The effects of storm water runoff on soil microbial communities in an urban wetland

Background/Question/Methods

Urban storm water can be a major source of contamination for aquatic and terrestrial soil microbial communities. Soil-dwelling bacteria have been used as a tool for assessing the effects of chemical inputs such as agricultural or urban wastewater storm water runoff to a system. Microbes are useful models for evaluating overall ecosystem health as they have high turnover rates and fulfill nutrient cycling roles. The La Crosse River Marsh is an urban wetland that receives storm water inputs from many surrounding residential and commercial locations providing an opportunity to examine the relationship between runoff and microbial community composition and function.  Transects adjacent to storm water influent sites were sampled to include both terrestrial soil and submerged sediment samples.  Microbial communities were characterized by density, composition, and carbon utilization profiles.  These data can be used to evaluate the structure and function of microbial communities in soils and sediments impacted by urban runoff.

Results/Conclusions

The density and structure of microbial communities differed between terrestrial and sediment samples along the transects.  A surprisingly high density of Chromobacterium violaceum was found in aquatic sediments which was nearly absent in terrestrial samples.  Overall nutrient utilization decreased with increasing distance from the influent site.  Based on cluster analysis, terrestrial communities used a distinct set of nutrients compared to aquatic sediment communities.  These results indicate clear differences in microbial community structure and carbon utilization between terrestrial and aquatic sediments.  These patterns suggest that contaminants in the influent could play a role in microbial community structure and function.