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

利用自然微生物种群对浮游植物光合作用产物的早期成岩过程进行了实验分析。过去一年的实验结果表明，在成岩作用的早期阶段，细菌迅速转化为难降解的有机化合物，细菌种群参与了这一过程。因此，在这一年里，我们把重点放在细菌产品的生物地球化学特征上。此外，还进行了示踪实验和示踪实验，以确定半难熔溶解有机质。主要研究结果如下：1.在240天的分解实验中，细菌细胞壁的一种成分--溶解的d-丙氨酸的浓度占细胞内d-丙氨酸最大浓度的2%。D-丙氨酸的“残留率”是其他氨基酸的10倍，说明细胞壁有机物是半难溶有机物的可能成分。2.采用示踪法对溶解有机氮的产生和分解过程进行监测。溶解有机氮的产生一直持续到培养系统转入黑暗后的30天，而溶解有机碳的产生在一周内达到最大值。因此，在浮游植物光合作用产物的早期成岩阶段，溶解有机质的C/N值变化很大。3.这些结果表明，构成半难溶溶解有机质的有机物种不太可能直接由浮游植物提供。向难降解有机物的转化可能发生在早期成岩阶段，利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.