Throwing shade: How trees limit stream productivity

Streams receive large subsidies of energy from bordering terrestrial systems in the form of organic matter, particularly leaves. These inputs can drive respiration meaning that most streams produce CO₂ in excess of their capacity for fixation from primary producers. However, before leaves reach the stream as energetic subsidies they outcompete stream algae for light and substantially reduce the ability of streams to fix carbon. The opposing forces of leaves enhancing CO₂ production and reducing its fixation means that in order to understand the dynamics of stream productivity we need to take a look up to the trees.