海洋表層における溶存有機化合物に関する生物地球化学的研究

抄録

Organic compounds produced by marine microbial organisms have various roles on the marine carbon cycles and the sea-air interaction. This paper introduces my studies of the dynamics of dissolved organic matter (DOM) and volatile organic compounds (VOCs) in the surface ocean. DOM forms one of the largest organic carbon pools on the surface of the earth. The vertical change in the DOM composition and its controlling factors were examined in the subtropical North Pacific, using fluorescence property of marine humic matter and molecular weight distribution. I revealed that fluorescent DOM is composed of some fractions with different photoreactivity, and that photoirradiation is the main factor controlling the compositional change in DOM with depth. The fate of photo-irradiated DOM is presumably one of the key processes in carbon accumulation in the surface ocean. Dimethyl sulfide (DMS) is one of marine VOCs and plays important roles in climate system. I found that DMS concentrations increased just after depletion of dissolved oxygen in seawater. Incubation experiments combined with an online mass spectrometry and stable isotope techniques were conducted to clarify mechanisms of the DMS increase. The results showed that anoxic stress is one of the important environmental factors controlling the DMS distribution.