Chapter 5 - Dynamics of DON

Abstract

This chapter describes the dynamics of dissolved organic nitrogen (DON). DON is that subset of the dissolved organic matter (DOM) pool that contains nitrogen (N). From the perspective of a microorganism, this is where the action is—one-stop shopping for N, carbon (C), and energy. Research in DON, however, has lagged far behind that of the larger dissolved organic carbon (DOC) pool. This situation is primarily the result of the substantial analytical challenges inherent in DON research: (1) DON exists in substantially lower concentrations than DOC, (2) multiple chemical analyses are required for a single DON measurement, (3) inorganic N removal is a nightmarish undertaking, and (4) unless one has an easy access to a nuclear reactor manufacturing short-lived 13N, he or she must be content with labor-intensive stable isotopes rather than the quicker and more sensitive radiotracers. Measurements of DON concentrations have become a routine component of many studies. Nonetheless, because of space limitations DON concentrations in lakes, streams, or groundwater—with some exceptions—are not included in studies.