Soil Bacterial Diversity and Community Structure in a River Floodplain Continuum

Abstract

The objectives were (1) to evaluate impact of chronic flooding with heavy metal contaminations on soil biota in a river floodplain continuum; and (2) to assess microbial responses to soil redox states. Soils were collected from four sites at each of two locations along Tisza River in Hungary. Each soil profile was divided into oxic, intermittent, and anoxic horizons: Using molecular, biochemical, and culture based methods, microbial biomass carbon and nitrogen contents, dehydrogenase activity, culturable bacterial populations, and depth- and redox-related variation in microbial community structure were determined. Results indicated that nutrient and oxygen availability regulated microbial distribution along a soil profile. Microorganisms were more active and abundant in oxic layers than anoxic layers. Abundance of gram-positive bacteria increased and those of gram-negative bacteria and fungi decreased with increasing soil depth. Among microbial parameters tested, dehydrogenase activity was most sensitive and responsive to heavy metal contaminations and environmental stress.