Effects of a diel oxygen cycle on nitrogen transformations and greenhouse gas emissions in a eutrophied subtropical stream

Abstract

Rivers and streams constitute a major pathway for material transport from land to sea and an important source of greenhouse gases. Short-term variation in stream chemistry due to day-night oxygen (O 2) fluctuations could significantly affect a stream's capacity to transport nutri- ents and produce greenhouse gases. Though it is well es- tablished that diel cycles are important in controlling O 2 and CO2 dynamics, the study of diel dynamics of other redox-sensitive elements has been fairly limited. Here we show that a subtropical stream can undergo complete re- duction and oxidation sequences in just a few hours. This redox fluctuation has important consequences for down- stream transfer of nutrients and for greenhouse gas pro-