Stream Size Determines the Response of Microbial Communities to Phosphorus Pulses During Storm Runoff

Elaine Langone Center, Terrace Room

Brief phosphorus (P) pulses associated with storm runoff have the potential to be important drivers of microbial community growth in stream ecosystems. We measured the capacity of stream microbial communities to respond to brief P pulse during natural storm events in a small headwater tributary of Fishing Creek and a larger fifth order section near Bloomsburg, PA. Storm runoff in the fifth order section of Fishing Creek resulted in substantial increases in algal polyphosphate, the primary P storage structure for microorganisms. P storage in this reach appeared to be followed by a period of rapid growth. In contrast, we did not observe such an increase in polyphosphates in the headwater section of Fishing Creek for natural storm runoff events or after we performed an artificial P release. Our results indicate that the combination algae domination of the microbial community and P pulses that are higher in concentration and duration might allow P delivered during storm runoff to have greater ecosystem-level effects in larger streams and rivers.