Pelagic shrimp, Sergia lucens, is an important commercial species of which fisheries are endemic to Suruga Bay. Although the wild shrimp are known to live for about 15 months, adults survived at most one month in previous culture studies. Therefore we challenged to keep the adult shrimp longer in the laboratory by using clean and cold deep-sea water (DSW) pipelined from a depth of 687 m in Suruga Bay in 2004. In the present paper, growth and survival of wild shrimps (nine or ten individuals of 10.15-11.69 mm in carapace length (CL)) were compared between two culture media, DSW and surface seawater (SSW, pipelined from a depth of 24 m). The shrimps were fed Artemia nauplii and kept individually in 1 liter beakers controlled at about 15°C. As the result, the average periods of survival were 58.8 days in DSW and 13.0 days in SSW. At the longest case, an adult could survive for 185 days in DSW. Even after 17 days, when no shrimps survived in SSW, 44.4 % of shrimps survived in DSW. The average (maximum) frequencies of molts per individual were 3.4 (15) times in DSW and 0.2 (1) times in SSW, respectively. The average period from start of rearing to the first molt was 15.8 days, and the average intermolt period was 12.0 days in DSW. The relationship between premolt and postmolt CLs could be described by the equation, y = 0.7156x + 2.71 (r = 0.80, n = 31, p< 0.001). The growth rate obtained in the laboratory was similar to that estimated from wild stock in the previous study. As shown in the present paper, DSW is a good tool for the long-term culture of adult shrimp, which may ensure the increase in ecological information of this shrimp.

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JuvenileEcklonia cavasporophytes were cultured in indoor tanks with flowing deep-sea water(DSW, known as clean, cold and nutrient-rich)pipelined from a depth of 397 m in Suruga Bay, central Pacific Coast of Japan, in 2004 to determine the best growth condition for its seed production. In the experiment I(April 26^thto June 6^th), growth was compared be-tween the deep-sea water and surface seawater(SSW)pipelined from a depth of 24 m at a temperature around 18°C. As a result, blade elongation in DSW was 2.9±0.4 mm day^-1, which was 1.2 times higher than that in SSW(2.4±0.5 mm day^-1). Therefore, the latter two experiments were merely conducted in DSW. In experiment II(May 10^thto June 6^th), in which growth was compared between two levels of irradiance(0.3 and 1.0 Em^-2day^-1)conditioned with and without a cover above the tanks, blade elongation in high irradiance(3.0±0.6 mm day^-1)was 3 times higher than that in low irradiance(1.0±0.1 mm day^-1). In Experiment III(June 29^thto July 26^th), growth was compared among three levels of water temperature(13, 16 and 20°C)conditioned by changing the mixing rate of ambient and heated DSW. Blade elongation at low and mid water temperatures(1.8±0.3 mm day^-1)was 1.2 times higher than that at high water temperature(1.5±0.5 mm day^-1). In stipe elongation, higher growth rates were obtained in high irradiance in Exp. II and low and mid water temperatures in Exp. III, while no difference was found between DSW and SSW in Exp. I. These results indicate that Suruga Bay deep-sea water is useful as a medium for culturing juvenileE. cavaand that optimal culture conditions were 1 E m^-2day^-1and 13-16°C.

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We investigated ion components (Li⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺, Cl^-, Br^-, SO₄^2-), and their vertical distributions through seawater close to Palau and Fiji islands, for the possible evaluation of recovery of valuable ion components, especially lithium ion. At all sites of both seas, Li⁺ concentrations were 0.15-0.16 mg/L, and kept constant through out the vertical depth, and main ion components in both seawaters also agreed with each other. The ion compositions of seawaters adjacent to Palau and Fiji were almost the same as those in Imari Bay in Japan. λ-MnO₂ adsorbent, which has been used for our benchmark plant experiment for Li⁺ recovery from seawater, could effectively adsorb Li⁺ from deep seawater with low temperature compared with surface seawater with high temperature. These results demonstrate that Li⁺ can be effectively recovered from the deep ocean water near Palau and Fiji islands using the adsorption technique with λ-MnO₂ adsorbent.

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The mesopelagic layer is known as “twilight zone” and is situated between the euphotic and aphotic layers, ca. 200-1000 m. As the mesopelagic ecosystem is fuelled by organic matter produced in the euphotic layer, some organisms are adapted to sense and feed on sinking particles from the euphotic layer. They are often inactive in dimlit and cold mesopelagic layer compared with organisms in the sunlit and warm epipelagic layer. On the other hand, many mesopelagic zooplankton and micronekton carry out vertical migration to the epipelagic layer for foraging. In this study, the structure of the mesopelagic ecosystem and dynamic interaction between epipelagic and mesopelagic ecosystems are described.

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