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

上层海洋密斜层附近海洋雪动力学与生物过程相互作用的研究。

基本信息

批准号：
16370010
负责人：
KOIKE Isao
金额：
$ 6.91万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2006
项目状态：
已结题

项目摘要

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.

虽然海洋雪对海洋上层产生的有机碳向海洋内部输送起着重要作用，但由于通道问题，其生物地球化学研究一直局限于沿海地区。本研究利用新开发的海洋雪相机，从生物过程和上层附近物理环境的相互作用出发，了解海洋雪的产生和垂直转移。在2004财政年度，对相机系统进行了改进和性能测试，即使用新的LED光源和增加清晰的视野等。主要的野外活动是在2005年7月至9月的白湖丸号巡航期间进行的，地点为太平洋中部样带（10°S - 53°N, 160°W），包括从营养匮乏地区到营养丰富的亚北极地区。在这片狭长的样带中，在使用海洋雪相机之前没有进行过调查。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，海洋雪丰度峰值的存在得到了证实。(2)样带0 ~ 200m深度的叶绿素a综合量差异约为2.5倍，相同处理的海洋雪量差异约为50倍。这一对比表明，该样带的物理环境、浮游植物的大小和食物网结构等因素控制了上层海洋雪的丰度。(3)研究区斜斜深度在30 ~ 110m之间。样带0 ~ 100m和100 ~ 200m深度的综合叶绿素a量比值与相同处理的海洋雪量比值具有较好的相关性。由于海洋雪（>0.5mm大小）的主要来源是0.8-100微米大小的浮游植物，因此形成海洋雪的聚集过程可能不需要这些源物质进行大的垂直运动。