Temperature dependence of oxygen respiration, nitrogen mineralization, and nitrification in Arctic sediments

Abstract

The temperature dependence of oxic minerahzation processes in perenn~ally cold coastal sediments from Arctic Svalbard, Norway, was determined in short-term incubations at -1 to 44'C and compared to similar incubations with warm temperate sediment. For oxygen respirat~on, nitrogen mineralization, and nitrification, adaptations to low temperature were evident with the microbial comrnunities from Svalbard. Oxygen respiration rates showed the same temperature dependence at all sites around Svalbard, with relatively high rates at O°C and a linear 3-to 4-fold increase from 0°C to a mean optimum temperature of 19.ZoC, whereas rates in the temperate sediment were close to zero at O°C and had optimum at 30 to 40°C. The temperature dependence of nitrogen mineralization was comparable to that of oxygen respiration, and C:N mineralization ratios in the Svalbard sediments were stable at 6 to 8 below 20°C. Thus, low temperature did not affect carbon and nitrogen mineralizatlon differentially. The most prominent adaptation to low temperatures was observed for nitrification, which had a mean optimum temperature of 14.0°C at Svalbard and decreased rapidly in rate at higher temperatures. In the warm temperate sediment the nitrification optimum was near 40°C. The catalytic efficiency of the nitrifying communities from Svalbard, at their in situ temperature, was as high as that reported for cornmunities from temperate regions. This implied that thermal adaptation fully compensated for direct temperature effects on this metabolism.

The Biogeography of Ammonia-Oxidizing Bacterial Communities in Soil

“…This has been demonstrated with Nitrosospira strains grown in pure culture [47] and with AOB communities from different soils [48]. If these observations are generalizable and there is minimal functional redundancy between taxa (i.e., phylogenetically distinct communities have distinct temperature sensitivities), it may explain why the temperature responses in nitrification activity can vary so widely across different soils [49,50] or sediment samples [51]. More broadly, if distinct AOB communities do indeed have different temperature responses, it would suggest that information on the spatial variability in AOB communities could be integrated into models of soil nitrogen dynamics in order to better predict how soil nitrogen dynamics may be affected by changes in climatic conditions.…”

Temperature effects on respiration and photosynthesis in three diatom-dominated benthic communities

“…Such studies have shown an insignificant difference in temperature adaptation of aerobic respiration between arctic and temperate communities (Thamdrup & Fleischer 1998). In contrast, lower Q 10 values have been reported for benthic sulphate reduction in Antarctic sediments compared to measurements performed at temperate latitudes (Isaksen & Jørgensen 1996).…”

“…A comparative study on short-term temperature effects of aerobic respiration in slurred coastal sediments also concluded that Arctic and temperate sediments had similar Q 10 values (Thamdrup & Fleischer 1998). However, a seasonal temperature acclimation was observed for the temperate site, with Q 10 (0-10°C) of 2.0 and 3.0 for winter (1 to 3°C) and summer (13 to 15°C), respectively .…”

“…The curve expresses a classical metabolic temperature response, thus the following criteria for cardinal temperatures were used for categorisation: for psychrophiles, T min < 0°C, T opt ≤ 15°C and T max ≤ 20°C; for psychrotrophs, T min ≤ 0°C, T opt ≤ 25°C and T max ≤ 35°C; and for mesophiles, T opt is~2 5 to 40°C and T max ≈ 35 to 45°C (Isaksen & Jørgensen 1996). Even though cardinal temperature ranges traditionally refer to thermal classes of growth, with narrower limits and lower optimums, they have also been used to describe metabolic activity (Isaksen & Jørgensen 1996, Thamdrup & Fleischer 1998. This generally accepted scheme categorises the gross photosynthetic response for both Nivå Bay and the Trondheimsfjord as psychrotrophic.…”

“…Temperature acclimation usually describes phenotypic changes in a community as a response to short-term temperature change, whereas temperature adaptation involves genetic differences in metabolism between communities from different thermal environments (Berry & Bjorkman 1980, Davison 1991. Temperature adaptation in microorganisms has typically been studied in cultures or in sediment slurries placed in benches at well-defined temperatures (Blanchard et al 1996, Isaksen & Jørgensen 1996, Thamdrup & Fleischer 1998. Based on data for minimum, optimum and maximum temperatures of the activity, the organisms are divided into groups, such as psychrophile, mesophile and thermophile, that tolerate low, medium and high temperatures, respectively (Davison 1991).…”