The results of the field survey were summarized as follows:<BR>(1) Oceanography: The water in the offshore of Nauru Island was vertically divided into the following three layers by the analysis of T-S diagram.<BR>a. Equatorial surface water; Less than 100m in depth, High temperature: 28.7°C, Low salinity: 34.1-34.6‰<BR>b. Tropical water; Around 200m in depth, Temperature: 11.6-21.8°C, High salinity: 35.3‰.<BR>c. Equatorial intermediate water; More than 500m in depth, Low temperature: less than 10.0°C, Low salinity: less than 35‰.<BR>(2) Quality of water: Nutrients (phosphate, silicate, nitrate) were poor in the equatorial surface water (0-100m) in the offshore of Nauru Island due to phytoplankton's consumption.The concentration of these nutrients gradually increased in the layer deeper than 100 m.It was a typical vertical-distribution pattern in the tropical water.Other parameters related to productivity such as COD, turbidity, chlorophyll-a and cell number of phytoplankton, reached the maximum around 100 m in depth which indicated the maximum standing crop of phytoplankton in this layer.<BR>(3) Plankton: At the sampling stations located in the offshore of the OTEC plant, phytoplankton showed a great variety in the composition of species without any particular dominant species. Diatoms, dinoflagellates, monods, and cocolithophorids were vertically most abundant in the 50-100m layer, which substantially coincided with the maximum of chlorophyll in the surface layer. Judging from the cell numbers of phytoplankton, the production of phytoplankton was considered high in the water around Nauru Island.Zooplankton consisted of protozoans (ciliates, radiolarians, foraminiferans), copepods, pteropods, oikopleurans and others. They were mainly distributed in the water shallower than 200m, but very few of them were found in the deeper layer.<BR>4) Attaching organisms: Twenty-five species were identified from all the sampling stations. Most of them were the secondary attaching organisms such as periwinkies, rockshells, impets and other crawling organisms. There were found very few primary attaching organisms such as algae, barnacles, worm shells and other sessile organisms, which were known to be fouling organisms attaching to underwater facilities. No attaching organisms were observed on the inner surface of intake and outlet pipes except a chalk-tube worm and sea anemones which were considered to have attached after the suspension of the, operation.<BR>(5) Intertidal organisms: The number of species by taxon was as shown below.<BR>Corals Several species<BR>Crabs and hermit crabs 23<BR>Seashells 66<BR>Sea urchins and sea cucumbers 10<BR>Sea weeds (macrophyte) 6