SOIL MICROBIAL PROCESSES AND TESTACEA (PROTOZOA) AS INDICATORS OF HEAVY-METAL POLLUTION

The influence of the emissions from a copper smelter on soil microbial processes was investigated at 4 meadow sites along a concentration gradient in Brixlegg (Austria). The first site is within 300 m of the source, further site are situated 1125 m, 2425 m and 5900 m from the smelter. Heavy metal pollution close to the smelter induced a decrease of microbial biomass, respiration, dehydrogenase activity and the related enzyme activities in soil samples (5-10 cm soil depth): Protease, alkaline phosphatase, arylsulfatase, actual and potential nitrification. Thus, soil microbial processes in the 5-10 cm layer appear to be directly affected by heavy metals. Regarding the testate amoebae, their low individual and species numbers at 5-10 cm soil depth obstruct clear trends of this animal group. However. comparing the heavy polluted site with the control area. abundances, species numbers and biomass of testate amoebae slightly decreased at the polluted site (5-10 cm). Contrary to the results in the 5-10 cm layer, most soil microbial processes as well as abundances, species numbers and biomass of testaceans in the upper soil (0-5 cm) seem to be more strongly influenced by the supply of organic substrate than by the content of heavy metals in the soil.