Origins of Dissolved Organic Matter in Southern California Coastal Waters: Experiments on the Role of Zooplankton

Abstract

The contribution of zooplankton to flows of dissolved organic carbon was studied for the food web of coastal plankton assemblages off Southern California, USA. Seawater samples including active macrozooplankton were labelled with super(14)Co sub(2). The time course of super(14)CO sub(2) incorporation into size fractions of the plankton and dissolved organic materials was determined. Changes in extracellular concentrations of free primary amines and dissolved saccharides were also measured. In addition, the time course of super(3)H-thymidine incorporation into bacteria was detemined along with bacterial cell counts. By comparing carbon flows in samples with macrozooplankton and without macrozooplankton, the authors evaluated the role of macrozooplankton in the flux of carbon to bacteria and dissolved organic matter. One-half or more of the super(14)C-carbon in the bacterial size fraction could be due to small photosynthetic forms or the remains of microplankton disrupted by the filtratioin used in the size fractionation.