Takayoshi Toyota, Toshimitsu Nakashima Japan Marine Science and Technology Center
Deep sea water has some favorable qualities: low temperature, rich in nutrients, free from man-made pollutants and organisms that cause diseases to fish. Moreover, deep water is self-reproduced due to the circulation of the resolved substance and water circulation. Its volume in the ocean is enormous. Presently, deep sea water is recognized to be the important biological and energetic resource.
Kochi Artificial Upwelling Laboratory (KAUL) was supported by Japan Marine Science and Technology Center (JAMSTEC) and Kochi Prefecture in March, 1989 to do the research and development on deep sea water utilization. This paper is a brief summary of the experiments at KAUL from April, 1989.
The focus of the experiments is the profits from the deep sea water. First, rich nutrients and cleanliness animates the culture of micro- and macro-algae. Second, low temperature and cleanliness are good for rearing marine organisms living in cold water. Finally, deep water is suitable for rearing deep sea species. It is necessary to develop technology to support biological production such as water temperature control technology, which can be achieved through the utilization of cold deep water and warm surface water. Temperature difference between deep water and surface water is advantageous to air conditioning ( mainly cooling) for offices and greenhouses, and desalination of seawater.
Basic study on deep sea water quality
Variations of temperature and nutrients
Studies on the long term variations of temperature and concentrations of nutrients on supplied sea water showed the temperature fluctuation of deep water was small ( in the range between 11¢XC and 14¢XC ) all year round. Concentrations of nitrate varied from 15 µ M to 30 µ M. This unstable pattern might be influenced by the Kuroshio Current. (JAMSTEC)
Chemical forms of trace metalOrganic and inorganic forms of copper and iron were measured with XAD-2 resin and atomic absorption spectrometry. Seasonal and secular trends of each chemical form and concentration were determined for basic information to control the water quality of aquaculture systems. ( Meteorological Research Institute )
Bacteria living in deep sea waterStudies on the growth potential of marine diatom, Chaetoceros cetatosporum were conducted in Muroto. When the culture of bacterial strains isolated from deep sea water were inoculated into the culture media of the diatom, both growth rates and maximum cell yields, increased ( 2.3 times higher at the maximum than untreated deep sea water). (Kochi University)
Utilization of deep sea water for biological production
- culture of food plankton
- In Japan, the microalgae Nannochloropsis sp.is a common food for mass culture of the rotifer, which is a live food for seed production of fish. The main composition, lipid class and fatty acid of Nannochloropsis sp. cultured at controlled temperature with flowing deep sea water were evaluated. For instance, Eicosapentaenoic acid, an important component for food, became rich in the culture using deep sea water. (Nansei National Research Institute, Fisheries Agency, Kochi )
- culture of seaweeds
- Studies were done on the growth difference of the macroalgae Kajime, Ecklonia cava, between deep sea water and surface sea water. The growth rate of Kajime in deep sea water was significantly greater than that in the surface sea water by 48.9% in average total length and 89.5% in average body weight. (Deep Seawater Laboratory of Kochi)
- rearing cold water organismsIn the past, there were few experiences about the cultivation of Atlantic Salmon ( Salmo salar ) in Japan. Through the experiment, it was seen that both males and females could mature in deep sea water. ( Joint study between JAMSTEC and Central Research Laboratory, Nippon Suisan Kaisha Ltd.)
- Surface water temperature in the summer around Japan is too high for Japanese flounder. However, differences appeared between the two-year old Japanese flounder reared in surface water ( 25-30¢XC ) and mixed water (half deep sea water and half surface water; 20-25¢XC ) during summer. The flounders in surface water did not gain weight, while those in mixed water did.
- rearing deep sea water organism(to be continued on next issue.......)
- Japanese butterfish Medai, Hyperoglyphe japonica is an important resource of deep sea fish. Young fish were caught in June, 1989 and were successfully reared in deep sea water for more than two years for the first time in Japan. The average increased weight and total length were 248 g to 3137 g and 21cm to 58cm, respectively. Survival rate was 30.4% during 18 months. (Deep Sea Water Laboratory of Kochi)