CARBON AND NITROGEN UPTAKE ACTIVITIES IN IRRIGATION SYSTEMS - POSSIBLE EFFECTS OF PRESSURES

Effects of pressures on phytoplankton in Kasumigaura irrigation system s in Japan were examined. Carbon and nitrogen uptake activities of phy toplankton, which were subjected to about 10 atm (10.13 x 10(6) Pa) in the pipeline in the irrigation systems, were not completely lost at t he exit of the pipeline, though the activities decreased. Percentage o f dark to light ammonium uptake was lower at the exit than at the entr ance of the pipeline. These results suggest that the decrease in uptak e activities were partly due to pressure itself, along with the decrea sed amounts of storage matter used for synthesis of nitrogen-containin g compounds. We examined changes in the uptake activities under added 10 atm, using cultured Oscillatoria sp. The uptake activities of carbo n and ammonium gradually decreased during the 10 days treatments. The uptake activities under 10 atm decreased more rapidly than those under atmospheric pressure. This indicates that pressure itself reduced the activities. The present results show that high pressure affects the u ptake activities of carbon and nitrogen uptake by phytoplankton in the pipeline in Kasumigaura irrigation systems.