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

尽管海洋雪在将上层海洋产生的有机碳输送到海洋内陆方面发挥了重要作用，但由于通道问题，其生物地球化学研究仅限于沿海地区。在这项研究中，我们重点研究了上层附近的生物过程和物理环境的相互作用，以了解海洋雪的产生和垂直输送，利用新研制的海洋雪相机。在2004财政年度，已对摄像系统进行了改进和性能测试，如使用新的LED光源和增加清晰视距等。白丸邮轮(2005年7-9月)至中太平洋样带(10°S-53°N，160°W)期间进行了主要的野外活动，包括从营养不良地区到营养丰富的亚北极地区。在这条长样带上，在使用海洋积雪相机之前没有进行过任何调查。以下是实地调查的主要结果。(1)营养丰富的亚北极地区的跃层存在海洋积雪高峰。(2)样带0-200m深度的叶绿素a积累量相差约2.5倍，而相同处理的海洋雪量相差约50倍。这种比较表明，包括物理环境、浮游植物的大小和该样带中的食物网结构在内的几个因素控制着上层海洋雪的丰度。(3)研究区的跃层深度在30~110m之间。样带0-100m和100-200m深度范围内的综合叶绿素a比值与相同处理得到的海洋雪量比值有很好的相关性。由于海洋雪(&gt；0.5 mm)的主要来源是0.8-100微米大小的浮游植物，因此在这些来源物质没有任何大的垂直移动的情况下，可能会发生聚集过程来产生海洋雪。

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.