Abstract
The rate of excretion of organic substances by natural phytoplankton population during photosynthesis was measured by using the 14C-method in the water body of Shiozu Bay, Lake Biwa. The relative rate of excretion in terms of carbon ranged from 1 to 11% of the photosynthetic assimilation of CO2. The excretion maximum was found at the depth of 3 m at which the light intensity was 10-20% of that at the surface of water. The rate of excretion was relatively high under illumination of light below the saturation intensity. Fractionation of the substances excreted after exposed to light in water samples added with 14CO2 revealed that more than 73 per cent of the total 14C-radioactivity existed in the anionic fraction. Glycolic acid was identified as the major component in the anionic fraction. In an oligotrophic water body such as Shiozu Bay of Lake Biwa, glycolic acid excreted by phytoplankton populations during photosynthesis may play an important role in the production of some bacteria and other microorganisms which utilize this compound as sources of carbon and energy.
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Schedule a callMore From: Japanese Journal of Limnology (Rikusuigaku Zasshi)
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