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Abstract:
The direct temperature dependence of aerobic respiration was determined in sediment from Aarhus Bay, Denmark, in incubations shorter than 12 h at temperature intervals of 1.7 degrees C. Oxygen consumption showed a bimodal distribution between -2 and 80 degrees C indicating the presence of distinct non-thermophilic and thermophilic populations. The thermophilic oxygen consumption had minimum, optimum, and maximum temperatures of 40, 55, and 65 degrees C, respectively, and accelerated strongly after a lag phase of 2-3 h, which may be due to an activation of spores. The sourer of this dormant thermophilic population is unknown. Oxygen consumption by the non-thermophilic population had minimum and maximum temperatures of < -1 and 45 degrees C, respectively. The optimum temperature increased from a broad plateau of 20-30 degrees C in late winter to 30-35 degrees C in late summer, and the apparent activation energy in the natural temperature range (0-15 degrees C) increased from similar to 50 to similar to 70 kJ mol(-1), corresponding to Q(10) values of similar to 2.0 and similar to 3.0, respectively. These changes indicated an adaptation of the aerobic population to seasonal temperature conditions. Due to the seasonal adaptation and to diffusive limitations, a relatively weak temperature dependence of the area-specific aerobic mineralisation rate in the sediment was calculated, Q(10)=1.8. Model calculations further demonstrated significant shifts in the relative importance of aerobic and anaerobic mineralisation due to seasonal temperature variation, with less importance of aerobic respiration and a larger fraction of benthic oxygen consumption coupled to the reoxidation of reduced inorganic compounds during summer than during winter. (C) 1998 Federation of European Microbiological Societies. Published by Elsevier Science B.V.
