We have reviewed available information on the global carbon cycle, which is vital to the atmospheric "green house effect". The ocean can store a vast amount of carbon without causing the green house effect; however, the transport systems of the ocean interior, e.g. oceanic conveyer belt, ensure that most of the carbon removed to the deep ocean is eventually returned to the ocean surface layer. The ocean may be delaying a pronounced change in weather systems. Since carbon must enter at the ocean surface from the atmosphere, the carbon budget in the Upper Ocean Layer (UOL) is crucial to understand the global carbon cycle. Particularly, the role of biological activities in UOL is significant. Despite the fact, considerable progress in the upper ocean monitoring systems, our knowledge on the dynamics of UOL is limited. We urge a concentrated research effort on the dynamics of the UOL dynamics research. Finally, we recognize that, as the dynamics of the bottom of UOL are poorly understood, it is an important subject to investigate.

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Some areal investigations were conducted along the coast of Osaka Prefecture from 1989 to 1991 and effects of Mytilus populations on the coastal bottom environment were examined on the basis of their distribution, production and elimination. Mytilus edulis galloprovinciallis predominated on vertical walls or block mounds of the northern and eastern coasts of Osaka Bay, and its maximum standing stock reached 230.4 kg m^&lt-1&gt in wet body weight at a breakwater outside Osaka South Outer-Port in July 1990. The total biomass of the mussels along the eastern coasts of Osaka Bay in July 1990 was estimated as ca. 1.2 × 10⁴ t in wet body weight, ca. 5.5 × 10³ t in wet tissue weight and ca. 90 t in dry tissue nitrogen. Population density and biomass of M. edulis galloprovinciallis markedly declined in Ozaki Harbor in late summer. As a result, elimination of the mussels (108.4 gN m^&lt-2&gt) exceeded by 1.7 times than their production (65.1 gN m^&lt-2&gt) in May to September, 1990. These findings suggested that the bulk of the mussels was deposited and decomposed on the sea bed in summer when oxygen saturations of the bottom seawater were low. For dense population of M. edulis galloprovinciallis on the vertical walls of the eutrophic Osaka Bay, more attention should be paid to their negative effects on the sea bottom environment by their mortality and decomposition in summer, rather than the positive effects through their filtering and purifying functions of the sea water.

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In general, enclosed coastal seas are more liable to eutrophicate owing to the reduced exchange of water. This study investigates the relationship between the water exchange index (Damping Ratio) and the enclosed index. The enclosed index is a measure of the degree of encloser in sea regions. The differences between the enclosed index values in sea regions where anoxic water masses occur and those in sea regions of nonoccurrence are also investigated. The results of the analysis indicate the sea regions which are subject to entrophication based on bay topography generally have an enclosed index value of 1.0 or greater. However, in selecting the sea regions it is thought to be necessary to also give consideration to other characteristics of sea regions such as the existence of eddies, thermocline intensity, submarine topography (existence of caldron) and so on. And, regional differences of the occurrence sea regions of anoxic water masses in Japan seem to be related to a finding which many enclosed coastal seas exist rather the southern district than the northern one of Japan.

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In this paper, my recent works on the organic nitrogen compounds, i.e. distribution and behavior of protein and DON in seawater and the amino acid sequence of metal binding peptide induced in marine diatom are described. The vertical profiles of dissolved protein and free amino acid show higher values at surface productive layer than those at deeper layer, as well as particulate protein. The protein is constituted of relatively low molecular weight fraction in the range of 10³∼10⁴ at surface layer. The concentration gradually decreases with depth and keep nearly a constant level, in which high molecular weight fractions above 10⁵ is enriched at the layer below 1000m depth. The changes of molecular nature are interpreted from the origin of protein and the alteration during vertical transport of sinking particles. The vertical profiles of DON are almost similar tendency in the samples collected from 33 stations in the north Pacific Ocean. The regional variation of DON is also small. The average DON concentration is in the range from 6.4±1.9 μ M at the surface to 2.9±1.9 μ M below 200m, decreasing with depth. The DON concentrations are nearly constant below 200m depth. In the upper water, DON exists as labile nitrogen compounds which can easily be decomposed by oceanic bacteria. In the middle and the deep waters, however, DON exists more as biologically refractive compounds. This suggests that a significant source of DIN is not DON, though about 25% of DIN depends upon DON above 200m depth, estimating from correlation between AOU and DON. Many studies conducted to date have shown that heavy metals have detrimental effects on organisms. However, many of them are resistant to certain amounts of those metals. It is known that a metallothionein containing high amount of sulfur amino acid is induced in animal tissues. In the case of marine diatom, Phaeodactylum tricornutum, a different kind of small peptide is induced in the cytosol of cells under the presence of cadminm in seawater medium. The peptide is consisted of three kinds of amino acid, i.e. γ-Glutamic acid, Cystein and Glycine. The sequence of the amino acid is (γ-Glu-Cys)n-Gly, where n=4 to 5. This peptide is named as phytochelatine, which is also found in a terrestrial plant (Grill et al., 1985). The behavior at various cadmium concentration and the possibility of induction under the natural cadmium concentration levels are also discussed.

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