Estimation of microbial biomass in natural and perturbated tundra by the ATP bioluminescence assay

Abstract

Arctic north slope tundra soil was found to contain sufficient microbial biomass for decomposition indicating that the slow decomposition of the tundra may be due to inhibited metabolic activity. Samples were collected from the International Biological Program Tundra Biome site at Barrow, Alaska and analyzed using classical soil population measurements and the ATP bioluminescence assay. Soils from various habitats typical of the north slope coastal landscape and oil, vehicle and temperature perturbations were examined. ATP content of the tundra soil was 4 g/gm soil in the 0 - 2 cm histic layer and 0.4 g/gm soil in the 2 - 7 cm clay loam silt horizon. Viable plate data were 10⁷ - 10⁸ bacteria/gm soil and direct microscopic data were 10¹⁰ cells/gm soil which indicates that the total microbial biomass of the tundra was predominately bacterial. Perturbation of the tundra soil decreased the ATP concentration by at least 50% in the 0 - 2 horizon. Comparison of 5 habitats showed a decrease in ATP concentration in the elevated well-drained polygon top compared to the lower wetter areas. Comparison of various extraction techniques demonstrated that ATP recovery was dependent upon solvent pH and the dilution of the extractant. The assay was found to be a quick diagnostic tool for major habitat changes within the soil regime.