Publication Abstract

Biphasic behaviour of anammox regulated by nitrate and nitrate in an estuarine sediment

M. Trimmer, J.C. Nicholls, N. Morley, C.A. Davies and J. Aldridge

The production of N₂ gas via anammox was investigated in sediment slurries at in situ NO₂^- concentrations in the presence and absence of NO₃^-. With single enrichment above 10 µM ¹⁴NO₂^- or ¹⁴NO₃^- and ¹⁵NH₄⁺, anammox activity was always linear (P < 0.05), in agreement with previous findings. In contrast, anammox exhibited a range of activity below 10 µM NO₂^- or NO₃^-, including an elevated response at lower concentrations. With 100 µM NO₃^-, no significant transient accumulation of NO₂^- could be measured, and the starting concentration of NO₂^- could therefore be regulated. With dual enrichment (1 to 20 µM NO₂^- plus 100 µM NO₃^-), there was a pronounced nonlinear response in anammox activity. Maximal activity occurred between 2 and 5 µM NO₂^-, but the amplitude of this peak varied across the study (November 2003 to June 2004). Anammox accounted for as much as 82% of the NO₂^- added at 1 µM in November 2003 but only for 15% in May 2004 and for 26 and 5% of the NO₂^- added at 5 µM for these two months, respectively. Decreasing the concentration of NO₃^- but holding NO₂^- at 5 µM decreased the significance of anammox as a sink for NO₂^-. The behavior of anammox was explored by use of a simple anammox-denitrification model, and the concept of a biphasic system for anammox in estuarine sediments is proposed. Overall, anammox is likely to be regulated by the availability of NO₃^- and NO₂^- and the relative size or activity of the anammox population.

Reference:

M. Trimmer, J.C. Nicholls, N. Morley, C.A. Davies and J. Aldridge (2005). Biphasic behaviour of anammox regulated by nitrate and nitrate in an estuarine sediment. Applied and Environmental Microbiology; 71 (4) 1923-1930.