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 (286Kb)
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44,351,000 Yen
We have developed a mesocosm(marine enclosure) at Seto-inland sea in order to understand the mechanism of ocean element cycles based on biochemical processes. The mesocosm enclosed cylindrical water column(5m in diameter and 18m in depth), and the upper layer(0-5m) was identified as the euphotic layer. Nutrients were added into the water column, and chemical/biological conditions have been monitored for 19 days.
Carbon tracer experiments were done within the water column. The transformation rates of dissolved inorganic and dissolved organic carbon(DIC and DOC) into biogenic particulate organic carbon(POC) were observed through the experiments.
Variations in the transformation rates, phytoplankton species and concentrations, carbon standing stocks and other oceanographic parameters were analyzed. Followings are the major results obtained through this research.
a) Phytoplankton species succession; the dominant species were categorized into Centrales, Pennales and Pyrrophyta. Succession of these was explained by the variations in nutrient concentrations.
b) Carbon standing stocks; POC was not increased both at the upper layer and the lower layer even after successive phytoplankton bloom, while DOC increasing at both layers.
c) Carbon transformation rates; the transformation rate of DOC into POC(through the bacterial loop) was 20% of that of DIC into POC(through the photosynthetic loop) at the upper layer in average, but just the same at the lower layer in average.
d) Methods developed; pigments analysis methods to understand the component of POC and continuous PCO2 monitoring system were developed.
Mesocosm, Carbon-cycles, photosynthesis, Grazing, Mineralization Sediment