Analysis of production processes of lower trophic levels in upwelling ecosystem

点击翻译按钮获取中文摘要

Research has been focussed on the propagation responses of lower trophic level organisms, particularly phyto- and zoo-plankton, to rapid and drastic changes in the environment in a given water mass of regional upwelling having small areal and short temporal scales such as a few kilometers at the sea surface and a few days to one week of temporal scale. Experimental setups of a surface monitoring system and OCTOPUS have been developed, and remote sensing technique from space and XBT were also introduced for the research. Since geophysical treatment was unavoidable for the research of regional upwelling, participation of US geophysicists were invited by the financial supports of "The Japan-US Cooperative Science Program" of the Japan Society for the Promotion of Science and the National Science Foundation in USA. Field experiments were carried out in the area of Izu Islands using R. V. Tansei-Maru of Ocean Research Institute, University of Tokyo, and "Tsukuba" of Marine Research Center o … More f University of Tsukuba. Major attention was given to the detection of a given upwelled water mass, and to follow the temporal changes of various biological processes in and out of the upwelled water mass. Results obtained are as follows. Water mass of 30 to 100m in depth was generally upwelled to the surface in the study area. Phytoplankton propagation was activated within a few days after upwelling, and phytoplankton biomass increased exponentially with time. Growth stimulation occurred in all the groups of phytoplankton, and a few species of diatom were particularly enhanced greatly. Photosynthetic products of phytoplankton in newly upwelled water mass was rich in proteins, which resulted in an enlargement of phytoplankton population size. In older upwelled water mass, on the other hand, photosynthetic products were mainly composed of energy sources such as sugars, which resulted in maintaining the existing population rather than size expansion. Similar growth stimulation in upwelled water mass also observed in zooplankton population in which females extensively increased egg production rate with the increase of phytoplankton biomass. Less