Studies on the Decompositive Processes of Phytoplanktonic Organic Matter

Abstract

Changes in the concentrations of inorganic nutrients, dissolved oxygen and phytaplanktonic organic materials were determined during the course of decompositive processes of phytoplankton in vitro in order to clarify the recycling of organic matter elements in natural waters.
Phytoplanktonic organic materials were degraded biologically with consumption of oxygen, production of carbon dioxide and regeneration of inorganic nutrients. The atomic ratio of these elements was estimated, although an initial lag-phase was observed for the change in concentrations of ammonium nitrogen as well as phosphate phosphorus.
The kinetic considerations indicated that the mechanism of the decomposition of phytoplanktonic organic materials depended on the quality of organic constituents used as a substrate for the biological utilization. The decompositive process consisted of two reaction steps, a rapid step during the first two weeks and a slow one occurring thereafter. Each of the reactions was a first-order reaction as reported by several workers. The reaction rate constants of each of the organic constituents were determined in both steps.