Quantitative samples of sediments and macrobenthos were collected with a spade corer to reveal the relationships between macrobenthos communities and bottom environments. Twenty-five stations were established along a transect in the lower sublittoral and bathyal zones between the depths of 120m and 2, 600m off Sanriku, the northeastern coast of the Japanese mainland, Northwestern Pacific.
These stations were clustered into two groups on the basis of the principal component analysis of environmental factors and topographic features of the study area. The clustering of stations corresponded to that based on polychaete species composition.
The biomass of macrobenthos followed two different patterns in two oceanographic environments; the first trend is found from the shelf to the seaward margin of the deep-sea terrace where macrobenthos biomass did not depend on depth, and the second trend on the lower continental slope, where biomass decreased exponentially with depth as Rowe's formula predicted. The density of macrobenthos showed a simple exponential decrease with depth over the two ecological zones. The data of stable carbon isotope ratio of organic matter in the sediments and topographic features suggested that the pattern of the biomass of macrobenthos corresponded with two different modes of food supply to the deep-sea bottom communities, i.e., vertical transport of the surface products and horizontal transport of food materials.

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This paper examines the influence of aSargassumforest on distributions of illuminance, dissolved oxygen content and pH in a small cove facing Wakasa Bay. Spatial distributions of illuminance, dissolved oxygencontent, water density and pH were observed for June 1982 during the season of luxuriant seaweed growth, and for August 1982 during the season of little growth. Observations of dissolved oxygen content, water density and pH were made during the day and at night. The values of illuminance at the sea surface were decreasedto less than 40% inside theSargassumforest when the sun was highest in the sky during the season of luxuriant growth. Density stratification occurred during every observation. Dissolved oxygen content and pH showed similar patterns of spatial distribution. Their horizontal distributions reversed from day to night, and consisted of two types:(1) higher values inshore and lower values offshore in the upper layer during the day with (2) lower values inshore and higher values offshore at night. Distributions of illuminance about noon, and dissolved oxygen content andpH at night showed patterns corresponding to the vertical distribution of algal density of theSargassumforest. Dissolved oxygen was supersaturated at every observation point during the daytime, but at night it was undersaturated in the lower part of the forest or along the bottom in June and August, respectively. Processes thatbrought about these spatial distributions are discussed.

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Environmental parameters that affect the growth ofChattonella antiquawere monitored throughout the outbreak period of this species around the le-shima Islands, the Seto Inland Sea, in the summer of 1987 (20 July-13 August). Averaged cell concentration ofC. antiquaover the water column (21 m) was below 10 cells·ml^-1 on 20 July, gradually increased to reach the maximum of 250 cells·ml^-1 on 7 August, and then rapidly decreased to the value of 30 cells·ml^-1 on 13 August.
Thermal stratifications were prominent from 20 July to 3 August and were destroyed after 4 August. Temperature and salinity were optimum for the growth ofC. antiquathroughout the survey period.
At the bloom initiation period (20-21 July), concentrations of N- and Pnutrients (S_NandS_F) were high throughout the water column. From 22 July to 3 August, whenC. antiquaincreased its populations, S_NandS_Pat the depth of 0-5 m were low but those at the depth of 10-20 m kept a high value. After 4 August, S_N and S_P at the depth of 10-20 m decreased rapidly due to wind mixing coupled with the nutrient uptake by C. antiqua. When the populations of C. antiqua reached the maximum (7-9 August), N-nutrients were depleted throughout the water column but P-nutrients were not. Concentrations of vitamin B₁₂ were almost in the same range as those of the previous years and were optimum for the growth of C. antiqua.
GP- value (growth potential of the seawater with respect to nitrogen and phosphorus) was higher than 0.6 even at the surface layer (0-5 m) at the bloom-initiation period. During the bloom development period (22 July-3 August), GP at the surface layer (0-5 m) was low (<0.2), but GP at the depth of 10-20 m kept a rather high value (>0.4). In situ growth rates of C. antiqua at the depth of 0 and 5 m estimated from bottle experiments coincided well with the values expected from GP. A high value of GP at the surface layer in the initiation period and a shallow GP-cline in the development period, combined with the ability of diurnal vertical migration seemed to be at least one reason that natural populations of C.antiqua grew at a rather high rate and formed red tides in the summer of 1987.

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Nitrate reductase activity and the concentrations of selenite and selenate were monitored for six months at the mouth of Chesapeake Bay (USA). A positive correlation was found between nitrate reductase activity and the concentration of selenite, suggesting that selenite may be formed in coastal waters and nitrate reductase may be involved in the process.

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The downward short-and long-wave radiation fluxes at the sea surface (S↓, εL↓) were measured aboard the R/VHakuho Maru, University of Tokyo, for the period of 117 days on six cruises from 1981 to 1985 in the western North Pacific near Japan. The upward fluxes of short- and long-wave radiation (S↑, εL↑) were calculated by Payne's (1972) table and the Stefan-Boltzmann's law, respectively. The sensible and laten heat fluxes (Q_h, Q_e) were also estimated from an aerodynamic bulk method.
From April to August, the daily mean value of S↓ varied with the amplitude of 100-200 Wm^-2. The value of S↑ was estimated approximately 6% of S↓ in all seasons. The difference between εL↓, and εL↑ was so small that the net radiation flux (Q_n) was dominated by S↓. In addition, the netheat flux at the sea surface was also dominated by S↓. due to small values of Q_h, and Q_e, and then the ocean was warmed at the rate of 111 Wm_-2 in April and 63 Wm^-2 in August in the Oyashio Area, and 132 Wm^-2 in May and 164 Wm^-2 in June in the Kuroshio Area, respectively.
From September to March, a remarkable negative correlation between the day to day variation of S↓, and that of sL↓ was observed except when an intense cold air outbreak occurred. It was found that the correlation was caused by the cloud climatological feature of the western North Pacific in this period. S↓ was not a dominant factor in the net heat flux. The value of Q_h+ Q_e in the Kuroshio Area ranged from 260 Wm^-2 to 630 Wm^-2, much larger than Q_n which ranged from -8Wm^-2 to 92Wm^-2 in the leg mean values (each leg period was about 10 days). Then the ocean was cooled at the rate of-160-620 Wm^-2 during this period. The net heat flux in the Kuroshio Area averaged over five legs from late November to February was -473 Wm^-2. This value is 50-100% larger than the climatological values reported so far.
The temporal and spatial variability of radiation fluxes and heat fluxes during each leg was also discussed.

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In January-February 1987, an urgent cruise “JENEX-87” was carried out in the central equatorial Pacific during the occurrence of the 1986-87 El Niño. This cruise, supported by the Japan Science and Technology Agency, supplied heat flux data through the sea surface, on the basis of direct measurements of short- and long-wave radiation fluxes.
In the time average, the heat gain due to the radiation flux (153 Wm^-2) was almost compensated by the heat loss due to latent heat flux (130 Wm^-2), and thus the net heat gain was small in magnitude (20 Wm^-2). On the other hand, dayto-day changes of the net heat flux ranged within ±130Wm^-2, mainly reflecting the downward short-wave radiation variations.
The heat balance in the surface oceanic mixed layer was investigated in two quadrangle areas (160°E-180°and 180°-160°W between 2°N and 2°S), using the surface heat flux and estimating the advective heat fluxes due to the geostrophic and Ekman currents. In these two quadrangles, we respectively derived -187±88 Wm^-2 and +27±95 Wm^-2. The former value, which is equivalent to about 1°C month^-1 drop of the mixed layer temperature, is evidence of the abnormal oceanic condition in the occurrence of the 1986-87 El Niño event.

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