Supply of Dissolved Organic Matter to Aquatic Ecosystems

This chapter discusses the role of autochthonous sources of Dissolved Organic Matter (DOM) in surface waters. Microalgae are important sources of organic matter in most aquatic systems, because they transform solar energy into reduced carbon compounds. It is clear that autochthonous DOM of algal and macrophyte origin is an important contributor to the total pool of organic matter in most aquatic environments. Production of DOM from aquatic algae and macrophytes occurs by several different mechanisms: predatory grazing, cell death and senescence, viral lysis, and extracellular release. Both algae and macrophytes release a significant proportion of their net primary production as dissolved organic matter during active growth. More in-depth assessment of the functional links between heterotrophic microorganisms and aquatic primary producers including: kinetic studies of DOM release, transformation and uptake, as well as population level coupling between primary producers and heterotrophic microorganisms, may help in understanding the influence of autochthonously produced DOM on aquatic ecosystems.