Abstract: Using the rolling tube technique, biomass of dissimilatory ironreducing bacteria (DIRB) was detected in sediments of three reservoirs in Guiyang in different seasons, and at the same time, physical and chemical parameters, such as the iron and sulfate contents of pore water, pH, organic matter contents in the sediments were measured. The biomass of DIRB in the sediments of Aha Reservoir, Baihua Reservoir and Hongfeng Reservoir ranged from 1.09×10⁴ to 8.829×10⁵, from 1.05×10⁴ to 3.425×10⁵ and from 4.8×10³ to 4.467×10⁵ cells·g^-1, respectively. The biomass of DIRB in the warm season (June and September) was 1-2 orders of magnitude higher than that in the cold season (February), and the dissolved oxygen (DO) in the watersediment intersurface was correlated to DIRB biomass in the surface sediment, suggesting that DO and temperature had a great effect on DIRB biomass. In addition, the active areas of DIRB migrated to the top of the upper sediment with the alternation of the cold to warm season, as other electron acceptors such as O₂, SO₄^2- in the sediment controlled the profile distribution of DIRB. Aha Reservoir had been polluted by acid mine drainage, but the biomass of DIRB had no difference in orders of magnitude among the three reservoirs, probably because the high sediment organic matter contents (60-140 g·kg^-1) and optimum pH (6.2-7.1) in these reservoirs contributed to the growth of DIRB, but the peaks of the sediment DIRB biomass in Aha Reservoir were higher than in the other two reservoirs.

Key words: NDVI, climate change, vegetation dynamics, permafrost degradation