ABSTRACT
This chapter focuses on the sources, forms, and fates of organic matter in estuaries. It addresses mechanisms and pathways of cycling and transformation of organic matter. The chapter examines the interactions between riverine, marsh, estuarine, and nearshore oceanic systems that affect the flux of organic matter through these complex coastal environments. Respiration and mineralization, biologically mediated processes, account for the breakdown and transformation of organic matter, respectively. The relative importance of organic carbon sources in the estuarine carbon cycle has been a matter of controversy. While photosynthesis is an instrumental mechanism in the formation of organic carbon in estuaries, natural external sources and anthropogenic influxes can also be significant. Organic matter occurs in natural waters in dissolved and particulate forms. The concentrations of these two fractions can be determined by filtration through filters with an average pore diameter of approximately 0.5 µm.
