How do we study the global environmental change? Among several approaches, paleoenvironmental reconstruction helps us to understand environmental response to abrupt climatic changes. The fossil remains of marine plankton which dwells in the ocean surface layer are deposited together with detritus on the sea bottom after their death, and then compose the sedimentary sequence which contains important information concerning the history of the marine environments. Precise analyses of assemblage of these microfossils (tiny fossils observed by microscopy) and chemical composition of the sediments in various ocean area reveal the past global changes occurred on the earth during hundreds of thousands of years. 　The Mutsu Institute for Oceanography aims to clarify the mechanisms of the past marine environmental changes and to provides useful information for predicting global changes in future climate. 　 　 　 　The ocean attracts attention for absorbing greenhouse gases, such as carbon dioxide, which are increasing in the atmosphere due to combustion of fossil fuel and so forth. Part of the carbon dioxide dissolved from the atmosphere into the sea is taken into phytoplankton, which settle to deposit on the deep-sea floor, and some is also carried and diffused by the surface and deep water currents. The Mutsu Institute for Oceanography conducts research to clarify the mechanism of material cycles in the Northwest Pacific Ocean, the area believed to be a major absorption source of carbon dioxide.