Microbial Community Characteristics in a Degraded Wetland of the Yellow River Delta

Five different sites with a soluble salt gradient of 3.0-17.7 g kg(-1) dry soil from the coast to the inland were selected, and the microbial population size, activity and diversity in the rhizospheres of five common plant species and the adjacent bulk soils (non-rhizosphere) were compared in a degraded wetland of the Yellow River Delta, Shandong Province, China to study the effects of soil environment (salinity, seasonality, depth, and rhizosphere) on microbial communities and the wetland's ecological function, thus providing basic data for the bioremediation of degraded wetlands. There was a significant negative linear relationship between the salinity and the total number of microorganisms, overall microbial activity, or culturable microbial diversity. Salinity adversely affected the microbial community, and higher salinity levels resulted in smaller and less active microbial communities. Seasonal changes were observed in microbial activity but did not occur in the size and diversity. The microbial size, activity and diversity decreased with increasing soil depth. The size, activity and diversity of culturable microorganisms increased in the rhizospheres. All rhizospheres had positive effects on the microbial communities, and common seepweed had the highest rhizosphere effect. Three halophilic bacteria (Pseudomonas mendocina, Burkholderia glumae, and Acinetobacter johnsonii) were separated through BIOLOG identification, and common seepweed could be recommended for bioremediation of degraded wetlands in the Yellow River Delta. Key Words: microbial activity, microbial diversity, rhizosphere, salinity, soil microorganisms