Biomass and Enzyme Activity of Two Soil Transects at King George Island, Maritime Antarctica

Abstract

Soil microbial properties were investigated to assess the potential of organic matter dynamics in mineral and ornithogenic soils in a cold climate. Microbial biomass, respiration, N-mineralization, and enzyme activities were measured along two catenary transects crossing penguin rookeries and seabird colonies. Ornithogenic excrements, total organic carbon (TOC), and phosphorus accumulation were major factors controlling microbial properties in Antarctic soils. Multivariate approaches (cluster and discriminant analysis) clearly distinguished the ornithogenic soils from the mineral soils based on their microbial characteristics. Microbial biomass, respiration, and N-mineralization were gradually inhibited by increasing P-inputs by penguins. The metabolic quotient (qCO2) was negatively correlated to P-content, whereas all other microbial properties (microbial biomass, respiration, N-mineralization, enzyme activities) followed the patterns of TOC. Urease, xylanase, phosphatase, and arylsulfatase activities were significantly favored by penguin and seabird excrements in the ornithogenic soils compared to the mineral soils. Microbial biomass-to-enzyme activity ratios were substantially higher at sites influenced by penguin guano than by other seabird excrement. We show that enzymes are active in antarctic soils, and that high levels of biomass-based specific activity in the ornithogenic soils, compared to those of mineral soils, result from continuous input of large quantities of enzyme-rich penguin guano.