Study on interaction of marine snow dynamics and biological processes within the vicinity of the pycnocline of upper ocean.

虽然海洋雪在海洋上层产生的有机碳向海洋内部的输送中起着重要的作用，但由于通道问题，其地球化学研究一直局限于沿海地区。在这项研究中，我们专注于在上层附近的生物过程和物理环境的相互作用，了解海洋雪的生产和垂直传输使用新开发的海洋雪相机。在2004财政年度，对摄像机系统进行了改进，并进行了性能测试，即，采用新的LED光源，增加了清晰的视野等。在Hakuho-Maru巡航期间（2005年7月至9月），对太平洋中部样带（10°S - 53°N，160°W）进行了主要的实地调查，其中包括从贫营养区到营养丰富的亚北极区。在这条长样带中，在使用海洋雪相机之前没有做过任何调查。以下是从实地研究中获得的主要结果。(1)在营养丰富的亚北极地区的密度跃层处，证实了海洋雪丰度的峰值。(2)在0- 200 m沿着样带叶绿素a的累积量差异约为2.5倍，而相同的海雪量处理差异约为50倍。这种比较表明，几个因素，包括物理环境，浮游植物的大小，食物网结构在这个样带控制丰富的海洋雪在上层。(3)研究区密度跃层深度在30- 110 m之间。样带内0- 100 m和100- 200 m沿着深度的叶绿素a含量比值与同一处理下的海洋雪量比值有较好的相关性。由于海洋雪（> 0.5毫米大小）的主要来源是0.8-100微米大小的浮游植物，因此产生海洋雪的聚集过程可能发生，而这些源材料没有任何大的垂直运动。

Although marine snow plays important role on the transport of organic carbon produced at the upper ocean into the ocean interior, its biogeochemical studies have been restricted to the coastal area, because of the access problems. In this study, we focused on the interaction of biological processes and physical environments in the vicinity of upper layer, to understand the production and vertical transfer of marine snow by using newly developed marine-snow camera. In FY2004, improvements of the camera systems and their performance test have been conducted, i.e., use of new LED light source and addition of clear sight and others. Main field campaign was performed during the Hakuho-Maru Cruise (July-September, 2005) to the central Pacific transect (10°S - 53°N, 160°W), which includes from oligotrophic region to rather nutrients rich sub-arctic region. In this long transect, no survey has been done before using marine snow camera. Followings are major results obtained from the field studies. (1) Presence of peak of marine snow abundance was confirmed at the pycnocline of the nutrients rich sub-arctic area. (2) Integrated amounts of chlorophyll a at the 0-200m depth along the transect showed about 2.5 fold difference, while the same treatments of marine snow volume gave about 50 times difference. This comparison suggests that several factors including physical environments, size of phytoplankton, and food web structures in this transect control abundance of marine snow in the upper layers. (3) The depth of pycnocline located between 30-110m depths in the study areas. The ratio of integrated chlorophyll a amounts between 0-100m and 100-200m depths along the transect showed a good correlation with the ratio of marine snow volume obtained by the same treatment. Since primary source of marine snow (>0.5mm size) is phytoplankton of 0.8-100 micron size, aggregation processes to produce marine snow may occur without any large vertical movement of these source materials.