We present analytical results of organic compounds in the deep sea sediments recovered from the Central Pacific and the western tropical Pacific and describe recent progresses in sedimentary biomolecules as tools for reconstructing paleoenviroments. Biomolecules derived from terrestrial higher plants such as C₂₅-C₃₅ n-alkanes, C₂₄-C₂₈ fatty alcohols, or C₂₃-C₃₄ fatty acids in the surface sediments from 175° E transect show high concentrations in the higher latitudes in the Northern Hemisphere. Relative abundances of these terrestrial biomarkers are markedly different between low (15°N-15°S) and high (48°N-19°N) latitudes. Such a difference could be interpreted in terms of different wind regimes between the two areas. Unsaturation degree of long-chain alkenones (U^k₃₇) derived from haptophyte algae suggests that sea surface temperature in the western tropical Pacific during the last glacial maximum was nearly the same as that of the present. We also found that the alkenone abundances over the last 20 kyr are anti-correlated with sedimentary nitrogen isotopic ratios, suggesting that a production rate of alkenones by haptophyte algae is controlled by the nutritional state of the algae.

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海底面は海水と堆積物の境界であり, 海水中を沈降してきた粒子の多くはこの境界付近で分解・変質すると考えられるので, 物質循環において重要な境界面の一つである. この境界付近の堆積物の物性とその変化の詳細を明らかにするため, 放射線を用いた物性測定装置の開発を行なった. この装置では, ガンマー線により堆積物湿潤密度を, 中性子線により水分量 (間隙率) を測定できる. 東シナ海の陸棚から陸棚斜面域及び南太平洋の深海底から採取された試料の測定結果は, 深度0.5～1cm, 2cm, 6cm付近に物性変化パターンの変わる層準があることを示している. すなわち, 密度, 間隙率とも減少する最表層 (0-0.5あるいは1cm), 間隙率に対して密度が大きく変化する0.5あるいは1cmから2cmの間, 次に密度に対して間隙率が大きく変化する2～6cm, 密度, 間隙率とも変化の少なくなる6cm以下に区分される. これらの物性変化は, 堆積物の圧密と粒子の変質で説明できる可能性がある.

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The increasing of the CO₂ concentration in the atmosphere might be induced by consumption of fossil fuel and destruction of tropical forests. In the research field of global warming, clarification of the global circulation mechanism of CO₂ is one of the important targets. Now, many kinds of option to reduce global warming have been proposed and researched. CO₂ sequestration into the ocean is one of hopeful methods from a view point of feasibility. CO₂ transfer mechanism between the atmosphere and the ocean in the North Pacific Ocean and the CO₂ circulation in the ocean are discussed, which has been surveyed in NOPACCSproject of MITI. Still more, the new method which can dissolve CO₂ in shallow sea-water and transport the solution to the deep sea-water is discussed. The method is an utilization of a gas lift effect by CO₂ bubbles in the pipeline inverse J shape.

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Bottom sediments in the open sea mainly originate from sinking particles. Therefore it is very important to investigate chemical properties, seasonality and interannual variability of sinking particles in order to reconstruct paleoenvironments in more detail. Data sets on total, carbonate, organic matter, and biogenic opal fluxes which were measured for more than 5 months are compiled from various areas of the world ocean. Mean total fluxes vary from 0.1 to 16.7 mg Cm^-2 day^-1 They reflect primary productivity. The enhanced values are observed in arctic, subarctic and equatorial upwelling regions. In general they decrease from coastal region to open sea. Although mean carbonate and biogenic fluxes generally reflect primary productivity, biogenic opal fluxes fluctuated more than carbonate fluxes. Carbonate and biogenic opal are dissolved in the deep sea, therefore it needs much efforts to reconstruct original assemblages of biogenic skeletons.
Particle fluxes are affected by river input and upwelling induced by Asian monsoon, upwelling in coastal and equatorial regions, sea ice formation, and volcanic eruption. Long term sediment trap experiments evaluate the surface to the deep sea and/or seafloor, which is one of the most important subjects for understanding paleoenvironments.

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I reviewed my research on analysis of temporal and spatial variability of phytoplankton by physical-biological models. This paper was prepared for a lecture of the member awarded the Okada Prize for 1991 from the Oceanographical Society of Japan.
Temporal change of phytoplankton in a local upwelling was studied by simulated upwelling experiments conducted with natural phytoplankton communities under natural surface light conditions. Results of the culture experiments was explained by a simple model. This model allows to predict the chlorophyll and nutrient concentration changes in a given upwelled water mass.
Above model was verified by a local upwelling observed off Izu, Japan, on May, 1982. Phytoplankton growth and nutrient decrease in surface water of the local upwelling were observed within two days followed by decrease of phytoplankton concentration under depleted nutrient environment. The phytoplankton growth and nutrient decrease could explained by the model with phytoplankton removal rate of about half of the growth rate. Centric diatom was the dominant phytoplankton group and pennate diatom showed less abundance in the upwelled water. Pennate diatom showed fast growth rate when nutrient was abundant and fast decreasing rate after nutrient depleted. On the other hand, flagellate and monads showed relatively slow change of biomass under the change of nutrient concentrations. Furthermore, resting spore formation of centric diatom, Leptocylindrus danicus, was observed in a response to nutrient depletion.
Temporal and spatial variability of phytoplankton in the southeastern U. S. continental shelf ecosystem was studied by physical-biological models. First, differences of the biological responses to frontal eddy upwelling during spring and to intrusion during summer was considered by Lagrangian particle tracing experi-ments with optimally-interpolated flow fields. In spring, particles showed residence time of a few days; however, particles in summer intrusion stayed on the shelf nearly 30 days. It was concluded that difference of particle residence time of upwelled water make the difference of plankton communities. Similar flow fields and particle tracing experiments were used to trace the features in chlorophyll distributions during spring of 1980 derived by Coastal Zone Color Scanner (CZCS). Phytoplankton patchness were created and deformed by frontal eddy events. Eularian physical-biological model was constructed to understand the CZCS-chlorophyll distributions. Statistical comparisons with series of numerical experiments indicate that horizontal advection is an important process for the chlorophyll distributions and that upwelling and associated phytoplankton growth are responsible for the across-shelf gradients and maintenance of concentrations. Furthermore, the CZCS data were assimilated to the model to improve the phytoplankton concentrations, and phytoplankton carbon flux across shelf was estimated. Processes causing the time changes of chlorophyll concentrations were estimated with the model and satellite data further indicated that the both physical and biological forcing is important for the time chages. Several other studies conducted presently were mentioned.

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