THE CHANGES OF CHEMICAL PROPERTIES AND OXYGEN CONSUMPTION OF SETTLING PARTICURATE ORGANIC MATTER : INSIGHTS FROM FATTY ACID ANALYSIS

Abstract

 The consumption of dissolved oxygen by settling particulate organic matter (POM) leads to the formation of hypoxia near the sea bottom in coastal marine systems. The goal of this study was to understand the changes of chemical properties of settling POM and its oxygen comsumption rate applying analyses of fatty acid compositions. We sampled the settling and suspend POM from four depth layers in Shizugawa Bay. Results showed that settling POM have relatively larger contents of C_≧20 PUFA than suspended POM. This suggests the POM which is rich in long-chained essential fatty acids selectively deposited. The contents of C_≧20 PUFA and C_≧20 PUFA/SFA of settling POM decreased significantly with depth, suggesting the POM which contain are mainly degraded in their settling process. Moreover the significant positive relationships between the content of C_≧20 PUFA and the oxygen consumption rate of settling POM imply that the potential of oxygen consumption of settling POM decreased due to its degradation during the deposition. These findings support that the fatty acid analysis help to understand the change of the chemical properties and oxygen consumption of settling POM due to the decomposition even in relatively shallow coastal systems.