ABSTRACT:

The Marino-Forum 21 initiated the research project on development of fishing grounds by utilizing Deep Ocean Water (called DOW here after) of 200 m deep. We plan to enhance the component of nutrient salts in the sea area concerned by discharging DOW into the euphotic layers aiming ultimately at enabling phytoplankton biomass to increase. Our group is responsible for biological sector to examine the change in phytoplankton biomass. The "sea area fertilizing apparatus: TAKUMI" has already been produced. Out of several applicable waters, we finally decided the site to be at the core part of gyre formed in the Sagami Bay to meet the purpose. The reason for this was that if DOW is poured at around center of the gyre, the dispersion of nutrients would assumedly be restrained. We are now further studying the technology for tracking the transfer and diffusion area of discharged. We present here the current state of our research and the future plan.

INTRODUCTION

The fertilization plan of the sea area by means of DOW was first proposed by Naka shima and Toyota in 1984 in Japan(Nakashima and Toyota 1989). After the proposal, the Science and Technology Agency constructed the equipment called "HOYOU" which en ables to pour DOW over the sea surface. By utilizing the HOYOU, the field experiment was carried out for the first time in 1989 and 1990 in Toyama Bay (Kitani and Nagata 1989, Iseki et al. 1994). However, the effect of fertilization was not detected, since the quantity of DOW applied was too small with about 26,000 ton s/day. A new technology development project was then initiated by the Ministry of Economy, Trade and Industry Agency of Natural Resources and Energy in 1999 for 5 years aiming at developing the rational utilization of marine resources.

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