Abstract
Rates of photosynthesis and respiration of biotic communities were measured in large-scale artificial streams and Kanda River. In the artificial streams, two types of bed were prepared - stony one and flat stainless steel one. Water was recirculated in the streams, each of which was polluted with different amount of powdered milk. The metabolic activities of the biotic community in each stream was estimated on both BOD and O2 balance bases. The results were as follows.
(1) The stream with stony bed, on which a large amount of periphyton was growing, showed lower net productivity or higher purification rate than with flat bed.
(2) The average net productivity, that had minus values in all cases, was proportional to the organic pollutant concentration. The behavior of organic pollutant in the flowing water - stream bed system could be approximately evaluated from the values of net community productivity obtained by TOD and 02 balance methods.
The characteristics of biotic product and respiration were surveyed in Kanda River, where algal communities were densly attendant on the concrete bed. O2 balance method was applied and following results were obtained.
(3) The activities of epibenthic communities was far more dominant than those of flowing suspended ones.
(4) Primary productivity was saturated when light intensity reached 5klux-10klux. The increment in light intensity over the limit therefore did not contribute to the primary production.
(5) Daily average values of the community respiration rate exceed those of primary productivity even in Kanda River, which is assumed to be one of the most eutrophicated rivers in Japan.
