Transformation of bio-polymers into dissolved and colloidal organic matters in the ocean

在海洋中，由各种浮游生物组合产生的生物聚合物的生化特性通过与微生物和非生物过程（如紫外线辐射）的相互作用而被改变，并被认为获得了它们的难降解特性。与此同时，改性的生物聚合物会聚集成悬浮或沉降的粒径。在这个项目中，生物聚合物在海洋上层的命运通过广泛的实地过程研究和实验室的简单模型实验来追逐。该项目的重点之一是确定控制胶体和亚微米有机颗粒聚集成具有足够沉降速度的大聚集体的生物和物理化学因素。从该项目中获得了以下发现和解释。(1)从沿海水域到寡营养开阔水域的亚微米级TEP浓度测定结果表明，无论深度和面积如何，亚微米级TEP浓度占总TEP浓度的70-80%，说明胶体级TEP对形成悬浮级TEP的重要性。2)在10-15 d内观察到微生物对氨基酸和葡萄糖等简单有机物的吸收和代谢产生半难降解有机碳和氮。新形成的半难熔有机质与开阔海洋样品的生物化学特征有显著的相似性，表明微生物作用可能是海洋中半难熔有机质形成的一个因素。3)附着微鞭毛虫对上层海洋亚微米颗粒聚集成大聚集体有显著贡献。通过人工亚微米颗粒的实验方法对上述可能性进行了验证，至少在沿海海洋环境中，附着微鞭毛虫的喂食电流对聚集过程有显著的刺激。4)利用原位粒度计数器检测沿海水域温跃层内100 ~ 150微米大小的团聚体。利用新研制的传感器，观测到混合层内和模斜内悬浮颗粒的粒径分布有明显差异，这是上层水柱活跃聚集过程的直接证据。少

In the ocean, biochemical characters of bio-polymers produced by various planktonic assemblages are modified through the interaction with microbes and abiotic processes such as UV-radiation, and are believed to obtain their refractory characters. At the same time, aggregation of modified bio-polymeis into suspended or settling particle size would occur. In this project, fate of bio-polymers in the upper layer of the ocean was chased through extensive field process studies together with simple model experiments in the laboratory. One of the focus of the project is to determine biological and physico-chemical factors controlling aggregation of colloidal and submicron organic particles into large aggregates having enough settling velocities. Following findings and interpretation were obtained from this project. 1) Determination of submicron sized TEP concentration in environmental gradient from coastal waters to oligotrophic open waters prevailed that, irrespective of the depth and areas, … More some 70-80% of total TEP concentrations were located in the submicron-sized fraction, suggesting importance of colloidal sized TEP to form TEP of suspended dimension. 2) Production of semi-refractory organic carbon and nitrogen through microbial uptake and subsequent metabolisms of simple organic matters such as amino acids and glucose was observed within 10-15 days. There is striking similarities of biochemical characters between those freshly formed semi-refractory organic matters and those obtained in open ocean samples, suggesting that microbial processes are a possible factor for the formation of semi-refractory organic matters in the ocean.. 3) Significant contribution of attached micro-flagellates on the aggregation of submicron particles into large aggregates in the upper ocean. The above possibility was tested by an experimental approach using artificial submicron particles, and we obtained significant stimulation of aggregation processes by feeding current of attached microflagellates at least in coastal marine environments. 4) Detection of 100-150 micron sized aggregates within thermocline of coastal waters, sensed by in situ particle size counter. Using a newly developed sensor, clear difference of size distribution of suspended particles between in the mixing layer and within theirmocline was observed, which is direct evidence of active aggregation processes in the upper water column. Less