Continuous automated measurement of rates of photosynthesis and respiration in an undisturbed river community1

A precise, continuous function (a Fourier series) describing undisturbed net community production throughout a day has been obtained from automatically recorded and processed oxygen concentration data from two stations in a river. The linear relationship found between light and productivity confirmed the precision of the method and was used to give a nearly continuous estimate of community photosynthesis, respiration, and gross productive efficiency. Respiration and efficiency may remain constant for one to several days, or may change over a few hours. Day‐to‐day variation in community photosynthesis and respiration may preclude extrapolation of a number of isolated single‐day measurements to determine seasonal or other long term trends.