Rates of ammonia release from sediments by chironomid larvae

Abstract

SUMMARY. 1. Microcosms of Lake Balaton mud and sterilized sand and aerated water were used to evaluate ammonia increments in the overlying water as influenced by chironomid density and temperature. In the two approaches, the effects of sediment disturbance and metabolic excretion of chironomids were measured.2. The activity of larvae increased the ammonia content of the overlying water at temperatures above 10°C. A rise of temperature to 20°C resulted in a 5–20‐fold increase in ammonia release in both systems with chironomids.3. At 10°C combined effects of sediment disturbance and of excretion produced lower release rates than did excretion rates alone (mud‐water v. sand‐water treatments). At higher temperatures (15 and 20°C) release rates of ammonia by sediment disturbance plus excretion were higher than excretion rates alone. Ammonia excretion contributed significantly to the total release at each temperature.4. Metabolic mineralization of nitrogen compounds appears to be an important mechanism contributing to nitrogen regeneration from aerobic lake sediments. High N:P ratio (14:1) of chironomid excretion materials supports this interpretation.