Warmer temperatures favor slower-growing bacteria in natural marine communities

Earth’s life-sustaining oceans harbor diverse bacterial communities that display varying composition across time and space. While particular patterns of variation have been linked to a range of factors, unifying rules are lacking, preventing the prediction of future changes. Here, analyzing the distribution of fast- and slow-growing bacteria in ocean datasets spanning seasons, latitude, and depth, we show that higher seawater temperatures universally favor slower-growing taxa, in agreement with theoretical predictions. Our results explain why slow growers dominate at the ocean surface, during summer, and near the tropics, and provide a framework to understand how bacterial communities will change in a warmer world.