Zoobenthos effects on the gaseous metabolism in lake sediments

Summary

The sediments which were used in the following experiments were taken from the center of Lake Suwa, an eutrophic lake in Japan, in August. Three kinds of experimental systems were constructed as follows: Sediments of the Exp. syst. No. 1: Greater part of benthos was removed by passing the sediments through a sieve. Sediments of the Exp. syst. No. 2: To the sediments removed benthos, the isolated benthos was added again and mixed well. Sediments of the Exp. syst. No. 3: The sieving treatment was not conducted. Each of these sediments was put in a vessel (length: 35 cm; width: 20 cm and depth: 20 cm) so as to adjust the thickness of sediment layer to 10 cm and then water was added so as to adjust the depth of the overlying water to 10 cm. These three kinds of Exp. systems were incubated at 28°C in a dark room for 39 days and then the gaseous components in these sediments were determined by the author's method.

The average amounts of N₂ and CH₄ of the Exp. syst. No. 1 were 22.1 and 16.7 ml · 1^-1, respectively. Those amounts of N₂ and CH₄ of the Exp. syst. No. 2 were 61.9 and 51.2 ml · 1^-1, respectively and those of the Exp. syst. No. 3 were 38.6 and 35.2ml · 1^-1, respectively of the interstitial water. These results indicate that the gaseous metabolism in sediments is greatly activated by the zoobenthos and also the activity is accelerated by an artificial excitation.