Organic Carbon in the Caura River, Venezuela

Samples were taken weekly over a 2-year period near the mouth of the Caura River, which drains a large watershed on Precambrian shield covered with tropical moist forest. The concentrations of dissolved organic carbon were essentially static despite a 10-fold seasonal change in discharge. Particulate carbon showed an unexpected but relatively weak inverse relationship to discharge. Yield of total organic carbon (12.3 g C m-2 yr-1) was higher than would have been expected from the literature. Yield can be predicted accurately from discharge because of the strong homeostasis in concentration of dissolved organic carbon.