Todd Johnson, California State University, Fresno

Class Year:

Mentor:

Abstract:

Spatial changes in the composition of natural microbial communities are complex and highly variable. Although underlying mechanisms are poorly understood, it is believed that both dispersal and environmental conditions are important factors. The present study investigates the influence of dispersal and environmental conditions on the development of microbial communities in tributaries of the Choptank River watershed. An in situ experiment was also conducted to determine the distribution of airborne microbial communities across a wide spatial scale (<1m to >100 km). Community composition was determined via PCR amplification of bacterial DNA followed by denaturing gradient gel electrophoresis (DGGE). Community composition in the tributaries was predominantly influenced by environmental conditions, specifically agricultural land use within the catchment and presence of suspended sediment. However, the nonrandom distribution of airborne bacteria at the largest distance scales of our study suggests that dispersal may influence aquatic microbial community structure, although this effect is overwhelmed by environmental conditions in Choptank River tributaries.