures stimulate faster rates of organic matter breakdown. But a new study suggests these decay rates may not increase as much as expected. In fact, the study indicates average breakdown rates may increase 5 percent to 21 percent with a 1 degree to 4-degree Celsius rise in water temperature — half as much as the 10 percent to 45 percent increase predicted by metabolic theory.