Identification of semi-refractory marine dissolved organic matter with life span from a half to one year.

利用天然微生物种群进行了实验分析，以研究浮游植物光合产物的早期成岩过程。去年获得的实验结果表明，在成岩过程的早期阶段，向难降解有机化合物的转化迅速进行，细菌种群参与了这一过程。因此，今年，我们专注于细菌产物的生物化学表征。此外，进行了^<15>N示踪实验以及^<13>C示踪实验，以确定半难溶有机质。结果表明：（1）在240天的降解实验中，细菌细胞壁中可溶性d-丙氨酸的浓度占菌体最大浓度的2%。d-丙氨酸的“残留率“比其他氨基酸高10倍，表明细胞壁有机物可能是半难溶有机物的组成部分。<15>采用氮示踪法对溶解性有机氮的产生和分解过程进行了监测。溶解有机氮的产生持续到培养系统变暗后的30天，而溶解有机碳的最大产生在一周内被发现。因此，溶解有机质的C/N值在成岩早期浮游植物光合产物中的变化是显著的。3.这些结果表明，构成半难降解溶解有机质的有机组分不太可能直接由浮游植物提供。转化为难降解有机质可能发生在早期成岩阶段使用不稳定的浮游植物有机化合物。

Experimental analyses have been carried out to study the early diagenetic processes of phytoplankton photosynthetic products, using natural microbial populations. The experimental results obtained in the last year showed that conversion to refractory organic compounds rapidly proceeds during the early stage of diagenetic process, and that bacterial population participates to this process. In this year, thus, we focused on the biogeochemical characterization of bacterial products. Further, the ^<15>N tracer experiment has been carried out as well as ^<13>C tracer one, to specify the semi-refractory dissolved organic matter. The following results have been obtained.1.The concentration of dissolved d-alanine, which is a component of bacterial cell wall, on 240 days of decomposition experiments, accounted for 2% of the maximum concentration of cellular d-alanine. The"remaining ratio"of d-alanine is ten times higher than the other amino acids, indicating that cell wall organic materials are the possible components of semi-refractory dissolved organic matter.2.^<15>N tracer method was applied to monitor the production and decomposition processes of dissolved organic nitrogen. The production of dissolved organic nitrogen continued until 30 days after the culture system has turned to dark, while the maximum production of dissolved organic carbon was found within a week. Thus, the C/N value of dissolved organic matter significantly varied through the early diagenetic stage of phytoplankton photosynthetic products.3.These results indicate that organic species constituting semi-refractory dissolved organic matter, are unlikely directly supplied by phytoplankton. The transformation to refractory organic matter probably occurs during the early diagenetic stage using labile phytoplankton organic compounds.